FI103641B - Gas filter - Google Patents

Description

1 103641

Gas filter

The invention relates to a gas filter which is intended, for example, to be installed in a ventilation duct to remove gaseous impurities from the supply air of the space.

Harmful gases are generally removed from the supply air by filters located in the ventilation duct and containing granular material with a high specific surface area. Sulfur dioxide, nitrogen oxides, chlorine, hydrogen chloride and ozone, among others, are common gases filtered through such filters.

In addition to the standard work and living areas, there are a number of special spaces that are subject to remarkably high standards of air cleanliness.

15 Such special facilities include, for example, so-called clean rooms, where components of sensitive electronic devices and / or the devices themselves. Also. the operating conditions of the devices often need to be protected, even with device-specific filters, to ensure their reliable operation.

20 Supply air filtration has increased, and will continue to increase substantially, for a variety of vehicles and machinery where filtering of exhaust fumes, in particular, and pollutants for which the vehicle or machine is used (eg application of pesticides on a tractor) is important.

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It is generally known to increase the filtering power of the filters by increasing the contact or residence time between the filter material and the air to be filtered, e.g. by increasing the thickness of the filter, i.e. the layer through which the air to be filtered flows. However, in this case, increasing pressure loss becomes a problem, which is not advantageous for the operation of the ventilation system.

Finnish patent FI-94724 discloses a method for making a gas filter, wherein the filter is formed from overlaid, corrugated and chemisorption-impregnated carrier material layers in which the wavelengths are convergent to the air flow direction and the layers form longitudinally flowable, 10 · 103641 separate. The carrier material is an aluminum sheet with alumina forming a porous surface on both surfaces. Such a filter does not cause flow resistance to the air to be filtered, but the contact surface is obtained considerably more compared to the same volume as when using granular materials. A filter of the same type of basic construction is further known from, for example, U.S. Patent No. 4,391,616.

Your ozone filtration, for example, has steadily increased. It is known, as an example, to filter ozone, in particular through filters containing activated carbon granules, through filing air. The structure according to FI-94724 is based in particular on filtration of relatively free-flowing air through the flow cells, whereby the walls containing the porous material of the flow cells are impregnated with chemicals that cause chemisorption, and thus the filter is not intended for e.g. A thin aluminum sheet coated on both sides with alumina is the most suitable carrier material for forming such cells.

U.S. Patent 3,800,515 discloses an air-adsorbent cell filter, which is an adsorbent-impregnated and compacted paper, as a carrier material, from which the cells are normally formed by corrugating and superimposing.

It is an object of the present invention to eliminate the above drawbacks and the problems caused by them and to provide a filter which can also filter eg the ozone from the supply air while reducing the air flow resistance caused by the filter and which can also be substantially reduced compared to known filters. To accomplish this purpose, the filters according to the invention are essentially characterized in that the filter carrier material is a paper-based material which is coated, at least in part, with fine particulate adsorbing material without impurities such as gases.

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Activated carbon is one of the most suitable and most widely used materials for ozone filtration. By forming a surface layer of a fine adsorbent material, such as activated carbon, on the carrier material, and further forming a filter according to the filter structure disclosed, for example, in FI-94724, an ozone filtering filter application is also provided.

The use of a paper-based material such as paper or board has the advantage that the filter is easy to dispose of, especially if the adsorbent is activated carbon.

It is also quite simple to make a filter according to the above structure, for example, of which only a part of the layers 15 of the carrier material is coated with activated carbon and a part with another porous layer containing, for example, a chemisorption agent, thus providing a very versatile filter solution.

The filter according to the invention is easily adapted to be made directly from a paper or board based carrier material, which is capable of substantially reducing the raw material costs of the filter. In addition, the fine activated carbon or other powdered adsorbent is easily adhered to the surface of the carrier material due to the coarse substrate formed by its cellulosic fibers. Indeed, the carrier material is characterized by its fibrous structure resembling paper or paperboard.

A notable advantage is also obtained by the fact that by using the filter structure according to the patent FI-94724 described above 30, the filtering power in relation to the filter volume can be considerably increased.

