A process 15 wherein {TAIL ~ said furnace} is heated by {HEAD ~ radiant burners} that are fed with preheated air 
A process 15 wherein { TAIL ~ said furnace } is heated by { HEAD ~ radiant burners } that are fed with preheated air
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH