Single shaft combined cycle plant and method for operating the same

• US 6,223,518 B1
• Filed: 12/21/1998
• Issued: 05/01/2001
• Est. Priority Date: 06/26/1996
• Status: Expired due to Term

• Current Assignee: mitsubishi hitachi power systems, ltd. (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Hashimoto, Tsuguo, Urushidani, Haruo, Wada, Norihisa
• Primary Examiner(s): Kim, Ted
• Application Number:
  US09/194,723
• Time in Patent Office: 862 Days
• Field of Search: 60/39.02, 60/39.141, 60/39.142, 60/39.182, 122/7 R, 122/7 B
• US Class Current: 60/783
• CPC Class Codes: F01K 13/025 Cooling the interior by injection during idling or stand-by
• CPC Class Codes: F01K 23/16 all the engines being turbines F01K23/14 takes precedence
• CPC Class Codes: Y02E 20/16 Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]

Abstract

A system configuration and operating method for a single shaft combined cycle plant includes a gas turbine, an exhaust heat recovery boiler for generating steam using exhaust heat discharged from the gas turbine, and a steam turbine driven by steam generated from the exhaust heat recovery boiler. Rotors of the gas turbine and rotors of the steam turbine are coupled. The steam turbine includes a high pressure turbine being supplied with and driven by high pressure steam generated at a superheater of the exhaust heat recovery boiler and a reheating turbine supplied with and driven by steam that passes through the high pressure turbine and is reheated by a reheater of the exhaust heat recovery boiler. The gas turbine operates independently and a regulated amount of cooling steam is supplied to the steam turbine in order to prevent superheating due to windage loss of the steam turbine rotating in an unventilated state. A bypass path is provided in parallel with the exhaust heat recovery boiler as a path through which cooling steam flows in order to further raise the cooling effect, and each turbine and a condenser are made to communicate so as to make pressure within the turbines low.

Claims

1. A single shaft combined cycle plant, comprising:

a gas turbine;

an exhaust heat recovery boiler for generating steam using exhaust heat discharged from the gas turbine; and

a steam turbine driven by steam generated from the exhaust heat recovery boiler;

rotors of the gas turbine and rotors of the steam turbine being coupled, and the steam turbine comprising;

a high pressure turbine being driven by high pressure steam generated at a superheater of the exhaust heat recovery boiler supplied via a first steam path, and a reheating turbine supplied with and driven by steam that passes through the high pressure turbine, and then through a second steam path back to the exhaust heat recovery boiler where it is reheated by a reheater of the exhaust heat recovery boiler, with the reheated steam then passing through a third steam path,

wherein;

first discharging means, arranged upstream of a check valve provided at the second steam path, discharges steam within the high pressure turbine to outside of the high pressure turbine;

separately provided steam supplying means supplies steam to the reheating turbine;

second discharging means discharges steam, that flows through the third steam path after being supplied from the steam supplying means via the reheating turbine, to outside of the third steam path, and

the second discharging means is positioned downstream from a reheated steam valve provided at the third path for regulating the amount of steam going to the reheating turbine.

2. A method of activating a single shaft combined cycle plant, comprising a gas turbine, an exhaust heat recovery boiler for generating steam using exhaust heat discharged from the gas turbine and a steam turbine driven by steam generated from the exhaust heat recovery boiler, rotors of the gas turbine and rotors of the steam turbine being coupled, and the steam turbine comprising:

a high pressure turbine being driven by high pressure steam generated at a superheater of the exhaust heat recovery boiler supplied via a first steam path, a reheating turbine supplied with and driven by steam that passes through the high pressure turbine, and then through a second steam path back to the exhaust heat recovery boiler where it is reheated by a reheater of the exhaust heat recovery boiler, with the reheated steam then passing through a third steam path, and a low pressure turbine supplied with steam via the reheating turbine, said activating method comprising;

a first step of activating the gas turbine and causing the rotational speed thereof to rise;

a second step of supplying gas turbine exhaust gas to the exhaust heat recovery boiler and causing steam to be generated at the exhaust heat recovery boiler;

a third step of discharging steam remaining within the high pressure turbine using a first discharging means, arranged upstream of a check valve provided at the second steam path, for discharging steam within the high pressure turbine to outside of the high pressure turbine, supplying steam to the reheating turbine and the low pressure turbine using separately provided steam supplying means, and discharging steam passing through the reheating turbine and flowing down the third steam path using a second discharging means, arranged at the third steam path, for discharging steam to outside of the third steam path;

a fourth step of supplying steam generated by the superheater to the reheating turbine via the reheater after desired conditions for the steam generated from the exhaust heat recovery boiler are reached; and

a fifth step of obtaining an output from the steam turbine.