JP2007064050A - Waste heat utilizing facility for steam turbine plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the utilization efficiency of unused energy by efficiently recovering waste heat as compared to conventional one, when recovering waste heat through the utilization of a heat pump for a waste heat utilizing facility of a steam turbine plant. <P>SOLUTION: A waste heat recovery facility for a steam turbine plant comprises a steam turbine 4 having an extraction pressure control mechanism for supplying steam from a boiler 1 which is a steam generating device, a condenser 8 provided to an exhaust side of the steam turbine 4, a deaerator 15 which is a heater or the like for extracting air from a stage having an extraction pressure control mechanism, and a heat pump 24 which is included in a circulation system of the condenser 8 to heat feed water to a steam generating device. The heat pump 24 takes waste heat to a circulation system of the condenser as a heat absorbing source, is provided to the upstream side of the deaerator 15 of the heater or the like mounted in the circulation system of feed water in the boiler 1 so as to recover the heat drawn up by a pump, and is equipped with a mechanism which changes pressure in the deaerator 15 in accordance with a temperature of inlet water of the deaerator 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a waste heat utilization facility for a steam turbine plant, and more particularly to a waste heat utilization facility for a steam turbine plant having an extraction pressure control mechanism using a heat pump.

  Conventionally, waste heat from a thermal power generation facility or a combined power generation facility is recovered by a heat pump, and heat recovery is performed for steam turbine condensate or boiler feedwater. In these systems, a heat exchanger using steam such as a deaerator or a feed water heater is generally installed, and the outlet hot water temperature of the heat exchanger ranges from about 50 to 60 ° C. to 200 ° C. It is an area that exceeds.

  On the other hand, the heat pump depends on its type, but even in the case of a single-effect steam absorption heat pump that is said to have the highest outlet hot water temperature of the condenser that is its internal component, the temperature is practically in the 90 ° C range. It is an upper limit. Therefore, when recovering heat to steam turbine condensate or boiler feedwater using a heat pump, it is rare that the boiler economizer inlet water is directly heated, and generally a deaerator or feed water heater, etc. The inlet water will be heated.

  For example, Patent Document 1 is an example of an apparatus that recovers unused energy in a steam turbine plant using a steam absorption heat pump. Patent Document 1 shows an example in which the inlet water supply of a low-pressure feed water heater is heated by a steam absorption heat pump installed on the upstream side of the low-pressure feed water heater.

JP-A-3-906

  However, in the case of Patent Document 1, the amount of steam used directly decreases by heating with a heat pump because the deaerator or feed water heater immediately on the high pressure side of the extraction source supplying steam to these heat pumps Is the amount of steam. Since these steams are generally extracted steam from steam turbines, even if the amount of extracted steam is reduced, the effect of the reduction is limited to the work in the steam turbine stage after extraction of the extracted steam. become.

  On the other hand, many industrial steam turbine power generation facilities often perform combined heat supply, and this facility has an extraction pressure control mechanism in the steam turbine. In the case of such a plant, process steam is supplied to the outside from the extraction pressure control stage, and extraction steam to a deaerator or a feed water heater as a component is also sent. Since the pressure setting of the extraction pressure control stage is set according to the conditions of the process steam use destination, when the steam is used as a deaerator or feed water heater steam, the pressure is generally reduced by a pressure control valve. It has been broken.

  Even if the feed water on the inlet side of such a deaerator or feed water heater is heated by a heat pump, the amount of steam used by the deaerator or feed water heater only decreases with the control mechanism as it is.

An object of the present invention, when performing the waste heat recovery with a heat pump, can be done efficiently waste heat recovery in comparison with the prior art, provides a waste heat utilization facilities steam turbine plant capable of improving the utilization efficiency of the unused energy There is to do.

  In the present invention, a waste heat recovery facility of a steam turbine plant includes a steam turbine having an extraction pressure control mechanism for supplying steam from a steam generator, a condenser provided on the exhaust side of the steam turbine, and an extraction pressure control mechanism. When comprising the heaters for extracting air from the paragraph having a heat pump for heating the feed water to the steam generator in the circulation system of the condenser, the heat pump is connected to the circulation system of the condenser. The waste heat is used as an endothermic source, and the heat pumped up by the heat pump is provided so as to recover heat upstream of the heaters installed in the boiler feed water circulation system, and depending on the temperature of the inlet water of the heater And a mechanism for changing the pressure of the heaters.

