UNIT OPERATION IN

CHEMICAL PROCESS

AND MASS BALANCE

BASIC CHEMICAL PROCESS

Raw Material

Preparation1 Main

Process 2 Purification3

EQUIPMENT IN CHEMICAL PROCESS

Transportation of Fluid / Heat

Transfer

Filtration and Size Handling

Reactor Purification

• Pump• Compressor• Blower• Shell and Tube HE• Plate HE• Double Pipe HE• Boiler• Evaporator• Etc.

• Rotary Vacuum Filter• Membrane Filtration• Bag Filter • Ball Mill• Cutter• Centrifuge• Clarifier • Cyclone• Etc.

• Plug Flow• Continuous Stirred Tank• Fixed Bed • Fluidized Bed• Etc.

• Dryer• Distillation• Adsorption and Striping• Extraction• Molecular Sieve• Evaporator• Etc.

Knowing Chemical Process Equipment

Equipment Symbol

Equipment Symbol

• Separating solid and liquid (water)

• Separating solid and liquid (water)

• Separating Solid and Solid

• Separating gas and solid (Bag Filter)

Filtration

1

2

3

1

2

3

1

2

3

Reactor

Equipment used for reaction to take place

Industrial Scale Polystyrene reactor

Plug Flow Reactor

CSTR Fixed Bed Fluidized Bed

• Mass enter the reactor = mass out of reactor• Component in component out

Purification

Extraction Distillation

Take Solute from one liquid to another liquid (solvent)

Evaporation of Liquid

Separate of minimum 2 liquid with different boiling point and form vapor-liquid equilibria

Same as distillation but mostly in vacuum pressure

Purification (Cont)

Adsorption/Stripping

Ads : Take Solute from gas to liquid (solvent)

Strip : Take Solute from Liquid to gas

Wet Feed

Dry Air

Dry Product

Wet Air

Dryer

General Concept of Mass Balance

Balance

Mass

Feed (F)

Distillate (D)

Residue (B)

General Concept of Mass Balance

1. Ethanol2. Water

1. Ethanol2. Water

1. Ethanol2. Water

Overall Mass Balance

Mass in F = Mass in D + Mass in BF = D + B

100 kg

45 kg

….? kg

Ex. B = 55 kg

Component Mass BalanceComponent Mass in F = Component Mass in D + Component Mass in B

1. Ethanol in F = Ethanol in D + Ethanol in B2. Water in F = Water in D + Water in B

Feed (F)

Distillate (D)

Residue (B)

How to express quantity of component?

1. Ethanol: 45 kg2. Water: 55 kg

1. Ethanol2. Water

1. Ethanol2. Water

100 kg

45 kg

55 kg

Mass Fraction

Mass Fraction of Ethanol (𝑋1) in stream F

𝑋1 =45 𝑘𝑔 𝑒𝑡ℎ𝑎𝑛𝑜𝑙 𝑖𝑛 𝐹

100 𝑘𝑔 𝑡𝑜𝑡𝑎𝑙 𝑚𝑎𝑠𝑠 𝑖𝑛 𝐹

= 0.45

Mass Fraction of Water (𝑋2) in stream F

𝑋2 =55 𝑘𝑔 𝑤𝑎𝑡𝑒𝑟 𝑖𝑛 𝐹

100 𝑘𝑔 𝑡𝑜𝑡𝑎𝑙 𝑚𝑎𝑠𝑠 𝑖𝑛 𝐹

= 0.55

Total of Mass Fraction = 1𝑋1 = 1- 𝑋2 𝑜𝑟 𝑋2 = 1- 𝑋1

1. A mixture of methanol (CH3OH, Mw = 32.04 g/mol) and ethanol (C2H5OH, Mw =46.07 g/mol) is flowing through a circular pipe at flow rate 3 m/s. The mixturecontain 30 %wt methanol and 70 %wt ethanol. The Specific gravity of themixture is 0.8. If the inside diameter of the pipe is 0.1 m, what is the flow rate ofmixture in kg/s and kmol/s.

2. A liquid stream containing only benzene, toluene and p-xylene (Mw=106 g/mol)(BTX) flows through pipe that has a square cross section. The total flow rate ofthe stream is 10 mol/s. if the mole fraction of benzene (Mw = 78 g/mol) is 0.3,that of toluene (Mw = 92) is 0.5, what is the mass fraction of each component?If the density of liquid is 0.87 g/cm3 and the pipe diameter is 0.1 m what is thevolumetric flow rate of the liquid inside the pipe?

Problem

Mass Balance

1. Ethanol, XD1= 0.752. Water, XD2…..?

Feed (F)

Distillate (D)

Residue (B)

1. Ethanol: 45 kg2. Water: 55 kg

1. Ethanol, XB1…..?2. Water, XB2…..?

100 kg

45 kg

…. kg

How to solve the mass balance in this problem:

1. Find Mass of stream B (from overall mass balance)2. Find Ethanol mass in Stream D (from mass fraction) 3. Find Ethanol mass in stream B (from comp mass balance)4. Find Water mass in stream D (from mass fraction)5. Find Water mass in stream B (from comp mass balance)

Component Mass Balance for EthanolEthanol in F = Ethanol in D + Ethanol in B

XF1 (F) = XD1 (D) + XB1 (B)

Component Mass Balance for WaterWater in F = Water in D + Water in B

XF2 (F) = XD2 (D) + XB2 (B)

F = D + B

Selecting System and Calculation Basis

Unit ExtractionComplex Plant

How to Calculate mass balance in complex plant?

Selecting System and Calculation Basis

1. Choose your system

- Choose the system based on most known variable

- Choose most simple unit operation

System boundary

Selecting System and Calculation Basis

2. Determine the Calculation Basis

Most used calculation basis is time of operation

- Flow rate (volume / hr, volume/ s, volume/ day)

- Mass rate (kg / hr, kg/ s, kg/ day)

Example of Basis : 1 (one) day operation

Selecting System and Calculation Basis

2. Determine the Calculation Basis

Feed (F)

Distillate (D)

Residue (B)

1. Ethanol: 56 %2. Water:…%

1. Ethanol, XB1…..?2. Water, XB2 : 95%

…. kg / hr

1. Ethanol, XD1 : 70%2. Water, XD2…..?

What is the most suitable basis for this problem?

Example of Basis : 1 (one) day operation

The Flow rate of:1. Feed2. Distillate3. Residue

…. kg / hr

Feed (F)

Distillate (D)

Residue (B)

Homework

1. Ethanol: 370 kg2. Water:…. kg

1. Ethanol, XD1= 0.752. Water, XD2…..?

1. Ethanol, XB1…..?2. Water, XB2…..?

560 kg/ hr

330 kg/ hr

…. kg / hr

Find the volume (in liter) of tank needed to store distillate for 3 days operation, if density of distillate is 500 kg/m3!!

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