JPH04347407A - Method for controlling combustion in fluidized bed type incinerator - Google Patents

Abstract

PURPOSE:To provide separate control for the speed of thermal decomposition, and the combustion speed in circulation mixing by tilting one of the wall bodies inwards and tilting downwards dispersion plates opposite to the side of this wall body respectively and changing the air speed from a divided wind box to control the time of circulation of a fluidizing medium in 1-10 minutes. CONSTITUTION:The rear wall body 4B of the combustion chamber 3 is tilted inwards with respect to vertical plane, and the front wall body 4A is provided with a refuse charging port 5 and the rear wall body 4B with a discharge port 6, and a dispersion plate 7 that tilts downwards to the rear wall body 4B is provided at the bottom section of the combustion chamber 3. The dispersion plate 7 is provided with a fluidizing air blow-out port 7a directed to the side of the rear wall body 4B, and a wind box section 8 consisting of wind boxes 8A-8C for supplying the fluidizing air is provided below the air blow-out port 7a. The speed of the air blown out of here is made faster in the order of 8A-8C, and the time of one circulation of the fludizing medium is regulated to 1-10 minutes. It is, therefore, possible to control the speed of thermal decomposition in the section where the air speed is low and the speed of combustion that depends on the high speed section separately and control the combustion of harmful gases in the whole furnace.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control method in a fluidized bed incinerator.

0002

[Prior Art] Generally, in incinerators for municipal waste,
No matter what kind of feeding device is used, it is difficult to supply accurately and stably (in terms of volume or weight) due to differences in the size, length, dryness and wetness of the garbage.

For this reason, when a fluidized bed type incinerator is used, the quality of waste varies greatly depending on the season and location, and also locally within the input line, resulting in a change in calorific value and required combustion air. The amount changes significantly, resulting in the following disadvantages:

[0004] In other words, the combustion time in a fluidized bed is as fast as 1 to 2 minutes despite the above-mentioned fluctuations in calorific value and required amount of combustion air. Rapid changes in oxygen levels (seasonal fluctuations result in steady imbalances) are a major factor in the generation of harmful gases such as NOX and CO (dioxins), along with large pressure fluctuations inside the furnace.

[0005] Conventionally, this problem has been dealt with in fluidized bed incinerators by changing the amount of waste input and the amount of air for fluidization. Specifically, in addition to changing the overall air volume according to the fluidized bed temperature and exhaust gas oxygen concentration, we also created a part of the fluidized bed where waste is thrown into areas where fluidization is poor and where it is thermally decomposed. Some of the above are designed to change the amount of air.

[0006]

[Problem to be Solved by the Invention] However, according to the above-mentioned control method, the amount of air is controlled, for example, by separating the wind box into a plurality of wind boxes and varying the amount of air blown out from each wind box. However, the effects within the fluidized bed due to differences in the amount of blowing, that is, the division of roles, are not clear, and as a result, the mixing condition of the entire fluidized bed also changes, and the rate of thermal decomposition and the combustion rate due to circulation mixing are There was a problem in that it was not possible to control each separately.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a combustion control method in a fluidized bed incinerator that can solve the above problems.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the combustion control method in a fluidized bed incinerator of the present invention is such that the horizontal cross-sectional shape of the combustion chamber is rectangular, and the four walls constituting the combustion chamber are inside the body, at least one of the first ones facing each other
The walls are provided vertically, and the other second wall is inclined inward with respect to the vertical plane, so that the dispersion plate disposed at the bottom of the combustion chamber is inclined 10 to 30 degrees toward the second wall. The air outlet holes provided in this distribution plate are inclined downward at the corners and directed toward the second wall, and the wind box provided below the distribution plate is connected to the first wall and the second wall. A combustion control method for a fluidized bed incinerator divided into a plurality of parts, in which the speed of air blown out from each wind box through the above-mentioned distribution plate is controlled, so that the entire amount of fluidized medium is This is a method in which the circulation time is varied within a range of 1 to 10 minutes.

[0009]

[Operation] According to the above control method, the air blown out at high speed independently controls the circulation amount of the fluidized medium, that is, the combustion rate in the fluidized bed, and the air blown out at low speed independently controls the thermal decomposition rate. be able to.

