A post-combustion lance for use in refining molten metal and recovering heat by combustion of combustible gases evolved from the molten metal bath is provided with a plurality of pairs of post-combustion nozzles arranged about the periphery of the lance above the lower end thereof. The nozzles of each pair are directed downwardly toward the lower end of the lance and at an angle to a radius of the lance, such that supersonic oxygen jets emanating from corresponding nozzles of adjacent pairs intersect, whereby the momentum of the individual supersonic jets is partially cancelled thereby forming a single, subsonic oxygen jet which burns combustible off-gases above the surface of the molten metal bath, reducing heat loss by the anti-post-combustion reaction and minimizes furnace lining wear due to shorter flames.