RU2385364C1 - Anode current conductor of aluminium electrolytic cell - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: here is disclosed anode current conductor of aluminium electrolytic cell consisting of central spent aluminium rod with additional side leads uniformly arranged in anode mass along height of aluminium rod at angle to its axis and inclined to anode sole; side leads freely adjoin central rod and form heterogeneous conducting structure wherein side leads are ohmic connected to central rod through conducting anode mass during its melting and coking in gaps between central rod and side leads in zone of their adjoining. Also the side leads can be made out of foam aluminium.

EFFECT: reduced labour expenditures at fabrication and implementation, stable operation of electrolytic cell and increased ecological safety of production.

2 cl, 1 dwg

Description

The invention relates to the field of aluminum production in electrolyzers equipped with anode consumable current leads made of aluminum.

Soderberg aluminum electrolyzer is known, containing steel anode pins for the upper current supply to the anode with additional aluminum consumable sheets equipped with holes for circulating the liquid anode mass and electrically connected to the anode busbar, with additional installed steel non-consumable pipes for venting gases from under the anode sole, rows placed in the anode, the lower ends of which are located above the electrolyte, and the upper ones are connected to the hollow buttress beams of the anode casing, steel e non-consumable pipes are made with a decreasing outer diameter down (USSR Author's Certificate, SU 351926, MKI C22d 3/02, C22d 3/12, application filing date 08/11/1970, publication date 09/21/1972, author Ryaguzov V.N., analogue) .

The disadvantage of this aluminum electrolyzer with steel current-carrying pins is the allocation of a large number of carcinogenic compounds when rearranging the current-carrying pins to new horizons as the anode mass is consumed, as well as the labor involved in installing metal sacrificial sheets used to create a gas duct in the bottom of the anode.

As a prototype that eliminates the problem of the isolation of carcinogenic compounds when rearranging the current-carrying pins to new horizons, an anode sacrificial current supply for the Soderberg electrolysis cell is used, containing consumable aluminum rods with current conductors that are located at an angle to its axis and are made in conjunction with the main rod, for example, by pressing by explosion, or attached to the main rod, for example by welding, riveting or using bolts, while materials for down conductors can be used Both aluminum powders and aluminum or its alloys are used. The principle of operation of the expendable current lead is that when the lower part of the main rod in the high temperature zone melts and flows into the bath, the electric current is supplied to the lower zones of the anode sole through the upper undisturbed conductive zone of the rod and then along the down conductors, the lower part of which does not reach the sole anode. After a current collector reaches the bottom of the anode and its destruction, the current is supplied to the zones in the bottom of the anode by the following upstream conductors (USSR Author's Certificate, SU 537130, MKI C22C 3/16, application filing date 02/10/1975, publication date 11/30/1976, author Tsomaev Z.S. et al., Prototype).

The disadvantages of the prototype are the high labor costs in the manufacture, installation and maintenance of the electrolyzer, due to the complex manufacturing technology of both a structurally integral current lead, and with fixed down conductors, as well as the difficulty of installing a current lead on the anode bus when it grows as it is spent.

The objective of the invention is to reduce labor costs in the manufacture and use of consumable current lead with efficient current supply of the sole of the anode and optimal energy consumption.

To solve the problem in the anode current lead of an aluminum electrolyzer containing a central consumable aluminum rod with additional lateral down conductors uniformly located in the anode mass along the height of the central rod at an angle to its axis and inclined to the base of the anode, according to the invention, the side down conductors are installed adjacent to the central rod with the formation of a gap filled with a conductive anode mass, forming a heterogeneous conductive structure during the operation of the cell, with this side down conductors are ohmically connected to the Central rod through a conductive anode mass due to its melting and coking in the gap.

According to the invention, the side down conductors can be made of foam aluminum.

The drawing shows a diagram of a heterogeneous sacrificial anode current lead for an aluminum electrolyzer.

The inventive anode current lead of an aluminum electrolyzer contains a central aluminum rod 1 with current leads 2 supplied to it as they are immersed in the anode mass. The current leads 2 are mounted freely adjacent to the central rod 1 at an angle to its axis and are inclined to the bottom of the anode. The gaps 3 between the down conductors 2 and the central rod 1 are filled with a conductive anode mass, forming a heterogeneous conductive structure that provides ohmic connection of the down conductors 2 to the central rod 1. At the same time, rods, plates, profiles made of aluminum, foam aluminum or can be used as down conductors aluminum alloys. When installing them, it is not required to be rigidly fixed on the central rod in order to ensure the initial good ohmic contact.

The principle of operation of a heterogeneous current supply is based on the formation of a heterogeneous conductive structure in the anode during operation of the electrolyzer. Moreover, as the rod 1 is immersed in the anode with the down conductors 2 connected in series to it, the gaps 3 between them are filled with the molten anode mass, which is subject to coking in the gaps. As a result of this, the conductive anode mass formed in the gaps due to melting and coking provides the necessary ohmic connection of the side down conductors 2 to the central rod 1.

In the lower part of the anode, where the lower part 4 of the central aluminum rod melts and flows to a certain height h, the side down conductors 2 also melt, but remain encapsulated in the cavities of their initial placement until the opening of their lower end on the lower surface of the anode. Accordingly, these down conductors make it possible to maintain current lead directly to the lower part of the sole of the anode.

The efficiency of current supply of the anode sole increases due to the use of side down conductors, provided that the average resistance of the heterogeneous structure with down conductors is lower than that for a continuous anode array in the sole area. In this case, the current supplied to the sole of the anode is maintained without increasing the voltage drops in the bottom of the anode and, accordingly, the electrical characteristics of the cell are improved:

where j _g and j _u are the average current density in a heterogeneous and continuous current supply, U is the voltage drop across the anode, U _p = j _g · R _p is the transition voltage drop at the Al-anode mass interface (R _p is the specific transition interface (Al is the anode mass), H is the thickness of the anode, l is the length of the individual lateral collector, θ is the angle of installation of the collector (measured from the vertical), ρ _Al and ρ _C are the resistivity of aluminum and the coked anode mass in the sole of the anode, respectively.

From the expression (1), the ratio of the installation parameters of down conductors in the anode is determined, such as the length and angle of installation of down conductors:

Under the additional condition, when the total cross-section of the collectors should not be less than the section of the central rod-current lead, the required current lead to the bottom of the anode will be provided without the need to increase the voltage drop across the anode due to burnout of the central rods. Accordingly, the use of the proposed design allows for optimal power consumption and increase the stability of the anode.

For an electrolytic cell with a current load of 250 kA using 32 aluminum current-conducting rods, the required thickness of the anode rod does not exceed 70 mm. The length of an individual collector and the installation angle are

l = 0.35 m, θ = 30 °,

at H = 1 m, U = 4 V, R _p = 2.83 · 10 ^-5 Ohm / m ² , ρ _Al = 2.7 · 10 · ⁶ Ohm · m, ρ _C = 1.4 · 10 ^-5 Ohm · m

at a melting temperature of aluminum T = 658.7 ° С (at the fracture boundary of the central anode rod at a distance h from the lower boundary of the anode base).

The total mass of the circulating flow rate of aluminum for the manufacture of a heterogeneous current supply does not exceed 2-2.5 tons per electrolyzer per one cycle of updating the anode mass. Accordingly, the specific turnover of aluminum does not exceed 30-40 kg / day or 2-5% of the daily production of the electrolyzer in 0.7-1.7 tons.

Thus, the proposed consumable heterogeneous current lead allows to reduce labor costs during its manufacture and operation as compared with the analogue, to provide stabilization of the electrolyzer operation, to increase the environmental safety of production by eliminating the emissions of carcinogenic compounds arising from the rearrangement of steel current lead rods in Soderberg electrolyzers.

Claims (2)

1. Anode current lead of an aluminum electrolyzer containing a central sacrificial aluminum rod with additional lateral current conductors uniformly located in the anode mass along the height of the central rod at an angle to its axis and inclined to the base of the anode, characterized in that the lateral current conductors are installed adjacent to the central rod with the formation the gap filled by the conductive anode mass, forming a heterogeneous conductive structure during the operation of the electrolyzer, while the lateral down conductors are ohmic connected to the Central rod through a conductive anode mass due to its melting and coking in the gap. 2. The anode current lead of an aluminum electrolyzer according to claim 1, characterized in that the side down conductors are made of foam aluminum.

Images