{HEAD ~ The invention} is characterized by {TAIL ~ a secondary separation zone} located in the inner free space between the upper and lower walls and the primary separation devices 
is characterized by
{ HEAD ~ The invention } is characterized by { TAIL ~ a secondary separation zone } located in the inner free space between the upper and lower walls and the primary separation devices
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH