Method for operating a power plant installation

Abstract

The invention relates to a method for operating a power plant, wherein in partial load operation the increase of temperature results at the outlet of the high-pressure turbine section as a consequence of a throttling by means of the intermediate pressure valve.

Claims

1. A method for operating a power plant installation comprising a steam turbine which is subdivided into a high-pressure turbine section, an intermediate-pressure turbine section and a low-pressure turbine section, and in which a reheater unit is arranged between the high-pressure turbine section and the intermediate-pressure turbine section, the method comprising: operating the power plant installation during a transition from a rated load to partial load, expanding steam in the high-pressure turbine section; delivering expanded steam to the reheater unit; and raising a temperature at an inlet to the reheater unit by throttling a valve arranged upstream of the intermediate-pressure turbine section and downstream of the high-pressure turbine section.

2. The method as claimed in claim 1, wherein the throttling is carried out such that expansion in the high-pressure turbine section is reduced.

3. The method as claimed in claim 1, wherein the throttling is chosen such that a magnitude of a temperature drop downstream of the reheater unit is halved when compared to a temperature drop that would occur if the valve were not throttled.

4. The method as claimed in claim 1, further comprising raising a temperature at an outlet of the high-pressure turbine section by an amount, and raising a temperature at an outlet of the reheater unit by the same amount.

5. The method as claimed in claim 1, wherein the partial load operation is carried out between 20% and 40% of a rated load.

6. A power plant operated according to the method as claimed in claim 1.

7. The power plant as claimed in claim 6, wherein the power plant is configured as a steam power plant.

8. The power plant as claimed in claim 6, wherein the power plant comprises an exhaust gas boiler that generates steam for the steam turbine.

9. The method as claimed in claim 1, wherein the partial load operation is carried out at 25% of a rated load.

10. A method for operating a power plant installation comprising a steam turbine which is subdivided into a high pressure turbine section, an intermediate pressure turbine section and a low pressure turbine section, and in which a reheater unit is arranged between the high pressure turbine section and the intermediate pressure turbine section, the method comprising: operating the power plant installation at partial load, while: delivering cold reheat steam from the high pressure turbine section, through a throttle valve, and to the reheater unit; reheating the cold reheat steam to form hot reheat steam in the reheater unit; delivering the hot reheat steam from the reheater unit to the intermediate pressure turbine section; wherein during a transition from a rated load to the partial load a temperature drop of steam entering the intermediate pressure turbine section occurs; the method further comprising reducing an amount of the temperature drop by increasing a temperature of the cold reheat steam exiting the high pressure turbine section when compared to a temperature of the cold reheat steam exiting the high pressure turbine section at the rated load.

11. The method as claimed in claim 10, further comprising increasing the temperature of the cold reheat steam exiting the high pressure turbine section by throttling the throttle valve.

12. The method as claimed in claim 10, wherein the intermediate pressure section is one component and the reheater unit comprises at least one component, the method further comprising: distributing the temperature drop among the reheater unit and the intermediate pressure section so that each component experiences a respective per-component temperature drop, and selecting the respective per-component temperature drop for a respective component selected based on a parameter of the respective component.

13. The method as claimed in claim 12, wherein the parameter of the respective component comprises at least one of a thickness of the respective component and a geometry of the respective component.

14. The method as claimed in claim 12, wherein the reheater unit comprises a cold reheater component and a hot reheater component.

15. The method as claimed in claim 10 wherein the intermediate pressure section is one component and the reheater unit comprises at least one component, the method further comprising: distributing the temperature drop among the reheater unit and the intermediate pressure section so that each component experiences a respective per-component temperature drop, and selecting the respective per-component temperature drops to be equal to each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Details of embodiments of the invention are described with reference to the sole FIGURE, which shows a schematic of the power plant disclosed herein.

DETAILED DESCRIPTION OF INVENTION

(2) An exemplary embodiment of the invention will now be described below in more detail. Conventional power plants 10 comprise a steam turbine 12 which can be subdivided into a high-pressure turbine section 14, an intermediate-pressure turbine section 16 and a low-pressure turbine section 18, and a reheater unit 30 having a first reheater 32 and a second reheater 34, wherein the reheater unit 30 is arranged between the high-pressure turbine section 14 and the intermediate-pressure turbine section 16. Upstream of the high-pressure turbine section 14, a boiler 40 generates hot fresh steam 42 which flows through the high-pressure turbine section 14 after which it is called cold reheat steam 44, and is then reheated in the reheater unit 30 to become hot reheat steam 46 before flowing into the intermediate-pressure turbine section 16 and then through the low-pressure turbine section 18. After the low-pressure turbine section 18, the steam condenses to water and is fed by means of pumps back to the boiler 40 where it is again converted into steam. Such a power plant installation is designed for a rated power and should be operated as permanently as possible at this rated power level. In partial load operation, meaning that the power plant installation is operated not at 100% of the rated load but for example at 25% of the rated load, the temperatures in the reheater unit 30 change. The temperature drops. A control valve 50 is arranged upstream of the intermediate-pressure turbine section 16 and is throttled during partial load operation such that the temperature rises at the 52 inlet to the reheater unit 30. This means that a controller 54 controls the intermediate-pressure valve 50 such that the steam flow is throttled such that the expansion in the high-pressure turbine section 14 is reduced. This reduction raises the temperature at the outlet 56 from the high-pressure turbine section 14.