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US 6,648,944 B1Granted
Carbon dioxide removal process
AssigneeMembrane Technology and Research, Inc.
InventorsRichard W. Baker, Andre R. Da Costa, Kaaeid A. Lokhandwala
Life of this patent
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Abstract
A process and apparatus for separating carbon dioxide from gas, especially natural gas, that also contains C3+ hydrocarbons. The invention uses two or three membrane separation steps, optionally in conjunction with cooling/condensation under pressure, to yield a lighter, sweeter product natural gas stream, and/or a carbon dioxide stream of reinjection quality and/or a natural gas liquids (NGL) stream.
Claims84
A process for separating carbon dioxide from a gas stream containing carbon dioxide, methane and C3+ hydrocarbons, comprising the steps of:
- (a) providing a first membrane having a first feed side and a first permeate side and being selective for C3+ hydrocarbons over methane;
- (b) passing the gas stream, under conditions in which the gas stream has a carbon dioxide partial pressure of at least about 30 psia and a C3+ hydrocarbons combined partial pressure of at least about 30 psia, to the first membrane on the first feed side;
- (c) withdrawing from the first feed side a first residue stream depleted in C3+ hydrocarbons compared with the gas stream;
- (d) withdrawing from the first permeate side a first permeate stream enriched in C3+ hydrocarbons compared with the gas stream;
- (e) providing a second membrane having a second feed side and a second permeate side and being selective for carbon dioxide over methane;
- (f) passing the first residue stream to the second membrane and across the second feed side;
- (g) withdrawing from the second feed side a second residue stream depleted in carbon dioxide compared with the first residue stream;
- (h) withdrawing from the second permeate side a second permeate stream enriched in carbon dioxide compared with the first residue stream;
- (i) providing a third membrane having a third feed side and a third permeate side and being selective for carbon dioxide over methane;
- (j) passing the second permeate stream to the third membrane and across the third feed side;
- (k) withdrawing from the third feed side a third residue stream depleted in carbon dioxide compared with the second permeate stream;
- (l) withdrawing from the third permeate side a third permeate stream enriched in carbon dioxide compared with the second permeate stream.
9 more elements
A process for separating carbon dioxide from a gas stream containing carbon dioxide, methane and C3+ hydrocarbons, comprising the steps of:
- (a) providing a first membrane having a first feed side and a first permeate side and being selective for C3+ hydrocarbons over methane;
- (b) passing the gas stream, under conditions in which the gas stream has a carbon dioxide partial pressure of at least about 200 psia and a C3+ hydrocarbons combined partial pressure of at least about 30 psia, to the first membrane on the first feed side;
- (c) withdrawing from the first feed side a first residue stream depleted in C3+ hydrocarbons compared with the gas stream;
- (d) withdrawing from the first permeate side a first permeate stream enriched in C3+ hydrocarbons compared with the gas stream;
- (e) providing a second membrane having a second feed side and a second permeate side and being selective for carbon dioxide over methane;
- (f) passing the first residue stream to the second membrane and across the second feed side;
- (g) withdrawing from the second feed side a second residue stream depleted in carbon dioxide compared with the first residue stream;
- (h) withdrawing from the second permeate side a second permeate stream enriched in carbon dioxide compared with the first residue stream.
5 more elements
A process for separating carbon dioxide from a gas stream containing carbon dioxide, methane and C3+ hydrocarbons, comprising the steps of:
- (a) compressing the gas stream;
- (b) cooling the gas stream, thereby inducing condensation of a portion of C3+ hydrocarbons;
- (c) separating the gas stream into a C3+ hydrocarbon liquid phase and an uncondensed gas stream;
- (d) providing a first membrane having a first feed side and a first permeate side and being selective for C3+ hydrocarbons over methane;
- (e) passing the uncondensed gas stream, under conditions in which the uncondensed gas stream has a carbon dioxide partial pressure of at least about 30 psia and a C3+ hydrocarbons combined partial pressure of at least about 30 psia, to the first membrane on the first feed side;
- (f) withdrawing from the first feed side a first residue stream depleted in C3+ hydrocarbons compared with the uncondensed gas stream;
- (g) withdrawing from the first permeate side a first permeate stream enriched in C3+ hydrocarbons compared with the uncondensed gas stream;
- (h) providing a second membrane having a second feed side and a second permeate side and being selective for carbon dioxide over methane;
- (i) passing the first residue stream to the second membrane and across the second feed side;
- (j) withdrawing from the second feed side a second residue stream depleted in carbon dioxide compared with the first residue stream;
- (k) withdrawing from the second permeate side a second permeate stream enriched in carbon dioxide compared with the first residue stream;
- (l) providing a third membrane having a third feed side and a third permeate side and being selective for carbon dioxide over methane;
- (m) passing the second permeate stream to the third membrane and across the third feed side;
- (n) withdrawing from the third feed side a third residue stream depleted in carbon dioxide compared with the second permeate stream;
- (o) withdrawing from the third permeate side a third permeate stream enriched in carbon dioxide compared with the second permeate stream.
12 more elements
A process for separating carbon dioxide from a gas stream containing carbon dioxide, methane and C3+ hydrocarbons, comprising the steps of:
- (a) compressing the gas stream;
- (b) cooling the gas stream, thereby inducing condensation of a portion of C3+ hydrocarbons;
- (c) separating the gas stream into a C3+ hydrocarbon liquid phase and an uncondensed gas stream;
- (d) providing a first membrane having a first feed side and a first permeate side and being selective for C3+ hydrocarbons over methane;
- (e) passing the uncondensed gas stream, under conditions in which the uncondensed gas stream has a carbon dioxide partial pressure of at least about 200 psia and a C3+ hydrocarbons combined partial pressure of at least about 30 psia, to the first membrane on the first feed side;
- (f) withdrawing from the first feed side a first residue stream depleted in C3+ hydrocarbons compared with the uncondensed gas stream;
- (g) withdrawing from the first permeate side a first permeate stream enriched in C3+ hydrocarbons compared with the uncondensed gas stream;
- (h) providing a second membrane having a second feed side and a second permeate side and being selective for carbon dioxide over methane;
- (i) passing the first residue stream to the second membrane and across the second feed side;
- (j) withdrawing from the second feed side a second residue stream depleted in carbon dioxide compared with the first residue stream;
- (k) withdrawing from the second permeate side a second permeate stream enriched in carbon dioxide compared with the first residue stream.
8 more elements
Apparatus for separating carbon dioxide from a gas stream containing carbon dioxide, methane and C3+ hydrocarbons, comprising:
- (a) a first compressor having a compressor inlet line and a compressor outlet line;
- (b) cooling means positioned in the compressor outlet line for cooling compressed gas passing through the compressor outlet line;
- (c) a phase separator positioned in the compressor outlet line such that condensed liquids can be removed from compressed, cooled gas;
- (d) a first membrane separation unit containing a first membrane selective for C3+ hydrocarbons over methane, and having a first feed side and a first permeate side, the first membrane separation unit being connected to the phase separator such that gas can flow from the phase separator to and across the first feed side of the first membrane;
- (e) a recirculation line connecting the first permeate side and the compressor inlet line;
- (f) a second membrane separation unit containing a second membrane selective for carbon dioxide over methane, and having a second feed side and a second permeate side, the second membrane separation unit being connected to the first membrane separation unit such that gas can flow from the first feed side to and across the second feed side;
- (g) a third membrane separation unit containing a third membrane selective for carbon dioxide over methane, and having a third feed side and a third permeate side, the third membrane separation unit being connected to the second membrane separation unit such that gas can flow from the second permeate side to and across the third feed side, and from the third feed side to and across the second feed side;
- (h) a second compressor connected between the second and third membrane separation units such that gas leaving the second permeate side can be compressed before flowing to the third feed side.
5 more elements
Dependencies are inferred from the claim text.