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
Mass Balance
Energy Balance
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
F = W + S + L2 ----------- (1)
F Xf = W Xw + S Xs + X1 L2 ----------- (2)
Hence from the graph no. of theoretical plates = 17
- 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
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
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
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, ΔT1 = 1.491
Now, taking overall HTC as 100 btu/hr ft2 0F = 567 W/m2.0C
Q = U A ΔT
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.
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
Plant Economics
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
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
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
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
ROR and BEP
By sale of O2- N2 = Rs 88, 90, 00,000.00
Profit = Receipt – Production cost = Rs 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%
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
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.
Read more about "" from Industrial Guide - Click here
[ads id="ads1"]
Thanks for reading -
Naitik Patel
Industrial Guide
