Pdpii May2011_07 Group Report

CAB 4023

PLANT DESIGN PROJECT II

MAY SEMESTER (2011)

PRODUCTION OF

543,000 METRIC TONS PER YEAR AMMONIA

GROUP 07

ABU RAIHAN BIN MOHAMMAD 10593

AHMAD FAISAL BIN AHMAD SAZALI 10179

MOHD AZFAR BIN MD JAAFAR 10743

NOOR SYAHIDAH BINTI RAMLI 10906

RUFAIDAH BINTI MOKHTAR 10580

CHEMICAL ENGINEERING PROGRAMME

UNIVERSITI TEKNOLOGI PETRONAS

May 2011

ii

CAB 4023

PLANT DESIGN PROJECT II

MAY SEMESTER (2011)

PRODUCTION OF

543,000 METRIC TONS PER YEAR AMMONIA

GROUP 07

ABU RAIHAN BIN MOHAMMAD 10593

AHMAD FAISAL BIN AHMAD SAZALI 10179

MOHD AZFAR BIN MD JAAFAR 10743

NOOR SYAHIDAH BINTI RAMLI 10906

RUFAIDAH BINTI MOKHTAR 10580

APPROVED BY,

____________________

(AP DR. M. IBRAHIM ABDUL MUTALIB)

DATE:

CHEMICAL ENGINEERING PROGRAMME

UNIVERSITI TEKNOLOGI PETRONAS

May 2011

iii

ACKNOWLEDGEMENT

First and foremost, Alhamdulillah and thank you to Allah the Almighty for guiding us

throughout our journey in completing the Plant Desing Project (PDP). All members of Group 07

are to be credited for their utmost participation and dedication in performing each task assigned.

A token of appreciation also goes to our supervisor AP Dr Mohamed Ibrahim bin Abdul Mutalib

for his valuable guidance and advice throghout the progress of creating a feasible, running design

of an Ammonia plant. His willingness to spend his valuable time to guide us has contributed

greatly to our project, and not to forget the effort he has taken to assist us.

Besides that, we would also like to thank the Department of Chemical Engineering of Universiti

Teknologi PETRONAS for providing the necessary resources for us to complete the project. To

all lecturers involved in PDP, we express our gratitude in assisting us throghout the course this

semester.

Deepest gratitude to the examiners for the oral presentation of PDP for being supportive and

guiding us through our mistakes to make the project even better. Lastly, we would like to thank

everyone who has provided us with the information, assistance, support and advices for this

project. Thank you to Mr. M Faudzi M Isa and Ir. Dr Chan Tuck Leong for sharing their valuable

insight on plant design and costing.

Special thanks to our classmates who are willing to share their information and knowledge with

us and also to our family for their support in making this PDP a success.

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Table of Contents List of Tables ................................................................................................................................ vii

EXECUTIVE SUMMARY ........................................................................................................... ix

CHAPTER 1 ................................................................................................................................... 1

1.0 INTRODUCTION ............................................................................................................ 1

1.1 Background ................................................................................................................... 1

1.2 Problem Statement ........................................................................................................ 2

1.3 Objective ....................................................................................................................... 2

1.4 Scope of Work .............................................................................................................. 3

CHAPTER 2 ................................................................................................................................... 4

2.0 LITERATURE REVIEW ................................................................................................. 4

2.1 Ammonia ...................................................................................................................... 4

2.2 Ammonia Market .......................................................................................................... 5

2.3 Ammonia Plant in Malaysia ......................................................................................... 7

2.4 Properties of Feedstock and Product ............................................................................ 7

2.5 Technology Comparison............................................................................................. 14

2.6 Site Feasibility Study .................................................................................................. 19

CHAPTER 3 ................................................................................................................................. 27

3.0 CONCEPTUAL DESIGN AND SYNTHESIS ............................................................. 27

3.1 Hierarchial Decomposition Approach ........................................................................ 27

3.2 Level 1 – Continuous or Batch ................................................................................... 28

3.3 Level 2 – Input-Output Structure ................................................................................ 28

3.4 Level 3 - Reactor Design and Recycle Structure of Flowsheet .................................. 30

3.5 Level 4 - Separation System Synthesis....................................................................... 33

3.6 Level 5 – Heat Exchanger Network ........................................................................... 39

CHAPTER 4 ................................................................................................................................. 47

4.0 INSTRUMENTATION AND CONTROL .................................................................... 47

4.1 Introduction ................................................................................................................ 47

4.2 Basic Control Strategies ............................................................................................. 48

4.2 Reactor Control Strategy ............................................................................................ 50

4.4 Absorption Column Control Strategy ......................................................................... 52

4.5 Compressor Control Strategy ..................................................................................... 53

4.6 Stripper Control Strategy ............................................................................................ 55

4.7 Pump Control Strategy ............................................................................................... 57

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4.8 Heat Exchanger Control Strategy ............................................................................... 58

4.9 Flash Vessel Control Strategy .................................................................................... 60

4.10 Conclusion ................................................................................................................... 61

CHAPTER 5 ................................................................................................................................. 62

5.0 SAFETY AND LOSS PREVENTION .......................................................................... 62

5.1 Hazard and Operability Studies (HAZOP) ................................................................. 62

5.2 Plant Layout ................................................................................................................ 72

CHAPTER 6 ................................................................................................................................. 78

6.0 WASTE TREATMENT ................................................................................................. 78

6.1 Introduction ................................................................................................................ 78

6.2 Laws and Regulations ................................................................................................. 79

6.3 Waste Identification .................................................................................................... 80

6.4 Waste Treatment/Disposal .......................................................................................... 83

CHAPTER 7 ................................................................................................................................. 92

7.0 PROCESS ECONOMICS AND COST ESTIMATION ................................................ 92

7.1 Introduction ................................................................................................................ 92

7.2 Capital Investment ...................................................................................................... 93

7.3 Operating Cost ............................................................................................................ 95

7.4 Economic Analysis ..................................................................................................... 96

CONCLUSION AND RECOMMENDATION .......................................................................... 101

REFERENCES ......................................................................................................................... 1014

APPENDICES ............................................................................................................................ 107

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List of Figures

Figure 2.1: Ammonia Structure . . . . . . . 4

Figure 2.2: World Ammonia Consumption . . . . . . 6

Figure 2.3: Gebeng Industrial Area Map . . . . . . 26

Figure 3.1: Input Output Structure . . . . . . . 29

Figure 3.2: Flash Drum Separator . . . . . . . 36

Figure 3.3: Sequencing of Separators . . . . . . . 37

Figure 3.4: Algorithm Table . . . . . . . . 43

Figure 3.5: Heat Cascade . . . . . . . . 44

Figure 3.6: Combined Composite Curve from Online Software . . . 45

Figure 3.7: Heat Exchanger Network . . . . . . . 46

Figure 4.1:Feedback Control . . . . . . . . 48

Figure 4.2: Feedforward control . . . . . . . 48

Figure 4.3: Cascade Control . . . . . . . . 49

Figure 4.4: Ratio Control . . . . . . . . 49

Figure 4.5: Reactor . . . . . . . . . 50

Figure 4.6: Absorbtion column . . . . . . . 52

Figure 4.7: Compressor . . . . . . . . 53

Figure 4.8: Stripper . . . . . . . . . 55

Figure 4.9: Pump . . . . . . . . . 57

Figure 4.10: Heat exchanger . . . . . . . . 58

Figure 4.11: Cooler . . . . . . . . . 59

Figure 4.12: Flash vessel . . . . . . . . 60

Figure 5.1: HAZOP Procedure . . . . . . . 63

Figure 5.2: System under study for HAZOP . . . . . . 65

Figure 6.1: Air Effluent Treatment Block Diagram . . . . . 85

Figure 6.2: Flare Gas System . . . . . . . . 86

Figure 6.3: Wastewater Treatment Block Diagram . . . . . 87

Figure 7.1: Graph of PV vs No of Years for Simple Payback Period . . 98

Figure 7.2: Graph of PV vs No of Years for Discounted Payback Period . . 100

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List of Tables

Table 2.1: Ammonia Plant in Malaysia . . . . . . 7

Table 2.2: Properties of Ammonia . . . . . . . 8

Table 2.3: Properties of Natural Gas . . . . . . . 9

Table 2.4: Properties of Hydrogen . . . . . . . 10

Table 2.5: Properties of Nitrogen . . . . . . . 11

Table 2.6: Properties of Carbon Dioxide . . . . . . 12

Table 2.7: Properties of MDEA . . . . . . . 13

Table 2.8: Technology Comparison . . . . . . . 14

Table 2.9: Technology Advantages and Disadvantages . . . . 17

Table 2.10: Weighted Table . . . . . . . . 18

Table 2.11: Comparison of Potential Industrial Area . . . . 22

Table 2.12: Weighted Marks and Explanation on the Plant Site Location Factors . 24

Table 2.13: Weighted Table Comparison . . . . . . 25

Table 3.1: Comparison between Batch and Continuous Flow . . . 28

Table 3.2: Input Output Condition . . . . . . . 29

Table 3.3: Comparison Between CSTR and PFR . . . . . 31

Table 3.4: Reactions for Each Reactor . . . . . . 32

Table 3.5: Stream Table . . . . . . . . 40

Table 3.6: Optimum Delta T min for Industrial Sector . . . . 41

Table 3.7: Shifted Temperature . . . . . . . 42

Table 4.1: Variable types . . . . . . . . 51





Table 4.6:Variable types . . . . . . . . 59


Table 5.1: List of Basic HAZOP Guide Words . . . . . 64

Table 6.1: Parameters for Standard A and B . . . . . . 79

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Table 6.2: Air Emissions Guidelines . . . . . . . 80

Table 6.3: Waste Identification . . . . . . . 82

Table 6.4: Comparison of Gaseous Pollutant Removal Systems . . . 84

Table 7.1: Installation Factor Table . . . . . . . 94

Table 7.2: Estimated Equipment Cost . . . . . . 95

Table 7.3: Non-Discounted Simple Payback Cashflow . . . . 97

Table 7.4: Discounted Payback Cashflow . . . . . . 99

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EXECUTIVE SUMMARY

The objective of this project is to design a petrochemical plant producing 543,000 metric tonnes

per year of Ammonia from nitrogen and hydrogen. The plant must be economically feasible with

a plant life of 20 years with 330 operating days per year. It is producing Ammonia with a 99.99%

purity according to specification to be sold both locally and also exported to other countries.

Ammonia is a very important raw material which is extensively used to manufacture fertilizers

and other nitrogen-containing chemicals such as nitric acid, nitrates and intermediates for dyes

and other pharmaceutical products. The market for Ammonia in the future is quite promising

with the increase in fertilizer demand worldwide following the growth in population.

The plant is to be located in Malaysia. After considering three different plant sites from many

different aspects, Gebeng Industrial Estate in Kuantan, Pahang is chosen as the most suitable

location for the plant. The criteria evaluated for the location include availability of raw material

in the area, reasonable land price, feasibility of transportation, wastewater management system

as well as government incentives provided in the area. The site is also equipped with centralized

tankage facilities, pipeline and pipe rack system connecting Gebeng to Kuantan Port along with

utilities such as water and steam supplied by Centralized Utilities Facilities (CUF) in Gebeng.

Before carrying out with the plant design, preliminary hazard analysis is conducted in order to

define safety related aspects that might influence the design. The analysis include information on

previous accidents in similar Ammonia plant in the world, identification of material and

chemical hazards in the process, study on reducing inventories at site and also identification of

any compliances or requirements by local safety regulations and design guidelines.

Extensive literature review is done to obtain the latest information on Ammonia price and market

that may lead to a more profitable design by evaluating the economic potential of the project. In

the context of conceptual design, several process routes for hydrogen production were evaluated

and the best alternative was chosen for the design. The feed for the steam-reforming process is

natural gas in order to produce hydrogen. This is then reacted in high and low shift temperature

converter in order to convert the excess carbon monoxide into carbon dioxide. The carbon

dioxide is removed in the CO2 removal unit before the unabsorbed carbon monoxide and carbon

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dioxide is reacted to produce methane. The final reaction is Ammonia synthesis to produce the

final product.

The designing phase of this project is executed using manual engineering calculation and also

PETRONAS iCON software. iCON is used to generate the Process Flow Diagram (PFD) which

is needed for the implementation of basic mass balance and heat integration. The heat integration

study is done by applying the pinch technology method. This is necessary in order to optimize

the energy usage in the plant. The Piping and Instrumentation Diagram (P&ID) with all process

equipments, piping systems, control loops and applied heat integration proecss is also generated.

The summaries of important specifications of major and minor equipments in the plant are as

shown below:

Raw Material Capacity/Requirement (MTPA)

Natural Gas 254,000

Steam 1,070,100

Product Capacity/Requirement (MTPA)

Ammonia 543,000

By-Product Capacity/Requirement (MTPA)

Carbon Dioxide 9,908,000

Major Equipment Description Operationg Condition

Primary Reformer

Reactor (R-101)

Converts natural gas to hydrogen and carbon

dioxide through reaction with steam.

CH4 + H2O 3H2 + CO

C2H6 + 2H2O 5H2 + CO

C3H8 + 3H2O H2 + 3CO

Temperature: 502°C

Pressure: 39 bar

Conversion: 0.75

Secondary Reformer

Reactor (R-102)

Further reaction to form more hydrogen gas.

CH4 + 1.5O2 2H2O + CO

CH4 + H2O 3H2 + CO

H2O + CO H2 + CO2

Temperature: 529°C

Pressure: 39 bar

Conversion: 0.85

High Temperature Shift

Reactor (R-103)

Reaction to convert carbon monixode gas to

carbon dioxide over a high temperature.

Temperature: 367°C

Pressure: 37 bar

Conversion: 0.75

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H2O + CO H2 + CO2

Low Temperature Shift

Reactor (R-104)

Shift reaction to further convert unreacted

carbon monoxide to carbon dioxide over a

lower temperature range.

H2O + CO H2+ CO2

Temperature: 217°C

Pressure: 35 bar

Conversion: 0.90

Methanator Reactor

(R-105)

Unreaced carbon monoxide and carbon

dioxide is reacted with hydrogen to form

methane which is recycled back to the

reformer.

3H2 + CO H2O + CH4

4H2 + CO2 CH4 + 2H2O

Temperature: 300°C

Pressure: 24 bar

Conversion: 0.99

Ammonia Converter

Reactor (R-106)

Main reactor for ammonia synthesis from

hydrogen and nitrogen (from air)

3H2 + N2 2NH3

Temperature: 378°C

Pressure: 198 bar

Conversion: 0.31/per pass

CO2 Absorption

Column (C-101)

Absorption column to absorb carbon dioxide

produce during the process of converting

methane to hydrogen from the vapour outlet

of low temperature shift converter

Temperature: 35°C

Pressure: 25 bar

No of tray: 25

Minor Equipment Description

Compressor To increase the pressure of the vapour outlet stream from the reactors to achieve a

prescribed operating condition in subsequent reactors.

Separator Vessel To separate mixture to its individual components according to its density (usually to

separate between liquid and gas).

Cooler Additional cooling requirement besides heat exchangers used in the plant among

process streams.

Heater Additional heating requirement besides heat exchangers used in the plant among

process streams.

Heat Exchanger Used to optimize the heat dissipation from process streams in order to save cost.

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The parameter limits of effluents are according to the Standard B of Environmental Quality Act

(EQA) 1974 in the constitution of Malaysia. The waste treatments in this plant are mainly

focused on wastewater treatment and air effluent. Wastes in the plant are first reduced through

waste minimisation before it is subjected to waste treatment/disposal. Water effluent will be

treated on site at the wastewater treatment plant while the air effluent will be burned using a flare

system.

For the process economics and cost estimation, we estimated the capital costs, operating costs

and economic potential of the plant. The Detailed Factorial Method with approximately 25%

accuracy must be used for detailed economic evaluation and the plant lifetime is fixed at 20

years. The economic potential at level 1 and level 2 are calculated according to Douglas (1988).

From the economic analysis, the Total Capital Investment for this project has been determined to

be $ 286,242,893.59 with an IRR of 12.8%. Further economic analysis on the project has proven

that the project is economically justified, having a payback period of 9 years since the project

commences, which is equal to 6 years after plant start-up. The calculated Discounted Cash Flow

Rate Of Return (DCFRR) is larger than the assumed Minimum Attractive Rate of Return

(MARR), enabling this project to be worth invested.

In the report, process control and instrumentation are included for each stage of the process.

Preliminary hazards analysis, safety and loss prevention are also included in this report. For

safety and loss prevention, a hazard and operability study, (HAZOP) was carried out with the

selection of process nodes revolving around the secondary reformer (R-102).

Overall, the designe plant is technically and economically feasible from the study condcuted and

analysis performed.

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CHAPTER 1

1.0 INTRODUCTION

1.1 Background

The objective of the project is to make a realizable plant which is profitable, safe and

environmentally friendly. The plant that is to be designed is an ammonia producing plant which

uses nitrogen and hydrogen as its raw material. There are 2 main parts to the plant, which

includes the hydrogen production section and the ammonia production section.

The design project will be split into 2 parts, which will be taken during the course of 2 semesters.

This report covers the first part of plant design project, they include the following:

1. Review of the technologies

2. Selection of the feedstock, appropriate technology and flow-sheet

3. Economically feasible production capacity

4. Plant location

5. Energy and material balances

6. Heat Integration

7. iCon simulation

In the initial stage of the project, a literature review will be conducted on several matters. The

purpose of the literature review is to learn and find data on the technologies available, safety,

environmental effects, cost data and so forth. The next step is the selection of the best route or

process of producing ammonia.

The plant normally is expensive to build and operate, and difficult to maintain within regulatory

requirements. The process technology that has the best balance out of the following characteristic

are preferred which includes cost, safety, impact to environment and ease of starting and

operation. The most expensive parts of a process that was discovered are engineering part and

extraordinary management attention and skills are required to keep the plants operating. Besides

that, improving the accuracy of the approximate-material and energy calculations is vital.

2

According to the design alternatives, the cost of each in terms of material balance is compared,

raw materials availability, environmental impact, new technology, economics, location, safety,

etc. The preliminary design work includes literature research, conceptual design, process flow

sheeting and heat integration as well as the pre-design economic evaluation. The detailed

equipment design and specification will be done at the middle stages of the design project, when

the process flow diagram is definite and finalized. Other task to be completed will follow up, that

is the instrumentation and control design, pipe and instrumentation diagram, economic

evaluation, HAZOP and safety considerations and waste treatment.

1.2 Problem Statement

Ammonia is one of the most widely produced substances around the world. It is mainly used for

the production of UREA which is a fertilizer, however there are also several other uses for

ammonia which include uses in medicine, explosives, a cleansing agent and so forth. The task

that was given to us is to design an ammonia plant which produced its own hydrogen and is

based on the costs of 2011. The scope of the project is for 20 years which has an interest rate

of10% per year.

1.3 Objective

The main objective of this project is to integrate the knowledge of Chemical Engineering over

the course of 3 years to solve design problems related to an industrial plant. Other objectives

include developing team work and leadership characteristics. The ammonia plant that is to be

designed has to have to following considerations:

i) The most suitable location in Malaysia for the plant

ii) Effect of the plant to the environment.

iii) Maximizing the recovery and recycling of the reactants and intermediates.

iv) Minimize energy consumption to the extent economically justified.

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v) The plant should be designed as simple and safe to operate that follows the corporate

HSE guidelines in Malaysia.

1.4 Scope of Work

The scope of study in this project is narrowed down so that the project is feasible and could be

completed within the allocated time frame. The parts of scope of study are:

i) Identify, select and developing the best flow sheet of the plant production

ii) Integrating of knowledge in considering of economical feasible production capacity

iii) Developing and simulating of material and energy balance for selected process

iv) Designing the proper equipment in the process plant like reactor, separator, heat exchanger,

pumps, storage and etc.

v) Developing the best control strategy

vi) Considering the environment and safety in relation to plant operation

vii) Conducting research to select the best possible plant location

viii) Preparing the preliminary and interim report as per standard format and present about the

plant design in the oral presentation.

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CHAPTER 2

2.0 LITERATURE REVIEW

2.1 Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula NH3. It is a colourless gas

with a characteristic pungent odour. Ammonia contributes significantly to the food and fertilizers

industry. Besides, ammonia is used in commercial cleaning products and other commercial

industry. Commercially, ammonia is known as anhydrous ammonia. This term shows that there

is absence of water in the material. Because NH3 boils at -33.34 °C (-28.012 °F), the liquid must

be stored under high pressure or at low temperature. The reaction of hydrogen and nitrogen to

form ammonia is: 3H2 + N2 2NH3.

Figure 2.1: Ammonia Structure

Ammonia is being use in many industry in the world. Examples of ammonia usages are :

1. Fertilizer industry

2. Used for Ammonium Salts

3. Industrial application for Nitric Acid

4. Laboratory Reagent

5. Cleansing Agent

6. Medicine

7. Source of hydrogen

8. Refrigerant

9. Sodium Carbonate

5

Ammonia is mainly used in fertlizer industry which contributes up to 85% from overall usage.

Ammonia is the basic building block of the world nitrogen industry and is the intermediate

product from which a wide variety of nitrogen-based fertilizers and industrial products are

produced. Ammonia is generally processed into a variety of fertilizer products before being

applied to the soil. These products include urea, ammonium nitrates, ammonium sulphate and

ammonium phosphates. Urea plants are integrated with ammonia production as they require the

carbon dioxide by-product from ammonia units.

As for that, ammonia market is being studied in order to have clear perspective of ammonia from

economic aspect.

2.2 Ammonia Market

Prices in the Asian ammonia market picked up momentum in the last couple of months of 2010,

driven by tight supply and healthy demand in the region. Robust conditions in the US and

Europe offered additional support to Asian pricing, and high numbers for other nitrogen products

also helped buoy ammonia levels. Prices rose from $445-475/tonne CFR (cost and freight) Asia

in mid-November to $465-500/tonne CFR Asia in early February 2011.

World apparent consumption of ammonia increased by 12.0% or 2.3% annually during 2005–

2010, although it slowed during the latter part of 2008 and 2009. Growth is forecast at 2.7%

annually during 2010–2015. There will be some regions that grow faster, in particular Africa, led

primarily by increased urea production.

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Figure 2.2: World Ammonia Consumption

Based on the pie chart above, China is the leading country that consumes ammoniam followed

by CIS, United States, Western Europe, India and others. Ammonia consumption is driven

primarily by the production of downstream fertilizer products, such as urea, ammonium nitrates,

ammonium phosphates, ammonium sulfates and nitrogen solutions. In addition, China is the only

country to use ammonium bicarbonate to any degree, while the United States is the leading

country for direct application of anhydrous ammonia, and, to a lesser extent, aqueous ammonia.

The growth of biofuels, and in particular, bioethanol, is having a major impact on nitrogen

fertilizer demand.

Production of urea accounted for about 54% of total world ammonia consumption. Ammonium

nitrate (directly and through nitric acid) accounted for about 14%, of which an estimated 75% is

consumed in fertilizer applications and the remainder in explosives and blasting agents.

Ammonium phosphates accounted for 5.8%, ammonium bicarbonate for 4.3% (primarily China)

and ammonium sulfate for 2.7%.

According to the International Fertilizer Industry Association (IFA), the world nitrogen market

in 2009 recovered from the depressed demand conditions seen in 2008 in both the fertiliser and

industrial sectors. World ammonia production in 2009 remained stable at 153m tonnes NH3.

Global ammonia trade fell 7.4% to an estimated 17.4m tonnes NH3.

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Global ammonia capacity was 153m tonne/year NH3 in 2009, with the main additions occurring

in China, Trinidad, Indonesia, Oman, India and Egypt. The IFA noted that many projects that

were slated for commissioning in 2009 have been delayed by six months or more.

According to the IFA 2010 world capacity survey, global ammonia capacity will increase by

20% to 224m tonne/year NH3 by 2014. The bulk of the growth will be in China, Middle East,

Latin America and Africa. IFA estimated global seaborne ammonia availability will be close to

19m tonnes in 2014, a net increase of 1.7m tonnes over 2009

2.3 Ammonia Plant in Malaysia

Table 2.1: Ammonia Plant in Malaysia

COMPANY LOCATION PRODUCTION (MT/yr)

PETRONAS Ammonia Sdn Bhd Kerteh, Terengganu 450,000

PETRONAS Fertilizer Kedah

Sdn Bhd Gurun, Kedah 400,000

Asean Bintulu Fertilizer Sdn Bhd Bintulu, Sarawak 400,000

Listed above are the plant in Malaysia that operate to produce ammonia. Most of the ammonia

plant in Malaysia produce around 400,000 MT/yr which is higher compare to average ammonia

produce by world. All of the ammonia plant in Malaysia are listed under PETRONAS. These

ammonia plant is located at Kerteh,Terengganu, Gurun, Kedah and Bintulu Sarawak.

2.4 Properties of Feedstock and Product

Basically the product desired in ammonia plant is ammonia. The feedstock for ammonia

production is hydrogen that comes from natural gas and nitrogen from air. During the ammonia

production, there is one main by product which is carbon dioxide. So, each of the component

have its own properties. Below are properties listed for each component.

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Table 2.2: Properties of Ammonia

PROPERTIES CHARACTERISTICS

Other names Ammonium hydrate, ammonia-aqueous solution

Molecular

Formula NH3

Molecular

Weight 35.06

State Liquid

Specific Gravity 0.9

Boiling Point Not available (stored at -330C in liquid form)

Flash Point Not available

Appearance Colourless alkaline liquid with strong pungent odour, mixes with water. Immiscible

with most organic solvents.

Stability FLAMMABILITY:

May form flammable/explosive vapour-air mixtures

CHEMICAL STABILITY:

Forms explosives mixtures with oxygen, chlorine, bromine, fluorine, iodine,

mercury, platinum and silver.

RISK:

- Toxic by inhalation

- Causes burns

- Risk of serious damage to eyes

- Very toxic to aquatic organisms

SAFETY:

- Keep locked up

- Avoid contact with eyes

- Wear suitable protective clothing

- Use only in well-ventilated areas

Hazard Rating

9

Table 2.3: Properties of Natural Gas


Other names Synthetic natural gas, natural gas C1-4

Molecular

Formula CH4 – main component

Molecular

Weight 16.04 as CH4

State Gas

Specific Gravity 0.58-0.63

Boiling Point -162°C as CH4

Flash Point -218°C

Appearance Invisible, highly flammable gas which readily forms explosive mixtures in air.

Supplied in bulk to consumers by pipeline at pressures up to 1000 kPa.


Extremely flammable – burns with a pale, luminous flame. Sudden release of

pressure or leakage will result in generation of a large volume of highly

flammable/explosive gas.

CHEMICAL STABILITY:

Reacts violently with oxidizing agents. Contact with chlorine dioxide causes

spontaneous explosion.

RISK:

- Risk of explosion if heated under confinement

- May be harmful to the foetus/embryo

- Vapours potentially cause drowsiness and dizziness

SAFETY:

- Keep away from sources of ignition

- Avoid exposure

Hazard Rating

10

Table 2.4: Properties of Hydrogen


Other names Industrial hydrogen, protium

Molecular

Formula H2

Molecular

Weight 2.106

State Non-Liquefied Gas

Specific Gravity Not applicable

Boiling Point -252.8°C

Flash Point 571°C (auto ignition temperature)

Appearance Colourless, odourless extremely flammable gas; slightly soluble in water.


Highly flammable – easily ignited by heat, sparks or flames.

CHEMICAL STABILITY:

Ignites easily with oxygen.

RISK:

- Extremely flammable

- Risk of explosion if heated under confinement

- Inhalation may cause effect, ingestion is not likely. Not irritating to skin and

eyes.

SAFETY:

- Keep away from sources of ignition

- Avoid exposure

Hazard Rating

11

Table 2.5: Properties of Nitrogen


Other names Nitrogen gas, tyrgas, praxair

Molecular

Formula N2

Molecular

Weight 28.02


Specific Gravity Not available


Flash Point Not applicable

Appearance Colourless, odourless compressed gas; sparingly soluble in water. Sudden release of

pressure or leakage may result in rapid generation of large volume of asphyxiant gas.


Risk of explosion if heated under confinement.

CHEMICAL STABILITY:

Stable when temperature protected and kept isolated as a compressed gas.

RISK:

- Inhalation may produce health damage


SAFETY:

- Do not breathe gas/fumes/vapour/spray

- Avoid contact with skin

- Use only in well-ventilated areas

- Keep container in a well-ventilated place

- Keep container tightly closed

Hazard Rating

12

Table 2.6: Properties of Carbon Dioxide


Other names Carbon anhydride, carbonic acid gas

Molecular

Formula CO2

Molecular

Weight 44.00


Specific Gravity 1.10 at -37°C


Flash Point Not applicable

Appearance Colourless, odourless gas; slightly soluble in water. A saturated solution of gas in

water has pH of 3.8. High pressure liquefiable gas.


Risk of explosion if heated under confinement.

CHEMICAL STABILITY:

Reacts violently with strong bases and alkali metals.

RISK:

- Inhalation may produce health damage

- Cumulative effects may result following exposure

- May affect fertility


SAFETY:

- Avoid exposure

- Keep container in a well-ventilated place

- Keep container tightly closed

Hazard Rating

13

Table 2.7: Properties of MDEA


Other names Methyldiethanolamine

Molecular

Formula CH3N(C2H4OH)2

Molecular

Weight 119.20

State Liquid

Specific Gravity 1.05 at 20°C

Boiling Point 240-255°C

Flash Point 115.6°C

Appearance Pale straw liquid with amine odour.


Oxides of carbon and nitrogen are hazardous products of combustion.

CHEMICAL STABILITY:

Chemically stable under normal and anticipated storage and handling conditions.

RISK:

- Inhalation and skin contact are expected to be primary routes of exposure

- Slightly toxic if swallowed, practically non-toxic if absorbed through skin,

severely irritation to eyes

- Avoid contact with strong acids, strong alkalis and strong oxidizers

- Thermal decomposition giving off toxic and corrosive products

SAFETY:

- Avoid contact with eyes

- Wash thoroughly after handling

- Not hazardous under normal storage conditions. However, material should be

stored in closed containers.

14

2.5 Technology Comparison

For ammonia production, there are several technologies or alternatives to produce hydrogen

which are steam reforming, electrolysis, coal gasification and biomass production.

Table 2.8: Technology Comparison

Process Steam

Reforming

Electrolysis Coal

Gasification

Biomass

Production

Cost of

Feedstock

RM 1.68/kg H2 RM 0.0089/kg

H2

RM 5.42/kg H2 RM 3.13/kg H2

Operation &

Maintenance

Cost

Low fuel cost

from natural gas

High electricity

cost to crack

Low fuel cost

from coal

High cost

because undergo

many processes

Conversion of

Feed

1 mol CH4: 3

mol H2

1 mol H2O: 1

mol H2

3 mol C: 1 mol

H2

1 mol C: 2 mol

H2

Emission Low CO2 gas

emission

No greenhouse

gas

High CO2 gas

emission

CO2 , NOx , SOx

emission – can

cause acid rain

Economic analysis for hydrogen production.

This analysis has been done to compare the cost of producing 1 kilogram of hydrogen from every

1 kilogram of feedstock.

1. Coal gasification

Primary reaction: 3C + O2 + H2O H2 + 3CO

From this reaction, 3 mol of carbon will produce 1 mol of hydrogen.

Assuming flowrate of feed of 1000 kg/hour, we calculate molar flowrate of feed as of:

Feed mass flowrate divided by the molecular weight of C.

1000 kg/hour divide by 12 kg/kmol = 83.3333 kmol/hour

Feed molar flowrate = 83.3333 kmol/hour

83.3333 kmol/hour C 1/3 x 83.3333 kmol/hour hydrogen

27.7777 kmol/hour hydrogen

15

The molar flowrate of hydrogen in the outlet is 27.7777 kmol/hour. From this value, we

determine the mass flowrate of hydrogen from the outlet.

Mass flowrate = molar flowrate x molecular weight of hydrogen

= 27.7777 kmol/hour x 2.02 kg/kmol

= 56.11 kg/hour

So from 1000kg/hour of feed, 56.11 kg/hour of hydrogen will be produced. It means that

to produced 1kg /hour of hydrogen, 17.82 kg/hour of feed is needed. Assuming coal

market price as 0.095USD per kg, the price to produce 1kg of hydrogen from 1kg of feed

(carbon) is:

0.095 USD x 17.82 = 1.69 USD/kg H2

2. Steam reforming

Primary reaction: CH4 + H2O 3H2 + CO (reversible reaction)

From this reaction, 1 mol of methane will produce 3 mol of hydrogen.

Assuming mass flowrate of feed of 1000 kg/hour, we calculate molar flowrate of feed as

of:

Feed mass flowrate divided by the molecular weight of methane:

1000 kg/hour divide by 16.04 kg/kmol = 62.34 kmol/hour


62.34 kmol/hour C 3 x 62.34 kmol/hour hydrogen

187.02 kmol/hour hydrogen





= 377.78 kg/hour

16

So from 1000kg/hour of feed, 377.78 kg/hour of hydrogen will be produced. It means

that to produced 1kg /hour of hydrogen, 2.6470 kg/hour of feed is needed. Assuming

methane market price as 0.198USD per kg, the price the produce 1kg of hydrogen from

1kg of methane is:

0.198 USD x 17.82 = 0.52 USD/kg H2

3. Electrolysis

Primary reaction: 2H2O 2H2 + O2

From this reaction, 1 mol of water will produce 1 mol of hydrogen.

Assuming flowrate of feed of 1000 kg/hour, we calculate molar flowrate of feed as of:

Feed mass flowrate divided by the molecular weight of water.

1000 kg/hour divide by 18.02 kg/kmol = 55.49 kmol/hour


55.49 kmol/hour C 55.49 kmol/hour hydrogen





= 112.09 kg/hour

So from 1000kg/hour of feed, 112.09 kg/hour of hydrogen will be produced. It means

that to produced 1kg /hour of hydrogen, 8.92 kg/hour of feed is needed. Assuming

industrial water tariff in Pahang as 0.0003USD per kg, the price to produce 1kg of

hydrogen from 1kg of water is:

0.0003 USD x 8.92 = 0.0028 USD/kg H2

17

Table 2.9: Technology Advantages and Disadvantages

Technology Advantages Disadvantages

Electrolysis Very environmentally friendly

as there is no emission of

greenhouse gases from the

process

Low cost for feedstock because

water is very cheap

Oxygen produced can be used

or sold as a relatively valuable

by-product

Huge amounts of electricity

is required – electricity is

quite costly in Malaysia

Energy consumption to

produce 1 MT ammonia is

about 12 megawatt-hours

1 MT of ammonia is more

expensive to produce from

electrolysis compared to

steam reforming – in terms of

energy cost

Coal

Gasification Most abundant source of

energy

Cheap source of energy

(95USD per metric tonne)

Easy for feedstock

transportation and storage

Reaction will produce many by

products which can also be

sold.

Low conversion, 3 moles of

C needed to produce 1 mol of

hydrogen

High CO2 and sulfur

emission

Highest cost to produce 1 kg

of hydrogen based on

economic analysis level one

Partial

Oxidation No external heat required for

the reaction

Process startup is fast.

Transient test is relatively easy

to control

Low hydrogen yield

The heat generated from the

reaction needs to be removed

or utilized by the system

High temperature

startup/shutdowns may cause

catalyst degradation

Steam

Reforming Burning value of the fuel

increased

Produces less exhaust

emissions

Soot is formed in the reactor

at high temperatures

Water sequestration from the

exhaust is not easy to

perform

The decision matrix is simple. Each item defines the critical points in producing hydrogen. The

weightage of the different items shows how each item is evaluated quantitatively. The score is

rated from 1 to 3. 1 marks as the lowest score while 3 is the highest. All in all, the highest total

score is the most viable process economically, in terms of its operational needs, production cost

18

and productivity. By comparing the marks from other hydrogen producing processes, we can

decide which of the processes has the best prospect based on the score line.

Table 2.10: Weighted Table

Criteria Weighted

%

Steam

Reforming Electrolysis

Coal

Gasification

Partial

Oxidation

Capital Cost 15 3 1 1.5 2

Cost of

Feedstock 20 2 2 2.5

2

Operation &

Maintenance

Cost

25 3 2 1.5

2

Conversion of

Feed/kg H2 30 3 2 1

1

Emission 10 1 3 0.5 1

TOTAL 100 260 195 145 160

Base on the weighted in the table above, it is clearly shown that steam reforming is the

best technology to be used in ammonia production. Besides, base on the calculation per H2

required as stated above, steam reforming is among the technologies that consume least cost. So,

the technology selected for ammonia production is Steam Reforming.

Steam reforming is the conventional way of producing hydrogen using methane and

mainly water vapor at temperature ranging from 600°C to 1000°C. The reaction utilizes nickel

based materials as the catalyst. However in recent years the development of new catalysts for

steam reforming calls for a new rhodium based catalyst to be used in the process. The capital

cost of building a steam reformer unit is more or less competitive in the market, therefore

making it a good prospect.

This process is by far the cheapest in terms of its feedstock and the most practical,

producing 3 mol of H2 for every mol of CH4. Its operation and maintenance cost is relatively

affordable and can be covered by the market price and demand. The process however produces

large amount of carbon dioxide, thus making it quite a problem in terms of its emission. Overall,

below is the table in which the process is evaluated by and also a quantitative analysis of the

process.

19

2.6 Site Feasibility Study

2.6.1 Criteria of selection

Site location plays an important role in ensuring the profitability and productivity of a plant. The

basic aim of the site selection is to choose a location that maximizes income and minimizes cost

where compromises are usually made. The suitable location should allow future expansion. The

potential location is considered by evaluating industrial areas in a few states to find the most

strategic place. There are a few factors involved in the selection of a location for the plant which

can be divided into primary and specific factors. The factors are explained further in the

following. Three existing industrial area have been evaluated to choose the most suitable location

for the construction of the new plant in Malaysia.

2.6.2 Primary Factors

i. Availability of feedstock

The cost of transportation can be reduced by a closer source of feedstock to the operating plant.

In order to produce large quantities of product which is ammonia in this case, large volumes of

raw materials would be required. Therefore, the closer the plant site is to the source of raw

materials, the lower the transportation and storage cost for raw materials. Besides, factors such as

supply, freight or transportation cost, availability and reliability of supply, level of purification of

raw materials and storage requirements also need to be considered. Location that is nearer to the

seaport would be very essential if the feedstock has to be imported, in order to minimize the cost

of shipping and fuel to the plant site.

ii. Market prospective

This chosen site should be close to the distribution centre. This is because the cost of product

distribution and requirement for cargo is influenced by this factor. It is very crucial to consider

the proximity of the major markets in locating suitable area for the plant development.

20

iii. Reasonable land price and size

The land price depends on the location and its size. Making the right choice of economical land

price can give a lower total investment cost. Besides, it is important to choose the lowest land

price and right size for constructing a new plant so that the highest profit and economic value can

be achieved.

iv. Utilities

Electricity supplies power to run the machines and equipments in a petrochemical plant. Large

amount of water supply would also be required to perform processes such as cooling and other

general uses in a chemical plant. Hence, adequate supply of power and water is very important to

ensure a smooth operation of the plant.

2.6.3 Specific factors

i. Transportation facilities

The plant should be situated near to the road network, seaport and airport. These main

transportation facilities enable a smooth import and export activities. Further more, the costs for

transportation of feedstock, product, plant equipments and personnel can be reduced.

ii. Availability of labour and services

A sufficient supply of labour should be considered in selecting the location of the plant.

Normally, non-local workers with high construction skills will be brought in while the low

skilled local workers will undergo training of plant operations. The operation costs will be

decreased if within the vicinity inexpensive manpower is readily available and could be used to

operate the plant.

iii. Waste and effluent disposal facilities

21

Location of the plant should provide capable and adequate disposal system. This is important to

ensure that the industrial waste and effluent will be treated properly if those are to be treated off-

site.

iv. Government incentives

The state governments attract other investors to invest in their state by giving a good offer of

incentives. The incentives are in the form of partial or total relief from income tax payment for a

specified period. Indirect tax incentives are also given to the investors where they receive

exemptions from import duty, sales tax and excise duty. All of the incentives assist a reduction in

the initial operating costs of the plant.

2.6.4 Characteristics of potential locations

The plant should be located in special zones set by the government. Three main locations have

been considered as strategic and feasible locations for the plant:

1. Kerteh Integrated Petroleum Complex, Terengganu

2. Gebeng Industrial Estate, Kuantan, Pahang

3. Pasir Gudang Industrial Estate, Johor

Evaluation for each location is summarized in the following tables:

22

Table 2.11: Comparison of Potential Industrial Area

Selection Criteria Kerteh Integrated Petroleum

Complex

Gebeng Industrial Estate Pasir Gudang Industrial

Estate

Main city Paka (5 km) Kuantan (30 km) Johor bahru (36 km)

Land price

(per m2)

RM2.00 to RM60.30 RM32.30 to RM118.40 RM88.10 to RM 236.80

Land availability

(Area )

± 2000.00 acres ± 1618.78 acres ± 44.16 acres

Raw material

Supplier

Optimal Glycol (M),

Kerteh

Amoco Chemicals (M),

Gebeng

Optimal Glycol (M),

Kerteh


Gebeng

Optimal Glycol (M),

Kerteh


Gebeng

Power Supply

Tasik Kenyir

Hydroelectric Dam

IPP YTL (600 MW)

Paka Power plant (900

MW)

CUF Kertih

Tanjung Gelang TNB

(1200MW),

CUF Gebeng (42MW)

Sultan Iskandar Power

Station (644 MW)

IPP YTL Power

Generation Sdn. Bhd.

Water Supply Bukit Sah

Sungai Cherol

Sungai Kemasik

CUF Gebeng

Loji Air Semambu

CUF Gebeng

Loji Air Sungai Layang

Syarikat Air Johor

Loji Air Sungai Buluh

Roadways Karak highway

(KT-Kuantan-KL)

East-West highway

(federal road KT-

Kerteh-Telok Kalung-

Gebeng-Kuantan-KL)

Karak highway

(KT-Kuantan-KL)

East-West highway

(federal road KT- Kerteh-

Telok Kalung-Gebeng-

Kuantan-KL)

Federal highway

(Bukit Kayu Hitam-Singapore)

Pasir Gudang

(Kim Kim River)

highway from Pasir

Gudang-Tanjung

Kupang-Tuas Singapore

23

Selection Criteria Kerteh Integrated Petroleum

Complex

Gebeng Industrial Estate Pasir Gudang Industrial Estate

Port Kerteh port (5 km)

Kemaman port (30 km)

Kuantan port (5 km) Johor port

Railway facilities Kuantan-Kerteh Railway Kuantan-Kerteh Railway Singapore and North

Peninsular Malaysia

Incentives

Infrastructure Allowance.

Five-year exemption on

import duty.

5 % discount on monthly

electrical bills for first 2 years.

25-38 % exemption on daily

water cost for 4545

m3 of water

Pioneer Status and Investment

Tax Allowance and

Reinvestment Allowance.

Incentives for high tech

industries

Infrastructure Allowance.

Five-year exemption on import

duty.

5 % discount on monthly

electricity bills for first 2 years.

85% tax exemption on gross

profit

Pioneer Status and Investment

Tax Allowance and

Reinvestment Allowance.


industries

Incentive for exports

Incentives for research

development

Incentives for training tariff

protection

Exemption from import duty

on direct raw

materials/components

Pioneer Status and

Investment Tax Allowance

and Reinvestment

Allowance.


industries

Waste water

management Effluent Treatment Plant of

CUF

Kualiti Alam Sdn Bhd

Indah Water Konsortium

Effluent Treatment Plant of

CUF



Effluent Treatment Plant of

CUF


Local people

(15-30 years old)

650 000 peoples 350 000 peoples 500 000 peoples

(Reference: Malaysia Industrial Development Authority, 2010)

24

Table 2.12: Weighted Marks and Explanation on the Plant Site Location Factors

Factors 0-1 Marks 2-3 Marks 4-5 Marks

Supply of feedstock Incapable to obtain feedstock from

close sources with the distance

exceeding 80km.

Forced to import from foreign

countries.

Uses a pipeline system as well.

Source of raw materials from

neighbouring states or countries

with the distance not exceeding

80km.

Uses a pipeline system as well.

Able to obtain large supply

locally thus saving on import

cost.

Having long pipeline

networks for the

transportation of raw

materials.

Land price and size Land area below 500 acres

Price of land exceeds RM30/m2

Land area below 1000 acres

Price of land exceeds RM 20/m2

Land area exceeding 1000

acres

Price of land less than RM

20/m2

Local Government

Incentives No incentives from the Local

Organization of Country

Development.

Incentives from the Local


Development.

Incentives from the Local


Development

Incentives from special

company

Transportation Average road systems

No close highway or expressway

system

No railway system.

Very distant from the ports and

airports

Good federal road and highway

systems

Limited railway system access

More distant from the ports

Airport facilities which may not

have international flight facilities

– only providing domestic

flights.

Complete network and well

maintained highways,

expressways and roads.

International Airport

facilities access to the main

locations around the world.

Location near to

international port with

import and export activities.

Reliable railway lines to

remote areas not accessible

by roads.

25

Table 2.13: Weighted Table Comparison

According to the weighted evaluation done, Gebeng Industrial Estate has maximum scores.

Hence, it has been chosen as the strategic location for the production plant of Ammonia due to a

few reasons as listed below:

i) Gebeng Industrial Estate is situated at East coast of peninsular Malaysia and it is

only 25 km from Kuantan city and 5 km from Kuantan Port. Any trade involving

the import and export of products and, if necessary, raw materials can be achieved

with relative ease.

ii) Raw materials required in large quantities, which is natural gas from PGB with

high purity of methane.

iii) Kuantan Port has centralized tankage facilities, pipeline and pipe rack system

connecting Gebeng to Kuantan Port, container and bulk liquid port and railway

linking Kerteh, Gebeng and Kuantan Port.

iv) Existence of all major transportation networks to the proposed plant location

offers wider range of marketability options, locally or internationally.

Selected Site Gebeng Industrial

Estate

Pasir Gudang

Industrial Estate

Kerteh Petrochemical

Integrated Complex

Types of Industrial 5 5 5

Price and Land Areas 4 3 5

Raw Material Sources 4 3 3

Transportation 4 4 3

Utilities 5 4 4

TOTAL MARKS 22/25 19/25 20/25

PERCENTAGES (%) 88 76 80

RANKING 1 (Selected) 3 2

26

v) Strategically located in the heart of South East Asia, one of the world‟s fastest

growing economic regions, where Kuantan Port allows for ease of transportation

all over the world with all year round deep-water seaport.

vi) Constant supply of utilities such as cooling water, power supply, steam and waste

management.

o Power supply: CUF Gebeng (42MW) & Tanjung Gelang TNB (1200 MW)

o Water supply: CUF Gebeng, Semambu Water Treatment Plant

o Waste management: Effluent Treatment Plant of CUF Kualiti Alam Sdn Bhd &


vii) Inexpensive cost of land and availability of vacant site for construction and

expansion.

The map of Gebeng Industrial Estate is shown in the Figure 2.3.

Figure 2.3: Gebeng Industrial Area Map

27

CHAPTER 3

3.0 CONCEPTUAL DESIGN AND SYNTHESIS

3.1 Hierarchial Decomposition Approach

From to Douglas‟ (1988) formulation of a decision hierarchy as a set of levels to guide the

selection of process alternatives, the levels are classified according to the following process

decisions:

Level 1: Batch versus Continuous

Level 2: Input–output structure of the flowsheet.

Level 3: Recycle structure of flowsheet

Decision 1. Reactor performance

Decision 2. Reactor operating conditions: (1) concentration, (2) temperature, (3)

pressure, (4) phase, (5) catalyst

Decision 3. Reactor configuration: reactor volume (capacity of reactor i.e., input and

output flow rates, orientation, and configuration;

Level 4: Separation system synthesis

Decision 1. Types of separators: type of suitable separators.

Decision 2. Sequencing of separators (for homogeneous mixtures): how are the

separators arranged? (sequencing of distillation columns)

Decision 3. Operating conditions: (a) temperature, (b) pressure, (c) concentration

Level 5: Heat exchanger network

28

3.2 Level 1 – Continuous or Batch

In the process of choosing between continuous or batch plant process, Douglas highlights three

main criteria in the decision making process which are production rates, market forces and

operational problems. The table below summarizes continuous or batch process decision making

basis.

Table 3.1: Comparison between Batch and Continuous Flow

Criteria Batch Continuous Decision and Reasoning

Production

Rates

Plant capacity less than 1x106

lb/yr

Plant capacity greater

than 10x106 lb/yr

Plant capacity is 8.1 x 109

lb/yr

Market

Forces

For seasonal product For yearly production Ammonia is in high demand

throughout the year

Operational

Problems

For slow reaction. For fast reaction. Economical ammonia

production requires a fast

reaction rate to produce the

required amount

Proposed plant concept required more than 10x106 lb product per year with high demand of

product in the market and fast reaction rate to produce required and substantial amount for

economical production. All criteria required the process to be in continuous flow and neglect the

selection of batch process. As a conclusion, continuous type of process is selected.

3.3 Level 2 – Input-Output Structure

3.3.1 Purifications of Feed

Feed purification process is considered as preprocess purification system. It certainly involved

cost in capital and operations but it is best to considered it in long term planning especially with

the case of high impurities in available feed source. More purified feed certainly cost more than

the less pure feed and installation of feed purification system is one of the way to reduce cost in

raw material purchase by producing own in-house purification process.

However, the available feed source of natural gas for the designated plant is quite pure. The feed

is already processed and purified at a natural gas plant where impurities such as mercury and

sulfur are already removed. The composition of the natural gas which is the main feed is

29

comprised of 95% methane, 3% ethane and 2% propane. Therefore there is no need for further

purification.

Figure 3.1: Input Output Structure

3.3.2 Reactants Recycle Streams

By recycling the unreacted reactant back to reactant input, the fresh reactant requirement will be

less thus reducing the raw material cost. Adhering to these guidelines to reduce those cost, the

unreacted hydrogen and nitrogen gas from the ammonia reactor is fed back to the mixer before

the ammonia reactor so that the unprocessed reactants are not wasted.

3.3.3 Number of Products Streams

The number of products streams option being evaluated as to adhere the common sense in design

guideline that it is never advantageous to separate two streams and then mix them together. It is a

good practice to list down the components and assigned each to a destination code. It will ease

latter work on separations system to identify best separation flow and sequence to practice.

Table 3.2: Input Output Condition

Component Boiling Point (oC) Destination code

Ammonia -33.34 Primary Product

Hydrogen -252.87 Recycle

Nitrogen -210.00 Recycle

30

Water 100.00 Waste

Carbon Dioxide -57.00 Waste

By considering the input-output structure, it gives clear indication on the required decision on

both input and output structure. Efficient input-output structure certainly proves to reduce raw

material consumption and improved the output flow structure.

3.4 Level 3 - Reactor Design and Recycle Structure of Flowsheet

Reactor design and recycle structure of flowsheet is one step ahead from Level 2 – Input Output

Structure. In this level, there are several factors that should be highlighted and discussed in order

to come up with the best decisions. Factors or questions that help the decisions making for

recycle structure of the flowsheet are:

1. How many reactor systems are required? Is there any separation between the reactor

systems?

2. How many recycle streams are required?

3. Do we want to use an excess of one reactant at the reactor inlet?

4. Is a gas compressor required? What are the costs?

5. Should the reactor be operated adiabically, with direct heating or cooling, or is a diluent

or heat carrier required?

6. Do we want to shift the equilibrium conversion? How?

7. How do the reactor costs affect the economic potential?

To achieve good reactor performance is the highest importance in deciding the most economical

and feasible design which is also vital towards the environment impact of the process. Among

the issues to consider for good reactor design are:

1. Reactor type selection

2. Catalyst selection

3. Reactor operating conditions (Concentration, Temperature, Pressure, Phase)

31

It is very important in selecting the suitable reactor, so that the feed can be optimized. From the

Douglas approach, guidelines for selecting the best reactor design are given. It is stated that the

reactor that always maintains the highest concentration could maximize the conversion of the

feed. A reactor type is necessary to select for the ammonia production. Below is the table

comparison for reactor type.

Table 3.3: Comparison Between CSTR and PFR

CSTR PFR

Characteristics Runs at steady state with

continuous flow of reactants

and products

Exit stream has the same

composition as in the tank

Primarily used for:

Liquid phase reaction

Steady state operation

Perfectly mixed reactions

Arranged as one long

reactor or many short

reactors in a tube bank;

concentration changes with

length down the reactor

Primarily used for:

Gas phase

Usages Continuous production

Suitable for agitating

processes

Series configurations for

different concentration

streams

Continuous production

Large scale

Fast reactions

Homogenous and

heterogeneous reactions

High temperature

Advantages Uniform temperature

throughout the reactor

because of perfect mixing

Easily adapts to two phase

runs

Low operating cost

Easy to clean

High conversion per unit

volume

Continuous operation

Heat transfer can be

optimized by using more

thinner tubes

Run for a long period of

time without maintenance

Residence time is the same

for all the reactants

32

Based on the characteristics, usages and advantages of the reactor, the reactor type selected for

ammonia production is PFR. PFR is primarily used for gas phase reaction where the designated

ammonia production is run in gas phase system. Besides, PFR is used for continuous production

and large scale of production where the designated ammonia plant is operated continuously

throughout the year and has large scale capacity which is 427,420 metric ton per year. PFR also

has its own usage particularly for high temperature reactions.

By using PFR as a selected reactor type, it gives a lot of advantages like high conversion per unit

volume, continuous operations; heat transfer can be optimized by using thinner tubes, run for a

long period of times without maintenance and residence time is the same for all reactants. These

advantages of PFR help ammonia production to be effective as what it should be since the

designated plant required large scale of production. Low temperature shift (LTS) converter needs

high conversion per unit volume, so it is clearly shows that PFR will be the best type of reactor

for the LTS.

There are six reactors required in ammonia plant which are:

Table 3.4: Reactions for Each Reactor

Reactor Reaction(s) Temperature

(oC)

Pressure

(bar)

Primary Reformer CH4 + H2O 3H2 + CO

C2H6 + 2H20 5H2 + CO

C3H8 + 3H2O H2 + 3CO

502 39.32

Secondary Reformer CH4 + 1.5O2 2H2O + CO

CH4 + H2O 3H2 + CO

H2O + CO H2 + CO2

438.9 38.64

High Temperature Shift

Converter

H2O + CO H2 + CO2 366.85 35.90

Low Temperature Shift

Converter

H2O + CO H2+ CO2 216.85 34.37

Methanator 3H2 + CO H2O + CH4 325 27.32

33

4H2 + CO2 CH4 + 2H2O

Ammonia Converter 3H2 + N2 2NH3 450 100

There is one recycle stream for this ammonia plant which is to recycle hydrogen and nitrogen in

order to achieve high conversion of ammonia. With the recycle stream, the production of

ammonia is absolutely higher compare to the non recycle system. Gas compressor is required in

ammonia plant to increase the pressure to achieve desired pressure for each reaction. Besides,

there are reactors that should be operated adiabatically in order to make sure there is no heat loss

to the surrounding.

3.5 Level 4 - Separation System Synthesis

Separation system is a system whereas mixed streams with two or more components are

separated. This is important as it can affect the process overall and also important in keeping the

product up to quality. In most process, the desired products from the reactors are always mixed

with byproducts and unreacted feed. Economically, this can affect the process since the feed is

not utilized fully and having unwanted byproducts can cause sales of product to go down.

Ammonia processes rely heavily on a good and efficient separation system. For instance, having

a good carbon monoxide and carbon dioxide removal system in the hydrogen synthesis section

helps protect the catalyst bed used in ammonia synthesis. Also, ammonia needs to be at 90%

purity and above in order for it to be marketable. Good separation systems will not only help in

purifying the ammonia, but also in recycling unreacted feed back into the reactor. This will

ensure maximum utilization of feed and reducing the amount of feed per product.

According to industrial practice, in industrial ammonia production, a system called the ammonia

synthesis loop has to be designed in order to capitalize fully on the hydrogen feed. The synthesis

loop is a network of reactor(s) and separators that is designed to recycle excess hydrogen from

the reactor. Some of the feed will of course have to be purged but mostly are recycled back into

the process and into the reactor as part of the feed. This is because ammonia reactors are known

34

to have low conversion of feed (20% - 30 %). And while nitrogen is fairly easy and free to get,

the same cannot be said for hydrogen.

In fact, the bulk of the ammonia process plant relies on the hydrogen synthesis. Therefore, losing

hydrogen as unreacted feed is unacceptable and economically deteriorating. In following the

industrial practices, this project will also utilize the ammonia synthesis loop, and therefore this

section will discuss further on the matter.

We know now that a separation system is required to optimize ammonia synthesis in the overall

process. But the question is how do we approach on designing the separation system? This can

be overcome by the three basic choosing criteria as per the general heuristics of separation

system, as listed below:

1. Type(s) of separators to be used.

2. Separator sequencing

3. Optimum operating conditions.

In summary, based on the outlet of the reactor, we need to decide the separator type we would be

using. The sequencing is based on the fact which stream has the vital component. The optimum

operating conditions are based on the physical properties of the components within the mixture.

All three criteria need to be fulfilled in order to achieve a good separation system.

Decision 1: Choosing Separator Types

Separators are differed mainly by the mixture they have to separate. Conventionally, there are

three types of mixture stream that are found in the industry. The mixture stream can either be all

vapor phase, a mixture of vapor and liquid phase or fully liquid phase. Solid phase are usually

not found in streams since solid phase cannot flow and can hinder the process overall.

For the ammonia process, the reactor effluent is mainly in vapor (gas) phase. In dealing with a

homogenous vapor mixture, there are a few methods that can be approached. We can either cool

the stream down, or pressurize the stream. Both will cause parts of the mixture components to

condense and a phase split can be achieved. This method is known as condensation. Other

methods include adsorption, absorption, membrane separation, and reaction systems. However,

35

since we want to reuse parts of the components in the mixture, adsorption, absorption and

reaction systems are not viable while membrane separation systems are complex and most are

still under research.

Therefore condensation method is the best for this process. This is achievable since ammonia,

the end product that we want can be easily condensed and since the other components are readily

gas even at room conditions. By considering the above factors, we can conclude that we would

be using condensers and horizontal separators in order to separate the desired product and

recyclable components.

Principal of Condensers and Flash Drum Separators

Condensers, as the name suggest, condense components in the vapor/gas phase that are readily

condensable at the given operating temperature and pressure. Our reactor effluent, consisting

mainly of ammonia, hydrogen, nitrogen and a little methane (0.1 PPM) is in vapor phase. Also,

in this case, ammonia, as the desired product, is easily condensed compared to other components

in the gas mixture.

Ammonia is also stored as liquid. Therefore, by condensing ammonia, we can create a two phase

mixture whereas the mixture can be separated via a phase split. Flash drum is one of the various

equipments that can be used to achieve the phase split. Flash drums are vessels that functions to

hold liquid-gas/vapor phase mixture together for a certain retention time to allow separation by

phase to occur. Reasons for choosing flash drum separators include the following:

a) Easiest method of separating liquid and vapor phase

b) Easy to operate

c) Widely used in industry to separate liquid and vapor phases

d) Easy to design

Basic Equipment Operation and Terminology

Condensers are simple heat exchangers meant to cool down the reactor effluent. This will cause

condensation to occur, leading to the formation of a heterogeneous mixture of liquid and

vapor/gas. Since hydrogen is not easily condensable, the condenser will be set as to condense

36

ammonia instead. This is also very convenient for our process since ammonia is usually

marketed in liquid phase. To achieve this condensation, a cooling liquid will be introduced into

the system to cool down the ammonia-hydrogen mixture. Afterwards, this heterogeneous mixture

will enter the flash drum to be separated by phase.

Flash drums operations are based on gravitational separation. Simply saying, the separation will

occur in such a way that the liquid, having higher density, will settle at the bottom of the vessel

whereas gas/vapor will move upwards towards the bottom. This is the simplest and easiest

method of separating a heterogeneous stream. In order to allow the separation to be optimum, the

liquid phase will have to be hold within the vessel for some time. This holding time is known as

the retention time. The retention time is to allow any gas/vapor that may have been trapped

within the liquid phase to be completely released. In other words, a suitable retention time is

needed for the heterogeneous mixture to reach phase equilibrium.

For our design, the reactor effluent mixture mainly consisting of ammonia and hydrogen, in

vapor phase, is to go through a condenser. The condenser will operate at such operating

conditions that it will cause the ammonia in the mixture to condense and form a heterogeneous

phase. This heterogeneous mixture will then enter the flash drum separator where separation will

then occur.

Figure 3.2: Flash Drum Separator

37

Decision 2: Separator Sequencing

Separators have mainly two types of sequencing: direct and indirect. Direct sequences are when

two or more separators are placed in sequence along the bottom side of the previous separator.

This sequence is preferred if the desired component exits in liquid phase and needed to be

purified or the component needs recovered. Indirect sequence is the opposite of direct

sequencing. Indirect sequencing places the next separator at the top exit of the previous

separator. Just as with direct sequencing, indirect sequencing is preferable when the desired

component is in gas/vapor phase.

Separator sequencing is especially important when there is a mixture containing three major

components, in which separating needs to be done in two or more columns. Also, considering

other factors like azeotrope mixtures, more complex heuristics will have to be applied in

deciding the sequence of separators.

Figure 3.3: Sequencing of Separators; (a) Direct Sequencing and (b) Indirect Sequencing

The target of this separation is mainly to recover ammonia from the reactor. For our ammonia

synthesis, however, the major components are only two, which is ammonia as the desired

product, and hydrogen, as the recyclable feed. Therefore, separation sequencing is not really

needed. However, in the case of ammonia not reaching the needed purity to be sold, a second

38

separator will have to be placed in direct sequence to the first one, since ammonia will be exiting

as liquid.

The purity of hydrogen as recycled feed can usually be neglected unless hydrogen reenters the

reactor with components that are poisonous towards the catalyst. In our ammonia synthesis, no

such component exist which is why no extra separation is needed to purify hydrogen.

Decision 3: Optimum Operating Conditions

The optimum operating conditions will be based on the physical properties of ammonia and

hydrogen. Since we would want ammonia to condense first before entering the flash drum, we

would first have to set the cooling temperature to the condensing temperature of ammonia at the

said pressure. Operating pressure also plays an important part as it affects hydrogen solubility

into aqueous ammonia plus the partial vapor pressure. In order to have low solubility, a low

pressure is preferred. However, this would ultimately result in the recycled hydrogen to be

compressed before reentering the feed stream.

In terms of sizing and designing, flash drums do not require tray numbers and spacing, unlike

distillation columns. This means that we would need only to determine the diameter and the

height of the vessel. We do need to determine the retention time, however. This shows that the

retention time will determine the vessel‟s capacity.

The efficiency of the flash drum separator is dependent on the retention time mainly. Therefore,

the main parameter would be the retention time itself. Based on a literature, the retention time for

the flash drum in the ammonia synthesis is around 10 minutes, which is the normal retention

time for most flash drums in the industry.

The flash drum separator is also set so as it is nominally half-full with liquid, another common

practice of the industry. These settings are normal settings for flash drums, and will be used as

assumptions to ease designing the flash drum. These assumptions are made based on the basis of

common industrial practices in ammonia synthesis, and are considered to be reliable.

39

Below are the operating conditions of the condenser flash drum. Note that the sizing and design

are not included in this report.

*Two condensers are needed since the temperature drop is very high (236°C to -20°C)

Condensers Operating Conditions

Condenser 1

Parameter Value/Item

Duty (kcal/hr) 3711.632

Coolant Cooling Water

Temperature Drop, ΔT

(°C)

202. 6

Outlet Temperature (°C) 30

Condenser 2


Duty (kcal/hr) 463

Coolant Ammonia

Refrigerant

Temperature Drop, ΔT

(°C)

50

Outlet Temperature (°C) -20

Flash Drum Operating Conditions


Temperature (°C) -20

Pressure (bar) 25

Retention Time

(minutes)

10

Liquid Level Half-full

3.6 Level 5 – Heat Exchanger Network

Heat integration emphasizes on energy conservation which is very crucial in process designing.

Heating and cooling duties for heat recovery system are done after the acceptance of major

processing steps (reactors, separators and recycles). ). Targets can be set for the heat exchanger

network to assess the performance of complete process design. These targets allow both energy

and capital cost for heat exchanger network to be assessed. The energy used during heating and

cooling process is maximized to its full potential by using pinch analysis.

40

3.6.1 Stream Identification

The analysis starts by identifying the source of heat (hot stream) and source of sink (cold

stream). Heat exchange streams for condensers and reboilers of distillation columns are not

included in heat integration as operation involving these unit operations are very sensitive

towards temperature changes and might affect product purity. The result as shown below:

Table 3.5: Stream Table

Stream Description Type Supply

temperature (°C)

Target

temperature (°C)

FCp

(kW/K) Q (kW)

E102

(S12)

Secondary

reformer

product

Hot 953.27 366.85 167.30 98107.68

AC-1

(S46)

Ammonia

converter

product

Hot 612.83 77.00 217.15 116353.66

E1 (S17) Methanator

product Hot 222.56 40.00 430.47 78588.31

E101 (S4) Primary

reformer feed Cold 258.49 502.00 117.73 28668.21

E5 (S50) Separator SP-

1 feed Cold -21.17 34.91 152.26 8537.89

where

dTFCH p

H = Enthalpy Change (kW)

FCp = Heat Capacity Flowrate (kW/K)

T = K

3.6.2 Minimum Temperature Difference, ΔTmin

The minimum temperature difference, ΔTmin is the driving force for heat transfer. The

importance of ΔTmin is that it sets the relative location of the hot and cold streams, and therefore

the amount of heat recovery. As the energy target (and hence ΔTmin) is increased, the capital cost

decreases. The optimum ΔTmin varies in different industries as shown in the table below:

41

Table 3.6: Optimum Delta T min for Industrial Sector

Industrial sector Optimum ΔTmin

values (oC)

Remarks

Oil refining 20 – 40

Relatively low heat transfer coefficients, parallel

composite curves in many applications, fouling

of heat exchangers

Petrochemical 10 – 20

Reboiling and condensing duties provide better

heat transfer coefficients, low fouling

Chemical 10 – 20 As for petrochemicals

Low temperature

Processes 3 – 5

Power requirement for refrigeration system is

very expensive. ΔTmin decreases with low

refrigeration temperatures

Source: Pinch Analysis Foundation Training Course (1997)

As production of ammonia is in petrochemical industries, ΔTmin of 10oC is chosen.

3.6.3 Pinch Technology Method

Pinch Technology Method is used to determine the energy requirement from the process and the

amount of energy recovery. This section will analyze how to calculate the amount of energy for

the process by constructing composite curves to set energy target or develop the problem table

algorithm and heat cascade diagram. Composite curves are useful in providing the conceptual

understanding of the process but the problem table algorithm is a more convenient calculation

tool.

The term Pinch Analysis is been used correspond to application of the tools and algorithms of

Pinch Technology related in industrial process. The application of First and Second Law of

Thermodynamics determine the direction of Pinch Analysis application. Heat energy only flows

in the direction of hot to cold. This prohibits the temperature crossovers of the hot and cold

stream profiles through the exchanger unit. There is two main important things in dealing with

transfer of heat between hot and cold stream which are, heat load and temperature. The minimum

heat load between the two streams is selected when comparing their value while in a heat

exchanger unit a hot stream cannot be cooled below cold stream supply temperature nor a cold

stream can be heated to temperature more than hot stream supply temperature.

42

The corrected temperature for hot streams and cold streams need to be determined first before

calculating the minimum utility requirement.

For hot stream, Corrected temperature = T – (ΔTmin)/2

For cold stream, Corrected temperature = T + (ΔTmin)/2

After calculating, the value of supply and target temperature for the hot stream will be deducted

by 5°C while for cold stream; 5°C will be added to the value of supply and target temperature.

Table 3.7: Shifted Temperature

Stream Description Type

Supply

Temperature

(°C)

Target

Temperature

(°C)

Shifted

Ssupply

Temperature

(°C)

Shifted

Target

Temperature

(°C)

E102

(S12)

Secondary

reformer

product

Hot 953.27 366.85 948.27 361.85

AC-1

(S46)

Ammonia

converter

product

Hot 612.83 77.00 607.83 72.00

E1

(S17)

Methanator

product Hot 222.56 40.00 217.56 35.00

E101

(S4)

Primary

reformer feed Cold 258.49 502.00 263.49 507.00

E5

(S50)

Separator SP-

1 feed Cold -21.17 34.91 -16.17 39.91

3.6.4 Problem Table Algorithm

Stream data are calculate in table algorithm as shown in Figure 3.4. From the figure below, for

normal case, we have to proceed to second cascade by using the highest negative value of the

first cascade as the first value of the cascade at T = 747.92 °C. But, since we have no negative

values, we understand that we only have one utility which is cold utility, thus we have only the

value of QC,min. As we only have one utility, we conclude that our pinch analysis has threshold

problem.

Instead of normal process pinch which divide the utilities into heat source (cold utilities) and

heat sink (hot utilities), we do have pinch but we call it “utility pinch” at the cold utilities means

43

that we only have the heat source. Because we have threshold problem, we must make sure all

hot utilities under our pinch is fully utilizes which will be explained under heat exchanger

network.

Figure 3.4: Algorithm Table

44

3.6.5 Heat Cascade

Figure 3.5: Heat Cascade

3.6.6 Online Software

ΔTmin = 10.00 °C

Pinch = 953.27 °C

Ideal Minimum Cooling Req = 253.73 kW

Ideal Minimum Cooling Req = 0.00 kW

From the pinch analysis method and online software, we found that that the pinch temperature is

found to be at 953.27 °C. About 253.73 kW minimum cold utilities requires to cool up the hot

streams while no hot utilities is required to heat the cold streams. For the conclusion of table

algorithm, both of the calculation by manual or online software are showing same result and

were verified.

45

3.6.7 Composite Curve by Sprint

Assumption made in constructing the composite curve is that all heat capacities for respective

streams are constant. It is represented on a T-H diagram by a line from stream supply

temperature to stream target temperature.

From figure, the red line indicates that the hot stream and blue line indicate the cold stream. Both

of the stream combined in a one graph to estimate the pinch temperature based on Tmin which is

equal to 10oC. Also, from this figure we can also indicate that we have only one major utility

which is the cold utility (hot stream) and therefore we only have the ideal minimum cooling

required, the enthalpy cold utilities QCmin .

3.6.8 Heat Exchanger Network

Pairing of streams is determined from the Maximum Energy Recovery (MER) method:

for the above pinch region, CPc > CPH

for the below pinch region, CPH > CPc

Heat Exchanger Network Diagram shows how the heat transfers operations. Hot streams run

from the left to the right and cold streams run from right to the left. A heat exchanger

transferring heat between the cold and hot streams are indicated by a vertical line connecting two

Figure 3.6: Combined Composite Curve from Online Software

46

circles on the two matched streams.

Figure 3.7: Heat Exchanger Network

From the figure, we can state that, we can only paired two streams thus only one heat exchanger

use to fully utilize cold stream. For heat exchanger E101; we match the stream S4 (cold) and S12

(hot) where the energy of 28668.21 kW from heater E101 is used to partially cool the hot stream

from cooler E102 from 953.27°C to 788.37°C.

By this heat exchanger network, we have fully utilizes all our hot utilities resulting in energy

recovery of 57336.42 kW or 14.45% of utility recovery.

47

CHAPTER 4

4.0 INSTRUMENTATION AND CONTROL

4.1 Introduction

For a plant to make profit, the quality of the product and the rate it is produced needs to be

controlled. By producing a high quality product at the lowest product cost, the profit can be

maximized. In a plant the factors that control the quality of a product, in this case it is ammonia,

are the temperatures and pressure which controls the conversion of the reactants. The ammonia is

then purified further through several flash vessels and a stripper. For each equipment there are

certain variables that influence the quality and rate of production, which needs to be controlled in

order to produce products at a desirable rate and quality. This is why a control system is

required.

Other than controlling the quality and rate of production the control system also ensures safe

plant operation. A control system involves 4 variables which are the controlled, measured,

disturbance and manipulated variable. A feedback control system for example measures the

controlled variable, compares it to a set point then sends a signal to a manipulated variable which

changes a variable of the process affecting the controlled variables value. There are 3

equipment‟s involved in this process which is the transmitter, controller and final control

element. The transmitter sends the measured value to the controller which makes a decision and

implements the decision through the final control element which is normally a valve

manipulating flowrate or pressure.

The importance of a control system is as follows:

1. Maintaining safe plant operation

Keeping the variables in their tolerable and safe limits

Providing interlocks and alarms to warn and prevent dangerous operating conditions

Avoid unnecessary shutdowns

2. Controlling the quality of the product

Keeping the process variables at the desired value to maintain product quality

3. Controlling the throughput

48

Keeping the process variables at the desired value to maintain product throughput

4. Keeping production cost low

To keep production costs low

Optimize the use of utilities such as steam and cooling water to keep costs low

4.2 Basic Control Strategies

4.2.1 Feedback Control Strategy

Figure 4.1: Feedback Control

In a feedback control strategy, the controlled variable is measured and compared to a set point,

which in the case of any deviations is corrected by the controller. The control action is

implemented through the final control element. In the feedback control , the controlled variable

is always measured and compared against the set point or reference, thus creating a loop. The

feedback control strategy is the most widely used control system due to its simplicy, impying

that is does not require a process model.

4.2.2 Feedforward Control Strategy

Figure 4.2: Feedforward control

49

The feedforward is different from the feedback in the measured variable, the feedback measures

the controlled variable where as the feedforward measures the disturbance variable affecting the

controlled variable. However, an accurate model of the process is required in order for the

feedforward controller to function properly, thus increasing costs. The advantage is that the

feedforward controller can take action before the controlled variable deviates from its setpoint.

4.2.3 Cascade Control

Figure 4.3: Cascade Control

The cascade control is essentially 2 or more feedback loops that is arreanged in a loop formation

as seen in figure 4.3. The cascade is used when there is a slow process interaction such as reactor

temperature changes. The cascade control improves control action time by taking and

intermediate measurement that has faster process dynamics and takes control action based on

that measurement. The cascade control is also used when the manipulated variable is also a

disturbance variable.

4.2.4 Ratio Control

Figure 4.4: Ratio Control

50

The ratio control is a simple type of feedforward control. The control strategy is useful in

applications where the stoichiometric ratio of two products are needed to be maintain. As seen

in figure 4.4 ratio control functions by measuring both streams and controlling the flowrate of

one of them to maintain a specific ratio.

4.2 Reactor Control Strategy

Figure 4.5: Reactor

The control system objective for the reactor is to maintain the reactor pressure and temperature at

a given set point, because there is no liquid flow in any of the reactors only the pressure is

controlled. The reactor pressure and temperature direcly affects the quality and throughput of the

product. Another importance of the control strategy is to stop the reactors from going out out

control. All reactors except fot the primary and secondary reactors are exohermic reactors, which

is why temperature and pressure control is even more crucial. All exothermic reactors are

jacketed to allow temperature control. Extreme temperatures or pressures could lead to reactor

damage and catalyst damage.

51

Table 4.1: Variable types

Controlled

Variable

Measured variable Manipulated

Variable

Disturbance

Variable

Controller

Type

Reactor

pressure

Reactor pressure Inlet stream

pressure

Inlet stream

pressure/Inlet

stream composition

Feedback

Reactor

temperature

Reactor

temperature/Jacket

temperature

Cooling water

flowrate

Inlet stream

temperature/Cooling

water

flowrate/Cooling

water temperature

Cascade

PIC-104

1. Control Strategy Used: Feedback control

2. Control Objective: To keep the reactor pressure at a desired set point

3. Control strategy concept: The reactor pressure is controlled by manipulating the inlet valve.If

the valve is opened, the reactor pressure will increase, if it is closed then the reactor pressure

will decrease.

TIC-107/TIC-108

1. Control Strategy Used: Cascade control

2. Control Objective: To keep the reactor temperature at a desired set point

3. Control strategy concept: Temperature control involves a slow process dynamics.Implying

that if no intermediate measurement is taken then the time taken to correct any process

variable devition will be lengthy.Which is why a cascade control strategy is chosen. TIC-107

will send a setpoint to TIC-108 which make a control decision based on the measured

cooling water flowrate.

52

4.4 Absorption Column Control Strategy

Figure 4.6: Absorbtion column

The objective of the control strategy is to control the composition of the top gas stream and the

level of liquid in the tank.The inlet and outlet pressure is controlled from the previous and next

equipment. The assay transmitter will measure the composition of CO2 in the outlet gas stream

and it will make adjustments to the MDEA stream. The level of liquid in the column is adjusted

by manipulating the valve at the bottom of the stream.


Controlled

Variable


Variable

Disturbance

Variable

Controller

Type

Gas outlet

composition

Gas outlet

composition

MDEA flowrate Inlet stream

pressure/Inlet

stream composition

Feedback

Reactor

temperature

Reactor

temperature/Jacket

temperature

Cooling water

flowrate

Inlet stream

temperature/Cooling

water

flowrate/Cooling

water temperature

Cascade

53

LIC-102


2. Control Objective: To keep the liquid level inside the column at a desired set point

3. Control strategy concept: The column liquid level is controlled by manipulating the outlet

valve.If the valve is opened, the column liquid level will increase, if it is closed then the

column liquid will decrease.The level will be controlled based on a setpoint.

AIC-101/FIC-109


2. Control Objective: To keep the outlet stream composition at a desired set point

3. Control strategy concept: The assay transmitter will measure the composition of CO2 in the

outlet stream which will then send a setpoint to the flow controller, which will implement a

control action based on the received setpoint and measured flowrate through the control

valve.

4.5 Compressor Control Strategy

Figure 4.7: Compressor

The objective of the control system is to keep the compressor outlet stream pressure at a set

value. This is achieved by taking a measurement of the pressure of the outlet stream , comparing

54

it to a set point and taking the necessary control actions through the turbine of the compressor. A

feedback control strategy is used. The other controller at the top is an anti surge compressor

safety precaution in which to avoid compressor damage.


Controlled

Variable

Measured

variable

Manipulated

Variable

Disturbance

Variable

Controller

Type

Outlet stream

pressure

Outlet stream

pressure

Inlet stream

pressure

Inlet stream

pressure

Feedback

Inlet stream

pressure

Inlet stream

pressure

Recycle stream Inlet stream

pressure

Feedback

PIC-102


2. Control Objective: To keep the outlet stream pressure at a desired set point

3. Control strategy concept: The controlled variable is the compressor outlet stream pressure,

which is influenced byturbine speed, by measuring the outlet stream pressure and comparing

it to the set point any deviations can be corrected by manpulating the turbine speed.

PIC-103


2. Control Objective: To keep the inlet stream pressure at a desired set point

3. Control strategy concept: The controlled variable is the compressor inlet stream

pressure.Below a certain inlet flowrate there is a posibility for the compressor to be damaged,

this is why a control system is required to keep the inlet pressure above a certain point.If the

measured pressure is below a certain point, a control action will be taken to increase the inlet

pressure.

55

4.6 Stripper Control Strategy

Figure 4.8: Stripper

The control objective of the stripper is to control the reflux ratio of the regenerated MDEA

solution, control the column temperature, pressure and liquid level. Several types of

controlstrategies are used to maintain the various variables at their setpoints.

56

Table 4.4:Variable types

TIC-102/FIC-111


2. Control Objective: To keep the stripper temperature at a desired set point.

3. Control strategy concept: The temperature of the stripper is taken which is then interpreted

by the temperature controller which is then sent to the flow controller. The flow controller

then does a control action through the valve controlling the utility.

LIC-103


2. Control Objective: To keep the liquid level inside the stripper at a desired set point.

3. Control strategy concept: The liquid level inside the tank is controlled by manipulating the

liquid out stream valve.

PIC-119


2. Control Objective: To keep the stripper pressure at the desired set point.

Controlled

Variable


Variable

Disturbance

Variable

Controller

Type

Stripper

pressure

Stripper pressure Gas outlet

stream pressure

Inlet stream

pressure

Feedback

Stripper liquid

level

Stripper liquid

level

Liquid outlet

stream flowrate

Inlet stream

pressure

Feedback

Stripper

temperature

Stripper

temperature/Utility

flowrate

Utility flowrate Utility

flowrate/Inlet

temperature

Cascade

Liquid reflux

flowrate

CO2 waste gas

flowrate,Liquid

reflux flowrate

Liquid reflux

flowrate

CO2 waste gas

flowrate

Ratio

57

3. Control strategy concept: The pressure inside the stripper is controlled by manipulating the

valve at the gas outlet. By closing the valve the pressure inside the stripper increases and by

opening the valve the pressure inside the stripper decreases.

FIC-113

1. Control Strategy Used: Ratio

2. Control Objective: To control the liquid reflux ratio

3. Control strategy concept: The liquid reflux flowrate is controlled by a control valve on the

same stream.The flowrate is based on the setpoint given by the ratio control.It is important to

keep the set ratio between the liquid reflux and CO2.

4.7 Pump Control Strategy

Figure 4.9: Pump

The purpose of the control strategy is to keep the pressure of the gas at the outlet of the pump

constant by manipulating the feed of the pump. Control is achieved by using feedback controller

which measures the pump outlet pressure and compares it to the set point. Any deviations of the

outlet with be corrected through manipulation of the valve at the inlet of the pump.All pumps use

this control method.


Controlled

Variable

Measured

variable

Manipulated

Variable

Disturbance

Variable

Controller

Type

Outlet stream

pressure

Outlet stream

pressure

Inlet stream

pressure

Inlet Stream

pressure

Feedback

58

PIC-107


2. Control Objective: To keep the outlet stream pressure at a desired set point

3. Control strategy concept: The controlled variable is the pump outlet stream pressure, which is

influenced by the pump inlet pressure, by measuring the outlet stream pressure and

comparing it to the set point any deviations can be corrected by manpulating the control

valve at the inlet. The higher the inlet pressure the highr the outlet pressure.

4.8 Heat Exchanger Control Strategy

Figure 4.10: Heat exchanger

59

Figure 4.11: Cooler

The objective of the control system is to keep the outlet temperature of the heat exchanger at a

certain setpoint.This is achieved by measuring the temperature of the outlet stream and

comparing it to a set point. An interpretation of the controller is then sent to a seconday

controller which makes a decision based on measurement of the ultility flowrate and takes

control action through the control valve. The control strategy used is the cascade control strategy.

The cascade control strategy is chosen because of the long process dynamics involved in

temperature control. The ultility flowrate may also become a disturbance variable, the cascade

control makes for a quicker control response. The cascade control strategy is used for all heat

exchangers, coolers and heater.

Table 4.6:Variable types

Controlled

Variable


Variable

Disturbance

Variable

Controller

Type

Outlet stream

temperatre

Outlet stream

temperature/Utility

flowrate

Utility flowrate Inlet

temperature/Utility

flowrate

Cascade

TIC-104/FIC-102


2. Control Objective: To keep the outlet stream temperature at a desired set point

60

3. Control strategy concept: The cascade control is used because of the long process dynamics

involved in temperature control and the utility used also being a distrubance variable. The

inner loop with the faster process dynamics does the control action on the final control

element.

4.9 Flash Vessel Control Strategy

Figure 4.12: Flash vessel

The flash vessel is used to separate a gas phase from a liquid phase.The objective of the control

strategy is to make sure that the liquid level and gas pressure inside the flash vessel remains at a

set value. A feedback control strategy is used for both cases. The gas pressure inside the vessel is

measured and controlled using the top outlet stream valve, whereas the level in the tank is

controlled by the bottom control valve.


Controlled

Variable

Measured

variable

Manipulated

Variable

Disturbance

Variable

Controller

Type

Tank gas

pressure

Tank gas

pressure

Top outlet

stream

Inlet

composition/Inlet

flowrate

Feedback

61

Tank liquid

level

Tank liquid

level

Bottm outlet

stream

Inlet

composition/Inlet

flowrate

Feedback

PIC-106

1. Control Strategy Used: Feedback

2. Control Objective: To keep the flash vessel pressure at a desired set point

3. Control strategy concept: The pressure of the vessel is measured, compared to a setpoint and

then corrected by manipulating thetop control valve.By closing the valve the pressure inside

the vessel increases, by opening the valve the pressure decreases.

LIC-101

1. Control Strategy Used: Feedback

2. Control Objective: To keep the flash vessel level at a desired level

3. Control strategy concept: The level of the vessel is measured, compared to a setpoint and is

then corrected by manipulating the bottom control valve.By closing the valve the level inside

the vessel increases, by opening the valve the level decreases.

4.10 Conclusion

A control system is vital for a plant to operate safely while producing quality product at a

specified rate. This is why great attention must be paid to the control strategy. It is also best to

avoid advance control techniques wherever possible to avoid high costs.

It is possible for controller contradictions to occur. Certain control strategies may be ineffective

because of too many constraints. By conducting a relative gain array test it is possible to check

whether the control strategy will work. The relative gain array test is also able to determine the

most appropriate control strategy.

62

CHAPTER 5

5.0 SAFETY AND LOSS PREVENTION

5.1 Hazard and Operability Studies (HAZOP)

5.1.1 Description

Process safety study is important prior to developing a chemical plant. A good management

practice of safety is vital in order to ensure safe operation that will also ensure efficient

operation. This can be achieved by identifying all the potential hazards or incident scenarios

while minimizing possible risks.

Process safety study is usually conducted as hazard and operability studies or, as it is more

commonly known as, HAZOP. It is a systematic technique used in identifying all plant and

equipment hazard and operation problems. Each segment such as pipeline, equipment parts,

instrumentation set-up and many more are carefully examined to identify all possible deviations

from normal operating conditions. This is avital tools in loss prevention throughout the life cycle

of the facility. The assessment method should be conducted during the early stages of conceptual

design phase, final design stage, and also pre-setart up period. Once the plant is in full operation,

the study must also be conducted regularly in order to identify possible new hazards to the plant

equipment and plant operation. During the final stage of plant design, a thorough hazard and risk

assessment of the new facility is essential as at this stage the piping and instrumental diagrams,

equipment details and maintenance procedures are finalised.

The HAZOP process is based on the principle that a team approach to hazard analysis will

identify more problems than when individuals working separately combine results. The HAZOP

team is made up of individuals with multi-discipline backgrounds and expertise. The expertise is

brought together during HAZOP sessions and through a collective brainstorming effort that

stimulates creativity and new ideas, a thorough review of the process under consideration is

made.

A typical study team would comprise of the following:

63

i. Team leader.

ii. Secretary.

iii. Process Engineer.

iv. Control Engineer.

v. Production Operations Manager/Supervisor.

vi. Instrument Engineer.

vii. Other Specialist (civil Engineer, electrical engineer etc).

5.1.2 The HAZOP Process

HAZOP study is done to identify all plant or equipment hazards and operability problems, which

the plant might face in future. A formal operability study is the systematic study of the design,

vessel by vessel, and line by line, using “guide words” to help generate thought about the way

deviations from the intended operating conditions can cause hazardous situations (R K Sinnot,

2005). This technique is systematically applied to parts of a system such that hazard and

operability problems on the complete system are eventually identified. The study follows

specific procedures or methodology, such as shown below:

Figure 5.1: HAZOP Procedure

Select a node ('sub-system')

Apply a parameter ('property word')

Apply a 'guide word' to a property word to give a 'deviation'

Identify the 'causes'

Identify the 'consequences'

Identify the existing 'safeguards'

Decide on any 'action' to eliminate or mitigate the identified problem

Repeat for other property words, guide words as relevant

Repeat for all nodes

64

As shown in the flowchart above, HAZOP study contains the following important features:

Property words

Guide words

Deviations from design intention

Causes

Consequences (hazards, operating difficulties)

The meanings for the commonly used guide words for HAZOP are as shown below:

Table 5.1: List of Basic HAZOP Guide Words

Guide Word Meanings Comments

NO or NOT The complete negation

of the intention

No part of the intentions is achieved but

nothing else happens.

MORE Quantitative increase or

decrease

These refer to quantities and properties such as

a flow rates and temperature, as well as heat

and reaction.

LESS Quantitative increase or

decrease

These refer to quantities and properties such as

a flow rates and temperature, as well as heat

and reaction.

AS WELL AS A qualitative increase All the design and operating intentions are

achieved together with some additional

activities.

PART OF A qualitative decrease Only some of the intentions are achieved; some

are not.

REVERSE The logical opposite of

the intention

Usually applied to activities, for example

reverse flow or chemical reaction. It can also

be applied to substances.

OTHER THAN Complete substitution No part of the original intention is achieved.

Something quite different happens.

65

5.1.3 HAZOP Study for Ammonia Plant

HAZOP study focused on specific sub-system of the process or operation called “study node”,

process sections, or operating steps. Three nodes have been chosen which involved process lines

and related equipments. The selection should be based on the process nodes that contain highly

hazardous materials and critical process conditions identified during preliminary hazard study.

The chosen study nodes are as the following:

Node 1: inlet stream S4 to primary reformer (R-101) to outlet stream S10

Node 2: inlet stream S10 to secondary reformer (R-102) to oulet stream S11

Node 3: inlet stream S11 to heat exchanger (E-6) and outlet stream S18 to cooler E-101

Figure 5.2: System under study for HAZOP

66

5.1.4 HAZOP Analysis Worksheet

Node 1: Primary reformer R-101

Process Parameter: Flow

Guideword Deviation Possible Cause Possible Consequence Recommendation

LESS Less flow

- Blockage in piping system,

valves or pumps

- Pumping system fails

- Control valve not working

- Wrong routine

- No reaction

- Fail in reaction rate

- Downtime to overall

process

- Install back up control

valve or manual by-pass

valve

- Fit low flow alarm

MORE More flow

- Control into reactor fails,

fully open

- Failure in ratio controller

- High reaction rate

- Uncompleted reaction

occurred

- Less purity in product

- High pressure

- Install back-up flow

controller

- Install back-up control valve

- Install high level of pressure

alarm

NO No flow

- Blockage in piping system,

valves or pumps

- Pumping system fails

- Control valve not working

- No reaction

- Fail in reaction rate

- Downtime to overall process

- Install back up control valve

or manual by-pass valve

- Fit low flow alarm to warn

operator of no flow


Process Parameter: Temperature


LESS Less

temperature

- Failed heat exchanger unit

before reformer

- Pressure changes

- Ineffective hydrogen

production

- Install a temperature

indicator

- Install a low temperature

alarm

67

MORE More

temperature

- Heat exchanger failure

- Valve failed or blocked

- Temperature controller

failure

- Damage bed inside the

reactor

- Catalyst used in the reactor

is destroyed under high

temperature

- Install high temperature

alarm to alert operator


Process Parameter: Pressure


LESS Less

pressure

- Changes in flow

- Reactor leakage

- Line leakage

- Temperature drops

- Ensure regular maintenance

MORE More

pressure

- Suction pressure increase

- Control valve failure

- Rupture of pipeline in vapor

phase

- Install pressure /temperature

indicator for process stream

- Install high

pressure/temperature alarm

to alert operator

Node 2: Secondary reformer R-102



LESS Less flow

- Control valve partially open

- Feed line experience

blockage/leakage

- Pipeline fractures along the

feed line

- Desired reaction is not

achievable (as it involved

equilibrium reaction)

- Pressure drop inside the

reactor less pressure

would mean less conversion

- Install by-pass valve

- FIC triggers emergency

alarm when the flow into

the reactor is below set

point

68

which leads to less product

MORE More flow

- Control valve fails to close

- By-pass valve fails to close

- Pressure build-up inside the

reacto

- Less reaction and so less

product is formed

- Alarm to warn if the reactor

flow is above set point

- Install pressure-relief valve

NO No flow

- Blockage or leakage along

the pipeline carrying inlet

stream

- Control valve fails to open

- No reaction in the reactor

- Bed damage inside the

reactor

- Accumulation of products

and reactants in the reactor

- Possibilities of reverse flow

out of the reactor

- Install back up control valve

or manual by-pass valve

- Fit low flow alarm to warn

operator of no flow




LESS Less

temperature

- Methane flowrate is low

- Combustion rate decrease

due to air flowrate/methane

flowrate being low

- Desired reaction is not

achieved

- Increase methane slip out of

the secondary reformer

resulting in the waste of

fuel

- Less reaction inside

primary reformer as heat

from secondary reformer is

supplied to the primary

reformer

- Install TC based on

methane flowrate

MORE More

temperature

- Combustion rate increase

due to excess methane

- Damage bed inside the

reactor

- Increase flowrate of the

cooling water inside the

69

flowrate - Catalyst used in the reactor

is destroyed under high

temperature

- Increase the reaction inside

the reactor

- Increase the heat duty,

causing energy costs as

well as equipment costs to

escalate

jacket




LESS Less pressure

- Changes in flow

- Reactor leakage

- Line leakage

- Temperature drops

- Ensure regular maintenance

MORE More

pressure

- Suction pressure increase


- More unreacted methane

from the reactor

- Less hydrogren production

- Install pressure indicator

for process stream

- Install high pressure alarm

to alert operator.

NO Vacuum

- Fracture of the pipelines

before and after

- Reactor rupture

- Gauge pressure inside the

reactor

- Shutdown of the reactor

and repair

- Regular maintenance and

close observation during

planned shutdown to

monitor condition

- Reinforced material of the

reactor

70

Node 3: Heat Exchanger E-101



LESS Less flow - Control valve failure

- No raw material sent to

the heat exchanger

- Install low flows alarm onto

control valve

MORE More flow


- Possible thermal runaway

- Desired temperature is not

achieved

- Install temperature indicator

- Install stop valve


alarm to alert operator


emergency shutdown

NO No flow

- Control valve is not

functioning properly


achieved

- Further process cannot be

carried out

- Install low flow alarm onto

control feed flow rate.

- Install temperature indicator

for process stream




LESS Less

temperature

- Control system is not

functioning

- Temperature will decrease

with that condition

- Install low temperature

transmission

MORE More - Temperature controller is - Possible thermal runaway. - Install high temperature

71

temperature not functioning

- Valve failure


achieved

indicator.

- Install stop valve.


alarm to alert operator.


emergency shutdown.




LESS Less

pressure

- High pressure drop - The flow of fluid stream is

disturbed

- Install the low pressure

alarm

MORE More

pressure

- The pressure inlet is not

stable (disturbance)

- Temperature will increase - Install stop valve

- Install high pressure alarm

to alert operator.

- Install high pressure

emergency shutdown.

72

5.2 Plant Layout

5.2.1 Introduction

Plant/site layout must be considered early in the design work to ensure economical

construction and efficient operation of the completed plant. This section of the report

provides the basic information and safety justifications on the plant layout designed for

the newly proposed ammonia plant. As with so many aspects of design, the layout of a

process plant is not an exact science but rather an art, where it embraces a high degree of

experience coupled with the need to anticipate the human elements in both operation and

maintenance. It is an important factor in that a carefully planned, functional arrangement

of equipment, buildings and pipe works is the key to economical construction and

efficient operation. Some of the principal to consider are:

The process unit and ancillary buildings should be laid out to give the most

economical flow of materials and personnel around the site.

Hazardous processes must be located at a safe distance from other buildings.

Consideration must also be given to the future expansion of the site.

The ancillary buildings and services required on a site, in addition to the main

processing unit (buildings) will include:

i. Storages for raw materials and products, tank farms and warehouses.

ii. Maintenance and workshops.

iii. Stores for maintenances and operating supplies.

iv. Laboratories for process control.

The distances for transfer of materials between plant/storage units to a minimum

to reduce risks and cost.

Locating hazardous materials facilities as far as possible from site boundaries and

people living in the local neighborhood.

The need to provide access for emergency services.

The need to provide emergency assembly point and escape routes for on-site

personnel.

However, the most important factors of plant layout as far as safety aspects are

concerned are those to:

Prevent, limit and/or mitigate escalation of adjacent events (domino).

73

Ensure safety within on-site occupied buildings.

Control access of unauthorized personnel.

5.2.2 Plant Layout Consideration Factors

Based on the previous factors stated, the factor to design plant layout for the ammonia

plant has been cut down to several factors as followed. Thus, to ensure that the final

design for plant layout is complied with all the factors that has been discussed earlier.

Cost - The most important thing is to have an arrangement for best operation and

maintenance. Besides that, minimization of construction cost is done by adopting

shortest pipeline between raw materials and product loading storage and the

ammonia synthesis plant.

Operation - Equipment such as valves, sample points and instruments are

considered as frequently attended equipments. They are located not far away

from control room, with convenient positions and heights, to ease the operators‟

job.

Maintenance - When laying out the plant, some considerations were made

regarding maintenance work. For examples, all equipments are accessible to

crane/lift truck.

Safety - Among the safety consideration that we have when laying out this plant

are:

o Operators have 3 assembly points if anything occurs in the plant. Escape

routes are available in each and all buildings.

o Storage farm which stores flammable materials are located at safe

distance from the main process area.

o Equipment subject to explosion hazard is set away from occupied

buildings and areas.

5.2.3 Site Layout

Based on the earlier decision made, the plant location is situated in Gebeng Industrial

Area. The site layout can be divided into two parts:

i. Non-Process area - area where there is no production activity and has low

risk and hazards to workers.

74

ii. Process Area - consists of all processing units and equipments, where

ammonia is produced.

5.2.4 Non-Process Area

The non-process area usually occupies a smaller fraction of the overall plant site area.

All the facilities in the non-process area should be located in a logical manner that

considers site terrain, accessibility to roads, soil bearing capability and the climate

including the wind direction and other unusual weather condition. This is important to

avoid any undesired incident due to explosion or fire from the process zone that will be

easily spread to the non-process area. Among the buildings or units in the non-process

area are:

a) Security Post

Security post are located at the entrance of the site in order to ensure that only

authorized personnel gets access into the plant. There are three security posts that

are situated at the crucial entrances in the plant:

i. Main entrance – there is only one main entrance to check in and out the

visitors, staffs and operators of the plant.

ii. Process area security post (Gate 2) – to control the flow in and out of

personnel or vehicles between the process area and the non-process area.

The personnel may be operators and engineers while the vehicles may be

of contractors‟, fire truck and ambulance with whom have gain access to

enter the process area to ensure security.

iii. Process entrance security post (Gate 3) – to only check in and out trucks.

This is to avoid congestion and at the same time reduce the hazard of

material spillage at the plant. With this, the public are less exposed to the

danger of chemicals exposure or accidents with the trucks.

b) Administration building

The administration block is built near the parking area which acts as assembly

area for staffs as well to ensure the staffs can arrive faster at the assembly point

during an emergency. Based on the plant layout, the administration building is

placed far from the process area in order to protect the staffs and visitors from

any potential hazards.

75

c) Canteen

The canteen is located near the administration office for ease of access to the

employees and visitors, and far away from the process area to avoid contaminant

in food and ensure safety of the public. The location is so strategic that in order to

avoid the food supplier from being exposed to the process area allowing them to

move in and out easily. There are other facilities that located in the non-process

area including prayer hall, clinic and parking lot. A multipurpose hall is built for

other non-production activities. Prayer hall (surau) is located near the multi-

purpose hall for Muslims employees to perform their prayers during breaks.

d) Warehouse, Maintenance and Workshop

Warehouse stores all the process equipments‟ spare parts. Thus, it is placed near

to the maintenance and workshop where maintenance job and workshop work

conducted. It is also located beside to the control building where the engineers

can easily monitor the contractors‟ work in the maintenance and workshop to

ensure security for warehouse stores expensive equipments.

5.2.5 Process Area

Process zone is deemed as hazardous area where all processing equipment is allocated.

Due to this, the safety precaution has to be applied at all time. The buildings or units

situated in this process zone are:

a) Process Area Security Post (Gate 2)

This facility is to ensure no unauthorized personnel will have access into the

process area only by using a security pass, to record the personnel activity, such

as check-in and check-out between process area and non-process area. The

purpose of this process area security post is to ensure that all the personnel will

obey to the plant rule and regulations.

b) Control Building

All the control valves for the whole process area will be controlled and monitored

from this central control building. The control building is designed with blast

proof construction and has emergency backup power and is air conditioned in

order to save and secure the vital documents of the process that it houses during

76

emergency.

c) Laboratory

The quality and purity of ammonia is tested after the product is recovered to

determine whether it meets the specifications or not. All the results will be sent to

the control room and some adjustments in controlling will be made, if needed.

The distance between laboratory and control room is near. Laboratory staffs will

also perform analysis of the waste of the process before being channeled to

wastewater treatment and flare system; or being released to atmosphere.

d) Waste Treatment Plants

The waste stream from the separation area will flow into the waste treatment

plant to separate the contaminant from the water. The treatment plant is located

away from the personnel in the process area.

e) Ammonia Synthesis Plant

This area places the major processing unit which is the reactors where the

hydrogen and ammonia is produced. Consideration is taken from aspects such as

economy, operability and maintenance has been made to ensure the area is safe.

f) Plant Utilities

The plant utilities site is operating to supply the utilities to the all plant and

administration area. It is located near the process area and the Control Central

Building. This unit will supply cooling water, high pressure steam and nitrogen to

the main process unit. Its location is perfectly suitable to give the most

economical run of pipe to and from the process unit.

g) Product Loading and Storage

Raw materials for ammonia production are placed in the storage before

distributed to the ammonia plant via pipe line. The end products from the

ammonia synthesis are stored in the product loading before distributed to the

customer.

77

h) Future Expansion

Empty area is allocated at the process area for future expansion in case the

management decides to increase production rate or other crucial considerations.

They occupy enough space for further expansion, whether for process reaction or

producing the plant‟s own utility such as cooling water and steam.

i) Water Tank, Fire Water and Tank Farms

A water tank is allocated to supply water for ammonia production while fire

water tank is built in case of fire emergency occur. A number of tanks for

production use are placed in the tank farms.

j) Raw Material and Chemical Storage

This warehouse is located near the process plant for transportation of the material

is easy. Since it was near to the process plant area, it is easy to evacuate the

chemical or raw material to the process and reduce the hazard during the loading

and unloading material.

k) Loading Area

Loading area is where the trucks deliver the chemicals used in running of the

plant and also load the products that are going to be distributed locally. Thus, it is

directly located to the storage. Security post is also place at the entrance to the

loading area.

l) Flare Area

Flare is used to burn excess gas that is emitted from the process units as well as to

burn some of the waste gas from waste treatment area. The flare is located far

from the process area and administration complex for this purpose

5.2.6 Conclusion

The scaled plant layout is designed in accordance to the available land size at the chonse

plant complex. Meteorological data such as wind direction is also taken into

consideration in designing the plant layout so as to ensure the health, safety and

environmen awareness is kept as a topmost priority. Refer to the appendix for the

drawing of the scaled plant layout. The approximate plant area is 810 m by 550 m.

78

CHAPTER 6

6.0 WASTE TREATMENT

6.1 Introduction

All companies have a duty of care to their neighbours and to the environment in general.

Vigilance is required in both the design and operation of process plant to ensure that

legal standards are met and no harm is done to the environment. Since the environmental

awareness is increasing globally and locally, it has pushed the authority to implement

stringent regulation to limit the release of proven and potentially hazardous materials by

chemicals plants. For example in Malaysia, we have Environment Rules and Regulations

Act, 1978. In order to meet Environmental Quality Act (EQA) 1974 Malaysia, the waste

treatment strategy for ammonia plant is carefully planned. Besides, disposal of hazardous

waste on-site or off-site is governed by DOE (Department of Environment, Malaysia)

regulations on scheduled waste.

Waste arises mainly as by-products or unused reactants from the process, or as off-

specification product produced through mis-operation. There will also be fugitive

emissions from leaking seals and flanges, and inadvertent spills and discharges through

mis-operation (Sinnot, 1998). Waste is divided into three sections which are air

emissions that should be monitored annually, effluents that should be monitored

continuously specially pH adjustment, and other parameters to be monitored monthly.

Monitoring data should be analyzed and reviewed at regular intervals and compared with

the operating standards so that any necessary corrective actions can be taken. Records of

monitoring results should be reported to the responsible authorities and relevant parties,

as required.

This chapter basically covers the regulations for waste treatment in Malaysia, including

air pollution and water effluent. Then, waste is identified base on iCON simulation with

flow rate and its composition for specific stream with any other possible waste that might

be produced in ammonia plant. After that, treatment strategy is proposed by using block

diagram for ammonia plant in order to make sure the emission meet the regulations

requirement.

79

6.2 Laws and Regulations

In the promotion of environmentally and sustainable development, the Government of

Malaysia has establish the necessary legal and institutional arrangements such that

environmental factors consider at the early stages. Environmental assessment is an

important technique for ensuring that the likely impacts on the environment of proposed

development are fully understood and taken into account before such development is

allowed to go ahead. In Malaysia, industries are required to comply with both effluent

discharge and air emission standards which are regarded as acceptable conditions

allowed in Malaysia as stipulated in

i. Environmental Quality (Sewage and Industrial Effluents) Regulations 1979

ii. Environmental Quality (Clean Air) Regulations 1978

iii. Environmental Quality (Scheduled Waste) Regulation 1989

6.2.1 Water Effluent Laws and Regulations

Based on the Environmental Quality (Sewage and Industrial Effluents) Regulations

1979, there are two standard which are standard A and standard B. Standard A is

applicable to discharges into any inland water within catchment areas listed in the Third

Schedule (see Appendix 6.1) while standard B is applicable to any other inland waters or

Malaysian waters. Since our ammonia plant is in Gebeng, Pahang, so the water effluent

is being discharge to Sungai Bakok where it is complied with Standard B regulations.

Complete standard A and B for industrial effluent is as in Appendix 6.2 Monitoring

parameters are temperature, pH, BOD, COD, suspended solid, oil and grease, ammonical

nitrogen, color or specific organic compound and solid catalyst.

Acceptable conditions for discharge in industrial effluent for mixed effluent of standards

A and B are listed in Table 6.1 below.

Table 6.1: Parameters for Standard A and B

Parameter Unit Standard A Standard B

Temperature oC 40 40

pH value -

6.0-9.0 5.5-9.0

BOD5 at 20 oC mg/l 20 50

Suspended Solids mg/l 50 100

80

Oil and Grease mg/l 1.0 10.0

Ammonical Nitrogen mg/l 10 20

Colour ADMI 100 200

6.2.2 Air Effluent Laws and Regulations

For industries emitting gaseous and air emission, they are required to comply with the

following air emission standards for the control of air pollution and gaseous emissions

which are:

i. Stack Gas Standards from Environmental Quality (Clean Air) Regulations 1978

ii. Recommended Malaysian Air Quality Guidelines (Ambient Standards).

Malaysia guideline for air emission based on Malaysian Air Quality Guidelines (Ambient

Standards) at 25oC and 101.13 kPa is stated as below:

Table 6.2: Air Emissions Guidelines

Pollutant Averaging Time Malaysia Guidelines

(ppm) (ug/m3)

Carbon Monoxide 1 hour 30 35

8 hour 9 10

Nitrogen Dioxide 1 hour 0.17 320

Sulfur Dioxide 10 minute 0.19 500

1 hour 0.13 350

24 hour 0.04 105

Detail for both air emission regulation stated above is shown in Appendix 6.3

6.3 Waste Identification

Basically, waste is divided into three groups which are water effluents, air effluents and

solid waste. Each of the waste group has its own criteria. For ammonia plant, all types of

waste have been discovered and discussed in general in this chapter, followed by specific

waste production base on iCON simulation.

81

6.3.1 Solid Waste

For ammonia plant, solid waste normally comes from spent catalyst in ammonia

production. Besides, solid wastes also include by-products such as pyrite ashes, calcium

carbonate, sand, and plastic bags used to transport the fertilizer. Sludge cake and

skimmed oil from the wastewater treatment plant is also considered as solid waste.

Currently, solid waste in Malaysia is dispose in landfills. The authority that responsible

to solid waste is Kualiti Alam Sdn Bhd. Solid waste further treatment is done by Kualiti

Alam including the handling for scheduled waste. The waste treatment facilities provided

are incineration, physical/chemical treatment, solidification and waste disposal in

secured landfill. In Malaysia, comprehensive set of legal provisions related to the

management of toxic and hazardous wastes. The regulation was based on the cradle to

grave principle. A facility which generates, stores, transports, treats or disposes schedule

waste is subject to Environmental Quality (Scheduled Waste) Regulation 1989.

6.3.2 Air Effluents

Air effluent in ammonia plant comes from purge gas stream. It normally consist of

nitrogen, carbon dioxide, methane, ammonia and hydrogen based on the process involve

for ammonia production. Some of the plant might have huge valuable component in

purge gas stream like hydrogen where it needs to be recovered for recycle purposes.

Besides, flue gases like NOx, CO2 and CO are among the air effluent from the primary

reformers that should be treated. Other than that, CO2 removal section might contribute

CO2 emission as well.

6.3.3 Water Effluents

Industrial wastewater contains different pollutants and is often more variable,

concentrated, and toxic. There are several possible contaminated effluents in ammonia

plant likes:

i. Cooling water including blow down water

ii. Filter washing drain water (CO2 removal)

iii. Floor washing water including oily water

iv. Effluent water from the laboratory

v. Regeneration wastewater from demineralizer condensate treatment units

vi. Off-spec process condensate from ammonia unit

vii. Filter backwash water from cooling tower unit

82

viii. Water treatment plant backwash

Water effluent normally divided into two parts which are non contaminated and

contaminated effluent. Non contaminated water effluent is like rain water in the clean

surface while the contaminated water effluent is like mention above. All the waster

effluent normally sends to waste water treatment plant. Wastewater mainly consists of

water with small portion of contaminate like hydrogen (H2), carbon dioxide (CO2) and

nitrogen (N2). The common pollutants on wastewater stream are oil and grease. Besides

that, this wastewater stream also includes raw materials and other by products that will

contaminate the water.

6.3.4 Waste Stream

Base on iCON simulation, there are four streams that need to be treated. One stream is in

liquid form while the other three streams are in gaseous form. For liquid form stream

which is Stream 26, this water effluent contains hydrogen (H2), carbon dioxide (CO2)

and nitrogen (N2) but just in a small portion since most of them is pure water. This can

be achieved by having a good process during the ammonia production. This stream

comes out from gas-liquid separator before the stream line goes into CO2 removal.

As for the gaseous form streams, it contains hydrogen (H2), nitrogen (N2), methane

(CH4), and ammonia (NH3) as a contaminated substance. Stream 47 and stream 53 are

streams come from purge gas. The nitrogen (N2) contain in stream 53 has the highest

flow rate and represent the biggest fraction in that stream which is up to 0.75. For stream

58, this gas is comes out from ammonia stripper. Waste identification from ammonia

production based on iCON simulation with details is shown in Table 6.3.

Table 6.3: Waste Identification

Properties H2O H2 CO2 N2 Methane NH3 O2

Stream

26 to waste treatment

Mass Flow (kg/h) 4467.36 0.05 9.20 0.29

Phase L L L L

Fraction 0.9979 1.17E-05 0.0021 6.47E-05

Stream


Mass Flow (kg/h) 6.16 306.26 2.74 14.75 27.83

Phase G G G

Fraction 0.1922 0.6878 0.0107 0.0545 0.0547

83

Stream


Mass Flow (kg/h) 242.7 15794.92 100.27 514.87 966.81

Phase G G G G G

Fraction 0.1603 0.7509 0.0083 0.0402 0.0403

Stream


Mass Flow (kg/h) 122.36 17.76 535.13 66.54 130.44 499.73

Phase G G G G G G

Fraction 0.1093 0.1418 0.3075 0.0668 0.1233 0.2514

6.4 Waste Treatment/Disposal

Industrial waste treatment consists of air effluent and wastewater treatment. Both of the

treatments are essential for chemical plant likes ammonia plant. Since ammonia plant

contributes effluents, so it needs to be treated with treatment strategy base on the waste

produced.

Basically, waste in ammonia plant can be minimized by waste minimization. There are

several ways that can be used to minimize the waste which are:

i. Use Natural Gas as feedstock to minimize air emissions

ii. Use hot process gas from the second to preheat primary reformer (exchanger-

reformer concept)

iii. Direct hydrogen cyanide (HCN) gas in a fuel oil gasification plant to a

combustion unit to prevent its release

iv. Purge gas from syngas can be used to fire reformer

v. Strip condensates to reduce ammonia and methanol

vi. Use CO2 removal that not release toxics to the environment

6.4.1 Air Effluent Treatment

Air effluent is emitted from variety of process during the ammonia production. There are

many techniques available to control air effluent from polluting the environment. The

techniques include are:

i. Wet Scrubber

ii. Paked Tower

iii. Air Stripper

iv. Chemisorption

v. Condenser

vi. Biological Control System

84

vii. Flare

Below is the comparison of gaseous pollutant removal systems base on Fundamentals of

Air Pollution (Vallero, 2007).

Table 6.4: Comparison of Gaseous Pollutant Removal Systems

Type of Equipment Pressure Drop

(cmH2O)

Installed Cost

(1990 US$ per m3)

Annual Operating Cost

(1990 US$ per m3)

Scrubber 10 9.80 14.00

Absorber 10 10.40 28.00

Condenser 2.5 28.00 7.00

Direct-flame

afterburner

1.2 8.2 8.40 + gas

Catalytic afterburner 2.5 11.60 28.0 + gas

Bioligical Control

Systems

Low (e.g < in

compost)

Variable ( low to

moderate)

Variable ( low to

moderate)

Based on the comparison table above, it shows that direct flame after burner is the best

way to remove gaseous pollutant as it has the lowest pressure drop, installation and

annual operating cost. Flare is used to dispose gaseous waste from many industries such

as:

i. Purged and wasted products from refineries

ii. Unrecoverable gases emerging with oil from oil wells

iii. Vented gases from blast furnaces

iv. Unused gases from coke ovens

v. Gaseous from chemical industries.

Besides that, flare is also used for waste gases generated by ammonia fertilizer plants.

An ammonia plant is handling hazardous gases like natural gas, synthesis gas, and

ammonia starting from front end to back end. For the safe and satisfactory operation of

the plant, the flare system is the single most important element for operational or

emergency relief of flammable gases (R.Desai, 2010).

6.4.2 Air Effluent Treatment Block Diagram

85

Below is the block diagram showing air eflluent treatment strategy for Ammonia Plant:

Figure 6.1: Air Effluent Treatment Block Diagram

Based on the block diagram for air effluents treatment, it shows that all waste gaseous in

ammonia plant are gathered at gas collector header, then it will send to the water seal

disinterment drum to drain and remove any condensable and entrained liquid contains in

the gaseous. After that, it will be send to the burner unit that is ignited by ignitor using

ignition gas. Then this gas will goes to flare stack and emit at the flare tip.

During the combustion, proper mixing of air and waste gas is needed to ensure complete

combustion occurs. Smoking may result from the combustion, depending on the waste

gas components and the quantity. Since in our ammonia plant do not have heavy

hydrocrbons like paraffins, so it might not cause smoke during the flaring session. Waste

gasoues containing in gas stream in our ammonia plant are methane (CH4) , hydrogen

(H2) , nitrogen (N2) and ammonia (NH3) which usually burn without smoke. Steam

injection will act as external momentum force to ensure the waste gas mixing which

promotes smokeless flaring.

Assist

Steam

Burner

Unit

Flare

Tip

Ignitor

Ignition

Gas

Emission

Source Gas

Gas Collector

Header

Purge

Gas

Water Seal

Disinterment Drum

Drain

86

Figure 6.2: Flare Gas System

6.4.3 Water Effluent (Wastewater) Treatment

Industrial wastewater treatment characteristic is different from sanitary wastewater. In

industrial wastewater treatment, considerations should be given to modifications in

industrial processes segregation of wastes, flow equalization and reduction of waste

strength. There are several characteristic that should be focus on like temperature, BOD,

COD and pH. Suspended solid concentration relative to BOD is important when

considering secondary biological treatment.

87

6.4.4 Wastewater Treatment Block Diagram

Figure 6.3: Wastewater Treatment Block Diagram

RA

S

Kualiti Alam

WA

S Thickener

Sludge

Basin

Dehydrator

Secondary

Clarifier

Neutralization

Basin

Treated

Wastewater

Effluent Basin

To Perimeter

Drain

Stabilization

Basin

Coagulation

and

Flocculation

Basin

Aeration

Tank

Primary

Clarifier

Squeezed Water

88

Process Description

The waste water treatment process description base on the above block diagram is:

i. Oily contaminated water is fed to the oil separator system to eliminate oil from the

effluent where oil is skimmed and the oil-free water will overflows to the equalization

basin. Density difference between oil and water helps the oil separator system

function well where oil is skimmed and the oil-free water overflows to the

Equalization Basin. The oil that has been recovered will be sent to the storage pit

before the disposal take place.

ii. Non oily contaminated water that comes from various sources is sent to the

equalization basin. The completely mixed equalization system is designed to

completely mix a single flow or multiple flow streams combined at the front end of

the wastewater treatment facility. The equalization basin is on-line and receives flows

continuously (Driscoll, 2008). This equalization basin is used to reduce variances in

each stream, minimize and control fluctuation in wastewater and provide optimum

conditions for subsequent treatment process.

iii. For contaminated water from the ammonia plant, it will be sent to the grit removal

before fed into equalization basin. In industrial wastewater, grit removal is one of the

preliminary treatments that have been used to ensure overall treatment process

reliability and effectiveness. Grit removal reduces abrasive wear on mechanical

equipment and prevents then accumulation of sand in tanks and piping (Eddy, 1991).

Grit is predominantly non-putrescible solids (e.g. sand, small gravel, metal shavings,

ash, and soot) that settle faster than putrescible and other solids. Grit removals is used

to protect downstream pre-treatment equipment and prevents heavy material from

accumulating in sewers and equalization, neutralization, and aeration tanks (Driscoll,

2008). Besides, it is also used in order to protect pumps, valves and downstream

pipelines.

iv. Next, the effluent is fed to coagulation and flocculation basin. Here, the basin is

provided with a motor driven stirrer to continuously ensure the coagulant added to the

coagulation basin is well mixed with the water. Coagulation is the destabilization of

colloids by addition of chemicals that neutralizes the negative charges. The coagulant

added will cause small groups of suspended solid. Then it will further agglomerate the

89

particles into large size particles known as flocs which can be effectively remove by

flotation or sedimentation.

v. The effluent then will be sent to primary clarifier where most of the coagulant and

flocculent will be eliminated and send to the thickener tank. In clarifier, the suspended

solid will go to the bottom center of the clarifier. Clear water will be send to the

activated sludge treatment for further treatment.

vi. After that, the wastewater is send to the activated sludge treatment which consists of

aeration tank and secondary clarifier. Purposes of activated sludge are to develop

biomass and substrate, predict of biomass and soluble substrates concentrations,

prediction of the reactor biomass and MLSS/MLVSS concentrations and the amount

of waste sludge produced daily. The water-absorbed ammonia is fed into an aeration

tank, where either air from atmosphere is bubbled into the tank or the mechanical

surface aerator is used to saturate the wastewater with oxygen. Microorganisms exist

in the aeration tank to digest the ammonia.

vii. Then, the wastewater is send to the secondary clarifier. Here, same concept in primary

clarifier applied. The suspended solid in secondary clarifier is send to the thickener

while the clean water is send to the stabilization basin.

viii. In stabilization basin, sludge is stabilize in order to reduce pathogen, eliminate

offensive odors, and inhibits, reduce or eliminate the potential for putrefaction.

Survival of pathogens, release of odors and putrefaction occur when microorganisms

are allowed to flourish in the organic fraction of the sludge. The means to eliminate

these nuisance conditions through stabilization are the biological reduction of volatile

content, the chemical oxidation of volatile matter, the addition of chemicals to the

sludge to render it unsuitable for the survival of microorganism and the application of

heat to disinfect or sterilize the sludge (Eddy, 1991). Then the effluent is fed to

naturalization basin.

ix. Naturalization basin act as final pH adjustment before the effluent is discharge. In

neutralization basin, alkalinity and acidity are useful concepts for determining

neutralization requirement. pH measurement is required in order to determine how

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much acid or alkali is needed to neutralize the wastewater. Water in the neutralization

basin is treated with either sulphuric acid or caustic soda to get the correct pH range

of 6.5 to 8.5.

x. Finally, the effluent is fed to treated wastewater effluent basin and being discharge to

the perimeter drain.

xi. For solid handling parts, it consists of thickener, sludge basin and dehydrator.

Thickener is used to thicken the sludge then the sludge is fed to the sludge basin.

Sludge basin is provided with an air mixing blower to prevent deposition / settlement

of sludge. The sludge in the basin is discharge to the dehydrator.

xii. Dehydrator is used to squeezes the intake sludge and discharges the water-free sludge

into a container. The squeezed water is recovered back to the Equalization Basin.

6.4.5 Specific Treatment for Ammonia Wastewater

Ammonia that generated is alkaline and reacts corrosively with all body tissues. For a 25%

solution of ammonia in water, the aqueous ammonia is a colorless liquid with pungent odor.

It forms strong base, which corrodes aluminum and zinc. The over exposure to this liquid in

closed area may extremely destructive to tissues of the mucous membranes and upper

respiratory tract (if inhaled). Symptoms may include burning sensation, coughing, wheezing,

shortness of breath, and so on.

For this plant, we have chosen the activated sludge treatment system. There is a constraint for

activated sludge system, i.e. the contents of the active component (for chemical plant, usually

organic in nature) in the liquid cannot exceed a certain value. It is because in activated

sludge, microorganisms (bacteria and protozoa) are used to biodegrade the organic

components in wastewater. High concentration of waste in the effluent destroys the proper

biological functions/operations of those microorganisms, killing them eventually. Therefore,

laboratory examination of the effluent is needed to determine the content and concentration

of the effluent to be treated.

91

In aeration tank (atmosphere pressure) the waste will treat with combination bacteria and

oxygen entering, this combination make reaction occurs in aeration tank. The reaction occur

in this show as below :

HeatboimassNewNHCOCHOOHmatterOrganic 324

bacteria

22

Notes: Organic matter such as Ammonia

The „biomass‟ from aeration tank will be pumped to Clarifier, settling tank to separate the

liquid and solid. In clarifier, the solid will go down to filter press and the water will pass to

final conditioning tank using pump. Filter Press pressed the solid to separate it into solid and

liquid form, whereas liquid is recycle back to aeration tank. The solid produced is called

sludge and sent to Quality Alam for disposal to environment without dangerous. Since the

components of in the effluent are all organic, the concentration of BOD is taken as a

guideline to determine whether the treated effluent is safe enough to be discharged into the

environment. (shown in Table 4.5)

The wastewater treatment plant is a tapered aeration activated sludge treatment facility. Take

BOD5 = 1000. This value corresponds to the BOD5 of the effluent of an Ammonia plant in

United States.

Therefore, BOD5 before treatment,

BOD5i = 1000 mg/L

To comply with the Environmental Quality Act (Amendment 1979), B Standard, we only

allow 20 mg/L BOD5 in the wastewater effluent from our chemical plant.

After treatment, BOD5f = 20 mg/L

We use typical design values for tapered aeration activated sludge plants for design. Typical

design values (see page 429, Table 15.4 (Reynolds, 1996)):

Mixed liquor suspended solids, MLSS = 2000 mg/L

Mixed liquor volatile suspended solids, MLVSS = 1500 mg/L (75% of MLSS)

Sludge density index, SDI = 10000 mg/L

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CHAPTER 7

7.0 PROCESS ECONOMICS AND COST ESTIMATION

7.1 Introduction

Process economics is an integral part of any process. Since building a plant is financially

huge, it is essential to estimate the costs. According to Peters et. al (2003), an acceptable

plant design must represent a plant that can produce a product which can sell profit.

