Guard layers for rapid cycle pressure swing adsorption devices
Guard layers are employed in the adsorbent beds of rapid cycle pressure swing adsorption (RCPSA) devices to protect the adsorbent therein from certain contaminants (e.g. water vapour). Conventional PSA devices typically pack the guard layer with as much guard material as is practical. In RCPSA devices however, the performance of the guard layer can be improved by using a reduced amount of guard material and increasing access to it. Such embodiments are characterized by guard layers with a channel fraction of greater than 50%.
1. An adsorption bed for a rapid cycle pressure swing adsorption (RCPSA) device comprising a guard layer at the feed end of the bed, the guard layer comprising a laminate sheet comprising a guard adsorbent, wherein the channel fraction of the guard layer is greater than 50%.
2. The adsorption bed of claim 1 wherein the channel fraction of the guard layer is between 50% and 75%.
3. The adsorption bed of claim 1 wherein the guard adsorbent is a dessicant.
4. The adsorption bed of claim 3 wherein the dessicant is activated alumina.
5. The adsorption bed of claim 1 wherein the thickness of the laminate sheet is between about 5 and 200 micrometers.
6. The adsorption bed of claim 1 wherein the surface area of the laminate sheet divided by guard layer volume is greater than about 5000 square meters per cubic meter.
7. The adsorption bed of claim 1 wherein the surface of the laminate sheet is textured thereby introducing a surface void to the laminate sheet.
8. The adsorption bed of claim 7 wherein the surface void is between about 20 and 50%.
9. The adsorption bed of claim 7 wherein the laminate sheet comprises a wire mesh.
10. The adsorption bed of claim 1 wherein the guard layer is a spiral winding of the laminate sheet and a spacer sheet comprising a wire mesh.
11. A rapid cycle pressure swing adsorption (RCPSA) device comprising at least one adsorption bed of claim 1 .
12. A method of protecting the beds in a RCPSA device against contamination, the RCPSA device comprising at least one adsorption bed and a guard layer at the feed end of the bed, and the guard layer comprising a laminate sheet comprising a guard adsorbent, wherein the method comprises employing a channel fraction in the guard layer of greater than 50%.
13. The method of claim 12 wherein the contaminant is water.
14. The method of claim 12 wherein the cycle speed of the operating RCPSA device is greater than about 5 cycles per minute.
15. The method of claim 12 comprising texturing the surface of the laminate sheet.
16. The method of claim 15 wherein the texturing comprises coating a wire mesh with a low solids content slurry.
17. The method of claim 12 wherein the guard layer is a spiral winding of the laminate sheet and a spacer sheet and the method comprises employing a wire mesh for the spacer sheet.