Gas turbine exhaust recirculation method and apparatus

• US 6,202,400 B1
• Filed: 03/09/2000
• Issued: 03/20/2001
• Est. Priority Date: 07/14/1993
• Status: Expired due to Term

• Current Assignee: mitsubishi hitachi power systems, ltd. (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Komatsu, Hideaki, Takeda, Yasushi, Sasaki, Toshihiko, Hoizumi, Shinichi, Utamura, Motoaki, Sasada, Tetsuo, Ikeguchi, Takashi, Suzumura, Takeshi, Sugita, Shigehisa, Kirikami, Seiichi
• Primary Examiner(s): Casaregola, Louis J.
• Application Number:
  US09/521,609
• Time in Patent Office: 376 Days
• Field of Search: 60/39.03, 60/39.182, 60/39.24, 60/39.52, 60/39.281
• US Class Current: 60/773
• CPC Class Codes: F01K 23/101 Regulating means specially adapted therefor F01K23/105, F01K23/108 take precedence
• CPC Class Codes: F02C 1/007 combination of cycles
• CPC Class Codes: F02C 3/34 with recycling of part of the working fluid, i.e. semi-closed cycles with combustion products in the closed part of the cycle
• CPC Class Codes: F02C 6/18 using the waste heat of gas-turbine plants outside the plants themselves, e.g. gas-turbine power heat plants using waste heat as source of energy for refrigeration plants F25B27/02; using the waste heat of a gasturbine for steam generation or in a steam cycle see F01K23/10
• CPC Class Codes: F02C 7/10 by means of regenerative heat-exchangers
• CPC Class Codes: F02C 9/16 Control of working fluid flow F02C9/48 takes precedence; control of air-intake flow F02C7/057
• CPC Class Codes: F02C 9/20 by throttling; by adjusting vanes
• CPC Class Codes: F05D 2220/72 a steam turbine
• CPC Class Codes: Y02E 20/16 Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]

Abstract

To improve the thermal efficiency when an exhaust heat recovery type combined cycle plant having a gas turbine and a steam turbine in combination is operated at a partial load, the gas turbine exhaust is recirculated and returned to the compressor, and the combustion temperature is prevented from being lowered at the partial load. Preferably, the temperature is maintained constant. In this way, the thermal efficiency during operation at partial load can be improved.

Claims

1. A controller for controlling an exhaust gas recirculation rate from a gas turbine to a compressor and for controlling a fuel amount to be charged into a combustor in a thermal power plant, comprising:

means for deriving an initial exhaust gas recirculation rate signal from a received load demand signal;

means for comparing the load demand signal with a load signal to generate a fuel amount target signal;

means for comparing the fuel amount target signal with a fuel flow rate signal and correcting in dependence on a determined combustion temperature determined on the basis of a temperature of the gas turbine exhaust gas and an outlet pressure of the compressor to determine the fuel amount to be charged into the combustor; and

means for correcting the initial exhaust gas recirculation rate signal in dependence on the determined combustion temperature to derive a recirculation rate control signal.

2. A controller for controlling an exhaust gas recirculation rate from a gas turbine to a compressor and a fuel amount to be charged into a combustor in a thermal power plant, comprising:

a function generator for deriving an initial exhaust gas recirculation rate signal from a received load demand signal;

a subtractor for comparing the load demand signal with a load signal to obtain a deviation between the load demand signal and the load signal;

an adjustor for generating a fuel amount target signal;

a subtractor for comparing the fuel amount target signal with a fuel flow rate signal and correcting in dependence on a determined combustion temperature determined on the basis of a temperature of the gas turbine exhaust gas and an outlet pressure of the compressor to determine the fuel amount to be charged into the combustor; and

a subtractor for correcting the initial exhaust gas recirculation rate signal in dependence on the determined combustion temperature to derive a recirculation rate control signal.

3. A method for controlling an exhaust gas recirculation rate from a gas turbine to a compressor and a fuel amount to be charged into a combustor in a thermal power plant, comprising:

deriving an initial exhaust gas recirculation rate signal from a received load demand signal;

comparing the load demand signal with a load signal to generate a fuel amount target signal;

comparing the fuel amount target signal with a fuel flow rate signal and correcting in dependence on a determined combustion temperature determined on the basis of a temperature of the gas turbine exhaust gas and an outlet pressure of the compressor to determine the fuel amount to be charged into the combustor; and

correcting the initial exhaust gas recirculation rate signal in dependence on the determined combustion temperature to derive a recirculation rate control signal.