Integrated LNG gasification and power production cycle
The present disclosure provides an integrated power generating system and method and liquefied natural gas (LNG) vaporization system and method. More particularly, heat from a CO 2 containing stream from the power generating system and method can be used to heat the LNG for re-gasification as gaseous CO 2 from CO 2 containing stream is liquefied. The liquefied CO 2 can be captured and/or recycled back to a combustor in the power generating system and method.
1. A method of generating power, the method comprising:
combusting a carbonaceous fuel in a combustor at a combustion pressure in the presence of oxygen and CO 2 to produce a combined combustion product stream at the combustion pressure;
expanding the combined combustion product stream in a turbine to generate power and form a turbine exhaust stream comprising CO 2 , the turbine exhaust stream comprising CO 2 having a pressure that is less than the combustion pressure;
passing the turbine exhaust stream comprising CO 2 through a first heat exchanger so as to transfer heat from the turbine exhaust stream comprising CO 2 to a CO 2 recycle stream and form a cooled turbine exhaust stream comprising CO 2 ;
separating CO 2 from the cooled turbine exhaust stream comprising CO 2 ;
passing a liquefied natural gas (LNG) stream and the CO 2 separated from the cooled turbine exhaust stream comprising CO 2 through a second heat exchanger so as to cool and liquefy the CO 2 separated from the cooled turbine exhaust stream comprising CO 2 and so as to heat and vaporize the LNG stream to form a liquefied CO 2 stream and a gaseous natural gas (NG) stream, wherein the pressure of the CO 2 separated from the cooled turbine exhaust stream comprising CO 2 entering the second heat exchanger is less than the pressure of the turbine exhaust stream comprising CO 2 exiting the turbine;
passing both a fraction of the gaseous NG stream and the cooled turbine exhaust stream comprising CO 2 through a third heat exchanger, the cooled turbine exhaust stream comprising CO 2 passing through the third heat exchanger after passing through the first heat exchanger and prior to passing through the second heat exchanger;
pressurizing the liquefied CO 2 stream to form the CO 2 recycle stream; and
passing the CO 2 recycle stream to the combustor.
2. The method of claim 1 , wherein the CO 2 recycle stream is passed to the combustor at a pressure of about 150 bar (15 MPa) to about 400 bar (40 MPa).
3. The method of claim 1 , wherein the combusting is carried out at a temperature of about 500° C. to about 1600° C.
4. The method of claim 1 , wherein a ratio of the combustion pressure to the pressure of the turbine exhaust stream comprising CO 2 is about 4 to about 12.
5. The method claim 1 , wherein the LNG stream passed into the second heat exchanger is at a pressure of about 50 bar (5 MPa) to about 90 bar (9 MPa).
6. The method of claim 1 , wherein a second fraction of the gaseous NG stream formed by the second heat exchanger is withdrawn and input to the LNG stream passed into the second heat exchanger.
7. The method of claim 6 , wherein the second fraction of the gaseous NG stream input to the LNG stream is sufficient to raise a temperature of the LNG stream to above the CO 2 solidification temperature and within about 20° C. of the CO 2 solidification temperature.
8. The method of claim 1 , wherein the CO 2 separated from the cooled turbine exhaust stream comprising CO 2 is cooled in the second heat exchanger to a temperature that is above the CO 2 solidification temperature and is within about 30° C. of the CO 2 solidification temperature.
9. The method of claim 1 , wherein pressurizing the liquefied CO 2 stream to form the CO 2 recycle stream comprises passing the liquefied CO 2 stream through a liquid pump.
10. The method of claim 9 , wherein the turbine produces shaft power, and wherein the shaft power is used to drive the liquid pump.
11. The method of claim 9 , wherein the CO 2 recycle stream exiting the liquid pump is heated.
12. The method of claim 11 , wherein the heating comprises passing the CO 2 recycle stream through the second heat exchanger.
13. The method of claim 1 , wherein the carbonaceous fuel combusted in the combustor comprises at least a portion of the gaseous NG stream.
14. The method of claim 13 , wherein the LNG stream is passed through a first pump, and a portion of the LNG stream is passed through a second pump after passing through the first pump and is then heated by passing through the second heat exchanger.
15. The method of claim 14 , wherein a second gaseous NG stream formed by passing the portion of the LNG stream through the second heat exchanger is further heated utilizing heat of compression from an air separation plant.
16. The method of claim 1 , wherein the passing through the third heat exchanger further cools the cooled turbine exhaust stream comprising CO 2 to a temperature of about 0° C. to about 10° C.
17. The method of claim 16 , wherein the cooled turbine exhaust stream comprising CO 2 passing through the third heat exchanger is cooled against the fraction of the gaseous NG stream.
18. The method of claim 16 , further comprising passing the cooled turbine exhaust stream comprising CO 2 through one or both of a liquid water separator and a desiccant drier so as to provide the CO 2 separated from the cooled turbine exhaust stream comprising CO 2 as a dried CO 2 stream.
19. The method of claim 1 , wherein a portion of the CO 2 recycle stream passing to the combustor is heated utilizing heat of compression from an air separation plant.
20. The method of claim 1 , wherein the CO 2 recycle stream passing to the combustor is separated into a first fraction and a second fraction.
21. The method of claim 20 , wherein the first fraction of the CO 2 recycle stream passing to the combustor is input directly to the combustor.
22. The method of claim 20 , wherein the second fraction of the CO 2 recycle stream passing to the combustor is combined with the oxygen to form an oxidant stream that is input to the combustor.