JPH0261402A - Water level control device for deaerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a deaerator water level control device in a steam turbine plant, and particularly relates to a deaerator water level control device in a steam turbine plant having a turbine bypass pipe. Related to water level control device.

(Prior art) In recent steam turbine plants such as thermal power plants and nuclear power plants, when power is temporarily cut off from the grid due to a grid accident or other cause, the heat source such as a boiler is used for stable combustion. In order to maintain this, some systems operate as they are and perform an operation in which the main steam bypasses the turbine (hereinafter referred to as PCB operation). After a predetermined period of time, when the grid is able to supply power, that is, when the grid is restored, the PCB operation is released and the turbine is driven directly, allowing power to be supplied to the grid. be made into

Therefore, the startup time of the power plant as a whole is shortened, and the turbine is started quickly.

The general configuration of such a steam turbine plant and its control circuit are shown in FIGS. 3 and 4, and will be described below.

The condensate condensed in the condenser 10.10 is pressurized by the condensate pump 12, and passes through the deaerator water level adjustment valve 11, which is controlled by a deaerator water level control circuit as shown in FIG. It is supplied to the low pressure heater 13 and heated there. The condensate heated by the low-pressure heater 13 is sent to a deaerator 14, where sodium sulfite, hydrazine, etc. contained in the condensate are degassed. The degassed condensate is sent as feed water to a high-pressure heater 16 via a water supply pump 15, heated by turbine oil, and then sent to a boiler 17. The main steam generated in the boiler 17 is sent to the high-pressure turbine 20 via the main steam stop valve 18 and the steam control valve 19, and the high-pressure turbine 20 performs work, and a generator (not shown) is rotationally driven to supply electric power to the grid. Supply is made. The main steam that has performed work in the high-pressure turbine 20 is sent to the reheater 21 and heated again, and then sequentially sent to the intermediate-pressure turbine 23 and the low-pressure turbine 24 via intercept valves 22, 22, where the work is performed respectively. The generator is driven to rotate. The steam that has performed work in the low-pressure turbine 24 is exhausted to the condenser 10, cooled by seawater, etc., and turned into condensate.

The deaerator water level adjustment valve 11 is provided with a water supply flow rate transmitter 25 that is installed on the inlet side of the boiler 17 and detects the water supply flow rate, and a condensate water flow rate transmitter 25 that is similarly installed on the discharge port side of the condensate pump 12 that detects the condensate flow rate. It is controlled by signals from a flow rate transmitter 26 and a deaerator water level detection transmitter 27 attached to the deaerator 15 and detecting the water level in the deaerator 14. That is, in the deaerator water level control circuit shown in FIG. 4, the output signal of the feed water flow rate transmitter 25 is sent to the function generator 28. This function generator 28
Since the condensate flows in a slightly smaller amount than the feed water, the level of the output signal of the feed water flow rate transmitter 25 is adjusted to match the output signal of the condensate flow rate transmitter 26.

The output signal of the function generator 28 is sent to the subtracter 29 together with the output signal of the condensate flow rate transmitter 26, and the deviation signal thereof is sent to the adder 31 via the switch 30.

Further, the output signal of the deaerator water level detection transmitter 27 is sent to the PID calculator 33 together with the setting signal of the water level setting device 32 that sets the water level of the deaerator 14, and the output signal and the setting signal are compared and calculated. The deviation signal is sent to the adder 31,
The deviation signals of the feed water and condensate and the deviation signals between the water level and its setting signal are added, and this added output signal is output to the deaerator water level adjustment valve 11, and the opening degree of the deaerator water level adjustment valve 11 is adjusted. is controlled.

Therefore, the flow rate balance between the feed water flow rate and the condensate flow rate is constantly monitored, and if the balance is lost, the deaerator water level adjustment valve 11 is automatically operated immediately, and the flow rate balance between the feed water flow rate and the condensate flow rate is lost. It is made sure that there is no such thing. Furthermore, the water supply flow rate and the condensate flow rate are corrected by the water level deviation signal of the deaerator 14, so that the water level of the deaerator 14 is maintained at a constant value. In this way, the deaerator water level is generally controlled by three-element control.

Further, in such control, at the time of start-up or cleanup, the feed water flow rate and the condensate flow rate are lost, and each output signal of the feed water flow rate transmitter 25 and the condensate flow rate transmitter 26 cannot be obtained, so the switching device 30 , only the deviation signal of the deaerator water level detection transmitter 27 is sent to the deaerator water level adjustment valve 11, and the deaerator water level adjustment valve 11 is controlled by this deviation signal, that is, one-element control is performed.

Therefore, if an accident or the like occurs in the system, the high-pressure turbine 20, intermediate-pressure turbine 23, and low-pressure turbine 24
Bypass valves 37.38 provided in bypass pipes 35.36 bypassing each are opened, and the main steam stop valve 18 and ink-separation valve 22.22 are closed,
Bypass operation, that is, PCB operation, in which the main steam bypasses the high-pressure turbine 20 and the reheated steam bypasses the intermediate-pressure turbine 23 and the low-pressure turbine 24 and is exhausted to the condenser 10.10 via the attemperator 39 is performed. It will be done.

In this case, since the exhaust gas exhausted to the attemperator 39 has a considerably high temperature, condensate cannot be obtained if this exhaust gas is exhausted to the condenser 10, 10 as it is. Therefore,
When this PCB operation is performed, the cooling water stop valve 4 of the cooling water pipe 40 provided on the discharge side of the condensate pump 12
1 is opened, a part of the condensate is forcibly sent to the attemperator 39, and the exhaust gas exhausted to the attemperator 39 is cooled and the condenser 10.
10, it can be easily converted into condensate.

(Problem to be solved by the invention) When an accident or the like occurs in the grid and power cannot be supplied,
As mentioned above, main steam and reheat steam are bypassed through the turbine and exhausted to the condenser via the attemperator, in which case a portion of the condensate from the condensate pump is forced into the attemperator. and the vapor is cooled.

However, such PCB operation requires condensate water for cooling as well as water supply for the normal steam turbine cycle, and the amount of condensate transferred by the condensate pump increases, and of course the amount of condensate sent to the deaerator water level control valve increases. The pressure of the cooling condensate sent to the desuperheater decreases, and the amount of water supplied to the deaerator becomes insufficient, which not only causes the water level in the deaerator to drop, but also causes insufficient cooling of the exhaust steam. Condensation may not be sufficient. This causes problems such as the inability to operate the steam turbine cycle.

In order to solve these problems, when a steam turbine cycle is operated by PCB and a part of the condensate is forcibly sent to the attemperator by the condensate pump, the present invention provides a solution to the condensate to be sent to the attemperator. To provide a deaerator water level adjusting device which prevents the water pressure of the deaerator from decreasing and also prevents the water level of the deaerator from decreasing below a planned level.

[Structure of the invention]

(Means for solving the problem) This plant has a bypass pipe that exhausts the main steam that bypasses the turbine to the condenser via a desuperheater, and connects it to the discharge port side of the condensate pump. The cooling water pipe forcibly sends part of the condensate to the desuperheater during bypass operation, as well as the condensate flow rate, feed water flow rate, and deaerator water level, and determines the opening of the deaerator water level adjustment valve. a deaerator water level control circuit that adjusts the water level of the deaerator to control the water level of the deaerator; and an open circuit provided in the deaerator water level control circuit that limits the opening control signal of the deaerator water level adjustment valve during the bypass operation. The opening limiter is provided with a time limit setting device for releasing the opening limit of the deaerator water level regulating valve in a time-limited manner, and the opening limiter The device is equipped with a switching control circuit that releases the opening limit of the deaerator water level adjustment valve in response to an abnormal drop in the deaerator water level.

(Function) When the steam turbine cycle is operated by PCB, a part of the condensate is forcibly sent to the attemperator as cooling water, and the bypassed steam is cooled by the part of the condensate. At this time, the deaerator water level control valve receives the PCB operation signal, and its opening degree is restricted to prevent a drop in the pressure of the condensate sent to the steam turbine cycle and the condensate sent to the attemperator. For example, when the PCB operation is canceled after a predetermined period of time has elapsed, in response to this PCB operation stop signal, the opening limit of the deaerator water level adjustment valve is lifted either temporarily or depending on the water level of the deaerator, etc., and the water level of the deaerator is lowered. is prevented from falling below the planned value.

