JP2863645B2 - Feedwater flow control system for an exhaust gas reburning combined cycle power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the flow rate of water supplied to a boiler of a combined power generation plant of an exhaust gas reburning type combined with a gas turbine and a steam turbine plant in thermal power generation.

[0002]

2. Description of the Related Art FIG. 3 is a system diagram showing a schematic configuration of a conventional combined-cycle exhaust-reign power plant, in which high-pressure and high-temperature steam generated in a boiler 1 is introduced into a steam turbine 3 via a conduit 2. Work is performed by the steam turbine 3 and power is generated by a generator 4 connected to the steam turbine 3.

[0003] The steam that has performed work in the turbine 3 is condensed in a condenser 5, and is condensed by a condensate pump 6 into a low-pressure feedwater heater 7.
The water is then sent to the deaerator 8, further pressurized by the water supply pump 9, heated by the high-pressure water heater 10, and then supplied to the boiler 1 again.

On the other hand, the air compressed by the compressor 11 is supplied to a combustor 12, where it combusts with fuel sent through a fuel supply pipe 13, and the high-temperature combustion gas is introduced into a gas turbine 14, where 14 is operated, and the generator 15 is driven. The gas turbine exhaust gas that has performed work in the gas turbine 14 is introduced into the boiler 1 and used for heat recovery, and unburned oxygen contained in the gas turbine exhaust gas is used for combustion of the boiler 1.

[0005] Meanwhile, in an exhaust-gas reburning combined cycle power plant, the purpose is to perform highly efficient operation by combined operation of gas turbine power generation and steam turbine power generation. Waste heat is recovered as much as possible by supplying water.

That is, an exhaust gas cooler 16 is provided in parallel with the high-pressure feed water heater 10, and a part of the feed water supplied to the boiler 1 by the feed pump 9 is introduced into the exhaust gas cooler 16, where it is discharged from the boiler 1. After the heat exchange with the exhaust gas from the high pressure feed water heater 10, the feed water is merged with the feed water and introduced into the boiler 1. On the other hand, the exhaust gas cooler 16
The exhaust gas cooled by the gas is discharged from the chimney 17 into the atmosphere.

[0007] Therefore, in such a plant, in the operation from high load to low load in combined operation, feed water is supplied to the boiler 1 stably and satisfactorily in a controlled manner, and at the same time, the high pressure in the steam turbine plant side Feed water heater 1
It is necessary to control the distribution of the water supply to the exhaust gas cooler 16 and the exhaust gas cooler 16 stably.

By the way, a boiler is one of the most important devices in the configuration of a steam turbine plant. Usually, a boiler controls three elements of fuel, combustion air and feed water in accordance with the operation output of the plant. Ensures stable operating conditions and reliability. For the water supply, a command signal is sent from the boiler control device to the water supply control device, and the flow rate of the water supply to the boiler is adjusted by controlling the rotation speed of the water supply pump or the opening degree of the control valve at the pump outlet. The same applies to the control of the boiler feedwater flow rate in an exhaust-refueling combined cycle power plant.

FIG. 4 is a diagram showing an exhaust gas cooler and a distribution control device for supplying water to a high-pressure feedwater heater, which are generally performed in the above-mentioned combined regenerative power plant, and corresponds to the operating state of the boiler. When a control signal is input to the boiler control device 20, an output signal from the boiler control device 20 is input to a water supply pump control device 22 via a water supply control device 21, and the water supply pump 9 is controlled by the water supply pump control device 22.
Is controlled, and the water supply amount is adjusted.

The amount of water supplied to the boiler 1 is measured by a flow meter 23.
The feedwater flow value is fed back to the boiler control device 20 again via the flow signal conversion device 24. Further, flow control valves 25a and 25b are provided on the respective water supply outlet sides of the exhaust gas cooler 16 and the high-pressure feed water heater 10, and the water supplied by the exhaust gas cooler 16 is provided downstream of the flow control valves 25a. A temperature detector 26 for detecting a temperature is provided.

The detection signal of the temperature detector 26 is input to the water supply distribution control device 27, and a control signal is sent from the water supply distribution control device 27 to the two flow control valves 25a and 25b, and the two flow control valves 25a , 25b are controlled, and the flow rate of the feedwater flowing through the exhaust gas cooler 16 and the high-pressure feedwater heater 10 is adjusted. On the other hand, the respective feed water flow rates are detected by flow meters 28a, 28b provided downstream of the respective flow control valves 25a, 25b, and the respective feed water flow values are fed back to the feed water distribution control device 27.

[0012]

In the control apparatus as described above, the boiler control and the feedwater flow rate control, which are also the master control of the plant, and the feedwater distribution control of the exhaust gas cooler and the high-pressure feedwater heater at the position of the plant local control, are performed. The problem is how to emphasize the nature of the information. In other words, since the distribution control side mainly focuses on the control and protection of the exhaust gas cooler, transient conditions such as load rejection and the like can be applied to a large load change or load change rate of the plant in response to a request from the power system. In this case, there is a problem that disturbance of water supply control on the boiler side is apt to occur, and in order to suppress the disturbance, plant operability such as reducing a load change rate of the plant must be sacrificed.

The upstream sides of the two flow control valves provided for controlling the distribution of water to the exhaust gas cooler and the high-pressure water heater are:
It becomes necessary to design according to the cutoff pressure of the water supply pump,
Since the design pressure of the equipment and piping valves that constitute the water supply system is significantly increased, there are also disadvantages of maintaining and securing reliability and increasing construction costs.

Furthermore, in low load operation during combined operation, almost all of the feedwater flows to the exhaust gas cooler side in consideration of the improvement of thermal efficiency and protection of the exhaust gas cooler. Would. If such a low load operation is performed for a long time, the feed water heater cools down by radiating heat to the air because there is no passage of hot water supply water, and in the subsequent rapid load increase excessive heat stress will occur. There is a problem that the water supply heater may be damaged due to repeated operation.

In view of the above, the present invention eliminates the possibility of disturbance in the control of water supply to the exhaust gas cooler and the high-pressure feed water heater, which is a plant local control, with respect to the important water supply control of the boiler of the plant. It is an object of the present invention to obtain a control device capable of performing the control.

[0016]

SUMMARY OF THE INVENTION The present invention relates to a high-pressure high-pressure system for heating water supplied to a boiler in a feed water flow control device in an exhaust gas reburning combined cycle power plant configured to supply exhaust gas from a gas turbine to a boiler of a steam turbine plant. An exhaust gas cooler that heats part of the water supplied to the boiler with exhaust gas from the boiler is connected in parallel to the feed water heater, and a flow control valve is provided only in the high-pressure feed water heater system, and the flow control valve is provided. Control of water supply to the high-pressure feed water heater system and the exhaust gas cooler system.

[0017]

When the load of the plant is high, the pressure loss is reduced by increasing the opening of the flow control valve, and the flow rate of the exhaust gas cooler is reduced relatively by increasing the flow rate to the high pressure feed water heater system. In this way, appropriate water supply distribution control is performed. That is, in two systems in which water is supplied by the same pump, the distribution of water to each is determined by the relative relationship between the pressure losses of the respective systems, so that the exhaust gas cooler and the high pressure Determines the relative pressure loss relationship with the feed water heater and distributes the feed water.In order to perform normal feed water distribution control, the pressure loss can be varied by restricting the opening of the flow control valve installed on one side. By doing so, good controllability can be obtained.

On the other hand, when the output of the plant is reduced,
Since the relative decrease in boiler exhaust gas volume is relatively slow relative to the load water supply volume relative to the load, the amount of heat recovered from boiler exhaust gas is relatively large. In this case, the flow control valve is throttled to increase the pressure loss and reduce the flow through the high pressure feed water heater system, thereby relatively increasing the flow through the exhaust gas cooler on the opposite side. Can be done.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the drawing, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

An exhaust gas cooler 16 is provided in parallel with the high-pressure feed water heater 10.
Is supplied to the exhaust gas cooler 16, where it is subjected to heat exchange with the exhaust gas from the boiler 1, and then merges with the water supplied from the high pressure feed water heater 10 to be introduced into the boiler 1.

By the way, stop valves 30a and 30b are provided on the inlet side and the outlet side of the exhaust gas cooler 16, respectively, and a stop valve 31 is provided on the inlet side of the high pressure feed water heater 10, and the high pressure feed water The flow control valve 32 is provided only on the outlet side of the vessel 10. Also, the exhaust gas cooler system branched from the high pressure feed water heater system has an orifice for pre-adjusting the pressure loss on the exhaust gas cooler side and the high pressure feed water heater side as a base point of feed water distribution control at a certain plant load during combined operation. Alternatively, a pressure adjusting device 33 such as a valve is provided.

On the other hand, the feed water distribution control device 27 includes a feed water flow signal a detected by the flow meter 23 and the temperature detector 2.
6, the temperature signal b of the feed water flowing out of the exhaust gas cooler 16 is input, and the feed water flow signal a
And the feed water temperature signal b are comprehensively calculated, and a flow control valve control signal is output.
2 is controlled.

When the plant is operating under a high load in the combined operation, the opening of the flow control valve 32 is increased and the pressure loss is reduced, and the flow is sent from the deaerator 8 by the water supply pump 9. The supplied water is supplied to the exhaust gas cooler 16.
The fuel is supplied to the exhaust gas cooler 16 and the high-pressure feed water heater 10 by distribution determined by the relative pressure loss between the system and the high-pressure feed water heater 10, and is then fed to the boiler 1 at the boiler inlet. On the other hand, when the plant has a partial load, the flow control valve 32 is throttled corresponding to the load, the pressure loss is increased, and the flow rate to the high-pressure feed water heater system is reduced. Therefore, the amount of water flowing into the exhaust gas cooler system is increased, and the water supply flow rate necessary for protecting the exhaust gas cooler is secured.

When the load is further reduced, all the feed water must be supplied to the exhaust gas cooler side. In this case, too, the flow control valve 32 is maintained at a predetermined minute opening, and the high pressure feed heater is operated. Is maintained and the warming is performed.

In the single operation of the steam turbine plant, the stop valves 30a and 30b are fully closed, and the entire water supply is supplied to the high-pressure water heater.

In the above embodiment, the flow control valve is provided on the outlet side of the high pressure feed water heater, but it may be provided on the inlet side. In addition, the feedwater distribution control device can improve the accuracy by taking the flow rate and outlet temperature of each of the exhaust gas cooler and the high-pressure feedwater heater and the output of the plant as control elements.

FIG. 2 is a view showing another embodiment of the present invention. A stop valve 34 is also provided on the outlet side of the high pressure feed water heater 10, and a flow control valve 32 is provided in parallel with the stop valve 34. Is provided. Thus, by controlling the opening degree of the flow control valve 32, the flow rate of the feedwater to the high-pressure feedwater heater system and the exhaust gas cooler system can be distributed as in the first embodiment.

In addition, during the sole operation of the steam turbine plant, it is necessary to supply the entire feedwater to the high-pressure feedwater heater side. Therefore, in the case where the flow control valve 32 is provided in series as in the first embodiment, It is necessary not only to increase the pressure loss but also to increase the diameter of the flow control valve 32. In the second embodiment, the stop valve 34 may be fully opened.
Pressure loss can be reduced. Further, during the combined operation, the amount of water supply is divided into two, so that the control amount is reduced, and the flow control valve 32 for controlling the flow rate can have a relatively small diameter.

[0029]

According to the present invention, the flow control valve is provided only in the high pressure feed water heater system, and the distribution of feed water to the high pressure feed water heater system and the exhaust gas cooler system is controlled by controlling the flow control valve. The above-mentioned water supply distribution control does not become a disturbance to the water supply control, good plant controllability can be obtained, and the water supply distribution control system is simplified. Also, even when the entire amount of water is supplied to the exhaust gas cooler side during partial load during combined operation and water is not supplied to the high-pressure feed water heater, the flow control valve is slightly opened to supply a small amount of high-pressure water. Warming can be performed by passing water through the heater, and it is not necessary to newly add a warming system that connects the feed water heater system to a condenser, a deaerator, or the like.

Further, when the flow control valve is provided in parallel with the stop valve provided in the high pressure feed water heater system, the control valve can be made small in diameter, thereby reducing the construction cost of equipment. By switching the stop valve of the high-pressure feed water heater system, the pressure loss of the system can be reduced during the steam turbine plant alone operation, and the power generation efficiency of the plant can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of a feedwater flow rate control device for an integrated refueling combined cycle power plant of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a system diagram showing a schematic configuration of an exhaust gas reburning combined cycle power plant.

FIG. 4 is a system diagram of a conventional feedwater flow control device for an exhaust gas reburning combined cycle power plant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler 3 Steam turbine 10 High pressure feed water heater 11 Compressor 14 Gas turbine 16 Exhaust gas cooler 20 Boiler control device 23 Flow meter 27 Feed water distribution control device 30a, 30b, 31, 34 Stop valve 32 Flow control valve

Claims (2)

(57) [Claims] 1. A feed water flow control device for an exhaust gas reburning combined cycle power plant configured to supply exhaust gas from a gas turbine to a boiler of a steam turbine plant, wherein a high pressure feed water heater for heating the feed water to the boiler is provided. An exhaust gas cooler that heats part of the water supplied to the boiler by exhaust gas from the boiler is connected in parallel, and a flow control valve is provided only in the high-pressure feed water heater system, and the high-pressure feed water heater system is controlled by controlling the flow control valve. And a water supply distribution control system for an exhaust gas reburning combined cycle power plant, wherein water supply distribution control to an exhaust gas cooler system is performed. 2. The feed water flow rate of the combined exhaust power generation system according to claim 1, wherein the flow control valve is provided in parallel with a stop valve provided in the high pressure feed water heater system. Control device.