JP2017187039A - Power generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat efficiency in a power generating system that drives a steam turbine by steam generated by a boiler to generate power.SOLUTION: The power generating system includes: a boiler 1 for heating water to generate steam; the steam turbine 2 driven by steam supplied from the boiler 1; a power generator 3 driven by the steam turbine 2 to generate power; and a steam compressor 4 for raising temperature of the steam supplied from the steam turbine 2 by adiabatic compression.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power generation system that generates electricity by driving a steam turbine with steam generated by a boiler.

  The combined cycle power plant generates steam by recovering heat remaining in the exhaust gas of a gas turbine with an exhaust heat recovery boiler. The generated steam is supplied to a steam turbine through a pipe and used for power generation. In large-scale combined cycle power generation facilities in recent years, power is recovered in the expansion process of each turbine using a triple-pressure steam turbine, which is a high-pressure turbine, a reheat turbine, and a low-pressure turbine, and then seawater and river water are collected inside the condenser. By exchanging heat with the used cooling tower, the low-pressure steam is condensed and returned to the condensate, and again supplied to the exhaust heat recovery boiler as high-pressure, medium-pressure, and low-pressure boiler feed water.

  In conventional thermal power using coal as fuel, water (feed water) extracted from a low-pressure turbine that is expanding in a steam turbine or condensed in a condenser is fed into high pressure, medium pressure, and A method of preheating with a low-pressure feed water heater and supplying it to the boiler has been put into practical use, and power generation efficiency has been improved.

  In general, a method is also used in which a part of the gas is extracted from a pipe on the outlet side of a medium-pressure or low-pressure steam drum and supplied to a fuel gas heater to preheat the fuel gas of the gas turbine. The higher the temperature of the fuel gas input to the gas turbine, the higher the thermal efficiency due to the effect of the regeneration cycle. Therefore, heat exchange with the gas is performed in the fuel gas heater using the steam whose temperature has been increased as a heat medium, and the fuel gas If the supply temperature is improved, the thermal efficiency of the gas turbine can be improved.

  Furthermore, as a recently proposed method, steam discharged from a low-pressure turbine in a large nuclear power plant is compressed by a steam compressor (heat pump) to increase the pressure and temperature, and normal high-pressure extraction steam is used. A method of utilizing low-temperature steam with higher efficiency than a heat source of a conventional moisture separator has been proposed (Patent Document 1).

  A combined cycle power plant that uses gas turbines and steam turbines does not have a large-scale steam cycle like a nuclear power plant or a large coal-fired power plant. Reusing low temperature water from charcoal is considered less cost effective.

International Publication No. 2010/087126

  In addition to nuclear power plants and large coal-fired power plants, there is a need for further efficiency improvements not only in small-scale power generation systems (for example, combined cycle power generation systems). An object of the present invention is to improve thermal efficiency in a power generation system that generates power by driving a steam turbine with steam generated by a boiler.

<Configuration 1>
A characteristic configuration of a power generation system for achieving the above-described object is that a boiler that generates steam by heating water, a steam turbine that is driven by steam supplied from the boiler, and that is driven by the steam turbine to generate power It has a generator and a steam compressor that adiabatically compresses the steam supplied from the steam turbine and raises the temperature.

  According to the above characteristic configuration, the steam compressor adiabatically compresses the steam supplied from the steam turbine and raises the temperature, so that the temperature and pressure of the steam from the steam turbine can be increased and effectively utilized. It becomes possible. In other words, this steam can be used for, for example, heating the fuel gas of a gas turbine or used as a working fluid for an expansion turbine, so that the thermal efficiency of the power generation system can be improved. Moreover, since the temperature of the steam in the steam compressor is increased by adiabatic compression, that is, self-heat regeneration, the temperature of the steam from the steam turbine can be increased and increased with less energy. Therefore, the thermal efficiency of the power generation system can be improved.

<Configuration 2>
If the steam compressor is configured so as to raise the temperature by adiabatically compressing the steam extracted from the steam turbine, steam having a relatively high temperature and pressure is compressed by the steam compressor. It is possible to improve.

<Configuration 3>
Further, when the steam compressor is configured to adiabatically compress and raise the temperature of the steam discharged from the steam turbine, the steam that has finished using heat and pressure in the steam turbine is regenerated and used in the steam compressor. Therefore, the thermal efficiency can be further improved, which is preferable.

<Configuration 4>
Another characteristic configuration of the power generation system according to the present invention includes a fuel heater that heats the fuel gas with steam from the steam compressor, and power generation by burning the fuel gas heated by the fuel heater. A gas turbine generator.

  According to the above characteristic configuration, the fuel gas of the gas turbine generator is heated by the steam adiabatically compressed by the steam compressor, so that the efficiency of the gas turbine generator is greatly improved. Therefore, the thermal efficiency of the power generation system can be further improved. When operating at a certain load, the total amount of heat given to the gas turbine from the outside is constant, and if the fuel gas temperature is raised, the fuel flow rate can be reduced by that amount, resulting in the thermal efficiency of the gas turbine alone. It leads to improvement.

<Configuration 5>
Another characteristic configuration of the power generation system according to the present invention is that it has a pre-stage fuel heater that heats the fuel gas with water extracted from the boiler economizer and supplies the fuel gas to the fuel heater.

  Extraction from the economizer uses the condensate that was originally heated by the condensate heater, so the fuel flow rate can be reduced by the amount of fuel gas that is heated by the preceding stage fuel heater. This leads to improvement of the thermal efficiency of the gas turbine alone. That is, according to the above-described characteristic configuration, the fuel gas of the gas turbine generator is heated not only by the steam from the steam compressor but also by the water drawn from the boiler economizer, so that the efficiency of the gas turbine generator is improved. Further improve. Therefore, the thermal efficiency of the power generation system can be further improved.

<Configuration 6>
Another characteristic configuration of the power generation system according to the present invention is supplied from the steam turbine to the steam compressor based on a fuel flow rate instruction value that is an instruction value of the amount of fuel supplied to the fuel warmer. It has a steam supply valve for controlling the amount of steam.

  According to the above characteristic configuration, the amount of steam supplied to the steam compressor, that is, the amount of steam supplied to the fuel warmer is controlled by the steam supply valve based on the fuel flow rate instruction value. By using such feedforward control, it is possible to cause the outlet temperature of the fuel warmer to follow the target value at an early stage and to suppress a time delay relatively.

<Configuration 7>
Another characteristic configuration of the power generation system according to the present invention is that it includes an auxiliary steam turbine driven by steam supplied from the fuel heater, and an auxiliary generator driven by the auxiliary steam turbine to generate electric power. is there.

  The steam supplied from the fuel heater is maintained at a high pressure although the temperature is lowered. According to the above characteristic configuration, since the generated electric power can be obtained by utilizing this steam as the working fluid of the auxiliary steam turbine, the thermal efficiency of the power generation system can be further improved.

<Configuration 8>
Another characteristic configuration of the power generation system according to the present invention includes a power control unit that controls power generated by the power generation system, and the power control unit is configured so that the power generated by the power generation system is constant. The power is generated by the auxiliary generator.

  According to said characteristic structure, the electric power which an auxiliary generator is controlled and a power generation system produces | generates becomes constant, and is suitable.

<Configuration 9>
The power generation system according to the present invention may be configured such that the power control unit controls the amount of steam supplied to the auxiliary steam turbine to control the electric power generated by the auxiliary generator.

Block diagram showing the outline of the power generation system

  The power generation system will be described below with reference to the drawings. The power generation system according to the present embodiment includes a boiler 1 that generates steam by heating water, a steam turbine 2 that is driven by steam supplied from the boiler 1, and a generator 3 that is driven by the steam turbine 2 to generate power. And a steam compressor 4 for adiabatically compressing the steam supplied from the steam turbine 2 and raising the temperature.

  The boiler 1 generates steam by heating the supplied water using heat generated by burning oil or coal or nuclear reaction. In the present embodiment, the boiler 1 includes a high-pressure boiler 1a, a reheat boiler 1b, and a low-pressure boiler 1c.

  The steam turbine 2 is rotationally driven by the expansion of the steam supplied from the boiler 1. The steam turbine 2 includes a high pressure steam turbine 2a, an intermediate pressure steam turbine 2b, and a low pressure steam turbine 2c. These three turbines are provided on a common rotating shaft, and the rotating shaft is connected to the generator 3. That is, the generator 3 is driven by the steam turbine 2 to generate power.

  The steam generated by the high-pressure boiler 1a is supplied to the high-pressure steam turbine 2a through the high-pressure steam path L1, and drives the high-pressure steam turbine 2a. The steam discharged by driving the high-pressure steam turbine 2a is returned to the reheat boiler 1b through the reheat return steam path L2.

  The steam heated by the reheat boiler 1b is supplied to the intermediate pressure steam turbine 2b through the reheat supply steam path L3, and drives the intermediate pressure steam turbine 2b. The steam discharged by driving the intermediate pressure steam turbine 2b is supplied to the low pressure steam turbine 2c through the connection steam path L4, and drives the low pressure steam turbine 2c.

  The steam generated in the low pressure boiler 1c is supplied to the low pressure steam turbine 2c through the low pressure steam path L5, and drives the low pressure steam turbine 2c. The steam discharged by driving the low-pressure steam turbine 2c is sent to the condenser 40 through the discharge steam path L6.

  The condenser 40 exchanges the supplied steam with seawater or the like to return it to water. This water is heated by the condensate heater 50, passes through the condensate supply path L10, is sent to the low pressure boiler 1c by the first condensate pump P1, and is sent to the high pressure boiler 1a by the second condensate pump P2. Water and steam circulate as described above, and power generation by the generator 3 is performed.

  Steam is extracted from the middle of the low-pressure steam turbine 2c and supplied to the steam compressor 4 through the steam supply path L7. Further, a part of the steam discharged from the low-pressure steam turbine 2 c joins the steam supply path L 7 via the three-way valve 30 from the discharge steam path L 6 and is supplied to the steam compressor 4. The ratio of the extracted steam from the low-pressure steam turbine 2c to the exhaust steam from the low-pressure steam turbine 2c in the steam supplied to the steam compressor 4 is determined by adjusting the opening degree of the three-way valve 30. It is adjusted according to etc. There may be a case where only the extracted steam from the low-pressure steam turbine 2 c or only the exhaust steam from the low-pressure steam turbine 2 c is supplied to the steam compressor 4.

  The steam compressor 4 adiabatically compresses the steam supplied from the steam supply path L7 and raises the temperature. In the steam compressor 4, high-temperature and high-pressure steam is obtained with relatively little energy by applying compression work from the outside and performing exergy recovery (self-heat regeneration) without heating the steam. be able to. Thereby, it becomes 80 to 90% energy saving compared with the heating by combustion of a fuel.

  Specifically, the steam compressor 4 is a compressor driven by a motor 4a. The steam compressed and heated by the steam compressor 4 is supplied to the fuel warmer 5 through the compression steam path L8.

  The fuel heater 5 warms the fuel gas flowing through the fuel gas supply path L9. Specifically, the fuel heater 5 heats the fuel gas up to about 250 ° C. by exchanging heat between the fuel gas flowing through the fuel gas supply path L9 and the steam flowing through the compressed steam path L8. The heated fuel gas is supplied to the gas turbine generator 7 through the fuel gas supply path L9.

  The pre-stage fuel warmer 6 is disposed on the upstream side of the fuel warmer 5 in the fuel gas supply path L9. The pre-stage fuel warmer 6 warms the fuel gas with water extracted from the economizer of the boiler 1 (low pressure boiler 1c) and supplies the fuel gas to the fuel warmer 5.

  The gas turbine generator 7 generates power by burning the fuel gas heated by the fuel warmer 5 and the preceding stage fuel warmer 6. Specifically, the gas turbine generator 7 includes a combustor 7a, a compressor 7b, a turbine 7c, and a generator 7d. The combustor 7a mixes and heats the heated fuel gas supplied from the fuel gas supply path L9 and the compressed air supplied from the compressor 7b, and sends the combustion exhaust gas to the turbine 7c. The compressor 7b is driven by the turbine 7c, compresses air, and sends it to the combustor 7a. The turbine 7c is driven by the combustion exhaust gas from the combustor 7a, and drives the compressor 7b and the generator 7d. The generator 7d is driven by the turbine 7c to generate power.

  The first auxiliary steam turbine 8a (an example of the auxiliary steam turbine 8) is disposed on the downstream side of the fuel warmer 5 in the compressed steam path L8. The first auxiliary steam turbine 8 a is driven by the steam supplied from the fuel warmer 5. The first auxiliary generator 9a is connected to the first auxiliary steam turbine 8a. The first auxiliary generator 9a is driven by the first auxiliary steam turbine 8a to generate electric power. The steam discharged from the first auxiliary steam turbine 8a is sent to the condensate heater 50 through the compression steam path L8.

  The condensate heater 50 is disposed downstream of the first auxiliary steam turbine 8a in the compressed steam path L8 and downstream of the condensate heater 50 in the condensate supply path L10. The condensate heater 50 heats the water sent to the boiler 1 by exchanging heat between the steam flowing through the compressed steam path L8 and the water flowing through the condensate supply path L10. The steam discharged from the condensate heater 50 is sent to the second auxiliary steam turbine 8b through the compression steam path L8.

  The second auxiliary steam turbine 8b (an example of the auxiliary steam turbine 8) is disposed on the downstream side of the condensate heater 50 in the compressed steam path L8. The second auxiliary steam turbine 8b is driven by the steam supplied from the fuel heater 5 and discharged from the first auxiliary steam turbine 8a. A second auxiliary generator 9b is connected to the second auxiliary steam turbine 8b. The second auxiliary generator 9b is driven by the second auxiliary steam turbine 8b to generate electric power. The steam discharged from the second auxiliary steam turbine 8b passes through the compression steam path L8, is sent to the condenser 40, is returned to water by the condenser 40, and is supplied to the boiler 1.

  The power generation system configured as described above has an efficiency of 0.07 compared to the case where the steam compressor 4, the fuel heater 5, the auxiliary steam turbine 8, the auxiliary generator 9, and the condensate heater 50 are not used. %improves.

Calculation is made for the case where 55 t / h of fuel gas is consumed in the gas turbine generator 7 of the power generation system. When steam of 20 t / h and 2780 kJ / kg is extracted from the low-pressure steam turbine 2c, the output reduction amount W2c of the low-pressure steam turbine 2c is calculated as follows. A factor of 0.9 is turbine efficiency.
W2c = 20 t / h × (2780-2400) kJ / kg × 0.9
= 1900kW

In the steam compressor 4, the extracted steam is adiabatically compressed from 0.2 MPa, 160 ° C. to 1.5 Mpa, 320 ° C. The power W4 required for this is calculated as follows. The coefficient 1.1 is the reciprocal of the compression efficiency.
W4 = 20 t / h × (3100-2780) kJ / kg × 1.1
= 1960 kW

In the fuel warmer 5, the steam gives heat to the fuel gas, and the temperature of the steam decreases from 320 ° C to 200 ° C. The gain due to the heating of the fuel gas in the fuel heater 5 is calculated as the heat W5 given from the steam to the fuel gas in the fuel heater 5 as follows.
W5 = 20 t / h × (3100-2800) kJ / kg
= 1670 kW
This ΔW corresponds to a reduction of 122 kg / h in terms of fuel consumption.

The electric power W8a generated by the first auxiliary steam turbine 8a and the first auxiliary generator 9a is calculated as follows, assuming that the steam expands from 1.5 Mpa, 200 ° C. to 0.1 Mpa, 100 ° C.
W8a = 20 t / h × (2800-2400) kJ / kg × 0.9
= 2000kW

In the condensate heater 50, the steam gives heat to the condensate, and the temperature of the steam decreases from 100 ° C to 90 ° C, whereby the heat W50 is recovered.
W50 = 20t / h × (2400-2300) kJ / kg
= 560kW
This ΔW corresponds to a reduction of 41 kg / h in terms of fuel consumption.
Therefore, the consumption amount corresponding to W5 and W50 is reduced from 55000 kg / h to 54837 kg / h.

The electric power W8b generated by the second auxiliary steam turbine 8b and the second auxiliary generator 9b is calculated as follows assuming that the steam expands from 0.09 Mpa, 90 ° C. to 0.01 Mpa, 55 ° C.
W8b = 20 t / h × (2300-2100) kJ / kg × 0.9
= 1000kW

The energy consumption WP2 at the second condensate pump P2 is calculated as 80 kW.
WP2 = 80kW

Summing up the above, the gain (improvement of power) ΔW by the above configuration is as follows.
ΔW = −W2c−W4 + W8a + W8b + WP2
= -780kW

Since this ΔW corresponds to −780 kW, the total output of the power plant decreases.
Moreover, since it corresponds to a reduction of 163 kg / h in terms of fuel consumption, it can be said that the efficiency is improved by 0.07% with respect to the fuel consumption of 55 t / h.

Second Embodiment
In the power generation system according to the present embodiment, the three-way valve 30 (steam supply valve) may be referred to as a fuel flow rate indication value (hereinafter referred to as “FSR”) that is an indication value of the amount of fuel supplied to the fuel warmer 5. )), The amount of steam supplied from the steam turbine 2 to the steam compressor 4 is controlled. In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof may be omitted.

  For example, the three-way valve 30 reduces the flow rate of the steam flowing through the compressed steam path L8 when the composition and heat amount of the fuel gas input to the gas turbine are significantly reduced. Then, the temperature of the fuel gas flowing out from the fuel heater 5 is reduced from about 250 ° C. to about 200 ° C. The temperature-reduced fuel gas is supplied to the gas turbine generator 7 through the fuel gas supply path L9, and by adjusting the combustion temperature, an effect of suppressing misfire and flashback can be obtained.

  Combustion adjustment adjusts the fuel distribution / combustion mode switching point for each combustion mode and adjusts the air-fuel ratio and combustion temperature for each combustion mode. In gas turbine control, the virtual combustion temperature is the exhaust temperature, compression It is calculated from a machine outlet temperature, compressor outlet pressure, atmospheric pressure, and atmospheric temperature using a predetermined table and used for control.

  Hereinafter, the control of the amount of steam by the three-way valve 30 (steam supply valve) will be described in more detail. First, the technical background of this control will be described.

  In the future, natural gas-fired power plant fuels will diversify, and methane-rich light gas and ethane / propane-rich heavy gas will be purchased from each country's production areas to fix natural gas pipeline production areas and LNG bases Without being operated, and it is fluidly mixed into a gas turbine or the like at any time. Until now, gas turbine manufacturers have tried to cope with the design aspects, but the facilities should be able to respond to sudden changes in fuel properties and the use of fuel gas so that it can be used in a wide range of fuel gas properties. Will become an increasingly important issue in the future.

  There are the following three issues regarding the suppression of misfire and flashback by improving the followability and stability of fuel gas warming control and the stable operation of the gas turbine.

  If the fuel gas properties suddenly change to light gas and the Wobbe index (WI value) decreases during rated operation (exhaust gas temperature control), the amount of heat supplied to the fuel gas heater is reduced and the modified Wobbe index ( Although it is desired to increase the MWI value (calculated value obtained by dividing WI by the square root of temperature), there is a possibility that the gas turbine misfires in time when the valve operation is delayed.

  In the process of starting the power plant, the fuel gas heating control is in the process of rapidly increasing the boiler water supply amount. When the fuel flow rate command FSR is increasing, when switching from light gas to heavy gas at the LNG terminal or gas pipeline, the Wobbe WI value increases rapidly, but the opening operation of the heating control valve cannot catch up and the gas The MWI value at the heater outlet is further increased, and combustion vibration and flashback are likely to occur.

  When the fuel gas reaches the set upper limit temperature after the load rises, the boiler water supply amount is reduced, but if the water supply valve is narrowed down too much and the gas temperature undershoots, the MWI value rises sharply, causing combustion vibration and flashback. Easy to do.

  The WI value is calculated from the analysis result of the upstream fuel gas composition, and when the change amount of the Wobbe WI value per unit time becomes smaller than the specified value due to the change in the composition of the supplied fuel gas, the BOG is added to the gas from the LNG base. A control function is set in preparation for when the amount of (Boil of Gas) changes suddenly. Since the allowable speed varies depending on the type of gas turbine, it is assumed that the temperature change function of the controller can be freely changed so that this function can be applied to any gas turbine.

  Therefore, in order to improve fuel gas heating control, instead of boiler feed water as a heating heat source, compressing low-pressure steam turbine bleed gas and using high-temperature steam with higher enthalpy as the heating source improves load followability. To go. Furthermore, even when the fuel gas properties change greatly during start / stop or during rated operation, the MWI value is stably controlled and the operation of the power plant is continued even if the heat quantity fluctuates.

  Specifically, the power generation system is preferably configured as follows. In order to increase the follow-up speed of the fuel gas temperature control and improve the stability at the target temperature, the hot water flow rate and the steam flow rate of the gas heating heat source are determined according to a function determined in advance from the increase / decrease signal of the fuel flow rate command FSR. Predict and control the relationship.

  By using this advance control method (feed forward control), it is possible to cause the fuel gas warmer outlet temperature to follow the target value at an early stage and to suppress a time delay relatively. Normally, when the fuel gas flow rate indication value (FSR) in the process of increasing the load is increasing, if it exceeds about 35%, the opening degree of the fuel gas temperature control valve is increased and the heating water at the inlet of the gas heater is increased. Increase the flow rate.

Further, only the feedback control using the gas heater outlet temperature as an index has a drawback that a control deviation becomes large when a time delay of the temperature control due to a change in the fuel gas property occurs. For example, the control amount for the decrease in the heat amount of the fuel gas is a reduction amount of the feed water temperature to the fuel gas heater, so that the fuel gas temperature can be controlled by using PID control that has a quick reaction and a short establishment time. Can contribute to stable operation.
That is, “proportional + integral calculation control” based on the deviation between the fuel gas temperature and the SV is performed, and the flow rate of the steam supplied from the steam compressor outlet is adjusted.

  For example, when the wobbe index WI value is lowered from 58 to 55 (MWI value: 43 to 41) due to the change in the fuel gas calorific value, the gas temperature at the outlet of the fuel gas heater is lowered from 250 ° C. to about 220 ° C. Since it is necessary, the three-way valve 30 (steam supply valve) at the inlet of the heater is throttled so as to reduce the supply steam flow rate.

  The power generation system is preferably configured as follows. Even during start-stop and during rated operation, the MWI value is stably converged even when the fuel gas properties change greatly and the heat quantity fluctuates. Thereby, the operation of the power plant can be continued stably.

  Specifically, the following control is performed. When the MWI value decreases due to switching to light gas or excessive opening operation after reaching the control lower limit of the fuel gas temperature, the heated steam is quickly reduced. When the MWI value rises rapidly due to a delay in the narrowing-down operation after switching to heavy gas or after reaching the control upper limit of the fuel gas temperature, the heated steam is rapidly increased.

<Third Embodiment>
In the present embodiment, a power control unit that controls the power generated by the power generation system is provided. The power control unit controls the power generated by the first auxiliary generator 9a and the second auxiliary generator 9b so that the power generated by the power generation system is constant. Specifically, the power control unit controls the amount of steam supplied to the auxiliary steam turbine 8 (the first auxiliary steam turbine 8a and the second auxiliary steam turbine 8b), and thereby the first auxiliary generator 9a and the second auxiliary generator. The power generated by 9b is controlled. The amount of steam can be controlled by controlling the opening degree of the three-way valve 30, for example.

When the gas turbine generator 7 is preferentially controlled to control the power transmission output, the output of the first auxiliary steam turbine 8a for self-heat regeneration is controlled by the rotational speed and the output control, so that the output of the entire power generation system can be controlled. It can also be controlled to be constant.
The first auxiliary steam turbine 8a is driven by the steam supplied from the fuel heater 5,
This turbine is provided with speed control, and operates as speed control during disconnection and operates as load control after insertion. The speed control (load) control has a function of maintaining the rotational speed of the first auxiliary steam turbine 8a at a rated value and a function of obtaining a predetermined load.

In the case of a gas with a low calorific value, the MWI swings from the reference point to the minus side, the volume of the fuel gas increases, the gas flow rate increases, and misfires are likely. In such a combustion state, low-frequency combustion vibration occurs.
The MWI limit value is defined as, for example, within +/− 5% with respect to the reference point in order to keep the pressure ratio of the fuel nozzle and the flow velocity in the nozzle appropriately, and to ensure tolerance to backfire or misfire. In the case of fuel gas exceeding this specified range, it is possible to cope with the minus side of the MWI, that is, the decrease in the heat generation amount, by variably controlling the fuel gas temperature. In the case of the fuel gas property having a low calorific value, the fuel gas temperature can be lowered and the MWI can be controlled close to the design value by narrowing the flow rate of the steam passing through the compression steam path L8.

  This will be described in more detail below. The load control (regulator control) of the first auxiliary steam turbine 8a has a function of maintaining the rotational speed of the turbine 8a at a rated value and a function of obtaining a predetermined load, and contributes to the control of the overall plant output. Respond quickly to changes in system voltage. Further, when the steam flow rate is very small, it is not possible to take a power transmission load, but it is possible to maintain a rated speed with no load.

  The speed control is activated when the first auxiliary steam turbine 8a is started, and the load control is activated after the start-up. The speed control (load) control has a function of maintaining the rotational speed of the first auxiliary steam turbine 8a at a rated value and a function of obtaining a predetermined load.

  A turbine output is obtained by operating an electric governor with a turbine back pressure set value as an initial value of 0.1 MPa (1 kg / cm 2) and performing pressure control with an expansion turbine nozzle. The electric governor has a rotation speed control function (PID), a back pressure control function (PID), and a lamp output function. The lowest value is selected and output to the turbine nozzle.

  When the rotational speed reaches a specified value or more (such as 3480 rpm), the rotational speed control is activated. Turbine output rises and the circuit breaker is turned on and synchronized while the rotation speed is gradually lowered while the synchronous verification device is working.

  When the circuit breaker is turned on, the turbine nozzle takes in only the amount of steam corresponding to the energy for synchronizing power sales, and the amount of power generation is 0 kW. Therefore, in order to load the load, the turbine nozzle is opened by increasing the rotation speed setting value at a speed of about 1 rpm / 5 s by the ramp function.

