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US 7,604,681 B2Granted
Three-stage membrane gas separation process
AssigneesLummus Technology Inc., Membrane Technology and Research, Inc.
InventorsMichael G. Malsam, Kaaeid A. Lokhandwala
Life of this patent
Estimating the term…
Abstract
A process for removing carbon dioxide or nitrogen from gas, especially natural gas. The process uses three membrane separation stages without compression between the second and third stages.
Claims33
A process for separating carbon dioxide from methane in a gas stream comprising the steps of:
- (a) providing a first membrane having a first feed side and a first permeate side and being selective for carbon dioxide over methane;
- (b) passing the gas stream as a first feed stream at a first pressure of at least about 400 psia across the first feed side;
- (c) withdrawing from the first feed side a first residue stream depleted in carbon dioxide compared with the gas stream;
- (d) withdrawing from the first permeate side a first permeate stream enriched in carbon dioxide compared with the gas stream;
- (e) compressing the first permeate stream;
- (f) providing a second membrane having a second feed side and a second permeate side and being selective for carbon dioxide over methane;
- (g) passing the compressed first permeate stream as a second feed stream across the second feed side;
- (h) withdrawing from the second feed side a second residue stream depleted in carbon dioxide compared with the second feed stream;
- (i) withdrawing from the second permeate side a second permeate stream enriched in carbon dioxide compared with the second feed stream;
- (j) recirculating the second residue stream to step (b);
- (k) providing a third membrane having a third feed side and a third permeate side and being selective for carbon dioxide over methane;
- (l) passing the second permeate stream as a third feed stream without compression across the third feed side;
- (m) withdrawing from the third feed side a third residue stream depleted in carbon dioxide compared with the third feed stream;
- (n) withdrawing from the third permeate side a third permeate stream enriched in carbon dioxide compared with the third feed stream;
- (o) recirculating the third residue stream to step (e).
12 more elements
The process of claim one wherein the first, second and third membranes have a selectivity for carbon dioxide over methane in the range 5-30.
A process for separating nitrogen from methane in a gas stream comprising the steps of:
- (a) providing a first membrane having a first feed side and a first permeate side and being selective for nitrogen over methane;
- (b) passing the gas stream as a first feed stream at a first pressure of at least about 400 psia across the first feed side;
- (c) withdrawing from the first feed side a first residue stream depleted in nitrogen compared with the gas stream;
- (d) withdrawing from the first permeate side a first permeate stream enriched in nitrogen compared with the gas stream;
- (e) compressing the first permeate stream;
- (f) providing a second membrane having a second feed side and a second permeate side and being selective for nitrogen over methane;
- (g) passing the compressed first permeate stream as a second feed stream across the second feed side;
- (h) withdrawing from the second feed side a second residue stream depleted in nitrogen compared with the second feed stream;
- (i) withdrawing from the second permeate side a second permeate stream enriched in nitrogen compared with the second feed stream;
- (j) recirculating the second residue stream to step (b);
- (k) providing a third membrane having a third feed side and a third permeate side and being selective for nitrogen over methane;
- (l) passing the second permeate stream as a third feed stream without compression across the third feed side;
- (m) withdrawing from the third feed side a third residue stream depleted in nitrogen compared with the third feed stream;
- (n) withdrawing from the third permeate side a third permeate stream enriched in nitrogen compared with the third feed stream;
- (o) recirculating the third residue stream to step (e).
12 more elements
Dependencies are inferred from the claim text.