JP2013087644A - Increase output operation method in steam power generation plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for increasingly outputting generator output to rated output or more without changing a facility, by increasing a steam turbine driving steam quantity by limiting an extraction use quantity of a steam turbine.SOLUTION: This increase output operation method of the steam power generation plant performs increase output by increasing a steam quantity for driving the steam turbine joined to a generator by reducing an extraction quantity consumed by a water supply heater by reducing a supply water flow rate of passing through the water supply heater by adjusting opening of a water supply heater bypass valve, and by setting a steam supply quantity generated by a steam generator constant.

Description

  The present invention relates to a method for increasing power output in a steam power plant that increases the amount of steam for driving a steam turbine by restricting the amount of steam extracted from the steam turbine, and increases the output of a generator beyond a rated output without changing equipment.

  As for power supply, in order to maintain a balance between demand and supply, supply is ensured to cover the maximum demand under all conditions. However, an increase in demand due to abnormal weather, unexpected equipment troubles, etc. may cause the supply volume to become tight against demand.

  In such a case, it is possible to add new equipment, remodel existing power generation equipment, install rental equipment, etc., but all of them require a certain period of time for installation. In some cases, it may not be in time for a rapid increase in demand, and in the case of emergency construction, the cost may increase.

  Therefore, if the generator output can be increased beyond the rated output by making use of the equipment margin of the existing power generation equipment without new construction or remodeling, supply stability can be improved for higher demand. .

  As a power plant that increases the output of the generator, for example, there is a steam power plant. In a steam power plant, a steam turbine coupled to a generator is driven by steam generated by a steam generator to generate power.

  In a typical steam power plant, a part of steam for driving a steam turbine is extracted as extracted air, and the extracted air is used as heating for feed water or power for a steam turbine for driving a feed water pump to improve the efficiency of the entire steam power plant. I am trying.

  As a method for increasing the generator output of a steam turbine plant, Patent Document 1 discloses an increase in output by flowing down the extracted air from an existing steam turbine to a steam turbine and a generator installed separately from the existing steam turbine plant. There is a coal fired thermal power generation system.

JP 2011-132899 A

  However, although the thing of patent document 1 can increase a generator output reliably in order to install a new installation, it cannot respond to the situation where the period and cost for installation require and the supply amount is suddenly insufficient. In addition, there is a problem that an installation space cannot be secured in the power plant.

  An object of the present invention is to provide an operation method that enables increased output of a steam power plant without installing new equipment.

  According to a first aspect of the present invention, there is provided a steam power plant increasing output operation method in which steam generated by a steam generator is driven to drive a steam turbine coupled to a generator to generate power, and the steam that drives the steam turbine is generated. In a steam power plant that adopts a method of extracting a part of the feed water heating bleed air in the feed water heater, the feed water flow rate passing through the feed water heater is reduced and the steam flow rate generated by the steam generator is constant. It is characterized by.

  A steam power plant increasing output operation method according to a second aspect of the present invention is the feed water heater according to the first aspect, wherein the feed water heater includes a feed water heater bypass pipe and is installed in the feed water heater bypass pipe By adjusting the opening degree of the bypass valve, the feed water flow rate passing through the feed water heater is adjusted.

  According to a third aspect of the present invention, there is provided a steam power plant increasing output operation method according to the second aspect, wherein a correlation curve between the opening degree of the feed water heater bypass valve and the generator output value is prepared in advance to operate the steam power plant. The generator output value with respect to the opening of the feed water heater bypass valve is adjusted to a bypass valve opening corresponding to the target generator output based on the correlation curve.

  According to a fourth aspect of the present invention, there is provided a method for increasing the output power of a steam power plant according to the third aspect, wherein the correlation curve between the opening degree of the feed water heater bypass valve and the generator output value is obtained by thermal calculation. It is created from the generator output value in the case where the inlet water supply temperature of the steam generator with respect to the bypass valve opening and the steam flow rate generated in the steam generator determined by plant heat calculation are constant. .

  According to the first aspect of the present invention, by reducing the feed water flow rate that passes through the feed water heater, the extraction flow rate that has a positive correlation with the feed water flow rate that flows through the feed water heater can be reduced. As for the relationship between the feed water flow rate and the heat exchange amount, the Dittus-Boelter equation, which is proportional to the 0.8th power of the heat passage rate flow velocity, is known.

  Since the amount of bleed air from the steam turbine is reduced and the steam flow rate at the inlet of the steam turbine is controlled at a constant level, the flow rate of steam that drives the steam turbine increases, resulting in an increase in the generator output coupled to the steam turbine. be able to.

  According to the second aspect of the present invention, it is made possible by adjusting the opening of the feed water heater bypass valve as means for reducing the feed water flow rate flowing to the feed water heater. By operating the feed water heater bypass valve, the feed water flow rate flowing to the feed water heater can be easily adjusted without changing the feed water flow rate at the inlet of the steam generator. This is because, in order to keep the steam flow rate at the steam turbine inlet constant at the rated value, it is desirable not to change the feed water flow rate at the steam generator inlet.

  According to the invention of claim 3, the feed water heater bypass valve opening according to the required output can be set based on the correlation curve of the output of the steam power plant with the opening of the feed water heater bypass valve prepared in advance. The opening degree of the bypass valve according to the required generator output can be easily set. An appropriate amount of increased output operation is possible depending on the power supply and demand situation.

  According to the invention of claim 4, it is possible to confirm the output value of the steam power plant with respect to the feed water heater bypass valve opening before the actual operation of the steam power plant. Increased output places some burden on the plant, so it is necessary to implement it while ensuring the soundness of the plant. It can be one of the means for confirming the soundness of the plant depending on whether or not it can be operated according to the correlation curve created in advance.

  In this way, it can be used to determine applicability during test operations that are actually carried out in a steam power plant, and if the difference between the operation value and the correlation curve becomes large during increased output operation, there is a problem somewhere in the plant. The possibility of appearing can be found at an early stage.

1 is a schematic configuration diagram of a steam power plant according to an embodiment of the present invention. The block diagram of Example 1 of the increase output operation method of the steam power plant which concerns on embodiment of this invention. The block diagram of Example 2 of the increase output operation method of the steam power plant which concerns on embodiment of this invention. The schematic block diagram of a feed water heater. Correlation curve (feed water heater bypass feed water flow rate-generator output) Correlation curve (feed water heater bypass feed water flow rate-steam generator inlet feed water temperature) Correlation curve (feed water heater bypass valve opening-generator output)

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The names, configurations, and the like shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified.

  FIG. 1 is a schematic configuration diagram of a thermal power plant that is a steam power plant according to an embodiment of the present invention. The steam power plant includes a boiler 60 that is a steam generator, a steam turbine 70 that is driven by steam generated by the boiler 60, a steam control valve 62 that adjusts the amount of steam flowing into the steam turbine 70, and the steam turbine 70. A generator 80 to be coupled, a condenser 90 that returns steam that has driven the steam turbine 70 to condensate, a feed water pump 100 that feeds the condensate in the condenser 90 to the steam generator 60 as feed water, and a feed water pump The feed water heater 10 that heats the feed water delivered by 100, the bypass pipe 20 that bypasses the feed water flowing through the feed water heater 10, the feed water heater bypass valve 30 that adjusts the feed water flow rate in the bypass pipe 20, and the steam turbine It is comprised from the extraction pipe | tube 40 which sends a part of the steam which drives 70 to the feed water heater 10 as extraction, and the extraction valve 50 installed in the extraction pipe 40 It is. In FIG. 1, a general configuration is simplified for the sake of explanation.

  The steam generated in the boiler 60 drives the steam turbine 70, generates electric power as an output of the generator 80 coupled to the steam turbine 70, and supplies the electric power to a power system (not shown). The output of the generator 80 is adjusted with the steam flow, pressure, temperature, flow rate generated by the boiler 60, and the opening degree of the steam control valve 62. Is going.

  The steam that has finished work in the steam turbine 70 is guided to the condenser 90 and returned to the water. The water in the condenser 90 is sent as feed water to the boiler 60 by the feed water pump 100, becomes steam again by the boiler 60, and drives the steam turbine 70. The feed water is heated by the feed water heater 10 using the bleed gas supplied from the steam turbine 70 as a heat source before entering the boiler 60, thereby improving the efficiency of the entire steam power plant.

  Therefore, if the amount of extraction supplied from the steam turbine 70 can be reduced, the efficiency of the entire steam power plant decreases, but the amount of steam for driving the steam turbine 70 increases, and as a result, the generator output is reduced. The output can be increased.

  However, even if the generator output is increased by reducing the amount of bleed air from the steam turbine 70, control is normally performed to keep the generator output constant, so the steam flow from the boiler 60 is reduced, and And return to the generator output.

  Therefore, the generator output can be increased without changing the output flow rate of the boiler 60 by controlling the steam flow rate to be constant rather than controlling the steam flow rate according to the generator output. However, it is possible to carry out within the range of the equipment margin for the rated value capable of increasing the output for each of the boiler 60, the steam turbine 70, and the generator 80.

  Next, a specific method for reducing the amount of extraction will be described with reference to FIGS. FIG. 4 is a schematic structural diagram showing the structure of the feed water heater 10. The feed water enters the feed water heater 10 and then flows to the outlet through a thin tube which is the heat exchanger 110. Since the extracted air from the steam turbine 70 flows into the heat exchanger 110, the extracted air and the feed water exchange heat to increase the temperature of the feed water.

  The bleed air is cooled by performing heat exchange with the water supply, is changed from gas to liquid and condensed, and the pressure in the heat exchanger decreases, so that new bleed air is supplied from the bleed pipe 40 having a high pressure. The bleed flow rate is not controlled by the bleed valve 50 provided in the bleed pipe 40, and a flow rate proportional to the heat exchange amount in the heat exchanger 110 of the feed water heater 10 flows to the last.

  In other words, by reducing the amount of water supply for exchanging heat with the bleed air, the amount of heat exchange with the bleed air is reduced, and the amount of bleed air condensing from gas to liquid is reduced, thereby reducing the bleed air flow rate.

  It is possible to reduce the amount of bleed by operating the bleed valve of each feed water heater, but there are multiple feed water heaters in the actual plant, and it is complicated for the operator to operate all the bleed valves, If the bleed valves of all feed water heaters cannot be opened and closed at the same time, the heat balance is lost and it takes time to stabilize the state of the plant.

  A new control device can be installed and the bleed valve can be operated, but the modification cost is increased accordingly. On the other hand, when the feed water flow rate is adjusted, the feed water of all the feed water heaters changes at the same time, so that the amount of bleed can be reduced quickly without destroying the overall heat balance.

  Next, a method for increasing output operation in a general thermal power plant will be described. FIG. 2 is a configuration diagram of a general thermal power plant. The steam generated in the boiler 60 which is a steam generator passes through the steam control valve 62 as main steam and drives the high-pressure turbine 71. The steam that has driven the high-pressure turbine 71 is heated again by the boiler 60, and then the medium-pressure turbine 72 is driven as reheated steam, and the low-pressure turbine 73 is driven by the exhaust gas. The generator 80 coupled to each turbine generates power. doing.

  Exhaust gas from the low-pressure turbine 73 is returned to water by the condenser 90 and sent to the deaerator 16 by the condensate pump 101. Between the condensate pump 101 and the deaerator 16, there are low-pressure feed water heaters 14 and 15 using the extraction of the low-pressure turbine 73, and the condensate temperature flowing into the deaerator 16 is increased. In the deaerator 16, oxygen contained in the condensate is removed by using extraction of the intermediate pressure turbine 72 or the like.

  Condensate from the deaerator 16 is sent to the boiler 60 as feed water by the feed pump 102. There are high-pressure feed water heaters 11, 12, and 13 between the feed water pump 102 and the boiler 60, and the feed water temperature is raised by using extraction of the intermediate pressure turbine 72 and the high pressure turbine 71. The feed water sent to the boiler 60 becomes steam again and is sent to the high-pressure turbine 71.

  In order to increase the output of the steam power plant, first, the main steam flow rate control at that time is switched from the generator output follow-up control to the main steam flow constant control in the state of stable operation at the rated output. Since it operates stably at the rated output, there is no change in the main steam flow rate, and there is no change in the plant even if the control method is switched.

  Subsequently, the opening of the high-pressure feed water heater bypass valve 30 is gradually opened from 0% during normal operation. As the feed water flows through the high-pressure feed water heater bypass valve 30, the amount of feed water flowing through the high-pressure feed water heaters 11, 12, and 13 decreases. By reducing the amount of water supplied to the high-pressure feed water heaters 11, 12, and 13, the amount of bleed air flowing in is reduced.

  Specifically, since the amount of water supplied to the plurality of high-pressure feed water heaters 11, 12, and 13 can be reduced by the high-pressure feed water heater bypass valve 30, the bleed flow rates at a plurality of locations can be reduced simultaneously. The number of high-pressure feed water heaters varies depending on the plant and is often three or four.

  By reducing the extraction flow rate, the driving steam of the high-pressure turbine 71, the intermediate-pressure turbine 72, and the low-pressure turbine 73 into which the outlet steam of the intermediate-pressure turbine 72 flows can be increased and the generator output can be increased. The main steam flow rate control may be changed from the generator output follow-up control to the main steam flow rate constant control and the main steam flow rate may be returned to the rated flow rate after the amount of feed water flowing to the high-pressure feed water heaters 11, 12, 13 is reduced. .

