Membrane separation element and process relating thereto
One exemplary embodiment is a membrane separation element. The membrane separation element can include a membrane and a feed spacer positioned adjacent to the membrane. The feed spacer may include a first layer, a second layer, and a third layer. Usually, a plurality of fibers of the second layer only touches a plurality of fibers of the first and third layers.
1. A membrane separation element, comprising:
A) a membrane sheet; and
B) a feed spacer positioned adjacent to the membrane sheet, and comprising:
1) a first layer comprising a plurality of fibers wherein each fiber of the plurality of fibers has a diameter and a length, and the fibers of the first layer are arranged substantially parallel with respect to their lengths to one another and positioned with respect to their lengths at a skewed angle to a bulk flow;
2) a second layer comprising a plurality of fibers wherein each fiber of the plurality of fibers has a diameter and a length, and the fibers of the second layer are arranged substantially parallel with respect to their lengths to one another and positioned with respect to their lengths to offset by about 100 to about 80° at least one fiber of the first layer; and
3) a third layer comprising a plurality of fibers wherein each fiber of the plurality of fibers has a diameter and a length, and the respective lengths of the plurality of fibers of the third layer are generally aligned with the respective lengths of the plurality fibers of the first layer;
wherein the plurality of fibers of the second layer only touches the plurality of fibers of the first and third layers.
2. The membrane separation element of claim 1 , wherein the feed spacer further comprises a fourth layer comprising a plurality of fibers wherein each fiber of the plurality of fibers has a diameter and a length, and the respective lengths of the plurality of fibers of the fourth layer are generally aligned with the respective lengths of the plurality of fibers of the second layer.
3. The membrane separation element of claim 1 , wherein each fiber of the plurality of fibers of the first layer has a substantially uniform diameter and each fiber of the plurality of fibers of the second layer has a substantially uniform diameter and the fiber diameter of the second layer is about twice the fiber diameter of the first layer.
4. The membrane separation element of claim 1 , wherein the feed spacer comprises an edge defining a feed channel height, and a ratio of the fiber diameter of the fibers of the first and third layers to the feed channel height is no more than 0.4:1, and a ratio of the fiber diameter of the fibers of the second layer to the feed channel height is at least 0.3:1 wherein the fiber diameter of the second layer is larger than the fiber diameter of the first layer or the third layer.
5. The membrane separation element of claim 2 , wherein the plurality of fibers of the first layer, the plurality of fibers of the second layer, the plurality of fibers of the third layer, and the plurality of fibers of the fourth layer have a substantially uniform diameter.
6. The membrane separation element of claim 2 , wherein the feed spacer comprises an edge defining a feed channel height, and a ratio of the fiber diameter of the first and fourth layers to the feed channel height is no more than about 0.3:1, and a ratio of the fiber diameter of the second and third layers to the feed channel height is at least about 0.25:1 wherein the fiber diameter of the second or third layer is larger than the fiber diameter of the first layer or the fourth layer.
7. The membrane separation element of claim 1 , wherein the feed spacer comprises at least one of polyethylene and polypropylene.
8. The membrane separation element of claim 2 , wherein the plurality of fibers of the third layer only touches the plurality of fibers of the second and fourth layers.
9. The membrane separation element of claim 1 , wherein the membrane sheet is a first membrane sheet and the membrane separation element comprises a second membrane sheet, and the first membrane sheet is positioned adjacent to the first layer of the feed spacer and the second membrane sheet is positioned adjacent to the third layer of the feed spacer.
10. The membrane separation element of claim 2 , wherein the membrane is a first membrane and the membrane separation element comprises a second membrane, and the first membrane is positioned adjacent to the first layer of the feed spacer and the second membrane is positioned adjacent to the fourth layer of the feed spacer.