EP0165166B1 - Process for treating complex manganese ores such as marine nodules - Google Patents

Description

The present invention relates to a process for the treatment of complex manganese ores such as the manganiferous modules of the deep seabed.

More specifically, it relates to a process making it possible to extract nickel, copper and cobalt present in manganiferous nodules with good yields and to regulate the quantity of manganese extracted from the treated nodules to the desired value.

Manganese nodules from the deep sea contain significant amounts of manganese and iron, minor amounts of nickel, cobalt and copper, and small amounts of other elements. Nickel, copper and cobalt are high value metals which it is interesting to extract from these nodules with good yields since the known reserves of these metals decrease significantly.

Among these, cobalt is particularly difficult to extract by conventional processes with good yields without simultaneously obtaining significant solubilization of manganese.

Indeed, according to the method described in French patent 2,156,079, a simultaneous solubilization of manganese, nickel, copper and cobalt is obtained by subjecting the nodules to a reduction step with hot sulfur dioxide and to a cold sulfuric acid leaching step.

Similarly, in American patent 3,169,856 which describes a process also comprising two stages, including a first reduction step with cold sulfur dioxide to dissolve manganese, nickel and copper and a second leaching step of the solid phase remaining with an acid to recover the cobalt, it is impossible to regulate the amount of manganese dissolved and to have good cobalt yields.

However, although manganese is a recoverable metal, it is not always desirable to recover all of the manganese present in the treated nodules.

In this spirit, numerous studies propose a selective recovery of nickel and copper, by sulfuric attack at temperatures below 100 ° C. It is specified that in accordance with what has been said previously, cobalt is only little extracted by this process. To overcome this drawback, other studies have been carried out and seem to demonstrate that in a sulfuric environment, attack in an autoclave at high pressure and high temperature (205 ° C) remains the only method of selective solubilization of nickel, copper and cobalt with good yields.

Consequently, among the aims of this invention is that of creating a new improved process for extracting precious metallic values from complex ores or manganese nodules or from any other ore containing for example a matrix of manganese oxide.

Another aim is to create a new improved process for extracting cobalt, which process can also provide recovery of the nickel and copper elements with excellent yields.

Another aim is to create a new process allowing the selective extraction of cobalt, nickel and copper in sulfuric medium with good yields without dissolving the iron.

Another goal is to create a new process for extracting cobalt in sulfuric medium in addition to nickel and copper with good yields, without dissolving the manganese.

Another aim is to create a new process making it possible to extract cobalt, nickel, copper with good yields without dissolving the iron, without dissolving the manganese, without involving attack conditions as severe as a sulfuric attack in an autoclave at 250 ° C.

It has been demonstrated in French Patent No. 2,098,454 that the presence of manganous ions in an ammoniacal leaching solution allows effective dissolution of nickel and copper. It is also mentioned that the presence of manganous ions facilitates the recovery of cobalt and mobybdenum. It is assumed that in an ammoniacal medium, manganese dioxide is reduced by manganous ions.

In another French patent FR-A-2 156 079 which aims at the solubilization of nickel, copper, cobalt and manganese contained in nodules, it is indicated that during a reducing attack of the nodules by SO ₂ , the presence of manganous sulfate has a favorable effect on the yields of nickel, copper and cobalt.

However, in the latter case, there is a reduction in the manganese of the nodules with solubilization of said manganese, which constitutes a drawback, since processes are precisely sought which do not dissolve the manganese.

The present invention relates to a process for the treatment of complex manganese ores such as manganiferous nodules from the deep seabed, which overcomes this drawback.

• a) broyer le minerai,
• b) séparer le minerai broyé en une première partie et une seconde partie,
• c) préparer une première pulpe à partir de la première partie du minerai broyé,
• d) faire réagir la première pulpe avec un agent réducteur pour obtenir une solution de sulfate manganeux,
• e) séparer la phase liquide, constituée par la solution de sulfate manganeux ainsi obtenue, de la phase solide de la première pulpe ainsi traitée,
• f) préparer une seconde pulpe à partir de la seconde partie du minerai broyé,
• g) soumettre la seconde pulpe à un traitement de solubilisation du nickel, du cuivre et du cobalt en la faisant réagir à chaud avec de l'acide sulfurique et la solution de sulfate manganeux obtenue dans l'étape e),
• h) séparer la phase liquide et la phase solide de la seconde pulpe ainsi traitée, et
• i) récupérer le nickel, le cuivre et le cobalt de la phase liquide séparée dans l'étape h).

The process according to the invention for treating a complex manganese ore such as manganese nodules comprises the following steps:

• a) crush the ore,
• b) separating the crushed ore into a first part and a second part,
• c) prepare a first pulp from the first part of the crushed ore,
• d) reacting the first pulp with a reducing agent to obtain a sulfate solution manganese,
• e) separating the liquid phase, consisting of the manganous sulphate solution thus obtained, from the solid phase of the first pulp thus treated,
• f) preparing a second pulp from the second part of the crushed ore,
• g) subjecting the second pulp to a treatment for dissolving nickel, copper and cobalt by reacting it hot with sulfuric acid and the manganous sulphate solution obtained in step e),
• h) separating the liquid phase and the solid phase from the second pulp thus treated, and
• i) recovering the nickel, copper and cobalt from the liquid phase separated in step h).

In the present invention, in the step g) of nickel, copper and cobalt, the manganous ions used in the solution of manganous sulphate obtained in step e) are used in the solubilization of nickel, copper and cobalt, in conditions where these Mn ² ions ⁺ should not be able to act as reducing agent for Mn0 ₂ and where the medium does not contain a reducing agent for manganese dioxide.

It is demonstrated in the invention that the manganous ions, in sulfuric medium, allow the extraction of cobalt with good yields and improve the yields of nickel and copper, under operating conditions where sulfuric acid alone gives poor yields , especially in cobalt. It is assumed that in this case, it is a complex equilibrium involving an oxidation-reduction mechanism between, on the one hand, the cobalt in solution and the manganese of the ore or nodule and, on the other hand , cobalt adsorbed or trapped in the manganese of the ore or nodules and manganese in solution. Adding Mn ²⁺ ions to the sulfuric attack solution makes it possible to enrich this solution and thus to shift the balance in favor of the solubilization of the cobalt.

Likewise, the yields of nickel and copper are favorably influenced, probably thanks to phenomena of ion exchanges existing in the presence of manganous ions.

According to a preferred embodiment of the process of the invention, the second part of the crushed ore is enriched with manganese before subjecting it to the treatment for dissolving nickel, copper and cobalt.

For this purpose, the second part of the ground ore is brought into contact with a manganous sulfate solution in order to fix on this ground ore at least a part of the manganese of this solution and thus to enrich the ground ore in manganese.

Advantageously, the manganous sulfate solution is saturated with HA.

Also, preferably, when several batches of ore are successively treated, the saturated H ₂ S solution obtained at the end of step i) of treatment of the preceding batch is used as the manganous sulphate solution. Thus, when a first batch and a second batch of crushed ore are successively treated, the manganous sulfate solution used to enrich the second part of the crushed ore coming from the second batch of ore with manganese, consists of the solution obtained after recovery. nickel, copper and cobalt at the end of step i) of processing the first batch of ore.

In fact, during step i), the nickel, copper and cobalt are generally separated from the liquid phase by precipitation of the corresponding sulfides by means of H ₂ S and after separation of these precipitates, the end of treatment is obtained. a solution of manganous sulfate saturated with H ₂ S which can be reused for the treatment of the next batch of ore.

This manganous sulphate solution has a manganous sulphate content much lower than that which must be used for carrying out step g). Also, it would have been necessary to concentrate it in order to be able to use it in step g), but the concentration by evaporation is excluded because of the energy cost which it imposes.

According to the invention, another method of recycling the manganous sulfate solution obtained at the end of treatment has been developed. This method implements an oxidation-reduction mechanism allowing the manganous ions to be concentrated in the form of Mn ₂ 0 ₃ by reaction with the manganese dioxide present in the complex manganese ore, then a mechanism of disproportionation of Mn ₂ 0 ₃ into Mn ²⁺ by passage through an acid medium during step g) of treatment for solubilization with sulfuric acid.

Indeed, for pH values of the order of 6 to 7, the manganous ions are oxidized by the manganous oxide Mn0 ₂ of the complex ore or of the nodules to Mn ₂ 0 ₃ according to the following reaction scheme:

Knowing that a manganiferous nodule generally contains 29% of manganese essentially in the state of MnO ₂ , the oxidation of a solution of manganous sulfate at pH 6 to 7 can be considered. However, there is a saturation threshold of the manganese nodule, which is a function of the concentration of manganous ions and of the pulp ratio, that is to say the ratio of the mass of solution to the mass of ground nodules.

During the next step g), of treatment of the second pulp with hot sulfuric acid, part of the manganous ions previously fixed on the nodules is resolubilized by disproportionation of Mn ₂ 0 ₃ into Mn ²⁺ and MnO ₂ . However, the presence of certain ions can totally or partially inhibit this disproportionation reaction and the solubilization yields obtained do not allow not to re-dissolve the total quantity of manganous ions fixed above, whatever the temperature and the quantity of sulfuric acid used in this step.

However, this mode of recycling makes it possible to reuse part of the manganous sulphate evacuated following step i) and to obtain following step h) a solid phase enriched in manganese from which it will be possible to recover the desired amount of manganese.

According to an alternative implementation of the method of the invention, which can be used in the case where the manganous sulphate solution obtained at the end of treatment is not recycled at the stage of production of the second pulp, the second part is subjected ore crushed in a washing step with sulfuric acid at room temperature to remove most of the alkaline elements and alkaline earth elements, the solid phase is separated from the washing liquid phase and said second pulp is prepared for from the solid phase thus separated.

When the manganous sulphate solution is recycled, this preliminary washing step with sulfuric acid is not necessary, since most of the alkaline elements and alkaline earth elements are eliminated during the placing in contact with the crushed ore with the manganous sulphate solution.

According to the invention, step d) of preparing a manganous sulphate solution is carried out by reacting the first pulp with an appropriate mineral or organic reducing agent such as SO ₂ , H ₂ S, carbohydrates and alcohols.

Preferably, this step is carried out by reacting the first pulp with sulfur dioxide.

However, this step can also be carried out by reacting the first pulp with sulfuric acid in the presence of an organic reducing agent consisting, for example, of a carbohydrate such as sucrose, other saccharides such as monosaccharides, oligosaccharides and polysaccharides, an alcohol, a polyalcohol, or even urea.

In this case, the organic reducing agent is used to reduce the manganese from the oxidation state (IV) to the oxidation state (II). Thus, manganese can be solubilized, which requires the consumption of sulfate ions and therefore the consumption of sulfuric acid. As a result, the pH of the pulp increases, and, depending on the quantity of sulfuric acid initially present and the quantity of organic agent added to the pulp, the pH of the solution can be increased until the pH necessary for precipitation, in the form of iron hydroxide, of the solubilized iron from the ore. However, if this increase is significant, precipitation of the dissolved copper from the ore is also obtained.

Also, preferably, quantities of sulfuric acid and organic reducing agent are used such that the precipitation pH of iron is reached (substantially 2) without reaching the precipitation pH of copper (approximately 4 to 5).

To obtain the total precipitation of the iron present in the nodules, a powerful organic reducing agent is preferably used, for example an organic reducing agent having several reducing functions such as saccharides and polyalcohols.

Preferably, sucrose is used.

In this case, the amounts of sucrose generally used are less than 500 kg per tonne of ore or nodules treated and, advantageously 200 to 400 kg per tonne of ore or nodules treated. The amount of sulfuric acid used is preferably from 700 to 850 kg per tonne of ore or nodules treated if it is desired to dissolve nickel, copper, cobalt and manganese with a yield reaching practically 100%; otherwise, smaller amounts can be used. The best results are obtained when 327 kg of sucrose and 750 to 800 kg of sulfuric acid are used per tonne of ore or nodules. It is specified that the solubilization of manganese alone requires 500 to 550 kg of sulfuric acid. There are therefore 200 to 250 kg of acid remaining for the other elements.

When the reducing agent consists of methyl alcohol or ethyl alcohol, advantageously 100 to 700 kg of alcohol are used per tonne of ore treated and 700 to 850 kg of sulfuric acid per tonne of ore treaty.

At the end of this step, a manganous sulphate solution also containing nickel, copper and cobalt present in the treated ore is obtained. This solution can be used directly for step g) which consists in subjecting the second pulp to a treatment for dissolving nickel, copper and cobalt by reaction with sulfuric acid.

Other characteristics and advantages of the invention will appear better on reading the description which follows given of course by way of illustration and not limitation with reference to the appended drawing which is a diagram illustrating the implementation of the method of the invention for the treatment of manganese nodules.

As shown in this diagram, we begin by grinding (in 1) the manganiferous nodules to an appropriate particle size, for example of 750 wm. It should be noted that this grain size is not critical, since the process applies to both smaller particle sizes and higher particle sizes, the variations in particle size not having a predominant influence on the extraction yield of the metals. After grinding, the nodules are separated into two parts, a first part (at 3) which will be subjected to attack by SO ₂ to dissolve the manganese and a second part (at 5) which will be subjected to the nickel solubilization treatment, copper and cobalt with H ₂ SO ₄ . Since the grinding is carried out in an aqueous medium, the first part is in the form of pulp and the pulp ratio is adjusted to the desired value by addition of water.

The pulp ratio is defined by the ratio of the mass of freshwater or seawater to the mass of ground nodules, and it should be such that the pulp behaves like a fluid, but preferably as low as possible so as to process minimum volumes of pulp.

Generally, for this first pulp, a pulp ratio ranging from 2 to 5 is used.

The first pulp is then reacted with sulfur dioxide (in 9) to obtain a manganous sulfate solution, which also leads to the solubilization of the nickel, copper and cobalt present in this first pulp. This reaction is carried out at room temperature by injecting the desired quantity of sulfur dioxide into the pulp, for example by bubbling, while maintaining regular agitation of the pulp. The quantity of sulfur dioxide injected is calculated by taking into account the stoichiometry of the reaction for the sulphation of manganese dioxide by sulfur dioxide so as to dissolve practically all of the manganese. Generally, a yield of 95% is obtained. The solid phase is then separated (at 11) from the liquid phase, the solid phase is subjected to washing (at 13) by recycling (at 24) the washing water in the reduction step with SO _z ; the residual solid phase which constitutes the waste rock is rejected (in 15); it generally contains around 5% of the manganese present in the nodules of the first pulp.

The second part 5 of the ground nodules which is also in the form of pulp, constitutes the second pulp. It is firstly enriched with manganese in a three-stage installation 6 in which it is brought into countercurrent contact with a manganous sulfate solution saturated with H ₂ S arriving at 8. During this treatment, the solution aqueous depletes in manganese and enriches in alkaline and alkaline earth elements from the ground nodules. This solution is removed at 10. Following this treatment, the second pulp of ground nodules is subjected to the treatment for dissolving nickel, copper and cobalt carried out in the autoclave 17.

As in the case of treatment with SO ₂ , the pulp ratio must be such that the pulp behaves like a fluid, but preferably as low as possible, so as to treat minimum volumes of pulp. However, too low a pulp ratio limits the copper extraction yield. Generally, a pulp ratio ranging from 2 to 5 is used, and preferably a pulp ratio equal to 2 or 3.

The solubilization treatment of nickel, copper and cobalt is then carried out by reacting (at 17) this second pulp with sulfuric acid and the manganous sulphate solution from 11 obtained by treatment of the first pulp with SO ₂ .

The amounts of manganese sulfate used for this reaction can vary over a wide range. However, above a certain threshold, the use of larger amounts does not improve the results obtained with regard to the extraction of cobalt.

Generally, the quantity of manganous sulphate present in solution during this treatment is from 50 to 400 kg per tonne of crushed ore, and preferably from 50 to 250 kg per tonne of crushed ore. The amount of H ₂ SO ₄ is generally 150 to 500 kg per tonne of crushed ore, and preferably 300 to 500 kg per tonne of crushed ore. It can optionally be introduced so as to continuously maintain a low acid pH, since this is favorable to the non-solubilization of iron.

Preferably, the hot solubilization treatment is carried out in an autoclave at medium or high pressure, for example under a pressure of 7 to 40 bars, and it is carried out at temperatures of 100 to 250 ° C., preferably from 150 to 200 ° C, and better still 180 ° C. Generally, the autoclave is preheated to 100 ° C. with live steam, then the whole is heated to the desired final temperature with live steam so as to reach the pulp ratio favorable for good attack. This temperature is then maintained for the desired duration which is generally from 1 to 8 h, which makes it possible to obtain a satisfactory solubilization of the nickel, copper and cobalt. The second pulp leaving the autoclave is then subjected to a separation (in 19) in order to obtain (in 21) a liquid phase containing mainly nickel, copper and cobalt. The solid phase is then subjected to washing with water (at 22), the washing water being able to be recycled (at 23) completely or partly in the autoclave for the treatment of solubilization of copper, nickel and cobalt with sulfuric acid. The washed solid phase 24 is then rejected in the form of waste rock which constitutes the manganiferous residues having a higher manganese content than the starting ore. From the separate liquid phase (at 21), nickel, copper and cobalt can be recovered by various treatments. Generally, this is achieved by precipitation of the corresponding sulfides at 25. First, a precipitation of the copper sulfide CuS is carried out using H ₂ S, then the pH of the residual solution is adjusted using calcium carbonate to then precipitate the nickel and cobalt sulphides by the action of H ₂ S. After the separation of the precipitates, the solution obtained which contains manganous sulphate is recycied (at 8) at the stage of preparation of the second pulp.

For the implementation of the process of the invention, the quantities of crushed nodules distributed respectively in the first part and the second part of the crushed ore are chosen so as to have the desired quantity of manganous sulfate for the solubilization treatment stage. nickel, copper and cobalt performed on the second pulp. This quantity, which is generally 50 to 250 kg of manganous sulphate in solution per tonne of crushed ore, is provided, on the one hand, by the solution for treating the first pulp with SO ₂ , and by the manganous ions which iron in sulfuric solution and which come from the manganese enrichment of the ore used to prepare the second pulp.

To obtain the desired quantity of manganous sulphate, the ore is generally divided into a first part which represents 10 to 15% by weight of the treated ore, the second part representing from 85 to 90% of the treated ore.

In the embodiment given in the figure, a tonne of ground nodules is treated, distributed as follows: 121 kg for the first part of nodules and 879 kg for the second part, which corresponds to manganese contents of 35 , 1 kg for the first part and 255 kg for the second part. During the treatment of the first pulp with SO ₂ , the yield is 95% and 33.3 kg of manganese go into solution. For the preparation of the second pulp, the enrichment of the ore with the recycled manganous sulphate solution leads to a manganese content of 309 kg. During the solubilization treatment with sulfuric acid, 7% of the manganese fixed on the ore of the second pulp passes back into solution and the solubilization treatment is thus carried out with H ₂ SO ₄ using 55 kg of manganese, or 150 kg of manganous sulfate.

