JP2002005406A - Drum level alarming device for boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drum level alarming device for a boiler, which is capable of preventing the output of a drum high level alarm upon increasing a load in a low load zone and capable of contriving the improvement of a load change rate. SOLUTION: The drum level alarming device is provided with a second function generator 36 for obtaining a drum level alarm setting value 35 based on the flow rate 21 of steam to output the same, a subtraction machine 38 for obtaining a difference between the drum level 19 of the steam and water drum and the drum level alarm setting value 35 outputted from the second function generator 36 to output a drum level alarm setting value difference 37 and a signal monitor switch 34 for outputting the drum level high alarm 33 when the drum level alarm setting value difference 37 outputted from the subtracting machine 38 has exceeded zero while the drum level alarm setting value 35, set in the second function generator 36, is set in the low load zone, wherein the flow rate 21 of steam is reduced, so as to be higher than the same value 35 set in a high load zone by a necessary amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Generally, as shown in FIG. 3, a boiler for generating auxiliary steam in a power plant or the like has a boiler body 1 in which a steam cylinder 1a is disposed at an upper part and a water cylinder 1b is disposed at a lower part. At the same time, the combustion air is supplied from the combustion air duct 3 through the wind box 4 by the forced draft fan 2, and the fuel F such as light oil is supplied from the fuel supply pipe 5 to the burner 6.
The steam in the heat transfer tube of the boiler body 1 is heated by the generated combustion gas to generate steam,
The steam is taken out from the steam cylinder 1a through the steam pipe 7 and introduced into the auxiliary steam header 8 on the main boiler side, while the combustion gas whose heat has been taken off is discharged from the chimney (not shown) through the flue 9 to the atmosphere. It is supposed to.

In FIG. 3, reference numeral 10 denotes a fuel cut-off 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.

On the other hand, a deaerator 13 is mounted on the upper part of the steam cylinder 1a, and water stored in a makeup water tank 14 passes through a water supply pipe 16 by an operation of a water supply pump 15, and the deaeration is performed. The steam cylinder 1a is supplied via the vessel 13.

The amount of water supplied to the steam cylinder 1a is adjusted by increasing or decreasing the opening of a feed water flow control valve 17 provided in the middle of the feed pipe 16. The opening of the control valve 17 is determined by the drum level meter 1
The output from the drum level controller 22 is based on the water level inside the steam cylinder 1a, that is, the drum level 19 detected by the steam flow meter 8, and the steam flow rate 21 detected by the steam flow meter 20 provided in the middle of the steam pipe 7. Opening command 2
3 '.

As shown in FIG. 4, the drum level controller 22 obtains a difference between a specified water level 24 of the drum level inside the steam cylinder 1a and an actual drum level 19 detected by the drum level meter 18. A subtractor 26 that outputs a level deviation 25, and a basic opening command 27 of the feedwater flow control valve 17 for eliminating the drum level deviation 25 by performing a proportional integration process on the drum level deviation 25 output from the subtracter 26. A proportional-integral controller 28 for outputting, a first function generator 30 for obtaining and outputting a corrected opening command 29 of the feedwater flow-rate adjusting valve 17 based on the steam flow 21 detected by the steam flow meter 20, In addition to the basic opening command 27 of the feed water flow control valve 17 output from the heater 28, the correction opening command 29 of the feed water flow control valve 17 output from the first function generator 30 is added. Opening command 2 of the feed water flow rate control valve 17 Te
3 and an opening command 23 output from the adder 31 are input. In the case of automatic operation, the opening command 23 is output as it is as an opening command 23 'to the water supply flow control valve 17 as it is. On the other hand, in the case of manual operation, an automatic / manual switch 32 for outputting an opening degree command 23 ′ based on a manual operation of an operator to the water supply flow control valve 17 is provided. The drum level 19 of the body 1a is a predetermined amount (for example, +100 [m
m]), a signal monitor switch 34 for outputting a high drum level alarm 33 when the signal monitor switch 34 rises.

As shown in FIG. 5, the first function generator 30 has a function for increasing or decreasing the correction opening command 29 of the water supply flow rate control valve 17 in substantially proportion to the increase or decrease of the steam flow rate 21. Is entered.

During operation of the boiler as described above, the drum level meter 18 detects the drum level 19 inside the steam cylinder 1a, and the steam flow meter 20 introduces the steam flow introduced into the main steam generator side auxiliary steam header 8. 2
1 is detected and the subtractor 26 of the drum level controller 22 outputs the specified water level 24 of the drum level inside the steam cylinder 1a.
And the actual drum level 19 detected by the drum level meter 18 is obtained, and the drum level deviation 2
5 is output to the proportional-integral adjuster 28, and the proportional-integral adjuster 28 performs a proportional-integral process on the drum level deviation 25 output from the subtracter 26, and
Basic opening command 2 of feed water flow control valve 17 to eliminate 5
7 is output to the adder 31 while the steam flow meter 20 is
Based on the steam flow rate 21 detected by the first function generator 30, the correction opening command 29 for the feed water flow rate control valve 17
Is output to the adder 31 and the adder 31
In the above, the correction opening command 29 of the feed water flow control valve 17 output from the first function generator 30 is added to the basic opening command 27 of the feed water flow control valve 17 output from the proportional-integral controller 28 to supply water. The opening command 23 of the flow control valve 17 is output as it is as the opening command 23 'via the automatic / manual switch 32, and the opening of the water supply flow control valve 17 is adjusted in accordance with the opening command 23'. The amount of water supplied to the drum 1a is adjusted so that the drum level 19 of the water drum 1a is maintained at the specified water level 24.

When the drum level 19 of the steam cylinder 1a detected by the drum level meter 18 rises by a predetermined amount (for example, +100 [mm]) from the specified water level 24, the signal monitor switch 34 outputs the drum level. A high alarm 33 is output.

[0010]

In the case of the conventional drum level controller 22 as described above, the entire load range (0 to 100) is required.
[%]), The set value of the drum level high alarm 33 is set to a constant value (for example, +100 [mm] from the specified water level 24), but the boiler (steam flow rate 60 [ton / h] class) having a large retained water amount In), when the load is increased, the change in the specific volume of the boiler water due to the decrease in the drum pressure due to the change in the steam flow rate is larger than the change in the boiler water volume.
In particular, when the load rises in a low load zone that is easily affected by the drum pressure, the drum level rises, and the drum level high alarm 33 is output instantaneously, but the load change rate cannot be increased. Was.

In view of such circumstances, the present invention can prevent a drum level high alarm from being output when the load rises in a low load zone, and can improve the load change rate of a boiler. It is intended to provide.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a function generator for obtaining and outputting a drum level alarm set value based on a steam flow rate detected by a steam flow meter, and a drum of a steam cylinder detected by the drum level meter. A subtractor for calculating a difference between the level and a drum level alarm set value output from the function generator and outputting a drum level alarm set value deviation; and a drum level alarm set value output from the subtractor being smaller than zero. A signal monitor switch for outputting a high drum level alarm when the drum level becomes high, wherein the drum level alarm set value set in the function generator is set to a low load with a small steam flow rate. The present invention relates to a drum level alarm device for a boiler, wherein a required level of the boiler is higher than that of a high load zone.

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

Based on the steam flow rate detected by the steam flow meter, the function generator determines a drum level alarm set value and outputs the set value to the subtractor, where the drum level of the steam cylinder detected by the drum level meter is detected. The difference from the drum level alarm set value output from the function generator is obtained, the drum level alarm set value deviation is output to the signal monitor switch, and the drum level alarm set value deviation output from the subtractor is smaller than zero. If the drum level is large, that is, if the drum level of the steam cylinder exceeds the drum level alarm set value, a drum level high alarm is output from the signal monitor switch.

However, the drum level alarm set value set in the function generator is set higher by a required amount in the low load zone where the steam flow rate is small than in the high load zone, and therefore, as in the conventional case, the drum level alarm setting value is set in the entire load range. In contrast to setting the drum level high alarm to a fixed value, in a boiler with a large water holding capacity, when the load is increased, the specific volume change of the boiler water due to a decrease in drum pressure due to a change in steam flow rate Even if the drum level rises when the load rises in a low load zone that is susceptible to the drum pressure, the drum level high alarm will not be output as the water volume increases, and the load change rate will not change. Can be raised.

[0016]

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

FIGS. 1 and 2 show an example of an embodiment of the present invention. In the drawings, the portions denoted by the same reference numerals as those in FIGS. 3 to 5
The present embodiment is the same as the conventional one shown in FIG.
Function generator 36 for obtaining and outputting a drum level alarm set value 35 based on the steam flow rate 21 detected by the
And the brackish drum 1a detected by the drum level meter 18
The difference between the drum level 19 and the drum level alarm set value 35 output from the second function generator 36 is obtained, and the drum level alarm set value deviation 37 is determined by the signal monitor switch 34.
The drum level alarm set value deviation 37 output from the subtractor 38 is larger than zero, that is, the drum level 19 of the steam cylinder 1a exceeds the drum level alarm set value 35. In this case, the drum monitor high alarm 33 is output from the signal monitor switch 34, and the drum level alarm set value 35 set in the second function generator 36 is changed to the high load zone in the low load zone where the steam flow rate 21 is small. In that it is higher than required.

A steam flow rate of 60 [ton /
h] class boiler, the second function generator 36 has a steam flow rate 21 of 0 to 30 [ton] as shown in FIG.
/ H] (low load zone), the drum level alarm set value 35 is set to +150 [mm], and the steam flow rate 21 is set to 42 to 6
In the area of 0 [ton / h] (high load zone), the drum level alarm set value 35 is set to +100 [mm], and the steam flow rate 21
Is in the range of 30 to 42 [ton / h].
Drum level alarm set value 3
A function to increase or decrease 5 from +150 [mm] to +100 [mm] is input.

