Dearator calculation

1. Deaerator Calculations
Assumption: Deaerator is a Pressure Deaerator
(max. 0.5% of Feed Water)
Guidelines for Sizing Deaerator
Maximum allowable flowrates per empty cross-sectional vessel area:
– For pressure deaerators - 18 gpm/ft2 (12.2 L/s/m2)
– For vacuum deaerators - 35 gpm/ft2 (23.8 L/s/m2)
Storage capacity with unit operating at 100% design throughput:
– For pressure deaerators - 20 minutes to the overflow level (Storage Drum)
– For vacuum deaerators - 20 minutes to the overflow level (Storage Drum)
Volume of the Deaerator
Feedwater from Deaerator = 313,500 lb/hr
Density @Inlet Water = 59.18 lb/ft
3
Volume Flow = 5297.40 ft
3
/hr 41.67 L/s
Hold-up time = 20 minutes
Volume Required = 1765.80 ft
3
50.00 m
3
Free Board = 0.75 (for vent steam disengagement)
Total Volume = 66.67 m
3
Minimum Allowable C/S area
Max allowable Vol. flux rate = 12.2 L/s/m2
Min Allowable c/s area = 3.42 m
2
(based on max allowable volume flux rate)
Diameter and Length
Diameter = 2.09 m
Length = 19.52 m
Length is very high. We want to adjust such that the L/D ratio is ≤3
For that we need to increase the diameter
Assumed Diameter = 3.05 m
Calculated Length = 9.13 m
Calculated L/D = 2.99
Calculated c/s Area = 7.31 m
2
Calculated Vol. Flux rate = 5.70 L/s/m
2
OKAY
Nominal Vol. of Deaertor = 66.64 m
3
Vent Condenser
Vented steam mass flow rate = 1600.00 lb/hr
Vented steam enthalpy = 1175.70 Btu/lb
Vent Condenser Heat Duty = 1.88 MMBtu/hr
Condenser Re-Heater
ACC Condensate Flow Rate = 137665.00 kg/h
303496.26 lb/hr
Inlet Temp. = 46.80 ⁰C
Outlet Temp. = 76.50 ⁰C
ΔT = 29.70 ⁰C
53.46 ⁰F
Avg Specific Heat = 4.21 KJ/kg.k
1.01 Btu/lb.⁰F
Heat Duty = 16.31 MMBtu/hr
Prepared by: Ankur Srivastava
Chemical Engineer
ankurcheme@gmail.com
Deaerator
39.2 psig steam @285.8°F
H1 = 1168.2 Btu/lb,
M1 = 17,400 lb/h
39.2 psig sub-cooled
water @238°F
sat. water @285.8°F
H3 = 255.1 Btu/lb, M3 =313,500 lb/hr
Vented Steam @285.8°F, 39.2 psig
H2 = 206.5 Btu/lb,
M2 = 297,700 lb/h
H4 =1175.7 Btu/lb,
M4 = 1600 lb/h