Tangential-flow filtration system
First Claim
1. A tangential-flow filter for selectively transferring a species from a fluid mixture to a fluid media, the filter comprising:
- a filtration membrane having a first surface and a second surface;
a cassette formed with a first channel and a second channel, the first channel having an input port and an output port being disposed to establish a tangential flow of the fluid mixture over the first surface of the membrane, the first channel having a cross-sectional area with the cross-sectional area decreasing in the direction of the tangential flow, and the second channel having an input port and an output port being disposed to establish a tangential flow of the fluid media over the second surface of the membrane, wherein the decrease in cross-sectional area in the first channel is chosen so that the velocity of the tangential flow of the fluid mixture is substantially constant over the length of the first channel and a pressure differential is substantially constant over the length of the filtration membrane; and
means for creating the pressure differential between the fluid mixture in the first channel and the fluid media in the second channel to cause the species to traverse the membrane from the fluid mixture to the fluid media.
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Abstract
The present invention includes a system and method for transferring a selected solute species from a fluid mixture to a fluid media. The system of the present invention includes a convergent channel for passing a fluid mixture containing a selected species tangentially across the first surface of a porous membrane. A fluid media is directed to flow tangentially over the second surface of the membrane. As the fluid mixture and the fluid media flow on opposite sides of the membrane, the selected species traverses the membrane leaving the fluid mixture and entering the fluid media. The volumetric loss to the fluid mixture associated with the loss of the selected species is compensated for by the convergency of the channel. As a result a constant velocity is maintained over the membrane, maximizing the selectivity of the filtration process.
53 Citations
20 Claims
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1. A tangential-flow filter for selectively transferring a species from a fluid mixture to a fluid media, the filter comprising:
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a filtration membrane having a first surface and a second surface; a cassette formed with a first channel and a second channel, the first channel having an input port and an output port being disposed to establish a tangential flow of the fluid mixture over the first surface of the membrane, the first channel having a cross-sectional area with the cross-sectional area decreasing in the direction of the tangential flow, and the second channel having an input port and an output port being disposed to establish a tangential flow of the fluid media over the second surface of the membrane, wherein the decrease in cross-sectional area in the first channel is chosen so that the velocity of the tangential flow of the fluid mixture is substantially constant over the length of the first channel and a pressure differential is substantially constant over the length of the filtration membrane; and means for creating the pressure differential between the fluid mixture in the first channel and the fluid media in the second channel to cause the species to traverse the membrane from the fluid mixture to the fluid media. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A tangential-flow filtration apparatus separating a fluid mixture into species of interest comprising:
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a cassette formed with a layered sequence of side-by-side channels including a convergent first channel and a last channel, the convergent first channel and at least one intermediate channel configured as recirculating channels having an inlet and an outlet, the last channel configured as a non-recirculating channel having an outlet; a series of filtration membranes, one filtration membrane positioned between each successive pair of channels in the layered sequence with each successive pair of channels in the layered sequence being separated by a filtration membrane having a successively smaller pore size, wherein the convergent first channel converges between the inlet and the outlet so that the flow velocity of the fluid mixture is substantially constant within the convergent first channel and so that a predetermined pressure differential between the convergent first channel and at least the first intermediate channel is substantially constant over the length of the filtration membrane positioned between the convergent first channel and the intermediate channel; means for creating the flow of the fluid mixture between the inlet and the outlet of each recirculating channel; and means for creating and maintaining the predetermined pressure differential between each successive pair of channels in the layered sequence. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A process for selectively transferring a species from a fluid mixture, comprising the steps of:
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passing the fluid mixture through a channel for tangential flow over a first surface of a primary filtration membrane, the channel shaped to have a cross-sectional area, the cross-sectional area decreasing in the direction of the tangential flow; passing a fluid media for tangential flow over a second surface of the primary filtration membrane, the tangential flow of the fluid mixture adjacent to the tangential flow of the fluid media, wherein the decrease in cross-sectional area in the channel is chosen so that the velocity of the tangential flow of the fluid mixture is substantially constant over the length of the channel and a predetermined pressure differential is substantially constant over the length of the filtration membrane; and creating and maintaining the predetermined pressure differential between the fluid mixture in the channel and the fluid media to cause the species to traverse the primary filtration membrane from the fluid mixture to the fluid media. - View Dependent Claims (15)
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16. A tangential-flow filter for selectively transferring a species from a fluid mixture to a fluid media, the filter comprising:
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filtration means having a first surface and a second surface; a first channel which causes the mixture to flow tangentially at a first pressure over the first surface of the filtration means, the first channel having a length, the first channel being shaped to decrease from a first cross-sectional area to a second cross-sectional area over the length of the first channel; wherein the decrease in cross-sectional area in the first channel is chosen so that the velocity of the tangential flow of the fluid mixture is substantially constant over the length of the first channel and a predetermined pressure differential is substantially constant over the length of the filtration membrane; and means for causing the fluid media to flow tangentially at a second pressure over the second surface of the filtration means, the first pressure and the second pressure creating and maintaining the predetermined pressure differential over the filtration means between the mixture and the fluid media, the pressure differential causing the species to traverse the filtration means from the fluid mixture to the fluid media. - View Dependent Claims (17, 18, 19, 20)
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Specification