˘ ˇˆ˙ - si.iut.ac.ir• water consumption can exceed 250 m3/t steel for many once-through cooling systems • less than 5 m3/t steel for more closed circuit cooling system and

دانشگاه صنعتي اصفهان

پژوهشكده فوالد

دهمين ميزگرد صنعت

راهبردهاي كاهش مصرف آب و فناوري هاي خشك در صنعت فوالد

ابوذر طاهري زاده

هيات علمي پژوهشكده فوالد دانشگاه صنعتي اصفهان

[email protected]

http://taherizadeh.iut.ac.ir

93ارديبهشت

93ارديبهشت 15راهبردهاي كاهش مصرف آب در صنعت فوالد، ابوذر طاهري زاده، : ميزگرد دهم صنعتپژوهشكده فوالد


سرفصل مطالب

2

انگيزه: مقدمه

بحران آب و توسعه صنعت فوالد •

مصرف آب در صنعت فوالد

موارد مصرف و آمار و ارقام•

مثال ها و مطالعات موردي•

)3R( راهبردهاي كاهش مصرف آب در دنيا

روش ها و راهبردها•

مثال ها و مطالعات موردي: كاهش آب مصرفي•

بازيابي و تصفيه پساب•

فن آوري هاي خشك در صنعت فوالد

CDQفن آوري •

فن آوري خنك سازي سرباره با هوا•

فن آوري غبارگيرهاي خشك•



تنش آب

3

)تنش آب(رتبه بندي كشورها بر مبناي ميزان منابع آب موجود در سال به ازاي هر فرد



تاثير تنش آب بر درآمد ناخالص ملي و مهاجرت در سال 2050

4

افزايش جمعيت•توسعه صنعتي•شيوه زندگي•گرمايش زمين•

پيش بيني مي شود مصرف آب در دنيا در •پنج برابر مصرف آب در سال 2030سال

.باشد 2000



مهمترين صنايع مصرف كننده آب

5

The most important industrial sectors in water consumption

• Forest products (pulp and paper)

• Steel

• Petroleum

• Chemicals

• Aluminum

• Metal casting

• Mining

• Glass, and

• Agriculture

Breakdown of the fresh sweet water in Japan (1999) bm3/yr



موارد مصرف آب در صنايع

6

Three major industrial use of water:

• Process water

• Cooling

• Heating

State of Texas, USA, 1999



Steelworks types

7

Three types of steelworks:

1. Mini-mills, which use scrap steel to make limited types of products for multiple markets

2. Finishing-mills, which use intermediate steel products to make products only for focused markets

3. Integrated steelworks, which use ore, coke, limestone, energy and water to produce multiple products:

• often located near coasts

• several square kilometres

• networks of interdependent material and energy flows

• iron-making, steel-making, rolling and finishing



Water Management Project (IISI, 2011)

8

Objectives & Goals:

• Comparing members' policies and strategies on water management

• Benchmarking global rates of water use and consumption

• Contribution by steel industries in providing water for communities in areas of water scarcity

• Cover all aspects of water issues (environmental, resource, commercial, operational, political, etc.)

• Identification of state-of-the-art water technologies and practices

• Evaluation of improvements of inventory technologies




9

Geographic distribution of the project team and meetings




10

Steel Plant water consumption and discharge figures

Water consumption at different steel plants varies from 1 to near 150 m3/ts




11

Steel plants water consumption and discharge per facility

Rest: cooling of power generation, equipment and indirect cooling activities (m3/ton of product)



Sustainable Water Management

12

SWM is a solution in areas with limited freshwater

3Rs of sustainability: Reduce, Reuse , Recycle

• plays a critical role in the viability of steel plants

• recycling of water is imperative

• recirculation rate of nearly 100%

• creating an almost zero-effluent site

• complex pipe networks

• pre and effluent treatment systems

• quality monitoring of the pipes (quality & volume)

• Challenge: the choice of final effluent treatment



National Steel Policy 2012- India

13

Drafting the next 20 ‐ 25 years roadmap of Indian steel

• Investment intentions and progress of the various on‐going steel projects

• Raw material rich states and adjoining areas

• Anticipated predominance of technologies

• Infrastructural needs: transportation, energy, land and water

• Investing $80 billion in steel production in India

• India ahead of Japan (second-largest steel producer)

• Consumption of water by the steel industry: 360 million m3 in 2016‐17 to >650 million m3 in 2025‐26




14

Objectives & Plans:

• Bridging the gap between international best practice norms of water use & recycling and Indian standard practices in steel plants

• Three largest iron‐ore bearing states have large surface water sources (i.e., river basins)

• Steel projects may face problems on account of low priority accorded to the industry in allocation of water

• Build external infrastructure for accessing for public

• Minimize the deleterious inter‐generational environmental and social impacts of depletion in ground water resources and contamination of water sources by industrial effluents




15

Efforts:

a. Involve all stake‐holders i.e., local community, the steel plants, the state agencies, in chalking out an optimum water sharing agreement and monitoring of the quality of water in the various water sources in the vicinity of steel units.

b. The government will initiate water footprint mapping and rainwater harvesting in steel industry and related mining areas.

c. Fix a system of penalty and rewards aimed at bridging the gap between international best practice norms of water use or recycling in steel plants and the Indian standard practices.




16



Water System Diagram in Steel Industry

17

Showing routes of water and wastewater in steel plant

USSteel, 1971



Water in Steel Industry

18

American Iron and Steel Institute (AISI): Steel industry’s most important commodities:

1. Iron

2. Energy

3. Water

Main consumptions

• Coolant (equipment, furnaces, intermediate steel, process water), (direct or indirect) 75%

• Cleansing agent to remove scale from steel products

• Source of steam

• Medium for lubricating oils and pickling solutions

• Air pollution control (wet scrubber, gas cleaning) 12%




19

• Steelmakers require approximately 290 m3 of water to produce one ton of steel (AISI, 2000) including recycledand reused process and cooling water. Integrated mills use more water per ton of steel than EAFs

• Typically, more than 95% of the water used in steelmaking can be recycled within the plant

• Due mainly to evaporation losses, steelmakers require 50–90 m3 of additional water per ton

• Steelmakers obtain water from municipal sources and adjacent water bodies




20

• For heat transfer, particularly for cooling (or “quenching”) coke after carbonization in coke ovens (30–33 m3/ton of coke)

• In boilers for converting coke oven gas, tars, and light oils (150–450 m3/ton of coke)

• In boilers for converting blast furnace gas (76–230 m3/ton of iron)

• In production and finishing processes, hot strip mills, use the most water (4.5–9 m3/ton of hot rolled strip)

Water demands may vary depending on :

• The type and shape of steel

• The efficiency of equipments and technology


21دانشگاه صنعتي اصفهان

Estimated water use by process expressed as gallons per

ton of product (U.S. DOE, 2003)

Water in Steel Industry Process




22

Water systems in operation:

• Completely closed circuit (e.g. Exch. water/water)

• Cooling with DM or softened water

• CCM moulds

• Power plant boilers

• Semi-closed circuit (small amount of water discharge)

• Second circuit (exch. water/water) cooling towers

• Open circuit

• Unlimited fresh water availability




23

Water consumption in different steelworks depends on

• Amount of once-through cooling systems

• water consumption can exceed 250 m3/t steel for many once-through cooling systems

• less than 5 m3/t steel for more closed circuit cooling system and combined with other water saving measures

• Average water consumption figures within steelworks are approximately 30 m3/t of steel

• Most of fresh water is used for once-through cooling purposes




24

Once-through systems: specific water intake of >100-200 m3/t of steel (valid for plants close to large bodies of water)




25

• In sites with very low fresh water availability (groundwater or spring water) we need to reduce water consumption intensely.

• In such cases, the specific water consumption can be lower than 5 m3/t of steel and the interdependencies can be much more intensive.

Comparison in water intake once-through systems versus extensive recirculation



Coke-oven water systems

26

Large quantities of water used in Coke-Ovens:

• Quenching of hot coke

• Cooling and washing of gas from battery ovens

• Fire hydrants

• Cooling on batteries

• Cooling in cascade coolers

• Re-circulating cooling towers

• Dust suppression at coal stockyard

Effluent Treatment:

• Wastewater pre-treatment: Ammoniastripping by alkalis, Tar removal

• Wastewater treatment: Biological treatment with nitrification/de-nitrification



Coke-oven water systems

27

Coke-Ovens water mass balance (1 mt/yr)



Sinter plant water systems

28

Sinter plant (3.9 mt/yr) & raw material handling water

mass balance



BF water systems

29

Blast furnace (3.9 mt/yr) water mass balance



BOF water systems

30

BOF (4.2 mt/yr) water mass balance

• 0.5-5 m3/ton steel

• Hood & lance & degasser cooling: 45 m3/h

• Total BOF plant consumption: 125 m3/h

Diagram of the off gas scrubber system for BOF



CCM water systems

31

Main water consumers in a continuous casting plant

• Copper water-cooled mould and jackets

• Slab spray water and machine (roll) cooling water

• The highest quality water available in a closed loop

• Filtration of direct cooling water for solids removal

• CCM (4.2 mt/yr): 502 m3/h

• Primary mould: DM water

• Primary roll: DM water

• Secondary: soft water



Hot mill water systems

32

Different water systems with different qualities:

• Roll coolant

• Service water

• De-scaling water

Hot mill (3 mt/yr)

• 4460 m3/h

• 2560 m3/h

• 360 m3/h

Rolling activities consume and lose great amounts of water via direct water cooling



Boilers and Steam Generators

33

• Perhaps no industrial application of water is more dependent on energy than process steam generation

• Energy utilized in boilers and steam generation more than half of the total energy consumed by the pulp and paper (82%), food processing (56%), and chemicals(52%), in addition to significant portions of steel (22%)

• Boiler and process steam generation and distribution systems likely the greatest potential area for the achievement of significant industrial water-related energy savings



Industrial Case Study 1

34

Water management of an integrated steelworks (1.2 billion m3/yr, 2005)

Recirculation: 97.2%Discharge: 1.2%Lost: 1.6%

water intake 3.16 m3/t crude steel




35

• Techniques to reduce water intake and discharge waste (Case 1)

• Avoiding potable water for production lines

• Increasing water circulating systems (new/revamping)

• centralizing the distribution of incoming fresh water

• Using water in cascades until single parameters reach their legal or technical limits

• Using water in other plants if only single parameters of the water are affected and further usage is possible

• keeping treated and untreated waste water separated

• using rainwater whenever possible




36

Water management of an integrated steelworks

Counter flow cascade system with steel production steps (from a cold rolling mill to the blast furnace)




37

Tata Steel (India) has reduced water intake by 60% from 2002 to 2012




38

• Efficient local recirculation and plugging of leakages

• Further reduction in water consumption, “Zero Discharge” scheme is under implementation in some plants



Cooling Systems in Steel Industry

39

Once-Through

Cooling Systems

Use water in a single pass to cool the plant before disposal to trade waste

Better to be replaced by cooling circuitsOr the outflow should be reused in other processes




40

Open Loop

Cooling Towers

spray the hot water into air inside the tower to cool as it falls




41

Closed Loop

Cooling Towers

a heat exchanger within the cooling tower to keep coolant flow and evaporative water flow separateThese systems are almost as effectiveas open loop, are more expensive and safer. They can be run dry or with reduced evaporative water flow on cooler days or when the heat load is low




42

Hybrid Cooling Towers

Use a closed circuit with a dry heat exchange followed by a closed loop cooling tower. However, with higher energy usage and higher system cost!




43

Increasing efficiency and decreasing water

consumption in cooling systems:

• Minimizing evaporative cooling

• Optimizing blowdown water

• Removing solids from blowdown water

• Reuse of blowdown for certain purposes

• Improving the quality of feed water

• Optimising cooling towers processes (location, cycles, designs, etc.)

• Minimizing drift, Splash-out, overflow and other losses



Wastewater in Steel Industry

44

Thermal power and steel plants are the major contributors to industrial wastewater discharge

Steelmaking pollutant discharged wastewater

(average: 25 m3/ton of steel):

• Coke-making quench water: coke and solids, carcinogenic particulates, ammonia, Phenol (mostly reused after removal of coke & solids)

• Mills, acid pickling and hot coating: scales, oils, grease, metals such as chromium, lead, nickel, zinc

• Sintering operations and blast furnace operations: discharges of phenols, suspended solids

• Blow down from cooling circuits

• CCM direct cooling: scale, oils

• Disposal of wastewater is the least favourable option!



Wastewater Treatment in Steel Industry

45

Treatment needed will depend on the type and concentration of pollutants in the wastewater:

• Physical/chemical treatment

• Biological treatment

• Thermal treatment




46

Physical/Chemical Treatment:

• Oil / Water Separators

• Chemical precipitation

• Filtration

• Ion Exchange (for metals, nitrate)

• Evaporation

• Oxidation

• Reduction

• Air stripping for removal of volatile organics

• Granular activated carbon adsorption

• Membrane separation




47

• Monitoring the quality and quantity of wastewater

• Conventional chemical precipitation treatment method

• Good treatment efficiencies

• Little capital and moderate operational spending

• Voluminous sludge with maximum sludge solid concentration (1%-5% solids) difficult to further dewater

• Costly disposal of sludge

• Problematic long-term storage due to metals leach




48

Thermal Treatment:

• Incinerate on or off-site

• Combustion of waste to heat, gas, steam & ash

• Not used as much (discharge of hazardous materials)

• Regulations are different by state

• Must be licensed for air pollutant discharges

• Expensive (usually for solid wastes or sludge)



Biological wastewater treatment

49

• More advanced processes for difficult wastes

• Promising for wastewaters treatment in steel plants

• A few applications throughout EU steel plants

• Methodologies have been assessed and developed

• An operational concept has been developed

1.Degreasing bath wastewater at a stainless steel pickling and annealing line (ASM model: activated sludge models )

2.Degreasing bath wastewater of an electrical steel pickling section (artificial neural network (ANN))

3.Two different coking plants (modified ASM model)



High Density Sludge treatment

50

• High Density Sludge (HDS) process is a mechanical technique for improving the physical properties of sludge (originated in Canada & USA)

• Conventional HDS is applied at numerous mine sites

• The first recorded HDS in Bethlehem Steel Corporation in the late 1960’s

• Improved solid concentrations (15% - 35%)

• Improved sludge settlement and dewater-ability



High Density Sludge treatment

51

Suitable design for HDS Process in steelworks (2011)



Dry Technologies in Steel Industry

52

Dry technologies in steel industry:

• Coke Dry Quenching (CDQ)

• Slag Dry Granulation

• Dry Dust Collectors



Conventional Coke Quenching

53



Coke Dry Quenching

54

:مزاياي خنک سازي کک بدون آب

کاھش اتف آب به صورت بخار•

کاھش اتف انرژي در اثر تبخير آب استفاده مجدد ھوا در سيستم•

کاھش توليد غبار کک معلق در ھوا •

کاھش مصرف سوخت فسيلي•

در محيط CO2کاھش ميزان •

کيفيت بھتر کک توليدي•

توليد الکتريسيته•

:معايب خنک سازي کک بدون آب

ھزينه اوليه با-•

محدوديت فضا•

پيچيدگي طراحي•

•pollutive wet quenching method•baking coal at temperatures of over 2,000•Water is used to cool the coke releasing air pollutants and wasting water and heat•In CDQ system, gas is circulated in an enclosed system to cool the hot coke•heated gas is then reused to create electricity for the coking plant



Coke Dry Quenching

55

نمايي از فرايند کک سازي بدون آب



Coke Dry Quenching

56

Dry quenching plant of the former coking plant Kaiserstuhl III (Germany)



Coke Dry Quenching

57

مقايسه کيفيت کک توليدي از ھر دو روش



Coke Dry Quenching

58

مزايای زيست محيطی روش خنک سازی کک بدون آب

•CO2 savings in excess of 100 000 t/y are estimated by converting two 25 t/h capacity quenching systems from wet to dry•Given about 300 Mt coke production without CDQ and savings of 600 g CO2/kWh, global CO2 emissions reduction potential is about 25 Mt CO2



Coke Dry Quenching

59

مزايای انرژی روش خنک سازی کک بدون آب

•CDQ: up to 40% less energy• In China energy for coking: 5.6 GJ/t-coke to 4.9 GJ/t-coke between 1995 and 2000, further decreased to 4.2 GJ/t-coke by 2004, due to CDQ and other advanced quenching technologies•Approximately 1.5 GJ heat/t-coke (as ~ 400 - 500 kg high temperature steam/t-coke) and 0.55 GJ electricity/t-coke can be recovered



Coke Dry Quenching

60

مزايای اقتصادی روش خنک سازی کک بدون آب

In Europe equipment costs for a 2 million ton-coke/year plant are estimated to be €70 million. Depending on the electricity costs, the payback time can be 3 years - if all the steam is used for electricity generation.

Converting two 25 t/h quenching plants from wet to dry systems



Coke Dry Quenching

61

برخی از کارخانه ھای استفاده کننده از

CDQفناوری



Coke Dry Quenching

62

•CDQ is widely applied in Japan and Korea.•Less than 30% of plants in China have this technology.•Application remains limited in the EU, in the US and in Canada -primarily due to low electricity prices and high IRR expectations



Slag Dry Granulation

63

:گرانوله سازي سرباره با آب

– L1500(مصرف با-ي آب • )به ازاي ھر تن سرباره مذاب 1000

عدم توانايي بازيابي مقدار با-ي گرماي موجود در سرباره•

:گرانوله سازي سرباره بدون آب

توليد سرباره شيشه اي براي توليد سيمان•

مورد استفاده در (بازيابي گرماي از دست رفته به صورت ھواي گرم •)فرايندھاي خشک کردن، پيشگرم کردن و توليد بخار

کاھش شديد مصرف آب•

)حذف نشر سولفور(کاھش آلودگي ھوا •

کاھش ھزينه ھا•

پيچيدگي تکنولوژي در طراحي و کنترل فرايند•




64

فرايند دو مرحله اي گرانوله سازي خشک سرباره و بازيابي حرارت

Molten slag is poured on to the centre of a rotary disc and flung to the edge during CSIRO's dry granulation process




65

Experimental apparatus for slag granulation using spinning disk atomizer




66

Air atomization with heat recovery system

Atomization by using a rotary-cup, air-blast atomizer



Dry Dust Collectors

67

Dust collectors types:

• Electro-static precipitators (ESP)

• Fabric collectors

• Wet collectors

• Dry centrifugal collectors

Wet collectors (wet scrubber) mechanism:

• Contact particles with a liquid (water)

• Collect the droplets



Dry Dust Collectors

68

Wet dust collector types:

1. chamber or spray tower

2. packed towers

3. wet centrifugal collectors

4. wet dynamic precipitator

5. orifice type

6. Venturi

:مزاياي غبارگيري با استفاده از آبامکان دستيابي به دماي با- و گازھاي مملو از رطوبت•عدم انفجار يا آتش سوزي غبارھا به دليل مرطوب بودن•

:مشک*ت غبارگيري با استفاده از آبايجاد شرايط خورنده •نياز به حفاظت در برابر انجماد در محيط ھاي با آب و ھواي سرد•بسته شدن نازل ھا به دليل عدم تعادل شيميايي در مايع•



Dry Dust Collectors

69

Dry centrifugal collectors:

Collection efficiency is influenced by

1. size, shape and weight of the particles

2. size and design of the collector

3. inlet velocity

4. concentration of dust

Types :

• gravity separators

• inertial separators

• cyclone collectors

• high efficiency centrifugals



تشكر و قدرداني

70

حضار محترم•

مديريت پژوهش، فناوري و بومي سازي شركت ذوب آهن •

آقاي مهندس جعفري، شركت ذوب آهن•

آقاي دكتر رضاييان، دانشگاه صنعتي اصفهان•

آقاي دكتر حسن پور، شهرك علمي تحقيقاتي•

Documents

˘ ˇˆ˙ - si.iut.ac.ir• water consumption can exceed 250 m3/t steel for many once-through cooling systems • less than 5 m3/t steel for more closed circuit cooling system and