JPS62169915A - Stable combustion method for fluidized bed furnace - Google Patents

Abstract

PURPOSE:To promote slow combustion of a substance to be incinerated, by a method wherein the temperature of a fluidized bed is held at a specified value, the speed of air for fluidization injected through diffusing pipes is varied in the magnitude of the speed with each diffusing pipe, and the magnitude of the speed is alternately switched. CONSTITUTION:Air for fluidization is injected through diffusing pipes 2 to fluidize a substance 3 to be incinerated on the diffusing pipes 2 to form a fluidized bed 9. By mounting a water spray pipe 19, spraying water, on the fluidized bed 9 or a water spray pipe 20 to a dust feeder 5, the substance 3 to be incinerated is previously wet, and temperature in the fluidized bed 9 is held at 520-650 deg.C by means of the evaporating heat of water. Air for fluidization having a high speed is injected, as shown by an arrow mark A, through a diffusing pipe 2a, air for fluidization having a low speed is injected, as shown by an arrow mark (b), through a diffusing pipe 2b, and a portion, having the high intensity of fluidization, and a portion, having the low intensity of fluidization, are alternately formed. By alternately continuously switching the magnitude of the fluidizing speed of the air for fluidization on each of the diffusing pipes 2 in a manner described above, the substance 3 to be incinerated is uniformly agitated, and can be burnt slowly on the entirety.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an incineration method for incinerating materials to be incinerated such as municipal waste in a fluidized bed, and in particular, to a method for stabilizing the combustion of materials to be incinerated in a fluidized bed. This paper relates to a stable combustion method for a fluidized bed furnace that can be swung.

[Prior Art] In general, fluidized bed incinerators for the purpose of incinerating materials to be incinerated such as municipal garbage eject air from an aeration pipe installed in the furnace body, and supply the material to be incinerated onto the aeration pipe. At the same time, a fluidized medium such as sand is supplied, and while the material to be incinerated and the fluidized medium are fluidized on the aeration pipe, the material to be incinerated is thermally decomposed and burned, and the generated decomposed gas and other combustible gases are transferred to secondary air. The incombustible materials are taken out from the furnace body at the bottom of the air diffuser tube together with the fluidized medium and then decomposed, and the fluidized medium is circulated over the air diffuser tube again.

In this fluidized bed incinerator, in the fluidized bed, the flow flJ
The sand, which is the medium, is in a hot sand state and stirs, making it possible to instantly dry, thermally decompose, and burn the input material to be incinerated, resulting in complete incineration. , Glass, Il! g.It is made of porcelain and is extremely clean.

[Problems to be Solved by the Invention] However, the heat transfer of the materials to be incinerated into the flow flJ layer changes depending on the input material and the quality of the garbage, and as mentioned above, the material to be incinerated after being input, Because combustion and thermal decomposition occur instantaneously, it is difficult to perform combustion stably. For example, immediately after a large amount of material is put in at once, it is instantly combusted, producing a large amount of combustible gas. However, there is a problem in that the amount of secondary air supplied cannot keep up with the amount of decomposed gas and dust that is likely to be generated in the human body.

Conventionally, the fluidized bed in this fluidized bed incinerator has a heating capacity of 700 to 800
℃ range, and there is often no temperature control.

[Object of the invention] The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide a stable combustion method for a fluidized bed furnace that can slowly burn a material to be burned in a fluidized bed. With the goal.

[Summary of the Invention] In order to achieve the above object, the present invention provides a fluidized bed furnace with a plurality of aeration pipes, and blows out fluidizing air from the aeration pipes to remove the fluidized medium on the aeration pipe and the material to be incinerated. In the stable combustion method of a fluidized bed furnace, which incinerates the material to be incinerated while fluidizing it, the temperature of the fluidized bed is maintained at 520 to 620°C, and the fluidization speed of the fluidizing air ejected from the aeration pipe is Each tube is made to have a different size and the size is alternately changed, and the temperature of the fluidized bed is controlled by spraying water etc.
By maintaining the temperature between 0 and 650℃, the thermal decomposition and combustion of the materials to be incinerated in the fluidized bed are slowed down, and the fluidization speed is set to a different size for each diffuser tube, and by switching this, it is possible to achieve strong fluidization. A hearth part and a weak part are created to promote the circulation of the fluidized medium and to further promote the slow combustion of the material to be incinerated.

