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