This document describes the design of a plant for cryogenic distillation of air into oxygen and nitrogen. It includes an introduction to air separation and the cryogenic process. Process equipment like compressors, heat exchangers, and distillation columns are designed. Mass and energy balances are performed. The distillation columns and condenser are designed and specifications are provided. An economic analysis includes capital costs, production costs, profitability metrics, payback period and safety considerations. References for design methods are also listed.

1. Plant Design of Cryogenic distillation
of Air to Oxygen and Nitrogen
 Project By: Bhusare Abhijit (Gr. No. 111390)
Ghalme Rahul (Gr. No. 111448)
Modi Vrajesh (Gr. No. 111027)
Guided By: Prof. A. K. Vaddi

2. Introduction
 Air (M.W. = 28.96 g/mol ) is composition of various gases.

3.  High purity components in air applied in different chemical
industries.
 1904- World’s first ASU for production of high purity air
components
 Largest markets - Chemicals and gasification, petroleum refineries,
electronics and metals industries.
 First industrial manufactures of oxygen was ‘Brin process’
 1806- Faraday liquefied many gases by application of pressure, but
not H2, O2, N2
 1877- Pictat and Caillete liquefied first O2 and many gases.
 Prof. Linde- First man producing liquid O2 on commercial scale.
 1970s- First application of computer control to improve efficiency
and productivity of ASU.

4. Kolhapur Oxygen Pvt. Ltd. (Kagal MIDC)

5. INOX AIR PRODUCTS Pvt. Ltd. (Jejuri MIDC)

6. Literature Survey
 Global market for industrial and specialty gases will reach 10.15
trillion cubic feet by 2015.
 Major growth Factors- high demand from end user industries such
as energy, healthcare and electronics.
 Growth due to R&D activities focusing on new applications.

7. Applications of Air Products
 Medical oxygen
 Oxygen- Glass manufacturing, chemicals and petroleum processing,
pharmaceuticals, pulp and paper (increase paper whiteness), aerospace,
wastewater treatment and even fish farming.
 Oxygen‐enriched air increases production efficiency in steel, rocket fuel, glass,
chemical, gasification and metallurgical processing applications.
 Manufacturers of Al, Cu, gold and lead use oxygen to remove metals from ore.
 Nitrogen- Oil and gas industries, metal working, electronics, food processing.
 Refineries, petrochemical plants and marine tankers use gaseous nitrogen to clean
out vapours and gases from the equipment they use.
 Recyclers use liquid nitrogen to cool plastic and rubber so they can grind them
and recover key raw materials to manufacture new products.

8. Process Selection
 Different Manufacturing Processes
1. Low temperature (Cryogenic) rectification of liquid air
2. Membrane separation
3. Electrolysis of water
4. Brin process
5. Brin process using cobalt compounds

9. Process Selection
Oxygen Production Process Selection Grid

10. Cryogenic Air Separation
 Two steps
1. Liquefaction
 Production of low temperatures
 Linde Process (JT Effect)
2. Separation of liquid air by rectification
 By integrated distillation column

11. Process Description
 Equipments used
1. Compressor
2. Heat Exchanger
3. Valve
4. Molecular Sieve
5. Separator
6. After Cooler

12. Process Description
 Five major steps of manufacturinfg O2 and N2
1. Air compression
2. Air purification
3. Cooling of air
4. Air separation
5. Product collection
 Product Validation
1. Oxygen Test
2. Nitrogen Test

14. Mass and Energy Balance
 Capacity of unit= 215 ton/day gaseous O2
=6300 m3/hr
 Quantity of intake air=34500 m3/hr
Component Volume %
Nitrogen 78.03
Oxygen 21.00
Argon 0.94
Hydrogen 0.01
Helium 0.0003
Krypton 0.00011
Xenon 0.00009
CO2 0.03-0.06
Moisture 0.02-0.05

15. Mass Balance
Equipment Material In (K mol/Hr) Material Out (K mol/Hr)
Input 1540.18 -
65% Stream 1001.17 -
After Cooler 1001.17 998.49
Heat Exchanger 998.492 997.03
35% Stream 539.063 -
Molecular sieve 539.03 538.478
Low pressure distillation column 1535.55
L2=209.734
S=456.746
W=869.07
High pressure distillation column
L2=209.734
S=456.746
W=869.07
N2=361.61
WN2=892.69
O2=281.25

