Vertical cylindrical skein of hollow fiber membranes and method of maintaining clean fiber surfaces

In a microfiltration membrane device, for withdrawing permeate essentially continuously from a multicomponent liquid substrate, said membrane device including:

• a multiplicity of hollow fiber membranes, or fibers, unconfined in a shell of a module, said fibers being swayable in said substrate, said fibers being subject to a transmembrane pressure differential in the range from about 0.7 kPa (0.1 psi) to about 345 kPa (50 psi);
• a first header and a second header disposed in transversely spaced-apart relationship with said second header within said substrate;
• said first header having a terminal end portion of each fiber secured therein, and said second header having an opposed terminal end portion of each fiber secured therein, all said fibers extending from a permeate-discharging face of at least one said header;
• said fibers being sealingly secured with open ends of the fibers secured in fluid-tight relationship with each other in at least one of said headers;
• permeate collection means to collect said permeate through at least one of said headers sealingly connected in open fluid communication with permeate-discharging faces of said headers;
• and, means for withdrawing said permeate;
• said fibers, said headers and said permeate collection means together forming a vertical cylindrical skein wherein said fibers are essentially vertically disposed;
• said first header being upper and disposed in vertically spaced-apart relationship above said second header, with opposed faces at a fixed distance;
• each of said fibers having substantially the same length, said length being from 0.1% to less than 5% greater than said fixed distance so as to permit restricted displacement of an intermediate portion of each fiber, independently of the movement of another fiber;
• the improvement comprising,
• each said header having said fibers spaced apart by a flexible support means having a thickness corresponding to a desired lateral spacing between adjacent fibers, said support means extending over only each terminal portion of said fibers near their ends so as to maintain said ends in closely-spaced apart relationship.

In a process for maintaining the outer surfaces of hollow fiber membranes essentially free from a build-up of deposits of particulate material while separating a permeate from a multicomponent liquid substrate in a reservoir, said process comprising,

• submerging skein fibers in an essentially vertical, cylindrical configuration within said substrate, said fibers being unconfined in a modular shell, and securely held in vertically opposed, upper and lower headers spaced-apart at a fixed distance, said fibers having substantially the same length and from at least 0.1% greater, to about 5% greater than said fixed distance, a transmembrane pressure differential in the range from about 0.7 kPa (0.1 psi) to about 345 kPa (50 psi), and length sufficiently greater than the direct distance between opposed faces of said first and second headers, so as to present said skein in a swayable configuration above a horizontal plane through the horizontal center-line of said lower header;
• mounting said headers in fluid-tight open communication with collection means to collect said permeate;
• flowing a fiber-cleaning gas through a gas-distribution means proximately disposed relative to said skein, within a zone beneath said skein, and contacting surfaces of said fibers with sufficient physical impact of bubbles of said gas to maintain essentially the entire length of each fibers in said skein awash with bubbles and essentially free from said build-up;
• maintaining an essentially constant flux through said fibers substantially the same as an equilibrium flux initially obtained after commencing operation of said process;
• collecting said permeate in said collection means;
• and, withdrawing said permeate,
• the improvement comprising,
• introducing said cleansing gas between said fibers within said skein to generate a column of said bubbles alongside and in contact with outer surfaces of said fibers;
• said fibers spaced apart by a flexible support means having a thickness corresponding to a desired lateral spacing between adjacent fibers, said support means extending over only each terminal portion of said fibers near their ends, so as to maintain said ends in closely apart relationship;
• restricting movement of said fibers to said vertical zone defined by lateral movement of outer fibers in said skein;
• vertically gas-scrubbing said fibers outside surfaces with bubbles which flow upward in contact with said surfaces;
• maintaining said surfaces substantially free from said deposits of particulate matter during a period when flux through said fibers has attained equilibrium;
• and simultaneously, essentially continuously, withdrawing said permeate.