JP2010096422A - Boiler unit and power generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler unit and a power generation system capable of shortening a time until a boiler is stopped and reducing the amount of an energy loss. <P>SOLUTION: The boiler unit includes: the boiler for generating steam; turbine drive pumps 51, 53 driven by using steam generated by the boiler; an electric motor drive pump 55 driven by using electricity; a water supply switch for switching water supply to the boiler between the turbine drive pumps 51, 53 and the electric motor drive pump 55; recirculation piping 61, 63 for connecting the discharge side and the suction side (deaerator 24) of the turbine drive pumps 51, 53; and recirculation valves 71, 73 for controlling a flow rate of water to be recirculated. When the boiler performing low load operation is stopped, after a set value for starting to open the recirculation valves 71, 73 is set larger compared to the case of the low load operation, the water supply switch switches water supply to the boiler from the turbine drive pumps 51, 53 to the electric motor drive pump 55. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a boiler unit having a constant pressure once-through boiler and a power generation system.

  In thermal power plants and the like, many power generation systems including a constant pressure once-through boiler and a steam turbine as main components are employed. This power generation system drives a steam turbine using steam generated by a constant pressure once-through boiler, and generates power by a generator coupled to the steam turbine.

In the power generation system described above, the constant pressure once-through boiler normally performs a constant pressure operation, that is, an operation in which the main steam pressure is constant without depending on the load. However, there is a limit to the load that the constant pressure once-through boiler can perform the constant pressure operation. For example, the constant pressure operation cannot be stably performed at a load of 25% or less. Therefore, a method of performing a transformer operation in which the main steam pressure is changed according to the load in order to expand the operable load range is known (see, for example, Patent Document 1 and Patent Document 2).
JP-A-57-82601 JP 2007-271189 A

  However, according to the techniques disclosed in Patent Document 1 and Patent Document 2, when the boiler is stopped from the minimum load of 15%, for example, the load is temporarily increased to, for example, 25%, and the operation mode is switched to the constant pressure operation. After that, the boiler was stopped after preparation for stopping. Therefore, there is a problem that, in addition to taking time to stop, energy such as fuel and power in the station until the stop is lost.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a boiler unit and a power generation system that can shorten the time until the boiler is stopped and reduce the amount of energy loss.

In order to solve the above problems, the present invention employs the following means.
A first aspect of the present invention includes a boiler that generates steam, a turbine drive pump that is driven using the steam generated by the boiler, and supplies water to the boiler, and is driven using electricity. An electric motor-driven pump for supplying water; a water supply switching unit for switching water supply to the boiler between the turbine-driven pump and the electric motor-driven pump; and a discharge side and a suction side of the turbine-driven pump, and the turbine-driven pump A recirculation pipe for recirculating the water discharged by the suction side to the suction side, and a suction flow rate of the turbine drive pump that is provided in the recirculation pipe is greater than or equal to a minimum suction flow rate necessary for driving the turbine drive pump. The recirculation valve for adjusting the flow rate of water to be recirculated and the opening degree of the recirculation valve based on the suction flow rate of the turbine drive pump A recirculation valve control unit, and when the boiler that performs low-load operation that generates steam at a pressure lower than normal operation is stopped, the recirculation valve control unit sets a set value at which the recirculation valve starts to open. The boiler unit is a boiler unit for switching the water supply to the boiler from the turbine drive pump to the electric motor drive pump after making it larger than during the low load operation.

When the boiler is stopped, the flow rate of water supplied to the boiler is reduced, so that the amount of steam necessary for driving the turbine drive pump cannot be obtained. Therefore, the feed water to the boiler is switched from the turbine drive pump to the electric motor drive pump. This switching is performed by increasing the feed water flow rate from the electric motor driven pump and decreasing the feed water flow rate from the turbine drive pump according to the increase amount.
Moreover, in order to prevent cavitation etc., it is necessary for the turbine drive pump and the electric motor drive pump to prevent the suction flow rate from being lower than the minimum suction flow rate. Therefore, open the recirculation valve before the suction flow rate of these pumps falls below the minimum suction flow rate, and increase the flow rate that circulates from the discharge side to the suction side (for example, the deaerator) so that the minimum suction flow rate is secured Be controlled.

  Here, at the time of low load operation of the boiler, the set value at which the recirculation valve starts to be opened is set lower than that during normal operation so that the opening and closing of the recirculation valve does not cause disturbance in the supply of water to the boiler. Therefore, according to the conventional boiler unit, when switching the pump, so-called hunting occurs in which the recirculation valve is repeatedly opened and closed in the process of decreasing the discharge flow rate of the turbine-driven pump, and the pump is stably switched. There was an inconvenience that they could not.

On the other hand, according to the first aspect of the present invention, when stopping the boiler that performs the low load operation, the set value for starting to open the recirculation valve by the recirculation valve control unit is made larger than that during the low load operation. After that, the water supply switching unit switches the water supply to the boiler from the turbine drive pump to the electric motor drive pump.
As a result, the water supply to the boiler can be switched from the turbine drive pump to the electric motor drive pump while the recirculation valve is opened and the suction flow rate of the turbine drive pump is sufficiently secured. Even when there are few, it is possible to stably switch the pump and stop the boiler.

  In the above aspect, when the set value during the normal operation is the first set value and the set value during the low load operation is the second set value, the recirculation valve control unit is When stopping the boiler during load operation, the set value may be changed from the second set value to the first set value.

  When stopping the boiler that performs low-load operation, recirculation is performed by changing the set value at which the recirculation valve starts to open from the second set value during low-load operation to the first set value during normal operation. The set value at which the valve starts to open can be made larger than during low-load operation. Thereby, the pump can be stably switched and the boiler can be stopped, and it is not necessary to separately provide a set value for stopping the boiler at the time of low load operation, so that the control can be facilitated.

  In the above aspect, the normal operation may be a constant pressure operation in which the pressure of the steam generated by the boiler is constant, and the low load operation may be a transformer operation that changes the pressure of the steam generated by the boiler.

  By performing constant pressure operation in normal operation and transforming operation in low load operation, high pressure steam can be generated efficiently by constant pressure operation, and low pressure steam can be generated by transform operation. The band can be expanded. Even for such a boiler unit, it is possible to stably switch the pump and stop the boiler performing the transformation operation.

  A second aspect of the present invention includes a boiler that generates steam, a pump that supplies water to the boiler, a water supply pipe that connects the boiler and the pump, and a water supply pipe that is provided in the water supply pipe. A first water supply valve that adjusts a flow rate; a bypass pipe that bypasses the first water supply valve and is connected to the water supply pipe; has a smaller cross-sectional area than the water supply pipe; and the bypass pipe, A second water supply valve that adjusts the water supply flow rate to the boiler, and a water supply valve control unit that controls the opening of the first water supply valve and the second water supply valve based on the water supply flow rate to the boiler, In the process in which the boiler stops from a low load operation that generates steam at a pressure lower than that of normal operation, the water supply valve control unit fully closes the first water supply valve and the second water supply valve. To the deviation of the water flow rate The opening change rate is a boiler unit to be larger than during the normal operation.

  In a normal operation in which the minimum load of the boiler is 25%, for example, and a low load operation in which the minimum load is 15%, the first water supply valve having a large flow rate is fully opened and the second water supply valve having a small flow rate is opened to a specified opening (for example 60%). In the process of stopping the boiler, the first water supply valve is fully closed, and the second water supply valve is switched to water supply flow rate (PI) control. Conventionally, when the control of the second water supply valve is switched from the specified opening to the water supply flow rate control, the opening change rate with respect to the deviation of the water supply flow rate is adjusted based on the normal operation in which the main steam pressure is constant. When the operation was stopped after low load operation with a low feed water flow rate, the feed water flow rate deviation was large. As a result, the difference between the feed water flow rate to the boiler and the flow rate required by the boiler is increased, and there is a disadvantage that the control of the second feed water valve is not stable.

On the other hand, according to the second aspect of the present invention, when the boiler at the time of low load operation is stopped by the water supply valve control unit, the first water supply valve is fully closed, and the second The rate of change of the opening with respect to the deviation of the feed water flow rate of the feed water valve is made larger than that during normal operation.
Thereby, since the responsiveness of the opening control of the 2nd water supply valve can be improved, even when stopping from the low load operation of a boiler, the 2nd water supply valve can be controlled stably. .