The invention will be further illustrated in the following description, with reference to the accompanying drawings, in which Figure 1 schematically illustrates the basic structure of a filter and. Figure 2 is a perspective view of an embodiment of a filter.

4, 103641

The filter according to the invention is made of corrugated paper-based plate 1 and straight paper-based plate 2, on both of which surfaces are attached finely divided adsorbent material 5 such as activated carbon. In contrast to US-A-3,800,515, the fine-adsorbent material and the carrier material formed by the plates 1, 2 form distinct independent layers. The discs 1,2 thus treated are superimposed to form a layer 4 with adjacent flow cells 3 To form a finished filter, the layers 4 10 are tightly superimposed so that there is always a straight plate 2 on each side of the corrugated plate 1, halfway between it and the straight plate 2.

Figure 1 also shows a way of forming the filter according to Figure 2, whereby the layer 4 is wrapped in a dense cylindrical body which can be easily inserted, for example, inside a circular air-conditioning pipe.

It is clear that other types of structures can also be used to form the filter. Separate layers 4 can be stacked on a plurality of Kap-20 pieces to form a compact stack or folded from a single wide layer 4, whereby the package thus assembled can be easily reshaped, e.g., to the requirements of the particular application.

By coating the sheets 1,2 specifically with a fine adsorbent and thereby forming a cellular adsorbent structure, a substantial increase in the adsorbing area is achieved without causing a significant increase in flow resistance, as would be the case, for example, with granular activated carbon within flow channels.

30

Adsorption materials may be used depending on the gas to be adsorbed. Thus, paper or board-based sheets 1, 2 can be coated with any porous layer-forming material that physically adsorbs to the surface gaseous impure disease.

When using fine materials that adsorb to the surface of the gases, it is not necessary to treat the filter with a chemisorption agent.

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However, the filter can also be formed such that some of the plates 1, 2 or layers 4 are arranged as above to adsorb with e.g. activated carbon and some are treated with e.g. a chemisorption agent, whereby the application area of one filter body can be significantly extended.

The following describes the production of the filter on a laboratory scale.

A method is used to coat a paper-based carrier material with a porous layer in which a finely divided adsorbent, such as activated carbon, is slurried in a suitable liquid and the resulting mixture is allowed to flow through elongated flow cells 3 whereby particles adhere to the cell walls. Here, for example, the capillary effect can be utilized as disclosed in FI-94724, i.e. the other end of the filter is immersed in the mixture, whereupon the mixture rises under the action of capillary forces on the cells. Preferably, an organic solvent which does not swell the paper like water is used to slurry the finely divided material. The activated carbon powder 20 is slurried in methanol and allowed to flow through the cells, whereby the surface of the paper is well coated.

On a production scale, methods are employed in which the paper-based carrier material is coated prior to forming it into a filter structure. In this case, there may be some known paper coating method in the paper industry in which small particles are made to adhere to the surface of a carrier material of paper or board. Here again, the adsorbent particles can form a mixture with the liquid material, the mixture is applied to the surface of the base material, the liquid material is evaporated, and a support material comprising a porous surface layer is formed to form a finished filter structure as described above.

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Claims (4)

A gas filter especially for ventilation, said gas filter consisting of superposed layers of corrugated material (4), the longitudinal direction of the corrugations coinciding with the direction of air flow in the way that separate elongated flow cells (3) are formed, which together form a flow and which carrier material is preferably treated on its lateral sides with a gas from the filtering air removing material, characterized in that the carrier material is a paper-based or cardboard-based material which is at least partially coated with a gaseous adsorbent porous layer consisting of adsorbent. 2. A gas filter according to claim 1, characterized in that the carrier material is at least partially coated with an ozone-absorbing material. 3. A gas filter according to claim 2, characterized in that the carrier material is at least partially coated with activated carbon. A gas filter according to any one of the preceding claims, characterized in that the filter is formed as a cylindrical piece by rolling a combination consisting of a flexible corrugated disc (1) and a flexible bottom disc (2). • ψ «» · '»» «· f»