AU2006203535A1 - Method and apparatus for forming seamless lining layers of aluminum reduction cells - Google Patents

Description

-1-

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Actual Inventors: Limited Liability Company "RUSAL Engineering Technological Center" Alexander V. Proshkin and Vitaly V. Pingin and Vitaly S. Timofeyev and Samuil Y. Levenson and Ludmila I. Gendlina and Yory I.

Eryomenko and Vyacheslav A. Goldobin Address for Service is: SHELSTON IP Margaret Street SYDNEY NSW 2000 CCN: 3710000352 Attorney Code: SW Telephone No: Facsimile No.

(02) 97771111 (02) 9241 4666 Invention Title: METHOD AND APPARATUS FOR FORMING SEAMLESS LINING LAYERS OF ALUMINUM REDUCTION CELLS The following statement is a full description of this invention, including the best method of performing it known to us:- File: 51303AUP00 500948547 1/5844 -2- METHOD AND APPARATUS FOR FORMING SEAMLESS LINING LAYERS OF ALUMINUM REDUCTION CELLS FIELD OF THE INVENTION The invention relates in general to the field of non-ferrous metallurgy associated with electrolytic production of aluminum, and in particular, it relates to formation of a cathode unit of an aluminum electrolytic cell.

BACKGROUND OF THE INVENTION Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Aluminum is typically produced by a method in which alumina is separated into its component parts of aluminum metal and oxygen gas by electrolytic reduction. It is a continuous process, whereby alumina is dissolved in cryolite bath material in electrolytic cells called pots and with oxidation occurring at the carbon anodes. The bath is kept in its molten state due to the resistance to the passage of a substantial electric current.

In each aluminum reduction cell or pot, direct current passes from carbon anodes, through the cryolite bath containing alumina in solution, to the carbon cathode cell lining. Steel bars embedded in the cathode carry the current out of the pot. The pot consists of a steel shell in which the carbon cathode lining is housed. This cathode is adapted to hold the molten cryolite and alumina in solution and the molten aluminum created in the process.

The lining is placed in the steel pot shell. Thermal insulation consisting of firebrick, vermiculite, or similar materials is typically placed between the cavity lining and the steel shell. The steel bars, serving as electrical current collectors, are embedded in the bottom portion of the cavity lining and extend through openings in the shell to connect with the electrical bus which links one pot to the next.

The lifespan of cathode pot linings is typically between 4 to 6 years.

When failure of the lining occurs, usually via the penetration of aluminum metal through the lining and to the cathode collectors, the collectors dissolve. This causes the metal, and sometimes the fused cryolite bath, to leak around the collectors. A sudden increase in iron levels in the aluminum usually indicates that a pot is nearing the end of its service life. The lining should then be repaired or replaced in the procedure called "relining". It is well known that such patching and relining procedures constitute a significant part of the aluminum production expense and should be conducted efficiently to ensure the proper lifespan and operation of the aluminum reduction cell.

A method of lining the aluminum electrolytic cell by filling the cathode shell with ground alumina and ramming the carbon paste on its top is known in the art. (See, for example, R. Weibel, Advantages and Disadvantages of Different Cathode Refractory Materials, Aluminum of Siberia. Krasnoyarsk, 2002 p. 14- 24). According to this prior art procedure, the unshaped materials are compacted by a static compaction method which consists of the steps of compression and rolling. The unshaped material can also be compacted utilizing a dynamic method including the phases of shock-free vibration, shock-vibration, and shock.

In these methods the working element generates an impact on the materials to be compacted. The static compaction methods most frequently carried out by means of ordinary rollers typically do not provide the required structure of the lining material. Among the structural requirements of the lining material are low porosity and small pore size thereof. Utilization of rollers with vibratory mechanisms (disclosed, for example, by U.S. Patent 4,184,787) somewhat increase the density of the compacted material, but the porosity of the barrier -4layer remains fairly high (up to Furthermore, after being treated by the prior art rollers-vibratory mechanism combinations, it is not uncommon for the surface of the barrier layer to contain wave-like defects.

Another lining method consists of the steps of filling the cathode shell with powdered material, leveling off the material with a board, positioning polyethylene film on the layer of powdered material, laying fiber-glass laminate or fiber board, and compacting the material dynamically with a vibratory plate compactor or a vibro-platform.

According to the above discussed method, the compaction is initiated at a cathode shell corner and is carried out spirally from a side of the shell towards the cathode center. With each rotation, the vibratory device moves inward while overlapping the previously compacted area by several centimeters. In order to achieve the required level of compaction of the barrier layer, the vibratory device has to make several full run cycles.

It has been observed that this lining method does not produce a highquality barrier layer. One of the main reasons for this drawback is that the utilized compaction procedure is of the dynamic nature only and works primarily with a low bulk density of lining material. Therefore, this method does not provide the required complete compaction of all levels of the formed barrier layer. Utilization of fairly thin fiber-glass laminate sheets having insufficient rigidity results in an uneven surface of the layer. As a result, the formed surface of the barrier material has a wave-like configuration, similar to the surface developed when the vibro-roller is utilized. Attempts to increase the rigidity of the material used as a cover have resulted in reduced efficiency of the compaction process.

The apparatus typically utilized in the above-discussed lining method is also known as the vibratory platform. A typical prior art vibratory platform, as O discussed in European Patent EP 1227983, includes a motor and vibrotbcompacting accessories provided on the platform. By means of the brackets, the platform is connected to a handle provided to control operation of the platform.

The handle is connected to the brackets by means of rubber joints which are adapted to reduce oscillations resulting from operation of the vibratory platform.

Ct t The main drawback of this apparatus lies in the non-optimal amplitudefrequency of the device, as well as in the substantial weight of the fairly small IND platform. As a result, to achieve the required quality of the material, it is often C) necessary to run the vibratory platform several times over the surface of the barrier material. Furthermore, the characteristics of the resulting barrier layer depend on the working skill of an operator. The most essential drawback, however, is that the operation of the vibratory platform is predominantly based on the dynamic compaction procedure. As such, both compaction and decompaction processes run simultaneously causing substantial dust formation of the compacted material.

OBJECT OF THE INVENTION It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

SUMMARY OF THE INVENTION One aspect of the present invention provides a method of forming a lining layer in a cathode shell of an aluminum reduction cell utilizing a compacting apparatus having at least a working element of static compaction and a working element of dynamic compaction, said method comprising the steps of: filling said cathode shell with a powdered material; levelling off said powdered material; -6positioning a dust-insulating layer on said leveled powdered material; conducting a step of static compaction by successively moving said working element of static compaction along an axis of said cathode shell over the entire width of the lining layer; and conducting a step of dynamic compaction by successively moving said working element of dynamic compaction along said longitudinal axis of the cathode shell over the entire width of the lining layer; whereby in said step of dynamic compaction a static load is being continuously applied on said working element of dynamic compaction.

Another aspect of the present invention provides an apparatus for forming a lining layer in a cathode shell of an aluminum reduction cell, said apparatus comprising: at least one module including at least one unit of static compaction and at least one unit of dynamic compaction; said at least one unit of static compaction including at least a shaft rotatably supporting at least one roller-type working element of static compaction; said at least one unit of dynamic compaction including at least one vibratory-type working element of dynamic compaction, at least one load arranged to generate a continuous force directed at said at least one working element of dynamic compaction; a primary connecting element extending between said at least one load and said at least one unit of static compaction; and a vibratory connecting element extending between said at least one unit of dynamic compaction so as to be movably arranged about said shaft of the unit of static compaction.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an elevational view of the compacting apparatus of one embodiment of the invention and showing the lining; Figure 2 is a detailed view thereof; Figure 3 is a diagram illustrating the relationship between the density of the layer to be formed and the vibratory oscillation of the working elements at various traveling speeds of the apparatus, without action of loads being applied on the vibratory units; Figure 4 is a diagram illustrating the relationship between the density of the layer to be formed and the mass of the applied loads; Figure 5 is a diagram illustrating the relationship between the density of the layer, the mass of the applied loads and the speed of movement of the apparatus of the embodiment of the invention; Figure 6 is the detailed elevational view of the apparatus of the embodiment of the invention; Figure 7 is a top plan view of the compacting apparatus of the embodiment of the invention; and Figures 8a, 8b, and 8c show various positions of the apparatus while performing the compaction steps of the method of one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in general and Figures 1 and 2, and 6 to 8, in particular, illustrating the compacting apparatus 10 of one embodiment of the invention which includes a block of static compaction 12 and a block of dynamic compaction or vibratory block 14. The static compaction block 12 consists of at least one or multiple static compaction units 16. Similarly, the dynamic compaction block 14 is formed with at least one or multiple vibratory units As best illustrated in Figures 7 and 8, the apparatus is formed by a plurality of modules combined together, wherein each module 17 includes at least one static compaction unit 16 and at least one vibratory unit 30. The modules 17 are combined together so as to form an integral structure of the apparatus of this embodiment of the invention.

In the block of static compaction 12 at least one drive 18 is provided for energizing a plurality of roller-type working elements rollers 26. The rollers 26 are rotationally arranged on a common shaft 25 which coincides with a longitudinal axis A-A of the static compaction block 12. As best illustrated in Figures 2 and 7, a static compaction unit 16 of each module 17 includes between two and four rollers 26 successively and rotationally arranged on the common shaft 25. However, the static compaction unit with any reasonable number of static compaction elements or rollers 26 rotatably arranged on the common shaft is within the scope of the invention. The drive 18 includes a motor-gearbox 22 having an output rotor 31. Upon being energized by the motor-gearbox 22, the rotational motion of the output rotor 31 and a driving disc 20 associated therewith are being transferred by means of a chain 24 to the driven disc 21 associated with 0 the substantially horizontally disposed shaft 25. A structural integrity of each bmodule is enhanced by means of primary connecting elements 28 and vibratory connecting elements 38 associated with the respective static and dynamic compaction units. The distal end 23 of a primary connecting element 28 is adapted to rotatably support the shaft 25, whereas a proximal end thereof 27 is rigidly connected to a supporting platform 32 associated with the respective n vibratory unit IThe block of the dynamic compaction 14 consists of single or multiple 0 vibratory units 30 associated with the respective static compaction units 16 in a manner which will be discussed hereinbelow. In each module 17 the respective vibratory unit 30 is formed with a supporting platform 32 adapted to accommodate loads 34 associated with a vibratory assembly 36. A vibratory generator 41 and a vibratory striking head 42 of the vibratory assembly 36 are spaced from a shelf 40, with vertically oriented vibratory links 44 extending therebetween, so as to form a unitary structure. In one embodiment of the invention the generator 41 is an inertia-type vibratory generator. The supporting platform 32 is adapted to accommodate single or multiple loads 34. In one embodiment of the invention, as shown in Figures 1 and 7, each load 34 is formed having a substantially cylindrical configuration with an aperture 35 passing through a central area of its body. Connecting members or rods 38 are provided for connection between the loads 34 disposed on the respective supporting platform 32 and the shelves 40. More specifically, each connecting member 38 passes through the longitudinal aperture 35 of the respective load 34, through the platform 32, so as to be connected to the shelf 40 in such a manner that a substantial gap separates the shelf 40 and the bottom of the supporting platform 32. A biasing member or spring 46 is positioned within the gap to surround the respective connecting member 38. In this manner, the vibratory assembly 36, including the striking head 42, the vibratory links 44, etc. are resiliently connected to the supporting platform 32 and the loads 34. The biasing member 36, compensates and absorbs the vibratory action of the generator 41 and the striking head 42 transferred to the supporting platform 32 and to the respective static unit 16 and to the entire block of static compaction 12. This arrangement enhances stability of operation of the entire apparatus A distal end 37 of the vibratory connecting element 38 is adapted to move about the shaft 25 and the longitudinal axis A-A of the rollers 26 of the static compaction block. A proximal end 39 of the vibratory connecting element 38 is rigidly connected to the respective vibratory unit 30. In the operation of the device of the embodiment of the invention, the static pressure or force generated by the loads 34 is continuously applied through the connecting members 41 to the shelf 40 and by means of the vibratory links 44 to the striking head 42 of the respective vibratory assembly.

