Membrane technology for use in a power generation process

A process for controlling carbon dioxide exhaust from combustion of a gaseous fuel, comprising:

• (a) performing a combined cycle 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,
• (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,
• (iii) withdrawing from the gas turbine a first portion of the turbine exhaust stream at a pressure higher than atmospheric pressure;
• (iv) routing the first portion of the turbine exhaust stream to a boiler, thereby generating steam and creating a first boiler exhaust stream,
• (v) routing the steam to a steam turbine, thereby generating additional electrical power;
• (b) routing the first boiler 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 first boiler exhaust stream across the first feed side,
• (iii) withdrawing from the first permeate side a partially concentrated carbon dioxide first permeate stream,
• (iv) withdrawing from the first feed side a carbon dioxide-depleted first residue stream;
• (c) routing the first residue 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 the first residue 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 second residue stream that is depleted in carbon dioxide compared to the feed gas,
• (v) withdrawing from the second permeate side a second permeate stream comprising oxygen and carbon dioxide;
• (d) passing the second permeate stream back to the power generation process;
• (e) passing the second residue stream to an expander unit,
• (f) withdrawing from the gas turbine a second portion of the turbine exhaust stream at approximately atmospheric pressure;
• (g) routing the second portion of the turbine exhaust stream to the boiler, thereby generating steam and creating a second boiler exhaust stream;
• and
• (h) routing the second boiler exhaust stream back to the power generation process as a recycle gas stream.