JPH0336406A - Control of water supply to boiler - Google Patents

Abstract

PURPOSE:To supply steam from a boiler stably by stopping a burner when the water level is not recovered to a set water level when a set time has passed after receiving from an upper limit water level detector a signal that water level is not yet detected and when a signal is received from a lower limit water level detector that the water level is not detected. CONSTITUTION:The water level in a water level control box 2 is raised by the operation of a supply water pump 7, and an receiving a water level detection signal from an upper limit water level detector 3 the supply water pump 7 is stopped by a stop signal from a supply water control device 5. After the signal from the upper limit water level detector 3 that water level is not detected due to a fall in the water level by evaporation is received, an operation signal for the supply water pump 7 is outputted to maintain the water level of a boiler 1 after a set time has passed which brings the water level of a boiler 1 to the lower limit of the water level control width of the boiler 1. If, after receiving the signal that water level is not detected, the water level of the boiler 1 does not return up to the water level that is detected by the upper limit water level detector 3 after a set time has elapsed in which the boiler body of the boiler 1 comes in the range of the danger of excess heating by evaporation and a signal from a lower limit water level detector 4 that water level is not detected is issued, a signal is issued to a fuel control valve 9 to prevent overheating of the boiler body.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method of controlling feed water in a steam generator such as a boiler, and in particular, to improving the safety and accuracy of water feed control when the water level of the boiler is low. It is something that

(Prior Art) Boilers are used to generate power for steam engines in thermal power plants, ships, general heaters, etc., and it is also well known that boilers are devices that heat water and convert it into steam.

What is important in boiler operation management is water supply control.

An example of a conventional water supply control method is to place a water level detector in a water level control box installed in communication with the water section of the boiler, and use the detection signal obtained from this water level detector to control the water supply. We are conducting comprehensive water supply management.

The above water supply control methods include the off-delay method, the on-delay method, and the on-delay method.
A delay method and a three-position method have been implemented in the past, but each had its advantages and disadvantages.

In other words, in the off-delay system, it is difficult to maintain constant dryness due to various reasons, and overheating of the boiler body cannot be prevented, and in the on-delay system, overheating of the boiler body due to abnormally low water levels cannot be prevented. In addition, although the 3-position system allows reliable water level control, the control circuit becomes complicated and the cost of the entire water supply control device increases.

Therefore, the present applicant has developed a water supply control system to prevent the above-mentioned problems of maintaining constant dryness and overheating of the can body by appropriately controlling the water level of the boiler using two water level detectors. I proposed it earlier (Actual situation: 1984-12352)
No. 2).

In the above precedent example, as shown in the second factor, the upper part is the boiler (1
), and a water level control box (2) whose lower part communicates with the water section of the boiler (1), and a water level control box (2) that is installed inside the water level control box (2) and which communicates with the water section of the boiler (1). An upper limit water level detector (3) for detecting the water level and an upper limit water level detector (3) similarly installed in the water level control box (2)
The configuration includes a lower limit water level detector (4) that detects the water level of the lower boiler (1), and for control operations, the water supply pump (7) receives a water level detection signal from the upper limit water level detector (3). It outputs a stop signal, and after receiving the water level non-detection signal, outputs a water pump (7) operating signal after a set time t1 has elapsed such that the water level of the boiler (1) becomes the lower limit of the water level control width due to evaporation, and then outputs a water pump (7) operation signal. The set time t when the boiler (1) reaches the dangerous overheating range due to evaporation after receiving the undetected signal! If the water level of the boiler (1) does not return to the water level of the upper limit water level detector (3) after the elapse of time, a combustion device stop signal is output, and a combustion device stop signal is output based on the water level not detected signal from the lower limit water level detector (4). The water supply is controlled by a controller (5) so as to output water.

(Problem to be solved by the invention) As mentioned above, in the water supply control in the conventional example, the third
As shown in the explanatory diagram of the figure, the water level of the boiler (1) becomes lower than the detection limit width of the lower limit water level detector (4), and after receiving the water level non-detection signal, it returns to the set water level after the set time t4 (seconds) has elapsed. If not, the water level will be low, and the water level in the boiler (1) will be lower than the upper limit water level detector (3) detection limit width, and if the water level does not return to the set level after the set time tz (seconds) has elapsed, the water level will be low. Standards were set for each water level, and based on these set standards, combustion equipment was operated and shut down when the water level was low.

According to the water supply control described above, since the operation of starting and stopping the combustion equipment is performed based on two setting standards, there is a technical advantage in that the overheating of the can of the boiler (1) can be reliably and safely prevented. Ta.

However, when the boiler (1) is in operation, accidents sometimes occur, such as a sudden increase in load or a decrease in the capacity of the water supply pump (1).

That is, as shown in the phenomenon explanatory diagram of Fig. 3, the boiler (1)
The water level may be maintained at an intermediate position A between the two upper and lower limit water level detectors (3) and (4).

In the above case, the water level is higher than the lower limit water level detection H (4), but if it does not return to the set water level even after the set time tz (seconds) in that state has elapsed, the water level is determined to be low, and the combustion A device stop signal was output, and combustion in the boiler (1) was controlled to stop.

However, the water level at the above-mentioned A position does not fall within the danger zone of overripe cans in the boiler (1), and if a control circuit is adopted that stops the combustion equipment each time, the combustion The number of stoppages becomes frequent, and as a result, a serious problem remains that a stable supply of steam cannot be provided.

On the other hand, as a countermeasure against the decrease in the capacity of the water supply pump (7), when the capacity of the water supply pump (7) decreases, there is a control that cancels the operation/stop control operation of the combustion device based on the detection signal of the upper limit water level detector (3). However, in this case, it is difficult to set the criteria for determining the decrease in the capacity of the water supply pump (7).
) When the water level becomes lower than the lower limit water level detector (4) due to a decrease in the capacity of the lower limit water level detector (4), if the lower limit water level detector (4) has poor insulation, it will make a false detection and the boiler (1) will run dry. The present invention, which has a problem, was invented in view of the above-mentioned point of view, and it is difficult to accurately control the shutdown of the combustion equipment when the water level in the boiler is low and does not fall into the danger zone of overripe cans. It is an object of the present invention to provide a boiler water supply control method that can be performed safely.

(Means for solving !II) In order to solve the above problems, the present invention employs the following means.

That is, as a boiler water supply control method, the water supply pump is started and stopped by output signals from upper and lower limit water level detectors inserted in a water level control box that communicates with the steam section of the boiler and the water surface. , the set time after receiving the water level undetected signal from the upper limit water level detector 1. The operation of starting the water supply pump after the elapsed time, the operation of stopping the water supply pump after receiving the water level detection signal from the upper limit water level detector, and the operation of stopping the water supply pump after receiving the water level non-detection signal from the upper limit water level detector, The present invention is characterized in that it includes an operation of stopping the combustion device when the water level does not return to the set water level and a water level non-detection signal is transmitted from the lower limit water level detector.

(Function) According to the above-mentioned water supply control method of the present invention, when the water level of the boiler is low and does not fall within the danger zone of water pipe overmaturity, the operation for controlling the stoppage of the combustion device can be performed accurately and safely.

Therefore, since stop control of the combustion device is not performed unnecessarily, steam can be stably supplied from the boiler.

Furthermore, when the water level is maintained at an intermediate position between the upper and lower limit water level detectors when the load suddenly increases or when the capacity of the water supply pump decreases, that is, the water level is below the water level detection end of the upper limit water level detector and the water level is lower than the water level detected by the lower limit water level detector. If the water is located above the edge, it is possible to quickly and accurately determine whether the capacity of the water supply pump has decreased or the insulation of the lower limit water level detector is defective. The result is economical.

Although the present invention is based on an embodiment in which an upper and lower limit water level detector is applied, the same applies to a case in which an underground lower limit water level detector is applied.

(Example) Hereinafter, an example of the water supply control method of the present invention will be described in detail based on FIG.

The code (1) in the figure is a boiler, and the code (2) is a water level control box attached to the boiler (1), with the upper part communicating with the boiler (1) and the lower part communicating with the water surface of the boiler (1). be.

