A process for heating a molten material by injecting oxygen and a fuel into a molten bath of the material at a bath temperature above the spontaneous combustion temperature of the fuel, at least a portion of the fuel forming a shroud around the oxygen, and combusting the fuel to provide heat to the molten material. Where the molten material is impure copper the amount of oxygen and fuel injected may also be controlled to alternately oxidize and reduce the copper impurities and remove them from the bath. Solid material may be melted in the bath during any stage of heating or refining. In a preferred embodiment, a portion of the fuel forms a shroud around the oxygen during injection, and the oxygen forms a shroud around the remaining fuel. |