Research Of Key Energy-saving And Life-enhancing Techniques For Large-scale Prebaked Aluminum Reduction Cells

Saving energy and increasing life of alumiunium reduction cells are the two research subjects which Chinese aluminium industry pays high attention to. With the support of a project of the National key Technology R&D Program and a project of the National Major Industrial Technology Development Program of China, new cathode and lining materials, cell structure and full-current cell stopping/starting equipment and techniques have been studied in this paper. Main innovations and achievements are as follows:(1) According to the characteristic of lining damage of aluminium reduction cells, a compressible structure of cathode lining was studied and designed, a new anti-electrolyte-penetration material of cathode lining—a kind of efficient anti-penetration brick, was developed and the technical conditions for its application was put forward. The industrial experiment shows that the cell life can be effectively prolonged by using the compressible lining material and structure.(2) A kind of400kA aluminium reduction cell with high energy efficiency has been developed and put into application. With the optimization of the design of physical fields of aluminium reduction cells and the use of ’double exhaust emision’ technics,’two-segment adverse current dry-purification’ technics and comprehensive automatic control techniques for the dry-puricication system, the following main technical and economic index have been achieved: Current intensity:400±10%kA; cell working voltage:<3.85V; DC energy consumption:<12328kWh/t-Al; gas collection efficiency:>99%; AE coefficient:≤0.015; total emision of fluoride:<0.6kg/t-Al; total emision of dust:<1.0kg/t-Al.(3) A ’quiet-flow-type’ structure of aluminium reduction cell was proposed. The cell with this structure leads the electric current to flow out of cathode vertically instead of horizontally, so as to reduce the horizontal current in molten aluminium layer to a large extent, lower the influence of electromagnetic forces on the melts in cells remarkably and weaken the flow and wave of molten aluminium. At the same time, a bus-bar scheme that can minimize magnetic field sufficiently was obtained through the optimization of bus-bar structure. By adopting this bus-bar scheme on400kA ’quiet-flow-type’ aluminium reduction cell, the maximum and average values of vertical magnetic flux density in the molten aluminium are8.93Gs and3.602Gs, respectively, much lower than that in common cells with the same scale, bringing the possibility of enhancing cell working stability, which creates conditions for the reduction of anode-cathode distance to a large degree and thereby brings condition for the saving of energy to a large extent.(4) A cell starting/stopping technique used under the condition of full current was developed and the corresponding equipment, consisting of a switch block device with separated units that can divide current at several points and run synchronizedly, a current partition device with variable resistance and so on was also developed. The application on more than forty potlines has proved that the technique thoroughly solves the problem of starting or stopping a cell under the condition of full current, avoiding the bad impact to rectifier and power network caused by the cutting off or cutting down of line current, improving the working stability of potline and thereby, bringing the benefit to increasing cell life and energy efficiency.