Cleaning of hollow fiber filters utilized in lumenal gas flow

• US 4,767,539 A
• Filed: 06/03/1987
• Issued: 08/30/1988
• Est. Priority Date: 09/30/1983
• Status: Expired due to Term

• Current Assignee: US Filter Wastewater Group Incorporated (Siemens AG)
• Original Assignee: Memtec Ltd. (Danaher Corporation)
• Inventors: Ford, Douglas L.
• Primary Examiner(s): Sever, Frank
• Application Number:
  US07/056,908
• Time in Patent Office: 454 Days
• Field of Search: 210/636, 210/652-654, 210/456, 210/791, 210/638, 210/793, 210/794, 134/21, 134/22.11, 55/158, 260/428
• US Class Current: 210/636
• CPC Class Codes: B01D 2321/04 Backflushing
• CPC Class Codes: B01D 2321/12 Use of permeate
• CPC Class Codes: B01D 2321/185 Aeration
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration

Abstract

A method of cleaning a filter having a plurality of elastic, porous hollow fibers with lumens within a shell or housing and in which filtration is carried out by applying a liquid suspension feedstock to the outer surface of the fibers whereby a portion of feedstock passes through the walls of the fiber to be drawn from the fiber lumens as a filtrate or permeate, and a portion of the solids in the feedstock are retained on or in the pores of the fibers, with the non-retained solids being removed from the shell or housing with the remainder of the feedstock, said method entailing introducing a pressurized gas into the fiber lumens which passes through the walls of the fibers to dislodge the retained solids, the gas being applied at a pressure which is sufficient to overcome the effect of the surface tension of the continuous phase of the feedstock within the pores of the membrane.

Claims

1. A method comprising cleaning a filter for filtering liquid suspension feedstocks, having a plurality of elastic, porous hollow fibers with lumens within a shell or housing in which filtration is carried out by applying a liquid suspension feedstock to the outer surface of the fibers by passing a portion of the feedstock through the walls of the fibers to be drawn from the fiber lumens as a filtrate or permeate, and by retaining a portion of the solids in the feedstock on or in the pores of the fibers, with the non-retained solids being removed from the shell or housing with the remainder of the feedstock, by introducing a pressurized gas at pressure of at least 10 KPA into the fiber lumens which passes through the walls of the fibers for a time sufficient to dislodge a substantial portion of the retained solids, the pressures being sufficient to overcome the effect of the surface tension of the continuous phase of the feedstock within at least the larger pores of the membrane.

2. The method according to claim 1, wherein the hollow fibers are formed from polymeric materials.

3. The method according to claim 1, wherein the hollow fibers have a hydrophilic coating.

4. The method according to claim 1, wherein the hollow fibers have a hydrophilic coating and a hydrophilic packing within the pores.

5. The method according to claim 1, wherein the gaseous cleaning step is preceded by a permeate back-wash step.

6. The method according to claim 1, wherein the gas is applied at a pressure in the range of 10-800 kPa.

7. The method according to claim 1, wherein the gas is applied at a pressure of 500 kPa.

8. The method according to claim 1, wherein the gas cleaning step is carried out for 1 to 5 seconds.

9. The method according to claim 1, wherein the volume of the gas introduced during the cleaning step is such that its expanded volume exceeds the volume of the feed side of the filter.

10. The method according to claim 1, wherein the duration of the gas cleaning step exceeds the residence time for feedstock flowing through the filter.

11. The method according to claim 1, wherein said pressurized gas is introduced into the fiber lumens for up to about eight seconds.

12. A method comprising operating a filter for filtering liquid suspensions feedstocks, having a plurality of elastic, microporous hollow fibers with lumens within a shell or housing by,

(a) introducing a liquid suspension feedstock into the shell or housing and directing said feedstock to the outer surface of the fibers by passing a portion of the feedstock through the walls of the fibers to be drawn from the fiber lumens as a filtrate or permeate, and retaining a portion of the solids in the feedstock on or in the pores of the fibers, with the non-retained solids being discharged from the shell or housing with the remainder of the feedstock, and

(b) periodically cleaning away the solids retained on or in the pores of the fibers by introducing a pressurized gas at pressures of at least 10 kPa into the fiber lumens which passes through the walls of the fibers for a time sufficient to dislodge a substantial portion of the retained solids, said pressure being sufficient to overcome the effect of the surface tension of the continuous phase of the feedstock within at least the larger pores of the membrane.

13. The method of operating a filter according to claim 12, wherein the hollow fibers are formed from polymeric material.

14. The method of operating a filter according to claim 12, wherein the hollow fibers have a hydrophilic coating.

15. The method of operating a filter according to claim 12, wherein the hollow fibers have a hydrophilic coating and a hydrophilic packing within the pores.

16. The method of operating a filter according to claim 12, wherein the gaseous cleaning step is preceded by a permeate back-wash step.

17. The method of operating a filter according to claim 12, wherein the gas is applied at a pressure in the range of 10-800 kPa.

18. The method of operating a filter according to claim 12, wherein the gas is applied at a pressure of 500 kPa.

19. The method of operating a filter according to claim 12, wherein the gas cleaning step is carried out for 1 to 5 seconds.

20. The method of operating a filter according to claim 12, wherein the volume of gas introduced during the cleaning step is such that its expanded volume exceeds the volume of the feed side of the filter.

21. The method of operating a filter according to claim 12, wherein the duration of the gas cleaning step exceeds the residence time for feedstock flowing through the filter.

22. The method according to claim 12, wherein said pressurized gas is introduced into the fiber lumens for up to about eight seconds.

23. A method comprising operating a filter for filtering liquid suspensions feedstocks, having a plurality of elastic, microporous hollow fibers with lumens within a shell or housing by

(a) introducing a liquid suspension feedstock into the shell or housing and applying the feedstock to the outer surface of the fibers by passing a portion of the feedstock through the walls of the fibers to be drawn from the fiber lumens as a permeate, and retaining a portion of the solids in the feedstock on or in the pores of the fibers with the non-retained feedstock, by introducing of the feedstock, and

(b) cleaning away the retained solids by applying through the fiber lumens a pressurized permeate back-wash which passes through the walls of the fibers to wash out at least a portion of the retained solids followed by a pressurized gas at pressure of at least 10 kPa which passes through the walls of the fibers for a time sufficient to stretch elastically at least a portion of the pores to dislodge a substantial portion of the solids retained in those pores and which washes the external walls of the fibers, said pressure being sufficient to overcome the resistance to gas flow of the surface tension of the continuous phase of the filtrate within at least the larger pores of the membrane.

24. The method according to claim 23, wherein said pressurized gas is introduced into the fiber lumens for up to about eight seconds.