JP2002005408A - Water feeding method and feed water controller for boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the elapse of a long period of time until a level in a boiler is lowered to the normal ON-level of a feed water pump after a level in a steam and water separator is swollen upon initial sending of steam after starting a boiler and permit the avoiding of the continuation of a low level. SOLUTION: A level detector 4, attached to the steam and water separator 3, is provided with an upper limit position sensor 4U for detecting an upper limit level, a lower limit position sensor 4L for detecting a lower limit level other than an intermediate position sensor 4M for detecting a preset intermediate level. A water level controller 5, starting water feeding when the set intermediate level is detected at first by the intermediate position sensor 4M after starting the sending of steam, then, neglecting a level signal outputted by the intermediate position sensor 4M until the operation of the boiler is stopped and commanding the feeding of water based on a level sensing signal outputted by the lower limit position sensor 4L, is employed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water supply method and a water supply control device for a boiler, and more particularly, to a boiler provided with a steam-water separator, which is caused by a swelling of the water surface that occurs immediately after starting from a full state. The present invention relates to water supply control that can prevent the first water supply after starting air supply after startup from being delayed.

[0002]

2. Description of the Related Art Even when a large number of vertical water pipes are arranged in multiple layers so as to annularly surround a combustion chamber, the vertical water pipes are densely arranged to exchange heat with introduced exhaust gas. However, in the multi-tube once-through boiler, the boiler tube is filled with water before starting in order to prevent burning of the boiler tube at the time of starting.

Referring to FIG. 7, a boiler main body 30 includes an upper pipe 30U, a lower pipe 30L, and a number of water pipes 30T connected therebetween. The steam generated in the water pipe is introduced into the steam separator 31 from the upper pipe section 30U, and the steam 31S from which the water droplet has been separated is taken out through the steam pipe 32.

[0004] The steam-water separator 31 is indispensable in a small multi-tube once-through boiler and is located at a higher position than the boiler main body 30, and the saturated water 31 w accumulated in the steam-water separator is passed through a pipe 33 through the boiler main body. Natural circulation is being carried out.
When the boiler starts operation, naturally the boiler water in the main body decreases, and the water level of the steam separator 31 also decreases. Therefore, a water level detector for detecting a drop in the water level is provided to supply boiler water.

In the example shown in the figure, a water level detector 34 is attached to the steam separator 31. Water is supplied to the boiler by driving the water supply pump 11 and introduced through the steam separator 31 or the boiler body 30. Or directly to the lower pipe 30L.
In any case, the water supply pump 11 is started and stopped by on / off control as described below.

The water level detector 34 is provided with an upper limit position detection sensor 34U for detecting a set upper limit water level and a lower limit position detection sensor 34L for detecting a set lower limit water level. Is to be entered. Then, the water supply pump 11 is operated and stopped according to a command from a water supply command control unit (not shown).

[0007] For example, if there is a command to fill the water before the operation of the boiler, water is supplied until the set upper limit water level is reached, and a signal indicating that the upper limit position detection sensor 34U has reached the upper limit position is output. Then, the water supply is stopped. Since the steam separator 31 communicates with the lower pipe 30L, its water level is the same as that of the water pipe 30T. Then, when there is a start command, the boiler water evaporates as described above, and if the boiler water falls to the set lower limit water level, the feed pump 1
1 is driven again, and the boiler water is always kept between the set lower limit water level and the set upper limit water level.

As described above, when a start command is input to the operation control device (not shown) of the boiler at the time when the water is first filled with water, the water pipe is heated to evaporate, and the air bubbles in the water pipe increase. Raise the water surface temporarily. It is well known that the water level rises immediately after startup in this manner, compared to when the water level is full. In addition, for example, when the steam valve is opened at once and steam is rapidly sent out after the start, the boiler pressure is temporarily reduced. Along with that, the saturated water in the water pipe self-evaporates,
At this time, the water surface is temporarily pushed up.

[0009]

By the way, in the steam separator, steam introduced from the water pipe is separated into steam and water, and only saturated water should stay. However, when the water circulation is activated by the first air supply after the start, a large amount of wet steam flows into the steam separator from the main water pipe, so that the water level in the steam separator also becomes higher than that when the water is full. at this point,
In the water level detector 34, the upper limit position detection sensor 34U indicates that the water level is at the set upper limit water level or higher.

Therefore, it takes a longer time for the water level to drop to a level at which the water supply pump is turned on than at the time of static setting. In addition, since the amount of water held by the boiler is smaller than at the time of static settling, it takes a long time to supply water to recover the water level. At this time, if the load is large, the water level decreases more than the water level recovery, and the water level may become low.

If the time until water is supplied is long in the case where an economizer is provided, the temperature of the supply water during standby in the economizer rises too much, and when this evaporates, a large pipe resistance is generated, making it difficult to supply water thereafter. There is also a problem of becoming. If it is started with full water, it is inevitable that a large amount of canned water will flow from the main body water pipe to the steam separator in the early stage, and the water level of the steam separator will rise, causing a delay in water supply.

[0012] The present invention has been made in view of the above-described problems, and an object of the present invention is to reduce the time required for water supply immediately after the water level rises immediately after startup and the water level detector detects an apparent water level. It is an object of the present invention to provide a water supply method and a water supply control device for a boiler that can perform water supply control without requiring a low water level and that can maintain stable operation of the boiler.

[0013]

SUMMARY OF THE INVENTION The present invention is directed to a boiler in which saturated water separated by a steam separator is naturally circulated to a water pipe. When the set upper limit water level is detected by the water supply, the water supply is stopped. The feature is that the first water supply after starting the air supply after the start is performed before the set lower limit water level is detected.

The first water supply may be performed when a set intermediate water level between the set upper water level and the set lower water level is detected, or may be set in advance immediately after the water level falls below the set upper water level for the first time. It may be performed continuously for a period of time.

Referring to FIG. 1, the invention of the water supply control device has a water level detector 4 including an upper limit position detection sensor 4U for detecting a set upper limit water level and a lower limit position detection sensor 4L for detecting a set lower limit water level. In addition, an intermediate position detection sensor 4M that detects a set intermediate water level is provided. On the other hand, when the intermediate position detection sensor 4M detects that the intermediate water level has fallen below the set intermediate water level, the water level control device 5 outputs a signal indicating that the air level has fallen below the set intermediate water level for the first time since the start of air supply after startup. Initial water level determination unit 5B for determining whether or not
When it is determined by the initial water level determination unit that the fall below the set intermediate water level is the first time since the start of air supply after startup, the water supply pump 11 is operated in response to the determination signal, and the set upper limit water level is determined. And an initial water supply command control unit 5C for instructing the supply of boiler water until the temperature reaches a predetermined value. In the water supply command control unit 5A, when it is determined by the initial water level determination unit 5B that the fall below the set intermediate water level is not the first time since the start of air supply after startup, the determination signal is received and the set upper limit water level is set. That is, a water supply command is issued by on / off control based on a detection signal of the lower limit water level.

Further, as shown in FIG. 4, when the upper limit position detection sensor 34U detects that the water level has fallen below the set upper limit water level, the detection signal falls below the set upper limit water level for the first time after the air supply is started after activation. When the initial water level determination unit 5E that determines whether the signal is a signal indicating that the initial water level determination unit determines that the air pressure has fallen below the set upper limit water level for the first time since the start of air supply after startup, In response to the determination signal, the initial water supply command control unit 5F that instructs to supply the boiler water by operating the water supply pump continuously for a preset time, and that the initial water level determination unit 5E drops below the set upper limit water level. When it is determined that it is not the first time since the start of air supply after startup, the determination signal is received and a water supply command is issued by on / off control based on detection signals of the set upper limit water level and the set lower limit water level. And a water supply instruction control unit 5D. The water level detectors 4 and 34 are attached to the steam separators 3 and 31 as shown in FIGS.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a water supply method and a water supply control device for a boiler according to the present invention will be described in detail with reference to the drawings showing examples. FIG. 1 shows that in the water supply control based on the water level detected by the steam separator, the first water supply after starting the air supply after the start can be performed before the set lower limit water level is detected, FIG. 1 shows a system diagram of a boiler including a control device capable of shortening a waiting time until water is first supplied.

