Cryogenic air separation method and system
The present invention relates to a cryogenic air separation process that provides high pressure oxygen for an oxy-fired combustion of a fuel (e.g., a carbonaceous fuel). The air separation process can be directly integrated into a closed cycle power production process utilizing a working fluid, such as CO 2 . Beneficially, the air separation process can eliminate the need for inter-cooling between air compression stages and rather provide for recycling the adiabatic heat of compression into a process step in a further methods wherein an additional heat supply is beneficial.
1. An air separation process for providing a purified O 2 stream and a heated working fluid stream comprising:
pressurizing air in a first compressor to a pressure of about 3.5 bar (0.35 MPa) to about 12 bar (1.2 MPa);
passing at least a portion of the pressurized air from the first compressor to a second compressor where the air is further pressurized to a pressure of up to about 150 bar (15 MPa), wherein the first compressor comprises at least one portion operating adiabatically with no intermediate cooling of the air and with a pressure ratio of 2.5 or greater, and wherein the second compressor is a multistage compressor with at least one stage operating adiabatically with no intermediate cooling at a pressure ratio of about 2.5 or greater, the first compressor and the second compressor thus forming adiabatically compressed air;
transferring heat from the adiabatically compressed air from each of the compressors to a stream of a CO 2 working fluid from an oxy-fuel power generation system such that the stream of the CO 2 working fluid is heated and the adiabatically compressed air is cooled; and
feeding the cooled, compressed air into a cryogenic oxygen plant having a pumped liquid oxygen cycle to produce an oxygen stream with a pressure of about 20 bar (2 MPa) to about 500 bar (50 MPa) and a purity of about 90% molar or greater.
2. The air separation process of claim 1 , wherein the produced oxygen stream has a purity of about 97% molar or greater.
3. The air separation process of claim 1 , wherein said transferring step comprises passing the adiabatically compressed air through one or more heat exchangers where the stream of the CO 2 working fluid is heated and the adiabatically compressed air is cooled.
4. The air separation process of claim 3 , wherein the heat exchanger transfers heat from the adiabatically compressed air to the stream of a CO 2 working fluid in the temperature range of about 80° C. to about 500° C.
5. The air separation process of claim 1 , wherein said transferring step comprises contacting the adiabatically compressed air with an intermediate circulating heat transfer fluid that transfers heat from the adiabatically compressed air to the stream of the CO 2 working fluid.
6. The air separation process of claim 5 , wherein the intermediate circulating heat transfer fluid transfers heat from the adiabatically compressed air to the stream of the CO 2 working fluid in the temperature range of about 80° C. to about 500° C.
7. The air separation process of claim 1 , wherein the produced oxygen stream is at a pressure of about 100 bar (10 MPa) to about 500 bar (50 MPa).
8. The air separation process of claim 1 , comprising mixing at least a portion of the produced oxygen stream with CO 2 from the stream of the CO 2 working fluid to produce a mixed oxygen and CO 2 stream.
9. The air separation process of claim 8 , wherein the mixed oxygen and CO 2 stream has an oxygen concentration of about 20% to about 50% molar.
10. The air separation process of claim 8 , wherein the produced oxygen stream is at a pressure of about 20 bar (2 MPa) to about 100 bar (10 MPa), and the process further comprises compressing the mixed oxygen and CO 2 stream to a pressure of up to about 500 bar (50 MPa).
11. The air separation process of claim 8 , further comprising passing at least a portion of the mixed oxygen and CO 2 stream to a combustor in the oxy-fuel power generation system.
12. The air separation process of claim 1 , further comprising passing a least a portion of the produced oxygen stream and at least a portion of the heated stream of the CO 2 working fluid to a combustor in the oxy-fuel power generation system.