JPS63223489A - Condensate control system - Google Patents

Abstract

PURPOSE:To enable superior controlling characteristics to be attained even in a low speed range by a method wherein a condensate recirculation valve 4 is forcedly and fully opened to increase the flow rate of condensate and the discharging pressure of a low pressure condensate pump is decreased. CONSTITUTION:Condensate accumulated in a condenser 1 is increased in its pressure by a low pressure condensate pump 2, a high pressure condensate pump 5 and a turbine driven water supplying pump 6 or an electric motor driven water supplying pump 7 and then fed to a stem generating unit 8. A condensate control unit 9 is operated such that a condensate flow rate adjusting meter 10 normally inputs a condensate flow rate signal from a condensate flow rate sensor 3, a control signal is converted by an electronuematic converter 11 from an electrical signal into an air signal to adjust the degree of opening of the condensate recirculation valve 4. However, when a changing-over signal 12 between the electric motor driven water supplying pump 7 and the turbine driven water supplying pump 6 is inputted, the condensate flow rate adjusting meter 10 may output a signal for fully opening and condensate recirculation valve 4. Then, correspondingly the flow rate of condensate is increased and a discharging output from a low pressure condensate pump 2 is decreased. A reduction in discharging pressure of the low pressure condensate pump 2 causes a suction pressure of the turbine driven water supplying pump 6 to be decreased and thereby the number of revolution of the turbine driven water supplying pump 6 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a condensate control device that adjusts the flow rate of condensate by the opening degree of a condensate recirculation valve in a nuclear or thermal power plant.

(Prior art) In a nuclear power or thermal power plant, as shown in FIG. Water supply systems are common. In this system, when the water supply to the steam generator 8 is at a low flow rate, such as when the plant is started up, the condensate recirculation valve 4 is opened to ensure the minimum flow of the low-pressure condensate pump 2 is above the specified value. A part of the condensate is returned to the condensate unit 1.

The opening degree of the condensate recirculation valve 4 is adjusted by the condensate control device 9 so that the condensate flow rate detected by the condensate flow rate detector 3 is equal to or higher than the minimum flow regulation value as shown in FIG.

(Problems to be Solved by the Invention) The water supply pump controls the water supply with a discharge water supply flow rate control valve. There is a motor-driven water supply pump 7 and a turbine-driven water supply pump 6 that controls water supply by changing the rotation speed. Generally, the motor-driven water supply pump 7 is used when the plant is first started up, and after the plant is installed. The operation method is to switch to a turbine-driven water supply pump 6.

Since the control range of the turbine-driven water pump 6 is determined so as to avoid the critical rotational speed of the turbine serving as the prime mover, there is a problem in that controllability deteriorates at low loads. In contrast, when the turbine-driven water supply pump 6 is started for the first time, the rotation speed of the turbine-driven water supply pump 6 is increased by opening the minimum flow valve of the discharge method, thereby increasing the margin for the critical rotation speed. However, since the rotation speed of the turbine-driven water supply pump 6 becomes low at low loads when the loss in the condensate system is small, it is necessary to further increase the rotation speed.

In addition, in recent nuclear couplers, from the perspective of cost reduction, it is being considered to reduce the conventionally two motor-driven water supply pumps 7 to one; however, in this case, the motor-driven water supply pump 7 may trip. In order to suppress the drop in the reactor water level within a range that does not cause problems, it is necessary to switch to the turbine-driven feed water pump 6 at a lower load than before, which also causes the rotation speed of the turbine-driven water pump 6 to decrease. , the margin for the critical rotational speed becomes even smaller, and problems with controllability also occur.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a condensate control device with good controllability even in a low speed range.

[Structure of the invention]

(Means for solving the problem) In order to solve such problems, it is necessary to increase the rotation speed of the turbine-driven water supply pump 6. One example of this is to transiently lower the water pump suction pressure when switching from the turbine-driven water pump 6 to the turbine-driven water pump 6. When the water supply pump suction pressure decreases, the difference between the water supply pump discharge pressure and the water supply pump discharge pressure increases, so the pump lift corresponding to that amount is required. Since the relationship between the pump head H and the pump rotation speed n is II cc n'' - CJ), the rotation speed must be increased in order to increase the head of the turbine-driven water supply pump 6.

