Liquid purification or separation – Casing divided by membrane into sections having inlet – Each section having inlet
Patent
1990-05-29
1992-12-01
Spear, Frank
Liquid purification or separation
Casing divided by membrane into sections having inlet
Each section having inlet
210356, B01D 6128
Patent
active
051678179
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
My EP-A-0111423 discloses a membrane assembly (hereinafter referred to as of the kind described) for use in mass or heat transfer apparatus, and comprising a pair of generally parallel plates spaced apart with a profiled surface of one plate facing a similarly profiled surface of the other plate, and a pair of sheets of transfer membrane material closely spaced, throughout substantially their whole area, face to face between the plates with each sheet supported by and partially nesting in the profiled surface of the adjacent plate, thereby providing between the membranes a first conduit for a first fluid, and between each membrane and the adjacent plate a second conduit for a second fluid, each membrane presenting in its surface facing the other membrane a regular close packed array of permanent dimple-like depressions each facing and substantially aligned with a similar depression in the other membrane, and the profiled surfaces of the plates being provided by depressions in alignment with the dimples in the respective membrane and interconnected by grooves; the arrangement being such that if, in use, one fluid is passed through the first conduit with a pulsatile flow, vortex mixing occurs in the dimples in the membranes.
The pulsatile flow may be produced by superimposing on a mean flow of the first fluid through the first conduit a pulsatile component which promotes the vortex mixing of the fluid. As particularly described in the EP specification, the dimples in each membrane are provided in parallel rows the dimples in each row being longitudinally offset halfway between adjacent dimples in the adjacent rows so that lateral nesting of adjacent rows occurs. The depressions in the plates are also arranged in longitudinal rows along the direction of the mean flow, the grooves interconnecting one depression to the next along the respective row.
In this kind of membrane assembly, the efficiency of the transfer across the membrane is high as the total volume of first fluid which can be brought into close proximity with the membrane, as a result of the vortex mixing, is high.
Apparatus using such a transfer membrane assembly has been used successfully for the oxygenation of blood, in which case blood is passed through the first conduit and oxygen-containing gas through the second conduits. In this case the membrane have usually been hydrophobic. The assembly has also been used successfully for filtration of aqueous liquid, in which case the membranes are preferably hydrophilic, so that good wetting occurs. For example, filters incorporating the membrane assembly have proved extremely successful for harvesting plasma from whole blood by plasmaphersis or using donated blood, as the assembly provides high filtration rates per unit membrane area, works well at low rates of blood flow (60-80 ml/min) and is not prone to the kind of fouling which is a complication of conventional membrane plasma filters. In fact filtration rate has been about four times as high as that achieved by conventional membrane filters of the same area. Also, filters incorporating such a membrane assembly have proved successful experimentally in the concentration by filtration of bacterial, mammalian or plant cells in biotechnological work. In these cases the whole blood or other liquid to be filtered is passed through the first conduit and the filtrate is collected in the second conduits.
Each second conduit will have an inlet and an outlet if through flow is required, e.g. in countercurrent to the flow of the first fluid through the first conduit. On the other hand, if the apparatus is set up for filtration, only an outlet from each second conduit may suffice.
In spite of these successes with the membrane assembly described in the EP specification, there are two areas where I have sought improvement.
The first is that, as clearly illustrated in FIG. 5 of the EP specification, the maximum diameter of each dimple in each membrane was the same as that of the associated depression in the adjacent profiled support plate. As a resul
REFERENCES:
patent: 3362540 (1968-01-01), Bluemle, Jr.
patent: 3540595 (1970-11-01), Edwards
patent: 4383921 (1983-05-01), Bellhouse et al.
patent: 4636309 (1987-01-01), Bellhouse
Transactions/American Soc. for Artificial Internal Organs, vol. XXVII, 1981 (Washington, D.C.), K. Abel et al.: "A Practical Secondar-Flow Hemodialyzer", pp. 639-643, see pages 639-640: Design for the Vortex-Mixing Hemodialyzer.
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