Liquid purification or separation – Filter – Supported – shaped or superimposed formed mediums
Patent
1988-10-28
1991-01-01
Fisher, Richard V.
Liquid purification or separation
Filter
Supported, shaped or superimposed formed mediums
21049701, 210504, 210506, 210503, B01D 2900
Patent
active
049815890
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns filter construction and a method for the formation of a filter construction.
In prior-art ceramic filter plates, which were already patented by Valmet earlier, the filter construction favourably comprises a first suction face and a second suction face, between which there is a space filled by granules. The said intermediate space acts as a water space or liquid space, into which the liquid sucked out of the material to be filtered is sucked first. The granules or equivalent are substantially confined by the first face and by the second face, and they act as rigidifiers of the construction. The granularity does, however, not prevent the flow of the liquid that has entered into the space, because the granules do not cause a high resistance to flow. Into the central space, a connecting duct is passed, which can further be connected to a source of negative pressure so as to produce flow of liquid through the suction faces into the central space and further out of the filter plate. In the filter construction, the suction faces of the plate are preferably made of a ceramic casting mix.
Filter constructions are known in which the filtering face of the filter consists of a synthetic membrane. However, a major drawback in the case of membrane filters is the risk of damage to the film on cleaning.
SUMMARY OF THE INVENTION
The object of the invention is such a filter construction and such a ceramic filter construction in which it has been possible to increase the flow rate of the liquid sucked out of the material to be filtered to a considerable extent as compared with the solutions of prior art and whereat, by means of the filter construction concerned, it is possible to increase the filtering capacity of the whole suction drier considerably. In accordance with the invention, a filter construction of an entirely novel type has been formed, wherein it has been possible to intensify the flow rate of liquid to a considerable extent.
The filter construction in accordance with the invention is mainly characterized in that the filter construction comprises a first filter material layer of a ceramic material, which is the first layer in relation to the flowing liquid, and a second filter material layer of a ceramic material, connected with said first layer, whereat the first filter material layer, relative the flow, acts as the filtering layer proper, and the second filter material layer acts as a layer that supports the construction.
The method in accordance with the invention for the formation of a filter construction is mainly characterized in that first a second filter material layer is formed as the inner layer, and onto its face ceramic mix is sprayed so as to form a first filter material layer, i.e. the surface layer, or upon drying of the second filter material layer the dry piece is submerged into a ceramic mix, and the said ceramic mix is allowed to adhere as a thin layer onto the second filter material layer.
The filter construction in accordance with the invention is used in connection with suction driers for the dewatering of web-like material such as paper, floury material such as peat, solid, such as wood, porous material. By the intermediate of a finely porous suction face filled with liquid, the object to be dewatered is brought into hydraulic connection with a liquid subjected to negative pressure relative the object to be dewatered.
The flow rate of water in a porous material complies with Darcy's law: the flow rate is proportional to the difference in pressure and inversely proportional to length of flow. Thus, in an attempt to increase the flow rate, the length of the flow passage in the filter material should be made shorter. Thus, the filtering layer should be as thin as possible.
According to the invention, a two-part filter construction of a ceramic material is formed, wherein the surface layer, which is the first layer in the direction of flow of the filtered liquid, acts as the filtering layer proper and is thin, being of a thickness of even
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Hindstrom Rolf
Peltonen Paivi
Fisher Richard V.
Nessler Cynthia L.
Valmet Paper Machinery Inc.
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