  When the load rises after synchronization with the grid, the turbine back pressure set value is lowered from the initial value of 0.1 MPa (1 kg / cm 2) to 0.09 MPa-0.08 MPa, and the output of the rotational speed control by the lamp increases. The back pressure control is selected by selecting a low value.

  By controlling the output of the first auxiliary steam turbine 8a for self-heat regeneration at the rotational speed and controlling the output, it is possible to have a function of controlling the output of the entire power generation system to be constant.

  The expansion turbine is operated when the steam temperature from the fuel gas warmer is 150 ° C. or higher.

  The common control unit performs output adjustment by adjusting the nozzle opening of the expansion turbine when an excess or deficiency of output occurs with respect to the combined cycle output in the power transmission output control.

  If the amount of power transmitted to the in-house power system (6.6 kV or 440 V) increases due to an increase in the amount of power generated by the expansion turbine, the amount of power transmitted to the combined power plant as a whole increases and the amount of power sold increases.

  The common control unit controls the expansion nozzle output steam nozzle control (governor control) when the output of the combined power plant is a plant load factor of 50% or more and the output change rate is 0.2% (about 1 MW). Is used to control the total plant output so that the system can respond quickly to slight changes in system voltage.

(Other embodiments)
(1) In the above embodiment, the extracted steam or the exhaust steam from the low-pressure steam turbine 2 c is supplied to the steam compressor 4. This may be modified so that the steam discharged from the intermediate pressure steam turbine 2 b is supplied to the steam compressor 4.

(2) Another steam compressor may be provided so that the extracted steam from the low-pressure steam turbine 2 c is adiabatically compressed and supplied to the condensate heater 50.

  Note that the structure disclosed in the above embodiment can be applied in combination with the structure disclosed in the other embodiment as long as no contradiction occurs, and the embodiment disclosed in this specification is It is an illustration and the embodiment of the present invention is not limited to this, and can be appropriately modified without departing from the object of the present invention.

1: Boiler 2: Steam turbine 3: Generator 4: Steam compressor 5: Fuel heater 6: Pre-stage fuel heater 7: Gas turbine generator 7c: Turbine 7d: Generator 8: Auxiliary steam turbine 30: Three-way Valve (steam supply valve)

Claims (9)

A boiler that generates steam by heating water;
A steam turbine driven by steam supplied from the boiler;
A generator driven by the steam turbine to generate electricity;
A power generation system comprising: a steam compressor that heats the steam supplied from the steam turbine by adiabatically compressing the steam.   The power generation system according to claim 1, wherein the steam compressor adiabatically compresses the steam extracted from the steam turbine and raises the temperature.   The power generation system according to claim 1, wherein the steam compressor heats the steam discharged from the steam turbine by adiabatically compressing the steam. A fuel heater that heats the fuel gas with steam from the steam compressor;
The power generation system according to any one of claims 1 to 3, further comprising a gas turbine generator that generates power by burning fuel gas heated by the fuel heater.   5. The power generation system according to claim 4, further comprising a front-stage fuel warmer that heats the fuel gas with water extracted from the boiler economizer and supplies the fuel gas to the fuel warmer.   The steam supply valve that controls the amount of steam supplied from the steam turbine to the steam compressor based on a fuel flow rate instruction value that is an instruction value of the amount of fuel supplied to the fuel warmer. The power generation system according to 4 or 5. An auxiliary steam turbine driven by steam supplied from the fuel warmer;
The power generation system according to claim 4, further comprising an auxiliary generator that is driven by the auxiliary steam turbine to generate electric power. A power control unit for controlling the power generated by the power generation system;
The power generation system according to claim 7, wherein the power control unit controls the power generated by the auxiliary generator so that the power generated by the power generation system is constant.   The power generation system according to claim 8, wherein the power control unit controls an amount of steam supplied to the auxiliary steam turbine to control electric power generated by the auxiliary generator.

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