Method of burning or sintering fine-grain material

Claim 1

In a method of burning or sintering fine-grained material, such as cement raw meal, lime, dolomite, magnesite or hydrate of alumina, which agglomerates above a critical temperature wherein a gas-carried flow of material is passed successively through a preheating zone, a final heating zone wherein the material is heated to a final treatment temperature higher than said critical temperature by passing a flame, and a separation-cooling zone wherein the material is separated from the hot exhaust gases of said final heating zone and the separated hot exhaust gases are conducted to said preheating zone to preheat material therein; the improvement comprising the steps of introducing material into an elevated portion of said preheating zone to cause said introduced material to fall downwardly through said zone, and introducing the exhaust gases from said final heating zone into a lower portion of said preheating zone in an upwardly directed stream establishing an upwardly directed flow operable to carry the introduced material upwardly through said preheating zone to an elevated discharge opening, the path of said material through said preheating zone including a downwardly directed section and an upwardly directed section and supplementing the preheating of said material by said exhaust gases by adding heat to said preheating zone at a location traversed by both the upward and downward sections of said path to supply enough additional heat to said preheating zone to heat the material therein to a temperature less than said critical temperature but high enough to enable the material to be heated to said final temperature during transmit of said final heating zone.