bottom temperature is calculated by a bubble point calculation of the bottom
product at this pressure of 34 psia (see Table 8).
Enthalpy of bottom product = 230 Btu/lb as liquid.
Calculating the Reboiler Duty
This is determined from the overall tower heat balance as shown in Table 9.
Table 7 Example of internal reflux from top tray calculation
Stream
V or L
F
lb/h
Btu/lb
MMBtu/h
In
Int. reflux
V
222
x
1,162
1,162x
Product
V
222
7,506
123
0.923
Total in
7,506 + x
0.923 + 1,162x
Out
Prod
V
100
7,506
155.7
1.169
Reflux
L
222
x
222
222x
Condenser
8.125
Total out
7,506 + x
9.294 + 222x
Table 8 Example of
calculation of stripper
bottom composition
Temperature
249
F
Comp
Moles/h
Mole frac
K@ 34 psia
y = xk
H 2 S
57.5
0.0062
45.4
0.2815
Water
8646.6
0.9256
0.79
0.7312
MEA
637.5
0.0682
0.09
0.0057
Total
9,341.6
1.0000
1.0184
Table 9 Calculation of reboiler duty
Stream
V or L
F
lb/h
Btu/lb
MMBtu/h
In
Feed
V + L
204
203,988
181.7
37.06
Reboiler
By Diff
22.049
Total in
203,988
59.109
Out
O/head prod
V
100
7,506
155.7
1.169
Bottoms
L
249
196,482
230
45.179
Ht. of reaction
4.696
Condenser
8.125
Total out
203,988
59.109
Refinery Gas Treating Processes
523