JPH0719441A - Method and apparatus for treating combustible waste - Google Patents

Abstract

PURPOSE:To prevent a fusion-bonding trouble of ash by suppressing to burn combustible waste by a rotary kiln, then bringing residue to be suppressed to be burned and discharged from the kiln into contact with predetermined gas such as exhaust gas containing steam, after burning unburned part of the residue, and simultaneously proceeding aqueous gas reaction. CONSTITUTION:Waste charged in a rotary kiln 3 is suppressed to be burned in a rotary kiln 3. Its residue is charged in a vertical moving charge tank 14, brought into contact with moisture to be supplied from a slit tuyere 29, burning reaction and aqueous gas reaction are simultaneously conducted to be ashed. The exhaust gas containing steam is completely burned in a secondary burning furnace 16, cleaned in a wet scrubbing tower 18, and part of exhaust gas to be exhausted to a stack 8 is introduced by a circulation fan 12. The exhaust gas containing steam for conducting the after burning, the aqueous reaction may be brought into contact with mixed gas of at least two more move of the exhaust gas containing the steam, the air and the steam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating combustible waste containing plastics among general wastes and industrial wastes by means of a controlled combustion rotary kiln.

[0002]

2. Description of the Related Art Conventionally, a rotary kiln is disposed as a treatment plant for combustible waste among general waste and industrial waste, and is disclosed in, for example, Japanese Examined Patent Publication No. 4-65289 and "Cleaning Technique" issued in 1989. This is because it has more plastics than general combustible waste that is difficult to apply in the conventional stoker type incinerator, and has applicability to unsuitable sorted waste that has a high heating value. It is said that it contributes to prolonging the life of the final landfill site because it can be made harmless and harmless.

This plant has a structure in which a rotary kiln 3 and a stoker 4 are connected as shown in FIG. 6, and a re-combustion chamber 5 is connected to the upper part of the stoker 4, and the rotary kiln is operated in a pyrolysis mode, that is, suppression combustion. To do. In the suppression combustion method, the combustion exhaust gas is charged or the air is dividedly charged to cause a combustion reaction of oxygen with a theoretical combustion oxygen amount or less and some combustible components, and the generated heat is used to pyrolyze other combustible components. This is a method in which fixed carbon, which is not gasified among combustibles, ash and incombustibles are left as residues after being gasified. Since the conventional purpose was to completely incinerate combustibles, the pyrolysis gas generated, that is, the suppressed combustion gas, is completely combusted in the reburn chamber 5, and the fixed carbon contained in the residue is post-combusted in the stoker 4 following the rotary kiln 3. However, the combustible component was completely burned. The reason why the suppression combustion is adopted in this method is that it does not cause the inconvenience of black smoke generation and fusion trouble. That is, when a substance with a large amount of gasification components such as plastics and oils contained in combustible waste is directly burned, not only is incomplete combustion that generates graphite, but also local overheating causes the inner wall of the rotary kiln 3 to be incombustible. This is because it is easy to cause a problem that the minutes are fused.

[0004]

However, even if the rotary kiln 3 is stabilized by suppressing combustion, air is blown into the connected stoker 4 and reburning chamber 5 in order to completely burn the remaining combustibles and pyrolysis gas. Therefore, there is an inconvenience that a rapid combustion occurs in the connection portion. That is, when air is supplied to the stoker 4 for post-combustion of the residue, the residue sufficiently preheated in the rotary kiln 3 rapidly burns at the inlet of the stoker 4 and the flame rises, and incombustibles and ash near the flame are generated. There is the inconvenience of locally radiatively heating and fusing to the outlet side of the rotary kiln 3, the inlet part of the stoker 4, etc. In addition, if air is supplied to the reburn chamber 5, the combustible gas from the rotary kiln 3 The radiation of the flames burned at the contact surface between the air and the supply air Q ₄ reaches not only the reburn chamber 5 but also the outlet of the rotary kiln 3 and the stoker 4, and the incombustible content and ash content are fused.

[0005]

According to the present invention, after combustible waste is suppressed and burned in a rotary kiln, the residue discharged from the suppressed combustion rotary kiln is brought into contact with exhaust gas containing steam to remove unburned matter in the residue. It is characterized in that the water-gas reaction proceeds simultaneously with burning.

The exhaust gas containing water vapor may be not only the exhaust gas containing water vapor but also a mixed gas of at least two or more of the exhaust gas containing water vapor, air and water vapor.

