The invention discloses an air supply device. The air supply device comprises an air blowing device, a furnace body and a gas supply system; the air blowing device is connected with the furnace body; the gas supply system is arranged on one side of the furnace body; a charging device is arranged at the top end of the furnace body; a coke layer is arranged in the furnace body; a discharge device is arranged on the side lower side of the furnace body; a gas supply system is arranged on the side upper side of the furnace body, and is respectively connected with the upper end and the lower end of the furnace body through gas guide pipes; a dispersing valve, a dust remover and a cooling device are arranged on one side of the furnace body; an exhaust port is formed in the lower end of the cooling device; the coke layer is arranged in the furnace body; the air blowing device uses air blown out through an exhaust nozzle for removing oxygen in waste gas by the coke layer to reduce pyrolysis of hydrocarbon so as to improve safety; and inert gas supplied by the gas supply system is matched to prevent oxidation of molten melt so as to guarantee the product quality.