RU2253702C1 - Method of supply of alumina to aluminum electrolyzer - Google Patents

Abstract

FIELD: aluminum production plants; supply of alumina to electrolyzers.

SUBSTANCE: alumina is delivered simultaneously with gas under pressure exceeding pressure of anode gases. Mixture of gas and alumina is delivered to inter-pole gap under anode center continuously for stabilization of technological mode, reduction of power requirements and enhancing of electrolyzer efficiency. Dehumidified air mixed with coke dust is used as gas carrier; rate of air flow ranges from 100 to 120 g/cu m.

EFFECT: enhanced efficiency.

2 dwg

Description

The invention relates to non-ferrous metallurgy, to the production of aluminum by the electrolytic method, and can be used in aluminum plants to power the electrolysis cells with alumina.

The traditional technology of feeding the electrolyzer with alumina and fluoride salts consists in loading them onto the crust along the sides of the electrolyzer, followed by forcing this crust and supplying the raw material to the liquid electrolyte.

The known method of nutrition has several significant disadvantages:

- significant losses of raw materials due to dust removal during transportation and loading;

- the impossibility of uniform power supply of the electrolyzer, which leads to technological disruptions (the formation of “cakes” on the bottom, unstable electrical mode);

- low efficiency of the electrolyzer, about 20%.

The closest technical solution is a method of supplying aluminum electrolysis cells with raw materials by feeding it in a metered amount through a vertical aperture in the anode, in which, in order to maintain a constant electrolyte composition, alumina concentration and reduce raw material consumption, electricity, the raw material is supplied simultaneously with an inert gas under pressure by 5 -20% higher than the pressure of the anode gases (SU No. 391185, C 22 V 3/12, publ. 28.11.1973).

The disadvantage of this solution is that the gas-alumina mixture supplied under the aforementioned pressure can lead to changes in the hydrodynamic characteristics of the electrolyte and liquid aluminum flows in the electrolyzer, which leads to disruption of the technological regime, a decrease in the technical and economic parameters of the electrolysis process, and a decrease in the life of the electrolyzer.

The objective of the proposed method is to reduce energy consumption and increase the efficiency of the electrolyzer.

The problem is achieved in that in the known method, comprising feeding alumina simultaneously with gas under a pressure higher than the pressure of the anode gases, according to the invention, the gas-alumina mixture is fed continuously into the inter-pole gap, under the center of the anode, and pre-dried air mixed with coke is used as the carrier gas dust in an amount of 100-120 g / m ³ .

The technical result of the proposed solution is the regulated supply of alumina to the electrolyte and stabilization of the technological regime, as well as reducing energy consumption and increasing the efficiency of the electrolyzer.

The technical essence of the proposed method is as follows.

In the proposed technology for feeding alumina to an aluminum electrolysis cell, a gas-alumina mixture is supplied to a metal pipe located in the inter-pole gap and located in the electrolyte in the repeating circuit of the anode. The gas-alumina mixture supplied under pressure passes through the pipe and heats up and passes through the holes located in the upper part of the pipe end under the center of the anode, where it is distributed, providing the electrolyte with alumina and improving its mixing. As a carrier gas, dried air with the addition of coke dust in the amount of 100-120 g / m ³ necessary for the combustion of oxygen in the incoming air was used. The metal pipe in the electrolyte is not destroyed, since it is cooled by a gas-alumina mixture from the inside, and its outer surface is covered with a layer of hardened electrolyte, which contributes to its hardening.

The proposed method for feeding alumina to an aluminum electrolyzer with the specified set of features ensures the achievement of a technical result due to the uniform supply of alumina to the electrolyte in the interpolar gap and voltage reduction (by several hundred millivolts), by increasing the anode-electrolyte contact area, thereby reducing the number of “locked” sections ( due to a lack of alumina), energy consumption is reduced and the efficiency of the electrolyzer is increased.

The technical result was achieved by solving the problem at the inventive step, in particular by uniformly supplying a gas-alumina mixture under the center of the anode, using pre-dried air mixed with coke dust in an amount of 100-120 g / m ³ as a carrier gas. The amount of coke dust necessary to create a mixture with air is determined based on the conditions for burning oxygen in the air. If the supplied amount of coke dust is less than 100 g / m ³ , then an increase in the rate of combustion of the anode is observed due to the additional supply of oxygen with air. The addition of coke dust in an amount exceeding 120 g / m ³ is impractical, since it was determined by calculation to be sufficient for complete oxygen burning - 120 g / m ^{3 of} coke dust. The dosage of coke dust is provided by a calibrated hole in the feed system to the jet pump.

In FIG. 1 shows a diagram of alumina feeding an aluminum electrolyzer; figure 2 is a diagram of the supply of alumina to the interpolar gap.

The proposed method is implemented as follows.

Compressed air from the air line 1 passes through a dehumidifier 2 of a centrifugal type, where it is cleaned of dust, moisture, and mechanical impurities. The cleaned and dried air enters the gearbox 3, which has the ability to smoothly control the pressure from 0 to 5 atm. Then, under a given pressure, air enters the mixing chamber of the jet pump 4, where alumina also enters from the hopper 5, and coke dust from the hopper 6. The resulting gas-alumina mixture is fed into the electrolyzer 7, into the interpolar gap through a metal pipe 8, repeating the contour of the anode 9.

The alumina feed is controlled by adjusting the air pressure. Depending on the technological state of the electrolyzer, the air pressure and the consumption of alumina may vary slightly, but this ensures a regulated guaranteed supply of alumina.

The system, which provides a continuous method of feeding alumina to an aluminum electrolyzer, is very compact, weighs about 20 kg, is simple to manufacture, and easy to control. It can be used as an autonomous (emergency) power supply of the electrolyzer, as well as to extinguish outbreaks.

Claims (1)

A method of feeding alumina to an aluminum electrolyzer, including feeding alumina simultaneously with gas under a pressure exceeding the pressure of the anode gases, characterized in that the gas-alumina mixture is fed continuously into the inter-pole gap under the center of the anode, and pre-dried air mixed with coke dust is used as a gas carrier 100-120 g / m ³ .

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