FR2513904A1 - Sepn. of metal from crushed accumulator scrap - which is fed down column in countercurrent to ascending stream of water removing materials with low density but not metals - Google Patents

Abstract

Accumulator scrap is milled, and is then fed down a vertical column in counter-current to an ascending stream of liq. The upward velocity of the liq. carries all the nonmetallic scrap upwards to a separator, from which the liq. can be reclaimed; but the metallic scrap falls to the base of the column, where it can be removed, pref. by a screw feeder. The column pref. has a dia. of 380 mm; and the liq. is pref. water flowing up the column at 1700-1900 litres/minute or at a speed of 15 metres/minute. The initial scrap pref. consists of polymers and a metal, esp. Pb; and is crushed; it is then pref. mixed with a soluble alkali to neutralise acid electrolyte in the scrap. All the materials in the scrap can be reclaimed, e.g. from Pb-acid, or Ni-Zn batteries.

Description

 The present invention relates to the recovery of the constituent materials of accumulators and it relates more particularly to the separation and recovery of the various components of accumulators such as, for example, lead-acid accumulators.

 Although the invention is described below with regard to the recovery of the components of lead-acid accumulators, the method and the installation according to the invention can easily be applied, as will be obvious to a person skilled in the art. ltart, for the recovery of materials from other types of accumulators.

 As is known, the main constituent materials of current conventional accumulators include ebonite, polypropylene, polyethylene or other similar materials which form the tank of the accumulator. These materials, in combination with the materials forming the vent plugs, spacers, separators, insulators and the casing, are usually called non-metallic or polymeric components. The electrode grids and electrical connections between the grids and the external circuit are traditionally made of metal. These metallic components, along with the active material of the electrodes, which in most cases contains metallic compounds, are usually called components containing metals or metallic components.

 Another important constituent material of conventional batteries is the electrolyte. In general, when treating lead-acid batteries, the electrolyte is removed before starting the recovery operations of the batteries. In known processes of the prior art, when the acid from the accumulator has been removed, the components remaining are introduced into an impact or shredder so that they are crushed or shredded into small pieces. heterogeneous mixture of debris from accumulators result of this operation has hitherto been divided by numerous screening operations and other mechanical or physical separation operations into non-metallic parts and metallic parts, the metallic parts comprising coarse metallic pieces, fragments metallic fine particles, which are essentially composed of zinc oxide and zinc sulphate and a pure lead powder resulting from the lining of the electrodes, as described in American patent 4,107,007.

 In another known method such as that described in German patent application 28.56.330, the debris containing lead sulphate is brought into contact with an aqueous solution of an alkaline substance which converts lead sulphate to a lead salt insoluble in water, such as lead carbonate and which also forms, as a by-product, a water-soluble sulfate such as sodium sulfate. Next, the water-insoluble lead salt is prepared for reduction by roasting.

These various recovery methods already known pose various problems. By way of illustrative example, before the mechanical treatment of accumulator debris can be carried out, the electrolyte from the accumulator must be removed to avoid corrosion of the apparatus under the effect of the electrolyte in the phases. consecutive treatment;
This elimination of the electrolyte from the accumulator in the dry mechanical process traditionally used constitutes an expensive, long and labor-intensive operation.

 Another problem which arises in the already known recovery process consists in the undesirable mutual contaminations of the constituents of the accumulator, which result from the lack of efficiency of the separation of the components. It is desirable to separate the components of the accumulators into as pure forms as possible in order to allow efficient recycling. In the known recovery methods, the significant effect of mutual contamination of the constituents has hitherto represented a serious obstacle to the economic production of a product which can be used for recycling.

 In addition, in the case of the recovery methods already known, the pollution regulations of I. ' the environment concerning the risks of employee exposure to toxic metallic compounds and the treatment of effluents pose serious problems. The cost of complying with these regulations has hitherto made this recovery impossible to achieve economically when the result is obtained by the use of conventional treatments and superadded installations.

 Due to the depletion of petroleum resources, it is clearly desirable to use electric vehicles and other electric devices powered by accumulators. It is very important to carry out an installation and a process for recovering accumulators which are free from environmental pollution. The present invention meets these severe environmental protection requirements and makes it possible to produce accumulator components which can be reprocessed with an effective reduction of the harmful effect on the environment.

 An object of the invention is therefore to create a process for the recovery of complete accumulators, including the electrolyte.

 Another object of the invention is to create a wet mechanical recovery process for the total recovery of accumulators, which produce several independent and isolated flows of accumulator constituents: active material of the electrodes, metallic material, electrolyte material and polymeric or other non-metallic materials.

 Another object of the invention is to improve the elimination of mutual contamination of the various streams of accumulator constituents during the recovery operation.

 Another object of the invention is to create a recovery treatment which separates all the various constituents of the accumulators into relatively pure forms suitable for recycling or subsequent disposal.

 Another object is to create a treatment for the recovery of accumulators which makes it possible to fully treat the accumulators, including the electrolyte and which does not however require that the mechanical installation used for the treatment be made of expensive materials resistant to corrosion. .

 Another aim is to create a treatment for the recovery of accumulators which is implemented while respecting both the standards relating to the environment and the standards relating to occupational safety.

 Another aim is to create a method for recovering accumulators which can easily be adapted to the different shapes and dimensions of accumulator tanks and to the different metallic or non-metallic constituents which constitute the accumulators.

 Another object of the invention is to create an installation and a method for recovering accumulators which are inexpensive and simple to use.

 The present invention relates to an installation and a method for dividing an accumulator into its components. An initial phase of the process consists in breaking the entire accumulator to transform it into a fragmented material. Then, the electrolyte and the majority of the active material of the electrodes of the broken accumulator is extracted during the treatment and the metallic material, the polymeric material or other non-metallic material, including the insulating materials are then separated and recovered.

Other characteristics and advantages of the invention will emerge during the description which follows. In the accompanying drawings, given solely by way of example,
- Fig. 1 is a flowchart showing the phases of an accumulator recovery process according to the invention;
- Fig. 2 is a side view of a dehydrating screen device used for implementing the method according to the invention
- Fig. 3 is a side view of an apparatus with a separation column used for the implementation according to the invention; and
- Fig. 4 is a flowchart showing another recovery method according to the invention.

 We will now describe the mode considered to be the best for implementing the invention.

 Fig. 1 is a flowchart illustrating the phases of the preferred embodiment of the method for breaking or crushing complete composite accumulators B and for classifying the broken pieces into different component materials.

 As shown, the first phase of the process comprises, by way of example, a phase consisting in breaking up or crushing the complete accumulators into fragments, the majority of which are found in a fraction of less than 38.1 mm. The fragmentation causes an almost complete separation between the metallic material and the non-metallic materials as well as the release of the electrolyte. The metallic material comprises the active material of the electrodes, the terminals and the electrical connectors between elements. The non-metallic material includes the polymeric materials and, possibly other electrically non-conductive materials, and they include the material of the tank, which is usually made up by polypropylene, polyethylene or ebonite, the spacers, possibly used, the material of the separators placed between the plates of the accumulator, and other non-conductive materials. It has been found that after passing accumulators through a conventional hammer mill H, 97% of the ground material of the accumulators is found in a fraction of less than 38.1 mm. As an illustrative example, such a hammer mill manufactured by Williams Patent Crusher and Pulverizer Co, of Saint-Louis (USA), includes hammers mounted on shafts arranged concentrically around a central drive shaft. strike the accumulator tank with a percussive force by projecting it against a steel breaker plate to break the accumulators into fragments. The accumulators can be introduced continuously into the hammer mill by suitable transport means. The hammer mill, with the feed conveyor, and the inlet hopper are almost completely closed and ventilated with evacuation of the atmosphere to a conventional device for eliminating acid mist.

The acid mist removal device used to treat lead-acid batteries removes electrolyte particles and lead compounds from the air, either by impact or by spraying a mist of wash water through these particles, thereby keeping the air practically free of acid and lead. Devices of this kind are well known and will not be described in detail in the present specification, since they can be found commercially.

 Many of the accumulators introduced into the hammer mill may contain electrolyte in their trays. The parts of the hammer mill which are exposed to this electrolyte are therefore preferably made of materials which are resistant to corrosion, with respect to the type of electrolyte which may be present in the treated accumulators, for example, with respect to the acid or alkaline electrolyte. The result is to simplify the process by the fact that one does not have to empty the electrolyte from the accumulator before the fragmentation phase.

 The ground material of the accumulator, which optionally comprises this electrolyte, is then transferred, for example by gravity, into a mixing reactor M. In a mixing reactor for the treatment of lead-acid accumulators, the electrolyte based on sulfuric acid is neutralized by the addition of sodium carbonate in the form of sodium ash. The phase of neutralization of the electrolyte can be carried out in a treatment by successive charges in the mixing reactor. However, the invention also includes the same phase carried out in a continuous treatment. In this treatment of lead-acid accumulators, one only has to adjust the amount of neutralizing reagent added to the electrolyte based on sulfuric acid to compensate for the differences in volume and concentration of the electrolyte present which may be due to variations in the quantity of accumulators to be treated. In the successive charge process, the pH is measured approximately every hour and the neutralization reagent is added accordingly.

 In the continuous process, a pH probe is preferably used to provide continuous pH monitoring and adjustments are made as necessary to maintain the pH at the desired level. To neutralize the acid, it is desirable to obtain a pH of 7. However, to ensure the conversion of lead sulphate to lead carbonate and of sodium carbonate to sodium sulphate, it is desirable to maintain the pH at a level of approximately 9.0 to 9.3. Sulfuric acid reacts with sodium carbonate to form sodium sulfate which is soluble and remains in solution if the concentration of sodium sulfate is kept below its saturation level, which is necessary to avoid crystallization and precipitation of the compound.

 It is desirable and advantageous to use a reagent which also reacts with the sulfur-containing lead compound from the active material of the electrodes to form a sulfur-free lead compound for recovery and further processing. Sodium carbonate also transforms a significant amount of the lead sulphate contained in the active material of the electrodes into lead carbonate. The quantity of sodium ash necessary to ensure the dual function of neutralizing the acid and transforming lead sulphate is preferably equal to the stoichiometric equivalent necessary for these reactions, more or less a 10% excess compared to the amount needed for the last reaction. In addition, it is desirable to add an amount of water sufficient to maintain the concentration of the neutralization product, i.e. sodium sulfate, at about 90% of its maximum solubility at room temperature.

 It was found, on the basis of a test sample of 50 lead-acid accumulators, that the neutralization of sulfuric acid required approximately 0.834 kg of Na2CO3 per accumulator. It has been found that neutralizing and removing sulfur from the active material of the electrodes in a test sample of 200 lead-acid batteries required 3.311 kg of Na2CO3 per battery. The difference in the amount of Na2CO3 required per accumulator represents the additional amount of Na2CO3 required to transform lead sulphate into lead carbonate. These approximations given by way of example should not be considered as limiting.

 According to the invention, other neutralizing reagents can be used to neutralize the electrolyte based on sulfuric acid, which include, without limitation, reagents such as ammonium carbonate, sodium hydroxide, ammonia , etc ... For example, when ammonium carbonate is used as reagent, the products are lead carbonate and ammonium sulfate; when sodium hydroxide is used as a reactant, the products are lead hydroxide and sodium sulfate and, when ammonia is used, the products are lead hydroxide and ammonium sulfate. Nautically, other reagents will be obvious to those skilled in the art and their use is included in the present invention.

 All products containing lead or lead compounds, as well as products which do not contain lead, are precious and are preferably separated and recovered both for their own value and for the control of the purity of the final product desired. - d. Important advantages of this neutralization phase are the reduction of the corrosion of the equipment due to the electrolyte of the accumulators and, in the case of the treatment of lead-acid accumulators, the desulfation of the active material of the electrodes containing sulfur, or a lead sulphate compound, by transformation of this compound into a sulfur-free metal compound, such as lead carbonate, which considerably simplifies the subsequent treatment of this compound.

 It is important to note that the reagent for neutralizing the electrolyte may be different from the reagent used to remove the sulfur from the lead sulphate contained in the active material of the electrodes.

In addition, neutralization of the electrolyte and desulfation of the active material, or its transformation, can occur at different times during the treatment.

Since the active material of the electrodes of lead-acid batteries comprises lead oxides and lead sulphate which is transformed in the preferred process into a lead compound practically free of sulfur, and that all these compounds are advantageously treated and recovered together, as lead compounds practically sulfur-free, advantageous for the protection of the environment, intended for a further treatment, the particular treatment and the timing of the transformation of lead sulphate into lead free of sulfur can be varied considerably . Alternatively, lead sulphate can be treated and recovered as lead sulphate to be further transformed into a sulfur-free compound in a further treatment. For these reasons, the invention is not limited to a treatment sequence nor to a particular nature of treatment used to recover and / or transform the active material of the electrodes, since the recovery of this material constitutes the main element, whether it is obtained in a transformed form free of sulfur, or in a form not transformed and not free of sulfur. This active material of the electrodes can therefore be called hereinafter "active material of the electrodes or" solid lead compounds "without taking into account whether this transformation has been carried out or has not been carried out , and these two expressions can therefore be interpreted in a broad sense as equivalent and interchangeable for the formulation of the description and of the claims relating to the process and to the vari Antes of this process which are mentioned herein, since the sequence of the process which is actually used for the transformation of lead sulfate into a sulfur-free form is not considered critical.

 In the next phase, the accumulator material and the neutralized electrolyte, which contains solid lead compounds in suspension, are sent to a dehydrating screen where the neutralized electrolyte and most of the solid lead compounds are removed. the way which will be described below. A vibrating feeder can be used to transfer the crushed material from the accumulators to a headbox of the dehydrating screen. Fig. 2 is a side view of the appropriate dehydrating screen. The operation of the dehydrating screen consists in introducing particles through a feeder 22, onto a screen 26 having the desired size of openings. The particles pass through the screen 26 if they are smaller than these openings.

They are retained on the screen 26 if they are larger. The small particles and the liquid fall into the chute 28 and the large particles fall from the screen 26 at point 30.

 It has been found that, in the process described, more than 90% of the solid lead compounds, with the neutralized acid, pass through the screen. The most common lead compound found in the active material of electrodes, apart from lead dioxide, is lead sulphate which, as mentioned above, is transformed into a practically sulfur-free compound , that is to say lead carbonate, in the previous neutralization phase, by adjusting the amount of neutralizing reagent consisting of sodium carbonate which is used.

 The solid compounds consisting of lead carbonate and lead oxides which are suspended in the neutralized liquid electrolyte, which contains sodium sulphate in solution, are then sent by a pump to a tank S constituting a solid separator. liquids, which is used to decant and concentrate the solids contained therein. Alternatively, the liquid which contains the suspended solids can be treated in a cyclone separator C which can be added to complete the solid-liquid separator, in order to concentrate and remove the solid matter from the liquid.

 The solid-liquid separator allows solid lead compounds consisting of lead carbonate and lead oxides to separate from the sodium sulfate solution, which is then separated from insoluble solids, for example by decantation. The sodium sulfate solution that adheres to lead-containing solids can be removed by washing with water. The sulfur-free lead compounds can then be melted without environmental contamination, for example without sulfur pollution. The liquors rich in sodium sulfate resulting from the operation can be concentrated and recovered by evaporation to produce a product consisting of anhydrous sodium sulfate.

 According to the invention, other techniques and other equipment can also be used for the solid-liquid separation. Any means can be used to separate the active material from the electrodes, transformed or unprocessed, from the electrolyte. In most cases, the active ingredients, whether processed or unprocessed, continue processing at the same time to be recovered simultaneously. The type of separation means chosen depends on the type of accumulator to be recovered. Thus, since the nickel-cadmium, silver-zinc, nickel-zinc and lead-acid batteries have different active materials and electrolytes, the recovery treatments will be chosen accordingly .

 Following the separation phases, the remaining solid material, crushed or fragmented, which does not pass through the dehydrating screen, is sent to the top of a fluid separation column or of an ascending current separation column. This coarse material normally includes metallic components and non-metallic components. According to the invention, various liquids or various suspensions of solids in liquids can be used as the fluid in the separation column. However, as will be indicated below, water is the preferred fluid.

 Fig. 3 is a side elevational view of the separation column. As indicated, water is introduced near the bottom of the column 42 through an inlet tube 40 and at a controlled pressure.

A collector 44 distributes the inlet water so as to establish an updraft. When the coarse crushed accumulator material is introduced at the top 46 of the column, the heavier metallic material 48 falls and collects at the bottom 50 of the column. A closed screw conveyor 52 continuously evacuates the collected metallic material 48. As shown in a broken sectional view, the screw conveyor 52 is of sufficient length to extend above the water level 56 established inside the column, so that the metallic material can easily be collected in a container without the need to separate water. Solid lead compounds and non-metallic materials, such as polymeric materials, for example, piece 58 of polypropylene, are kept in suspension in the fluid in the separation column. Polymeric or non-metallic materials and suspended solids are transported by the ascending stream of water, over an overflow weir 59, in a circular collecting channel 60 from which the stream exits through the chute 61, which allows non-metallic materials to be processed in a subsequent processing phase.

 It has been found that a critical factor which affects the efficiency of the separation in the separation column is the use of an optimum flow rate of the fluid. With an appropriate flow rate, and using water as the fluid, for example, it was possible to obtain a yield of more than 97% for the separation of a polymer material containing ebonite and lead compounds in suspension from lead metallic material. As an illustrative example, a separation column having a diameter of 381 mm and a water flow rate of approximately 1,700 to 1,800 liters per minute, which gives an average linear speed of approximately 15 m / min, it has been found that the column has this high yield.

 The fluid used in the separation column can be recycled, for example, by pumping into a return pump reservoir T. When the fluid has circulated in the column, it can be returned to the pump reservoir in which the lead compounds suspended solids are removed by a low flow current flow. It has been found that it is advantageous to remove the solids contained in the low-flow stream leaving the pump reservoir, for example, by means of a hydraulic cyclone separator, as already mentioned more high, or by another desired solid-liquid separator.

The remaining coarse or rejected solids, which may include fragmented polymeric material, such as propylene, ebonite and separator materials, are sent to a solid-solid separator
SS which consists of a tank filled with liquid in which the different materials are separated. In the preferred embodiment, this phase is a flotation phase. The density of the material to be classified determines the choice of liquid or suspension of solids in a liquid which should be used as a separating medium. In the preferred embodiment, water is used. Ebonite and other polymeric materials which have a density greater than that of water fall to the bottom of the separation tank, where a screw conveyor SS removes the material from the liquid bath from to a collection point. In order for the dense polymeric material to be free of liquid at the time when it is collected, it suffices that the screw is of sufficient length to extend above the level of the liquid bath. The other polymeric materials, which have a density lower than that of the liquid used, float on the surface of the bath and are evacuated by a continuous belt conveyor with cleats BC which extends just above the level of the liquid. advantage of this phase for product purity is the elimination of unwanted heavy polymeric materials such as polyvinyl chloride and ebonite, which fall to the bottom and are thus separated from the lighter polymeric materials which float. This makes it possible to recycle the material more efficiently by providing a starting material which contains only a smaller quantity of contaminants such as the chlorinated compounds originating from the other polymer materials and the lead compounds to be treated.

 Although the operation described above is a solid-solid separation, other means can also be used to classify the solid materials without departing from the scope of the invention. These other means can also be based on the density of the solid materials or they can take advantage of other chemical or physical properties of the materials to be treated in order to carry out the classification.

 Another embodiment of the invention is illustrated by the flow diagram of FIG. 4. In this embodiment of FIG. 4 r 4, electrolyte, the active material of the electrodes and the other solid materials passing through the screen are separated from the other materials of accumulated or crushed accumulators without neutralization of the electrolyte, so that the latter can be collected and reused. As can be seen, the active material of the electrodes is separated from the non-neutralized electrolyte by solid-liquid separating means.

 The electrolyte can possibly be neutralized at a later point in the treatment. The electrolyte neutralizing reagent may be different from the reagent used to remove sulfur from the active material of the electrodes. In addition, in the treatment of lead-acid accumulators, desulfation can be carried out at a later time and in different phases of the treatment.

 The coarse screened solid which is separated from the finer ground battery material is normally wetted with neutralized electrolyte. It has been found that about 10% of the electrolyte adheres to the coarse solid material screened out and, during subsequent treatment, it may therefore be desirable to neutralize the electrolyte which adheres to the coarse solid material before treatment consecutive. The other phases of the mode of implementation shown in FIG. 4 are similar to that of the embodiment described above.

 As has been demonstrated by the embodiments described, the invention provides a method making it possible to recover the various components of the accumulators in a relatively pure form and in the form of separate products. The recovered products include, in the case of lead-acid accumulators, an active material free of sulfur, advantageous for the protection of the environment. Since the electrolyte does not have to be emptied from the accumulators before treatment, the work is simple and economical. In the case where the electrolyte of the accumulators is neutralized, as in the preferred embodiment described above, the mechanical equipment used in the following phases of the process does not have to be made of corrosion-resistant metals which are costly.

The environment of the factory is thus made less dangerous for the personnel and the problems of pollution of the environment posed by the rejection of waste and by the presence of sulfur and lead in the air are considerably reduced.

 The invention creates a simplified process for the separation of the various constituents of the accumulators, including the active material, the grids of plates and the other metallic materials, the electrolyte, the polymeric materials, including the spacers, the tank, the insulators and other non-metallic materials. These materials are separated and recovered in a form sufficiently free from contamination to be able to be recycled efficiently and economically with the minimum of detrimental influence on the environment. The invention can be adapted to be applied to the recovery of battery components other than lead-acid batteries.

Claims (21)

 1. Process for separating a metallic component material from another component material of accumulators (B), materials which have been produced by crushing accumulators which transform them into component materials of crushed accumulators, which comprise a non-metallic component material fragmented and a fragmented metallic component material which itself comprises metallic material and active material of the electrodes, characterized in that it comprises the phases in which: the ground material of accumulators is introduced into a column (42) fluid separation using an upwardly flowing fluid having a flow rate sufficient to drive upward all materials except the metallic material at the top of the column (42); the fluid and the entrained material are discharged upwards from the top of the column (42) in order to separate the entrained matter upwards; and the metallic material (48) is removed from the column (42) at a point situated below the level of the top (46) of the column (42).  2. Method according to claim 1, characterized in that the phase in which the metallic material is removed (48) consists in removing the metallic material from the bottom (50) of the column (42).  3. Method according to claim 1, characterized in that the phase in which the metallic material is removed (48) consists in removing the metallic material from the bottom (50) of the column (42) by means of a conveyor (52) having an entry at the bottom of the column (42).  4. Method according to claim 1, characterized in that the phase in which the metallic material is removed (48) consists in removing the metallic material from the bottom of the column (42) by means of a conveyor having an inlet at the bottom of the column (42) and an outlet above the level of the top (46) of the column.  5. Method according to claim 1, characterized in that the phase in which the metallic material is removed (48) from the bottom of the column (42) consists in removing the metallic material from the bottom of the column (42) by means of a conveyor (52) having an inlet at the bottom of the column and an outlet above the upper level (56) of said fluid.  6. Method according to claim 1, characterized in that said fluid consists of water.  7. Method according to claim 1, characterized in that said separation column (42) has a diameter of approximately 380 mm, the fluid consists of water and the flow rate in the range of approximately 1700 to 1900 liters per minute.  8. Method according to claim 1, characterized in that said separation column has a diameter of approximately 380 mm, the fluid consists of water and the flow speed is approximately 15 meters per minute.  9. Method for separating a metallic component material from another component material of accumulators (B), materials which have been produced by crushing the accumulators which transforms them into material of electrolyte, into component materials of crushed accumulators, which comprise a fragmented non-metallic polymeric component material and a fragmented metallic component material which itself comprises metallic material and active material of electrodes, characterized in that it comprises the phases in which the electrolyte is separated from the component material of crushed accumulators; the ground accumulator material is introduced into a fluid separation column (42) containing an upwardly flowing fluid having a flow rate sufficient to entrain all of the material except the metallic material up to the top of the column ; the fluid and the entrained material are discharged upwards from the top of the column (42) in order to separate the entrained matter upwards; and the metallic material is removed from the column at a point below the top (46) of the column  10. Process according to Claim 9, characterized in that the electrolyte is neutralized before separating it from said ground component materials.  11. Method according to claim 9, characterized in that the electrolyte is neutralized before separating it from the ground component materials, the neutralization phase consisting in adding at least one reagent composed of alkali metal salts soluble in water and of alkali metal hydroxides in an amount at least sufficient to neutralize the electrolyte.  12. Method according to claim 9, characterized in that said active material of the electrodes is suspended in said electrolyte and in that the phase of separation of the electrolyte comprises a dehydrating screen (26) which separates the electrolyte and the active material in suspension of the rest of the ground material.  13. Method according to claim 9, characterized in that the phase of separation of the electrolyte comprises a phase of solid-liquid separation in which the electrolyte is separated from said active material from the electrodes.  14. Method according to claim 13, characterized in that said solid-liquid separation is carried out in a settling tank.  15. The method of claim 9, characterized in that it comprises a phase of removing sulfur from the active material of the electrodes.  16. Method according to claim 15, characterized in that the sulfur elimination phase consists in reacting the active material of the electrodes containing sulfur with a reagent serving to remove the sulfur and in forming a metal compound free of sulfur as reaction product.  17. The method of claim 9, characterized in that said metallic material (48) removed from the separation column (42) by means of a screw conveyor (52) which extends up above the level (56) of the fluid contained in said separation column.  18. The method of claim 9, characterized in that the fluid used in said separation column (42) serving for the phase of separation of metallic materials consists of water.  19. The method of claim 15, characterized in that said sulfur removal phase consists in reacting the active material of the sulfur-containing electrodes with a reagent to remove the sulfur and form a lead carbonate as reaction product.  20. Method according to claim 9, characterized in that the grinding phase consists in introducing the accumulators into a crusher (H) which is almost completely closed and ventilated with evacuation of the atmosphere towards a device for eliminating the mist. of acid, and in that the major part of said ground material is presented in fractions of less than 38.1 mm.  21. The method of claim 9, characterized in that said active material is recovered from the electrodes in the form of solid lead compounds.