Patent ID: 7422675

Claim:
Process for changing an anode of a cell for the production of aluminum by fused bath electrolysis, the cell comprising a plurality of anodes, at least one cathode block, and containing an electrolytic bath, each of said anodes comprising at least one anode block and a metal rod and being fixed removably by mechanical attachment means to a mobile metal frame, each said anode block having a reference surface, comprising the steps of: establishing a reference line or plane using a beam of sound waves or electromagnetic waves; selecting a spent anode for replacement by a replacement anode; using at least one anode handling tool comprising a positioning device, a position sensor and a gripping device to grip the metal rod of the spent anode, and measuring with the position sensor a vertical distance A traveled by the gripping device in reaching a position in which the metal rod is gripped; withdrawing the spent anode from the electrolytic cell, passing the anode block of the spent anode vertically through the beam and measuring with the position sensor a vertical distance B traveled by the gripping device at a moment when a reference surface of the spent anode passes through the beam; gripping the metal rod of a replacement anode using a gripping device, passing the anode block of the replacement anode vertically through the beam and measuring with the position sensor a vertical distance C traveled by the gripping device at a moment when a reference surface of the replacement anode corresponding to the reference surface of the spent anode passes through the beam; and determining a desired vertical position of the replacement anode corresponding to the vertical position of the spent anode in the cell, from values obtained for the traveled distances A, B and C, and placing the replacement anode in the desired vertical position.