FR2504940A1 - PROCESS FOR PROCESSING SULFATE LEAN COMPOUNDS FOR RECOVERING THE METAL LEAD AND HIGH-PURITY SULPHATE AND INSTALLATION THEREFOR - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS A PROCESS FOR TREATING SULPHATED LEAD COMPOUNDS, IN PARTICULAR THOSE COMING FROM DEEP BATTERIES, TO RECOVER METAL LEAD AND A HIGH PURITY SULPHATE, CHARACTERIZED BY THE FACT THAT IT COMPRISES THE PHASES: OF THE SAID SULPHATES WITH SODIUM CARBONATE IN AQUEOUS SOLUTION; SEPARATION, BY FILTRATION OF THE LEAD CARBONATE PRECIPITE IN THIS FORM, SODIUM SULPHATE REMAINING IN SOLUTION; REDUCTION OF LEAD CARBONATE IN METAL LEAD; SEPARATION OF SODIUM SULPHATE BY CRYSTALLIZATION OF FILTERED SOLUTIONS; AND RECYCLING OF MOTHER WATERS FROM CRYSTALLIZATION TO THE LIXIVIATION PHASE. THE INVENTION ALSO RELATES TO A PLANT FOR CARRYING OUT THE ABOVE DEFINED PROCESS.

Description

The present invention relates to a method of treatment

  sulphated lead compounds to recover the lead lead

  and at the same time a sulphate of high quality,

  as well as the installation necessary to carry out this process.

  The process to be described herein is particularly suitable for the treatment of lead compounds derived from

  lead acid batteries exhausted ("mass").

  There are various known methods for recovering metallic lead from the "mass" and sludge from spent batteries;

  among the most common are, for example,

  pyrometallurgical derivatives, in which sulphated lead derivatives, mostly sulphates and sulphides, are reduced to lead by heat; these processes have, however, serious disadvantages: on the one hand, the need

  use reagents, such as iron or pyrolysis

  soda ash or lime at elevated temperatures and, on the other hand, the fact that a high percentage of the sulfur present in the starting materials is converted into harmful sulphurous gases which, if are vented to the atmosphere, cause ecological damage in

  these conditions, it becomes necessary to provide

  in which the sulfur gases to be discharged

  are washed, for example with alkaline solutions

  lines, based on lime, or ammoniacal It is clear that these equipments constitute a heavy load which weighs on the construction and operating costs of this type.

  recovery facilities and, therefore, a

  important for this technology.

  To achieve the same goals mentioned above, there is

  also other known methods, such as those described in U.S. Patents 3,883,348 and 4,118,219.

  processes in which the sulfa lead-containing materials

  They are treated with a solution of ammonium carbonate to obtain lead carbonate and ammonium sulphate, the latter being recovered for use as a fertilizer. However, the following disadvantages are typical of these processes: releases of ammonia gas, and therefore harmful to

  treatment conditions, and the need for

  Suitable for concentrating ammonium sulphate solutions

  that and to recover reagents, o negative aspect of

  these processes from the economic point of view.

  RI 8123 of the Bureau of Mines

  writes the use of calcium hydroxide to convert lead

  sulphate of lead hydrates Sulfate

  of insoluble calcium and it is therefore necessary to perform a melting reducing the mixture obtained in the presence of a large amount of flux, for example a mixture of sodium chloride and

potassium chloride.

  Even if the temperature at which this reduction takes place is low, the large quantity of substance to be melted makes the process not really interesting; moreover, others

  treatments are necessary for the recovery of

dent.

  In British Patent 1,535,025 the dissolution is described.

  a "mass" containing oxides and lead sulfates in an alkaline electrolyte, in the presence of sugar to complex lead; the solution thus obtained is subject to

  electrolysis with insoluble anodes to recover the lead

  Metallic. This process is also rather complicated and expensive

economic point of view.

  U.S. Patent No. 4,018,567 relates to an apparatus rather

  complex for the separation of the various components of the bat-

lead acid.