Therefore, plant designers need to be able to design different alternative plant designs,

estimate the costs rather effectively, and choose the best profitable design, which in turn will

pull in shareholders. Cost estimation would also help in determining whether the plant is

economically stable and sustainable in the long run, since chemical plants will be operating to

an expected 15 to 20 years‟ lifetime.

Process economics cover a wide range, from capital plant costs, up to operating, taxes,

transportation and administrative costs. The main focus on process economics however, is the

capital costs and the operating costs, which is usually a substantial part in plant finance and

economics. Capital cost, or CAPEX for short, is usually consists of plant equipments while

operating costs, or OPEX is the cost of running the plant and usually estimated by 2% from

CAPEX. However, detailed calculations are needed for more accurate estimation; the

estimation accuracy is dependent upon the request of the client and extensive design.

For our ammonia plant, the production is 1744 MTPD, or 576,000 MT per year. As per

required of plant designs, a substantial process economics and cost estimation of our

proposed plant is done to assess the economics of the plant. The assessment will help to

determine whether the proposed design is profitable and prospective for construction.

The location for the plant is planned at the Gebeng Industrial Park, due to reasons listed

below:

a) Raw material

The raw materials for the ammonia synthesis are natural gas (methane) and steam.

Natural gas is acquired from a dedicated pipeline from PETRONAS Gas Bhd., while

steam is a part of the utility provided by Centralized Utilities Facilities (CUF) in

Gebeng. As such, no additional costs are needed for transportation of natural gas and

generation of steam.

93

b) Realistic land price

Since Gebeng is declared as an industrial park by the government, incentives are

provided for any development of plants in the area, which include reduced land prices

to attract more investors. This is a boost to the economics of the plant construction.

c) Product demand

The ammonia demand is growing rapidly every year, and not only in Malaysia, but

worldwide as well. This is due to the fact that ammonia is very important reactant in

urea production which is widely used in agriculture as a fertilizer and is tied to the

growing food demand.

d) Power and water supply

Both supplies are available since Gebeng provides CUF.

e) Accessibility

Gebeng is accessible by sea and train transportations, since Gebeng is near the

Kuantan Port, and there is also an integrated train line.

f) Labor force

Malaysia has a large labor force, including able engineers and technicians that can

operate the plant effectively. The Malaysian economy also encourages a healthy and

competitive labor force for better personnel selectivity.

All the calculations are done via Detailed Factorial Method, and to provide enough values to

be able to construct detailed cash flows for the proposed process economics.

7.2 Capital Investment

As stated previously, the capital investment is mainly the equipment cost. The equipment cost

mainly consist of the equipment body, the installation costs, type of material, and other

factors such as wiring and instrumentation. All these cost can be calculated superficially from

the equipment‟s body cost via factors. This method is otherwise known as the detailed

factorial method.

94

There are two major factor tables that are widely used by engineers today. The two major

tables are:-

a) Lang factors

b) Guthrie factors (also known as bare-module factors)

The differences between the two factor tables are the factors‟ weightage and basis. Lang

factors base on the type of the plant to be built (either solids processing, solids-fluids

processing, or fluids processing) while Guthrie factors emphasize on the types of equipment.

The Lang factor was recently broken down into more sub-factors by Peters, Timmerhaus, and

West (2003) to increase its accuracy. The Guthrie factor, already a complex calculation

method in itself, was not known to be updated recently as it was noted that the factors are

quite substantial.

For our equipment F.O.B. (free on board) estimation, the cost estimation mainly follows

Elsevier (2010) and Seider, Seader, Lewin, and Widagdo (2010) for supplementary

calculations. As such, the basis method is based on the Lang factors, since Seider et al.,

(2010) gives a total capital investment multiplier that is based on Lang factor to estimate the

installation costs including piping and labor. Following this method, we can estimate total

cost of capital cost based on total F.O.B. of equipment. Seider, Seader, Lewin and Widagdo

(2010) provide basic calculations method for pricing of equipment like heat exchangers,

ammonia synthesis, and catalysts prices. The table below depicts the modified Lang factor for

each type of plant as mentioned in Seider et al., (2010). Note that this table only depicts the

total capital investment factor with each respect to plant type.

Table 7.1: Lang factor for Total Capital Investment

Lang factor for Total Capital Investment

Type of Plant Factor

Solids Processing 4.67

Solids – Fluid Processing 5.03

Fluids Processing 5.93

Columns 2.1

The cost index that will be used along in the project is based on Marshall and Swift (MS).

Since all the F.O.B costs are estimated as of 2006, the index for total F.O.B cost will be based

on 2006 MS index, which is 1365. The MS index for year 2011 is 1519.8. Based on the

95

F.O.B total cost below and the Lang factor from above, we can estimate the total investment

cost for 2011.

The table below showcases the costs of all the equipment in the proposed plant.

Table 7.2: Estimated Equipment Cost

Equipments Total Pricing

Compressor $ 23,590,141.87

Reactors $ 11,789,438.75

Heat Exchangers (including coolers and heaters) $ 632,692.28

Flash Vessels $ 1,632,454.10

Towers $ 410,692.32

Total F.O.B Equipment Cost $ 38,055,419.32

Total Capital Cost = $ 286,242,893.59

7.3 Operating Cost

The operating cost can be divided into two types, which are:-

a) Fixed Operating Cost

Fixed operating costs are operating costs that are consistent and fixed every year.

Among them are:-

- Maintenance

- Operating manpower

- Plant overheads

- Insurance

b) Variable Operating Cost

Variable operating costs are operating costs that changes with the economy and

market from day to day. Among them are:-

- Raw materials

- Utilities

- Shipping and packaging

- Sales expense

Seider et al., (2010) gave the modified Cost Sheet Outline by Busche (1995) in order to

estimate the operating cost of the project. The cost sheet outline is extensive however, and

we only consider using it to estimate Total Production Cost.

Based on the available data, we get the total operating cost to be $178,279,406.53. This is

96

after we have considered operating cost on general, which includes feed stocks, operations,

maintenance, overhead, depreciation, and general expenses.

7.4 Economic Analysis

A standardized economic analysis will require the project to be analyzed for its Internal Rate

of Return (IRR) and its Payback Period. For the payback period, two different scenarios are

analyzed, one where the payback is without discount and the other with discount. Since we

are counting the time value of money, only discounted cash flow is considered for full

analysis including

- IRR

- Pay Back Period

- NPV

- Cumulative PV

97

Table 7.3: Non-Discounted Simple Payback Cashflow

98

Figure 7.1: Graph of PV vs No of Years for Simple Payback Period

$(400,000,000.00)

$(200,000,000.00)

$-

$200,000,000.00

$400,000,000.00

$600,000,000.00

$800,000,000.00

$1,000,000,000.00

$1,200,000,000.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

PV

($

)

Year

99

Table 7.4: Discounted Payback Cashflow

100

Figure 7.2: Graph of PV vs No of Years for Discounted Payback Period

101

CONCLUSION AND RECOMMENDATION

As a conclusion, constructing the proposed 543,000 metric tones per year of ammonia plant

is in Malaysia highly feasible. As the demand of ammonia is increasing highly every year,

the construction of this plant would help in assisting in supplying ammonia to the world

market. Plus, ammonia as an important part of urea production is in turn affecting the world

food supply, therefore making this project highly prospective. For our plant location,

Gebeng Industrial Park, located in Pahang, is chosen due to its availability of CUF and

accessibility to land (train) and sea transportations.

Literature review has shown that ammonia is highly demanded around the globe. The

ammonia market shows that demand is far higher than the market could supply. Due to this,

the ammonia selling price rarely drops; a factor that will surely help in attracting investors.

However, a good process design is needed in order for the plant to give a revenue that highly

substantial than the cost incurred. Process optimization includes a recycle system to recover

unreacted hydrogen and the utilization of HEN. It is noted that by utilizing HEN, energy loss

as much as up to 14.45% can be saved. The recycle system, meanwhile, increased the

production rate up to 2.7 times, while at the same time using the same amount of feedstock.

Equipment design, sizing, and cost estimates are shown in an Equipment Specification Sheet

with the appropriate standards. For each of the part that is design, sizing, and cost estimates

are done with great understanding of engineering knowledge.

Integrated process control was also designed and included into the proposed plant design.

The control and instrumentation was designed to ensure the plant runs at a safe and

workable environment, while at the same time, able to good great quality ammonia

consistently. The control system proposed in the design consists of only feedback and

cascade systems to ensure simplistic yet efficient control of the plant processes.

102

Designing of the proposed plant also take into account the safety and wellbeing of the

workers. This includes Hazard and Operability (HAZOP) studies as well as safety

requirements for all equipment, for instance, having pressure relief valves at every reactor.

The proposed plant layout was design with safety and environment concerns so as to

minimize accidents in the plant. However, since safety and environmental issues always at

large, it is recommended that extra precautions are taken once the plant is under

commencement.

In recent literature reviews, reportedly there have been extensive researches whereas

reforming process, where hydrogen for ammonia is conceived, can have a built-in

membrane separator within the reformer unit itself, thus increasing the plant output while at

the same decreasing the plant costs, due to less cost incurred for operation of hydrogen

cleansing. Other technological advancements, like newfound catalysts and membrane

separators within the ammonia synthesis, have also been researched recently. Hopefully, this

new technologies can increase the efficiencies of ammonia plants.

As CO2 and global warming is threatening the environment more and more these days, a

better separation process is in need. Not only that, since CO2 produced from this plant might

not be suitable in the market, a need comes as to where can the CO2 can be dumped. A better

CO2 removal method that comes with a good CO2 storage system is currently under research

and field testing. The method we are referring to is known as sequestration. Since MDEA

waste itself is hazard, safer ways of CO2 capture can be designed and replace the MDEA

method. There are already methods like pressure swing adsorption that shows considerable

CO2 capture capabilities. Potential new methods like hydrate formation to capture CO2 gases

can also be tested and tried.

In terms of the economic analysis, the plant shows that it is economically feasible to

continue on with the project since its MARR (10%), or hurdle rate, is lower than that of the

project‟s IRR (12.80% for the discounted cash flow). The payback period for non-

discounted cash flow is 8 years while it is 9 years for the discounted payback period. Since

there are no sensitivity study regarding the discount rate and the payback period, no

103

conclusive evidence is there to support the link between the discount raye and the payback

period, however.

To conclude, the proposed 543,000 metric tones per year of ammonia plant is in Gebeng

Industrial Park is technologically and economically feasible and prospective. Added with the

aid of the Malaysian government incentives, we can say that the project is a good investment

for any investors.

104

REFERENCES

Bare, S. R., Strongin, D. R., & Somorjai, G. A. (1986). Ammonia Synthesis over Iron Single-

Crystal Catalysts: The Effects of Alumina and Potassium. California: J. Phys. Chem.

Berkowitz, N. (1979). An Introduction to Coal Technology. New York: Academic Press.

Bhakta, M. L., & Grotz, B. J. (1994). High Conversion Ammonia Synthesis. US Patent No.

5352428.

Brady, S. B., Farnell, P. W., & Fowles, M. (2010). Steam Reforming. US Patent No.

7731935B2.

Cassey Lee (2005), Water Tariff and Development: The Case of Malaysia. Faculty of

Economics and Administration, University Malaya.

Danckwerts, P.V. (1970), Gas Liquid Reactions, McGraw Hill, New York.

Douglas, J. M. (1988). Conceptual Design of Chemical Processes. Singapore: McGraw-Hill

Book Company.

Driscoll, T. P. (2008). Industrial Wastewater Management, Treatment and Disposal.

Alexandri, Virginia: Mc Graww Hill.

DuPart, M., et al. (2001), A New Deep CO2 Removal Solvent for Ammonia Industry,

Freeporrt, Texas.

Eddy, M. &. (1991). Wastewater Engineering, Treatment, Disposal, Reuse. Singapore: Mc-

Grawwhill International Editions.

European Fertilizer Manufacturers' Association. (2000). Best Available Techniques for

Pollution Prevention and Control in the European Fertilizer Industry: Booklet No. 1 of 8:

Production of Ammonia. Brussels: Fisherprint Ltd.

John C. Molburg, Richard D. Doctor, (2003). Hydrogen with stream-methane reforming

with C02 capture. 20th

Annual International Pittsburgh Coal Conference.

Jusino, A., & Schobert, H. H. The use of sulfur to extract hydrogen from coal. Pennsylvania:

The Pennsylvania State University.

Lovell, R., & Harvey, D. G. (1950). A Preliminary Study of Ammonia Production by

Corynebacterium renale and some other Pathogenic Bacteria. London: Royal Veterinary

College.

Kothari, R., Buddhi, D., & Sawhney, R. L. (2006). Comparison of Environmental and

Economic Aspects of Various Hydrogen Production Methods. ScienceDirect .

105

McKee, R.L., et al. (1991), “CO2 Removal: Membrane Plus Amine”, Hydrocarbon

Processing.

McKellar, M. G., O'Brien, J. E., Stoots, C. M., & Hawkes, G. L. (2007). Process Model for

The Production of Syngas Via High Temperature Co-Electrolysis. ASME International

Mechanical Engineering Congress & Exposition (p. 8). Idaho: Idaho National Library

(INL).

Meng Ni (2005), An Overview of Hydrogen Production from Biomass, University of Hong

Kong, China.

Meyer, H.S. and J.P. Gamez (1995), Gas Separation Membranes: Coming of Age for

Carbon Dioxide Removal from Natural Gas, presented at the Laurence Reid Gas

Conditioning Conference.

Meyers, R. A. (2005), Handbook of Petrochemicals Production Processes. McGraw-Hill,

USA

M.H. Spritzer, G.T.Hong (2003), Supercritical Water Partial Oxidation, FY 2003 Progress

Report, National Renewable Energy Laboratory.

Mori, N., Nakamura, T., Sakai, O., Iwamoto, Y., & Hattori, T. (2008). CO-Free Hydrogen

Production by Membrane Reactor Equipped with CO Methanator. Japan: Ind. Eng.

Chem. Res.

Moulijn, J. A., Makke, M., & Van Diepen, A. (2001). Chemical Process Technology.

Singapore: John Wiley and Sons.

R.Desai, R. S. (2010). Self-Supported Flare Stack Vibrations in Ammonia Plant. AIChe -

Wiley online Library , 10.

Rochelle, G.T. and M.M. Mshewa (1994), Carbon Dioxide Absorption/Desorption Kinetics

in Blended Amines, presented at the Laurence Reid Gas Conditioning Conference.

Savage, D.W., and E.W. Funk (April 5-9, 1981), “Selective Absorption of H2S and CO2 into

Aqueous Solutions of Methyldiethanolamine”, paper presented at AIChE Meeting,

Houston, Texas.

Seider, W. D., Seader, J. D., Lewin, D. R., & Widagdo, S. (2010). Product and Process

Design Principles: Synthesis, Analysis, and Evaluation. Singapore: John Wiley and Sons.

Sinnot, R. (1998). Chemical Engineering. Britain: Butterworth-Heinemann.

Smith, R. (2005). Chemical Process Design and Integration. Singapore: John Wiley and

Sons.

106

Vallero, D. (2007). Fundamentals of Air Pollution. Durham, North Carolina: Academic

Press.

van Delft, Y. C., Overbeek, J. P., Saric, M., de Groot, A., & Jansen, D. (2009). Towards

Application of Palladium Membrane Reactors in Large Scale Production of Hydrogen.

8th World Congress on Chemical Engineering. Montreal: Energy Research Center of the

Netherlands (ECN).

Veritech (2009). Pinch Analysis: For the Efficient Use of Energy, Water and Hydrogen.

National Resources Canada.

Wang, R., & Rohr, D. (2002). Natural Gas Processing Technologies for Large Scale Solid

Oxide Fuel Cells . Fuel Chemistry Division Preprints , 506-507.

Gebeng Industrial Estate. (2010). Retrieved February 2011, from

http://www.investinpahang.gov.my

Low Temperature Methanation Catalyst . (2010). Retrieved February 2011, from

http://www.haldortopsoe.com

http://www.investinpahang.gov.my/

http://www.haldortopsoe.com/

107

APPENDICES

108

APPENDIX 4.1

Process Flow Diagram (PFD)

109

110

APPENDIX 4.2

Piping and Instrumentation Diagram (P&ID)

111

112

APPENDIX 5.1

Plant Layout

113

114

APPENDIX 6.1

List of Catchment Areas where Standard A Applies

115

116

117

118

APPENDIX 6.2

Parameter Unit Standard A Standard B

Temperature oC 40 40

pH value -

6.0-9.0 5.5-9.0

BOD5 at 20 oC mg/l 20 50

Suspended Solids mg/l 50 100

Mercury mg/l 0.005 0.05

Cadmium mg/l 0.01 0.02

Chromium, Hexavalent mg/l 0.05 0.05

Chromium, Trivalent mg/l 0.20 1.0

Arsenic mg/l 0.05 0.10

Cyanide mg/l 0.05 0.10

Lead mg/l 0.10 0.50

Copper mg/l 0.20 1.00

Manganese mg/l 0.20 1.0

Nickel mg/l 0.20 1.0

Tin mg/l 0.20 1.0

Zink mg/l 2.0 2.0

Boron mg/l 1.0 4.0

Iron mg/l 1.0 4.0

Silver mg/l 0.1 1.0

Aluminium mg/l 10 15

Selenium mg/l 0.02 0.50

Barium mg/l 1.0 2.0

Fluoride mg/l 2.0 5.0

Formaldehyde mg/l 1.0 2.0

Phenol mg/l 0.001 1.0

Free Chlorine mg/l 1.0 2.0

Sulphide mg/l 0.5 0.5

Oil and Grease mg/l 1.0 10.0

119

Ammonical Nitrogen mg/l 10 20

Colour ADMI 100 200

APPENDIX 6.3

Recommended Malaysian Air Guideline

Recommended Malaysian Secondary Guideline

120

APPENDIX 6.4

Gas Stack Emission Standards

121

122

Documents

Pdpii May2011_07 Group Report