In the present invention, as a method for lowering the feedwater pump suction pressure, the condensate recirculation valve 4 is forcibly fully opened to increase the condensate flow rate and lower the low-pressure condensate pump discharge pressure. Flow rate of low pressure condensate pump 2 and 'u
The relationship with stage II is as shown in FIG. 4, and as the flow rate increases, the head decreases, that is, the discharge pressure of the low pressure condensate pump 2 decreases. As a result, the water pump suction pressure decreases, and the rotational speed of the turbine-driven water pump 6 increases.

(Function) In the present invention, when the turbine-driven water supply pump 6 is switched, the condensate control device 9 sends a signal to forcibly fully open the condensate recirculation valve 4, thereby increasing the condensate flow rate, thereby reducing the low pressure. Decrease the discharge pressure of the condensate pump 2.

This decrease in the discharge pressure of the low-pressure condensate pump 2 causes a decrease in the suction pressure of the turbine-driven water supply pump 6, thereby increasing the rotation speed of the turbine-driven water supply pump 6, thereby providing a margin for the critical rotation speed in the low range. Can be done.

(Example) FIG. 1 shows a system diagram of a power plant to which the present invention is applied.

The condensate accumulated in the condenser 1 is pressurized by a lowering condensate pump 2, a high-pressure condensate pump 5, and a turbine-driven water supply pump 6 or an electric motor-driven water supply pump 7, and is sent to a steam generator 8. In the condensate control device 9, a condensate flow rate controller 10 normally inputs the condensate flow rate signal from the condensate flow rate detector 3, and an electro-pneumatic converter 11 converts the control signal from an electric signal to an air signal. The opening degree of the condensate recirculation valve 4 is adjusted by.

However, when the switching signal 12 between the motor-driven water supply pump 7 and the turbine-driven water supply pump 6 is input, the condensate flow rate controller 10 outputs a signal that fully opens the condensate recirculation valve 4.

When the feed water pump switching signal 12 is input as described above, the condensate recirculation valve 4 is fully opened. Then, the total condensate flow rate increases, and thereby the discharge pressure of the low-pressure condensate pump 2 decreases.

This decrease in the discharge pressure of the low-pressure condensate pump 2 results in a decrease in the suction pressure of the turbine-driven water supply pump 6, thereby increasing the rotational speed of the turbine-driven water supply pump 6.

By applying the present invention, the rotational speed at the time of startup of the turbine-driven water supply pump can have a large margin with respect to the critical rotational speed in the low range.

〔Effect of the invention〕

As described above, by applying the present invention, even in a low load range such as when starting a turbine-driven water supply pump, the rotational speed has a large margin with respect to the critical rotational speed, and stable control becomes possible.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a power generation plant to which the present invention is applied, Figure 2 is a system diagram of a conventional power generation plant, and Figure 3 shows the relationship between the opening degree of the condensate recirculation valve and the flow rate of water supply in the conventional power generation plant. FIG. 4 is a graph showing the relationship between the condensate flow rate and the low-pressure condensate pump discharge pressure. 1... Condenser 2... Low pressure condensate pump 3... Condensate flow rate detector 4... Condensate recirculation valve 5... High pressure condensate pump 6... Turbine driven water supply pump 7 ...Electric motor driven water supply pump 8...Steam generator 9...Condensate control device 10...Condensate flow rate controller 11...Electro-pneumatic converter 12.
...Water pump switching signal representative Patent attorney Nori Chika
Yudo Hirofumi Mitsumata 8 = Figure 1/l Figure 2

Claims (1)

[Claims] A condensate recirculation valve installed in a system where a part of the condensate is branched from the discharge of a low-pressure condensate pump that boosts the pressure of condensate from the condenser and returned to the condenser is controlled by the condensate flow rate signal. In a power generation plant having a condensate control device, the condensate recirculation valve is forced when switching between a motor-driven feed water pump and a turbine-driven feed water pump that are downstream of the low-pressure condensate pump and supply water to the steam generator. A condensate control device that is characterized by fully opening the water at a certain time and fully closing it after switching is completed.