  To form with the finest particles of the active mass of the battery the dense medium necessary to obtain the floating of lighter components, such as bins and separators, and the deposition at the bottom of metal components, such as the grid terminal bridges , this patent uses

  sodium carbonate solution This patent essentially describes

  a complex device for the hydromechanical separation of the various components involved, but does not give any indications.

  sufficient information on how to make the recovery system

  economically advantageous components, as could be a process which, in addition to a satisfactory recovery of the metal, would at the same time ensure complete recovery.

  and advantageous sulfated components, thereby also avoiding

  environmental damage caused by their dispersion

in the air.

  It can thus be seen that the processes hitherto used for the recovery of metallic lead from its sulphated derivatives pose serious problems, especially with regard to

  the harmful and uneconomic nature of the conditions

treatment.

  The present invention proposes to solve the problems

  my inherent technical processes known in this sector.

  To achieve this goal, it proposes a method of

  sulfated lead compounds, particularly those from spent batteries, characterized in that it comprises the following phases: leaching of said

  sulfated compounds with sodium carbonate in aqueous solution

  is; separation by filtration of the carbonate precipitate

  lead thus formed sodium sulphate remained in solution; re-

  production of lead carbonate as metallic lead; separation

  sodium sulphate by crystallization of the filtered solutions, and recycling of mother liquors from the crystallization

to the leaching stage.

  The invention also relates to an installation for practicing the process defined above, essentially comprising: a reactor for leaching

  said sulphated lead components with sodium carbonate

  than; means for providing the reagents; means for effecting filtration of the solution exiting the reactor; an oven for the thermal reduction of lead carbonate

  to obtain metallic lead; tanks of cris

  filtration to separate sodium sulfate from filtered solutions; and ways to recycle mother waters from the

  crystallisation to said reactor.

  To facilitate the understanding of the characteristics and

  advantages of the invention, hereinafter we give the description

  description of an exemplary embodiment with reference to the attached drawing which represents a schematic diagram of the

process according to the invention.

  As shown in this diagram, a "mass" from depleted batteries containing mainly lead sulphate (11) is charged in a reactor (12), for example a tank equipped with heating and stirring means, which is fed from (13) and (14) with an aqueous solution of Na 2 Co 3 of average concentration The "mass" loaded at (12) is obtained by separating the battery components by any means adequate, for example one of

  those described in U.S. Patents 3,456,886 and 3,614,003.

  In the reactor (12), maintained at a temperature of 30 to 400 ° C. and stirred for approximately 1 hour, the leaching phase takes place with the realization of a double exchange reaction between the reactive salts and the formation of lead carbonate. , in the form of an insoluble precipitate, and of sodium sulphate, extremely soluble in hot water and which, by

  therefore, remains in solution. The reaction is complete, the

  The mixture thus obtained is sent to the filtration phase (15), for example to a filter press, to separate the precipitate from the solution. At the exit of this phase, (16)

  a solid containing the derivatives, mainly lead

  The solid is dried at (17) and sent to the reduction stage in the furnace (18), which is fed with the necessary coal.

(4%) starting from (19).

  Reduction furnace, maintained at about 9000 C during

  1 hour, the crude metal lead is extracted (20).

  filter (21) from the filtering performed in (15)

  This solution is collected in crystallization tanks (22) where, by simple cooling to room temperature, the formation of sodium sulphate crystals decahydrate takes place. This crystallization completed, the mother liquors (23) from (22)

  are recycled to the reactor (12) for subsequent operations.

  The sodium sulphate crystals from the tanks (22) are dewatered by centrifugation at (24), collected in (25) and subjected in (26) to drying in a low air stream.

  temperature, which makes it possible to obtain an anhydrous sodium sulphate

  high purity, ready for use in malting or

  in the glass industry, which does not need other

purification.

  The process described makes it possible to convert the starting sulphated lead compounds into two high quality recovery products, such as crude metal lead and pure anhydrous sodium sulphate, without posing any of the problems indicated previously inherent to the current technique applied in

that sector.

  The almost complete conversion of lead charge into its

  non-sulphated derivatives, mainly Pb CO 3, makes it possible to

  a reduction in the furnace with temperatures and reaction times significantly lower than those of known sulphate (or sulphide) reduction processes without

  require, in addition, the use of fluxes or slagpers.

  Compared with known pyrometallurgical methods, it can be said that the process according to the invention makes it possible to increase

  about 15% the productivity of the reduction furnace, of allon-

  approximately 60% of the refractory life of the oven,

  about 65% of the fumes and slag, 50%

  loss of lead by dispersion in the fumes and

  slag and, finally, about 30% energy consumption.

Getic.

  Especially, the method of the invention, providing for the

  total version of lead sulphate lead derivatives

  before the reduction phase, eliminates, during the latter, the emission of sulfurous gas, which, on the other hand, inevitably occurs with the processes where the reduction is carried out on sulfur-containing lead derivatives.

  departure, not only is it not dispersed in the

  in the form of harmful gases, but is in turn

  verti in a compound of high purity, that is to say in sodium sulphate, the commercial value of which is sufficient

  to cover the cycle costs for the reagent.

  Another considerable advantage of the process of the invention is that the sodium sulfate leaving the cycle, because it

  crystallizes with 10 moles of water for each mole of salt,

  significantly reduces the amount of water involved, which

  promotes the recycling of the mother liquors from the treatment and

  naked considerably any possible water pollution around

of the installation.

  It can therefore be said that the process of the invention allows

  undertakes a recovery of lead contained in sulphated lead-bearing residues with minimal metal losses, an optimal economic return and significantly reducing any risk of environmental pollution.

  The present invention thus provides a "technology for

  pre "for the treatment of all sulphated lead compounds.

  The method described herein may be used not only for "masses" and sludges from spent batteries,

  but also for the treatment of fumes and sulphides

  leaded, after sulfation of the material to be treated

  It is clear that the practical embodiment described above

  above is only one example; in the spirit of the

  According to the invention, many variations, both on the treatment and on the installation intended to achieve it, can be adopted by the expert in this technique, without departing from the essential framework of this patent.

Claims (8)

claims   1. Process for the treatment of sulphated lead compounds to recover the metallic lead and a sulphate of high purity, characterized in that it comprises the following phases: leaching of said sulphated compounds with sodium carbonate in aqueous solution; separation   by filtration of the precipitate of lead carbonate thus formed   sodium sulfate remained in solution; carbon reduction   leaded nate of metallic lead; separation of the sulfate   crystallization of the filtered solutions; and recy   clage of the mother liquors from the crystallization towards the leaching stage. The method of claim 1, wherein said   phase of reduction is carried out thermally, in pre-   coal at a temperature below 1 000 C. 3. Method according to claim 1, wherein said crystallization phase is carried out by cooling   of said solution to obtain sodium sulfate crystals decahydrate.   The method of claim 4, wherein said crystals separated from the mother liquors are subjected to drying.   to obtain anhydrous sodium sulphate for shipment to   ge. 5. Installation to implement the process according to   one of the preceding claims, characterized by the   it essentially comprises: a reactor for ef-   to leach the said sulphated lead compounds   with sodium carbonate; means to provide feedback   tive; means for filtering the solu-   leaving the reactor; an oven for the thermal reduction of lead carbonate to obtain metallic lead; crystallization vessels for separating the sodium sulfate into crystals of the mother liquors from said filtration; and means for recycling mother liquors separated from said crystals to said reactor.   6. Installation according to claim 7, wherein   said filtering means are constituted by a filter-   press. 7. Installation according to claim 7, wherein there is provided a centrifuge for the separation of sulfate   sodic mother waters of crystallization.   8. Installation according to claim 7, wherein there are provided means for drying the sulphate crystals.   hydrated sodium obtained during said crystallization phase tion.