How Does a Rotary Kiln Work?
How Rotary Kilns Work
A rotary kiln works by combining three forces: rotation, incline and heat. A long steel drum, set at a gentle slope, turns slowly on its axis while material is fed in at the higher end. The rotation tumbles and mixes the material, the incline urges it forward toward the lower discharge end, and a heat source raises the drum to its process temperature along the way.
Rotation, Incline and Residence Time
The slope and rotation speed together set the residence time, how long material spends inside the heated drum. Turn faster or steepen the incline and material moves through quicker; slow it down and it dwells longer. Matching these to the material’s heat-up and reaction profile is what makes the difference between a fully processed product and an under-cooked one.
Controlling the Atmosphere
How the kiln is heated decides the atmosphere. In a direct-fired kiln, combustion gases flow through the drum. In an indirect-fired kiln, the drum is sealed and heated through its shell, so the inside can be kept inert, which is essential for pyrolysis, where material must decompose without burning. This control of oxygen, alongside temperature and time, is what gives the kiln its flexibility.
Learn More:
See How a Kiln Fits Your Process
Klean Industries engineers rotary kilns to the rotation, incline and atmosphere each feedstock requires.
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