Taking a 2.3 m×55 m carbon rotary kiln for example

numerical simulations were conducted on gas and solid spaces of the kiln by using Fluent and Matlab softwares. Through changing air pipe length and air flow of secondary and tertiary air

temperature field distributions and gas concentration distributions were obtained under different conditions. The results indicated that air pipe length had insignificant influence on kiln temperature

so air could be supplied without pipe in practical engineering to resolve the burning out of air pipe. When the length of air pipe equaled a specific value

kiln temperature was up to a higher temperature. At the same time

the concentration of the remaining combustible gas was lower under that condition. As the secondary and tertiary air flowed to the kiln outlet

the remaining combustible gas was higher at the kiln inlet

but the temperature of the calcining zone was higher

and the length of the calcining zone was longer.  Conversely

the remaining combustible gas was lower at the kiln inlet

the temperature of the calcining zone was lower

and the length of the calcining zone was shorter as the secondary and tertiary air flowed to the kiln inlet.