It is a characteristic feature of the invention that the air fed to at least one air level is preheated by using vapor generated in {HEAD ~ the concentration} of {TAIL ~ the black liquor} as heat source 
of
It is a characteristic feature of the invention that the air fed to at least one air level is preheated by using vapor generated in { HEAD ~ the concentration } of { TAIL ~ the black liquor } as heat source
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH