JPH0375406A - Combustion control in fluidized bed furnace - Google Patents

Abstract

PURPOSE:To maintain substantially constant the state of combustion regardless of the variation in the charge to be incinerated that is charged into a furnace by changing the volume of air that is sent into a furnace from below its fluidized bed so as to maintain the temperature of the fluidized bed in a specified range of temperature by the output of furnace bed temperature detection means. CONSTITUTION:A calculator 11 carries out the calculation Y1 to calculate a fluidizing air volume setting value, SV1 from its brightness signal PV0. A calculator 12 carries out the calculation Y2 to calculate a fluidizing air volume setting value, SV2 from its fluidizing air volume setting value SV1 and furnace bed temperature detection signal PV1 of a furnace bed temperature detection end 6, and outputs the calculation result to a flow rate control regulator 13. A flow rate control regulator 13 outputs control signal MV to control a bypass control valve 3 to a bypass control valve 3 from a fluidizing air volume setting value SV2 and a fluidizing air detection signal PV3 for the fluidizing air volume that is sent into a fluidized layer 4 from a fluidizing air detection end 7, and controls the volume of air that bypasses to the free board 2 and controls the volume of the fluidizing air that is sent into the fluidized layer 4. With this arrangement the combustion quantity can be maintained substantially constant regardless of a change in the charge to be incinerated that is charged into the furnace.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a combustion control method in a fluidized bed furnace, and in particular maintains the combustion state (combustion amount) in the furnace substantially constant,
The present invention also relates to a combustion control method in a fluidized bed furnace that maintains the hearth temperature within a range where combustion is stable.

[Prior art]

Due to its good combustion performance, fluidized bed furnaces are often used as incinerators for municipal waste and industrial waste. However, due to its good combustion performance, when incineration materials such as municipal waste that cannot be continuously supplied in a fixed quantity due to their nature are input into this fluidized bed furnace, the incineration materials are quickly combusted, resulting in variations in the amount of input materials. This directly led to variations in the oxygen concentration in the combustion gas, and there was a problem of air pollution due to the discharge of unburned gas. Furthermore, in order to be able to adequately cope with the fluctuations in the amount of combustion, it is necessary to install large-capacity ventilation equipment and exhaust gas system equipment, which poses problems in terms of equipment costs and the like.

Therefore, as a measure to prevent a large amount of incinerated material from being instantly combusted when incineration materials are thrown into a fluidized bed furnace in a disparate manner as described above, the present applicant has previously applied for PCT/J.
There is a combustion control method in a fluidized bed disclosed in P8 B100437. This combustion control method suppresses the gasification of the amount of combustion by reducing the so-called fluidized air sent from the bottom of the fluidized bed when combustion is active in the furnace, and increases the amount of fluidized air when combustion is inactive. It is designed to activate the gasification of materials. This makes it possible to maintain a substantially constant combustion state within the furnace regardless of fluctuations in the amount of material to be incinerated that is introduced into the furnace.

[Problem to be solved by the invention]

By the way, in a fluidized bed furnace, in order to maintain stable combustion, the hearth temperature needs to be maintained at 600°C to 800°C. However, in the combustion control method that is performed by controlling the amount of flowing air, the amount of flowing air is 10,100ON.
/ H-m! 300~60ONm”/H
- m" depending on the combustion state. Therefore, in general, fluidization of the fluidized medium in the fluidized bed becomes inactive, and the temperature of the hearth tends to decrease, and the hearth temperature falls within the above temperature range. There was a problem that combustion became unstable.

The present invention has been made in view of the above-mentioned points, and it is possible to maintain the combustion state substantially constant regardless of fluctuations in the incineration material put into the furnace, and to maintain the hearth temperature within a range where combustion is stable. An object of the present invention is to provide a method for controlling combustion in a fluidized bed furnace that can maintain the following conditions.

[Means to solve the problem]

In order to solve the above problems, the present invention fluidizes a fluidized medium using air sent from the lower part of the fluidized bed, and changes the amount of air sent from the lower part of the fluidized bed depending on the combustion state,
In a combustion control method in a fluidized bed furnace in which the amount of combustion is maintained substantially constant regardless of fluctuations in the amount of combustion material fed into the furnace, a hearth temperature detection means for detecting the temperature of the fluidized bed is provided, and the hearth temperature is The method is characterized in that the amount of air sent from the lower part of the fluidized bed is changed based on the output of the detection means so as to maintain the temperature of the fluidized bed within a predetermined temperature range.

