US 4,755,300 A · Couette membrane filtration apparatus for separating suspended components in a fluid medium using high shear

Abstract

The present invention provides significant improvements in the design and performance of a specific type of Rotary Membrane Filter (RMF) apparatus which has the capability of separating particles from a fluid having the same and nearly the same density as the particles by utilizing shear to achieve separation, not centrifugal forces. A particular application for the apparatus is in the processing of fluid suspensions in which the suspensions contain fragile particles which are subject to damage due to excessive shear stresses. The prior art describes processing at constant shear rate, whereas the present invention provides the design and optimization of operation of such an apparatus at constant shear stress, which is maintained at a value below that at which significant damage to the fragile particles is encountered. The use of the invention in plasmapheresis (blood separations) is described in detail, it being understood that the teachings of the invention are also directly applicable to other fluids containing fragile particles. The application of the RMF in a continuous flow processing system designed to extract blood plasma from a donor is described, including return of corpuscular components to the donor.

Claims16

Dependent claims

A method of separating fluid from a fluid suspension using a couette membrane filter having facing surfaces which define a gap therebetween, there being inlet means for introducing fluid into the gap, and outlet means for removing fluid from the gap remotely from said inlet means, comprising the steps of:

(1) locating the facing surfaces of the filter in coaxial relation:
(2) mounting a semi-porous membrane having a plurality of pores on at least one of said facing surfaces;
(3) increasing the thickness of the gap between the facing surfaces from inlet to outlet to compensate for changes in suspension viscosity;
(4) introducing the fluid suspension into the gap between the facing surfaces of the filter;
(5) rotating one surface coaxially relative to the other;
and
(6) controlling the relative speed of rotation of the facing surfaces such that shear stress imparted to the fluid suspension is maintained at a constant value below a certain predetermined level whereby fluid from the suspension passes through the pores of the membrane.

4 more elements

In the method of operating filter apparatus to separate blood components in a fluid suspension, including:

(a) a first surface of revolution;
(b) a membrane having a plurality of pores therethrough, the membrane defining a second surface of revolution spaced from and facing the first surface and defining therewith a shear gap of predetermined radial dimensions which are non-uniform in the axial length direction of the membrane, said first and second surfaces extending coaxially,
(c) inlet means for introducing the fluid suspension into the gap;
(d) means for rotating one of said surfaces about its axis of revolution relative to the other surface and at an angular velocity such that shear stress is imposed on the fluid suspension in the gap and laminar flow of the fluid suspension in the gap is created whereby fluid is separated from the fluid suspension and passes through the membrane pores;
and
(e) first outlet means for removal of fluid passing through the membrane pores, and other outlet means for removing fluid from the gap remotely from the inlet means, the steps that include:
(f) introducing the fluid suspension into the gap between the first and second surfaces;
(g) operating said means for rotating one surface relative to the other;
and
(h) controlling the speed of said relative rotation, whereby fluid passage through the pores of the membrane is maintained along the length of the membrane, said suspension consisting of blood from which fluid plasma is to be separated, the blood filling the gap, and including the steps,
(i) producing laminar flow regions adjacent the pores and producing Taylor vortices in the gap, adjacent said laminar flow regions, with Taylor number maintained essentially constant over the length of the membrane,
(j) and increasing the thickness of the gap between said surfaces, along length of the membrane between the inlet means and the other outlet means and in a direction toward said other outlet means to compensate for changes in fluid viscosity such that the shear stress imparted to the fluid suspension in and along the gap region adjacent the membrane pores is maintained substantially constant and below a level at which a component of the blood in the suspension would otherwise be damaged.

9 more elements

Dependencies are inferred from the claim text.

Couette membrane filtration apparatus for separating suspended components in a fluid medium using high shear

Life of this patent

Couette membrane filtration apparatus for separating suspended components in a fluid medium using high shear

Life of this patent

Abstract

Claims16