JP2007064048A - Waste heat recovery facility of power plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste heat recovery facility of a power plant, which can apply and recover the exhaust heat from a steam turbine using a heat pump for heating the water supply of a steam generating device. <P>SOLUTION: The waste heat recovery facility of the power plant supplies the steam from the steam generating device into the steam turbine 1 to convert the steam into power. The heat recovery facility comprises an air-cooled condenser 3 at the exhaust side, and a heat exchanger 9 at the exhaust side of the steam turbine 1 to recover the heat of the exhaust steam into heating medium in heating the water supply for the steam generating device with the heat pump. A circulating pipe 11 through which heating medium circulates is disposed between the heat exchanger 9 and the heat pump 12, and the circulated heating medium is formed as heat source water of the heat pump 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a waste heat recovery facility of a power plant, and more particularly, to a waste heat recovery facility of a power plant that includes a heat pump that recovers heat from steam and heats feed water to a steam generator.

  When installing a power plant, in an area where a large amount of seawater and cooling water from a cooling tower cannot be obtained, an air-cooled condenser is often used as a means for condensing the exhaust steam of the steam turbine. In a power plant that employs this air-cooled condenser, the proportion of heat radiation from the air-cooled condenser to the atmosphere is as large as about 60%, and if this heat loss can be recovered. The power plant efficiency can be improved.

  However, the air temperature after cooling of the air-cooled condenser is generally about 50 to 60 ° C., and the specific heat of the air is small, so that the heat transfer area of the heat exchanger used for recovery by the heat exchanger is small. Need to be very large. Therefore, conventionally, the exhaust heat of the steam turbine is radiated as it is to the atmosphere without being effectively used.

  As an example of effectively recovering the exhaust heat of the steam turbine in the power plant, the power generation facility described in Patent Document 1 introduces the steam turbine exhaust steam directly into the evaporator of the absorption heat pump, thereby generating the latent heat of the steam as a heat source. It has been proposed that the drain after condensation is heated by an absorber or condenser of an absorption heat pump and used again as water supply for a steam generator.

JP-A-5-263610

  In general, the diameter of the steam turbine exhaust pipe is empirically designed so that the steam flow rate in the exhaust pipe is 60 to 70 m / s in consideration of the pressure loss of the exhaust pipe, the vibration generation limit, and the like. Further, the lower the steam turbine exhaust pressure is, the better the performance of the steam turbine is. Therefore, the exhaust pressure of the steam turbine is designed to be almost vacuum, so that the diameter of the exhaust pipe of the steam turbine becomes considerably large.

  For this reason, in the example described in Patent Document 1 in which the exhaust steam of the steam turbine is directly introduced into the evaporator of the absorption heat pump, the diameter of the connection pipe becomes considerably large. Arrangement problems such as having to do occur. Further, since it is necessary to increase the heat transfer area of the evaporator of the absorption heat pump, there is a problem in arrangement, and there is a possibility that the equipment investment increases due to a special specification.

  The object of the present invention is to reduce the exhaust heat from the steam turbine to the feed water of the steam generator without increasing the capital investment because the layout problem such as the routing in the connecting pipe and the heat pump must be a special specification. It is to provide a waste heat recovery facility for a power plant that can be recovered by heating.

  In the present invention, the steam generator is supplied to a steam turbine that converts steam into power, and an air-cooled condenser is provided on the exhaust side of the steam turbine, and a heat pump that heats water supplied to the steam generator is provided. When configuring the waste heat recovery equipment of a power plant, a heat exchanger is provided on the exhaust side of the steam turbine to recover the heat of the exhaust steam to the heat medium, and there is a heat medium between the heat exchanger and the heat pump. Circulating circulation piping is interposed, and the circulated heat medium is used as heat source water for the heat pump.

  If the waste heat recovery equipment of the power plant is configured as in the present invention, even when an air-cooled condenser is used, there is a problem in arrangement such as connection piping routing, and an increase in capital investment by making the heat pump a special specification The exhaust heat from the steam turbine can be used for heating the feed water of the steam generator, and the waste heat can be effectively recovered.

  Embodiments of the waste heat recovery facility for a power plant according to the present invention will be described in detail below using embodiments shown in the drawings.

  In the power plant of FIG. 1 which is the first embodiment of the present invention, an air-cooled condenser 3 and an exhaust condensate tank 4 are provided in the exhaust pipe 2 on the exhaust side in order to condense the exhaust steam from the steam turbine 1. In addition, the moisture in the wet steam becomes condensed water from the drain pod 5 provided in the exhaust pipe 2 to the drain tank 6 and is drained to the exhaust condensate tank 4 by the drain pump 7.

  Therefore, the steam generated from the steam generator (not shown) works in the steam turbine 1 and then flows into the air-cooled condenser 3 through the exhaust pipe 2, and this air-cooled condenser 3 The steam that has flowed into is cooled with air to become condensed water, and is discharged to the exhaust condensate tank 4. The condensed water stored in the exhaust condensate tank 4 is supplied to the steam generator by the exhaust condensate pump 8. In order to effectively utilize the heat quantity of the exhaust steam from the steam turbine 1, a heat exchanger 9 is installed in the exhaust pipe 2 on the steam exhaust side. In this heat exchanger 9, a heat pump 12 is provided in order to use the heat amount of the heat medium raised by heat exchange with the exhaust steam, and the heat medium heated by heat exchange is supplied to the circulation pipe 11. The circulation pump 10 supplies the heat pump evaporator 13. As a result, the heat of the exhaust steam is recovered by the heat exchanger 9 and the feed water that returns to the steam generator by using the heat pump 12 is heated.