[Effect]

By carrying out the combustion control method in the fluidized bed furnace as described above, the amount of air sent from the lower part of the fluidized bed is changed according to the combustion state in the furnace, and the amount of air sent from the lower part of the fluidized bed is changed according to the temperature of the fluidized bed.
Since the amount of air sent from the lower part of the fluidized bed is varied to maintain the temperature of the fluidized bed within a range where combustion is stable, the amount of combustion can be maintained approximately constant despite fluctuations in the amount of combustible material introduced into the furnace, and By reducing the amount of fluidizing air sent from the lower part of the fluidized bed, fluidization of the fluidized medium becomes inactive, preventing a drop in fluidized bed temperature due to a decrease in the amount of heat recovery, and stably maintaining combustion in the furnace.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the configuration of a combustion control device in a fluidized bed furnace to which the combustion control method according to the present invention is applied. In the figure, 10 is a fluidized bed incinerator, and the fluidized bed incinerator 10 has a structure including a lower fluidized bed 4 and a facade 2 above the fluidized bed 4. 1 is a blower that sends flowing air to the fly board 2; 3 is a blower that sends flowing air from the blower 1 to the fly board 2;
5 is a brightness detection end provided at the upper part of the frame 2 to detect the brightness inside the furnace;
6 is a hearth temperature detection end for detecting the temperature of the fluidized bed 4, that is, the fluidized bed; 7 is a fluidized air detection end; 11 is an arithmetic unit that performs calculation Y8; 12 is an arithmetic unit that performs calculation Y; 13 is from the blower 1 This is a flow rate controller that controls the fluidized air sent into the fluidized bed 4.

Since the combustion state in the furnace, that is, the magnitude of the combustion amount, is reflected in the brightness inside the furnace, the brightness signal P which is the output of the brightness detection terminal 5
V. will change depending on the amount of combustion in the furnace. The arithmetic unit 11 receives this brightness signal PV. Calculation Yl is performed to calculate the flowing air amount setting value Svl from. The calculator 12 performs a calculation Y to calculate the flowing air amount set value Svl from this flowing air amount set value Svl and the hearth temperature detection signal P V of the hearth temperature detection end 6, and then calculates the flowing air amount set value Svl. Output to. The flow rate control controller 13 generates a control signal for controlling the bypass control valve 3 based on the flow air amount set value S■ and the flow air detection signal PV of the flow air amount fed into the fluidized bed 4 from the flow air detection end 7. The MV is outputted to the bypass control valve 3 to control the amount of air bypassed to the cold door 71 and the amount of fluidized air sent to the fluidized bed 4.

FIG. 2 is a diagram for explaining the contents of the calculation Yl performed by the calculator 11 to calculate the flowing air amount set value SVl from the brightness signal PV from the brightness detection terminal 5. As shown, the brightness signal PV. The flowing air amount setting value SvI changes in a polygonal manner according to the change in the flow rate. That is, the flow air amount setting value Svl is changed within a certain range ΔSv1 according to the brightness signal Pvo. That is, when the brightness signal P V o is small, the flowing air volume set value SvI is increased to activate the fluidization of the fluid medium, and when the brightness signal P V o is large, the flowing air volume set value SvI is decreased. , making the fluidization of the fluid medium inert. Thereby, the combustion state can be maintained substantially constant regardless of fluctuations in the amount of incineration material introduced into the furnace. That is, when the amount of incineration is large, the brightness signal PV, which is the output of the brightness detection end 5, becomes large, so the fluidized air amount setting value Svl becomes small, the fluidized air amount decreases, and the fluidized bed 4 The fluidization of the fluid medium becomes inactive. As a result, the gasification of the incinerated material is delayed and the combustion rate is slowed down. On the other hand, when the amount of incinerated material is small, the brightness signal PV, which is the output of the brightness detection terminal 5, becomes small.
The fluidized air amount setting value Sv increases, the fluidized air amount increases, and the fluidization of the fluidized medium in the fluidized bed 4 becomes active. As a result, the gasification of the incinerated material becomes faster and the combustion rate becomes faster.

When the amount of fluidized air is controlled by the signal from the brightness detection end 5 as described above, the amount of fluidized air in a normal fluidized bed furnace is 1100.
ON”/Hem”, 300 to 600 Nm
Since the temperature is changed between ``/H*m'' (SV in Figure 2) depending on the combustion state, the hearth temperature tends to decrease, and the hearth temperature may drop below 600''C. .

Therefore, in this embodiment, the hearth temperature from the hearth temperature detection end 6, that is, the temperature of the fluidized bed 4 is detected, and the amount of fluidized air is controlled to prevent the temperature of the fluidized bed 4 from falling below a predetermined temperature. That's what I do. Figure 3 shows the flow air amount set value S from the calculator 11.
vI and the hearth temperature detection signal P V from the hearth temperature detection end 6
Calculation Yl to calculate the flowing air amount set value Svl from t
FIG. Flowing air amount setting value S
The function that defines the relationship between V 1 and the flow air amount set value Svl is changed by the hearth temperature detection signal P V t. That is, basically, the relationship between the fluidized air amount set value SV8 and the fluidized air amount set value Svl is a proportional relationship; when the hearth temperature falls, the fluidized air amount is increased, and when the hearth temperature rises, the fluidized air amount is increased. It lowers the amount of air.

This can be expressed as a formula as shown below.

5Vx-f(SVt) (E(PV+m) However,
α is a proportionality constant, and m is a reference value.

FIG. 4 is a diagram for explaining the contents of the operation Yl of the arithmetic unit 12. As shown in the same figure (a), the relationship between the flowing air amount setting value SvI and the flowing air amount setting value Svl is in a proportional relationship, and by changing the proportionality constant by the hearth temperature detection signal PV, the above can be achieved. Similar combustion control can be performed. This can be expressed as a formula as shown below.

SVt-m-3V.

However, m is a function of Pv shown in FIG. 4(b). That is, when the hearth temperature is low, the slope is steep, and when the hearth temperature is high, the slope is gentle. For example, m w −m t P
Let it be V I+ C1.

However, ml is a positive proportionality constant and α is a constant.

As described above, in this embodiment, the combustion state in the furnace, that is, the amount of combustion, is detected by the brightness detection end 5, and the amount of fluidized air sent from the lower part of the fluidized bed to the fluidized bed 4 is changed depending on the amount of combustion. The temperature of the fluidized bed is detected by the hearth temperature detection end 6, and depending on the temperature of the fluidized bed, if the temperature is low, the amount of fluidized air is increased, and if the temperature is high, the amount of fluidized air is decreased. Since the temperature is controlled, the temperature of the fluidized bed can be maintained within a temperature range where combustion is stable, and combustion in the furnace can be maintained stably.

〔Effect of the invention〕

As described above, according to the present invention, the amount of air sent from the lower part of the fluidized bed is changed depending on the combustion state in the furnace, and the amount of air sent from the lower part of the fluidized bed is changed depending on the temperature of the fluidized bed. Since the temperature of the fluidized bed is maintained within a predetermined temperature range, the amount of combustion can be maintained approximately constant despite fluctuations in the combustible material introduced into the furnace, and the amount of fluidizing air sent from the bottom of the fluidized bed can be reduced. This reduction has the excellent effect of preventing the fluidized bed temperature from decreasing due to inactivity of the fluidized medium and maintaining stable combustion in the furnace.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of a combustion control device for a fluidized bed furnace to which the combustion control method according to the present invention is applied, Fig. 2 is a diagram for explaining the contents of calculation YI, and Fig. 3 is a diagram showing the contents of calculation YI. FIGS. 4(a) and 4(b) are diagrams for explaining the contents of calculation YI. In the diagram, 1...Blower, 2...F+P Zood, 3
... Bypass control valve, 4 ... Fluidized bed, 5 ...
・Brightness detection end, 6... Hearth temperature detection end, 7...
・Flowing air detection end, 11... Arithmetic unit, 12...
Arithmetic unit, 13...Flow rate control controller.

Claims (1)

[Claims] The fluidized medium is made to flow by the air sent from the bottom of the fluidized bed, and the amount of air sent from the bottom of the fluidized bed is changed depending on the combustion condition, so that the amount of combustion is kept approximately constant regardless of fluctuations in the combustible materials introduced into the furnace. In the method for controlling combustion in a fluidized bed furnace, a hearth temperature detection means for detecting the temperature of the fluidized bed is provided, and the fluidized bed temperature is maintained within a predetermined temperature range by the output of the hearth temperature detection means. A combustion control method in a fluidized bed furnace characterized by changing the amount of air sent from the bottom of the bed.