{HEAD ~ A reactor} enclosed in {TAIL ~ a pressure vessel} in a manner that the walls of the pressure vessel are thermally insulated and chemically isolated from the harsh environment of the reaction zone in the reactor 
enclosed in
{ HEAD ~ A reactor } enclosed in { TAIL ~ a pressure vessel } in a manner that the walls of the pressure vessel are thermally insulated and chemically isolated from the harsh environment of the reaction zone in the reactor
HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH