Method of determining degree of wear of silicon carbide blocks for side lining of cover of aluminium electrolysis cells

FIELD: chemistry.

SUBSTANCE: method involves immersing mounted samples of silicon carbide blocks into an electrolyte at aluminium electrolysis temperature and bubbling the electrolyte with carbon dioxide, air or a mixture thereof, moving the samples and comparing the obtained samples with the original samples. After immersion, the samples are held in the electrolyte which is in contact with aluminium at electrolysis temperature, with the controlled area of the sample in the electrolyte. The samples are then raised and held with the controlled area of the sample in a gas phase for not more than 20 minutes. The samples are then moved in the vertical plane while alternately holding the controlled area in the electrolyte and in the gas phase for not more than 10 minutes and the degree of wear thereof is determined from change in the volume of the samples.

EFFECT: shorter time for testing samples of blocks and obtaining visible reduction in cross dimensions of samples of said blocks owing to intensification of the wear process by increasing the rate of wear.

3 cl, 3 dwg, 2 ex, 2 tbl

 

The invention relates to ferrous metallurgy, in particular to the analysis of the blocks used in electrolytic production of aluminum, namely, to determine the degree of wear in the environment aluminium electrolysis cells samples of silicon carbide blocks used for side lining casing aluminium electrolysis cells.

Blocks of silicon carbide in the environment of aluminium electrolysis cells are chemically unstable and can wear up to damage by contact of the block with a gas phase aluminum electrolysis cells (hereinafter, the gas phase); electrolyte aluminum electrolytic cells (hereinafter - electrolyte); and liquid aluminum (hereinafter referred to aluminum). Wear under other equal conditions depends on the properties of the blocks defined by the technology of their production.

Currently in the aluminum industry in the side lining casing aluminum electrolysis cell used silicon-carbide blocks, made of particles (pieces) of silicon carbide (SiC) - filler on the nitride bond (Si3N4) - binder.

Thermodynamic analysis of the changes in Gibbs free energy and equilibrium constants for the possible reactions of the substances of the filler and the binder with the components of the electrolyte and the gas phase and with aluminum at 1000°C show that the carbide and silicon nitride can react with all components of e is carolita and gas phase and aluminum.

There is a method of determining the degree of wear of the samples of silicon carbide blocks used for side lining casing aluminium electrolysis cells in the environment of industrial aluminum electrolysis cell and tested in laboratory conditions (Light Metals. - 2006. - P.313-318; Light Metals. - 2005. - P.773-778; Light Metals. - 2008. - P.955-959).

Analysis of the status of blocks in industrial conditions after stopping aluminium electrolysis cells, in principle, allows to draw conclusions about the mechanisms of wear. This analysis method has the disadvantages that from the date of commencement of operation of the unit before signing about it as it takes a long time and, in addition, because the conclusion is made after stopping aluminium electrolysis cells, it is impossible to prevent the use of substandard units.

The known method consisting in testing blocks in the environment: gas phase - electrolyte - aluminum by electrolysis in laboratory conditions simulating actual operating conditions of industrial aluminum electrolysis cells (Light Metals. - 1999. - P.215-222). The sample is placed in an experimental cell for the study of the wear of the samples of silicon carbide blocks in the process of electrolysis. Analysis of the status of the blocks after the test allows to make a conclusion about the degree of wear.

There is a method of determining the degree of wear of silicon carbide samples the locks in the environment of the gas phase the electrolyte. Samples partially immersed in the electrolyte, through which is purged with carbon dioxide. The samples are placed in a static state (doktoringenioravhendling: 08.01 / Laure Delmas. - Trondheim, 2001. - 102 p.).

There is a method of determining the degree of wear of the samples of silicon carbide blocks in the environment: gas phase - electrolyte - aluminum. Samples of different parts which are in contact with a gas phase, electrolyte or aluminum, are maintained in the environment for a specified time (Light Metals. - 2001. - P.257-265).

The disadvantage of the above methods of determining the degree of wear of the samples of silicon carbide blocks used for side lining covers aluminium electrolysis cells is the inability of a substantial intensification of the process of wear and tear, resulting in time trials to produce visible changes of the transverse dimensions of the sample is large enough (more than 24 hours).

There is a method of determining the degree of wear of the samples of silicon carbide blocks in the environment: the gas - phase electrolyte with rotation. When testing samples of silicon carbide blocks secured in the holder, immersed in an electrolyte, is placed in a graphite crucible, set in the oven. The high temperature in the furnace is maintained by means of heating elements and is measured by a thermocouple. The rotation of the samples is carried out in an electrolyte in a horizontal pleskot is at a high temperature. Through the electrolyte is skipped carbon dioxide or air or a mixture. Testing is carried out at a temperature of the electrolyte 1000°C, flow rate of carbon dioxide 1 l/min, the speed of rotation of samples of silicon carbide blocks 45 rpm, the test time of 24 hours (Light Metals. - 2006. - P.663-668).

For the purpose and have similar essential features of the known method is adopted as a prototype.

The disadvantage of this method, selected as a prototype, is the inability of a substantial intensification of the process of wear due to the screening by the electrolyte surface samples carbide blocks from the gas phase and due to entrainment of electrolyte samples of silicon carbide blocks during their rotation, resulting in the oxidation rate of the material is low and the wear rate of samples of silicon carbide blocks is small.

The objective of the proposed solutions is to reduce the time of testing samples of silicon carbide blocks and obtaining a visible reduction of the transverse dimensions of the sample silicon-carbide blocks used for side lining covers aluminium electrolysis cells, due to the intensification of the process of wear by increasing the rate of wear.

The technical result is to develop a method for determining the degree of wear of the samples of silicon carbide blocks used for the iron lining covers aluminium electrolysis cells, that allows significantly intensify the process of wear and thereby reduce the test time to obtain a visible reduction of the transverse dimensions of the sample silicon-carbide blocks with subsequent determination of the relative volume change of the samples of silicon carbide blocks in the testing process, which characterizes the degree of wear.

The problem is solved in that in the method of determining the degree of wear of the samples of silicon carbide blocks side-lining casing aluminium electrolysis cells, including immersion fixed samples carbide blocks in the electrolyte at a temperature aluminum electrolysis, and the bubbling of the electrolyte carbon dioxide, air or mixtures thereof, the movement of the samples and comparison samples obtained from the source, in accordance with the inventive solution, first, the samples are immersed and incubated in the electrolyte at the temperature of electrolysis in contact with aluminum, with the location of the controlled area of the sample in the electrolyte, then the samples are picked up and stand with the location of the controlled area of the sample in the gas phase, after which move the sample in the vertical plane with the alternate shutter speed controlled zone in the electrolyte and the gas phase.

Way to complement private significant features that contribute to the achieving the task.

Samples incubated with the location of the controlled area of the sample in the gas phase is not more than 20 minutes.

Samples move in a vertical plane with the alternate location of the controlled area in the electrolyte and the gas phase is not more than 10 minutes.

Industrial and laboratory studies on the resistance of the silicon carbide blocks in the environment of aluminium electrolysis cells show that the greatest wear occurs at the interfacial boundary of the electrolyte with a gas phase. Therefore, we can assume the following mechanism of wear: as a result of reactions of the material silicon carbide blocks with a gas phase formed of a solid (e.g., silicon dioxide - SiO2) and gaseous products (e.g., SiF4). The formation of SiO2 should inhibit all reactions, however, disturbances of electrolyte silicon oxide is dissolved, the reaction surface is exposed and the reactions are accelerated. The intensity of wear process samples of silicon carbide blocks depends on the rate of oxidation of the material of the blocks and the speed of dissolution of a solid oxidation products in the electrolyte.

In the proposed method, compared with the prototype for process intensification wear samples of silicon carbide blocks is invited: - to withstand the first sample in the electrolyte at the temperature of electrolysis in contact with aluminum, in the initial position, with RA is position-controlled area of the sample in the electrolyte; then the samples carbide blocks to stand in the top position with the location of the controlled area of the sample in the gas phase, so that the film of electrolyte managed to drain and to expose the surface of samples of silicon carbide blocks for the reaction of oxidation at high speed; and to bring samples of silicon carbide blocks in an oscillatory motion in a vertical plane, with the alternate shutter speed controlled zone in the electrolyte and the gas phase. The time of vibration, the amplitude and the frequency is chosen so that most fully to remove the solid oxidation products as fast as possible.

Thus, when using the proposed method, the intensification of the process of wear is achieved by exposure of samples of silicon carbide blocks in an oxidizing atmosphere, followed by dissolving the formed oxides in the electrolyte.

The comparison of the proposed technical solutions to the prototype shows the following:

The proposed solution and the closest analogues are characterized by similar features:

- samples of silicon carbide blocks are fixed in the holder on the circumference;

- samples of silicon carbide blocks are immersed in the electrolyte at high temperatures;

the bubbling of the electrolyte gas.

The proposed solution is different from the well-known solution to track the relevant characteristics:

changing the position of the samples of silicon carbide blocks in the vertical plane;

- extract samples of silicon carbide blocks in the upper position;

the time of exposure of samples carbide blocks in the upper position can be changed within wide limits;

the fluctuation in the samples of silicon carbide blocks in the vertical plane (up-down);

the time, amplitude and frequency of vibrations of samples of silicon carbide blocks in the vertical plane can be changed within wide limits.

The method is illustrated by drawings, where figure 1 shows a diagram of a device for implementing the method, figure 2 - location of the controlled zone samples in different positions, figure 3 - a sample of the silicon carbide block before testing and after testing.

On the submitted drawings 1 - cover of the furnace; 2 - samples of silicon carbide blocks in the initial position; 3 - electrolyte; 4 - graphite crucible; 5 - aluminum; 6 - metal glass; 7 - fireclay pedestal; 8 - shaft furnace; 9 - gas phase; 10 - tube for supplying a gas; 11 - graphite cover; 12 - ferrule for fixing samples; 13 - the level of electrolyte in the initial (lower) position of the sample silicon carbide block; 14 - controlled sample area of the silicon carbide block, alternating contact with the gas phase and the electrolyte; 15 - the level of the electrolyte at the top is ulozhenie of the silicon carbide sample block; 16 is a sample of the silicon carbide block in the upper position, 17 - sample of the silicon carbide block after testing; and - the area in contact with the aluminum and the electrolyte; b - controlled area of the sample plot, alternately in contact with the gas phase and the electrolyte; in - phase in contact with a gas phase.

The method of determining the degree of wear was carried out as follows.

During the tests used samples of silicon carbide blocks carved out of solid carbide block in the form of rectangular parallelepipeds size (80-200)×(5-20)×(5-20) mm, not less than four. Used electrolyte composition, % wt.: Na3AlF6 (60-94), AlF3 (2-12), CaF2 (4-8), MgF2 (up to 4), LiF (4), KF (up to 4), Al2O3 (2-10) and aluminum, is placed in a crucible with an inner diameter of 50-120 mm, made of ceramic material or graphite. Produced heating the electrolyte to a temperature of 950-1200°C. When tested alternated fluctuations of samples in the vertical plane (up - down) with the amplitude of 5-30 mm and a frequency of 10-40 min-1. Were able to sample up to 20 minutes in the top position while bubbling carbon dioxide gas, air or mixtures thereof through a tube immersed in the electrolyte to a depth of 5-30 mm Samples of silicon carbide blocks resulted in an oscillatory motion in a vertical plane with given amplitude and frequency during the 5-10 minutes. After that, the samples of silicon carbide blocks again recorded in the upper position and then again resulted in an oscillatory motion. This procedure was continued for 4-8 hours - time tests.

Example 1. Four specimens of silicon carbide blocks, cut from the silicon carbide blocks received from different suppliers, in the form of rectangular parallelepipeds size(125)×(10)×(10) mm, fixed in the apparatus shown in figure 1, in a housing (12) around the circumference, and was immersed in the electrolyte composition, % wt.: Na3AlF6(84), AlF3(5), CaF2(6), Al2O3(5) and in aluminum, placed in a crucible (4) with an inner diameter of 60 mm, made of graphite. Samples of silicon carbide blocks were loaded so that the controlled zone of the sample were in the electrolyte and was located near its middle part. Approximately 1/2 of the height of the sample in contact with a gas phase, approximately 1/3 of the height in contact with the electrolyte, approximately 1/6 of the height in contact with the aluminum. Along the axis of the crucible was set and immersed to a depth of 10 mm into the electrolyte tube made of silicon carbide with a diameter of 5 mm, through which passed the carbon dioxide at the rate of 1 l/min. and the temperature of the electrolyte at trial established 1070°C. After reaching the set temperature is changed the position of the samples.

With the help of the device (figure 1 samples of silicon carbide blocks were fixed in the upper position for 10 minutes. At this time controlled zone samples carbide blocks that are above the level of the electrolyte, was oxidized in the gas phase above the electrolyte with the formation of a protective oxide film.

After the specified time samples of silicon carbide blocks were subjected to movement in a vertical plane, oscillatory movements up and down for 5 minutes. Variations were made at 30 min-1and the amplitude of 2.2 cm corresponding to the height of lifting of samples of silicon carbide blocks. When the raising and lowering of samples of silicon carbide blocks ranged electrolyte level, around the height of the samples carbide blocks 3.5 cm with a given oscillation frequency (figure 2). During this period, the oxide film formed on the surface of the silicon carbide samples of blocks in the controlled area of the sample, when the shutter speed is in the upper position, dissolved in the electrolyte. Oscillatory movement accelerated the removal of the products of dissolution from the surface samples of silicon carbide blocks and thereby intensified the process of wear. After that, the samples of silicon carbide blocks again recorded in the upper position and then again resulted in an oscillatory motion.

Then the cycle is 10 minutes in the upper position and a 5-minute oscillations in the electrolyte is repeated throughout about what it, which lasted 8 hours. After testing samples of silicon carbide blocks were removed from the electrolyte and aluminum, cooled in air, washed from the electrolyte and aluminum and used to calculate the degree of wear (determination of volume change of the samples), using standard procedures.

The test results of samples of silicon carbide blocks are shown in table 1 (the relative volume change of the samples of silicon carbide blocks in the test result).

Table 1.
No. sample1234
Relative volume change, %1,14-3,03-7,97-1,1

Example 2. Four specimens of silicon carbide blocks, cut from the silicon carbide blocks received from different suppliers, in the form of rectangular parallelepipeds size(122)×(11)×(11) mm, fixed in the apparatus shown in figure 1, in a housing (12) around the circumference, and was immersed in the electrolyte composition, % may: Na3AlF6(84), AlF3(5), CaF2(6), Al2O3(5) and in aluminum, placed in a crucible (4) vnutrenniy diameter 60 mm, made of graphite. Samples of silicon carbide blocks were loaded so that the controlled zone of the sample were in the electrolyte and was located near its middle part. Approximately 1/2 of the height of the sample in contact with a gas phase, approximately 1/3 of the height in contact with the electrolyte, approximately 1/6 of the height in contact with the aluminum.

Along the axis of the crucible was set and immersed to a depth of 10 mm into the electrolyte tube made of silicon carbide with a diameter of 5 mm, through which passed the air with a speed of 1 l/min

The temperature of the electrolyte was set to 1000°C - temperature tests. After reaching the set temperature is changed the position of the samples. With the help of the device (figure 1) samples were fixed in the upper position for 10 minutes. At this time controlled zone samples carbide blocks that are above the level of the electrolyte, was oxidized in the gas phase above the electrolyte with the formation of a protective oxide film. After the specified time, the samples were subjected to oscillatory movements up and down within 5 minutes of the Oscillations produced with a frequency of 30 min-1and amplitude of 2.2 see the level of electrolyte is moved along the height of the samples at 3.5 cm with a given oscillation frequency.

Then the cycle is 10 minutes in the upper position and a 5-minute oscillations in the electrolyte is repeated for only the experience, which lasted 8 hours.

The test results of samples of silicon carbide blocks is shown in figure 3 (a visible change in the transverse dimensions of the image, the silicon carbide block on the border of the electrolyte and gas phase) and table 2 (the change in the transverse dimensions and the relative volume change of the samples of silicon carbide blocks in the test result).

Table 2
No. sample1234
Relative volume change, %-6,7-7,0to-9.2-5,5

The results obtained in the experiments for 8 hours of testing, when using the method, taken as a prototype, is achieved only within 24 hours of test.

1. The method of determining the degree of wear of the samples of silicon carbide blocks side-lining casing aluminium electrolysis cells, including immersion fixed samples carbide blocks in the electrolyte at a temperature aluminum electrolysis, the bubbling of the electrolyte carbon dioxide, air or mixtures thereof, moving the samples in the Electrol is the same and the comparison of the samples from the source, characterized in that after immersing the samples incubated in the electrolyte with the location of the controlled area of the sample in it, then the samples are picked up and stand with the location of the controlled area of the sample in the gas phase, and then move the sample in the vertical plane with the alternate shutter speed controlled zone in the electrolyte in the gas phase and the volume change of the samples to determine their degree of wear.

2. The method according to claim 1, characterized in that the samples are incubated with the location of the controlled area of the sample in the gas phase is not more than 20 minutes.

3. The method according to claim 1, characterized in that the sample is moved in a vertical plane with the alternate location of the controlled area in the electrolyte and the gas phase is not more than 10 minutes.



 

Same patents:

FIELD: metallurgy.

SUBSTANCE: method involves introduction of carbon-bearing substrate material to a mould and application onto it of a layer of composite heat-resistant material containing metal boride, sealing of the contents of the mould in the form of a cathode block and annealing of the cathode block; as material of carbon-bearing substrate and the layer of composite heat-resistant material there used are materials having close coefficients of thermal linear expansion and values of sodium expansion and the following particle size distribution: content of fractions in carbon-bearing substrate (-10+0.071) mm - 76±10 wt % and (-0.071+0) mm - 24±10 wt %, content of fractions in the layer of composite heat-resistant material (-10+0.071) mm - 50±30 wt % and (-0.071+0) mm - 30±50 wt %; with that, material of the carbon-bearing substrate is added to a mould pre-heated to the material temperature. The composite heat-resistant material layer in a sealed state is maximum 8.0% of height of the cathode block and contains 20.0-80.0 wt % of metal diboride. Sealing of the cathode block is performed by vibration moulding, and annealing is performed at 1100°C during 5 hours.

EFFECT: improving quality and service life.

3 cl, 3 dwg, 1 tbl

FIELD: metallurgy.

SUBSTANCE: invention relates to a design of a cathode section of an aluminium electrolyser. The cathode section includes a cathode carbon unit, a cathode current-carrying rod with an electrically conducting part from material with high specific electric conductivity, which is installed in an internal cavity of the cathode carbon unit and fixed in it by means of a cast iron cast. The electrically conducting part of the rod is made in the form of an insert of individual elements attached to each other with a gap, which is installed on one or more outer surfaces of the cathode current-carrying rod through a cast iron casting layer. The individual elements of the insert can be of round or rectangular shape or any other type of cross section. Inserts can be installed throughout the length from 10% to 100% of length of the cathode current-carrying rod.

EFFECT: reduction of voltage drop in a cathode unit and low electric contact resistance between a cathode current-carrying rod and an electrically conducting insert with high specific electric conductivity throughout the length of the cathode current-carrying rod.

3 cl, 3 dwg

FIELD: metallurgy.

SUBSTANCE: on hearth surface placed are baffles and/or grates, and/or open-pore cellular structures wetted by aluminium made of material with lower electric conductivity compared with that of aluminium perpendicular and/or at 45°-90° to heart surface, perpendicular and/or at 45°-90° to lengthwise axis of cathode rods preventing partially or completely the flow of horizontal components of cathode currents in aluminium layer along the hearth. Electrolytic cell can operate with consumable or nonconsumable anodes, that is, "inert" anodes.

EFFECT: uniform current distribution, smaller electrode gap, lower power consumption, higher yield.

15 cl, 5 dwg

FIELD: metallurgy.

SUBSTANCE: electrolysis unit includes a cathode device containing a bath provided with a coal bottom and composed of coal blocks enclosed in a metal housing, with refractory and heat-insulating materials arranged between the metal housing, an anode assembly containing coal anodes connected to anode sludge, arranged in upper part of the bath and submerged into molten electrolyte; at the coal bottom, under each of the anodes there located are floats with higher specific electric conductivity in comparison to that of electrolyte, stable to destruction in cryolite-alumina melts and liquid aluminium; with that, upper surface of the float projects above the level of cathode aluminium and the floats can be moved and/or replaced to reduce inter-pole gap between anode and cathode. The floats are made from carbon, or from silicon carbide, or from a mixture of titanium diboride and carbon based on high-temperature binding substance and are covered with titanium diboride. Upper surface of the float is flat, or convex, or concave, or inclined to horizon and has capillaries and/or channels, and/or planes attaching the upper surface of a pedestal to cathode metal.

EFFECT: reduction of specific power consumption.

15 cl, 4 dwg

FIELD: metallurgy.

SUBSTANCE: composite has composition defined by formula (C-N-B-MR)x(Al-MR)y(R)z, where MR is one or several carbides, nitrides or borides of one or more heat-resiatant metals of IV, V, VI groups, C-N-B-MR is one or several carbides, nitrides or borides of one or more heat-resistant metals of IV, V or VI groups, Al-MR is one or several aluminides of one or several aforesaid heat-resistant metals. Note here that if MR=Nb, Ta, Hf, Zr, Ti, V, then Al-MR=Al3MR; is MR-W, Cr, then Al-MR=Al4MR; if MR=Mo, then Al-MR=Al8Mo3 or Al17Mo4. Note here that the condition should be satisfied whereat if C-N-B-MR=TiB2, Al-MR is not Al3Ti; R is residual component other than carbon containing one or several phases from Al4C3, AlN, AlB2, Al1·67B22, MRtAlu(C-N-B)v, where t, u, v are numbers larger than or equl to zeto; x, y, z are volume fractions of appropriate components. Note here that x>y; x+y>0.5; x+y+z=1 and 0.01<y<0.5.

EFFECT: composite features good wettability due to decreased grain size and higher density of interface surface to allow using said composite as coating of components wetted by liquid aluminium.

12 cl, 15 dwg

FIELD: metallurgy.

