{HEAD ~ The reactor} is {TAIL ~ a bubble/particle contacting device} where collection takes place while bubbles are being formed 
{ HEAD ~ The reactor } is { TAIL ~ a bubble / particle contacting device } where collection takes place while bubbles are being formed
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH