RU2659512C1 - Method for extinguishing of anode effect in an aluminum electrolytic cell - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to the production of aluminum in electrolytic cells with burned anodes. Method comprises supplying an air-aluminous mixture for 5÷60 s at an angle of 3 to 10° relative to the anode at a ratio of alumina and compressed air of 1:0.1÷0.15.

EFFECT: extinguishing of anode effect is ensured.

1 cl, 1 dwg

Description

The invention relates to the production of aluminum in electrolyzers with a baked anode and can be used to dampen the anode effect resulting from the depletion of the concentration of alumina in the electrolyte.

A known method of automatically suppressing the anode effect in an aluminum electrolysis cell, comprising alternately supplying gas to two vertical channels in the body of the anode, with a frequency of 1-4 Hz [A.S. USSR No. 1610935, publ. 08/27/1996].

The disadvantage of this method is the risk of transferring electrolyte droplets into the liquid aluminum layer, which can lead to a decrease in current efficiency, as well as the need for additional equipment of the electrolyzer with a gas supply system.

A known method of damping the anode effect with compressed air supplied tangentially to the sole of the anode [A.S. USSR No. 341868, publ. 06/14/1972]. The disadvantage of this method is to increase the consumption of the anode due to its oxidation by compressed air.

The closest analogue is the method of quenching the anode effect by introducing under the sole of the anode a mixture of salts - alumina and cryolite, in a jet of carrier gas [SU No. 1216253, publ. 03/07/1986]. The disadvantage of this method is the introduction of additional cryolite into the electrolyte with a depleted concentration of alumina.

The task of the invention is the provision of quick and effective damping of the anode effects that occur in an aluminum electrolyzer.

This is achieved by the fact that in the method of quenching the anode effect in an aluminum electrolysis cell, comprising supplying an air-alumina mixture to the bottom of the anode for 5 ÷ 60 s, at an angle of 3 to 10 ° with respect to the bottom of the anode, with a ratio of alumina and compressed air equal to 1: 0.1 ÷ 0.15.

The duration of supplying an air-alumina mixture under the anode for 5 ÷ 60 s is justified by the need to saturate the concentration of electrolyte with alumina to a level leading to the cancellation of the anode effect. The duration of the supply of the air-alumina mixture of less than 5 s will not provide sufficient saturation of the electrolyte under the anode to a level sufficient to extinguish the anode effect. The duration of the supply of an air-alumina mixture of more than 60 s can lead to supersaturation of the electrolyte with alumina and the latter to precipitate on the bottom in the form of sediment.

The ratio of phases alumina: compressed air is selected from the considerations of ensuring the possibility of transporting the mixture through pipelines, as well as reducing the risk of oxidation of the anode by the air supplied as part of the mixture. Reducing the phase ratio of alumina: compressed air less than 1: 0.1 ÷ 0.15 will complicate the movement of alumina in the pipeline supplying it under the anode. An increase in the ratio of phases of alumina: compressed air more than 1: 0.1 ÷ 0.15 will increase the oxidation of the anode by air introduced with alumina.

The introduction of alumina under the anode at an angle of 3 ÷ 10 ° with respect to the anode ensures maximum mixing of the electrolyte and the most complete contact of the alumina saturated with alumina with the anode. Entering alumina at an angle of less than 3 ° carries the risk of exposure to air introduced into the electrolyte as part of the air-alumina mixture directly on the bottom of the anode. An increase in the input angle of more than 10 ° can lead to the ingress of alumina into the liquid aluminum layer, where it will fall onto the bottom in the form of a precipitate that worsens the current distribution conditions in the electrolytic cell, as well as the risk of dropping electrolyte droplets into the liquid aluminum layer, which reduces the current efficiency.

The inventive method is illustrated in the drawing, where: the anode is 1, the pipe is 2, through which an air-alumina mixture is introduced under the anode, 3, saturating the electrolyte, 4 with alumina, a gas layer, 5, and a liquid metal, 6.

The inventive method is as follows. During operation of an aluminum electrolyzer, an anodic effect periodically occurs in it, caused by a low concentration of alumina in the electrolyte. To quench the anode effect, an air-alumina mixture is introduced under the anode for 5-60 s at an angle with respect to the base of the anode from 3 to 10 ° with an alumina: compressed air phase ratio of 1: 0.1 ÷ 0.15. The resulting intensive mixing of the electrolyte and its saturation with alumina contribute to the removal of the gas layer from under the anode. The introduction of an air-alumina mixture under the anode at an angle α = 3 ÷ 10 degrees excludes oxidation of the anode by air, and also eliminates the ingress of alumina into the liquid metal layer.

Claims (1)

A method of suppressing the anode effect in an aluminum electrolyzer, comprising supplying an air-alumina mixture to the bottom of the anode, characterized in that the air-alumina mixture is supplied for 5 ÷ 60 s at an angle of 3 to 10 ° with respect to the anode base with an alumina: compressed ratio air equal to 1: 0.1 ÷ 0.15.

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