A cathode structure for reducing precipitation in aluminum electrolytic cell

Abstract

A cathode structure for reducing the formation of aluminum electrolytic cell precipitation, which is composed of a cathode group and a boss above it, and the boss is formed by the upper part of the boss and the lower part of the boss to form an integrated structure; The gap between the two anodes is the longitudinal middle slot, the gap between the two rows of anodes is the horizontal middle slot, and the intersection of the horizontal middle slot and the longitudinal middle slot is the feeding area; the top surface of the upper part of the boss is opposite to the feeding area, and the upper part of the boss is located at The middle of the top surface of the lower part of the boss. The cathode structure of the present invention prevents the lower precipitation from reaching the bottom of the aluminum liquid, and the precipitation is at the electrolyte-aluminum liquid interface and its vicinity, and the precipitation is dissolved through the action of melt fluid mechanics and interface reaction; the generation of insoluble precipitation at the cathode is avoided, and the cathode is reduced. Uneven wear.

Description

technical field [0001] The invention belongs to the technical field of aluminum electrolysis, in particular to a cathode structure for reducing precipitation in an aluminum electrolytic cell. Background technique [0002] As the only process for commercial aluminum smelting, since the Hall-Elut process was commercialized in the 20th century, the voltage of the aluminum electrolytic cell has been continuously reduced, and the current efficiency has been gradually increased, which has reduced the energy consumption of aluminum electrolysis. During the production process of aluminum electrolysis, the surface of the cathode of the electrolytic cell will gradually accumulate precipitation with high resistance, which not only increases the pressure drop at the bottom of the furnace, but also increases the horizontal current in the aluminum liquid, enhances the fluctuation of the aluminum liquid, reduces the current efficiency, and finally makes the The energy consumption of alumin...

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Problems solved by technology

[0005] The precipitate is first formed in the electrolyte below the feeder, and gradually accumulates at the electrolyte-aluminum liquid interface and passes through the aluminum liquid to reach the cathode surface. At this time, the precipitate is located under the middle slot of the electrolytic cell; The influence is small, but with the flow of aluminum liquid, the sediment below the slot in the electrolytic tank will move to both sides of the tank, because the resistivity of the precipitate is about 0.001Ω·m, which is about twice the resistivity of the electrolyte, which is the same as that of molten aluminum. 35,000 times of that, so that the current flows horizontally to the edge of the precipitation, and the aluminum liquid above the precipitation forms a horizontal current. Such a horizontal current interferes with the vertical current of the electrolysis, and generates an electromagnetic force under the vertical magnetic field to cause electrolysis instability; on the other hand, The precipitation prevents the aluminum liquid from corroding the cathode under the precipitation, but due to the high resistivity of the precipitation itself, the distribution of the current density of the cathode around it is too high, which aggravates the wear, which causes uneven wear on the entire cathode surface and reduces the cathode wear. life span

[0006] The incompletely dissolved alumina in the electrolyte below the discharge port combines with the electrolyte to form a precipitate, and sinks under the action of gravity to reach the electrolyte-liquid aluminum interface. At this time, the density of the precipitate is small, but as time goes by, the precipitate accumulates and eventually wears out. Passing through the aluminum liquid to reach the surface of the cathode; compared with the precipitation on the cathode surface, the precipitation at the electrolyte-liquid aluminum interface is easier to dissolve, because: 1) The precipitation at the electrolyte-liquid aluminum interface can still flow back into the electrolyte through the fluid flow in the electrolytic cell for redissolution 2) The eutectic point of alumina and the electrolyte is 962.5°C, and the lower temperature is not conducive to the dissolution of the cathode surface precipitation due to the large heat loss at the bottom of the electrolytic cell; 3) Due to the Without the presence of electrolyte, the precipitation on the surface of the cathode is difficult to contact with the electrolyte and redissolved

[0007] There are many ways to reduce precipitation, such as increasing the degree of superheat to promote the dissolution of aluminum oxide in the electrolyte to reduce precipitation, but this method will cause energy consumption and when the superheat is too high, it will cause the inner wall of the electrolytic cell to become thinner. Potential safety hazard; it is also a feasible method to reduce precipitation by changing the electrolyte composition, such as increasing the molecular ratio, but in actual production, the electrolyte composition in the electrolyzer is relatively stable, and changing the electrolyte composition will bring cost problems

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