  When the waste heat utilization facility of the steam turbine plant is configured as in the present invention, the waste heat recovery is performed using the heat pump in the combined heat and steam turbine plant having the extraction pressure control mechanism in the industrial steam turbine power generation facility. In addition, waste heat can be recovered more efficiently than before, and the utilization efficiency of unused energy can be improved. Moreover, since it has a simple configuration, it can be widely applied to industrial steam turbine power generation facilities.

  Hereinafter, the waste heat utilization equipment of the steam turbine plant of the present invention will be described in detail with reference to the embodiments shown in the drawings.

  In one embodiment of the present invention shown in FIG. 1, steam generated in a boiler 1 as a steam generator is guided to a steam turbine 4 through a main steam pipe 2 and a main steam control valve 3, and the steam turbine 4 performs work. Is converted into electrical energy by the generator 9. Part of the steam that has entered the steam turbine 4 is, for example, sent to the outside from the extraction pipe 6 before the extraction control valve 5, and the steam exhausted from the steam turbine 4 that has passed through the extraction control valve 5 passes through the exhaust pipe 7. Pass through the condenser 8.

  If the extraction steam pressure is within the range set in advance for the steam turbine 4, the extraction of the main steam control valve 3, the extraction control valve 5, etc. of the steam turbine 4, regardless of the amount of the extraction flow from the extraction pipe 6. The pressure control mechanism is controlled to a substantially constant pressure while keeping the electrical output of the generator 9 constant.

  In the steam flow after the condenser 8, the steam cooled by the cooling water in the condenser 8 and deprived of the latent heat of evaporation becomes condensed water, and the condensate pipe 10 becomes a circulation system as condensate to the steam turbine. It is pressurized by the condensate pump 11 above and sent to the condensate tank 12. And it pressurizes with the deaeration water supply pump 14 installed in the condensate pipe 13 used as the circulation system of the condensate tank 12 exit, and it sends to the deaerator 15 which is heaters, and is heated.

  The heating steam source of the deaerator 15 branches from the extraction pipe 6 taken out before the extraction control valve 5, and uses the steam reduced in pressure by the steam reduction valve 16. The pressure to be reduced is controlled by the steam pressure regulator 17 to a constant pressure required as the deaerator 15 pressure. Boiler feed water after the deaerator 15 is pressurized by the boiler feed pump 19 on the boiler feed pipe 18 and then returns to the boiler 1.

  The supply water for the entire system is adjusted by adjusting the opening of the water level adjustment valve 42 by a water level regulator 41 installed in the condensate tank 12 and replenishing treated water treated for boiler feed water from the makeup water pipe 20. Done.

  The cooling water in the condenser 8 is sent to the condenser 8 through the cooling water supply main pipe 25 by the cooling water pump 21 at the outlet of the cooling tower 22, and again to the cooling tower 22 through the cooling water return main pipe 27. Cycle to return. The latent heat of vaporization of the exhaust steam exhausted from the steam turbine 4 to the condenser 8 heats the cooling water of the condenser 8, and the heat energy of the heated water is evaporated in the cooling tower 22 to the atmosphere. The lost cooling water is automatically replenished to the cooling tower lower water tank 23.

  In this invention of FIG. 1, the example at the time of using the single effect vapor | steam absorption heat pump 24 is shown. Cooling water after the heat absorption source water supply pipe 28 branches from the cooling water return main pipe 27 at the outlet of the condenser 8, and heat is exchanged with the latent heat of vaporization of the exhaust steam of the steam turbine 4 in the condenser 8 to increase the temperature. Is used as the heat absorption source water of the heat pump 24. The endothermic source water is pressurized by an endothermic source water supply pump 29 provided in the endothermic source water supply pipe 28 and supplied in parallel to an evaporator 30 which is a component device inside the heat pump 24. The return heat source water from the evaporator 30 of the heat pump 24 passes through the endothermic source water return pipe 26 and merges with the cooling water return main pipe 27 at the inlet of the cooling tower 22.

  The supply system of the heating steam of the heat pump 24 is branched from the steam turbine extraction pipe 6, and the steam reduced in temperature by the temperature reducer 32 installed in the heat pump steam pipe 31 is guided to the generator 33 constituting the heat pump 24. Finally, it becomes condensed water inside this.

  The temperature-reduced water for reducing the temperature of the steam by the temperature reducer 32 is taken out by the temperature-reduced water pipe 49 branched from the water supply pipe 18 at the outlet of the boiler feed pump 19, and is supplied to the temperature controller 48 installed at the steam pipe at the outlet of the temperature reducer 32. The cooling water return main pipe 50 is controlled so that the detected temperature becomes a predetermined temperature. Further, the steam condensate of the heat pump 24 is recovered by the condenser 8 through a drain pipe 34 having a drain outlet valve 35. Here, the drain outlet valve 35 is set to have a differential pressure so that the discharged condensed water does not flush inside the pipe.

  The control valve installed in the steam pipe at the inlet of the heat pump 24 is an outlet hot water temperature control valve 44, and the outlet hot water is set so that the water temperature detected by the outlet hot water temperature controller 45 installed in the heat pump outlet condensate pipe 43 becomes the target temperature. The amount of steam is controlled by the temperature control valve 44.

  Next, on the condensate piping side, the waste heat pumped up from the cooling water system of the condenser 8 by the heat pump 24 is collected in the inlet condensate pipe 13. The heat pump 24 is installed on the outlet side of the deaerated water supply pump 14, branches from the condensate pipe 13 at the inlet condensate pipe 40, and joins the condensate pipe 13 again through the heat pump outlet condensate pipe 43. Here, the three-way valve at the junction with the condensate pipe 13 is a switching valve 46 when the heat pump 24 is operating and when it is stopped. The condensate after the merge is sent to the deaerator 15. Note that the condensate that has entered the heat pump 24 passes through an absorber 36 and a condenser 37, which are internal components of the heat pump.

  Here, the inlet condensate temperature of the deaerator 15, which is a heater, is measured by an inlet condensate thermometer 39 installed in the condensate pipe 13, and the inlet steam pressure of the deaerator 15 is measured by the pressure regulator 17. It is measured. Further, the command to the steam pressure reducing valve is given an instruction value of the opening degree for changing the pressure from the arithmetic unit 38. Note that the control method of the arithmetic unit 38 will be described later.

  A condensate steam turbine having a bleed pressure control mechanism is used, and a cooling water system that is a circulation system of the steam turbine condenser is disposed on the inlet water side of the deaerator that is bleed from the paragraph having the bleed pressure control mechanism. The effect of the present invention in which a heat pump that uses waste heat as a heat absorption source is provided and the heat pumped up by the heat pump is collected in the water supply pipe will be specifically described below.

  The inlet steam condition of the main turbine of the target steam turbine power generation facility is 3.9 MPa (gauge pressure, the following is all gauge pressure), 400 ° C., and the control pressure of the extraction pressure constant control stage is 0.65 MPa. The steam of the deaerator is reduced to 0.25 MPa by a pressure reducing valve installed in the steam pipe after branching from the steam pipe sent from the control stage to the outside of the system, and then introduced into the deaerator. Is set to −94.66 kPa.

  The water supply path from the condenser to the boiler is pressurized by the condensate pump at the outlet of the condenser, collected once in the condensate tank, and degassed by the deaerated water booster pump provided at the condensate tank outlet. Water is sent to the vessel. It is assumed that, after heating and deaeration by steam turbine bleed in the deaerator, the boiler feed pump supplies water to the boiler economizer, and the replenishment water is replenished with treated water to the condensate tank.

  In this case, the deaerator inlet water supply temperature is about 40 ° C., which is approximately room temperature, whereas the deaerator outlet water is a saturation temperature of the internal pressure of the vessel, and thus is close to about 140 ° C. At this time, if heat recovery is performed by a heat pump between the deaerator and the deaerated water supply pump and the water supply at about 40 ° C. is heated to 90 ° C., the deaerator bleed flow rate before and after the operation of the heat pump is What was raised to 140 ° C from 40 ° C water supply with an air vent is about 50% because 90 ° C water supply should be raised to 140 ° C, but the deaerator outlet water supply temperature is constant. Therefore, the boiler feed water temperature does not change.

  On the other hand, the dewaterer inlet feed water temperature has risen from 40 ° C. to 90 ° C. in the waste heat recovery by the heat pump, so the internal pressure of the deaerator is the control pressure of the bleed pressure constant control stage of the steam turbine. If the pressure is increased by opening the pressure reducing valve to 0.60 MPa, which is close to 0.65 MPa, the internal pressure of the deaerator can be set to about 165 ° C. In this case, before the heat pump is introduced, the 40 ° C. feed water that has been heated to 140 ° C. in the deaerator will raise the 90 ° C. feed water to 165 ° C. The amount will be about 75%.

  From the standpoint of the amount of steam in the deaerator only, the reduction is small and the advantage is small. However, by increasing the deaerator pressure, the deaerator outlet water supply temperature can be increased from 140 ° C to 165 ° C. Become. Here, the amount of steam saved in the deaerator only affects the amount of work after the supply stage of the extracted steam to the deaerator in the steam turbine, but the pressure increase in the deaerator is the increase in boiler inlet water supply temperature. Therefore, the boiler fuel amount can be reduced or the boiler evaporation amount can be increased as it is.

  A mechanism for obtaining this effect will be described with reference to FIGS. 2 (a) and 2 (b), which show the amount of work in the steam turbine when applied to the embodiment. FIG. 2 (a) is for a condensing steam turbine having a constant extraction pressure control mechanism in which the heat pump is not operated. The steam flow rate at the steam turbine inlet is the main steam flow rate indicated by (b-a), and its enthalpy is The main steam enthalpy shown on the vertical axis.

  In the embodiment, since the process steam and the deaerator steam are extracted from the extraction pressure control stage, the flow rates of (f−g) and (e−f) are decreased from the steam turbine, respectively. The turbine internal flow rate is (cd). The enthalpy of the extraction pressure control stage and the steam turbine exhaust is a vertical axis value of the extraction enthalpy and the exhaust enthalpy shown in FIG. The work to be done by the steam turbine at this time is indicated by the area of the figure surrounded by a, b, c, d, e, f and g.

  On the other hand, FIG. 2 (b) shows the amount of work in the steam turbine that is operating the heat pump with respect to (a), and in the conventional case where the present invention is not applied, the heat pump is connected to the condensate system at the deaerator inlet. When unused waste heat is recovered, the degasser inlet condensate temperature rises, so the amount of steam to the deaerator decreases. The steam turbine output gain A, which is the area surrounded by e, d, d ', and f in FIG. 2B, is the increase in work in the steam turbine when the deaerator steam amount is reduced by half in the past. It is.

  On the other hand, by increasing the deaerator pressure by applying the present invention, when the recovery temperature by the heat pump is shifted to the high temperature side and the recovery position is shifted to the boiler inlet side, the main steam flow rate itself can be increased. Therefore, the increase in the work in the steam turbine is an area surrounded by i, j, c, and b shown in the steam turbine output gain B, and in the conventional steam turbine indicated by the steam turbine output gain A, An increase in output effect that is greater than the increase in the amount of work can be obtained.

  FIG. 2B shows the effect of increasing the amount of steam. However, when there is no margin in the amount of evaporation of the boiler, the amount of evaporation is not changed, and the boiler feed water temperature according to the present invention is increased. It is also possible to obtain the effect of reducing the boiler fuel amount.

  The control of the arithmetic unit 38 will be described with reference to the control flow chart showing the concept of the deaerator pressure control of FIG. 3 in the above embodiment. The deaerator inlet steam pressure measured by the steam pressure controller 17 is P1, the inlet steam pressure of the deaerator is Ts, the saturation temperature in the deaerator calculated by the calculation device 38 from P1, and the inlet condensate thermometer. Tf is the deaerator inlet condensate temperature measured by 39, and Td is the temperature difference between the preset deaerator saturation temperature and the deaerator inlet condensate temperature.

  The arithmetic unit 38 compares (Ts−Tf), which is a temperature difference calculated from the actually measured temperature, with Td, which is a set temperature difference, and opens the opening of the steam pressure reducing valve 16 so that (Ts−Tf) = Td. The command is issued. That is, when the deaerator inlet temperature Tf rises and the measured temperature difference (Ts−Tf) shows a decreasing tendency with respect to the control command condition of (Ts−Tf) = Td, the condition is not deviated. On the other hand, the arithmetic unit 38 controls to change the opening of the steam pressure reducing valve 16 in the opening direction, and conversely, when (Ts−Tf) shows an increasing tendency, the arithmetic unit 38 does not deviate from the condition. Control to change the opening of the pressure reducing valve 16 is performed.

  The temperature difference Td set in advance is set for the deaerator 15 inlet condensate flow rate, the boiler 1 evaporation amount, or the generator 9 output, and is converted into a function. As a concept of the set temperature difference Td, switching control is performed by functionalizing, for example, a case where it is incorporated as a polygonal line function in the arithmetic unit 38, or by determining a threshold temperature difference in advance and changing the opening of the steam pressure reducing valve 16. There is a case.

  In the embodiment of the present invention, the type of heat pump is described as an example of a single-effect steam absorption heat pump, but other types of heat pumps such as a double-effect steam absorption heat pump and a compression heat pump are used. The same effect can be obtained.

  The means for detecting the internal temperature of the deaerator can be used not only to calculate the saturation temperature of the pressure measured with a pressure gauge but also to directly measure the internal water storage temperature. Further, the extraction from the extraction pressure control stage of the steam turbine does not reach the deaerator, but the same effect can be obtained with other heaters such as a feed water heater.

  When the downstream side of the heaters such as the target deaerator or feed water heater is not a boiler immediately but has a feed water heater or deaerator, the steam flow rate of the feed water heater or deaerator is Since it is reduced, a similar effect can be expected. Moreover, when there is a margin in the amount of evaporation of the boiler and the output of the steam turbine generator, instead of saving the amount of fuel in the boiler, it is possible to meet the increased demand for the amount of steam supplied outside the system and the power generation output.

  If the feed water temperature for avoiding steaming in the boiler economizer is more restrictive than the extraction pressure control stage pressure of the steam turbine as the upper limit of the deaerator pressure, the inlet temperature of the boiler economizer However, the pressure of the deaerator is limited so as to be below that temperature.

  In the above embodiment, the cooling water of the condenser is cooled by the cooling tower, but it can be easily applied to direct cooling by river water or seawater. If there is a problem with water quality as a direct heat absorption source water, a non-contact heat exchanger can be inserted in between and the heat absorption source water can be used indirectly.

  Waste heat for steam turbine bearing cooling equipment and condenser cooling water systems can be used as a heat pump heat sink, and heat pump heat sink water is not limited to turbine plants, It is possible to use unused energy. Further, the cycle of the steam turbine plant is a non-reheat type condensate turbine, but the same principle applies to a reheat type steam turbine.

  In addition, when the main turbine is a back-pressure steam turbine and the condenser is not installed, the waste heat source that is the heat absorption source of the heat pump is not limited to the steam turbine plant, and heat recovery If the system is a circulation system such as a makeup water system or a boiler water supply system, the same effect as the present invention can be obtained.

  Although it is possible to provide a recirculation system on the steam turbine condensate system side of the heat pump and control the temperature at the outlet and inlet, temperature control by recirculation flow control is generally performed not only for heat pumps but also for heat exchangers. It is easy to apply. Moreover, it can apply similarly to suppression of a rapid temperature change by newly installing new water tanks at the entrance / exit.

It is a system flow figure of the waste heat utilization equipment of the steam turbine plant which is one example of the present invention. It is explanatory drawing before the application for explaining the effect of the present invention, and before and after application. It is a control flow figure of the way of thinking of control in the waste heat utilization equipment of the steam turbine plant of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 2 ... Main steam pipe, 3 ... Main steam control valve, 4 ... Steam turbine, 5 ... Extraction control valve, 6 ... Extraction pipe, 7 ... Exhaust pipe, 8 ... Condenser, 10, 13 ... Condensate pipe, DESCRIPTION OF SYMBOLS 12 ... Condensate tank, 15 ... Deaerator, 16 ... Steam pressure reducing valve, 17 ... Steam pressure regulator, 18 ... Boiler feed pipe, 19 ... Boiler feed pump, 21 ... Cooling water pump, 22 ... Cooling tower, 24 ... Heat pump 25 ... Cooling water supply main pipe, 26 ... Endothermic source water return pipe, 27 ... Cooling water return main pipe, 28 ... Endothermic source water supply pipe, 29 ... Endothermic source water supply pump, 30 ... Evaporator, 31 ... Steam Pipe, 32 ... Temperature reducer, 33, 34, 35 ... Generator, 36 ... Absorber, 37 ... Condenser, 38 ... Computing device, 39 ... Inlet condensate thermometer, 40 ... Inlet condensate pipe, 43 ... Heat pump outlet Condensate pipe, 44 ... outlet hot water temperature control valve, 45 ... outlet hot water temperature controller, 46 ... condensate flow rate switching , 48 ... inlet steam temperature controller, 49 ... reduced hot water pipe, 50 ... cooling water return header pipe.

Claims (3)

  A steam turbine having a bleed pressure control mechanism for supplying steam from a steam generator, a condenser provided on the exhaust side of the steam turbine, heaters for bleed from a paragraph having a bleed pressure control mechanism, and the condenser In the waste heat recovery facility of the steam turbine plant provided with a heat pump for heating the feed water to the steam generator in the circulation system, the heat pump uses the waste heat to the circulation system of the condenser as a heat absorption source, The heat pumped up is provided to recover heat upstream of the heaters installed in the boiler feed water circulation system, and the pressure of the heaters is changed according to the temperature of the inlet water of the heater. A facility for utilizing waste heat of a steam turbine plant, characterized by comprising a mechanism.   The waste heat utilization equipment for a steam turbine plant according to claim 1, wherein the heat pump is a single effect steam absorption heat pump. In Claim 1 or 2, the mechanism for changing the pressure of the heaters includes the heat pump, a pressure regulating valve for the extracted steam, a pressure gauge provided in the heaters, and an inlet water thermometer. A facility for utilizing waste heat from a steam turbine plant.

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