Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Patent
1995-12-18
1997-12-02
Straub, Gary P.
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
431 5, 110215, 110344, B01D 5300
Patent
active
056932936
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP94/01985 filed 17 Jun. 1994.
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The invention relates to a method and an apparatus for the purification of waste gas that develops in particular in plants for chemical vapor-phase deposition (CVD) and for the removal or separation by plasma processes.
2. Prior Art
Apart from substances generally regarded as unobjectionable, such as nitrogen and argon, waste gas of this kind contains toxic agents which are completely removed or reduced to admissible limits by the purification method. For the purpose of purification, the waste gas is conducted through the purification apparatus directly after leaving the production plant or after being collected from several plants.
Quite a number of methods are known for the purification of waste gas. It is very often effected by the sorption of the toxic agents for instance in an oxidizing aequous solution. To this end, intense contact of the waste gas and the sorption agent takes place in a column, a spray tower or in any other kind of a washer. Toxic agents that are not, or not efficiently, sorbed in this way can be converted by methods of thermal decomposition by heating or by combustion and removed from the waste gas. If the toxic agents themselves are not combustible, they are burnt in a flame by the addition of excess oxygen. The combustion takes place in a burner-type combustion chamber, on the walls of which solid combustion products such as SiO.sub.2 will deposit. Since the separation of solid reaction products in the combustion chamber is not complete, and, in particular, since the combustion is mostly accompanied by secondary, gaseous toxic agents forming, multistage purification methods are known to be used, in which partial processes of purification take place one after the other, such as thermal decomposition or oxidation, cooling, hydrolysis, sorption and ablution of solid reaction products (EP 0 347 754 A1). Subsequent to the combustion chamber, the waste gas is transferred to a separate reaction chamber, there being subjected to intense contact with a sorbent.
To this end, the waste gas is conducted successively through a combustion chamber and at least one device that works on the washing principle. Also, apparatuses have been proposed for the purification of waste gas. To this end, the waste gas is conducted successively through a device comprising a combustion chamber and at least another device that works on the washing principle, the two forming a unit constructionally (EP 0 347 753 A1). The combustion chamber and an external separate reaction chamber are separated by an inner wall.
A disadvantage of the waste gas purification based on the thermal decomposition or oxidation of the toxic agents in a combustion chamber with the formation of solid reaction products resides in that the latter will deposit on the walls of the combustion chamber. With high throughputs of toxic agents, thick layers will grow on these walls. After a while these deposits can become so thick that the process will be strongly affected by faulty flow conditions or even become impossible by "overgrowth".
Another disadvantage resides in the corrosion of the material of the walls and of other components of the combustion chamber under the influence of gaseous reaction products of the combustion. This corrosion is increased critically owing to the high temperature of the waste gas burnt or to their composition, if the waste gas contains for instance hydrogen halogenide (e.g. HCL HF) and water vapor.
Furthermore, negative effects may reside in that secondary toxic agents, for instance dioxins, form upon the cooling of the burnt waste gas on the way from the combustion chamber into a subsequent sorption chamber or sorption device.
Use is also made of absorption or adsorption methods in which a partial removal of toxic agents from the waste gas is performed (Japanese patent 812 2025, Japanese patent 6203 0525, Japanese patent 6213 6230).
However, the main disadvantage of these methods resi
REFERENCES:
patent: 4555389 (1985-11-01), Soneta et al.
Firkert Gunter
Gehmlich Konrad
Hennig Volkmar
Hentrich Michael
Labs Lutz
DAS-Dunnschicht Anlagen Systeme GmbH Dresden
Straub Gary P.
Vanoy Timothy C.
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