Electrolyser for aluminium production

FIELD: chemistry.

SUBSTANCE: partitions and/or grids, and/or aluminium-moistened open-pore cellular structures from material lass electrically conductive than aluminium are placed under each anode on the bottom surface, perpendicular and/or at angle 45-90° to bottom plane, perpendicular and/or at angle 45-90° to longitudinal axis of cathode rods, which completely of partially prevent horizontal components of cathode current from flowing in aluminium layer.

EFFECT: reduction of horizontal components of currents in melt layer, uniform distribution of current, reduction of inter-pole distance and reduction of electric energy consumption for aluminium production or increase of output by current.

15 cl, 8 dwg

 

The invention relates to ferrous metallurgy, in particular to the electrolytic production of aluminum, namely the construction of electrolytic cells for aluminium production.

Known cell [1]containing cathode device and the anode of the device. Cathode device has a bath with a coal furnace hearth, laid out coal-fired units with integrated tinsel leads enclosed in a metal casing. Between the metal casing and coal blocks placed refractory and insulation materials. The anode of the device contains a carbon anode connected to the anode bus. The anodes are placed in the upper part of the bath and immersed in the molten electrolyte.

A disadvantage of the known design of the electrolyzer is the fact that the developed technology is characterized by a very high specific consumption W defined by the equation

W=vkηwhere V is the voltage across the room; η is the current output, k is the electrochemical equivalent [kg/kA*h].

Typically the technologies to produce aluminium W=13-15 kWh/kg of metal. However, this energy consumption is approximately 2 times larger than theoretically predicted. For this there are two reasons:

1. The voltage V greater part is occupied by the ohmic drop the voltage in the electrolyte, measured by the electrode (interpolar) gap (EMF). Usually this distance is about 5 cm;

2. The current efficiency η decreases with a sharp increase in the interaction (the so-called "reverse interaction) anode products (carbon dioxide) and cathodic products (dissolved aluminum) with increasing magnetohydrodynamic (MHD) stirring (circulation) of the metal and the electrolyte (MHD circulation of the melt increases with a decrease in inventories as a result of increasing the strength of interaction between the horizontal components of the current in the melt and magnetic fields).

Thus, one of the major drawbacks of the above construction is relatively high ohmic resistance, EMF and high energy consumption.

Known electrolytic cell for aluminium production ([2], figure 1), consisting of anode current supply, carbon anode, a carbon cathode located under the anode of additional elements "mushrooms", made of titanium diboride, isolation, electrolyte, liquid aluminum, Blums. The design serves to reduce inventories and, thus, to reduce the voltage V and specific energy consumption.

The disadvantage of this design of the cell is small thermo-mechanical and chemical resistance of "fungi", made of titanium diboride, especially on the borders of the metal-electr is lit; the complexity of attachment "mushrooms" to the furnace hearth and the impossibility of attaching the existing electrolyzers, a small area of contact of the fungus with the coal furnace hearth, as well as the relatively high cost and the inability surgical removal of "mushrooms" from the interelectrode gap, if necessary, for example lowering the anode to the cathode.

Known electrolytic cell for aluminium production adopted for the prototype ([3]), including cathode device containing a bath with a coal furnace hearth, laid out coal-fired units with built-in cathode current leads enclosed in a metal casing, is placed between the metal casing and coal blocks of refractory and insulating materials, anode device containing a carbon anode connected to the anode bus bar placed at the top of the bath and immersed in the molten electrolyte, characterized in that the coal furnace hearth under each of the anodes are tables with higher specific conductivity than the electrolyte, which is resistant to destruction in cryolithology melts and liquid aluminum, and the top surface of the Cabinet is above the level of the cathode aluminum, and tables made with the ability to move and/or replace if necessary.

The disadvantages of the known constructions of the cell ablauts is:

the relatively large amount of space in the EMF occupied tables, weight and cost of the TABLES, the complexity of the movement and/or replacement of tables if necessary. If necessary, use mass located inside the Cabinet, for example cast iron "weights" or fill, this may reduce the reliability of the design due to the difference of coefficients of thermal expansion of the materials, and the penetration of the electrolyte through the pores of the tables to the filler material, leading to premature corrosion and contamination of the cathode metal. Difficult the possibility of automatic control vertical movement of the tables when changing the thickness of the cathode metal. Tables is not enough to reduce the horizontal components of the cathodic current and MHD stirring of the melt.

