The packaged, compressed or flattened cans are first processed into fragments of about 4 cm by a shredder, and then added to the drum of the continuous carbonization furnace through a spiral feeder. Because the furnace is almost a closed space, it meets the anaerobic conditions, so that the cans are pyrolyzed and carbonized at a temperature of more than 400 degrees inside the carbonization furnace. The generated flue gas passes through the recovery pipeline, the flue gas purification system, and then to the burner to heat the main furnace, achieving the effect of reciprocating heating and carbonization. During the initial carbonization preheating, the surface paint of the cans begins to carbonize and pyrolyze, and the pyrolysis produces combustible gas to achieve normal combustion, gas circulation combustion and no flue gas discharge. The normal production state, finally obtaining pure aluminum.