EP0094308B1 - Process and apparatus for the electrolytic preparation of metal, especially lead - Google Patents

Process and apparatus for the electrolytic preparation of metal, especially lead Download PDF

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Publication number
EP0094308B1
EP0094308B1 EP83400915A EP83400915A EP0094308B1 EP 0094308 B1 EP0094308 B1 EP 0094308B1 EP 83400915 A EP83400915 A EP 83400915A EP 83400915 A EP83400915 A EP 83400915A EP 0094308 B1 EP0094308 B1 EP 0094308B1
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Prior art keywords
electrolyte
chloride
particles
process according
lead
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German (de)
French (fr)
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EP0094308A3 (en
EP0094308A2 (en
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Claude Palvadeau
Claude Scheidt
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Societe Miniere et Metallurgique de Penarroya
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Societe Miniere et Metallurgique de Penarroya
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    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25CPROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/18Electrolytic production, recovery or refining of metals by electrolysis of solutions of lead
    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25CPROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C5/00Electrolytic production, recovery or refining of metal powders or porous metal masses
    • C25C5/02Electrolytic production, recovery or refining of metal powders or porous metal masses from solutions

Definitions

  • the present invention relates to the preparation of a metal by electrolysis, and in particular the preparation of lead from metal chloride. It relates in particular to the electrolysis of very pure solutions of lead chloride.
  • French Patent No. 2,240,956 describes a process for depositing metallic lead from aqueous solutions of lead chloride. More precisely, this patent describes the electrolysis of such a solution in a diaphragm cell, in the presence of ferrous chloride which oxidizes to ferric chloride during the operation; in Example 1 of this patent, the concentration of lead in the electrolyte is reduced to a value between 25 and 11 grams per liter, in a 3M solution of ferrous chloride, with a current density of 323 Alm 2 and a Faradic yield of 70%.
  • the patent does not indicate the properties of metallic lead deposition such as its density, its adhesion to the cathodic support (lead sheet), its compact or pulverulent nature or its purity, nor the mode of extraction of lead.
  • French Patent No. 2,427,401 describes a process for recovering lead from sulphide ores. This process ensures the regeneration of the reagent, ferric chloride, at the anode of an electrolyser comprising neither a diaphragm nor a membrane.
  • Lead is deposited on a cathode formed by an assembly of rods mounted in special supports so that shocks can be applied to the rods due to their rotation or their mounting device. The lead formed is detached under the action of shocks and falls to the bottom of the tank. It is then evacuated.
  • This patent does not describe the effects of the electrolysis current in the vicinity of the electrode and neither describes the recovery of the lead fragments, nor the treatment of the latter before fusion.
  • US Patent No. 3,785,950 describes a process for recovering copper by electrolysis in which an electrolysis cell comprising separate vertical electrodes, a diaphragm, a cathode, a pump for circulating the electrolyte and a removal device metal, is implemented to recover copper from an attack of metallic copper.
  • the faradic yields obtained are most often less than 90%.
  • the anodic reaction is not described in general and it is not indicated if chlorine is released at the anode or if on the contrary this release is avoided, and in what way.
  • the invention relates to the preparation by electrolysis of a very pure metal, preferably lead.
  • the subject of the invention is the preparation by electrolysis of a metal present in the electrolyte in a non-cationic and in particular anionic form.
  • It relates to such a method which implements a continuous detachment of the metal which forms on the cathodes.
  • the electrolyte circulates parallel to the cathodes which are placed vertically with a speed such that its flow is of the laminar or slightly turbulent type, so that this current, in cooperation with the apparent weight of the particles, ensures detaching them from the cathodes and, simultaneously, renewing the electrolyte near the surfaces of the electrodes.
  • the invention relates to a process for the preparation of a metal, defined in claim 1.
  • the metal of the electrolysis is lead, it is present, in the form of chloride, in an amount of between approximately 5 and 50 grams per liter, preferably between 15 and 25 grams per liter in the electrolyte.
  • the alkali or alkaline earth metal chloride is preferably sodium chloride. Its concentration in the electrolyte is preferably between 230 and 300 grams per liter.
  • the density of the electrolysis current is between 500 and 1,500 A / M 2 , preferably between 700 and 1,000 Alm 2. It is preferable that this current density increases gradually since the start-up electrolysis.
  • the temperature of the electrolyte is advantageously between 70 and 95 ° C.
  • the cathode surface having a low density of nucleation sites is preferably formed of titanium, stainless steel or graphite.
  • the electrolyte also contains iron in the form of chloride.
  • concentration of iron is then advantageously greater than 10 grams per liter and preferably between 20 and 60 grams per liter.
  • the laminar or slightly turbulent flow of the electrolyte along the cathode surface is obtained when the electrolyte current flows near the cathodes at a speed of between 0.01 and 0.15 meters per second.
  • the removal of the particles collected at the bottom of the cell is advantageously carried out by transporting the particles out of the cell, then by densification of the particles by compression.
  • the densified particles can undergo a rolling intended to drive out the electrolyte inclusions.
  • the densified particles can also undergo fusion in the presence of soda.
  • the invention also relates to an apparatus for the preparation of a metal by electrolysis defined in claim 15.
  • the apparatus comprises bipolar electrodes.
  • the device advantageously includes a recovery hood when chlorine gas is released at the anodes.
  • the anodes are advantageously formed from a metal which cannot be attacked by the electrolyte and in deployed form.
  • the transport device can advantageously be a worm, a bucket elevator or a conveyor belt and preferably the gooseneck system described below.
  • the apparatus may also include an extruder for receiving the particles and for densifying them.
  • the method and the apparatus according to the invention have all the advantages of apparatuses in which the metal detaches automatically from the cathodes.
  • the main advantage is the almost total elimination of manipulations of the electrodes. This reduction in handling increases the useful service time of the electrolysers so that the number of electrolysis cells can be reduced, with corresponding reduction in investments.
  • the electrolyte solution contains chlorides of lead, alkali or alkaline earth metals, iron and possibly other metals, for example zinc.
  • the lead chloride solution is advantageously formed from a concentrate of lead sulphide ore which, in addition to lead, contains small amounts of zinc, copper, iron, calcium and magnesium.
  • the solution contains practically only lead and iron , the other metals being in negligible quantity.
  • the amount of lead in chloride form, present in the electrolyte is preferably greater than 5 grams per liter but it does not preferably exceed 50 grams per liter. These two values are determined according to the current densities used during the electrolysis and the circulation speeds of the electrolyte in the vicinity of the electrodes, so that the faradaic efficiency and the capacity of production are optimal.
  • the electrolyte also contains in high concentration an alkaline or alkaline-earth chloride.
  • the most advantageous is sodium chloride, for reasons of cost and availability.
  • the quantity of this chloride in solution is advantageously chosen so that the concentration of chloride ion is greater than 3 equivalent-grams (that is to say in the case of sodium chloride at approximately 200 grams per liter), preferably between 4 and 5 gram equivalent (i.e. for sodium chloride between 230 and 300 grams per liter).
  • the role of this chloride is to increase the concentration of chloride ions in the electrolyte, which makes it possible to dissolve the metals whose chlorinated complexes are soluble, and to reduce the losses by Joule effect.
  • the electrolyte also contains iron in the form of chloride.
  • the chloride ions oxidize at the anode to chlorine gas at an electrode potential of 1.2 V compared to the saturated calomel electrode (DHW).
  • the apparatus must then include a suitable collecting system.
  • the electrolyte advantageously contains iron so that, at the anode, the ferrous ion oxidizes to ferric ion at a potential close to 0.6 V / DHW. It is therefore necessary that the electrolyte contains iron in the form of ferrous iron. Not only is the chlorine no longer released at the anode, but also the energy efficiency is clearly increased.
  • the ferric chloride formed at the anode is recovered and can be used again for the treatment of lead sulphide ores and the transformation of galena into elemental sulfur and lead chloride.
  • the concentration of iron in the electrolyte, in the chloride form is preferably between 20 and 60 grams per liter, and advantageously it is of the order of 40 grams per liter. It is important that this concentration is at least equal to 20 grams per liter in the anolyte, that is to say near the anodes.
  • the nature of the electrodes used and in particular of the cathodes is important for the implementation of the invention. It is found in fact that many materials are too "active, that is to say form too many nucleation sites. As a result, lead particles begin to form at too many locations on the surface of the cathodes and cannot magnify individually. For this reason, it is essential according to the invention that the density of the nucleation sites, under the electrolysis conditions used, is sufficiently low so that the particles can reach a dimension of at least 100 micrometers without joining with the particles. adjacent. Preferably, the particles retain their individuality until they reach a dimension of at least 600 micrometers and preferably one millimeter.
  • the particles individually have a large enough surface so that, when the electrolyte moves along the surface of the cathode, it exerts a tearing force which, in combination with the force of gravity, is sufficient for detachment particles when they have a dimension of a few hundred micrometers.
  • This density of sites is important according to the invention because, if the number of sites is too large, the particles formed are small and numerous and, when they are subsequently placed in the air, they oxidize easily because they form a pyrophoric powder. On the contrary, if the density of nucleation sites is too low, the production capacity is reduced.
  • a suitable density of nucleation sites is obtained by the use of cathodes whose surface is formed of smooth titanium. Stainless steel or graphite surfaces can also be used. Of course, other materials can also be used for carrying out the process of the invention, when these have the appropriate density of nucleation sites. This density can be obtained by an activation treatment or, more often, deactivation according to techniques known to those skilled in the art.
  • the anodes can be formed from graphite. However, as it is desirable that the transport of material is favored, it is preferable that the anodes be formed from an expanded metal, for example ruthenized titanium. However, the nature of the anode is much less important for the implementation of the method of the invention than that of the cathode.
  • the linear speed of the catholyte, parallel to the cathodes be at least 0.01 meters per second and preferably between 0.01 and 0.15 meters per second.
  • the speed of circulation of the solution which may be zero, is preferably at least 0.01 meter per second; the maximum value can be moderate, for example 0.05 meters per second, given the shape of the anodes which promote the creation of turbulence.
  • the temperature of the electrolyte is advantageously between 70 and 95 ° C, preferably between 70 and 90 ° C. No heating is necessary because the normal losses by Joule effect are sufficient to maintain the temperature in the aforementioned range.
  • the implementation of the method of the invention allows the use of very high current densities. They can be between 500 and 1,500 A / M 2 . Preferably, they are between 700 and 1000 A / M 2 .
  • the electrolysis begins at a low current density, lower than the values indicated above, and gradually increases to the chosen value, included in the aforementioned range.
  • the solution contains ferrous chloride
  • iron can deposit at the same time as lead, on the cathodes, when the current density is initially very high. The metal then adheres to the entire surface of the cathodes, so that the latter no longer have a suitable density of nucleation sites.
  • the initial use of a high current density can cause the evolution of hydrogen whose bubbles tend to cling to the metal particles so that these, instead of falling to the bottom of the electrolysis cell, tend to float.
  • the period during which the current density increases progressively or in stages, up to the desired final value, is advantageously a few hours.
  • the product obtained was in the form of individual particles having a dimension of a few hundred micrometers, for example from 300 to 600 micrometers.
  • Their shape can be branched and relatively flat, but their surface is relatively small for their volume. It is this characteristic which gives the particles formed their non-pyrophoric nature.
  • the particles are formed from very pure lead.
  • metals such as zinc, copper, cadmium, magnesium, etc. are present in an amount less than 1 ppm by weight.
  • the amount of iron is less than a few ppm by weight. It is therefore lead which does not subsequently require any refining for most applications.
  • the examples which follow give the purity of the lead obtained under different conditions.
  • the lead particles which deposit at the bottom of the cell are then extracted, using a suitable mechanism, as indicated in the remainder of this specification with reference to an apparatus intended for carrying out the method according to the invention.
  • the lead particles, when they are removed, are associated with occluded electrolyte, present in an amount between 20 and 30% by weight approximately. It is therefore desirable that the material undergoes compaction or rolling. It is in particular desirable that the particles be densified by extrusion, in a piston or roller press, exerting pressures greater than about 70 MPa. Filtration of the product is undesirable since the smallest particles may partially oxidize in air.
  • the semi-finished product of lead obtained for example in the form of a strip, is stable with respect to oxidation in air. It can be used as is in some applications.
  • lead can undergo fusion in the presence of sodium hydroxide, according to a well known technique.
  • the above description relates to the electrolysis of a solution containing ferrous chloride. This feature is not essential. When the process is carried out without ferrous chloride in the electrolyte, chlorine is released at the anodes.
  • the device used must therefore include a chlorine collection system. Such systems are well known in the electrochemical industries and are therefore not described in detail.
  • the current density can then have an increased value, between 800 and 2,000 A / m 2 , preferably between 800 and 1,200 A / m 2 .
  • the pH of the electrolyte is at an equilibrium value between 1.2 and 1.7, at a temperature of 70 to 80 ° C. This pH depends on the concentration of sulfate ions and the current density. However, it may be advantageous to work at a pH of between 2 and 3 so as to avoid the proton electrolysis reactions to give hydrogen. In this case, a pH regulation system must then be provided by adding a base which is preferably chosen so as not to add foreign ions to the electrolytes.
  • the basic sodium compounds sodium hydroxide, soda ash, or even basic lead compounds, lead hydroxide, litharge, basic lead carbonate, etc.
  • the device of the present invention comprises very many anode-cathode pairs placed in a non-isopotential manner.
  • the process which has just been explained above involves the use of numerous pumps for recirculation. These numerous pumps lead to investment costs which can be significant. This is why we have sought to develop an electrolysis device which makes it possible to reduce the number of electrolyte recirculation pumps and which in general, significantly reduce the investment costs of electrolysis devices.
  • the above electrolytic cell commonly known as a “swimming pool cell” is equipped with a series of substantially parallel rows of electrolytic cells.
  • Each cell is made up of the couple formed by an anode surface and a cathode surface.
  • all the cells are mounted in parallel, in a comb (or rake), that is to say that all the anodes in the same row have the same potential, however, as all the cathodes in the same row are also at the same potential.
  • the rows of said electrolytic-pool tank are mounted in electrical series; there is therefore a potential gradient in the tank-pool.
  • the present device which can be called “tank-channel” in order to implement the invention consists of a series of rows of anodes and cathodes mounted in parallel, the anodes of each row being preferably offset parallel to themselves by a value of between 5 and 20 centimeters in the direction of the decreasing potentials in the electrolysis cell, the distance between two rows being between 0.8 and 2 meters.
  • the cathodes of different rows and located on the same plane are joined together by partitions made of insulating material so as to limit stray or leakage currents. Although this is less important, the anodes of different rows and located in the same anode channel can be joined together by partitions made of insulating material so as to limit parasitic and / or leakage currents.
  • the assembly forms a juxtaposition of channels parallel to each other and perpendicular to the rows of electrodes.
  • Pump systems similar to those described in the present application impose a circulation of the catholyte and the anolyte, while between each cathode and each anode there is the diaphragm which was mentioned during the description of the process.
  • the device can be of the monopolar or bipolar type.
  • Bipolar mounting has advantages because it reduces energy losses (by reducing ohmic drops in the electrodes and related structures), it reduces the cost of the electrodes since they have a double role, and it simplifies the mounting of sets of electrodes, while allowing better energy efficiency.
  • This advantageous assembly poses certain configuration problems at the ends of the electrodes, in particular to avoid leakage currents, as those skilled in the art know.
  • FIG. 1 is a diagram of an example of an apparatus for implementing the method according to the invention.
  • the reference 1 designates an electrolysis tank containing an anode box 2.
  • the diaphragm is schematically identified by the reference 3.
  • the catholyte circulation circuit comprises a reservoir 4 and a circulation pump 5.
  • the catholyte circulates parallel to the plane of the cathodes which are mounted in the tank 1.
  • the anolyte circuit includes a reservoir 6 and a pump 7 which circulates the anolyte.
  • Reference 8 designates a pump intended to extract part of the anolyte which has concentrated in ferric chloride and is suitable for the treatment of lead sulphide ores.
  • Reference 9 designates the feed solution which restores the catholyte to the appropriate composition in the reservoir 4.
  • the particles which detach from the cathodes fall to the bottom of the cell and are taken up by an endless screw 10 mounted on a shaft 11 driven in rotation by a motor 12.
  • the particles arriving at the end of the screw arrive at a recipe 13 and are then treated as described above.
  • the nature of the electrodes and their mounting are as described above.
  • the diaphragm and anodes also have the properties indicated above.
  • a collecting hood must be mounted above the anodes so that it collects the chlorine which is released.
  • the adjustment of the weir makes it possible to maintain a difference in level between the catholyte and the anolyte, as indicated previously.
  • the flow rates of pumps 5 and 7 are adjusted so that the speeds of the anolyte and the catholyte, along the anodes and cathodes, have the values indicated above, that is to say at least equal to 0.01 meter per second.
  • the flow through the diaphragm is almost equal to the flow of the feed solution. In this way, the ferric iron can hardly pass into the catholyte.
  • the additional feed solution flow rates pass by overflow from the catholyte reservoir 4 to the anolyte reservoir 6.
  • the cell preferably has a trapezoidal or rounded bottom so that the falling particles are guided towards the worm.
  • a worm driven by a motor has been shown, other mechanisms are suitable.
  • bucket elevators or conveyor belts can also be advantageously used.
  • the product can also pass through an extruder which makes it undergo a prior densification, up to an apparent density of 3 to 6.
  • the extruder can be provided with a die long enough for it to seal the liquid.
  • the metallic particles formed are recovered using a gooseneck operating in batch mode.
  • the bottom of the cell is given a pyramid-like shape in order to direct the lead particles towards a swan neck which rises vertically along the cell.
  • the liquid level in the swan neck is in hydrostatic equilibrium with that of the electrolysis cell, i.e.
  • the swan neck rejection point is located 2 to 20 centimeters above the level of the surface of the catholyte: lead aggregates accumulate in the lower part of the swan neck, constituting a real plug; intermittently one or more ejectors, which can be produced by nozzles, are supplied by catholyte without solid at a rate sufficient to create a suction effect at the bottom of the cell and to achieve a linear speed of flow of the liquid in the neck swan of at least 0.5 meters per second.
  • the lead is entrained and recovered after separation of the liquid in a suitable system which is hydraulically disconnected from the electrolysis cell.
  • Lead agglomerates can also be entrained by air entrainment (air-lift).
  • the ejector (s) are disposed under the swan neck at the appropriate locations known to those skilled in the art to obtain a good “suction” or “air-lift” effect.
  • a sulfurized raw material consisting of a galena concentrate, containing 75.5% lead, 0.70% zinc, 0.85% copper, 1.40% iron, is treated with a solution of ferric chloride and sodium. , 1.0% calcium and 0.6% magnesium.
  • the electrolyzer supply solution and the electrolyte have the following compositions:
  • the electrolysis is carried out in an installation of the type shown in the figure; the circulation speed of the catholyte is 0.06 meters per second and that of the anolyte is 0.01 meters per second.
  • the cathodes are made of smooth titanium.
  • the current density, in steady state, is 550 A / m 2 .
  • the distance between the electrodes is 70 millimeters.
  • the lead obtained is in the form of particles having a length of the order of 300 to 600 micrometers and does not adhere to the cathodes.
  • the faradaic efficiency observed is 95%, and the energy yield is 0.57 kWh per kilo of lead.
  • Example 1 The same installation is used and an electrolyte of the same composition as in Example 1.
  • the circulation speed of the catholyte is 0.10 meters per second and that of the anolyte of 0.02 meters per second.
  • the current density used is 850 A / m 2 and the distance between the electrodes is the same as in Example 1.
  • the lead produced is similar to that described in Example 1.
  • the energy efficiency of electrolysis is 0.74 kWh per kilo.
  • Example 2 An installation similar to that of Example 1 is used.
  • the cathodes are formed from smooth titanium and the anodes from expanded titanium covered with ruthenium oxide. The distance between them is 70 millimeters.
  • the anodes are placed in an anode box in which the anolyte does not circulate.
  • the pressure difference between the anolyte and the catholyte is 20 millimeters of water column.
  • the installation is intended to allow the recovery of chlorine.
  • the energy efficiency of electrolysis is 1 kWh per kilo of lead.
  • the lead particles form a powder with an apparent density of between 1.5 and 2.5 and contain 20 to 30% by weight of occluded electrolyte. After densification with a rolling mill, this electrolyte is extracted from the powder.
  • the following table indicates not only the composition of the electrolyte but also the purity of the products obtained, on the one hand after rolling and on the other hand after shaping an ingot.
  • Example 3 The operating conditions are identical to those of Example 3, but the electrolyte contains 10 grams per liter of sulfate. At this concentration, the electrolysis is not disturbed by the sulfate ions and the energy yield remains substantially equal to 1 kWh per kilo of lead deposited.
  • the lead particles obtained have the same purity and the same level of electrolyte occluded as in Example 3.
  • the energy efficiency reaches 1.24 kWh per kilo of lead deposited.
  • the purity of the lead particles obtained and the characteristics before densification remain the same as in the previous example.
  • Example 6 Installation of electrodes of the same type of electrical series in the same tank
  • each cell consists of an anode and a cathode.
  • the electrolysis of copper sulphate was chosen to facilitate the measurements which essentially relate to the evolution of the leakage currents and the distribution of the current density at the surface of the cathodes.
  • the copper deposits are compact and the faradaic yield of the deposits very close to unity in a current density range of 200 to 300 amperes per square meter. Under these conditions, it is possible, by cutting the deposit into strips of equal width, to determine from the weight of each, the average current density of electrolysis on each surface element and thus to know the distribution profile of the average current density at the surface of the cathodes.
  • FIG. 2 represents the experimental device used.
  • the copper sulphate solution is kept in circulation between the tank 4, heated 5 and the channel type electrolysis tank 1 by the centrifugal pump 6.
  • Each cell 2 consists of a lead anode and a steel cathode stainless, spaced 1.6 cm apart.
  • one, two or three cells 2 can be mounted in electrical series and the spacing L between each cell can vary.
  • the diagram mainly represents the electrical connections between the anodes 7 and the cathodes 8.
  • Each cell 2 is connected externally by a conductor 9. Between each cell 2 there is a leakage current I F which decreases the overall energy efficiency of the electrolyser and which disturbs the distribution of the current density on the edges of the electrodes, mainly between the anode of a cell and the cathode of the neighboring cell.
  • the following table shows the main results obtained with an electrolyte containing 40 grams per liter of copper and 165 grams per liter of sulfuric acid. All the experiments were carried out at a temperature of 40 ° C for 15 to 20 hours.
  • the leakage currents are an important relative value with respect to the intensity of the current supplied by the rectifier 3. This relative importance will be considerably attenuated on a larger scale.
  • FIG. 4 gives by way of example the average density profile obtained on the cathodes 8 for test 2.
  • the overcurrent on the edges of the cathodes is not acceptable due to the increase in the local electrode overvoltage which may cause the appearance of parasitic reactions.
  • Figures 5 and 6 show the distribution profiles of true current density for cathodes with or without offset.