  In the above aspect, the normal operation may be a constant pressure operation in which the pressure of the steam generated by the boiler is constant, and the low load operation may be a transformer operation that changes the pressure of the steam generated by the boiler.

  By performing constant pressure operation in normal operation and transforming operation in low load operation, high pressure steam can be generated efficiently by constant pressure operation, and low pressure steam can be generated by transform operation. The band can be expanded. Even for such a boiler unit, the responsiveness of the opening control of the second water supply valve can be improved, so that the second water supply valve can be stably controlled even when stopping from the transformation operation. It can be performed.

  A third aspect of the present invention is a power generation system including the boiler unit described above, a steam turbine driven using steam generated by the boiler, and a generator that generates power by being driven by the steam turbine. is there.

  According to the third aspect of the present invention, stable pump switching and / or stable feed water flow rate control can be performed even during low-load operation, so the time until the boiler is stopped. The amount of energy loss until the boiler is stopped can be reduced.

  According to the present invention, it is possible to shorten the time until the boiler is stopped and to reduce the amount of energy loss.

[First Embodiment]
Below, 1st Embodiment of the boiler unit which concerns on this invention is described with reference to drawings. Here, the example which applied the boiler unit which concerns on this invention to the electric power generation system 1 is demonstrated.
In FIG. 1, a power generation system 1 includes a boiler 2 that burns fuel to generate steam, a boiler feed pump unit 25 that feeds water to the boiler 2, a feed water control device 27 that controls a feed water flow rate to the boiler 2, Boiler circulation pump 3 that distributes the feed water flow rate controlled by the feed water control device 27 to the boiler 2, a steam turbine 4 that is driven using steam generated in the boiler 2, and power generation that is driven by the steam turbine 4 to generate power A superheater 7 that is provided between the boiler (not shown), the boiler 2 and the steam turbine 4, superheats the steam, connects the boiler 2 and the superheater 7, and the superheater 7 Connected to the second steam pipe 12 connected to the steam turbine 4, the BT valve 15 provided in the first steam pipe 11, the steam control valve 17 provided in the second steam pipe 12, and the first steam pipe 11. The The third steam pipe 13 bypassing the BT valve 15, the BTB valve 16 provided in the third steam pipe 13, and the steam for adjusting the opening of the BT valve 15 and the BTB valve 16 according to the load of the steam turbine 4. A valve control unit (not shown) is provided as a main component.

In the present embodiment, the steam turbine 4 includes a high-pressure steam turbine 4a and a low / medium-pressure steam turbine 4b, and the steam discharged from the high-pressure steam turbine 4a passes through the reheater 20 to the low / medium-pressure steam turbine. 4b is supplied.
Moreover, the superheater 7 is provided with the 1st superheater 7a provided in the upstream, and the 2nd superheater 7b provided in the downstream, The vapor | steam which distribute | circulates between the 1st superheater 7a and the 2nd superheater 7b. A temperature reducer 9 is provided to reduce the temperature.

The water overheating cycle in the power generation system 1 having the above configuration will be described below.
The flow rate of the water supplied by the boiler water supply pump unit 25 is controlled by the water supply control device 27. In the boiler 2, fuel is combusted, and water whose flow rate is controlled by the feed water control device 27 is circulated by the boiler circulation pump 3 to generate steam. The steam generated in the boiler 2 flows through the first steam pipe 11 and is guided to the first superheater 7a. In the first superheater 7a, the steam is superheated, and the steam superheated in the first superheater 7a is guided to the temperature reducer 9. The temperature reducer 9 lowers the temperature of the steam by injecting water. The steam reduced in temperature by the temperature reducer 9 is guided to the second superheater 7b and reheated again by the second superheater 7b. The steam reheated by the second superheater 7b flows through the second steam pipe 12, is introduced into the high-pressure steam turbine 4a, and is used to drive the high-pressure steam turbine 4a.

  The steam after driving the high-pressure steam turbine 4 a is led to the reheater 20 and is reheated again by the reheater 20. The steam superheated by the reheater 20 is introduced into the low and medium pressure steam turbine 4b and used to drive the low and medium pressure steam turbine 4b.

  The steam after driving the low intermediate pressure steam turbine 4 b is guided to the condenser 21 and returned to water (liquid) by the condenser 21. The water generated in the condenser 21 is pumped by the condensate pump 22 in the order of the low-pressure feed water superheater 23 and the deaerator 24. The water deaerated by the deaerator 24 is pumped to the high-pressure feed water superheater 26 by the boiler feed pump unit 25 and is pumped to the temperature reducer 9 or the economizer 28. The water pumped to the temperature reducer 9 is used to lower the temperature of the steam. Moreover, the flow rate is controlled by the water supply control device 27 and the water pressure-fed to the economizer 28 is guided to the boiler 2 by the boiler circulation pump 3 and used again as steam.

In the power generation system 1 that generates steam by the above cycle, a constant pressure operation in which the pressure of the steam generated by the boiler 2 is constant, and a steam pressure generated by the boiler 2 for the purpose of operating at a lower load than the constant pressure operation. Transforming operation is performed.
Specifically, during the constant pressure operation, the opening degree of the BTB valve 16 and the BT valve 15 is fully opened, and the steam pressure _PT at the inlet of the steam control valve 17 is set to the maximum pressure (for example, 24 MPa) regardless of the load of the high pressure steam turbine 4a. Is driven to maintain). On the other hand, during the transformer operation, the opening of the BT valve 15 and the BTB valve 16 is adjusted according to the load of the high-pressure steam turbine 4a, and the steam pressure _PT is changed. In addition, at the time of the transformation operation, each pressure is set so that the differential pressure between the steam pressure P _{WWO at the} outlet of the boiler 2 and the steam pressure _PT at the inlet of the steam control valve 17 does not exceed the allowable differential pressure of the BT valve 15 and the BTB valve 16. The valve opening is adjusted.

  By controlling the BT valve 15 and the BTB valve 16 as described above, a constant pressure operation in which the minimum load of the boiler 2 is 25%, for example, can be performed during normal operation. Moreover, at the time of low load operation, the transformer operation which makes the minimum load of the boiler 2 15%, for example can be performed. As a result, high-pressure steam can be efficiently generated by constant pressure operation, low-pressure steam can be generated by transformation operation, and the operational load zone of the boiler 2 can be expanded.

FIG. 2 is a schematic configuration diagram of the boiler feed water pump unit 25 and the feed water control device 27. In order to simplify the description, the high-pressure feed water superheater 26 is omitted in FIG.
As shown in FIG. 2, the boiler feed pump unit 25 includes turbine drive pumps 51 and 53 that are driven using steam generated by the boiler 2, an electric motor drive pump 55 that is driven using electricity, and a boiler 2. A water supply switching unit (not shown) for switching water supply between the turbine drive pumps 51 and 53 and the electric motor drive pump 55, and recirculation pipes 61 and 63 connecting the discharge side of the turbine drive pumps 51 and 53 and the deaerator 24; The recirculation valves 71 and 73 provided in the recirculation pipes 61 and 63, the recirculation pipe 65 connecting the discharge side and the suction side (deaerator 24) of the motor drive pump 55, and the recirculation pipe 65 The recirculation valve 75 provided, the adjustment valve 57 for adjusting the discharge flow rate of the electric motor driven pump 55, the flow rate sensors 52, 54, 56 provided on the suction side of each pump, and the opening degree of each recirculation valve Gosuru and a recirculation valve control unit (not shown).

  The recirculation pipes 61, 63, 65 and the recirculation valves 71, 73, 75 are provided to make the suction flow rate of each pump equal to or higher than the minimum suction flow rate. That is, by opening the recirculation valves 71, 73, 75, the flow rate circulating from the discharge side of each pump to the suction side (deaerator 24) is increased, and the minimum suction flow rate of each pump is ensured.

  The recirculation valve control unit controls the openings of the recirculation valves 71, 73, and 75 based on the suction flow rates of the pumps detected by the flow rate sensors 52, 54, and 56. That is, the recirculation valve control unit controls each recirculation valve to open before the suction flow rate of each pump detected by the flow rate sensors 52, 54, and 56 becomes equal to or lower than the minimum suction flow rate.

In addition, the recirculation valve control unit increases the set value at which the recirculation valves 71 and 73 start to open when the boiler 2 is stopped during the low load operation than when the low load operation is performed. Specifically, when the set value during normal operation is the first set value and the set value during low-load operation is the second set value, the recirculation valve control unit sets the boiler during low-load operation. When 2 is stopped, the set value at which the recirculation valves 71 and 73 start to open is changed from the second set value to the first set value.
The water supply switching unit switches the water supply to the boiler 2 from the turbine drive pumps 51 and 53 to the electric motor drive pump 55 after the set value for starting to open the recirculation valves 71 and 73 is changed by the recirculation valve control unit.

In the boiler feed pump unit 25 having the above-described configuration, 50% load is allocated to each of the turbine drive pumps 51 and 53. When the operation exceeds the 50% load, two turbine drive pumps are driven and 50% One turbine drive pump is driven during operation below the load.
Here, when the boiler 2 is stopped, since the feed water flow rate to the boiler 2 is reduced, the amount of steam necessary for driving the turbine drive pumps 51 and 53 cannot be obtained. Therefore, the water supply to the boiler 2 is switched from the turbine drive pumps 51 and 53 to the electric motor drive pump 55. This switching is performed by increasing the feed water flow rate from the electric motor drive pump 55 and decreasing the feed water flow rate from the turbine drive pumps 51 and 53 according to the increase amount.

Below, the effect | action of the boiler feed water pump unit 25 at the time of stopping the boiler 2 which performs low load driving | operation is demonstrated. Here, the case where the electric motor drive pump 55 is driven from the state where only the turbine drive pump 51 is driven will be described.
When the pump switching command is input from the outside, the set value at which the recirculation valve controller starts opening the recirculation valve 71 changes from the second set value to the first set value that is larger than the second set value. Be changed. Here, as described above, the first set value is the suction flow rate of the turbine drive pump 51 when the recirculation valve 71 starts to be opened during normal operation, and the second set value is during low load operation. This is the suction flow rate of the turbine drive pump 51 when the recirculation valve 71 starts to open.

When the suction flow rate of the turbine drive pump 51 detected by the flow rate sensor 52 becomes equal to or lower than the first set value in the pump switching process, the recirculation valve 71 is opened and the discharge side of the turbine drive pump 51 is switched to the suction side (deaeration). The flow rate circulating to the vessel 24) is increased.
Then, after the recirculation valve 71 is opened, switching of the pump is started. Specifically, the motor-driven pump 55 is activated, and the feed water switching unit reduces the feed water flow rate from the turbine drive pump 51 in accordance with the discharge flow rate of the motor drive pump 55, so that the feed water to the boiler 2 is driven by the turbine. The pump 51 is switched to the electric motor drive pump 55.

The operation | movement at the time of the stop of the electric power generation system 1 which comprises the boiler feed water pump unit 25 controlled as mentioned above is demonstrated using FIG.
FIG. 3 shows the relationship between time and output when the boiler is stopped, the dotted line shows the conventional power generation system, and the solid line shows the power generation system 1 according to the present embodiment.
As shown in FIG. 3, the conventional power generation system is configured on the assumption that it is stopped during normal operation. Therefore, even when the boiler 2 performs low-load operation (transformation operation), it is stopped. After the command was input, it was necessary to raise the output and once make a normal operation (constant pressure operation) before preparing to stop. One of the reasons for this control is when the pump is switched, so-called hunting occurs in which the recirculation valve is repeatedly opened and closed in the process of decreasing the discharge flow rate of the turbine-driven pump. Because it was not possible to do.

On the other hand, according to the power generation system 1 according to the present embodiment, when the boiler 2 that performs the low load operation is stopped, the set value at which the recirculation valve control unit starts opening the recirculation valve 71 is the low load operation time. After that, the water supply to the boiler 2 is switched from the turbine drive pump 51 to the electric motor drive pump 55.
Thereby, the water supply to the boiler 2 can be switched from the turbine drive pump 51 to the electric motor drive pump 55 in a state where the recirculation valve 71 is opened and the suction flow rate of the turbine drive pump 51 is sufficiently secured. That is, even when the feed water flow rate is small, the boiler 2 can be stopped by stably switching the pump. Thereby, the time until the boiler 2 is stopped can be shortened, and the amount of energy loss until the boiler 2 is stopped can be reduced.

[Second Embodiment]
Next, a second embodiment of the present invention will be described below.
The difference between the power generation system 5 of the present embodiment and the first embodiment is that the responsiveness to the flow rate deviation of the feed water control device 27 is changed when the boiler 2 performs low load operation. Hereinafter, regarding the power generation system 5 of the present embodiment, description of points that are common to the first embodiment will be omitted, and different points will be mainly described.

  As shown in FIG. 2, the water supply control device 27 includes a water supply pipe 81 that distributes water from each pump to the boiler 2, a first water supply valve 83 provided in the water supply pipe 81, and a first water supply valve 83. Bypass pipe 91 connected to water supply pipe 81, second water supply valve 93 provided in bypass pipe 91, flow rate sensor 95 for detecting the flow rate of water flowing through bypass pipe 91, and water supply pipe 81 and a flow rate sensor 85 for detecting the flow rate of water flowing through the bypass pipe 91, and a water supply valve control unit (not shown) for controlling the opening degree of the first water supply valve 83 and the second water supply valve 93. Yes.

The bypass pipe 91 and the second water supply valve 93 are configured to have a smaller channel cross-sectional area than the water supply pipe 81 and the first water supply valve 83.
In the boiler stop process, the water supply valve control unit fully closes the first water supply valve 83 and increases the rate of change in the opening degree with respect to the deviation of the water supply flow rate of the second water supply valve 93 than during normal operation.

The operation of the water supply control device 27 having the above configuration will be described below.
In the normal operation in which the minimum load of the boiler is 25%, for example, and the low load operation in which the minimum load is 15%, for example, the first water supply valve 83 having a large flow rate is fully opened and the second water supply valve 93 having a small flow rate is provided. Is performed at a specified opening (for example, 60%). At this time, the opening degree of the first water supply valve 83 is controlled by the water supply valve control unit based on the flow rate of the water flowing through the water supply pipe 81 and the bypass pipe 91 detected by the flow sensor 85.

  In the process of stopping the boiler 2 that operates as described above, the first water supply valve 83 is fully closed and the second water supply valve 93 is switched to water supply flow rate (PI) control by the water supply valve control unit. At this time, the opening degree of the second water supply valve 93 is controlled by the water supply valve control unit based on the flow rate of the water flowing through the bypass pipe 91 detected by the flow rate sensor 95. Moreover, the opening rate change rate with respect to the deviation of the feed water flow rate of the second feed valve 93 is made larger by the feed valve control unit than during normal operation.

Here, the control in the conventional boiler unit is demonstrated as a comparative example.
In the normal operation in which the minimum load of the boiler is 25%, for example, and the low load operation in which the minimum load of the boiler is 15%, for example, the first water supply valve having a large flow rate is fully opened and the second flow rate having a small flow rate is set. This is done by setting the water supply valve to a specified opening (for example, 60%). Further, in the boiler stop process, the first water supply valve is fully closed, and the second water supply valve is switched to water supply flow rate (PI) control. Conventionally, when the control of the second water supply valve is switched from the specified opening to the water supply flow rate control, the opening change rate with respect to the deviation of the water supply flow rate is adjusted based on the normal operation in which the main steam pressure is constant. When the operation was stopped after low load operation with a low feed water flow rate, the feed water flow rate deviation was large. As a result, the difference between the feed water flow rate to the boiler and the flow rate required by the boiler is increased, and there is a disadvantage that the control of the second feed water valve is not stable.

  On the other hand, according to the power generation system 5 according to the present embodiment, as described above, when the boiler 2 shifts from the normal operation to the low load operation, the second water supply valve 93 opens with respect to the deviation of the water supply flow rate. Since the degree change rate is made larger than that during normal operation, the responsiveness of the opening control of the second water supply valve 93 can be enhanced. Thereby, even when the boiler 2 is stopped from the low load operation, the second water supply valve 93 can be stably controlled.

As mentioned above, although each embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention. .
For example, in the first embodiment, when the boiler 2 that performs low-load operation is stopped, the set value of the turbine drive pump 51 that starts opening the recirculation valve 71 is changed to the first set value during normal operation. As described above, the present invention is not limited to this example, and the second set value may be increased so that the recirculation valve 71 has a sufficient opening degree when the pump is switched.

