The powdered or granulated feed material is melted in a rotary drum furnace, where the drum is in a lying position. Due to their construction and their high operational flexibility, rotary drum furnaces are particularly suitable for inhomogeneous starting materials. For this reason, they are often used to melt recycled starting materials such as batteries or valuable lead-containing materials. There is a difference between stationary and tiltable rotary drum furnaces. Fundamentally, environmental regulations stipulate whether the rotary drum furnace can be operated with soda slag at process temperatures of approx. 900 °C or with a silicate slag at up to 1200 °C. Energy input is through burners mounted on the front of the drum.
In the case of stationary rotary furnaces, the metal and slag is removed via spouts. With tiltable rotary furnaces the entire furnace is lifted hydraulically and metal and slag is tapped at the feed opening. The required energy input is carried out with burner systems such as Oxyfuel.