JP5739302B2 - Condenser cooling water system - Google Patents

Description

  The present invention relates to a condenser cooling water system for supplying cooling water to a condenser of a steam turbine.

  The condenser is used to condense exhaust steam that has finished work in the steam turbine with cooling water (seawater or water from the cleaning tower) that passes through the inside of the cooling pipe, and to return it to the system again. Is. The condenser includes a trunk that is a box-shaped container that accommodates a plurality of cooling pipes, and is installed in a thermal power plant, a nuclear power plant, or the like. The cooling pipe is inserted into a through hole provided in a plurality of tube plates arranged at intervals in the longitudinal direction of the cooling tube, and is supported in the cylinder by the plurality of tube plates.

  The condenser cooling water system is for supplying cooling water pumped up by a pump (cooling water pump) to the condenser. In the power plant, various conditions regarding the cooling water of the condenser are imposed according to the location conditions. For example, when seawater is used as the cooling water, there is a restriction on the upper limit of the rising temperature of the cooling water from the viewpoint of environmental conservation (cooling water temperature increase restriction). That is, the water temperature rise value (ΔT) during drainage relative to the water temperature during intake is limited. Therefore, it is required to control the flow rate of the cooling water supplied to the condenser while complying with various restrictions imposed on the cooling water.

  As a technique for controlling the cooling water flow rate, a movable blade type cooling water pump (CWP) for supplying cooling water to the condenser, a bypass pipe that bypasses the condenser, and the bypass pipe are provided. There is a condenser cooling system including a valve and a control device (CWP control device) for controlling the opening degree of a blade of a cooling water pump and the opening degree of a bypass pipe (see Japanese Patent Application Laid-Open No. 2002-340483). . The control device in this system predicts and calculates the optimum required vacuum degree flow rate (cooling water required flow rate determined from the condenser optimum vacuum degree) from the generator output, and the seawater temperature rise value required flow rate (cooling water temperature rise restriction). Cooling water demand flow rate determined from the generator output and intake port temperature, and based on the larger value of the two calculated values, the moving blade opening of the cooling water pump (condenser and bypass piping In addition to controlling the total flow rate), the valve opening degree of the bypass pipe (the flow rate of the bypass pipe) is controlled so that cooling water having a flow rate corresponding to the difference between the two calculated values is introduced into the bypass pipe.

Japanese Patent Laid-Open No. 2002-340483

  Usually, the flow rate of the cooling water supplied to the condenser is kept substantially constant by adjusting the opening degree of the outlet valve of the condenser or adjusting the blade opening degree when the cooling water pump is a movable blade type. On the other hand, the cooling pipes in the condenser have a poor heat exchange performance due to adhesion of marine organisms, so reverse washing (back washing) in which cooling water flows through the condenser in the opposite direction to normal (normal washing) Ball cleaning is performed regularly. When backwashing is performed in this way, a pressure loss occurs in the system, so that the amount of cooling water introduced into the condenser is reduced as compared with that during normal washing. Therefore, the cooling water temperature at the time of drainage rises rather than at the time of regular washing, and approaches the limit value of the cooling water temperature rise. For example, a condenser generally has a structure of one barrel and two water chambers having two water chambers (tube nests) inside one barrel. Are supplied to the respective water chambers, and flows that are opposed to each other are formed in the body. During backwashing, the water inlet / outlet valve of the water chamber to be backwashed is closed, and the water chamber communication valve for communicating adjacent water chambers is opened, so that cooling water flows from the adjacent water chamber in the reverse direction. Form a flow. In this case, about twice the normal flow rate flows through the condenser water chamber inlet / outlet piping, system loss increases, and the amount of cooling water decreases.

  In this regard, the condenser cooling system described in the above-mentioned Japanese Patent Application Laid-Open No. 2002-340483 calculates the seawater temperature rise value required flow rate based on the generator output and intake port temperature. When the flow rate decreases, the limit value of the cooling water temperature rise is approached. In this type of system, in order to cope with the decrease in flow rate during backwashing, the flow rate should be corrected to a value that is relatively larger than the required flow rate calculated from the generator output and intake port temperature (required flow rate of seawater temperature). However, in this correspondence, the cooling water flow rate is always set to a relatively large value, so that the cooling water pump power is increased. The power that is the power of the cooling water pump is often supplied from the generator of the power plant, but an increase in power consumption of the cooling water pump leads to a decrease in power generation efficiency of the plant. In nuclear power plants, there are cases where the reactor thermal output is kept constant throughout the year (rated reactor thermal output operation), but in the summer when the seawater temperature rises, Since the degree of vacuum decreases and the condenser heat load increases, the margin for the limit value of the cooling water temperature rise becomes particularly small. Further, in such a case, it is necessary to consider the restriction of the reactor heat output caused by the decrease in the amount of cooling water during backwashing, and the original power generation capacity may be restricted.

  An object of the present invention is to provide a condenser cooling water system that can suppress an increase in cooling water temperature accompanying a decrease in the amount of cooling water during backwashing.

(1) In order to achieve the above object, the present invention provides a cooling system for supplying cooling water to a condenser in a condenser cooling water system for supplying cooling water to a condenser of a steam turbine. A water pump, a bypass pipe for bypassing the condenser, a flow rate adjusting means for adjusting a flow rate of cooling water flowing through the bypass pipe, and a pressure detection for detecting a discharge pressure of the cooling water pump And a control device for controlling the amount of cooling water in the bypass pipe by the flow rate adjusting means so that the pressure detected by the pressure detecting means approaches both a normal value and a backwash time. Shall be characterized.

  (2) In the above (1), preferably, the control device includes a deviation in cooling water temperature at an inlet and an outlet of the condenser, and a heat output of a steam generating means for generating steam for the steam turbine. The amount of cooling water flowing through the condenser is calculated from the output of the generator driven by the steam turbine, and the discharge pressure of the cooling water pump is determined from the amount of cooling water and the flow rate / head characteristics of the cooling water pump. It is calculated and the set value is corrected so that the deviation between the discharge pressure and the set value becomes small.

  (3) In the above (1) or (2), preferably, further comprising another condenser, and the downstream end of the bypass pipe is an outlet pipe of the condenser and the other condenser. It is connected to at least one of them, and is further provided with other flow rate adjusting means for adjusting the cooling water flow rate installed in the bypass pipe downstream of the flow rate adjusting means and introduced into the outlet pipe. .

  (4) In any one of the above (1) to (3), preferably, the steam generating means for generating steam for the steam turbine is a nuclear reactor.

  (5) In any of the above (1) to (4), preferably, the flow rate adjusting means is a valve device installed in the bypass pipe.

  ADVANTAGE OF THE INVENTION According to this invention, the cooling water temperature rise accompanying the reduction | decrease in the amount of cooling water at the time of backwashing can be suppressed.

1 is a schematic system diagram of a condenser cooling system according to a first embodiment of the present invention. The schematic system diagram of the condenser cooling system which concerns on the 2nd Embodiment of this invention. The processing flow of the control apparatus in the condenser cooling system of FIG. The schematic system diagram of the condenser cooling system which concerns on the 3rd Embodiment of this invention. The schematic system diagram of the condenser cooling system which concerns on the 4th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic system diagram of a condenser cooling system according to a first embodiment of the present invention. The condenser cooling system shown in this figure includes a cooling water pump 1, a condenser 2, a ball collector 3, a water discharge tank 4, a bypass pipe 5, a valve device 6, an orifice 7, a pressure A total of 8 and a control device 9 are provided. The condenser cooling system described here is for condensing steam from a steam turbine in a nuclear power plant, and steam that is a working fluid of the steam turbine is generated by reaction heat of the reactor. (For example, in a boiling water reactor (BWR), steam is generated in a reactor pressure vessel, and in a pressurized water reactor (PWR), it is generated in a steam generator). However, it can also be used as a condenser cooling system for a thermal power plant equipped with a boiler as steam generating means.

  The cooling water pump 1 is for supplying cooling water (seawater) pumped from a water intake (not shown) to the condenser 2 via the inlet pipe 41. The system shown in the figure includes three units. A cooling water pump 1 is installed. In addition, as the cooling water pump 1, a fixed blade type or a movable blade type can be used.

  A pressure gauge 8 for detecting the discharge pressure of the cooling water pump 1 is installed on the downstream side of the cooling water pump 1 in the inlet pipe 41. In addition, the inlet pipe 41 connected to one cooling water pump 1 is connected to the downstream side of the installation position of the pressure gauge 8 and the connecting pipe 43 for connecting to the other inlet pipe 41. The two branches on the downstream side of the connecting portion with 43 are connected to the two inlet water chambers 31 of the condenser 2 via the inlet valve 33.

  The condenser 2 includes two inlet water chambers 31 and outlet water chambers 32 that are installed obliquely with respect to the trunk. The adjacent inlet water chamber 31 and outlet water chamber 32 in each condenser 2 are connected via a water chamber communication pipe in which a water chamber communication valve 35 is installed. An outlet pipe 42 is connected to each outlet water chamber 32, and an outlet valve 34 is installed in the outlet pipe 42. The outlet pipe 42 connects the outlet water chamber 32 of the condenser 2 and the water discharge tank 4 and discharges the heated cooling water to the ocean. A ball collector 3 is provided in the middle of the outlet pipe 42. In the ball collector 3, a cleaning ball (sponge ball) that is thrown into the condenser 2 together with the cooling water in order to remove slime and foreign matters in the cooling pipe is collected.

  In the condenser 2 configured as described above, during normal times (during normal washing), the two inlet valves 33 and the outlet valves 34 are opened, and all the water chamber communication valves 35 are closed to restore the condenser. Cooling water is flowed from the inlet water chamber 31 toward the outlet water chamber 32 with respect to two tube nests (not shown) in the water device 2. As a result, the cooling water flows through the two pipe nests in the condenser 2 in directions opposite to each other. On the other hand, at the time of backwashing, by closing one set of the inlet valve 33 and the outlet valve 34 and opening all the water chamber communication valves 35, the outlet water chamber 32 to the inlet water chamber 31 with respect to one pipe nest. Flow cooling water toward As a result, the cooling water flows in the same direction through the two pipes in the condenser 2.

  The bypass pipe 5 is for bypassing the condenser 2 by connecting the upstream side of the branch portion to the inlet water chamber 31 in each inlet pipe 41 and the water discharge tank 4. The bypass pipe 5 in the present embodiment bypasses the condenser 2 by connecting the communication pipe 43 and the water discharge tank 4. The bypass pipe 5 is provided with a valve device 6 and an orifice 7 as flow rate adjusting means for adjusting the amount of cooling water flowing through the bypass pipe 5. The valve device 6 has a drive device for controlling the flow rate, and the opening degree of the valve device 6 can be controlled based on an operation signal. In the present embodiment, the orifice 7 is installed with a focus on the cavitation suppression of the valve device 6 and the operation at an appropriate opening, but the orifice 7 may be omitted.

  The control device 9 is for controlling the opening degree of the valve device 6 so that the pressure detected by the pressure gauge 8 approaches the set value Po. When the rated reactor heat output operation is carried out, the set value Po is a limit for the cooling water temperature to rise under conditions where the heat load of the condenser 2 is maximized during normal washing (for example, summer). It is preferable to set based on the flow rate kept within the value.

  The pressure (detection signal) detected by the pressure gauge 8 is input from the pressure gauge 8 to the control device 9, and the drive device of the valve device 6 is controlled by the control device 9 to control the opening degree of the valve device 6. An operation signal is output. In the present embodiment, the discharge pressures of the cooling water pumps 1 are detected by the three pressure gauges 8, but it is assumed that the discharge pressures of all the cooling water pumps 1 are held at the set value Po. Therefore, the opening degree of the valve device 6 may be controlled using the detection value of any one pressure gauge 8.

  In the condenser cooling water system configured as described above, if backwashing is started from the time of normal washing in which the discharge pressure of the cooling water pump 1 is maintained at the set value Po, the pressure loss of the system increases. As the water flow rate decreases, the discharge pressure of the cooling water pump 1 increases from Po. However, in the present embodiment, the control device 9 detects a change in the discharge pressure of the cooling water pump 1 with the pressure gauge 8 and automatically controls the opening degree of the valve device 6 according to the pressure change. Since the flow rate of the bypass pipe 5 increases, the cooling water pump discharge pressure is maintained at the set value Po. If the discharge pressure of the cooling water pump 1 is constant, the pump flow rate is constant. Therefore, the sum of the cooling water flow rate of the condenser 2 and the cooling water flow rate of the bypass pipe is maintained at the same value as during normal washing. . That is, since the cooling water amount of the entire system is maintained even during backwashing, an increase in cooling water temperature can be suppressed. Therefore, according to this Embodiment, while being able to suppress the motive power increase of the cooling water pump 1, the fall of the power generation efficiency of a plant can be suppressed.

  In the present embodiment, the cooling water amount of the entire system is controlled using the discharge pressure of the cooling water pump 1 that is directly affected by the pressure loss due to backwashing as a parameter. Therefore, it is possible to control the cooling water flow rate with excellent followability against pressure loss, and because it can instantly follow changes in the system operating state at the time of transition to backwashing, it is a remarkable advantage in terms of controllability. Play. As another means for controlling the cooling water flow rate of the entire system, for example, a method of controlling the cooling water flow rate based on the temperature change of the cooling water discharged from the condenser 2 during backwashing can be considered. Then, it takes time until the temperature change of the waste water appears. That is, it cannot be coped with the decrease in the flow rate until the temperature change of the drainage appears, and it can be pointed out that the followability is poor and insufficient as a method for suppressing the temperature change accompanying backwashing.

  FIG. 2 is a schematic system diagram of the condenser cooling system according to the second embodiment of the present invention, and FIG. 3 is a processing flow of the control device in the condenser cooling system of FIG. In addition, the same code | symbol may be attached | subjected to the same part as the previous figure, and description may be abbreviate | omitted (it is the same also in later figures).

  The condenser cooling water system shown in FIG. 2 calculates an inlet thermometer 10 and a discharge tank thermometer 11 for monitoring the temperature rise of the cooling water by the condenser 2, and a reactor heat output and a generator output. 1 is mainly different from the one shown in FIG. 1 in that a computer 12 for monitoring plant performance is provided. The inlet thermometer 10 is for detecting the cooling water temperature on the upstream side of the condenser 2, and is installed in the inlet pipe 41. The coolant temperature (detection signal) detected by the inlet thermometer 10 is output to the control device 9A. The water tank thermometer 11 is for detecting the cooling water temperature when discharged into the water tank 4, and is installed in the water tank 4. The coolant temperature (detection signal) detected by the water discharge tank thermometer 11 is output to the control device 9A. The reactor heat output and generator output calculated by the plant performance monitoring computer 12 are output to the control device 9A.

  In the condenser cooling water system configured as described above, the control device 9A first inputs the inlet temperature Ti from the inlet thermometer 10 (S13) as shown in the processing flow of FIG. The water discharge tank temperature To is input from 11 (S14). Then, by subtracting the inlet temperature Ti from the water discharge tank temperature To input in S13 and S14, the coolant temperature rise (ΔT) that is the deviation of the coolant temperature at the inlet and outlet of the condenser 2 is calculated (S15). ). Further, the control device 9A inputs the reactor thermal output Qr and the generator output Qw from the plant performance monitoring computer 12 (S16, 17), and subtracts the generator output Qw from the reactor thermal output Qr. The appliance heat load ΔQ is calculated (S18).

  The control device 9A calculates the cooling water amount W flowing through the condenser 2 from the cooling water temperature rise ΔT calculated in S15 and the condenser heat load ΔQ calculated in S18 (S19), and the initial stage of the cooling water pump 1 is calculated. The discharge pressure P of the cooling water pump 1 is calculated based on the flow rate / lift characteristic (QH characteristic) set in advance as a value and the cooling water flow rate W calculated in S19 (S21).

  Then, the control device 9A obtains a value (deviation) obtained by subtracting the set value Po from the discharge pressure P calculated in S21, and determines whether the deviation (P-Po) is within the set threshold value α. Perform (S23). As a result of the determination in S23, when the deviation exceeds the threshold value α, a correction calculation is performed to subtract the predetermined value β from the discharge pressure set value Po of the cooling water pump 1, so that the deviation between the discharge pressure P and the set value Po is reduced. The set value Po is corrected. Then, the corrected value is set as a new set value Po (S24), and a series of processing is terminated. On the other hand, if the deviation is equal to or smaller than the threshold value α as a result of the determination in S23, the series of processing ends without correcting the set value Po.