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Abstract

The present invention is directed to an apparatus for preparing a lead or copper metal by electrolysis in a cell having a cathode and an anode which are separated by a diaphragm. The surface of the cathode is arranged in a substantially vertical direction and has a sufficiently low density of sites of nucleation so that metallic particles which are formed from the sites keep their individuality in relation to the adjacent particles, until the particles reach a dimension of at least 100 micrometers. An electrolyte is circulated between the cathode and an anode parallel to the surface of the cathode at a flow rate in a laminar to weakly turbulent manner so that under the action of the weight of the particles and the force exercised by the flow of the electrolyte the metallic particles are detached and fall into the electrolyte and are collected and are removed from the bottom of the cell.

Description

La présente invention concerne la préparation d'un métal par électrolyse, et notamment la préparation du plomb à partir de chlorure métallique. Elle concerne en particulier l'électrolyse de solutions très pures de chlorure de plomb.The present invention relates to the preparation of a metal by electrolysis, and in particular the preparation of lead from metal chloride. It relates in particular to the electrolysis of very pure solutions of lead chloride.

Les procédés courants de traitement métallurgique des minerais de plomb permettent la préparation de solutions de chlorure de plomb qui sont très pures, par exemple après purification par un solvant ou cristallisation. L'invention concerne la préparation du plomb à partir de telles solutions.Current metallurgical treatment processes for lead ores allow the preparation of lead chloride solutions which are very pure, for example after purification by a solvent or crystallization. The invention relates to the preparation of lead from such solutions.

Le brevet français n° 2.240.956 décrit un procédé de dépôt de plomb métallique à partir de solutions aqueuses de chlorure de plomb. Plus précisément ce brevet décrit l'électrolyse d'une telle solution dans une cellule à diaphragme, en présence de chlorure ferreux qui s'oxyde en chlorure ferrique pendant l'opération ; dans l'exemple 1 de ce brevet, la concentration du plomb dans l'électrolyte est réduite à une valeur comprise entre 25 et 11 grammes par litre, dans une solution 3M en chlorure ferreux, avec une densité de courant de 323 Alm2 et un rendement faradique de 70 %. Le brevet n'indique pas les propriétés du dépôt de plomb métallique telles que sa densité, son adhérence au support cathodique (feuille de plomb), sa nature compacte ou pulvérulente ou sa pureté, ni le mode d'extraction du plomb.French Patent No. 2,240,956 describes a process for depositing metallic lead from aqueous solutions of lead chloride. More precisely, this patent describes the electrolysis of such a solution in a diaphragm cell, in the presence of ferrous chloride which oxidizes to ferric chloride during the operation; in Example 1 of this patent, the concentration of lead in the electrolyte is reduced to a value between 25 and 11 grams per liter, in a 3M solution of ferrous chloride, with a current density of 323 Alm 2 and a Faradic yield of 70%. The patent does not indicate the properties of metallic lead deposition such as its density, its adhesion to the cathodic support (lead sheet), its compact or pulverulent nature or its purity, nor the mode of extraction of lead.

L'ouvrage « Electrometallurgy of Chloride Solutions » de V.V. Stender, Consultants Bureau, New York, (1965) indique qu'un dépôt de plomb non compact, à cristallisation grossière et présentant un éclat métallique, peut être obtenu à partir d'une saumure concentrée de chlorure de sodium contenant du plomb. La concentration du plomb diminue de 40 à 10 grammes par litre au cours d'une électrolyse réalisée avec une densité de courant comprise entre 500 et 1 000 A/m2. L'ouvrage ne donne pas de précision sur les propriétés du plomb telles que sa pureté, sa densité, son adhérence à la cathode qui est constituée d'une feuille de plomb, ni sur le mode d'extraction du dépôt. Le rendement faradique serait compris entre 85 et 90 %. Le même ouvrage indique par ailleurs qu'une poudre de plomb peut être obtenue à partir de solutions contenant 300 grammes par litre de NaCI et 10 grammes par litre de plomb sous forme de chlorure, avec un rendement faradique de 80 % environ.The book "Electrometallurgy of Chloride Solutions" by VV Stender, Consultants Bureau, New York, (1965) indicates that a deposit of non-compact lead, with coarse crystallization and having a metallic luster, can be obtained from brine concentrated sodium chloride containing lead. The lead concentration decreases from 40 to 10 grams per liter during an electrolysis carried out with a current density of between 500 and 1000 A / m 2 . The work does not give details on the properties of lead such as its purity, its density, its adhesion to the cathode which is made of a lead sheet, nor on the mode of extraction of the deposit. The faradic yield would be between 85 and 90%. The same book also indicates that a lead powder can be obtained from solutions containing 300 grams per liter of NaCl and 10 grams per liter of lead in the form of chloride, with a faradaic yield of about 80%.

Le rapport « Aqueous electrolysis of lead chloride de F.P. Haver, D.L. Bixby et M.M. Wong, USBM Report of Investigations, 8276 (1978) décrit l'électrolyse de chlorure de plomb cristallisé sur une cathode horizontale placée en fond de cellule, si bien que la concentration de plomb en solution reste constante. Ce document indique que, dès que le dernier cristal de chlorure de plomb disparaît, le dépôt devient spongieux, d'aspect non métallique et adhérent. En présence de cristaux, le rendement faradique obtenu est de 96 % pour une densité de courant de 150 A/M 2, dans une solution à 20 % de HCI à 25 °C.The report “Aqueous electrolysis of lead chloride by FP Haver, DL Bixby and MM Wong, USBM Report of Investigations, 8276 (1978) describes the electrolysis of lead chloride crystallized on a horizontal cathode placed at the bottom of the cell, so that the lead concentration in solution remains constant. This document indicates that, as soon as the last lead chloride crystal disappears, the deposit becomes spongy, non-metallic in appearance and adherent. In the presence of crystals, the faradic yield obtained is 96% for a current density of 150 A / M 2 , in a 20% solution of HCl at 25 ° C.

Le brevet français n° 2.427.401 décrit un procédé de valorisation de plomb à partir de minerais sulfurés. Ce procédé assure la régénération du réactif, le chlorure ferrique, à l'anode d'un électrolyseur ne comportant ni diaphragme, ni membrane. Le plomb se dépose sur une cathode formée d'un assemblage de tiges montées dans des supports spéciaux afin que des chocs puissent être appliqués aux tiges du fait de la rotation de celles-ci ou de leur dispositif de montage. Le plomb formé se détache sous l'action des chocs et tombe au fond de la cuve. Il est ensuite évacué. Ce brevet ne décrit pas les effets du courant d'électrolyse au voisinage de l'électrode et ne décrit ni la récupération des fragments de plomb, ni le traitement de celui-ci avant fusion.French Patent No. 2,427,401 describes a process for recovering lead from sulphide ores. This process ensures the regeneration of the reagent, ferric chloride, at the anode of an electrolyser comprising neither a diaphragm nor a membrane. Lead is deposited on a cathode formed by an assembly of rods mounted in special supports so that shocks can be applied to the rods due to their rotation or their mounting device. The lead formed is detached under the action of shocks and falls to the bottom of the tank. It is then evacuated. This patent does not describe the effects of the electrolysis current in the vicinity of the electrode and neither describes the recovery of the lead fragments, nor the treatment of the latter before fusion.

Le brevet US n° 3.785.950 décrit un procédé de récupération du cuivre par électrolyse dans lequel une cellule d'électrolyse comprenant des électrodes verticales séparées, un diaphragme, une cathode, une pompe destinée à faire circuler l'électrolyte et un dispositif de retrait du métal, est mise en ceuvre pour récupérer du cuivre provenant d'une attaque de cuivre métallique.US Patent No. 3,785,950 describes a process for recovering copper by electrolysis in which an electrolysis cell comprising separate vertical electrodes, a diaphragm, a cathode, a pump for circulating the electrolyte and a removal device metal, is implemented to recover copper from an attack of metallic copper.

Ce procédé toutefois promeut la formation de dendrites de cuivre en calant la température de l'interface cathode-solution au moyen d'une cathode creuse dans laquelle circule un réfrigérant ; les dendrites ne se détachent pas toutes seules et nécessitent un dispositif d'arrachage.This process, however, promotes the formation of copper dendrites by setting the temperature of the cathode-solution interface by means of a hollow cathode in which a refrigerant circulates; the dendrites do not come off on their own and require a lifting device.

Ainsi, les procédés décrits présentent des inconvénients et les documents précités possèdent des lacunes. En particulier, on ne sait pas quelle est la qualité de la poudre obtenue, notamment sa pureté, sa densité, ses propriétés d'oxydation par l'air, toutes propriétés essentielles dans l'exploitation industrielle d'une telle poudre.Thus, the methods described have drawbacks and the aforementioned documents have shortcomings. In particular, it is not known what is the quality of the powder obtained, in particular its purity, its density, its air oxidation properties, all essential properties in the industrial exploitation of such a powder.

Ces documents n'indiquent aucun procédé d'extraction du plomb formé, pouvant être utilisé dans un électrolyseur industriel.These documents do not indicate any process for extracting the lead formed, which can be used in an industrial electrolyser.

Les rendements faradiques obtenus sont le plus souvent inférieurs à 90 %. La réaction anodique n'est pas décrite en général et il n'est pas indiqué si le chlore se dégage à l'anode ou si au contraire ce dégagement est évité, et de quelle manière.The faradic yields obtained are most often less than 90%. The anodic reaction is not described in general and it is not indicated if chlorine is released at the anode or if on the contrary this release is avoided, and in what way.

L'invention concerne la préparation par électrolyse d'un métal très pur, de préférence le plomb.The invention relates to the preparation by electrolysis of a very pure metal, preferably lead.

L'invention a pour objet la préparation par électrolyse d'un métal présent dans l'électrolyte sous une forme non cationique et notamment anionique.The subject of the invention is the preparation by electrolysis of a metal present in the electrolyte in a non-cationic and in particular anionic form.

Elle concerne un tel procédé qui met en oeuvre un détachement continu du métal qui se forme sur les cathodes.It relates to such a method which implements a continuous detachment of the metal which forms on the cathodes.

Elle concerne un tel procédé qui permet la préparation d'un métal particulaire, notamment de plomb particulaire qui n'est pas pyrophorique et qui peut être facilement mis sous forme d'un demi-produit intéressant.It relates to such a process which allows the preparation of a particulate metal, in particular particulate lead which is not pyrophoric and which can be easily formed into a semi-finished product interesting.

Elle concerne aussi un tel procédé qui permet l'obtention d'un rendement faradique très élevé.It also relates to such a process which makes it possible to obtain a very high faradic yield.

Selon une caractéristique de l'invention, l'électrolyte circule parallèlement aux cathodes qui sont placées verticalement avec une vitesse telle que son écoulement est de type laminaire ou faiblement turbulent, si bien que ce courant, en coopération avec le poids apparent des particules, assure le détachement de celles-ci des cathodes et, simultanément, le renouvellement de l'électrolyte à proximité des surfaces des électrodes.According to a characteristic of the invention, the electrolyte circulates parallel to the cathodes which are placed vertically with a speed such that its flow is of the laminar or slightly turbulent type, so that this current, in cooperation with the apparent weight of the particles, ensures detaching them from the cathodes and, simultaneously, renewing the electrolyte near the surfaces of the electrodes.

L'invention concerne un procédé de préparation d'un métal, défini dans la revendication 1.The invention relates to a process for the preparation of a metal, defined in claim 1.

Lorsque le métal de l'électrolyse est le plomb, il est présent, sous forme de chlorure, en quantité comprise entre environ 5 et 50 grammes par litre, de préférence entre 15 et 25 grammes par litre dans l'électrolyte.When the metal of the electrolysis is lead, it is present, in the form of chloride, in an amount of between approximately 5 and 50 grams per liter, preferably between 15 and 25 grams per liter in the electrolyte.

Le chlorure de métal alcalin ou alcalino-terreux est de préférence le chlorure de sodium. Sa concentration dans l'électrolyte est de préférence comprise entre 230 et 300 grammes par litre.The alkali or alkaline earth metal chloride is preferably sodium chloride. Its concentration in the electrolyte is preferably between 230 and 300 grams per liter.

Au cours de l'électrolyse, la densité du courant d'électrolyse est comprise entre 500 et 1.500 A/M 2, de préférence entre 700 et 1 000 Alm2. Il est préférable que cette densité de courant augmente progressivement depuis la mise en route de l'électrolyse.During the electrolysis, the density of the electrolysis current is between 500 and 1,500 A / M 2 , preferably between 700 and 1,000 Alm 2. It is preferable that this current density increases gradually since the start-up electrolysis.

Pendant l'électrolyse, la température de l'électrolyte est avantageusement comprise entre 70 et 95 °C.During the electrolysis, the temperature of the electrolyte is advantageously between 70 and 95 ° C.

La surface cathodique ayant une faible densité de sites de nucléation est de préférence formée de titane, d'acier inoxydable ou de graphite.The cathode surface having a low density of nucleation sites is preferably formed of titanium, stainless steel or graphite.

Il est avantageux que l'électrolyte contienne aussi du fer sous forme de chlorure. La concentration du fer est alors avantageusement supérieure à 10 grammes par litre et de préférence comprise entre 20 et 60 grammes par litre.It is advantageous that the electrolyte also contains iron in the form of chloride. The concentration of iron is then advantageously greater than 10 grams per liter and preferably between 20 and 60 grams per liter.

L'écoulement de type laminaire ou faiblement turbulent de l'électrolyte le long de la surface cathodique est obtenu lorsque le courant d'électrolyte circule à proximité des cathodes à une vitesse comprise entre 0,01 et 0,15 mètre par seconde.The laminar or slightly turbulent flow of the electrolyte along the cathode surface is obtained when the electrolyte current flows near the cathodes at a speed of between 0.01 and 0.15 meters per second.

Le prélèvement des particules rassemblées au fond de la cellule est avantageusement réalisé par transport des particules hors de la cellule, puis par densification des particules par compression. En outre, les particules densifiées peuvent subir un laminage destiné à chasser les inclusions d'électrolyte. Les particules densifiées peuvent aussi subir une fusion en présence de soude.The removal of the particles collected at the bottom of the cell is advantageously carried out by transporting the particles out of the cell, then by densification of the particles by compression. In addition, the densified particles can undergo a rolling intended to drive out the electrolyte inclusions. The densified particles can also undergo fusion in the presence of soda.

L'invention concerne aussi un appareil de préparation d'un métal par électrolyse défini dans la revendication 15.The invention also relates to an apparatus for the preparation of a metal by electrolysis defined in claim 15.

Dans un mode de réalisation avantageux, l'appareil comprend des électrodes bipolaires.In an advantageous embodiment, the apparatus comprises bipolar electrodes.

L'appareil comporte avantageusement une hotte de récupération lorsque du chlore gazeux se dégage aux anodes.The device advantageously includes a recovery hood when chlorine gas is released at the anodes.

Les anodes sont avantageusement formées d'un métal inattaquable par l'électrolyte et sous forme déployée.The anodes are advantageously formed from a metal which cannot be attacked by the electrolyte and in deployed form.

Le dispositif de transport peut être avantageusement une vis sans fin, un élévateur à godets ou une bande transporteuse et de préférence le système de col de cygne décrit ci-après.The transport device can advantageously be a worm, a bucket elevator or a conveyor belt and preferably the gooseneck system described below.

L'appareil peut aussi comprendre une extrudeuse destinée à recevoir les particules extraites et à les densifier.The apparatus may also include an extruder for receiving the particles and for densifying them.

Le procédé et l'appareil selon l'invention présentent tous les avantages des appareils dans lesquels le métal se détache automatiquement des cathodes. Le principal avantage est la suppression presque totale des manipulations des électrodes. Cette réduction de la manipulation augmente le temps de service utile des électrolyseurs si bien que le nombre de cellules d'électrolyse peut être réduit, avec réduction correspondante des investissements.The method and the apparatus according to the invention have all the advantages of apparatuses in which the metal detaches automatically from the cathodes. The main advantage is the almost total elimination of manipulations of the electrodes. This reduction in handling increases the useful service time of the electrolysers so that the number of electrolysis cells can be reduced, with corresponding reduction in investments.

En outre, grâce au rendement faradique très élevé assuré par l'invention, supérieur à 90 % et souvent à 95 %, les pertes d'énergie sont réduites.In addition, thanks to the very high faradaic efficiency ensured by the invention, greater than 90% and often 95%, the energy losses are reduced.

On considère maintenant plus en détail les différents paramètres qui influent sur la mise en oeuvre du procédé, d'abord dans le cas où la solution de départ contient du fer sous forme de chlorure, en plus du plomb.We now consider in more detail the various parameters which influence the implementation of the process, first in the case where the starting solution contains iron in the form of chloride, in addition to lead.

La solution qui consiste l'électrolyte contient des chlorures de plomb, de métaux alcalins ou alcalino-terreux, de fer et éventuellement d'autres métaux, par exemple de zinc.The electrolyte solution contains chlorides of lead, alkali or alkaline earth metals, iron and possibly other metals, for example zinc.

La solution de chlorure de plomb est avantageusement formée à partir d'un concentré de minerai sulfuré de plomb qui, en plus du plomb, contient de petites quantités de zinc, de cuivre, de fer, de calcium et de magnésium. Après purification, par exemple selon les techniques décrites dans les brevets français n°* 2.323.766, 2.359.211 et 2.387.293 et dans la demande de brevet européen n° 0024987, la solution ne contient pratiquement plus que du plomb et du fer, les autres métaux étant en quantité négligeable. Ces techniques sont utilisées de préférence à d'autres, notamment pour les raisons économiques, et ont pour objet la purification des solutions de chlorure de plomb par mise en contact avec différents produits, notamment des galènes, et au moyen de résines échangeuses d'ions à groupement thiol.The lead chloride solution is advantageously formed from a concentrate of lead sulphide ore which, in addition to lead, contains small amounts of zinc, copper, iron, calcium and magnesium. After purification, for example according to the techniques described in French patents n ° * 2,323,766, 2,359,211 and 2,387,293 and in European patent application n ° 0024987, the solution contains practically only lead and iron , the other metals being in negligible quantity. These techniques are used in preference to others, in particular for economic reasons, and have as their object the purification of lead chloride solutions by contacting with various products, in particular galenes, and by means of ion exchange resins. with thiol group.

La quantité de plomb sous forme chlorure, présente dans l'électrolyte, est de préférence supérieure à 5 grammes par litre mais elle ne dépasse pas de préférence 50 grammes par litre. Ces deux valeurs sont déterminées d'après les densités de courant utilisées au cours de l'électrolyse et les vitesses de circulation de l'électrolyte au voisinage des électrodes, afin que le rendement faradique et la capacité de production soient optimaux.The amount of lead in chloride form, present in the electrolyte, is preferably greater than 5 grams per liter but it does not preferably exceed 50 grams per liter. These two values are determined according to the current densities used during the electrolysis and the circulation speeds of the electrolyte in the vicinity of the electrodes, so that the faradaic efficiency and the capacity of production are optimal.

L'électrolyte contient aussi en forte concentration un chlorure alcalin ou alcalino-terreux. Le plus avantageux est le chlorure de sodium, pour des raisons de coût et de disponibilité. La quantité de ce chlorure en solution est avantageusement choisie de manière que la concentration en ion chlorure soit supérieure à 3 équivalent-grammes (c'est-à-dire dans le cas du chlorure de sodium à 200 grammes par litre environ), de préférence comprise entre 4 et 5 équivalent-grammes (c'est-à-dire pour le chlorure de sodium entre 230 et 300 grammes par litre). Le rôle de ce chlorure est d'augmenter la concentration des ions chlorure dans l'électrolyte, ce qui permet de solubiliser les métaux dont les complexes chlorurés sont solubles, et de réduire les pertes par effet Joule.The electrolyte also contains in high concentration an alkaline or alkaline-earth chloride. The most advantageous is sodium chloride, for reasons of cost and availability. The quantity of this chloride in solution is advantageously chosen so that the concentration of chloride ion is greater than 3 equivalent-grams (that is to say in the case of sodium chloride at approximately 200 grams per liter), preferably between 4 and 5 gram equivalent (i.e. for sodium chloride between 230 and 300 grams per liter). The role of this chloride is to increase the concentration of chloride ions in the electrolyte, which makes it possible to dissolve the metals whose chlorinated complexes are soluble, and to reduce the losses by Joule effect.

Dans le mode de réalisation considéré, l'électrolyte contient aussi du fer sous forme de chlorure. En l'absence de fer, les ions chlorure s'oxydent à l'anode en chlore gazeux à un potentiel d'électrode de 1,2 V par rapport à l'électrode au calomel saturé (ECS). L'appareil doit comporter alors un système collecteur convenable. Lorsqu'il n'est pas souhaitable que du chlore se dégage, l'électrolyte contient avantageusement du fer si bien que, à l'anode, l'ion ferreux s'oxyde en ion ferrique à un potentiel voisin de 0,6 V/ECS. Il est donc nécessaire que l'électrolyte contienne du fer sous forme de fer ferreux. Non seulement le chlore ne se dégage plus à l'anode, mais encore le rendement énergétique est nettement accru. En outre, le chlorure ferrique formé à l'anode est récupéré et peut être utilisé à nouveau pour le traitement des minerais sulfurés de plomb et la transformation de la galène en soufre élémentaire et en chlorure de plomb.In the embodiment considered, the electrolyte also contains iron in the form of chloride. In the absence of iron, the chloride ions oxidize at the anode to chlorine gas at an electrode potential of 1.2 V compared to the saturated calomel electrode (DHW). The apparatus must then include a suitable collecting system. When chlorine is not desirable, the electrolyte advantageously contains iron so that, at the anode, the ferrous ion oxidizes to ferric ion at a potential close to 0.6 V / DHW. It is therefore necessary that the electrolyte contains iron in the form of ferrous iron. Not only is the chlorine no longer released at the anode, but also the energy efficiency is clearly increased. In addition, the ferric chloride formed at the anode is recovered and can be used again for the treatment of lead sulphide ores and the transformation of galena into elemental sulfur and lead chloride.

La concentration du fer dans l'électrolyte, sous forme chlorure, est de préférence comprise entre 20 et 60 grammes par litre, et avantageusement elle est de l'ordre de 40 grammes par litre. Il est important que cette concentration soit au moins égale à 20 grammes par litre dans l'anolyte, c'est-à-dire à proximité des anodes.The concentration of iron in the electrolyte, in the chloride form, is preferably between 20 and 60 grams per liter, and advantageously it is of the order of 40 grams per liter. It is important that this concentration is at least equal to 20 grams per liter in the anolyte, that is to say near the anodes.

Le tableau I qui suit indique les principales caractéristiques de la composition de l'électrolyte.

Figure imgb0001
Table I which follows indicates the main characteristics of the composition of the electrolyte.
Figure imgb0001

La nature des électrodes utilisées et notamment des cathodes est importante pour la mise en oeuvre de l'invention. On constate en effet que de nombreuses matières sont trop « actives c'est-à-dire forment des sites de nucléation en trop grand nombre. En conséquence, des particules de plomb commencent à se former à un trop grand nombre d'emplacements à la surface des cathodes et ne peuvent pas grossir individuellement. Pour cette raison, il est essentiel selon l'invention que la densité des sites de nucléation, dans les conditions d'électrolyse utilisées, soit suffisamment faible pour que les particules puissent atteindre une dimension d'au moins 100 micromètres sans se solidariser avec les particules adjacentes. De préférence, les particules gardent leur individualité jusqu'à ce qu'elles atteignent une dimension d'au moins 600 micromètres et de préférence un millimètre. Dans ces conditions, les particules ont individuellement une surface suffisamment grande pour que, lorsque l'électrolyte se déplace le long de la surface de la cathode, il exerce une force d'arrachement qui, en combinaison avec la force de pesanteur, suffit au détachement des particules lorsqu'elles ont une dimension de quelques centaines de micromètres.The nature of the electrodes used and in particular of the cathodes is important for the implementation of the invention. It is found in fact that many materials are too "active, that is to say form too many nucleation sites. As a result, lead particles begin to form at too many locations on the surface of the cathodes and cannot magnify individually. For this reason, it is essential according to the invention that the density of the nucleation sites, under the electrolysis conditions used, is sufficiently low so that the particles can reach a dimension of at least 100 micrometers without joining with the particles. adjacent. Preferably, the particles retain their individuality until they reach a dimension of at least 600 micrometers and preferably one millimeter. Under these conditions, the particles individually have a large enough surface so that, when the electrolyte moves along the surface of the cathode, it exerts a tearing force which, in combination with the force of gravity, is sufficient for detachment particles when they have a dimension of a few hundred micrometers.

Cette densité de sites est importante selon l'invention car, si le nombre de sites est trop grand, les particules formées sont petites et nombreuses et, lorsqu'elles sont mises ultérieurement à l'air, elles s'oxydent facilement car elles forment une poudre pyrophorique. Au contraire, si la densité de sites de nucléations est trop faible, la capacité de production est réduite.This density of sites is important according to the invention because, if the number of sites is too large, the particles formed are small and numerous and, when they are subsequently placed in the air, they oxidize easily because they form a pyrophoric powder. On the contrary, if the density of nucleation sites is too low, the production capacity is reduced.

On constate qu'on obtient une densité convenable de sites de nucléation par utilisation de cathodes dont la surface est formée de titane lisse. On peut aussi utiliser des surfaces d'acier inoxydable ou de graphite. Bien entendu, on peut aussi utiliser pour la mise en oeuvre du procédé de l'invention d'autres matières, lorsque celles-ci ont la densité convenable de sites de nucléation. Cette densité peut être obtenue par un traitement d'activation ou, le plus souvent, de désactivation selon des techniques connues de l'homme de l'art.It is found that a suitable density of nucleation sites is obtained by the use of cathodes whose surface is formed of smooth titanium. Stainless steel or graphite surfaces can also be used. Of course, other materials can also be used for carrying out the process of the invention, when these have the appropriate density of nucleation sites. This density can be obtained by an activation treatment or, more often, deactivation according to techniques known to those skilled in the art.

Les anodes peuvent être formées de graphite. Cependant, comme il est souhaitable que le transport de matière soit favorisé, il est préférable que les anodes soient formées d'un métal déployé, par exemple de titane ruthénisé. Cependant, la nature de l'anode a beaucoup moins d'importance pour la mise en oeuvre du procédé de l'invention que celle de la cathode.The anodes can be formed from graphite. However, as it is desirable that the transport of material is favored, it is preferable that the anodes be formed from an expanded metal, for example ruthenized titanium. However, the nature of the anode is much less important for the implementation of the method of the invention than that of the cathode.

L'obtention de rendements faradiques élevés nécessite la maîtrise du transport de fer ferrique formé à l'anode vers le catholyte. Le choix d'un diaphragme convenable, ayant une faible perméabilité, l'utilisation d'une densité élevée de courant et le maintien d'une différence de pressions hydrostatiques entre le catholyte et l'anolyte, cette différence de pression étant d'au moins 20 millimètres de colonne liquide, permettent d'éviter le passage du Fe III vers le catholyte. De cette manière, la totalité en pratique du débit d'alimentation de la cellule passe à travers le diaphragme. Celui-ci est avantageusement formé de fibres textiles chimiquement inertes dans l'électrolyte. Des matières qui conviennent sont le polyester revêtu d'une silicone, les fibres de verre téflonnées, et de préférence des fibres synthétiques à base de polymères fluorés.Obtaining high faradaic yields requires control of the transport of ferric iron formed at the anode to the catholyte. The choice of a suitable diaphragm, having a low permeability, the use of a high current density and the maintenance of a difference in hydrostatic pressures between the catholyte and the anolyte, this difference in pressure being at least 20 millimeters of liquid column, make it possible to avoid the passage of Fe III towards the catholyte. In this way, the entire practical feed rate of the cell passes through the diaphragm. It is advantageously formed from chemically inert textile fibers in the electrolyte. Suitable materials are polyester coated with silicone, teflon-coated glass fibers, and preferably synthetic fibers based on fluorinated polymers.

Les phénomènes de transport de matières au cours de l'électrolyse ont une importance primordiale sur la morphologie des particules formées et sur le rendement faradique obtenu. On a déjà noté qu'il était avantageux que les anodes soient formées d'un métal déployé, permettant un bon transport des matières, par un effet analogue à celui des promoteurs de turbulences. Cependant, ce phénomène d'accentuation des turbulences n'est avantageusement utilisé qu'au niveau des anodes. Il est prévu, pour l'obtention de particules de morphologie convenable, que le courant d'électrolyte le long des cathodes soit de type laminaire ou au moins faiblement turbulent seulement, tout en assurant un renouvellement suffisant de l'électrolyte au niveau des cathodes. Il est en effet important que la concentration du plomb ne varie que faiblement dans tout l'électrolyte. L'obtention d'un écoulement laminaire ou faiblement turbulent au niveau de la cathode dépend non seulement de la nature de la surface des cathodes mais aussi de la vitesse du liquide le long des cathodes. Il est ainsi souhaitable, selon l'invention, que la vitesse linéaire du catholyte, parallèlement aux cathodes, soit d'au moins 0,01 mètre par seconde et de préférence comprise entre 0,01 et 0,15 mètre par seconde. Au niveau des anodes, la vitesse de circulation de la solution qui peut être nulle, est de préférence d'au moins 0,01 mètre par seconde ; la valeur maximale peut être modérée, par exemple de 0,05 mètre par seconde, étant donné la forme des anodes qui favorisent la création de turbulences.The phenomena of transport of materials during electrolysis are of primary importance on the morphology of the particles formed and on the faradaic yield obtained. It has already been noted that it was advantageous for the anodes to be formed from an expanded metal, allowing good transport of the materials, by an effect analogous to that of the turbulence promoters. However, this phenomenon of increased turbulence is advantageously used only at the anodes. It is intended, for obtaining particles of suitable morphology, that the electrolyte current along the cathodes is of the laminar type or at least slightly turbulent only, while ensuring sufficient renewal of the electrolyte at the cathodes. It is indeed important that the concentration of lead varies only slightly throughout the electrolyte. Obtaining a laminar or slightly turbulent flow at the cathode depends not only on the nature of the surface of the cathodes but also on the speed of the liquid along the cathodes. It is thus desirable, according to the invention, that the linear speed of the catholyte, parallel to the cathodes, be at least 0.01 meters per second and preferably between 0.01 and 0.15 meters per second. At the anodes, the speed of circulation of the solution, which may be zero, is preferably at least 0.01 meter per second; the maximum value can be moderate, for example 0.05 meters per second, given the shape of the anodes which promote the creation of turbulence.

La température de l'électrolyte est avantageusement comprise entre 70 et 95 °C, de préférence entre 70 et 90 °C. Aucun chauffage n'est nécessaire car les pertes normales par effet Joule suffisent au maintien de la température dans la plage précitée.The temperature of the electrolyte is advantageously between 70 and 95 ° C, preferably between 70 and 90 ° C. No heating is necessary because the normal losses by Joule effect are sufficient to maintain the temperature in the aforementioned range.

La mise en oeuvre du procédé de l'invention permet l'utilisation de densités de courant très élevées. Elles peuvent être comprises entre 500 et 1 500 A/M 2. De préférence, elles sont comprises entre 700 et 1 000 A/M 2.The implementation of the method of the invention allows the use of very high current densities. They can be between 500 and 1,500 A / M 2 . Preferably, they are between 700 and 1000 A / M 2 .

Le tableau Il résume les diverses conditions précitées.

Figure imgb0002
Table II summarizes the various conditions mentioned above.
Figure imgb0002

Il est souhaitable, lors de la mise en oeuvre du procédé selon l'invention, que l'électrolyse commence à une faible densité de courant, inférieure aux valeurs indiquées précédemment, et croisse progressivement jusqu'à la valeur choisie, comprise dans la plage précitée. En effet, lorsque la solution contient du chlorure ferreux, le fer peut se déposer en même temps que le plomb, sur les cathodes, lorsque la densité de courant est initialement très élevée. Le métal adhère alors sur toute la surface des cathodes, si bien que celles-ci ne possèdent plus une densité convenable de sites de nucléation.It is desirable, during the implementation of the method according to the invention, that the electrolysis begins at a low current density, lower than the values indicated above, and gradually increases to the chosen value, included in the aforementioned range. In fact, when the solution contains ferrous chloride, iron can deposit at the same time as lead, on the cathodes, when the current density is initially very high. The metal then adheres to the entire surface of the cathodes, so that the latter no longer have a suitable density of nucleation sites.

Lorsque l'électrolyte ne contient pratiquement pas de chlorure de fer, l'utilisation initiale d'une densité élevée de courant peut provoquer le dégagement d'hydrogène dont les bulles ont tendance à s'accrocher aux particules métalliques si bien que celles-ci, au lieu de tomber au fond de la cellule d'électrolyse, ont tendance à flotter.When the electrolyte contains practically no iron chloride, the initial use of a high current density can cause the evolution of hydrogen whose bubbles tend to cling to the metal particles so that these, instead of falling to the bottom of the electrolysis cell, tend to float.

La période pendant laquelle la densité de courant augmente progressivement ou par paliers, jusqu'à le valeur finale voulue, est avantageusement de quelques heures.The period during which the current density increases progressively or in stages, up to the desired final value, is advantageously a few hours.

Comme indiqué précédemment, on a vu qu'il était souhaitable que le produit obtenu soit sous forme de particules individuelles ayant une dimension de quelques centaines de micromètres, par exemple de 300 à 600 micromètres. Leur forme peut être ramifiée et relativement aplatie, mais leur surface est relativement faible pour leur volume. C'est cette caractéristique qui donne aux particules formées leur caractère non pyrophore.As indicated above, it has been seen that it was desirable for the product obtained to be in the form of individual particles having a dimension of a few hundred micrometers, for example from 300 to 600 micrometers. Their shape can be branched and relatively flat, but their surface is relatively small for their volume. It is this characteristic which gives the particles formed their non-pyrophoric nature.

Les particules sont formées de plomb très pur. Par exemple, les métaux tels que le zinc, le cuivre, le cadmium, le magnésium, etc... sont présents en quantité inférieure à 1 ppm en poids. La quantité de fer est inférieure à quelques ppm en poids. Il s'agit donc de plomb qui ne nécessite ultérieurement aucun affinage pour la plupart des applications. Les exemples qui suivent donnent la pureté du plomb obtenu dans différentes conditions.The particles are formed from very pure lead. For example, metals such as zinc, copper, cadmium, magnesium, etc. are present in an amount less than 1 ppm by weight. The amount of iron is less than a few ppm by weight. It is therefore lead which does not subsequently require any refining for most applications. The examples which follow give the purity of the lead obtained under different conditions.

Un paramètre important pour la mise en oeuvre d'une électrolyse est le rendement faradique obtenu puisque celui-ci indique l'importance des pertes électriques. Selon l'invention, ce rendement faradique est au moins égal à 90 % et il atteint et dépasse en général 95 %. Bien entendu, ces rendements ne sont obtenus que lorsque les différents paramètres ont les valeurs voulues, correspondant par exemple aux tableaux précités I et Il.An important parameter for carrying out an electrolysis is the faradaic yield obtained since this indicates the importance of the electrical losses. According to the invention, this faradaic yield is at least equal to 90% and it generally reaches and exceeds 95%. Of course, these yields are only obtained when the different parameters have the desired values, corresponding for example to the abovementioned tables I and II.

Les particules de plomb qui se déposent au fond de la cellule sont ensuite extraites, à l'aide d'un mécanisme convenable, comme indiqué dans la suite du présent mémoire en référence à un appareil destiné à la mise en oeuvre du procédé selon l'invention. Les particules de plomb, lorsqu'elles sont retirées, sont associées à de l'électrolyte occlu, présent en quantité comprise entre 20 et 30 % en poids environ. Il est donc souhaitable que la matière subisse un compactage ou un laminage. Il est en particulier souhaitable que les particules soient densifiées par extrusion, dans une presse à pistons ou à rouleaux, exerçant des pressions supérieures à environ 70 MPa. La filtration du produit est peu souhaitable étant donné que les plus petites particules risquent de s'oxyder partiellement à l'air.The lead particles which deposit at the bottom of the cell are then extracted, using a suitable mechanism, as indicated in the remainder of this specification with reference to an apparatus intended for carrying out the method according to the invention. The lead particles, when they are removed, are associated with occluded electrolyte, present in an amount between 20 and 30% by weight approximately. It is therefore desirable that the material undergoes compaction or rolling. It is in particular desirable that the particles be densified by extrusion, in a piston or roller press, exerting pressures greater than about 70 MPa. Filtration of the product is undesirable since the smallest particles may partially oxidize in air.

Lorsque les particules sont prélevées au fond de la cuve, elles présentent une densité apparente de l'ordre de 1,5 à 2,0. Après extrusion, cette densité dépasse 10,5. Le demi-produit de plomb obtenu, par exemple sous forme d'un feuillard, est stable vis-à-vis de l'oxydation à l'air. Il peut être utilisé tel quel dans certaines applications.When the particles are taken from the bottom of the tank, they have an apparent density of the order of 1.5 to 2.0. After extrusion, this density exceeds 10.5. The semi-finished product of lead obtained, for example in the form of a strip, is stable with respect to oxidation in air. It can be used as is in some applications.

Dans une variante, le plomb peut subir une fusion en présence de soude, selon une technique bien connue.Alternatively, lead can undergo fusion in the presence of sodium hydroxide, according to a well known technique.

La description qui précède concerne l'électrolyse d'une solution contenant du chlorure ferreux. Cette caractéristique n'est pas indispensable. Lorsque le procédé est mis en oeuvre sans chlorure ferreux dans l'électrolyte, il se dégage du chlore au niveau des anodes. L'appareil utilisé doit donc comporter un système collecteur de chlore. De tels systèmes sont bien connus dans les industries électrochimiques et on ne les décrit donc pas en détail.The above description relates to the electrolysis of a solution containing ferrous chloride. This feature is not essential. When the process is carried out without ferrous chloride in the electrolyte, chlorine is released at the anodes. The device used must therefore include a chlorine collection system. Such systems are well known in the electrochemical industries and are therefore not described in detail.

La densité de courant peut alors avoir une valeur accrue, comprise entre 800 et 2 000 A/m2, de préférence entre 800 et 1 200 A/m2.The current density can then have an increased value, between 800 and 2,000 A / m 2 , preferably between 800 and 1,200 A / m 2 .

Le pH de l'électrolyte est à une valeur d'équilibre comprise entre 1,2 et 1,7, à une température de 70 à 80 °C. Ce pH dépend de la concentration des ions sulfate et de la densité de courant. Toutefois, il peut être avantageux de travailler à un pH compris entre 2 et 3 de manière à éviter les réactions d'électrolyse du proton pour donner de l'hydrogène. Dans ce cas, il faut alors prévoir un système de régulation du pH par addition d'une base qui est de préférence choisie de manière à ne pas ajouter dans les électrolytes des ions étrangers. On utiliserait de préférence les composés basiques du sodium (soude, carbonate de soude, voire composés basiques du plomb, hydroxyde de plomb, litharge, carbonate basique de plomb, etc...).The pH of the electrolyte is at an equilibrium value between 1.2 and 1.7, at a temperature of 70 to 80 ° C. This pH depends on the concentration of sulfate ions and the current density. However, it may be advantageous to work at a pH of between 2 and 3 so as to avoid the proton electrolysis reactions to give hydrogen. In this case, a pH regulation system must then be provided by adding a base which is preferably chosen so as not to add foreign ions to the electrolytes. Preferably, the basic sodium compounds (sodium hydroxide, soda ash, or even basic lead compounds, lead hydroxide, litharge, basic lead carbonate, etc.) would be used.

Par ailleurs, les différents paramètres considérés précédemment doivent avoir sensiblement les mêmes valeurs. On ne les décrit donc pas à nouveau en détail.Furthermore, the different parameters considered previously must have substantially the same values. They are therefore not described again in detail.

Bien qu'on ait décrit le procédé de référence au dépôt de plomb, il n'est pas limité à ce seul métal. En effet, le procédé permet aussi la formation de particules de cuivre, dans des conditions similaires et ce notamment à partir de chlorure cuivreux.Although the reference method for depositing lead has been described, it is not limited to this single metal. Indeed, the process also allows the formation of copper particles, under similar conditions and this in particular from cuprous chloride.

Le dispositif de la présente invention comporte de très nombreux couples anodes-cathodes placés de manière non isopotentielle. En effet, le procédé qui vient d'être exposé ci-dessus implique l'utilisation de nombreuses pompes pour la recirculation. Ces nombreuses pompes conduisent à des frais d'investissement qui peuvent être importants. C'est pourquoi on a cherché à mettre au point un dispositif d'électrolyse qui permette de réduire le nombre de pompes de récirculation d'électrolyte et qui d'une manière générale réduise de façon importante les frais d'investissement des dispositifs d'électrolyse.The device of the present invention comprises very many anode-cathode pairs placed in a non-isopotential manner. In fact, the process which has just been explained above involves the use of numerous pumps for recirculation. These numerous pumps lead to investment costs which can be significant. This is why we have sought to develop an electrolysis device which makes it possible to reduce the number of electrolyte recirculation pumps and which in general, significantly reduce the investment costs of electrolysis devices.

Il s'agit d'un dispositif non isopotentiel, tel que défini dans la revendication 15 dérivé de ceux dont la mise en oeuvre a déjà été réalisée pour l'électro-raffinage du cuivre en milieu sulfate. On peut se reporter à « Mining Annual Review 1982, page 282 ainsi qu'à l'article « Technologically advanced smelter incorporates latest design concepts », Journal of Metals, July 1978, pages 16-26.It is a non-isopotential device, as defined in claim 15 derived from those whose implementation has already been carried out for the electro-refining of copper in sulphate medium. One can refer to “Mining Annual Review 1982, page 282 as well as to the article“ Technologically advanced smelter incorporates latest design concepts ”, Journal of Metals, July 1978, pages 16-26.

La cuve électrolytique ci-dessus, communément appelée « cuve-piscine •, est équipée d'une série de rangées sensiblement parallèles entre elles de cellules électrolytiques. Chaque cellule est constituée du couple formé par une surface anodique et une surface cathodique. Chaque anode et chaque cathode, sauf à l'extrémité de chaque rangée, appartiennent à deux cellules. Dans une même rangée toutes les cellules sont montées en parallèle, en peigne (ou en rateau), c'est-à-dire que toutes les anodes d'une même rangée sont à un même potentiel cependant que toutes les cathodes d'une même rangée sont également à un même potentiel. Les rangées de ladite cuve électrolytique-piscine sont montées en série électrique ; il y a donc un gradient de potentiel dans la cuve-piscine.The above electrolytic cell, commonly known as a "swimming pool cell", is equipped with a series of substantially parallel rows of electrolytic cells. Each cell is made up of the couple formed by an anode surface and a cathode surface. Each anode and each cathode, except at the end of each row, belong to two cells. In the same row all the cells are mounted in parallel, in a comb (or rake), that is to say that all the anodes in the same row have the same potential, however, as all the cathodes in the same row are also at the same potential. The rows of said electrolytic-pool tank are mounted in electrical series; there is therefore a potential gradient in the tank-pool.

Une telle technologie toutefois ne peut être utilisée pour l'électro-raffinage du cuivre qu'en raison de la très faible différence de potentiel entre anode et cathode, de l'ordre de 0,25 volt, et même ainsi, il est nécessaire que la distance séparant deux rangées d'électrodes soit de 0,5 mètre environ, faute de quoi les pertes énergétiques dues au courant parasite et/ou de fuite de cellule à cellule deviennent considérables.However, such a technology can only be used for electro-refining copper because of the very small potential difference between anode and cathode, of the order of 0.25 volts, and even so, it is necessary that the distance separating two rows of electrodes is approximately 0.5 meters, otherwise the energy losses due to stray current and / or cell-to-cell leakage become considerable.

C'est pourquoi ces dispositifs décrits dans les articles ci-dessus devaient être profondément modifiés pour être adaptés au procédé selon la présente invention afin de minimiser les courants de fuite et les différentes pertes énergétiques provoquées par ces courants de fuite.This is why these devices described in the above articles had to be deeply modified to be adapted to the method according to the present invention in order to minimize the leakage currents and the various energy losses caused by these leakage currents.

Selon l'invention, il a été constaté que lorsque l'on reliait les cathodes de deux rangées différentes situées dans un même plan par des cloisons isolantes en matériau non conducteur et lorsque l'on constituait des « chenaux anodiques en reliant les boîtes anodiques entre elles au moyen de matériau non conducteur de manière à isoler l'anolyte du catholyte, il est possible de réaliser ces dispositifs non équipotentiels sans que les pertes énergétiques deviennent trop grandes dès lors que la distance séparant deux rangées d'électrodes était comprise entre 0,8 et 2 mètres et de préférence entre 1 et 1,5 mètres. Ces cloisons isolantes présentent sensiblement la même hauteur que les électrodes.According to the invention, it was found that when connected the cathodes of two different rows located in the same plane by insulating partitions and non-conductive material when constituted "c h Enaux anode by connecting the boxes anodic to each other by means of non-conductive material so as to isolate the anolyte from the catholyte, it is possible to produce these non-equipotential devices without the energy losses becoming too great as soon as the distance separating two rows of electrodes was between 0.8 and 2 meters and preferably between 1 and 1.5 meters. These insulating partitions have substantially the same height as the electrodes.

Il convient ici de noter que les fortes densités de courant permettent de diminuer de manière importante la proportion des courants parasites ou de fuite. Toutefois, lors de la mise en oeuvre de tels dispositifs, on a constaté des phénomènes susceptibles d'altérer la qualité des électrodes car la densité de courant cessait d'être homogène sur toute la surface des électrodes. Cette inhomogénéïté conduit à des phénomènes de surtension sur les bords des cathodes, ce qui se traduit par des réactions parasites telles que par exemple dégagement d'hydrogène et dépôt de fer, ce qui conduit à modifier les structures des cathodes dont il a été écrit plus haut combien elles étaient importantes pour le procédé selon la présente invention.It should be noted here that the high current densities make it possible to significantly reduce the proportion of stray or leakage currents. However, during the implementation of such devices, phenomena liable to deteriorate the quality of the electrodes have been observed since the current density ceased to be homogeneous over the entire surface of the electrodes. This inhomogeneity leads to phenomena of overvoltage on the edges of the cathodes, which results in parasitic reactions such as for example release of hydrogen and deposit of iron, which leads to modify the structures of the cathodes of which it has been written more top how important they were for the process according to the present invention.

C'est pourquoi une étude a été nécessaire pour pallier ces phénomènes nuisibles lors de la réalisation de ce dispositif non isopotentiel. Cette étude a montré qu'il était possible d'éliminer ou à tout le moins de pallier le phénomène en décalant les anodes par rapport aux cathodes d'une distance comprise entre 5 et 20 centimètres, de préférence de 20 centimètres, ce décalage étant réalisé dans le sens des potentiels décroissants dans la cuve d'électrolyse.This is why a study was necessary to remedy these harmful phenomena during the production of this non-isopotential device. This study showed that it was possible to eliminate or at least mitigate the phenomenon by shifting the anodes relative to the cathodes by a distance of between 5 and 20 centimeters, preferably by 20 centimeters, this shift being achieved. in the direction of the decreasing potentials in the electrolysis tank.

Ces conditions, ainsi que cela est décrit dans les exemples 6 et 7, permettent d'obtenir d'excellents résultats.These conditions, as described in Examples 6 and 7, allow excellent results to be obtained.

Ainsi, le présent dispositif, que l'on peut appeler « cuve-canal », en vue de mettre en oeuvre l'invention est constitué par une série de rangées d'anodes et de cathodes montées en parallèles, les anodes de chaque rangée étant de préférence décalées parallèlement à elles-mêmes d'une valeur comprise entre 5 et 20 centimètres dans le sens des potentiels décroissants dans la cuve d'électrolyse, la distance entre deux rangées étant comprise entre 0,8 et 2 mètres.Thus, the present device, which can be called "tank-channel", in order to implement the invention consists of a series of rows of anodes and cathodes mounted in parallel, the anodes of each row being preferably offset parallel to themselves by a value of between 5 and 20 centimeters in the direction of the decreasing potentials in the electrolysis cell, the distance between two rows being between 0.8 and 2 meters.

Les cathodes des rangées différentes et situées sur un même plan sont réunies entre elles par des cloisons réalisées en matériau isolant de manière à limiter les courants parasites ou de fuite. Quoique cela soit moins important, les anodes des rangées différentes et situées dans un même chenal anodique peuvent être réunies entre elles par des cloisons réalisées en matériau isolant de manière à limiter les courants parasites et/ou de fuite.The cathodes of different rows and located on the same plane are joined together by partitions made of insulating material so as to limit stray or leakage currents. Although this is less important, the anodes of different rows and located in the same anode channel can be joined together by partitions made of insulating material so as to limit parasitic and / or leakage currents.

L'ensemble forme une juxtaposition de chenaux parallèles entre eux et perpendiculaires aux rangées d'électrodes. Des systèmes de pompes semblables à ceux qui sont décrits dans la présente demande impose une circulation du catholyte et de l'anolyte, cependant qu'entre chaque cathode et chaque anode on retrouve le diaphragme qui a été évoqué lors de la description du procédé.The assembly forms a juxtaposition of channels parallel to each other and perpendicular to the rows of electrodes. Pump systems similar to those described in the present application impose a circulation of the catholyte and the anolyte, while between each cathode and each anode there is the diaphragm which was mentioned during the description of the process.

On considère maintenant plus précisément les caractéristiques d'un appareil destiné à la mise en oeuvre du procédé de l'invention. On ne considère pas à nouveau les caractéristiques des cathodes et des anodes qui ont déjà été précisées. L'appareil peut être de type monopolaire ou bipolaire. Le montage bipolaire présente des avantages car il réduit les pertes d'énergie (par réduction des chutes ohmiques dans les électrodes et les structures afférentes), il réduit le coût des électrodes puisque celles-ci ont un double rôle, et il simplifie le montage des ensembles d'électrodes, tout en permettant l'obtention d'un meilleur rendement énergétique. Ce montage avantageux pose cependant certains problèmes de configuration aux extrémités des électrodes, notamment pour éviter des courants de fuite, comme le savent les hommes du métier.We now consider more precisely the characteristics of an apparatus intended for implementing the method of the invention. The characteristics of the cathodes and anodes which have already been specified are not considered again. The device can be of the monopolar or bipolar type. Bipolar mounting has advantages because it reduces energy losses (by reducing ohmic drops in the electrodes and related structures), it reduces the cost of the electrodes since they have a double role, and it simplifies the mounting of sets of electrodes, while allowing better energy efficiency. This advantageous assembly, however, poses certain configuration problems at the ends of the electrodes, in particular to avoid leakage currents, as those skilled in the art know.

La figure 1 est un schéma d'un exemple d'appareil pour la mise en oeuvre du procédé selon l'invention.FIG. 1 is a diagram of an example of an apparatus for implementing the method according to the invention.

Sur les figures, la référence 1 désigne un cuve d'électrolyse contenant une boîte anodique 2. Le diaphragme est schématiquement repéré par la référence 3.In the figures, the reference 1 designates an electrolysis tank containing an anode box 2. The diaphragm is schematically identified by the reference 3.

Le circuit de circulation de catholyte comporte un réservoir 4 et une pompe 5 de circulation. Le catholyte circule parallèlement au plan des cathodes qui sont montées dans la cuve 1.The catholyte circulation circuit comprises a reservoir 4 and a circulation pump 5. The catholyte circulates parallel to the plane of the cathodes which are mounted in the tank 1.

Le circuit d'anolyte comprend un réservoir 6 et une pompe 7 qui fait circuler l'anolyte.The anolyte circuit includes a reservoir 6 and a pump 7 which circulates the anolyte.

La référence 8 désigne une pompe destinée à extraire une partie de l'anolyte qui s'est concentré en chlorure ferrique et convient au traitement de minerais sulfurés de plomb. La référence 9 désigne la solution d'alimentation qui redonne au catholyte la composition convenable dans le réservoir 4. Les particules qui se détachent des cathodes tombent au fond de la cellule et sont reprises par une vis sans fin 10 montée sur un arbre 11 entraîné en rotation par un moteur 12. Les particules arrivant à l'extrémité de la vis parviennent à une recette 13 et sont ensuite traitées comme décrit précédemment.Reference 8 designates a pump intended to extract part of the anolyte which has concentrated in ferric chloride and is suitable for the treatment of lead sulphide ores. Reference 9 designates the feed solution which restores the catholyte to the appropriate composition in the reservoir 4. The particles which detach from the cathodes fall to the bottom of the cell and are taken up by an endless screw 10 mounted on a shaft 11 driven in rotation by a motor 12. The particles arriving at the end of the screw arrive at a recipe 13 and are then treated as described above.

Dans l'appareil schématiquement représenté sur la figure 1, la nature des électrodes et leur montage sont tels que décrits précédemment. Le diaphragme et les anodes ont aussi des propriétés indiquées précédemment. Lorsque la solution ne contient pas de chlorure ferreux, un capot collecteur doit être monté au-dessus des anodes afin qu'il recueille le chlore qui se dégage.In the device shown diagrammatically in FIG. 1, the nature of the electrodes and their mounting are as described above. The diaphragm and anodes also have the properties indicated above. When the solution does not contain ferrous chloride, a collecting hood must be mounted above the anodes so that it collects the chlorine which is released.

Le réglage du déversoir permet de maintenir une différence de niveau entre le catholyte et l'anolyte, comme indiqué précédemment. Les débits des pompes 5 et 7 sont réglés de manière que les vitesses de l'anolyte et du catholyte, le long des anodes et des cathodes, aient les valeurs indiquées précédemment, c'est-à-dire au moins égales à 0,01 mètre par seconde. Le débit qui traverse le diaphragme est pratiquement égal au débit de la solution d'alimentation. De cette manière, le fer ferrique ne peut pratiquement pas passer dans le catholyte. Le complément des débits de solution d'alimentation transite par débordement du réservoir 4 du catholyte vers le réservoir d'anolyte 6.The adjustment of the weir makes it possible to maintain a difference in level between the catholyte and the anolyte, as indicated previously. The flow rates of pumps 5 and 7 are adjusted so that the speeds of the anolyte and the catholyte, along the anodes and cathodes, have the values indicated above, that is to say at least equal to 0.01 meter per second. The flow through the diaphragm is almost equal to the flow of the feed solution. In this way, the ferric iron can hardly pass into the catholyte. The additional feed solution flow rates pass by overflow from the catholyte reservoir 4 to the anolyte reservoir 6.

La cellule a de préférence un fond trapézoïdal ou arrondi de façon que les particules qui tombent soient guidées vers la vis sans fin.The cell preferably has a trapezoidal or rounded bottom so that the falling particles are guided towards the worm.

Bien qu'on ait représenté une vis sans fin entraînée par un moteur, d'autres mécanismes conviennent. Par exemple, des élévateurs à godets ou des bandes transporteuses peuvent aussi être avantageusement utilisés. Le produit peut aussi passer dans une extrudeuse qui lui fait subir une densification préalable, jusqu'à une densité apparente de 3 à 6. L'extrudeuse peut être munie d'une filière suffisamment longue pour qu'elle assure l'étanchéité au liquide.Although a worm driven by a motor has been shown, other mechanisms are suitable. For example, bucket elevators or conveyor belts can also be advantageously used. The product can also pass through an extruder which makes it undergo a prior densification, up to an apparent density of 3 to 6. The extruder can be provided with a die long enough for it to seal the liquid.

Selon une mise en oeuvre préférée de l'invention, on récupère les particules métalliques formées à l'aide d'un col de cygne fonctionnant en discontinu. Dans ce cas, on donne au fond de la cellule une forme de type pyramidal afin de diriger les particules de plomb vers un col de cygne qui remonte verticalement le long de la cellule. Le niveau liquide dans le col de cygne est en équilibre hydrostatique avec celui de la cellule d'électrolyse, c'est-à-dire que le point de rejet du col de cygne est situé de 2 à 20 centimètres au-dessus du niveau de la surface du catholyte : les agrégats de plomb s'accumulent dans la partie inférieure du col de cygne, constituant un véritable bouchon ; par intermittance un ou plusieurs éjecteurs, qui peuvent être réalisés par des ajutages, sont alimentés par du catholyte sans solide à un débit suffisant pour créer un effet de succion en fond de cellule et pour atteindre une vitesse linéaire d'écoulement du liquide dans le col de cygne d'au moins 0,5 mètre par seconde. Le plomb est entraîné et récupéré après séparation du liquide dans un système approprié qui est déconnecté hydrauliquement de la cellule d'électrolyse.According to a preferred implementation of the invention, the metallic particles formed are recovered using a gooseneck operating in batch mode. In this case, the bottom of the cell is given a pyramid-like shape in order to direct the lead particles towards a swan neck which rises vertically along the cell. The liquid level in the swan neck is in hydrostatic equilibrium with that of the electrolysis cell, i.e. the swan neck rejection point is located 2 to 20 centimeters above the level of the surface of the catholyte: lead aggregates accumulate in the lower part of the swan neck, constituting a real plug; intermittently one or more ejectors, which can be produced by nozzles, are supplied by catholyte without solid at a rate sufficient to create a suction effect at the bottom of the cell and to achieve a linear speed of flow of the liquid in the neck swan of at least 0.5 meters per second. The lead is entrained and recovered after separation of the liquid in a suitable system which is hydraulically disconnected from the electrolysis cell.

On peut aussi entraîner les agglomérats de plomb par entraînement à l'air (air-lift). Le ou les éjecteurs sont disposés sous le col de cygne aux endroits appropriés connus de l'homme de l'art pour obtenir un bon effet de « succion » ou d'« air-lift ».Lead agglomerates can also be entrained by air entrainment (air-lift). The ejector (s) are disposed under the swan neck at the appropriate locations known to those skilled in the art to obtain a good “suction” or “air-lift” effect.

Les exemples de réalisation de la présente invention, non limitatifs, suivants ont pour but de mettre les spécialistes à même de déterminer aisément les conditions opératoires qu'il convient d'utiliser dans chaque cas particulier.The following nonlimiting exemplary embodiments of the present invention are intended to enable specialists to easily determine the operating conditions which should be used in each particular case.

Exemple 1Example 1

On traite par une solution de chlorure ferrique et de sodium une matière première sulfurée constituée par un concentré de galène, contenant 75,5 % de plomb, 0,70 % de zinc, 0,85 % de cuivre, 1,40 % de fer, 1,0 % de calcium et 0,6 % de magnésium.A sulfurized raw material consisting of a galena concentrate, containing 75.5% lead, 0.70% zinc, 0.85% copper, 1.40% iron, is treated with a solution of ferric chloride and sodium. , 1.0% calcium and 0.6% magnesium.

Après purification, la solution d'alimentation de l'électrolyseur et l'électrolyte ont les compositions suivantes :

Figure imgb0003
After purification, the electrolyzer supply solution and the electrolyte have the following compositions:
Figure imgb0003

L'électrolyse est effectuée dans une installation du type représenté sur la figure ; la vitesse de circulation du catholyte est de 0,06 mètre par seconde et celle de l'anolyte de 0,01 mètre par seconde. Les cathodes sont formées de titane lisse. La densité de courant, en régime permanent, est de 550 A/m2. La distance séparant les électrodes est de 70 millimètres.The electrolysis is carried out in an installation of the type shown in the figure; the circulation speed of the catholyte is 0.06 meters per second and that of the anolyte is 0.01 meters per second. The cathodes are made of smooth titanium. The current density, in steady state, is 550 A / m 2 . The distance between the electrodes is 70 millimeters.

On constate que le plomb obtenu est sous forme de particules ayant une longueur de l'ordre de 300 à 600 micromètres et n'adhère pas aux cathodes. Le rendement faradique observé est de 95 %, et le rendement énergétique de 0,57 kWh par kilo de plomb.It is found that the lead obtained is in the form of particles having a length of the order of 300 to 600 micrometers and does not adhere to the cathodes. The faradaic efficiency observed is 95%, and the energy yield is 0.57 kWh per kilo of lead.

La pureté du plomb obtenu d'une part sous forme simplement laminée et d'autre part sous forme d'un lingot est la suivante :

Figure imgb0004
The purity of the lead obtained on the one hand in simply laminated form and on the other hand in the form of an ingot is as follows:
Figure imgb0004

Exemple 2Example 2

On utilise la même installation et un électrolyte de même composition que dans l'exemple 1. La vitesse de circulation du catholyte est de 0,10 mètre par seconde et celle de l'anolyte de 0,02 mètre par seconde. La densité de courant utilisée est de 850 A/m2 et la distance entre les électrodes est la même que dans l'exemple 1.The same installation is used and an electrolyte of the same composition as in Example 1. The circulation speed of the catholyte is 0.10 meters per second and that of the anolyte of 0.02 meters per second. The current density used is 850 A / m 2 and the distance between the electrodes is the same as in Example 1.

Le plomb produit est analogue à celui décrit dans l'exemple 1. Le rendement énergétique de l'électrolyse est de 0,74 kWh par kilo.The lead produced is similar to that described in Example 1. The energy efficiency of electrolysis is 0.74 kWh per kilo.

Exemple 3 .Example 3.

On utilise une installation analogue à celle de l'exemple 1. Les cathodes sont formées de titane lisse et les anodes de titane déployé recouvert d'oxyde de ruthénium. La distance qui les sépare est égale à 70 millimètres. Les anodes sont disposées dans une boîte anodique dans laquelle l'anolyte ne circule pas. La différence de pressions entre l'anolyte et le catholyte est de 20 millimètres de colonne d'eau. L'installation est destinée à permettre la récupération du chlore.An installation similar to that of Example 1 is used. The cathodes are formed from smooth titanium and the anodes from expanded titanium covered with ruthenium oxide. The distance between them is 70 millimeters. The anodes are placed in an anode box in which the anolyte does not circulate. The pressure difference between the anolyte and the catholyte is 20 millimeters of water column. The installation is intended to allow the recovery of chlorine.

Dans cet exemple, la teneur en plomb de l'électrolyte est maintenue par introduction continue de chlorure de plomb cristallisé. Les cristaux contiennent les impuretés suivantes, exprimées en grammes par tonne :

  • Fe : 15 Ni : 1 Mg : 4,4
  • Na : 10-50 Zn : 4,0 Ca : 5,0
  • Cu 2,5 Cd : 5
  • Ag 1 S : 40
In this example, the lead content of the electrolyte is maintained by continuous introduction of crystallized lead chloride. The crystals contain the following impurities, expressed in grams per tonne:
  • Fe: 15 Ni: 1 Mg: 4.4
  • Na: 10-50 Zn: 4.0 Ca: 5.0
  • Cu 2.5 Cd: 5
  • Ag 1 S: 40

Les conditions d'électrolyse sont les suivantes :

  • densité de courant : 1 000 A/m2
  • température : 75 °C
  • vitesse linéaire du catholyte : 0,04 mètre par seconde.
The electrolysis conditions are as follows:
  • current density: 1000 A / m 2
  • temperature: 75 ° C
  • linear speed of the catholyte: 0.04 meters per second.

Le rendement énergétique de l'électrolyse est de 1 kWh par kilo de plomb. Les particules de plomb forment une poudre de densité apparente comprise entre 1,5 et 2,5 et contiennent 20 à 30 % en poids d'électrolyte occlu. Après densification au laminoir, cet électrolyte est extrait de la poudre.The energy efficiency of electrolysis is 1 kWh per kilo of lead. The lead particles form a powder with an apparent density of between 1.5 and 2.5 and contain 20 to 30% by weight of occluded electrolyte. After densification with a rolling mill, this electrolyte is extracted from the powder.

Le tableau qui suit indique non seulement la composition de l'électrolyte mais aussi la pureté des produits obtenus, d'une part après laminage et d'autre part après mise en forme d'un lingot.

Figure imgb0005
Figure imgb0006
The following table indicates not only the composition of the electrolyte but also the purity of the products obtained, on the one hand after rolling and on the other hand after shaping an ingot.
Figure imgb0005
Figure imgb0006

Exemple 4Example 4

Les conditions opératoires sont identiques à celles de l'exemple 3, mais l'électrolyte contient 10 grammes par litre de sulfate. A cette concentration, l'électrolyse n'est pas perturbée par les ions sulfate et le rendement énergétique reste sensiblement égal à 1 kWh par kilo de plomb déposé.The operating conditions are identical to those of Example 3, but the electrolyte contains 10 grams per liter of sulfate. At this concentration, the electrolysis is not disturbed by the sulfate ions and the energy yield remains substantially equal to 1 kWh per kilo of lead deposited.

Les particules de plomb obtenues ont une même pureté et un même taux d'électrolyte occlu que dans l'exemple 3.The lead particles obtained have the same purity and the same level of electrolyte occluded as in Example 3.

Exemple 5Example 5

On utilise des conditions opératoires identiques à celle de l'exemple 4, mais on porte la densité de courant à 1 500 A/m2.Operating conditions identical to that of Example 4 are used, but the current density is brought to 1500 A / m 2 .

Le rendement énergétique atteint 1,24 kWh par kilo de plomb déposé. La pureté des particules de plomb obtenues et les caractéristiques avant densification restent les mêmes que dans l'exemple précédent.The energy efficiency reaches 1.24 kWh per kilo of lead deposited. The purity of the lead particles obtained and the characteristics before densification remain the same as in the previous example.

Exemple 6 : Montage d'électrodes de même nature de série électrique dans la même cuveExample 6: Installation of electrodes of the same type of electrical series in the same tank

Dans une cellule d'électrolyse de laboratoire de 2 mètres de long, 0,15 mètre de haut et 0,03 mètre de largeur, on a évalué l'importance des courants de fuite entre deux cellules. Chaque cellule est constituée d'une anode et d'une cathode. On a choisi l'électrolyse du sulfate de cuivre pour faciliter les mesures qui portent essentiellement sur l'évolution des courants de fuite et la répartition de la densité de courant à la surface des cathodes. En effet, en milieu sulfate, les dépôts de cuivre sont compacts et le rendement faradique des dépôts très voisin de l'unité dans une plage de densité de courant de 200 à 300 ampères par mètre carré. Dans ces conditions, il est possible, en découpant le dépôt en bandes d'égale largeur, de déterminer à partir du poids de chacune, la densité de courant moyenne d'électrolyse sur chaque élément de surface et de connaître ainsi le profil de répartition de la densité de courant moyenne à la surface des cathodes.In a laboratory electrolysis cell 2 meters long, 0.15 meters high and 0.03 meters wide, the magnitude of the leakage currents between two cells was evaluated. Each cell consists of an anode and a cathode. The electrolysis of copper sulphate was chosen to facilitate the measurements which essentially relate to the evolution of the leakage currents and the distribution of the current density at the surface of the cathodes. In fact, in a sulphate medium, the copper deposits are compact and the faradaic yield of the deposits very close to unity in a current density range of 200 to 300 amperes per square meter. Under these conditions, it is possible, by cutting the deposit into strips of equal width, to determine from the weight of each, the average current density of electrolysis on each surface element and thus to know the distribution profile of the average current density at the surface of the cathodes.

La figure 2 représente le dispositif expérimental utilisé. La solution de sulfate de cuivre est maintenue en circulation entre le réservoir 4, chauffé 5 et la cuve d'électrolyse type chenal 1 par la pompe centrifuge 6. Chaque cellule 2 est constituée d'une anode en plomb et d'une cathode en acier inoxydable, espacées de 1,6 centimètre. Dans la cuve 1, une, deux ou trois cellules 2 peuvent être montées en série électrique et l'écartement L entre chaque cellule peut varier.FIG. 2 represents the experimental device used. The copper sulphate solution is kept in circulation between the tank 4, heated 5 and the channel type electrolysis tank 1 by the centrifugal pump 6. Each cell 2 consists of a lead anode and a steel cathode stainless, spaced 1.6 cm apart. In the tank 1, one, two or three cells 2 can be mounted in electrical series and the spacing L between each cell can vary.

Dans la figure 3, le schéma représente principalement les connections électriques entre les anodes 7 et les cathodes 8. Chaque cellule 2 est reliée extérieurement par un conducteur 9. Entre chaque cellule 2 il existe un courant de fuite IF qui diminue le rendement énergétique global de l'électrolyseur et qui perturbe la répartition de la densité de courant sur les bords des électrodes, principalement entre l'anode d'une cellule et la cathode de la cellule voisine.In FIG. 3, the diagram mainly represents the electrical connections between the anodes 7 and the cathodes 8. Each cell 2 is connected externally by a conductor 9. Between each cell 2 there is a leakage current I F which decreases the overall energy efficiency of the electrolyser and which disturbs the distribution of the current density on the edges of the electrodes, mainly between the anode of a cell and the cathode of the neighboring cell.

Dans le tableau suivant on trouve les principaux résultats obtenus avec un électrolyte contenant 40 grammes par litre de cuivre et 165 grammes par litre d'acide sulfurique. Toutes les expérience ont été conduites à une température de 40 °C pendant 15 à 20 heures.The following table shows the main results obtained with an electrolyte containing 40 grams per liter of copper and 165 grams per liter of sulfuric acid. All the experiments were carried out at a temperature of 40 ° C for 15 to 20 hours.

(Voir tableau page 11)(See table on page 11)

Figure imgb0007
Figure imgb0007

A petite échelle les courants de fuite sont une valeur relative importante vis-à-vis de l'intensité du courant fournie par le redresseur 3. Cette importance relative sera considérablement atténuée à plus grande échelle.On a small scale, the leakage currents are an important relative value with respect to the intensity of the current supplied by the rectifier 3. This relative importance will be considerably attenuated on a larger scale.

La figure 4 donne à titre d'exemple le profil de densité moyenne obtenu sur les cathodes 8 pour l'essai 2.FIG. 4 gives by way of example the average density profile obtained on the cathodes 8 for test 2.

Exemple 7Example 7

La surdensité de courant sur les bords des cathodes n'est pas acceptable en raison de l'accroissement de la surtension locale d'électrode qui risque de provoquer l'apparition de réactions parasites.The overcurrent on the edges of the cathodes is not acceptable due to the increase in the local electrode overvoltage which may cause the appearance of parasitic reactions.

On a pallié cet inconvénient majeur en décalant les axes verticaux des anodes et des cathodes de chaque cellule et en imposant une intensité calculée en tenant compte de la densité de courant choisie et des surfaces d'électrode en regard. L'objectif est de pouvoir assurer une densité de courant vraie à la surface des cathodes, inférieure à la densité de courant choisie.This major drawback has been overcome by shifting the vertical axes of the anodes and cathodes of each cell and by imposing a calculated intensity taking into account the current density chosen and the facing electrode surfaces. The objective is to be able to ensure a true current density at the surface of the cathodes, less than the chosen current density.

Ce type de montage a été expérimenté avec le dispositif expérimental décrit précédemment. Dans le tableau suivant on a fait figurer les résultats comparatifs entre deux montages électriques de trois cellules espacées de 0,63 mètre, l'un avec les électrodes décalées et l'autre avec les électrodes non décalées dans chaque cellule.This type of assembly was tested with the experimental device described above. The following table shows the comparative results between two electrical assemblies of three cells spaced 0.63 meters apart, one with the electrodes offset and the other with the electrodes not offset in each cell.

Les figures 5 et 6 représentent les profils de répartition de la densité de courant vraie pour les cathodes avec ou sans décalage.Figures 5 and 6 show the distribution profiles of true current density for cathodes with or without offset.

Figure imgb0008
Figure imgb0008

Claims (19)

1. Process for the preparation of a metal by electrolysis in a diaphragm celle, of the type which comprises :
- the formation of an electrolyte containing a chloride of the metal to be prepared and at least one chloride of an alkaline or alkaline-earth metal, and
- the circulation of the electrolyte between the electrodes, parallel to the surface of a cathode disposed in a substantially vertical direction
- the detachment of the particles of metal, which fall in the electrolyte
- the taking of the metallic particles collected at the base of the cell characterized in that:
- the metal of the cathode and the density of current are selected such that the cathode surface has a sufficiently low density of nucleation sites so that the metallic particles which form from these sites retain their individuality with regard to adjacent particles, until they reach a dimension of at least 100 micrometres
- the flow of the electrolyte along the cathode surface is linear and of the laminar or slightly turbulent type.
2. Process according to claim 1, characterized in that the metal to be prepared is lead.
3. Process according to claim 2, characterized in that the lead is present in the electrolyte in the form of chloride in a quantity comprised between approximately 5 and 50 grammes per litre, preferably between approximately 15 and 25 grammes per litre.
4. Process according to one of claims 2 and 3, characterized in that the surface of the cathode is formed of titanium, stainless steel or graphite.
5. Process according to any one of claims 2 to 4, characterized in that the electrolyte in addition contains iron in the form of chloride, essentially ferrous chloride.
6. Process according to claim 5, characterized in that the concentration of iron in the form of chloride in the electrolyte is comprised between 20 and 60 grammes per litre.
7. Process according to any one of the preceding claims, characterized in that the concentration of at least one chloride of alkaline or alkaline-earth metal is comprised between 4 and 5 equivalent grammes per litre.
8. Process according to any one of the preceding claims, characterized in that the said chloride of alkaline or alkaline-earth metal is sodium chloride.
9. Process according to any one of the preceding claims, characterized in that the density of the electric current of electrolyte is comprised between 500 and 1 500 A/m2 and preferably between 700 and 1 000 A/m2.
10. Process according to claim 9, characterized in that it comprises the progressive increase or increase by stages of the density of current up to a value of permanent working conditions.
11. Process according to any one of the preceding claims, characterized in that the electrolyte circulates along the cathodic surface at a velocity comprised between 0.01 and 0.15 metres per second.
12. Process according to any one of the preceding claims, characterized in that the taking of the particles collected at the base of the cell comprises the transport of the particles outside the cell and their densification by compression.
13. Process according to claim 12, characterized in that it further comprises, after densification, the lamination of the particles so that the largest part of the inclusions of electrolyte is driven out.
14. Process according to one of claims 12 and 13, characterized in that it comprises the fusion of the densified particles, in the presence of soda.
15. Apparatus for the preparation of metal by electrolysis, of the type which comprises a diaphragm cell in which the cathodes and the anodes are disposed vertically, the cathodes being formed of a material selected from titanium, stainless steel and graphite, and comprising at least one pump intended to circulate a current of electrolyte of the laminar or slightly turbulent type along the cathodes, and a transport device intended to draw the solid divided materials which may fall at the base of the cell, characterized in that the cathodes and the anodes form a non-isopotential device constituted by a series of rows of anodes and cathodes connected to the same current supply where the electrodes of two different rows situated in the same plane are joined by partitions of non-conductive material, the distance separating the two rows of electrodes being comprised between 0.8 and 2 metres.
16. Apparatus according to claim 15, characterized by the fact that the anodes are staggered in relation to the cathodes by a distance comprised between 5 and 20 centimetres, preferably of 20 centimetres, this staggering being carried out in the direction of decreasing potentials in the electrolysis tank.
17. Apparatus according to claim 15, characterized in that it comprises bipolar electrodes.
18. Apparatus according to any one of claims 15 to 17, characterized in that the transport device is selected in the group which comprises a swan-neck, an endless screw, a bucket-elevator and a conveyor belt.
19. Apparatus according to claim 18, characterized in that it further comprises an extruder intented to densify the solid divided materials displaced by the transport device.
EP83400915A 1982-05-06 1983-05-05 Process and apparatus for the electrolytic preparation of metal, especially lead Expired EP0094308B1 (en)

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ZA833237B (en) 1984-10-31
GR78859B (en) 1984-10-02
MX158327A (en) 1989-01-25
JPS5931879A (en) 1984-02-21
FI74306C (en) 1988-01-11
FR2526446A1 (en) 1983-11-10
EP0094308A3 (en) 1984-05-23
US4601805A (en) 1986-07-22
FI831530L (en) 1983-11-07
NO831606L (en) 1983-11-07
PT76645A (en) 1983-06-01
FI74306B (en) 1987-09-30
EP0094308A2 (en) 1983-11-16
AU1427283A (en) 1983-11-10
AU572455B2 (en) 1988-05-12
CA1234070A (en) 1988-03-15
DK201183A (en) 1983-11-07
FI831530A0 (en) 1983-05-04
BR8302379A (en) 1984-01-10
FR2526446B1 (en) 1986-02-21
ATE36013T1 (en) 1988-08-15
DK201183D0 (en) 1983-05-05
PT76645B (en) 1986-02-26
ES8402626A1 (en) 1984-02-01
ES522128A0 (en) 1984-02-01
NO165033C (en) 1990-12-12
US4507182A (en) 1985-03-26
DE3377507D1 (en) 1988-09-01
PL241834A1 (en) 1984-06-18
NO165033B (en) 1990-09-03

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