JP2002195507A - Soot blower control device of boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the soot blower control device of a boiler permitting the optimization of the number of motions of a soot blower to any kinds of coal without setting a threshold value for each kind of coal, avoiding the adverse effects on the main body of the boiler due to the fixation of ash and contriving to prevent the occurrence of erosion due to the reduction in the consumption of an atomizing medium and the atomizing medium on the inner surface of the furnace wall of a furnace and the surface of various heating tubes. SOLUTION: The state value that becomes a maximum in the case when an actual furnace heat yield rate 39 to the entire heat yield shifts from the tendency to rise to the tendency to fall is stored as the standard value of the furnace heat yield rate 37', and the relative reduction in the furnace heat yield rate 39 from the standard value of the furnace heat yield rate 37' by a predetermined rate is detected. Then, a soot blower-starting command 42' is outputted. Thus, this device is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art FIG. 3 shows an example of a boiler. In FIG. 3, reference numeral 1 denotes a boiler main body having a furnace 1a and a rear heat transfer portion 1b, and 2 denotes a fuel into the furnace 1a of the boiler main body 1. Burner to inject and burn, 3 is primary superheater, 4 is secondary superheater, 5 is tertiary superheater, 6 is final superheater, 7 is primary reheater, 8 is secondary reheater, 9 is node It is a charcoal device, and generates fuel gas by injecting fuel from the burner 2 into the furnace 1a of the boiler main body 1 and circulates the generated fuel gas. The secondary superheater 4, the tertiary superheater 5, heat exchange with the final superheater 6, the secondary reheater 8, the primary superheater 3, the primary reheater 7 and the economizer 9, and the exhaust gas after the heat exchange is discharged into the exhaust gas duct 10, and the downstream side After removing nitrogen oxides and sulfur oxides with a flue gas treatment device (not shown) such as denitrification and desulfurization installed in It is adapted to release to.

FIG. 4 shows a water supply / steam system of the above-described boiler. The boiler water is supplied to an evaporator 1 formed on a furnace wall of a furnace 1a of a boiler body 1 in which fuel is burned.
1, the steam is separated into water and steam by the steam separator 13 through the nose portion 12, and the steam separated from the water by the steam separator 13 is supplied to the ceiling of the boiler main body 1 and the peripheral wall 1 of the rear heat transfer section.
4 and is superheated by the primary superheater 3, the secondary superheater 4, the tertiary superheater 5, and the final superheater 6, guided to the high-pressure turbine 15, and the high-pressure turbine 15 is driven to generate electric power. The steam after driving the high-pressure turbine 15 is:
After being guided to the primary reheater 7 and the secondary reheater 8 and being reheated by the primary reheater 7 and the secondary reheater 8, it is introduced into the medium / low pressure turbine 16, 16 is driven to generate power, and the steam after driving the medium / low pressure turbine 16 is guided to the condenser 17 and returned to the boiler feed water.
The boiler feed water is supplied to the condensate desalination unit 18 and the low pressure feed water heater 1
9 and the deaerator 20, the water is fed to the economizer 9 by the feedwater pump 21 via the high-pressure water heater 22, heated by the economizer 9, fed to the evaporator 11, and circulated. It is supposed to be.

[0004] In the case of a coal-fired boiler, ash is generated with the combustion of coal as a fuel, and the inner surface of the furnace wall of the furnace 1a, the primary superheater 3, the secondary superheater 4, the tertiary superheater 5, and the like. Although it adheres to the surfaces of various heat transfer tubes such as the final superheater 6, the primary reheater 7, the secondary reheater 8, and the economizer 9, the ash is formed on the inner wall of the furnace 1a and the surfaces of the various heat transfer tubes. If adhered, the heat collection in the boiler main body 1 is reduced. Therefore, a soot blower 23 as shown in FIG. 5 is provided at required places in the furnace 1a of the boiler main body 1 and in the rear heat transfer section 1b.
The soot blower 23 sprays a spray medium 24 such as steam onto the inner wall of the furnace 1a or the surface of various heat transfer tubes, and blows off the attached ash.

As shown in FIG. 5, for example, the soot blower 23 advances and retreats a lance tube 26 having an injection hole 25 for injecting a spray medium 24 such as steam in a direction perpendicular to the axial direction at the tip end. It has a configuration movably arranged. Here, the lance tube 26 is housed in a box-shaped beam 28 installed on a support base 27 and slides against a fixed feed tube 30 to which the spray medium 24 is supplied via a poppet valve 29. It is movably fitted to the outside and is supported by the feed tube 30 and the front support 31 at the front end of the beam 28. At the rear end of the lance tube 26, there is mounted a carriage 32 which allows the feed tube 30 to penetrate the air tightly and slidably, such as a motor integrated with the carriage 32. A driving device 33 rotates a driving pinion 35 meshed with a rack 34 attached to a ceiling surface in the beam 28 so that the carriage 32 advances and retreats together with the lance tube 26.
The lance tube 26 is turned around its axis via a gear mechanism (not shown) during the forward / backward movement.

On the other hand, in the furnace 1a, the primary superheater 3, the secondary superheater 4, the tertiary superheater 5, the final superheater 6, the primary reheater 7, the secondary reheater 8, and the economizer 9 respectively. Heat is
It can be obtained based on the pressure and temperature of the steam on each of the inlet and outlet sides. In general, the heat received by the furnace 1a occupies about 40% of the whole, and the ratio of the furnace heat received to the total heat received is Since it tends to decrease with the progress of dirt due to the ash and can be used as a criterion for determining the operation of the soot blower 23, in the conventional case, the control device of the soot blower 23 is based on the boiler load command 36 as shown in FIG. A function generator 38 for obtaining and outputting a furnace heat receiving ratio threshold 37, an actual furnace heat receiving ratio 39 with respect to the total heat collection, and a furnace heat receiving ratio threshold 37 output from the function generator 38; A subtractor 41 that calculates and outputs the furnace heat transfer ratio deviation 40 of the furnace, and a furnace heat transfer ratio deviation 40 output from the subtracter 41 is a preset value (for example, −1.5).
[%]), And a signal monitor switch 43 that outputs a signal of “1” as a soot blower start command 42 when the value becomes smaller.

[0007] Since the actual furnace heat transfer ratio 39 to the total heat transfer tends to slightly decrease as the load increases, the function generator 38 includes a boiler load as shown in FIG. A function for increasing or decreasing the furnace heat-recovery-ratio threshold value 37 in such a manner as to be substantially in inverse proportion to the increase or decrease of the command 36 is input.

In the conventional control device shown in FIG. 6, a furnace generator heat recovery ratio threshold value 37 is obtained in a function generator 38 based on a boiler load command 36 and output to a subtractor 41. Furnace heat transfer ratio deviation 4 between the actual furnace heat transfer ratio 39 to the total heat transfer and the furnace heat transfer ratio threshold 37 output from the function generator 38
0 is obtained and output to the signal monitor switch 43, and the furnace heat recovery ratio deviation 40 output from the subtracter 41 in the signal monitor switch 43 is a preset value (for example, -1.5 [%]). When it becomes smaller, a signal of "1" is output as a soot blower start command 42, and the lance tube 26 of the soot blower 23 shown in FIG. 5 rotates around its axis while being inserted into the boiler main body 1, The spray medium 24 such as steam is sprayed on the inner surface of the furnace wall of the furnace 1a and the surfaces of various heat transfer tubes to remove attached ash.

[0009]

However, in the conventional control device for the soot blower 23 as described above, a certain furnace heat recovery ratio threshold value 3 corresponding to the boiler load command 36 is used.
7, only the soot blower 23 is activated when the actual furnace heat transfer ratio 39 to the total heat transfer becomes somewhat lower than the furnace heat transfer ratio threshold 37, and the coal used as fuel is used. Is not taken into account when the coal type is changed, so if coal with a relatively high heat recovery is used as fuel, the actual furnace heat transfer ratio 39 to the total heat recovery is the furnace heat transfer ratio Threshold 37
It takes time until the temperature becomes lower to some extent, and the number of operations of the soot blower 23 decreases, so that the ash hardens and cannot be removed, which may adversely affect the boiler body 1, while conversely, the heat collection is relatively low. When coal of the coal type is used as fuel, the operation is always performed near the furnace heat-reception-ratio threshold value 37, and the soot blower 23 operates frequently,
In addition to the increased consumption of the spray medium 24 such as steam, which leads to an increase in cost, there is a problem that erosion of the inner wall of the furnace 1a and various heat transfer tube surfaces by the spray medium 24 occurs.

Incidentally, in order to deal with such a problem,
It is conceivable to change the furnace heat collection ratio threshold value 37 for each type of coal, but this takes a lot of trouble and time, and requires confirmation of operation when changing the type of coal. It is difficult to set the unknown coal type in advance, making it difficult to implement.

In view of such circumstances, the present invention can optimize the number of soot blower operations for any type of coal without setting a threshold for each type of coal, An object of the present invention is to provide a soot blower control device for a boiler capable of avoiding adverse effects on a main body, reducing consumption of a spray medium, and preventing occurrence of erosion due to the spray medium on the inner wall of a furnace and various heat transfer tube surfaces. is there.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a state value which becomes maximum when the furnace heat-receiving ratio with respect to the total heat transfer changes from an upward trend to a downward trend is stored as a furnace heat-receiving ratio reference value. The present invention relates to a soot blower control device for a boiler, which is configured to detect that the furnace heat collection ratio has decreased by a predetermined ratio relatively from a furnace heat collection ratio reference value and to output a soot blower start command. .

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

[0014] The state value which becomes the maximum when the actual furnace heat transfer ratio to the total heat transfer changes from an upward trend to a downward trend is stored as a furnace heat transfer ratio reference value, and is relative to the furnace heat transfer ratio reference value. When it is detected that the furnace heat collection rate has decreased by a predetermined rate, a soot blower start command is output, the soot blower is inserted into the boiler main body, and the spray medium is sprayed on the furnace wall inner surface of the furnace and various heat transfer tube surfaces. The sprayed ash is removed.

As a result, there is no need to set a threshold value for each coal type, and even if coal of a coal type having a relatively high heat recovery is used as fuel, the number of times of operation of the soot blower is small. There was no risk of ash hardening and getting rid of it, and it was possible to avoid adversely affecting the boiler body.On the other hand, coal of a coal type with relatively low heat recovery was used as fuel In this case, the soot blower is prevented from operating frequently, which reduces the consumption of spray medium and leads to cost reduction, and also prevents erosion caused by spray medium on the inner wall of the furnace and the surface of various heat transfer tubes. It becomes possible.

[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 FIG. 1 and FIG. 2, parts denoted by the same reference numerals as those in FIG. The state value which becomes the maximum when the heat collection ratio 39 changes from the rising trend to the downward trend is stored as the furnace heat collection ratio reference value 37 ', and the furnace heat collection ratio is relatively determined from the furnace heat collection ratio reference value 37'. It is configured to detect that the ratio 39 has decreased by the predetermined ratio ΔQ and output a soot blower start command 42 ′.

In the illustrated example, an OR circuit 47 outputs a logical sum signal 46 of a soot blower operating signal 44 and a boiler load changing signal 45, and a negative signal of the logical sum signal 46 output from the OR circuit 47. 48, and a NOT signal 48 output from the NOT circuit 49.
Is “1” (when the soot blower 23 is not operating and the boiler load is not changing), the furnace is switched to the side a in FIG. 1 and serves as a high selection signal output from a high selector 52 described later. Comparison signal 5 with heat collection ratio reference value 37 '
When the output is 0, the negation signal 48 output from the NOT circuit 49 is "0" (when the soot blower 23 is operating or the boiler load is changing).
In FIG. 1, the switch 51 is switched to the side b and outputs the actual furnace heat collection ratio 39 with respect to the total heat collection as a comparison signal 50, and the comparison signal 5 output from the switch 51.
A high selector 52 which outputs the higher one of 0 and the actual furnace heat transfer ratio 39 to the total heat transfer as the furnace heat transfer ratio reference value 37 ′; an actual furnace heat transfer ratio 39 to the total heat transfer; A subtractor 41 'for obtaining and outputting a furnace heat-reception-ratio deviation 40' from the furnace heat-reception-ratio reference value 37 'output from the high-selector 52, and a furnace heat-reception ratio output from the subtracter 41' The deviation 40 'is a predetermined value (for example,-
1.5 [%]), a signal monitor switch 43 'for outputting a signal of "1" as a soot blower activation command 42'.

The soot blower operating signal 44 is input to an OR circuit 47 via an off-delay timer 53, so that the soot blower operating signal 44 is output after a lapse of a required time from the completion of the ash removing operation by the soot blower 23. Is switched from "1" to "0", and the boiler load changing signal 45 is input to the OR circuit 47 via the off-delay timer 54 to change the boiler load from the state where the boiler load is changing. When it becomes constant, the boiler load changing signal 45 is switched from "1" to "0" after the required time has elapsed, and by doing so,
Avoid the state where the actual furnace heat collection ratio 39 with respect to the entire heat collection fluctuates due to the operation of the soot blower 23 or the change in the boiler load. I have to be.

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

When the soot blower 23 is not operating and the boiler load is not changing, the soot blower operating signal 4
4 and the boiler load changing signal 45 are both "0",
An OR signal 46 of “0” is output from an OR circuit 47 to a NOT circuit 49, and a NOT signal 48 of “1” is output from the NOT circuit 49 to a switch 51.
Is switched to a side in FIG.

Thus, in a state where the actual furnace heat collection ratio 39 with respect to the total heat collection tends to increase, the high selector 5
2, the furnace heat transfer ratio 39 is output to the subtractor 41 'as it is as the furnace heat transfer ratio reference value 37'.
The furnace heat recovery ratio deviation 40 'output from 1' to the signal monitor switch 43 becomes "0", and the soot blower activation command 42 'is not output.

However, when ash adheres to the inner wall of the furnace 1a and the surfaces of various heat transfer tubes, and the actual furnace heat collection ratio 39 relative to the total heat collection changes from an upward trend to a downward trend, the high selector 52 In, the higher of the comparison signal 50 output from the switch 51 and the furnace heat absorption ratio 39 is output as the furnace heat absorption ratio reference value 37 ′, so that the furnace heat absorption ratio 39 tends to decrease from an upward trend. When the state changes to the maximum, the state value is output while being stored as the furnace heat absorption ratio reference value 37 '. In this state, the furnace heat absorption ratio 39 continues to fall as it is and the furnace heat absorption ratio 39' The signal monitor switch 43 'detects that the furnace heat collection ratio 39 has decreased relatively by the predetermined ratio ΔQ from the heat ratio reference value 37' based on the furnace heat collection ratio deviation 40 'output from the subtractor 41'. Sa Then, a soot blower activation command 42 'is output from the signal monitor switch 43', and the lance tube 26 of the soot blower 23 shown in FIG. A spray medium 24 such as steam is sprayed on the inner wall of the furnace wall 1a and the surfaces of various heat transfer tubes to remove attached ash.

The soot blower start command 42 'is output from the signal monitor switch 43' and the soot blower 2
3 starts operation and the soot blower operating signal 44 becomes "0"
Is changed to “1”, the OR signal 46 of “1” is output from the OR circuit 47 to the NOT circuit 49, and the NOT circuit 4
A negative signal 48 of “0” from 9 is output to the switch 51,
The switch 51 is switched to the b side in FIG. 1, and the high-selector 52 directly outputs the furnace heat-reception ratio 39 at that time, and the furnace heat-reception ratio as the maximum state value up to that time. The reference value 37 'is reset.

When the boiler load starts to change from a constant state and the boiler load changing signal 45 changes from "0" to "1", the furnace heat collection ratio 39 also changes. , The switch 51 is switched to the b side in FIG.
From the high-selector 52, the furnace heat collection ratio 39 at that time is obtained.
Is output as it is, and the furnace heat recovery ratio reference value 37 'as the maximum state value up to that time is reset.

When the operation of the soot blower 23 is completed and the boiler load is not changing, a soot blower operating signal 44
When both the boiler load changing signal 45 and the boiler load changing signal 45 become “0”, the actual furnace heat collection ratio 3
9 is stored as the furnace heat-reception-ratio reference value 37 ', and the furnace heat-recovery ratio 39 is relatively determined from the furnace heat-reception-ratio reference value 37'. When it is detected that the temperature has decreased by the predetermined ratio ΔQ, a soot blower start command 42 ′ is output, and the soot blower 23 shown in FIG. 5 rotates around its axis while being inserted into the boiler main body 1, and the furnace 1 a The spray medium 24 such as steam is sprayed on the inner surface of the furnace wall and the surfaces of various heat transfer tubes to remove attached ash, and the same operation is repeated thereafter.

For example, as shown in FIG. 2, when the boiler load is reduced from a certain state and then maintained at a certain state again, the actual furnace heat collection ratio 39 to the total heat collection is shown. Is changed so that the furnace heat receiving ratio reference value 37 'changes as shown in the figure, and the furnace heat receiving ratio 39 becomes the furnace heat receiving ratio reference value 37'.
, The soot blower 23 is activated at a point in time when it is relatively decreased by a predetermined ratio ΔQ.

As a result, there is no need to set a threshold value for each coal type, and even if coal of a coal type having a relatively high heat recovery is used as fuel, the number of times of operation of the soot blower 23 is reduced. There is no danger that the ash will not be removed due to ash hardening and it will not adversely affect the boiler body 1. On the other hand, coal of a coal type with relatively low heat recovery will be used as fuel. In this case, the soot blower 23 is prevented from frequently operating, the consumption of the spray medium 24 such as steam is reduced, which leads to cost reduction. In addition, the inner surface of the furnace wall of the furnace 1a and the surface of various heat transfer tubes are reduced. Erosion due to the spray medium 24 can also be prevented.

In this manner, the number of times of operation of the soot blower 23 can be optimized for any type of coal without setting a threshold value for each type of coal, and adverse effects on the boiler body 1 due to ash sticking can be avoided. In addition, it is possible to reduce the consumption of the spray medium and prevent the erosion caused by the spray medium 24 on the inner surface of the furnace wall of the furnace 1a and various heat transfer tubes.

The soot blower control device for a boiler of the present invention is not limited to the illustrated example described above, and it is a matter of course that various changes can be made without departing from the gist of the present invention.

[0031]

As described above, according to the soot blower control apparatus for a boiler of the present invention, the number of times the soot blower operates for any type of coal can be set without setting a threshold value for each type of coal. It is possible to optimize the temperature, avoid the adverse effect on the boiler body due to the sticking of ash, and reduce the consumption of spray medium and prevent the erosion from occurring on the inner wall of the furnace and the surface of various heat transfer tubes due to the spray medium. The effect can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing transitions of a boiler load, a furnace heat receiving ratio, and a furnace heat receiving ratio reference value in an example of an embodiment of the present invention.

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

FIG. 4 is a schematic configuration diagram showing a water supply / steam system of the boiler shown in FIG.

FIG. 5 is a side view illustrating an example of a soot blower.

FIG. 6 is a control block diagram illustrating an example of a conventional soot blower control device.

FIG. 7 is a diagram showing a function input to the function generator shown in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiler main body 1a Furnace 1b Rear heat transfer part 23 Soot blower 24 Spraying medium 37 'Furnace heat transfer ratio reference value 39 Furnace heat transfer ratio 40' Furnace heat transfer ratio deviation 42 'Soot blower start command ΔQ Predetermined ratio

Claims (1)

[Claims] 1. A state value which becomes maximum when the furnace heat transfer ratio to the total heat transfer changes from an upward trend to a downward trend is stored as a furnace heat transfer ratio reference value, and a state value relative to the furnace heat transfer ratio reference value is stored. A soot blower control device for a boiler, wherein the soot blower control device is configured to detect that the furnace heat collection ratio has decreased by a predetermined ratio and to output a soot blower start command.