US 4,047,005 A · Combined cycle electric power plant with a steam turbine having a throttle pressure limiting control

Abstract

A combined cycle electric power plant includes two gas turbines, a steam turbine, and a digital control system with an analog or manual backup. Each of the gas turbines has an exhaust heat recovery steam generator connected to a common header from which the steam is supplied by one or both of the steam generators for operating the steam turbine. The digital/analog system includes a steam throttle pressure limiting control, which maintains a minimum steam throttle pressure as a function of steam flow to limit the maximum steam velocity through the steam generators, and reduce the probability of water carryover into the steam turbine. In response to a reduction in the number of steam generators in service, the pressure flow relationship is transferred from one characterization to another, and during such transfer, the analog system operates the steam turbine control valves to limit the rate of steam pressure decay as a function of steam flow.

Drawings

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Drawings

Claims18

Dependent claims

A combined cycle electric power plant comprising:

a. gas turbine means;
b. means for generating steam at a lower distinct rate and a higher distinct rate in response to heat energy from the gas turbine means;
c. a steam turbine driven by steam supplied to it from the steam generating means;
d. means for generating electric power under the driving power of said turbines;
e. means for controlling the operation of said turbines including a steam turbine control system;
f. said steam turbine control system including
f1. means to generate a first representation of actual steam pressure to the turbine,
f2. means to generate a second representation of steam flow,
f3. means to generate a third representation of a predetermined minimum steam pressure,
f4. means governed by the first representation and the third representation to restrict the flow of steam to the turbine only at times when the third representation exceeds the first representation while the steam generating means is generating steam at the higher of the two distinct rates, and
f5. means responsive to the steam generating means changing to the lower distinct rate to restrict the flow of steam to the turbine at times when the second representation exceeds the first representation.

8 more elements

A combined cycle electric power plant, comprising:

a. at least one steam turbine;
b. at least two gas turbines;
c. means for generating steam in response to heat energy from each of the gas turbines to drive the steam turbine;
d. means for generating electric power under the driving power of said turbines;
e. means for controlling the operation of said turbines and the steam generating means;
f. said controlling means including a steam turbine control system having an automatic control and a backup control;
g. said steam turbine control system including means for controlling the steam pressure to at least equal a predetermined minimum under both the automatic and the back-up control;
h. said back-up control including
h1. means to generate a first representation of actual steam pressure to the turbine,
h2. means to generate a second representation of a predetermined minimum sliding pressure characterized as a function of steam flow for steam generated by heat from each of the gas turbines,
h3. means responsive to the reduction to a predetermined minimum of the generation of the steam by one of the gas turbines, with the second representation for steam generation by the other gas turbine,
h4. means governed by the comparison means to generate a valve closing representation at times when the second representation for the other pas turbine exceeds the first representation;
and
i. valve means operative to move toward the closed position to restrict the flow of steam of the steam turbine in response to the valve closing representation.

11 more elements

A combined cycle electric power plant, comprising

a. at least one steam turbine;
b. at least two gas turbines;
c. steam generating means associated with the gas turbines for generating steam in response to the heat energy from the gas turbines;
d. means for generating electric power under the driving power of said turbines;
e. means for controlling the operation of the turbines and the steam generating means, said controlling means having a steam turbine control system;
f. said steam turbine control system including;
g. a means to generate a first representation of steam flow generated by the heat of one gas turbine;
h. a means to generate a second representation of steam flow generated by the heat of the other gas turbine;
i. means to generate a third representation of the actual pressure of the steam to the turbine;
j. means governed by the first and second representation to generate a fourth representation which varies as a function of flow according to a predetermined characterization;
k. means responsive to a predetermined lack of steam generation for the steam turbine by one of the gas turbines to compare the third representation and the fourth representation;
and
l. means governed by the comparison means to restrict the flow of steam to the steam turbine at times when the third representation is less than the fourth representation.

10 more elements

A control system of the sliding pressure type for a steam turbine adopted to be powered by steam generated by heat from either one or both of two sources, comprising:

a. valve means to control the flow of steam to the turbine,
b. first means to generate a first representation of actual steam pressure to the turbine,
c. second means governed by the first representation while the steam turbine is powered by steam from both of the sources to control the valve means toward a closed position only at times when the first representation is less than a predetermined minimum, and
d. third means to generate a second representation which varies as a function of steam flow according to a predetermined characterization,
e. fourth means responsive to a change in the effective generation of steam by both of the sources to the effective generation of steam by either one of the sources only to operate the valve means toward a closed position at times when the first representation is less than the second representation.

2 more elements

Dependencies are inferred from the claim text.

