JP2007064047A - Waste heat recovery facility for steam turbine plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste heat recovery facility for a steam turbine plant capable of increasing the recovery quantity of unused energy and enhancing recovery efficiency. <P>SOLUTION: A waste heat recovery facility for a steam turbine plant comprises a steam turbine 4 for supplying steam from a boiler 1 which is a steam generating device, a condenser 7 provided to an exhaust side of the steam turbine 4 and heat pumps included in a circulation system of the condenser 7 to heat feed water to the boiler 1. At least two heat pumps which take waste heat to a circulation system of the condenser 7 as a heat absorbing source are utilized, wherein a compression type heat pump 22 and a vapor absorption type heat pump 23 are provided to constitute the heat pumps. The compressor of the compression type heat pump 22 drives a back pressure steam turbine 30 by a steam source on the steam turbine 4 side. A part of or the whole of exhaust steam after driving is taken as a heat source of a steamer 32 in the vapor absorption type heat pump 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a waste heat recovery facility for a steam turbine plant, and more particularly to a waste heat recovery facility for a steam turbine plant provided with a plurality of heat pumps in a circulation system of a condenser.

  Conventionally, waste heat from a thermal power generation facility and a combined power generation facility is recovered by a heat pump, and heat recovery is performed for steam turbine condensate and boiler feedwater.

  Examples of using waste heat include a gas turbine, a waste heat recovery boiler, a steam turbine, and a combined power generation facility that includes a generator directly connected to each of the gas turbine and the steam turbine. And a vapor absorption refrigerator are proposed, for example, described in Patent Document 1. In the example described in Patent Document 1, a compressor that constitutes a turbo refrigerator is directly connected to a rotating shaft of a steam turbine and a generator, and the extracted steam of the steam turbine is used as a heating source for the steam absorption refrigerator. The exhaust condensate after use is reused as feed water for the exhaust heat recovery boiler.

  On the other hand, the exhaust steam of the steam turbine is condensed in the condenser and then circulated again as feed water for the exhaust heat recovery boiler. The condenser cooling water is steamed from the turbo refrigerator by a cooling water pump. The cold water that is supplied in series in the order of the absorption chiller and the condenser, and cooled in the order of the steam absorption chiller from the turbo chiller, circulates between consumers.

  Patent Document 2 describes that a steam absorption heat pump is provided in a steam turbine plant in order to improve the power generation efficiency of the steam power plant. In this example, the steam extracted from the steam turbine is introduced into the regenerator of the steam absorption heat pump to heat the absorption liquid, and the low pressure extraction steam from the steam turbine or the steam turbine exhaust steam is used as unused energy to evaporate the steam absorption heat pump. The refrigerant is evaporated by introducing it into the vessel. On the output side, boiler feed water is introduced into the absorber and condenser of the vapor absorption heat pump and heated.

  Furthermore, Non-Patent Document 1 describes an example in which a steam absorption heat pump is used alone to recover waste heat of a steam turbine plant. In this example, the steam exhaust heat pump is driven by a steam absorption heat pump that uses the boiler exhaust heat to the circulating water of the desulfurization unit of the coal-fired power generation facility as the heat sink, and the extracted steam from the steam turbine for power generation as the heat source. Heat is recovered in the condensate system at the air inlet.

JP 2001-141286 A JP-A-3-906 Energy Conservation Center Foundation 1993 Excellent Energy Conservation Examples 42. Low temperature waste heat recovery in power generation facilities

  The system described in Patent Document 1 that expands the supply area of the cold water supply load and the generated power load to consumers outside the steam turbine plant is a cogeneration plant that supplies both electricity and cold heat to the outside. In other words, in addition to the power generation output, cold heat is supplied to the outside, so if the fuel supply to the gas turbine is the same, operating the turbo chiller and the steam absorption chiller, the gas turbine generator and steam turbine power generation The machine's electrical output is a decreasing system.

  In addition, a structure that uses a condensing turbine directly connected to a generator for driving a compressor that constitutes a turbo chiller, and uses the extraction air of the condensing turbine in a steam absorption refrigeration machine, a steam turbine and a generator are newly provided. Although it is easy to design, it is necessary to connect and drive new equipment to the shaft of the existing power generation steam turbine, and to open a new bleeder port in the steam turbine. There is a problem with significant remodeling of the gantry.

