GB2028477A

GB2028477A - An Apparatus for Compacting Carbonated Pastes in the Linings of Metallurgical Furnaces

Info

Publication number: GB2028477A
Application number: GB7928188A
Authority: GB
Original assignee: Aluminium Pechiney SA
Current assignee: Rio Tinto France SAS
Priority date: 1978-08-16
Filing date: 1979-08-14
Publication date: 1980-03-05
Also published as: CH630457A5; JPS6181599U; YU43117B; GB2028477B; AU4987179A; ATE1632T1; AU530353B2; MX151585A; JPS5528496A; ES483359A1; YU197579A; FR2433725A1; EP0008561B1; PL217748A1; DE2963810D1; IN152480B; FR2433725B1; EP0008561A1; BR7905230A; CA1124044A

Abstract

The invention relates to an apparatus for compacting carbonated pastes. The apparatus comprises a device (1) for generating vibrations of low amplitude, a device (5) for generating static pressure and means (2, 3, 4, 10, 12) for shifting the assembly along the linings and joints to be produced. The apparatus is useful for the lining of metallurgical and electro-metallurgical furnaces and, in particular, for compacting joints during assembly of carbon or graphite blocks which act as the cathode in igneous electrolysis cells for the production of aluminium. <IMAGE>

Description

SPECIFICATION An Apparatus for Compacting Carbonated Pastes in the Linings of Metallurgical Furnaces This invention relates to an apparatus for compacting carbonated pastes in the linings of metallurgical and electrometallurgical furnaces. In particular, the invention relates to apparatus for compacting joints during the assembly of carbon or graphite blocks which constitute the lining of cells and act as the cathode for the production of aluminium by electrolysis of alumina dissolved in molten cryolite. Hereinafter, the term "carbonated pastes" will designate pastes constituted by an aggregate which is at least partly carbonated and a binder, and "lining paste" will designate a carbonated paste consisting essentially of coke and pitch. Conventional lining pastes are applied at a relatively high temperature of the order of 110 to 140.C, whether they are intended to constitute joints or lining elements. In order to make the joint or lining sufficiently compact and sealed, the paste has to be deposited in successive layers which are a maximum of 15 to 20 cm thick and each layer has to be compressed by means of a rammer or a pounding device mounted on a pneumatic hammer. This oeration is carried out manually and it is often difficult for the operator owing to the vibrations as well as the heat and liberation of tars and fumes. The active life of an electrolysis cell for the manufacture of aluminium, for example, is closely linked to the care with which the joints between the cathode blocks have been made.The problem therefore arises of mechanising the operation of compacting the carbonated pastes both for the comfort of the personnel and for the regularity and quality of the joints or linings. It is known, in particular, from French Patents Nos. 2,236,654 and 2,017,343, that blocks of anodes intended for igneous (i.e. fused salt) electrolysis cells for the manufacture of aluminium can be compacted in presses where a strong static pressure combined with a vibration is exerted on the carbonated paste. However, on the one hand, these are fixed machines designed to produce a series of moulded articles of constant shape and sizes and, on the other hand, most of the compacting work is carried out by the strong static pressure, the vibrations only serving to make it easier to fill the mould. The present invention provides an apparatus for compacting carbonated pastes which are hot or cold moulded, comprising a vibration generator, means for transmitting the vibrations and the thrust to the carbonated paste, and means for shifting the generator and orientating it in all the positions in space demanded by the compacting and finishing operations. The apparatus can also comprise a generator of static pressure, the effect of which is combined with that of the vibrations in order to effect compacting. The static thrust and the main component of the vibrations have to be directed in or close to the direction of compacting. They are transmitted to the paste to be compacted by means of a tool, generally called a rammer, the shape and dimensions of which are adapted to the form and dimensions of the lining to be produced. The apparatus can also comprise various additional devices such as automatic supply of carbonated paste and a means of programming its automatic shifting, for example along the various joints or linings to be produced in each type of metallurgical furnace. Reference is now made to the accompanying drawings which illustrate preferred apparatus according to the invention. Figure 1 is a general assembly diagram of the apparatus mounted in a small travelling crane above a furnace where joints are produced in carbonated paste. Figure 2 shows the fixing of a compacting rammer for producing a narrow joint. Figure 3 shows a type of rammer for a wide joint. A compactor 1 is constituted by a metal box in which is placed a vibration-generating device. Of all ths possible means of producing vibrations, motors with eccentric unbalance have turned out to be particularly practical, economical and strong. They can be activated, for example, by electricity or by compressed air. The eccentric unbalance motor is arranged in such a way that its rotational axis is in a substantially horizontal plane. If better equilibrium is desired, it is possible to use two eccentric unbalance motors, the directions of rotation of which are reversed and the rotations of which are synchronised so that the two unbalances can simultaneously pass or not pass the top and the bottom. The lateral vibratory component can thus be adjusted to an average or low value or to zero. The same result can be obtained from a single motor driving two synchronised unbalances rotating in opposite directions as above. Other types of vibration generators can be used without departing from the scope of the invention, for example a generator having a magnetostrictive effect or a pneumatic vibrator. Irrespective of the origin and mode of production of the vibrations, we have found that the best results are obtained if the maximum amplitude of the vibratory movements, measured from peak to peak, does not exceed 50 mm and is preferably in the range of from 1 to 10 mm. Above this number it is not correct to speak of vibrations but of repeated impacts which are not sufficiently effective to produce the optimum compaction. The compactor 1 is mounted at the end of a suspension arm 2 fixed at the end of a bracket 3 which is movable about a vertical axis 4. The static thrust is produced by the jack 5. The inclination of the compactor is adjustable, for example by means of a double effect rotary jack or by any other known means. The handle 14 allows the operator to guide the movements and to facilitate the positioning of the apparatus at the level of the joint. The compacting tool or "rammer" which has to be interchangeable so that it can be adapted to the shape and size of the joint or lining to be produced transmits the vibratory energy and the static thrust to the paste. It is fixed detachably beneath the compactor. The rammer 6 (Figure 2) is adapted to compact a long and narrow joint. It is perforated to reduce its weight so as to transmit the vibrations correctly. It is fixed by two stirrups 7, 7' arranged symmetrically on the sides of the compactor and by clamp screws 8,8' on the bed plate of the compactor. The rammer 9 (Figure 3) is suitable for ramming a "talus", that is to say the inclined portion which joins the bottom of an electrolysis cell to the vertical lateral walls. The suspension and shifting device of the apparatus can be of any known type. The one illustrated in Figure 1 is only one particular embodiment which is suitable for an electrolysis cell. It comprises a carriage 10 which can move on the horizontal beam 11 of a gantry 12 which is movable along rails 13, 13' arranged along the electrolysis cell or the series of cells if necessary. Embodiment and Mode of Operation We have produced a compacting apparatus according to the invention which comprises: a) a compactor 1 constituted by a pneumatic motor rotating at 3000 rpm when it is supplied with air compressed to 6 bars and rotating a 4 kg unbalance which is 3 cm off centre. The total weight of the compactor is 100 kg and the amplitude of the vibrations is from 3 to 10 millimetres. b) the jack 5 exerts on the compactor a thrust which can be adjusted between 1000 and 20,000 daN. The suspension bracket 3 is connected to the direction carriage 10 by a crown having crossed rollers which allows it to be rotated about 360[deg].It is provided with a locking device to keep the apparatus in a fixed direction. c) the direction carriage 10 rolling on the cross beams of the gantry is provided with silicone wheels to dampen the vibrations, is driven with . the aid of a toothed rack device by a pneumatic motor reducer (under 4.5 bars, 0.7 horsepower and 2600 rpm) producing a speed of movement of 9 rpm. The motor is provided with brakes to keep the carriage in place during the ramming operation. d) The gantry moving on the rails 13, 13' arranged along the cell is driven by a pneumatic motor reducer identical to that of the direction carriage.The wheels of this gantry are driven from each side so as to prevent "crab" type travel and the speed of translation is 9 m/mn. e) Control device: all the control switches of the various members, gantry, carriage, compactor (vibration) and raising-lowering and inclination jacks are grouped at the level of the bracket at human height. The shifting of the gantry and of the carriage are brought to a single switch which allows the instructions to be transmitted either to the gantry or to the carriage so as to shift the compactor, whatever the orientation of the bracket 3, in the direction of movement imprinted on the switch. This control device can be brought outside the cell and connected to the machine by a remote control system. f) The pressures adopted vary according to the size of the tool and the pressure exerted on the jack 5. In order to test the quality of the joints obtained using the apparatus, a series of joints have been produced in the actual size from lining paste between some carbon blocks intended to form the bottom of an igneous electrolysis cell for the production of aluminium. The joints to be produced were 2.36 m long, 40 mm wide and 450 mm deep. The joint was made up in four successive layers with a 2.35 meter long rammer. A layer of carbonated paste about 20 cm high was firstly deposited. The rammer was installed and the paste was then compacted by vibration and static pressure for 45 seconds. A second, third and fourth layer of paste were deposited, then compressed and compacted in the same way until the level of the joint correspond to the height of the carbon blocks to be assembled. The joint was cooled and dismantled and a density of between 1.52 and 1.56 was found along the joint on samples taken from various levels and different positions, and this indicated excellent homogeneity. The rate of compaction (ratio between the volume of compacted paste and the crude paste) is of the order of 45% and can attain and even exceed 50%, which is very satisfactory. No adhesion of paste on the rammers was observed, even in the case of a superheated paste, and paste was not seen to rise anywhere from the tool during compaction. Numerous similar tests were carried out with the same success on various types of electrolysis cell. They confirmed that the machine forming the subject of the invention could produce all the cathode joints of an electrolysis cell merely by changing the rammer. Furthermore, the machine is particularly suitable for making up the lining of metallurgical furnaces produced partially or totally from carbonated pastes. It can additionally comprise a paste distributor constituted by a tank which is optionally heated and/or insulated and an endless screw or any other device allowing the paste to be introduced into the joint to be produced or on the position to be covered. It is also possible to remotely control or to complely automate its operation and this is of particular value when making, for example, joints over a series of electrolysis cells comprising several tens of identical units. In the latter case, the control is thus assured by a programmable automation which contains the respective positions and dimensions of the various joints and the various cells in a memory and which acts simultaneously on the shifting of the compactor, the supply of paste and the start up and stoppage of compaction.

Claims

1. An apparatus for compacting carbonated pastes in the linings of metallurgical and electrometallurgical furnaces, which comprises in combination a device for generating vibrations having an amplitude of from 1 to 50 mm, means for transmitting the vibrations to the carbonated paste, a device for generating static pressure, the thrust of which is directed substantially in the direction of compaction, and means for shifting and orientating it in all the positions in space demanded by the compacting operations.

2. An apparatus according to claim 1, wherein the amplitude of the vibrations is from 1 to 10 mm.

3. An apparatus according to claim 1 or 2, wherein the means for transmitting the vibrations and the static thrust is a tool connected to the vibration generator, the shape and size of which are adapted to the shape and size of the space where compaction is carried out and of the profile of paste to be obtained.

4. An apparatus according to any one of claims 1 to 3, wherein the vibration generator comprises at least one motor adapted to rotate at least one eccentric unbalance.

5. An apparatus according to any one of claims 1 to 3, wherein the vibration generator comprises at least one motor adapted to rotate two synchronised eccentric unbalances in opposite directions, the two unbalances being able to pass simultaneously to the top and to the bottom.

6. An apparatus according to any one of claims 1 to 5, also comprising a carbonated paste distributor.

7. An apparatus according to any of claims 1 to 6, the functioning and shifting of which are remotely controllable by a console which is independent from the machine.

8. An apparatus according to any one of claims 1 to 7, the functioning and shifting of which are remotely controllable by a programmable automaton in which the position and the shape of the compacting operations to be produced have been memorised.

9. An apparatus for compacting carbonated pastes substantially as hereinbefore described with reference to the accompanying drawings.