Patent ID: 8220248

Claim:
A process for controlling carbon dioxide exhaust from combustion of a gaseous fuel, comprising: (a) performing a power generation process, comprising (i) performing a combustion step by combusting a mixture comprising a gaseous fuel and an oxygen-containing gas, thereby generating a combustor exhaust stream comprising carbon dioxide and nitrogen, and (ii) routing the combustor exhaust stream as at least a portion of a working gas stream to a gas turbine, thereby generating electrical power and creating a turbine exhaust stream; (b) routing a first portion of the turbine exhaust stream back to the power generation process as a recycle gas stream; (c) routing a second portion of the turbine exhaust stream to a membrane-based carbon dioxide capture step, wherein the capture step comprises (i) providing a first membrane having a first feed side and a first permeate side, and being selectively permeable to carbon dioxide over nitrogen and to carbon dioxide over oxygen, (ii) passing the second portion of the turbine exhaust stream across the first feed side, (iii) withdrawing from the first permeate side a partially concentrated carbon dioxide product stream, (iv) withdrawing from the first feed side a carbon dioxide-depleted stream (d) routing the carbon dioxide-depleted stream to a sweep-based membrane separation step, wherein the sweep-based membrane separation step comprises (i) providing a second membrane having a second feed side and a second permeate side, and being selectively permeable to carbon dioxide over nitrogen and to carbon dioxide over oxygen, (ii) passing a feed gas comprising the carbon dioxide-depleted stream across the second feed side, (iii) passing air, oxygen-enriched air, or oxygen as a sweep stream across the second permeate side, (iv) withdrawing from the second feed side a stream that is depleted in carbon dioxide compared to the feed gas, (v) withdrawing from the second permeate side a permeate stream comprising oxygen and carbon dioxide; and (e) passing the permeate stream back to the power generation process.