ANS:C - rotary

A rotary dryer is a type of industrial dryer commonly used for continuous drying of granular or crystalline materials. It consists of a cylindrical drum or shell that rotates around its axis, usually inclined slightly to facilitate the movement of the material through the dryer. Here's how it typically works:

1. Loading: The material to be dried is fed into one end of the rotary dryer.
2. Heat Source: Heat is applied to the drum either directly or indirectly. In direct rotary dryers, hot gases or heated air are passed through the drum, coming into direct contact with the material. In indirect rotary dryers, heat is transferred to the material through the drum shell via conduction.
3. Rotation: The drum rotates slowly, causing the material to tumble and move along the length of the drum. This tumbling action ensures that the material is evenly exposed to the heat, promoting efficient drying.
4. Drying: As the material moves through the rotating drum and is exposed to the heat source, moisture is evaporated from the material, resulting in dried product.
5. Discharge: Once the material reaches the other end of the drum, it is typically discharged from the dryer. The dried product may then undergo further processing or be packaged for distribution.

Rotary dryers are favored for their high throughput capacity, continuous operation, and ability to handle a wide range of materials and moisture contents. They are commonly used in industries such as agriculture (for drying grains), mining (for drying ores and concentrates), and chemical processing (for drying various chemicals and minerals).