Two Types Of Rotary Kilns
A rotary kiln is used in thermal processing applications in industrial settings. The machine functions by heating solids to a particular temperature in order to produce the desired physical and/or chemical reaction. Rotary kilns are used to process different types of materials such as waste products down to high-value minerals.
There are two major types of rotary kilns; one is the direct fired rotary kiln and indirect fired rotary kiln. Both types are applied with the same thermal processing disciplines but they differ in the way heat is introduced into materials. The two types of rotary kilns are used for two different applications.
- Direct Fired Rotary Kiln
Direct fired rotary kiln works by pushing the heat through the interior of the kiln. The material comes in direct contact with the heat source. This is how the name of the variation was obtained. This type of rotary kiln is generally used for heat transfers and pyroprocessing applications. It is also used in metal recovery and waste combustion to process waste products such as products that contain nickel. Some of these products are electronic gadgets like cellular phones, tablets and its batteries, among others. These electronic wastes contain a certain amount of nickel, which is a type of valuable mineral. To recover this mineral, the waste product is oxidized or burned with a rotary kiln using direct fire to remove the organic materials and leave behind ash and the sought-after nickel content. With an effective recovery process, nickel contents are recycled and reused in other forms.
- Indirect Fired Rotary Kiln
Indirect fired rotary kiln is also called a calciner. It is used for materials that cannot be subjected to direct contact with combustion gases. The temperature of indirect fired rotary kiln is controlled externally. The heat is applied to the material from the outside of the machine using a gas burner or an electric heater. With this, the material is protected from direct contact from the heat source. The temperature of indirect fired type can be closely monitored and controlled making the desired result more achievable than the other type.