Tailings are recycled back into the reactor and combined with {HEAD ~ fresh feed} for {TAIL ~ bubble control} 
for
Tailings are recycled back into the reactor and combined with { HEAD ~ fresh feed } for { TAIL ~ bubble control }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL