JP2016065486A - Combined cycle power generation facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supply water heating system capable of reducing power for a pump used in supply water circulation from a waste heat recovery boiler, and capable of improving heat efficiency.SOLUTION: A combined cycle power generation facility in this embodiment includes: a supply water heater that heats supply water generated in a condenser with extraction steam from a steam turbine, and supplies the water to a waste heat recovery boiler; a circulation pump that branches part of supply water heated in the waste heat recovery boiler, and supplies the water to supply water supplied to the waste heat recovery boiler; and a control unit that controls the circulation pump so as to selectively drive the circulation pump.SELECTED DRAWING: Figure 1

Description

The present invention relates to a combined cycle power generation facility with improved feed water temperature control.

In a combined cycle power generation facility using a steam turbine and a gas turbine, an exhaust heat recovery boiler is provided for generating steam from the feed water by using the heat of the exhaust gas of the gas turbine to generate working steam of the steam turbine.

The temperature of the feed water obtained by condensing the steam that has worked in the steam turbine may be lower than the predetermined temperature when the temperature of the seawater supplied to the condenser is low. If the feed water is supplied to the exhaust heat recovery boiler at a temperature lower than the specified temperature, the heat transfer tube of the exhaust heat recovery boiler may condense due to the temperature difference between the feed water and the moisture in the exhaust gas, and the heat transfer tube may corrode. Therefore, measures are taken to make the temperature of the feed water entering the exhaust heat recovery boiler equal to or higher than the dew point temperature of the moisture in the exhaust gas of the gas turbine.

One is to divide a part of the heated feed water at the exit of the economizer of the exhaust heat recovery boiler, and provide a circulation system for joining the branched feed water to the feed water supplied to the exhaust heat recovery boiler. In the heating method, the other is a method in which a feed water heater is provided in the feed water supply system supplied to the exhaust heat recovery boiler, and the extracted steam from the turbine is supplied to the feed water heater to heat the feed water.

JP 2011-127786 A

In the first method for circulating the heated feed water at the economizer outlet of the exhaust heat recovery boiler, it is necessary to always drive a pump for circulating the feed water to be used, and power for that is required.

In the method of heating the feed water by supplying the extracted steam from the steam turbine to the feed water heater, the feed water is heated only by the feed water heater, so that the operation of the plant operation is not full load, that is, in partial load operation, the pressure of the extracted steam As the flow rate decreases and the flow rate decreases, it may not be possible to heat the feed water to the same temperature as at full load only with extracted steam.

This invention was made in order to solve such a subject, and it aims at implement | achieving the feed water heating system which can reduce the motive power for pumps used for the feed water circulation from an exhaust heat recovery boiler, and can improve thermal efficiency. To do.

In order to achieve the above object, the present invention provides a gas turbine driven by combustion gas, an exhaust heat recovery boiler that generates steam using the heat of exhaust gas from the gas turbine, and steam generated by the exhaust heat recovery boiler A combined cycle power generation facility comprising: a steam turbine driven by a steam turbine; a condenser that condenses steam that has finished work in the steam turbine; and a generator driven by the gas turbine and the steam turbine. A feed water heater that heats the feed water generated by the water heater with the extracted steam from the steam turbine and supplies the waste water to the exhaust heat recovery boiler;
A control for branching a part of the feed water heated and entering the exhaust heat recovery boiler to supply the feed water supplied to the exhaust heat recovery boiler, and for selectively driving the circulation pump And a section.

[First Embodiment]
FIG. 1 is a configuration diagram of a combined cycle power generation facility according to a first embodiment of the present invention. In this embodiment, the gas turbine equipment 1 is combined with a steam turbine equipment 2, a generator 3 and an exhaust heat recovery boiler 4.

The gas turbine equipment 1 includes an intake equipment 5, an air compressor 6, a combustor 7, and a gas turbine 8. The atmosphere sucked in by the intake equipment 5 is compressed by the air compressor 6 and is increased in pressure. The high-pressure air is combusted in the combustor 7 together with the fuel supplied through the fuel control valve 9 and the fuel supply pipe 10, and the combustion gas flows to the gas turbine 8 and expands to drive the gas turbine 8. Then, it flows into the exhaust heat recovery boiler 4 through the exhaust gas duct 21.

