METHOD FOR OPERATING A COMBINED CYCLE POWER PLANT AND PLANT TO CARRY OUT SUCH A METHOD

• US 20130239573A1
• Filed: 03/19/2013
• Published: 09/19/2013
• Est. Priority Date: 03/19/2012
• Status: Active Grant

• Current Assignee: Ansaldo Energia IP UK Limited (Ansaldo Energia SPA)
• Original Assignee: Alstom Limited (Alstom SA)
• Inventors: Lilley, Darrel Shayne, Franitza, Karsten, Nemet, Anton, Brighenti, Andrea
• Granted Patent: US 9,394,808 B2
• Time in Patent Office: Days
• US Class Current: 60/643
• CPC Class Codes: F01K 21/00 Steam engine plants not otherwise provided for
• CPC Class Codes: F01K 23/101 Regulating means specially adapted therefor F01K23/105, F01K23/108 take precedence
• CPC Class Codes: F02C 3/30 Adding water, steam or other fluids for influencing combustion, e.g. to obtain cleaner exhaust gases F02C7/141, F02C7/30, F01D21/00, F01K21/04, F23D11/10 take precedence
• CPC Class Codes: F02C 6/18 using the waste heat of gas-turbine plants outside the plants themselves, e.g. gas-turbine power heat plants using waste heat as source of energy for refrigeration plants F25B27/02; using the waste heat of a gasturbine for steam generation or in a steam cycle see F01K23/10
• CPC Class Codes: F02C 9/20 by throttling; by adjusting vanes
• CPC Class Codes: F05D 2270/083 by monitoring combustion conditions
• CPC Class Codes: F05D 2270/0831 indirectly, at the exhaust
• CPC Class Codes: F05D 2270/303 Temperature
• CPC Class Codes: Y02E 20/14 Combined heat and power generation [CHP]
• CPC Class Codes: Y02E 20/16 Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]

Abstract

Disclosed is a method for operating a gas turbine (11) comprising a compressor (14), which is equipped with variable inlet guide vanes (13) and receives at its inlet an inlet air flow, which has passed a temperature-affecting air inlet system (12a), a combustor (15, 15′) and a turbine (16, 16′). In a closed loop control scheme, a control variable indicative of the turbine outlet temperature (TAT2) is generated, and the air inlet system (12a) and/or the variable inlet guide vanes (13) are controlled in accordance with said control variable such that the turbine outlet temperature (TAT2) is kept at or above a desired setting value (TAT2_min).

Claims

1. Method for operating a combined cycle power plant comprising, a gas turbine (11) with an inlet temperature affecting air inlet system (12a-c) for adjusting the temperature of inlet air, a compressor (14) downstream of the inlet temperature affecting air inlet system (12a-c), for increasing the pressure of the air, and which is equipped with variable inlet guide vanes (13) for adjusting the inlet mass flow, at least one combustor (15, 15′

) downstream of the compressor for combustion of fuel with compressed air from the compressor (14), and at least one turbine (16, 16′

) downstream of the combustor (15, 15′

) for expanding hot combustion gases thereby generating mechanical power;

a HRSG (18) downstream of the gas turbine (11) for generating live steam;

a steam turbine (19) for expanding the live steam thereby generating mechanical power; and

a control system (22), characterized in that, in a closed loop control scheme, a control variable indicative of the live steam temperature (T_steam) is generated, and that the inlet temperature affecting air inlet system (12a-c) and/or the variable inlet guide vanes (13) are controlled in accordance with said control variable such that the live steam temperature (T_steam) is kept at or above a desired target steam temperature (T_steam,t).

2. Method according to claim 1, characterized in that the live steam temperature (T_steam) is directly measured and the measured temperature is used as the control variable.

3. Method according to claim 1, characterized in that the turbine outlet temperature (TAT2) is used as variable indicative of the live steam temperature (T_steam), and in that the turbine outlet temperature (TAT2) is used as the control variable.

4. Method according to claim 3, characterized in that the turbine outlet temperature (TAT2) is directly measured.

5. Method according to claim 3, characterized in that the turbine outlet temperature (TAT2) is calculated from an on-line heat balance calculation.

6. Method according to claim 3, characterized in that emissions, at the outlet of the gas turbine (11) are measured and used as the control variable.

7. Method according to claim 1, characterized in that a temperature is measured at other parts of the gas turbine (11), especially at the last stage vanes of the turbine (16, 16′

), and this measured temperature is used as a control variable.

8. Method according to claim 1, characterized in that the inlet air is heated in the inlet temperature affecting air inlet system (12a) until the live steam temperature (T_steam) is at or above the target steam temperature (T_steam,t).

9. Method according to claim 8, characterized in that compressed air from a rear stage of the compressor is used to heat up the inlet air in the inlet temperature affecting air inlet system (12a).

10. Method according to claim 8, characterized in that part of flue gases are recirculated and admixed to the inlet air in the inlet temperature affecting air inlet system (12d) to heat up the inlet air.

11. Method according to claim 1, characterized in that during part load operation a cooling air mass flow of the gas turbine (11) is reduced and/or a re-cooling temperature of a cooling air cooler is increased to increase the live steam temperature (T_steam).

12. Method according to claim 1, characterized in that the intake air is cooled in the inlet temperature-affecting inlet system (12b) to reduce the live steam temperature (T_steam) to the target steam temperature (T_steam,t).

13. Method according to claim 1, characterized in that the output power of the plant is controlled by controlling the position of the variable inlet guide vanes (13) and the turbine inlet temperature, and in that the live steam temperature (T_steam) is controlled by adjusting the inlet temperature in the inlet temperature affecting air inlet system (12c).

14. Method according to claim 1, characterized in that the live steam temperature (T_steam) is determined as function of a temperature of a steam turbine rotor and/or a steam turbine stator part.

15. Combined cycle power plant comprising, a gas turbine (11) with an inlet temperature affecting air inlet system (12a-c) for adjusting the temperature of inlet air, a compressor (14) downstream of the inlet temperature affecting air inlet system (12a-c), for increasing the pressure of the air, and which is equipped with variable inlet guide vanes (13) for adjusting the inlet mass flow, at least one combustor (15, 15′

) downstream of the compressor for combustion fuel with compressed air from the compressor, at least one turbine (16, 16′

) downstream of the combustor for expanding hot combustion gases thereby generating mechanical power;

a HRSG (18) downstream of the gas turbine (11) for generating live steam;

a steam turbine (18) for expanding the live steam thereby generating mechanical power; and

a control system (22) characterized in that, the control system (22) comprises a closed loop control scheme, which is configured to generate a control variable indicative of the live steam temperature (T_steam1), and to control the inlet temperature affecting air inlet system (12a-c) and/or the variable inlet guide vanes (13) in accordance with said control variable such that during operation of the combined cycle power plant the live steam temperature (T_steam) is kept at or above a desired target steam temperature (T_steam,t).