RU2308549C1 - Charge for sealing near-anode space of aluminum cell - Google Patents

Abstract

FIELD: non-ferrous metallurgy, namely production of aluminum by electrolysis, particularly compositions of charge used for sealing near-anode space of aluminum cell.

SUBSTANCE: charge for sealing contains alumina, fluorine -containing salts and ground electrolyte with fraction size -20 mm at next relation of ingredients, mass%: alumina, 9 - 88; fluorine containing salts, 1 -2; ground electrolyte, the balance. Ground electrolyte is in the form of electrolyte-containing ground waste material extracted from bath of aluminum cell.

EFFECT: reduced quantity of harmful outbursts to environment, increased electric current yield.

1 tbl, 1 ex

Description

The invention relates to non-ferrous metallurgy, in particular to the electrolytic production of aluminum, and in particular to the composition of the charge used to seal the anode space of the cell.

It is known that the anode space of the electrolyzer is sealed with alumina to produce aluminum after leakage in feeding the electrolyzer with alumina by the in-line method (Terentyev V.G. et al. Aluminum production, Irkutsk, 2001, pp. 160-161).

When the electrolyzer is fed using automatic alumina dispensers, the alumina that seals the anode space is gradually dissolved by the electrolyte, as a result of which the anode space is depressurized.

Closest to the claimed is a mixture for sealing the anode space of an aluminum electrolyzer, consisting of alumina and 1-2% fluoride salts (wt.%). The mixture is used both for sealing and for powering the electrolyzer (Mintsis M.Ya., Polyakov P.V., Sirazutdinov G.A. Electrometallurgy of aluminum. Nauka, Novosibirsk, 2001, p.237).

The disadvantage of this mixture is its rapid dissolution from below with a thin film of electrolyte rising from the electrolyte layer due to the action of surface tension forces, which leads to harmful emissions into the environment. Due to the periodic destruction of the electrolyte-alumina crust, which seals the anode space, an uncontrolled amount of alumina enters the electrolyte, which makes it difficult to automatically maintain the optimal concentration of alumina in the electrolyte by controlling the operation of the automatic alumina feeding system using ACS TP and reducing the current output.

The basis of the invention is the task of developing the composition of the charge for sealing the anode space of an aluminum electrolyzer, the use of which would reduce the likelihood of harmful emissions into the environment, the uncontrolled amount of alumina entering the electrolyte and provide an increase in current efficiency due to improved quality of automatic control of the APG operation.

The achievement of the above technical result is ensured by the fact that in the known charge for sealing the anode space of an aluminum electrolyzer, which includes alumina and fluoride salts, according to the invention, a crushed electrolyte with a particle size of minus 20 mm is additionally introduced, in the following ratio of ingredients (in wt.%): Alumina - 9-88, fluoride salts - 1-2, crushed electrolyte - the rest.

The invention complements a particular distinguishing feature, also aimed at achieving a technical result.

As crushed electrolyte use crushed, extracted from the bath of the aluminum electrolysis cell waste containing electrolyte.

The introduction of crushed electrolyte into the charge of more than 10% leads to hardening of the electrolyte-alumina crust and reduces the concentration of alumina in it, which reduces the uncontrolled amount of alumina entering the electrolyte. It also facilitates the automatic maintenance of the optimal concentration of alumina in the electrolyte by controlling the operation of the APG using an automatic process control system, which ensures an increase in current efficiency by improving the quality of automatic control. When crushed electrolyte is introduced into the charge over 90%, the strength of the electrolyte-alumina crust decreases, which increases the likelihood of harmful emissions into the environment.

The addition to the crushed electrolyte of waste containing electrolyte with a particle size of minus 20 mm allows them to be processed without compromising the quality of the electrolyte-alumina crust.

The analysis conducted by the applicant showed that the set of features is new, and the charge for sealing satisfies the inventive step condition due to the novelty of the cause-effect relationship “distinctive features - technical result”.

To obtain a charge for sealing, the ingredients were dosed and thoroughly mixed.

Example.

During the tests, the anode space of aluminum electrolysis cells was sealed with specially prepared charges from alumina used in dry gas purification with a content of fluoride salts of 1-2% and crushed electrolyte with a particle size of minus 20 mm. The addition of crushed electrolyte led to a reduction in charge consumption for sealing the anode space of an aluminum electrolyzer. With the introduction of 50% crushed electrolyte, the charge consumption was reduced by 10 times, and not the controlled entry of alumina into the bath, by 20 times. The results of the tests are shown in the table.

Table The ratio of ingredients in the mixture,% Charge Consumption, t / month Uncontrolled intake of alumina in the electrolyte, t / month Alumina Fluoride
salt Crushed electrolyte 98 (prototype) 2 0 9 9 92 2 8 8 7.2 88 2 10 four 3.6 58 2 40 0.9 0.54 48 2 fifty 0.9 0.45 39 one 60 0.9 0.36 19 one 80 1,2 0.24 9 one 90 2 0.20 7 one 92 6 0.48

Claims (2)

1. The mixture for sealing the anode space of an aluminum electrolyzer containing alumina and fluoride salts, characterized in that it additionally contains crushed electrolyte with a particle size of minus 20 mm in the following ratio of ingredients, wt.%: Alumina 9-88, fluoride salts 1-2, crushed electrolyte rest. 2. The mixture according to claim 1, characterized in that the crushed, extracted from the bath of the aluminum electrolyzer waste containing electrolyte is used as a crushed electrolyte.