  In the example described in Patent Document 2 in which unused energy of a steam turbine plant is recovered in boiler feedwater by a steam absorption heat pump, the steam introduced into the steam absorption heat pump has superheated saturated steam or a slight degree of superheat. A vapor of 1.0 MPa or less is sufficient. For this reason, after using steam extracted from the steam turbine and introducing it into the steam absorption heat pump, the steam exchanges heat in the order from the regenerator to the condensate cooler, and then becomes condensed water and is discharged outside the device. Heat recovery is not possible.

  Furthermore, even in the example of Non-Patent Document 1 in which waste heat is recovered to a steam turbine plant using a steam absorption heat pump alone, steam heat is not used except that the heat absorption source is circulating water of a desulfurization system for boiler exhaust gas. Since the configuration of waste heat recovery to the turbine plant is the same as that in Patent Document 2, there is a similar problem.

  The steam absorption heat pump introduces steam in the vicinity of superheat saturation, condensates it inside, and discharges it, so it can be said that it is a device with high utilization efficiency of steam that can be used up to its latent heat of vaporization. In addition, although depending on the type of the vapor absorption heat pump, in the single effect type vapor absorption heat pump, it is possible to heat room temperature water of about 20 ° C. at the maximum to warm water of 90 ° C. or more on the heat dissipation side, Both the temperature rise and output temperature can be increased. However, the coefficient of performance, which is the ratio of the heat amount on the output side to the heat amount on the steam side, is about 2.0 at the maximum in the case of the vapor absorption heat pump.

  On the other hand, in the case of using a steam turbine for the compressor drive, the compression heat pump can hardly use the latent heat of vaporization of steam regardless of the back pressure type or condensate type steam turbine. The utilization efficiency of is low. Further, since the compression heat pump can only heat room temperature water of about 20 ° C. to about 50 ° C., both the temperature rise width and the output temperature are smaller than those of the vapor absorption heat pump. However, the coefficient of performance of the compression heat pump is expressed by the ratio of the heat energy on the output side to the energy input as the driving force of the compressor, which is about 6.0, which is from the heat absorption source compared to the vapor absorption heat pump. The pumping efficiency of heat energy is about 3 times.

  An object of the present invention is to provide a waste heat recovery facility for a steam turbine plant that uses a compression heat pump and a steam absorption heat pump appropriately to increase the recovery amount of unused energy and improve the recovery efficiency. is there.

  In the present invention, a steam turbine for supplying steam from a steam generator, a condenser provided on the exhaust side of the steam turbine, and a heat pump for heating water supplied to the steam generator in a circulation system of the condenser are provided. When the waste heat recovery equipment of the steam turbine plant is configured, the heat pump is provided with at least two heat sinks that use waste heat to the condenser circulation system and compresses one of the heat pumps. The compressor of the compression heat pump is a back pressure steam turbine driven by a steam source on the steam turbine side, and a part or all of the exhaust steam after the drive is absorbed by the steam. It is comprised so that it may become a heat source of the evaporator of a type | formula heat pump.

  If the waste heat recovery facility of the steam turbine plant is configured as in the present invention, the performance characteristics of the steam absorption heat pump and the compression heat pump are utilized, so that it can be used compared to using only the same heat pump. Both the amount of recovered energy and the recovery efficiency can be improved. Therefore, since it can be recovered in a steam turbine plant, it can be widely applied from a small power generation facility for private power generation of several thousand kW class to a large power generation facility for business use of 1 million kW class.

  Hereinafter, the waste heat recovery equipment of the steam turbine plant of the present invention will be described in detail using the embodiment shown in FIG.

  In the embodiment of FIG. 1 according to the present invention, steam generated in a boiler 1 which is a steam generating apparatus reaches a steam turbine 4 through a main steam control valve 3 from a main steam pipe 2 and works in the steam turbine 4. After generating electricity with the generator 5, it enters the condenser 7 through the exhaust pipe 6. The steam is cooled by the condenser 7 to become condensed water, pressurized as a steam turbine condensate by the condensate pump 8 of the condensate pipe 10 that is a circulating system of the cooling water, and sequentially desorbed from the ground steam condenser 9. It is sent to the air vessel 11 and heated. The heated steam source is the ground steam of the steam turbine 4 in the ground steam condenser 9 and the steam extracted from the steam turbine 4 through the extraction steam pipe 27 in the deaerator 11.

  The boiler feed water is pressurized by the boiler feed pump 13 of the boiler feed pipe 12 after the deaerator 11 and further heated by the high-pressure feed heater 14 by the extraction steam from the high-pressure extraction pipe 26 from the high-pressure turbine 4. Return to boiler 1. Steam condensate from the high-pressure feed water heater 14 is recovered by the deaerator 11 through the high-pressure feed water heater water level control valve 15 of the drain pipe 16. The condenser cooling water is circulated between a condenser 7 and a cooling tower 17 by a cooling water pump 18 through a cooling water supply main pipe 19 and a condenser cooling pipe 24 which are a circulation system of cooling water. The latent heat of vaporization of the steam turbine exhaust steam exhausted from the turbine 4 to the condenser 7 heats the condenser cooling water, and the heat energy of the warmed water is evaporated in the cooling tower 17 and radiated to the atmosphere. is doing. The lost cooling water is automatically supplied to the cooling tower lower water tank 21.

  In the present invention, at least one of the different types of the compression heat pump 22 and the single effect vapor absorption heat pump 23 is used and installed. In the illustrated example, the heat absorption source water to both the heat pumps 22 and 23 exchanges heat with the latent heat of vaporization of the exhaust steam of the steam turbine 4 in the condenser 7, and the condensate at the outlet of the condenser 7 after the temperature rises. The heat absorption source water supply pipe 25 is branched from the condenser cooling pipe 24, and the heat absorption source water supply pump 23 A provided in the branch pipe 25 is used in parallel with the evaporators 51 and 53 of the constituent devices inside the heat pumps 22 and 23. Supply. The return heat source water from the evaporators 51, 53 of each heat pump 22, 23 is joined to one heat absorption source water return pipe 20, and then joined to the condenser cooling water pipe 24 at the inlet of the cooling tower 17.

  In the steam supply system to each of the heat pumps 22, 23, for example, a steam pipe 28 is branched from a high pressure extraction pipe 26 from the steam turbine 4 to the high pressure feed water heater 14, and the back pressure steam turbine 30 is driven. The back pressure steam turbine 30 drives a compressor 31 of a compression heat pump 22 that is directly connected, and the compressor 31 forms a circulation path with the condenser 35, the expansion valve 52, and the evaporator 51. The steam regulator valve 29 at the inlet of the compression heat pump 22 detects the water temperature at the outlet of the condenser 35, which is an internal component of the compression heat pump 22, by the temperature controller 49, and controls the amount of steam.

  The supply steam to each of the heat pumps 22 and 23 is used by installing a pipe constituting the steam supply system so that it can be selected from any of the inlet steam, extraction steam, and exhaust steam of the steam turbine 4. Can do.

  Exhaust steam from the back pressure steam turbine 30 is heated to the other single-effect steam absorption heat pump 23 and led to the generator 32, and finally becomes condensed water inside the condenser 32 through the drain pipe 33. 6 recovered. The drain discharge valve 34 is set to have a differential pressure so that the discharged condensed water does not flush inside the pipe.

  The temperature of the exhaust steam of the back pressure steam turbine 30 has a degree of superheat that is higher than required by the single effect steam absorption heat pump 23, and therefore, a temperature reducer 58 and a temperature detection are provided at the steam inlet of the heat pump 23. The boiler feed water taken out from the boiler feed water pump 13 outlet is used as temperature-reduced water, and the steam temperature of the heat pump 23 is controlled to a constant temperature by the inlet steam temperature control valve 57 provided in the source hot water pipe 56.

  As for the steam pressure, the outlet temperature of the condenser 37 constituting the single-effect steam absorption heat pump 23 is provided on the steam inlet side of the single-effect steam absorption heat pump 23 to respond to the condenser outlet temperature controller 50. It is controlled by the water temperature control valve 43. For this reason, when there is a shortage of steam in the single effect steam absorption heat pump 23, the indication value of the pressure regulator 38 installed in the inlet steam pipe 42 of the single effect steam absorption heat pump 23 is lower than the preset pressure. In this case, steam is introduced from a steam backup valve 41 installed in the backup system 40 branched from the deaerator bleed pipe 27.

  Conversely, when the amount of steam used by the single-effect steam absorption heat pump 23 decreases and the indicated value of the pressure regulator 38 exceeds the preset pressure, the surplus steam discharge valve 39 installed in the surplus steam discharge system 38A. The steam is discharged from the steam to the condenser 7. With this backup and surplus steam discharge system, even if both or one of the compression heat pump 22 and the single effect steam absorption heat pump 23 are stopped, the operation of the heat pump on the operating side or the entire steam turbine plant is hindered. You wo n’t be hurt.

On the other hand, the heat recovery destination is the condensate pipe 10 of the steam turbine 4 on the outlet side of the ground steam condenser 9, and the compression heat pump 22 and the single effect steam absorption heat pump 23 are arranged in this order from the upstream side. . As a result, the condensate of the steam turbine that has exited the ground steam condenser 9 is heated by the condenser 35 that is a component of the compression heat pump 22 and then sent to the single-effect steam absorption heat pump 23. Inside, the condensate is heated from the absorber 36 through the condenser 37 in sequence, and the condensate discharged from the single effect vapor absorption heat pump 23 is sent to the deaerator 11.
The condensate pipe 10 is provided with flow control valves 39 and 40A, which set the flow rate ratio of the steam turbine condensate flowing through the compression heat pump 22 and the steam turbine condensate flowing through the single-effect steam absorption heat pump 23. The water flow rate ratio is set respectively.

  The compression heat pump and the vapor absorption heat pump are devices having different use efficiency of steam, output temperature width, outputable temperature, and coefficient of performance, and have a complementary relationship.

  Considering the steam side in the example of the present invention, the steam absorption heat pump 23 exchanges heat until the steam in the vicinity of superheat saturation is condensed to water, whereas the back pressure type that drives the compressor of the compression heat pump 22. Since the steam turbine is used in the superheated steam region, the exhaust of the back pressure steam turbine can be used for the steam absorption heat pump without hindering the performance of the steam absorption heat pump.

  Considering the heat recovery destination in the example of the present invention, the vapor absorption heat pump 23 can raise the temperature of normal temperature water at a maximum of 20 ° C. to about 90 ° C., whereas the compression heat pump 22 has a temperature of 20 ° C. About room temperature water is about 50 ° C. Therefore, even when considering the heat recovery destination, heat recovery can be performed in the order of the compression heat pump and the vapor absorption heat pump, or heat recovery can be performed without any problem by recovering heat in a parallel configuration. .

  The waste heat recovery facility of the steam turbine plant shown in FIG. 2 which is another embodiment is a case of a bleed condensate turbine in which the main turbine 4 for power generation also supplies steam to the outside of the power plant. The steam supply to the outside is sent from a process steam pipe 47 branched from the deaerator bleed pipe 27. If the steam pressure is within the range set in advance for the steam turbine 4, power is generated by the main steam control valve 3 and the extraction control valve 44 of the steam turbine 4 regardless of the amount of extraction flow from the extraction pipe 27. The electric output of the machine 5 is controlled to a substantially constant pressure while keeping it constant.

  In addition, since a large amount of steam is sent out of the system, the amount of makeup water increases, but in such a plant, a condensate tank 46 is provided in the condensate system in order to make effective use of the heat quantity of the makeup water. The condensate tank water level adjustment valve 54 provided in the make-up water system 48 is configured to adjust the amount of make-up water to the condensate tank 46 by a signal from the condensate tank water level adjuster 55. Since the condensate tank 46 is generally an atmospheric pressure tank, a condensate booster pump 45 is installed on the outlet side thereof, and the condensate pressurized by the condensate booster pump 45 is sent to the deaerator 11.

  This steam turbine plant has a structure in which a compression heat pump 22 is installed on the downstream side of the ground steam condenser 9 in the system on the condensate side, and the condensate after heating is put in a condensate tank 46. The single-effect steam absorption heat pump 23 is installed in the makeup water system 48 of the condensate tank 46, and this steam-side system has a structure in which the steam is recovered from the steam drain pipe 33 to the condensate tank 46.

  In the present invention, instead of installing the steam absorption heat pump in the makeup water system 48 serving as a circulation system for supplying water to the condensate tank 46, it is also applicable to the case where it is installed in the condensate pipe on the outlet side of the condensate booster pump 45. Can do.

  Further, the present invention can be applied to a configuration in which the compression heat pump 22 is installed in the makeup water system 48 and the double effect steam absorption heat pump 23 is installed in the condensate pipe 10 on the outlet side of the ground steam condenser 9. Further, two heat pumps in the order of the compression heat pump 22 and the single effect or double effect steam absorption heat pump 23 are configured in the make-up water system 48 in series, or both the heat pumps 22 and 23 are installed in parallel. It can also be used.

  In the embodiment shown in FIG. 1 and FIG. 2, the backup steam source to the single effect steam absorption heat pump 22 is taken from the deaerator bleed steam pipe 27, but this is limited to this steam source. Instead, the main steam pipe 2 and the high-pressure feed water heater bleed pipe 26 can be used by bleed from locations having a pressure that can be supplied as the heating steam source of the single-effect steam absorption heat pump 23. In addition, the single-effect steam absorption heat pump 23 uses the double-effect steam heat pump instead of this, and the configuration on the steam and condensed water side is the same.

  In each of the above embodiments, the discharge destination of the surplus steam discharge system 38 is the direct condenser 7, but when there is a heat exchanger that can recover the heat quantity of the surplus steam discharge system 38, the heat exchanger includes It can also be recovered.

  Furthermore, in each embodiment, the cooling water of the condenser 7 is cooled by the cooling tower 17, but it can also be applied to the case of direct cooling by river water or seawater. In the case of direct cooling by river water or seawater, When there is a problem in water quality as a direct heat absorption source water of the heat pump, a heat absorption source water can be indirectly used by inserting a non-contact type heat exchanger.

  The heat source water of the heat pump is not limited to the turbine plant, but can use unused energy outside the boiler plant and the system. Further, as the cycle of the steam turbine plant, in the embodiment shown in FIGS. 1 and 2, the steam turbine 4 for power generation is a non-reheat type condensate turbine, but it can also be used in a reheat type steam turbine. it can.

  Furthermore, when the main turbine is a back-pressure steam turbine and the condenser is not installed, the waste heat source as the heat absorption source of the heat pump is not limited to the steam turbine plant, and the heat recovery destination The same effects as those of the present invention can be obtained as a make-up water system and a boiler water supply system.

  Although it is possible to provide a recirculation system on the steam turbine condensate system side of each heat pump 22 and 23 and control the temperature of the outlet and inlet, temperature control by recirculation flow rate control not only for the heat pump but also for heat exchangers Is commonly done and can be easily applied. Further, it can be similarly applied to the prevention of transient temperature change by newly installing new water tanks at the entrance / exit.

  In a power generation facility of a steam turbine plant, unused waste heat energy pumped from a heat absorption source by a heat pump is used to raise the temperature of the condensing system of the steam turbine, and the installed heat pump is composed of a compression heat pump and a single effect steam absorption heat pump. In the case where the exhaust steam of the back pressure steam turbine for driving the compressor of the compression heat pump is used in a single effect steam absorption heat pump, the effect will be specifically described below.

  First, it is assumed that the inlet steam condition of the main turbine in the power generation facility of the target steam turbine plant is 3.9 MPa, 400 ° C., the exhaust condition is −94.66 kPa, and the condenser outlet condensate flow rate is 30 t / h. To do. As a driving steam source for a back pressure steam turbine for a compression heat pump, steam extraction steam having a steam pressure, a temperature of 1.2 MPa, and 300 ° C. is used. Assuming that the internal efficiency of the back pressure steam turbine is 50%, the exhaust temperature when the back pressure is 0.4 MPa is about 240 ° C. The exhaust steam is cooled down to 170 ° C. by a temperature reducer using the boiler feed pump outlet water at 5.0 MPa and 175 ° C., and used as a 0.4 MPa, 170 ° C. steam for a single effect steam absorption heat pump. The steam condensate temperature at the outlet of the heat pump used is 90 ° C.

  The coefficient of performance of each heat pump is the coefficient of performance of the compression heat pump, that is, the ratio of the amount of heat output to the turbine condensate system with respect to the amount of heat received by the compressor is 6.0, which is a typical value for a compression heat pump. The turbine condensate temperature is increased from 45 ° C. by 10 ° C. to 55 ° C. The coefficient of performance of the single-effect steam absorption heat pump is 1.7, which further increases the temperature of the steam turbine condensate heated by the compression heat pump.

  From the above conditions, the amount of heat pumped from the heat absorption source to the steam turbine condensate system by the compression heat pump is about 350 kW because the temperature of 30 t / h condensate is raised by 10 ° C. The power of the back pressure steam turbine used for this is about 58 kW, which is 1/6 because the coefficient of performance of the compression heat pump is 6.0.

  On the other hand, the inlet steam flow rate of the single-effect steam absorption heat pump is such that the steam at 0.4 MPa and 240 ° C. at the outlet of the back pressure turbine is reduced with hot water at 5.0 MPa and 175 ° C. This is a 7.4% increase in the steam flow at the turbine outlet. Since the steam at this flow rate is discharged from the single effect steam absorption heat pump as condensed water at 90 ° C., the heat input from the steam side is about 1440 kW. Now, since a single effect steam absorption heat pump with a coefficient of performance of 1.7 is used, the heat input to the condensate system is 1.7 times that of 1440 kW, which is about 2450 kW.

  From this, the condensate system of the steam turbine can receive about 2800 kW of thermal energy for 1498 kW heat input from the steam turbine bleed system. That is, about 1300 kW of unused energy is pumped up.

  This output of about 1300 kW exceeds 16% of about 8000 kW, which is the assumed power generation end output of the steam turbine power generation facility, and is an extremely effective energy saving means.

It is a block diagram of the waste heat recovery equipment of the steam turbine plant which shows one Example of this invention. It is a block diagram of the waste heat recovery equipment of the steam turbine plant which shows the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Boiler, 2 ... Main steam pipe, 3 ... Main steam control valve, 4 ... Steam turbine, 6 ... Exhaust pipe, 7 ... Condenser, 8 ... Condensate pump, 10 ... Condensate pipe, 11 ... Deaerator, DESCRIPTION OF SYMBOLS 12 ... Feed water pipe, 13 ... Boiler feed pump, 17 ... Cooling tower, 18 ... Cooling water pump, 19 ... Cooling water supply main pipe, 20 ... Endothermic water return pipe, 22 ... Compression heat pump, 23 ... Single effect steam absorption Type heat pump, 24 ... condenser condenser pipe, 25 ... heat absorption source water supply pipe, 26 ... high pressure extraction pipe, 27 ... extraction steam pipe, 28 ... steam pipe, 29 ... steam control valve, 30 ... back pressure steam turbine, 31 Compressor, 32 generator, 35, 37 condenser, 36 absorber, 42 inlet steam pipe, 43 steam inlet valve, 44 extraction valve, 46 condensate tank, 47 process steam pipe 48 ... makeup water system 51, 53 ... evaporator, 52 ... expansion valve, 56 ... dewarmed water , 57 ... inlet steam temperature control valve, 58 ... desuperheater, 59 ... temperature detectors.

Claims (3)

  A steam turbine plant comprising: a steam turbine that supplies steam from a steam generator; a condenser that is provided on an exhaust side of the steam turbine; and a heat pump that heats feed water to the steam generator in a circulation system of the condenser In the waste heat recovery facility, the heat pump is provided with at least two units that use waste heat to the circulation system of the condenser as a heat absorption source, and one of the heat pumps is a compression heat pump and a vapor absorption heat pump. The compressor of the compression heat pump drives a back pressure steam turbine with a steam source on the steam turbine side, and a part or all of the exhaust steam after the drive is used as a heat source of the evaporator of the steam absorption heat pump. A waste heat recovery facility for a steam turbine plant, characterized in that   2. The waste heat recovery equipment for a steam turbine plant according to claim 1, wherein each of the heat pumps is provided in series with a circulation system of a water supply in the order of a compression heat pump and a steam absorption heat pump. 2. The waste heat recovery facility for a steam turbine plant according to claim 1, wherein each of the heat pumps includes a compression heat pump and a steam absorption heat pump provided in parallel to a circulation system of water supply.

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