The illustrated boiler includes a steam-water separator 3 into which steam 2 is introduced from a number of water pipes 1T (shown in a simplified manner) of the boiler body 1 via an upper pipe 1U. Although this is an example of a small multi-tube once-through boiler, a steam-water separator 3 for separating steam 2 into steam is provided at a position higher than the water pipe 1T, and the saturated water separated by the steam-water separator 3 is provided. The water 3w is naturally circulated to the water pipe 1T via the lower pipe 1L.

The water supply system employed in this boiler is as follows:
At the time of settling, water supply is started when the water amount decreases and the set lower limit water level is detected, and when the set upper limit water level is detected by the water supply, the water supply can be stopped and turned on / off. Depending on.

More specifically, a water level detector 4 is attached to the steam separator 3, and the water level detector includes:
In order to detect the amount of saturated water 3w staying in the steam separator, an upper limit position detection sensor 4U for detecting a set upper limit water level and a lower limit position detection sensor 4L for detecting a set lower limit water level are provided. And an intermediate position detection sensor 4M that detects a set intermediate water level located between the two water levels.
In addition, well-known water test electrodes and the like are used for all the sensors.

On the other hand, a water supply command control unit 5A for performing the above-mentioned on / off control is provided in the water level control device 5, and is constituted by a microcomputer or the like. This is a command to start the water supply in response to the water level detection signal from the lower limit position detection sensor 4L until the operation of the boiler is stopped. In addition to the water supply command control unit 5A, the water level control device 5 includes an initial water level determination unit 5B and an initial water supply command control unit 5C.

When the intermediate position detecting sensor 4M detects that the intermediate water level has fallen below the set intermediate water level, the initial water level judging section 5B indicates that the detection signal has fallen below the set intermediate water level for the first time after the air supply is started after activation. It is to determine whether the signal is a signal. Initial water supply command control unit 5C, when the initial water level determination unit 5B determines that the lower than the set intermediate water level is the first time after starting the air supply after startup,
Upon receiving the determination signal, the water supply pump 11 is operated to instruct the supply of boiler water until the water reaches the set upper limit water level.

When the initial water level determining unit 5B determines that the fall below the set intermediate water level is not the first time since the start of air supply after startup,
Upon receiving the determination signal, a water supply command is issued by on / off control based on detection signals of the set upper limit water level and the set lower limit water level.

In general, the entire control sequence is to instruct water supply based on the signal when the set intermediate water level is detected for the first time after the intermediate position detection sensor 4M starts air supply after the start-up. During the stabilization until the subsequent boiler operation is stopped, the intermediate position detection sensor 4
Ignore the water level detection signal by M and detect the lower limit position detection sensor 4
This is achieved by receiving a water level detection signal from L and issuing a water supply command.

According to the water level control device that executes the above-described control sequence based on the operations of the above-described initial water level determination unit 5B, initial water supply command control unit 5C, and water supply command control unit 5A, air supply is started after startup as described above. Then, the first water supply can be performed before the set lower limit water level is detected.
That is, the first water supply is started when the set intermediate water level is detected. The operation will be described below with reference to the flowchart of FIG.

In order to supply boiler water prior to activation, the water supply pump 11 is driven by an electric motor (not shown) (see step 1 (hereinafter referred to as S1) in the flowchart). The water supplied to the steam separator 3 via the water supply pipe 12 (see FIG. 1) is introduced into the main body water pipe 1T from the liquid pool of the steam separator through the lower pipe 1L. The water supply is continued until the water pipe is full to prevent burning due to overheating of the boiler pipe. When the boiler body is full, the steam-water separator also stores an equivalent water level.

When the water is filled by the water supply, the reaching of the set upper limit water level is detected by the upper limit position detecting sensor 4U (S2). When the detection signal is input to the water level control device 5, the operation of the water supply pump 11 is stopped in response to the signal (S3). When the boiler is started in this state (S4), the boiler water (can water) in the main body water pipe is heated by the combustion gas and the exhaust gas.

In each water pipe, the boiler water boils to generate a bubble flow, and a gas-liquid two-phase is formed by the floating flow and the spray flow generated by further heating, and the water surface rises as the steam and bubbles move. Also, in the steam separator 3, the water level rises due to the inflow of the wet steam.

The upper limit position detection sensor 4U up to this point
According to the time chart shown in FIG. 3, when the water supply pump is turned off, the upper limit position detection sensor 4U is turned on. To detect the water surface
It still outputs an ON signal.

When the boiler water evaporates sequentially, the water level naturally rises even though the water level rises, so that the water level generally falls, and the upper limit position detection sensor 4U is turned off when the water level drops below the set upper limit water level. (Refer to the portion indicated by the symbol A in FIG. 3). However, the water level control device 5 continues to stop supplying water without regard to the off signal. When the amount of water is significantly reduced and the intermediate position detection sensor 4M detects the set intermediate water level (S5), that is, when the water level falls below the set intermediate water level (see the portion B in FIG. 3), the initial water level determination unit 5
In B, it is determined whether or not the detection signal is a signal that is lower than the first set intermediate water level detected after the start of air supply after activation (S6).

If it is the first set intermediate water level detection signal after the start of air supply after the start-up, the water supply pump 11 is driven in response to the detection signal (S7). The water supply is continued until the upper limit position detection sensor 4U detects the set upper limit water level (S8), at which time the water supply pump 11 is stopped (S8).
9).

Incidentally, if the water level difference between the set upper limit water level and the set lower limit water level in the water level detector 4 is, for example, 100 mm, the set intermediate water level is set at a height position, for example, 60 mm from the set lower limit water level. The set height can be determined in advance to a desired value, which is defined, for example, by the length of the water sample electrode.
If the amount of droop of the electrode can be adjusted by a screw mechanism or the like in the electrode support portion, it goes without saying that the set value can be changed later.

For example, in the case of an on / off boiler, ignition and fire-extinguishing operations are common, but as long as the operation of the boiler itself is continued, even if the fire is extinguished, the above-mentioned water level control device 5
Is continued (S10, S5). Regardless of whether the fire is being extinguished or not, the set intermediate water level is detected (S
5) If the detection of the water level is not the first time after the activation (S6), the signal is ignored (S11). If the set lower limit water level is detected by the lower limit position detection sensor 4L (S12, see the portion of the symbol C in the time chart),
Upon receiving the output signal, the water supply pump 11 is operated again (S7). Thereafter, the water supply control at the time of the static determination is continued until a command to stop the operation of the boiler is issued.

In step 6, whether or not the detection of the set intermediate water level by the intermediate position detection sensor 4M is the first detection after the start of the air supply after the start-up is known by setting a flag in control software. Can be determined by an appropriate method.

As can be understood from the above description of the operation, the first water supply after the start of the air supply after the start-up is performed when the intermediate position detecting sensor detects that the set intermediate water level has been reached for the first time. Water supply is started only when the lower limit position detection sensor detects that the set lower limit water level has been reached. As a result, immediately after startup, even if a large amount of wet steam flows into the steam separator from the main water pipe and the water level in the steam separator is higher than that when the water is full, the set lower limit water level is detected. Since the water supply is started before the water supply is started, the water supply immediately after the start is performed early.

If water supply is started when the intermediate position detection sensor detects the set intermediate water level, it goes without saying that the amount of remaining boiler water is larger than when water supply is started after the set lower limit water level is detected. Therefore, if water is supplied after detecting the set lower limit water level, the time required for water supply immediately after startup, which will be lost late, or even when the low water level is likely to continue due to a large boiler load, It can be resolved early. For example, when an economizer is provided, the boiler operation is stabilized, including overheating and evaporation of the boiler water in the standby state is avoided.

FIG. 4 is a circuit diagram of FIG.
However, the method according to the present invention can be applied to a case having such a known configuration. Of course, the water level control device 5M includes FIG.
As in the case of (1), an initial water level determination unit 5E and an initial water supply command control unit 5F are introduced in addition to the water supply command control unit 5D, but their functions are slightly different from those in the case of FIG.

More specifically, the initial water level determination unit 5E
When the upper limit position detection sensor 34U detects that the water level has fallen below the set upper limit water level, it is determined whether or not the detection signal is a signal indicating that the air flow has fallen below the set upper limit water level for the first time since the start of air supply after startup. is there. The initial water supply command control unit 5F receives the determination signal when the initial water level determination unit 5E determines that the water level falls below the set upper limit water level for the first time after the start, and continues for a preset time T. The water supply pump 11 is operated to instruct supply of boiler water.

When the initial water level determining unit 5E determines that the lowering of the set upper water level is not the first time since the start of air supply after the start,
Receiving the determination signal, thereafter, an instruction is given to supply water by on / off control based on detection signals of the set upper limit water level and the set lower limit water level.

In any case, the water is supplied continuously for a preset time when the water level falls below the set upper limit water level for the first time after startup. That is, the first-time water supply command control unit 5E receives the signal indicating that the upper limit position detection sensor 34U has first dropped below the set upper limit water level after activation, and instructs to continuously supply water for a preset time (T). After that, until the operation of the boiler is stopped, the water supply command control unit 5D instructs water supply based on the water level detection signal from the lower limit position detection sensor 34L.

The operation is as shown in the flowchart of FIG. 5, and the parts common to FIG. 2 are assigned the same step numbers and their explanation is omitted. After the boiler is started (S4), the water surface rises. However, when the upper surface position detection sensor 34U detects that the water surface has dropped below the set upper limit water level for a while (S21), the detection is performed first after the start. (S22) If the water supply pump 11 is in the T time, for example, 3
It is driven for 0 seconds (S23) and then stopped. This means that the process starts at a portion indicated by reference numeral E in the time chart of FIG.

Although the water level immediately exceeds the set upper limit water level due to the water supply immediately after the startup, the water supply is continued until the set time T ends. The length of this time is determined in consideration of design specifications such as boiler capacity and feed pump capacity.

If the first water supply after the start of the air supply after the start is completed, the upper limit position detecting sensor 3
Even if it detects that 4U has fallen below the set upper limit water level, the detection signal is ignored (S24). The control after Steps 12 and 7 is executed, that is, when the set lower limit water level is detected (S12, see the part of the time chart G), the water supply is restarted (S7).

By the way, in each of the examples described above, each sensor for detecting the water level is described as outputting the ON / OFF signal independently of the presence or absence of the water surface. Each water level may be detected by a combination of signals from the section,
In short, the water level control device only needs to be able to start and stop the water supply pump based on the water level.

[0045]

As can be understood from the above detailed description, according to the present invention, even if the water surface rises at the start of air supply after startup, in the first water supply after starting air supply after startup, Rather than starting water supply based on a signal at which the lower limit position detection sensor detects the lower limit position as in the case of water supply at the time of static setting, the water supply is performed before the set lower limit water level is detected, and therefore, based on the signal at which the lower limit position is detected. Water supply can be started earlier than when water supply is started.

Therefore, the water supply immediately after the start-up does not take a long time or an undesirably low water level does not continue, and even if an economizer is provided, excessive heat exchange in the economizer is prevented and smooth. Water supply becomes possible, and stable operation of the boiler is maintained immediately after the start-up, as in the case of static settling.

Even when a known water level detector comprising an upper limit position detection sensor and a lower limit position detection sensor is employed, the intended purpose can be achieved only by adding the sequence according to the present invention to the water level control device. This has the advantage that it can be easily applied to existing boilers.

[Brief description of the drawings]

FIG. 1 is a boiler system diagram in which water supply control by a water supply method according to the present invention is adopted.

FIG. 2 is a flowchart showing control for realizing water supply in the boiler system shown in FIG.

FIG. 3 is a time chart when a water supply pump is operated based on the control of FIG. 2;

FIG. 4 is a boiler system diagram in which different examples of water supply control are adopted.

FIG. 5 is a flowchart showing control for realizing water supply in the boiler system shown in FIG.

FIG. 6 is a time chart when the water supply pump is operated based on the control of FIG. 5;

FIG. 7 is a boiler system diagram by a conventional water supply control device.

[Explanation of symbols]

1, 30: boiler body, 1T, 30T: water pipe (main body water pipe), 3, 31: steam-water separator, 3w, 31w: saturated water,
4, 34: water level detector, 4L, 34L: lower limit position detection sensor, 4M: intermediate position detection sensor, 4U, 34U: upper limit position detection sensor, 5, 5M: water level control device, 5A, 5D
... water supply command control unit, 5B, 5E ... initial water level determination unit, 5
C, 5F: initial water supply command control unit, 11: water supply pump.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Fumitoshi Masai 1000 Aomachi-cho, Kusatsu-shi, Shiga Prefecture Kawagei-Hiroshi Kogyo Co., Ltd. 3L021 AA02 CA01 DA07 DA13 FA03

Claims (6)

[Claims] 1. A boiler in which saturated water separated by a steam separator is naturally circulated to a water pipe. When the amount of water decreases and a set lower limit water level is detected, water is supplied, and the water is set. In a water supply method in which water supply is stopped when an upper limit water level is detected, the first water supply after starting air supply after startup is performed before a set lower limit water level is detected. Water supply method. 2. The water supply method for a boiler according to claim 1, wherein the first water supply is performed when a set intermediate water level between the set upper water level and the set lower water level is detected. . 3. The water supply method for a boiler according to claim 1, wherein the first water supply is performed continuously for a preset time immediately after the water supply first falls below a set upper limit water level. 4. A boiler in which saturated water separated by a steam-water separator is naturally circulated to a water pipe, wherein the amount of water decreases and the lower limit position detection sensor detects that the set lower limit water level has been reached. In this case, the water supply pump is operated to supply water, and the water supply control device having a water supply command control unit that instructs to stop supplying water when the upper limit position detection sensor detects that the set upper limit water level has been reached by the water supply, In addition to the upper limit position detection sensor and the lower limit position detection sensor, a water level detector having an intermediate position detection sensor that detects a set intermediate water level located between the set upper limit water level and the set lower limit water level is adopted, When the position detection sensor detects that the water level has fallen below the set intermediate water level, a signal indicating that the detection signal has fallen below the set intermediate water level for the first time since the start of air supply after startup. An initial water level determination unit for determining whether there is a gas, and when the initial water level determination unit determines that the water level has fallen below the set intermediate water level for the first time since the start of air supply after startup, receiving the determination signal An initial water supply command control unit that operates the water supply pump and instructs to supply boiler water until the water reaches the set upper limit water level.The water supply command control unit is below the set intermediate water level by the initial water level determination unit. A water supply control device for a boiler, characterized in that when it is determined that this is not the first time since the start of air supply after startup, the determination signal is received and water supply control is performed thereafter. 5. A boiler in which saturated water separated by a steam separator is naturally circulated to a water pipe, wherein the amount of water decreases and the lower limit position detection sensor detects that the set lower limit water level has been reached. In this case, the water supply pump is operated to supply water, and the water supply control device having a water supply command control unit that instructs to stop supplying water when the upper limit position detection sensor detects that the set upper limit water level has been reached by the water supply, When the upper limit position detection sensor detects that the temperature has fallen below the set upper limit water level, an initial water level determination is performed to determine whether or not the detection signal is a signal indicating that the air pressure has fallen below the set upper limit water level for the first time after starting the air supply after startup. And, when it is determined that the initial water level determination unit is below the set upper limit water level for the first time after starting the air supply after startup, receiving the determination signal, An initial water supply command control unit that instructs to supply a boiler water by operating a water supply pump continuously for a set time, wherein the water supply command control unit falls below a set upper limit water level by the initial water level determination unit. A water supply control device for a boiler, characterized in that when it is determined that it is not the first time since the start of air supply after startup, the determination signal is received and water supply control is performed thereafter. 6. The water supply control device for a boiler according to claim 4, wherein the water level detector is attached to the steam separator.