JP3764670B2 - Waste pyrolysis method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for thermally decomposing waste, and more particularly to a method for simultaneously removing chlorine and / or sulfur at the time of pyrolysis and treating the waste at low cost.
[0002]
[Prior art]
Automobile shredder dust is generated during recycling of discarded automobiles, accounting for 20 to 30% of the automobile weight and hindering resource recycling.
[0003]
Shredder dust is composed of various materials such as metals such as iron, copper, zinc, and aluminum, plastics, rubbers, glasses and fibers, and contains various elements. Similarly, municipal waste also contains various elements. All of them inevitably contain environmentally hazardous substances such as chlorine due to vinyl chloride and sulfur.
[0004]
Conventionally, various methods have been proposed for treating waste containing a large amount of chlorine compounds.
[0005]
JP-A-7-55121 and JP-A-8-278015 disclose methods for removing chlorine from waste. The essence consists of a dechlorination decomposition process for removing chlorine from the waste and a combustible combustion process for completely burning the dechlorinated waste. However, with this method, the processing is two stages and the equipment cost is enormous.
[0006]
On the other hand, Japanese Patent Laid-Open No. 7-119939 is disclosed as a method for removing chlorine and sulfur originating from waste. The publication discloses a method for thermal decomposition, combustion, or gasification of waste containing plastic in which a Ca compound is added to waste containing plastic and chlorine in the waste is reacted with Ca for treatment. A treatment method is described in which the addition is carried out by spraying an aqueous solution of a Ca compound onto a waste containing plastic. In this method, it is necessary to prepare a calcium compound in the form of an aqueous solution and to provide a spray mechanism, which increases the equipment investment load and complicates the operation method.
[0007]
In general, a method is known in which fine powder of a calcium compound is added to combustion exhaust gas and reacted with chlorine and sulfur, and then the fine powder is recovered. Becomes expensive.
[0008]
[Problems to be solved by the invention]
In the conventional method, as described above, the problem that the equipment cost and the processing cost are high when dechlorination and desulfurization are performed in the thermal decomposition treatment of waste cannot be solved.
[0009]
Therefore, the present invention provides a method that can easily and inexpensively perform dechlorination and desulfurization during thermal decomposition, and also provides a method that can effectively use resources.
[0010]
[Means for Solving the Problems]
The gist of the present invention is as follows.
(1) In a waste treatment method in which waste is thermally decomposed by indirect heating from outside, a steelmaking slag having a size of 5 mm or more is supplied together with the waste, and is thermally decomposed by using an external heating type rotary kiln and is subjected to a thermal decomposition treatment temperature. Is a 550-750 degreeC , The thermal decomposition processing method of the waste characterized by the above-mentioned.
(2) The waste pyrolysis method according to (1), wherein iron slag mixed from the residue after pyrolysis is recovered and the slag is treated in the same manner as in slag applications such as roadbed materials.
(3) The waste pyrolysis method according to (1), wherein slag having a basicity of 1.6 or more is used.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors conducted a thermal decomposition experiment of shredder dust containing chlorine at 600 to 650 ° C. using an externally heated rotary kiln having an inner diameter of 125 mm and a length of 1530 mm.
[0012]
At this time, the steelmaking slag generated in a general steelworks, particularly the converter slag having a basicity of 1.6 or more and the cold iron source melting furnace slag remain in a lump of 20 mm or more in the kiln like the shredder dust. Supplied. The amount of slag used was 0.2 kg per 1 kg of shredder dust. FIG. 1 shows the result of obtaining the dechlorination rate from the chlorine concentration in the shredder dust before and after the experiment.
[0013]
It was found that the dechlorination rate was 50% or more in the range of 550 to 750 ° C. This is expressed by the interaction between the rate at which chlorine reacts with calcium and the reaction at which the reaction product decomposes. It was also found that S was also removed by about 60%.
[0014]
The reason why the steelmaking slag having a basicity of 1.6 or more contributed to dechlorination and desulfurization is that the steelmaking slag is porous and that unreacted CaO remains, so that the CaO, chlorine and sulfur in the slag remain. This is thought to be due to the reaction and immobilization on the slag side.
[0015]
Steelmaking slag is discharged from a high-temperature furnace at several hundreds of degrees Celsius, so if it is crushed and supplied to a pyrolysis furnace such as a rotary kiln before cooling to room temperature, sensible heat recovery in the pyrolysis furnace is also possible. This contributes to saving the fuel supplied to the pyrolysis furnace.
[0016]
Furthermore, it has been found that by setting the size of the slag to 5 mm or more, it is possible to separate the pyrolysis residue and the slag at the pyrolysis furnace outlet side by simple sieving. This is because the pyrolysis residue is mainly composed of carbonaceous material and metal pieces, and has a property of easily breaking down to about 5 mm or less.
[0017]
A process flow showing an example of the embodiment of the present invention is shown in FIG.
[0018]
Chlorine-containing waste 1 such as shredder dust and waste plastic is supplied to a pyrolysis furnace 3 typified by an externally heated rotary kiln together with a steelmaking slag 2 with adjusted particle size, and pyrolyzed at a temperature of about 700 ° C. in the kiln. To do. On the exit side of the kiln, it can be divided into generated gas, tar content 4 and solid matter, and further separated into pyrolysis residue 5 and post-reaction steelmaking slag by a separation method such as sieving. The pyrolysis residue 5 further collects iron and the like as appropriate. On the other hand, the steelmaking slag after the reaction is diverted to the slag product 6 (for example, roadbed material).
[0019]
In addition, you may combine the process of isolate | separating and collect | recovering the chlorine and sulfur which transfered to slag suitably by the existing methods, such as a wet method.
[0020]
【Example】
Using an externally heated rotary kiln having an inner diameter of 800 mm and a length of 6000 mm, a thermal decomposition experiment was conducted using a reduced volume solidified product of automobile shredder dust having an outer diameter of about 50 mm at 670 to 720 ° C. The waste supply rate is 150 kg / hr. Steelmaking slag of 10 to 20 mm was supplied to the kiln at 20 kg / hr.
[0021]
The dechlorination rate was found to be 82% when the chlorine content of the pyrolysis residue collected during the experiment and the chlorine content of the shredder dust before the experiment were determined.
[0022]
Further, when the solid matter coming out of the rotary kiln after pyrolysis was sieved with a 5 mm sieve mesh, slag was transferred 5 mm above and pyrolysis residue was transferred 5 mm below. The amount of the pyrolysis residue mixed on the slag side was 4% by weight.
[0023]
On the other hand, some of the slag powder moved to the pyrolysis residue side, but this residue was used as a substitute for coal used in the steelmaking process, so some contamination was available without problems.
[0024]
【The invention's effect】
According to the present invention, dechlorination and desulfurization during pyrolysis can be performed easily and inexpensively, and sensible heat of slag, which is an unused energy of a steelworks furnace, can be effectively used and generated in a rotary kiln. It can contribute to the suppression of the coking phenomenon and can provide an industrially useful method.
[Brief description of the drawings]
FIG. 1 shows dechlorination behavior during pyrolysis.
FIG. 2 shows one embodiment of the present invention.
[Explanation of symbols]
1 Waste 2 Steelmaking slag 3 Pyrolysis furnace 4 Generated gas and tar content 5 Pyrolysis residue 6 Slag products

Claims (3)

In pyrolyzing waste treatment method by indirect heating of the waste from the outside, the thermal decomposition and thermal decomposition treatment temperature using external heating rotary kiln size with waste by supplying more steelmaking slag 5mm is 550 A method for thermally decomposing waste, wherein the temperature is 750 ° C.   The waste pyrolysis treatment method according to claim 1, wherein iron slag mixed from the residue after pyrolysis is recovered, and the slag is treated in the same manner as slag applications such as roadbed materials.   The waste pyrolysis method according to claim 1, wherein slag having a basicity of 1.6 or more is used.

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