Further, the power generation system having the lowest load in two stages has been described as an example, but a power generation system having the lowest load in three stages or more may be used.
Further, the configuration having two turbine drive pumps and one electric motor drive pump has been described as an example, but one or more turbine drive pumps and electric motor drive pumps may be provided.
Moreover, although the case where the electric motor drive pump 55 is driven from the state where only the turbine drive pump 51 is driven has been described, instead of this, only the turbine drive pump 53 or the turbine drive pumps 51 and 53 are driven. It is good also as driving the electric motor drive pump 55 from the state which both drive.

1 is a schematic configuration diagram of a power generation system according to an embodiment of the present invention. It is a schematic block diagram of the boiler feed water pump unit and feed water control apparatus of FIG. It is a figure explaining the effect of the electric power generation system of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,5 Electric power generation system 2 Boiler 3 Boiler circulation pump 4 Steam turbine 4a High pressure steam turbine 4b Low and medium pressure steam turbine 7 Superheater 7a First superheater 7b Second superheater 9 Temperature reducer 11 First steam piping 12 Second steam Pipe 13 Third steam pipe 15 BT valve 16 BTB valve 17 Steam control valve 20 Reheater 21 Condenser 22 Condensate pump 23 Low pressure feed water heater 24 Deaerator 25 Boiler feed pump unit 26 High pressure feed water heater 27 Feed water control Device 28 Carbon-saving device 40 Superheater spray adjustment valve 41 Superheater spray pressure adjustment valve 51, 53 Turbine drive pump 55 Electric motor drive pump 52, 54, 56 Flow sensor 57 Control valve 61, 63, 65 Recirculation piping 71, 73, 75 Recirculation valve 81 Water supply piping 83 First water supply valve 85 Flow rate sensor 91 Bypass piping 93 Second water supply valve 95 Flow rate sensor

Claims (6)

A boiler that generates steam;
A turbine drive pump that is driven using steam generated by the boiler and supplies water to the boiler;
An electric motor driven pump that drives using electricity and supplies water to the boiler;
A water supply switching unit for switching water supply to the boiler between the turbine drive pump and the electric motor drive pump;
A recirculation pipe that connects a discharge side and a suction side of the turbine-driven pump, and recirculates water discharged by the turbine-driven pump to the suction side;
A recirculation valve which is provided in the recirculation pipe and adjusts the flow rate of water to be recirculated so that the suction flow rate of the turbine drive pump is equal to or higher than the minimum suction flow rate required for driving the turbine drive pump;
A recirculation valve controller that controls the opening of the recirculation valve based on the suction flow rate of the turbine drive pump;
When stopping the boiler that performs low-load operation that generates steam at a lower pressure than normal operation,
After the recirculation valve control unit increases the set value for starting to open the recirculation valve than during the low load operation,
The boiler unit in which the water supply switching unit switches water supply to the boiler from the turbine drive pump to the electric motor drive pump. When the set value during the normal operation is the first set value and the set value during the low load operation is the second set value,
The boiler unit according to claim 1, wherein the recirculation valve control unit changes the set value from the second set value to the first set value when stopping the boiler during the low load operation. .   3. The normal operation is a constant pressure operation in which the pressure of steam generated by the boiler is constant, and the low load operation is a transformer operation in which the pressure of steam generated by the boiler is changed. Boiler unit. A boiler that generates steam;
A pump for supplying water to the boiler;
A water supply pipe connecting the boiler and the pump;
A first water supply valve which is provided in the water supply pipe and adjusts a water supply flow rate to the boiler;
A bypass pipe that bypasses the first water supply valve and is connected to the water supply pipe and has a smaller cross-sectional area than the water supply pipe;
A second water supply valve provided in the bypass pipe for adjusting a flow rate of water supplied to the boiler;
A water supply valve control unit for controlling the opening of the first water supply valve and the second water supply valve based on the water supply flow rate to the boiler,
In the process in which the boiler stops from a low load operation that generates steam at a pressure lower than that of normal operation, the water supply valve control unit fully closes the first water supply valve and the second water supply valve. A boiler unit that increases the degree of change in opening with respect to the deviation of the feed water flow rate than during normal operation.   5. The boiler unit according to claim 4, wherein the normal operation is a constant pressure operation in which a pressure of steam generated by the boiler is constant, and the low load operation is a transformer operation in which the pressure of steam generated by the boiler is changed. The boiler unit according to any one of claims 1 to 5,
A steam turbine driven using steam generated by the boiler;
A power generation system comprising a generator driven by the steam turbine to generate power.

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