Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Reexamination Certificate
1998-10-05
2003-03-18
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
C422S171000, C422S177000, C055SDIG003
Reexamination Certificate
active
06534021
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a filter body for retaining particles from a gas flow flowing through the filter body, including flow paths for the gas flow. The filter body is heat-resistant and regeneratable. The invention also relates to a process for the production of a heat-resistant and regeneratable filter body which serves for retaining particles, in particular soot particles, from a gas flow flowing through the filter body, preferably from an internal combustion engine. The filter body which is produced in that way also has predetermined flow paths.
A preferred area of use of the invention is an application thereof in the field of exhaust gas filtering in relation to internal combustion engines. Environmental awareness which is ever increasingly growing world-wide has resulted in endeavors being made, particularly in that area, to find ways of reducing, cleaning and neutralizing emissions and ultimately reducing them to a potential which is as low as possible for mankind and its environment. In the middle of the Eighties, for example, that directed attention to soot particles in relation to motor vehicles. Various filter structures were also produced for being able to filter such particles out of exhaust gases. Set out below is an overview of some filter installations which are known in the state of the art and to the structural configurations, materials and disclosure of which the invention also has recourse.
German Patent DE 37 44 265 C2 discloses a soot filter for exhaust purification in connection with internal combustion engines, which has corrugation configurations and fold configurations for changing direction of exhaust gas in the soot filter. Flat filter material is integrated into the layers of the soot filter. A production process for introducing corrugation configurations and fold configurations is also described, wherein bar portions extending transversely at spacings are introduced into steel sheets being used. German Published, Non-Prosecuted Patent Application DE 33 30 020 A1 discloses a Diesel exhaust gas filter including wire mesh having sieve mesh configurations that are illustrated in many different forms. Respectively open and closed end surface portions are disposed in a mutually opposite relationship, thereby predetermining the flow path in that Diesel exhaust gas filter. The closed end surface portions are produced by squashing components of the Diesel exhaust gas filter. European Patent 0 134 002 B1 shows configurations which are possible in that respect and discloses a production process for winding a sieve mesh with a cover layer to form a gas-permeable assembly. A further document, German Published, Non-Prosecuted Patent Application DE 29 51 316 A1, describes a catalytic filter for Diesel exhaust gas purification, which includes a metal sieve mesh configuration with alternate layers of corrugated sieve mesh and a closed cover layer. The surfaces of the filter are closed by a cover device in such a way that a closed end surface portion is disposed opposite an open end surface portion. The filter action of that catalytic filter is achieved by way of the mesh width and by way of the porosity of an oxide layer to be applied to the sieve mesh. Another technical way of producing flow paths in a filter body is illustrated in German Published, Non-Prosecuted Patent Application 27 33 640. A carrier matrix is described for a catalytic reactor for exhaust gas purification in connection with internal combustion engines, with coated steel surfaces. Raised portions and recessed portions in a steel sheet co-operate in form-locking relationship with an adjacent steel sheet whereby flow paths are formed in the carrier matrix. German Patent DE 37 44 265 C2 again discloses a soot filter, wherein layers of corrugated or folded material are closed transversely with respect to the longitudinal direction of the corrugation or fold.
Besides the filters which have just been described above and which are made from metal sheets or foils, the state of the art also includes extruded or ceramic filters. German Utility Model G 87 00 787.8 discloses a soot filter for Diesel engines, wherein ceramic fibers which are disposed in a random or irregular array form an open-pore filter body. Embedded in the filter body is a heating wire which is intended to heat substantially the entire volume of the filter body to a temperature. Patent Abstracts of Japan 57-163112 discloses a soot filter in which ceramic foam is surrounded on both sides by metal foils. The metal foils can be heated with electrical energy. The ceramic foam with the metal foils is wound or coiled to form a filter body. German Patent DE 35 01 182 C2 discloses an exhaust gas filter for Diesel engines, which includes a monolithic filter block of porous ceramic. That filter block has a multiplicity of passages extending in the main flow direction of the exhaust gas. The passages are closed alternately by plugs which are introduced into the same. The plugs are intended to cause the exhaust gas to flow through more than one passage wall in succession. In that configuration the porosity of the passage walls which are connected in succession by the operative plugs is intended to decrease in the through-flow direction. The reduction in porosity is intended to be achieved by applying a porosity-reducing agent to a filter block blank, wherein multiple application is intended to produce different zones of varying porosity over the exhaust gas filter produced in that way. That exhaust gas filter is very expensive to produce due to the necessary plugs and the wall coating which is required a plurality of times under some circumstances. Division of the monolithic filter block into zones of different wall coating porosity is intended to considerably reduce a back pressure upstream of the filter, which increases with increasing operating life. The configuration of the flow through the filter block, which is compelled by virtue of its structure, admittedly ensures that the gases flow through successively disposed porosity zones. However, it is not possible to gather information about the precise flow path. In addition, individual gas flows are repeatedly mixed together in the filter block and due to the effects which occur in that situation, they produce an undesirable pressure drop in the filter block itself.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a heat-resistant and regeneratable filter body with flow paths and a process for producing the filter body, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and processes of this general type, in which the body combines a high level of filter capacity with low pressure drops in a filtration effect and in terms of through-flow, production thereof is to be possible in a small number of working steps and the process permits a particularly labor-saving structure with respect to filter bodies.
With the foregoing and other objects in view there is provided, in accordance with the invention, a heat-resistant and regeneratable filter body for retaining particles from a gas flow flowing through the filter body, comprising mutually separate flow paths for a gas flow; and at least one respective first filter stage and one respective second finer filter stage disposed in succession in flow direction in each of the flow paths.
Separation of the flow paths ensures on one hand that a predetermined defined path through the individual filter stages is followed by each partial gas flow. On the other hand, pressure losses by virtue of mixing phenomena with respect to different partial gas flows are prevented. Separation of the individual flow paths also facilitates the structural configuration of the filter body. The respective filter stages in a flow path are then disposed independently of adjacent flow paths.
The first filter stage retains particles which are of a certain minimum size from the gas flow flowing therethrough. It therefore serves as a kind of coarse filter wh
Emitec Gesellschaft fuer Emissions-technologie mbH
Greenberg Laurence A.
Locher Ralph E.
Stemer Werner H.
Tran Hien
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