Anode dimension effect in aluminum electrolysis

May 01, 2023

Introduction of anode dimension effect in aluminum electrolysis
For the electrolytic aluminum production process, the anode is the "heart" of the electrolytic cell. It requires good anode quality to ensure the normal, stable and efficient operation of electrolytic production; However, the anode cost accounts for almost 10% ~ 15% of the production cost of electrolytic aluminum. Therefore, in order to save energy, reduce emission and reduce production cost, the anode size is very important for electrolytic aluminum production.
Prebaked anode has the advantages of producing little asphalt smoke and reducing its own voltage. However, due to the defects in the structure and process of prebaked anode aluminum electrolytic cell, it needs to replace the anode regularly to maintain the continuity of electrolytic production. Prebaked anode has the characteristics of residual electrode and regular replacement. When the height of the residual electrode is fixed, with the increase of the anode height, the residual electrode rate will decrease, the workload of anode assembly and anode replacement will be reduced, and the heat loss caused by opening the electrolyte shell due to anode replacement will also be relatively reduced. However, the higher the anode height, the better. With the increase of anode height, the conductive height and anode heat dissipation area will increase, thus increasing energy consumption.



Economic effect of anode dimension in aluminum electrolysis
The best anode height is the anode height with the lowest total anode cost for the production of molten aluminum in an anode change cycle. To determine the optimal anode height is to seek the balance point between the advantages and disadvantages of the anode in the process of increasing or decreasing from the perspective of economic benefits, so it is also called the economic height of the anode.

The basic cost of anode change cycle:
1) Purchase cost of anode carbon block;
2) The cost of electric energy consumed by the current passing through the anode;
3) The cost of electric energy consumed by the surface heat loss of carbon anode;
4) Costs of anode assembly process and anode replacement;
5) Residual recovery value.

Advantages of anode increase:
1) The anode gross consumption decreases with the increase of anode height;
2) The anode changing period increases with the increase of anode height, which can save the workload of labor and crown block or pole changing trolley;
3) Reduce the interference factors caused by pole change to the electrolytic cell;
4) Reduce the process cost of anode assembly workshop.

Disadvantages of high anode:

1) If the anode height is too high, the position of the upper metal structure will be raised, the anode bus stroke will be increased, the load will be increased, and the lifting mechanism, wear and failure probability will be increased;
2) As a result, the resistivity of the anode increases and the energy consumption increases, especially when the electricity price is high;
3) It makes it difficult for the insulation material on the anode side, which increases the heat loss of the new pole, especially for the electrolytic cell with narrow machining surface. Moreover, the insulation performance of high anode is worse than that of low anode block, resulting in increased energy consumption;
4) It affects the anode current distribution and prolongs the conduction time of the new electrode.

In short, the dimension of anode carbon block determines the pole changing cycle, which affects the labor consumption of pole changing operation, the gross consumption of anode, the voltage drop of anode itself, and the effect of anode heat dissipation and heat preservation.