As an apparatus for carrying out this method, a vertical moving packing layer is connected to the lower part of the furnace bottom fixing hood of a rotary kiln, and a gas blowing means for blowing exhaust gas containing water vapor is arranged in the moving packing layer. be able to.

Further, it is possible to provide an apparatus in which a fluidized bed is connected to the lower part of the rotary butt of the rotary kiln to fix the bottom of the furnace, and a gas injection means for injecting exhaust gas containing water vapor is provided in the fluidized bed.

Furthermore, a stoker may be connected to the lower part of the furnace bottom fixing hood of the rotary kiln, and a gas blowing means for blowing exhaust gas containing water vapor may be provided in the air blowing part of the stoker.

Further, two rotary kilns are connected via a fixed hood, and a discharge means for combustible gas such as pyrolysis gas is arranged in the fixed hood, and the fixed kiln in front of the rotary kiln in the preceding stage is combustible. A device can be provided in which a means for charging waste and a means for blowing gas for suppressing combustion containing oxygen are provided, and a gas blowing means for blowing exhaust gas containing water vapor is provided in the rotary kiln bottom fixed hood of the preceding stage. .

[0011]

According to the present invention, by suppressing and burning combustible waste in the rotary kiln, it is possible to prevent fusion problems in the rotary kiln, and at the same time, the residue from the rotary kiln is guided to the post-combustion gasifier, and the post-combustion gas is generated. In the gasification device, the combustible component mainly composed of fixed carbon in the residue is brought into contact with the exhaust gas containing steam or the mixed gas of at least two or more of the exhaust gas containing steam and air and steam to cause the combustion reaction and the water gas reaction at the same time. As a result of combustible components being post-combustion gasified, partial overheating is eliminated,
It is possible to incinerate combustible waste without causing fusion problems at the post-combustion gasifier and the outlet side of the rotary kiln.
That is, due to the presence of water vapor around carbon that is post-combusted due to the presence of oxygen, even if heat is generated in the combustion reaction shown in formula I, it is also endothermic in the water gas reaction shown in formula II. It is possible to incinerate combustible waste without reaching the area.

C (solid) + O ₂ (gas) = CO ₂ (gas) +8100 Kcal / kg-C Exothermic reaction-I formula C (solid) + H ₂ O (gas) = CO (gas) + H ₂ (gas) -4820 Kcal / Kg-C Endothermic reaction-II formula

[0013]

【Example】

Example 1 FIG. 1 shows the overall equipment for carrying out the present invention. Figure 1
In the figure, reference numeral 1 denotes a waste supply hopper which communicates with the lower charging device 2.

The supply hopper 1 and the lower charging device 2 are provided with a hydraulic unit 11 which operates to control the amount of waste supplied and the amount of waste delivered into the kiln.

A rotary kiln 3 has a vertical moving filling tank 14 connected to the lower part of the furnace bottom fixed hood, and a lateral slit tuyere 29 is provided on the side surface of the moving filling tank 14 to prevent dust from being easily blocked. A pipe for supplying the exhaust gas containing water vapor from the exhaust gas circulation fan 12 is connected to the port 29. Further, the lower portion of the moving filling tank 14 communicates with the water sealing tank 9 through the discharging device 28, and the water ash 10 of the waste which has been granulated and cooled is discharged from the water sealing tank 9.

Reference numeral 16 denotes a secondary combustion furnace which completely combusts the combustible gas generated from the rotary kiln 3 and the moving filling tank 14 with the combustion air from the forced draft fan 13, and the exhaust gas thereof is cooled and concentrated in the can 17, the wet type. Washing tower 18,
It is discharged from the chimney 8 through the mist removing device 19 and the induced draft fan 20.

The control of the combustion temperature T ₃ of the secondary combustion furnace 16 is controlled by adjusting the combustion air amount Q ₃ .

Reference numeral 26 is a circulation pump for the absorbing liquid, which is connected by a pipe so that a part of the liquid can flow into the cooling condensing can 17. In the cooling condensing can 17, the salt produced by evaporation of water is concentrated and deposited to form a slurry. It is in the shape of. The slurry circulation pump 24 connected to the cooling condensing can 17 is connected to the centrifugal separator 25, and is arranged so that the precipitated salt 27 can be continuously separated.

FIG. 2 is an enlarged view showing the structures of the rotary kiln 3, the moving filling tank 14 and the water sealing tank 9 following it, which are shown in FIG.

The waste charged in the rotary kiln 3 is suppressed and combusted, and the residue is brought into contact with the exhaust gas containing water from the slit tuyere 29 in the vertical moving filling tank 14 to cause combustion reaction and water gas reaction. At the same time to incinerate the waste.

At this time, the temperature T ₂ in the filling tank is controlled by adjusting the amount Q ₂ of gas blown into the tuyere 29, or steam or air is added to the exhaust gas to change the ratio of oxygen to steam in the gas. It can be controlled by

It should be noted that although the present invention is sufficient, FIG. 1 and FIG.
As shown in, the high temperature gas duct leading to the furnace butt fixing hood of the rotary kiln 3 is partially branched and the cyclone 1
5. By providing the external circulation duct 21 connected to the gas burner 23 provided in the furnace front fixed hood via the steam ejector 22, the suppression combustion is further stabilized and the gasification rate of the combustible material is improved, and the residue is reduced. The amount of heat loss can be reduced.

That is, a part of the combustible gas discharged from the rotary kiln is pushed in and the air from the blower fan 13 and the gas burner.
Since the gas is combusted at 23, most of the heat quantity necessary for the thermal decomposition of the combustibles can be supplied by the stable burner combustion in the rotary kiln 3. Therefore, the temperature T _{1 at the} outlet of the rotary kiln is equal to the quantity of combustible gas Q ₄ circulated outside. It can be easily controlled by adjusting the air supply amount Q _1, and more stable suppression combustion can be performed as compared with the conventional method in which exhaust gas of high temperature and low oxygen is circulated.

In addition, the suppressive combustion by the gas burner combustion does not have solid combustion in the vicinity of the combustible material and can suppress the rapid coking of the combustible material, so that highly efficient gasification can be achieved, and most of the combustible content is Is gasified in a rotary kiln.

Therefore, by combining an external circulation system having high gasification efficiency with an inexpensive and simple gasification system such as a moving filling tank, combustible waste can be easily ashed and most of combustibles can be removed. It can be obtained as pyrolysis gas, and ashing and gasification are possible in one process.

Example 2 FIG. 3 shows a first apparatus for contacting a residue discharged from a suppressed combustion rotary kiln with an exhaust gas containing water vapor to post-combust unburned components in the residue and to simultaneously promote a water gas reaction. 2 shows an example in which the moving filling tank is a fluidized bed.

In the figure, a residue is separated by a sieve 33 at the residue outlet at the bottom of the furnace bottom fixing hood of the rotary kiln 3 so that the residue separated from the coarse product enters the moving fluidized bed 31. The coarse product is the coarse product. It is discharged from the discharge port 34. The furnace bottom of the moving fluidized bed 31 is inclined toward the incombustibles discharge port 35, and a gas blowing device for blowing exhaust gas containing water vapor is connected to the diffuser nozzle group 32 provided on the furnace bottom. The upper space of the furnace bottom provided with the air diffusion nozzle group 32 is configured as a free board for connecting the furnace bottom fixing hood of the rotary kiln 3.

Embodiment 3 FIG. 4 shows an example in which a stoker furnace is provided in the latter stage of the suppression combustion rotary kiln as a third embodiment of the present invention. The difference between this example and the conventional method shown in FIG. 6 is that the gas blowing device connected to the stoker furnace is replaced with air from the conventional forced air blowing fan 13, and an exhaust gas duct containing water vapor from the exhaust gas circulating fan 12 is used. 36, the removal of the re-combustion chamber of the rotary kiln furnace bottom fixed hood, and the highly efficient gasification of the rotary kiln, the external circulation duct 21,
The three points are that an external circulation system including a gas burner 23 and the like is arranged.

The stoker furnace is supplied with the residue sufficiently gasified by the rotary kiln in the previous stage, and the unburned component in the residue is post-combusted in the stoker furnace and the water-gas reaction proceeds at the same time, so that the unfused portion is fused. Stable ashing without any trouble.

Fourth Embodiment FIG. 5 shows an example in which a post-combustion rotary kiln is provided after the suppression combustion rotary kiln as a fourth embodiment of the present invention. In the same figure, the lower part of the fixed hood of the rotary kiln 3 communicates with a countercurrent type post-combustion rotary kiln 39 via a chute 37 and a hydraulic unit 38. Since it comes into countercurrent contact with the exhaust gas containing water vapor blown from 40, and the post-combustion and the water-gas reaction proceed at the same time, stable ashing occurs without causing fusion problems.

[0031]

The present invention has the following effects.

(1) By blowing an exhaust gas containing water vapor into the outlet residue of the suppression combustion rotary kiln, stable ashing of the residue can be achieved without causing a fusion problem which has been a problem in the past.

(2) Suppressing combustion Combustible waste can be easily ashed by combining with a simple and inexpensive gasification system such as a moving packed bed after the rotary kiln, and almost all of the combustibles are pyrolyzed. It can be obtained as a gas, and ashing and gasification can be performed in one process.

(3) An external circulation type system in which a part of the combustible gas discharged from the rotary kiln is circulated to a gas burner provided in the fixed hood in front of the furnace is used to prevent solid combustion in the vicinity of the combustible material and to combust it. Since rapid coking of the substance can be suppressed, highly efficient gasification can be achieved, and as a result, the amount of residue burned can be reduced.

(4) By guiding the obtained pyrolysis gas to a separate upper combustion type secondary combustion furnace, it is possible to make a device structure which can be easily used as a heat source for waste liquid incineration, and at the bottom of the secondary combustion furnace. If the blower water of the wet smoke washing device can be introduced and concentrated in the cooled condensing can to precipitate the salt, and at the same time, the present precipitated salt can be continuously separated by the centrifuge, the discharge treatment becomes unnecessary.

[Brief description of drawings]

1 shows the overall equipment for carrying out the invention.

FIG. 2 shows an enlarged view of a rotary kiln portion shown in FIG.

FIG. 3 shows a second embodiment of the present invention in which the moving packed bed is a fluidized bed.

FIG. 4 is a third embodiment of the present invention in which the moving packed bed is a stoker furnace.
An example of is shown.

FIG. 5 shows an example in which a rotary kiln is provided in two stages as a fourth embodiment of the present invention.

FIG. 6 shows a conventional combustible waste treatment device.

[Explanation of symbols]

1 Supply hopper 14 Moving packed bed 27 Precipitated salt 2 Input device 15 Cyclone 28 Discharge device 3 Rotary kiln 16 Secondary combustion furnace 29 Slit tuyeres 4 Grate (stoker) 17 Cooling concentrator 30 Freeboard 5 Reburning chamber 18 Wet washing tower 31 Movable fluidized bed 6 Gas cooling device 19 Mist removal device 32 Air diffuser nozzle 7 Exhaust gas treatment device 20 Induced draft fan 33 Sieve 8 Chimney 21 External circulation duct 34 Coarse waste discharge device 9 Water granulation device 22 Steam ejector 35 Incombustibles discharge port 10 Waste Waste ash 23 Gas burner 36 Duct of exhaust gas containing water vapor 11 Hydraulic unit 24 Slurry circulation pump 37 Chute 12 Exhaust gas circulation fan 25 Centrifuge 38 Hydraulic unit 13 Pushing fan 26 Absorbing liquid circulation pump 39 Post-combustion rotary kiln 40 Outlet hood

Claims (5)

[Claims] 1. A suppressive combustion residue discharged from a suppressive combustion rotary kiln after suppressing combustion of combustible waste in a rotary kiln, and at least two or more of exhaust gas containing steam or exhaust gas containing steam, air and steam. A method for treating combustible wastes, which comprises contacting with a mixed gas to post-combust unburned components in a suppressed combustion residue and simultaneously advancing a water-gas reaction. 2. A vertical moving packing layer is connected to a rear stage of a furnace bottom fixed hood of a rotary kiln, and at least two or more of exhaust gas containing steam, or exhaust gas containing steam, air and steam are connected to the moving packing layer. An apparatus for treating combustible waste, comprising a gas blowing means for blowing the mixed gas. 3. A fluidized bed is connected to the latter stage of the furnace bottom fixed hood of the rotary kiln, and an exhaust gas containing steam or a gas in which at least two of exhaust gas containing steam, air and steam are mixed is blown into the fluidized bed. An apparatus for treating combustible waste, which is provided with a gas blowing means. 4. A stoker furnace is connected to a rear stage of a rotary kiln bottom fixed hood, and at least two or more of exhaust gas containing water vapor or exhaust gas containing water vapor and air and water vapor are mixed in the blower part of the stoker oven. A combustible waste treatment device comprising a gas blowing means for blowing gas. 5. The two rotary kilns are connected via a fixed hood, and the fixed hood is provided with means for discharging combustible gas such as pyrolysis gas, and the fixed kiln in front of the rotary kiln of the preceding stage is flammable. A means for charging waste and a means for blowing in a gas for suppressing combustion containing oxygen are provided, and the rotary kiln furnace fixed hood in the latter stage has exhaust gas containing water vapor, or exhaust gas containing water vapor, air, and water vapor. A device for treating combustible waste, characterized in that a gas blowing means for blowing a gas in which at least two or more are mixed is provided.