Page 281 - Petroleum and Gas Field Processing

11.5 LIQUID-PHASE PROCESSES

This is one of the most commonly used processes for acid gas treatment.
Chemical solvents are used in the form of aqueous solution to react
with H 2 SandCO 2 reversibly and form products which can be regenera-
ted by a change of temperature or pressure or both. Physical solvents
can be utilized to selectively remove sulfur compounds. They are
regenerated at ambient temperature by reducing the pressure. A
combination of physical and chemical solvents can be used. A comparison
of chemical solvents (amines, carbonates) and physical solvents is shown
in Table 2.

Table 2 Comparison of Chemical and Physical Processes
Chemical adsorption
Physical
Feature Amine processes Carbonate processes absorption
Absorbents MEA, DEA, K 2 CO 3 ,K 2 CO 3 þ MEA Selexol, Purisol,
DGA, MDEA K 2 CO 3 þDEA Rectisol
K 2 CO 3 þarsenic trioxide
Operating Insensitive to > 200 250–1000
pressure (psi) pressure
Operating 100–400 200–250 Ambient
temperature temperature
( F)

Recovery of Reboiled Stripping Flashing, reboiled,
absorbents stripping or stream
stripping
Utility cost High Medium Low/medium
Selectivity Selective for some May be selective Selective for H 2 S
H 2 S, CO 2 amines (MDEA)
Effect of O 2 Formation of None Sulfur
in the feed degradation precipitation
products at low
temperature
COS and CS 2 MEA: not Converted to CO 2 Removed
removal removed and H 2 S
DEA: slightly and removed
removed
DGA: removed
Operating Solution Column instability; Absorption of
problems degradation; erosion; corrosion heavy
foaming; hydrocarbons
corrosion

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