The rotary kiln burner is designed in accordance with the process requirements for the standard fuels coal dust, fuel oil and/or natural gas. Alternatively or parallel to these standard fuels, substitute fuels or special gases (e.g. blast furnace gas, carbonisation gas) can be used. The flame shape can be varied over a wide range of possibilities by altering the air/gas outlet cross section. This produces the required flame shape for the burning and sintering while ensuring environmentally compatible combustion.