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