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