{HEAD ~ The purity} of the gas product stream or sales gas product is achieved by controlling {TAIL ~ a reflux stream} returned to a purification zone 
is achieved by controlling
{ HEAD ~ The purity } of the gas product stream or sales gas product is achieved by controlling { TAIL ~ a reflux stream } returned to a purification zone
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH