Combined cycle power plant having condensate recirculation pump using venturi effect

Patent metadata

Field	Value
Publication number	US-11041409-B2
Application number	US-201616094505-A
Country	US
Kind code	B2
Filing date	May 23, 2016
Priority date	May 23, 2016
Publication date	Jun 22, 2021
Grant date	Jun 22, 2021

Abstract

A combined cycle power plant and a method for operating a combined cycle power plant are presented. The combined cycle power plant includes a condensate recirculation pump to recirculate flow medium from downstream of a condensate preheater system to upstream of the condensate preheater system. An adequate flow temperature at the upstream of the condensate preheater system may be maintained to prevent acid gas dew point corrosion. The condensate recirculation pump may use a venturi effect to convert a high pressure of a condensate supplied by a condensate extraction pump to a suction pressure for the recirculation.

First claim

What is claimed is:

1. A combined cycle power plant comprising:
a gas turbine that is configured to generate power output and produce exhaust gas;
a heat recovery steam generator that is configured to receive the exhaust gas from the gas turbine and produce steam by extracting energy from the exhaust gas;
a steam turbine that is configured to receive the steam produced in the heat recovery steam generator and generate power output; and
a condenser positioned at an exit of the steam turbine to receive condensate from the steam turbine,
wherein the heat recovery steam generator comprises:
a condensate extraction pump that is configured to extract the condensate from the condenser;
a condensate preheater system arranged downstream of the condensate extraction pump that is configured to preheat the condensate; and
a condensate recirculation pump that is configured to recirculate flow medium from downstream of the condensate preheater system to upstream of the condensate preheater system to maintain a temperature of the condensate at the upstream of the condensate preheater system at a predetermined temperature,

wherein the condensate recirculation pump comprises a suction zone formed by a venturi effect for the recirculation,
wherein the condensate recirculation pump comprises a condensate inlet operatively connected to the condensate extraction pump, wherein the condensate is pumped into the condensate recirculation pump through the condensate inlet, and
wherein a motive fluid nozzle is arranged at the condensate inlet such that after condensate enters the condensate recirculation pump through condensate inlet it flows through the motive fluid nozzle,
wherein the condensate recirculation pump comprises a converging nozzle, wherein the converging nozzle is configured to create the suction zone by converting pressure energy of the condensate to kinetic energy, and
wherein the condensate recirculation pump comprises a suction inlet operatively connected to and downstream of the condensate preheater system, wherein the flow medium from downstream of the condensate preheater system is drawn into the condensate recirculation pump through the suction inlet and mixed with the condensate to form a mixed flow.

2. The combined cycle power plant as claimed in claim 1 , wherein the condensate recirculation pump comprises a diverging nozzle arranged downstream of the converging nozzle, wherein the diverging nozzle is configured to increase a pressure of the mixed flow.

3. The combined cycle power plant as claimed in claim 2 , wherein the condensate recirculation pump comprises an outlet located at an exit of the diverging nozzle, wherein the outlet is operatively connected to a point upstream of the condensate preheater system, wherein the mixed flow is discharged from the condensate recirculation pump into the condensate preheater system through the outlet at the predetermined temperature.

4. The combined cycle power plant as claimed in claim 2 , wherein the condensate recirculation pump comprises a chamber arranged between the converging nozzle and the diverging nozzle.

5. The combined cycle power plant as claimed in claim 1 , wherein the flow medium from downstream of the condensate preheater system comprises water.

6. The combined cycle power plant as claimed in claim 1 , wherein the flow medium from downstream of the condensate preheater system comprises steam.

7. The combined cycle power plant as claimed in claim 1 , further comprising a flow control valve operatively connected to the condensate recirculation pump.

8. The method as claimed in claim 1 , wherein the method comprising recirculating water from downstream of the condensate preheater system.

9. The method as claimed in claim 1 , wherein the method comprising recirculating steam from downstream of the condensate preheater system.

10. A method for operating a combined cycle power plant, wherein the combined cycle power plant comprises a gas turbine, a heat recovery steam generator, a steam turbine and a condenser, the method comprising:
operating the gas turbine to generate power output and produce exhaust gas;
producing steam in the heat recovery steam generator by extracting energy from the exhaust gas;
operating the steam turbine to generate power output from the steam produced in the heat recovery steam generator; and
positioning the condenser at an exit of the steam turbine so that condensate is directly received from the steam turbine to the condenser,
wherein the heat recovery steam generator comprises a condensate exaction pump, a condensate preheater system arranged downstream of the condensate exaction pump, and a condensate recirculation pump,
wherein the method further comprises:
extracting the condensate from the condenser by the condensate exaction pump;
preheating the condensate in the condensate preheater system;
recirculating flow medium from downstream of the condensate preheater system to upstream of the condensate preheater system by the condensate recirculation pump, wherein the condensate recirculation pump comprises a suction zone formed by a venturi effect for the recirculation; and
maintaining a temperature of the condensate at the upstream of the condensate preheater system at a predetermined temperature by mixing the flow medium from downstream of the condensate preheater system with the condensate extracted from the condenser,

wherein the condensate recirculation pump comprises a condensate inlet operatively connected to the condensate extraction pump, wherein the method comprising pumping the condensate into the condensate recirculation pump through the condensate inlet by the condensate extraction pump,
wherein the condensate recirculation pump comprises a converging nozzle, wherein the method comprising creating the suction zone by converting pressure energy of the condensate to kinetic energy when flowing through the converging nozzle,
wherein the condensate recirculation pump comprises a suction inlet operatively connected to and downstream of the condensate preheater system, wherein the method comprising drawing the flow medium from downstream of the condensate preheater system into the condensate recirculation pump through the suction inlet and mixing with the condensate to form a mixed flow.

11. The method as claimed in claim 10 , wherein the condensate recirculation pump comprises a diverging nozzle arranged downstream of the converging nozzle, wherein the method comprising increasing a pressure of the mixed flow when flowing through the diverging nozzle.

12. The method as claimed in claim 11 , wherein the condensate recirculation pump comprises an outlet at an exit of the diverging nozzle, wherein the outlet is operatively connected to a point upstream of the condensate preheater system, wherein the method comprising discharging the mixed flow from the condensate recirculation pump into the condensate preheater system through the outlet at the predetermined temperature.

Assignees

• Siemens Energy Inc

Inventors

• Elfadli Mohamed

Classifications

• F22B37/025

  Devices and methods for diminishing corrosion, e.g. by preventing cooling beneath the dew point · CPC title

• F01K23/10 Primary

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

• F01K9/02

  Arrangements or modifications of condensate or air pumps · CPC title

• Y02E20/16

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