초록 ▼

Power plants and process for lowering CO2 emissions generally includes extracting a portion of the recirculated CO2-rich flue gas mid-way through the compression pathway of a gas turbine and removing the CO2 in a separation unit. The remaining portion of the CO2 rich flue gas (i.e., the portion of t

Power plants and process for lowering CO2 emissions generally includes extracting a portion of the recirculated CO2-rich flue gas mid-way through the compression pathway of a gas turbine and removing the CO2 in a separation unit. The remaining portion of the CO2 rich flue gas (i.e., the portion of the recirculated flue gas that was not fed to the separation unit) is mixed with fresh air coming from an additional compressor-expander and then fed back to the compression pathway. As a result, flue gas recirculation increases the CO2 concentration within the working fluid, leading to an additional increase in CO2 partial pressure. As the concentration and partial pressure of CO2 is increased, a lower energy penalty is observed to remove the CO2. Moreover, a reduced volume is fed to the CO2 separation unit during operation. Consequently, the size of the separation equipment can be reduced as well as the energy required for the separation process.

대표청구항 ▼

What is claimed is: 1. A method of generating energy in a power plant including a gas turbine, the method comprising: generating a flue gas from a gas turbine, wherein the gas turbine comprises a compression section having at least two stages comprising a low-pressure compressor and a high-pressure

What is claimed is: 1. A method of generating energy in a power plant including a gas turbine, the method comprising: generating a flue gas from a gas turbine, wherein the gas turbine comprises a compression section having at least two stages comprising a low-pressure compressor and a high-pressure compressor, a combustion section fluidly coupled to the compression section, and an expander fluidly coupled to the combustion section; recirculating the flue gas to the low-pressure compressor; diverting a portion of the recirculated flue gas to a carbon dioxide (CO2) separator and a remaining portion to the high-pressure compressor; separating CO2 from the diverted portion in the CO2 separator to generate a CO2 lean gas; and expanding the CO2 lean gas coming from the CO2 separator in a separate expander. 2. The method of claim 1, further comprising mixing fresh air with the remaining portion of the recirculated flue gas prior to diverting to the high pressure-compressor. 3. The method of claim 1, wherein diverting to the CO2 separator comprises cooling the flue gas portion in a heat exchanger prior to entering the CO2 separator. 4. The method of claim 1, wherein the remaining portion of the recirculated gas flows through an intercooler before entering the high-pressure compressor. 5. The method of claim 1, wherein the portion of the flue gas to the CO2 separator is about 10 to about 70 percent of the recirculated flue gas. 6. The method of claim 1, further comprising humidifying the remaining portion of the recirculated gas prior to flowing to the high-pressure compressor. 7. The method of claim 1, wherein the separate expander is mechanically linked to an oxidant compressor. 8. The method of claim 1, further comprising preheating the CO2 lean gas coming from the CO2 separator in a gas/gas heat exchanger prior to entering the separate expander. 9. The method of claim 1, further comprising humidifying the CO2 lean gas; and feeding the humidified CO2 lean gas to the separate expander, wherein the separate expander is an expander of a compressor/expander, wherein the compressor/expander is power independent. 10. The method of claim 1, wherein separating the CO2 from the diverted portion in the CO2 separator removes greater than 50 percent of the CO2. 11. The method of claim 1, wherein all of the flue gas from the gas turbine exits the power plant via the CO2 separator. 12. The method of claim 1, further comprising bleeding off a portion or all of the flue gas for transient operations or mixing with air prior to entry into said low-pressure compressor. 13. The method of claim 1, wherein the flue gas exits the low-pressure compressor at a pressure of 2 to 20 bars. 14. The method of claim 1, further comprising mixing fresh air with the remaining portion of the recirculated flue gas and cooling the mixture prior to diverting to the high pressure-compressor. 15. The method of claim 1, wherein the flue gas is cooled in a heat exchanger prior to recirculation to the low pressure-compressor such that a part of its water content is condensed and separated. 16. A power plant configured for lowering CO2 emissions, the power plant comprising: a gas turbine comprising a compression section having at least two stages, the at least two compression stages comprising a low-pressure compressor fluidly coupled to a high-pressure compressor; a combustor having a first inlet adapted for receiving compressed gas, a second inlet adapted for receiving fuel and an outlet adapted for discharging hot flue gas; and a main expander section having an inlet adapted for receiving the hot flue gas and an outlet, the outlet of the main expander fluidly coupled to the low-pressure compressor; and a CO2 separator fluidly coupled to the low-pressure compressor for receiving a portion of the flue gas from the low-pressure compressor and provide a CO2 lean gas that is then fed to an additional expander, wherein a remaining portion of the flue gas is provided directly to the high-pressure compressor via the low-pressure compressor being fluidly coupled to the high-pressure compressor. 17. The power plant of claim 16, further comprising a heat exchanger intermediate the CO2 separator and the low-pressure compressor for treating the portion of the flue gas from the low-pressure compressor. 18. The power plant of claim 16, further comprising a device arranged for generating steam at an outlet of the expander and fluidly coupled to the low-pressure compressor. 19. The power plant of claim 16, further comprising an intercooler for fluidly receiving and cooling the recirculated flue gas prior to introduction into the high-pressure compressor. 20. The power plant of claim 16, further comprising a heat recovery and steam generator at the outlet of the main gas turbine expander for treating the hot flue gases prior to recirculating the flue gas to the low-pressure compressor. 21. The power plant of claim 16, further comprising linking the gas turbine with at least one additional gas turbine. 22. A power plant configured for lowering CO2 emissions, the power plant comprising: a gas turbine comprising a compression section having at least two stages, the at least two compression stages comprising a low-pressure compressor fluidly coupled to a high-pressure compressor; a combustor having a first inlet for receiving compressed gas from the high-pressure compressor, a second inlet for receiving fuel and an outlet for discharging hot flue gas; and a main expander section having an inlet for receiving the discharged hot flue gas and an outlet, the outlet of the main expander fluidly coupled to the low-pressure compressor; and a CO2 separator fluidly coupled to the low-pressure compressor for treating a portion of the flue gas and provide a CO2 lean gas that is then fed to a humidifier downstream from the CO2 separator to produce a humidified flue gas and recuperated, wherein the humidified flue gas drives a second expander/compressor unit having an outlet in fluid communication with the high-pressure compressor, wherein a remaining portion of the flue gas is provided directly to the high-pressure compressor via the low-pressure compressor being fluidly coupled to the high-pressure compressor. 23. The power plant of claim 22, further comprising a heat exchanger intermediate the outlet of the second expander/compressor and the high-pressure compressor. 24. The power plant of claim 22, further comprising a heat exchanger disposed intermediate the low-pressure compressor and the CO2 separator. 25. The power plant of claim 22, wherein the second expander/compressor comprises a low-pressure compressor, a high-pressure compressor and an intercooler intermediate the low-pressure compressor and the high-pressure compressor. 26. The power plant of claim 22, further comprising a heat exchanger at the outlet of the main gas turbine expander for treating the hot flue gas and the humidified flue gas prior to recirculating the flue gas to the low-pressure compressor and the second expander/compressor unit. 27. The power plant of claim 22, further comprising linking the gas turbine with at least one additional gas turbine. 28. The power plant of claim 22, further comprising an intercooler for fluidly receiving and cooling the remaining portion of the recirculated flue gas prior to introduction into the high-pressure compressor.