  In addition to the above operation, the low pressure feed water heater bypass valve 37 can be opened to further increase the output. However, since the condensate flow rate that flows into the deaerator 16 decreases due to an increase in the condensate flow rate that bypasses the low-pressure feed water heaters 14, 15, the oxygen content in the condensate supplied to the deaerator 16 is appropriately adjusted. In order to lower it, it is necessary to increase the extraction flow rate. As a result, it may be possible that the output cannot be increased depending on the plant.

  Although only the condensate flow rate of the low-pressure feed water heaters 14 and 15 may be reduced, the amount of bleed into the low-pressure feed water heaters 14 and 15 is reduced, but the condensate temperature to the deaerator and the next The amount of heat exchange increases in the deaerator and the water heater in the next stage, for example, the temperature of the feed water to the stage water heater decreases. Become. Depending on the plant, it may be almost zero.

  FIG. 3 is a configuration diagram of the steam power plant in the second embodiment. When the feed water heater bypass valve is installed for each feed water heater, each feed water heater bypass valve may be operated. In that case, it is desirable to operate from the feed water heater on the side where the feed water temperature becomes high.

  For example, if the first high-pressure feed water heater bypass valve 31 is operated and the feed water flow rate of the first high-pressure feed water heater 11 is lowered, the flow rate of the second high-pressure feed water heater 12 on the higher temperature side is reduced before and after that. Although it does not change, since the low temperature water supply flows, the heat exchange amount of the extraction air increases and the extraction flow rate increases.

  Thereafter, when the second high-pressure feed water heater bypass valve 32 is operated and the feed water flow rate of the second high-pressure feed water heater 12 is lowered, the once-extracted bleed flow rate is greatly reduced, so that the driving steam flow rate of the high-pressure turbine 71 fluctuates. The impact on the plant will increase. Therefore, when the amount of water supplied from the third high-pressure feed water heater 13 is decreased, the amount of increase / decrease in the extraction flow rate is small compared to the case where the amount of water supplied from the first high-pressure feed water heater 13 is reduced. Operation as a power plant becomes possible.

  Further, when only the feed water flow rate of either the high pressure feed water heaters 11 and 12 or the low pressure feed water heaters 14 and 15 is reduced, the amount of bleed into the feed water heater is reduced, but the feed water heating of the next stage is performed. Since the feed water temperature to the vessel decreases, the heat exchange amount increases in the feed water heater at the next stage. As a result, the amount of bleed from the feed water heater at the next stage increases, so the output increase effect is reduced. Depending on the plant, it may be almost zero.

  Subsequently, when the present invention is applied to an actual power plant, it is necessary to sufficiently check whether it can be applied. The applicability of the steam power plant according to the opening of the feed water heater bypass valve is determined. Obtain the output in advance by heat balance calculation, and examine whether it is possible to carry out the calculation operation.

  When it is determined that the calculation can be performed, a test operation is actually performed to compare the actual measurement values of each part of the steam power plant with the heat balance calculation values. During actual test operation, it is desirable to calculate and calculate the heat balance not only for the generator output but also for the items such as boiler inlet feed water temperature, fuel flow rate, feed water flow rate, main steam flow rate, etc. .

  The heat balance calculation is performed according to the following procedure. First, the feed water flow rate for bypassing the reference feed water heater is set. If the feed water flow rate for bypassing the feed water heater relative to the feed water heater bypass valve opening is known in advance, the feed water heater bypass valve opening may be set directly.

  Subsequently, the feed water temperature at the feed water heater outlet is obtained by heat calculation from the feed water flow rate flowing to the feed water heater that decreases by bypassing. Furthermore, the feed water temperature obtained by mixing the feed water at the outlet of the feed water heater and the feed water at the outlet of the feed water heater bypass pipe is obtained. This is the boiler inlet water supply temperature. Furthermore, the main steam flow is fixed, the plant heat balance calculation is performed, and the generator output at that time is obtained.

  These heat balance calculations are performed by changing the feed water heater bypass feed water flow rate as a reference, for example, 10%, 20%, and 30%, respectively, and the feed water heater bypass feed water flow rate and the steam power plant as shown in FIG. Create a correlation curve for generator output. In addition, in the heat balance calculation, a correlation curve between the feed water heater bypass feed water flow rate and the boiler inlet feed water temperature as shown in FIG. 6 may be created.

