Patent ID: 7429287
Filing Date: 2008-09-30
Classification: B01D,C10L,Y02C

Abstract:
1. A method for sweetening a raw natural gas feed stream by removing undesired contaminants selected from acid gases, non-combustibles, or mixtures thereof to produce a sweetened natural gas stream, the method comprising: (a) contacting the raw natural gas feed stream with a first stage separation membrane to obtain a sweetened natural gas product stream rich in methane and reduced in contaminant content relative to the raw natural gas stream, and a first stage permeate gas stream comprised of methane and having a contaminant content which is greater than that of the raw natural gas stream; (b) compressing the first stage permeate gas stream to provide a compressed first stage permeate gas stream; (c) contacting the compressed first stage permeate gas stream with a second stage separation membrane to obtain a recycle gas stream and a second stage permeate gas stream; (d) directing the recycle gas stream to be combined with the raw natural gas feed stream at any point prior to being contacted with the first stage separation membrane; and (e) directing the second stage permeate gas stream to be used as a fuel gas for a gas turbine that combusts the second stage permeate gas stream and thereby generates mechanical work.