RU2697149C1 - Anode block of aluminum electrolytic cell - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to anode block of aluminum electrolyzers. Anode block of aluminum electrolytic cell is made with channels located on its lower working surface, for this purpose in the anode bottom there are arranged aluminum grates made of aluminum rod, located under an inclination so that the upper end of the underlying grid is tightly in contact with the lower end of the overlying grid, which when heated to operating temperature and melted with formation of channels for removal of anode gases.EFFECT: ensuring preservation of voltage drop in the electrolyte associated with accelerated removal of gas from under the anode, and providing the required circulation of electrolyte in areas of supply of alumina.5 cl, 2 dwg

Description

The invention relates to ferrous metallurgy, in particular to the electrolytic production of aluminum, namely to the anode device of aluminum electrolysis cells.

Known Calcined anode of an aluminum electrolyzer (RU 2239005 from 11.25.2002, publ. 10/27/2004 Bull. No. 30.

The technical result of the invention is to maintain the voltage drop in the electrolyte associated with accelerated gas removal from under the anode, and ensuring the required electrolyte circulation in the areas of alumina supply. The technical result is achieved by the fact that the calcined anode contains an anode block with one or more vertical channels on its lower working surface. Vertical channels are made with a differentiated recess along the length in the form of a section with a fixed uniform recess equal to 0.25-0.30 of the block height, or with a fixed recess equal to 0.25-0.30 of the block height and made with an inclination of up to 3 °, and the associated area with a gradual deepening to 0.75 block height. The place of conjugation of the sections is located within 0.45-0.75 of the block length when the channels are located along its longitudinal axis or the block width when the channels are located across its longitudinal axis. When using several vertical channels, they are located in increments of 0.35-0.5 of the width of the block when they are located along its longitudinal axis or in increments of 0.25-0.33 of the length of the block when they are located across its longitudinal axis.

Despite the advantages of the known device for the manufacture of such anodes, a complex manufacturing technology is required.

It is known to use prebaked anodes with carbon anode blocks that contain one or more grooves in their lower part to help remove gas bubbles and prevent their accumulation, which should lead to the solution of the above problems and reduce energy consumption, as shown in Light Metals 2005 "Energy saving in Hindalco's Aluminum Smelter", SC Tandon & R.N. Prasad. Grooves can reduce the average mean free path of gas bubbles under the anode to exit the interelectrode space and, therefore, reduce the size of the bubbles that form under the anode.

The benefits of using grooves have already been studied and proven, for example, in Light Metals 2007 p. 305-310 "The impact of slots on reduction cell individual anode current variation", Geoff Bearne, Dereck Gadd, Simon Lix or Light Metals 2007 p. 299-304 "Development and deployment of slotted anode technology at Alcoa", Xiangwen et al.

Also from the following documents it is known:

- WO 2006/137739 the use of smaller grooves (of the order of 2 to 8 mm) than commonly used ones (of the order of 8 to 20 mm) in order to optimize the useful carbon mass and the exchange surface;

- US 7179353 the use of an anode block having grooves extending only on one side of the anode block and, in particular, to the center of the electrolyzer to improve the dissolution of alumina.

The limitation in the use of these grooves is well known due to the fact that the depth of the grooves relative to the bottom surface of the anode blocks is limited so as not to disturb the mechanical and physical integrity of the carbon anode blocks. In this case, the carbon anode blocks are gradually consumed during the electrolysis reaction to a height exceeding the depth of the grooves, so that the lifetime of the grooves in the anode is less than the life of the anode. Therefore, for some time during the life of the anodes, the lower part of the anode blocks no longer has any groove. In this case, the problems mentioned above for anodes without grooves become noticeable.

The problem of the removal of anode gases and, in particular, carbon dioxide (carbon dioxide), which naturally accumulate in the form of gas bubbles under the underside of the anode, is usually essentially flat and horizontal, which affects the overall stability of the electrolyzer stated IV RU No. 2559381 from 07/21/2010, publ. 08/10/2015 Bull. No. 22 ,. This analogue can be taken as a prototype.

The objective of the invention is to develop a calcined anode of an aluminum electrolyzer, the design of which would provide the possibility of reducing the thickness of the gas layer at the lower working surface of the unit, uniform and accelerated gas flow from the working surface and the ability to control the flow of the outgoing gas for almost the entire period of operation of the anode while maintaining sufficient mechanical strength unit, which will allow to save the decrease in voltage drop in the electrolyte associated with accelerated gas removal from under a node, and provide the required circulation of the electrolyte in the areas of alumina supply during the operation of the anode.

равном 0,20…0,25 высоты Н анода, нижний торец нижней решетки размещен на расстоянии

от подошвы анода, равном 0,03…0,06 высоты Н анода, боковые и торцевые стороны решеток спрятаны вглубь анода на расстояние

от боковых и торцевых стенок анода, равном 0,03…0,06 высоты Н анода, а газоотводящие канавки на подошве анода формируются в результате плавления введенных в анод алюминиевых решеток.This is achieved by introducing into the anode an electrically conductive material with a resistance lower than the resistance of the coal part of the anode, while the electrically conductive material are gratings made of aluminum rods with a diameter of 3 ... 10 mm, which are inclined to be placed in the anode at an angle of 4 ... 8 ° with respect to the horizontal surface such so that the upper end of the underlying grating is in close contact with the lower end of the overlying grating, while the upper end of the uppermost grating is placed from the upper edge of the anode charm

equal to 0.20 ... 0.25 of the height H of the anode, the lower end of the lower lattice is placed at a distance

from the bottom of the anode, equal to 0.03 ... 0.06 of the height H of the anode, the side and end sides of the gratings are hidden deep into the anode at a distance

from the side and end walls of the anode, equal to 0.03 ... 0.06 of the height H of the anode, and the gas outlet grooves at the bottom of the anode are formed as a result of melting of the aluminum gratings introduced into the anode.

The feasibility of introducing into the anode an electrically conductive material with a resistance less than the resistance of the carbon part of the anode ensures the passage of electric current through the anode with a lower voltage drop in it.

The feasibility of using gratings for these purposes with mesh sizes from 50 × 50 to 100 × 100 mm, made of aluminum rods with a diameter of 3 ... 10 mm, is justified by the following. When aluminum rods are melted, grooves of 3 to 10 mm wide and 2 to 5 mm high are formed on the base of the anode, along which the anode gases formed as a result of oxidation of the anode move to the side and end sides of the anode, increasing the circulation of the electrolyte along its entire perimeter. In this case, under each cell with a size of 50 × 50 to 100 × 100 mm, depending on the overall size of the anode, 0.1 to 3.0% of the total volume of the formed anode gases is formed, which are almost immediately discharged through the gas outlet grooves into the inter-anode space .

The presence on the sole of the anode of grooves with a width of up to 10 mm and a height of up to 5 mm increases the useful area of the anode in contact with the electrolyte by an average of 3 ... 5%, which reduces the current density in the anode by the same amount and, accordingly, the resistance of the latter.

The placement of the grids at an angle of 4 ... 8 ° with respect to the horizontal surface ensures gradual melting of the rods, as the anode burns, and also eliminates the deformation of the grids when forming the anode.

The tight electrical contact between the ends of adjacent gratings provides a minimum voltage drop when an electric current passes through them.

от верхней кромки анода, равном 0,20…0,25 высоты Н анода обусловлено необходимостью исключения попадания в анодный огарок металлического алюминия, из которого изготовлены решетки. Как привило, высота анодного огарка составляет 0,1…0,2 первоначальной высоты анода и заявляемое ограничение высоты размещения обеспечивает полный переход расплавленного алюминия из анода в электролит и далее в слой прикатодного жидкого алюминия.The placement of the upper end of the uppermost lattice at a distance

from the upper edge of the anode, equal to 0.20 ... 0.25 of the height H of the anode due to the need to exclude the ingress of metal aluminum into the anode cinder, from which the gratings are made. As a rule, the height of the anode cinder is 0.1 ... 0.2 of the original height of the anode and the claimed limitation of the placement height ensures a complete transition of molten aluminum from the anode to the electrolyte and then to the layer of cathode liquid aluminum.

от подошвы анода, равном 0,03…0,06 высоты Н анода обусловлено тем, что в период обжига анода при температуре 1200…1400°С и выше исключается уход расплавленного алюминия из тела анода.The placement of the lower end of the lower lattice at a distance

from the base of the anode, equal to 0.03 ... 0.06 of the height H of the anode due to the fact that during the anode firing at a temperature of 1200 ... 1400 ° C and above, molten aluminum leaves the body of the anode.

от боковых и торцевых сторон анода, равное 0,03…0,06 высоты Н анода обосновывается следующим. Как правило, высота эксплуатируемых обожженных анодов находится в диапазоне 600…900 мм. Следовательно, в новом аноде боковые и торцевые стороны решеток защищены слоем угольного анода толщиной 3…5 мм. После установки анода в электролизер и его нагрева до рабочей температуры защитный слой окисляется, открывая таким образом газоотводящие канавки, образующиеся на подошве анода после плавления решетки.Removing the side and end sides of the gratings deep into the anode at a distance

from the side and end sides of the anode, equal to 0.03 ... 0.06 of the height H of the anode is justified as follows. As a rule, the height of the operated calcined anodes is in the range of 600 ... 900 mm. Therefore, in the new anode, the lateral and end sides of the gratings are protected by a layer of a carbon anode 3 ... 5 mm thick. After the anode is inserted into the electrolyzer and heated to the operating temperature, the protective layer is oxidized, thus opening the venting grooves formed on the base of the anode after the grating is melted.

The inventive device is illustrated graphically. In FIG. 1 shows a section AA of the calcined anode; in FIG. 2 - section BB of FIG. 1 - the location of the grid in the anode before it is installed in the cell; in FIG. 3 location of gas outlet grooves on the sole of the operated anode, where: 1 - annealed anode; 2 - aluminum grilles; 3 - venting channels on the bottom of the anode; 4 - retaining aluminum rods.

The operation of the device is as follows.

At the bottom of the mold (not shown in FIG.), Where the anode 1 is molded, a layer of anode mass is filled up with a height equal to 0.06 ... 0.10 of the height H of the anode. Next, aluminum grilles 2 are mounted on this layer, fastened together at the ends according to the principle of "herringbone". Such a fastening of the gratings makes it possible to control the angle of their inclination relative to the horizontal surface. Fixing the gratings in the mold at the required angle is carried out using vertically mounted aluminum rods 3. After fixing the gratings and checking the gaps between them and the end and side sides of the mold, the latter is filled with the anode mass. After filling, the anode mass is pressed, its bulk volume is reduced by about 2 times. Thus, it turns out that the lower end of the lower lattice is a protected layer of a carbon anode 3 ... 5 mm thick, which, when anode is fired, eliminates the risk of molten aluminum leaking from it. At the same time, the gratings together with the pressed anode mass move down, reducing their angle of inclination with respect to the horizontal surface from 8 ... 16 ° to 4 ... 8 °. Deformed aluminum retaining rods after installation of the anode in the electrolyzer serve as additional current conductors.

After installing the anode in the electrolyzer and heating it to operating temperature, the protective carbon layer at the base of the anode, its lateral and end sides is oxidized, thereby exposing the lattice. As the lattice melts, venting grooves 4 are formed at the base of the anode, along which the generated anode gases are removed from under the anode.

The technical result of the invention is to maintain the voltage drop in the electrolyte associated with accelerated gas removal from under the anode, and ensuring the required electrolyte circulation in the areas of alumina supply.

Claims (5)

1. The anode block of an aluminum electrolyzer containing a lower working surface, characterized in that in its lower working surface are placed aluminum rods made of rods, located one at another at an angle to the horizontal lower working surface to ensure that the upper end of the underlying grating is in contact with the lower end of the overlying gratings for the formation of channels for removing anode gases during the melting of the rods when the anode is heated to operating temperature. 2. The anode block according to claim 1, characterized in that the aluminum gratings are made with a cell size of 50 × 50 to 100 × 100 mm and are made of rods with a diameter of 3 ... 10 mm. 3. The anode block according to claim 1, characterized in that the upper end of the grating is placed at a distance from the upper edge of the anode

equal to 0.20 ... 0.25 of the height H of the anode. 4. The anode block according to claim 1, characterized in that the lower end of the lattice is placed at a distance

from the sole of the anode, equal to 0.03 ... 0.06 of the height H of the anode. 5. The anode block according to claim 1, characterized in that the side and end sides of the gratings are deepened into the anode by a distance

from the side and end walls of the anode, equal to 0.03 ... 0.06 of the height H of the anode.

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