0010

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In FIG. 1, reference numeral 1 denotes a fluidized bed incinerator, in which the horizontal cross section of the combustion chamber 3 of the furnace body 2 is rectangular, and one of the four walls 4 of the combustion chamber 3, e.g. Among the front, left, and right walls 4A to 4D, the rear wall (second wall) 4B has a predetermined inclination angle (for example, 1
The front and rear walls 4 are tilted at an angle of 0 degrees to 30 degrees (Θ) and are opposed to at least the rear wall 4B.
A is provided vertically. In addition, the left and right walls 4C, 4
D may be vertical or may be inclined at the same angle of inclination as the rear wall 4B.

The front wall 4A is provided with a garbage inlet 5, and the rear wall 4B is provided with an incineration residue outlet 6. In addition, at the bottom of the combustion chamber 3 of the furnace body 2,
A dispersion plate 7 is provided to be inclined downward at an inclination angle of about 10 degrees from the front wall 4A to the rear wall 4B, and a large number of fluidizing air jets are formed on the dispersion plate 7. As shown in FIG. 2, the ejection direction of the hole 7a is substantially horizontal and is provided toward the rear wall 4B side.

A wind box 8 is provided below the dispersion plate 7 for supplying air for fluidization. This wind box 8 is divided into three parts, a front wind box 8A, a central wind box 8B, and a rear wind box 8C, between the unslanted front wall 4A and the inclined rear wall 4B. It is provided.

It should be noted that on the lower surface of the dispersion plate 7 and the ejection hole 7
A receiving plate 9 for preventing the fluid medium from falling is installed at the position corresponding to a, and a secondary air supply pipe for combustion is installed on each wall 4 corresponding to the free board in the combustion chamber 3. 10 are connected.

Further, the speed of the air blown out from each of the air boxes 8 is varied from the front wall 4A side where the garbage inlet 5 is provided to the rear wall 4B where the incineration residue outlet 6 is provided. Specifically, if the flow start speed is U, the air speed from the front wind box 8A is U/2~
U, the air velocity from the central wind box 8B is in the range of 3 x U to 5 x U, the air velocity from the rear wind box 8C is in the range of 5 x U to 10 x U
The range of

In this way, the air is blown out at a high speed on the rear wall 4B side, so as shown in FIG. It rains down on the wall 4A side and falls.

The fluid medium that has fallen onto the front wall 4A is sequentially moved toward the rear wall 4B by the air blown out from each air box 8. That is, the fluid medium makes one round inside the combustion chamber 3.

[0017] Furthermore, the speed of air (that is, the amount of air) blown out from the wind boxes 8A to 6C is adjusted so that the time for one round of the fluid medium is 1 to 10 minutes. In this way, the lower limit of the time for one round of the fluidized medium to be 1 minute corresponds to the maximum combustion speed in a conventional fluidized bed incinerator. This is because even in the case of garbage, combustion does not take place sufficiently, and the reason why the upper limit was set at 10 minutes is that even if the amount and quality of garbage changes within a few minutes, which is a particular problem, combustion will not take place. This is because fluctuations can be sufficiently suppressed.

The relationship between the circulation time of the fluidized medium and the amount of fluidizing air on the high-speed side is as shown in FIG. Here, a specific control method will be explained.

That is, a video camera 12 installed inside the furnace body 2 monitors the inside of the combustion chamber 3 and detects the internal state, and the temperature (TB) of the fluidized bed, for example, changes depending on the quality of the waste. The amount of air blown out from each wind box 8A to 8C is adjusted so that the temperature of the free board (TF) is about 700°C and about 900°C.

For example, for short-term control,
The following control is performed. If TB is rising, the air volume in the middle wind box 8B →
Increase, air volume in rear wind box 8C → decrease TB If TB is a downward trend, air volume in middle wind box 8B →
If the air volume in the front wind box 8A → decrease, secondary air volume → increase TF indicates a downward trend, then the air volume in the front wind box 8A →increase, secondary air volume →decrease, and also take into account increases and decreases in the total air volume and water spray volume. ) control is performed.

Incidentally, an increase in the amount of air from the front air box 8A leads to an increase in the rate of thermal decomposition due to an increase in the mixing and stirring effect, but the amount of combustion there increases and the temperature rises.
Thermal decomposition will proceed further.

As described above, according to the control method of the above embodiment, the speed of the air blown into the fluidized bed is divided into three stages, and the circulating amount of the fluidized medium is controlled by the air blown out at high speed, that is, the flow rate of the fluidized bed is increased. The internal combustion rate and the thermal decomposition rate can be controlled independently by the air blown out at low speed.

[0023] Of course, an increase in the amount of circulation increases the amount of circulation to the low-speed side, which has a negative effect on the thermal decomposition rate to some extent;
The effect of sufficiently negating this adverse effect can be compensated for by changing the flow velocity on the low velocity side.

[0024] Furthermore, the unidirectional movement mechanism of the lower part of the fluidized bed included in the dispersion plate moves the upper part of the freeboard, that is, the primary combustion chamber, when the air velocity on the high speed side is reduced to the lowest level. Even if the circulation amount through the upper part becomes zero, the minimum circulation amount can be maintained (it is not unidirectional movement, but it can be maintained only by the movement of the upper and lower parts in the fluidized bed).

[0025] By independent control of both of them, that is, the pyrolysis rate and the combustion rate in the fluidized bed, it is possible to completely control the combustion rate field of the entire furnace. (which has a large effect on the burning rate).

[0026] By the way, in the case of municipal waste incineration, since the gas component is particularly large, combustion in freeboard increases.
Since the generation rate of pyrolysis gas can be controlled, by changing the surplus air on the high-speed side or the secondary air supplied to the freeboard, it is possible to control the combustion on the freeboard, and also to control the combustion on the freeboard. The circulation rate in the furnace can be controlled by the flow rate on the high speed side, that is, the mixing and stirring in the medium speed range can be controlled by the flow rate on the high speed side. Therefore, the combustion speed in the freeboard and fluidized bed can be controlled independently, The temperature of the fluidized bed and freeboard as well as the burning off of harmful gases within the furnace can be controlled through overall control of the furnace.

In the case of extremely low-calorie waste, the air on the high-speed side is throttled to zero the amount of circulation passing through the upper part of the primary combustion chamber, and the amount of air on the low-speed side is increased to the extent that it becomes slightly fluidized. Control may also be performed to cause the fuel to burn.

Furthermore, in order to promote thermal decomposition on the low speed side and suppress combustion at that portion, control may be performed to circulate the combustion exhaust gas toward the low speed side.

[0029]

As described above, according to the structure of the present invention, one of the walls facing each other is provided so as to be inclined inwardly, and the dispersion plate is also provided so as to face downward toward the inclined wall. Furthermore, the wind box installed below the dispersion plate is divided into multiple parts between the two walls, and the air velocity blown out from each divided wind box is changed to improve the flow inside the combustion chamber. Medium circulation time from 1 to
Since it is controlled within a range of 10 minutes, the rate of thermal decomposition that occurs in the low-speed section and the combustion rate that depends on the high-speed section can be controlled separately, and therefore the combustion of harmful gases in the entire furnace is controlled. can do.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a fluidized bed incinerator according to an embodiment of the present invention.

FIG. 2 is a sectional view of essential parts of the incinerator in the same embodiment.

FIG. 3 is a graph showing the relationship between the high-speed side air amount and the intralayer circulation time in the incinerator of the same example.

[Explanation of symbols]

1 Fluidized bed incinerator 2
Furnace body 3 Combustion chamber 4 Wall 4A Front wall 4B Rear wall 7 Dispersion plate 7a Spout hole 8 Wind box 8A Front wind box 8B Intermediate wind box 8C Rear wind box

Claims (1)

[Claims] Claim 1: The horizontal cross-sectional shape of the combustion chamber is rectangular, and among the four walls constituting the combustion chamber, at least one first wall facing each other is provided vertically, and the other second wall is provided vertically. The body is tilted inward with respect to the vertical plane, and the dispersion plate placed at the bottom of the combustion chamber is tilted inward toward the second wall side.
The dispersion plate is tilted downward at an inclination angle of 100°, and the air ejection holes provided in the dispersion plate are directed toward the second wall, and the wind box provided below the dispersion plate is connected to the first wall and the second wall. A combustion control method for a fluidized bed incinerator divided into a plurality of parts between the wall and the fluidized bed incinerator. 1. A method for controlling combustion in a fluidized bed incinerator, characterized in that the time for one circulation of the incinerator is varied within a range of 1 to 10 minutes.