Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – With means applying electromagnetic wave energy or...
Reexamination Certificate
2001-01-04
2003-01-07
Mayekar, Kishor (Department: 1741)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
With means applying electromagnetic wave energy or...
C588S253000
Reexamination Certificate
active
06503463
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to process and apparatus for treating a harmful substance, in particular, to process and apparatus for treating dioxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxins.
BACKGROUND
Dioxins are referred to, for example, the following literature.
Reference 1: “An introduction to dioxins” translated by Ryota Fujiwara and Higashi Kido, edited by Masatoshi Morita, and published by JESC (Japan Environmental Sanitation Center) on June 1991 (Original document: U.S. EPA Research Reporting Series, “Dioxins”).
1. <Structure and Production Cause of Dioxins>
Dioxins were synthesized at first in Germany in the mid-19th century, but their strong toxicity wasn't known until 1950s. Ever since, the toxicity of dioxins has been widely known through the news of frequently broken out occupational diseases and environmental pollution, Vietnam War and etc. in connection with dioxins, and studied widely. In 1990s, it has been known that dioxins spread out widely around their surroundings through the incineration of refuse/waste and other processes. Consequently, studies on the influence, measurement and removal method of dioxins have been suddenly required. To attain this end, these studies have become active, and the number of papers concerning dioxins is rapidly increased now.
At first, an outline of dioxins is given below. General chemical structure of dioxins may be represented as follows.
To the substitution sites of the numbers 1 to 4 and 6 to 9, chlorine and other halogen atoms, organic radical and hydrogen atom may be bonded. These kinds of compounds are usually called as “dioxins homologues”, and 77 or more kind of isomers belonging thereto are known.
Among these dioxins homologues, the most remarkable compound in the field of environmental science and others is 2,3,7,8-tetrachlorodibenzo-p-dioxins (C
12
H
4
Cl
4
O
2
; which is abbreviated as “TCDD” to the 2-, 3-, 7- and 8-positions of which chlorine atoms are bonded.
TCDD has no functional group of high reactivity, thereby showing extremely high chemical stability, belongs to molecules soluble in high molecular weight paraffin, dissolves very little in water and most of organic solvents, and exhibits a colorless crystalline solid at room temperatures.
For synthesizing dioxins, various processes are known. Their reaction temperatures range from 180 to 400° C., and the reaction products are stable up to 700° C. Accordingly, it is necessary to apply heat up to temperatures of not less than 800° C., or of not less than 1150° C. under certain conditions to decompose dioxins.
Typical organic compounds potentially by-producing dioxins include chlorophenols and their derivatives; and hexachlorobenzene. These compounds are classified into the following 3 large groups.
The first: polyhalogenated phenols (1st group).
The second: o-halophenols, and halogen- and other-substituted phenols (2nd group).
The third: substances not classified into 1st and 2nd groups but possibly producing dioxins (3rd group). However, the possibility is low that the substances of the 3rd group produce dioxins.
As a material belonging to the above groups and commercially produced not less than 1,000 pounds in a year in U.S., there are known 12 kinds of chemical substances belonging to the 1st group, 16 kinds of chemical substances belonging to the 2nd group, and chemical substances of 50 kinds or so belonging to the 3rd group.
By the process for preparing pesticides such as insecticide and herbicide, dioxins are potentially by-produced. A large number of agricultural chemicals are known that contain dioxins at high concentration.
Recently, the precision of measuring dioxins has been improved to enable measuring a very small amount of dioxins. Consequently, the discovery has been made that dioxins are contained in agricultural chemicals and also in a basic chemical material of chlorophenols although the content contained in the latter material is very little. Moreover, it is known that not only these substances but also industrial wastes generated in the course of producing the same contain dioxins at high concentration. The aforementioned chemical material is used as a preservative of foods, crude rubber, leather or the like, or, otherwise as a raw material for preparing insecticides.
In addition to the above, these are applied directly to the human body in disinfecting swimming pool, home, hospital, bathroom and etc. All of these compounds are registered as an insecticide in EPA (Environmental Protection Agency) in U.S.
The fact that dioxins are produced according to the above process has been hitherto known. Recently, owing to the press and other media, attention has been paid to production and diffusion of dioxins originated from “combustion source”, that is, waste/refuse incineration or other incinerating facilities. This finding is much owing to the improvement in the precision of measuring dioxins in Japan. However, before this time, 17 kinds of dioxins were detected by the analysis of floating particulate matter collected out of 3 municipal refuse-incinerating facilities in the Netherlands in 1977. Diffused dioxins are contained in combustion gas and fly ashes.
On the synthesis of dioxins through the step of burning, chemists of the Dow Chemical Company considered that many precursors of dioxins are produced through a complicated process such as burning, and suggested in 1978 that dioxins are synthesized naturally through the combustion of natural materials. Then, many chemical substances of the precursors have been studied until today.
It is necessary in decomposing dioxins by combustion at least to apply heat up to temperatures of not less than 800° C. and watch whether dioxins are regenerated or not at temperatures ranging from 180 to 400° C. when the temperature of the resultant decomposition product becomes lowered. It is also known that dioxins contained in fly ashes never decompose without heating up to around 1200° C.
2. <Dioxins Analyzing Method>
Because dioxins have very strong toxicity, microanalysis is required. General analyzing methods of dioxins include gas chromatography, mass spectrometry, UV spectrophotometry, ESR (electron spin resonance) spectroscopy, low temperature phosphorimetry and etc. There is no analyzing method now that can provide both high sensitivity and selectivity at the same time applicable to substantially all the samples and surroundings.
It is said that the detection limit of dioxins is about 0.001 ppb (ppb: parts per one billion) at the present time. However, fluctuations in the measured value, which are large especially at low concentration, arise depending on measuring system, person and etc. On account of this, it is important to standardize the measurement, and for attaining this purpose, a joint study is started now by plural organizations such as research institutions and universities in Japan. Through the above activities, the measurement in and of itself is accepted as one of important research and development themes.
3. <Dioxins Exposure Accident to the Human Body>
Up to this time, there have been reported a lot of accidents caused by dioxins. Among them, an accident that happened in Meda, Italy on Jul. 10, 1976 is very terrible. In this accident, 300 g to 130 kg of dioxins were scattered around to pollute their surroundings and to cause 134 cases of children suffering from acute toxicity of chloracne. Further, 170 labors were directly polluted, and hundreds of animals were taken ill and killed in the worst case.
It is said that the largest-scale pollution which has ever happened in the world until now is the pollution caused by the United States Air Force burning 10,400 tons of a defoliant containing dioxins on the Pacific Ocean in 1977, and that this fixed the dioxins' background of the world.
Further, it is said that the birth of many malformations found in Vietnam is due to pollution caused by spraying the defoliant. However, some U.S. report told that there is no correlation between the sprayed defoliant and the birth abnormality. It is said that t
Hasegawa Yasuhiro
Yamaguchi Sataro
Armstrong Westerman & Hattori, LLP
Kabushiki Kaisha Y. Y. L.
Mayekar Kishor
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