초록 ▼

In at least one embodiment, a membrane filtration element is provided. The element may include at least one feed spacer including a first set of parallel strands extending in a first direction and including a plurality of first strands having a first thickness and a plurality of second strands havin

In at least one embodiment, a membrane filtration element is provided. The element may include at least one feed spacer including a first set of parallel strands extending in a first direction and including a plurality of first strands having a first thickness and a plurality of second strands having a second thickness that is smaller than the first thickness. A second set of parallel strands may extend in a second direction that is transverse to the first direction. The second set of parallel strands may include a plurality of third strands having a third thickness and a plurality of fourth strands having a fourth thickness that is smaller than the third thickness. In one embodiment, the first and second sets of strands include alternating thick and thin strands, which reduce pressure drop in membrane filtration systems.

대표청구항 ▼

1. A spiral wound filtration element comprising: a central collection tube having at least one hole defined therein;at least one membrane envelope attached to the central collection tube and having two membrane sheets separated by a spacer, the at least one membrane envelope configured to be wrapped

1. A spiral wound filtration element comprising: a central collection tube having at least one hole defined therein;at least one membrane envelope attached to the central collection tube and having two membrane sheets separated by a spacer, the at least one membrane envelope configured to be wrapped around the central collection tube to form a spiral; andat least one feed spacer configured to be disposed adjacent to at least one of the two membrane sheets when wrapped around the central collection tube and to create a channel to receive liquid to be filtered, the at least one feed spacer configured to allow fluid flow through the membrane envelope, the at least one feed spacer comprising a netting including: a first set of solid, parallel strands extending in a first direction and including a plurality of first strands having a first thickness, and a plurality of solid second strands having a second thickness that is smaller than the first thickness, the first and second strands spaced apart from one another with an open spacing to readily allow the fluid flow between the first and second strands; anda second set of solid, parallel strands fused to the first and second strands, and extending in a second direction that is transverse to the first set of parallel strands, and including a plurality of third strands having a third thickness and a plurality of fourth strands having a fourth thickness that is smaller than the third thickness the third and fourth strands spaced apart from one another with an open spacing to readily allow the fluid flow between the third and fourth strands;wherein the thickness of the at least one feed spacer is not uniform, such that the at least one feed spacer is thickest where the first and third strands intersect, thinnest where the second and fourth strands intersect, and having an intermediate thickness where the first and fourth strands intersect and an intermediate thickness where the third and second strands intersect that is the same as the intermediate thickness where the first and forth strands intersect;wherein the first and third strands, the first and fourth strands, the second and fourth strands, and the third and second strands merge by 0.1 to 30 percent where each of the first and third strands, the first and fourth strands, the second and fourth strands, and the third and second strands intersect;wherein the overall strand surface area is reduced by at least 10 percent relative to having strands of uniform thickness; andwherein the at least one feed spacer make contact with the two membrane sheets at contact points, and the feed spacer has three thicknesses at the contact points: a first thickness and a second thickness greater than the first thickness, and wherein the number of contact points at the second thickness are substantially equal to the sum of contact points of the first thickness. 2. The spiral wound filtration element of claim 1, wherein the first set of parallel strands comprises alternating the first and second strands. 3. The spiral wound filtration element of claim 1, wherein the first set of parallel strands comprises alternating the first and second strands and the second set of parallel strands comprises alternating the third and fourth strands. 4. The spiral wound filtration element of claim 1, wherein the first strands and the third strands have thicknesses of 5 to 40 mils and the second strands and the fourth strands have thicknesses of 3 to 35 mils. 5. The spiral wound filtration element of claim 1, wherein the first strands and the third strands have thicknesses of 8 to 35 mils and the second strands and the fourth strands have thicknesses of 5 to 15 mils. 6. The spiral wound filtration element of claim 1, wherein the first strands and the third strands have thicknesses of 10 to 30 mils and the second strands and the fourth strands have thicknesses of 7 to 12 mils. 7. The spiral wound filtration element of claim 1, wherein the first strands and the third strands have the same thickness and the second strands and the fourth strands have the same thickness. 8. The spiral wound filtration element of claim 1, wherein the at least one feed spacer has a total thickness at an intersection of the first strands and the third strands of 25 to 50 mils. 9. The spiral wound filtration element of claim 1, wherein the first set of parallel strands is perpendicular to the second set of parallel strands. 10. The spiral wound filtration element of claim 1, wherein the first set of parallel strands intersects the second set of parallel strands at an angle of 65 to 110 degrees in a direction parallel to a longitudinal axis of the spiral wound filtration element. 11. The spiral wound filtration element of claim 1, wherein a pressure drop of the fluid flow through the spiral wound filtration element is reduced by at least 10% compared to a same spiral wound filtration element having a feed spacer with strands having substantially identical thicknesses. 12. The spiral would filtration element of claim 1, wherein the at least one feed spacer includes from 0.1 to 10% by weight of ultra-high molecular weight polyethylene. 13. An extruded netting comprising: a first set of parallel strands extending in a first direction and including a plurality of first strands having a first thickness and a plurality of second strands having a second thickness that is smaller than the first thickness; anda second set of parallel strands extending in a second direction that is transverse to the first direction and including a plurality of third strands having a third thickness and a plurality of fourth strands having a fourth thickness that is smaller than the third thickness;wherein the first set of strands and the second set of strands are always located on the same side of each other; andthe first set of parallel strands comprises alternating the first and second strands, and the second set of parallel strands comprises alternating the third and fourth strands;wherein the thickness of the netting is not uniform, such that the netting is thickest where the first and third strands intersect, thinnest where the second and fourth strands intersect, and having an intermediate thickness where the first and fourth strands intersect and an intermediate thickness where the third and second strands intersect that is the same as the intermediate thickness where the first and forth strands intersect. 