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

During the operation of the boiler, the drum level 19 inside the steam cylinder 1a is detected by the drum level meter 18 and introduced into the main boiler side auxiliary steam header 8 by the steam flow meter 20, as in the prior art. The steam flow rate 21 is detected, and the subtractor 26 of the drum level controller 22 determines the difference between the specified water level 24 of the drum level inside the steam cylinder 1a and the actual drum level 19 detected by the drum level meter 18. The drum level deviation 25 is output to the proportional-integral controller 28, and the proportional-integral controller 28 performs a proportional-integral process on the drum-level deviation 25 output from the subtracter 26 to supply water for eliminating the drum-level deviation 25. While the basic opening degree command 27 of the flow control valve 17 is output to the adder 31, it is detected by the steam flow meter 20. The first function generator 30 calculates a correction opening command 29 for the feedwater flow rate control valve 17 based on the steam flow rate 21 and outputs the same to the adder 31. The adder 31 outputs the correction opening command 29 from the proportional integration controller 28. The corrected opening command 29 of the feedwater flow control valve 17 output from the first function generator 30 is added to the basic opening command 27 of the feedwater flow control valve 17, and the opening command 23 of the feedwater flow control valve 17 is obtained. Opening command 2 as it is via automatic / manual switch 32
3 ', the opening of the water supply flow control valve 17 is adjusted in accordance with the opening command 23', the amount of water supplied to the steam cylinder 1a is adjusted, and the drum level 1 of the steam cylinder 1a is adjusted.
9 is held at the specified water level 24.

At the same time, in the case of the illustrated example, the drum level alarm set value 35 is set in the second function generator 36 based on the steam flow rate 21 detected by the steam flow meter 20.
Is output to the subtractor 38, and the steam cylinder 1a detected by the drum level meter 18 in the subtractor 38
The difference between the drum level 19 and the drum level alarm set value 35 output from the second function generator 36 is obtained, and the drum level alarm set value deviation 37 is output to the signal monitor switch 34 and output from the subtractor 38. Drum level alarm set value deviation 37 is greater than zero, ie,
When the drum level 19 of a exceeds the drum level alarm set value 35, the signal monitor switch 34 outputs a drum level high alarm 33.

However, the drum level alarm set value 35 set in the second function generator 36 is required more in the low load zone where the steam flow rate 21 is small than in the high load zone (50 [mm] in the example of FIG. 2). ), The set value of the drum level high alarm 33 is constant (for example, the specified water level 24) over the entire load range (0 to 100%) as in the related art.
Boiler with a large retained water volume (steam flow rate 60 [ton /
h] class), when the load is increased, a change in the specific pressure of the boiler water due to a decrease in the drum pressure due to a change in the steam flow rate causes a change in the specific volume of the boiler water to become larger than a change in the amount of water held in the boiler. Even if the drum level rises when the load increases, the drum level high alarm 33
Is not output, and the load change rate can be increased.

Thus, it is possible to prevent the drum level high alarm 33 from being output when the load increases in the low load zone, and to improve the load change rate.

The boiler drum level alarm device of the present invention is not limited to the above-described illustrated example, and various changes can be made without departing from the scope of the present invention.

[0025]

As described above, according to the boiler drum level alarm apparatus of the present invention, it is possible to prevent a drum level high alarm from being output when the load rises in a low load zone, and to reduce the load change rate. It is possible to achieve an excellent effect that it is possible to improve the quality.

[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 diagram illustrating a function set in a second function generator illustrated in FIG. 1;

FIG. 3 is a schematic configuration diagram of an example of a boiler.

FIG. 4 is a block diagram of a conventional example.

FIG. 5 is a diagram showing a function set in the first function generator shown in FIGS. 1 and 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler main body 1a Steam cylinder 18 Drum level meter 19 Drum level 20 Steam flow meter 21 Steam flow rate 33 Drum level high alarm 34 Signal monitor switch 35 Drum level alarm set value 36 Second function generator (function generator) 37 Drum level alarm Set value deviation 38 Subtractor

Claims (1)

[Claims] 1. A function generator for obtaining and outputting a drum level alarm set value based on a steam flow rate detected by a steam flow meter, and a drum level of a steam cylinder detected by the drum level meter and output from the function generator. A subtractor that outputs a drum level alarm set value deviation by calculating a difference between the drum level alarm set value and the drum level alarm set value output from the subtractor. A signal monitor switch for outputting a high alarm, the drum level alarm device for a boiler comprising: a drum level alarm set value set in the function generator in a low load zone having a small steam flow rate than in a high load zone. A boiler drum level alarm device, which is increased by an amount.