  When the correlation between the feed water heater bypass valve opening and the feed water heater bypass feed water flow rate is unclear, measure the opening of the feed water heater bypass valve and the boiler feed water temperature at the time of normal plant operation that is not in the increased output operation, A correlation curve between the feed water heater bypass valve opening and the generator output of the steam power plant as shown in FIG. 7 can be created from the correlation curve created by heat balance calculation.

  By using such a correlation curve, the feed water heater bypass valve opening according to the required generator output can be adjusted more easily than the correlation curve in the increased output operation in the steam power plant. In addition, if there is a deviation in the feedwater heater bypass valve opening corresponding to the generator output during increased output operation, it is understood that there may be a problem with the plant, and it is possible to respond quickly It becomes. If the deviation is large, an alarm may be issued to notify the operator.

  As described above, it is possible to increase the output power of the steam power plant without renewing the equipment and the like, and it is possible to perform stable operation such as determining whether it can be applied to the actual plant and checking the malfunction during the operation.

DESCRIPTION OF SYMBOLS 10 ... Feed water heater, 11 ... 1st high pressure feed water heater, 12 ... 2nd high pressure feed water heater, 13 ... 3rd high pressure feed water heater, 14 ... 1st low pressure feed water heater, 15 ... 2nd low pressure feed water heater , 16 ... deaerator, 20 ... feed water heater bypass pipe, 21 ... first high pressure feed water heater bypass pipe, 22 ... second high pressure feed water heater bypass pipe, 23 ... third high pressure feed water heater bypass pipe, 24 ... 1st low pressure feed water heater bypass pipe, 25 ... 2nd low pressure feed water heater bypass pipe, 27 ... low pressure feed water heater bypass pipe, 30 ... feed water heater bypass valve, 31 ... 1st high pressure feed water heater bypass valve, 32 ... 2nd high pressure feed water heater bypass valve, 33 ... 3rd high pressure feed water heater bypass valve, 34 ... 1st low pressure feed water heater bypass valve, 35 ... 2nd low pressure feed water heater bypass valve, 37 ... Low pressure feed water heater bypass valve , 40 ... bleed pipe, 41 ... first Pressure feed water heater bleed pipe, 42 ... second high pressure feed water bleed pipe, 43 ... third high pressure feed water bleed pipe, 44 ... first low pressure feed water bleed pipe, 45 ... second low pressure feed water bleed pipe 50 ... Bleed valve, 51 ... First high pressure feed water heater bleed valve, 52 ... Second high pressure feed water bleed valve, 53 ... Third high pressure feed water bleed valve, 54 ... First low pressure feed water bleed valve, 55 ... second low pressure feed water heater bleed valve, 60 ... boiler, 61 ... main steam pipe, 62 ... steam control valve, 70 ... turbine, 71 ... high pressure turbine, 72 ... medium pressure turbine, 73 ... low pressure turbine, 80 ... power generation 90 ... Condenser, 100, 102 ... Feed water pump, 101 ... Condensate pump, 110 ... Heat exchanger

Claims (4)

A method of generating electricity by driving a steam turbine coupled to a generator with steam generated by a steam generator, and extracting a part of the steam that drives the steam turbine as extraction water for feed water heating in a feed water heater. In the steam power plant to be adopted,
A method for increasing output operation of a steam power plant, wherein the flow rate of feed water passing through the feed water heater is reduced and the flow rate of steam generated by the steam generator is constant.   The feed water heater includes a feed water heater bypass pipe, and adjusts a feed water flow rate passing through the feed water heater by adjusting an opening degree of a feed water heater bypass valve installed in the feed water heater bypass pipe. The method for increasing output operation of a steam power plant according to claim 1.   A correlation curve between the opening degree of the feed water heater bypass valve and the generator output value is prepared in advance, and the generator output value with respect to the opening degree of the feed water heater bypass valve during operation of the steam power plant is used as the correlation curve. 3. The method for increasing the output power of a steam power plant according to claim 2, wherein the opening degree of the bypass valve is adjusted to correspond to the target generator output. The correlation curve between the opening degree of the feed water heater bypass valve and the generator output value is the inlet feed water temperature of the steam generator with respect to the opening degree of the feed water heater bypass valve obtained by heat calculation, and the above-mentioned obtained by plant heat calculation. The method for increasing output operation of a steam power plant according to claim 3, wherein the output is generated from the generator output value when the flow rate of steam generated by the steam generator is constant.