PURPOSE: To center the flow of high temp. gas and to apply effectively heat to the briquettes in a pipe by feeding the coke-contg. bauxite briquettes through a center feed pipe to the high temp. region at the top end of a raceway and charging coke on the circumferential wall side.

CONSTITUTION: The coke in a coke bunker 16 is supplied successively through a coke feed port 15 into the position in proximity to the furnace wall in a furnace mouth part 14 and forms a conical pile, from which the coke flows into the upper part of a raceway 3 and reacts with the O2 from a tuyere 2, thus forming high temp. gas. Since the high temp. gas has the smaller pressure drop in the central part of the furnace than in the wall part thereof, the gas is easier to rise along a center feed pipe 4 at the center. On the other hand, the coke-contg. bauxite briquettes or aluminum ores in a briquette bunker 5 are preheated by the high temp. gas ascending through many small holes of the pipe 4 during falling in the pipe 4 and are reduced in the bottom end part of the pipe 4, by which the ores are made into a crude Al alloy. Said alloy drops onto a furnace bottom 24 without passing through the inside of the raceway 3.