Device and method for removing water and carbon dioxide from a gas mixture using pressure swing adsorption
A pressure swing adsorption (PSA) dryer for separating water and carbon dioxide from a gas stream includes two compound adsorbent columns [ 32, 42 ]. Each column comprises a primary adsorption material for adsorbing water and a secondary adsorbent that adsorbs carbon dioxide. The secondary adsorbent comprises a solid amine. The secondary adsorbent may be, for example, a highly porous polystyrene matrix with amine groups bonded to the porous resin structure. Preferably, a mixture of the primary and secondary adsorbent materials forms an intermediate layer [ 38, 48 ] sandwiched between a top layer [ 34, 44 ] and bottom layer [ 36, 46 ] of pure water adsorbent material in each of the columns [ 32, 42].
1. A pressure swing adsorption (PSA) dryer comprising two adsorption columns, wherein each of the adsorption columns comprises a mixture of primary and secondary adsorbents, wherein the primary adsorbent adsorbs water and the secondary adsorbent adsorbs carbon dioxide, wherein the secondary adsorbent comprises a solid amine;
wherein the mixture is packed in the columns in three layers: a top layer, a bottom layer, and a middle layer sandwiched between the top layer and bottom layer,
wherein both the top layer and the bottom layer contain just primary adsorbent material, and wherein the middle layer contains a mixture of the primary and secondary adsorbent materials.
2. The PSA dryer of claim 1 wherein the secondary adsorbent comprises a macroporous, divinylbenzene-crosslinked polymer with benzylamine groups.
3. The PSA dryer of claim 1 wherein the secondary adsorbent comprises a porous polystyrene matrix with amine groups bonded to a porous resin structure.
4. The PSA dryer of claim 1 wherein a volume ratio of the primary adsorbent to the secondary adsorbent in the mixture is approximately 80% to 20%.
5. The PSA dryer of claim 1 wherein the mixture is inhomogeneously packed in the columns in stratified layers.
6. The PSA dryer of claim 1 wherein a volume ratio of the primary adsorbent to the secondary adsorbent in the middle layer is in the range 80:20 to 60:40.
7. The PSA dryer of claim 1 wherein a volume ratio of the middle layer to the top layer is approximately 60% to 20%, and a volume ratio of the middle layer to the bottom layer is approximately 60% to 20%.
8. A method for reducing the concentration of water and carbon dioxide in a gaseous stream using pressure swing adsorption, the method comprising:
a) passing the gaseous stream through a first adsorbent column to produce a dry flow having reduced water and carbon dioxide content;
b) dividing the dry flow into a product flow and a purge flow;
c) increasing the volume and decreasing the pressure of the purge flow to produce an expanded purge flow;
d) passing the expanded purge flow through a second adsorbent column to produce a moist exhaust flow having increased water and carbon dioxide content; and
e) reversing the direction of flow through the first and second adsorbent columns;
wherein each of the first and second adsorbent columns comprises a mixture of primary and secondary adsorbents, wherein the primary adsorbent adsorbs water and the secondary adsorbent adsorbs carbon dioxide, wherein the secondary adsorbent comprises a solid amine;
wherein the mixture is packed in the columns in three layers: a top layer, a bottom layer, and a middle layer sandwiched between the top layer and bottom layer,
wherein both the top layer and the bottom layer contain just primary adsorbent material, and wherein the middle layer contains a mixture of the primary and secondary adsorbent materials.
9. The method of claim 8 wherein the secondary adsorbent comprises a macroporous, divinylbenzene-crosslinked polymer with benzylamine groups.
10. The method of claim 8 wherein the secondary adsorbent comprises a porous polystyrene matrix with amine groups bonded to a porous resin structure.
11. The method of claim 8 wherein a volume ratio of the primary adsorbent to the secondary adsorbent in the mixture is approximately 80% to 20%.
12. The method of claim 8 wherein the mixture is inhomogeneously packed in the columns in stratified layers.
13. The method of claim 8 wherein a volume ratio of the primary adsorbent to the secondary adsorbent in the middle layer is in the range 80:20 to 60:40.
14. The method of claim 8 wherein a volume ratio of the middle layer to the top layer is approximately 60% to 20%, and a volume ratio of the middle layer to the bottom layer is approximately 60% to 20%.