Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Halogenous component
Patent
1992-04-15
1993-11-09
Lewis, Michael
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Halogenous component
588206, 588207, 4232453, C01B 701, C01B 322
Patent
active
052600440
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for removing, from a combustion waste gas discharged from an incinerator, detrimental organic chlorine compounds such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans contained in the combustion waste gas.
BACKGROUND OF THE INVENTION
As to methods for removing detrimental substances such as sulfur oxide, nitrogen oxide, hydrogen chloride and cyanogen contained in a combustion waste gas produced from an incinerator, for example, for incinerating industrial and household wastes, many research reports have so far been released, and some of them have already been industrialized.
However, research efforts have been started only recently as to methods for removing, from the above-mentioned combustion waste gas, organic chlorine compounds, though slight in amount, having a strong toxicity, such as polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyl and chlorophenol contained in the combustion waste gas. A method for removing such organic chlorine compounds from the combustion waste gas in an industrial scale has not therefore as yet been established.
Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans are stable substances and are insoluble in water, so that the toxicity thereof is semipermanently retained. In particular, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans are very detrimental substances which pollute the environment by their strong toxicity.
Polychlorinated dibenzo-p-dioxins are classified, in terms of the number of chlorines, into dichloride, tetrachloride, pentachloride and hexachloride, and there are more than 70 types of isomers. Among these polychlorinated dibenzo-p-dioxins, tetrachlorinated dibenzo-p-dioxin has the strongest toxicity.
For the purpose of removing detrimental organic chlorine compounds such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from a combustion waste gas discharged from an incinerator, the following methods are known:
(1) Removing method based on combustion:
This method comprises the steps of: increasing the temperature in an incinerator to at least 1,000.degree. C., and causing a decomposition reaction of organic chlorine compounds contained in a combustion waste gas under the effect of this high temperature, thereby removing the organic chlorine compounds from the combustion waste gas.
An alternative method comprises the steps of: introducing a combustion waste gas discharged from an incinerator into another combustion furnace, and causing a decomposition reaction of organic chlorine compounds contained in the combustion waste gas at a temperature of at least 1,000.degree. C., thereby removing the organic chlorine compounds from the combustion waste gas.
(2) Removing method based on adsorption:
This method comprises the steps of: passing a combustion waste gas discharged from an incinerator through an adsorbent such as activated charcoal and causing the adsorption by the adsorbent of organic chlorine compounds contained in the combustion waste gas for removal.
(3) Removing method based on washing:
This method comprises the step of: washing with a chemical solution a combustion waste gas discharged from an incinerator to remove organic chlorine compounds contained in the combustion waste gas.
The removing method based on combustion mentioned in (1) above has the following problems:
(a) In order to remove organic chlorine compounds from the combustion waste gas in the incinerator, it is necessary to increase the temperature in the incinerator to at least 1,000.degree. C. Usually, however, the temperature in the incinerator is within a range of from about 800.degree. to about 900.degree. C. In order to increase the temperature in the incinerator to at least 1,000.degree. C., therefore, it is necessary to totally reconstruct the incinerator.
(b) Most of the incinerators currently in use are stoker furnaces, and low-temperature portions may easily be locally produced in such a stoker f
REFERENCES:
patent: 3845191 (1974-10-01), Bruce, Jr.
patent: 4957717 (1990-09-01), Imamura et al.
patent: 4983366 (1991-01-01), Deller et al.
patent: 5098687 (1992-03-01), Skeels et al.
Hara Katsunosuke
Hiraoka Masakatsu
Imoto Yoshinori
Ishikawa Osamu
Iwasaki Toshihiko
Hiraoka Masakatsu
Kacinchaic Stephen G.
Lewis Michael
NGK Insulators Ltd.
NKK Corporation
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