CA2547055A1

CA2547055A1 - A method and equipment for positioning when replacing anodes in an electrolysis cell

Info

Publication number: CA2547055A1
Application number: CA002547055A
Authority: CA
Inventors: Arnt Helge Fidjeland
Original assignee: Individual
Current assignee: Norsk Hydro ASA
Priority date: 2003-11-26
Filing date: 2004-11-15
Publication date: 2005-06-09
Anticipated expiration: 2024-11-15
Also published as: CA2547055C; AU2004293726B2; RU2006122532A; ATE466973T1; ZA200604323B; RU2361968C2; DE602004027070D1; EP1689914A1; AR047316A1; EP1689914B1; BRPI0416999A; NO20035253D0; CN1898414B; AU2004293726A1; US20070214626A1; WO2005052217A1; NO319212B1; CN1898414A

Abstract

The present invention concerns a method and equipment for replacing anodes in an electrolysis cell in which a crane with an anode gripper is used to lift out used anodes and to insert new anodes. The new anode is inserted at a height in accordance with a calculated height based on the height of the anode removed, the height of the anode removed and the height of the new anode being measured against a common reference level. Laser-based measuring equipment is arranged between a point on the crane, which is stationary in terms of height during the operation, and a point on the anode gripper, which moves together with the anode, and measures the heights stated. The measured values are processed by a PLC-based system, which determines a more precise insertion height of the new anode in accordance with a specific algorithm.

Claims

1. A method for positioning when replacing anodes in an electrolysis cell of Hall-Héroult type with prebaked anodes,in which a crane with an anode gripper is used to lift out used anodes and to insert new anodes, the gripper act in a predetermined, fixed point in the hanger of the anodes, and in which a new anode is inserted at a height in accordance with a calculated height based on the height of the anode removed, the height of the anode removed and the height of the new anode being measured against a common reference level, characterised in that laser-based measuring equipment for length measurements is arranged between a point on the crane, which is stationary in terms of height during the operation, and a point on the anode gripper, which moves together with the anode, that the equipment measures the heights stated and that the measured values are processed by a PLC-based system, which determines the insertion height of the new anode in accordance with a specific algorithm.

2. A method in accordance with claim 1, characterised in that the algorithm comprises the following formula:
D=A-B+C-X, where:
D is the desired position of the new anode.
A is the position of the used anode in the cell.
B is the position of the used anode on the reference level.
C is the position of the new anode on the same reference level.
X is the additional height for insertion of the new anode in relation to the used anode.

3. A method in accordance with claim 1, characterised in that, before the height stated is measured, play is eliminated in the anode gripper and connected mechanical structures in the crane by the anode gripper being subjected to a first lifting force that is less than the weight of the burned-out anode.

4. Equipment for positioning when replacing anodes in an electrolysis cell of Hall-Héroult type with prebaked anodes, comprising a crane with an anode gripper to lift out used anodes and to insert new anodes, the gripper acts in a predefined point of the anode's hanger, with which a new anode is inserted at a height in accordance with a calculated height based on the height of the anode removed, the height of the anode removed and the height of the new anode being measured against a common reference level, characterised in that laser-based measuring equipment for length measurements is arranged between a point on the crane, which is stationary in terms of height during the operation, and a point on the anode gripper, which moves together with the anode, and that the equipment measures the heights stated and transfers the data signals to a PLC, which processes measured, saved values and determines the insertion height of the new anode in accordance with a specific algorithm.

5. Equipment in accordance with claim 4, characterised in that the laser-based measuring equipment comprises a laser cell, which both emits laser light and detects reflected laser light and which is mounted at a location that is stationary in terms of height on the crane and that a reflective device for reflection of the laser light is mounted on the anode gripper.

6. Equipment in accordance with claim 5, characterised in that the laser cell is contained in a dust-tight cabinet with a downward-facing opening, to which is attached a tube through which the laser light passes.

7. Equipment in accordance with claim 6, characterised in that the cabinet is supplied with compressed air to establish air overpressure so that dust cannot reach up into the cabinet via the tube.

8. Equipment in accordance with claim 7, characterised in that the PLC is arranged so that the measured values transferred are stored and processed after interlocking to eliminate play.

9. Equipment in accordance with claim 8, characterised in that the interlocking involves the anode gripper being subjected to a lifting force equivalent to 60-70% of the weight of the anode, and that this must be applied for at least 2 seconds before the measurement can be stored.

10. Equipment in accordance with claims 8-9, characterised in that a display, a light signal or similar visualises the completion of the sequence in accordance with the method and interlocking specified, and that measured values are saved in accordance with this.