Method of starting a steam turbine

Abstract

The present invention has the technical effect of reducing the start-up time associated with starting a steam turbine. Embodiments of the present invention provide a new methodology for reducing the steam-to-metal temperature mismatch present during the start-up of a steam turbine. Essentially, embodiments of the invention may raise the pressure of the steam upstream of an admission valve associated with a High Pressure (HP) section of a steam turbine. The initial high pressure of the steam may reduce the enthalpy of steam, reducing temperature of the steam admitted to the HP section.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates generally to the operation of a turbomachine, and more particularly, to a method of reducing the start-up time of a steam turbine.[0002]The start-up and loading process of some known steam turbines, typically involves a plurality phases occurring at different load ranges. One reason for this method of starting and loading the steam turbine is rotor stress control. A rotor of the steam turbine can experience an overstress event during the start-up and the initial loading phases. Overstressing can degrade the material properties of the rotor. A rotor stress control may stage the loading of the steam turbine with the goal of maintaining the rotor stress within an allowable range.[0003]Known methods of reducing the likelihood of an overstress event involve maintaining the temperature of the steam exiting a boiler, such as, but not limiting of, a Heat Recovery Steam Generator (HRSG) at a relative low temperature. For example,...

AI Technical Summary

Benefits of technology

[0006]In an embodiment of the present invention, a method of starting a powerplant machine, the method comprising: providing a steam turbine configured for converting steam to a mechanical torque; wherein the steam turbine comprises an HP section; and increasing a pressure of steam upstream of an admission valve to a pressure matching range, wherein the admission valve is located upstream of the HP section; wherein the step of increasing the pressure of the steam decreases a temperature of the steam prior to admission into the HP section.

[0007]In an alternate embodiment of the present invention, a method of starting a powerplant comprising a steam turbine, the method comprising: providing a steam turbine configured for converting steam to a mechanical torque; wherein the steam turbine comprises an HP section and a bypass system; determining whether a cold start of the steam turbine is requested; increasing a pressure the steam upstream of an admission valve to a pressure matching range, wherein the admission valve is located upstream of the HP section; determining whether the steam upstream of the admission valve is within the pressure matching range; initiating a start-up of the steam turbine if a start-up permissive is satisfied; and modulating the admission valve such that allow the steam flows into the HP section; wherein the step of increasing the pressure of the steam decreases a temperature of the steam before steams flows into the HP section.

Problems solved by technology

Overstressing can degrade the material properties of the rotor.

During a cold start of the steam turbine, this reduction in steam temperature may be insufficient to prevent an overstressing event on the turbine rotor.

Images