Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1989-06-12
1991-04-16
Bennet, Henry A.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34 73, 55 5, F26B 300
Patent
active
050071807
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method of and an apparatus for separating condensable harmful substances and solid particles from the process gas or used air particularly from a textile finishing plant such as for example a drier or a coating plant for example in the paper or synthetic plastics industry, wherein wasted air is pre-filtered, cooled and passed through a mechanical final filtering apparatus.
DESCRIPTION OF THE PRIOR ART
In a prior art method or a prior art apparatus, the used air from a plant is first fed to a mechanical pre-filter and then to the final filtering apparatus in the form of a glass fibre deep bed filter. If the used air which is to be cleansed is at a temperature of between 40.degree. C. and 80.degree. C. or is at more than 80.degree. C., then between the pre-filter and the final filtering apparatus a single or two-stage cooling of the used air takes place via one or two heat exchanger stages. Only when the used air which is to be cleaned has cooled to about 40.degree. C. prior to entering the final filtering apparatus is it fed to this latter in which only the impurities (condensable harmful substances and solid particles) which are present in aerosol form are separated off and extracted as a condensate. Therefore, the condensable harmful substances and the solid particles, particularly their dispersions, will be referred to hereinafter as aerosols.
This prior art method or this prior art apparatus does in particular have the disadvantage that the major part of the aerosol separation has to be undertaken by the mechanical final filtering apparatus which means that the glass fibre deep bed filter used for the purpose becomes very expensive and bulky, Not only the necessary size of the glass fibre deep bed filter but also the provision of the said mechanical pre-filter results in a considerable pressure loss in the flow of used air which has to be compensated for by correspondingly dimensioned ventilators. All these measures lead to considerable investment costs.
The problem on which the present invention is based is that of providing a method and an apparatus for the separation of condensable harmful substances and solid particles of the types mentioned at the outset, in which a considerable amount of separation from the used air is possible already at the pre-filtering stage.
SUMMARY OF THE INVENTION
In the case of a method for separating condensable harmful substances and solid particles of the types mentioned at the outset, this problem is resolved by pre-filtering of a warm waste air by cooling this air to below the dew point of the condensable harmful substances and dispersed solid particles, and extracting the resultant condensate containing impurities.
In the case of an apparatus for separating condensable harmful substances and solid particles of the types mentioned at the outset, this problem is resolved by an apparatus which comprises for pre-filtering the waste air at least one heat exchanger stage provided with a condensable extractor.
As a result of the measures according to the invention, already at the pre-filtering stage, separation of condensable harmful substances and solid particles or aerosols and thus an extraction of the condensate occurring is achieved by means of a cooling of the used air (to below the dewpoint of the aerosols). This can already represent an amount of up to 60% of the aerosols which have to be separated. This means that the mechanical final filtering apparatus can be substantially more compact and of smaller dimensions since it only has to accommodate or separate off a part of the quantity of aerosol which previously had to be eliminated from the used air. At the same time, this means that the pressure losses in the flow of used air are reduced and that the ventilators can be of smaller dimensions. All these factors result in investment economy. At the same time, even air which is at more than 100.degree. C. is cooled.
Expediently, according to, two heat exchanger stages are provided of which one uses
REFERENCES:
patent: 4012847 (1977-03-01), Rand
patent: 4171243 (1979-10-01), Brooks et al.
patent: 4715965 (1987-12-01), Sigerson et al.
A. Schraud, Melliand Textilberichte, "Exhaust Air Decontamination for Drying and Heat Treatment Plants with Regard to Heat Recovery" Dec. 1976, pp. 1014-1019.
P. Richner, Textilveredlung, "Effects of Carriers on Water and Air as Well as Fundamental Solutions to the Problem of Decontamination of Textile Exhausted Air", No. 4, 1978, pp. 134-139.
Christ Michael
Teichmann Wolfgang
Bennet Henry A.
Sueddeutsche Kuehlerfabrik Julius Fr. Behr GmbH & Co. KG
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