APPARATUS FOR STARTING A STEAM TURBINE AGAINST RATED PRESSURE

• US 20100162721A1
• Filed: 12/31/2008
• Published: 07/01/2010
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: GE Infrastructure Technology, LLC (General Electric Company)
• Original Assignee: General Electric Company
• Inventors: Kudlacik, Edward L., Welch, David E., Mondello, James C., Sathyanarayana, Dileep
• Granted Patent: US 8,176,723 B2
• Time in Patent Office: Days
• US Class Current: 60/778
• CPC Class Codes: F01D 17/145 by means of valves, e.g. for steam turbines valves in general F16K
• CPC Class Codes: F01D 19/00 Starting of machines or engines; Regulating, controlling, or safety means in connection therewith warming-up before starting F01D25/10; turning or inching gear F01D25/34
• CPC Class Codes: F01K 13/02 Controlling, e.g. stopping or starting
• CPC Class Codes: F01K 23/101 Regulating means specially adapted therefor F01K23/105, F01K23/108 take precedence
• CPC Class Codes: F05D 2220/31 in steam turbines
• CPC Class Codes: F05D 2260/85 Starting
• CPC Class Codes: Y02E 20/16 Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]

Abstract

An external steam turbine main steam startup control valve bypass loop is provided to facilitate a full pressure combined cycle rapid response/fast start powerplant. The main steam startup bypass control loop particularly includes a main steam startup bypass control valve, which allows for the implementation of high efficiency, low pressure drop main steam control valve that otherwise would not be able to handle the severe throttling duty during a full pressure steam turbine startup and enhances the controllability of the steam turbine allowing for the high fidelity controls necessary to minimize steam turbine rotor stresses.

Claims

1. A combined-cycle power generation system comprising:

an electrical generator, a gas turbine coupled to the electrical generator, a steam turbine coupled to the electrical generator, a heat recovery steam generator adapted for supplying steam to the steam turbine, at least one attemperator coupled to the heat recovery steam generator, a main steam control valve adapted for controlling admission of steam to the steam turbine during normal operation of the steam turbine; and

a main steam startup bypass control loop, adapted for controlling admission of steam to the steam turbine during fast startup.

2. The combined-cycle power generation system according to claim 1, the main steam startup control bypass loop comprising:

a main steam startup control bypass valve; and

a main steam piping connected from upstream of the main steam control valve to an inlet of the main steam startup bypass control valve and steam piping connected from an outlet of the main steam bypass control valve to downstream of the main steam control valve.

3. The combined-cycle power generation system according to claim 2, wherein the main steam piping from the outlet of the main steam bypass control valve is configured for at least one of single entrance and dual entrance to the steam turbine.

4. The combined-cycle power generation system according to claim 2, further comprising:

a main steam bypass stop valve upsteam from the main steam startup control valve in the startup control bypass loop.

5. The combined-cycle power generation system according to claim 2, further comprises:

an upstream strainer from the main steam startup control bypass valve.

6. The combined-cycle power generation system according to claim 4, wherein the main steam bypass stop valve fails closed on loss of hydraulic control.

7. The combined-cycle power generation system according to claim 6, wherein the main steam bypass stop valve fails closed on loss of hydraulic control, wherein the main steam bypass stop valve fails closed due to spring action.

8. The combined-cycle power generation system according to claim 2, wherein the main steam bypass control valve fails closed on loss of hydraulic control.

9. The combined-cycle power generation system according to claim 8, wherein the main steam bypass control valve fails closed due to spring action.

10. The combined-cycle power generation system according to claim 8, wherein the mains steam bypass control valve comprises:

at least one of a linear flow characteristic and an equal percentage flow characteristic over a full range of operation

11. An apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant including a gas turbine, a heat recovery steam generator adapted for supplying steam to the steam turbine, at least one attemperator adapted to controlling temperature of steam to a steam turbine, and at least one bypass path to a condenser adapted for controlling temperature of the steam to the steam turbine, the apparatus comprising:

a startup bypass control loop including a main steam bypass stop valve and a main steam bypass control valve.

12. The apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant according to claim 11, the main steam bypass control valve comprising:

a linear flow characteristic at a fast startup steam flow.

13. The apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant according to claim 12, the main steam bypass control valve further comprising:

a hydraulic control from a turbine controller.

14. The apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant according to claim 13, the main steam bypass control valve further comprising:

spring shutting on loss of hydraulic control.

15. The apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant according to claim 12, the main steam bypass stop valve further comprising:

a hydraulic control from a turbine controller.

16. The apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant according to claim 15, the main steam bypass stop valve further comprising:

spring shutting on loss of hydraulic control.

17. The apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant according to claim 11, a startup bypass control loop further comprising;

a strainer upstream from the main steam startup control bypass valve.

18. The apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant according to claim 11, further comprising:

a main steam piping connected from upstream of the main steam control valve to an inlet of the main steam startup control bypass valve and steam piping connected from an outlet of the main steam startup control bypass valve to downstream of the main steam control valve.

19. The apparatus adapted for controlling steam flow to a steam turbine in a fast startup of a combined cycle plant according to claim 18, wherein the main steam piping from the outlet of the main steam control bypass valve is configured for at least one of a single entrance and a dual entrance to the steam turbine.

20. A method for starting a combined cycle power generation system, the system including a gas turbine and a steam turbine, the combined cycle system further including a heat recovery steam generator that receives exhaust heat from said gas turbine and is equipped with attemperators at the discharge terminals of the high pressure superheater and reheater and is connected to the steam turbine, a condenser connected to the steam turbine, and bypass paths from the heat recovery steam generator to the condenser and from the high pressure steam piping to the hot reheat steam piping, and the main steam piping including a main steam control valve and a main steam bypass control valve, the method comprising:

loading the gas turbine at up to it'"'"'s maximum rate;

maintaining steam temperature of steam supplied to the steam turbine at substantially constant temperature from initial steam admission into the steam turbine until all steam generated by the heat recovery steam generator with the gas turbine operating at up to maximum load is being admitted to the steam turbine through the main steam startup bypass valves;

modulating the flow of steam through the bypass paths so as to control the high pressure steam pressure, reheat pressure and low pressure steam pressure from the heat recovery steam generator and provide alternate paths for the steam while the main steam startup bypass control valves are modulated during loading; and

shifting control of the steam admission to the steam turbine from the main steam bypass control valve to the main steam control valve; and

after all steam flow is admitted to the steam turbine, raising the steam temperature at a rate compatible with allowable steam turbine stress and differential expansion to achieve normal steam turbine output and efficiency.