JP2001165404A - Feedwater control device for boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent drastic variation of water level and stabilize the dryness of steam in an once-through boiler. SOLUTION: A boiler comprises a water level detector 8 for detecting the water level in the boiler 1, feedwater devices 6, 7 for feeding feedwater to the boiler and an operation control device 12 for controlling the feedwater devices on the basis of the water level detected by the water level detector. The water level detector detects a water level at a water level position E1 and a water level position E2 which is lower than the position E1. The feedwater devices can control feedwater feed velocity. When the water level goes down to the position E2 during the operation of the boiler, the operation control device conducts H% of water feed, and when the water level goes up to the position E1, the device conducts L% of water feed. The feedwater feed velocity of the H% water feed is larger than the set value of the water feed velocity of the L% water feed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler water supply control device.

[0002]

2. Description of the Related Art In the case of a once-through boiler in which the water level is maintained in the middle of a water pipe, if the water level is too high, the water quality is deteriorated because the can water is taken out together with the steam. The water level must be kept within a certain narrow range because the top is overheated. Therefore, in a once-through boiler,
The upper and lower limits of the water level are set in a narrow range, and water supply starts when the water level falls to the lower limit, and stops when the water level rises to the upper limit due to water supply. The pump has a problem that the service life is shortened because the pump starts and stops in a short time.

[0003] In addition, when rapid water supply is performed, the temperature of the still water in the boiler decreases and the time required to reach the evaporating temperature increases, so that the gas-liquid mixture rising in the water pipe has a low liquid ratio. And the steam removed from the boiler may contain a large amount of liquid, resulting in reduced steam dryness.
Water supply is stopped when the water level rises to the upper limit, but there is a time difference between when the water level reaches the upper limit and when water supply is actually stopped. There is also a problem that the value is significantly higher than the value, and the dryness of steam may be reduced.

[0004]

An object of the present invention is to prevent a sudden change in water level and to stabilize the dryness of steam in a once-through boiler.

[0005]

A water level detector for detecting a water level in a boiler, a water supply device for feeding water into the boiler, and an operation control device for controlling the water supply device based on the water level detected by the water level detector. Wherein the water level detector obtains the water level by detecting the presence or absence of water at the E1 water level and the E2 water level, which is lower than the E1 water level, to obtain a water level. Is a device capable of adjusting the water supply speed. During operation of the boiler, the operation control device changes the detection result at the E2 water level from water-less to water-less or water-less to water-present. The H% water supply command is output when the water supply device is turned on, and the water supply device supplies water with the H% capacity of the water supply device according to the H% water supply command.
Water is supplied, and when the detection result at the E1 water level is changed from “with water” to “without water”, or from “without water” to “with water”, L
% Water supply command is output, and the water supply device performs L% water supply in which water is supplied with the capacity of L% of the water supply device according to the L% water supply command. The set value of the water supply speed of H% water supply is L% water supply. Is set to be larger than the set value of the water supply speed.

The set values of the H% water supply and the L% water supply are each allowed to be corrected, and the water level detector detects a high water level higher than the E1 water level and a low water level lower than the E2 water level. The presence or absence of water is also detected at the position, and when the absence of water is detected at the low water level, the set value of the water supply speed performed at the time of L% water supply and H% water supply is corrected to a larger value than before, When the presence of water is detected at the high water level, the set value of the water supply speed performed at the time of L% water supply and H% water supply is corrected to a smaller value than before.

[0007] The water level lowering time required from when the water level becomes lower than the E1 water level to when the water level becomes lower than the E2 water level is detected, and the water level lowering time is calculated from a preset time T1 set in advance. If the water level is also short, the set value of the water supply speed performed at the time of L% water supply and H% water supply is corrected to a larger value than before, and the water level becomes higher than the E1 water level position when the water level becomes higher than the E2 water level position. The rising time of the water level required up to this point is detected, and when the rising time of the water level is shorter than the preset time T2 set in advance, the set value of the water supply speed performed at the time of L% water supply and H% water supply is changed. Correct to a smaller value than.

If the boiler is capable of increasing or decreasing the amount of heating, and if the amount of heating in the boiler is small, the set values of the water supply rates performed during L% water supply and H% water supply are set to small values, respectively. When the heating amount in the boiler is large, the set values of the water supply speeds to be performed at the time of L% water supply and H% water supply are set to large values, respectively.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of a boiler embodying the present invention. The boiler 1 has an upper header 2 at the upper part and a lower header 3 at the lower part.
Are connected by The central portion of the boiler is a combustion chamber 10, and by generating a flame in the combustion chamber by a burner 11 provided at the upper part of the combustion chamber, the can water in the water pipe is heated to generate steam. And the like. Water is supplied to the boiler through a water supply pipe 5 connected to the lower header 3.
Is provided with a water supply pump 6 and an electric water supply valve 7 downstream of the water supply pump 6.
Corresponds to the water supply device. The degree of opening of the water supply electric valve 7 is allowed to be changed, and the water supply speed when the water supply pump 6 is operated is adjusted by changing the degree of opening of the water supply electric valve 7.

[0010] The water level in the boiler is detected by a water level detector 8 connected to a steam portion in the upper portion of the boiler and a canned water portion in the lower portion of the boiler. In the water level detector 8, four water levels are detected. Are provided. The four electrode rods 9 have different tip positions, and each electrode rod detects whether the water level is higher or lower than the electrode rod tip position depending on whether the tip is in contact with water. The four electrode rods detect the presence or absence of water at four positions, a high water position, an E1 water position, an E2 water position, and a low water position, from the high side. The water level can be determined based on the signal.

The operation of the boiler is controlled by the water level detector 8,
The operation is performed by the operation control device 12 connected to the burner 11, the water supply pump 6, the water supply electric valve 7, the pressure detection device 13, and the like. The operation control device 12 controls the operation of each device. If the boiler performs the combustion control at three positions of high combustion, low combustion, and stop, the operation control device 12 will perform high combustion, low combustion,
A control signal for one of the stops is output to change the combustion amount in the burner 11. The operation control device 12 includes the water level detector 8
The combustion control is performed based on the water level detected by the pressure sensor 13 and the steam pressure value detected by the pressure detection device 13. When the water level is lower than the low water level, the combustion is stopped, and the water level is lower than the low water level. When the steam pressure is high and the steam pressure is low, combustion is performed. During the combustion, high combustion or low combustion is performed according to the steam pressure value.

The operation control device 12 controls the water supply according to the water level detected by the water level detector 8, and the water supply pump 6 is operated continuously, and the opening of the electric water supply valve 7 is controlled according to the water level. By changing, the amount of water passing through the water supply pipe 5 is adjusted, and the water supply speed is adjusted. Therefore, in this case, the set value of the water supply speed is determined by the opening degree of the electric water supply valve 7.

When the water level becomes lower than the low water level,
The operation control device 12 outputs a 100% water supply command, makes the opening of the water supply motorized valve 7 fully open, and performs 100% water supply, which is water supply according to the capacity of the water supply pump 6. When the detection result at the E2 water level is changed from water to no water, and when the detection result at the E2 water level is changed from no water to water, the operation control device 12 outputs an H% water supply command, H% water supply is performed in which water is supplied for H%, with the opening of the water supply electric valve 7 being H% (for example, 80%). When the detection result at the E1 water level is changed from water to no water, and when the detection result at the E1 water level is changed from no water to water, the operation control device 12 outputs an L% water supply command. L% water supply is performed in which the opening degree of the water supply electric valve 7 is set to L% (for example, 30%) to supply water for L%. When the water level becomes higher than the high water level position, the operation control device 12 outputs a water supply stop command, and stops the water supply by fully closing the opening of the water supply electric valve 7.

When the opening of the H% feed water and the opening of the L% feed water are appropriate values and the steam generation amount is stable, the water level of the boiler is set at the E1 water level and the E2 water level as shown in FIG. Move up and down between positions in long cycles. First, a description will be given based on FIG. Initially, the operation control device 12 outputs the H% water supply command,
The H% water supply is performed by setting the opening of the water supply electric valve 7 to the H% opening. If the set value of H% is 80%, the water supply speed is 80% when the water supply motor-operated valve 7 is fully opened, and the water supply speed in the H% water supply is higher than the decrease speed of the water volume in the can due to the generation of steam. If it is large, the water level will rise.

At this time, the operation control device 12 requires the time from when the detection result at the E2 water level is changed from no water to water to when the detection result at the E1 water level is changed from no water to water. Detect the rise time of the water level. The rising time of the water level is compared with a predetermined time T2 set in advance to determine that the water level has risen sharply. If the rising time of the water level is longer than the time T2, a rapid change in the water level occurs. You can see that he did not.

When the water level rises due to the H% water supply and the water level becomes higher than the E1 water level and the detection result of the electrode rod 9 at the E1 water level changes from no water to water, the operation control device 12 sets The L% water supply is performed by outputting the L% water supply command and setting the opening of the water supply electric valve 7 to the L% opening. If the set value of L% is 30%, the water supply speed is 30% when the water supply motor-operated valve 7 is fully opened, and the water supply speed in the L% water supply is higher than the reduction speed of the water volume in the can due to the generation of steam. If it is small, the water level will drop.

Also at this time, the operation control device 12 needs the time from when the detection result at the E1 water level is changed from water to no water to when the detection result at the E2 water level is changed from water to water. Detected water level drop time. The water level drop time and a set time T set in advance to determine that the water level has dropped sharply.
Comparison of 1 shows that when the water level drop time is longer than the set time T1, no rapid change in the water level occurs.

When the L% water supply reduces the water level, the water level becomes lower than the E2 water level, and the detection result of the electrode rod 9 at the E2 water level changes from the presence of water to the absence of water. The H% water supply is performed by outputting the H% water supply command and setting the opening of the water supply electric valve 7 to the H% opening. When the steam generation amount is stable, the above contents are repeated.

FIGS. 3 to 6 show examples in which the set value of the water supply speed is corrected. In the case of FIG. 3 to FIG. 6, the initial set values are 80% for H% and 30% for L%, the water level is increased by the H% water supply, and the water level is increased to the E1 water level position and the L% water supply is performed. Is the same as in FIG.

FIG. 3 shows that the amount of generated steam is larger than that in FIG. 2 so that the rate of decrease in the water level in the can is large, and the time required for the water level to decrease from the E1 level to the E2 level is reduced. ing. The operation control device 12 compares the water level lowering time until the water level drops from the E1 water level to the E2 water level with the set time T1, and since the water level lowering time is shorter than the set time T1, the water level sharply drops. Recognize that is occurring.

In the operation control device 12, H% water supply and L%
The set value of the water supply is corrected to a larger value than before, and H
% To 90% and L% to 40%. Next H
In the case of% water supply, the opening of the electric water supply valve 7 is set to 90%, and in the case of L% water supply, the opening of the electric water supply valve is set to 40%. When the water level of the L% water supply motor-operated valve 7 is set to 40% during the second water level lowering, the water level lowering time is longer than the previous water level lowering time, but is still shorter than the set time T1. In this case, the operation control device 12 sets the set values of the H% water supply and the L% water supply to larger values (H% is set to 100% and L% is set to 5%).
0%).

In the first half of FIG. 4, contrary to FIG. 3, the rising time of the water level is short because the rate of reduction of the water content in the can is small. In this case, in the operation control device 12, H% water supply and L
The set value of% water supply is corrected to a smaller value than before,
Correct H% to 70% and L% to 20%. In the L% water supply performed thereafter, the opening degree of the water supply electric valve 7 is set to 20%,
In the case of H% water supply, the opening of the electric water supply valve is set to 70%. The latter half of FIG. 4 shows a case in which the water level drops sharply with the corrected value because the reduction rate of the water volume in the can has reached the normal level. When the water level decrease time is shorter than the set time T1, the operation control device 12 corrects the set values of the H% water supply and the L% water supply to values larger than before, and changes H% to 80%.
Correct L% to 30%. Since the set value of H% water supply and the set value of L% water supply are simultaneously corrected in the same direction,
If conditions change, you can return immediately.

FIG. 5 shows the case where the water level rises even when the set value of the L% water supply is 30%. When the water level rises to the high water level and the detection result by the electrode rod 9 at the high water level changes from no water to water, the operation control device 12 outputs a water supply stop command and the opening degree of the water supply electric valve 7 is fully adjusted. Water supply is stopped by closing. In this case, the operation control device 12 corrects the set values of the H% water supply and the L% water supply to values smaller than before, and sets the H% to 70%.
% And L% are corrected to 20%. Water level drops and E1
Stop supplying water until the water level is lower than the water level.
When it becomes lower than the first water level, the operation control device 12 outputs an L% water supply command, and sets the opening of the water supply electric valve 7 to 20%.
Although the description using the figure is omitted, the same correction is performed when the water level becomes lower than the low water level, in which case the set values of the H% water supply and the L% water supply are set to larger values. to correct.

FIG. 6 shows a case where the heating amount of the boiler is changed from high combustion to low combustion in the first half, and is changed from low combustion to high combustion in the second half. When the heating amount is changed from high combustion to low combustion, the operation control device 12 sets H% to 50% and L% to 2%.
It is corrected to 0%, and the degree of opening of the water supply electric valve 7 is changed from 80% to 50% during the H% water supply. L performed after that
In the case of% water supply, the opening degree of the feed water electric valve 7 is set to 20%, and in the case of H% water supply, the opening degree of the electric water supply valve 7 is set to 50%. When the heating amount of the boiler is changed from low combustion to high combustion in the latter half of FIG. 6, the operation control device 12 corrects H% to 80%, L% to 30%, and sets the opening of the feed water motorized valve 7 to 50%. Change from% to 80%.

When the water level drops sharply, when the water level drops to a low water level, or when the heating amount of the boiler is increased, the water level rise at the time of H% water supply becomes gentle. The water level does not rise significantly than the position, and the water level drops sharply when L% water is supplied.
It is more likely that the water level will be significantly lower than the E2 level. In this case, by correcting the set values of the H% water supply and the L% water supply to large values, it is possible to prevent the water level from dropping rapidly, and it is not necessary to change the water supply speed in a short time.

Conversely, when the water level rises sharply, when the water level rises to a high water level, and when the heating amount of the boiler is reduced, the water level decreases gradually during L% water supply. The water level does not drop significantly from the E2 water level, and the water level rises abruptly at the time of H% water supply. Therefore, the possibility that the water level becomes significantly higher than the E1 water level increases. In this case, by correcting the set values of the H% water supply and the L% water supply to small values, it is possible to prevent the water level from rising rapidly, and it is not necessary to change the water supply speed in a short time.

[0027] Further, when there is still water near the upper limit and the temperature of the still water drops due to rapid water supply, the gas-liquid mixture having a large proportion of liquid is lifted, and the dryness of the steam decreases, When the water supply speed immediately before stopping the water supply is high, the water level becomes high between the time when the water level reaches the upper limit and the time when the water supply is actually stopped. As in the present invention, when the water level rises, the water supply speed is reduced to prevent the steam dryness from decreasing.

In this embodiment, the water supply pump 6 is operated continuously, and the water supply speed is changed by the opening of the electric water supply valve 7. However, the apparatus for controlling the rotation speed of the water supply pump 6 and the water supply pump is used. A water supply device may be configured, and the water supply speed may be changed by changing the rotation speed of the water supply pump 6. Further, the increase / decrease of the heating amount of the boiler is not limited to the one that performs the three-position combustion control, and may be applied to, for example, an exhaust gas boiler in which the exhaust gas supply amount is changed.

[0029]

According to the present invention, a rapid change in water level can be suppressed, and the dryness of steam can be stabilized.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an outline of a boiler embodying the present invention.

FIG. 2 is an explanatory diagram of a water level and an opening of a water supply electric valve in one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a water level and a water supply electric valve opening degree in one embodiment of the present invention.

FIG. 4 is an explanatory diagram of a water level and an opening of a water supply electric valve in one embodiment of the present invention.

FIG. 5 is an explanatory view of a water level and an opening of a water supply electric valve in one embodiment of the present invention.

FIG. 6 is an explanatory view of a water level and an opening of a water supply electric valve in one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler 2 Upper header 3 Lower header 4 Water pipe 5 Water supply pipe 6 Water supply pump 7 Water supply electric valve 8 Water level detector 9 Electrode rod 10 Combustion chamber 11 Burner 12 Operation control device 13 Pressure detection device

Claims (5)

[Claims] A water level detector for detecting a water level in a boiler,
A boiler provided with a water supply device for feeding water into the boiler and an operation control device for controlling the water supply device based on a water level detected by a water level detector, wherein the water level detector is E1
The water level is obtained by detecting the presence or absence of water at the water level position and the E2 water level, which is a position lower than the E1 water level, so that the water supply apparatus can adjust the water supply speed. During the operation of the boiler, the operation control device sets the H% when the detection result at the E2 water level is changed from the presence of water to the absence of water, or from the absence of water to the presence of water.
A water supply command is output, and the water supply device performs H% water supply in which water is supplied at the H% capacity of the water supply device according to the H% water supply command.
The L% water supply command is output when the detection result at the first water level is changed from water-less to water-less or from water-less to water-filled, and the water supply device receives the L% water supply command according to the L% water supply command.
L% to supply water with the capacity of one minute
A water supply control device for a boiler, wherein a set value of a water supply speed of the water supply is set to be larger than a set value of a water supply speed of the L% water supply. 2. The boiler water supply control device according to claim 1, wherein the set values of the H% water supply and the L% water supply are each capable of being corrected, and when the set values are corrected, the H% water supply and the L% water supply are corrected.
A water supply control device for a boiler, wherein a set value of% water supply and a set value of L% water supply are corrected simultaneously and in the same direction. 3. The water supply control device for a boiler according to claim 1, wherein the water level detector includes a high water level position higher than the E1 water level position and a low water level position lower than the E2 water level position. The presence or absence of water is detected, and when the absence of water is detected at the low water level,
The water supply speed set at the time of L% water supply and H% water supply is corrected to a larger value than before, and when the presence of water is detected at the high water level, the water supply speed performed at the time of L% water supply and H% water supply. A boiler water supply control device, wherein the set value of the boiler is corrected to a smaller value than before. 4. The water supply control device for a boiler according to claim 1, wherein a water level lowering time required from when the water level becomes lower than the E1 water level to when the water level becomes lower than the E2 water level is detected. If the water level lowering time is shorter than the preset time T1 set in advance, the set value of the water supply speed performed at the time of L% water supply and H% water supply is corrected to a larger value than before, and the water level becomes the E2 water level. The water level rise time required from when the water level rises above the position to when the water level rises above the E1 water level position is detected, and when the water level rise time is shorter than a preset time T2, L% A water supply control device for a boiler, wherein a set value of a water supply speed performed at the time of water supply and H% water supply is corrected to a value smaller than before. 5. The water supply control device for a boiler according to claim 1, wherein the boiler can increase or decrease the amount of heating, and if the amount of heating in the boiler is small, L% water supply and H% water supply. When the amount of heating in the boiler is large, the set value of the water supply speed performed at the time of L% water supply and H% water supply is set to a large value, respectively. Characteristic boiler water supply control device.