A method 6 wherein vapor employed as {HEAD ~ a heat source} is withdrawn at {TAIL ~ a point} of feed introduction 
A method 6 wherein vapor employed as { HEAD ~ a heat source } is withdrawn at { TAIL ~ a point } of feed introduction
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH