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Concentration of solids in a suspension

  • US 4,931,186 A
  • Filed: 10/27/1986
  • Issued: 06/05/1990
  • Est. Priority Date: 03/05/1985
  • Status: Expired due to Term
First Claim
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1. A method of concentrating solids in a liquid suspension using a microfilter, said liquid suspension containing either a high solids content or solids which substantially form a gel-limiting layer on a filter surface or in pores of said filter, said microfilter comprising a plurality of hollow microporous, elastic fibres within a shell or housing, each fibre having an outer surface, an inner surface defining a lumen, and a porous wall therebetween, said method comprising the steps of:

  • (i) applying the liquid suspension to the outer surface of the elastic microporous, hollow fibres;

    whereby;

    (a) a portion of the liquid suspension passes through the walls of the fibres, thereby being drawn off as clarified liquid from the fibre lumens,(b) at least a portion of the solids of said suspension is retained on or in the fibres or otherwise within the shell while the remaining solids not being retained are removed from the shell with the remaining portion of the liquid suspension;

    (ii) discharging the retained solids from the shell by;

    (a) applying to the fibre lumens a gas at a pressure sufficient to stretch substantially all of the pores, followed by;

    (b) maintaining the flow of the gas at said pressure through the lumens for a time sufficient to drive the liquid from the pores having a bubble point below the pressure of the gas so as to wash out any solids retained in those pores and to substantially dislodge solids retained on the outer surface of the fibres whereby the washed and dislodged solids are removed from the shell to an external collection point, and then(c) reducing the pressure of the gas so that the pores will substantially return to their original size whereupon the gas is removed so that a portion of the liquid suspension passes through the walls of the fibres to be drawn off as a clarifying liquid from the fibre lumens.

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