A method 6 wherein vapor employed as a heat source is withdrawn at {HEAD ~ a point} of {TAIL ~ feed introduction} 
A method 6 wherein vapor employed as a heat source is withdrawn at { HEAD ~ a point } of { TAIL ~ feed introduction }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