JPH03260503A - Drain water level controller for water supplying and heating device - Google Patents

Abstract

PURPOSE:To prevent an over-shooting or an under-shooting of a water level and perform a stable water level control for a water supplying and heating pipe by a method wherein a drain water level controller is provided for calculating a degree of opening of a water level adjusting valve corresponding to an increased or decreased amount of flow rate in which a drain flow rate and a flow rate of extracted steam are added and a control over a degree of opening of the water level adjusting valve is corrected in advance on the basis of the calculated value. CONSTITUTION:In this type of drain water level controller, even if the flow rare of drain water from the first water supplying heater 1 flowing into the second water supplying heater 2 or the flow rate of extracted steam flowing into the second water supplying heater 2 is rapidly varied, a degree of opening of a water level adjusting valve 5 corresponding to an increased or decreased amount of the flow rate of drain or the flow rate of extracted steam into the second water supplying heater 2 is calculated by the drain water level controller 20, this is corrected with the calculated value prior to an output signal from a normal water level sensor 6, thereby opening or closing of the water level adjusting valve 5 is controlled and then a stable drain water level control can be carried out by preventing fluctuation of the drain water level within the second water supplying heater 2.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a drain water level control device for a feed water heater used as a heat exchanger in thermal or nuclear power plants, etc. This invention relates to an improvement in a drain water level control device for a feed water heater that controls the drain water level to be maintained at a normal water level even if the drain flow rate and the extracted steam flow rate simultaneously change suddenly when the load suddenly changes.

(Prior art) Generally speaking, power generation facilities, especially steam turbine facilities, are
A so-called regeneration cycle is used in which feed water is preheated or heated before being sent to a steam generator such as a boiler. In using this regeneration cycle, high-pressure, high-temperature steam drawn from a steam turbine is used as a heating source. There is.

In addition, a feed water heater is used as a device to preheat or heat condensate/feed water.
Heat exchangers are commonly used in which condensate and feed water pass through heat transfer tubes, and steam passes outside the tubes.

As shown in Fig. 2, this type of feed water heater is arranged in multiple stages in series, and the condensate and feed water are supplied to the third feed water heater 3, the second feed water heater 2, and the first feed water heater. While passing through the feedwater heater 1, the water is preheated and heated to raise its temperature, and the heating source required for raising the temperature is steam extracted from a turbine for each of the feedwater heaters 1 to 3. After heat exchange, the extracted steam becomes drain water, but since it still retains heat, it is sent to the lower feed water heater and used as part of the heating source.

By the way, as mentioned above, since extracted steam and drain water are sent to the feed water heater, unless the drain water level in the heater is controlled, efficient heat exchange will not be possible. , each feedwater heater is typically provided with a drain level control device.

To explain this drain water level control device with respect to the first feed water heater 1 (the same applies to other feed water heaters), there is a drain pipe 4 between the first feed water heater 1 and the second feed water heater 2. A water level control valve 5 is interposed in this drain pipe 4, and a water level detector 6 is installed in the feed water heater 4, and this water level detector 6 and the above control valve 5 are connected to A total of 7 are connected to each other.

A standard water level setting signal is input in advance to this water level controller 7, and the standard water level (N W L mm) is set as a set value, and the output of the water level detector 6 is transmitted to this water level controller 7. The first feed water is heated by the output signal from the control calculation (PID calculation) in the water level controller 7 based on the deviation between the water level signal from the water level detector 6 and the set value (N W L mm ) of the water level controller 7. It was configured to control the opening degree of a water level control valve 5 interposed in a drain pipe 4 between the container 1 and the second feed water heater 2.

(Problem to be Solved by the Invention) However, depending on the circumstances of the plant, there are cases where the operating load suddenly or suddenly decreases, and in this case, the flow rate of extracted steam to the feed water heater changes suddenly, and the flow rate of these extracted steam Since the water becomes drain water, the flow rate of the drain flowing into the lower feed water heater also changes suddenly. As a result, if only the opening degree of the water level control valve 5 is controlled based on the deviation between the water level signal of the water level detector 6 and the water level setting value of the water level controller 7 as in the conventional example, the change in the amount of inflow drain is large. However, there were problems in that water level control had poor followability and overshoot or undershoot of the water level could occur.

In some cases, the water level may become hunting, and in the worst case, the water level may become divergent and flow back to the turbine through the drain pipe that is sending the extracted steam, causing a supercooling phenomenon (
This may lead to destructive damage to the turbine, such as water induction.

In view of the above, an object of the present invention is to provide a system that prevents overshoot or undershoot from occurring in the drain water level even if the operating load of the plant suddenly changes.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, a drain water level control device for a feed water heater according to the present invention includes a water level controller that sets a standard water level in the feed water heater, and a water level controller that sets a standard water level. In the drain water level control device for the feed water heater, which controls the opening degree of the water level control valve installed in the drain pipe connecting the feed water heater located at the lower stage based on the signal from the feed water heater, Detecting the drain flow rate and extracted steam flow rate to the system, calculating the valve opening degree of the water level control valve corresponding to the increase/decrease in the total flow rate,
A drain water level controller is provided which corrects the control of the opening degree of the water level control valve in advance based on this calculated value.

(Function) According to the present invention configured as described above, even if the flow rate of condensate flowing into the feed water heating pipe or the flow rate of extracted steam changes due to a change in the load of plant operation, the drain water level controller
The valve opening degree of the water level control valve corresponding to the increase/decrease in these flow rates is first added to the valve opening degree of the water level control valve measured by a normal water level controller for correction. In other words, the water level control valve opens and closes in advance by the amount of valve opening that corresponds to this increase/decrease, and as a result, the drain water level is always kept constant regardless of changes in the drain flow rate or bleed steam flow rate. You can do it like this.

(Example) An embodiment of the present invention will be described below with reference to FIG.

This figure shows a schematic control block diagram of a feed water heater equipped with a drain water level control device according to the present invention, in which a first feed water heater 1, a second feed water heater 2, and a third feed water heater 3 are sequentially installed. The first
A water level control valve 5 is interposed in each drain pipe 4 that connects the feed water heater 1 and the second feed water heater 2 and the second feed water heater 2 and the third feed water heater 3, respectively.

The drain water level control device that controls the drain water level of the second feed water heater 2 will be described below (the same applies to other feed water heaters).

A water level detector 6 for detecting the internal drain water level is installed in the second feed water heater 2.
Drain pipe 4 between feed water heater 2 and third feed water heater 3
A water level regulator 7 that controls the opening degree of the water level regulating valve 5 installed in the water level regulator 7
It is connected to the.

This controller 7 has a standard water level (N W L +
nm) is input in advance as a set value and is always set, and the signal received from the water level detector 6 during plant operation is compared with this water level set value (N W L mm), and the deviation is determined by the water level control valve 5. It is configured to emit a signal that controls the opening degree of the valve.

A drain flow rate detector 8 is provided in the drain pipe 4 that connects the first feed water heater 1 and the second feed water heater 2, and the extracted steam flow rate into the second feed water heater 2 is detected by the extracted steam flow rate detection. It is designed so that it can be detected by the device 9. Furthermore, the drain pipe 4 connecting the second feed water heater 2 and the third feed water heater 3 includes
A valve pressure detector 1 is inserted between the water level control valve 5 installed here.
0 and a post-valve pressure detector 11 are respectively installed,
A temperature detector 12 is provided to detect the temperature of drain water flowing through the drain pipe 4.

The rain detection signals from the drain flow rate detector 8 and the extracted steam flow rate detector 9 are respectively input to the first adder 13 and added there. The output signal from this first adder 13 becomes the total amount of drain water flowing into the second feed water heater 2 and the flow rate of extracted steam, and the valve capacity counting calculator (
Hereinafter, it will be referred to as a CV calculator. ) 14 will be done manually.

On the other hand, the valve pressure detector 10 and the valve rear pressure detector 11
The two image power signals are input to a subtracter 15, where the pressure difference is calculated and inputted to a CV calculator 14, and the output signal from the temperature detector 12 is also input to this CV calculator 14, respectively.

This CV calculator 14 calculates a valve capacity counting formula (Cv calculation formula), which is generally used as a formula for calculating the valve capacity coefficient of a water level control valve, v f (flow rate, drain pressure before and after the valve, drain temperature). Calculations are performed according to the following, and the CV value, which is the valve capacity coefficient, is obtained, and the opening/valve capacity counter (hereinafter referred to as opening CV unit) 1
6 will be man-powered.

During this time, a valve opening (valve lift)-valve capacity count curve (CV convex curve) determined by the diameter and flow rate characteristics of the water level control valve 5 is input into the Cv unit 16 in advance, and the C7 from the Cv calculator 14 is inputted in advance. By inputting the value, a required opening signal of the water level control valve 5 can be obtained.

The required opening signal from the water level control valve 5 is input to the lead/lag compensator 17, thereby controlling the systematic fluid flow, the condensation time of the extracted steam, and the operation delay of the water level control valve 5 for draining the drain. The system is designed to improve the stability of water level control by correcting this.

The output signal from the lead/lag compensator 17 is input to the second adder 18, while the output signal from the water level controller 7 is also input to the second adder 18 and added there. The output signal from this second adder 18 is manually input to the water level control valve 5, and based on this manual signal, the water level control valve 5
This opening is controlled by operating the valve.

Thus, drain water level control is performed to control the operation of the water level control valve 5 by the first adder 13, CV calculator 14, subtracter 5, opening CV device 16, lead/lag compensator 17, and second adder 18. A container 20 is configured.

According to such a drain water level control device, even if the drain flow rate from the first feed water heater 1 flowing into the second feed water heater 2 or the flow rate of extracted steam to the second feed water heater 2 suddenly changes, the drain water level control device The water level controller 20 calculates the valve opening degree of the water level control valve 5 corresponding to the increase/decrease in the drain flow rate or the extracted steam flow rate into the second feed water heater 2, and uses this calculated value to calculate the opening degree of the water level control valve 5 from the normal water level detector 6. By correcting the output signal in advance and controlling the opening/closing of the water level control valve 5 based on this, fluctuations in the drain water level in the second feed water heater 2 can be prevented and stable drain water level control can be performed. .

〔Effect of the invention〕

Since the present invention has the above-described configuration, even if the load changes suddenly due to plant operating conditions, and the amount of drain flowing into the feed water heater or the flow rate of extracted steam changes, the water level control valve will be able to compensate for this increase or decrease. By opening and closing the drain water level controller in advance by the amount of valve opening corresponding to As a result, accidents such as overcooling of the turbine can be prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic control system diagram showing one embodiment of the present invention, and FIG.
The figure is a schematic control system diagram of a conventional example. 1-3... Water supply heater, 4... Drain piping, 5...
・Water level control valve, 6...Water level detector, 7...Water level controller, 8...Drain water amount detector, 9...Bleed steam flow rate detector, 10.11...Pressure detector, 12... Temperature detector, Engineering 3... First adder, 14... C computing unit,
16...Opening degree C device, 17...Lead/lag compensator, 18
...Second adder, 20...Drain water level controller.

Claims (1)

[Claims] A water level controller is installed on the feed water heater to set the standard water level.
In a drain water level control device for a feed water heater that controls the opening degree of a water level control valve installed in a drain pipe connecting the feed water heater located at the lower stage based on a signal from the water level controller, The drain flow rate and the extracted steam flow rate into the feed water heater are detected, the valve opening of the water level control valve is calculated based on the increase/decrease in the total flow rate, and the opening of the water level control valve is adjusted based on this calculated value. A drain water level control device for a feed water heater, comprising a drain water level controller that corrects control in advance.