Liquid purification or separation – Processes – Separating
Patent
1991-07-19
1993-11-02
Dawson, Robert A.
Liquid purification or separation
Processes
Separating
210236, 210791, B01D 3700
Patent
active
052581284
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for splitting off small pieces of filter cake from a pressure filter for liquid-solid mixtures comprising an outer casing, a lid for releasably closing the outer casing, a tubular filter element which protrudes from the lid into the outer casing and on the outside of which the filter cake which is to be split off settles, a reversible membrane which is located between the outer casing and the filter element when the filter is in operation, a pressure connection piece on the outer casing, an inlet line for the liquid-solid mixture leading to the space between membrane and filter element and an outlet line for the filtrate leading out of the interior of the filter element.
In such pressure filters with a reversible membrane, the filter cake has until now been split off from the filter element when the membrane has turned inside out and the filter element has been pulled out of the outer casing completely, with the splitting-off being promoted by the filter element being turned back and forth about its axis. However, it is only in the rarest of cases that one succeeds in splitting off the filter cake in small pieces. Normally the filter cake falls off the filter element in the form of large, board-like pieces, with the result that it can only be conducted out of the outlet opening of the housing surrounding the pressure filter after separate comminution, for example, crushing by a special apparatus. The subsequent comminution of the split-off filter cake is, of course, an undesired, additional operation which one would like to avoid.
With a pressure filter of the kind in question, the object of the invention is to disclose a process for splitting off small pieces of filter cake which results in such breaking-up of the filter cake into small fragments that subsequent comminution, in particular crushing of the filter cake, is no longer necessary and the resulting pieces can readily pass out through the outlet opening of the housing surrounding the pressure filter.
The object is accomplished in accordance with the invention in that after formation of the filter cake on the outside of the filter element, a gaseous pressure medium is introduced into the interior of the filter element as long as the filter cake is still completely or partly surrounded by the reversible membrane.
The following description serves in conjunction with the appended drawings to explain the invention in further detail. The drawings show:
FIGS. 1 to 4 various operating stages of a pressure filter with a reversible membrane.
The pressure filter for liquid-solid mixtures illustrated in the drawings comprises a boiler-shaped outer casing 1 which is closed on one side thereof (on the right in the drawings). The opposite, open end face of the outer casing 1 is sealingly closable by a lid 2. A tubular filter element 3, for example, in the form of a screen cylinder covered with a filter cloth protrudes rigidly from the lid 2 into the interior of the outer casing 1. A flexible, reversible, tubular membrane 4 impermeable to liquid is clamped with its one rim on an opening flange 5 of the outer casing 1 and with its other rim on an end face flange 6 of the filter element 3. The outer casing 1 comprises a pressure connection piece 7 for the introduction and discharge of a liquid pressure medium. An inlet line 8 for the liquid-solid mixture leading to the space between filter element 3 and membrane 4 is formed on the lid 2. The lid also comprises an outlet line 9 leading out of the interior of the filter element 3.
The pressure filter described herein is surrounded in its entirety by a sealed-off housing (not illustrated).
The pressure filter described herein is operated as follows: The liquid-solid mixture to be filtered is introduced through the inlet line 8 in the direction of arrow A to the space between filter element 3 and membrane 4. After closure of the line 8, liquid pressure medium is introduced into the space between outer casing 1 and membrane 4 through the pressure connection piece 7, and a pressure is t
REFERENCES:
patent: 3753499 (1973-08-01), Gwilliam
patent: 4246122 (1981-01-01), Keat
patent: 4702831 (1987-10-01), Gerteis
patent: 4707256 (1987-11-01), Gerteis
patent: 5139665 (1992-08-01), Gerteis
Dawson Robert A.
Fortuna Ana M.
Heinkel Industriezentrifugen GmbH & Co.
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