SUBSTANCE: proposed cathode comprises jacket and lining with base made of heat-insulation and refractory materials, side lining, bottom of hearth sections with cathode rods and cathode downleads. The latter are made from the stack of flexible aluminium tapes, contact plate and steel adapter to be welded as-assembled to cathode rod and plugged to cathode bus. Cathode downleads are assembled in installing the lining by welding them to cathode rods and bolting downlead contact plates to the bracket. After disassembly of side lining, cathode rods with their downleads are extracted from cathode jacket, cleaned and transferred to cutting bay. Cutting is performed along the line or in zone of joint between rod and downlead metal adapter. After skinning the metal adapter end, cathode downlead is transferred for reassembly.

EFFECT: higher reliability due to larger number of aluminium tapes.

2 cl, 1 dwg

FIELD: electrical engineering.

SUBSTANCE: cathode device of an aluminium electrolytic cell with an embossed hearth contains a lined cathode shell ad a hearth composed of higher bottom blocks with projections and lower bottom blocks. The lower bottom blocks are installed at the cathode device hearth butt ends. The lower bottom blocks alternate with higher bottom blocks with projections or are installed in the projection centre of the electrolytic cell anode array, with at least two higher bottom blocks with projections, alternating with lower bottom blocks, installed at the both ends of the electrolytic cell anode array. The bottom block projection height is equal to 0.1÷0.6 of that of the smaller bottom block. The top parts of higher bottom blocks have level edges. The bottom blocks projections are made of a refractory non-carbon material, resistant to hot melt effect.

EFFECT: reduction of hot melt circulation rate and decrease of metal slant due to projecting barriers in the metal layer; decrease of heat and mass transfer inside the aluminium layer which reduces loss of heat from the electrolytic cell surface and enables work at a lower voltage.

4 cl, 5 dwg

FIELD: chemistry.

SUBSTANCE: method for electrolytic production of metal in an electrolysis cell, having a cathode, an anode and collectors of impurities dissolved in the electrolyte, involves passing cathodic current through the cathode to obtain metal at the cathode and deposit impurities on the collector. The collector, which is placed between the anode the cathode, is a bipolar porous collector electrode which is a cellular matrix which is inert to the metal deposited at the cathode and the electrolyte. The bipolar porous collector electrode is in form of an open porous structure having internal pores or capillaries, or channels, or cavities, which are particularly V-shaped and/or W-shaped and/or S-shaped and are filled with the metal which is deposited at the cathode. The method employs a bipolar porous collector electrode, wherein the internal pores or capillaries, or channels or cavities are wettable by metal, and have dimensions, particularly diameter and length, which are sufficient for them to hold the metal and prevent spontaneous flow of metal from them due to surface tension forces of the metal.

EFFECT: efficient separation of cathode and anode process products, high current output, lower ohmic resistance of the pole gap and specific power consumption, and removing impurities from the cathode metal.

11 cl, 4 dwg

FIELD: metallurgy.

SUBSTANCE: cathode device of aluminium electrolyser includes housing, bottom blocks with cathode rods, refractory casing under bottom blocks, side refractory, insert blocks from carbide-silicon material mounted close to side refractory. From above the side refractory is equipped with flange sheet mounted horizontally, between the upper surface of insert carbide-silicon block and flange sheet there is combined fire-resisting insert that is equipped with filling material and fire-resisting dielectric elements, the height of the insert is equal to 0.10-0.20 of insert block height.

EFFECT: possibility to increase destruction resistance of side refractory in the upper part in case of possible interaction with aluminium silicate and fluoride salts during melt penetration, service life of cathode device of aluminium electrolyser, reduction of specific consumption of energy and labour costs.

4 cl, 1 dwg, 1 ex

FIELD: chemistry.

SUBSTANCE: invention relates to sintered articles made from zircon and zirconium dioxide for use in a glass-melting furnace, particularly in articles used as supporting blocks for electrodes, or in an electrolysis cell in contact with molten cryolite. The initial load for producing the articles contains 5-50% zircon and has the average chemical composition given below, in wt % based on oxides with sum total of 100%: silicon dioxide SiO2 and zirconium dioxide, where content of zirconium dioxide ZrO2 is at least 75%, 0.2-6% dopant selected from Nb2O5, Ta2O5 and mixtures thereof, possibly a stabiliser selected from Y2O3, MgO, CaO, CeO2 and mixtures thereof in amount of 6% or less, 'other oxides' in amount of 6.7% or less. Components are formed from the initial charge and then sintered to obtain articles.

EFFECT: obtaining articles having high electrical resistance at temperatures of up to 1500°C and good resistance to corrosion caused by molten glass.

27 cl, 1 tbl, 32 ex, 1 dwg

FIELD: metallurgy; graphitic cathodes for production of aluminum.

SUBSTANCE: the invention presents a graphitic cathode for electrolysis of aluminum and is dealt with the field of metallurgy, in particular, with the graphitic cathodes used in production of aluminum by an electrolysis. The graphitic cathode for electrolysis of the aluminum is produced by graphitization of the cathodic block from a carbonaceous material. At that the cathode is made as the entire block with different specific electrical resistance along its longitudinal axis. At that the specific electrical resistance in the end areas of the cathode is more, than in its central area. The technical result - increased service life of the graphitic cathode at the expense of increased erosion resistance in the end areas of the cathode.

EFFECT: the invention ensures increased service life of the graphitic cathode at the expense of increased erosion resistance in the end areas of the cathode.

6 cl, 7 dwg, 1 tbl

FIELD: metallurgy; production of graphitic cathodes.

SUBSTANCE: the invention presents an impregnated graphitic cathode for production of aluminum by electrolysis and is pertinent to the field of metallurgy, in particular, to production of the graphitic cathodes used in production of aluminum by electrolysis. The invention offers an impregnated graphitic cathode for electrolysis of aluminum and a method of its production. The cathode contains in its pores an impregnating product heat-treated. At that in the capacity of the impregnating product the cathode contains a carboniferous product heat treated under the temperature of no less than 1600°С to provide resistance to erosion at the expense of protection by the formed graphitized binding substance. The method includes production of the graphitic cathode, its impregnation by dipping into the impregnating product in vacuum and a thermal treatment. At that the graphitic cathode is produced from coke, with graphite or without it, and also from a pitch, and before impregnation it is exposed to calcination at the temperature exceeding 2400 °С. The impregnation is realized by a carboniferous product at the temperature of its viscous state and the thermal treatment of the impregnated cathode is conducted at the temperature of less than 1600 °С, but sufficient for hardening and-or sintering of the impregnating product and formation of the non-graphitized coal layer for protection of graphitizing binding substance against erosion. The technical result is an increase of service life of the graphitic cathode.

EFFECT: the invention ensures an increase of service life of the graphitic cathode.

4 cl, 2 dwg, 1 ex

FIELD: nonferrous metallurgy; production of aluminum by electrolysis of fused salts.

SUBSTANCE: the invention I pertinent to nonferrous metallurgy and may be used in a design of electrolyzers for production of aluminum by electrolysis of fused salts. The technical result of the invention is hardening of a hearth, a decrease of thickness of a metal layer on the hearth and an interpolar space, a decrease of speeds of circulatory flows of cathodic metal, a decrease of losses of current. The cathodic device contains a lined cathodic housing and a hearth made out of from carbonaceous blocks with channels of a rectangular cross section. On the surface of the hearth there is a wetted with aluminum cover and the channels have the length equal to the width of the stack of the cathodic device, and with a width equal 1,1-2,2 well of the carbonaceous block, depth, equal to 0.2-0.4 of height of the carbonaceous block and thy are formed by the lateral longitudinal surfaces of the carbonaceous blocks and the carbonaceous blocks of the lateral cathodic lining. The electro-conductive cover wetted with aluminum is made out of titanium diboride.

EFFECT: hardening of a hearth, a decrease of thickness of a metal layer on the hearth and an interpolar space, a decrease of speeds of circulatory flows of cathodic metal, a decrease of losses of current.

2 cl, 2 dwg

Aluminum cell // 2256009

FIELD: major repair of aluminum cells.

SUBSTANCE: cathode casing of aluminum cell includes lengthwise walls with windows for outlet of cathode rods, end walls, bottom and ring frames rigidly joined with walls and bottom. In order to lower labor consumption, simplify mounting and dismounting operations. Ring frames adjacent at least to one of lengthwise walls (except boundary ring frames) from their upper part till inner edge in range of height of windows for outlet of cathode rods are freely adjoined to said lengthwise wall. According to other variant of invention at least one lengthwise wall is detachable. Parting places of said wall are arranged between boundary ring frames in range of height of windows for outlet of cathode rods. In parting places members providing rigid joint of detachable wall with fixed portion of casing wall are mounted.

EFFECT: improved design, simplified works at major repair.

4 dwg

FIELD: formation of protective coatings for carbon containing components of electrolytic cell at aluminum production.

SUBSTANCE: method comprises steps of preparing liquid suspension of refractory material dispersed in solution of lignosulfonate binder; applying suspension as coating on surface of carbon containing component; drying coating.

EFFECT: improved resistance of carbon containing component against rupture at operation of electrolysis cell.

34 cl, 1 dwg, 4 tbl, 7 ex

FIELD: non-ferrous metallurgy; electrolytic production of aluminum; cathode units of aluminum electrolyzers.

SUBSTANCE: proposed side lining includes interconnected members - plates and blocks made from non-metallic refractory compounds possessing high resistance and interconnected by means of end faces in form of inversed symmetrical projections and recesses and adhesive or cementing mix. Plates and blocks are made from silicon carbide. Angular blocks are made in form of strip, 70 mm thick and 600-800 mm long which is bent at center around longitudinal axis at angle of 90° relative to vertical whose end faces are inclined at angle of 18° relative to vertical and are narrowing downward by 219 mm each. End faces are made in form of inversed symmetrical projections and recesses at radius of 14-15 mm which are parallel to vertical axis of walls of aluminum electrolyzer.

EFFECT: increased service life; enhanced strength and reliability; saving of lining material; increased useful volume of electrolyzer; increased yield of aluminum.

4 dwg

FIELD: aluminum cells, namely cathode facing for them.

SUBSTANCE: cathode facing includes carbon blocks, heat insulation layer and refractory part having two protection layers, upper layer adjoining to carbon blocks and lower layer made of powder materials. Upper protection layer includes alumosilicate composition resistant against action of electrolyte components containing 27 -35% of Al2 O3 with fraction size no more than 2.5 mm and with thickness consisting 10 - 50% of height of refractory part. Lower protection layer is made at least of one sealed metallic vessel filled with refractory material including carbon-containing composition resistant against action of melt aluminum and electrolyte components and having heat conductivity factor no more than 0.1 Wt/(mK). In lower protection layer vessels are filled with carbon black; thickness of said layer consists 50 - 90% of height of refractory part.

EFFECT: increased useful life period, improved operational characteristics of cell.

3 cl, 7 dwg, 1 tbl

FIELD: aluminum production electrolyzers of all types.

SUBSTANCE: proposed method includes mounting the heat-insulating and refractory components of electrolyzer and applying protective material on base of covalent nitrides to surface of side lining. Used as protective material is boron nitride-based material which ensures reduction of after-start period, increases electrolyzer service life, enhances aluminum grade, increases yield by current and daily productivity of electrolyzer; protective material is applied flush with top in continuous layer. Lower boundary of coat is located below "electrolyte-metal" interface. Thickness of coat is maintained within 0.1-1 mm. Open surface porosity is maintained within 2-3%. Consistency of material of coat changes from fluid to viscous-flow state. Application of coat is performed by spraying, painting or concrete-spraying method.

EFFECT: increased service life of electrolyzer; increased daily productivity of electrolyzer.

4 cl, 2 dwg, 1 tbl

FIELD: installation of aluminum electrolyzer hearth.

SUBSTANCE: proposed method includes preliminary estimation of quality of hearth modules by proximate ultrasonic inspection, mounting of complete set of hearth modules and forming of hearth; electrolyzer is equipped with hearth modules at inhomogeneity index not exceeding 0.65 relative units according to ultrasonic inspection; inhomogeneity index is determined by the following formula Iinhom = (tmax/tmin-1), where Iinhom is inhomogeneity index according to ultrasonic inspection; tmax is maximum magnitude of index of ultrasonic inspection for definite electrolyzer; tmin is minimum magnitude of index of ultrasonic inspection for definite electrolyzer; hearth is formed in such way that adjacent modules with close indices of ultrasonic inspection are mounted in longitudinal and transversal directions; modules with minimum indices of ultrasonic inspection are mounted in center of hearth at smooth increase of this index toward end faces of electrolysis bath.

EFFECT: increased service life of hearth; reduced yield of low-grade metal; reduced power requirements.

3 dwg, 1 ex

FIELD: mounting aluminum electrolyzers at major repair or in capital construction.

SUBSTANCE: current-supply metal rod is placed in slot of carbon block on layer of carbon-containing conducting material. Surface of carbon block slot is preliminarily coated with carbon-based surfactant and layer of carbon-containing conducting material is compacted by vibration applied on current-supply metal rod, thus ensuring reliable electromechanical "conducting rod-carbon block" contact and reducing probability of penetration of aluminum melt into hearth body. At application of vibration in local zone on side of flush area, maximum reduction of voltage drop is ensured in contact layer between rod and block slot. Maximum thickness of layer of carbon-containing conducting material before vibration is equal to optimal magnitude determined by definite formula.

EFFECT: enhanced efficiency.

4 cl, 4 dwg, 1 tbl

Up!