The objective of the invention is the reduction in specific energy consumption by reducing the ohmic resistance and the voltage drop in inventories, increase of the output current due to the reduction of the horizontal components of the cathodic electrical current in the melt, increasing the hydrodynamic resistance to movement of the melt at the border of the aluminum-electrolyte, reduced magnetohydrodynamic (MHD) stirring of the melt and reverse reactions of the metal with an anodic gases, as well as the convenience of the location of additional elements in MP is on the furnace hearth and the possibility of their rapid and automated handling and/or removal of the electrode gap (mPas) if necessary, for example, lowering of the anode to the cathode, and reducing the cost of construction.

The technical result is to create a structure of aluminum electrolytic cell comprising a cathode device containing a bath with a coal furnace hearth, laid out coal-fired units with integrated tinsel leads enclosed in a metal casing, is placed between the metal casing and coal blocks of refractory and insulating materials, anode device containing a carbon anode connected to the anode bus bar placed at the top of the bath and immersed in a molten electrolyte, in which, according to the proposed solution, on the surface of the bottom and/or in the space between the anode and cathode, under each of the anodes of the hosted partitions and/or grill, of refractory material, and/or wetted aluminum Otkrytiye cellular structure of carbon or refractory material, filled or saturated partially or fully aluminum, with uniform or anisotropic conductivity, greater along the axis of the anode-cathode and less in the perpendicular direction, of a material less conductive than aluminum, perpendicular and/or at an angle of ±45° to ±90° to the plane of the bottom, perpendicular and/or at an angle of ±45° to ±90° to the longitudinal axis of the cathode rods, which reduces horizontal the components of the cathode current along the bottom in the layer the melt. Due to the damping of horizontal currents in the melt is reduced MHD circulation and may reduce the EMF between the anode and cathode, i.e. to reduce specific energy consumption and/or increase the current output.

The invention complement private distinctive signs, also aimed at solving the task.

Partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure have a height equal and/or unequal depending on their location on the furnace hearth and below and/or above the level of the metal, or on the boundary of the metal-electrolyte interface, defined using the appropriate optimality criterion of the distribution of electrical potentials and currents, i.e. depending on specific purposes: for example, reducing the interpolar distance (MPR), the reduction of energy consumption; and/or increase the current output, etc.

Partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure is configured to move and/or replacement, if necessary.

Partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure rely on the cathode surface, or glued to the cathode, or swim near the surface of the partition aluminum-electrolyte interface.

Wetted aluminum Otkrytiye cellular structure have anisotropy the second conductivity along the axis of the anode-cathode and less in the perpendicular direction.

Partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure made of carbon blocks, in particular from waste in the form of a battle standard deck blocks of baked anodes and/or electrodes, silicon carbide and/or material type ANAPLAST.

Partitions and/or gratings, and/or wetted aluminum Otkrytiye honeycomb structure coated or impregnated with a substance containing, for example, titanium diboride, ensuring wetting of aluminum.

The outer surface of the septum and/or gratings, and/or wetted aluminum Otkrytiye cellular structure pre-treated/impregnated inhibitory substances that protect against oxidation.

Partitions and/or lattice, before to be placed in the space inventories, tight in the vacuum packaging of aluminium foil and heated to a temperature as close as possible to the temperature of electrolysis, but less than the melting temperature of the cathode metal. Then partition and/or the grating is placed in the space inventories.

Under each anode set from 1 or more partitions and/or gratings, the distance between the partition walls and/or railings is inversely proportional to their number, and the pore size wetted aluminum otkritosty cellular structures is inversely proportional to the number of pores per unit area of the cathode.

P is raigorodsky and/or lattice, and/or wetted aluminum Otkrytiye cellular structure can be of various shapes, for example, a parallelepiped, prism, cube, hexagonal, orthogonal, hemispherical, cylindrical, and in the side walls of the partitions and/or gratings, performed through hole rectangular or round shape, primarily located closer to the bottom surface of the bottom (cathode), to facilitate horizontal flow of aluminum in the bottom layer at the surface of the bottom (cathode).

On the surface of the carbon part of the bottom (cathode) can be performed in the longitudinal and/or transverse drainage channels for accumulation and evacuation of aluminum.

Partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure can be of various shapes, for example, a parallelepiped, prism, cube, hexagonal, orthogonal, hemispherical, cylindrical, etc. but symmetry and unification of the partitions and/or gratings can be taken into account for optimal design and process of electrolysis according to the criteria of reducing the unit cost of energy, and/or increase the current output.

Septum and/or the grating, and/or wetted aluminum otkrytiya cellular structure, can be captured on the edges of the brackets are made of electroconductive material resistant to the electrolyte, and R is polozhennymi along the side surfaces of the anode and/or along the bottom plane of the anode, with the ability to move vertically, and/or in the horizontal plane, if necessary.

The invention is illustrated by sketches (Fig.2-8).

The cell contains a carbon anode with anode current supply 1, a coal-fired furnace hearth (cathode) 2. The bottom surface of the carbon anode immersed in the electrolyte 3. Inside of the cell is lined with a lining 4. The cell is equipped with a traditional device for the supply of raw materials (alumina, forsale) and exhaust anode gas 5, a device for supplying a current of 6 to the cathode 2. In the interpolar gap (mPas), in addition to the cathode metal 9 are partitions and/or grating 7 and/or wetted aluminum Otkrytiye structure 8. The upper part of the septum and/or grating 7, and/or wetted aluminum otkrytosti mesh structure 8 is in the electrolyte 3 and the lower part is in the cathode metal (liquid aluminium) 9.

On the surface bottoms, along the longitudinal axis of the cell and/or along the projection of the perimeter of the anode to the cathode surface, one or more recesses 12 (Fig) for drainage and evacuation of the metal of the bath.

Installation of the aluminum cell is as follows.

Partitions and/or grating 7, and/or wetted aluminum Otkrytiye cellular structure 8 may be coated or impregnated with a substance/substances containing/mi and/or abrazos the m/mi, for example, titanium diboride, providing/mi wetting by aluminum. Wetted aluminum Otkrytiye cellular structure 8 or glued to the furnace hearth, or inserted into the septum and/or lattice so that Otkrytiye cellular structure 8 was within the walls and/or gratings 7 and the lower surface otkrytosti cellular structure was in cathode metal (liquid aluminium) 9. Partitions and/or grating 7, and/or wetted aluminum Otkrytiye mesh structure 8, before to be placed in the space inventories, can be, if necessary, are covered in the vacuum packaging of aluminium foil with the aim of closing the surface pores, protection against oxidation in air, improving heat transfer and heated to a temperature as close as possible to the temperature of electrolysis, but less than the melting temperature of the cathode metal. Then partition and/or grating 7 is placed in the space inventories.

For pots with burnt anodes installation and/or replacement of the septum and/or grating 7, if necessary, is carried out directly during the replacement of the corresponding anode block, bath off from the power supply is not required. For cells with self-baking Soderberg anodes installation of partitions and/or grating 7 is also directly under the Academy of Sciences of the d in the preliminary raising of the anode 1, this bath may be disconnected from the power source current. In both cases, the locations of the partitions and/or grating 7 is the clean coal hearth 2 of accumulated sediment.

To move the partition and/or the grating 7 is captured by the edges with hooks or brackets 10, made of electroconductive material resistant to the electrolyte and cathode metal and located along the side surfaces of the anode and/or along the bottom plane of the anode, with the ability to move walls and/or lattice 7 vertically, and/or partially in the horizontal plane, if necessary. The bracket 10 is attached to a floating thrust 11, which may be made from conventional structural materials.

When this happens improvement following TEP electrolysis: reduction in specific energy consumption, increase current output.

LITERATURE

1. H. Chang, V. de Nora and GA Sekhar "the Materials used in the production of aluminum by the method of the Era-Hall. - Ed. Krasnoyarsk. state University, Krasnoyarsk, 1998.

2. J.R. Rayne: US Patent, 4.405.433, April 1981.

3. Patent # 111540. - Electrolytic cell for aluminium production./ Popov, Y., Poles PV, Ostrovskii I.V. Priority from 30.06.2011.

1. An electrolytic cell for producing aluminum, comprising cathode device containing a bath with a coal furnace hearth made of coal the blocks with built-in cathode current leads, prisoners in the metal casing, is placed between the metal casing and coal blocks of refractory and insulating materials, anode device containing a carbon anode connected to the anode bus bar placed at the top of the bath and immersed in the molten electrolyte, characterized in that it is equipped with baffles and/or gratings and/or wetted aluminum Otkrytiye honeycomb structures made of a material that is less electrically conductive than aluminum, is placed under each of the anodes on the surface of the bottom of the cathode and/or in the space between them, perpendicular and/or at an angle of 45°-90° to the plane of the bottom, perpendicular and/or at an angle of 45°-90° to the longitudinal axis of the cathode rods.

