COMBINED-CYCLE POWER PLANT WITH EXHAUST GAS RECYCLING AND CO2 SEPARATION, AND METHOD FOR OPERATING A COMBINED CYCLE POWER PLANT

• US 20090145127A1
• Filed: 11/14/2008
• Published: 06/11/2009
• Est. Priority Date: 12/06/2007
• Status: Active Grant

• Current Assignee: General Electric Technology GmbH (GE Aerospace)
• Original Assignee: Alstom Technology Ltd. (Alstom SA)
• Inventors: Pedretti, Camille, Vollmer, Michael, Kjellberg, Tobias
• Granted Patent: US 8,424,282 B2
• Time in Patent Office: Days
• US Class Current: 60/618
• CPC Class Codes: F01K 23/103 with afterburner in exhaust boiler
• CPC Class Codes: F02C 3/34 with recycling of part of the working fluid, i.e. semi-closed cycles with combustion products in the closed part of the cycle
• CPC Class Codes: F02C 6/006 Open cycle gas-turbine in which the working fluid is expanded to a pressure below the atmospheric pressure and then compressed to atmospheric pressure
• CPC Class Codes: Y02E 20/16 Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
• CPC Class Codes: Y02E 20/32 Direct CO2 mitigation

Abstract

A combined cycle power plant (10) has a gas turbine (11), a heat recovery steam generator (16) which is connected downstream to the gas turbine (11) and delivers steam to a steam turbine (19), an exhaust gas recycling line (28) which returns some of the exhaust gases, which flow from the exhaust of the gas turbine (11) through the heat recovery steam generator (16), to the inlet of the gas turbine (11), and also a CO₂ separating plant (25) which separates from the non-returned part of the exhaust gases the CO₂ which is contained therein and delivers it to a CO₂ outlet. A reduction of the equipment cost or a flexible adaptation of the operation can be achieved by a supplementary firing (17) being associated with the heat recovery steam generator (16), which by combusting a carbonaceous fuel produces additional exhaust gases with CO₂ content and transmits them through the heat recovery steam generator (16).

Claims

1. A combined cycle power plant comprising:

a gas turbine having an inlet and an exhaust;

a steam turbine;

a heat recovery steam generator connected downstream to the gas turbine and configured and arranged to deliver steam to the steam turbine;

an exhaust gas recycling line which returns some of the exhaust gases, which flow from the gas turbine exhaust through the heat recovery steam generator, to the gas turbine inlet;

a CO₂ separating plant having a CO₂ outlet and having a inlet in fluid communication with the gas turbine exhaust, the CO₂ separating plant configured and arranged to separate CO₂ from a non-returned part of the gas turbine exhaust gases and delivers said CO₂ to the CO₂ outlet; and

a supplementary firing device associated with the heat recovery steam generator, the supplementary firing device configured and arranged to combust a carbonaceous fuel to produce additional exhaust gases with CO₂ content, and to transmit the additional exhaust gases through the heat recovery steam generator.

2. The combined cycle power plant as claimed in claim 1, wherein the supplementary firing device is integrated in the heat recovery steam generator.

3. The combined cycle power plant as claimed in claim 1, further comprising:

a first heat exchanger configured and arranged to exchange heat with exhaust gases after discharging from the heat recovery steam generator and before distribution to the exhaust gas recycling line and to the CO₂ separating plant.

4. The combined cycle power plant as claimed in claim 3, further comprising:

an exhaust gas bypass branching off between the heat recovery steam generator and the first heat exchanger.

5. The combined cycle power plant as claimed in claim 3, further comprising:

a second heat exchanger arranged in the exhaust gas recycling line.

6. The combined cycle power plant as claimed in claim 1, further comprising:

a compressor for the exhaust gases arranged upstream of the CO₂ separating plant.

7. The combined cycle power plant as claimed in claim 1, further comprising:

a steam extraction line configured and arranged to guide steam from the steam turbine or from the heat recovery steam generator to the CO₂ separating plant.

8. The combined cycle power plant as claimed in claim 1, further comprising:

a first adjusting device, in the exhaust gas recycling line, configured and arranged to adjust the recirculation rate.

9. The combined cycle power plant as claimed in claim 8, wherein the first adjusting device comprises a control valve.

10. The combined cycle power plant as claimed in claim 8, further comprising:

a device configured and arranged to control the supplementary firing device.

11. A method for operating a combined cycle power plant, the method comprising:

providing a combined cycle power plant as claimed in claim 1; and

maintaining constant the portion of the returned exhaust gases, the output of the supplementary firing device, or both.

12. The method as claimed in claim 11, wherein maintaining comprises maintaining the portion of the returned exhaust gases at zero.

13. A method for operating a combined cycle power plant, the method comprising:

providing a combined cycle power plant as claimed in claim 1; and

varying the portion of the returned exhaust gases, the output of the supplementary firing device, or both.

14. The method as claimed in claim 13, wherein varying comprises varying the portion of the returned exhaust gases, the output of the supplementary firing, or both, oppositely.

15. The method as claimed in claim 13, wherein, for temporary increase of the output of the combined cycle power plant, varying comprises:

reducing the portion of the returned exhaust gases;

or

increasing the output of the supplementary firing device;

or

both.