[Example] A preferred example of the stable combustion method for a fluidized bed furnace according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the whole fluidized bed furnace according to the present invention. In the figure, 1 is a furnace body, a plurality of air diffuser pipes 2 are provided in parallel on the hearth 1, and the furnace body 1 above the furnace body 1 is shown. An inlet 4 for incinerating materials 3 such as municipal garbage and industrial waste is formed in the wall, and a feeder [5] for incinerating materials 3 is connected to the inlet 4. Further, on the wall of the furnace body 1 above the air diffuser pipe 2, a lower charging chamber for a fluidized medium 6 such as sand is formed.

A fluidizing air supply pipe 8 is connected to the aeration pipe 2, and the fluidizing air is ejected from the aeration pipe 2 to fluidize the material to be incinerated 3 and the fluidized medium 6 on the aeration pipe 2 to form a fluidized bed 9. .

At the bottom of the furnace body 1, a fluidized medium 6 flowing down from between the diffuser tubes 2 is placed.
and an outlet 11 for incombustible materials 10 in the incineration material 3, and a discharge FIs 12 such as a screw conveyor is provided at the outlet 11.
is connected. Non-combustible material 10 flows into the discharge basin 12! fIl
A classifier 113 for separating the medium 6 is connected, and the incombustibles 10 on the sieve are discharged from the discharge port 14, and the fluid medium 6 under the sieve is sent to the input lower of the fluid medium 6 by a circulation line 15 such as a vertical conveyor. is supplied to A secondary air supply nozzle 17 is provided on the furnace body 1 in a fluidized bed in which the material to be incinerated 3 is combusted and the thermally decomposed combustible gas is combusted within the freeboard portion 16 of the furnace body 1. An exhaust port 18 is provided at the top of the furnace body 1 to discharge combustion exhaust gas.

Normally, when the material to be incinerated 3 is burned as is in the fluidized bed 9, its temperature reaches 100 to 800 degrees Celsius, and as mentioned above, it is dried, thermally decomposed, and burned instantly after being input, resulting in the generation of decomposed gas and dust. This tends to cause problems such as increased volume.

In the present invention, the temperature inside the fluidized bed 9 is set at 520 to 650°C.
The feature is that the material to be incinerated 3 is slowly burned in the fluidized bed 9 while maintaining the temperature within the range of .

To maintain the temperature within the fluidized bed 9 at 520 to 650°C, any device may be used as long as it suppresses the combustion temperature of the material to be incinerated 3, such as a water spray pipe 19 that sprays water onto the fluidized bed 9.
is attached to the hearth 1, or a water spray pipe 20 is attached to the dust supply Ia5, and the material to be incinerated 3 is wetted in advance so that the temperature in the fluidized bed 9 is suppressed by the heat of evaporation of the water.

Further, the temperature of the fluidized bed 9 can be controlled by controlling the temperature of the fluidizing air supplied to the fluidizing air supply pipe 8 and its supply amount, or by providing a cooling device 21 for the fluidizing medium 6 in the circulation line 15, The cooled fluidized medium 6 may be supplied to the fluidized bed 9.

Further, the present invention is characterized in that the fluidization speed of the fluidizing air jetted from the diffuser pipe 2 is made to vary in size for each pipe.

That is, as shown in FIG. 2, fluidized air supply headers 22a and 22b are provided on both sides of the furnace body 1, and air diffuser pipes 2a and 2a disposed inside the furnace body 1 are provided on both headers 22a and 22b.
2b are connected alternately one by one. Each diffuser pipe 2a, 2
b has jet nozzles 23a spaced apart in its length direction.
, 23b are provided.

Both headers 22a, 22b are connected to the above-mentioned flowing air supply pipe 8, and both headers 22a, 22b.

22b or the diffuser pipes 2a, 2b includes a control valve (not shown).
Flowing air with different pressures is alternately supplied at , for example, the fluidization speed uma of the flowing air jetted from the jet nozzle 23a of one diffuser pipe 2a is high, and the fluidization speed uma of the fluidizing air jetted from the jet nozzle 23b of the other diffuser pipe 2b is high. The fluidization speed umb of the ejected fluidizing air is changed to be small, and this speed is changed to be reversed.

The fluidization speed um of the fluidizing air ejected from the nozzle 23 of the air diffuser 2 is higher than the fluidization start speed un+r.
For (Jm /umf = 1.0 ~ 2.5, the lower the speed, the lower the speed is um /umf = 0.5~
1.5.

In the above, the material to be incinerated 3 is supplied from the feeder 5 to the aeration pipe 2 through the inlet 4, the fluid medium 6 such as sand is supplied from the circulation line 15, and the air for fluidization is supplied from the aeration pipe 2. The material to be incinerated 3 is combusted while fluidizing the material to be incinerated and the fluidized medium 6 on the aeration pipe 2 .

During combustion, water is sprayed from the water spray pipe 19, etc., and the temperature of the stream #J layer 9 is maintained in the range X of 520 to 650°C, so that the material to be incinerated 3 is slowly dried, thermally decomposed, and burned. As a result, stable combustion can be performed despite variations in the input amount of the material to be incinerated 3 and fluctuations in the quality of the garbage, and moreover, the combustible material can be completely incinerated.

Figure 5 is a diagram showing the relationship between the fluidized bed temperature and the combustion rate ratio of the materials to be incinerated. It is a hailstorm.

As can be seen from this figure, the conventional fluidized bed temperature was 100 to 80.
In the range of 0°C, the combustion speed ratio is 0.7 to 1.0, but by keeping it in the range of 520 to 650°C as in the present invention, the speed ratio can be reduced to about 0.4 to 0.6. The combustion speed can be reduced to about 60% of the conventional combustion speed.

In this case, if the temperature of the fluidized bed is below 520°C, the speed will be slow and unburned substances will mix with the nonflammable substances, which is undesirable.
If it is higher than 0°C, the speed becomes faster and the instantaneous fluctuation of soot and dust increases, which is not preferable.

Further, as shown in FIG. 3, high velocity flowing air is ejected from one diffuser pipe 2a as shown by the arrow A2 in the figure, and from the other diffuser pipe 2b next to it, flowing air is ejected from the other diffuser pipe 2a as shown by the arrow b2 in the figure.
Flowing air with a low velocity is ejected as shown in FIG. The incinerated material 3 flows to a weakly fluidized portion as indicated by a dotted arrow 24 in the figure. In this weak portion, the amount of air in the IJl material to be burned and the fluidized medium 6 is small, so that the material to be incinerated 3 is slowly burned. Also, from the state shown in Figure 3, one of the diffuser pipes 2
If the velocity of the fluidizing air from the air diffuser 2b is made small as shown by arrow a2 in FIG. A strong and weak portion opposite to that is formed, and the incineration material 3 on the side that has been slowly burned will flow to the previously strong portion as shown by the dotted arrow 25 in the figure. In this way, the fluidization speed of the fluidizing air is set to be different for each one on the aeration pipe 2, and by switching this speed alternately and continuously, the material to be incinerated 3 in the fluidized bed 9 is uniformly stirred. At the same time, it becomes possible to burn it slowly as a rest.

When the fluidization speed of the fluidizing air ejected from the air diffuser pipes 2a and 2b is high, it is not preferable to set it below the fluidization start speed because fluidization will not occur. If the J51 ratio is set to 5 or more (um/umf>2.5), the amount of air in the fluidized portion becomes large and combustion becomes too fast, which is not preferable. On the other hand, when the fluidization speed is made small, the fluidization start speed umf
Preferably, the speed is less than 1.5 times the speed umf and approximately half or more of the speed umf.uIII/umf/fi0.
If it is less than 5, stirring of the material to be incinerated 3 will be insufficient, and unburned material will increase, which is not preferable.

Incidentally, in the smell of the material 3 to be incinerated being slowly burned in the fluidized bed 9, a part of the material 3 to be incinerated is thermally decomposed, and the generated combustible gas rises inside the freeboard section 16, where it is It is combusted by the secondary air blown from the secondary air supply nozzle 17 and is exhausted from the exhaust port 18 as exhaust gas.

The incombustible materials 10 in the material to be incinerated 3 flow down to the lower part of the furnace body 1 from between the diffuser tubes 2a and 2b together with the fluidized medium 6, and flow to the lower part of the furnace body 1 through the outlet 11.
It is transferred to the classification 1113 via the discharger 12, where it is separated from the fluidized medium 6 and recovered from the discharge port 14, and the fluidized medium 6 is again dropped into the fluidized bed 9 from the circulation line 15.

FIGS. 6 and 9 show changes over time in the temperature of the fluidized bed and the temperature of the combustion gas in the present invention and the conventional example.

FIG. 6 and FIG. 9 each show an example in which municipal waste was used as the material to be incinerated in the same incinerator, the throughput was 2.5 t/H, and the temperature of each part was measured for 6 to 7 hours.

As shown in FIG. 9, in the conventional example, the temperature in the fluidized bed is not controlled, so the fluidized bed temperature a is 650°C or higher, but at this time the humidity in the freeboard section is lower than the lower temperature.
It can be seen that the temperature is gradually increasing, with the upper temperature C being around 50°C and the upper temperature C being around 850°C, and the temperature d of the combustion gas leaving the furnace and entering the gas cooling tower being around 950°C.

This means that the combustible gas thermally decomposed in the fluidized bed is burned until it enters the gas cooling tower, and it can be seen that the combustible gas is not completely burned in the freeboard section.

