JP2001139962A - Thermal decomposition of inflammable waste material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for decomposing an inflammable waste material, capable of suppressing the generation of a tar component, enabling the stable operation of a thermal decomposition unit such as a fluidized bed type gasification furnace and also maintaining or improving the amount of heat generation of the thermally decomposed gas to reuse the energy of the waste material effectively in its thermally decomposition by bringing the inflammable waste material into contact with a heated powder fluidized medium. SOLUTION: This method for decomposing the inflammable waste material by bringing the inflammable waste material into contact with the powder fluidized medium, comprises performing the thermal decomposition by using a zeolite having 3.0-100 molar ratio of silica to alumina (SiO2/Al2O3) and 400-800 m2/l specific surface area as at least a part of it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pyrolyzing combustible waste, and more particularly to industrial waste such as municipal solid waste, waste plastic, waste oil, and RDF (Refuse Der).
The present invention relates to a method for pyrolyzing combustible waste suitable for treatment of ived fuel, sewage sludge, and the like by a fluidized-bed gasification and melting system.

[0002]

2. Description of the Related Art In recent years, gasification melting treatment has been developed as a new waste treatment technology that replaces incineration treatment of combustible waste. The gasification and melting treatment is, for example, using a fluidized-bed gasification furnace to convert combustible waste into a reducing atmosphere under a reducing atmosphere.
Pyrolysis and gasification at 0-700 ° C, methane and ethane,
Volatile combustible gas components such as acetylene and char, which is a combustible solid, are generated, and these are mixed in a melting furnace.
Completely burn at 200-1450 ° C. to melt ash,
It is a method of discharging as slag. This method has the advantages that almost no dioxins are generated, the ash in the waste can be recovered as harmless slag, and the energy generated by the gasification furnace, such as gas and tar, can be reused for melting the ash. are doing.

[0003] However, in the fluidized-bed gasification and melting furnace, tar and soot components generated during the pyrolysis and gasification of combustible waste are generated by the freeboard portion of the gasification furnace and the gasification and melting furnaces. May adhere to and solidify in the pipes connecting the pipes, reducing the volume of the freeboard section or blocking the pipes, resulting in problems such as an increase in the internal pressure of the gasification furnace and inability to operate stably. Was. For this reason, various proposals have been made for preventing or removing tar from adhering to a free board portion of a fluidized-bed gasification furnace or a pipe connecting the gasification furnace and the melting furnace. For example, Japanese Patent Application Laid-Open No. 9-196337 proposes a method of burning a part of combustible gas components in a pipe connecting a gasification furnace and a melting furnace to prevent tar from adhering to the inner surface of the pipe. ing.

[0004]

However, in this method, if the pipes are cleaned while the gasification and melting system is operating, the decomposition gas from the gasification furnace flows through the pipes at a high speed. It is not cleaned upstream of the location where air was introduced. This problem can be solved by installing air introduction pipes at each location in the pipe where cleaning is required, but in that case, it is necessary to introduce a large amount of air. The temperature may decrease, and the temperature in the melting furnace may decrease due to intermittent introduction of air, which may make it difficult to control the entire system.

Accordingly, the present invention is to solve such a problem, and suppresses the generation of tar components when a combustible waste is thermally decomposed by contact with a heated powder flowing medium, In addition to enabling stable operation of pyrolyzers such as fluidized-bed gasifiers, the heat generated by combustible waste that effectively reuses the energy held by the waste by maintaining or improving the calorific value of the pyrolysis gas It is an object to provide a decomposition method.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve such problems, and as a result, have found that when pyrolyzing combustible waste with a pyrolysis apparatus such as a fluidized-bed gasifier, etc. By using a zeolite having a specific silica / alumina molar ratio of SiO ₂ / Al ₂ O ₃ and a specific specific surface area for part or all of the powder fluidized medium, the generation of tar can be suppressed, The inventors have found that the calorific value of the cracked gas can be maintained or improved, and the thermal cracking device can be operated stably, and have reached the present invention.

[0007] That is, the present invention for solving the above-mentioned problem is that, when the flammable waste is brought into contact with a heated powder flowing medium and thermally decomposed, at least a part of the powder flowing medium contains silica. _2. The molar ratio of SiO ₂ / Al ₂ O ₃ to alumina is 3.
The gist of the present invention is a method for thermally decomposing flammable waste, wherein the pyrolysis is performed using zeolite having a specific surface area of 0 to 100 and a specific surface area of 400 to 800 m ² / l.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the combustible waste to be treated in the present invention,
There is no particular limitation, and examples thereof include municipal solid waste, industrial waste such as waste plastic and waste oil, combustible waste such as RDF and sewage sludge, and a mixture containing these combustible wastes.

[0009] Zeolite used as a powder flowing medium is a solid acid which is composed of silica and alumina and has strong acidity. Incidentally, zeolite is used for cracking (decomposing) heavy oil, etc., utilizing its acid properties. The zeolite used as a powder flowing medium in the present invention has a silica / alumina molar ratio of SiO ₂ / Al ₂ O ₃ of 3.0 to 100 and a specific surface area of 40.
0 to 800 m ² / l, and especially the molar ratio of silica to alumina SiO ₂ / Al ₂ O ₃ is 4.0 to 50,
The specific surface area is preferably from 500 to 700 m ² / l. Molar ratio of silica to alumina of zeolite SiO ₂ / Al ₂
When O ₃ and the specific surface area are out of the above ranges, thermal decomposition of combustible waste does not sufficiently proceed, and a large amount of tar may be generated.

The specific surface area referred to in the present invention is BET.
BET specific surface area measured by the method. Further, the average particle size of the zeolite is not particularly limited,
Preferably it is 1000 μm, especially 100 to 50
It is preferably 0 μm. When the average particle size is less than 50 μm, it is easily led to a subsequent processing system (for example, a melting furnace) together with a pyrolysis gas generated in a pyrolysis apparatus such as a gasification furnace, and maintains catalytic activity in the gasification furnace. It may be necessary to add additional zeolite to achieve this. On the other hand, when the average particle size exceeds 1000 μm, it may be necessary to supply excess air in order to activate the motion state of the fluidized bed. Further, the zeolite preferably has a pore diameter of 0.2 to 1.5 nm, more preferably 0.5 to 0.8 nm. As the counter ion species of silica / alumina in the zeolite, either of Na ⁺ type and H ⁺ type may be used.

[0011] Commercially available zeolites having such properties can be obtained. In the present invention, all of the powder flowing medium may be the above-mentioned zeolite, but if cost is taken into account, the zeolite is mixed with another powder flowing medium so as to be 0.1 to 20% by weight and used. It is more preferable to mix and use 1 to 10% by weight.

The other powder flowing medium used by mixing with the above zeolite is not particularly limited as long as it does not hinder the action of suppressing the generation of tar components by the zeolite. , Sand such as olivian sand, silica, alumina, dolomite, or a known catalyst powder such as lime powder. As an apparatus for applying the present invention to thermally decompose flammable waste by contacting the same with a heated powder fluidized medium, the flammable waste is heated under a reducing atmosphere using a high temperature powder fluidized medium and a fluidized bed in a furnace. The shape of the gasification furnace is not particularly limited as long as it is a device that generates flammable gas, flammable solids, etc. by contacting with heat and generating a combustible gas, specifically, fluidized bed gasification. Furnaces.

The temperature of the fluidized bed at the time of pyrolyzing the combustible waste is preferably 300 to 700 ° C., and more preferably 450 to 650 ° C.
Is more preferred. In the fluidized bed, the gas supplied from the bottom of the furnace such that the powder fluidized medium actively moves and moves is air, oxygen-gas-enriched air, heated air, exhaust gas, nitrogen gas, oxygen gas, carbon dioxide. A gas composed of one or two or more such as gas.

Further, the apparatus for thermally decomposing such combustible waste may be a single waste treatment system itself, or may be a system in which a system is attached before or after the thermal decomposition apparatus. You may. Examples of systems associated with the preceding stage include waste mixing, drying, crushing, molding, dosing systems, and the like. In addition, examples of a system attached to the subsequent stage include a cyclone classifier, a melting furnace, an exhaust gas treatment facility (a gas cooling device, a dust removal device, a denitration, a desulfurization, a dioxin decomposition or removal system, and the like. Combinations), heat recovery systems (combinations of one or more of boilers, heat exchangers, etc.). In particular, if used in a gasification and melting furnace provided with a melting furnace in the subsequent stage, there is no adhesion of tar components in the pipe connecting the gasification furnace and the melting furnace, and the tar components are converted to low molecular gas components, The calorific value of the combustible gas component sent to the melting furnace can be increased, and as a result, the amount of auxiliary fuel such as heavy oil can be reduced and stable gasification and melting operation can be performed.

In the present invention, a monocyclic aromatic hydrocarbon such as benzene, toluene and xylene, naphthalene, phenanthrene, anthracene and pyrene can be obtained by using a zeolite having the above-mentioned specific properties as a powder fluidizing medium. , Polycyclic fused aromatic hydrocarbons such as chrysene,
Tar components such as phenol, cresol, and xylenol, or tar bases such as pyridine, picoline, lutidine, and quinoline are reduced in molecular weight by the catalytic activity of the zeolite, and are volatilized in low molecular weight such as methane, ethane, and acetylene. Since it is decomposed into volatile substances, tar does not adhere to the freeboard portion of the gasification furnace or the pipe connecting the gasification furnace and the melting furnace, and a stable operation state can be maintained.

(Examples) Next, the present invention will be specifically described with reference to examples. In the following examples, the amount of generated tar and the carbon number ratio of hydrocarbons in the tar were measured as follows. (1) Amount of tar generation (mg) The tar component in the generated gas was collected in a collection bin, and the tar component attached to the collection bin was dissolved in diethyl ether and collected from the collection bin. Using a rotary evaporator, the collected tar-dissolved diethyl ether solution was concentrated and dried, and the obtained tar was weighed with a microelectronic balance.
The amount of tar generation was used. (2) Carbon number ratio of hydrocarbons in tar (proportion for each carbon number of hydrocarbons) (%) The tar-dissolved diethyl ether solution collected in (1) above was used as a sample and measured by gas chromatography.
In the gas chromatography, the column was set to TC-1 (manufactured by GL Sciences: 0.25 mm × 60 m), the sample was injected at 40 ° C., kept for 2 minutes, and then heated at a rate of 20 ° C./min. It was kept for 5 minutes and detected by FID.

All reagents used were those manufactured by Nacalai Tesque. Examples 1 to 5 and Comparative Examples 1 to 5 10 g of a mixed fine powder of waste plastic having different types of plastics was mixed with 10 g of silica sand (average particle diameter 500 μm) and various properties shown in Table 1 (molar ratio SiO ₂ of silica and alumina). / A
l ₂ O ₃ : 1.5 to 150, specific surface area: 100 to 900 m ²
/ L) (average particle size 500 µm)
1 g and 500 ° C. in the presence of 5% by volume of oxygen gas.
Was thermally decomposed for 15 minutes in an electric furnace maintained at a temperature of.

Table 1 shows the measurement results of the amount of tar generated and the carbon number ratio of hydrocarbons in the tar.

[0019]

[Table 1] From Table 1, the molar ratio of silica to alumina is SiO ₂ / Al ₂ O ₃ of 3.0 to 100, and the specific surface area is 400 to 800 m ² / l.
Examples 1 to 5 using powdered fluid media containing zeolite
In Table 1, it can be seen that the amount of tar generated can be significantly reduced, and that the hydrocarbons in the generated tar are also reduced in molecular weight. On the other hand, in Comparative Examples 1 to 5 using the powdered fluid medium containing zeolite that does not satisfy the above conditions, it can be seen that the amount of generated tar is large and the carbon number of the hydrocarbon in the generated tar is large.

[0020]

As described above, according to the present invention, zeolite having a specific molar ratio of silica and alumina and a specific specific surface area is used as a powder fluidizing medium when pyrolyzing combustible waste. The generated tar components are converted to low-molecular compounds with low molecular weight, and the amount of tar generated can be reduced, and tar generated in the freeboard part of the thermal decomposition unit and the piping connected to the subsequent processing unit Adhesion can be prevented, and the calorific value of the pyrolysis gas can be maintained or improved. As a result, the combustible waste treatment system including the pyrolysis device can be operated stably.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B01J 29/00 F23G 5/027 ZABB F23G 5/027 ZAB 5/30 ZABR 5/30 ZAB B09B 3 / 00 303G 303K (71) Applicant 000001834 Sanki Kogyo Co., Ltd. 1-4-1, Yurakucho, Chiyoda-ku, Tokyo (72) Inventor Satoshi Kawanaka 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Laboratory (72) Inventor Katsuyuki Mukai 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Laboratory (72) Inventor Satoshi Nagano 1-12-19 Kitahorie, Nishi-ku, Osaka City, Osaka Prefecture Kurimoto Iron Works Co., Ltd. (72) Inventor Seikaichiro Enatsu 1-1-1 Sonoyama, Otsu City, Shiga Prefecture Toray Engineering Co., Ltd. (72) Inventor Tsuyoshi Iwata Higashi 3-4-1, Yurakucho, Chiyoda-ku, Kyoto Sanki Industries Co., Ltd. F-term (reference) 3K061 AA11 AB02 AC20 BA01 BA07 BA09 BA10 EB18 4D004 AA02 AA07 AA46 BA03 CA27 CA29 CC11 4G069 AA02 BA07A BA07B BC16A BC16B BD05A BD05 CA04 EA01Y EC03X EC04X

Claims (1)

[Claims] When the combustible waste is thermally decomposed by contact with a heated powder fluid medium, at least a part of the powder fluid medium has a silica / alumina molar ratio of SiO ₂ / Al ₂ O _3. A pyrolysis method for combustible waste, comprising pyrolyzing a zeolite having a specific surface area of 3.0 to 100 and a specific surface area of 400 to 800 m ² / l.