JPH03199810A - Stable combustion method in fluidized bed type incinerator - Google Patents

Abstract

PURPOSE:To perform a slow and stable combustion of ignited substance and reduce a discharging of non-ignited gas by a method wherein an ignited substance feeding direction changing- over device is cooperatively operated in such a way as the ignited substance is fed into a part of fluidizing medium where its fluidizing is weakened. CONSTITUTION:A gas dispersion plate 2 or a group of gas dispersion pipes 5 and 6 at a lower part of a bed of a fluidized bed type incinerator 1 are divided into a plurality of segments. A part 10 of the fluidizing medium in the fluidized bed is highly fluidized, another part 9 for its fluidizing action is weakened and then the high fluidizing part 10 is changed over to a weakened fluidizing state and at the same time an ignited substance feeding direction changing-over device 12 is cooperatively operated in such a way as the ignited substance is fed into the part where the fluidization is weakened just after its changing-over operation. In this way, the ignited substance is fed into a part where the weak fluidizing state of the fluidizing bed is found, thereby a thermal decomposition, gasification and combustion of the ignited substance are carried out smoothly, the fluidizing operation is intensified at a time when its volatile component is almost eliminated, a circulating mixing of the substance in the fluidized bed is sufficiently carried out and then a stable combustion is carried out while the rapid generation of gas is being restricted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of incinerating municipal waste, etc. in a fluidized bed incinerator, and in particular, the present invention relates to a method of incinerating municipal waste, etc. in a fluidized bed incinerator, and in particular, the fluidized bed is divided into a strongly fluidized part and a weakly fluidized part. This is a stable combustion method for fluidized bed incinerators in which the materials to be incinerated are placed in the areas where fluidization is weak, by switching sequentially.

[Conventional technology]

Fluidized bed incinerators are often used as incinerators for municipal waste and industrial waste because their combustion performance is good and the amount of unburned matter in the residue is small.

The reason for the good combustion performance is that the material to be incinerated is dried and thermally decomposed in a very short time by the large amount of hot sand that is the fluidizing medium, but this can also be a drawback.

That is, due to the nature of municipal waste, etc., it is difficult to supply it with a constant amount of input and calorific value, so fluctuations in supply conditions almost directly result in fluctuations in the amount of combustible gas generated.

Therefore, immediately after a large amount of material to be incinerated is thrown in, the supply of secondary air cannot keep up with the amount of combustible gas generated, resulting in an air shortage and the problem of unburned gas generation.

As a way to improve these problems, for example, the amount of fluidizing air blown out from the diffuser pipe can be alternately increased or decreased.
A method of stabilizing combustion by suppressing the rate of thermal decomposition and gasification while maintaining the agitation and mixing effect of the fluidized bed by alternating the blowing amount at regular intervals, or dividing the diffuser tube group into multiple sections. A method has been proposed in which the fluidization is differentiated into large, medium, and small for each divided group, and these are slowly switched at regular intervals. This is not a sufficiently effective solution because the influence of flammable gas generated from strong parts cannot be ignored.

[Problem to be solved by the invention]

The present invention has been made in order to solve the above problems, and aims to ensure that burnable materials are always burned slowly and stably in a fluidized bed incinerator, and to minimize the emission of unburned gas. The purpose is to provide a method.

[Means to solve the problem]

The present invention divides the diffuser plate or the diffuser tube group in the lower part of the hearth of a fluidized bed incinerator into a plurality of parts, so that part of the fluidized medium in the hearth is more fluidized, and the other part is less fluidized. Then, the large part of the fluidization is switched to weaken the fluidization at appropriate intervals, and immediately after switching to the weak fluidization, the material to be incinerated is put into the part where the fluidization is weakened. It is characterized by interlocking a device for switching the direction of incineration of the incinerated material, and by introducing the incinerated material into the weakly fluidized part of the fluidized bed, the thermal decomposition, gasification, and combustion of the incinerated material are performed slowly. This is a method to achieve stable combustion while suppressing rapid gas generation by increasing fluidization and sufficient circulation mixing within the fluidized bed when most of the volatile matter has been eliminated.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 shows a cross-sectional view of an incinerator for implementing the present invention in which the diffuser plate at the lower part of the hearth is divided into two parts, where 1 is the incinerator, 2 is the diffuser plate, and 3 is the diffuser plate ( 4 is a flow (combustion) air supply pipe, 5.6 is an air supply pipe to the first division and the second division, respectively, and 7 and 8 are air supply pipes 5 to each. and an air supply amount adjustment valve provided on 6, 9 is a weakly fluidized part, 10 is a strong fluidized part, 11 is a garbage (material to be incinerated) input port, 12 is a garbage input direction switching device, 13 is a secondary air supply pipe, and 14 is an exhaust gas discharge pipe.

First, fuel is supplied from an auxiliary fuel supply pipe (not shown), and at the same time, air is supplied via the fluidizing air supply pipes 4, 5.6 and the distribution plate 2, and the fluidized medium is heated while being fluidized.
When the fluidizing medium reaches a predetermined temperature, the air supply amount control valve on the air supply pipe 5 is throttled down, and the amount of air supplied to the first division part via the distribution plate 2 is reduced to reduce the amount of fluidizing medium to a portion of 9. At the same time, the garbage input direction switching device is switched so that the fluidization is weakened and the garbage is input into the portion 9 where the fluidization is small.

After a certain amount of waste has been put in for a certain period of time, the flow continues slowly for a while, and then the air volume control valve 7 of the air supply pipe 5 is opened wide to strengthen the fluidization at the part 9, and the point at which the fluidization is weak is increased. oxidizes and completely burns the carbonized materials.

On the other hand, regarding the part of the fluidized bed 10 in the second division part where fluidization is large, when the waste has been input to the part 9 where fluidization is weak, the air adjustment valve 8 is throttled down to weaken the fluidization in the part 10. At the same time, the garbage input direction switching device is switched to input the garbage into the fluidization section 10 where the fluidization is weakened.

The amount of air blown into areas where fluidization is weak is in the range of 0.5 to 2 Gmf, and the amount of air blown into areas where fluidization is strong is 3 to 7 Gmf.
Preferably, it is in the range of mf.

FIG. 2 is a diagram illustrating the above-mentioned waste input cycle and fluidized bed switching.

That is, garbage is thrown into the part of the first dividing section 9 where the flow is weak,
At time a, the garbage input is switched to the second dividing section 10, and at the same time, the flow in the second dividing section is weakened. On the other hand, the first division part 9
At time b, the air supply amount is changed so that the flow becomes large, and at the time C, the air supply amount is changed so that the flow becomes small, and at the same time, the garbage supply is switched to the first dividing section, and d
At the point in time, the amount of air supplied to the second divided section 10 is increased so that the flow of the fluid medium in the second divided section 10 is increased,
Thereafter, the above operation is repeated.

By repeating such operations, it becomes possible to continuously charge the materials to be incinerated into the incinerator.

Figure 3 illustrates changes in the state of input and fluidization of the material to be incinerated, changes in heat input (i.e. amount of waste input x calorific value), and changes in gasification and combustion amount in one divided section. It is something.

FIG. 3 shows that stable gasification and combustion can be achieved by charging the waste (material to be incinerated) into divided sections where fluidization is small.

The material to be incinerated is thrown into the weakly fluidized area only when the fluidizing medium is weakly fluidized, that is, only when the amount of fluidizing air blown is small, so even if the heat input is large, it will not be incinerated. Thermal decomposition and gasification occur slowly from the surface of the combustible material, so even if combustible material with a high volatile content is thrown in, rapid gasification is suppressed and stable combustion takes place. Even if fluidization is increased after a suitable time after switching to another division, most of the volatile components have already been decomposed at this point, and some of the volatile components themselves, such as cellulose and fixed carbon, are combustible. Since slow-velocity components account for most of the combustibles, stable combustion can be maintained even if the fluidization is increased, that is, even if the fluidizing air supply amount is increased, and the combustibles remain in the fluidized bed. Since it is burned, even if the fluidized bed is strongly circulated and mixed, the fluidized medium is sufficiently heated by the heat of combustion and can be prepared for the next charge of the material to be incinerated.

Figures 4 and 5 show that the heat input of the material to be incinerated is 100% ± 10
The total gasification amount in the case of 2 divisions and the case of 4 divisions is simulated, assuming that it repeatedly fluctuates from 0%, that is, 0 to 200%. From this result, it can be seen that the more divisions there are, the smaller the fluctuation in the amount of gasification can be.

In addition, in FIGS. 4 and 5, the chain line indicates the amount of heat, and the solid line indicates the total amount of gasification.

In addition, gasification can be stabilized to 100% ± 30 to 40% with two divisions, and 100% ± 20% with four divisions.
Adjustment of the secondary air makes it possible to sufficiently supplement the combustion air.

Figures 6 and 7 show an example of a switching device for inputting materials to be incinerated in the case of dividing into four parts. 9 shows another example of a switching device for inputting materials to be incinerated in the case of four divisions, and FIG. 9 shows a cross-sectional view taken along the line B--B in FIG. 8.

In the example shown in FIGS. 6 and 7, the garbage inputted from the garbage input port 1 is passed through the chute nozzle 12' whose inclination direction can be changed by the air cylinder 13 to the lower chute 12-1 or 12-1. 12-2.

Furthermore, since the direction of inclination of the chute 12 can be switched by the air cylinder 13', the garbage can be thrown in either the C direction or the D direction. By changing the combination of the inclination directions of these two-stage shoes 12' and 12, the waste is thrown into four divided sections where fluidization is weak.

In the example shown in FIGS. 8 and 9, the garbage thrown in from the garbage input port 1 is moved into a corresponding flow by rotating the garbage sliding plates 18 to 21 at predetermined angles by the air cylinders 15 to 17, respectively. It operates in such a way that it can be input into a division with a weaker ratio.

Next, other embodiments of the present invention will be described.

In FIG. 10, a noncombustible material outlet is provided in the center of an incinerator 101, and two dispersion plates 102 and 102' are provided at an angle so that the noncombustible material outlet side is lower.
and 102' are divided into three parts, so that the amount of air □ introduced from the inner pipes 104 and 108 is larger than the amount of air introduced from the outer pipes 105, 106 and 109, 110, A swirling flow in the direction of the arrow is generated in the first division 90 and the second division 10, respectively, and a weakly fluidized part 9 and a strongly fluidized part 10 are formed in the first and second divisions. Garbage is put into the part, and after an appropriate time has elapsed after the end of the charging, the fluidization of the part is strengthened, and the amount of air blown into the part 10 where the fluidization was strong is reduced to weaken the fluidization, and the garbage is added to the part 10. It is designed to switch between parts,
Its operation is similar to that described with reference to FIG.

In addition, in the example shown in FIG. 11, a mountain-shaped dispersion plate is provided at the bottom of the incinerator 201, incombustible material draw-out openings are provided at both skirts of the mountain-shaped distribution plate, and outer piping 2 is provided in each division.
The amount of air introduced from 06 and 210 is transferred to the inner pipe 20.
5. The amount of air introduced from 204, 209, and 210 is made larger in order to form a swirling flow in the first divided portion 9 and the second divided portion 10, respectively, and the first divided portion 9 and the second divided portion 10 are The only difference from the embodiment shown in FIG. 10 is that the parts are made into a weakly fluidized part and a strongly fluidized part, and its operation is the same as that explained based on FIG. 1. be.

Incidentally, in FIG. 11, the inclined walls 211 and 211' provided on the dispersion plate that blows a large amount of air are provided to facilitate the formation of a swirling flow of the fluid medium.

The configuration of the present invention and the operating method of the present invention will be described above.

1) A fluidized bed furnace in which the fluidized bed section is divided into a plurality of parts in a plane, is equipped with a charging switching device that can charge the material to be incinerated at a predetermined position in any one divided part, and An incinerator with adjustable conditions is used and operated under the following conditions.

(1) The flow condition in each divided section is weakened as a whole so that the combustible material is thermally decomposed and gasified slowly, and the flow is made pulsed or sawtooth in one section at a time. Try to strengthen it temporarily.

1 2 (2) The material to be incinerated should be placed only in the divided section immediately after the above-mentioned strong flow has ended, and never be placed in the divided section that is in a strong flow state. The state should be changed sequentially.

(3) In any divided section, materials to be incinerated are introduced only when the flow is weak, but even if the material to be incinerated is switched to another section, the flow continues to be weak for a certain period of time and then becomes a strong flow. Switch.

That is, the operation is performed so that the weak flow duration≧the incineration material input duration in any division.

2) Each division in the above method is further divided into smaller parts, and the amount of air blown into each part of the smaller divisions is gradually increased to cause swirling motion of the fluid medium in each division,
The input material to be incinerated is effectively engulfed in the sand to efficiently burn it (see Figs. 10 and 11).

(Effects of the invention) (1) Materials to be incinerated (
Garbage) first receives contact heat transfer from the upper surface of the sand and radiant heat from the furnace wall and surrounding combustion gas, and is gasified and ignited from the surface layer, but the core part causes small-scale bubbling, although the flow is weak. The heavy garbage gradually settles into the sand, and even the lighter garbage becomes a pile of garbage that is subsequently thrown in, and most of it gradually settles into the sand by gravity.

