JP2002039506A - Drum level controller for boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drum level controller for a boiler, which can suppress lowering of the drum level to a minimum at the occurrence of runback, and can stabilize control. SOLUTION: The controller is constructed, such that a control command is outputted to a feed water pump 15 for eliminating feed water flow rate deviation 33 between a feed water flow rate set value 31 and an actual feed water flow rate 29 detected by a feed water flowmeter 22. After the occurrence of runback, the value 31 is set higher by a required amount α [t/h] for a required period β [second].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Generally, as shown in FIG. 2, a boiler such as a drum boiler for generating steam in a power plant or the like has a brackish water separating drum 1a at an upper portion and a water drum 1b at a lower portion. In the boiler body 1, combustion air is supplied from a combustion air duct 3 through a wind box 4 by a forced draft fan 2, and a fuel F such as light oil is supplied from a fuel supply pipe 5 and injected from a burner 6. The steam in the heat transfer tube of the boiler main body 1 is heated by the generated combustion gas to generate steam, and the steam is taken out from the steam separation drum 1a via the steam pipe 7 and sent to the steam header 8. On the other hand, the combustion gas whose heat has been taken away is discharged from a chimney (not shown) to the atmosphere via a flue 9.

In FIG. 2, reference numeral 10 denotes a fuel cutoff valve provided in the middle of the fuel supply pipe 5, reference numeral 11 denotes a main steam stop valve provided in the middle of the steam pipe 7, and reference numeral 12 denotes ignition of propane gas or the like when the boiler is started. Is a burner for ignition to which the fuel F 'is supplied.

[0004] On the other hand, a deaerator 13 is mounted on the upper part of the brackish water separation drum 1a.
The water stored in 4 is supplied to the brackish water separation drum 1 a via the water supply pipe 16 by the operation of the water supply pump 15 and the deaerator 13. Although not shown, a plurality of water supply pumps 15 are juxtaposed in order to cope with a failure or the like.

The amount of water to be supplied to the brackish water separation drum 1a is adjusted by controlling the water supply pump 15. The water supply pump 15 is detected by a drum level meter 18. The water level or drum level 19 inside the brackish water separating drum 1a, the steam flow rate 21 detected by a steam flow meter 20 provided in the middle of the steam pipe 7, and the feed water flow meter 22 provided in the middle of the feed pipe 16 Command 25 output from the drum level controller 24 based on the feed water flow rate 23 detected by the
Is controlled by the

As shown in FIG. 3, the drum level controller 24 finds the difference between the specified drum level 26 inside the brackish water separation drum 1a and the actual drum level 19 detected by the drum level meter 18. Subtractor 28 which outputs a drum level deviation 27 by means of a water supply flow rate 29 which is necessary to eliminate the drum level deviation 27 by performing a proportional integration process on the drum level deviation 27 outputted from the subtracter 28.
And a proportional-integral controller 30 that outputs
The steam flow rate 21 detected by the steam flow meter 20 is added to the feed water flow rate 29 output from 0, and the feed water flow rate set value 3
An adder 32 that outputs 1 and a subtraction that calculates a difference between a set value 31 of the feed water flow output from the adder 32 and an actual feed water flow 23 detected by the feed water flow meter 22, and outputs a feed water flow deviation 33. And a proportional-integral adjuster 35 for outputting a control command 25 for eliminating the feedwater flow deviation 33 to the feed pump 15 by proportionally integrating the feedwater flow deviation 33 outputted from the subtractor 34. It has the structure which consists of.

During operation of the boiler as described above, the drum level 19 inside the brackish water separation drum 1a is detected by the drum level meter 18, and the steam flow rate 21 introduced into the steam header 8 is detected by the steam flow meter 20. ,
Further, the actual feed water flow rate 23 supplied to the brackish water separation drum 1a is detected by the feed water flow meter 22, and the respective detected values are input to the drum level controller 24, and the subtractor of the drum level controller 24 At 28, the difference between the specified water level 26 of the drum level inside the brackish water separation drum 1a and the actual drum level 19 detected by the drum level meter 18 is obtained, and a drum level deviation 27 is output to the proportional integral controller 30. And the proportional-integral controller 30
In the above, the drum level deviation 27 output from the subtracter 28 is proportionally integrated, and a feedwater flow rate 29 for eliminating the drum level deviation 27 is output to an adder 32. In the adder 32, the proportional integration controller The steam flow rate 21 detected by the steam flow meter 20 is added to the feed water flow rate 29 output from the feed water flow rate 30, and the feed water flow rate set value 3
1 is output to the subtractor 34, where the feedwater flow rate set value 31 output from the adder 32 is output.
And the actual feedwater flow rate 23 detected by the feedwater flowmeter 22 is obtained, and a feedwater flow rate deviation 33 is output to a proportional-integral adjuster 35, where the output from the subtractor 34 is output. The supplied water flow rate deviation 33 is proportionally integrated, and a control command 25 for eliminating the supplied water flow rate deviation 33 is output to the water supply pump 15. The water supply pump 15 is controlled in accordance with the control command 25, and the brackish water separating drum is used. The amount of water supplied to 1a is adjusted so that the drum level 19 of the brackish water separation drum 1a is maintained at the specified water level 26.

[0008]

In the above-mentioned conventional boiler, when runback (emergency load drop) must be performed for some reason, the fuel F and the combustion air are rapidly supplied. Simultaneously with the narrowing down, the required number of burners 6 out of the plurality of burners 6 are extinguished. With this, the bubbles in the can water are crushed, and the drum level 19 is rapidly reduced due to the crush of the bubbles in the can water. Will drop.

Here, in the case of the conventional drum level controller 24 as described above, basically, while supplying the same amount of water as the steam flow rate 21 flowing out through the steam pipe 7, the specified water level of the drum level 19 is controlled. 26, the water supply flow rate 23 is increased or decreased. However, when the runback occurs as described above, the control cannot follow the rapid decrease in the drum level 19, and the drum level 19 rapidly decreases. After that, the level is pulled back, and the control becomes unstable.

The present invention has been made in view of the above circumstances, and has as its object to provide a drum level control device for a boiler capable of minimizing a decrease in drum level when runback occurs and stabilizing control. is there.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a feed pump for supplying water to a steam separation drum of a boiler, a drum level meter for detecting a drum level of the steam separation drum, and a steam supply drum. A steam flow meter for detecting the flow rate of the steam flowing out, a feed water flow meter for detecting the flow rate of the feed water supplied to the brackish water separation drum, and a drum level deviation between the specified water level and the actual drum level detected by the drum level meter The feedwater flow rate required to eliminate the water flow rate and the steam flow rate detected by the steam flowmeter are added to obtain a feedwater flow rate set value, and the feedwater flow rate set value and the actual feedwater flow rate detected by the feedwater flowmeter are calculated. It is configured to output a control command for eliminating the feedwater flow deviation to the feedwater pump, and after the occurrence of runback, the feedwater flow set value is increased by the required time and required amount. In which according to the drum level controller of the boiler being characterized in that a drum level controller which is adapted to the constant.

According to the above means, the following effects can be obtained.

The amount of water supplied to the brackish water separation drum is
When runback occurs, the required time and amount are increased immediately after the runback, so when runback occurs, fuel and combustion air are rapidly reduced, and at the same time, the required number of burners out of multiple burners is used. When the fire is extinguished, even if the bubbles in the can water are crushed, the drum level does not drop sharply, and the control is performed stably.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment of the present invention. In the drawing, portions denoted by the same reference numerals as those in FIGS. 2 and 3 represent the same components, and the basic configuration is shown in FIGS. 3 is the same as the conventional one shown in FIG. 3, but the feature of this illustrated example is that, as shown in FIG. The point is that it is configured to be set higher by [t / h].

In the illustrated example, after the occurrence of runback, β
It is switched to the a side only for [sec], and α [t / h] is output as the increment 36 of the water supply flow rate set value 31, while at other normal times, it is switched to the b side and 0 [t / h]
37 as an increase 36 of the feedwater flow set value 31, and the increase 36 of the feedwater flow set value 31 output from the switch 37 is added to the feedwater flow set value 31 output from the adder 32. Further, an adder 38 that outputs the water supply flow rate set value 31 ′ to the subtractor 34 is additionally provided.

It should be noted that α [t / h] as an increment 36 of the feedwater flow rate set value 31 when a runback occurs and β [second] as a time for increasing the feedwater flow rate set value 31 during runback. The optimum value is selected according to the load.

Next, the operation of the illustrated example will be described.

During operation of the boiler, the drum 1 for brackish water separation is used.
The drum level 19 inside is detected by the drum level meter 18, the steam flow rate 21 introduced into the steam header 8 is detected by the steam flow meter 20, and the actual water supply to the steam separation drum 1 a is further performed. The flow rate 23 is detected by the feed water flow meter 22, and the respective detected values are input to the drum level controller 24. The subtractor 28 of the drum level controller 24 defines the drum level inside the brackish water separation drum 1 a. The water level 26 and the actual drum level 19 detected by the drum level meter 18
Is obtained and the drum level deviation 27 is output to the proportional-integral controller 30. In the proportional-integral controller 30, the drum level deviation 27 output from the subtracter 28 is proportionally integrated, and the drum level deviation is calculated. The feedwater flow rate 29 for eliminating 27 is output to an adder 32, and the adder 32
In, the steam flow rate 21 detected by the steam flow meter 20 is added to the feed water flow rate 29 output from the proportional-integral controller 30, and is output to the adder 38 as a feed water flow rate set value 31.

Here, at the normal time when no runback occurs, the switch 37 is switched to the b side, and the switch 3
From [0], 0 [t / h] is the increment 3 of the feedwater flow rate set value 31.
6 to the adder 38, the adder 3
8, the feed water flow set value 31 is output as it is to the subtracter 34 as the feed water flow set value 31 ′, where the feed water flow set value 3 output from the adder 38
The difference between 1 ′ and the actual feedwater flow rate 23 detected by the feedwater flowmeter 22 is obtained, and a feedwater flow rate deviation 33 is output to a proportional-integral controller 35, where the subtractor 34 Water supply flow deviation 33 output from
Is proportionally integrated, and a control command 25 for eliminating the feedwater flow rate deviation 33 is output to the feedwater pump 15, the feedwater pump 15 is controlled according to the control command 25, and the water supplied to the brackish water separation drum 1a is controlled. Is adjusted, and the drum level 19 of the steam separation drum 1a is maintained at the specified water level 26.

On the other hand, if a runback (emergency load drop) occurs for some reason, the switch 37 is switched to the a side for β [sec] after the runback occurs, and α [t /
h] is an increment 36 of the water supply flow rate set value 31 as the adder 3
8, the water supply flow rate set value 3 obtained by adding α [t / h] to the water supply flow rate set value 31 from the adder 38.
1 ′ is output to the subtractor 34, where the subtractor 34 outputs
The difference between the feed water flow set value 31 'output from the adder 38 and the actual feed water flow 23 detected by the feed water flow meter 22 is obtained, and the feed water flow deviation 33 is output to the proportional integral controller 35, In the proportional-integral controller 35,
The feedwater flow rate deviation 33 output from the subtractor 34 is proportionally integrated, and a control command 25 for eliminating the feedwater flow rate deviation 33 is output to the feedwater pump 15.
The water supply pump 15 is controlled in accordance with the control value, and the amount of water supplied to the brackish water separation drum 1a is adjusted.

As a result, the amount of water replenished to the brackish water separation drum 1a becomes β
During [seconds], the value is increased by α [t / h].
At the time of runback, even if fuel F and combustion air are rapidly squeezed and the required number of burners 6 out of the plurality of burners 6 are extinguished, bubbles in the can water may be crushed. Therefore, the drum level 19 does not drop sharply, and the control is performed stably.

In this manner, a decrease in the drum level 19 at the time of occurrence of runback can be minimized, and control can be stabilized.

The boiler drum level control device of the present invention is not limited to the above-described example, but may be variously modified without departing from the gist of the present invention.

[0025]

As described above, according to the drum level control apparatus for a boiler of the present invention, it is possible to minimize the decrease in the drum level when runback occurs and to stabilize the control. The effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an example of a boiler.

FIG. 3 is a block diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler main body 1a Drum for brackish water separation 15 Feedwater pump 18 Drum level gauge 19 Drum level 20 Steam flow meter 21 Steam flow rate 22 Feedwater flowmeter 23 Feedwater flow rate 24 Drum level controller 25 Control command 26 Standard water level 27 Drum level deviation 28 Subtractor 29 Water supply flow rate 30 Proportional integral controller 31 Water supply flow set value 31 'Water supply flow set value 32 Adder 33 Water supply flow deviation 34 Subtractor 35 Proportional integral controller 36 Increase 37 Switch 38 Adder α Required amount β Required time

Claims (1)

[Claims] 1. A feed pump for supplying water to a steam separation drum of a boiler, a drum level meter for detecting a drum level of the steam separation drum, and a steam for detecting a flow rate of steam flowing out of the steam separation drum. A flow meter, a feed water flow meter for detecting a feed water flow supplied to the brackish water separation drum, and a feed water flow necessary for eliminating a drum level deviation between a specified water level and an actual drum level detected by the drum level meter. And a steam flow rate detected by the steam flow meter to obtain a feed water flow rate set value, and control for eliminating a feed water flow rate deviation between the feed water flow rate set value and the actual feed water flow rate detected by the feed water flow meter. A command that is configured to output a command to the water supply pump and that after the occurrence of runback, the water supply flow rate set value is set higher by a required time and a required amount. Boiler drum level control apparatus characterized by comprising a level control.