The connecting members 38 are oriented to extend along or coincide with longitudinal axes B-B of the respective vibratory units 30, so as to pass through central areas of the respective vibratory generators 41 and the striking heads 42.

In this manner, in operation of the embodiment of the device of the invention, the static pressure or force generated by the respective loads 34 is continuously applied to the central area of the striking head, generating forces of asymmetric nature acting on the vibratory unit and providing substantially improved engagement between the respective striking head 42 and the material to be compacted.

As illustrated in Figures 1 and 6, in each module 17, the respective unit of static compaction 16 and the vibratory unit 30 are combined by means of primary connecting elements 28 and a vibratory connecting element 38. The primary connecting element 28 extends between a distal end 23 thereof situated at the shaft 25, and a proximal end 27 which is rigidly associated with the respective -11supporting platform 32. The primary connecting element 28 is formed with a substantially hollow chamber 29. As to the vibratory connecting element 38, its distal end 37 is adapted to be movably received within the hollow chamber 29, so as to facilitate the motion of the connecting element 38 about the shaft 25. A bearing 52 is provided at the distal end 37. An inner space 54 of the bearing is adapted to movably receive the common shaft 25. In this manner, radial motion of the vibratory connecting element 38 is achieved within the hollow chamber 29 relative to the common shaft 25. In the preferred embodiment, as illustrated in Figure 8, the amplitude of the motion of the vibratory connecting element with respect to the shaft 25 is about 150 in either direction from the vertical. The proximal end 39 of the vibratory connecting element 38 is rigidly connected to the respective vibratory unit In operation of each module 17, the respective static compaction units 16 and the vibratory compaction units 30 are remotely activated from the control panel. Rotational motion of the output rotor 31 of the motor gear box 32 is transferred by means of the chain 24 from the driving discs 20, so as to energize the driven discs 21 associated with the shaft 25. The rotation of the rollers 26 is transferred into the longitudinal motion of the apparatus on the materials to be compacted. As a result, an initial phase of static compaction of the unshaped lining material takes place. The final compaction of the material results from the vibratory action of the striking head 42 and the entire vibratory unit 30 on the compacted material. The striking head 42 is activated by the vibratory generator 41 which can be energized by any conventional means. For example, the vibratory generator can be energized by pressurized air.

As clearly illustrated in at least Figure 7, the modules 17 are combined together so as to form the compaction apparatus 10, wherein all roller-type working elements of static compaction 26 are rotatably supported by the same shaft 25 extending along the longitudinal axis A-A. In one embodiment, the -12primary connecting elements 28 and the respective vibratory connecting elements 48 are positioned within planes substantially parallel to each other.

The method of forming a seamless lining layer 81 in the cathode shell (partially illustrated in Figures 1 and 8) of an aluminum reduction cell consists of the following steps. Initially, the cathode shell 80 is filled with a powdered material 82 which is then being leveled off by means of a conventional implement. For example, the filled powdered material 82 can be leveled off by a leveling board. Then, the powdered material is covered by a layer of flexible, dust-insulating material 84. In one embodiment of the invention, the layer of flexible, dust-insulating material 84 is a plastic film. In order to improve efficiency of the compacting procedure and prevent squeezing the powdered material from under the working elements of static and dynamic compaction, a layer of semi-elastic material 86 is positioned on top of the dust-insulating layer.

The layer 86 also facilitates development of the smooth surface of the barrier and prevents dust formation. In the preferred embodiment of the invention, such layer of the semi-elastic material 86 is in the form of a rubber or rubberized fabric having a thickness between 5% and 25% of the height of the barrier layer 81 which is being formed.

The actual steps of compacting the filled powdered material 82 is carried out in the following manner. In the initial step of static compaction, the working elements of static compaction or rollers 26 are moved over the layer of semielastic material 86 along a longitudinal axis of the cathode shell 80. In this manner, the entire width of the lining layer is being covered. The speed of movement of the static working element 26 in this step is between 0.21 and 0.24 m/min. In the step of dynamic compaction, which follows the static compaction step with a time interval of approximately 1 minute, the working element of dynamic compaction 36, 41, 42 is moved on the layer of semi-elastic material 86 along the longitudinal axis of the cathode shell, so as to cover the entire width of 13the lining layer 81 to be formed. In the step of dynamic compaction, the vibratory unit 30 is also moved at a speed between 0.21 and 0.24 m/min, .with the oscillation frequency not exceeding 55 Hz. As indicated hereinabove, the step of dynamic compaction is accompanied by applying constant static force or pressure, generated by the loads 34, onto the vibratory assembly 36 in general and the striking head 42, specifically. In each vibratory unit 30, such force is directed from the loads 34 to the vibratory assembly 36 and the striking heads 42 through the biasing arrangement or spring 46. As illustrated in FIGs 1 and 8, in the preferred embodiment, the force generated by the loads 34 is directed along the longitudinal axis B-B of the vibratory unit 30 so as to pass through a central element of dynamic compaction 41, 42, 46. In this manner, the specific weight of the loads 34 (per unit length of the compacting apparatus) is at least 150 kg/m.

According to the conducted experiments the cryolite resistance of the formed lining material has an inverse relationship with the porosity of the material. This means that the lower the porosity of the material, the higher is the resistance of the barrier to the penetration of fused cryolite bath.

One of the main results of the embodiment of the invention is the decrease in the porosity of the lining layer. This ultimately causes the decrease in penetration rate of molten fluorides and aggressive gaseous components through the barrier layer into the thermal insulation of the cathode. Such a decrease reduces the power consumption during production of aluminum which, in turn, increases the lifespan of the cell.

As a result of the increase in the density of the material and the decrease in the open porosity of the material the following positive developments occur.

Penetration of the barrier materials by both liquid and gas phases of the bath components decreases, i.e. the chemical reactions take place not within the entire body of the barrier, but at the levels of phrase interfaces. Furthermore, the -14- O amount of lining material in the unit volume of the lining layer increases. This b1 directly causes the increase in the life expectancy of the electrolytic cell.

Example In order to test the apparatus and method of one embodiment of the S 5 invention, a model of the cathode shell was prepared in the form of a platform Cc having dimensions of 1.51 m x 1.57 m. The powdered material or medium to be compacted during the testing procedure was E-50 dry barrier mix made in China.

\O

O The filling layer of dry barrier mix was developed having the following characteristics: thickness 122 mm; volume 1.52 x 1.57 x 0.122 0.291 m3; density 1.57 103kg/m 3 with filing mass 457.5 kg.

The experimental embodiment of the compacting apparatus of the invention utilized during the experimental testing consisted of the three static compaction units and three dynamic compaction units having the total length substantially equal to the width of the testing platform. A hoisting device was used for positioning of the apparatus on the experimental model of the cathode shell which was also connected by a cable to alternate current mains having voltage of about 380 V and to the compress air source having pressure of about MNPa.

Prior to conducting each experiment, the testing area was filled with fresh dry barrier mix which was leveled off, i.e. a testing strip was prepared having a uniform preliminary density and an even surface. During the experiments, vibratory generators were utilized having various amplitude frequency characteristics. The apparatus operated both in the shock and shock-free modes.

This was also necessary in order to determine the optimal vibratory mode of the working element during the compaction process, so as to provide the dry barrier mix of targeted or near targeted density. Furthermore, this was necessary to verify the effect of acceleration on the dynamic phase of the compaction process.

O Acceleration and oscillation frequency of the working element were measured by KD 35-type piezoaccelerometer and vibration-measurement apparatus. Material density at the predetermined fixed points locations have been _determined by reviewing the changes in the volume of the compacted dry barrier mix and then averaged. Both acceleration and density were measured numerous times and the results were averaged.

O Review of the results of the tests demonstrated that the most efficient for IN the compaction of the dry barrier mix was the shock mode of operation of the vibratory generators. It has also been determined that the maximum vibratory frequency of the head of the pneumatic vibrator should not exceed 55 Hz, while the coercive force should be not less than 1.7kN.

The results of the performed experimental studies are graphically illustrated in Figures. 3-5. The relationship illustrated in Figure 3 was produced without use of the loads 34 acting on the respective vibratory assemblies 36.

Figure 3 illustrates the relationship between the density of the lining layer and the acceleration of the working element vibrations at various traveling speed of the apparatus. It should be apparent from the graphs of Figure 3 that the density of the material increases linearly with acceleration of the vibrations of the working elements of dynamic compaction. However, the resulted high dynamic loads negatively affected the structural elements of the cathode shell and the lining of the experimental area.

It should be apparent from Figure 3 that as the travel speed of the apparatus over the experimental platform increases, the density of the processed material decreases. This is because the duration of both static and dynamic actions on the experimentally treated platform area decreased. However, the decrease in the density of the processed medium has taken place in addition to the decrease in the traveling speed of the apparatus with respect to a certain value at -16which the density of the barrier layer was maximal. This can be explained as having a decompaction effect. It is a matter of common knowledge that with the increase of the action time, the density of material, after having reached maximum level, might decrease. As it follows from Figure 3, the optimum travel speed of the apparatus of the embodiment of the invention at the vibratory modes of the vibratory utilized without loads is considered to be between 0.21 and 0.24 m/min. Deviations in the speed of travel in either direction cause the decrease in the resulted density of the barrier layer.

In view of the conducted experiments, it has been determined that the thickness of the rubberized fabric sheet used in the compaction process should be approximately 15 mm. When the thickness of the material is less than the recommended value, the material can be squeezed form under the roller. If the thickness of the material is greater than the recommended value, the vibrocompaction will result in much greater energy consumption. The height of the lining layer can vary in accordance with design of the cell, so as to be between and 250 mm. This is the reason why the thickness of elastic rubberized fabric sheet should be between 5 and 25% of the thickness of the lining layer.

The selection of the amplitude-frequency characteristics is based on the revealed regularity in the decrease in the compaction density with the increase of vibratory frequency of the vibratory unit over 55 Hz, as well as in the decrease in the compaction density with decrease of the coercive force below 1.7 kN.

Continuous static pressure provided by the loads on the vibratory units causes the coercive forces of asymmetric nature, which forces are resulted in constant contact of the working elements of the apparatus with the compacted material. This increases stability during operation of the apparatus of the embodiment of the invention. Furthermore, experiments demonstrated that use of the loads 34 with the vibratory units increases performance of the compaction -17-

\O

O process. Use of the loads 34 enables embodiments of the invention to achieve the b1 required density of material at higher traveling speed of the apparatus. This is confirmed by the diagram of Figure 4 reflecting the traveling speed of the IN apparatus of about 0.3 m/min. When the apparatus of the embodiment of the invention was used without loads 34, the density of the dry barrier mix was at the level of p=1.98.10 3 kg/m 3 On the other hand, when the load having the mass of ¢q about 220 kg was used, the density of the dry barrier mix was about p=2.12.103 ,kg/m 3 with all other conditions being equal. In view of the above, the specific O weight of loads as applied to the unit width of the lining layer) should be at least 150 kg/m.

Compared to the prior art, use of the method of lining an aluminum cell of the invention resulted in the increased lifespan of the electrolytic cell, reduced penetration rate of cryolite-alumina melt components into the thermal insulation of the cathode shell and preserved the thermal-physical properties of the latter.

The above described method and apparatus for lining cathodes of the invention results in increased life of the electrolytic cell and decreased specific power consumption by so as to have total annual economic effect not less than $14,000.00 per each electrolytic cell.

Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims (20)

1. A method of forming a lining layer in a cathode shell of an aluminum reduction cell utilizing a compacting apparatus having at least a working element of static compaction and a working element of dynamic compaction, said method comprising the steps of: filling said cathode shell with a powdered material; levelling off said powdered material; positioning a dust-insulating layer on said leveled powdered material; conducting a step of static compaction by successively moving said working element of static compaction along an axis of said cathode shell over the entire width of the lining layer; and conducting a step of dynamic compaction by successively moving said working element of dynamic compaction along said longitudinal axis of the cathode shell over the entire width of the lining layer; whereby in said step of dynamic compaction a static load is being continuously applied on said working element of dynamic compaction.

2. The method according to claim 1, further comprising the step of positioning a layer of semi-elastic material on said layer of dust insulating material, so that said steps of static and dynamic compaction are carried out over said layer of semi-elastic material.

