JP2942084B2 - Water supply control device for multi-tube once-through boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-tube type once-through boiler feed water control device capable of supplying high-quality steam while preventing an excessive rise in metal temperature of a heating tube.

[0002]

2. Description of the Related Art In a multi-tube once-through boiler, in order to prevent troubles such as damage to a can body, water level control is performed so that the metal temperature of a heating tube does not rise excessively.
In this method, the steam dryness tends to deteriorate. In order to improve the steam dryness, it is possible to set the water level in the boiler low, but the metal temperature of the heating pipe tends to rise excessively.

[0003] A specific example of a small-capacity once-through boiler having a small capacity of about 0.5 to 5 t / h will be described with reference to FIG.

In FIG. 1, reference numeral 1 denotes a boiler main body, and a plurality of heating tubes 3 are vertically disposed at predetermined intervals in a circumferential direction so as to surround a combustion chamber (furnace) 2 of the boiler main body 1. Yes,
The upper portion of the heating tube 3 is supported by an annular upper header 4 and the lower portion of the heating tube 3 is supported by an annular lower header 5 in communication with each other. A vertical burner 6 that can inject fuel oil into the combustion chamber 2 is provided.

A water supply pipe 7 connects the lower header 5 and a water supply source (not shown). The water supply pipe 7 includes a water supply pump 8 for supplying water to the lower header 5 and a lower pipe. A check valve 9 for preventing water from flowing back from the drawer 5 to the water supply pump 8 is incorporated.

Reference numeral 10 denotes a steam separator. The upper portion of the steam separator 10 and the upper surface of the upper header 4 are connected by a communication pipe 11, and the bottom and lower portions of the steam separator 10 are connected to each other. The side of the header 5 is connected by a downcomer 12,
In addition, a steam pipe 13 in which a steam valve 14 is incorporated is connected to the upper surface of the steam separator 10 so that steam is led to a steam consuming area.

Reference numeral 15 denotes a vertical water column tube used for detecting the level (water level) of water in the heating tube 3 of the boiler main body 1. The upper surface of the water column tube 15 is connected to an upper tube via a communication tube 16. The bottom of the water column pipe 15 is connected to the lower header 5 via a communication pipe 17. In the water column pipe 15, the lower end of the high water level detection electrode 18 is common to the water level (set upper limit water level) A, and the lower end of the low water level detection electrode 19 is common to the water level (set lower limit water level) B (B <A). The lower end of the electrode 20 is at the water level B
It is arranged vertically so as to be located below each.

Reference numeral 21 denotes a water level discriminator, which includes an upper limit water level detector 21A, a lower limit water level detector 21B,
And an instruction signal output section 21C for judging the water level based on the outputs from A and 21B and outputting an instruction signal.
The upper limit water level detection unit 21A and the high water level detection electrode 18 are provided, and the lower limit water level detection unit 21B and the low water level detection electrode 1 are provided.
9 are connected to each other, and the upper limit water level detector 21
A and the lower limit water level detection unit 21B are connected to the common electrode 20 via the power supply 21D. When the high water level detection electrode 18 and the common electrode 20 are energized, the output from the upper limit water level detection unit 21A is output. When the low water level detection electrode 19 and the common electrode 20 are in a non-energized state, the low water level detection unit 21B outputs a signal.

The instruction signal output unit 21 of the water level discriminator 21
C holds the input signal from the lower limit water level detection unit 21B when it is input from the lower limit water level detection unit 21B and continuously outputs the operation instruction signal of the water supply pump 8 until it is input from the upper limit water level detection unit 21A. Along with
When input from the upper limit water level detection unit 21A, the upper limit water level detection unit 21 is input until input from the lower limit water level detection unit 21B.
The input signal from A is held, and a stop instruction signal for the water supply pump 8 is continuously output.

An instruction signal output unit 21 of the water level discriminator 21
C is connected to a feed water pump actuator 22 that operates and stops the feed water pump 8, and an instruction signal output unit 21
The operation and stop of the water supply pump 8 can be performed based on the output from C.

When the multi-tube once-through boiler is started, it is checked whether or not the water level is at a normal level (set water level) (a water level between water levels A and B). Water level B
If it is below, the water supply pump 8 is operated. The water introduced into the heating tube 3 through the lower header 5 of the boiler main body 1 through the water supply pipe 7 by the water supply pump 8 becomes steam by the combustion heating of the burner 6, and becomes steam from the upper header 4 to the communication pipe 11.
The steam from which the moisture has been separated by the steam-water separator 10 is sent to a required location through a steam pipe 13, and the water separated by the steam-water separator 10 is passed through a downcomer. 12 returns to the lower header 5. As described above, the water level is set to the normal level, the fan is operated at the same time as the start, the prepurge (ventilation of the combustion chamber 2) is performed, the fuel valve is opened, and the burner 6 is ignited to start combustion.

In the multi-tube once-through boiler, if the water level in the heating tube 3 is too low with respect to the amount of fuel burned by the burner 6 in the combustion chamber 2, the heating tube 3 is overheated, which adversely affects the life of the boiler. On the contrary, if the water level in the heating pipe 3 is too high, the dryness of the steam led out through the steam pipe 13 decreases and the quality of the steam deteriorates. There is a close relationship with the amount of fuel to be heated. For this reason, the water level A and the water level B are set so that high-quality steam can be obtained without overheating the heating pipe 3 and having a low steam dryness. The water level of the heating pipe 3 is adjusted by supplying water in accordance with the amount of steam generated by the water supply pump 8.

During the operation of the boiler as described above, when the water level of the water column pipe 15 falls below the water level B, the high water level detection electrode 18 and the common electrode 20 and the low water level detection electrode 19 and the common electrode 20 In the meantime, each is in a non-energized state. In such a state, in the water level discriminator 21, the upper limit water level detection unit 21A
From the lower limit water level detector 21B,
This output is input to the instruction signal output unit 21C, and the instruction signal output unit 21C outputs an operation instruction signal of the water supply pump 8 to the water supply pump actuator 22. The feed water pump 8 starts operating by the feed water pump actuator 22.

When the water level rises due to the operation of the water supply pump 8 and exceeds the water level B, a current flows between the low water level detection electrode 19 and the common electrode 20. In such a state, the lower limit water level detector 2
Although the output from 1B disappears, the instruction signal output unit 21C keeps the input of the lower limit water level detection unit 21B, so that the instruction signal output unit 21C continuously outputs the operation instruction signal of the water supply pump 8, The operation of the pump 8 is continued. When the water level further rises and exceeds the water level A, the high water level detection electrode 18 and the common electrode 20 are energized and output from the upper limit water level detection section 21A to the instruction signal output section 21C. The holding input from the lower limit water level detecting section 21B of the section 21C is released and the water supply pump 8
At the same time, the input from the upper limit water level detection unit 21A is held in the instruction signal output unit 21C, and the stop instruction signal for the water supply pump 8 is output,
Based on this output, the water supply pump actuator 22 operates and the water supply pump 8 stops.

Even when the water supply pump 8 is in a stopped state, the combustion in the burner 6 continues, so that the water in the heating pipe 3 is heated and turned into steam to be drawn out from the communication pipe 11.
Accordingly, the water level in the heating pipe 3 gradually decreases, and the water level in the water column pipe 15 decreases in synchronization with this lowering. When the water level falls below A, the space between the high water level detection electrode 18 and the common electrode 20 is reduced. Although the state is de-energized and the output from the upper limit water level detecting unit 21A stops, the instruction signal output unit 21C keeps the input of the upper limit water level detecting unit 21A,
The stop instruction signal for the water supply pump 8 is continuously output from C, and the water supply pump 8 is in a stopped state.

When the water level further falls and falls below the water level B,
The state between the low water level detection electrode 19 and the common electrode 20 is de-energized, and the lower limit water level detection unit 21B sends the instruction signal output unit 2
1C, the output of the instruction signal output unit 21
The holding input from the upper limit water level detection unit 21A of C is released and the stop instruction signal of the water supply pump 8 is not output, and at the same time, the input from the lower limit water level detection unit 21B is held in the instruction signal output unit 21C and the water supply pump is The operation instruction signal of No. 8 is output, and based on this output, the water supply pump actuator 22 operates and the water supply pump 8 starts operating. When the water level rises again by the operation of the water supply pump 8 and exceeds the water level A, the water level is output from the upper limit water level detection unit 21A to the instruction signal output unit 21C, and the output from the lower limit water level detection unit 21B of the instruction signal output unit 21C. The holding input is released and the water supply pump 8
At the same time, the input from the upper limit water level detection unit 21A is held in the instruction signal output unit 21C, and the stop instruction signal for the water supply pump 8 is output,
Based on this output, the water supply pump actuator 22 operates and the water supply pump 8 stops.

As described above, according to the amount of generated steam,
The operation and stop of the water supply pump 8 that supplies water according to the water level
FIG. 5 shows the cycle. In FIG. 5, time T₁~
T_Two, The water supply pump 8 is operated during the time T_Two~ T_ThreeAmong
Means that the water supply pump 8 is stopped and the time T _Three~ T_FourBetween the water supply pon
In the step 8, the cycle of operation is repeated.

[0018]

However, when the water level in the heating pipe 3 exceeds the water level A, the water supply pump 8 is stopped, and when the water level in the heating pipe 3 falls below the water level B, the water supply pump 8 is turned off. Although the water level is adjusted by driving, since the water level A and the water level B are different, the heating pipe 3 does not overheat at the water level A, but the dryness of the steam is reduced, so that high quality steam cannot be obtained. In addition, at the water level B, the steam dryness was improved, but the phenomenon that the heating pipe 3 was overheated and the life of the boiler was adversely affected was unavoidable.

In order to cope with the above-mentioned phenomenon, it is necessary to find a water level that does not overheat the heating pipe 3 and does not decrease the steam dryness. Therefore, the length of the high water level detection electrode 18 and the low water level detection electrode 19 are determined. Adjustment of the mounting position of the water column pipe 15 with respect to the header 4, the lower header 5, and the heating pipe 3, etc., must be performed so as to be within a certain precision range, and it must be strictly manufactured. It took a lot.

In view of the above circumstances, the present invention can extend the life of a boiler without overheating a heating tube and supply water of a multi-tube once-through boiler capable of obtaining high-quality (good steam dryness) steam. It is intended to provide a control device.

[0021]

According to the present invention, a water level detector is provided on a water column pipe whose water level fluctuates in synchronism with the water level of a vertical heating pipe provided around a combustion chamber. A water level discriminator that determines the water level based on the detected water level of the fixture and outputs the operation and stop instruction signals of the water supply pump is connected to the water supply pump actuator that operates and stops the water supply pump that supplies water to the heating pipe. In a water supply control device of a multi-tube once-through boiler in which water supply control is performed by operating or stopping a pump, a steam dryness detector for detecting steam dryness is provided in a steam pipe for leading out steam generated from a heating pipe. A steam dryness discriminator that discriminates the steam dryness based on the detected steam dryness of the steam dryness detector and outputs an operation / stop instruction signal of the water supply pump, is connected to the water supply pump actuator, Water level discriminator and feed water pump actuator And a contact b of the switcher is incorporated in one of the connection lines of the steam dryness discriminator and the feed water pump actuator, and a contact b of the other is connected to the contact a. And a switching actuator for switching the switching device based on output signals from the vapor pressure detector and the combustion indicator.

[0022]

When the required time elapses after the start of combustion and the steam pressure exceeds the required pressure, the switching actuator is activated and the switching operation of the switching unit is performed, and water is supplied based on the steam dryness detected by the steam dryness detector. Enables pump operation and stop operation.

When the water level of the heating pipe falls and the steam dryness rises and exceeds the upper limit, an operation instruction signal is output from the steam dryness discriminator, and the feed water pump actuator is operated by this output to operate the water feed pump. Start. When the water level of the heating pipe rises due to the operation of the water supply pump, and the steam dryness falls below the upper limit and further falls below the lower limit, a stop instruction signal is output from the steam dryness discriminator, and the feed water pump actuator is output by this output. Operates and stops the water supply pump. The stop of the feedwater pump is continued until the steam dryness rises and exceeds the upper limit.

Therefore, the water supply can be controlled so that the steam dryness is maintained within a required range, and high-quality steam having a good steam dryness can be obtained.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the figure, the same components as those in FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted. Only the configuration unique to the present invention will be described.

In the figure, reference numeral 23 denotes a steam dryness detector,
The steam dryness detector 23 converts a physical quantity, ie, steam dryness, into an electric signal.
Is connected. The steam dryness discriminator 24 includes an upper limit steam dryness detector 24A, a lower limit steam dryness detector 24B, and an instruction signal output unit 24C.
When the detected steam dryness from step 3 exceeds the set upper limit value X, the upper limit steam dryness detector 24A sends the instruction signal output unit 2
4C, and when the detected steam dryness from the steam dryness detector 23 is equal to or larger than the set lower limit Y, the steam dryness is output from the lower steam dryness detector 24B to the instruction signal output unit 24C, and the upper steam dryness is also detected. When output from both the degree detector 24A and the lower limit steam dryness detector 24B, the operation instruction signal of the water supply pump 8 is transmitted from the instruction signal output unit 24C to the upper limit steam dryness detector 24A and the lower limit steam dryness detector. The output from the instruction signal output unit 24C is continued when there is no output from both the upper steam dryness detector 24A and the lower steam dryness detector 24B. The stop instruction signal of the pump 8 is continuously output until it is output from both the upper limit steam dryness detector 24A and the lower limit steam dryness detector 24B.

An instruction signal output section 24C of the steam dryness discriminator 24 is directly connected to the feedwater pump actuator 22, and a connection line between the instruction signal output section 21C of the water level discriminator 21 and the feedwater pump actuator 22. 25 and a connection line 26 between the instruction signal output portion 24C of the steam dryness discriminator 24 and the feed water pump actuator 22, a switch 27 is provided. An a contact 27a interlocked with 27b is incorporated in the connection line 26. The switch 27 may have a contact structure or a non-contact structure, and a delay release relay may be employed as the feed pump actuator 22.

A steam pressure detector 29 for detecting the steam pressure in the steam pipe 13 is connected to a switching actuator 28 of the switching device 27.
It is connected via a steam pressure discriminator 30 that outputs when the detected steam pressure is equal to or higher than the required pressure, and instructs to burn by opening the fuel valve and igniting the burner 6 to start combustion. The combustion indicator 31 is connected to the switching actuator 28 via the timer 32, and is inputted from the timer 32 and inputted from the vapor pressure discriminator 30 when the detected vapor pressure of the vapor pressure detector 29 becomes higher than a required pressure. At times, the switching actuator 28 operates. As the vapor pressure detector 29, a device that outputs when the detected vapor pressure becomes equal to or higher than a required pressure may be employed, and the vapor pressure discriminator 30 may be omitted.
The output signal of the combustion indicator 31 disappears when the combustion stops, the timer 32 is cleared to zero, and when the combustion starts again, the timer 32 operates to output a time-up signal.

Next, the operation of the water supply control device for the multi-tube once-through boiler of the present invention will be described.

When the multi-tube once-through boiler is started, it is checked whether or not the water level is at a normal level (a water level between water levels A and B). Is operated to bring the water level to the normal level, the fan is operated at the same time as the start-up, the pre-purge is performed, the fuel valve is opened and the burner 6 is ignited to start combustion.

Combustion is started by a combustion instruction signal from the combustion indicator 31, and a signal instructing combustion is output from the combustion indicator 31 to the timer 32. Based on the output, the timer 32 operates after a required time. When the steam pressure is output to the switching actuator 28 and the steam generation from the water in the heating pipe 3 becomes active with the continuation of the combustion and the detected steam pressure of the steam pressure detector 29 becomes higher than a required pressure, the steam pressure discriminator 30 And the switching actuator 28 is operated, and the b contact 27 of the switching
When b is closed to open and the a contact 27a is opened to closed, the connection line 25 is disconnected and the connection line 26 is connected.
That is, from the start of combustion until the steam pressure reaches the required pressure, the water supply to the heating pipe 3 is controlled by operating and stopping the water supply pump 8 based on the detected water level as shown in the chart on the left side of FIG. When the required time elapses after the start of combustion and the steam pressure becomes equal to or higher than the required pressure, the water supply control by the water supply pump 8 is performed based on the detected steam dryness of the steam dryness detector 23 as shown in the chart on the right side of FIG. become.

The steam generated from the heating pipe 3 and reaching the steam pipe 13 is detected by the steam dryness detector 23 as the steam dryness. When the steam is continuously generated by the combustion heating of the heating pipe 3 and the water level of the heating pipe 3 falls and the steam dryness exceeds the upper limit X, the steam dryness is output from the upper steam dryness detector 24A and the lower steam dryness is output. The operation signal of the water supply pump 8 is also output from the instruction signal output unit 24C to the water supply pump actuator 22 because it is also output from the degree detection unit 24B, and the operation of the water supply pump actuator 22 causes the water supply pump 8 to operate. Start. By the operation of the water supply pump 8, water is supplied to the heating pipe 3 and the water level rises, and the heating of the heating pipe 3 is prevented. As a result, the life of the boiler can be extended.

As the water level of the heating pipe 3 rises due to the operation of the water supply pump 8, the temperature of the heating pipe 3 falls, and when the steam dryness falls to the upper limit value X or less, the steam dryness discriminator. Although the output is not output from the upper limit steam dryness detector 24A of 24, but is output from the lower limit steam dryness detector 24B, the operation instruction signal is output from the instruction signal output unit 24C and the operation of the feedwater pump 8 is continued. Have been.

Further, when the water level of the heating pipe 3 rises and the steam dryness detected by the steam dryness detector 23 falls and becomes lower than the lower limit Y, the lower limit steam dryness detector 24B of the steam dryness discriminator 24 also sends a signal. Therefore, the output signal is not output, and the instruction signal of the instruction signal output unit 24C is switched from the operation instruction signal of the water supply pump 8 to the stop instruction signal and output. The water supply pump actuator 22 is operated based on the stop instruction signal, and the water supply pump 8 is turned off. Stops.

Even if the water supply pump 8 is stopped, the heating pipe 3
Steam generation is continuing and the steam dryness detector 2
3, when the steam dryness rises and exceeds the lower limit Y, the lower limit steam dryness detector 24 of the steam dryness discriminator 24
Although output from B, since it is not output from the upper limit steam dryness detection unit 24A, a stop instruction signal is output from the instruction signal output unit 24C, and the water supply pump 8 is still in a stopped state.

Further, when the water level falls due to the heating of the heating pipe 3 and the steam dryness detected by the steam dryness detector 23 rises and exceeds the upper limit X, the upper limit steam dryness detector 24A of the steam dryness discriminator 24. Therefore, the instruction signal of the instruction signal output unit 24C is switched from the stop instruction signal of the water supply pump 8 to the operation instruction signal and output. The water supply pump actuator 22 is operated based on the operation instruction signal, and the water supply pump is operated. 8 starts operation.

As described above, after the required time elapses and the required pressure steam is generated after starting and burning the boiler,
As shown in the chart on the left side of FIG. 3, the water supply pump 8 is operated and stopped by the output instruction signal of the water level discriminator 21 for performing water level discrimination based on the water levels A and B, and the water supply is controlled to generate steam of a required pressure. After that, as shown in the chart on the right side of FIG. 3, the water supply control is performed by operating and stopping the water supply pump 8 based on the detected steam dryness of the steam dryness detector 23. The steam can be corrected upward or downward, the control width (the water level interval between the water levels A and B) can be widened or narrowed, and high-quality steam with good steam dryness can be supplied from the steam pipe 13 to the steam consuming area. And the length of the high water level detection electrode 18 and the low water level detection electrode 19, and the mounting position of the water column pipe 15 with respect to the upper header 4, lower header 5 and heating pipe 3, etc. Adjustment can be simplified.

FIG. 2 shows the operation and stop cycles of the water supply pump 8 for supplying water based on the steam dryness described above. In Figure 2, the water supply pump 8 Between times T ₅ through T ₆ is operated, it stops the water supply pump 8 is between the time T ₆ through T _7, the time T
Feed pump 8 Between ₇ through T ₈ will be the cycle is repeated as the driver.

It should be noted that the present invention is not limited to the embodiment shown and described.
An upper limit steam dryness detector 24A that outputs in the following cases;
A lower limit steam dryness detector 24B and an upper limit steam dryness detector 24A that output when the detected steam dryness is equal to or less than the lower limit Y.
Forming a steam dryness discriminator 24 from an instruction signal output unit 24C that outputs a stop instruction signal when there is an output from both the lower limit steam dryness detector 24B and an operation instruction signal when there is no output. By incorporating a delay circuit into the combustion indicator 31 and instructing combustion to output after a required time, the timer 32 is omitted, and a float switch is used as a water level detector instead of the water level detection electrode. It is optional to adopt a boiler that detects the water level.
Of course, various changes can be made without departing from the spirit of the present invention.

[0040]

As described above, the water supply control device of the multi-tube once-through boiler of the present invention controls the water supply based on the steam dryness, so that the steam dryness can always be kept within a certain range. It can supply good quality steam with good dryness,
It can prevent overheating of the heating pipe and extend the life of the boiler, and it can be manufactured with the same precision as the boiler in which the water level is adjusted by operating the water supply pump appropriately based on the detected water level without considering the steam dryness. Various excellent effects are exhibited, such as the production of the water level detecting portion without being restricted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a water supply control device for a multi-tube once-through boiler of the present invention.

FIG. 2 is a diagram showing the relationship between the steam dryness and the operation and stop of a water supply pump by a water supply control device for a multi-tube once-through boiler of the present invention.

FIG. 3 is a chart showing an operation state of a water supply control device for a multi-tube once-through boiler of the present invention.

FIG. 4 is a block diagram showing a conventional water supply control device for a multi-tube once-through boiler.

FIG. 5 is a diagram showing the relationship between the water level and the operation and stoppage of a water supply pump by a conventional water supply control device for a multi-tube once-through boiler.

[Explanation of symbols]

 2 Combustion chamber 3 Heating pipe 7 Water supply pipe 8 Water supply pump 13 Steam pipe 15 Water column pipe 18 High water level detection electrode (water level detection tool) 19 Low water level detection electrode (water level detection tool) 20 Common electrode (water level detection tool) 21 Water level Discriminator 22 feedwater pump actuator 23 steam dryness detector 24 steam dryness discriminator 25, 26 connection line 27 switch 27a a contact 27b b contact 28 switching actuator 29 steam pressure detector 31 combustion indicator

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-148102 (JP, A) JP-A-56-155304 (JP, A) JP-A-4-306404 (JP, A) JP-A-56-155 155304 (JP, A) JP-A-61-235602 (JP, A) JP-A-49-7601 (JP, A) Japanese Utility Model Laid-Open No. 60-105909 (JP, U) (58) Fields investigated (Int. ⁶ , DB name) F22B 35/00 F22D 5/00

Claims (1)

(57) [Claims] A water level detector is provided on a water column pipe whose water level fluctuates in synchronization with the water level of a vertical heating pipe provided around a combustion chamber, and the water level is detected based on the water level detected by the water level detector. A water level discriminator that determines and outputs a water supply pump operation / stop instruction signal is connected to a water supply pump actuator that performs operation and stop operation of a water supply pump that supplies water to the heating pipe, and starts or stops the water supply pump to supply water. In a water supply control device for a multi-tube once-through boiler that performs control, a steam dryness detector that detects a steam dryness is provided in a steam pipe that leads out steam generated from a heating pipe, and the steam dryness detection is performed. A steam dryness discriminator for discriminating the steam dryness based on the steam dryness detected by the detector and outputting an operation / stop instruction signal for the water supply pump is connected to the water supply pump actuator, and the water level discriminator and the water supply pump actuator are connected. And the steam drying The contact a of the switch is incorporated into one of the connection lines between the feeder discriminator and the feed water pump actuator, and the contact b is interlocked with the contact a in the other connection line. A water supply control device for a multi-tube once-through boiler, comprising a switching actuator for switching the switching device based on an output signal from a combustion indicator.