JP4343610B2 - Power generation apparatus and power generation method - Google Patents

Description

  The present invention relates to a power generation apparatus and method.

  The improvement of the efficiency of the thermal power generation system will be described.

  FIG. 1 is a schematic diagram for explaining the thermal balance of a thermal power generation system. In the following example, the reference temperature (environment temperature) is 0 ° C. In addition, the following patent documents 1, 2 grade | etc., Are referred about a thermal power generator.

  As shown in FIG. 1, a boiler 101 constituting a steam generator, a high-pressure turbine 102 driven by main steam supplied from the boiler 101, and driven by steam discharged from the high-pressure turbine 102 and reheated by the boiler 101. An intermediate pressure turbine 103 and a low pressure turbine 104 driven by steam discharged from the intermediate pressure turbine 103. A generator 105 is connected to the low pressure turbine 104. The high-pressure turbine 101 and the medium-pressure turbine 102 are provided with an extraction system, and extraction steam is supplied to the high-pressure feed water heater 107 and the deaerator 110, which are heating devices provided in the water supply system to the boiler 101, respectively. The low-pressure turbine 104 is also provided with an extraction system, and extraction steam is supplied to the low-pressure feed water heater 108. A condenser 106 is provided on the exhaust side of the low-pressure turbine 104. The feed water boosted by the boiler feed pump 109 is heated by the high-pressure feed water heater 107, heated by the main steam pipe of the boiler 101, then supplied to the high-pressure turbine 102, and power generation by the generator 105 is performed. Part of the steam that has worked in the high-pressure turbine is extracted and supplied to the high-pressure feed water heater 107, and the remainder is supplied to the intermediate-pressure turbine 103 after being heated by the reheater of the boiler 101 as low-temperature reheat steam. . The steam leaving the intermediate pressure turbine 103 is supplied to the low pressure feed water heater 104 and finally returned to the condenser 106 from the low pressure turbine.

  Regarding the feed water heater described above, for example, the description of Non-Patent Document 1 below is referred to. The following non-patent document 1 describes the following. Two stages of steam are extracted from the middle of the turbine, and each steam is supplied to a feed water heater to the boiler. If it does in this way, in a condenser, since the rate of the amount of heat thrown away into cooling water decreases, thermal efficiency improves. The effect of improving the thermal efficiency by the regeneration cycle increases as the pressure and temperature of the steam to be extracted increase. Further, although the thermal efficiency is improved as the number of extraction stages is increased, the effect of improving the thermal efficiency with respect to the increase in the number of stages is gradually reduced. FIG. 2 is a diagram based on FIG. 2.16 of Non-Patent Document 1 below. In FIG. 2, 201 is a boiler (heater), 202 is a turbine, 203 is a generator, 204 and 206 are feed water heaters, 205 is a feed water pump, and 207 is a condenser. Two-stage steam is extracted from the turbine 202 and supplied to the high-pressure feed water heater 204 and the low-pressure feed water heater 206, respectively.

JP 2000-240404 A (FIG. 4) Japanese Patent Laid-Open No. 11-229820 (FIG. 1) Japanese Patent Laid-Open No. 2001-140657 (FIG. 1) The Institute of Electrical Engineers, supervised by Toru Sema, “General Thermal Power Generation”, FIG. 2, page 33, published by Ohmsha, October 2002 BWR Nuclear Power Plant (Electric power 800MWe, Thermal Nuclear Power Technology Association, “Nuclear Power Plant Course”, p. 33, p. 36, May 1982. (Incorporated) Thermal Power Generation Technology Association, “Turbine / Generator (Revised)”, FIG. 8, page 9, published in January 1990

  An object of the present invention is to provide a power generation apparatus and method that are advantageous in terms of exergy loss. An object of the present invention is to provide a completely new power generation apparatus and method that enables optimization design based on energy efficiency and exergy loss.

  As a result of analyzing and examining the configuration of the extraction system based on exergy, the present inventor found a completely new device configuration advantageous in terms of the second type exergy loss, and completed the present invention. That is, the method according to one aspect of the present invention for achieving the above object is to provide a feed water heater for generating power using rotation of the turbine without supplying steam from the turbine and supplying water to the turbine. It is characterized in that exergy loss due to heat exchange in the feed water heater is reduced by not extracting and supplying steam from the water.

  An apparatus according to another aspect of the present invention includes: a feed water heater that heats feed water that has been boosted by a boiler feed pump; a boiler that heats steam from the feed water heater; and steam from the boiler or from the boiler One or a turbine to which reheated steam is supplied, a generator connected to the turbine to generate electric power, and a condenser to which the steam from the turbine is returned, and the steam from the turbine is extracted and extracted Instead of providing a system for supplying water to the feed water heater, instead of extracting steam that can turn the turbine to the turbine and generating electricity, the second type exergy loss is reduced. Is.

  Further, according to the present invention, the exergy loss in the condenser and the exergy loss in the heating water supply are compared, and when the exergy loss in the heating water supply becomes large, the steam of the turbine is extracted. The feed water heater is not supplied.

  According to the present invention, it is advantageous in terms of exergy loss over a system having an extraction system for supplying boiler steam to a feed water heater, and the optimization design of the system based on thermal efficiency and exergy loss can be achieved. It is feasible.

  The best mode for carrying out the present invention will be described below. In a preferred embodiment of the present invention, referring to FIG. 7, a feed water heater 204 heats feed water from a feed water pump 205, rotates a turbine 202 with steam from a boiler (heater) 201, and generates power in a generator 203. When generating electric power, steam is not extracted from the turbine 202 but is used for rotating the turbine to generate electric power. With this configuration, exergy loss due to heat exchange in the feed water heater is reduced by not supplying the extracted steam to the feed water heater (204, 206).

  Alternatively, in one embodiment of the present invention, the exergy loss in the condenser 207 where steam from the turbine 202 is returned is compared with the exergy loss in the feed water heaters 204 and 206, and the feed water heater If the exergy loss is greater, steam is not extracted from the turbine.

  In one embodiment of the present invention, at least one or all of the turbine and feed water heater pairs are configured not to include an extraction system for extracting steam from the turbine and supplying the steam to the feed water heater. The

  In this embodiment, steam with a wetness of zero is not extracted.

  In the present embodiment, the turbine includes a first turbine (for example, a high-pressure turbine) and a second turbine (medium-pressure or low-pressure turbine) to which steam having a lower pressure than that of the first turbine is supplied. It is good also as a structure which supplies the steam which reheated the steam from the 1st turbine with the boiler 201 to a turbine.

  The principle operation of the present invention for improving the efficiency of the power plant will be described.

  The introduction of exergy and type 2 exergy loss will be described. When examining thermodynamics and efficiency of a heat engine, it is common to use entropy or enthalpy in addition to the amount of heat. The entropy used in thermodynamics is a dimensionless parameter. In 1953, Exergy E was introduced by Z. Rant.

… (1)

… (1)

Here, T ₁ is the absolute temperature of the object, and T ₀ is the reference condition absolute temperature of the outside world. Q is the amount of heat. Exergy is the amount of heat (energy) multiplied by the Carnot efficiency. Carnot efficiency gives the upper limit of the work efficiency that the heat engine can do to the outside world. Exergy refers to the maximum amount of work that can be converted dynamically among various types of stored energy such as heat and chemical energy. That is, it represents the amount of mechanical work obtained when reversible state change is achieved before equilibration with the standard state (exergy is also referred to as “effective energy”). Exergy subtracts the loss in consideration of the ambient condition from the input _{heat, Q-T 0 × ΔS (} ΔS is entropy increment) represented by. Fuel exergy refers to the reversible work that is obtained until the unit fuel is completely burned with atmospheric oxygen and the combustion gas reaches ambient temperature.

  Exergy has the same units as energy and is easy to understand quantitatively because the increase in exergy becomes the increase in effective energy. Explain the quality of energy using exergy. An example is shown in FIG. This is a process of mixing water at different temperatures. At this time, it is a conservation system in terms of energy and no loss occurs, but there is a loss in exergy, which is referred to as “second-type exergy loss”. The first type exergy loss means a case where both energy and exergy are lost. In the example shown in FIG. 2, the reference temperature is 0 ° C. In the description using conventional entropy, if water of different temperatures is mixed, there is entropy production, and the quality of energy deteriorates by the amount of new entropy production. To create 1 kg of 100 ° C. water from 50 kg of 16.7 ° C. water, additional energy is required.

  Loss occurs when mixing media with different temperatures. In heat exchangers widely used in heat engines, the amount of heat does not change before and after the process, but there is a loss of energy quality. This can be expressed quantitatively using exergy. This means a loss of energy that can be directly used as a heat engine.

  In addition, in the above-mentioned Patent Document 3 in which the power generation efficiency is analyzed using exergy, a configuration for increasing the power generation efficiency at the partial load by the gas turbine cogeneration apparatus is disclosed, and the steam generation amount, the effective exergy efficiency, the power generation efficiency, Changes in overall thermal efficiency are shown.

  In the thermal power generation system shown in FIG. 1, feed water heaters (FWH) 107 and 108 as large heat exchangers are provided. In the feed water heater, no energy loss occurs, but the quality of energy associated with entropy production deteriorates. That is, type 2 exergy loss occurs. For specific estimation, the configuration of FIG. 1 is simplified and shown in FIG.

  Referring to FIG. 4, when water having a temperature of 33.8 ° C. enters the feed water heater 304 from the condenser 305 and exits the feed water heater 304 at 1328.9 ton / hr, it is 290 ° C., 2249 ton / hr. It has become. For this reason, most of the heat comes from the extracted steam from the turbine 302. Accordingly, since mediums having different temperatures are mixed, a large second-type exergy loss occurs in the feed water heater 304.

  Based on the data of FIG. 1, the second type exergy loss is estimated. In FIG. 4, the temperature of the steam extracted from the turbine 302 is calculated backward from the thermodynamic properties of the superheated steam. As a result, the type 2 exergy loss is about 15% to 5% of the output of the generator.

  FIG. 5 cites the description of Non-Patent Document 2 above.

The steam from the reactor
Pressure = 66.8 kg / cm ² g,
Temperature = 282.4 ° C.
Flow rate = 4737.7 ton / hr
(See Non-Patent Document 2, page 33). The steam generates 800 MWe.

On the other hand, the steam going to the high-pressure feed water heater 107 in the final stage shown in FIG.
Pressure = 78.0 kg / cm ² g,
Temperature = 380 (292) ° C.,
Flow rate = 225.3 ton / hr
It is.

  The value in parentheses for the temperature is the value when leaving the feedwater heater. In calculation, it was set to 380 ° C. The temperature of the water leaving the final high-pressure feed water heater is 290 ° C., and the high-pressure feed water heater has a temperature of 292 ° C. because the water cannot be overheated. The value of 380 ° C. is an approximate value based on the above-mentioned Non-Patent Document 2 from the enthalpy value, assuming that the pressure is 78.2 atmospheres.

  Thus, it can be seen that the steam extracted from the turbine of the thermal power plant and going to the feed water heater is better in quality than the steam immediately after leaving the reactor of the nuclear power plant. That is, temperature and pressure are high.

  Therefore, power can be generated by rotating the steam turbine using the extracted steam. If the steam extracted and supplied to the feed water heater can generate the same power, the power generation output is estimated to be low, and the following equation (2) is obtained.

… (2)

… (2)

  From the above equation (2), the exergy loss is 5.4% of the 700 MWe generator.

  That is, only steam that is extracted and goes to the high-pressure feed water heater in the final stage can rotate the turbine to generate power (5.4% of the 700 MWe generator). Therefore, the initial calculated value that the exergy loss is 5% to 15% of the generator output is reasonable.

  In the system of the design method shown in FIG. 1 and the like, steam that can sufficiently turn the turbine is extracted and mixed with water, which causes a large loss. This is completely opposite to the contents described in Non-Patent Document 1 (“The effect of improving the thermal efficiency by the regeneration cycle is greater as the pressure and temperature of the steam to be extracted is higher”). In the configuration described in Non-Patent Document 1, exergy loss increases as the steam pressure temperature increases.

  FIG. 6 is cited from Non-Patent Document 3 and shows specific enthalpies and specific entropy diagrams for nuclear power and thermal power generation. It can be seen that thermal power generation uses steam with better conditions than nuclear power generation. That is, in nuclear power generation, power is generated almost using saturated steam, whereas in thermal power generation, superheated steam is used. In FIG. 6, y represents the wetness and y = 0, 5, 10, 15%.

  In nuclear power, steam turbines are used almost wet. Since most thermal turbines are operated at zero wetness, turbine design is also easier. It can be used for a long time with little damage.

  As can be seen from FIG. 6, in nuclear power generation, it is understood that the steam is of sufficient quality that can be generated by a turbine. Accordingly, steam that can sufficiently turn the turbine is turned to the turbine without extraction to generate electricity. Accordingly, the temperature of the water that is reduced to the boiler decreases. Although fuel consumption increases, exergy calculations include how much gain there is in the net including them. This is because the second type exergy loss is an energy (calorie) storage process.

  As described above, in the conventional apparatus, when all the steam is exhausted to the condenser, the amount of heat to be thrown out is increased, so that the structure is extracted (see Non-Patent Document 1). However, the steam temperature leaving the final stage of the turbine is low, so the heat engine cannot do much work. That is, exergy as effective energy is not large. Therefore, even if a large amount of heat is thrown away, the efficiency does not decrease. This is because the turbine outlet temperature and the ambient temperature are very close.

  In FIG. 1, the amount of heat at the boiler outlet is Q, and the temperature is 560.degree. Then, assume that 62% of the flow rate is led to the condenser. At this time, the outside air temperature (reference temperature) is 30 ° C., and the turbine outlet temperature is 60 ° C.

  In the present embodiment, the steam extracted from the turbine 202 and supplied to the feed water heaters 204 and 206 in FIG. 2 is all returned to the condenser 207 by turning the turbine. In this embodiment having such a configuration, the newly generated exergy loss is only 3.4% with respect to the exergy of the original steam.

  On the other hand, the exergy loss lost by exchanging heat with the feed water heater as in the conventional apparatus is 5% to 15% of the whole.

  From the above, it is clear that exergy gains in this embodiment.

  The temperature of the water exiting from the lowermost feed water heater 108 in FIG. 1 is 72.2 ° C., and since there is a temperature after heat exchange, the turbine outlet temperature is higher than 60 ° C. Actually, the extraction is not from the lowest stage of the turbine.

  FIG. 5 shows the thermal balance of the nuclear power plant. The temperature going from the feed water heater in the final stage to the condenser is 42.5 ° C, which is about 30 ° C lower than 72.2 ° C. This is because the steam quality of the nuclear power plant is poor and the steam temperature is used to a considerably low temperature in order to increase the power generation efficiency. Therefore, in this example, the rate of exergy loss from the condenser is smaller than that of the thermal power plant.

  FIG. 7 is a diagram showing the configuration of this embodiment. Referring to FIG. 7, a boiler 201 that heats steam from the feed water heater 204, a turbine 202 that is supplied with steam from the boiler 201 or reheated steam from the boiler 201, and power generation that is connected to the turbine 202 and generates power. Machine 203 and a condenser 207 to which steam from the turbine 202 is returned, and a bleed system for supplying the steam from the turbine 202 to the feed water heaters 204 and 206 is not provided. That is, power generation is performed by using steam that can turn the turbine to rotate the turbine 202 without extracting the steam. At least steam with a wetness of zero is not extracted. Note that heat extraction of the extracted steam in the feed water heater is not performed, but the steam from the high pressure turbine may be reheated by the boiler 201 and supplied to the intermediate pressure turbine.

  In this embodiment, when the exergy loss in the condenser 207 is compared with the exergy loss in the heating water supply 204 or 206, and the exergy loss in the heating water supply 204 or 206 is large, The steam from the turbine 202 may not be extracted.

  Although the present invention has been described with reference to the above-described embodiments, the present invention is not limited only to the configuration of the above-described embodiments, and various modifications that can be made by those skilled in the art within the scope based on the principle of the present invention, Of course, modifications are included.

  From the viewpoint of exergy, we reviewed the thermal balance design of thermal power plants and examined the possibility of improving efficiency. The present invention has proposed a power generation apparatus configured to reduce exergy loss caused by heat exchange of steam extracted from a turbine with a feed water heater. The present invention enables optimization design of a power generation system based on energy efficiency and exergy.

It is a figure which shows an example of a structure of a thermal power generator. It is a figure which shows an example of the basic composition of the regeneration cycle in a thermal power generator. It is a figure for demonstrating the exergy loss by mixing of the water from which temperature differs. It is a figure which simplifies and shows the heat balance of a thermal-power-generation apparatus. It is a figure which simplifies and shows the heat balance of a nuclear power plant of 800 MWe. It is a figure which shows the steam expansion of a thermal turbine and a nuclear power turbine. It is a figure which shows the structure of the thermal-power-generation apparatus of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Boiler 102 High pressure turbine 103 Medium pressure turbine 104 Low pressure turbine 105 Generator 106 Condenser 107 High pressure feed water heater 108 Low pressure feed water heater 109 Feed water pump 201 Boiler 202 Turbine 203 Generator 204 Feed water heater 205 Feed water pump 206 Feed water heater 207 Condenser 301 Boiler 302 Turbine 303 Generator 304 Feed water heater 305 Condenser

Claims (2)

In a method of generating electricity by turning a turbine with steam from a boiler,
Comparing the exergy loss in the condenser where the steam from the turbine is returned to the exergy loss in the feed water heater supplying water to the turbine;
When the exergy loss in the feed water heater is larger, steam is not extracted from the turbine, and power is generated using the rotation of the turbine. In a power generator that generates electricity by turning a turbine with steam from a boiler,
Comparing the exergy loss in the condenser where the steam from the turbine is returned to the exergy loss in the feed water heater supplying water to the turbine;
When the exergy loss in the feed water heater is larger, the power generator is provided with means for generating electric power by using steam to rotate the turbine without extracting steam from the turbine.

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