16. Energy Balance
Equipment
Enthalpy at Inlet
(K cal/Hr)
Enthalpy Out
(K cal/Hr)
Compressor 1 5701515.3 5800672.1
Compressor 2 2030235.2 1752557.962
After Cooler 3770436.8 3567701.7

17. Energy Balance
Heat (K cal/Hr) Heat Exchanger
High Pressure
HE
Heat given by dry air 1476342.02 -
Heat lost by CO2 1308.78 -
Heat lost by water 1609.632 -
Heat gained by N2 422037.5 -
Heat Lost by Air - 442741.5
Heat gained by O2 - 312603.33

18. Equipment Design
 Design of Distillation Column
 L/V ratio at the top of both columns to be 0.58
 F = amount of feed = 1535.55 kmol/hr
 W = Bottom product from lower, refluxed back to the top
column (rich liquid)
 S = Side stream from lower column, refluxed back to top
column (impure liquid)
 Xf = mole fraction of N2 in feed = 0.79
 Xw = mole fraction of N2 in IPL = 0.96
 X1 = mole fraction of N2 in top product = 0.99

19.  F = W + S + L2 ----------- (1)
F Xf = W Xw + S Xs + X1 L2 ------------- (2)
Number of Plates (Graphically)
Hence from the graph no. of theoretical plates = 17

20.  Average molal μ of feed = 0.6127
 Actual number of plates = 17/ 0.6127 = 27.74 ≈ 28 plates
 From graph feed enters 12 plates
 Actual plate at which feed enters = 12/ 0.6127
 Feed enters plate = 19
 Total Height = 9.146 m

21. Mechanical Design of Distillation Tower
 Calculation Cylindrical Body of the Tower
Cylinderical wall thickness (bottom)
t = PL*DL/ (2 f J - PL) + C = 5.12 mm
Now, t = 6 mm thickness are acceptable.
 Permissible pressure in the selected wall thickness against top
wall
[P] = [2 f J (t - C)]/ (DL + t - C) = 7.67 kg/cm2
f = PL (DL + t - C)/ 2.3*J (t - C) = 785.2 kg/cm2
 Cylindrical body wall thickness (upper)
t = [PH DH / 2 f J - PH] + C = t = 0.272 cm = 2.72 mm
Now, t = 6 mm thickness are acceptable.
 Permissible pressure in selected wall thickness [P] and seizure
against top wall
[P] = [2 f J (t - C)]/ (DH + t - C) = 8.84 kg/cm2
f= [PH (DH + t - C)]/ 2.3*J*(t - C)= 181.5 kg/cm2

22.  Calculation of Elliptical Cap and Bottom
Elliptical bottom wall thickness
t = PL*DL/ (2 f J - PL) + C = 5.12 mm
Now, t = 6 mm thickness are acceptable.
Permissible pressure in the selected wall thickness and seizure
against the top wall
[P] = [2 f J (t - C)]/ (DL + t - C) = 7.67 kg/cm2
f = PL (DL + t - C)/ 2.3*J (t - C) = 903 kg/cm2
Wall thickness of elliptical cap
t = [PH*DH/ 2 f J - PH] + C = 2.72 mm
Now, t = 6 mm thickness are acceptable.
Permissible pressure in selected wall thickness [P] and seizure
against top wall
[P] = [2 f J (t - C)]/ (DH + t - C) = 8.84 kg/cm2
f = [PH (DH + t - C)]/ 2.3*J*(t - C) = 208.8 kg/cm2

23. Condenser Design
• Tha is inlet temperature of nitrogen vapor = -176.5 0C
Thb is outlet temperature of nitrogen = -178.2 0C
Tca is inlet oxygen liquid = -179.5 0C
Tcb is outlet oxygen = -178.2 0C
Therefore, ∆T1 = 1.491
Now, taking overall HTC as 100 btu/hr ft2 0F = 567 W/m2.0C
Q = U A ∆T
By using this equation A comes around 460 m2
Let N is the number of tubes so total heat transfer area = NπDL
Where, D = outer diameter, L = length
We are choosing 1 inch OD and 14 BWG tubes of 8 inch lengths and
calculating the
number of tubes obtained is 2360.
Taking triangular pitch of 1.25 inch and shell diameter = 1.67 m
Now, as this values of Heat transfer coefficient U becomes 560.6 W.

