Annular kilns contain a concentric internal cylinder.

Pre-heated air is gathered from the cooling zone

  • The pre-heated air is used to pressurize the middle, annular zone of the kiln
  • Air spreading outward from the pressurized zone causes counter-current flow upwards, and co-current flow downwards
  • This produces a long, relatively cool calcining zone

Fuel consumption is in the range of 4 to 4,5 MJ/kg and the lime is typically medium burned.