Spiral wound membrane with bi-directional permeate flow
Disclosed is a spiral wound membrane element that provides two permeate streams through a permeate carrier sheet. The spiral wound membrane element is sealed such that the only communication with the permeate carrier is through a membrane sleeve. The first permeate stream flows spirally inward and the second permeate stream flows in the opposite direction, spirally outward. The permeate carrier sheet is sealed at two edges so that the permeate streams can only discharge from opposite, unsealed edges of the permeate carrier sheet. The first permeate stream may be collected in a central collection tube and the second permeate stream may be collected in a peripheral region of the membrane element.
1. A spiral wound membrane element, comprising:
a central tube;
one or more membrane sleeves, each sleeve comprising two membrane sheets enclosed at two opposed edges around a feed spacer sheet;
a permeate carrier sheet in a one to one ratio with the membrane sleeves and attached to the central tube at a first edge opposite a second edge; and
a seal on a third and fourth edge of the permeate carrier, extending from the first to the second edges
wherein the one or more membrane sleeves and permeate carrier sheets are wrapped in a spiral and the second edge of each permeate carrier sheet is open and extends beyond one of the membrane sleeves lying over it in a peripheral region of the element such that the permeate carrier is in fluid communication with the central tube and the peripheral region of the membrane element.
2. The spiral wound membrane element of claim 1 , further comprising an anti-telescoping device.
3. The spiral wound membrane element of claim 2 , further comprising an outer wrap that wraps around the one or more membrane sleeves and the permeate carrier.
4. The spiral wound membrane element of claim 3 , wherein the anti-telescoping device includes an interior passage that communicates from the peripheral region of the membrane element to the central tube.
5. The spiral wound membrane element of claim 4 , wherein the permeate carrier extends from the second edge beyond the membrane sleeve.
6. The spiral wound membrane element of claim 4 , wherein the membrane element is housed within a pressure vessel.
7. A method for filtering a feedstock, the method comprising:
providing a spiral wound membrane element as in claim 1 ;
driving the feedstock in a first direction through the one or more membrane sleeves;
collecting a reject stream on the first side of the membranes and collecting permeate fluid on a second side of the membranes;
collecting the reject fluid;
dividing the permeate fluid into a first permeate stream and a second permeate stream;
directing the first permeate stream in a second direction that spirals towards and communicates with the central tube;
directing the second permeate flow in a third direction that spirals towards and communicates with the peripheral region;
collecting the permeate from the central tube and the peripheral region.
8. The method of claim 7 , wherein the first direction is co-axial with the central axis and the second direction is substantially normal to the first direction and approaching the central axis.
9. The method of claim 8 , wherein the third direction is substantially parallel to the second direction and away from the central axis.
10. The method of claim 9 , wherein the second permeate flow flows from peripheral region to an anti-telescoping device.
11. The method of claim 10 , wherein the second permeate flows from the anti-telescoping device to the central tube.
12. The method of claim 11 , wherein the membrane is selected from a group of membranes suitable for microfiltration, ultrafiltration, nanofiltration and reverse osmosis.