An apparatus 30, wherein said mechanism for regenerating the first adsorbent bed comprises {HEAD ~ a mechanism} for passing {TAIL ~ a regeneration gas} through the bed 
for passing
An apparatus 30 , wherein said mechanism for regenerating the first adsorbent bed comprises { HEAD ~ a mechanism } for passing { TAIL ~ a regeneration gas } through the bed
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH