JP2888396B2 - Fluidized bed combustion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, polyethylene,
It relates to fluidized bed incinerators such as fluidized bed incinerators that burn and incinerate waste such as shredder dust containing plastics such as polypropylene and vinyl chloride, rubbers, urethane, wood, and fibers. The present invention relates to a fluidized bed combustion apparatus suitable for burning and incinerating waste such as waste plastic containing particles.

[0002]

2. Description of the Related Art Conventionally, fluidized bed incinerators such as fluidized bed incinerators for burning and incinerating wastes such as shredder dust containing plastics such as polyethylene, polypropylene and vinyl chloride have exhaust gas discharge ports downstream. The fluidized medium such as sand is fluidized by air dispersed and supplied from the lower air chamber through the air distribution plate in the fluidized combustion chamber to form a high-temperature fluidized bed, and the fluidized bed has a space above the fluidized bed. Part, that is, the waste as an object to be burned is injected and burned through the free board, and the combustion exhaust gas is discharged from the fluidized bed to the outside of the furnace through an exhaust gas outlet provided on the free board downstream side through the free board through the free board. Processing.

[0003]

As described above, the material to be burned falls through the free board and is introduced into the fluidized bed, and the material to be burned having a predetermined large particle size is burned in the fluidized bed. Small-diameter particles, such as fine particles, contained in the object to be burned are carried along with the flue gas flowing up the freeboard. If the small-diameter particles entrained in the flue gas stream are, for example, plastic, they are thermally decomposed and gasified by the high-temperature flue gas on a freeboard, generating volatile components such as hydrocarbons such as methane, ethane, and ethylene. Is done. Some of these volatiles are burned by the freeboard, but the flue gas has a certain gas flow velocity, the freeboard height is also set to the predetermined height, and the time to pass through the freeboard is short. Because of their limited nature, these volatiles are not completely burned while present on the freeboard, and some of the volatiles and small-sized particles are taken out of the combustion chamber as unburned and discharged. . When the unburned components are discharged to the outside of the combustion chamber, the combustion efficiency naturally deteriorates.

The present invention has been made in view of such a problem, and reduces small particles such as volatiles and fine particles which are taken away from the freeboard as unburned components in the combustion exhaust gas during the supply of the material to be burned. Accordingly, it is an object of the present invention to obtain a fluidized bed combustion device capable of burning waste such as plastic as a burnable material with high efficiency.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has an air chamber at a lower portion, and a fluid combustion chamber at an upper portion through an air distribution plate. The fluidized medium is fluidized by air supplied from the air chamber to form a high-temperature fluidized bed, a substance to be burned is supplied to the fluidized bed to be burned, and a combustion exhaust gas is discharged through a free board at an upper portion of the fluidized bed. In the fluidized bed combustion apparatus as described above, a part of the free board surrounds the periphery of the furnace wall where the part to be burned is opened, and is formed with the lower part facing the fluidized bed. A gas outlet is provided at a different position of the furnace wall facing the chamber away from the burnable material supply port,
The gas outlet and the air chamber were connected by a gas circulation line.

[0006]

In the fluidized combustion chamber, a fluidized medium such as sand is fluidized by high-temperature air for fluidization and combustion supplied from a lower air chamber through an air dispersion plate to form a high-temperature fluidized bed. In this state, a waste as a combustible, for example, a shredder dust containing a plastic such as polyethylene or polypropylene is formed from the combustible supply port around the periphery of the combustible supply port. The large-size waste fed into the furnace falls down to the hot fluidized bed and is burned. The flue gas passes through the free board and is discharged from a downstream exhaust gas outlet. On the other hand, the thermally decomposable small-sized particles such as fine-particle plastics in the waste are thermally decomposed by high-temperature exhaust gas discharged from the fluidized bed in the space inside the chamber, and are converted into volatile components such as hydrocarbon gas such as methane. The gas is discharged into a gas circulation pipe outside the apparatus from a gas discharge port provided in a furnace wall facing the chamber, and supplied to an air chamber.

The volatile matter which is the hydrocarbon gas such as methane returned to the air chamber is burned by the action of high-temperature air in the air chamber, or passes through a gas dispersion plate together with high-temperature air for fluidization and combustion. The fuel is dispersed and supplied to a high-temperature fluidized bed in a fluidized combustion chamber, and efficiently combusts with a high-temperature fluidized medium to efficiently burn. As described above, the volatile components are finally burned in the fluidized bed, so that they are reliably burned, and small-diameter particles such as fine particles supplied to the combustion device are burned efficiently.