  It should be noted that immediately after the end of the process, the process may return to the beginning immediately and the above processes may be repeatedly executed, or the above processes may be executed at a predetermined interval. In the above description, the threshold value α used in the determination in S23 is different from the predetermined value β used in the correction in S24. However, a common value (for example, α) may be used in both processes. Furthermore, in the example of FIG. 3, the processing from S13 to 15 and the processing from S16 to 18 are shown to be performed in parallel, but both may be performed in an arbitrary order.

  In the first embodiment, the cooling water flow rate is set with the set value Po set based on the flow rate / pump characteristic (QH characteristic) of the cooling water pump 1, but the flow rate / pump characteristic changes over time. . On the other hand, according to the condenser cooling water system according to the present embodiment configured as described above, even if the flow rate / head characteristics of the cooling water pump 1 change over time, the reactor heat during plant operation Since the cooling water flow rate W can be calculated from the condenser heat load ΔQ calculated from the difference between the output and the generator output and the cooling water temperature rise ΔT, the set value Po of the pump discharge pressure can be corrected. The amount of water can be controlled appropriately.

  FIG. 4 is a schematic system diagram of a condenser cooling system according to the third embodiment of the present invention. In the condenser cooling water system shown in this figure, the outlet pipe 42 of each condenser 2 and the bypass pipe 5 are connected via a connecting pipe 25 and the cooling water of the bypass pipe 5 is directly discharged to the water discharge tank 4. The second embodiment is different from the first embodiment in that the discharge is made through the outlet pipe 42 without any problems. Each communication pipe 25 is provided with a valve device 26 as a flow rate adjusting means for adjusting the flow rate of the cooling water introduced into the outlet pipe 42 of the connection destination. In the example shown in FIG. 3, the number of connecting pipes 25 is three, which is the same as the number of condensers 2 and outlet pipes 42. Further, the bypass pipe 5 and each connecting pipe 25 are connected downstream of the valve device 6 and the orifice 7.

  In general, the temperature on the outlet side of the condenser 2 is measured in a joining tank installed in the middle of the water discharge tank 4, but the cold water flowing through the bypass pipe 5 is evenly discharged into the water discharge tank 4. It is preferable to mix with the warm water which flowed 2 appropriately. According to the present embodiment, in the condenser cooling system composed of a plurality of condensers 2, the cooling water (cold water) flowing through the bypass pipes 5 can be distributed to the outlet pipes 42 of the respective condensers 2. Therefore, the cold water that has passed through the bypass pipe 5 and the hot water that has passed through the condenser 2 can be mixed efficiently before being discharged into the water discharge tank 4. Thereby, it is possible to suppress the occurrence of temperature unevenness on the downstream side after the water discharge tank 4, and it is possible to suppress the occurrence of a situation in which the temperature changes according to the measurement position.

  The amount of cold water distributed to each outlet pipe 42 is appropriately distributed according to the level of the water temperature in each pipe 42 so that the temperature of the cooling water discharged from each outlet pipe 42 to the water discharge tank 4 approaches evenly. Alternatively, it may be equally distributed to each outlet pipe 42 regardless of the water temperature in each outlet pipe 42.

  FIG. 5 is a schematic system diagram of a condenser cooling system according to the fourth embodiment of the present invention. The condenser cooling water system shown in this figure is different from the third embodiment in that a part of the outlet piping 42 in the system and the bypass piping 5 are connected via a connecting piping 25. Thus, when there are a plurality of outlet pipes 42 in the system, temperature unevenness after the water discharge tank 4 can be suppressed by connecting to at least one of them through the connecting pipe 25.

  The water discharge tank 4 shown in FIG. 5 includes a water channel (a two-part water discharge channel) having a partition 44 at the center, and the outlet of the condenser 2 disposed in the center among the three condensers 2. The pipe 42 opens at a position substantially equal to the partition 44. In such a case, the cooling water discharged from the central outlet pipe 42 is discharged almost equally to the two water channels by using the partition 44 as a water divide, so that the cooling water discharged from the other two outlet pipes 42 is discharged. Less likely to cause temperature unevenness than water. Therefore, in the present embodiment, the bypass pipe 5 and the connecting pipe 25 are connected so that the cold water is supplied only to the two outlet pipes 42 arranged at both ends.

  In addition, in the condenser cooling system utilized for description of each said embodiment, although the three condensers 2 were provided, this invention is not limited by the number of condensers, A condenser is Other numbers may be used.

  Moreover, although each said embodiment demonstrated the case where only one bypass piping 5 was demonstrated, multiple bypass piping 5 provided with the valve apparatus 6 is installed, and the said several valve apparatus 6 is discharged from the cooling water pump 1. You may comprise so that it may control according to a pressure.

  Furthermore, in each of the above-described embodiments, the pressure gauges 8 are installed at all the discharge ports of the three cooling water pumps 1, but the pressure gauges 8 are provided at the discharge ports of at least one cooling water pump 1, The present invention can be configured by using the detected value of the pressure gauge 8. Further, the method of using the detected values of the plurality of pressure gauges 8 has not been specifically described. From the viewpoint of improving the reliability of the system, the valve device 6 is controlled using the average value of the three detected values. You can go. In addition, when a value greatly different from the other two detection values is detected, it is considered that an abnormality has occurred in the pressure gauge 8 that has detected the different value, and the detected value from the pressure gauge 8 is used. May be configured not to control the valve device 6.

  DESCRIPTION OF SYMBOLS 1 ... Cooling water pump, 2 ... Condenser, 3 ... Ball collector, 4 ... Water discharge tank, 5 ... Bypass piping, 6 ... Valve apparatus with a drive mechanism, 7 ... Orifice for flow control, 8 ... Pressure gauge, 9 DESCRIPTION OF SYMBOLS ... Control apparatus, 10 ... Inlet thermometer, 11 ... Drain tank thermometer, 12 ... Computer for plant performance monitoring, 25 ... Connection pipe to condenser outlet piping, 26 ... Flow control valve

Claims (5)

In a condenser cooling water system for supplying cooling water to a steam turbine condenser,
A cooling water pump for supplying cooling water to the condenser;
Bypass piping for bypassing the condenser;
Flow rate adjusting means for adjusting the flow rate of cooling water flowing through the bypass pipe;
Pressure detecting means for detecting the discharge pressure of the cooling water pump;
And a control device that controls the amount of cooling water in the bypass pipe by the flow rate adjusting means so that the pressure detected by the pressure detecting means approaches both a normal value and a backwash time. Condenser cooling water system to do. The condenser cooling water system according to claim 1,
The controller is
The condensate is derived from the deviation of the cooling water temperature at the inlet and outlet of the condenser, the heat output of the steam generating means for generating steam for the steam turbine, and the output of the generator driven by the steam turbine. Calculate the amount of cooling water flowing through the vessel,
The discharge pressure of the cooling water pump is calculated from the amount of cooling water and the flow rate / head characteristics of the cooling water pump,
The condenser cooling water system, wherein the set value is corrected so that a deviation between the discharge pressure and the set value becomes small. In a condenser cooling water system for supplying cooling water to a steam turbine condenser,
A cooling water pump for supplying cooling water to the condenser;
Bypass piping for bypassing the condenser;
Flow rate adjusting means for adjusting the flow rate of cooling water flowing through the bypass pipe;
Pressure detecting means for detecting the discharge pressure of the cooling water pump;
A control device for controlling the amount of cooling water in the bypass pipe by the flow rate adjusting means so that the pressure detected by the pressure detecting means approaches a set value;
And a another condenser,
The downstream end of the bypass pipe is connected to at least one of the outlet pipe of the condenser and the other condenser,
The condenser cooling water system further comprising other flow rate adjusting means for adjusting the flow rate of the cooling water installed in the bypass pipe downstream of the flow rate adjusting means and introduced into the outlet pipe. In the condenser cooling water system according to claim 3 ,
The condenser cooling water system, wherein the steam generating means for generating steam for the steam turbine is a nuclear reactor. In the condenser cooling water system according to claim 3 or 4 ,
The condenser cooling water system, wherein the flow rate adjusting means is a valve device installed in the bypass pipe.

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