Spiral wound gas separation membrane module

1. A gas separation module comprising one or more gas separation elements, said elements comprising at least two membrane sheets and a permeate carrier sandwiched between the membrane sheets, wherein the contact area of the membrane sheets with the permeate carrier is less than 50%, wherein:

(i) the permeate carrier comprises at least two macroporous layers and a gas impermeable sheet located between the two macroporous layers; and

(ii) the contact area is as determined before use by forming a membrane sheet—permeate carrier laminate using a laminator, peeling off the membrane sheets and determining the contact area by performing measurements using a microscope.

2. The gas separation module according to claim 1 wherein the contact area is less than 45%.

3. The gas separation module according to claim 1 being a spiral wound gas separation module.

4. The gas separation module according to claim 1 wherein the membrane sheets and/or the permeate carrier have a surface profile which causes the contact area of claim 1 .

5. The gas separation module according to claim 1 wherein the membrane sheets and/or the permeate carrier have a surface profile comprising surface projections.

6. The gas separation module according to claim 5 wherein the surface projections comprise ribs and/or grooves.

7. The gas separation module according to claim 1 wherein the permeate carrier comprises a knitted fabric.

8. The gas separation module according to claim 1 wherein the gas impermeable sheet has a thickness of less than 0.1 cm.

9. The gas separation module according to claim 1 wherein at least one of the gas separation elements reduces in thickness by <25% when it is subjected to a pressure of 7 million Pascal for 5 hours.

10. The gas separation module according to claim 1 which further comprises a central tube and the one or more gas separation elements are wound around that tube and are in gas communication therewith.

11. The gas separation module according to claim 1 wherein the gas separation elements are fixed to the central tube such that gas which permeates through the membrane sheets can flow through the permeate carrier and into the central tube but gas which does not permeate through the membrane sheets cannot enter the central tube.

12. The gas separation module according to claim 1 which comprises two or more gas separation elements and a feed spacer screen located between the gas separation elements.

13. A process for separating gases and/or purifying a feed gas comprising at least two different gaseous components comprising passing the feed gas through a module according to claim 1 such that feed gas is separated into a permeate gas and a retentate gas, one of which is enriched in at least one of the said gaseous components and one of which is depleted in at least one of the said gaseous components.

14. The gas separation module according to claim 1 wherein the membrane sheets and/or the permeate carrier have a surface profile comprising surface projections which causes the contact area of the membrane sheets with the permeate carrier to be than 45%.

15. The gas separation module according to claim 14 being a spiral wound gas separation module.

16. The gas separation module according to claim 1 wherein (i) the permeate carrier comprises at least two macroporous layers and a gas impermeable sheet located between the two macroporous layers; (ii) the gas separation elements are fixed to a central tube such that gas which permeates through the membrane sheets can flow through the permeate carrier and into the central tube but gas which does not permeate through the membrane sheets cannot enter the central tube; and (iii) the membrane sheets and/or the permeate carrier have a surface profile comprising surface projections which cause the contact area of the membrane sheets with the permeate carrier to be less than 45%.

17. The gas separation module according to claim 16 wherein the gas impermeable sheet has a thickness of less than 0.1 cm.

18. A process for separating gases and/or purifying a feed gas comprising at least two different gaseous components comprising passing the feed gas through a module according to claim 16 such that feed gas is separated into a permeate gas and a retentate gas, one of which is enriched in at least one of the said gaseous components and one of which is depleted in at least one of the said gaseous components.