Rotary Kilns

Rotary kilns are rotating inclined cylindrical shaped furnaces that find application in the heating of solids to the point of chemical reaction either through the dry/wet process. Here, the rotating inclined cylinder is fired from one end for generating heat along its length.

These kilns are generally direct fired and come lined with refractory material for providing protection to steel shell as well as for achieving a reduction in radiation losses and in transferring heat to the material.


Working principle :

• All kilns work like heat exchangers where heat is transferred in different ways like through convection, radiation and conduction
• Different fuel types can be used to fire kiln including petroleum coke, ground coal, gasses, fuel oils
• With the rotation of kiln, the processed material travels towards discharge end

Design Features :

• Rotary kiln comprises cylindrical shell that comes in slightly inclined position and comes supported on two/more tyre stations that rest on supporting rollers
• Here, one tyre comes fixed axially through set of thrust rollers for countering thrust load during kiln movement and in turn preventing shifting of kiln from its axis
• Drum assembly along with tyres are rotated using girth gear & pinion arrangement
• Common prime movers used here include gear reducers that are used for reducing speed or increasing of the torque as required
• For compensating thermal expansion, girth gears are mounted on tangential spring plates that comes attached to shell
• Driving pinion comes mounted on output shaft of worm/helical gear unit
• Use of different types of bearings on kiln with high loads
• Shell diameter & length normally designed for suiting specific products and production capacities
• Suitable sealing arrangement is provided for preventing ambient air from entering process
• Suitable refractory lining is provided that provides working as high temperature & abrasive material wear resistant lining
• Firing system works as integral component of rotary kiln system and assists in optimizing combustion of fuels for releasing heat in kiln
• Dust Collection arrangement is of cyclone type and finds use as a pollution control measure

Applications :
Rotary kilns find wide application in production of -

• Cement
• Metals
• Construction materials
• Sponge iron
• Refractories
• Petroleum coke
• Alumina
• Gypsum