Some light garbage and dry combustible garbage burn up without settling, but since the reducing atmosphere is relatively low in oxygen and there is no agitation caused by vigorous flow, they are subject to slow combustion that progresses from the surface layer and are incinerated. Gas generation exceeding the capacity of the freeboard section at the top of the furnace is prevented.

In addition, the garbage swallowed up in the sand gradually sinks while receiving heat from the surrounding sand, slowly evaporates water in a reducing atmosphere, and is thermally decomposed and gasified, gradually shifting to a state with a large amount of fixed carbon. 4 rows.

In this state, the waste input is switched to another division, but since the state of weak flow continues for a certain period of time, most of the moisture and volatile matter disappear, and the combustion shifts to mainly fixed carbon.

At this point, the flow is switched to strong flow, so that the residue mainly consisting of fixed carbon is completely combusted without generating excessive unburned gas under the promotion of agitation in the sand and the supply of sufficient oxygen.

(2) It is difficult to avoid temporal fluctuations in the input quantity and quality of items such as garbage that have non-uniform properties and shapes, but it is possible to fluidize inputs with such fluctuation factors. By injecting only into weak areas of the sand, the amount of gasification can be suppressed even when the amount of input is excessive, and when the amount of input is too low or interrupted, the gas from the garbage previously retained in the sand can be suppressed. As the gas continues to flow, the weakly flowing portion acts as a kind of accumulator, and the amount of unburned gas released into the freeboard portion becomes uniform over time.

5. As a result, after-combustion in the freeboard section can be sufficiently followed by supplementary adjustment of the secondary air, and generation of unburned harmful gases can be prevented.

(3) In general, volatile matter generated from garbage is mainly gasified in sand, and after reaching the surface of the sand, it ignites a flame and burns. Therefore, the rate of reduction of the heat generated in this case to the sand is relatively small.

On the other hand, fixed carbon burns as a solid even in sand as long as oxygen is supplied, so the rate of heat reduction to sand is high.

Therefore, gasification of volatile matter and evaporation of water mainly take place in the weakly fluidized part where new waste is supplied, so there is little heat reduction to the sand, and the temperature of the sand gradually decreases. The amount of fixed carbon in the sand gradually increases, and in this state, by increasing fluidization after a predetermined period of time, the fixed carbon in the sand is actively burned, and the heat of combustion is returned to the sand, causing the temperature of the sand to rise again. Recover high temperature.

Since each division continuously repeats this temperature cycle6, the average hearth temperature remains at a stable level, allowing stable operation without compromising the ease of batch operation, which is one of the advantages of fluidized bed furnaces. be able to.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of an incinerator used in the present invention for explaining one embodiment of the present invention, and Fig. 2 shows the state of garbage input and fluidization in the first dividing section and the second dividing section. Figure shown, 3rd
The figure shows the relationship between the supply of waste and the fluidized state of the fluidized bed, heat input, gasification, and combustion amount. FIGS. 6 to 9 are cross-sectional views showing two different examples of the input direction switching device in the case of four divisions, and FIG. 9 is a cross-sectional view taken along line B-B in FIG. 8, and FIGS. 10 and 11 are cross-sectional views of an incinerator implementing the present invention that is different from the incinerator shown in FIG. 1. The figure is shown below. 1.101.201...Incinerator, 2.102,202,202'...Diffuser plate, 4,
103. 107. 203. 207 ・ ・
- Flowing (combustion) air introduction pipe, 9...-th division part, 10... second division part, 11... garbage input port, 12... garbage input direction switching device.

Claims (1)

[Claims] 1. Fluidized bed incineration, in which fluidized air is supplied from a diffuser plate or a group of diffuser tubes in the lower part of the hearth, and the fluidized medium and the material to be incinerated on the diffuser plate or group of diffuser tubes are fluidized and the material to be incinerated is incinerated. In a furnace, a diffuser plate or a group of diffuser tubes is divided into a plurality of parts, and the fluidization of a part of the fluidized medium in the hearth is strengthened, while the fluidization of other parts is weakened. By interlocking the incineration material input direction switching device so that the material to be incinerated is switched to another part at a certain cycle, and immediately after switching to the part where the fluidization is weakened, the incineration material is put into the part where the fluidization is weakened.
The material to be incinerated is put into the area where fluidization is weak, and the material to be incinerated is slowly pyrolyzed, gasified, and burned, and when the volatile matter is almost gone, fluidization is increased and circulation within the fluidized bed is started. A stable combustion method for a fluidized bed furnace characterized by sufficient mixing.