Method of lining of cathode device of electrolyser by unshaped materials
SUBSTANCE: method includes charging of the powdered material in the cathode casing of the electrolyser, its levelling using rack, coverage of the charged material by dust isolating film and compaction performed by two stages: preliminary static and final dynamic action by means of the successive movement of the work organs of the static and dynamic compaction along the longitudinal axis of the cathode of the aluminium electrolyser via the resilient gasket made out of at least two layers: bottom preventing extrusion of the powdered material in front along the movement , and top ensuring gasket engagement with the work organ of the static compaction, at that the dynamic action is performed by vibration unit connected with the static treatment unit by means of the resilient elements with possibility of simultaneous movement relatively to the horizontal and vertical axes.
EFFECT: reduced expenses for lining materials and reduced labour costs during their installation.
7 cl, 9 dwg
The invention relates to ferrous metallurgy, in particular to the mounting of the cathode devices of electrolysis for the production of primary aluminium using unshaped materials.
The cathode of the device for electrolytic cells for the production of primary aluminium consists of a conductive cathode blocks, insulated from the bottom. Between the cathode blocks and thermal insulation is a barrier layer of refractory material to prevent the ingress of Tortola and sodium vapor in insulating layers. The process of infiltration and interaction of the liquid phase components of the electrolyte from the bottom blocks in refractory materials is a complex phenomenon involving the physical and chemical interaction at the boundary of the liquid melt, consisting of NaF and Na3AlF6 and refractory material, whose structure is the primary factor in the specified interaction.
In accordance with the law Darcy the driving force for the penetration of molten fluoride salts in the barrier material is a pressure gradient along the height of the barrier material.
where: q - volume flow of molten fluoride salts through the cross section S, m3/(m2C); k - coefficient of permeability, m2;
dP/dx is the pressure gradient� height of the barrier material, PA; μ - dynamic viscosity, PA*s.
Because the barrier material is a heterogeneous structure with different distributions of pore size, conventionally, the interval of the pore size can be divided into three areas. For large pores (100 μm), the pressure gradient is primarily due to hydrostatic and gravitational forces. For smaller channel then along with these forces begin to manifest capillary forces. Due to the potential energy of the field of capillary forces, the pressure gradient is much higher than for large pores and the capillaries are able to intensively absorb the molten forsale. In this case, the depth of penetration of the molten vtortola may be determined by the ratio resulting from the law of Poiseuille flow:
where h is the penetration depth; d - the diameter of the pores; σ - surface tension; µ is the viscosity of the melt.
With further reduction in the size of the pore pressure gradient, caused by capillary forces increases, however, a much faster growing of the hydraulic resistance to the movement of liquid and the penetration of florala such pores can be neglected.
As follows from equation (2), the penetration depth of fluorine-containing melt decreases with increasing its viscosity, lower surface tension and decreasing cu�left angle. Physico-chemical characteristics of the melt contained in the equation (2) depend both on temperature and melt composition.
In the initial period of the process of penetration of the main component in podkolodnii area is NaF, which is explained by the occurrence of the next reaction in the body of the cathode block with infiltration of cryolite:
The interaction between pure alumina refractories and sodium fluoride occurs by the reaction of formation of β-alumina:
However, due to the significantly lower density of the reaction product of β-alumina volume changes occur in the lining, causing the vertical stresses at the bottom and its possible destruction. With the advent of refractory relatively small amounts of SiO2 (~25%) in addition to reaction (4) will be the reaction of formation of nepheline (5):
The excess refractory material and a small amount of NaF, nepheline reacts with silicon dioxide with the formation of albite NaAlSi3O8, who will be in a viscous glassy molten state, which prevents further movement of the front interaction in the lower part of the cathode device of the cell:
The increase of melt viscosity due to the presence of albite in the area of R�shares between aluminosilicate refractory lining and the molten cryolite reduces the likelihood of penetration of Tortola in the lower insulating layers of the cap.
Further increase the content of SiO2 in the silica-alumina refractory material (over 47%) leads to the fact that in the reaction zone of β-alumina is absent, and nepheline and albite are formed by using combinations of the reactions (5) and (6). At very high content of SiO2 (72%) due to the lack of Al2O3 will be impeded the formation of nepheline.
Therefore, among a significant number of refractories used in the bases of the pots, the most widespread materials aluminosilicate composition with a content of 28%<Al2O3<34%. An important role is their relatively low cost.
The foregoing shows that the barrier materials with thin sinuous channels with a dense packing of small particles, characterized by low gas permeability and obviously, a slow process of infiltration of molten fluoride salts or products of their reaction with barrier materials.. in addition, the presence of temperature gradient in the direction of implementation, the increase of melt viscosity due to the formation of albite also will slow down the implementation process.
Traditionally in the lining of the cathode devices of electrolyzers are used molded products in the form of bricks of various sizes, predominantly aluminosilicate composition having low gas permeability and low porosity. However �isopropylacetate barrier masonry in General is not determined by the properties of the individual bricks, but mostly the condition of the joints between them. Used for sealing by grouting mortar on the basis of which mortar is made, is vulnerable to tarsoly and aggressive gases due to its high porosity. Besides used in the preparation of masonry mortars water, causes installation problems with electrolytic cells in conditions of low temperatures and has a negative influence on the resistance of insulating materials in the cathode cell unit.
Along with a molded barrier materials to date have accumulated considerable experience in the application of loose powders of different grain-size and mineralogical compositions, which allow to obtain seamless layers. The technology of using unshaped during mounting of the cathode devices of the pots favorably with technology using masonry reduced time of installation of lining materials and lower labor costs.
A method of lining comprising filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, characterized in that is used the charging unshaped material that reacts with percolate with the formation of the product in the solid state at operating temperature�RAH cathode device. (A. Seltveit, Diffusion barrier for aluminium electrolysis fernaces, United States Patent Pat. No.4,536/273, 1985). However, none of the tests confirmed the viability of this method of lining is because of the high porosity of the unconsolidated layer ensured a continuous supply of gaseous and liquid components of Tortola in insulation.
A method of lining comprising filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, characterized in that the compaction was carried out using ordinary rollers (Forsblad L. Vibratory compaction of soils and grounds. TRANS. angl. ed Kostalova M. P. Transport, 1987, 191). However, evaluation of the results of the static formation shows that they are not providing the desired structure of lining material-low porosity and small pore size.
A method of lining comprising filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, characterized in that for sealing rollers are used, provided with a vibrating mechanism (Patent US 4184787; E01C 19/38). This leads to a slight increase in packing density; however, the resulting barrier layer has a sufficiently high porosity (25%), and, in addition, the surface has a wave-like defects.
A method of lining, including�by filling a powder material in the cathode casing of the cell, levelling it with the help of Reiki, characterized in that the seal unshaped materials, is performed by the external vibration of the train platform, onto which the cathode of the device (Siljan O, Junge O, Trygve B., Svendsen, T., Thovsen K. Experiences with dry barrier powder materials in aluminium electrolysis cells - Light Metals, 1998, p.573-581). The disadvantage of this method is razreklamirovana material and separation of particles along the height of the layer, and hence an insufficient degree of resistance to penetration of the fluoride salts. This leads to high rates of chemical reactions, which reduces the life of pots.
A method of lining a cathode device of the aluminum electrolysis cell comprising filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, characterized in that the seal produced by pneumotubograme top through gracenabulo carbon mass (R. Weibel Advantages and disadvantages of various refractory materials for cathodes. In the book: Aluminium Of Siberia. Krasnoyarsk, 2002, pp. 14-24). However, the use gracenabulo weight environmentally dangerous, and with the transition to holodnokatanuju mass and decrease cryolite ratio the service life of electrolytic cells became low.
A method of lining (Refractory cathodes for aluminum reduction cells / S. G. Sennikov and �R. - Refractories and technical ceramics, 2003, No. 10, pp. 22-31), which consists in filling a powder material in the cathode casing of the cell, levelling it with the help of Reiki, sequential stacking of a buried material layer polyethylene sheets of fiberglass or fiberboard and compaction of the material by the dynamic method using a sled with a vibrator). However, using such devices occur simultaneously as processes of compaction and decompaction of the mixture, whereby there is a dusting of stamps of the material.
A method of lining comprising filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, characterized in that the compaction rollers, equipped with vibratory mechanisms (Patent US 4184787; E01C 19/38). This leads to a slight increase in packing density; however, the resulting barrier layer has a sufficiently high porosity (25%), and, in addition, the surface has a wave-like defects.
A method of lining a cathode device of the aluminum electrolysis cell, comprising filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, characterized in that the seal starts from the corner of the cathode casing and is made in a spiral on �the direction from the outside to the center of the cathode. The displacement of the vibrator is made with an overlap of a few inches the previous compacted plot. For the final seal of barrier mixtures need to make a few complete cycles of passes of the vibrator.
The main disadvantage of this method of lining are the need for multiple passages of the flow table on the surface of the barrier material in the cathode ustoroystvo due to the small size of the platform. The parameters of the resulting barrier layer depend on the expertise and trustworthiness of the operator. But the most significant drawback is the fact that vibroblade based primarily on dynamic molding method at optimum amplitude-frequency and weight characteristics. In low bulk density of lining material this leads to the fact that simultaneously occur as the processes of compaction and decompaction of the mixture. As a result, there is a dusting of stamps of the material. The use of relatively thin sheets of fiberglass or fiberboard, not having sufficient stiffness that results in a rough surface, resulting in after laying the surface of the barrier material as well as when using the vibratory roller has an undulating shape. Attempts to increase the gesture�spine material used to cover, hampered by the reduction in the efficiency of the compaction process (Patent EP 1127983; E01C 19/38; E02D 3/046).
The known method of forming a seamless lining layers in aluminium reduction cells, comprising filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, the shelter material covered paleozoology wrap and seal, characterized in that the sealing material is carried out in two stages: preliminary static and final dynamic effects, by sequential displacement of the working bodies of static and dynamic seals along the longitudinal axis of the cathode aluminum reduction cell for the entire width of the lining layers formed through the elastic pad, wherein the dynamic seal material carried vibroblade with a permanent static load on them.
As intended, the significant presence of similar features, the solution chosen as a prototype.
In the known solution, the sealing is carried out in two stages: preliminary static and final dynamic effects, by sequential displacement of the working bodies of static and dynamic seals along the longitudinal axis of the cathode aluminum reduction cell the entire width of the Fort�interface lining layer through the elastic strip, thus the dynamic compaction of the material is carried vibroblade with a permanent static load on them.
This method of lining does not meet the requirement of receipt of high quality great barrier layer of depth with a low bulk density.
Technical device by which the above process is carried out lining, an apparatus for forming seamless lining layer in an aluminum electrolytic (Russian Federation Patent RU 2296819 CL. C25C 3/06, C25C 3/08, publ. in BI No. 10, 2007).
As intended, the significant presence of similar features, the solution chosen as a prototype.
Apparatus for forming seamless lining layers in aluminium reduction cells contains the actuator, the sealing device consisting of a static block for processing and dynamic processing unit, a unit for static treatment made in the form of the rink with the actuator and connected to the rink through the rocker arm and thrust block dynamic handling, made in the form of vibroblade, including the vibration exciter directional driving force and mounted with possibility of its movement around the horizontal axis of the rink.
The main disadvantage of the prototype device are the extrusion of the sealing material before the static block processing when f�frmirovanii great barrier layer of depth with a low bulk density. In addition, the absence in the prior art device, the structural elements that contribute to the damping of the horizontal component of vibration lead to technical difficulties when using as sources of oscillations with circular exciters driving force or exciters with a directional driving force installed on vibroblade at an acute angle to the machined surface due to the transfer of the vibration of the whole structure. When using such sources of vibrations to the vibration motors are subjected to the static block processing and other elements of the device that can lead to failure and therefore reduces the reliability and durability of the device as a whole.
The objective of the proposed technical solution is the reduction in apparent porosity of lining layers derived from unshaped materials and improving the reliability of its work.
The technical result of the invention is to slow the rate of penetration of the molten Forcola and corrosive gaseous components through the barrier layer in thermal insulation of the cathode, the improvement of the performance of the electrolyzer (reduction of energy consumption for production of 1 tonne of aluminium, the growth of life).
The problem is solved in that in the method paterova�Oia cathode device of the aluminum electrolysis cells, includes filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, the shelter material covered paleozoology film and compaction carried out in two stages: preliminary static and final dynamic effects, by sequential displacement of the working bodies of static and dynamic seals along the longitudinal axis of the aluminum cell cathode through the elastic strip, the elastic strip is made of at least two layers: the bottom, preventing the extrusion of powdered material forward in the direction of motion and upper - bonding strip with the working body of the static seal. The seal is produced along the longitudinal sides of the cathode device to a width of not less than 0.5 of the width of the cathode of the device; the rigidity of the strip varies in the range 80÷270 Nm2and as the bottom layer strip use thick steel sheets (2,5÷4)*10-4, width 0,12÷0,15 and a length of 0,2÷0,25 width mouldable layer, wherein the steel sheets are stacked on the entire sealing square butt joint along the long side of the cathode of the device in 3-4 rows, and the upper layer bonding strip with the working body of the static seal stack of rubber material� thickness of 2-3 on the thickness of the steel sheet.
The task is achieved in that in the device for implementing the method containing the block static treatment made in the form of the rink driven and dynamic processing unit mounted with a vibration exciter, a dynamic processing unit is connected to the static block processing using elastic elements with the possibility of simultaneous movement relative to the horizontal and vertical axes of the rink.
The proposed device complement private distinctive features aimed at solving the problem.
The device may be arranged so that the connection unit dynamic processing with static block processing can be performed by means of elastic elements by means of rubber or metal springs. This prevents the transfer of vibration on the motor and other elements, in particular, on the metal structure of the device when used as a vibration source with circular exciters driving force or exciters with a directional driving force installed on vibroblade at an acute angle to the machined surface, as well as improving the reliability and durability of the device as a whole.
Comparative analysis of the features of the claimed solution and the signs of the analog prototype with�imetelstat about compliance solutions to the criterion "novelty".
As the experience of operation of said device characterized by the following positive developments:
- Expanding the range of materials used in futarani cells due to the possibility of the seal of the latter, while larger sizes of layers.
- Increases the degree of compaction of the upper layers of lining material
The achievement of the above is possible only if the claimed relationship of process parameters and structural elements of the device. Comparison of the proposed solutions not only prototype, but also with other technical solutions in this field of technology is not allowed to reveal in them the features distinguishing the claimed solution to the prototype that allows to conclude that the criterion of "inventive step".
The essence of the technical solution is illustrated by example of a specific implementation and drawings. Fig.1 shows apparatus for forming seamless lining layers in aluminium reduction cells (side view) with elastic elements of metal springs; Fig.2 - apparatus for forming seamless lining layers in aluminium reduction cells (side view) with elastic elements made of rubber.
Apparatus for forming seamless lining layers in aluminium reduction cells consists of a leading disk 1 forming Pref�ne block for static seal in the form of a roller, vibroblade 2 with the vibrator 3, weights 4 disposed on the loading platform 5, which is connected to vibroblades 2 by means of the elastic elements 6 and 7 (of metal springs of Fig.1, made of rubber Fig.2) connecting fibroblast and block for a static effect on the material in the sealing fixture using the rocker 8 with the possibility of free movement of vibroblade about horizontal and vertical axes (anchor) of the rink. The drive device for forming seamless lining layers in aluminium reduction cells consists of a motor-reducer 9, the chain transmission 10. The geared motor 9 is mounted on a yoke 8, which is attached to also load platform 5.
The technical essence of the proposed solution is as follows.
The geared motor 9 and the vibrators 3 are run from the control panel. The rotation from the gear motor 9 through a chain transmission 10 is transmitted to the drive wheels 1 rink. Leading drive 1 rotates, moves the device over the surface of the elastic strip laid on the material being processed. This is a preliminary static seal unshaped refractory materials. The final seal comes from the impact on the processed material vibroblade 2, making the movement about horizontal and vertical axes of the rink and nehruji�tion weights 4 through blocks of elastic elements.
To determine the optimal design and process parameters SPM experimental study of the compaction of particulate material was carried out at the stand shown in Fig.4. The facility includes a capacity to accommodate bulk material and the local block of SPM, to ensure that the deformation of granular media static loading with superimposed vibration of different frequency spectrum and intensity.
When moving in the container with the material SPM creates a preliminary static loading rollers 1, which are also the mechanism of movement and the dynamic loading is carried out by vibroblades 2, the amplitude-frequency characteristic which is set by the vibration exciter 3. As vibration source was used for the vibration exciter directional or circular driving force. SPM is installed in container 4 filled with particulate material 5, the filling height was 300...500 mm.
The compaction of the material was carried out through the elastic coating consisting of a metal sheet 6 (Fig.4) with a thickness of 2 mm and a rubber plate 7 with a thickness of 5 mm. In the process of seal coating prevented the extrusion of material from under the rollers, contributed to the reduction of airborne dust and kept the mount on the surface of the material at large t�line compacted layer. There are two possible ways of loading: the first is static (fibroblast off), the second combined (simultaneous static and dynamic loading). For the combined effect of the material between rollers and vibroblades, is locked into a limited volume. To be squeezed from vibroblade obstructing the compacted material from the side of the rink - pre-compacted material, top - elastic coating.
Vibration acceleration in the material and on vibroblade was recorded by the piezoelectric transducer 8 and 9 (Fig.5), which allowed us to simultaneously monitor the horizontal and vertical components of vibrations. The signal from the sensors were amplified, integrated and transferred to a personal computer.
The density of the layers of the obtained compact was assessed using the static density-1 and density of the obtained compact was characterized by a dynamic elastic modulus, which was measured with a portable meter ground shrinkage HMP LFG (Fig.3).
Information gathering and subsequent processing of the measurement results was carried out using the Software of automation of experimental and technological installations ACTest©".
In the experiments, six-channel measurement system (Fig.4), comprising the following devices:
- piezoelectric accelerometers (firm brühl and cher, Denmark);
the charge amplifiers of the type 2635 (firm brühl and cher, Denmark);
- analog-to-digital Converter E-440 (JSC L-Card, Russia);
- personal computer.
When you start SPM moves along a vessel filled with fine material (Fig.5). If this is possible or only a static effect on the material, if viroblock disabled, or combined action of static and dynamic loads. Static seal is of no particular interest, as no different from an ordinary rolling. In the second case in a fixed moment of time part of the pre-compacted material 1 between vibroblade 2 and the roller 3 (Fig.5 the boundaries are marked by the letters a and B), is closed to a limited extent. His movement (squeezing) interfere with one side already compacted material and the pressure roller, the top plate 4. Directly under vibroblade there is a wave of compression deforming the material, while some of it is squeezed in a closed region, putting pressure on there loose weight. In addition, in this area under the action of vibration and associated rheological effects there is a mutual displacement of the material particles, which tend to form b�more dense structure, as well as the displacement of moisture and air, is advanced dynamic seal. The deformation process of the material ends after direct exposure to compressive loads created by vibroblades.
To determine the optimal parameters during experimental studies varied the amplitude-frequency characteristics of the vibration exciter, movement speed, static load.
The results of experimental studies in the form of graphs shown in Fig.6. The most effective compaction of particulate material in a confined space is carried out in the frequency range of 45-60 Hz; at the same time effects an increase in the frequency of vibration from 35 to 60 Hz density will be increased by 5-10%; a further increase in the frequency does not cause a noticeable change in the packing density. Increasing the exposure time at constant parameters of vibration (acceleration and frequency) causes an increase in density, and, the basic formation of a relatively dense packing occurs in the first 6-7 h; with the further loading continues to increase density, but with a significantly lower velocity.
It is established that with increasing frequency of vibration of the dynamic modulus of elasticity of the sealing material varies more quickly, h�m with increase in vibration due to the vibration amplitude, that is confirmed by the results of the experiments shown in figure 7. Curves 1a and 1B represent dependencies of the modulus of elasticity of the sealing material on the magnitude of the force acting on the system, which varies the frequency at constant static torque curves 2A, 2B corresponds to the dependence of elastic modulus on the magnitude of the force changes from static torque at a constant frequency.
It was established experimentally that the density of particulate material during vibration compaction the main influences the acceleration of the vibrations transmitted granular environment, with increasing frequency of vibration of the dynamic modulus of elasticity of the sealing material varies more quickly than the increase in vibration due to the oscillation amplitude (Fig.7). At frequency below 35 Hz efficiency vibration is significantly reduced.
Experiments have shown that the static load has no significant effect on dynamic modulus of elasticity of the packaging. However, she, being a part of the vibrating system, affects only the dynamic parameters of the latter. Fig.8 presents the dependence of the dynamic modulus, related to the acceleration, the magnitude of the static load.
Fig.9 shows the results of measurement of vibration velocity on depth in the array of sealed m�of the material. The origin of coordinates is aligned with the surface of the sealing material. The dependencies presented in figure 3 correspond to frequencies of 25 Hz, 34 Hz and 49.6 Hz (curves 1, 2 and 3 respectively). Markers ■and ● mark the points obtained experimentally and correspond to the frequencies of 25 Hz, 34 Hz and 49.6 Hz.
It is found that in the considered frequency range, the attenuation of vibration in sealing the array occurs according to the exponential law:
where ν0- the velocity on vibroblade (on the surface of the sealing material), m/s; ν is the velocity in the layer of sealing material at a depth h, m/s; λ is the damping factor, determined experimentally (λ=4,4); h - the distance from the surface to the compacted layer of material, m.
For a given material (SBS) in the frequency range 25...50 Hz, the frequency of vibration has no significant effect on the density of the material depth for a given frequency range.
The highest density of recorded material in the upper layers of the sealing array to the penetration depth (the depth at which the oscillations are damped in time), which amounted to 230 mm, at greater depths, the packing density decreases, due to the decrease in the intensity of vibration caused satuja�amount of force fluctuations.
Despite the decrease in velocity in the downstream layers, their density with increasing depth decreases slightly (by 5...10%) compaction homogeneous granulometric composition and physico-mechanical properties of the material.
Using the above-described cathode lining will allow to obtain the total economic effect per 1 cell of not less than $ 2 thousand per year by reducing the costs of lining materials and the reduction of labor costs at the site.
1. Method of lining cathode device of the aluminum electrolysis cell, comprising filling a powder material in the cathode casing of the cell, leveling it with the help of Reiki, the shelter material covered paleozoology film and compaction carried out in two stages preliminary static and final dynamic effects by sequential movement of the working bodies of static and dynamic seals along the longitudinal axis of the aluminum cell cathode through the elastic strip, characterized in that the dynamic effect is carried vibroblade connected to the static block processing using elastic elements with the possibility of simultaneous movement relative to the horizontal and vertical axes, and the movement of the working bodies of a hundred�algebraic and dynamic sealing is made through the elastic strip, made of a lower layer that prevents the extrusion of powdered material forward in the direction of movement, and the upper layer bonding strip with the working body of the static seal.
2. A method according to claim 1, characterized in that the spacer performs with stiffness in the range 80÷270 Nm2.
3. A method according to claim 1, characterized in that the strip of the lower layer using thick steel sheets (2,5÷4)*10-4width 0,12÷0,15 and a length of 0,2÷0,25 width of the compacted layer.
4. A method according to claim 1, characterized in that the seal is produced along the longitudinal sides of the cathode device to a width of not less than 0.5 of the width of the cathode of the device.
5. A method according to claim 1, characterized in that the steel sheets are placed throughout the sealing area of a butt joint along the long side of the cathode of the device in 3-4 rows.
6. A method according to claim 1, characterized in that as the top layer of bonding pads with the working body of the static seal, put a rubber material with a thickness of 2-3 thickness of the steel sheet.
7. A method according to claim 1, characterized in that the dynamic effect is carried vibroblade connected to the static block processing by means of elastic elements made of rubber or metal springs.
SUBSTANCE: electrolysis unit consists of the following: cathode device with a pool with carbon bottom, the pool is formed by carbon blocks enclosed in metallic casing with flame proof and heat-insulating materials arranged between metallic casing and carbon blocks; anode device including carbon anodes connected to anode bus, the anodes are arranged in upper part of bath and absorbed in fused electrolyte; on the carbon hearth along the anode perimeter the pedestals, or the floats resistant to destruction in cryolite aluminous fusions and liquid aluminium are located. The top surface of a pedestal or a float acts higher than a level of cathodic aluminium and a pedestal or floats can be moved and/or replaced if necessary. Pedestals or floats are made of carbon, carbide of silicon, their combination. The top surface of the pedestal or the float is flat, convex, concave, or inclined to the horizon.
EFFECT: decrease of specific power consumption due to reduction of interpolar gap, ohmic resistance and voltage drop in interpolar gap, increase of current output due to increase of hydrodynamic resistance to movement of fusion near the aluminium-electrolyte interface along the anode perimeter and decrease of mixing of fusion and counter reactions of metal with anode gases.
6 cl, 6 dwg
SUBSTANCE: invention relates to a carbon article which is produced by burning a mixture at least containing coke. The coke has low graphitisability. Also disclosed is a method of producing a carbon article, which includes mixing anthracite, graphite and/or low-graphitisability coke or mixtures thereof with at least one binding material selected from a group of oil- or carbon-based binding materials, as well as binding materials based on synthetic polymers and any mixtures of said binding materials and optional additives, endowing the mixture with a given shape, firing the moulded mixture and optional graphitisation of the fired moulded article. The invention discloses use of the carbon article as a cathode block of an aluminium electrolysis cell and a blast-furnace brick.
EFFECT: longer service life of the article, particularly a cathode block.
SUBSTANCE: lining comprises a bottom and current-carrying elements made of aluminium, liquid in the upper part contacting melted aluminium and solid in the lower part, and installed so that they pass through the bottom vertically. The bottom is made from taller bottom blocks having projections and shorter bottom blocks, at that the shorter bottom blocks are mounted at the ends of the bottom. The shorter bottom blocks alternate with the taller bottom blocks having projections. Vertical channels are provided in the projections of the blocks over the entire thickness of the block for the mounting of current-carrying elements. The current-carrying elements are attached in the lower part to a current-carrying collector shaped as a plate which extends horizontally out of the ends of the bottom blocks and longitudinal sides of the cathode casing. The current-carrying elements are L- or T-shaped. The bottom blocks are made of high-aluminous concrete annealed up to 1200°C or comprised of several layers: a working layer, made of high-aluminous concrete with the thickness equal to 0.4-0.6 of the bottom block thickness, and the secondary layer, made of fireclay castable concrete - the remaining part. Interconnection of the bottom blocks is made of high-aluminous concrete with reduced viscosity or by means of a gluing or cementing composite with the joint thickness of 5-20 mm.
EFFECT: decreased labour intensity at mounting, reduced power consumption and improved operational reliability of the electrolyser.
4 cl, 9 dwg
SUBSTANCE: cathode shell comprises longitudinal and end walls with vertical reinforcement ribs, a bottom, frames, which cover the walls and bottom and flanged sheet. Flanged sheet is fixed rigidly to intermediate ribs installed between frames at longitudinal walls of the shell by means of detachable joints through horizontal pads. The intermediate ribs are made of sheet metal with thickness from 0.3 up to 1 time of the shell wall thickness.
EFFECT: longer service life of the electrolysis unit.
3 cl, 2 dwg
SUBSTANCE: invention relates to a cathode pack for an aluminium electrolytic cell. The cathode pack comprises a layer of composite containing graphite and solid material such TiB2, present with single mode granulometric composition, while d50 amounts to 10 - 20 mcm, in particular to 12 - 18 mcm, preferably to 14 - 16 mcm. Method for the production of a cathode pack with the said characteristics is described as well.
EFFECT: improved wear resistance of a cathode pack and simple manufacturing.
16 cl, 1 dwg
SUBSTANCE: cathode's top is turned towards the electrolytic bath, and the bottom has contacts for current input. Top and bottom parts, at least, on some sections are connected to each other in disconnectable manner using the protective interlayer.
EFFECT: lowering of the cathode cost and optimisation of the cathode operation.
10 cl, 5 dwg
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
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
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
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; 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
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.
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.
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