A rotary kiln has a rotatable cylinder through which a product passes in counter-current to a hot gas stream which dries the product. At the product entrance end, a vent annulus enters into the kiln for a length sufficient to allow entrained particles in the exhaust gas to either fall out within the rotating cylinder or pass through the annulus at a velocity sufficient to maintain their entrainment until discharge at a downstream location. Utilizing a vent annulus which enters into the kiln prevents entrained particles from becoming disentrained in the feed breech of the kiln which causes accumulation requiring periodic shut-downs for clean-outs which are disruptive of continuous operation. Utilizing the present invention incorporating a vent annulus in the rotary kiln minimizes down time and increases the efficiency and utilization of the rotary kiln. Additionally, the Separate vent annulus substantially simplifies the feed breech structure of the kiln simplifying construction.
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