JP2018162739A - Power generation plant and method for operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generation plant that does not adversely affect a boiler or a steam turbine when heating steam is supplied to a feed water heater in addition to extraction steam.SOLUTION: A power generation plant comprises: a boiler 3 for generating steam; a steam turbine 5 driven by the steam generated in the boiler 3; a condenser 25 for liquefying the steam exhausted from the steam turbine 5; a power generator 19 driven by the steam turbine 5; a feed water heater 28 for heating feed water to be supplied to the boiler 3 by the extraction steam extracted from the steam turbine 5; a biomass boiler 7 for generating additional heating steam to be supplied to the feed water heater 28; and an additional steam bypass pipe 44 bypassing the feed water heater 28 for introducing additional steam to the condenser 25.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power plant including a feed water heater for heating boiler feed water, and an operation method thereof.

  In a power plant where steam generated by a boiler using fossil fuels such as coal and oil is supplied to a steam turbine and the steam turbine is driven to rotate, and power is generated by the generator using this rotating drive, power generation efficiency is improved There is a need to reduce fuel consumption and environmental impact. Further reductions in environmental impact include reductions in carbon dioxide emissions that are being addressed globally. For example, Patent Document 1 discloses an invention in which external steam such as surplus steam of another plant is led to a feed water heater together with extracted steam extracted from a steam turbine to improve power generation efficiency.

JP 2004-190546 A

  However, Patent Document 1 discloses that external steam is guided from another plant, but when external steam is mixed with extracted steam guided from a steam turbine, the state of the external steam suddenly fluctuates. And may adversely affect the steam turbine. Moreover, there is a possibility that the cost associated with an increase in equipment when introducing equipment for introducing external steam from another plant is increased.

  On the other hand, biomass-derived biomass fuels such as woody, agricultural, and sludge are carbon neutral that does not emit carbon dioxide, which is a global warming gas, because carbon dioxide is taken in during the growth of biomass. Various uses have been studied. For example, a power plant that performs co-firing in a boiler using fossil fuel and biomass fuel has been studied.

  However, high-quality biomass fuels are expensive, and there are problems in terms of cost competitiveness with respect to fossil fuels. In addition, since inexpensive biomass fuels contain many corrosive components, only a small amount can be mixed in a boiler. Furthermore, there is an upper limit to the mixed combustion rate due to technical limitations of boiler fuel supply facilities and environmental devices, and when the output of the boiler is low, the amount of biomass fuel input must be further reduced.

The present invention has been made in view of such circumstances. When heating steam is supplied to a feed water heater in addition to extraction steam, the boiler or steam turbine is adversely affected by a sudden change in the state of the heating steam. An object of the present invention is to provide a power plant and a method for operating the same.
Another object of the present invention is to provide a power plant that can reduce the cost of introducing equipment for supplying heated steam to a feed water heater and an operating method thereof.
In addition, when carbon-neutral biomass fuel is used to reduce environmental impact, the present invention increases the use ratio of biomass fuel to reduce fossil fuel consumption and reduce carbon dioxide emissions that do not become carbon-neutral. An object of the present invention is to provide a power plant that can be operated and a method for operating the power plant.

In order to solve the above problems, the power generation plant and the operation method thereof according to the present invention employ the following means.
That is, a power plant according to the present invention includes a boiler that generates steam, a steam turbine that is driven by the steam generated by the boiler, a condenser that liquefies the steam exhausted from the steam turbine, A generator driven by the steam turbine, a feed water heater for heating feed water supplied to the boiler by the extracted steam extracted from the steam turbine, and heated steam mixed and supplied to the extracted steam of the feed water heater And a heating steam bypass system that bypasses the feed water heater and guides the heating steam to the condenser.

Heat steam generated by the boiler for heating steam is supplied to the feed water heater to increase the feed water temperature, and the extraction amount of the extraction steam is reduced according to the heating amount of the feed water by the heating steam boiler. The steam flow through can be increased within a specified range of the mechanical limits of the steam turbine to increase the turbine output. In addition, when comparing the amount before and after reducing the amount of steam extracted, if the total amount of steam supplied from the boiler to the steam turbine is adjusted so as to have the same turbine output, by reducing the amount of extraction, Since the total steam flow can be reduced, turbine efficiency can be improved. The turbine efficiency of the steam turbine can be increased to improve the power generation efficiency for fossil fuel energy (hereinafter referred to as “power generation efficiency”). As a result, when generating the same amount of power as before the power generation efficiency is improved, the amount of fossil fuel that is put into the boiler can be reduced, and the amount of carbon dioxide that does not become carbon neutral can be reduced.
It was decided to provide a bypass system for heating steam that bypasses the feed water heater and guides the heating steam to the condenser. Thereby, when the heating steam supplied to the feed water heater is unnecessary, for example, when the heating steam boiler is started or stopped (including emergency stop such as boiler trip), the heating steam bypass system is used. Heated steam can be directed to the condenser. Thereby, even if the state of the heating steam suddenly changes, it is possible to avoid adversely affecting the boiler and the steam turbine. Moreover, since the heating steam can be recovered by the condenser, the loss of the total water amount of the water / steam system can be suppressed.

  Furthermore, in the power plant of the present invention, an extraction steam control valve is provided that controls the flow rate of the extraction steam according to the flow rate of the heating steam guided from the boiler for heating steam.

  By controlling the flow rate of the extraction steam with the extraction steam control valve in accordance with the flow rate of the heating steam, the extraction steam amount can be reduced as much as possible to improve the efficiency of the steam turbine.

  Furthermore, the power plant according to the present invention includes a pure water supply system for heating steam that supplies water to the heating steam boiler from the condenser.

  By supplying water from the condenser to the heating steam boiler using the heating steam water supply system, the steam turbine water supply system that distributes the boiler and the steam turbine and the heating steam supply system that distributes the heating steam boiler are shared. can do. Thereby, a condensate system can be shared and cost can be reduced by reducing the number of equipment. In addition, by managing the steam turbine water supply system and the heating steam water supply system in accordance with a common water quality standard, the cost can be reduced by reducing the number of equipment by using a common chemical solution injection facility. .

  Furthermore, the power plant according to the present invention includes a drain water supply system that guides drain water condensed by the feed water heater to the boiler for heating steam.

  The drain water condensed in the feed water heater is guided to the heating steam boiler via the drain water supply system. Thereby, the water supply piping for heating steam from the condenser to the boiler for heating steam and the supplementary water pump for additional steam can be omitted. When the water led from the condenser is not used, the chemical liquid injection equipment used for the steam turbine water supply system cannot be shared. Therefore, the heating steam boiler chemical liquid injection equipment should be provided in the heating steam water supply system. Is preferred.

  The power plant of the present invention further includes a pure water tank that supplies pure water to the boiler, and a pure water transfer system for heating steam that supplies pure water from the pure water tank to the heating steam boiler. It is characterized by being.

  The pure water tank is shared by connecting the pure water transfer system for heating steam from the pure water tank that supplies pure water to the boiler to the heating steam boiler. Thereby, cost can be reduced by reducing the number of devices.

  Furthermore, the power plant of the present invention comprises a wastewater treatment facility for treating the wastewater discharged from the boiler, and a heating steam drainage system for guiding the wastewater discharged from the heating steam boiler to the wastewater treatment facility, It is characterized by having.

  The wastewater treatment facility that treats the wastewater discharged from the boiler is connected to the boiler for heating steam, and the wastewater treatment facility is shared. Thereby, cost can be reduced by reducing the number of devices.

  Furthermore, in the power plant of the present invention, the boiler for heating steam is a biomass boiler that uses biomass fuel as a main fuel.

  By making the boiler for heating steam into a biomass boiler using biomass fuel as the main fuel, the biomass fuel can be exclusively fired in the boiler for heating steam without co-firing the biomass fuel in the boiler. Therefore, the use ratio of biomass fuel to fossil fuel burned in a boiler as a power plant can be increased. Moreover, inexpensive biomass fuel containing a corrosive component can be used without affecting the combustion in the boiler body, and highly efficient power generation can be performed for fossil fuel energy. In addition, carbon dioxide emissions that do not become carbon neutral can be reduced.

  The power plant operating method of the present invention includes a boiler that generates steam, a steam turbine that is driven by the steam generated by the boiler, and a condenser that liquefies the steam exhausted from the steam turbine. A generator driven by the steam turbine, a feed water heater that heats feed water supplied to the boiler by the extracted steam extracted from the steam turbine, and mixed and supplied to the extracted steam of the feed water heater An operation method of a power plant comprising a heating steam boiler that generates heating steam, wherein the heating steam is led to the condenser by bypassing the feed water heater.

By providing a bypass system for the heated steam that bypasses the feed water heater and guides the heated steam to the condenser, it is possible to avoid adverse effects on the boiler and steam turbine even if the state of the heated steam suddenly changes .
In addition, since a common chemical solution injection facility, a pure water tank, and a wastewater treatment facility are used, the number of devices can be reduced and the cost can be reduced.
In addition, by making the boiler for heating steam into a biomass boiler, the biomass fuel is exclusively fired in the boiler for heating steam without co-firing biomass fuel in the boiler, so the use ratio of biomass fuel can be increased, The power generation efficiency for fossil fuel energy can be improved. In addition, the amount of fossil fuel that is input to the boiler can be reduced, and the amount of carbon dioxide that does not become carbon neutral can be reduced.

It is a schematic structure figure showing a power plant concerning one embodiment of the present invention. It is the flowchart which showed the control flow at the time of throwing in additional heating steam from a biomass boiler to a feed water heater. It is the flowchart which showed the control flow of the temperature and pressure of the feed water supplied to a boiler. It is the flowchart which showed the control flow when the temperature and pressure of the additional heating steam led from the biomass boiler are significantly high. It is the flowchart which showed the control flow of the supplementary water pump for additional steam. It is the flowchart which showed the control flow of the water quality management of the feed water supplied to a biomass boiler. It is the flowchart which showed the control flow of the pure water transfer pump for additional steam. It is the schematic block diagram which showed the modification of the power plant of FIG. It is the schematic block diagram which showed the comparative example of the power plant of FIG. It is the graph which showed the comparison about the presence or absence of the component apparatus in embodiment, a modification, and a comparative example. It is the graph which showed the amount of heating before and after applying a biomass boiler. It is the graph which showed the power generation efficiency with respect to the fossil fuel energy before and after applying a biomass boiler. It is the graph which showed the energy breakdown before and after applying a biomass boiler.

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 shows a power plant 1 according to the present embodiment. The power plant 1 includes a boiler 3, a steam turbine 5, and a biomass boiler (heated steam boiler) 7. In FIG. 1, the water-state piping is indicated by a solid line, and the steam-state piping is indicated by a broken line.

  The boiler 3 is a so-called conventional boiler, and includes a burner (not shown) that forms a flame in a furnace using a fossil fuel such as coal or oil (not shown). Combustion exhaust gas (not shown) generated by the flame of a burner (not shown) passes around the heat transfer pipes of a superheater, reheater, and economizer (not shown) disposed in the boiler 3 and then exchanges heat to the outside. And discharged.

  A water supply pipe 10 for supplying water is connected to the boiler 3. The water supply pipe 10 is provided with a pH sensor 11 that measures a pH value as the quality of water supplied to the boiler 3. The measured value of the pH sensor 11 is sent to the control unit 12.

  A wastewater treatment facility 9 is connected to the boiler 3 via a drainage pipe 9a. The wastewater treatment facility 9 treats wastewater generated when the boiler 3 is cleaned up or blown.

  The feed water passing through the feed water pipe 10 passes through an economizer (not shown) and a superheater (not shown) provided in the boiler 3 and becomes superheated steam. The superheated steam is guided to the high-pressure turbine 16 of the steam turbine 5 through the main steam pipe 14.

  The steam turbine 5 includes a high-pressure turbine 16 and a low-pressure turbine 17. The generator 19 is rotationally driven by the rotational power generated in the turbines 16 and 17 to generate power. In FIG. 1, the generator 19 is provided in each of the high-pressure turbine 16 and the low-pressure turbine 17, but the output shafts of the high-pressure turbine 16 and the low-pressure turbine 17 may be combined to form one generator 19.

  A high pressure turbine outlet pipe 21 is connected to the exhaust side of the high pressure turbine 16. The downstream end of the high-pressure turbine outlet pipe 21 is connected to a reheater (not shown) provided in the boiler 3, and the steam that has been subjected to predetermined expansion in the high-pressure turbine 16 and rotationally driven the turbine is regenerated. It is led to a heater.

  Between the steam outlet side of the reheater and the low pressure turbine 17, a reheat steam supply pipe 23 for supplying the reheat steam to the low pressure turbine 17 is provided. In the present embodiment, the steam turbine 5 includes the high-pressure turbine 16 and the low-pressure turbine 17, but an intermediate-pressure turbine may be added between the high-pressure turbine 16 and the low-pressure turbine 17 so as to be a three-pressure type. In this case, the reheat steam led from the reheater is supplied to the intermediate pressure turbine.

  A condenser 25 is connected to the exhaust side of the low-pressure turbine 17. In the condenser 25, the steam is cooled to a vacuum by a cooling water (not shown) and is condensed and liquefied. The condensate liquefied by the condenser 25 becomes feed water and is led to the feed water heater 28 by the feed pump 26.

In the present embodiment, as an example of heating the feed water guided from the condenser 25, high-pressure steam extracted from the high-pressure turbine 16 is guided to the feed water heater 28 via the high-pressure extraction pipe 29. Thereby, the water supply led from the condenser 25 is heated by the high-pressure extraction steam. The high pressure extraction pipe 29 is provided with a high pressure extraction control valve (extraction steam control valve) 29V. The valve opening degree of the high pressure extraction control valve 29V is controlled by the control unit 12.
A feed water heater using low-pressure steam extracted from the low-pressure turbine 17 may be separately provided, and the feed water heated by the low-pressure steam may be heated by the feed water heater 28.

  A chemical solution injection facility 30 is connected to the water supply pipe 10 between the water supply pump 26 and the water supply heater 28. The chemical solution injection facility 30 is a facility for injecting chemical solutions such as ammonia, hydrazine, and phosphoric acid into the feed water, and is used for managing the quality of the feed water supplied to the boiler 3. In the chemical solution injection facility 30, the injection amount of the chemical solution is controlled by the control unit 12 based on the measurement by the pH sensor 11. The water quality is managed, for example, according to standard values defined in JIS B 8223 (boiler feed water and boiler water quality). Specifically, since the elution of iron becomes remarkable at about pH 8.0, a chemical solution is introduced into the water supply line to adjust the water supply to be alkaline, and the pH control value is a value between 8.5 and 10.3. More preferably, it is about 9.3 to 10.

  After being heated by the feed water heater 28, the feed water passes through the feed water pipe 10 and is guided to the boiler 3. A feed water pipe 10 between the feed water heater 28 and the boiler 3 is provided with a feed water temperature sensor 10T and a feed water pressure sensor 10P. The measured values of these sensors 10T and 10P are sent to the control unit 12.

  The drain water condensed after the feed water is heated by the feed water heater 28 is guided to the condenser 25 through the drain pipe 32. The drain pipe 32 is provided with a drain water control valve 32V. The opening degree of the drain water control valve 32 </ b> V is controlled by the control unit 12.

  The condenser 25 is provided with a pure water supply facility 8 that supplies pure water as makeup water. The pure water supply facility 8 includes a pure water device 34 for producing pure water, a pure water tank 35 for receiving pure water produced by the pure water device 34, and pure water for supplying pure water from the pure water tank 35. A supply pump 36 and a makeup water tank 37 for receiving pure water guided from the pure water supply pump 36 are provided. Pure water stored in the makeup water tank 37 is supplied to the condenser 25 as makeup water. The makeup water is used to supplement an amount corresponding to the amount of water circulating through the boiler 3 and the steam turbine 5 being taken out of the system. A pure water bypass pipe 38 that bypasses the makeup water tank 37 is provided between the pure water tank 35 and the condenser 25. The pure water bypass pipe 38 is used when supplying pure water when the boiler 3 is started up and stored.

  Between the condenser 25 and the main steam pipe 14, a main steam discharge pipe 15 that guides the main steam to the condenser 25 at the time of starting or stopping is provided. The main steam discharge pipe 15 is provided with a main steam discharge valve 15 </ b> V, and the opening and closing of the main steam discharge pipe 15 is controlled by the controller 12.

  The biomass boiler 7 generates steam by burning biomass fuel. The output which is the steam generation amount of the biomass boiler 7 is controlled by the control unit 12. Specifically, the control unit 12 controls the supply amount of biomass fuel to be introduced into the biomass boiler 7, the flow rate of combustion air, the supply amount of steam generated with the vapor properties of a predetermined temperature and pressure, and the like.

  The additional heating steam (heating steam) generated by the biomass boiler 7 is guided to the high-pressure extraction pipe 29 via the additional steam supply pipe 40. The additional steam supply pipe 40 is provided with an additional steam flow sensor 40F for measuring the additional steam flow rate, and a temperature sensor 40T and a pressure sensor 40P for controlling the properties of the additional heating steam. The additional steam flow sensor 40F and the measured values of the temperature sensor 40T and the pressure sensor 40P are sent to the control unit 12, and output control as the steam generation amount of the biomass boiler 7 is performed based on the measured values.

  The additional steam supply pipe 40 is provided with an additional steam on-off valve 40V1 and an additional steam control valve 40V2. The opening and closing of these valves 40V1 and the opening degree of 40V2 are controlled by the control unit 12. The additional steam on-off valve 40V1 is fully closed when the additional heating steam supplied from the biomass boiler 7 is not used, and is fully opened when the additional heating steam is used. The opening degree of the additional steam control valve 40V2 is controlled by the control unit 12 based on the measured values of the temperature sensor 10T and the pressure sensor 10P provided in the water supply pipe 10.

  The additional steam supply pipe 40 is provided with a safety valve 42. When the pressure of the additional heating steam exceeds a predetermined value, the safety valve 42 is opened, and the steam is released out of the system.

  An additional steam bypass pipe (heating steam bypass system) 44 is provided upstream of the safety valve 42 in the steam flow. The additional steam bypass pipe 44 is provided with an additional steam bypass control valve 44V. The opening and closing of the additional steam bypass control valve 44V is controlled by the control unit 12. An additional steam bypass pipe 44 bypasses the feed water heater 28 and guides the additional steam to the condenser 25. The additional steam bypass pipe 44 is used when the biomass boiler 7 is started or stopped (including an emergency stop such as a boiler trip).

  The biomass boiler 7 is provided with an additional steam supply pipe (heated steam pure water supply system) 46 for supplying water. The additional steam pure water supply pipe 46 is provided between the condenser 25 and the biomass boiler 7. In the additional steam pure water feed pipe 46, an additional steam make-up water pump 47, an additional steam make-up water tank 48, an additional steam feed water pump 49, and a biomass boiler pH sensor 50 are sequentially provided from the upstream side of the feed water flow. And are provided.

  The additional steam supply water pump 47 is based on the measured value of the additional steam flow sensor 40F provided in the additional steam supply pipe 40, and the additional steam feed water pump 49 is based on the measured value of the pressure sensor 40P. Thus, the discharge flow rate of the feed water supplied to the supplemental water tank 48 for additional steam and the supply pressure to the biomass boiler 7 are controlled. That is, the supplementary steam supply water pump 47 and the additional steam feed water pump 49 are controlled in conjunction with the amount of steam generated by the biomass boiler 7.

  Connected between the supplemental steam supply water tank 48 and the pure water tank 35 is an additional steam pure water transfer pipe (heated steam pure water transfer system) 52 for replenishing the pure water of the pure water supply equipment 8. Has been. The additional steam pure water transfer pipe 52 is provided with an additional steam pure water transfer pump 54. The additional steam makeup water tank 48 is provided with a level sensor 48L for measuring the water level in the tank. The measurement value of the level sensor 48L is sent to the control unit 12. The controller 12 controls the operation of the additional steam pure water transfer pump 54 based on the measurement value of the level sensor 48L. That is, when the water supply flow rate by the supplementary steam supply water pump 47 is insufficient with respect to the water supply flow rate by the additional steam water supply pump 49 and the control unit 12 determines that the water level is equal to or lower than the predetermined value based on the measured value of the level sensor 48L The pure water transfer pump 54 for additional steam is activated to transfer pure water to the supplementary water tank 48 for additional steam. Thereby, the water level in the supplementary water tank 48 for additional steam is kept above a certain level.

  The biomass boiler pH sensor 50 measures and monitors the pH of the water supplied to the biomass boiler 7 as the water quality. The measured value of the biomass boiler pH sensor 50 is sent to the control unit 12. Based on the measurement value of the biomass boiler pH sensor 50, the chemical solution injection facility 30 is controlled. The chemical injection facility 30 is controlled based on not only the pH sensor 11 for the boiler 3 but also the pH sensor 50 for the biomass boiler so that the pH sensor 11 and the pH sensor 50 are within a predetermined appropriate set value range. That is, the chemical liquid injection facility 30 is shared by the boiler 3 and the biomass boiler 7.

  A heating steam pure water bypass pipe 56 is provided that branches from the additional steam pure water transfer pipe 52, bypasses the supplemental steam supply water tank 48, and supplies pure water to the biomass boiler 7. The pure water bypass pipe 56 for heating steam is used when supplying pure water when the biomass boiler 7 is started or stored.

  A wastewater treatment facility 9 is connected to the biomass boiler 7 via a biomass boiler drainage pipe (heated steam drainage system) 57. The wastewater treatment facility 9 treats wastewater generated when the biomass boiler 7 is cleaned up or blown. Moreover, the waste water treatment equipment 9 is connected via the drain pipe 9a from the boiler 3, and the waste water treatment equipment 9 can perform the waste water treatment of both the boiler 3 and the biomass boiler 7, and is shared.

  The control unit 12 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions are realized. The program is preinstalled in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

The power plant 1 having the above-described configuration operates as follows.
The superheated steam generated in the boiler 3 is guided to the high-pressure turbine 16 of the steam turbine 5, and after the high-pressure turbine 16 is driven to rotate, the superheated steam is guided to a reheater (not shown) of the boiler 3. The steam led to the reheater is reheated by the boiler 3 and led to the low pressure turbine 17 as reheated steam. The reheat steam drives the low-pressure turbine 17 to rotate. The generator 19 is rotationally driven by the rotational power thus obtained, and power is generated.

  The steam that has been subjected to a predetermined expansion in the low-pressure turbine 17 and has finished the work of rotating the turbine becomes condensate in the condenser 25, and the steam is cooled to a vacuum by a cooling water (not shown) to be condensed and liquefied. The condensate liquefied by the condenser 25 becomes water supply and is supplied to the boiler 3. The feed water to the boiler 3 is heated when passing through the feed water heater 28. The heating by the feed water heater 28 is performed after the biomass boiler 7 is started and becomes in a steady state, without using all of the high-pressure steam extracted from the high-pressure turbine 16 and from the biomass boiler 7 to the additional steam supply pipe 40. Heating is performed by additional heating steam guided through the. After the activation of the biomass boiler 7, the additional steam opening / closing valve 40 </ b> V <b> 1 is opened, and the flow rate of the additional heating steam guided from the biomass boiler 7 is controlled by the control unit 12 using the additional steam control valve 40 </ b> V <b> 2. . The controller 12 controls the additional steam control valve 40V2 based on the measured values of the feed water temperature sensor 10T and the feed water pressure sensor 10P. The additional heating steam from the biomass boiler 7 supplied to the feed water heater 28 is drained by the feed water heater 28 and recovered as condensate to the condenser 25, and then a part of the condensate is supplied to the boiler 3. Supplied as

FIG. 2 shows a control flow when adding additional heating steam from the biomass boiler 7 to the feed water heater 28.
As shown in the figure, the biomass boiler 7 is activated (step S11). At this time, the additional steam on-off valve 40V1 and the additional steam control valve 40V2 are closed. Next, after the biomass boiler 7 is in a steady state, the high pressure extraction control valve 29V is closed to fully close or reduce the opening, and stop the extraction of high pressure steam from the high pressure turbine 16 or reduce the extraction flow rate. (Step S12). Then, the additional steam on-off valve 40V1 is opened, and the additional steam control valve 40V2 is opened to control the opening degree (step S13). Thereby, the additional heating steam is guided from the biomass boiler 7 to the feed water heater 28.

FIG. 3 shows a control flow of the temperature and pressure of the feed water supplied to the boiler 3.
When controlling the feed water temperature measured by the feed water temperature sensor 10T or the feed water pressure measured by the feed water pressure sensor 10P to be within the set value range, it is determined whether or not the set value is higher than the upper limit value. (Step S21). When the feed water temperature or the feed water pressure is higher than the upper limit value of the set value range, the process proceeds to step S22, and the control unit 12 controls the opening degree of the additional steam control valve 40V2 in the feed water heater 28. While reducing the heating amount of the feed water, the amount of fuel input to the biomass boiler 7 is controlled so that the feed water temperature and the feed water pressure are less than or equal to the upper limits of the set value range. When the feed water temperature or the feed water pressure is within the set value range and is lower than the upper limit value, the process proceeds to step S23, and the operation is continued as it is as the steady operation.
Although not shown in FIG. 3, a situation occurs in which the feed water temperature or feed water pressure supplied to the boiler 3 is lower than the lower limit of the set value range due to the state of the additional heating steam of the biomass boiler 7. In addition, the control unit 12 controls the opening degree of the additional steam control valve 40V2 to increase the heating amount of the feed water in the feed water heater 28, and controls the fuel input amount of the biomass boiler 7 to Control is performed so that the temperature and the feed water pressure are equal to or higher than the lower limit of the set value range. When the feed water temperature or the feed water pressure is within the set value range and is higher than the lower limit value, the operation is continued as it is as the steady operation in step S23.
Although not shown, when the opening of the additional steam control valve 40V2 is controlled, such as when the operating conditions of the biomass boiler 7 are limited, the feed water temperature or feed water pressure is lower than the lower limit of the set value range. In this case, the heating amount of the feed water in the feed water heater 28 can be increased by slightly opening the opening of the high-pressure extraction control valve 29V and slightly increasing the extraction flow rate of the high-pressure steam from the high-pressure turbine 16. It becomes.

In FIG. 4, the temperature and pressure of the additional heating steam measured by the temperature sensor 40T and the pressure sensor 40P for controlling the properties of the additional heating steam output and guided from the biomass boiler 7 are significantly high. When the control flow is shown.
It is determined whether or not the temperature and pressure of the additional heating steam led from the biomass boiler 7 are significantly higher than the set temperature and the set pressure (step S31). The set temperature and set pressure are stored in the control unit 12 in advance. If the additional heating steam exceeds the set temperature or set pressure, the process proceeds to step S32. When the pressure of the additional steam pressure sensor 40P of the additional steam supply pipe 40 increases rapidly due to a high pressure of the additional heating steam and exceeds the set value of the safety valve 42 (for example, 1. 1 times), the safety valve 42 is opened, and additional heating steam is released out of the system. When the amount of additional heating steam generated increases and the pressure of the additional steam pressure sensor 40P in the additional steam supply pipe 40 is lower than the set value at which the safety valve 42 opens, the set temperature or set flow rate is further increased by a predetermined amount. If it exceeds (for example, about 1.1 times the set value), the additional steam bypass control valve 44V is temporarily fully opened according to a command from the control unit 12, and additional heating steam is supplied via the additional steam bypass pipe 44. By guiding to the condenser 25, additional heating steam is prevented from being discharged out of the system. When the temperature of the additional steam temperature sensor 40T or the pressure of the additional steam flow sensor 40F returns to a state lower than the upper limit value of the setting range, the process proceeds to step S33, and the operation is continued as it is as a steady operation.

FIG. 5 shows a control flow of the supplemental steam supply water pump 47.
As shown in step S41, when the control unit 12 determines that the amount of additional heating steam generated in the biomass boiler 7 has increased by the measured value of the additional steam flow sensor 40F (step S41), the process proceeds to step S42. The pure water supplied from the supplemental steam supplementary water pump 47 to the supplemental steam supplementary water tank 48 is supplied to the supplementary steam supplementary water pump 47 so that the amount of water supplied corresponds to the increase in the amount of additional heating steam generated. Increase the discharge flow rate. Thereby, pure water commensurate with the increased amount of additional heated steam generated is supplied from the condenser 25. On the other hand, if it is determined that the amount of additional heating steam generated in the biomass boiler 7 has decreased (step S41), the process proceeds to step S43, and the supplemental steam supply water pump 47 supplies the supplemental steam to the supplemental steam tank 48 for additional steam. The discharge flow rate of the supplemental water supply pump 47 for additional steam is decreased so that the pure water to be supplied has a water supply amount corresponding to the amount of decrease in the amount of additional heating steam generated.

FIG. 6 shows a control flow of water quality management of feed water supplied to the biomass boiler 7.
When the control unit 12 determines that the measured value of the biomass boiler pH sensor 50 is equal to or lower than the lower limit value of the set value range (step S51), the process proceeds to step S52, and the amount of the chemical solution injected from the chemical solution injection facility 30 Is increased based on the chemical injection amount estimated from the difference between the pH value of the feed water and the target pH value provided in the set value range. Thereby, the pH value of feed water is raised. On the other hand, when the measured value of the biomass boiler pH sensor 50 is higher than the upper limit value of the set value range (step S51), the process proceeds to step S53, and the amount of the chemical solution injected from the chemical solution injection facility 30 is maintained or reduced. . Thereby, the water quality is maintained within the standard value by keeping the pH value of the feed water within the set value range.
Here, it is preferable to consider not only the biomass boiler pH sensor 50 but also the measured value of the boiler 3 pH sensor 11. The value of the biomass boiler pH sensor 50 is generally similar to that of the boiler 3 pH sensor 11. However, in an unsteady state in which the feed water flow rate is unbalanced, the chemical liquid injection facility 30 is configured so that the pH sensor 11 and the pH sensor 50 are set based on both the pH sensor 11 for the boiler 3 and the pH sensor 50 for the biomass boiler. Controlled to be in range.

FIG. 7 shows a control flow of the additional steam pure water transfer pump 54.
When the control unit 12 determines that the water level in the tank 48 is equal to or lower than the set value by the level sensor 48L provided in the supplemental water tank 48 for additional steam (step S61), the process proceeds to step S62 and the pure water for additional steam is used. The transfer pump 54 is started, and pure water is supplied from the pure water tank 35 to the supplementary water tank 48 for additional steam. Thereby, the water level in the tank 48 is maintained at a set value or more. On the other hand, when the control unit 12 determines that the water level in the tank 48 is higher than the set value (step S61), the process proceeds to step S63, and the additional steam pure water transfer pump 54 is stopped.

FIG. 8 shows a modification of the above-described embodiment.
In the embodiment shown in FIG. 1, the pure water supply pipe 46 for additional steam is connected from the condenser 25 to the supplementary water tank 48 for additional steam, but in this modification shown in FIG. A feed water pipe 46 ′ is connected to a supplementary water tank 48 for additional steam from a drain pipe 32 led from the feed water heater 28. The additional steam water supply pipe 46 ′ is provided with an additional steam water supply control valve 46 ′ V and a drain pump 59. Thereby, the drain water led from the feed water heater 28 is not led to the condenser 25 during the steady operation after the additional heating steam of the biomass boiler 7 is put into the feed water heater 28 (for drain water). The control valve 32V is fully closed), and the high-pressure extraction control valve 29V is fully closed to stop extraction of high-pressure steam from the high-pressure turbine 16, so that the total amount of drain water is added via the additional-steam supply pipe 46 '. Guided to the make-up water tank 48.

Further, in the present modification, a biomass boiler chemical injection facility (heating steam boiler chemical injection facility) 60 is provided downstream of the additional steam feed water pump 49. This is because the drain water flowing out from the feed water heater 28 is not guided to the condenser 25, and the chemical solution is supplied from the chemical solution injection facility 30 provided in the feed water pipe 10 between the condenser 25 and the feed water heater 28. Because there is no.
Other configurations of the present modification are the same as those of the above-described embodiment, and thus the same reference numerals are given and description thereof is omitted.

FIG. 9 shows a comparative example of the present embodiment and the modified example. In the comparative example shown in FIG. 9, the steam generated in the biomass boiler 7 is not supplied to the feed water heater 28 as additional heating steam, but an additional feed water heat exchanger 62 provided separately from the feed water heater 28. To supply steam for heating. Steam for heating that has exchanged heat with water supplied to the boiler 3 in the additional feed water heat exchanger 62 is led to the biomass boiler 7 as a drain water drained after the heat exchange and circulates. Therefore, the water supply system of the biomass boiler 7 is different from the water supply system of the boiler 3.
In the comparative example, an additional pure water tank 64 is provided in the water supply system of the biomass boiler 7.
In the comparative example, an additional wastewater treatment facility 66 for treating the wastewater of the biomass boiler 7 is provided.
In the comparative example, the steam is discharged from the biomass boiler 7 at the time of start-up or emergency, and discharged from the steam recovery equipment 68 for effectively using water and the additional steam supply pipe 40 to the steam recovery device 68. An on-off valve 69 is provided. This is because the condenser 25 connected to the steam turbine 5 cannot be used because the water supply system of the biomass boiler 7 is separate from the water supply system of the steam turbine 5.
Other configurations of the comparative example are the same as those of the embodiment and the modification described above, and thus the same reference numerals are given and the description thereof is omitted.

  FIG. 10 summarizes a comparison of the presence / absence of components in the present embodiment (FIG. 1), the modified example (FIG. 8), and the comparative example (FIG. 9). In the table, a circle indicates that a device is required, and a cross indicates that a device is not required.

  As shown in item number (1) -1, the additional feed water heat exchanger 62 is provided with a comparative example, but is not provided in the present embodiment and the modification. That is, in this embodiment and the comparative example, since the feed water heater 28 is shared with the feed water system of the boiler 3, it is not necessary to add a feed water heater.

  As shown in the item number (1) -2, the biomass boiler chemical injection facility 60 is additionally provided in the comparative example and the modified example, but the biomass boiler chemical injection facility 60 is required in the present embodiment. Since it can share with the chemical | medical solution injection equipment 30 used for water supply, the installation of the chemical injection equipment for biomass boilers becomes unnecessary.

  As shown in item number (1) -3, additional installation of the drain pump 59 for circulating the drain water generated by the feed water heater 28 and the additional feed water heat exchanger 62 is necessary in the comparative example and the modified example. However, this is not necessary in this embodiment.

  As shown in item number (2) -1, the additional steam pure water transfer pump 54 for transferring pure water to the additional steam makeup water tank 48 is required not only in the comparative example but also in the present embodiment and the modification. Become. Therefore, the pump 54 is necessary for generating additional heating steam or heating steam in the biomass boiler 7, and can be omitted even in the present embodiment or modification.

  As shown in item number (3) -1, in the comparative example, when pure water is supplied from the pure water device 34, an additional pure water tank 64 is provided in the water supply system of the biomass boiler 7. And it is made unnecessary in the comparative example. In other words, in the present embodiment and the comparative example, pure water is supplied from the pure water tank 35 for supplying pure water to the condenser 25 when pure water is supplied to the supplemental water tank 48 for additional steam. Because it is.

  As shown in item number (3) -2, the supplemental water supplementary water pump 47 for supplying supplemental water to the supplemental steam supplemental water tank 48 is required in the comparative example and the present embodiment. In the modification, it is unnecessary. This is because in the modified example, the makeup water is supplied by the drain pump 59, and therefore the supplementary water makeup water pump 47 is substituted.

  As shown in item number (3) -3, the supplementary steam supply water tank 48 is required not only in the comparative example but also in the present embodiment and the modification. Therefore, the tank 48 is necessary for generating additional steam or steam for heating in the biomass boiler 7 even in the present embodiment or modification, and cannot be omitted.

  As shown in item number (3) -4, the additional steam feed pump 49 is required not only in the comparative example but also in the present embodiment and the modified example. Therefore, the feed water pump 49 is necessary for generating additional heating steam or heating steam in the biomass boiler 7 even in the present embodiment or the modified example, and cannot be omitted.

  As shown in item number (4) -1, in the comparative example, an additional wastewater treatment facility 66 is required, whereas in this embodiment and the modification, the wastewater treatment facility 9 of the boiler 3 is shared. There is no need to install a separate wastewater treatment facility.

  As shown in item number (5) -1, the comparative example requires a steam recovery facility 68 for discharging excess steam from the additional steam supply pipe 40 and recovering it as water at the time of start-up or emergency stop. On the other hand, in the present embodiment and the modified example, the steam can be discharged to the condenser 25 through the additional steam bypass pipe 44, so that the steam recovery facility 68 as in the comparative example is not required.

  In FIG.11 and FIG.12, the feed water heating by the biomass boiler 7 is performed as a reference example when performing feed water heating using the generated steam of the biomass boiler 7 (after the biomass boiler is additionally installed) as in this embodiment and the modification. The effect when not performed (before additional biomass boiler) will be described.

In FIG. 11, the horizontal axis represents the output of the power plant 1, and the vertical axis represents the amount of heating given to the feed water from the biomass boiler 7. As shown in FIG. 11, the amount of heat is given to the feed water by the feed water heating by the biomass boiler 7. In the figure, the amount of heat given to the water supply when the output of the power plant 1 is 100% is represented as 1.0 as a relative value.
The amount of heating by the additional heating steam from the biomass boiler 7 is the amount of heat corresponding to the amount of heat of the high-pressure steam extracted from the high-pressure turbine 16 before the biomass boiler is additionally installed as a reference example. That is, the heating amount given by the feed water heater 28 is evaluated as equivalent in the reference example and this embodiment.

In FIG. 12, the horizontal axis indicates the output of the power plant 1, and the vertical axis indicates the power generation efficiency with respect to fossil fuel energy input to the power plant. In the figure, the power generation efficiency before the biomass boiler additional installation when the output is 100% is represented as 1.0 as a relative value. As can be seen from the figure, even if the output of the power plant 1 changes, the power generation efficiency for fossil fuel energy is higher after the biomass boiler is added than before the biomass boiler is added.
The power generation efficiency in FIG. 12 is defined as (obtained electric energy) / (energy of fossil fuel to be input). The turbine efficiency is defined as (electric energy obtained) ÷ [(steam energy flowing into the turbine) − (steam energy flowing out of the turbine)].

FIG. 13 shows the relationship and breakdown between the electric energy obtained by the power generation of the power plant 1 and the fuel energy input to the power plant 1 (boiler 3 and biomass boiler 7). Here, the case where the output is set to 50% in the middle is compared.
The vertical axis | shaft of Fig.13 (a) and (b) makes the fuel energy thrown in before adding a biomass boiler 1.0. FIG. 13A shows a state before the biomass boiler 7 is additionally installed, and FIG. 13B shows a state after the biomass boiler 7 is additionally installed.
When the electric energy obtained by the power generation before and after the additional installation of the biomass boiler 7 is the same amount, as shown in the figure on the lower side of the page (after the additional installation of the biomass boiler 7), after the additional installation of the biomass boiler This fuel energy reduces the amount of fossil fuel input and can reduce carbon dioxide emissions that are not carbon neutral.
More specifically, additional heating steam generated in the biomass boiler 7 is supplied to the feed water heater 28 to heat the feed water supplied to the boiler 3, and the amount of steam extracted from the steam turbine 5 is stopped. Alternatively, the amount of fossil fuel input to the boiler 3 can be reduced in accordance with the amount of energy change caused by the reduction (reduction of the amount of extraction), and the amount of carbon dioxide that does not become carbon neutral can be further reduced.

  As described above, according to the present embodiment and the modification, the following operational effects are obtained.

  By supplying additional heating steam generated by the biomass boiler 7 to the feed water heater 28 and raising the feed water temperature, the power generation efficiency for fossil fuel energy can be improved. By stopping or reducing the extraction amount of the extraction steam of the steam turbine 5 according to the heating amount of the feed water by the biomass boiler 7, the flow rate of the steam passing through the steam turbine 5 is within the specified range of the mechanical limit of the steam turbine 5. Increase the turbine output. Further, when comparing the amount before and after reducing the amount of steam extracted, if the total amount of steam supplied from the boiler 3 to the steam turbine 5 is adjusted so that the same turbine output is obtained, the amount of extraction is reduced. Therefore, the total steam flow rate can be reduced, so that the turbine efficiency can be improved. The turbine efficiency of the steam turbine 5 can be increased to improve the power generation efficiency for fossil fuel energy. Thereby, when generating electric power equivalent to the amount of power generation before the power generation efficiency is improved, the amount of fossil fuel to be introduced into the boiler 3 can be reduced, and the amount of carbon dioxide emissions that are not carbon neutral can be reduced.

  An additional steam bypass pipe 44 that bypasses the feed water heater 28 and guides additional heating steam generated in the biomass boiler 7 to the condenser 25 is provided. Thereby, when the additional heating steam supplied to the feed water heater 28 is unnecessary, for example, when the biomass boiler 7 is started or stopped (including an emergency stop such as a boiler trip), the additional steam bypass pipe 44 is provided. The additional heating steam can be used to guide the condenser 25. Thereby, adverse effects on the boiler 3 and the steam turbine 5 can be avoided. Moreover, since the additional heating steam can be collected by the condenser 25, the loss of the total water amount of the water / steam system can be suppressed.

  By supplying water from the condenser 25 to the biomass boiler 7 by the additional steam pure water supply system 46, the steam turbine water supply system for circulating the boiler 3 and the steam turbine 5, and the heating steam pure water for distributing the biomass boiler 7 The water supply system 46 can be shared. Thereby, a condensate system can be shared and cost can be reduced by reducing the number of equipment. Moreover, since the water supply system for steam turbines and the water supply system for additional steam can be managed by a common water quality standard, the cost can be reduced by reducing the number of equipment by using the common chemical solution injection facility 30. Can do.

  The pure water tank 35 is shared by connecting the pure water transfer system for heating steam to the biomass boiler 7 from the pure water tank 35 that supplies pure water to the boiler 3. Thereby, cost can be reduced by reducing the number of devices.

  The wastewater treatment facility 9 for treating the wastewater discharged from the boiler 3 is connected to the biomass boiler 7 so that the wastewater treatment facility 9 is shared. Thereby, cost can be reduced by reducing the number of devices.

  By using the biomass boiler 7 that uses the biomass fuel as the main fuel, the biomass fuel can be exclusively burned in the biomass boiler 7 without co-firing the biomass fuel in the boiler 3. Therefore, the use ratio of the biomass fuel to the fossil fuel burned in the boiler 3 can be increased. Moreover, inexpensive biomass fuel containing a corrosive component can be used without affecting the combustion in the boiler 3, and power generation with reduced fossil fuel usage can be performed at a low fuel cost. The amount of fossil fuel input to the boiler 3 can be reduced, and the amount of carbon dioxide that does not become carbon neutral can be reduced.

  In the modification, as shown in FIG. 8, the drain water condensed in the feed water heater 28 is guided to the biomass boiler 7 via the additional steam feed pipe 46 ′. Thereby, the water supply by the pure water supply system 46 for additional steam from the condenser 25 to the biomass boiler 7 can be abbreviate | omitted.

  Although the biomass boiler 7 is used as an additional steam generator for heating the feed water, the biomass may not be used as fuel. As the fuel, for example, garbage or combustible waste can be used.

1 Power Plant 3 Boiler 5 Steam Turbine 7 Biomass Boiler (Boiler for Heating Steam)
8 Pure water supply equipment 9 Waste water treatment equipment 10 Water supply pipe 10T Water supply temperature sensor 10P Water supply pressure sensor 11 pH sensor 12 Control unit 14 Main steam pipe 15 Main steam discharge pipe 16 High-pressure turbine 17 Low-pressure turbine 19 Generator 21 High-pressure turbine outlet pipe 23 Reheat steam supply pipe 25 Condenser 26 Feed water pump 28 Feed water heater 29 High pressure extraction pipe 29V High pressure extraction control valve (extraction steam control valve)
30 Chemical liquid injection equipment 32 Drain pipe 34 Pure water device 35 Pure water tank 36 Pure water supply pump 37 Makeup water tank 38 Pure water bypass pipe 40 Additional steam supply pipe 40F Additional steam flow sensor 40V1 Additional steam on-off valve 40V2 For additional steam Control valve 42 Safety valve 44 Additional steam bypass piping (heating steam bypass system)
44V additional steam bypass control valve 46, 46 'additional steam water supply piping (pure water supply system for heating steam)
46'V Additional steam feed water control valve 47 Additional steam makeup water pump 48 Additional steam makeup water tank 48L Level sensor 49 Additional steam feed pump 50 Biomass boiler pH sensor 52 Additional steam pure water transfer pipe (for heated steam) Pure water transfer system)
54 Pure water transfer pump for additional steam 56 Pure water bypass piping for heating steam 57 Drain piping for biomass boiler (drainage system for heating steam)
59 Drain pump 60 Biomass boiler chemical injection equipment (heating steam boiler chemical injection equipment)
62 Additional Water Heat Exchanger 64 Additional Pure Water Tank 66 Additional Waste Water Treatment Equipment 68 Steam Recovery Equipment

Furthermore, in the power plant of the present invention, a pure water tank that supplies pure water to the boiler, a pure water transfer system for heating steam that supplies pure water from the pure water tank to the heating steam boiler, and the heating steam And a pH sensor for measuring the pH of pure water supplied to the boiler .

The power plant operating method of the present invention includes a boiler that generates steam, a steam turbine that is driven by the steam generated by the boiler, and a condenser that liquefies the steam exhausted from the steam turbine. A generator driven by the steam turbine, a feed water heater that heats feed water supplied to the boiler by the extracted steam extracted from the steam turbine, and mixed and supplied to the extracted steam of the feed water heater A boiler for heating steam that generates heating steam ; a pure water tank that supplies pure water to the boiler; a pure water transfer system for heating steam that supplies pure water from the pure water tank to the boiler for heating steam; a pH sensor for measuring the pH of the pure water supplied to the heating steam boiler, a method of operating a power plant wherein the heated steam to bypass the feed water heater -Out guide to the condenser, the supplying pure water from the pure water tank to the heating steam boiler through the pure water transport system for the heating steam, by the pH sensor, it is supplied to the heating steam boiler It is characterized by monitoring the pH of pure water .

Claims (8)

A boiler that generates steam;
A steam turbine driven by the steam generated in the boiler;
A condenser for liquefying the steam exhausted from the steam turbine;
A generator driven by the steam turbine;
A feed water heater for heating the feed water supplied to the boiler by the extracted steam extracted from the steam turbine;
A boiler for heating steam that generates heating steam mixed and supplied to the extracted steam of the feed water heater;
A bypass system for heating steam that bypasses the feed water heater and guides the heating steam to the condenser;
A power plant characterized by comprising:   2. The power plant according to claim 1, further comprising: an extraction steam control valve that controls a flow rate of the extraction steam in accordance with a flow rate of the heating steam guided from the heating steam boiler.   The power plant according to claim 1 or 2, further comprising a heating steam water supply system for supplying water from the condenser to the heating steam boiler.   The power plant according to claim 1 or 2, further comprising a drain water supply system that guides the drain water condensed in the feed water heater to the boiler for heating steam. A pure water tank for supplying pure water to the boiler;
A heating steam pure water transfer system for supplying pure water from the pure water tank to the heating steam boiler;
The power plant according to any one of claims 1 to 4, further comprising: Equipped with a wastewater treatment facility for treating the wastewater discharged from the boiler,
A heating steam drainage system for guiding wastewater discharged from the heating steam boiler to the wastewater treatment facility;
The power plant according to any one of claims 1 to 5, further comprising:   The power plant according to any one of claims 1 to 6, wherein the boiler for heating steam is a biomass boiler using biomass fuel as a main fuel. A boiler that generates steam;
A steam turbine driven by the steam generated in the boiler;
A condenser for liquefying the steam exhausted from the steam turbine;
A generator driven by the steam turbine;
A feed water heater for heating the feed water supplied to the boiler by the extracted steam extracted from the steam turbine;
A boiler for heating steam that generates heating steam mixed and supplied to the extracted steam of the feed water heater;
A power plant operating method comprising:
A method of operating a power plant, wherein the heating steam is led to the condenser by bypassing the feed water heater.

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