Patent ID: 8070921
Filing Date: 2011-12-06
Classification: C25C

Abstract:
1. A method for operating high-intensity electrolysis cells of the Hall-Héroult type for producing aluminium, the cells being successively arranged in one or more series, where a first electric current sustains the electrolysis process in each cell, this current being named the line current, where the arrangement of the line current passing through each individual cell reduces the unwanted magnetic field in the cell, acting as an internal compensation current (CCS,IC) and where a second, separate current is provided to compensate for the remaining unwanted magnetic field in each individual cell, where said second separate current is named external compensation current (CCS,EC), wherein the internal compensation current (CCS,IC) , has at least one component that is located outside the cell footprint, around at least one pot head of the cell, where the said component of the internal compensation current (CCS,IC) is between 5 and 25% of the line current, and that the arrangement and the balance between the internal compensation system (CCS,IC) and the external compensation system (CCS,EC), denoted as a combined compensation system (CCS), is further designed in a manner optimising the weight and the voltage drop of the electrical connection system in accordance with the following steps: I. CCS is applied when the compensation need, I II. if the inequality in step I. is fulfilled, then the amount of compensation current carried out with the internal compensation system (CCS,IC), around that pot head or both pot heads, is individually approximated to: III. the rest of the compensation need for that pot head or both pot heads, is carried out with an external compensation system (CCS,EC);