Description22,000 words

Summary1,070 words

#Reference is made to the following patent applications:

#1. Serial No. 399,790, filed on Sept. 21, 1973 by L. F. Martz, R. W. Kiscaden and R. Uram, entitled "An Improved Gas Turbine And Steam Turbine Combined Cycle Electric Power Generating Plant Having A Coordinated And Hybridized Control System And An Improved Factory Based Method For Making And Testing Combined Cycle And Other Power Plants And Control sytems Therefor", assigned to the present assignee and hereby incorporated by reference.

#2. Ser. No. 408,972, which is a continuation of Ser. No. 247,877, now abandoned, which is a continuation-in-part of Ser. No. 247,440, now abandoned, which is a continuation-in-part of Ser. No. 246,900, filed Apr. 24, 1972, entitled "General System And Method For Starting, Synchronizing And Operating A Steam Turbine With Digital Computer Control", all filed by T. C. Giras and R. Uram and assigned to the present assignee, and hereby incorporated by reference. 3. Ser. No. 495,765 filed concurrently herewith by Lyle F. Martz and Richard J. Plotnick, entitled "Combined Cycle Electric Power Plant Having A Control System Which Enables Dry Steam Generator Operation During Gas Turbine Operation", assigned to the present assignee and thereby incorporated by reference.

Brief description of the drawings21 figures

#FIG. 1 shows a schematic diagram of a combined cycle electric power plant in which there is employed a steam turbine in accordance with the principles of the invention;

#FIGS. 2A, 2B and 2C when placed side-by-side show a detailed schematic diagram of one embodiment of a combined cycle electric power plant in which the principles of the present invention are utilized;

#FIG. 3 shows a schematic view of a control system arranged to operate the plant of FIGS. 1, 2A, 2B and 2C in accordance with the principles of the invention;

Detailed description20,422 words

#Referring to FIG. 1 of the drawings, there is shown a functional block diagram of a representative embodiment of a combined cycle electric power generating plant constructed in accordance with the present invention. Reference numeral 10 is used to identify the combined cycle plant as a whole. As such, the plant 10 includes a first gas turbine 12 (sometimes referred to as "gas turbine No. 1") which drives a first electric generator 13. Fuel is supplied to the gas turbine 12 by way of a fuel control valve or throttle valve 14. Air enters the gas turbine 12 by way of a variable inlet guide vane mechanism 15 which controls the degree of opening of the turbine air intake and which is used to adjust air flow during the startup phase and to increase part load efficiency. The fuel supplied by the throttle valve 14 is burned in the gas turbine 12 and the resulting high temperature exhaust gas is passed through an afterburner 16 and a heat recovery steam generator 18 and is thereafter exhausted into the atmosphere.

#Heat recovery steam generator 18 (sometimes referred to as "heat recovery steam generator No. 1") includes therein various sets of boiler tubes which are heated to a relatively high temperature by the gas turbine exhaust gas passing through the steam generator 18. Afterburner 16 includes a burner mechanism for further increasing the temperature of the gas turbine exhaust gas before it enters the steam generator 18. Fuel is supplied to the burner mechanism in the afterburner 16 by way of a fuel control valve or throttle valve 19. The primary heat source for the steam generator 18 is the gas turbine 12, the afterburner 16 being in the nature of a supplemental heat source for providing supplemental heat when needed. In terms of typical fuel usage, approximately 80% of the fuel is used in the gas turbine 12 and 20% is used in the afterburner 16.

#The combined cycle plant 10 further includes a second gas turbine 22 (sometimes referred to as "gas turbine No. 2") which drives a second electric generator 23. Fuel is supplied to the gas turbine 22 by way of a fuel control valve or throttle valve 24. Air enters the gas turbine 22 by way of a variable inlet guide vane mechanism 25 which is used to adjust air flow during turbine startup and to increase part load efficiency. The fuel supplied to throttle valve 24 is burned in the gas turbine 22 and the resulting high temperature exhaust gas is passed through an afterburner 26 and a heat steam generator 28 and is thereafter exhausted into the atmosphere.

Facts

Application

05/497,345Filed 13 Aug 1974

Granted

6 Sep 1977

Term ended

6 Sep 1994

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification8 codes

F22B 35/008
Control systems for steam boilers: control systems for two or more steam generators
F01K 23/108
With water evaporated or preheated at different pressures in exhaust boiler: regulating means specially adapted therefor
Y02E 20/16
Combustion technologies with mitigation potential: combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
Y02P 80/15
Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier: on-site combined power, heat or cool generation or…

Combined cycle electric power plant with a steam turbine having a throttle pressure limiting control

Life of this patent

Combined cycle electric power plant with a steam turbine having a throttle pressure limiting control

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims18

Description22,000 words

Drawings

Classification8 codes

Life of this patent

Description22,000 words