Method for calcining carbonaceous materials

In a method for calcining carbonaceous materials comprising passing said carbonaceous materials through a rotary kiln and heating said carbonaceous material to a temperature sufficient to drive off volatile components of said carbonaceus material from said carbonaceous material the improvement comprising heating said rotary kiln to an operating temperature by means of an air-combustion fuel burner positioned at the lower end of said rotary kiln during start-up of said rotary kiln, impinging gaseous oxygen onto said carbonaceous material at said lower end of said rotary kiln when said rotary kiln has reached said operating temperature to agitate a portion of said carbonaceous material at said lower end of said rotary kiln and thereby ignite said portion of said carbonaceous material, burning said portion of said carbonaceous material to provide the necessary energy input to maintain said operating temperature in said rotary kiln and shutting down said air-combustion fuel burner when said rotary kiln has reached said operating temperature, whereby said oxygen completely replaces said air-combustion fuel burner after said start-up of said rotary kiln.