Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Patent
1998-09-22
2000-05-16
Griffin, Steven P.
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
588207, 588209, 588213, 588251, A62D 300
Patent
active
060639792
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method for decomposing dioxins, and more particularly to a method for effectively decomposing polychloro-p-dibenzodioxins (PCDD) and polychlorodibenzofurans (these compounds are hereinafter referred to as "dioxins") contained in flyash and bottom ashes (these materials are hereinafter referred to as "incineration ashes") discharged from various incineration plants such as an incineration plant for municipal solid waste, industrial waste and/or medical waste.
BACKGROUND OF THE INVENTION
In the incineration plants such as incineration plants for municipal solid waste, industrial waste and/or medical waste, the dioxins precursors including organic compounds such as phenols, benzene and acetylene, and chlorinated aromatic compounds such as chlorophenols and chlorobenzenes are formed during incineration. When flyash coexists in these precursors, the precursors change to dioxins under the catalytic action of flyash, and thus generated dioxins exist in incineration ashes.
Conventionally proposed methods for treating such dioxins-containing flyash are as follows.
(1) To keep the dioxins-containing flyash for 1-2 hours at a temperature between 320 and 400.degree. C. under a reductive atmosphere (for instance, 2 hours at 320.degree. C. or 1-1.5 hours at 340.degree. C.) (Hagenmaier process, "ORGANOHALOGEN COMPOUNDS Vol. 27 (1996)" p. 147-152)
(2) A heat treatment of the dioxins-containing flyash at 300-500.degree. C. under the existence of a dioxins formation inhibitor (JPA 4-241880). It has been said that dioxins do not heat-decompose at a temperature lower than 300.degree. C. This method is basically in accordance with the above mentioned theory, decomposing dioxins at above 300.degree. C., and a dioxins formation inhibitor is added to the flyash in order to prevent the formation of dioxins during the heat treatment in a temperature range in which dioxins decompose. For particulars, flyash is heated at 400.degree. C. for 2 hours under the existence of pyridine vapor as the dioxins formation inhibitor.
The aforementioned conventional methods have a drawback in that their high treatment temperature and long treatment time require much energy and high cost. Especially, in the above mentioned method (1) it is required to perform the treatment under a reductive atmosphere such as nitrogen gas, bringing about complexity and a high cost.
DISCLOSURE OF THE INVENTION
The object of the present invention is to solve the problems of the prior art and to provide a method which makes it possible to decompose and eliminate the dioxins under a low temperature region in which dioxins have been thought not to decompose, and to perform the treatment even under the existence of oxygen.
According to the method of the present invention for decomposing dioxins, dioxins are decomposed by bringing dioxins or dioxins-containing materials into contact with at least one treating chemical selected from the group consisting of amine compounds and ammonium compounds at a temperature lower than 300.degree. C.
According to the present invention, chlorines in dioxins react with the amine compound and/or the ammonium compound and this reaction causes quick dechlorination or replacement of chlorine atoms of dioxins and eventually, the detoxifications of dioxins at a temperature below 300.degree. C., at which dioxins have been thought usually undecomposable.
Such effect of the amine compound and/or ammonium compound to decompose dioxins at a temperature below 300.degree. C. has been hitherto unknown.
PREFERRED EMBODIMENT OF THE INVENTION
Dioxins to be treated according to the present invention may be contained in the exhaust gas discharged from various incineration plants such as municipal solid waste incineration plants, industrial wastes incineration plants, medical waste incineration plants and so on. The dioxins-containing materials are such as incineration ash which has dioxins adsorbed thereon, activated carbon powder used in the adsorption treatment of dioxins, and soil contaminated with dio
REFERENCES:
patent: 5113772 (1992-05-01), Karasek et al.
patent: 5260047 (1993-11-01), Berger
patent: 5358657 (1994-10-01), Sawyer et al.
patent: 5925156 (1999-07-01), Motoki et al.
Fujiwara Noboru
Fujiyoshi Naoaki
Izumikawa Hirofumi
Mashiko Mitsuhiro
Miyata Hiroshi
Griffin Steven P.
Kurita Water Industries Ltd.
Nave Eileen E.
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