Power plant with integrated fuel gas preheating

Patent metadata

Field	Value
Publication number	US-10006313-B2
Application number	US-201414317723-A
Country	US
Kind code	B2
Filing date	Jun 27, 2014
Priority date	Jul 8, 2013
Publication date	Jun 26, 2018
Grant date	Jun 26, 2018

Abstract

The invention refers to a CCPP comprising a gas turbine, a water steam cycle with a steam turbine and a HRSG with at least two pressure levels, and a fuel preheater for preheating the fuel of the gas turbine. The fuel preheater includes a first heat exchanger for preheating the fuel to a first elevated temperature, which is connected to a feed water line from a pressure level of the HRSG, which is below the highest HRSG pressure level, and a second heat exchanger for further preheating the fuel gas to a second elevated temperature, which is connected to the high pressure feed water with the highest pressure level of the HRSG. The disclosure further refers to a method for operating a CCPP with such a fuel preheater.

First claim

The invention claimed is:

1. A combined cycle power plant (CCPP) comprising:
a gas turbine, a water steam cycle with a steam turbine and a heat recovery steam generator (HRSG), and a fuel preheater for preheating fuel for the gas turbine, wherein the fuel preheater comprises:
a first heat exchanger for preheating the fuel to a first temperature, by extracting heat from water at a first pressure from a first feed water system of the HRSG;
a second heat exchanger for further preheating the fuel to a second temperature, by extracting heat from water at a second pressure from a second feed water system of the HRSG, wherein the second temperature is higher than the first temperature and the second pressure is higher than the first pressure;
a return water feed line connected between the second heat exchanger and the first feed water system for feeding return water from the second heat exchanger to the first feed water system; and
a control valve of the second heat exchanger in the return water feed line for controlling water flow through the second heat exchanger.

2. The CCPP according to claim 1 ,
wherein the first heat exchanger is connected to a feed water line of the first feed water system, and in that the second heat exchanger is connected to a feed water line of the second feed water system.

3. The CCPP according to claim 1
wherein the first heat exchanger is connected to an exit of an economizer of the first feed water system.

4. The CCPP according to claim 1 ,
wherein the second heat exchanger is connected to an exit of an economizer of the second feed water system.

5. The CCPP according to claim 1 ,
wherein the return water feed line of the second heat exchanger is connected to a pressure drum of the first feed water system.

6. A method of operating a combined cycle power plant (CCPP) having a gas turbine, a water steam cycle with a steam turbine and a heat recovery steam generator (HRSG), and a fuel preheater for preheating fuel for the gas turbine, the method comprising:
preheating the fuel using a first heat exchanger to a first temperature by extracting heat from water at a first pressure from a first feed water system of the HRSG;
further preheating the fuel to a second temperature in a second heat exchanger by extracting heat from water at a second pressure from a second feed water system of the HRSG, wherein the second temperature is higher than the first temperature and the second pressure is higher than the first pressure;
feeding return water from the second heat exchanger to the first feed water system using a return water feed line connected between the second heat exchanger and the first feed water system; and
controlling water flow through the second heat exchanger using a control valve of the second heat exchanger in the return water feed line.

7. The method of operating a CCPP according to claim 6 ,
wherein the HRSG is operated with three pressure levels, and feed water from an economizer of the first feed water system is fed to the first heat exchanger for preheating the fuel, and in that feed water from an economizer of the second feed water system is fed into the second heat exchanger for preheating the fuel.

8. The method of operating a CCPP according to claim 6 , comprising using the control valve of the second heat exchanger to control a water level of a drum of the first feed water system into which the return water from the second heat exchanger is returned.

9. The method of operating a CCPP according to claim 6 , comprising controlling a water level of a drum of the first feed water system using a first feed water control valve, and using the control valve of the second heat exchanger to control the second temperature by controlling the water flow through the second heat exchanger.

Assignees

• Alstom Technology Ltd
• General Electric Technology Gmbh

Inventors

• Drouvot Paul
• Droux François
• Berg Klara

Classifications

• F02C7/224 Primary

  Heating fuel before feeding to the burner · CPC title

• F01K17/025 Primary

  in combination with at least one gas turbine, e.g. a combustion gas turbine · CPC title

• Y02E20/16

  Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT] · CPC title

• F01K23/10

  with exhaust fluid of one cycle heating the fluid in another cycle (F01K17/025 takes precedence) · CPC title

• F02C6/18

  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 title