H 2 S in product gas ¼ 0:1 grain=100 scf
¼ 0:126 mol=day
¼ 0:00521 mol=h
H 2 S absorbed in amine ¼ 212:5 À 0:00521
¼ 212:49 mol=h
The amine ratio is 3.0 mol amine per mole H 2 S.
Moles amine circulating = 637.47 mol/h = 38,949 lb/h (mol wt. MEA = 61.1),
or for 20 % wt solution = 194,747 lb/h, made up of 155,798 lb water and 38,949
amine.
lb/gal MEA = 8.45
lb/gal water = 8.328
MEA gals/h = 4,609
Water gals/h = 18,708
Amine solution circulation rate = 23,317 gals/h (volumes are additive in
these solutions).
Calculating the Number of Trays and the Overall Dimensions
of the Contactor
The number of theoretical stages required in the contactor will be calculated using
the equation
N ¼
Log 1=q A À 1
ð
Þ
ð
Þ
Log A
ð
Þ
À 1
(10)
where:
N = number of theoretical trays
q = mole H 2 S in lean gas/mole H 2 S in feed gas
A = the absorption factor L/V ∙ K
“q” in this case ¼
moles H 2 S in lean gas
moles H 2 S in feed gas
¼
0:00521
212:5
¼ 2:45 Â 10
À5
Refinery Gas Treating Processes
515