Page 301 - Petroleum and Gas Field Processing

Table 6 Gas Permeation Rates
Spiral wound
Gas membrane
100.0
H 2
He 15.0
H 2 O 12.0
H 2 S 10.0
CO 2 6.0
O 2 1.0
Ar —
CO 0.3
CH 4 0.2
N 2 0.18
C 2 H 6 0.1

Figure 20 Two-stage membrane process.

H 2 S and CO 2 will permeate much faster than other hydrocarbons.
However, the permeate gas will also contain hydrogen and water vapor if
they were present in the natural gas feed. It is possible to enhance the mass
transfer rates by either blowing an inert gas in the permeate side or using
amines on the permeate side to chemically react with the acid gas
permeated and removed from the surface of the membrane. Several
membrane modules may be connected in series and parallel arrangements
to meet specific requirements. In Figure 20, a two-stage system is shown.
If a gas stream contains a high acid content (50%), it is possible to reduce

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