If a collector such as a cyclone is interposed in the middle of the circulation pipe, some of the small-diameter particles are not yet gasified or sand, which is a fluid medium not subject to thermal decomposition. Even when non-combustible substances such as are introduced into the circulation pipe from the gas discharge port, they are collected by the collector, and the collected substances are collected through the combustion substance supply port or the like. What can be returned to the supply chamber and thermally decomposed can be again gasified by giving it the opportunity of thermal decomposition, so that small-diameter particles can be more reliably burned and burned more efficiently. Incombustibles that do not undergo thermal decomposition can be returned to the freeboard, placed in the exhaust gas stream, and collected downstream.

[0009]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing one embodiment of a fluidized bed combustion apparatus according to the present invention. The fluidized bed combustion apparatus 1 is entirely surrounded by a furnace wall 1a, an air chamber 2 is located at the lowermost part, a fluidized combustion chamber 10 is located above the air chamber 2 via an air distribution plate 3, and a downstream side of the air chamber 2 is located at the lower part. A desulfurization / dechlorination chamber 30 is located at the upper part via a gas dispersion plate 20, and an exhaust gas discharge port 33 is provided downstream thereof.

The configuration of the fluidized bed combustion apparatus 1 will be described in more detail. The bottom of the fluidized combustion chamber 10 has a furnace wall 1a on the left side in the figure.
A discharge port (hereinafter, referred to as a non-combustible substance discharge port) 13 for the incombustible substance and the fluid medium is formed facing the non-combustible substance discharge port 1.
An air distribution plate 3 inclined so as to become lower toward 3 is attached. In the lowermost part, the air distribution plate 3, the noncombustible material outlet 13, and the air chamber 2 surrounded by the furnace wall 1a.
Are formed. A cooling pipe is laid inside the air distribution plate 3, and a large number of air distribution tubes 4 are attached to the upper end of the air distribution plate 3 so as to protrude from the air distribution plate 3. Air dispersion pipe 4
At the upper end thereof, an air ejection hole is opened and directed toward the noncombustible material outlet 13 side, and high-temperature air is dispersedly supplied from the air chamber 2 into the fluidized combustion chamber 10 through the air ejection holes of the many air dispersion pipes 4. It is configured to be.

A non-combustible material discharger 15 such as a screw conveyor and a fluid medium are attached below the non-combustible material discharge port 13, and a screen device 16 for sifting the non-combustible material and the fluid medium is attached downstream thereof. I have. A sieve 17 is provided inside the screen device 16, an outlet 16 a for the fluid medium that has passed through the sieve 17 is provided below the sieve 17, and remains below the sieve 17 on the side of the sieve 17. A discharge port 16b is provided for discharging non-combustible substances such as glass and metal dropped from above. Fluid medium outlet 16
A circulation transport circuit 18 for returning the fluidized medium to the fluidized bed combustion device 1 again is connected to a.

The air chamber 2 is divided into left and right sides, and a hot air supply pipe 47 connected to the discharge side of a pushing fan 48 is connected to each of the left and right air chambers 2. Push fan 4
An air introduction pipe 80 is connected to the suction side of the tube 8. Although not shown, an air preheater (not shown) for preheating the air to 200 to 300 ° C. by the combustion exhaust gas discharged from the exhaust gas outlet 33 of the combustion device 1 is provided in the middle of the high-temperature air supply pipe 47.

In the fluidized combustion chamber 10, a fluidized medium made of sand or limestone having a particle size of 0.5 to 1.0 mm is fluidized with high-temperature air on the air dispersion plate 3 to form a fluidized bed 11. A free board 12 is formed above the fluidized bed 11. Further, a gas dispersion plate 20 is installed across the free board 12, and a desulfurization / dechlorination chamber 30 is formed above the gas dispersion plate 20. The gas dispersion plate 20 is provided with a large number of gas dispersion tubes 21. On the gas dispersion plate 20, the adsorbent such as limestone particles is fluidized by the combustion exhaust gas dispersedly supplied from the many gas dispersion tubes 21 to form the desulfurization / dechlorination bed 31. An exhaust gas outlet 33 for discharging desulfurized and dechlorinated exhaust gas is attached to the upper side of the desulfurization and dechlorination chamber 30. 14, 19,
32 is a heat transfer tube for exhaust heat recovery.