14. The extruded netting of claim 13 further comprising from 0.1 to 10% by weight of ultra-high molecular weight polyethylene. 15. The extruded netting of claim 13, wherein the first strands and the third strands have thicknesses of 5 to 40 mils and the second strands and the fourth strands have thicknesses of 3 to 35 mils. 16. The extruded netting of claim 13, wherein the first strands and the third strands have thicknesses of 8 to 35 mils and the second strands and the fourth strands have thicknesses of 5 to 15 mils. 17. The extruded netting of claim 13, wherein the netting has a total thickness at an intersection of the first and second set of parallel strands of 25 to 50 mils. 18. The extruded netting of claim 13, wherein the first set of parallel strands intersects the second set of parallel strands at an angle of 65 to 110 degrees in a direction parallel to a longitudinal axis of a spiral wound filtration element. 19. A spiral wound filtration element comprising: a central collection tube having at least one hole defined therein;at least one membrane envelope attached to the central collection tube and having two membrane sheets separated by a spacer, the at least one membrane envelope configured to be wrapped around the central collection tube to form a spiral; andat least one feed spacer disposed adjacent to at least one membrane sheet of the two membrane sheets when wrapped around the central collection tube and to create a channel to receive liquid to be filtered, the at least one feed spacer comprising a netting including: a first set of parallel strands extending in a first direction and including a plurality of first strands having a first thickness and a plurality of second strands having a second thickness that is smaller than the first thickness; anda second set of parallel strands extending in a second direction that is transverse to the first direction and including a plurality of third strands having a third thickness and a plurality of fourth strands having a fourth thickness that is smaller than the third thickness; wherein the first set of parallel strands and the second set of parallel strands form opposite faces of the at least one feed spacer; and wherein the thickness of the at least one feed spacer is not uniform, such that the at least one feed spacer is thickest where the first and third strands intersect, thinnest where the second and fourth strands intersect, and having an intermediate thickness where the first and fourth strands intersect and an intermediate thickness where the third and second strands intersect that is the same as the intermediate thickness where the first and forth strands intersect. 20. A spiral wound filtration element comprising: a central collection tube having at least one hole defined therein;at least one membrane envelope attached to the central collection tube and having two membrane sheets separated by a spacer, the at least one membrane envelope configured to be wrapped around the central collection tube to form a spiral; andat least one feed spacer configured to be disposed adjacent to at least one membrane sheet of the two membrane sheets when wrapped around the central collection tube and to create a channel to receive liquid to be filtered, the at least one feed spacer being capable of having a substantially planar shape which is rolled into a spiral orientation when inside the spiral wound filtration element, the at least one feed spacer comprising a netting including: a first set of parallel strands extending in a first direction and including a plurality of first strands having a first thickness and a plurality of second strands having a second thickness that is smaller than the first thickness anda second set of parallel strands extending in a second direction that is transverse to the first set of parallel strands, and including a plurality of third strands having a third thickness and a plurality of fourth strands having a fourth thickness that is smaller than the third thickness;wherein the first and third strands are fused to one another at fused areas at intervals along the at least one feed spacer, and the second and fourth strands are fused to one another at fused areas at intervals alternating diagonally with the first and third strands. 21. The spiral wound filtration element of claim 20, wherein the second and third strands are fused to one another at fused areas spaced at intervals and the first and fourth strands are fused to one another at fused areas spaced at intervals. 22. The spiral wound filtration element of claim 21, wherein the fused areas of the first and third strands; the fused areas of the second and fourth strands; and the fused areas of the first and fourth strands are all co-planar when the at least one feed spacer is unrolled. 23. The spiral wound filtration element of claim 20, wherein the first strands, second strands, third strands, and fourth strands are substantially linear in shape when the at least one feed spacer is unrolled; wherein at least one of the two membrane sheets forming the at least one membrane envelope make contact with the at least one feed spacer primarily along the first strands; and a second membrane sheet of the two membrane sheets makes contact with at least one feed spacer primarily along the third strands;wherein nodes where the first set of parallel strands and the second set of parallel strands of the at least one feed spacer meet have a first thickness which is less than or equal to the combined thickness of the first and third strands; and a second thickness equal to the combined thickness of the second and fourth strands. 24. The spiral wound filtration element of claim 20, wherein the first, second, third, and fourth strands are coextruded. 25. The spiral wound filtration element of claim 24, wherein the maximum thickness of the at least one feed spacer is less than or equal to the thickness of the first and third strands. 26. The spiral wound filtration element of claim 25, wherein the maximum thickness of the at least one feed spacer is twice the thickness of the first strands; and wherein the maximum thickness of the at least one feed spacer is approximately twice the thickness of the third strands. 27. The spiral wound filtration element of claim 20, wherein the highest surface on a first face of the at least one feed spacer is defined by the first strands; and the lowest surface on a second face of the at least one feed spacer is defined by the third strands. 28. The spiral wound filtration element of claim 1, the first strands having a first edge that is substantially even with the top of the at least one feed spacer when the at least one feed spacer is unrolled, but an opposite edge that is not substantially even with the bottom of the at least one feed spacer when the at least one feed spacer is unrolled; the third strands having a first edge that is substantially even with the bottom of the at least one feed spacer when the at least one feed spacer is unrolled, but an opposite edge that is not substantially even with the top of the at least one feed spacer when the at least one feed spacer is unrolled.