PROJECT TOPIC

MANUFACTURE OF CHLORINE–CAUSTIC

SODA USING ELECTROLYSIS PROCESS

BHARATI VIDYAPEETH COLLEGE OF ENGINEERING

CHEMICAL DEPARTMENTProf. R.K.Kulkarni

Presented by Ankush Gupta

PROCESS FLOW DIAGRAM

Membrane Cell Process

MATERIAL BALANCE

Basis : 1150 kg/hr NaOH , 1000 kg/hr Chlorine

2NaCl + 2H2O 2NaOH + H2 + Cl2

(58.5) (18) (40) (2) (70)

( 28.75) (28.75) (28.75) (14.375) (14.375) Kmoles/hr

(1681.8) (517.5) (1150) (28.75) (1006) kg/hr

• Sample calculationMoles = weight / molecular weight

For NaCl

Moles = 1150/40 28.75 Kmol/hr

NaCl required (Kg) = 28.75 * 58.5 1681.8 kg (1700 Kg/hr).

Assumption : 1700 kg/hr of NaCl 20 kg/hr Na2Co3

• 15/100 x Feed =1700 Feed = 11333.33 Kg/hr.

OVERALL MATERIAL BALANCEFeed (F) + Na2Co3 = |Sludge|4 + |NaCl|311333.33 + 20 = |Sludge|4+ |NaCl|3………………………eqn(1)

MATERIAL BALANCE OF NaCl 1700 = 28%|NaCl|3 + 10%|Sludge|4170000 = 28|NaCl|3 + 10|Sludge|4…………………………….eqn(2)

On Solving Eqn(1) & eqn(2) we get|NaCl|3 = 3137.03 Kg/hr.|Sludge|4 = 8216.3 Kg/hr.

For 55% efficiency of Caustic Soda &Cl2:

2NaCl + 2H2O = 2NaOH + H2 + Cl2

Mass flow(kg/hr) 878.36 270.25 330.28 8.256 289.01

Molecular Weight 58.5 18 40 2 70

Moles flow(Kmol/hr) 15.014 15.014 15.104 7.552 7.552

Moles flow(Kmol/hr) 8.257 8.257 8.257 4.153 4.153 (55%)

Sample Calculation: For NaOH : • Amount of NaCl entering a membrane cell = 28%|NaCl|3=28% (3137.03)=878.368kg/hrConverting into molar flow rate = 878.368/58.5=15.014 Kmol/hr

•By Stoichiometry , No of moles of NaCl = No of moles of NaOH = 15.014 Kmol/hr.But since we have for 55% efficiency for Membrane cell

• No of moles of NaOH = 55%(15.014)= 8.257 Kmol/hr.Therefore the amount of NaOH obtained= 8.257*40=330.28 Kg/hr

OVERALL MATERIAL BALANCE OVER EVAPORATOR Aq. NaOH(35%NaOH) = Aq.NaOH(50% NaOH) + Water vapour 330.28 = 231.196 + 99.081

Calculation for amount of aq.NAOH obtained as a main product:• Pure NaOH out of aq. NaOH = 35% of (330.28) = 115.598 kg/hr• Water content in incoming aq. NaOH = 330.28 – 115.98 = 214.68 kg/hr

Amount of NaOH obtained after 50% concentration is• 50% of (aq. NaOH) = 115.598 kg/hr• Therefore aq. NaOH (50%) obtained as product = 231.196 kg/hr• Water content in obtained aq. NaOH (50%) = 231.196-115.598=115.598 kg/hr• Therefore Water Vapour = 214.68-115.98=99.082 kg/hr

OVERALL MATERIAL BALANCE OVER DRYER:

Wet Cl2 + H2SO4(98% conc) = Dry Cl2 + H2SO4 (70% conc)289.019 + 98% of (25kg) = Dry Cl2 + H2SO4 (70%)

…….eqn1

MATERIAL BALANCE OF H2SO4 OVER DRYER:

Inlet H2SO4 (98%conc) = Outlet H2SO4 (70%conc) 98%(25) = 70% H2SO4

98x25 = 70% H2SO4

H2SO4 (70%) = 35 kg/hrSubstituting in …..eq1 Dry Cl2 = 278.519 kg/hr.

ENERGY BALANCE

STEAM REQUIREMENT FOR HEATING BRINE

m = mass flow rate of Aq NaCl in kg/hrCP = specific heat capacity of Aq NaCl At 60OCΔT = Temperature Difference λ = latent Heat of evaporization in kJ/kg m1 = Flow rate of steam kJ/hr

mcPΔT = m1 λ

3137.03 x 3.274 (333-298) = m x 2358.40 m1 = 151.186 kJ/hr

ENERGY BALANCE OVER MEMBRANE CELL

Assumption Datum temperature = 25oC

INLET STREAM

OUTLET STREAM

MATERIAL NAME

SPECIFIC HEAT AT 60oC FLOW RATES kg/hr

H2O 4.185 kJ/kgK 270.252

Aq.NacL solution

3.247 kJ/kgK 876.368

MATERIAL NAME SPECIFIC HEAT AT 80oC FLOW RATES kg/hr

Hydrogen (g) 14.43 kJ/kgK 8.256

Chlorine (l) 0.48 kJ/kgK 289.019

NaoH (35% by wt) 3.594 kJ/kgK 330.28

Depleted brine 3.247 kJ/kgK 521.065

• INPUT STREAM Material mcPΔT Aq .NaCl 876.368 x 3.247x (333-298) = 99594.84 kJ/hr H2O 270.252 x 4.185 x (333-298) = 39585.16 kJ/hr

TOTAL HEAT INPUT = 99594.84 + 39585.16 = 139180 kJ/hr

• OUTPUT STREAMMaterial mcPΔT Hydrogen (g) 8.256 x 14.43 x (353-298) = 6552.37 kJ/hrChlorine (l) 0.48 x 289.019 x(353-298) = 4855.51 kJ/hr Aq.NaoH 3.594 x 330. 28 x (353-298) = 41545.92 kJ/hr Depleted Brine 3.247 x 521. 065 x (353-298)= 59216.43 kJ/hr

TOTAL HEAT OUTPUT = 6552.37 + 4855.51 + 41545.92 + 59216.43 = 112170.23 kJ/hr

2Na (s) + 2H2O 2NaOH + H2O ΔH = -368.4 kJ/gmNa

Depleted brine = 526.064 kg/hr (50% by wt of NaCl)0.5 x 526.064 x -368.4 = - 96900.98 J/hr

MATERIAL NAME

SPECIFIC HEAT AT 80oC FLOW RATES kg/hr

Aq.NaoH 35% by wt

3.594 kJ/kgK 330.28

MATERIAL NAME SPECIFIC HEAT AT 110oC FLOW RATES kg/hr

50 % Caustic soda 3.564 kJ/kgK 231.196

INLET STREAM

OUTLET STREAM

MATERIAL NAME Latent Heat AT 110oC FLOW RATES kg/hr

Steam 2231.86 kJ/kg 94.127

ENERGY BALANCE OVER EVAPORATOR

• INPUT STREAM Material mcPΔT Aq .NAOH 330.28 x 3.594 x (353-298) = 65286.44 kJ/hr

TOTAL HEAT INPUT = 65286.44 kJ/hr

• OUTPUT STREAMMaterial mcPΔT Aq.NaoH (50% by wt) 231.196 x 3.564 x (383-298) = 45319.03 kJ/hr Material mλ Water vapour (g) 94.127 x 2231.86 = 210078.28 kJ/hr

TOTAL HEAT OUTPUT = 45319.03 + 210078.28 = 255397.31 kJ/hr

MATERIAL NAME

SPECIFIC HEAT FLOW RATES kg/hr

Wet chlorine 0.48 kJ/kgK 289.019

H2SO4 (98% by wt)

1.465 kJ/kgK 10

MATERIAL NAME

SPECIFIC HEAT FLOW RATES kg/hr

Dry chlorine 0.48 kJ/kgK 285.019

H2SO4 (70% by wt)

2.177 kJ/kgK 14

INLET STREAM

OUTLET STREAM

ENERGY BALANCE OVER DRYER

• INPUT STREAM Material mcPΔT Wet Chlorine 289.019 x 0.48 x (353-298) = 7630.10kJ/hr

TOTAL HEAT INPUT = 7630.10 kJ/hr

• OUTPUT STREAMMaterial mcPΔT Dry Chlorine (l) 285.019 x 0.48 x (343-298) = 6156.41 kJ/hr H2SO4 70% 14 x 2.177 x (303-298) = 152.39 kJ/hr

TOTAL HEAT OUTPUT = 6156.41 + 152.39 = 6308.8 kJ/hr

% conversion NaCl = (Reacted moles / Total no moles) x 100

= {(878.36 – 261.032)/878.36} x 100= 70.28 %

%Yield = (NaoH moles Formed /Reacted moles of NaCl) x 100

= {(115.598/ 40) / (617.328/58.5) } x 100 = 27.37 %

REFERENCES1 ) Subrata Basu , Swapan Kumar Mukhopadhyay , Amitava Gangopadhyay

and Sujata G. Dastidar “International Research Journal of Environment Sciences Characteristic Change of Effluent from a Chlor-alkali Industry of India due to Process Modification” 2013.

2) S.Koter.A.Warszawski “Polish Journal of Environmental Studies Electro- membrane Processes in Environment Protection” (2000)

3) Yohannes Kiros and Martin Bursell “International Journal Electrochemistry Science Low Energy Consumption in Chlor-alkali Cells Using Oxygen Reduction Electrodes (2008)”

4) Rezaee, J. Derayat, S.B. Mortazavi,Y. Yamini and M.T. Jafarzadeh “American Journal of Environmental Sciences Removal of Mercury from Chlor-alkali Industry Wastewater using Acetobacter xylinum Cellulose(2005)”

5) Dryden’s outlines of chemical technology (2012)