24. Inside and Outside Coefficient Calculations
 Nitrogen in tube side
hi = 240 btu/hr.ft2.0F
ho = hi*(id/od) = 22.16 btu/hr.ft2.0F
 Oxygen in shell side
ho = jHK/ De(cμ/k)-1/3 = 223.61 btu/ft2.hr.0F = 1267.8 W/m2.0C
 Clean overall coefficient
UC = hio*ho/ (hio+ ho) = 598.865 W/m2. 0C
 Pressure Drop
Shell Side:
Ps = f.Gs
2.Ds. (N + 1)/ (5.22*1010 De*S) = 1.5222 psi
Tube side:
Pt = f.Gt
2.Ln/ (5.22*1010*Ds) = 0.155*103 psi

25. Plant Economics
 Plant Capacity and Basis
 Rated Plant Capacity = 215 tons/day of gaseous Oxygen
99.95% purity
= 61500 tons/annum of Oxygen
 Basis: Number of working days = 25 days/month
= 300 days/annum
 Number of shifts = 3 per day
 One shift = 8 hours

26. Fixed Capital
 Land and Building= 3, 85, 50,000.00
 Plant and Machinery= 37, 58, 68,000.00
 Other Fixed Assets= 6, 15, 00,000.00
 Total Fixed Capital= 47, 59, 18,000.00

27. Working Capital
 Salary and Wages= 86, 19,000.00
 Utilities and Overheads= 29, 71, 00,000.00
 Total working capital per annum = 30, 57, 19,000.00

28. Production Cost Per Annum
 Total Working Capital per Month
Total……………… 2, 54, 76,583.00
Working capital for two months = 5, 09, 53,167.00
Total fixed capital = 47, 59, 18,000.00
Total Capital Investment = 52, 68, 71,167.00
 Production Cost per Annum
Working capital for one year = 30, 57, 19,000.00
Interest @ 13.50% on TCI = 7, 11, 27,608.00
Dep. @ 33% on plant and machinery = 12, 40, 36,440.00
Total…………………… 50, 08, 83,050.00

29. ROR and BEP
 By sale of O2- N2 = 88, 90, 00,000.00
 Profit = Receipt – Production cost = 38, 81, 16,950.00
 Profit sales ratio = Profit/ Sales*100 = 43.65%
 Rate of return = Operating profit/ TCI*100 = 72%
 Break- Even Point (BEP) = Fixed Cost/ (Fixed cost+ profit) = 45%

30. Payback Period
 Payback Period= (Project Cost+ working capital borrowing)/
Gross Profit Per year
 Payback Period= 52, 68, 71,167.00/ 38, 81, 16,950.00
 Payback Period is around 1 Year and 5 Months

31. Safety
 Thoroughly wash all oxygen fittings, valves and parts with clean
Tricolor Ethylene /carbon tetra chloride (CTC) before installation.
 Do not lubricate oxygen valves, regulators, gauges or fitting with
oil or any other substance.
 Do not fasten electric conduits to the plant or its pipelines.
 Do not experiment with liquid oxygen by putting solids or liquids
into it for watching the effect of cold liquid as it may catch fire
 Pressure gauges across pipes at regular intervals as a check against
leaks in the pipes and pressure relief valves for safety vent over
pressurized gases
 No Smoking signs
 Workers should wear clean, loose fitting, thermal‐insulated gloves;
a long‐sleeved shirt and safety shoes.
 Do not breathe cold oxygen vapor. The temperature of the vapour
rising from liquid oxygen is approximately -181 0C.

32. Conclusion
 As a part of feasibility study, we have investigated the
feasibility of constructing a new green-field 215 tpd oxygen
plant.
 As a part of study we have successfully designed major
equipment like distillation column, heat exchanger etc.
 The plant is totally feasible and gives 99.95% pure product
efficiently. The project can create employment for persons.

33. References
 Luyben, William L. "Design and Control of a Fully Heat
Integrated Pressure-Swing Azeotropic Distillation System.“
Industrial & Engineering Chemistry Research 47.8 (2008): 2681-
695. Print.
 Perry R.H. Chilton, C.H. and Kirkpatrick, S. D. (eds). (1963)
Chemical Engineers’ Handbook, 6th ed., Section 3 (New York:
McGraw-Hill Book Company, Inc.)
 C. J. Geankoplis, Transport Processes and Separation Process
Principles (Includes Unit Operations), 4th Edition, Prentice Hall,
2003.

34. THANK YOU