The hot air supplied from the burner is directly proportional with the amount of the material which is fed to the vertical kiln. The material is mixed by means of mixer blades (agitator) in the mixing unit at the bottom of the machine. The purpose of the mixing unit is preventing the occlusion and clogging of the material during discharging from the outlet port. The agitator is mainly important for the kiln start-up as it puts the material inside kiln in motion. However once the kiln is started the material flows by itself under gravity.