Method and apparatus for lining the cathode of the electrolytic cell

Abstract

The invention relates to method and apparatus for lining the cathode of the electrolytic cell. The method comprises filling the cell's shell with powder material, leveling it with a rack, covering the fill material with a dust-proof film, and compaction. Compaction is performed in two stages: preliminary static and final dynamic treatment by consequent movement of static and dynamic work tools of compaction along the longitudinal axis of the cathode of the electrolytic cell through a cushion, which is made of at least 2 layers: a lower layer, which prevents pushing powder material forward in the direction of travel, and an upper layer, which provides for a coupling between the cushion and the static work tool. Static treatment unit of the apparatus, designed in the form of a roller with a drive, is connected to a dynamic treatment unit with a vibratory exciter by means of elastic elements.

Claims

1. A method for lining the cathode of the electrolytic cell, comprising filling the cell's shell with powder material, leveling it with a rack, covering the fill material with a dust-proof film, and compaction performed in two stages: preliminary static and final dynamic impact, by consequent movement of static and dynamic work tools of compaction along the longitudinal axis of the cathode of the electrolytic cell through a cushion, wherein the cushion is made of at least 2 layers: a lower layer, which prevents pushing powder material forward in the direction of travel, and an upper layer, which provides for a coupling between the cushion and the static work tool; wherein steel plates (2.5 to 4)*10.sup.4 in thickness, with a width of 0.12 to 0.15 and a length of 0.2 to 0.25 of the width of the layer being formed, are used as a lower layer of the cushion; and for a coupling between the cushion and the static work tool, rubber-fabric material with a thickness of 2-3 times the thickness of the steel plate is put as a top layer.

2. The method of claim 1, wherein the hardness of the cushion varies in the range of 80 to 270 Nm2.

3. The method of claim 1, wherein compaction is performed along the longitudinal sides of the cathode within a width of at least 0.5 of the width of the cathode.

4. The method of claim 1, wherein the steel plates are put edge-to-edge on the entire area being compacted along the long side of the cathode in 3-4 rows.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the vibrating compaction tool (VCT) for molding seamless lining layers in aluminum pots (side view) with flexible elements made of metal springs;

(2) FIG. 2 shows the VCT with flexible elements made of rubber;

(3) FIG. 3 shows a diagram of a stand for determining the optimal design and process parameters of the VCT;

(4) FIG. 4 shows an image of a six-channel measuring unit for determining the optimal parameters of the VCT;

(5) FIG. 5 shows a graph of dynamic modulus of elasticity of the compressed material versus machining time at various vibration generator amplitude frequency responses;

(6) FIG. 6 shows a graph of dynamic modulus of elasticity of the compressed material versus force acting on the system;

(7) FIG. 7 shows dynamic modulus of elasticity relative to acceleration versus static load;

(8) FIG. 8 shows a graph of vibration velocity versus depth in the compressed material.

(9) FIG. 9 shows the results of measuring the vibration velocity along the depth of the mass of the material being compacted.

(10) The essence of this technical solution is illustrated by an example of specific design and drawings. FIG. 1 shows an apparatus for forming seamless lining layers in electrolytic cells (side view) with elastic elements made of metal springs; and FIG. 2 shows an apparatus for forming seamless lining layers in electrolytic cells (side view) with elastic elements made of rubber.

(11) The apparatus for forming seamless lining layers in electrolytic cells consists of driving disks 1, which form a drive unit for static compaction (in the form of a roller), vibratory unit 2 with vibrator 3, weights 4 located on load platform 5, which is connected to vibratory unit 2 by means of elastic elements 6 and 7 (made of metal springs in FIG. 1 and rubber in FIG. 2), which combine the vibratory unit and the static treatment unit into a compaction device by means of rocker arm 8, including the ability to freely move the vibratory unit along the horizontal and vertical axes (anchor) of the roller. The drive of the apparatus for forming seamless lining layers in electrolytic cells consists of gear motor 9, and chain gear 10. Gear motor 9 is mounted on rocker arm 8, to which load platform 5 is also mounted.

(12) The technical essence of the claimed solution is as follows:

(13) Gear motor 9 and vibrators 3 are started from the control panel. Rotation of gear motor 9 via chain gear 10 is transmitted to driving disks 1 of the roller. Driving discs 1, when rotating, move the apparatus over the surface of the cushion put on the treated material. Preliminary static compaction of unshaped lining materials is performed. Final compaction occurs due to an impact (on the material being treated) from vibratory unit 2, moving along the horizontal and vertical axes of the roller and loaded with weights 4 via elastic element units.

(14) For determining the optimum design and process parameters of the Vibratory Compaction Unit (VCU), experimental studies of the process of compacting fine (granular) material were carried out on the bench shown in FIG. 4. The bench includes a container with granular material and a local VCU, allowing providing deformation of granular media by static loads together with vibration loads of different frequency and intensity.

(15) When moving the VCU within the container with material, the VCU creates a preliminary static load by rollers 1, which are also a moving mechanism, and a dynamic load is created by vibratory unit 2, the amplitude versus frequency response characteristics of which are set by exciter 3. As a source of oscillations, the exciter with a directional or circular driving force is used. The VCU was placed in container 4 filled with granular material 5; the filling height (innage) was 300 to 500 mm.

(16) The material was compacted through a cushion, consisting of metal plate 6 (FIG. 4) 2 mm in thickness and rubber plate 7 (5 mm thick.) During compaction, the cushion prevented material push-outs from under the rollers, helped reduce the content of dust in the air and kept the VCU on the surface of the material (when a layer of material under compaction was of great thickness.) There are two possible ways of loading (compacting): the first one is static (the vibratory unit is off), the second one is combined (both static and dynamic). Under combined impact (compaction) conditions, the material, located between the roller and the vibratory unit, is closed within a limited volume. Pushing-out of the material from the side of the vibratory unit is prevented by finally compacted material; from the side of the rollerby preliminary compacted material, from aboveby the cushion.

(17) Vibratory acceleration in the material and at the vibratory unit was registered by piezosensors 8 and 9 (FIG. 5), which allowed simultaneous monitoring of the horizontal and vertical components of the oscillations. The signal from the sensor was amplified, integrated and transferred to a personal computer.

(18) The density of the layers of the compacted material was determined by a static densitometer B-1, and the density of the obtained compacted material was characterized by the dynamic modulus of elasticity as measured by a portable HMP LFG deflectometer (FIG. 3).

(19) Information collection and measuring result processing were carried out by using ACTesta software system for automation of experimental and process units.

(20) For experiments, a six-channel measurement system was used (FIG. 4), including the following devices: Piezoelectric accelerometers (Brel & Kjr, Denmark); Charge amplifiers Type 2635 (Brel & Kjr, Denmark); Analog-to-digital converter E-440 (CJSC L-Card, Russia); and Personal computer.

(21) After starting, the VCU moves along the container filled with fine (granular) material (FIG. 5). Either only a static impact on the material (if the vibratory block is off) or a combined impact (static and dynamic loads) is possible. Static compaction is of no particular interest, as it is no different from conventional rolling (compaction). In the second case, at a fixed point of time, a portion of preliminary compacted material 1 located between vibratory unit 2 and roller 3 (FIG. 5, the boundaries are marked by letters A and B) becomes closed within a limited volume. Its displacement (push-out) is prevented by already compacted material, from one side; by the pressure created by the roller, from the other side; and by plate 4, from above. Directly under the vibratory unit, a compression wave occurs and deforms the material, while some of the material is squeezed out into the closed area, which puts pressure on bulky (granular) mass in the area. Moreover, under the influence of vibration and rheological effects related thereto, a relative motion of material particles occurs in this area (particles tend to form a denser structure), as well as air and moisture are displaced, i.e. preliminary dynamic compaction is carried out. The process of deformation of the material is completed after a direct impact of compressive loads (generated by the vibratory unit) on the material.

(22) For determining the optimum parameters (during the experimental studies), the amplitude vs. frequency response characteristics of the exciter, the velocity of movement (travel), the static load were adjusted.

(23) The results of the experimental studies are presented in FIG. 6 in the form of graphs. The process of compacting fine (granular) material, within a closed volume (area), takes place most efficiently in the frequency range of 45-60 Hz; under the same treatment time, an increase in the frequency from 35 to 60 Hz can lead to an increase in the density by 5 to 10%; a further increase in frequency causes no noticeable change in packing density. An increase in the treatment time, under constant vibration parameters (acceleration and frequency), leads to an increase in density, wherein quite a dense packing is formed within the first 6 to 7 seconds; further loading leads to a further increase in density but at a substantially lower rate.

(24) It was found out that with an increase in the vibratory impact frequency, the dynamic modulus of elasticity of the material being compacted changes more rapidly than if there is an increase in the vibratory impact due to the amplitude of oscillations, which is confirmed by the results of the experiments shown in FIG. 7. Curves 1a and 1b represent the dependence of the modulus of elasticity of the material being compacted on the value of the force affecting the system that changes depending on the frequency under a constant (static) torque; curves 2a and 2b correspond to modulus vs. value of the force relationships (the force that changes depending on the static torque under a constant frequency).

(25) It was experimentally determined that the density of fine (granular) material, during vibratory compaction, was mainly influenced by the acceleration of oscillations transmitted to the granular medium; and with an increase in the vibratory impact frequency, the dynamic modulus of elasticity of the material being compacted changes more rapidly than if there is an increase in the vibratory impact due to the amplitude of oscillations (FIG. 7). At a frequency below 35 Hz, the efficiency of the vibratory impact significantly reduces.

(26) The experiments showed that the static load did not significantly influence the dynamic modulus of elasticity of the packing. However, the static load, being part of the oscillatory system, effects only the dynamic parameters of the system. FIG. 8 shows dynamic modulus of elasticity relative to acceleration vs. static load value.

(27) FIG. 9 shows the results of measuring the vibration velocity along the depth of the mass of the material being compacted. The origin of coordinates is combined with the daylight surface of the material being compacted. The curves (relationships) shown in FIG. 3 correspond to oscillation frequencies of 25 Hz, 34 Hz and 49.6 Hz (curves 1, 2 and 3, respectively). Markers .square-solid., and are used for the points obtained experimentally; they correspond to oscillation frequencies of 25 Hz, 34 Hz and 49.6 Hz.

(28) It was determined that, within the considered (above) frequency range, the attenuation of vibration in the compacted mass was exponential:
v=v.sub.0.Math.e.sup..Math.h,

(29) where v.sub.0vibration velocity at the vibratory unit (at the daylight surface of the material being compacted), m/s; vvibration velocity of the material being compacted at a depth of h, m/s; attenuation coefficient, determined experimentally (=4.4); hdistance from the daylight surface to the compacted layer of the material, m.

(30) For this material (dry barrier mix) within the range of 25 to 50 Hz, the vibratory impact frequency does not substantially affect the density of the material along the depth for this frequency range.

(31) The highest density of the material is found to be in the upper layers of the compacted massup to the depth of penetration (the depth at which the oscillations are damped by e times), which amounted to 230 mm, at greater depths the packing density decreases (due to a decrease in the intensity of vibration caused by the damping of the oscillations.)

(32) Despite a decrease in the vibration velocity in the lower layers, their density decreases insignificantly with an increase in depth (by 5 to 10%), when compacting the material with the same granulometry, and physical and mechanical properties.

(33) The use of the above cathode lining will help have a total cost benefit, in terms of one electrolytic cell, of not less than USD 2,000 per year (by means of reducing the cost of lining materials and reducing labor costs during lining.)