Combined cycle gas turbine plant

Patent metadata

Field	Value
Publication number	US-10358947-B2
Application number	US-201515121587-A
Country	US
Kind code	B2
Filing date	Mar 27, 2015
Priority date	Mar 28, 2014
Publication date	Jul 23, 2019
Grant date	Jul 23, 2019

Abstract

This combined cycle gas turbine plant has a gas turbine ( 104 ) and a steam turbine ( 106 ) mounted on the same shaft. A control system is configured for switching the plant from a rated mode of operation, in which the plant is operated on gas turbine output and steam turbine output, to a reduced load mode of operation, in which the plant is operated on gas turbine output alone. The switch from the rated mode of operation to the reduced load mode of operation occurs if plant demand decreases below a predetermined threshold. The steam turbine is run under full speed no load conditions in the reduced load mode of operation, and is heated using controlled steam admission, to maintain the steam turbine in a heated ‘stand-by’ state.

First claim

The invention claimed is:

1. A combined cycle gas turbine plant of single shaft configuration, wherein the plant has a gas turbine and a steam turbine mounted on the single shaft, and wherein the plant comprises a control system configured for switching the plant from a rated mode of operation, in which the plant is operated on gas turbine output and steam turbine output, to a reduced load mode of operation, in which the plant is operated on gas turbine output alone,
the control system is configured to switch from the rated mode of operation to the reduced load mode of operation if plant demand decreases below a predetermined threshold.

2. A combined cycle gas turbine plant as set forth in claim 1 , wherein the control system is configured to run the steam turbine under full speed no load conditions in the reduced load mode of operation.

3. A combined cycle gas turbine plant as set forth in claim 1 , wherein the control system is configured to maintain the steam turbine in a heated ‘stand-by’ state under full speed no load conditions during the reduced load mode of operation.

4. A combined cycle gas turbine plant as set forth in claim 1 , wherein the control system is configured to maintain a desired or minimum temperature level inside the steam turbine when the steam turbine is operating in full speed no load conditions.

5. A combined cycle gas turbine plant as set forth in claim 2 , wherein the control system is configured to regulate the level of steam admission to the steam turbine under full speed no load conditions.

6. A combined cycle gas turbine plant as set forth in claim 1 , wherein the steam turbine is a multi stage steam turbine, and the plant includes steam control valves for controlling the admission of steam to one or more stages of the steam turbine, and further wherein the control system is configured to open the steam control valves to only a fraction of their normal operating capacity when the steam turbine is operating under full speed no load conditions.

7. A combined cycle gas turbine plant as set forth in claim 5 , wherein the control system is configured to keep the level of steam admission to the steam turbine below a threshold level, in order to prevent the production of power in the steam turbine during full speed no load conditions.

8. A combined cycle gas turbine plant as set forth in claim 5 , wherein the control system is configured to operate bypass valves to allow excess steam to bypass the steam turbine and allow the excess steam to be delivered to a condenser during regulation of steam admission to the steam turbine under full speed no load conditions.

9. A combined cycle gas turbine plant as set forth in claim 1 , wherein the control system is configured to re-switch from the reduced load mode of operation to the rated mode of operation if the plant demand increases beyond a predetermined threshold.

10. A combined cycle gas turbine plant as set forth in claim 1 , further comprising:
a supply line for supplying steam from a steam generator to the steam turbine;
a bypass line one end of which is connected to the supply line between the steam generator and the steam turbine; and
a bypass valve provided in the bypass line,
wherein the control system is configured to switch the plant from the rated mode to the reduced load mode by opening the bypass valve to make part of or all of the steam which is flowing in the supply line and which is flowing toward the steam turbine flow into the bypass line, and wherein the bypass valve is closed in the rated mode.

11. A method of controlling a combined cycle gas turbine plant of single shaft configuration, the method comprising the steps of monitoring plant demand, and switching the plant from a rated mode of operation, in which the plant is operated on gas turbine output and steam turbine output, to a reduced load mode of operation, in which the plant is operated on gas turbine output alone, if the plant demand decreases below a predetermined threshold.

12. A method according to claim 11 , the method comprising the step of running the steam turbine under full speed no load conditions in the reduced load mode of operation.

13. A method according to claim 11 , the method comprising the step of maintaining the steam turbine in a heated ‘stand-by’ state under full speed no load conditions during the reduced load mode of operation.

14. A method according to claim 11 , the method comprising the step of controlling steam admission in order to maintain a desired or predetermined minimum temperature inside the steam turbine when the steam turbine is operating in full speed no load conditions.

15. A method according to claim 11 , the method comprising the step of controlling the level of steam admission to the steam turbine below a threshold level, in order to prevent the production of power in the steam turbine during full speed no load conditions.

16. A method according to claim 11 , the combined cycle gas turbine plant comprises:
a supply line for supplying steam from a steam generator to the steam turbine;
a bypass line one end of which is connected to the supply line between the steam generator and the steam turbine; and
a bypass valve provided in the bypass line,
wherein, the method switches the plant from the rated mode to the reduced load mode by opening the bypass valve to make part of or all of the steam which is flowing in the supply line and which is flowing toward the steam turbine flow into the bypass line, and wherein the bypass valve is closed in the rated mode.

17. A control system of a combined cycle gas turbine plant of single shaft configuration, wherein the control system is configured to perform:
monitoring plant demand, and switching the plant from a rated mode of operation, in which the plant is operated on gas turbine output and steam turbine output, to a reduced load mode of operation, in which the plant is operated on gas turbine output alone, if the plant demand decreases below a predetermined threshold.

18. A system according to claim 17 , wherein the system is configured to perform running the steam turbine under full speed no load conditions in the reduced load mode of operation.

19. A system according to claim 17 , wherein the system is configured to perform maintaining the steam turbine in a heated ‘stand-by’ state under full speed no load conditions during the reduced load mode of operation.

20. A system according to claim 17 , wherein the system is configured to perform controlling steam admission in order to maintain a desired or predetermined minimum temperature inside the steam turbine when the steam turbine is operating in full speed no load conditions.

21. A system according to claim 17 , wherein the system is configured to perform controlling the level of steam admission to the steam turbine below a threshold level, in order to prevent the production of power in the steam turbine during full speed no load conditions.

22. A system according to claim 19 , wherein the system is configured to perform operating steam control valves to control steam admission to the steam turbine during full speed no load conditions.

23. A system according to claim 22 , wherein the system is configured to perform operating bypass valves to divert excess steam to a condenser during full speed no load conditions.

Assignees

• Mitsubishi Hitachi Power Sys
• Mitsubishi Hitachi Power Systems Europe Ltd

Inventors

• Yokoyama Yoshiyuki
• Martinez Jose Manuel
• RUBIO Elvio
• RATIA Pablo

Classifications

• F01K7/345

  Control or safety-means particular thereto · CPC title

• F05D2220/62

  with energy recovery turbines · CPC title

• F01K5/02 Primary

  used in regenerative installation · CPC title

• F01K23/101

  Regulating means specially adapted therefor (F01K23/105, F01K23/108 take precedence) · CPC title

• F05D2220/31

  in steam turbines · CPC title