Gas separation: processes – Selective diffusion of gases – Selective diffusion of gases through substantially solid...
Reexamination Certificate
1999-07-26
2002-01-22
Fortuna, Ana (Department: 1723)
Gas separation: processes
Selective diffusion of gases
Selective diffusion of gases through substantially solid...
C210S500250, C210S500260, C210S490000, C096S011000, C264S045100, C055S523000, C055S524000, C428S307700, C427S372200
Reexamination Certificate
active
06340379
ABSTRACT:
A gas filter, a process for producing a gas filter and use of this gas filter are claimed.
Air pollution is known to present a serious problem in many parts of the world. Depending on composition, the pollution can lead to health problems among the human population. Furthermore, the air pollution results in not inconsiderable economic loss. The air pollution can be in the form of gases or of liquids dispersed very finely in the air or in the form of tiny solid particles present in the air. The solid particles which may be present in the air and have been and are classified as carcinogenic include soot, especially soot (particulates) which gets into the air via the exhaust gases of diesel vehicles.
In many nations, regulations to regulate the maximum permissible emission of particulates from motor vehicles have been put in force.
Various methods and apparatus have already been developed for treating solids-containing gases.
U.S. Pat. Nos. 4,972,889 and 4,948,403 claim ceramic filter system which are able to filter soot or solid particles from the exhaust gases of diesel-powered vehicles.
A problem with these methods and apparatus is that the solid particles block the filter relatively quickly and the filters thus have to be replaced or regenerated at short intervals.
To regenerate blocked filters, there have been proposals for methods which burn the solids blocking the pores of the filter in motor vehicles by additional combustion of fuel. The disadvantage of these methods is that regeneration leads to an increased fuel consumption. In addition, the deep action of this method is only weak, so that blockages caused by particles in the filter cannot be remedied.
More recently, methods and apparatus which remove filtered-out solids from the filter by heating to 600° C. have been developed.
According to DE 3800723, additional heating wires are used for heating the filter.
EP 0275372 uses heating elements comprising wire, expanded metal or perforated foils for heating the filter.
GB 2193656 teaches a method and an apparatus which make use of wires between which a current flows when a conductive bridge of deposited soot forms.
U.S. Pat. No. 5,202,548 describes a filter which can be baked out by application of a voltage since it is equipped with electrically conductive honeycomb structures. U.S. Pat. No. 5,246,672 teaches the use of woven wire meshes and U.S. Pat. No. 5,254,840 teaches the use of a combination of metallic and ceramic honeycombs.
The filter materials used in the abovementioned methods or apparatus have relatively small surface areas and thus either a low filter action or, when the pores are made smaller to increase the filter action, a small gas throughput. If the surface area is large due to the use of porous materials, the pores become blocked very quickly. Filtering relatively large amounts of gas requires the use of large, relatively cumbersome gas filters which restricts the possible uses of such gas filters.
It is therefore an object of the present invention to find an economical process for producing a gas filter which, despite a small size, is able to filter large amounts of gas and which can be regenerated in a simple manner.
It has surprisingly been found that a gas filter which comprises a material-permeable composite material based on at least one open-structured and material-permeable support and having on at least one side of the support and in the interior of the support at least one inorganic component which comprises essentially at least one compound of a metal, a semimetal or a mixed metal with at least one element of main groups III to VII is able, even when small in size, to filter large amounts of gas and can be regenerated in a simple manner.
The present invention accordingly provides a regenerable gas filter for filtering gases which comprises a composite material based on at least one open-structured and material-permeable support and having on at least one side of the support and in the interior of the support at least one inorganic component which comprises essentially at least one compound of a metal, a semimetal or a mixed metal with at least one element of main groups III to VII.
The present invention likewise provides a reaenerable gas filter which comprises a composite material which is obtainable by application of a suspension which comprises at least one inorganic component comprising a compound of at least one metal, a semimetal or a mixed metal with at least one element of main groups III to VII and a sol to an open-structured and material-permeable support and by subsequent heating at least once during which the suspension comprising at least one inorganic component is solidified on or in or on and in the support.
The present invention also provides a process for producing a gas filter as claimed in any of claims
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, which comprises producing a material-permeable composite material by applying, in and on at least one open-structured and material-permeable support, at least one suspension which comprises at least one inorganic component comprising at least one compound of at least one metal, a semimetal or a mixed metal with at least one of the elements of main groups III to VII and a sol and by solidifying the suspension on or in or on and in the support material by subsequent heating at least once.
The present invention likewise provides for the use of a gas filter as claimed in any of claims
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for cleaning waste or feed gases.
For the purposes of the present invention, material-permeable means that materials which have this property are permeable to at least a gas, a liquid or a solid. The permeability is dependent on the size of the pores, mesh openings or holes which these materials have.
The gas filter of the invention can be used for the filtration of an,; waste and feed gases from Which, for example, solid particle are to be removed. The gases to be filtered can also comprise vapor or droplets of liquid. The advantage of the gas filter of the invention is that, as a result of the use of an electrically conductive support material in the composite material, the latter can be baked out in a simple manner by application of a voltage and thus be regenerated. If the composite material comprises catalytically active materials, this heating only has to be carried out once if the decomposition of the thermally decomposable liquid droplets or solid particles is, in the case of a sufficiently hot filter, catalyzed by the catalytically active materials and thus proceeds swiftly. As a result, advantageously, a virtually constant amount of gas can pass through the filter since blocking of the filter by materials which are not thermally decomposable increases only very slowly.
A further advantage of the gas filter of the invention is that the novel composite material or gas filter can, due to the fact that it is bendable, be rolled or folded and the filter-active surface area of the filter can be very large in a small volume.
The gas filter of the invention is described below by way of example without being restricted thereby.
The regenerable gas filter of the invention for the filtration of gases comprises at least one composite material based on at least one open-structured and material-permeable support and having on at least one surface of the support and in the interior of the support at least one inorganic component which comprises essentially at least one compound of a metal, a semimetal or a mixed metal with at least one element of main groups III to VII. For the purposes of the present invention, interior of a support means, for example, hollow spaces or pores in a support. According to the invention, the regenerable gas filter comprises a composite material ,-which is obtained by application of a suspension which comprises at least one inorganic component comprising a compound of at least one metal, a semimetal or a mixed metal with at least one element of main groups III to VII and a sol to an open-structured and material-permeable support and by heating at least once during which the suspension comprising at
Hoerpel Gerhard
Hying Christian
Penth Bernd
Creavis Gesellschaft fuer Technologie und Innovation mBH
Fortuna Ana
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