JP2003090507A - Method of controlling feed water to boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress low water level cutoff of a boiler due to lowering of a water feed pump, in a boiler. SOLUTION: A water level in the boiler 1 and water feed capacity of a water feed pump 3 are monitored and when the water level reaches that at a given water feed starting timing, the water feed pump 3 is operated. When lowering of the water feed capacity is detected, the water feed starting timing is regulated according to lowering of the water feed capacity.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler water supply control method. 2. Description of the Related Art In a recent boiler, conditions inside a can such as a steam pressure and a water level are monitored, and devices such as a combustion device and a feedwater pump are controlled based on the monitoring results of these conditions. Thereby, the automatic operation of the boiler is performed. [0003] For example, in the boiler, water supply control is performed to maintain the water level within a predetermined water level range by controlling the water supply pump based on the monitoring result of the water level. In this water supply control, a low water level cutoff is performed in order to reliably prevent overheating of the boiler can body.
The low water level cutoff means that when the water level falls below the predetermined water level range and reaches a preset minimum water level,
Stopping the combustion device. Therefore, when the low water level cutoff is performed, the supply of steam from the boiler is interrupted. Meanwhile, the water supply pump deteriorates due to continuous use, and the water supply capacity gradually decreases. here,
The water supply capacity is an amount of water that the water supply pump can supply to the boiler for a predetermined unit time (for example, one minute). As described above, when the water supply capacity is reduced, when the water level is rapidly reduced due to the influence of the combustion amount of the combustion device or the load from the steam-using equipment connected to the boiler, the low water level cutoff is performed. May occur. Then, as the deterioration of the water supply pump progresses, the low water level cutoff is likely to occur, and the supply of steam from the boiler is also easily interrupted. Therefore, a predetermined permissible limit is provided for the water supply capacity, and when the water supply capacity reaches the permissible limit, the water supply pump is replaced. [0005] However, in the boiler, continuous supply of steam is also important for operating the steam-using equipment. That is, even if the water supply capacity of the water supply pump is reduced, as long as water supply to the boiler is possible, by suppressing the occurrence of the low water level cutoff, the operation of the boiler is continued, and It is desirable to continue supplying steam. An object of the present invention is to suppress a low water level cutoff of a boiler in a boiler due to a reduction in the capacity of a water supply pump. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 monitors a water level of a boiler and a water supply capacity of a water supply pump. When the water level reaches a predetermined water supply start time, the water supply pump is operated, and when a decrease in the water supply capacity is detected, the water supply start time is adjusted according to the decrease in the water supply capacity. And Next, an embodiment of the present invention will be described. The present invention can be suitably implemented in a boiler, particularly in a steam boiler. [0009] The steam boiler is provided with heating means for feed water in addition to the feed pump. As the heating means, in addition to using a combustion device, an electric heater, etc., an incinerator,
A configuration utilizing heat of exhaust gas from an exhaust gas generation source such as a prime mover can be used. The boiler controls the heating means in accordance with the result of monitoring the steam pressure in the boiler. In the water supply control method of the present invention,
The boiler includes water level detection means for monitoring the water level of the boiler and water supply capacity detection means for monitoring the water supply capacity of the water supply pump. To explain each of the detecting means, first, the water level detecting means is an appropriate type of detecting means, for example, an electrode type water level detecting means for detecting the water level by contact with the can water in the boiler. Next, the water supply capacity detection means is configured to detect a decrease in capacity by comparing the amount of evaporation or combustion of the boiler with the operation time of the water supply pump. Also,
The water supply capacity detecting means may be configured to detect based on a change in water level in the boiler due to the operation of the water supply pump. Further, the water supply capacity detecting means may be configured to detect a flow rate of water supplied into the boiler using a flow meter. Next, a water supply control method according to the present invention will be described. The boiler, when the water level reaches the water supply start time, based on the monitoring result by the water level detection means,
By operating the water supply pump and stopping the water supply pump when the water level reaches the water supply end time, the water level is maintained within a predetermined water level range. Here, the water supply start time is a time at which the operation of the water supply pump is started in order to maintain the water level within the predetermined water level range. The water supply start timing is, for example, a point in time when a predetermined first set time has elapsed since the water level became equal to or lower than a predetermined water level set within the predetermined water level range. Further, the water supply end time is a time when the operation of the water supply pump is ended in order to maintain the water level within the predetermined water level range. The water supply end time is, for example, a point in time when a predetermined second set time has elapsed after the water level became equal to or higher than a predetermined water level set within the predetermined water level range. When the water supply capacity detecting means detects the water supply capacity decrease, the water supply start timing is adjusted in accordance with the water supply capacity decrease. That is,
When the decrease in the water supply capacity is detected, the first set time is reduced according to the decrease in the water supply capacity. Then
The water supply start time is advanced, and water supply can be started before the water level falls significantly from the predetermined water level range.
Here, the shortening of the first set time can be performed continuously according to the decrease in the water supply capacity, or can be performed stepwise according to the decrease in the water supply capacity. [0013] Here, the decrease in the water supply capacity occurs not only when the water supply pump itself deteriorates but also when a water supply line provided with the water supply pump is clogged. As described above, even when the decrease in the water supply capacity is due to the blockage of the water supply line, the water level is reduced to the predetermined water level by shortening the first set time in accordance with the decrease in the water supply capacity, as described above. Water supply can start before it falls significantly from the range. As described above, according to the water supply control method of the present invention, when the decrease in the water supply capacity is detected, the water supply start timing is advanced to prevent the water level from dropping below the predetermined water level range. Since the water can be supplied to the water, the low water level cutoff can be avoided. Therefore, the operation can be continued until the water supply pump is checked, repaired, or replaced. Here, in the above description, the water supply start timing is set to a point in time when the first set time has elapsed after the water supply level has become equal to or less than the predetermined water level. However, in the water supply control method of the present invention, the water level is set to It may be the time when the water level falls to the lower limit water level in the predetermined water level range. in this case,
The adjustment of the water supply start timing according to the decrease in the water supply capacity is performed by adjusting the lower limit water level. That is, a predetermined number of lower water levels when the water supply capacity is reduced is set above the lower water level in normal times, and a plurality of water level detection means for detecting each of these lower water levels is provided. Then, when a decrease in the water supply capacity is detected, the respective water level detection means are sequentially switched to a water level detection means for detecting an upper lower limit water level in accordance with the decrease in the water supply capacity. Also in the water supply control method of this embodiment, the water supply start time can be advanced, and water can be supplied before the water level falls below the predetermined water level range, so that the low water level cutoff can be avoided. . Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram schematically showing an example of a boiler embodying the present invention. Here, the boiler of this embodiment is a boiler provided with an on-off control type combustion device. First, the basic configuration of a boiler embodying the present invention will be described with reference to FIG. In FIG. 1, an on-off control type combustion device 2 is provided above a boiler 1.
Is provided. A water supply line 4 having a water supply pump 3 is connected to a lower portion of the boiler 1. Next, a control configuration of the boiler 1 will be described. First, each of the combustion device 2 and the feedwater pump 3 is connected to a controller 6 via a line 5. Further, the boiler 1 includes the boiler 1
A pressure detecting means 7 for detecting a steam pressure in the inside and a water level detecting means 8 for detecting a water level in the boiler 1 are provided. Each of these detection means 7, 8 is also
Each is connected to the controller 6 via the line 5. The controller 6 turns on and off the combustion device 2 based on a vapor pressure detection signal from the pressure detection means 7 according to a preset program, thereby controlling the boiler 1. A combustion control for maintaining the vapor pressure within a predetermined pressure range is performed. Further, the controller 6
Is based on a water level detection signal from the water level detection means 8 to control the water supply pump 3 to be on / off,
Water supply control is performed to maintain the water level in the boiler 1 within a predetermined water level range. Here, the water level detecting means 8 will be described in detail. The water level detection means 8 is provided in a water level detection container 10 in the middle of a pipe 9 which communicates between a steam section in the upper part of the boiler 1 and a canned part in a lower part of the boiler 1. As shown in FIG. 1, the water level detecting means 8 is an electrode type water level detecting means, and includes two water level detecting electrodes 11 and 12 having different lengths from each other. The shorter first water level detection electrode 11 of these water level detection electrodes 11 and 12 controls the water supply pump 3 so as to maintain the water level of the boiler 1 within the predetermined water level range. It is provided in. The control of the water supply pump 3 by the first water level detection electrode 11 is performed as follows. That is, after the water level falls below the lower end of the first water level detection electrode 11, after the first set time has elapsed, the water supply pump 3 is operated, and the water level reaches the lower end of the first water level detection electrode 11. After the lapse of the second set time, the water supply pump 3 is stopped. Therefore, the time when the first set time has elapsed after the water level falls below the lower end of the first water level detection electrode 11 is the water supply start time. Further, a point in time when the second set time has elapsed since the water level reached the lower end of the first water level detection electrode 11 is a water supply end time. The longer second water level detecting electrode 12 is
The lowest water level in the boiler 1 is detected, and the boiler 1
Is provided for an emergency stop. That is, the second water level detection electrode 12 is provided to cut off the low water level of the boiler 1. Next, in the water supply control method of the present invention, a means for detecting the water supply capacity of the water supply pump 3 (hereinafter referred to as "water supply capacity")
(Referred to as "water supply capacity detecting means"). The water supply capacity detecting means is configured to detect the water supply capacity by comparing the operation time of the combustion device 2 with the operation time of the water supply pump 3. Therefore, in this embodiment, the water supply capacity detecting means
The program is stored in the controller 6 as a program. Then, the controller 6 is configured to determine that the water supply capacity is reduced when the detection result of the water supply capacity by the water supply capacity detection means is lower than a predetermined reference value. Here, the reason why the water supply capacity can be detected by comparing the operation time of the combustion device 2 with the operation time of the water supply pump 3 will be described. First,
As described above, in the boiler 1, the water supply is controlled so as to maintain the water level within the predetermined water level range. Therefore, the evaporation amount of the boiler 1 per predetermined time and the water supply amount to the boiler 1 are determined as follows. Almost the same. Next, the evaporation amount of the boiler 1 can be obtained based on the operation time of the combustion device 2, and the water supply amount to the boiler 1 can be obtained based on the operation time of the water supply pump 3. . Therefore, the combustion device 2 per the predetermined time
By comparing the operation time of the water supply pump 3 with the operation time of the water supply pump 3, the water supply capacity can be detected. By the way, the water supply amount of the water supply pump 3 is as follows.
The operation time of the water supply pump 3 becomes longer because the water supply capacity decreases in accordance with the decrease in the water supply capacity. Therefore, by comparing the operation time of the combustion device 2 with the operation time of the water supply pump 3 at every predetermined time, it is possible to detect a decrease in the water supply capacity. Next, a water supply control method in the boiler 1 will be described together with the control contents of the controller 6. In the water supply control method, the controller 6 monitors the water level by the water level detection means 8 and the water supply capacity by the water supply capacity detection means during the operation of the boiler 1. And the controller 6
Controls the water supply pump 3 based on a detection signal from the water level detection means 8 so as to maintain the water level within the predetermined water level range. That is, after the water level falls below the lower end of the first water level detection electrode 11, after the first set time has elapsed, the water supply pump 3 is operated, and the water level reaches the lower end of the first water level detection electrode 11. After the elapse of the second set time, the water supply pump 3 is stopped. Then, the water supply capacity detecting means:
When the decrease in the water supply capacity is detected, the controller 6
Reduces the first set time continuously according to a decrease in the water supply capacity. Then, the time from when the water level falls below the lower end of the first water level detection electrode 11 to when the water supply pump 3 operates is shortened. Therefore, according to the water supply control method, it is possible to suppress the occurrence of the low water level cutoff by operating the water supply pump 3 before the water level falls too low from the predetermined water level range. Therefore, the time until the water level cannot be maintained within the predetermined water level range due to a decrease in the water supply capacity of the water supply pump 3 can be lengthened. Therefore, inspection, repair,
Until the replacement or the like, the operation of the boiler 1 can be continued, and the supply of steam to the steam-using equipment (not shown) connected to the boiler 1 can be continued. Further, the water supply capacity is reduced when the water supply line 4 is clogged in addition to the deterioration of the water supply pump 3 itself. Also in this case, similarly to the above, by reducing the first set time according to the decrease in the water supply capacity, water supply is started before the water level falls significantly from the predetermined water level range, and the low water level is started. The occurrence of interruption can be suppressed. Here, after the water supply pump is repaired or replaced, or after the water supply line 4 is clogged, the water supply capacity is restored. In this way, when the water supply capacity has recovered, the controller 6 determines that the water supply capacity has recovered based on the monitoring result of the water supply capacity detection means, and reduces the shortened first set time. The water supply control is performed after returning to the original set time. According to the present invention, the occurrence of low water level cutoff of the boiler can be suppressed when the capacity of the water supply pump is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view schematically showing an example of a boiler for implementing a water supply control method of the present invention. [Description of Signs] 1 Boiler 3 Feedwater pump

Claims (1)

Claims: 1. A water level of a boiler 1 and a water supply capacity of a water supply pump 3 are monitored, and when the water level reaches a predetermined water supply start time, the water supply pump 3 is operated to supply the water supply capacity. When a decrease in the water supply capacity is detected,
A water supply control method for a boiler, wherein the water supply start timing is adjusted.