{HEAD ~ Channel} shaped fluid bed devices, preferably subdivided into {TAIL ~ several zones}, are preferred 
{ HEAD ~ Channel } shaped fluid bed devices , preferably subdivided into { TAIL ~ several zones } , are preferred
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH