GB557262A - An improved furnace for the electrical melting and/or heating of aluminium and alloys thereof, and for the recovery of the metal from aluminium dross residues - Google Patents

Abstract

557,262. Melting aluminium and aluminium alloy. BIRMINGHAM ALUMINIUM CASTING (1903) CO., Ltd., PRITCHARD, P., and TAYLOR, G. O. April 10, 1942, No. 4721. [Class 82 (i)] [Also in Groups XI and XXXVI] Aluminium and its alloys are melted in contact with a fused mixture of salts heated by the passage of alternating current, said mixture containing cryolite to dissolve alumina and being of lower density than the metal. A furnace chamber d of magnesite is surrounded by sand c, heat insulation b and a steel casing a, and has a graphite sole plate e with a tap-hole h, and an annular electrode or plurality of electrodes i to which alternating current can be supplied. Additional electrodes p, m are provided in a recess in the upper part of the furnace and are connected to a direct current supply whereby alumina dissolved in the cryolite is electrolysed and prevented from accumulating and being deposited therefrom. Liberated aluminium falls from electrode p to the bottom of the furnace. In operation, molten electrolyte is charged into the furnace above the electrode i and is kept molten by the passage of current, or the molten bath may be gradually accumulated and melted by additional electrodes above the sole e until it reaches the upper electrode i. The electrolyte may be sodium chloride 60 parts and cryolite 40 parts; or sodium chloride 60 parts, potassium chloride 30 parts, and cryolite 10 parts. Metal to be melted is placed on a grid k, and on melting falls to the bottom. In a modification Fig. 2 (not shown), the heating electrodes are arranged in opposite walls, and the metal is charged on to a sloping hearth instead of a grid.