The furnace wall 1a of the fluidized combustion chamber 10 opposite to the noncombustible material discharge port 13 is provided with a raw material supply port 43 as a burnable substance supply port at a position above the upper surface of the fluidized bed 11 by a predetermined distance. The raw material supply port 43 is provided with a raw material supply device 42 composed of a screw conveyor. Further, a partition wall 41 which is located on the free board 12 and extends in the vertical direction so as to surround the raw material supply port 43 is joined and attached to the inner surface of the furnace wall 1a,
The fluidized bed 1 extends downward between the partition wall 41 and the inner wall surface of the furnace wall 1a.
A raw material supply chamber 40 is formed so as to face a part of the first raw material supply chamber 1.
The lower end 41 a of the partition wall 41 is located at a position lower than the upper surface of the fluidized bed 11 by a desired amount and is set at a position where it enters the inside of the fluidized bed 11. As described above, the raw material supply chamber 40 is provided in the free board 12 in a state where the inside thereof is isolated from the free board 12.

The raw material supply chamber 40 extends up to a predetermined distance above the raw material supply port 43 to form a space, and a space having a predetermined width is also formed in a direction perpendicular to the drawing. I have. A gas outlet 44 is formed in the furnace wall 1a above the source supply port 43 of the source supply chamber 40, and a gas exhaust pipe 44a is attached to the gas outlet 44. An ejector burner 60 is provided on the furnace wall 1a of the air chamber 2.
A high-pressure air supply pipe 61 to which an air supply device such as a Roots blower (not shown) is connected is connected to an end of the ejector burner 60. A gas circulation line 45 (45a, 45b) is provided between the ejector burner 60 and the gas discharge tube 44a.
In the middle of the gas circulation line 45, a cyclone collector 46 is provided.
Is installed.

In the lower part of the cyclone is a dust cooler 7 in order.
0, a rotary valve 71 and a fork-direction switching damper 52 are attached, and a line 5 is provided between one outlet on the downstream side of the fork-direction switching damper 52 and the raw material inlet of the raw material feeder 42.
1 is connected, and a raw material supply pipe 50 is connected in the middle of the pipe line 51. The other outlet of the bifurcated direction switching damper 52 is connected to an opening of the furnace wall 1a facing the free board 12 by a conduit 53.

Next, the operation of the embodiment of the apparatus of the present invention having such a configuration will be described. The air chamber 2 in the fluidized combustion chamber 10
The fluidized bed of sand is fluidized by the high-temperature air supplied through the air dispersion plate 3 from the air to form a fluidized bed 11, and the fluidized bed 11 is heated by the heat of combustion of the high-temperature air and the raw material. It is kept at a high temperature of ８850 ° C.
In the fluidized bed 11, high-temperature air is ejected toward the incombustible discharge port 13 because the air ejection holes of the air dispersion pipe 4 are opened toward the noncombustible substance discharge port 13 of the fluidized combustion chamber 10. In FIG. 1, the fluidized bed 11 swirls clockwise and flows to the right.

The fluidized bed 11 formed in this manner has a shredder dust containing wastes such as plastics such as polyethylene, polypropylene and vinyl chloride, rubbers, urethane, wood, fibers and the like. Is supplied from the raw material supply pipe 50 to the raw material supply device 42, supplied into the raw material supply chamber 40 by the raw material supply device 42, dropped into the fluidized bed 11, and burned. During this combustion, the fluidized bed 11 is swirled to the right in the figure, so that the fluidized medium and the waste to be burned are well stirred and mixed, and are efficiently burned and contained in the waste. Non-combustible materials such as iron scraps and glass and glass are
Further, since the air distribution plate 3 is inclined so as to become lower toward the incombustible material outlet 13 side, it is collected at the incombustible material outlet 13 side and drops to the incombustible material outlet 13 together with some fluid medium. I do.

A part of the fluid medium and the incombustible material are supplied to a screen device 16 by a discharger 15, and the fluid medium having passed through the sieve 17 is discharged from a discharge port 16 a by a circulation transport circuit 18 to a free board 12 of a fluid combustion chamber 10. Is returned and used cyclically. Non-combustible substances such as glass and metal remaining on the sieve 17 are discharged from the discharge port 16b to the outside of the machine.

Thus, among the wastes supplied to the raw material supply chamber 40, the waste of small-diameter particles including fine particles and the like is reduced by the action of the pushing fan 48 into the gas outlet 4 of the raw material supply chamber 40.
Fluidized bed 11 sucked from 4 and rising inside the chamber 40
The temperature rises in the chamber 40 due to the high temperature (800 to 850 ° C.) combustion exhaust gas. Among the small-diameter particles, the burnable matter such as plastics, which is thermally decomposed, rises inside the chamber 40 and is gasified into hydrocarbon gas such as methane and ethane by a high-temperature exhaust gas to be volatilized. Together with the combustion exhaust gas from the gas discharge port 44 through the discharge pipe 44a to the pipe 45
a, and reaches the cyclone collector 46, where the dust entrained in the exhaust gas is collected and sent to the lower pipeline 51. This dust includes small-sized plastic particles having relatively large particle size, which are not yet gasified, and other combustible materials such as wood chips and fibers, and non-combustible particles such as glass fine particles and fluidized medium particles.

The flue gas containing volatile matter such as the hydrocarbon gas is separated from the dust by a cyclone collector 46 and supplied to an ejector burner 60 through a pipe 45b, and then supplied from a high-pressure air supply pipe 61. Volatile components are sucked by the ejector action of the high-pressure air and supplied to the air chamber 2, where the volatile components are supplied with the high-temperature air and burned efficiently. The hot air for combustion and fluidization preheated to, for example, 200 to 300 ° C. by the air preheater by the action of the pushing fan 48 is supplied to the air chamber 2 through the high temperature air supply pipe 47.

The bifurcated direction switching damper 52 attached to the pipe line 51 is set so as to communicate with the raw material feeder 42. After the dust captured by the cyclone collector 46 is cooled by the dust cooler 70, Then, the combustibles such as thermally decomposable small-diameter particles such as plastics and rubber and small-diameter wood chips, which are supplied to the raw material supply device 42, are again supplied to the raw material supply chamber 40 and subjected to regasification decomposition operation and combustion operation.

In order to eliminate the accumulation of the non-combustible particles in the circulation system including the pipe 45a, the cyclone collector 46, the pipe 51, the raw material feeder 42 and the raw material supply chamber 40, Or a bifurcated direction switching damper 5 at timing
2 is operated so as to communicate with the pipe 53, these particles are introduced into the free board 12 of the fluidized combustion chamber 10, carried downstream along with the combustion exhaust gas passing through the free board 12, and It is collected by a dust collector separately provided downstream. Of course, once the combustible particles of small diameter,
In the case where gas is almost completely gasified or burned by being supplied to the raw material supply chamber 40, the bifurcated direction switching damper 52 is set so as to communicate with the conduit 53,
Non-combustible particles contained in the collected matter can be thrown into the free board 12.

However, as described above, volatile components such as hydrocarbon gas supplied from the ejector burner 60 to the air chamber 2 are efficiently burned by the action of the high-temperature air supplied from the high-temperature air supply pipe 47 here. The exhaust gas and a part of the unburned gas of the volatile components are dispersed and supplied together with the high-temperature air from the air distribution plate 3 into the high-temperature fluidized bed 11, where they are efficiently burned to be almost completely burned. In this way, the volatile components are prevented from being discharged from the fluidized combustion chamber 10, and the combustion efficiency is improved.

The flue gas discharged from the fluidized bed 11 is subjected to appropriate heat recovery in the heat transfer tubes 14 above the fluidized bed 11 while ascending the freeboard 12, and the temperature of the fluidized bed 11 is adjusted so that the fluidized fluid is discharged. The floor 11 is at a predetermined temperature, in this case 800-8
It is kept at 50 ° C. This heat transfer tube 14 is used, for example, as a first evaporator. Then, the flue gas rises on the free board 12 to reach the top of the fluidized combustion chamber 10, where the heat is recovered again by the heat transfer tube 19 located there, and the temperature is adjusted so as to be suitable for desulfurization and / or dechlorination. You. The heat transfer tube 19 is used, for example, as a second evaporator.

Thus, the combustion exhaust gas is supplied to the gas dispersion plate 20.
Through the desulfurization / dechlorination chamber 30, where the flue gas itself passes through a desulfurization / dechlorination bed 31 formed by fluidizing a desulfurization / dechlorination agent composed of limestone particles. Sulfur oxide and hydrogen chloride contained in sulfur are desulfurized and dechlorinated. In addition, when rubber contained in the shredder dust as waste to be burned is burned, sulfur oxides are generated, and vinyl chloride (PVC) and chloroprene, which are plastics contained in the shredder dust, are burned. In some cases, hydrogen chloride is generated. Desulfurization
The exhaust gas that has passed through the dechlorination bed 31 is supplied to the heat transfer tube 32
Receives waste heat recovery. This heat transfer tube 32 is used, for example, as a heater.

The exhaust gas that has passed through the heat transfer tube 32 is
The exhaust gas is discharged from the exhaust gas discharge port 33 to the exhaust gas duct, and the heat is further recovered by an exhaust heat recovery device such as an exhaust heat boiler or an air preheater (not shown) installed here to lower the temperature.

If the volatile matter is introduced into the air chamber 2 by the ejector burner 60 and burned there as in this embodiment, the volatile matter (combustible gas) is kept at a high temperature of 800 to 850 ° C. In addition, combustion can be performed in a state where the concentration is high, and combustion can be performed with high combustion efficiency. The heat of combustion of the volatile matter in the air chamber 2 is transferred to the heat transfer tube 1 above the fluidized bed 11.
4, heat can be efficiently recovered. Thus, the load on the exhaust heat boiler provided downstream of the exhaust gas outlet 33 of the combustion device 1 can be reduced, and its size can be reduced.

Although not shown, instead of providing the ejector burner 60 in the air chamber 2 as described above, one end of the gas circulation line 45b on the outlet side of the cyclone collector 46 is connected to the suction side of the pushing fan 48. And a heat exchanger of a plate type or the like is installed in the middle of the gas circulation line 45b to form a gas circulation line, and the gas circulation line 45b is sent from 800 to 850. After the high-temperature volatile matter is lowered to a predetermined temperature lower than the ignition temperature of the volatile matter, for example, 300 ° C. by the heat exchanger, the volatile matter is combined with the air in the air inlet pipe 80, The air can be supplied to the air chamber 2 through the supply pipe 47.
In this case, a small proportion of the volatile matter is burned in the air chamber 2 and most of the volatile matter is burned in the fluidized bed 11.

[0030]

As described in detail above, in the present invention, even when the burnable material as a raw material contains small-diameter particles such as fine particles which can undergo thermal decomposition such as plastics and fine particles which can burn. It is gasified in the burnable material supply chamber, the volatile matter generated thereby is supplied from the burnable material supply chamber to the air chamber by a circulation line, and the volatile matter is burned in the air chamber; and Alternatively, it can be supplied from the air chamber to the high temperature fluidized bed of the fluidized combustion chamber through the air dispersion plate and burned, so that the volatiles are finally burned in the fluidized bed and become free as in the past. The proportion of volatile components that escape from the fluidized combustion chamber through the board can be extremely reduced. Therefore, it is possible to obtain a fluidized bed combustion apparatus capable of burning a burnable material such as shredder dust while maintaining high efficiency.

It is to be noted that a collector is provided in the middle of the circulation line, and is carried along with the circulation line, and combustibles and other small-diameter combustibles which have not been thermally decomposed yet are captured here. If these are again supplied to the combustion object supply chamber to give an opportunity for thermal decomposition and combustion, the combustion efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a fluidized bed combustion apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluid bed combustion apparatus 1a Furnace wall 2 Air chamber 3 Air dispersion plate 10 Fluid combustion chamber 11 Fluid bed 12 Free board 30 Desulfurization / dechlorination chamber 40 Raw material supply chamber (combustibles supply chamber) 41 Partition wall 42 Raw material feeder 43 Material supply port (combustibles supply port) 44 Gas discharge port 45 (45a, 45b) Gas circulation line 46 Cyclone collector 47 High-temperature air supply tube 48 Push-in fan 50 Material supply tube 60 Ejector burner

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F23G 5/30 F23G 5/027 F23C 11/02

Claims (1)

(57) [Claims] An air chamber is provided at a lower portion, and a fluidized combustion chamber is provided at an upper portion thereof through an air distribution plate. The fluidized medium is fluidized by air supplied from the air chamber in the fluidized combustion chamber. In a fluidized bed combustion apparatus in which a high-temperature fluidized bed is formed, a substance to be burned is supplied to the fluidized bed and burnt, and a combustion exhaust gas is discharged through a freeboard at the upper part of the fluidized bed. A burnable material supply chamber is provided which surrounds the periphery of the furnace wall at the portion where the burnable material supply port is opened, and is formed so as to face downward to the fluidized bed, and the burnable material supply port of the furnace wall facing this chamber is provided. Gas outlets at different locations away from
A fluidized bed combustion apparatus, wherein the gas outlet and the air chamber are connected by a gas circulation line.