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