In addition, the water level of the water level control box <2) above is the same as that of the boiler (
1) Can you relate it to display the water level? 11 has been done.

Reference numeral (3) denotes an upper limit water level detector, which is inserted into the water level control box (2) and has a circuit configuration so as to send a water level detection signal to the water supply $111 device (5), which will be described later. The water level detection position is set at the highest position where the dryness of the steam is best maintained.

Reference numeral (4) denotes a lower limit water level detector, which is inserted into the water level control box (2) and is connected to the water supply control device (described later).
5) A circuit TL is installed to transmit a water level detection signal in the same way as the upper limit water level detector (3), and the water level detection position is set at the lowest water level position to prevent overheating of the can body. .

Symbol (5) is a water supply control device, which detects the upper limit water level H(
3), outputs a stop signal for the water supply pump (7), and after a set time elapses after receiving the water level non-detection signal from the upper limit water level detection (3), the water supply pump (7) The operating signal is output, and the water level detection signal is not received until the set time t8 elapses, and the lower limit water level detector (
4) When a water level undetected signal is sent from the fuel control valve (
The circuit configuration is such that the opening/closing signal is output to 9).

In addition, the above setting time 1. is set based on the time required for the water level in the boiler (1) to reach the lower limit of the standard flu width during normal operation due to evaporation after receiving the water level non-detection signal from the upper limit water level detector (3), and The set time t8 is set based on the time required for the water level of the boiler (1) to reach the dangerous overheating range due to evaporation after receiving the water level undetected signal from the upper limit water level detector (3). , the above-mentioned set times t+ and tx are determined by the specifications of the boiler (1), such as its evaporation capacity, the amount of water it retains, and the structure of the boiler (1).

Reference numeral (8) is a check valve provided in the water supply line, which prevents canned water from flowing back into the water supply line due to the internal pressure of the boiler (1) when the water supply pump (7) is stopped.

The water supply pump (7) receives 0N from the water supply control device.
- Activated by OFF signal.

Reference numeral OΦ is a pressure sensor connected to the boiler (1), and is provided so that the load pressure within the boiler (1) is detected and the detection signal is received by the combustion controller.

The symbol GD is a blow valve, which is used when blowing canned water to remove impurities accumulated in the boiler (1) or to prevent canned water from concentrating.

Reference numeral Q21 is a steam supply line provided at the top of the boiler (1).

The example of the device used in the embodiment of the water supply control method of the present invention is as described above, but the control standard for stopping combustion when the water level control box (2) is low when performing water supply control is the upper limit water level detector ( Water level B (3) has fallen below the detection limit width of the lower limit water level detector (4), has not returned to the set water level even after the set time t2 has elapsed since receiving the undetectable signal, and has fallen below the detection limit width of the lower limit water level detector (4). (See Figure 3) was set as the standard.

However, the water level A in the figure, in other words, the upper limit water level detector (
3), and the water level is below the detection end of the lower limit water level detector (4).
), but in this case, it is not the low water level setting standard range, but if the second condition is repeated several times, the capacity of the water supply pump (7) will decrease or the lower limit water level Since there is a possibility that the detector (4) has poor insulation, etc., in this case, an alarm signal is sent from an alarm device provided in the alarm circuit (not shown).

The capacity of the water supply pump (7) has decreased or the lower limit water level detector (4)
) was determined as follows: That is, ■ When the water supply pump (7) is forcibly stopped and burned for a certain period of time, if a water level detection signal is output from the lower limit water level detector (4), the lower limit water level detector (4) It is determined that the insulation is defective.

■When the water supply pump (7) is forcibly stopped and burned for a certain period of time, if a water level undetected signal is output from the lower limit water level detector (4), it is determined that the capacity of the water supply pump (7) has decreased. do.

■When the water supply pump (7) is forcibly stopped and the canned water is blown for a certain period of time or a certain amount.If a water level detection signal is output from the lower limit water level detector (4), the lower limit water level is detected. It is determined that the insulation of the device (4) is defective.

■When the water supply pump (7) is forcibly stopped and the canned water is blown for a certain period of time or a certain amount.If a water level undetected signal is output from the lower limit water level detector (4), the water supply pump (7) is 7) is determined to be a decline in ability.

We have set criteria for this.

The configuration of the present invention is as described above, but to explain an example of its operation, when the boiler (1) is operated, the feed water pump (7) and the combustion device are operated to generate steam.

Water level control box (2) due to operation of water supply pump (7)
When the water level within the tank rises and a water level detection signal is received from the upper limit water level detector (3), the water supply pump (7) is stopped by a stop signal from the water supply control device w (5).

Then, the water level decreases due to evaporation and the upper limit water level detector (
After receiving the water level non-detection signal from the boiler (1), an operation signal for the water supply pump (7) is output after a set time has elapsed such that the water level of the boiler (1) reaches the lower limit of the water level control width, and the operation signal for the water supply pump (7) is output.
) to maintain the water level in the boiler (1) at the set water level.

In addition, after receiving the water level non-detection signal, the boiler (1
) The water level in the boiler (1) does not return to the water level of the upper limit water level detector (3) after the elapse of the set time t2 in which the can overheating danger zone occurs, and a water level not detected signal is sent from the lower limit water level detector (4). When this occurs, a signal is output to the fuel control valve (9) to prevent the can body from overheating.

In this embodiment, the control criteria for stopping combustion when the water level of the water level control box (2) is low and the criteria for determining whether there is a decrease in the capacity of the water supply pump (7) or poor insulation of the lower limit water level detector (4) are as follows: Since the setting is made as described above, when the water level is low, for example, the set time t! falls below the lower limit of the detection limit width of the upper limit water level detector (3) and the water level is not detected. The water level does not return to the set level even after the elapsed time, and the water level is at the lower limit water level detector (4)
If the water level B (see Figure 3) is below the lower limit of the detection limit width, a combustion stop signal is output to prevent the can body from overheating, and the water level A (see Figure 3) is ), and if this continues several times, a judgment is made to determine whether the capacity of the water supply pump (6) has decreased or the insulation of the lower limit water level detector (4) is defective, based on the above-mentioned criteria. Treatment is carried out according to each condition.

(Effects of the Invention) According to the above-mentioned water supply control method according to the present invention, the combustion equipment can be accurately and safely controlled to stop when the water level in the boiler is low enough not to fall into the dangerous range of overripe cans.

Therefore, stop control of the combustion device is not performed unnecessarily, so that steam can be stably supplied from the boiler.

Furthermore, when the water level is maintained at an intermediate position between the upper and lower limit water level detectors when the load suddenly increases or the capacity of the water supply pump decreases, that is, when the water level is below the water level detection end of the upper limit water level detector and the water level is not detected by the lower limit water level detector. When it is above the edge,
It is possible to quickly and accurately determine whether the capacity of the water supply pump has decreased or the insulation of the lower limit water level detector is defective, which makes maintenance management of each device effective and economical. has.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram for explaining an embodiment of the water supply 91m method of the present invention, Fig. 2 is an explanatory diagram showing a conventional water supply control method,
FIG. 3 is an explanatory diagram for explaining a situation where the boiler water level is low. The names of the codes are as follows. (1) Boiler, (2) Water level control box, (3) Upper limit water level detector, (4) Lower limit water level detector, (5) Water supply control device, (6) Fuel supply pump, (7) Water supply pump, (8) Check valve, (9) Fuel control valve, 0■ Boiler pressure detection sensor, 00... blow valve, tm-.
- steam supply line,

Claims (1)

[Claims] The water supply pump is operated and stopped by the output signals from the upper and lower limit water level detectors installed in the water level control box that communicates with the steam and water parts of the boiler. The operation of operating the water supply pump after the set time t_1 has elapsed after receiving the water level not detected signal, the operation of stopping the water supply pump after receiving the water level detection signal from the upper limit water level detector, and the operation of stopping the water level not detected signal from the upper limit water level detector. Water supply to a boiler characterized by including an operation of stopping a combustion device when the water level does not return to the set level even after a set time t_2 has elapsed after reception, and a water level non-detection signal is transmitted from the lower limit water level detector. Control method.