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When it comes to thermal processing, how do you know if you need a rotary kiln, or a rotary dryer? Though these two products share similar thermal processing principles, they are used in very different applications. While rotary kilns can dry a product, their main concern is not in drying, but simply heating.
Rotary dryers are almost always used for drawing moisture out of a material.
Typically, they operate at temperatures between 800º – 1400ºF. Rotary kilns, however, are concerned with causing a chemical reaction. Therefore, they need to operate at much higher temperatures, between 1000º – 3000º.
Rotary Kilns are designed to withstand much higher temperatures than a rotary dryer.
Typically, if you are dealing with a direct fired rotary kiln, it is refractory lined with a brick or castable lining. This lining protects the steel shell. Rotary dryers are typically not lined, and their steel is not able to withstand such high temperatures. If you are dealing with an indirect rotary kiln, the kiln is not normally lined, so the shell of the drum has to be made out of a temperature resistant alloy instead of steel.
Whether you need a rotary kiln or a rotary dryer is all dependent on what you are trying to do with your material. Are you simply looking to dry your material via thermal processing, or are you trying to cause a thermally-driven chemical reaction? The difference between a rotary dryer and a rotary kiln is simple: a rotary dryer will dry your material, and a rotary kiln will heat it up to cause a chemical reaction.