JPS6154122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure control method and a control device for a deaerator in a steam power plant.

The conventional configuration around the deaerator of a steam power plant and its operation method will be explained with reference to FIG. A deaerator 1 in a steam power generation plant receives extracted steam from a steam turbine 2 via an extracted steam pipe 8 having a check valve 9, condensate from a low pressure feed water heater 3 via a condensate pipe 10, and high pressure feed water. Drain water flows from the heater 4 through the drain pipes 12, respectively. Of these, the amount of turbine bleed steam is not controlled and flows due to the differential pressure between the bleed point pressure of the steam turbine 2 and the internal pressure of the deaerator 1, and the drain water from the high pressure feed water heater 4 also flows into the high pressure feed water heater 4. It flows in due to the differential pressure between the pressure inside the deaerator 1 and the pressure inside the deaerator 1. On the other hand, the condensate flowing through the condensate pipe 10 is controlled by the water level control device 14 to control the opening degree of the condensate flow rate regulating valve 15 based on the water level signal from the water level detector 13 attached to the deaerator 1. The flow rate is adjusted and the water level in the deaerator 1 is controlled. In addition, 5 is a condenser, 6a is a condensate pump, 6b is a booster pump, 7 is a water supply pump that sends the water held in the deaerator to the high-pressure water supply system,
16 is a water supply regulating valve, and 11 is a water supply pipe to the boiler.

As mentioned above, the general deaerator 1 is operated only to control the water level of its retained water, which is not very important in steady operation and normal load change rate in current power plants. Not a problem. However, as the rate of load change becomes larger and larger in the future, there is a risk that problems such as the inability to secure turbine extraction steam during rapid load reduction may occur. That is, as shown in FIG. 2A,
The deaerator characteristic during normal load reduction is the bleed point pressure P ₁
The deaerator internal pressure P ₂ also decreases following the decrease in , and therefore, there is no problem because the extracted steam amount F is secured. However, if the load is rapidly reduced as shown in Figure 2B, the deaerator internal pressure _P2 will no longer be able to follow the bleed point pressure _P1 , for example at about 10% of the time. The deaerator internal pressure _P2 becomes higher than the extraction point pressure _P1 , the check valve 9 closes, and the extraction steam amount F becomes zero.

As mentioned above, in the case of a rapid load reduction that is expected in the future, it will no longer be possible to secure bleed steam, resulting in a decline in the degassing performance of the deaerator. In addition, when the differential pressure between the deaerator internal pressure P ₂ and the bleed point pressure P ₁ is small, the self-evaporation phenomenon of saturated water in the deaerator may be rapid, the response of the check valve may be slow, and the operation of the check valve may be slow. If there is a problem with the
This causes the self-evaporated steam generated in the deaerator to flow back into the steam turbine. Such a phenomenon may lead to a decrease in degassing performance and a very serious accident in the operation of the power plant.

An object of the present invention is to provide a deaerator pressure control method and a control device thereof, which enable highly reliable deaerator operation that can always ensure extracted steam even during rapid load reduction.

The feature of the deaerator pressure control method according to the present invention is that part of the water held in the deaerator is sent to a device having a pressure lower than the pressure in the deaerator to remove water from the steam turbine. By reducing the ratio of the amount of extracted steam to the amount of condensate inflow from the low pressure feed water heater,
The purpose is to lower the temperature of the water held in the deaerator to control the pressure in the deaerator to always be lower than the pressure of the extracted steam, thereby ensuring the extracted steam.

Further, the pressure control device for a deaerator according to the present invention includes a drain pipe that sends a part of the water held in the deaerator to a device having a pressure lower than the pressure inside the deaerator, and a drain pipe provided in the drain pipe. The present invention is characterized in that it includes a drain water amount adjusting valve, and a valve control device that controls the drain water amount adjusting valve based on a deviation between the steam pressure in the deaerator and the bleed steam pressure.

The details of the present invention will be explained below with reference to embodiments shown in the drawings. 3 and 4 show an embodiment of the present invention, and the same reference numerals as in FIG. 1 indicate those having the same functions. In this embodiment, a drain pipe 18 is provided to send a part of the water held in the deaerator 1 to the condenser 5, which is one of the devices with a pressure lower than the internal pressure of the deaerator. In addition to providing a drain water amount regulating valve 17, a valve control device 19 is provided that controls the drain water amount regulating valve 17 based on the deviation between the pressure of extracted steam and the steam pressure in the deaerator, and as shown in FIG. 2B, the turbine extracted pressure is adjusted. Before P ₁ falls below the deaerator internal pressure P ₂ , open the drain water flow adjustment valve 17 and drain the drain pipe 1.
By sending a part of the water held in the deaerator 1 into the condenser 5 through 8, the amount of condensate flowing from the low-pressure feed water heater 3 to the deaerator 1 through the condensate pipe 10 is increased. The deaerator 1 is controlled so that the internal pressure of the deaerator 1 is always lower than the bleed steam pressure by reducing the ratio of the bleed steam amount to the condensate inflow amount.

In this example, when calculating the deviation between the pressure of the extracted steam and the steam pressure inside the deaerator 1, we took into consideration the temperature distribution that occurs in the water held in the deaerator, and calculated the difference between the pressure inside the deaerator 1. As a safety evaluation, the temperature of the water held in the water storage tank of the deaerator 1 is measured by the temperature detector 21.
As shown in FIG.
1 is converted into pressure by a vapor pressure calculator 22. Further, a pressure detector 20 is provided to detect the pressure on the upstream side of the check valve 9 in the bleed steam piping 8 to determine the bleed steam pressure.

In order to determine the pressure inside the deaerator 1, a pressure detector 29 may be installed to directly determine the pressure as shown in FIG.
The vapor pressure calculator 22 in the illustrated example becomes unnecessary.

In addition, in the examples shown in Figures 4 and 5, the extraction steam pressure
In order to open the drain water amount adjustment valve 17 when the deviation between P ₁ and the deaerator internal pressure P ₂ is below a certain reference level, the standard deviation ΔP is set with the deviation setting device 23, and the adder 24, 25, P ₂ +ΔP−P ₁ =ΔP
−(P ₁ −P ₂ )=P _A is calculated, and when the value of P _A is positive, the controller 28 controls the drain water amount adjustment valve 17.
A signal is generated to open the valve at an opening degree corresponding to the value of P _A.

In addition, in the examples shown in FIGS. 4 and 5, the controller 2
A switch 26 such as a relay is provided on the input side of the controller 28 so that an operation signal can be obtained from the controller 28. ), the switch 26 is turned on and the P _A signal is sent to the controller 28.
On the other hand, when the load is increasing (when the load reduction rate 27 is negative), the switch 26 is turned off.

That is, in this example, the drain water flow adjustment valve 17 opens only when the pressure deviation is below a certain level and the load is decreasing, and the drain water flow adjustment valve 17 is closed when the pressure deviation is above a certain level or the load is increasing. That's how I do it.

FIG. 6 shows another embodiment of the present invention, in which a detector 30 detects the valve opening degree or torque of the check valve 9.
is provided to obtain a signal corresponding to the deviation signal of P ₁ −P ₂ , and this signal and the set value ΔP from the deviation setter 31 are input to the adder 32 to obtain the same signal of P _A as described above. This is what I did. According to this embodiment, there is an advantage that the configuration of the control device is simplified.

As described above, in the present invention, a part of the water held in the deaerator is sent to a device having a pressure lower than the pressure in the deaerator to increase the amount of steam extracted from the steam turbine and the low-pressure water supply. By reducing the ratio to the condensate inflow from the heater, the temperature of the water held in the deaerator is lowered and the steam pressure in the deaerator is always lower than the pressure of the bleed steam. It becomes possible to operate the deaerator so that steam is always available. Moreover, this makes it possible to prevent the aforementioned self-evaporated steam of the water held in the deaerator from flowing into the steam turbine, making it possible to operate the steam power plant in a highly reliable and stable manner.

[Brief explanation of the drawing]

Figure 1 is a system diagram around a deaerator in a conventional steam power plant, Figures 2A and B are explanatory diagrams of the characteristics of the deaerator when the load is reduced, and Figure 3 shows an embodiment of the present invention. The system diagrams around the deaerator, FIGS. 4 to 6, are block diagrams showing specific examples of the control device according to the present invention. DESCRIPTION OF SYMBOLS 1... Deaerator, 2... Steam turbine, 3... Low pressure feed water heater, 5... Condenser, 7... Water feed pump, 8... Steam extraction piping, 9... Check valve, 10...
...Condensate piping, 17...Drain water flow adjustment valve, 18...
...Drain piping, 19...Valve control device, 20, 29
...Pressure detector, 21...Temperature sensor, 22...
Steam pressure calculator, 23, 31... Deviation setting device, 26
...Switch, 30...Detector.

Claims (1)

[Claims] 1. (a) Installed in the water supply system of a steam power generation plant,
(b) a water level detector; (c) a condensate flow rate adjustment valve that receives the output signal of the water level detector to open and close the condensate flow rate control valve; (d) the condensate flow rate adjustment valve. Condensate is introduced from the low pressure feed water heater through the
(E) Equipped with a drain pipe that introduces the drain of the high-pressure feed water heater, (F) Equipped with an extracted steam pipe that introduces the extracted steam from the steam turbine via a check valve, and (G) Pumps the retained water into the water supply pump. In a deaerator configured to be sent to a high-pressure side water supply system by a deaerator, a part of the water held in the deaerator is sent to a device having a pressure lower than the pressure in the deaerator, and the water is sent to the steam turbine. By reducing the ratio of the amount of steam extracted from the bleed water heater to the amount of condensate flowing in from the low-pressure feed water heater, the temperature of the water held in the deaerator is lowered so that the pressure of the water in the deaerator is lower than the pressure of the bleed steam. A deaerator pressure control method characterized by controlling the pressure so that it is always low. 2 (a) Installed in the water supply system of a steam power plant,
(b) a water level detector; (c) a condensate flow rate adjustment valve that receives the output signal of the water level detector to open and close the condensate flow rate control valve; (d) the condensate flow rate adjustment valve. Condensate is introduced from the low pressure feed water heater through the
(E) Equipped with a drain pipe that introduces the drain of the high-pressure feed water heater, (F) Equipped with an extracted steam pipe that introduces the extracted steam from the steam turbine via a check valve, and (G) Pumps the retained water into the water supply pump. In a deaerator structured to be sent to a high-pressure side water supply system by A deaerator comprising: a drain water volume adjustment valve provided in a drain pipe; and a valve control device that controls the drain water volume adjustment valve based on a deviation between the steam pressure inside the deaerator and the turbine extraction steam pressure. pressure control device. 3. Pressure control of a deaerator according to claim 2, characterized in that the valve control device is provided with a switch that generates an operation signal for the drain water flow adjustment valve only when the load of the steam turbine is reduced. Device. 4. As a means for detecting the steam pressure inside the deaerator, a temperature detector that detects the temperature of water held in the deaerator, and a steam pressure calculator that converts a temperature signal that is the output of the temperature detector into a steam pressure signal. 3. A pressure control device for a deaerator according to claim 2, comprising: 5. Deaeration according to claim 2, characterized in that the means for determining the deviation includes a detector that detects the opening degree or torque of a check valve provided in the steam turbine extraction steam flow path. Pressure control device for the vessel. 6 The valve control device is equipped with a deviation setting device for setting the level of the deviation, and sends a signal to open the drain water flow control valve when the deviation becomes equal to or less than a set value set by the deviation setting device. Claim 2 is characterized in that it is configured to cause
Pressure control device for the deaerator described in Section 1. 7. The deaerator pressure control device according to claim 2, wherein the device is a condenser.