On the other hand, as shown in FIG.
Water is sprayed onto the fluidized bed, and the temperature of the fluidized bed is set to 600℃±1.
It can be seen that when maintained at 5°C, the lower temperature bO, upper temperature CO, and gas cooling tower inlet temperature do of the freeboard section are approximately the same temperature (900 to 950°C).This means that the generated combustible gas is It can be seen that combustion is completely carried out within the chamber by secondary air.

Figures 7 and 10 show the colored smoke emitted from the chimney after the incinerated exhaust gas passes through a gas cooler and is removed by an electrostatic precipitator. It was measured over time using a smoke density indicator.

In the case of the conventional example, as can be seen from FIG. 10, smoke with an indication value of 0.5 or more, which is the visible area of smoke, is frequently emitted, but in the present invention, as shown in FIG. It can be seen that almost no smoke is generated.

FIGS. 8 and 11 show examples in which changes over time in CO gas concentration and 02 gas concentration were measured when materials to be incinerated were incinerated in the fluidized bed furnace of the present invention and the conventional fluidized bed furnace.

In the conventional example, as shown in FIG. 11, a high concentration e of CO gas as a combustible gas of 5000 ppm or more is generated almost regularly, and at that time, the oxygen 11Uf is also about 3% or less. This indicates that stable combustion of the materials to be incinerated is not occurring in the fluidized bed, and CO gas is generated due to changes in the type of materials to be incinerated, the amount of input, or the temperature of the fluidized bed. It can be seen that the oxygen concentration has dropped and combustion is not complete.

On the other hand, in the present invention, as shown in FIG.
It can be seen that the gas concentration eo can be made to be 1 oooppm or less at the maximum, and the oxygen concentration fo can also be made to be within 5 to 15%, thereby stably burning the combustible gas.

[Effects of the Invention] As is clear from the detailed description above, the present invention exhibits the following excellent effects.

(1) By keeping the temperature of the flowing e-layer between 520 and 650°C, the materials to be incinerated can be burned slowly, and the combustion is stable without being affected by changes in the amount of materials input or the quality of waste. Combustion can be performed.

(2) 8 ejected from the diffuser pipe! Since the fluidization speed of the moving air is alternately made large and small for each diffuser pipe and is switched, the material to be incinerated can be burnt slowly.

[Brief explanation of drawings]

Fig. 1 is an overall sectional view showing an example of an apparatus for implementing the stable combustion method of a fluidized bed furnace of the present invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Figs. 3 and 4 are respectively In the present invention, the state of the flowing air ejected from the diffuser pipe is shown. FIG. 5 is a diagram showing the relationship between the fluidized bed temperature and the combustion rate ratio of the material to be incinerated in the present invention, and FIG. 6 is a diagram showing the temporal changes in the fluidized bed temperature and the exhaust gas temperature of each part in the present invention. Fig. 7 is a diagram showing changes over time in the soot and dust generation state of exhaust gas after incineration treatment in the present invention, Fig. 8 is a diagram showing changes over time in the degree of CO gas and 02 gas in the present invention, and Fig. 9 is a diagram showing changes over time in the dust generation state of exhaust gas after incineration treatment. Figure 10 shows the change over time in the fluidized bed temperature and exhaust gas temperature at each part in the furnace. Figure 10 is a diagram showing the change over time in the state of soot and dust generation in the exhaust gas in a conventional incinerator.
FIG. 3 is a diagram showing changes in O gas and 02 gas over time. In the figure, 1 is the furnace body, 2a and 2b are air diffusers, 3 is the material to be incinerated,
6 is a fluidizing medium, 9 is a flow rA layer, and 19° and 20 are water spray pipes. Patent applicant: Ishikawajima-Harima Heavy Industries Co., Ltd. Representative Patent Attorney Nobuo Kinutani 9...flow v/74 7q20゛''''1 Figure 1 Figure 4 Byeong-layer Hatono (@C) Figure 5 9tt Chō (Hl Fig. 6 vF Ho (H) Gin 1tI (minute) Fig. 8 a - Meat (H) Gin Shun [Hl Fig. 10

Claims (1)

[Claims] A stable combustion method for a fluidized bed furnace in which a fluidized bed furnace is equipped with a plurality of diffuser pipes, and fluidizing air is ejected from the diffuser pipes to fluidize the fluidized medium on the diffuser pipes and the material to be incinerated while incinerating the material to be incinerated. In this method, the temperature of the fluidized bed is maintained at 520 to 620° C., and the fluidization speed of the fluidizing air ejected from the diffuser tubes is alternately made large and small for each diffuser tube, and this is alternately switched. Stable combustion method for bed furnaces.