3. The method according to claim 2, wherein said layer of semi-elastic material is a layer of rubber or rubberized fabric, having thickness between and 25% of the height of the lining layer, said layer of dust-insulating material is a layer of dust insulating film.

4. The method according to claim 2 or claim 3, wherein a longitudinal axis of the respective static load extends along a longitudinal axis of said working -19- element of dynamic compaction, so that in said step of dynamic compaction, the force generated by said load is being continuously applied through a central area of said working element of dynamic compaction.

The method according to any one of the preceding claims, wherein there is a time delay between said step of static compaction and said step of dynamic compaction.

6. The method according to any one of claim 2 to 5, wherein in said steps of static and dynamic compaction, movements of said working elements of static and dynamic compaction are carried out at speed between 0.21 and 0.24 m/min.

7. The method according to any one of the preceding claims, wherein said step of dynamic compaction is carried out with vibratory frequencies said working element of dynamic compaction of at least 55 Hz and the coercive force of at least 1.7 kN.

8. The method according to any one of the preceding claims, wherein the specific weight of said load which is continuously applied on the working element of dynamic compaction, over a unit of length of the compaction apparatus, is at least 150 kg/m.

9. An apparatus for forming a lining layer in a cathode shell of an aluminum reduction cell, said apparatus comprising: at least one module including at least one unit of static compaction and at least one unit of dynamic compaction; said at least one unit of static compaction including at least a shaft rotatably supporting at least one roller-type working element of static compaction; 20 said at least one unit of dynamic compaction including at least one vibratory-type working element of dynamic compaction, at least one load arranged to generate a continuous force directed at said at least one working element of dynamic compaction; a primary connecting element extending between said at least one load and said at least one unit of static compaction; and a vibratory connecting element extending between said at least one unit of dynamic compaction so as to be movably arranged about said shaft of the unit of static compaction.

10. The apparatus according to claim 9, said at least one module further comprising a platform for receiving said at least one load, wherein said primary connecting element extends between distal and proximal ends thereof, said proximal end is adapted to rotatably receive said shaft and said proximal end is rigidly connected to said platform, said primary connecting element being formed with a substantially hollow chamber, said vibratory connecting element being formed with distal and proximal ends, and said distal end of the vibratory connecting element being movably positioned within said substantially hollow chamber.

11. The apparatus according to claim 9 or claim 10, wherein said at least one vibratory-type working element further comprises: at least a striking head connected by vibratory links to a shelf; and a connecting member for connection between said at least one load and said shelf.

12. The apparatus according to claim 11, wherein said connecting member passes through a central region of said load, so as to be arranged along a longitudinal axis of said vibratory unit in such a manner that said force -21 generated by said load is continuously applied to the central region of the striking head.

13. The device according to any one of claim 11 or claim 12, wherein a biasing member is interposed between said shelf and said supporting platform so as to provide resilient connection and absorb vibratory action of the vibratory unit on said platform and said unit of static compaction.

14. The apparatus according to any one of claims 9 to 13, wherein said at least one module further comprises a plurality of roller-type working elements of static compaction, wherein said plurality of the working elements of static compaction are rotationally supported by said shaft; and said at least one load of the dynamic compaction unit comprises a plurality of loads.

The apparatus according to claim 14, wherein said at least module comprises a plurality of modules combined together, so that said multiple roller-type working elements of static compaction are rotatably joined on said shaft.

16. The apparatus according to any one of claims 9 to 15, wherein said at least one unit of dynamic compaction includes at least one inertia-type vibratory generator generating the circular coercive force.

17. The apparatus according to any one of claims 9 to 16, wherein said unit of dynamic compaction includes an internal combustion energy drive.

18. The apparatus according to any one of claims 11 to 17, further comprising a vibratory generator for activating said striking head, wherein said vibratory generator is activated by means of pressurized air.

19. A method of forming a lining layer in a cathode shell of an aluminum reduction cell utilizing a compacting apparatus having at least a working -22- element of static compaction and a working element of dynamic compaction, substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.

20. An apparatus for forming a lining layer in a cathode shell of an aluminum reduction cell, substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. DATED this 16th day of August 2006 Shelston IP Attorneys for: Limited Liability Company "RUSAL Engineering Technological Center"