Concentration of solids in a suspension

• US 5,024,762 A
• Filed: 01/05/1990
• Issued: 06/18/1991
• Est. Priority Date: 03/05/1985
• Status: Expired due to Term

• Current Assignee: US Filter Wastewater Group Incorporated (Siemens AG)
• Original Assignee: Memtec Ltd. (Danaher Corporation)
• Inventors: Anderson, Eric W., Kopp, Clinton V., Ford, Douglas L.
• Primary Examiner(s): Spear, Frank
• Application Number:
  US07/461,297
• Time in Patent Office: 529 Days
• Field of Search: 210/636, 210/247.2, 210/500.23, 210/321.69, 210/410, 210/412
• US Class Current: 210/321.69
• CPC Class Codes: B01D 2313/48 Mechanisms for switching between regular separation operations and washing
• CPC Class Codes: B01D 2321/18 Use of gases
• CPC Class Codes: B01D 61/18 Apparatus therefor
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration
• CPC Class Codes: B01D 69/02 characterised by their properties

Abstract

A method of concentrating solids in a liquid suspension using a filter having a plurality of hollow, microporous, elastic fibres with a shell or housing, comprising applying the suspension to an outer surface of the fibres whereby a portion of the suspension passes through the fibre walls and at least a portion of the solids is retained on or in the fibres; and discharging the retained solids by stretching the fibre pores and washing out solids retained in the pores by application of gas under pressure.

Claims

1. A concentrator for concentrating the fine solids of a liquid feed suspension comprising:

(i) a shell,

(ii) a plurality of elastic, hollow, microporous, polymer fibres within the shell,

(iii) means for supplying pressurised feed suspension to the outside of the fibres,

(iv) means for withdrawing clarified liquid from the fibre lumens,

(v) means for applying liquid followed by gas under pressure to the fibre lumens to effect a transmembrane cleaning of the fibres, the pressure of the liquid being sufficient to stretch substantially all of the pores of the fibres and the pressure of the gas being sufficient to ensure that the gas will pass through the larger pores of the fibres to dislodge any solids retained therein and to wash the external walls of the fibres and the interior of the shell to remove all solids from the shell to an external collection point.

2. The concentrator according to claim 1, and further includes, means for sealing the relatively incompressible feed suspension in the shell upon displacement of liquid from the fibre lumens by the pressurised gas so that the gas may be trapped in the lumens at a pressure above the bubble point of the fibre walls and means to allow the sudden release of the gas substantially uniformly through the fibre walls.

3. The concentrator as claimed in claim 1 or claim 2, which incorporates means whereby the resumption of flow of feed suspension through the fibres after said liquid and said gas are applied to the fibre lumens so as to wash the external walls of the fibres and the interior of the shell is delayed for sufficient time to allow the expanded pores to recover to their original size so that oversized particles from the feed suspension will not be able to pass into or through the enlarged pores.

4. The concentrator according to claim 3, wherein said means for delaying the resumption of the flow of feed suspension effects said delay by applying the gas at a pressure higher than that of the feed suspension and allowing the pressure of the gas to fall below the feed pressure at a rate which will allow the pores of the fibres to recover to their original size before the flow of feed is resumed.

5. The concentrator as claimed in claim 2, wherein said means for sealing the relatively incompressible feed suspension within said shell comprises the feed liquid itself.

6. The concentrator as claimed in claim 1, wherein flow of treated suspension from said shell is controlled by valve means so as to apply a back pressure to the feed.

7. The concentrator as claimed in claim 1, wherein means is provided to wet the pores of said fibres following removal of all solids from said shell to an external collection point.

8. The concentrator as claimed in claim 1, wherein means is provided to shrink the gas bubbles retained in the pores of the fibres following discharge of the solids so as to aid the passage of the bubbles from the pores and to maintain sufficient solubility of the gas in the feed or clarified liquid or both.

9. The concentrator as claimed in claim 8, wherein said means to shrink the gas bubbles effects the shrinking of the gas bubbles following resumption of feed by application of sufficient pressure of feed to cause said shrinkage.