JPH10176505A - Combined power plant - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When starting up a combined cycle power plant, in the process of raising or increasing the set temperature or pressure of a steam turbine inlet, the amount of heat discarded in a condenser by a steam turbine bypass is recovered to start up the plant. And increase the output. In a combined cycle power plant including gas turbines (1) and (2) and a steam turbine (5), an outlet temperature of a water supply pump (21) is increased by a water supply system heat exchanger (12) using heat discarded in a condenser (10) as an operation exchange heat source. , To reduce plant startup time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combined cycle power plant.

[0002]

2. Description of the Related Art Conventionally, as a device for starting a combined cycle power plant, a turbine bypass control device for a combined cycle power plant (Japanese Patent Laid-Open No. 55-114821) and a turbine bypass control device for a combined cycle power plant (Japanese Patent Laid-Open No. 61-294105). There is. These devices reduce the start-up time of the entire plant by controlling the turbine bypass and increase the efficiency of plant operation such as an exhaust heat recovery boiler. Usage is not considered. Therefore, all exhaust heat from the turbine bypass is discarded outside the plant.

[0003]

In the prior art, as described above, all the exhaust heat from the turbine bypass is discarded out of the plant system. Could not be used effectively. The amount of heat that has been discarded is a large amount of several [Gcal], and corresponds to a heat source of about atmospheric temperature plus several [° C.] in terms of temperature level. This is a problem in the energy use efficiency of the plant.

[0004] It is an object of the present invention to increase the pressure and temperature of the steam turbine inlet set pressure and temperature during startup of the combined cycle power plant, to increase the temperature of the steam turbine bypass, and to discard the steam turbine bypass into the condenser. Accordingly, the amount of heat discarded in the condenser is recovered to increase the output of the plant and shorten the startup time.

[0005]

In order to achieve the above object, the present invention raises the temperature of the waste heat recovery boiler feed pump by increasing the amount of heat discarded in the condenser in addition to the structure of a general combined cycle power plant. And a control device that can arbitrarily adjust the heat exchange amount of the heat exchanger.

In addition, a control device is provided for adjusting a required amount of heat of the water supply system heat exchanger from the magnitude of the heat amount of the steam turbine bypass by adjusting a water supply system heat exchanger bypass valve.

[0007] The temperature of the exhaust heat recovery boiler feedwater pump outlet of the steam heat source discarded by the steam turbine bypass is increased by a feedwater heat exchanger. As a result, the time required to reach the set pressure and temperature of the steam turbine can be shortened, and the plant efficiency is improved.

Further, the temperature of the exhaust heat recovery boiler feedwater pump outlet is arbitrarily set by the control device, and the amount of heat exchange of the feedwater heat exchanger is optimally controlled. This improves the efficiency of the plant by recovering the amount of heat discarded by the steam turbine bypass and shortening the plant startup time.

Further, by controlling the amount of steam flowing into the heat exchanger for feedwater temperature in accordance with the bypass amount of the steam turbine by the control device, the entire plant can be operated with high efficiency.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a system diagram of a combined cycle power plant as an embodiment of the present invention.

In FIG. 1, a combined cycle power plant includes a compressor 1 for compressing air, and air compressed by the compressor 1 and L
An expander 2 driven by a gas obtained by mixing and burning fuel such as NG, a generator 3 connected to the expander 2, and an exhaust heat recovery boiler that generates steam by high-temperature exhaust gas discharged from the expander 2. 4, a steam turbine 5 driven by steam generated from the exhaust heat recovery boiler 4, a generator 6 connected to the steam turbine 5, and a condition of generated steam of the exhaust heat recovery boiler 4 is set at an inlet steam setting of the steam turbine 5. Until the conditions are reached, a steam turbine bypass 7 that directly guides steam to the condenser 10, a steam turbine bypass valve 8 installed in the steam turbine bypass 7, and a steam turbine control installed in the steam inlet of the steam turbine 5. A valve 9, a condenser 10 for condensing steam from the steam turbine 5, and a water supply system heat exchanger 1 using an amount of heat discarded to the condenser 10 as an operation exchange heat source.
2, a feedwater heat exchanger path 18 that guides steam from the steam turbine bypass 7 to the feedwater heat exchanger 12, a feedwater heat exchanger control valve 14 that adjusts the steam temperature flow rate of the feedwater heat exchanger 12, and A water supply system heat exchanger desuperheater 13 for adjusting the steam temperature to the water supply system heat exchanger 12, a water supply system heat exchanger bypass 19 for discarding steam from the steam turbine bypass 7 to the condenser 10, and a water supply system. A water supply system heat exchanger bypass valve 15 installed in the system heat exchanger bypass 19, a seawater temperature detector 20 for detecting seawater temperature, a seawater pump 24 for adjusting seawater flow, and a cooling water supply system. A cooling water pump 22 for adjustment, a water supply system heat exchanger water supply pump 23 for adjusting the water supply flow rate from the condenser 10, and a water supply pump 21 for adjusting the water supply flow rate from the water supply system heat exchanger 12. , Water supply system heat exchanger water supply pump 2 Detecting the flow rate from the flow detector 2
6, a flow rate detector 25 for detecting a flow rate from the feed water pump 21, a flow rate detector 27 for detecting a flow rate of steam flowing into the steam turbine 5, and a pressure detector 28 for detecting a steam pressure flowing into the steam turbine 5 A temperature detector 35 for detecting the temperature of the steam flowing into the steam turbine 5, a temperature detector 29 for detecting the steam temperature from the water supply system heat exchanger feed water pump 23, and a steam flow rate of the steam turbine bypass 7 A flow rate detector 30, a feed water system heat exchanger desuperheater control valve 31 for adjusting the spray flow rate of the water feed system heat exchanger desuperheater 13,
A temperature detector 32 for detecting an inlet temperature of the feedwater heat exchanger desuperheater 13, a temperature detector 33 for detecting an outlet temperature of the feedwater heat exchanger desuperheater 13, a temperature detector 32, and a temperature detector. A control device 34 that outputs a command to the feedwater heat exchanger desuperheater control valve 31 to adjust the feedwater heat exchanger desuperheater 13 based on the magnitude relationship of the signals detected by the detector 33 and a temperature detector 35 detects Water supply system heat exchanger based on the magnitude relationship between the determined steam temperature and a preset steam turbine inlet steam temperature setting, and the magnitude relationship between the steam pressure detected by the pressure detector 28 and the preset steam turbine inlet steam pressure setting. A control device 36 for outputting a command to the bypass valve 15 to adjust the flow rate of steam flowing into the water supply system heat exchanger 12, a generator output of the generator 3, a generator output of the generator 6, a temperature detector 32, and temperature detection Size relation of vessel 33 Et a control unit 37 that the water supply system outputs a command to the heat exchanger control valve 14 adjusts the flow rate of steam flowing into the feed water system heat exchanger 12, the generator and the generator output of the generator 3 machine 6
Water supply heat exchanger desuperheater 13 calculated from the generator output of
A command for adjusting the heat exchanger seawater flow rate based on the required heat quantity, the steam flow rate detected by the flow rate detector 30, and the temperature detected by the seawater temperature detector 20, and adjusts the seawater pump 24 and the cooling water pump 22, A control device 16 for controlling the heat exchanger 11 and a flow rate detected by a flow rate detector 26 at an outlet of the water supply system heat exchanger water supply pump 23 control an outlet flow rate of the water supply system heat exchanger water supply pump 23 to control the water supply pump 21. The control device 17 controls the outlet flow rate of the water supply pump 21 based on the flow rate detected by the flow rate detector 25 at the outlet of.

Next, the operation of the combined cycle power plant will be described.

Air is introduced into the compressor 1, and the introduced air is pressurized and compressed in the compressor 1 to produce LNG.
, And becomes a high-temperature, high-pressure gas of about 1000 ° C. This gas drives the expander 2, and the generator 3 connected to the expander 2 rotates to generate electricity. The gas that has driven the expander 2 has a relatively low temperature of about 500 ° C., is introduced into the exhaust heat recovery boiler 4, and evaporates water in the heat transfer tube installed therein, and then has a temperature of about 100 ° C. Released into the atmosphere.

The steam generated by the waste heat recovery boiler 4 is guided to the condenser 10 through the steam turbine bypass 7 until the inlet setting condition of the steam turbine 5 is satisfied, and after being condensed, the waste heat recovery is performed. Return to boiler 4. On the other hand, when the inlet setting condition of the steam turbine 5 is satisfied, the steam generated in the exhaust heat recovery boiler 4 is introduced into the steam turbine 5 and drives the steam turbine 5. Then, the generator 6 connected to the steam turbine 5 rotates to generate power. The steam that has been driven to a low temperature and a low pressure by driving the steam turbine 5 is guided to a condenser 10, where the steam is condensed, and then returns to the exhaust heat recovery boiler 4.

The exhaust heat from the steam turbine bypass 7 or the steam turbine 5 raises the temperature of the cooling water in the condenser 10 and gives heat to the heat exchanger 11 or the water supply system heat exchanger 12. By the heat exchange of the water supply system heat exchanger 12, the temperature of the water supplied from the condenser 10 and the water supply system heat exchanger water supply pump 23 is increased. The difference of the heat exchange in the water supply system heat exchanger 12 is led to the condenser 10. The amount of heat received by the cooling water of the condenser 10 is released outside the plant system by the cooling water such as seawater of the heat exchanger 11.

Next, control functions of the control device 36, the control device 17, the control device 34, the control device 37, and the control device 16 will be described.

FIG. 2 shows a control block of the control device 34, wherein 100 is a deviation calculator, and 101 is a proportional-integral calculator. The temperature detector 25 shown in FIG. 1 and a preset temperature set value are input to a deviation calculator 100 to obtain a temperature deviation.
This temperature deviation is input to the proportional-integral calculator 101 to obtain a water supply system heat exchanger desuperheater spray control valve opening command to control the water supply system heat exchanger desuperheater spray control valve.

FIG. 3 shows a control block of the control device 37, wherein 201 and 202 are deviation calculators, 203 and 204 are analog / digital converters, and 205 is a logical sum calculator. Steam turbine 5 detected by temperature detector 28 in FIG.
The deviation calculator 2 calculates the inlet steam temperature of the steam turbine and the steam turbine inlet steam temperature setting of the steam turbine steam condition set in advance.
01, a steam turbine inlet temperature setting deviation is obtained, and a deviation calculator 202 calculates the steam turbine inlet steam pressure detected by the pressure detector 27 and the steam turbine inlet steam pressure setting of steam turbine steam conditions set in advance. To obtain a steam turbine inlet pressure set deviation, and a deviation calculator 201
The steam turbine inlet temperature setting deviation obtained in
It is input to the digital converter 203, and outputs 1 if it is positive and outputs 0 if it is negative, and outputs the temperature condition satisfaction flag of the steam turbine steam condition. The steam turbine inlet pressure set deviation obtained by the deviation calculator 202 is input to the analog / digital converter 204, and if positive, 1 is output if negative, and a pressure condition satisfaction flag for steam turbine steam conditions is output. The temperature condition satisfaction flag of the steam turbine steam condition obtained by the analog / digital converter 203 and the pressure condition satisfaction flag of the steam turbine steam condition obtained by the analog / digital converter 204 are input to a logical OR calculator 205, and the water supply system heat Outputs the opening and closing of the exchanger bypass valve. If the output of the OR operation unit 205 is 1, the steam supply steam condition is not satisfied and the water supply system heat exchanger bypass valve is closed. If the output is 0, the steam supply system heat condition is satisfied and the water supply system heat exchanger bypass valve is opened. FIG. 4 is a control block of the control device 36,
01 is a function generator, 302 is a deviation calculator, 303 is a proportional-integral calculator, 304 is a signal generator, and 305 is an analog switch. The plant output calculated from the sum of the outputs of the generator 3 and the generator 6 shown in FIG. 1 is input to the function generator 301 to obtain the required heat amount with respect to the required water supply flow rate of the exhaust heat recovery boiler 4. Waste heat recovery boiler 4 obtained from output of function generator 301
The required amount of heat with respect to the required feedwater flow rate and the feedwater flow rate obtained by the flow transmitter 29 are input to the deviation calculator 302 to obtain an optimum deviation of the steam turbine bypass flowrate when performing heat exchange in the feedwater heat exchanger. The output of the deviation calculator 302 is input to the proportional-integral calculator 303 to obtain a water supply system heat exchanger control valve opening command. The water supply system heat exchanger control valve opening command and the output of the signal generator 304 obtained from the output of the proportional-integral calculator 303 are
When the steam turbine steam condition is satisfied, the output of the signal generator 304 is output as a water supply system heat exchanger control valve opening command, and when the steam turbine steam condition is not satisfied, the output of the proportional integral calculator 303 is output. The output is output as a water supply system heat exchanger control valve opening command. The function generator 3
The function of 01 is the feedwater flow rate to plant output (T / H)
The amount of heat required to raise the temperature by 1 ° C. (1 cal to raise 1 g of water by 1 ° C.) FIG. 5 is a control block of the control device 16, 401, 402, and 404 are deviation calculators,
Reference numeral 3 denotes an integrator. The difference between the required heat quantity of the water supply system heat exchanger and the steam turbine bypass flow rate from the steam turbine bypass 7, that is, the heat quantity discharged to the condenser 10, is obtained, while the difference between the seawater inlet temperature and the seawater outlet temperature of the heat exchanger 11 is obtained. That is,
The deviation temperature of the seawater is obtained, the deviation temperature of the seawater is integrated with the heat capacity of the seawater (Kcal / kg ° C), the calorific value of the wastewater is divided by the integrated value, and a control command of the flow rate of the seawater of the heat exchanger 11 is issued.
The seawater pump 24 is controlled. Further, the deviation between the cooling water inlet temperature and the cooling water outlet temperature of the heat exchanger 11, that is, the deviation temperature of the cooling water, is obtained, and the deviation temperature of the cooling water is added to the cooling water heat capacity (Kc
al / kg ° C), the required heat quantity of the water supply system heat exchanger is divided by this integrated value, a control command for the cooling water flow rate of the heat exchanger 11 is issued, and the cooling water pump 22 of the condenser 10 is controlled. I do. As a result, the difference between the required heat amount of the water supply system heat exchanger and the heat amount of the steam turbine bypass is processed by the seawater.
The cooling heat discharged from 1 is discharged to the outside of the plant system, and the cooling water heated to correspond to the required heat of the water-based heat exchanger is supplied to the water-based heat exchanger 12.

FIG. 6 is a control block of the control device 17, in which reference numerals 701, 702, 705, and 706 denote an AND operator,
Numerals 03 and 704 denote logical OR operators, and numeral 707 denotes a NOT operator. If the water supply system heat exchanger water supply pump outlet flow rate is positive and the plant start command, the water supply system heat exchanger water supply pump is started. At this time, the reverse of the condition for starting the plant, that is, the negative operation during the stop or stop of the plant is given as the condition of the start command of the feedwater heat exchanger feedwater pump, and the feedwater heat exchanger feedwater pump start command is output to output the feedwater heat. Control the exchanger feed pump. On the other hand, if the feed command of the feed pump is a positive feed pump outlet flow rate and the plant start command, the feed pump is started. At this time, the reverse of the condition for starting the plant, that is, the negative operation of stopping or stopping the plant is given as the condition of the feed pump start command, and the feed pump start command is output to control the feed pump.

[0020]

According to the present invention, when the combined cycle power plant including the gas turbine and the steam turbine is started, the steam turbine bypass discards the steam at the set pressure and temperature in the condenser by the steam turbine bypass during the startup. Since the amount of heat is effectively used, the plant output can be increased.

Also, in the combined cycle power plant, the exhaust heat recovery boiler feedwater pump outlet temperature is set to an arbitrary temperature and the feedwater heat exchanger exchange heat is optimally controlled, so that the maximum plant output is always maintained. Is possible.

Further, in the combined cycle power plant, when the heat exchange capacity of the feed water system heat exchanger is smaller than the heat capacity of the steam turbine bypass waste water, the excessive heat capacity of the steam turbine bypass is discharged through the feed water system heat exchanger bypass path.
The control effect can be improved.

[Brief description of the drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

FIG. 2 is a control block diagram of an embodiment of a control device.

FIG. 3 is a control block diagram of a second embodiment of the control device.

FIG. 4 is a control block diagram of a third embodiment of the control device.

FIG. 5 is a control block diagram of a forty-first embodiment of the control device.

FIG. 6 is a control block diagram of a fifth embodiment of the control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Expander, 5 ... Steam turbine, 10 ... Condenser, 12 ... Water supply heat exchanger, 21 ... Water supply pump.

Claims (8)

[Claims] In a combined cycle power plant comprising a gas turbine and a steam turbine, when starting, when the steam turbine inlet set pressure and temperature are in the process of increasing the pressure, the amount of heat discarded to the condenser by the steam turbine bypass is reduced. A water supply system heat exchanger for raising the temperature of the water discharged from the waste heat recovery boiler water supply pump, the water supply system heat exchanger decooler for adjusting the temperature of the water supply system heat exchanger, and the water supply system heat A feedwater heat exchanger steam flow control valve for adjusting the flow of steam flowing into the exchanger, a feedwater heat exchanger bypass path for bypassing steam flowing into the feedwater heat exchanger to the condenser, and the feedwater heat A feedwater heat exchanger bypass valve that adjusts the steam flow rate of the exchanger bypass path, a control device that controls the feedwater warming exchanger desuperheater, and a control device that controls the feedwater heat exchanger bypass valve Combined cycle power plant characterized in that it comprises a. 2. The water supply system heat exchanger according to claim 1, wherein the control device inputs a water supply pump outlet temperature and a preset water supply pump outlet temperature setting and adjusts a heat exchange amount of the water supply system heat exchanger. Combined cycle power plant that outputs a heater spray control command. 3. The water supply system heat according to claim 1, wherein a magnitude relationship between the steam turbine inlet temperature and a preset steam turbine inlet temperature setting, and a magnitude relationship between the steam turbine inlet pressure and a preset steam turbine inlet pressure setting. A combined cycle plant equipped with a control device for operating or stopping the exchanger. 4. The steam turbine bypass according to claim 1, wherein the control unit calculates the amount of heat required in the water supply heat exchanger from an output of a generator generated by driving the turbine. A combined cycle power plant having a control device for adjusting the flow rate. 5. The heat exchanger according to claim 1, wherein the heat exchanger for discharging residual heat used in the condenser and the heat exchanger of the water supply system to the outside of the plant system such as seawater and the heat exchange of the water supply system. A combined power plant equipped with a control device that adjusts and controls the heat exchanger cooling water flow rate of the heat exchanger or the cooling water flow rate of seawater, etc., based on the magnitude relationship between the required heat quantity of the heat exchanger and the steam turbine bypass heat quantity. 6. In a combined power plant comprising a gas turbine and a steam turbine, when the steam turbine inlet pressure and the steam turbine inlet temperature are in the process of raising or increasing the pressure at the time of startup, the steam turbine is discarded from the steam turbine bypass to the condenser. A combined power generation plant characterized in that heat is exchanged in a water supply system heat exchanger using the heat amount as an operation exchange heat source to increase the steam temperature or pressure at a feed water pump outlet. 7. The water supply system heat exchanger bypass passage according to claim 1, wherein when the combined cycle power plant is stopped, a steam turbine bypass flow rate flowing into the water supply system heat exchanger is bypassed to a condenser. Combined power plant that shuts down without overheating when the plant is stopped. 8. The water supply system heat exchanger according to claim 6, wherein an inlet temperature of the water supply system heat exchanger and an outlet temperature of the water supply system heat exchanger are compared to obtain a necessary heat amount of the water supply system heat exchanger. A combined power plant comprising: a control unit for calculating a flow rate of the water supply system heat exchanger by comparing a necessary heat amount setting of a water supply system heat exchanger calculated from an output of a generator that generates heat by driving a turbine.