  In the heat pump 12, heat is absorbed from the heat medium, and the heat absorption is used to heat the feed water of the steam generator. Therefore, the amount of heat of the heat medium at the outlet of the heat pump evaporator 13 is reduced, and the heat medium at the outlet is returned to the heat exchanger 9. It circulates and repeats heating. In addition, a part of the exhaust steam recovered by the heat exchanger 9 is condensed and drained through the drain tank 6 and discharged to the exhaust condensate tank 4.

  When configured as in the present invention, the heat medium circulating from the heat exchanger 9 to the heat pump 12 through the circulation pipe 11 needs to balance the amount of heat received from the heat exchanger 9 and the amount of heat absorbed by the heat pump evaporator 13. Therefore, for example, a thermometer is installed at the inlet of the heat pump evaporator 13, and the circulation amount is controlled by controlling the number of revolutions of the circulation pump 10 so that the temperature is constant, the circulation amount is controlled by the flow rate control valve, Control the temperature by installing a buffer tank. Further, the same effect can be expected by fixing the circulation amount of the heat medium and adjusting the feed water heating amount of the steam generator with a control valve or the like, for example.

  In the power plant of the present invention, an absorption heat pump or a compression heat pump can be applied as the heat pump 12 combined with the heat exchanger 9, and the same effect can be achieved by using any of the first type heat pumps 12 as described above. Can do.

  The present invention can be applied not only to a newly constructed power plant but also to a power plant that has already been constructed, and can be implemented with reduced capital investment.

  In the example of FIG. 2 showing another embodiment of the present invention, branch pipes 15 and 16 are added to the exhaust pipe 2 of the steam turbine 1, and a heat exchanger 9 is installed in the branch pipes 15 and 16. The other parts are configured in the same manner as in FIG. 1, and in this example, the same effects as in the example of FIG. 1 can be achieved. In addition, with this configuration, when the heat transfer area of the heat exchanger 9 installed in the exhaust pipe 2 is large as in the example of FIG. 1, the pressure loss increases, so the exhaust pressure of the steam turbine 1 is high. Thus, the performance of the steam turbine 1 deteriorates, but this can be avoided.

  In FIG. 3 showing another embodiment of the present invention, a bypass pipe 19 having a bypass valve 18 interposed in a main steam pipe 17 for supplying steam to the steam turbine 1 is provided so as to reach the exhaust pipe 2. 19 is provided with a heat exchanger 9, and the other parts are configured in the same manner as in FIG. 1, and this can also achieve the same effects as in the example of FIG. Further, in this embodiment, unlike the example of FIG. 2, the heat exchanger 9 is installed in the turbine bypass pipe 19 so that the exhaust pressure of the steam turbine 1 can be prevented from becoming high, and further, the steam turbine 1 during normal operation. Since the steam flows from the exhaust pipe 2 to the heat exchanger 9, the bypass pipe 19 can be warmed during normal operation.

  In FIG. 4 showing still another embodiment of the present invention, the embodiment of FIGS. 1 to 3 uses the first type heat pump to recover the waste heat of the exhaust steam, whereas the embodiment of FIG. A two-type heat pump is used. In order to use the heat quantity of the exhaust steam as a drive heat source for the second type heat pump, a heat exchanger 9 is installed in the exhaust pipe 2 as in the case of the steam, and the heat medium is heated by heat exchange with the steam turbine exhaust steam. Is supplied to the heat pump evaporator 20 and the heat pump generator 22 by the circulation pump 10, and the cooling water is circulated through the heat pump condenser 23. Even in such a configuration, it is the same as the example of FIG. The effect can be achieved.

It is a block diagram which shows the waste heat recovery equipment of the power plant which is one Example of this invention. It is a block diagram which shows the waste heat recovery equipment of the power plant which is another Example of this invention. It is a block diagram which shows the waste heat recovery equipment of the power plant which is another Example of this invention. It is a block diagram which shows the waste heat recovery equipment of the power plant which is another Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steam turbine, 2 ... Exhaust pipe, 3 ... Air-cooled condenser, 4 ... Exhaust condensate tank, 5 ... Drain pod, 6 ... Drain tank, 7 ... Drain pump, 8 ... Exhaust condensate pump, 9 ... Heat Exchanger, 10 ... circulation pump, 11 ... circulation pipe, 12 ... heat pump, 13, 20 ... heat pump evaporator, 14 ... pump, 15 ... branch pipe, 16 ... drain pipe, 17 ... main steam pipe, 18 ... bypass valve, DESCRIPTION OF SYMBOLS 19 ... Bypass pipe, 21 ... Heat pump absorber, 22 ... Heat pump generator, 23 ... Heat pump condenser

Claims (4)

  The power generation plant is provided with an air-cooled condenser on the exhaust side of the steam turbine, and a heat pump for heating the feed water to the steam generator. In the heat recovery facility, a heat exchanger for recovering the heat of the exhaust steam to a heat medium is provided on the exhaust side of the steam turbine, and a circulation pipe for circulating the heat medium is interposed between the heat exchanger and the heat pump. A waste heat recovery facility for a power plant, wherein the circulated heat medium is configured as heat source water for the heat pump.   2. The waste heat recovery facility for a power plant according to claim 1, wherein the heat exchanger is provided with a branch pipe branched from the exhaust side of the steam turbine to the exhaust condensate tank.   2. The waste heat recovery facility for a power plant according to claim 1, wherein the heat exchanger is provided in a branch pipe connecting steam from a steam generator to an exhaust pipe on an exhaust side of a steam turbine. 2. The waste heat recovery facility for a power plant according to claim 1, wherein the heat medium circulated from the heat exchanger is configured as a heat source water of a second type heat pump.

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