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62 Gas PuniJication
’ GAS OUT
COUNTER CURRENT
CONTACTOR
COCURRENT
CONTACTOR
GAS IN+
’ LIQUID OUT
Figure 2-13. Combined cocurrent-countercurrent absorption system. (Isom and
Rogem, 1994)
PURIFIED GAS
FROM STRIPPING
COLUMN
PARTlALLY PURIFIED GAS
HEAT-EXCHANGER SEPARATOR ABSORBER COLUMN
ABSORBER
Figure 2-14. Flow system employing heat exchanger for initial gas contact.
DESIGN DATA
Acid Gas-Amine Solution Equilibria
The relationship between the concentration of acid gas in an amine solution and its partial
pressure in the gas phase at equilibrium is probably the most important item of data required
for the design of treating plants. The relationship may be referred to as gas solubility or
vapor-liquid equilibrium (VLE). The concentration in the liquid phase is normally reported
as moles acid gas per mole of amine (moldmole or mol/mol). Since this value varies with
the partial pressure (or more precisely with the fugacity) of the acid gas, temperature, type of
amine, amine concentration in the solution, and nature and concentration of other compo-
nents in the solution, the amount of data required to cover all possible conditions is enor-
