| 摘要 |
A process for drying and/or calcining bulk material in a rotary kiln when hot gases are passed countercurrent to the flow of bulk material thereto, and the bulk material is dried and/or calcined in the rotary kiln is disclosed. According to the invention, the bulk material is dried and/or calcined, as it passes from the feed end of the rotary kiln to the discharge end thereof, by contacting the same with hot gases and thereafter, as the bulk material passes towards the discharge end of the rotary kiln, the bulk material is heated by indirect heat exchange with such hot gases. An apparatus for carrying out such process is also disclosed. The apparatus is a rotary kiln equipped with a centrally disposed tube, disposed axially within the rotary kiln toward the bulk material discharge end of the rotary kiln whereby an annular space is defined between the outer wall of the central tube and inner wall of the rotary kiln. The apparatus is equipped with means for passing hot gases within the central tube, means for passing bulk material on the outer wall of the central tube whereby the bulk material can be heated by indirect heat exchange with hot gases within the tube.
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