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