The exhaust heat recovery boiler 4 includes a economizer 17, a steam drum 18, an evaporator 23, a superheater 19, and a reheater 20. Condensate (hereinafter referred to as feed water) supplied from the condenser 14 of the steam turbine facility 2 is boosted by the condensate pump 15 and heated by the feed water heater 30, and the economizer of the exhaust heat recovery boiler 4. 17 is supplied. A flow from the condensate pump 15 to the exhaust heat recovery boiler 4 is defined as a water supply system 32.

In the economizer 17, the temperature is raised in advance through the heat of the exhaust gas flowing through the exhaust heat recovery boiler 4. The heated feed water is supplied to the steam drum 18 to generate steam in the evaporator 23. The generated steam is superheated by the superheater 19 to become superheated steam, and the superheated steam is supplied to the steam turbine equipment 2. The

The steam turbine facility 2 includes a high pressure steam turbine 11, an intermediate pressure steam turbine 12, a low pressure steam turbine 13, and a condenser 14. Of the steam from the exhaust heat recovery boiler 4, high-pressure steam from the superheater 19 is supplied to the high-pressure turbine 11. The steam that has expanded in the high-pressure turbine 11 is exhausted, enters the reheater 20, is reheated, and is supplied to the intermediate-pressure steam turbine 12 to perform expansion work. The exhaust steam from the intermediate pressure steam turbine 12 is supplied to the low pressure steam turbine 13 to work in the turbine. The steam that has finished the work is led to the condenser 14, condensed by the seawater 14 a to become condensate, and sent to the water heater 30 as feed water by the condensate pump 15 to the exhaust heat recovery boiler 4.

The generator 3 is driven by the gas turbine 8 and the steam turbines 11, 12, and 13 to generate electricity.

Steam is extracted from the low-pressure steam turbine 13 and supplied to the feed water heater 30 to heat the feed water.

Moreover, a part of water supply heated with the economizer 17 of the waste heat recovery boiler 4 is supplied to the water supply system 32 in the case of the conditions mentioned later, and heats water supply. Water supplied from the steam drum 18 is supplied from the flow control valve 2.
4 controls the flow rate and temperature of the feed water. Further, the temperature detector 26 for detecting the feed water temperature in the feed water system 32 and the detected feed water temperature information are supplied to the control unit 28.

When the generator load of the combined cycle power generation facility is normal operation (full load operation), the control unit 28 recognizes this, stops the circulation pump 22, closes the flow control valve 24,
The feed water to the exhaust heat recovery boiler 4 is heated only by the feed water heater 30. Low pressure steam turbine 1
The extraction steam from 2 is designed to be extracted at the steam temperature necessary for heating the feed water in the feed water system.

On the other hand, when the generator load is lower than normal operation (partial load operation), the amount of heat of the extracted steam is lower than that during full load operation, so the temperature of the outlet of the economizer 17 of the exhaust heat recovery boiler 4 is increased. In order to heat the water supplied to the exhaust heat recovery boiler 4, that is, the water supplied to the water supply system 32, the control unit 28 operates the circulation pump 22, opens the flow control valve 24, and adjusts the opening degree. Based on the detected temperature of the temperature detector 26, the feed water temperature of the feed water system is adjusted to an appropriate value.

(effect)
When the feed water is heated only by the feed water heater 30 as in the prior art, the pressure of the extraction steam is reduced and the flow rate is reduced during partial load operation. Therefore, the temperature is the same as that during full load operation only with the extraction steam. In contrast to the fact that the feed water cannot be heated, in the present embodiment, the feed water heated by the exhaust gas from the economizer 17 of the exhaust heat recovery boiler 4 in addition to the feed water heating by the extracted steam from the steam turbine during partial load operation. The feed water can be heated to the same temperature as during full load operation.

Further, in the operation at full load operation, a sufficient amount of extracted steam heat can be obtained, so water supply from the economizer 17 of the exhaust heat recovery boiler 4 is not required, and the circulation pump 22 can be prevented from operating, so that Power can be reduced, and power in the power generation facility can be reduced.

[Second Embodiment]
In the second embodiment, the power generation system is the same as that in FIG. 1, and the control method is shown in FIG.

FIG. 2 is an example of the time transition of the temperature of the feed water entering the entrance of the economizer 17 of the exhaust heat recovery boiler 4. The temperature of this water supply is always detected by the temperature detector 26. When the detected temperature is higher than the target temperature of the inlet water of the economizer 17 to prevent the heat transfer pipe of the exhaust heat recovery boiler 4 from dewing, the control unit 28 monitors the temperature of the detected feed water. The circulating pump 22 is stopped, and when it is low, the circulating pump 22 is operated to raise the feed water temperature.

As described above, the operation of the circulation pump 22 is controlled according to the operating state of the power generation facility,
The feed water temperature of the feed water system is monitored, and if the feed water temperature is insufficient, control is performed so as to activate even if the circulation pump 22 is stopped during full load operation.

Further, even when the circulation pump 22 is in an operating state at the time of partial load operation, it is possible to control the circulation pump 22 to be in a stopped state if a sufficient water supply temperature is obtained.

(effect)
Therefore, even at the full load at which sufficient extraction can be obtained, the circulation pump 22 is appropriately operated when the feed water temperature falls below the target temperature, so that it is possible to cope with unexpected condensation on the heat transfer tubes in the exhaust heat recovery boiler. . In addition, since the operation of the circulation pump is appropriately stopped according to the feed water temperature even during partial load operation, only the necessary power is required as compared with the case where the circulation pump 22 is continuously operated.
Operation without waste is possible.

The operation of the circulation pump 22 may be completely stopped during full load operation, and the control of the second embodiment may be applied only during partial load operation. In this way, there is an effect that power can be further reduced compared to the case where water branched from the exhaust heat recovery boiler 4 is always used during partial load operation.

The systematic diagram showing 1st Embodiment of the combined cycle power generation equipment which concerns on this invention The figure which shows the control method of the 2nd Embodiment of this invention.

DESCRIPTION OF SYMBOLS 1 ... Gas turbine equipment 2 ... Steam turbine equipment 3 ... Generator 4 ... Exhaust heat recovery boiler 5 ... Intake equipment 6 ... Air compressor 7 ... Combustor 8 ... -Gas turbine 11 ... High pressure steam turbine 12 ... Medium pressure steam turbine 13 ... Low pressure steam turbine 14 ... Condenser 15 ... Condensate pump 17 ... Conservator 18 ... Steam drum 19 ... Superheater 20 ... Reheater 21 ... Exhaust gas duct 22 ... Circulation pump 23 ... Evaporator 24 ... Flow control valve 26 ... Temperature detector 28 ...・ Control unit 30 ... Water heater

Claims (5)

Gas turbine driven by combustion gas, exhaust heat recovery boiler for generating steam using heat of exhaust gas of gas turbine, steam turbine driven by steam generated in exhaust heat recovery boiler, and steam turbine In a combined cycle power generation facility having a condenser for condensing steam that has finished work in the above, and a generator driven by the gas turbine and the steam turbine,
A feed water heater for heating the feed water generated by the condenser with the extracted steam from the steam turbine and supplying the waste water to the exhaust heat recovery boiler;
A circulation pump for branching a part of the heated water entering the exhaust heat recovery boiler and supplying it to the feed water supplied to the exhaust heat recovery boiler;
A combined cycle power generation facility comprising: a control unit that controls to selectively drive the circulation pump. 2. The combined cycle power generation according to claim 1, wherein the exhaust heat recovery boiler has a economizer for heating the supplied water, and a part of the water in the economizer is supplied to the circulation pump. Facility. The control unit pauses the circulation pump during full load operation with a steady load of the generator,
2. The combined cycle power generation facility according to claim 1, wherein during the partial load operation with a load smaller than the steady load, the circulating pump is controlled to be driven. 2. The combined cycle power generation facility according to claim 1, wherein the controller selectively drives the circulation pump based on a temperature of water supplied to the exhaust heat recovery boiler. The combined cycle power generation facility according to claim 4, wherein the control based on the feed water temperature by the control unit is performed only during partial load operation.

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