2. The electrolyzer according to claim 1, characterized in that the partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure made of a height equal and/or unequal, depending on their coordinate locations on the furnace hearth, which is below and/or above the level of the metal, and/or corresponds to the boundary of the metal-electrolyte interface.

3. The electrolyzer according to claim 1, characterized in that the partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure is configured to move and/or replacement, if necessary.

4. The cell according to any one of claims 1 to 3, otlichayushiesya, what barriers and/or gratings, and/or wetted aluminum Otkrytiye cellular structure bonded to the cathode.

5. The cell according to any one of claims 1 to 4, characterized in that the wetted aluminum Otkrytiye cellular structure have anisotropic conductivity along the axis of the anode-cathode and less in the perpendicular direction.

6. The electrolyzer according to claim 1, characterized in that the partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure made of carbon blocks, in particular from waste in the form of a battle standard deck blocks of baked anodes and/or electrodes, silicon carbide and/or material type ANAPLAST.

7. The electrolyzer according to claim 1, characterized in that the partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure to wetting by aluminum coated or impregnated with a substance containing, for example, titanium diboride.

8. The electrolyzer according to claim 1, characterized in that the outer surface of the walls and/or gratings, and/or wetted aluminum otkritosty cellular structures pre-treated/impregnated protective inhibitory substances.

9. The electrolyzer according to claim 1, characterized in that the partitions and/or gratings, and/or wetted aluminum Otkrytiye honeycomb structure before placing in the space of the interpolar gap MP is tight in the vacuum packaging of aluminium foil and heated to a temperature the most close to the temperature of electrolysis, but less than the melting temperature of the cathode metal, and then partition and/or the grating is placed in the space inventories.

10. The electrolyzer according to claim 1, characterized in that under each anode set of one or more partitions and/or gratings, and/or wetted aluminum otkritosty cellular structures, distance between septa and/or the grating is inversely proportional to their number, and the pore size wetted aluminum otkritosty cellular structures is inversely proportional to the number of pores per unit area of the cathode.

11. The electrolyzer according to claim 1, characterized in that the partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure made of any shape, for example, in the form of a parallelepiped, prism, cube, or a hexagonal orthogonal, hemispherical, cylindrical form.

12. The electrolyzer according to claim 1, characterized in that the septum and/or the grating, and/or wetted aluminum otkrytiya cellular structure captured by the edges of the brackets are made of electroconductive material resistant to the electrolyte and located along the side surfaces of the anode and/or along the bottom plane of the anode, so that they can move vertically and/or in the horizontal plane, if necessary.

13. Electrical wiring in alizer according to claim 1, wherein the septum and/or gratings, and/or wetted aluminum Otkrytiye cellular structure, anisotropic conductivity which is greater along the axis of the anode-cathode and less in the perpendicular direction, is made mainly of aluminium oxide/alumina, for example from high-alumina unshaped concrete and/or plates and/or granite-like.

14. The electrolyzer according to claim 1, characterized in that the partitions and/or gratings, and/or wetted aluminum Otkrytiye cellular structure located on an extra layer otkrytosti cellular structure.

15. The electrolyzer according to claim 1, characterized in that on the surface of the bottom along the longitudinal axis of the cell and/or along the projection of the perimeter of anode to cathode surface one or more grooves for drainage and evacuation of metal from the bath.



 

Same patents:

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.

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3 cl, 3 dwg, 2 ex, 2 tbl

FIELD: metallurgy.

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3 cl, 3 dwg, 1 tbl

FIELD: metallurgy.

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FIELD: metallurgy.

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FIELD: metallurgy.

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FIELD: metallurgy.

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4 cl, 5 dwg

FIELD: chemistry.

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11 cl, 4 dwg

FIELD: metallurgy.

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4 cl, 1 dwg, 1 ex

FIELD: metallurgy; graphitic cathodes for production of aluminum.

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6 cl, 7 dwg, 1 tbl

FIELD: metallurgy; production of graphitic cathodes.

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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

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