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 {TAIL ~ the concentration} of the black liquor as {HEAD ~ heat source} 
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 { TAIL ~ the concentration } of the black liquor as { HEAD ~ 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 TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD