JP2020002931A - Fire power power-generating plant - Google Patents

Abstract

A thermal power plant capable of easily realizing a sufficient increase in generator output when the frequency of a power system is rapidly reduced.
In a thermal power plant according to an embodiment, when a control device detects a decrease in system frequency in an electric power system, the control device reduces the flow rate of a heating medium supplied to a feedwater heating unit as compared with the normal operation. Then, an output increasing operation is performed in which the output of the generator is increased as compared with the normal operation by setting the opening of the bleeding throttle valve to be smaller than the predetermined amount. At the same time, the control device controls the operation of the bleed throttle valve based on the temperature of the water flowing from the condenser to the boiler via the feedwater heating unit when the output increasing operation is being performed.
[Selection] Figure 2

Description

  Embodiments of the present invention relate to a thermal power plant.

  2. Description of the Related Art A thermal power plant is required to increase a generator output when a system frequency decreases in a power system. In this case, in general, the main steam control valve, which is operated to reduce the opening during normal operation (operation performed when the system frequency is stable), is operated by reducing the system frequency. Open up to the opening according to. Thereby, the amount of steam (swallowed steam amount) supplied as a working medium to the steam turbine is increased. As a result, the generator output (load) increases, and the system frequency recovers.

  However, a sudden change in the amount of power generation may occur due to an increase in power generation by natural energy, and the system frequency may suddenly decrease. For example, the system frequency may decrease by about 1% in a short time of about 10 seconds. For this reason, it may be difficult to achieve the required increase in the generator output only by performing the above operations.

  Various technologies have been proposed to address such issues. For example, it has been proposed to execute a “condensing throttle operation”. In the "condensing throttle operation", the flow rate of extracted steam supplied as a heating medium from the steam turbine to the feedwater heater is reduced, and the flow rate of condensed water supplied as the medium to be heated to the feedwater heater is reduced. By performing the “condensing throttle operation”, the amount of steam that performs expansion work in the steam turbine increases, so that the generator output increases. For example, in the "condensing throttle operation", after 30 seconds have elapsed from the start of the "condensing throttle operation", the power generation output can be increased by 2 to 5% with respect to the power generation output of the normal operation.

JP 2013-53531 A JP-A-62-291402

  However, in the above, since various problems may occur, it may be difficult to sufficiently increase the generator output when the frequency of the power system decreases.

  Therefore, the problem to be solved by the present invention is to provide a thermal power plant capable of easily realizing a sufficient increase in generator output on the turbine plant side when the frequency of the power system is reduced. That is.

  The thermal power plant according to the embodiment includes a steam turbine, a condenser, a feedwater heating unit, a boiler, and a generator. The condenser cools and condenses steam exhausted from the steam turbine. The feedwater heating unit heats the water condensed in the condenser using the steam extracted from the steam turbine as a heating medium. The boiler generates steam by heating the water heated in the feed water heating section. When the steam generated by the boiler is supplied to the steam turbine, the generator is driven to generate power. The power generated by the generator is output to a power system. The thermal power plant according to the embodiment further includes a bleed throttle valve and a control device. The bleeding throttle valve is a hydraulic valve and adjusts the flow rate of the heating medium supplied to the feed water heating unit. The control device controls the operation of the bleed throttle valve. Here, in the case of normal operation, the control device adjusts the opening of the bleeding throttle valve to a predetermined amount, and when detecting a decrease in the system frequency in the power system, the flow rate of the heating medium supplied to the feedwater heating unit. By reducing the opening of the bleeding throttle valve to a value smaller than a predetermined amount so as to reduce the output from the normal operation, the output of the generator is increased as compared with the normal operation. At the same time, the control device controls the operation of the bleed throttle valve based on the temperature of the water flowing from the condenser to the boiler via the feedwater heating unit when the output increasing operation is being performed.

FIG. 1 is a diagram schematically illustrating a main part of the thermal power plant according to the first embodiment. FIG. 2 is a diagram illustrating a detailed configuration of a feedwater heating unit in the thermal power plant according to the first embodiment. FIG. 3 is a diagram schematically illustrating a configuration of a bleed throttle valve in the thermal power plant according to the first embodiment. FIG. 4 is a diagram schematically illustrating the content of the calculation performed by the control device in the thermal power plant according to the first embodiment. FIG. 5 is a flowchart showing a flow when the “power increase operation” is executed in the thermal power plant according to the first embodiment. FIG. 6 shows a temperature difference between an inlet temperature and an outlet temperature of the first high-pressure feedwater heater and a second high-pressure bleed throttle in the thermal power plant according to the first embodiment when performing the “power increase operation”. It is a figure showing the relation with the opening of a valve. FIG. 7A is a flowchart illustrating a flow when executing the “power increase operation” in the modified example 1-1 of the first embodiment. FIG. 7B is a flowchart illustrating a flow when executing the “power increase operation” in the modified example 1-1 of the first embodiment. FIG. 7C is a flowchart illustrating a flow when executing the “power increase operation” in the modified example 1-1 of the first embodiment. FIG. 8 is a diagram illustrating a relationship between the temperature of the high-pressure feed water heater and the opening of the high-pressure bleed throttle valve when the “output increasing operation” is performed in Modification 1-1 of the first embodiment. . FIG. 9 is a diagram illustrating a detailed configuration of a feedwater heating unit in the thermal power plant according to Modification Example 1-3 of the first embodiment. FIG. 10 is a diagram illustrating a detailed configuration of a feedwater heating unit in the thermal power plant according to the second embodiment. FIG. 11 is a diagram schematically illustrating the content of the calculation performed by the control device in the thermal power plant according to the second embodiment. FIG. 12 is a diagram schematically illustrating a configuration of a bleed throttle valve in a thermal power plant according to Modification 2-1 of the second embodiment. FIG. 13 is a diagram illustrating a detailed configuration of a feedwater heating unit in a thermal power plant according to Modification Example 2-2 of the second embodiment. FIG. 14 is a diagram schematically illustrating the content of the calculation performed by the control device in the thermal power plant according to Modification Example 2-2 of the second embodiment.

<First embodiment>
A main part of the thermal power plant according to the first embodiment will be described with reference to FIG.

  As shown in FIG. 1, in the thermal power plant according to the present embodiment, steam F1 (exhausted steam) exhausted from the steam turbine 1 is cooled by the condenser 2 and condensed. The water F2 (condensed water) condensed in the condenser 2 is heated by the feed water heating unit 3. Then, the water F3 (water supply) heated in the water supply heating unit 3 is heated by the boiler 4 to generate steam F4 (main steam). Steam F4 generated by the boiler 4 is supplied to the steam turbine 1 as a working medium. Thereby, the steam turbine 1 drives the generator 14 to generate power.

  In the present embodiment, in the thermal power plant, the steam turbine 1, the condenser 2, the feedwater heating unit 3, and the boiler 4 are configured to constitute a regeneration cycle and a reheating cycle. Hereinafter, the details of each component constituting the thermal power plant will be sequentially described.

  In the present embodiment, the steam turbine 1 includes a high-pressure turbine unit 11, an intermediate-pressure turbine unit 12, and a low-pressure turbine unit 13. The steam turbine 1 drives the generator 14 by rotating a turbine rotor (not shown) in the high-pressure turbine section 11, the medium-pressure turbine section 12, and the low-pressure turbine section 13. Power generated by driving the generator 14 is output to a power system (not shown).

  Specifically, the high-pressure turbine section 11 of the steam turbine 1 is of a single-flow type, in which steam F4 flows in from the boiler 4 as a working medium from a supply port A11, and steam B1b flows out from an exhaust port A11b. Here, the steam F4 generated by the boiler 4 is introduced into the high-pressure turbine unit 11 via a steam stop valve (not shown) and a steam control valve (not shown). Most of the steam B1b_1 out of the steam B1b flowing out of the exhaust port A11b of the high-pressure turbine unit 11 flows to the boiler 4 and is heated again by the boiler 4. On the other hand, of the steam B1b flowing out of the exhaust port A11b, the remaining steam B1b_2 flows to the feedwater heating unit 3. In addition, the high-pressure turbine unit 11 is provided with a bleed port A11a, and steam B1a flows out of the bleed port A11a, and the steam B1a flows to the feedwater heating unit 3.

  In the steam turbine 1, in the medium-pressure turbine section 12, steam B4 (reheated steam) heated again in the boiler 4 flows in from a supply port A12 as a working medium, and steams B1d and B12 flow out from exhaust ports A12b and A12c. I do. Here, the steam B4 reheated in the boiler 4 is introduced into the intermediate pressure turbine section 12 via an intercept valve (not shown). The steam B1d flowing out from the exhaust port A12b of the intermediate pressure turbine section 12 flows to the feedwater heating section 3. Further, the steam B12 flowing out from the exhaust port A12c of the intermediate pressure turbine section 12 flows to the low pressure turbine section 13. In addition, the medium pressure turbine section 12 is provided with a bleed port A12a, and steam B1c flows out of the bleed port A12a, and the steam B1c flows to the feedwater heating section 3.

  In the steam turbine 1, the low-pressure turbine section 13 is of a double-flow type, and steam B12 flowing as a working fluid from the supply port A13 branches and flows inside the low-pressure turbine section 13, and steam F1 flows out from the exhaust port A13c. . The steam F1 flowing out of the exhaust port A13c flows to the condenser 2. In addition, the low-pressure turbine section 13 has a plurality of bleed ports A13a and A13b. In the low-pressure turbine section 13, together with the steam B1e flowing out of the bleed port A13a, the steam B1f flowing out of the bleed port A13b located downstream of the bleed port A13a flows to the feedwater heating section 3.

  The condenser 2 is installed to cool and condense the steam F1 discharged from the exhaust port A13c of the low-pressure turbine unit 13. The condenser 2 cools the steam F1 using, for example, seawater or the atmosphere as a cooling medium. The water F2 condensed in the condenser 2 is pressurized by the condensate pump P2 and transferred to the feed water heating unit 3.

  The feed water heating unit 3 heats the water F2 condensed in the condenser 2 using the steam B1a, B1b_2, B1c, B1d, B1e, B1f extracted from the steam turbine 1, and converts the heated water F3 into a boiler 4 It is configured to supply to. That is, the thermal power plant of the present embodiment constitutes a regeneration cycle.

  The feed water heating unit 3 includes a plurality of feed water heaters 31 to 35.

  In the feed water heating section 3 of the present embodiment, the first high pressure feed water heater 31 (31a, 31b), the second high pressure feed water heater 32 (32a, 32b), and the third high pressure feed water heater 33 (33a, 33b). ) Are provided, and constitute a high-pressure feedwater heating unit (high-pressure feedwater heater group). Here, the first high-pressure feedwater heater 31a, the second high-pressure feedwater heater 32a, and the third high-pressure feedwater heater 33a are arranged in series. At the same time, the first high pressure feed water heater 31b, the second high pressure feed water heater 32b, and the third high pressure feed water heater 33b are arranged in series. One set of the first high pressure feed water heater 31a, the second high pressure feed water heater 32a, and the third high pressure feed water heater 33a, the first high pressure feed water heater 31b, and the second high pressure feed water heater 32b And the other set including the third high-pressure feed water heater 33b are arranged in parallel.

  Further, in the feedwater heating section 3, a first low-pressure feedwater heater 34 and a second low-pressure feedwater heater 35 are installed, and constitute a low-pressure feedwater heating section (low-pressure feedwater heater group).

  Each of the feedwater heaters 31 to 35 is, for example, a shell-and-tube heat exchanger in which a tube is housed inside a shell.

  Further, in the feed water heating unit 3, a deaerator 311 is provided. The deaerator 311 is, for example, a direct contact heat exchanger.

  In the feedwater heating unit 3, each of the steams B1a, B1b_2, B1c, B1d, B1e, and B1f (extracted steam) supplied as a heating medium to each of the plurality of feedwater heaters 31 to 35 and the deaerator 311 is condensed. The pressure increases sequentially along the flow of the water F2 condensed in the vessel 2. Then, in the feedwater heating unit 3, the water F2 condensed in the condenser 2 is supplied to the low-pressure feedwater heater (the second low-pressure feedwater heater 35, the first low-pressure feedwater heater 34), the deaerator 311 and the high-pressure feedwater heater. When sequentially flowing through the (third high-pressure feedwater heater 33, the second high-pressure feedwater heater 32, and the first high-pressure feedwater heater 31), they are heated by the heat of the steams B1a, B1b_2, B1c, B1d, B1e, B1f. And the temperature rises.

  In the high-pressure feedwater heaters (the third high-pressure feedwater heater 33, the second high-pressure feedwater heater 32, and the first high-pressure feedwater heater 31), the water F311 flowing out of the deaerator 311 branches into two and flows. . Here, one of the branched waters F311a is heated by flowing through one set of a first high-pressure feedwater heater 31a, a second high-pressure feedwater heater 32a, and a third high-pressure feedwater heater 33a. You. In addition, the other water F311b that is branched is heated by flowing through one set of the first high-pressure feedwater heater 31b, the second high-pressure feedwater heater 32b, and the third high-pressure feedwater heater 33b. . As described above, the feed water heating unit 3 of the present embodiment includes a plurality of feed water heaters 31 to 35 in multiple stages.

  Each part constituting the feed water heating unit 3 will be described in more detail.

  In the feed water heating unit 3, the first high pressure feed water heaters 31a and 31b are provided with steam B1a supplied from the bleed port A11a of the high pressure turbine unit 11 and water F32a supplied from the second high pressure feed water heaters 32a and 32b. Heat exchange is performed with the F32b. By this heat exchange, the water F32a, F32b flowing out of the second high-pressure feedwater heaters 32a, 32b is heated by the first high-pressure feedwater heaters 31a, 31b. On the other hand, the steam B1a flowing out of the extraction port A11a of the high-pressure turbine unit 11 is cooled and condensed by heat exchange in the first high-pressure feedwater heaters 31a and 31b, and is heated as the second high-pressure feedwater as drain water B31a and B31b. It flows out to vessels 32a and 32b.

  In the feed water heating unit 3, the second high pressure feed water heaters 32a and 32b include steam B1b_2 supplied from the exhaust port A11b of the high pressure turbine unit 11, and water F33a supplied from the third high pressure feed water heaters 33a and 33b. Heat exchange is performed with F33b. By this heat exchange, the water F33a, F33b flowing out of the third high-pressure feedwater heaters 33a, 33b is heated by the second high-pressure feedwater heaters 32a, 32b. On the other hand, the steam B1b_2 flowing out from the exhaust port A11b of the high-pressure turbine unit 11 is cooled and condensed by heat exchange in the second high-pressure feedwater heaters 32a and 32b, and is heated as the third high-pressure feedwater as drain water B32a and B32b. It flows out to vessels 33a and 33b.

  In the feed water heating section 3, the third high pressure feed water heaters 33a and 33b are between the steam B1c supplied from the bleed port A12a of the intermediate pressure turbine section 12 and the water F311a and F311b supplied from the deaerator 311. In, heat exchange is performed. By this heat exchange, the water F311a, F311b flowing out of the deaerator 311 is heated by the third high-pressure feedwater heaters 33a, 33b. On the other hand, the steam B1c flowing out from the bleed port A12a of the intermediate-pressure turbine section 12 is cooled and condensed by heat exchange in the third high-pressure feedwater heaters 33a and 33b, and is deaerated as drain water B33a and B33b. Outflow to

  In the feed water heating unit 3, the deaerator 311 is heated by mixing steam B 1 d supplied from the exhaust port A 12 b of the intermediate pressure turbine unit 12 with water F 34 supplied from the first low pressure feed water heater 34. Thereby, the water F34 is degassed. The deaerator 311 is a kind of feedwater heater in a broad sense, and removes gas dissolved in the water F34 supplied from the first low-pressure feedwater heater 34 and performs heating. The water F311 degassed by the deaerator 311 is branched after being pressurized by the water supply pump P311, and the branched water F311a, F311b is transferred to the third high-pressure water heaters 33a, 33b.

  In the feed water heating unit 3, the first low pressure feed water heater 34 is provided between the steam B1e supplied from the extraction port A13a of the low pressure turbine unit 13 and the water F35 supplied from the second low pressure feed water heater 35. Heat exchange takes place. By this heat exchange, the water F35 flowing out of the second low-pressure feedwater heater 35 is heated. On the other hand, the steam B1e flowing out of the extraction port A13a of the low-pressure turbine section 13 is cooled and condensed by heat exchange in the first low-pressure feedwater heater 34, and flows out to the second low-pressure feedwater heater 35 as drain water B34. I do.

  In the feed water heating unit 3, the second low pressure feed water heater 35 is configured to supply steam B 1 f supplied from the bleed port A 13 b of the low pressure turbine unit 13 and water F 2 supplied from the condenser 2 via the condensate pump P 2. In between, heat exchange takes place. By this heat exchange, the water F2 flowing out of the condenser 2 is heated by the second low-pressure feedwater heater 35. On the other hand, the steam B1f flowing out of the extraction port A13b of the low-pressure turbine section 13 is cooled and condensed by heat exchange in the second low-pressure feedwater heater 35, and flows out to the condenser 2 as drain water B35.

  The water F <b> 3 heated by the feedwater heating unit 3 flows into the boiler 4. Here, in the feedwater heating unit 3, after the waters F31a and F31b heated by the first high-pressure feedwater heaters 31a and 31b join, the combined water F3 is supplied as a medium to be heated. And the boiler 4 evaporates by heating the water F3 supplied from the feed water heating part 3 using the combustion exhaust gas generated by combustion, for example. The steam F4 generated in the boiler 4 is supplied to the high-pressure turbine unit 11 as a working medium.

  In addition, in the boiler 4, most of the steam B1b_1 out of the steam B1b flowing out from the exhaust port A11b of the high-pressure turbine section 11 flows in, and heats the steam B1b_1 again. The steam B <b> 4 heated again by the boiler 4 is supplied to the medium pressure turbine unit 12 as a working medium. As described above, the thermal power plant according to the present embodiment is configured by the reheat cycle in which the steam is reheated by the boiler 4.

  The detailed configuration of the feed water heating unit 3 will be described with reference to FIG.

  In the feed water heating section 3 of the present embodiment, as shown in FIG. 2, a plurality of bleeding throttle valves V31 to V35 are provided. In the present embodiment, the plurality of bleeding throttle valves V31 to V35 are provided at each stage of the multi-stage feed water heaters 31 to 35.

  Specifically, the first high-pressure bleeding throttle valve V31 is provided for adjusting the flow rate of steam B1a supplied as a heating medium to the first high-pressure feedwater heaters 31a and 31b. The second high-pressure bleeding throttle valve V32 is provided to adjust the flow rate of steam B1b_2 supplied as a heating medium to the second high-pressure feedwater heaters 32a and 32b. The third high-pressure bleeding throttle valve V33 is provided for adjusting the flow rate of steam B1c supplied as a heating medium to the third high-pressure feedwater heaters 33a and 33b.

  At the same time, the first low-pressure bleeding throttle valve V34 is provided for adjusting the flow rate of steam B1e supplied as a heating medium to the first low-pressure feedwater heater 34. The second low-pressure bleeding throttle valve V35 is provided to adjust the flow rate of steam B1f supplied as a heating medium to the second low-pressure feedwater heater 35.

  The configuration of the bleed throttle valve will be described with reference to FIG. FIG. 3 schematically shows a cross section of the first high-pressure bleeding throttle valve V31 among the plurality of bleeding throttle valves V31 to V35, but the same applies to other sections.

  As shown in FIG. 3, the first high-pressure bleeding throttle valve V <b> 31 is a butterfly valve, and the opening / closing operation is performed by rotating the disc-shaped valve element 310 together with the valve rod 320 inside the tubular valve casing 300. It is configured to be performed.

  Here, the valve stem 320 is installed so as to extend in a direction orthogonal to the pipe axis direction of the valve casing 300. Then, the valve stem 320 is rotated by the driving device 330 about the extending direction of the valve stem 320 as a rotation axis.

  The drive device 330 is a hydraulic drive device in which a piston (not shown) is housed inside a cylinder, and the piston moves by controlling the oil pressure inside the cylinder. The driving device 330 has a first high-pressure valve in which an operation rod connected to a piston is connected to a valve stem 320 via a link member, and the valve 310 is rotated together with the valve stem 320 in accordance with the movement of the piston. The bleeding throttle valve V31 is configured to open and close. That is, in the present embodiment, the first high-pressure bleed throttle valve V31 is a hydraulic valve, and is configured such that the opening degree is adjusted according to the hydraulic pressure.

  To bring the first high-pressure bleeding throttle valve V31 into the fully opened state, the valve 310 rotates so that the disc-shaped valve 310 extends along the pipe axis of the valve casing 300. As a result, the outermost surface of the valve 310 and the innermost surface of the valve casing 300 are in the most distant state (the state shown by the solid line in the figure). As a result, in the valve casing 300, the steam B1a flows from the inlet 300A to the outlet 300B.

  On the other hand, when the first high-pressure bleeding throttle valve V <b> 31 is fully closed, the valve 310 is rotated so that the disc-shaped valve 310 is orthogonal to the pipe axis direction of the valve casing 300. I do. As a result, the outer peripheral surface of the valve body 310 and the inner peripheral surface of the valve casing 300 come into contact with each other (the state shown by the broken line in the figure). As a result, the steam B1a flowing from the inlet 300A to the outlet 300B in the valve casing 300 is shut off.

  As shown in FIG. 2, in the feed water heating section 3 of the present embodiment, a plurality of feed water thermometers T31a to T33a, T31b to T33b, T34, T35, T311a, T311b, and T2 are installed.

  Specifically, the feedwater thermometers T31a and T31b are installed in the flow path of the water F31a and F31b flowing out of the first high-pressure feedwater heaters 31a and 31b, and measure the temperature of the water F31a and F31b. The feedwater thermometers T32a and T32b are installed in the flow path of the water F32a and F32b flowing out of the second high-pressure feedwater heaters 32a and 32b, and measure the temperature of the water F32a and F32b. The feedwater thermometers T33a and T33b are installed in the flow path of the water F33a and F33b flowing out of the third high-pressure feedwater heaters 33a and 33b, and measure the temperature of the water F33a and F33b.

  At the same time, the feed water thermometers T311a and T311b measure the temperature of the water F311 so that the temperature of the water F311 flowing into the third high-pressure feedwater heaters 33a and 33b via the feedwater pump P311 after flowing out of the deaerator 311 is measured. It is installed on the road.

  Further, a feedwater thermometer T34 is provided in the flow path of the water F34 so as to measure the temperature of the water F34 flowing out of the first low-pressure feedwater heater 34. A feedwater thermometer T35 is installed in the flow path of the water F35 so as to measure the temperature of the water F35 flowing out of the second low-pressure feedwater heater 35. Further, a feed water thermometer T2 is installed in the flow path of the water F2 so as to measure the temperature of the water F2 flowing into the second low-pressure feed water heater 35 via the condensate pump P2 after flowing out of the condenser 2. ing.

  In the present embodiment, each of the plurality of feedwater thermometers T31a to T33a, T31b to T33b, T34, T35, T311a, T311b, and T2 flows into the feedwater heaters 31a to 33a, 31b to 33b, 34, and 35, respectively. It is installed to calculate the temperature difference between the inlet temperature of flowing water and the outlet temperature of flowing water.

  Specifically, regarding the temperature difference between the inlet temperature of the water F32a and F32b supplied to the inlet and the outlet temperature of the water F31a and F31b discharged from the outlet in the first high-pressure feedwater heaters 31a and 31b, a feedwater thermometer is used. It is calculated by performing a difference process in which the temperatures detected by the feedwater thermometers T32a and T32b are subtracted from the temperatures detected by T31a and T31b. Regarding the temperature difference between the inlet temperature and the outlet temperature in the second high-pressure feed water heaters 32a and 32b, the difference obtained by subtracting the temperature detected by the feed water thermometers T33a and T33b from the temperature detected by the feed water thermometers T32a and T32b. It is calculated by performing the processing. Similarly, regarding the temperature difference between the inlet temperature and the outlet temperature in the third high-pressure feedwater heaters 33a and 33b, the temperature detected by the feedwater thermometers T311a and T311b is calculated from the temperature detected by the feedwater thermometers T33a and T33b. It is calculated by performing the subtraction processing.

  At the same time, with respect to the temperature difference between the inlet temperature and the outlet temperature in the first low-pressure feed water heater 34, a difference process of subtracting the temperature detected by the feed water thermometer T35 from the temperature detected by the feed water thermometer T34 is performed. It is calculated by: The temperature difference between the inlet temperature and the outlet temperature in the second low-pressure feedwater heater 35 is calculated by performing a difference process of subtracting the temperature detected by the feedwater thermometer T2 from the temperature detected by the feedwater thermometer T35. Is done.

  The thermal power plant according to the present embodiment further includes a control device 800. The control device 800 includes an arithmetic unit (not shown) and a memory device (not shown). The arithmetic unit performs arithmetic processing using a program stored in the memory device to control each unit. It is configured.

  Here, the control device 800 receives an operation command, detection data, and the like as an input signal. Then, control device 800 performs arithmetic processing based on the input signal that has been input, and outputs the control signal CTL as an output signal to each unit, thereby controlling the operation of each unit.

  Control device 800 adjusts the degree of opening of bleed throttle valves V31 to V35 to a predetermined amount during normal operation. Then, when the system frequency is rapidly reduced in the power system, control device 800 performs “output increasing operation” in which the output of generator 14 is increased more rapidly than in the case of “normal operation”. When executing the “power increase operation”, the control device 800 controls the operation of the bleed throttle valves V31 to V35 to thereby control the heating medium (steam B1a, B1b_2, B1c, B1e, The flow rate of B1f) is reduced as compared with the case of normal operation.

  Although the details will be described later, when the start of the “power increase operation” is executed, the control device 800 controls the water F31a to F33a, F31b supplied from the condenser 2 to the boiler 4 via the feedwater heating unit 3. Based on the temperatures of F33b, F34, and F35, the operation of the bleed throttle valves V31 to V35 is controlled. That is, the control device 800 adjusts the degree of opening of the bleeding throttle valves V31 to V35 according to the temperatures of the water F31a to F33a, F31b to F33b, F34, and F35 flowing as the medium to be heated in the feedwater heating unit 3.

  In the present embodiment, the control device 800 controls the feedwater heaters 31a to 33a, 31b to based on the temperature data obtained by the plurality of feedwater thermometers T31a to T33a, T31b to T33b, T34, T35, T311a, T311b, and T2. At 33b, 34 and 35, the temperature difference between the temperature of the inflowing water and the temperature of the outflowing water is calculated. Then, control device 800 determines whether or not the calculated value of the temperature difference exceeds a preset upper limit value for the temperature difference.

  Then, when the calculated value of the temperature difference exceeds the upper limit value, control device 800 adjusts the degree of opening of bleed throttle valves V31 to V35. On the other hand, when the calculated value of the temperature difference is equal to or smaller than the preset upper limit, the control device 800 holds the opening degrees of the bleeding throttle valves V31 to V35.

  The detailed configuration of the control device 800 will be described with reference to FIG. In FIG. 4, when performing the “power increase operation”, the controller 800 opens the second high-pressure bleed throttle valve V32 in order to adjust the flow rate of the steam B1b_2 supplied to the second high-pressure feedwater heater 32a. The part for controlling the degree is shown as a representative example.

  As shown in FIG. 4, the control device 800 includes a frequency drop detector 80, a function generator 81, a PID controller 813, and a high-value selector 83 (PID; Proportional-Integral-Differential).

  As shown in FIG. 4, the frequency sudden decrease detector 80 receives a detection value Sf of the system frequency from the outside as an input signal. The frequency sudden decrease detector 80 obtains a value obtained by subtracting the input detection value Sf of the system frequency from the preset value of the system frequency. Then, when the subtracted value is larger than the threshold value, the frequency sudden decrease detector 80 outputs the output increase command value S0 according to the subtracted value.

  As shown in FIG. 4, the function generator 81 receives the output increase command value S0 from the sudden drop detector 80 as an input signal. Then, the function generator 81 outputs an opening command value SV32_0 corresponding to the output increase command value S0 as an output signal. Here, the function generator 81 outputs an opening command value SV32_0 for decreasing the opening of the second high-pressure bleed throttle valve V32 according to the output increasing command value S0.

  As shown in FIG. 4, the PID controller 813 outputs, as an input signal, a calculated value ΔST31a_2 calculated using the temperature ST31a detected by the feedwater thermometer T31a and the temperature ST32a detected by the feedwater thermometer T32a. Will be entered. Specifically, the temperature difference ΔST31a is obtained by subtracting the temperature ST32a detected by the feedwater thermometer T32a from the temperature ST31a detected by the feedwater thermometer T31a. The temperature difference ΔST31a is a temperature difference between the temperatures of the water F32a, F32b supplied to the inlet and the temperatures of the water F31a, F31b discharged from the outlet in the first high-pressure feedwater heaters 31a, 31b. Then, the difference value ΔST31a_1 is obtained by subtracting the temperature difference ΔST31a calculated as described above from the temperature difference upper limit value ΔST_U1 set in advance for the temperature difference. Thereafter, the difference value ΔST31a_1 is multiplied by “−1” and the sign is inverted to obtain a calculated value ΔST31a_2. Then, the calculated value ΔST31a_2 is input to the PID controller 813. The PID controller 813 outputs an opening command value SV32_3 corresponding to the calculated value ΔST31a_2 as an output signal.

  For example, when temperature difference upper limit ΔST_U1 is 20 ° C. and temperature difference ΔST31a is 22 ° C., calculated value ΔST31a_2 input to PID controller 813 is “+ 2 ° C.”. The PID controller 813 outputs an opening command value SV32_3 for increasing the opening of the second high-pressure bleeding throttle valve V32 according to the calculated value ΔST31a_2.

  4, the opening command value SV32_0 output from the function generator 81 and the opening command value SV32_3 output from the PID controller 813 are input to the high value selector 83 as input signals. The high value selector 83 selects the highest value among the opening command value SV32_0 output by the function generator 81 and the opening command value SV32_3 output by the PID controller 813. Then, the high value selector 83 outputs the selected opening command value SV32 to the second high-pressure bleeding throttle valve V32 as an output signal.

  Although not shown, the control device 800 further includes a PID controller similar to the above PID controller 813 in order to adjust the flow rate of the steam B1b_2 supplied to the second high-pressure feedwater heater 32b. Have. Also, in the control device 800, a portion that controls the operation of the bleed throttle valve other than the second high-pressure bleed throttle valve V32 is configured in the same manner as described above.

  Hereinafter, the operation of the thermal power plant according to the present embodiment will be described separately for a case where “normal operation” is performed and a case where “output increase operation” is performed.

  An example of the operation when performing “normal operation” in the thermal power plant of the present embodiment will be described.

  When “normal operation” is performed in the above-described thermal power plant, steam F4 is supplied from the boiler 4 to the steam turbine 1, and the steam turbine 1 performs work. In the steam turbine 1, the steam F4 is supplied to the high-pressure turbine unit 11 as a working medium to perform work. Then, after most of the steam B1b_1 among the steam B1b exhausted from the high-pressure turbine unit 11 is heated again by the boiler 4, the steam B4 reheated by the boiler 4 is supplied to the intermediate-pressure turbine unit 12 as a working medium. Supplied to do work. Thereafter, the steam B12 discharged from the intermediate pressure turbine section 12 is supplied to the low pressure turbine section 13 as a working medium to perform work. The steam F1 discharged from the low-pressure turbine unit 13 is condensed in the condenser 2, and the water F2 condensed in the condenser 2 is heated in the feedwater heating unit 3. In the feed water heating unit 3, the water F2 condensed in the condenser 2 is heated by the heat of the steams B1a, B1b_2, B1c, B1d, B1e, and B1f extracted from the steam turbine 1. Then, the water F3 heated in the feed water heating unit 3 is heated in the boiler 4, so that the steam F4 is generated in the boiler 4. Thereafter, the steam F4 generated by the boiler 4 is supplied to the steam turbine 1 as a working medium, as described above.

  In the feedwater heating unit 3, the steam B1a, B1b_2, B1c, B1e, B1f extracted from the steam turbine 1 is supplied as a heating medium via the extraction throttle valves V31 to V35. When performing “normal operation”, in a state where the thermal power plant is stably operating at a constant power generation output (rated output), in order to maintain the power generation efficiency to the maximum, the control device 800 uses the bleed throttle valve. V31 to V35 are, for example, fully opened.

  An example of the operation when the “power increase operation” is performed in the thermal power plant according to the present embodiment will be described. The “power increase operation” is performed to rapidly increase the output of the generator 14.

  An example of the flow when executing the “power increase operation” will be described with reference to FIGS. 5 and 6.

  First, as shown in FIG. 5, a sudden decrease in the system frequency is detected (ST10).

  Specifically, when a value obtained by subtracting the set value from the detected value of the system frequency becomes larger than a predetermined threshold, an output increase command value S0 (see FIG. 4) is output as an operation command for an output increase request. .

  Next, as shown in FIG. 5, "power increase operation" is started (ST20).

  Here, the “power increase operation” is started by the control device 800 controlling the operation of each unit according to the output increase command value S0. The “power increase operation” is an operation of the bleeding throttle valves V31 to V35 such that the flow rate of the heating medium (steam B1a, B1b_2, B1c, B1e, B1f) supplied to the feedwater heating unit 3 is reduced as compared with the normal operation. It is started by controlling.

  When starting the "power increase operation", the opening degree of at least one of the plurality of bleeding throttle valves V31 to V35 is reduced. In the present embodiment, the opening degree of the second high-pressure bleeding throttle valve V32 is changed to a state smaller than the fully opened state. Thereby, the flow rate of the steam B1b_2 supplied as the heating medium to the second high-pressure feedwater heaters 32a and 32b is reduced. As a result, the amount of steam that performs expansion work in the intermediate-pressure turbine unit 12 that configures the steam turbine 1 increases, so that the output of the generator 14 can be increased more rapidly than in the case of “normal operation”.

  Next, as shown in FIG. 5, it is determined whether or not the temperature differences ΔST31a, ΔST31b between the inlet temperature and the outlet temperature of the first high-pressure feed water heaters 31a, 31b exceed the temperature difference upper limit value ΔST_U1 (ST30). .

  When the flow rate of the steam B1b_2 supplied as the heating medium to the second high-pressure feedwater heaters 32a and 32b is reduced as described above to execute the “power increase operation”, the water F2 condensed in the condenser 2 is reduced. In the flow direction, the first high-pressure feed water heaters 31a and 31b located downstream of the second high-pressure feed water heaters 32a and 32b have a large heat exchange amount. As a result, the temperature differences ΔST31a, ΔST31b between the temperatures ST32a, ST32b of the water F32a, F32b supplied to the inlet and the temperatures ST31a, ST31b of the water F31a, F31b discharged from the outlet in the first high-pressure feedwater heaters 31a, 31b. The temperature difference ΔST31a, ΔST31b becomes more likely to exceed a preset temperature difference upper limit value ΔST_U1 (see FIG. 6). Further, in order to increase the amount of heat exchange in the first high-pressure feed water heaters 31a and 31b, there is a high possibility that the flow rate of the heating medium (extracted steam) exceeds the flow rate limit of the pipe.

  For this reason, in the present embodiment, as described above, the control device performs a difference process in which the temperatures ST32a and ST32b detected by the feedwater thermometers T32a and T32b are subtracted from the temperatures ST31a and ST31b detected by the feedwater thermometers T31a and T31b. By performing 800, the temperature differences ΔST31a and ΔST31b in the first high-pressure feedwater heaters 31a and 31b are calculated. Then, control device 800 performs a comparison process between temperature differences ΔST31a and ΔST31b in first high-pressure feedwater heaters 31a and 31b and a preset temperature difference upper limit value ΔST_U1. Thereby, control device 800 determines whether or not temperature differences ΔST31a and ΔST31b in first high-pressure feedwater heaters 31a and 31b exceed temperature difference upper limit ΔST_U1.

  As shown in FIG. 5, when the temperature differences ΔST31a and ΔST31b in the first high-pressure feed water heaters 31a and 31b exceed the temperature difference upper limit ΔST_U1 (Yes), the opening degree of the second high-pressure bleed throttle valve V32 is set. Is adjusted (ST41).

  Here, the heating medium is supplied to the feed water heaters 32a and 32b located upstream of the feed water heaters 31a and 31b, which have exceeded the upper limit in which the opening degree is smaller than the fully opened state due to the start of the "power increase operation". The control device 800 opens the second high-pressure bleeding throttle valve V32 for adjusting the pressure. That is, the flow rate of the steam B1b_2 supplied as the heating medium to the second high-pressure feedwater heaters 32a and 32b is increased (see FIG. 6).

  For example, a difference process is performed by subtracting the temperature difference upper limit value ΔST_U1 from the temperature differences ΔST31a and ΔST31b, and control is performed such that the opening degree of the second high-pressure bleed throttle valve V32 increases according to the difference value calculated by the difference process. I do.

  As a result, the temperature differences ΔST31a and ΔST31b in the first high-pressure feedwater heaters 31a and 31b are equal to or less than a preset temperature difference upper limit value ΔST_U1.

  On the other hand, as shown in FIG. 5, when the temperature difference ΔST31 between the first high-pressure feed water heaters 31a and 31b is equal to or smaller than the temperature difference upper limit value ΔST_U1 (No), the second high-pressure bleed throttle valve V32 is turned off. The opening is held (ST42).

  Here, since the second high-pressure bleeding throttle valve V32 is in a state in which the opening degree is smaller than the fully opened state by the start of the “power increase operation”, the control device 800 keeps the state. That is, the flow rate of the steam B1b_2 supplied as the heating medium to the second high-pressure feedwater heaters 32a and 32b is maintained.

  In the above, for simplification of the description, the case where the temperature differences ΔST31a and ΔST31b in the two first high-pressure feedwater heaters 31a and 31b are the same is illustrated. When the temperature differences ΔST31a and ΔST31b in the two first high-pressure feedwater heaters 31a and 31b are different, a comparison is made between the larger value of the two temperature differences ΔST31a and ΔST31b and the temperature difference upper limit ΔST_U1. Then, based on the result of the comparison, the operation of the second high-pressure bleed throttle valve V32 is controlled in the same manner as described above.

  As described above, in the present embodiment, when the output increase operation is performed, the temperatures of the water F31a to F33a, F31b to F33b, F34, and F35 flowing from the condenser 2 to the boiler 4 via the feedwater heating unit 3 are set. , The operation of the bleed throttle valves V31 to V35 is controlled. Here, the temperature difference between the inlet temperature of the inflowing water and the outlet temperature of the outflowing water in each of the plurality of feedwater heaters 31a to 33a, 31b to 33b, 34, and 35 constituting the feedwater heating unit 3 is calculated, It is determined whether or not the calculated value of the calculated temperature difference exceeds a preset upper limit value. If the calculated value exceeds the upper limit value, the bleeding throttle valve closed when the output increase operation is started in the plurality of bleeding throttle valves V31 to V35 (in the present embodiment, the second high-pressure bleeding throttle valve V32 ) Open. As a result, the temperature difference between the feedwater heaters (in the present embodiment, the first high-pressure feedwater heaters 31a and 31b) exceeding the upper limit value is equal to or less than the upper limit value. Further, the flow rate of the heating medium supplied to the feed water heater (in the present embodiment, the first high-pressure feed water heaters 31a and 31b) can be maintained at or below the flow rate limit of the pipe.

  In addition, the upper limit of the temperature difference between the inlet temperature and the outlet temperature of the feedwater heater is set to protect the feedwater heater. For this reason, in the present embodiment, as described above, even when the “power increase operation” is performed, the temperature difference between the inlet temperature and the outlet temperature of the feedwater heater can be made equal to or less than the upper limit value. The effect of preventing breakage of the heater can be obtained.

  In the above embodiment, the case where the opening degree of the second high-pressure bleeding throttle valve V32 among the plurality of bleeding throttle valves V31 to V35 is reduced from the fully open state in order to execute the “power increase operation” has been described. However, it is not limited to this. Hereinafter, specific modifications will be described.

(Modification 1-1)
Modification 1-1 will be described with reference to FIGS. 7A, 7B, 7C, and 8. FIG. Each of FIGS. 7A to 7C is a flowchart showing a flow when executing the “power increase operation”. FIG. 8 is a diagram illustrating a relationship between the temperature of the high-pressure feedwater heater and the opening of the high-pressure bleeding throttle valve when performing the “power increase operation”.

  As shown in FIG. 7A, when the sudden decrease of the system frequency is detected (ST10), the “power increase operation” is started (ST20).

  When the “power increase operation” is started in this modification, the opening degree of the first high-pressure bleeding throttle valve V31, the opening degree of the second high-pressure bleeding throttle valve V32, and the third high-pressure bleeding throttle valve V33 Is changed to a state smaller than the fully opened state.

  After the “power increase operation” is started, in the present modification, as shown in FIG. 7A, it is determined whether or not the outlet temperatures of the first high-pressure feed water heaters 31a and 31b are lower than the lower temperature limit (ST30a). Here, as shown in FIG. 8, the control device 800 makes the above determination based on the temperatures detected by the feedwater thermometers T31a and T31b (see FIG. 2).

  Then, as shown in FIG. 7A, when the outlet temperatures of the first high-pressure feedwater heaters 31a and 31b (the temperatures detected by the feedwater thermometers T31a and T31b) are lower than the lower temperature limit (Yes), the first high-pressure feedwater heaters 31a and 31b are turned off. Adjustment is performed to increase the opening of the high-pressure bleeding throttle valve V31 (ST41a). Thereby, as shown in FIG. 8, the outlet temperature of the first high-pressure feedwater heaters 31a and 31b is changed from a state where the outlet temperature is lower than the lower temperature limit to a state where the outlet temperature is higher than the lower temperature limit.

  On the other hand, as shown in FIG. 7A, when the outlet temperatures of the first high-pressure feed water heaters 31a and 31b (the temperatures detected by the feed water thermometers T31a and T31b) are not less than the lower temperature limit (No), The degree of opening of the first high-pressure bleeding throttle valve V31 is kept smaller than the fully opened state (ST42a).

  In this modification, as shown in FIG. 7B, the inlet temperatures of the water F32a, F32b supplied to the inlet and the outlet temperatures of the water F31a, F31b discharged from the outlet in the first high-pressure feedwater heaters 31a, 31b. It is determined whether or not the temperature differences ΔST31a and ΔST31b exceed a preset temperature difference upper limit value ΔST_U1 (ST30b). Here, as shown in FIG. 8, the control device 800 makes the above determination based on the temperature differences ΔST31a and ΔST31b between the temperatures detected by the feedwater thermometers T31a and T31b and the temperatures detected by the feedwater thermometers T32a and T32b. (See FIG. 2).

  Then, as shown in FIG. 7B, when the temperature differences ΔST31a and ΔST31b in the first high-pressure feedwater heaters 31a and 31b exceed the temperature difference upper limit ΔST_U1 (Yes), the second high-pressure bleed throttle valve V32 is opened. Adjustment is made to increase the degree (ST41b). For example, as shown in FIG. 8, when the temperature difference ΔST31a, ΔST31b in the first high-pressure feed water heaters 31a, 31b exceeds the temperature difference upper limit value ΔST_U1, after the opening degree of the first high-pressure bleeding throttle valve V31 is increased. Next, the opening degree of the second high-pressure bleeding throttle valve V32 is increased. As a result, the temperature differences ΔST31a, ΔST31b in the first high-pressure feedwater heaters 31a, 31b are reduced from the temperature difference upper limit value ΔST_U1 to the temperature difference upper limit value ΔST_U1 or less.

  On the other hand, as shown in FIG. 7B, when the temperature differences ΔST31a and ΔST31b in the first high-pressure feedwater heaters 31a and 31b are equal to or smaller than the temperature difference upper limit ΔST_U1, the opening of the second high-pressure bleeding throttle valve V32 is performed. The degree is kept smaller than the fully open state (ST42b).

  Furthermore, in this modification, as shown in FIG. 7C, the inlet temperature of the water F33a, F33b supplied to the inlet and the outlet temperature of the water F32a, F32b discharged from the outlet in the second high-pressure feedwater heaters 32a, 32b. The control device 800 determines whether or not the temperature differences ΔST32a and ΔST32b exceed a preset temperature difference upper limit ΔST_U2 (ST30c). Here, as shown in FIG. 8, control device 800 makes the above determination based on temperature differences ΔST32a and ΔST32b between the temperatures detected by feedwater thermometers T32a and T32b and the temperatures detected by feedwater thermometers T33a and T33b. (See FIG. 2).

  Then, as shown in FIG. 7C, when the temperature differences ΔST32a and ΔST32b in the second high-pressure feed water heaters 32a and 32b exceed the temperature difference upper limit ΔST_U2 (Yes), the third high-pressure bleed throttle valve V33 is opened. Adjustment is made to increase the degree (ST41c). For example, as shown in FIG. 8, when the temperature difference ΔST32a, ΔST32b in the second high-pressure feed water heaters 32a, 32b exceeds the temperature difference upper limit value ΔST_U2 after the opening degree of the second high-pressure bleeding throttle valve V32 is increased. Next, the opening degree of the third high-pressure bleeding throttle valve V33 is increased. As a result, the temperature difference ΔST32a, ΔST32b in the second high-pressure feedwater heaters 32a, 32b becomes lower than the temperature difference upper limit ΔST_U2 from the state exceeding the temperature difference upper limit ΔST_U2.

  On the other hand, as shown in FIG. 7C, when the temperature differences ΔST32a and ΔST32b in the second high-pressure feedwater heaters 32a and 32b are equal to or smaller than the temperature difference upper limit ΔST_U2, the opening of the third high-pressure bleed throttle valve V33 is performed. The degree is kept smaller than the fully open state (ST42c).

(Modification 1-2)
In the modified example 1-2, when performing the “power increase operation”, for example, the opening degree of the second low-pressure bleeding throttle valve V35 is changed to a state smaller than the fully opened state. In this case, the possibility that the amount of heat exchange becomes large in the first low-pressure feedwater heater 34 located downstream of the second low-pressure feedwater heater 35 increases. For this reason, whether the temperature difference between the inlet temperature of the water F35 supplied to the inlet and the outlet temperature of the water F34 discharged from the outlet in the first low-pressure feedwater heater 34 exceeds a preset temperature difference upper limit value or not. Is determined by the control device 800.

  When the temperature difference in the first low-pressure feed water heater 34 is equal to or less than the temperature difference upper limit value, the opening degree of the second low-pressure bleeding throttle valve V35 is kept smaller than the fully opened state.

  On the other hand, when the temperature difference in the first low-pressure feedwater heater 34 exceeds the upper limit of the temperature difference, the second low-pressure bleeding throttle valve V35 is opened. As a result, the temperature difference between the inlet temperature of the water F35 supplied to the inlet and the outlet temperature of the water F34 discharged from the outlet in the first low-pressure feedwater heater 34 is equal to or less than a preset temperature difference upper limit value.

  In this modification, when performing the “power increase operation”, the flow rate of the heating medium supplied to the second low-pressure feedwater heater 35 located upstream of the deaerator 311 is set to the “normal operation”. It is lower than the case. Therefore, in the present embodiment, it is possible to effectively prevent the temperature (water supply temperature) of the water F34 flowing into the deaerator 311 from decreasing and causing flooding in the deaerator 311.

(Modification 1-3)
The detailed configuration of the feed water heating unit 3 according to the modified example 1-3 will be described with reference to FIG.

  In the feed water heating section 3 of the present modification, unlike the above embodiment, as shown in FIG. 9, a first high-pressure bleed throttle valve V31, a second high-pressure bleed throttle valve V32, and a third high-pressure bleed throttle valve V32 Each of the bleeding throttle valves V33 is two.

  Specifically, one first high-pressure bleeding throttle valve V31a is provided to adjust the flow rate of steam B1a supplied as a heating medium to one first high-pressure feedwater heater 31a. And the other 1st high pressure bleeding throttle valve V31b is installed in order to adjust the flow rate of steam B1a supplied as a heating medium to the other 1st high pressure feed water heater 31b. The one second high-pressure bleeding throttle valve V32a is provided for adjusting the flow rate of steam B1b_2 supplied as a heating medium to the one second high-pressure feedwater heater 32a. And the other 2nd high pressure bleeding throttle valve V32b is installed in order to adjust the flow rate of steam B1b_2 supplied as a heating medium to the other 2nd high pressure feed water heater 32b. One third high-pressure bleeding throttle valve V33a is provided to adjust the flow rate of steam B1c supplied as a heating medium to one third high-pressure feedwater heater 33a. The other third high-pressure bleeding throttle valve V33b is provided for adjusting the flow rate of steam B1c supplied as a heating medium to the other third high-pressure feedwater heater 33b.

  In the present modified example, when performing the “power increase operation”, for example, the opening degree of the second high-pressure bleeding throttle valve V32b is changed to a state smaller than the fully opened state.

  In this case, the possibility that the heat exchange amount becomes large in the first high-pressure feedwater heater 31b located downstream of the second high-pressure feedwater heater 32b increases. Therefore, whether the temperature difference between the inlet temperature of the water F32b supplied to the inlet and the outlet temperature of the water F31b discharged from the outlet in the first high-pressure feed water heater 31b exceeds a preset temperature difference upper limit value or not. Is determined by the control device 800.

  When the temperature difference in the first high-pressure feed water heater 31b is equal to or less than the temperature difference upper limit value, the opening degree of the second high-pressure bleeding throttle valve V32b is kept smaller than the fully opened state.

  On the other hand, when the temperature difference in the first high pressure feed water heater 31b exceeds the upper limit of the temperature difference, the opening degree of the second high pressure bleeding throttle valve V32b is increased. As a result, the temperature difference in the first high-pressure feedwater heater 31b becomes equal to or less than the preset temperature difference upper limit value.

(Other)
In the above, the first high-pressure feedwater heater 31 (31a, 31b), the second high-pressure feedwater heater 32 (32a, 32b), the third high-pressure feedwater heater 33 (33a, 33b), and the first low-pressure feedwater heater 34. And the case where the feed water heating unit 3 includes the second low-pressure feed water heater 35 as the feed water heater has been described, but the present invention is not limited to this. The number of the feed water heaters may be appropriately changed to a number other than the above number.

<Second embodiment>
The main part of the thermal power plant according to the second embodiment will be described with reference to FIG. As shown in FIG. 10, the present embodiment is the same as the above-described first embodiment except for a part of the configuration, and therefore, the description of the overlapping portions will be appropriately omitted.

  As shown in FIG. 10, in the feed water heating section 3 of the present embodiment, a plurality of bleeding throttle valves V31 to V35 are provided as in the case of the first embodiment.

  The feed water heaters 31a to 33a, 31b to 33b, 34, and 35 are, for example, shell-and-tube heat exchangers. In the feed water heaters 31a to 33a, 31b to 33b, 34, and 35, steam B1a, B1b_2, B1c, B1e, and B1f extracted from the steam turbine 1 are supplied to the shell as a heating medium and condensed in the condenser 2. Water F2 is supplied to the tube as a medium to be heated, and heat exchange is performed between the heating medium and the medium to be heated. The water F2 is heated by the heat exchange performed in the feedwater heating unit 3. Then, the steams B1a, B1b_2, B1c, B1e, and B1f extracted from the steam turbine 1 are cooled and condensed by heat exchange performed in the feedwater heating unit 3, and are changed into drain water.

  As shown in FIG. 10, a plurality of drain water thermometers X31a to X33a, X31b to X33b, X34, and X35 (in-chamber thermometers) are installed in the feed water heating unit 3 of the present embodiment. At the same time, a plurality of pressure gauges P31a to P33a, P31b to P33b, P34, and P35 (internal pressure gauges) are installed in the feedwater heating unit 3.

  Specifically, drain water thermometers X31a and X31b are installed so as to measure the temperature of the drain water existing inside the shell to which the steam B1a is supplied as a heating medium in the first high-pressure feed water heaters 31a and 31b. In addition, pressure gauges P31a and P31b are installed to measure the pressure inside the shells of the first high-pressure feedwater heaters 31a and 31b. Drain water thermometers X32a and X32b are installed so as to measure the temperature of the drain water existing inside the shell to which the steam B1b_2 is supplied as the heating medium in the second high-pressure feed water heaters 32a and 32b. Pressure gauges P32a and P32b are installed to measure the pressure inside the shells of the two high-pressure feed water heaters 32a and 32b. Drain water thermometers X33a and X33b are installed so as to measure the temperature of the drain water existing inside the shell to which the steam B1c is supplied as the heating medium in the third high pressure feed water heaters 33a and 33b. Pressure gauges P33a and P33b are installed to measure the pressure inside the shells of the three high-pressure feedwater heaters 33a and 33b.

  At the same time, a drain water thermometer X34 is installed so as to measure the temperature of the drain water existing inside the shell to which the steam B1e is supplied as the heating medium in the first low-pressure feed water heater 34, A pressure gauge P34 is provided to measure the pressure inside the shell of the low-pressure feedwater heater 34. A drain water thermometer X35 is installed so as to measure the temperature of the drain water existing inside the shell to which the steam B1f is supplied as a heating medium in the second low-pressure feed water heater 35, and the second low-pressure feed water heating is performed. A pressure gauge P35 is provided to measure the pressure inside the shell of the vessel 35.

  In the present embodiment, the drain water thermometers X31a to X33a, X31b to X33b, X34, X35 and the pressure gauges P31a to P33a, P31b to P33b, P34, P35 are feed water heaters 31a to 33a, 31b to 33b, 34, 35. It is installed to monitor the occurrence of drain flash which turns the drain water generated inside into steam.

  The control device 800 controls the operation of the bleed throttle valves V31 to V35 to execute the heating to be supplied to the feedwater heating unit 3 when performing the “output increasing operation”, as in the first embodiment. The flow rate of the medium is reduced as compared with the normal operation. In reducing the flow rate of the heating medium, in order to adjust the bleeding throttle valves V31 to V35 in a range in which the temperature of the drain water inside the heating medium supplied to the heating medium in the feedwater heating unit 3 is lower than the saturation temperature of the heating medium, The procedure in which the order and how much the bleeding throttle valves V31 to V35 are opened after the output increasing operation is started is stored based on past knowledge, and the bleeding throttle is performed in accordance with the predetermined procedure. The openings of the valves V31 to V35 are adjusted.

  Although the details will be described later, when the “power increase operation” is being executed, the control device 800 determines the temperature of the drain water inside the heating water supply unit 3 to which the heating medium is supplied, and the pressure inside the drain water. Thus, the operation of the bleeding throttle valves V31 to V35 is controlled. That is, the control device 800 is based on the temperature data obtained by the drain water thermometers X31a to X33a, X31b to X33b, X34, and X35 and the pressure data obtained by the pressure gauges P31a to P33a, P31b to P33b, P34, and P35. Then, the opening degree of the bleeding throttle valves V31 to V35 is adjusted.

  The detailed configuration of the control device 800 will be described with reference to FIG. In FIG. 11, when performing the “power increase operation”, the control device 800 opens the second high-pressure bleed throttle valve V32 in order to adjust the flow rate of the steam B1b_2 supplied to the second high-pressure feedwater heater 32a. The part for controlling the degree is shown as a representative example.

  As shown in FIG. 11, the control device 800 includes a frequency sudden decrease detector 80, a steam table T80, a function generator 81, a PID controller 815, and a high value selector 83.

  As shown in FIG. 11, the frequency sudden decrease detector 80 receives the detection value Sf of the system frequency from the outside as an input signal. The frequency sudden decrease detector 80 obtains a value obtained by subtracting the input detection value Sf of the system frequency from the preset value of the system frequency. Then, when the subtracted value is larger than the threshold value, the frequency sudden decrease detector 80 outputs the output increase command value S0 according to the subtracted value.

  As shown in FIG. 11, the function generator 81 receives the output increase command value S0 from the sudden drop detector 80 as an input signal. Then, the function generator 81 outputs an opening command value SV32_0 corresponding to the output increase command value S0 as an output signal. Here, the function generator 81 outputs an opening command value SV32_0 for decreasing the opening of the second high-pressure bleed throttle valve V32 according to the output increasing command value S0.

  As shown in FIG. 11, the PID controller 815 receives, as an input signal, a calculation value ΔSC32a calculated using the temperature SX32a detected by the drain water thermometer X32a and the pressure SP32a detected by the pressure gauge P32a. Is done. Specifically, the saturated steam temperature SS32a corresponding to the pressure SP32a detected by the pressure gauge P32a is obtained using a steam table T80 configured by a look-up table or the like. Then, the temperature difference ΔSX32a is obtained by subtracting the temperature SX32a detected by the drain water thermometer X32a from the obtained saturated steam temperature SS32a. Then, the calculated value ΔSC32a is obtained by subtracting the temperature difference ΔSX32a calculated as described above from the temperature difference lower limit value ΔSC_L2 (subcool temperature lower limit value) preset for the temperature difference. Then, the calculated value ΔSC32a is input to the PID controller 815. The PID controller 815 outputs an opening command value SV32_5 corresponding to the calculated value ΔSC32a as an output signal.

  For example, when the temperature difference lower limit SC_L2 (subcool temperature lower limit) is 5 ° C. and the temperature difference ΔSX32a is 3 ° C., the calculated value ΔSC32a input to the PID controller 815 is “+ 2 ° C.” Become. The PID controller 815 outputs an opening command value SV32_5 for increasing the opening of the second high-pressure bleed throttle valve V32 according to the calculated value ΔSC32a.

  As shown in FIG. 11, the opening command value SV32_0 output from the function generator 81 and the opening command value SV32_5 output from the PID controller 815 are input to the high value selector 83 as input signals. The high value selector 83 selects the highest value among the opening command value SV32_0 output from the function generator 81 and the opening command value SV32_5 output from the PID controller 815. Then, the high value selector 83 outputs the selected opening command value SV32 to the second high-pressure bleeding throttle valve V32 as an output signal.

  Although not shown, the control device 800 further includes a PID controller similar to the above PID controller 815 in order to adjust the flow rate of the steam B1b_2 supplied to the second high-pressure feedwater heater 32b. Have. Also, in the control device 800, a portion that controls the operation of the bleed throttle valve other than the second high-pressure bleed throttle valve V32 is configured in the same manner as described above.

  In the present embodiment, an example of the operation when executing the above-described “power increase operation” will be described.

  When a sudden decrease in the system frequency is detected in the present embodiment, the control device 800 determines, for example, each of the first high-pressure bleed throttle valve V31, the second high-pressure bleed throttle valve V32, and the third high-pressure bleed throttle valve V33. , Reduce the opening. Here, with respect to all the opening degrees of the first high-pressure bleeding throttle valve V31, the second high-pressure bleeding throttle valve V32, and the third high-pressure bleeding throttle valve V33, from the fully open state (K = Kmax = 100%), The opening degree is changed to a predetermined opening degree (K = Kx (for example, Kx = 10%)) larger than that in the closed state. For example, the opening degree is changed to a predetermined degree within 0.5 seconds after the detection of the sudden decrease of the system frequency. As a result, the flow rate of the heating medium supplied to each of the first high-pressure feedwater heaters 31a and 31b, the second high-pressure feedwater heaters 32a and 32b, and the third high-pressure feedwater heaters 33a and 33b increases the "output increase operation". Is narrowed down from the state before execution.

  As described above, when the “power increase operation” is being performed, the amount of steam that performs expansion work in the steam turbine 1 increases, so that the output of the generator 14 increases more rapidly than in the “normal operation”. Can be done.

  When the “power increase operation” is being performed, the internal pressure of the first high-pressure feedwater heaters 31a and 31b to which the heating medium is supplied increases as the opening degree of the first high-pressure bleed throttle valve V31 decreases. descend. Thereafter, as the opening of the first high-pressure bleeding throttle valve V31 increases, the internal pressure of the first high-pressure feed water heaters 31a and 31b to which the heating medium is supplied increases. As described above, when the “power increase operation” is being performed, the internal pressure of the first high-pressure feedwater heaters 31a and 31b to which the heating medium is supplied fluctuates. Inside the first high-pressure feedwater heaters 31a and 31b, the saturation temperature of the heating medium also changes with a change in pressure. The temperature inside the first high pressure feed water heaters 31a and 31b to which the heating medium is supplied fluctuates so as to be lower than the saturation temperature of the heating medium. Therefore, drain flush does not occur in the first high pressure feed water heaters 31a and 31b.

  Similarly, in each of the second high-pressure feedwater heaters 32a and 32b and the third high-pressure feedwater heaters 33a and 33b, the internal pressure at which the heating medium is supplied fluctuates. Accordingly, the saturation temperature of the heating medium also varies, but the temperature inside the supply of the heating medium varies so as to be lower than the saturation temperature of the heating medium. Therefore, no drain flush occurs in the second high-pressure feedwater heaters 32a, 32b and the third high-pressure feedwater heaters 33a, 33b.

  Furthermore, in the present embodiment, when the “power increase operation” is being performed, the first high-pressure feedwater heaters 31a and 31b, the second high-pressure feedwater heaters 32a and 32b, and the third high-pressure feedwater heaters 33a and 33b are used. The control device 800 controls the operation of the bleed throttle valves V31 to V33 based on the measured drain water temperature and the internal pressure. Here, the first high-pressure feed water heaters 31a and 31b, the second high-pressure feed water heaters 32a and 32b, and the third high-pressure feed water heaters 33a and 33b keep the temperature of the drain water lower than the saturation temperature. Next, the control device 800 controls the operation of the bleed throttle valves V31 to V33.

  Specifically, pressure measurement is performed on the internal pressure of the heating medium supplied to the first high-pressure feedwater heaters 31a and 31b, the second high-pressure feedwater heaters 32a and 32b, and the third high-pressure feedwater heaters 33a and 33b. The saturation temperature of the heating medium is calculated from the value. Then, the temperature of the drain water existing inside the first high-pressure feed water heaters 31a and 31b, the second high-pressure feed water heaters 32a and 32b, and the third high-pressure feed water heaters 33a and 33b is calculated by the saturation calculated as described above. The temperature difference is calculated by subtracting from the temperature. Then, the high-pressure bleeding throttle valves V31, V32,... According to the calculated value obtained by subtracting the temperature difference calculated as described above from the temperature difference lower limit values ΔSC_L1 to ΔSC_L3 (subcool temperature lower limit value) preset for the temperature difference. The opening degree of V33 is controlled.

  Then, the high-pressure bleeding throttle valves V31, V32,... According to the calculated value obtained by subtracting the temperature difference calculated as described above from the temperature difference lower limit values ΔSC_L1 to ΔSC_L3 (subcool temperature lower limit value) preset for the temperature difference. The opening degree of V33 is controlled. Here, the opening is increased according to the calculated value. As a result, the internal pressure of the first high-pressure feedwater heaters 31a and 31b, the second high-pressure feedwater heaters 32a and 32b, and the third high-pressure feedwater heaters 33a and 33b to which the heating medium is supplied increases, and the pressure increases. As the temperature rises, the saturation temperature rises. As a result, the occurrence of drain flash can be prevented.

  As described above, in the present embodiment, when the output increasing operation is performed, the temperature inside the supply of the heating medium in the feedwater heating unit 3 is predetermined so as to be lower than the saturation temperature of the heating medium. In the procedure, the degree of opening of the bleeding throttle valves V31 to V35 is adjusted. At the same time, in the present embodiment, when the output increasing operation is being performed, the temperature data of the drain water present inside the heating medium supplied to the feed water heating unit 3, the pressure data therein, and the subcool temperature lower limit The operation of the bleed throttle valves V31 to V35 is controlled based on the value calculated using the value. Here, while detecting the internal pressure of the feed water heating unit 3, the temperature of the drain water present at the location where the heating medium is supplied in the feed water heating unit 3 is detected, and the saturation temperature of the heating medium is determined based on the internal pressure. The operation of the bleeding throttle valves V31 to V35 is controlled such that the temperature of the drain water that is obtained and detected becomes lower than the obtained saturation temperature.

  Therefore, in the present embodiment, as described above, it is possible to effectively prevent the drain flush from occurring in the supply water heating unit 3 where the heating medium is supplied. Further, it is easy to rapidly increase the output, and the plant operation can be stabilized.

  A modified example of the second embodiment will be described.

(Modification 2-1)
Modification 2-1 of the second embodiment will be described with reference to FIG. FIG. 12 schematically shows the cross section of the first high-pressure bleeding throttle valve V31 among the plurality of bleeding throttle valves V31 to V35, but the same applies to other sections.

  In the present embodiment, it is preferable that the first high-pressure bleeding throttle valve V31 includes a stopper 310S as shown in FIG. Here, the stopper 310S is installed at a position where the opening degree of the first high-pressure bleeding throttle valve V31 is prevented from being fully closed. Here, the stopper 310S is installed at a position where the disc-shaped valve element 310 contacts when the opening degree of the first high-pressure bleeding throttle valve V31 is reduced when a sudden decrease in the system frequency is detected.

  Specifically, when closing the first high-pressure bleeding throttle valve V31, the valve 310 contacts the stopper 310S before the valve 310 becomes orthogonal to the pipe axis direction of the valve casing 300. As a result, the steam B1a flowing as a heating medium from the inlet 300A to the outlet 300B in the valve casing 300 is not completely shut off, and the steam B1a is supplied to the first high-pressure water heaters 31a and 31b as a heating medium.

  When the first high-pressure bleeding throttle valve V31 is fully closed, the internal pressure of the first high-pressure feed water heaters 31a and 31b to which the heating medium is supplied sharply decreases, so that a drain flush may occur. The nature increases. However, in this modification, the opening of the first high-pressure bleeding throttle valve V31 is reduced when the sudden decrease of the system frequency is detected because the opening of the first high-pressure bleeding throttle valve V31 is not fully closed. Even in this case, it is possible to prevent the internal pressure of the first high-pressure feed water heaters 31a and 31b to which the heating medium is supplied from suddenly lowering. As a result, in this modified example, the occurrence of drain flash can be more effectively prevented.

(Modification 2-2)
Modification 2-2 of the second embodiment will be described with reference to FIG.

  FIG. 13 schematically shows a detailed configuration of the feed water heating unit 3. FIG. 13 shows a high-pressure feedwater heating unit (high-pressure feedwater heater group) in the feedwater heating unit 3.

  As shown in FIG. 13, in the feed water heating unit 3 of this modification, different from the case of the second embodiment, a plurality of flow meters FT31 to FT33, a plurality of level meters LT31a to LT33a, LT31b to LT33b, and , A plurality of feed water thermometers T31a to T33a and T31b to T33b are further provided.

  Specifically, as shown in FIG. 13, the flow meter FT31 is provided for measuring the flow rate of the steam B1a supplied as a heating medium to the first high-pressure feedwater heaters 31a and 31b. The flow meter FT32 is installed to measure the flow rate of the steam B1b_2 supplied as a heating medium to the second high-pressure feedwater heaters 32a and 32b. The flow meter FT33 is installed to measure the flow rate of the steam B1c supplied as a heating medium to the third high-pressure feedwater heaters 33a and 33b.

  As shown in FIG. 13, the level meters LT31a and LT31b are installed to measure the level of drain water existing inside the first high-pressure feedwater heaters 31a and 31b. The level meters LT32a and LT32b are installed to measure the level of drain water present inside the second high-pressure feedwater heaters 32a and 32b. The level meters LT33a and LT33b are installed to measure the level of drain water present inside the third high-pressure feedwater heaters 33a and 33b.

  As shown in FIG. 13, the feedwater thermometers T31a and T31b are installed in the flow path of the water F31a and F31b flowing out of the first high-pressure feedwater heaters 31a and 31b, and measure the temperature of the water F31a and F31b. . The feedwater thermometers T32a and T32b are installed in the flow path of the water F32a and F32b flowing out of the second high-pressure feedwater heaters 32a and 32b, and measure the temperature of the water F32a and F32b. The feedwater thermometers T33a and T33b are installed in the flow path of the water F33a and F33b flowing out of the third high-pressure feedwater heaters 33a and 33b, and measure the temperature of the water F33a and F33b.

  When executing the “power increase operation”, the control device 800 further includes flow rate data obtained by the flow meters FT31 to FT33, water level data obtained by the level meters LT31a to LT33a, LT31b to LT33b, and a water supply thermometer. Based on the temperature data obtained by T31a to T33a and T31b to T33b, the openings of the bleeding throttle valves V31 to V33 are adjusted. That is, the control device 800 further controls the flow rate of steam supplied to the feedwater heating unit 3 as a heating medium, the level of drain water present inside the heating medium supplied to the feedwater heating unit 3, The degree of opening of the bleeding throttle valves V31 to V33 is adjusted based on the temperature of the water flowing as the heating medium.

  A detailed configuration of the control device 800 according to the present modification will be described with reference to FIG. In FIG. 14, when performing the “power increase operation”, the control device 800 opens the second high-pressure bleeding throttle valve V32 in order to adjust the flow rate of the steam B1b_2 supplied to the second high-pressure feedwater heater 32a. The part for controlling the degree is shown as a representative example.

  As shown in FIG. 14, the control device 800 includes a frequency drop detector 80, a steam table T80, a function generator 81, PID controllers 811 to 815, a low value selector 82, and a high value selector 83. .

  As shown in FIG. 14, the frequency sudden decrease detector 80 receives the detection value Sf of the system frequency from the outside as an input signal. The frequency sudden decrease detector 80 obtains a value obtained by subtracting the input detection value Sf of the system frequency from the preset value of the system frequency. Then, when the subtracted value is larger than the threshold value, the frequency sudden decrease detector 80 outputs the output increase command value S0 according to the subtracted value.

  As shown in FIG. 14, the function generator 81 receives the output increase command value S0 from the sudden drop detector 80 as an input signal. Then, the function generator 81 outputs an opening command value SV32_0 corresponding to the output increase command value S0 as an output signal. Here, the function generator 81 outputs an opening command value SV32_0 for decreasing the opening of the second high-pressure bleed throttle valve V32 according to the output increasing command value S0.

  As shown in FIG. 14, the PID controller 811 receives, as an input signal, a calculation value ΔSFT32 calculated using the flow rate SFT32 measured by the flowmeter FT32. Specifically, by subtracting the flow rate SFT32 measured by the flow meter FT32 from a preset flow rate upper limit value SFT_U (a value obtained by adding a margin to the value determined by the design of the bleed piping and the feedwater heater), The calculated value ΔSFT32 is obtained. Then, the calculated value ΔSFT32 is input to the PID controller 811. The PID controller 811 outputs an opening command value SV32_1 corresponding to the calculated value ΔSFT32 as an output signal.

  For example, when the flow rate upper limit value SFT_U is 50 kg / s and the measured flow rate SFT32 is 55 kg / s, the calculated value ΔSFT32 input to the PID controller 811 is “−5 kg / s”. . The PID controller 811 outputs an opening command value SV32_1 for decreasing the opening of the second high-pressure bleed throttle valve V32 according to the calculated value ΔSFT32.

  As shown in FIG. 14, the PID controller 812 receives, as an input signal, a calculated value ΔSLT32a_U calculated using the water level SLT32a measured by the level meter LT32a. Specifically, the calculated value ΔSLT32a_U is obtained by subtracting the water level SLT32a measured by the level meter LT32a from the preset water level upper limit value SLT_U (the value obtained by adding a margin to the value determined by the design of the device). Can be Then, the calculated value ΔSLT32a_U is input to the PID controller 812. The PID controller 812 outputs an opening command value SV32_2 corresponding to the calculated value ΔSLT32a_U as an output signal.

  For example, when the water level upper limit SLT_U is “+10 mm” and the measured water level SLT 32 a is “+12 mm”, the calculated value ΔSLT32a_U input to the PID controller 812 is “−2 mm”. The PID controller 812 outputs an opening command value SV32_2 for decreasing the opening of the second high-pressure bleed throttle valve V32 according to the calculated value ΔSLT32a_U.

  As shown in FIG. 14, the PID controller 813 outputs, as an input signal, a calculated value ΔST31a_2 calculated using the temperature ST31a detected by the feedwater thermometer T31a and the temperature ST32a detected by the feedwater thermometer T32a. Will be entered. Specifically, the temperature difference ΔST31a is obtained by subtracting the temperature ST32a detected by the feedwater thermometer T32a from the temperature ST31a detected by the feedwater thermometer T31a. The temperature difference ΔST31a is a temperature difference between the temperature of the water F32a supplied to the inlet and the temperature of the water F31a discharged from the outlet in the first high-pressure feedwater heater 31a. Then, the difference value ΔST31a_1 is calculated by subtracting the temperature difference ΔST31a calculated as described above from the temperature difference upper limit value ΔST_U1 (a value obtained by adding a margin to the value determined from the device design) preset for the temperature difference. Is required. Thereafter, the difference value ΔST31a_1 is multiplied by “−1” and the sign is inverted to obtain a calculated value ΔST31a_2. Then, the calculated value ΔST31a_2 is input to the PID controller 813. The PID controller 813 outputs an opening command value SV32_3 corresponding to the calculated value ΔST31a_2 as an output signal.

  For example, when temperature difference upper limit ΔST_U1 is 20 ° C. and temperature difference ΔST31a is 22 ° C., calculated value ΔST31a_2 input to PID controller 813 is “+ 2 ° C.”. The PID controller 813 outputs an opening command value SV32_3 for increasing the opening of the second high-pressure bleeding throttle valve V32 according to the calculated value ΔST31a_2.

  As shown in FIG. 14, the PID controller 814 receives, as an input signal, a calculation value ΔSLT32a_L calculated using the water level SLT32a measured by the level meter LT32a. Specifically, the calculated value ΔSLT32a_L is obtained by subtracting the water level SLT32a measured by the level meter LT32a from a preset water level lower limit value SLT_L (a value obtained by adding a margin to the value determined by the design of the device). Can be Then, the calculated value ΔSLT32a_L is input to the PID controller 814. The PID controller 814 outputs an opening command value SV32_4 corresponding to the calculated value ΔSLT32a_L as an output signal.

  For example, when the water level lower limit SLT_L is “−10 mm” and the measured water level SLT 32 a is “−12 mm”, the calculated value ΔSLT32a_L input to the PID controller 814 is “+2 mm”. The PID controller 814 outputs an opening command value SV32_4 for increasing the opening of the second high-pressure bleed throttle valve V32 according to the calculated value ΔSLT32a_L.

  As shown in FIG. 14, the PID controller 815 receives, as an input signal, a calculation value ΔSC32a calculated using the temperature SX32a detected by the drain water thermometer X32a and the pressure SP32a detected by the pressure gauge P32a. Is done. Specifically, the saturated steam temperature SS32a corresponding to the pressure SP32a detected by the pressure gauge P32a is obtained using a steam table T80 configured by a look-up table or the like. Then, the temperature difference ΔSX32a is obtained by subtracting the temperature SX32a detected by the drain water thermometer X32a from the obtained saturated steam temperature SS32a. Then, the calculated value ΔSC32a is obtained by subtracting the temperature difference ΔSX32a calculated as described above from the temperature difference lower limit value ΔSC_L2 (subcool temperature lower limit value) preset for the temperature difference. Then, the calculated value ΔSC32a is input to the PID controller 815. The PID controller 815 outputs an opening command value SV32_5 corresponding to the calculated value ΔSC32a as an output signal.

  For example, when the temperature difference lower limit ΔSC_L2 (subcool temperature lower limit) is 5 ° C. and the temperature difference ΔSX32a is 3 ° C., the calculated value ΔSC32a input to the PID controller 815 is “+ 2 ° C.” Become. The PID controller 815 outputs an opening command value SV32_5 for increasing the opening of the second high-pressure bleed throttle valve V32 according to the calculated value ΔSC32a.

  As shown in FIG. 14, the low value selector 82 includes an opening command value SV32_1 output from the function generator 81, an opening command value SV32_1 output from the PID controller 811 and an opening command SV output from the PID controller 812. The value SV32_2 is input as an input signal. The low value selector 82 is the lowest among the opening command value SV32_0 output by the function generator 81, the opening command value SV32_1 output by the PID controller 811 and the opening command value SV32_2 output by the PID controller 812. Select a value. Then, the low value selector 82 outputs the selected opening command value SV32L to the high value selector 83 as an output signal.

  As shown in FIG. 14, the high value selector 83 includes an opening command value SV32L output by the low value selector 82, an opening command value SV32_3 output by the PID controller 813, and an opening command value output by the PID controller 814. The degree command value SV32_4 and the opening degree command value SV32_5 output from the PID controller 815 are input as input signals. The high value selector 83 includes an opening command value SV32L output from the low value selector 82, an opening command value SV32_3 output from the PID controller 813, an opening command value SV32_4 output from the PID controller 814, and a PID. The highest value is selected from the opening command value SV32_5 output by the controller 815. Then, the high value selector 83 outputs the selected opening command value SV32 to the second high-pressure bleeding throttle valve V32 as an output signal.

  Although not shown, the control device 800 adjusts the flow rate of the steam B1b_2 supplied to the second high-pressure feed water heater 32b by using a PID controller similar to the PID controllers 811 to 815 described above. Is further provided. Also, in the control device 800, a portion that controls the operation of the bleed throttle valve other than the second high-pressure bleed throttle valve V32 is configured in the same manner as described above.

  In the present modified example, an example of the operation when executing the above “power increase operation” will be described.

  In this modified example, when the “power increase operation” is being executed, the temperature of the drain water and the internal pressure measured in the feed water heaters 31a to 33a and 31b to 33b are the same as in the above-described second embodiment. , The control device 800 controls the operation of the bleed throttle valves V31 to V33. Therefore, it is possible to effectively prevent the drain flush from occurring in the feed water heating unit 3.

  Then, in the present modified example, unlike the case of the above-described second embodiment, the control device 800 controls the operation of the bleeding throttle valves V31 to V33 based on the flow rate data obtained by the flow meters FT31 to FT33. Here, based on the flow rate data obtained by the flow meters FT31 to FT33, the flow rates of the steams B1a, B1b_2, and B1c (extracted steam) supplied as the heating medium to the feed water heaters 31a to 33a, 31b to 33b are set in advance. The control device 800 determines whether or not the value is equal to or less than the upper limit. When the flow rate exceeds the upper limit value, control device 800 closes the opening of bleeding throttle valves V31 to V33. On the other hand, when the flow rate is equal to or less than the upper limit value, the control device 800 holds the opening degrees of the bleeding throttle valves V31 to V33. Therefore, the flow rates of the steams B1a, B1b_2, and B1c (extracted steam) supplied as heating media to the feedwater heaters 31a to 33a and 31b to 33b can be adjusted to be equal to or less than the upper limit value.

  Further, in the present modified example, unlike the case of the above-described second embodiment, the operation of the bleed throttle valves V31 to V33 is controlled based on the water level data obtained by the level meters LT31a to LT33a and LT31b to LT33b. Here, based on the water level data obtained by the level meters LT31a to LT33a, LT31b to LT33b, the water level of the drain water present inside the feed water heaters 31a to 33a, 31b to 33b is set to a preset upper limit value and lower limit value. The control device 800 determines whether or not the range is within the range. When the water level of the drain water exceeds the upper limit, the control device 800 closes the opening of the bleeding throttle valves V31 to V33. When the level of the drain water is lower than the lower limit, the control device 800 opens the bleeding throttle valves V31 to V33. On the other hand, when the level of the drain water is within the range between the upper limit value and the lower limit value, control device 800 holds the opening degree of bleeding throttle valves V31 to V33. For this reason, the level of the drain water can be adjusted within the range defined by the upper limit and the lower limit.

  Further, in the present modified example, the operation of the bleeding throttle valves V31 to V33 is controlled based on the temperature data obtained by the feedwater thermometers T31a to T33a and T31b to T33b, as in the case of the above-described first embodiment. Here, based on the temperature data obtained by the feedwater thermometers T31a to T33a and T31b to T33b, the temperature difference between the temperature of the water flowing in and the temperature of the flowing water in the feedwater heaters 31a to 33a and 31b to 33b is calculated as follows. The control device 800 calculates. Then, control device 800 determines whether or not the calculated value of the temperature difference exceeds a preset upper limit value for the temperature difference. If the calculated value of the temperature difference exceeds the upper limit, control device 800 adjusts the opening of bleed throttle valves V31 to V33. On the other hand, when the calculated value of the temperature difference is equal to or smaller than the preset upper limit, the control device 800 holds the opening degrees of the bleed throttle valves V31 to V33. For this reason, the temperature difference between the feed water heaters 31a to 33a and 31b to 33b can be made equal to or less than the upper limit value, so that breakage of the feed water heaters 31a to 33a and 31b to 33b can be effectively prevented.

<Others>
While some embodiments of the invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 ... Steam turbine, 2 ... Condenser, 3 ... Feed water heating part, 4 ... Boiler, 11 ... High pressure turbine part, 12 ... Medium pressure turbine part, 13 ... Low pressure turbine part, 14 ... Generator, 31 (31a, 31b) ) ... first high pressure feed water heater (feed water heater), 32 (32a, 32b) ... second high pressure feed water heater (feed water heater), 33 (33a, 33b) ... third high pressure feed water heater (feed water heater) ), 34: first low-pressure feedwater heater (feedwater heater), 35: second low-pressure feedwater heater (feedwater heater), 300: valve casing, 300A ... inlet, 300B ... outlet, 310 ... valve body, 310S ... Stopper, 311 deaerator, 320 valve stem, 330 driving device, 800 control device, 81 function generator, 811 to 815 PID controller, 82 low value selector, 83 high value selector, FT31 to FT33: Flow meter, LT31 LT33a, LT31b to LT33b: Level gauge, P2: Condenser pump, P311: Water supply pump, P31a, P31b, P32a, P32b, P33a, P33b, P34, P35: Pressure gauge, T2, T311a, T311b, T31a, T31b, T32a, T32b, T33a, T33b, T34, T35: water supply thermometer, V31, V31a, V31b: first high-pressure bleed throttle valve (bleed throttle valve), V32, V32a, V32b: second high-pressure bleed throttle valve (bleed air) V33, V33a, V33b: third high-pressure bleed throttle valve (bleed throttle valve), V34: first low-pressure bleed throttle valve (bleed throttle valve), V35: second low-pressure bleed throttle valve (bleed throttle) Valves), X31a, X31b, X32a, X32b, X33a, X33b, X34, X35 ... Drain water thermometer, 8 ... Frequency sudden decrease detector 80, T80 ... steam tables

Claims (10)

A steam turbine,
A condenser for cooling and condensing the steam exhausted from the steam turbine,
Using a steam extracted from the steam turbine as a heating medium, a feedwater heating unit that heats water condensed in the condenser,
A boiler that generates steam by heating water heated in the feedwater heating unit,
A generator that is driven by the steam generated by the boiler being supplied to the steam turbine to generate power, wherein the power generated by the generator is output to a power system. ,
A bleed throttle valve that adjusts the flow rate of the heating medium supplied to the feedwater heating unit,
A control device for controlling the operation of the bleeding throttle valve,
The control device adjusts the opening of the bleed throttle valve to a predetermined amount during normal operation,
When detecting a decrease in system frequency in the power system, the opening degree of the bleed throttle valve is set to the predetermined amount so that the flow rate of the heating medium supplied to the feedwater heating unit is reduced as compared with the case of the normal operation. By making the output smaller, the output of the generator is increased compared to the case of the normal operation, and the output increasing operation is performed.When the output increasing operation is performed, the temperature of the water flowing through the feedwater heating unit is reduced. Controlling the operation of the bleed throttle valve based on
Thermal power plant. The feedwater heating unit,
With multiple feedwater heaters,
The pressure of the heating medium supplied to each of the plurality of feed water heaters is configured to increase sequentially along the flow of the water condensed by the condenser, and the water condensed by the condenser By sequentially flowing through the plurality of feed water heaters, the plurality of feed water heaters are configured in multiple stages so that the temperature of water condensed in the condenser rises,
The bleeding throttle valve is plural, and is provided at each stage of the multi-stage feed water heater,
The control device includes:
When starting the output increase operation, at least one of the plurality of bleeding throttle valves is closed,
When performing the output increase operation, the temperature difference between the temperature of the inflowing water and the temperature of the outflowing water in each of the plurality of feedwater heaters is calculated, and the calculated value of the calculated temperature difference is calculated in advance. Determine whether or not exceeds the set upper limit, if the calculated value exceeds the upper limit, the flow rate of the heating medium to the feed water heater located upstream of the feed water heater exceeded the upper limit Open the bleed throttle valve to adjust the
The thermal power plant according to claim 1. The feedwater heating unit,
A first feed water heater,
A second feedwater heater having a pressure of the heating medium lower than that of the first feedwater heater, wherein the water condensed in the condenser includes the second feedwater heater and the first feedwater. It is configured so that the temperature rises by sequentially flowing through the heater,
The bleeding throttle valve,
A first bleeding throttle valve for adjusting the flow rate of the heating medium to the first feedwater heater;
A second bleeding throttle valve for adjusting the flow rate of the heating medium in the second feedwater heater,
The control device includes:
When starting the output increase operation, the second bleed throttle valve is closed,
When performing the output increase operation, a temperature difference between the temperature of the water flowing into the first feedwater heater and the temperature of the water flowing out of the first feedwater heater is calculated, and the calculated temperature difference is calculated. It is determined whether the calculated value exceeds a preset upper limit value, and when the calculated value exceeds the upper limit value, the second bleed throttle valve is opened,
The thermal power plant according to claim 2. The feedwater heating unit,
High pressure feed water heating section,
A low-pressure feedwater heating unit in which the pressure of the heating medium is lower than the high-pressure feedwater heating unit, wherein the water condensed in the condenser sequentially flows through the low-pressure feedwater heating unit and the high-pressure feedwater heating unit. Is configured to rise,
The first feedwater heater, and the second feedwater heater constitute the high-pressure feedwater heating unit,
The thermal power plant according to claim 3. The feedwater heating unit,
High pressure feed water heating section,
A low-pressure feedwater heating unit in which the pressure of the heating medium is lower than the high-pressure feedwater heating unit, wherein the water condensed in the condenser sequentially flows through the low-pressure feedwater heating unit and the high-pressure feedwater heating unit. Is configured to rise,
The first feedwater heater, and the second feedwater heater constitute the low-pressure feedwater heating unit,
The thermal power plant according to claim 3. A steam turbine,
A condenser for cooling and condensing the steam exhausted from the steam turbine,
A feedwater heating unit that heats water condensed in the condenser, using steam extracted from the steam turbine as a heating medium,
A boiler that generates steam by heating water heated in the feedwater heating unit,
A generator that is driven by the steam generated by the boiler being supplied to the steam turbine to generate power, and wherein the power generated by the generator is output to a power system. ,
A bleeding throttle valve for adjusting the flow rate of the heating medium supplied to the feedwater heating unit,
A control device for controlling the operation of the bleeding throttle valve,
The control device, when the system frequency is reduced in the power system, the output increase operation in a range in which the temperature inside the supply of the heating medium is lower than the saturation temperature of the heating medium in the feedwater heating unit. Has a predetermined procedure to determine in which order and how much to open the bleeding throttle valve since the start,
By adjusting the opening of the bleeding throttle valve in the predetermined procedure, the flow rate of the heating medium supplied to the feed water heating unit is reduced as compared with the case of normal operation, and the output of the generator is reduced. Perform an output increase operation that increases compared to the case of normal operation.
Thermal power plant. The control device detects the internal pressure of the feed water heating unit and executes the temperature of the drain water present at a location where the heating medium is supplied in the feed water heating unit when the output increasing operation is being performed. Detecting, determining the saturation temperature of the heating medium based on the internal pressure, controlling the operation of the bleed throttle valve so that the detected drain water temperature is lower than the determined saturation temperature,
The thermal power plant according to claim 1. In the bleeding throttle valve, a stopper is provided at a position that prevents the opening degree from being in a fully closed state.
The thermal power plant according to claim 6. The control device includes:
When the output increasing operation is being performed, the flow rate of steam supplied to the feedwater heating section as the heating medium, the level of drain water present inside the heating medium supplied to the feedwater heating section, Controlling the operation of the bleed throttle valve based on one or more temperatures of water flowing as a heated medium in the heating unit,
A thermal power plant according to claim 7. The bleeding throttle valve is a hydraulic valve,
The thermal power plant according to any one of claims 1 to 9.

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