Material efficiency and fabrication of membrane elements
Membrane elements that use multiple membrane leaves may have a limited total active membrane area due to an increased diameter at the ends of the element. Membrane leaves may comprise a permeate carrier positioned between one or more membrane sheets. Adhesive may be used to seal one or more edges of the membrane leaf. The membrane sheets, permeate carrier and the adhesive contribute to the thickness of the edges of the membrane leaf and the diameter at the ends of the element. A reduced thickness of the edges of the permeate carrier may reduce the diameter at the ends of an element. Another permeate carrier sheet may also be used that is distanced from at least one edge of the membrane sheet so the permeate carrier sheet does not contribute towards the increased diameter at the ends of the element.
1. A spiral wound membrane element comprising:
a) a central tube; and
b) at least one membrane leaf comprising a permeate carrier and at least one membrane sheet, wherein the at least one membrane sheet is sealed at an edge and the permeate carrier is positioned within the at least one membrane sheet with a side edge of the permeate carrier distanced from an associated side edge of the at least one membrane sheet, wherein the side edge of the permeate carrier is distanced between about 5.0 cm and 10 cm from the associated side edge of the at least one membrane sheet,
wherein the at least one membrane leaf includes an open edge that is in fluid communication with the central tube, and
wherein the at least one membrane leaf is wrapped around the central tube in at least a one to one relationship with a feed spacer sheet.
2. The spiral wound membrane element of claim 1 , wherein the side edge of the permeate carrier is distanced between about 5.0 cm and 7.5 cm from the associated side edge of the at least one membrane sheet.
3. The spiral wound membrane element of claim 1 , wherein the permeate carrier is sealed to the at least one membrane sheet.
4. The spiral wound membrane element of claim 3 , wherein the permeate carrier is sealed to the at least one membrane sheet by an adhesive that penetrates into the side edge of the permeate carrier.
5. The spiral wound membrane element of claim 4 , wherein the adhesive penetrates at least 0.254 cm into the side edge of the permeate carrier.
6. The spiral wound membrane element of claim 5 , wherein the adhesive penetrates into the side edge of the permeate carrier between about 0.635 cm to 2.54 cm.
7. The spiral wound membrane element of claim 1 , wherein the at least one membrane leaf includes a sealed distal edge that is opposite to the open edge, wherein the sealed distal edge is distanced from an associated distal edge of the at least one membrane sheet.
8. The spiral wound membrane element of claim 1 , wherein the feed spacer sheet is at least 7.87×10 −2 cm thick.
9. The spiral wound membrane element of claim 1 , wherein the feed spacer sheet is between about 8.13×10 −2 cm to 8.89×10 −2 cm thick.