(Example) The deaerator water level control device of the present invention will be described below with reference to FIGS. 1 and 2. In addition, in the same figure, Figures 3 and 4
The same parts as those of the conventional deaerator water level control device shown in the figure will be explained using the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, a limiter 46 is connected to the adder 31 so that the output signal from the adder 31 is applied to the deaerator water level regulating valve 11 via the limiter 46. . In addition, the deaerator water level control circuit is provided with a normal opening limiter 42 and a bypass opening limiter 43 during FCB operation, and the control of either one of these opening limiters 42 or 43 is provided. The signal is passed through the switch 44 to the change rate limiter 4.
5, and the output signal from the rate of change limiter 45 is output to the limiter 46.

By the way, in normal times, the limit signal from the normal opening limiter 42 is applied to the limiter 46 via the change rate limiter 45 by the switch 44, and the control signal from the adder 31 is applied to, for example, 100% degassing. water level adjustment valve 11.

Therefore, the deaerator water level adjustment valve 11 receives each output signal of the feed water flow rate transmitter 25, the condensate flow rate transmitter 26, and the deaerator water level transmitter 27 that detects the water level of the deaerator 15,
The deaerator water level regulating valve 11 is controlled by these output signals.

On the other hand, when the switch 44 is switched, the limiting signal from the bypass opening limiter 43 is applied to the rate of change limiter 45, and the limiting signal is applied to the limiter 46 via the rate of change limiter 45. , the control signal from the adder 31 is limited, for example, the opening is limited to 50%. Therefore, the opening degree of the deaerator water level adjustment valve 11 is controlled to be limited to a limited opening degree of 50% or less by each output signal of the water supply flow rate transmitter 25 and the like.

When the signal from the normal opening limiter 42 or the bypass opening limiter 43 is sent to the limiter 46, the rate of change limiter 45 is operated temporarily or temporarily so that the limiter 46 is not activated suddenly. This is done on a temporary basis, and is intended to control the deaerator water level adjustment valve 11, that is, to prevent an urgent change in condensate.

Switching of the switch 44 is performed by a switching control circuit shown in FIG. That is, from the PCB signal generator 47 to the switch 44
When the PCB signal is input to the switch 44, the b-c
switched to the circuit. Also, the above PCB signal is NOT
The signal is sent to the OR circuit 50 via the circuit 48 and four time setting devices, and a low water level signal is also input to this OR circuit 50 when the deaerator water level is below the standard water level by a predetermined value. When the output signal from the OR circuit 50 is input to the switch 44, the switch 44 switches to the a-c circuit.

Therefore, the switching device 44 is connected to the PCB during normal operation.
Since the signal generator 47 is not generating a PCB signal, the switch 44 is switched to the a-C circuit. Therefore, the limit signal of the normal opening limiter 42 is
The output signals of the feed water flow transmitter 25, the condensate flow transmitter 26, and the deaerator water level transmitter 27 which are applied to the limiter 46 through the circuit and rate of change limiter 45 to detect the water level of the deaerator 15; The deaerator water level regulating valve 11 is controlled within a range of 100% by these output signals.

When receiving the PCB signal, the switch 44 receives the output signal of the PCB signal generator 47 and switches to the b-c circuit. Therefore, the limit signal of the bypass opening limiter 43 is applied to the limiter 46 via the b-c circuit of the switch 44 and the rate of change limiter 45, and is applied to the feed water flow rate transmitter 25, the condensate flow rate transmitter 26, and the degassing The opening degree control signal of the deaerator water level adjustment valve 11 based on each output signal of the deaerator water level transmitter 27 that detects the water level of the deaerator 15 is limited to 50%, and the deaerator water level adjustment valve 11 is limited to 50%. % opening. Therefore, the condensate discharged from the condensate pump 12 and supplied to the steam turbine cycle is restricted, and a drop in the pressure of the cooling water sent to the attemperator 39 is prevented.

When the PCB signal disappears and a predetermined period of time has elapsed, the output signal from the NOT circuit 48 is input to the switch 44 via the time setter 49 and the OR circuit 50.
4 is switched to the a-C circuit as described above. Therefore, the output signal of the normal opening limiter 42 is sent to the limiter 46, and the deaerator water level regulating valve 11 receives a signal from the water supply flow rate transmitter 25, etc., and is controlled as usual.

In addition, when the water level of the deaerator 14 falls below the scheduled value,
The OR circuit 50 receives the decrease signal from the deaerator transmitter 27, and this decrease signal causes the switch 44 to switch to the a-c circuit, and similarly to the above, the output signal of the normal opening limiter 42' changes to the It is sent to the restrictor 46 and this deaerator water level adjustment valve 1
1 receives a signal from the water supply flow rate transmitter 25 or the like and performs normal control, thereby preventing an abnormal drop in the water level in the deaerator 14.

Since this operation usually occurs shortly before the PCB signal stops, it has little effect on the operation of the steam turbine cycle.

During these operations, the deaerator water level regulating valve 11 is opened and closed gradually or gradually by the change rate limiter 45, so that the double water in the steam turbine cycle is not suddenly changed, so that the steam turbine cycle can be operated smoothly.

〔Effect of the invention〕

Since the present invention is configured as described above, in a steam turbine plant, when a system accident or the like occurs and the steam turbine cycle is operated by PCB, the deaerator water level control valve is controlled in a limited manner, and the condensate water is The condensate pressure discharged from the pump can be sent to the desuperheater while maintaining it at a predetermined value, the bypass steam can be sufficiently cooled, and the steam can be quickly converted to condensate. Since the deaerator water level regulating valve is returned to the normal state in a time-limited manner, the deaerator can be operated while the water level of the deaerator remains almost at the normal state.

Furthermore, during PCB operation, the deaerator water level adjustment valve is controlled depending on the state of the water level in the deaerator, so the water level in the deaerator does not fall below a predetermined value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a deaerator water level control circuit of the deaerator water level control device of the present invention, FIG. 2 is a block diagram showing a switching control circuit of the switch in FIG. 1, and FIG. The diagram is
FIG. 4 is a block diagram of a conventionally commonly used steam turbine cycle. FIG. 4 is a block diagram showing a deaerator water level control circuit of a conventional deaerator water level control device. 10... Double water tank, 11... Deaerator water level adjustment valve, 12
...Condensate pump, 13...Low pressure heater, 14...
Deaerator, 15... Water supply pump, 16... High pressure heater, 17... Boiler, 18... Main steam stop valve, 19.
...Steam control valve, 20...High pressure turbine, 21...
Reheater, 22... Intercept valve, 23... Medium pressure turbine, 24... Low pressure turbine, 25... Feed water flow rate transmitter, 26... Condensate flow rate transmitter, 27... Desorption Air/water level transmitter, 28... Function generator, 29... Subtractor, 30.44... Switcher, 46... Limiter, 31.
...Adder, 32...Deaeration water level setting device, 33...P
ID calculator, 35. 36... Bypass pipe line, 37.
38... bypass valve, 39... desuperheater, 40...
Cooling pipe line, 41... Cooling water stop valve, 42... Normal opening limiter, 43... Bypass opening limiter, 45...
Rate of change limiter, 47...FCB transmitter, 48...N
OT circuit, 49... time limit setter, 50... OR circuit. Figure 1

Claims (1)

[Claims] 1. A bypass pipe that exhausts steam bypassing the turbine to the condenser via a desuperheater, and a bypass pipe connected to the discharge port side of the condensate pump, which discharges a portion of the condensate during bypass operation. The water level of the deaerator is controlled by detecting the cooling water pipe that forcibly sends water to the desuperheater, the condensate flow rate, the feed water flow rate, and the water level of the deaerator, and adjusting the opening degree of the deaerator water level adjustment valve. and an opening limiter provided in the deaerator water level control circuit to limit the opening control signal of the deaerator water level regulating valve during the bypass operation. Deaerator water level control device. 2. The deaerator water level control device according to claim 1, wherein the opening limiter has a time limit setting device that releases the opening limit of the deaerator water level adjustment valve in a time-limited manner. 3. The deaerator according to claim 1, wherein the opening limiter has a switching control circuit that releases the opening limit of the deaerator water level adjustment valve due to an abnormal water level drop in the deaerator. Water level control device.