Following this step, the solid phase recovered (at 24) has a manganese content of 35%, which corresponds to 288.3 kg of manganese.

The desired amount of manganese can be recovered from this solid phase, in the form of ferro or silicomanganese, by direct conventional pyrometallurgical treatments, after a pelletizing step.

It is also possible to envisage manufacturing pure metallic manganese or pure MnO ₂ by passing through a solubilization, for example by subjecting to a reduction part or all of the solid phase recovered.

For this purpose, a pulp can be prepared from the solid phase and subjected to reduction by an appropriate reducing agent such as SO ₂ , H ₂ S, a carbohydrate or an alcohol.

In particular, this pulp can be reacted with sulfuric acid in the presence of an organic reducing agent such as a carbohydrate or an alcohol.

The following examples are given without implied limitation to illustrate the process of the invention.

Example 1

This example illustrates the fixation of the manganese present in a solution of manganous sulphate on ground nodules.

In this example, the ground nodules are brought into contact with the MnSO ₄ solution against the current to obtain self-regulation of the pH by the basicity of the nodule. Indeed, the oxidation of the nodules by Mn ²⁺ releases an acidity equivalent to the quantity of sulfuric acid necessary for the neutralization of the alkali and alkaline earth metals present in the nodules.

In addition, the fact of operating against the current makes it possible to obtain maximum manganese purification from the solution and maximum manganese enrichment of the nodule.

This countercurrent contacting is carried out in three stages with a manganous sulphate solution containing 25 g ^-1 of manganese, a pulp ratio equal to 3 and a residence time of one hour in each stage. The results obtained are given in table 1 appended.

Under these conditions, the manganese fixing yield is 71%. The manganese nodule content is then 32.6% and the Mn concentration of the outgoing solution is 7 gl ^-1 .

However, if one operates with a manganous sulfate solution containing 25 gl ¹ of manganese saturated in HS as is the case of the solution recovered at the end of the treatment of the nodules, after the precipitation with H ₂ S, the yield fixation is 84%. The manganese content of the nodule is then 33.2% and the manganese concentration of the outgoing solution is 5.5 g.1- ¹ .

If an installation comprising four stages with a pulp ratio of 3 and a manganese content of the manganous sulphate solution of 25 g / l ^-1 or 15 gl ¹ saturated with H ₂ S is used under the same conditions can obtain a fixing yield of manganese which varies from 82 to 96%.

Example 2

In this example, the disproportionation yield of manganese fixed on the nodules is studied, during the reaction with sulfuric acid, in an autoclave, at different temperatures, for 2 h, using different quantities of sulfuric acid and a ratio of pulp equal to 2.

The results obtained and the reaction conditions are given in the attached Table 2.

In view of this table, it can be seen that the temperature and the sulfuric acid content of the solution have practically no effect on the solubilization yield and that in all cases it is not possible to resolubilize all of the manganous ions attached to the nodules. .

Examples 3 to 26

In these examples, different treatment conditions were used to carry out step g) of dissolving the nickel, copper and cobalt on the second pulp.

In all cases, the manganous sulphate introduced into the autoclave was partly produced by reduction of the first pulp by means of SO ₂ and for the other part by re-solution in the autoclave of the fraction of manganese carried by the nodules enriched with manganese of the second pulp.

After the solubilization reaction, the solid phase and the liquid phase are separated by decantation from the pulp and the nickel, iron, copper, cobalt and manganese contents of the liquid phase are determined. The results obtained are given in table 3 attached. In this table, the figures in brackets represent the results obtained under the same conditions, but in the absence of manganous sulfate. In view of these results, it can be seen that the presence of manganous sulphate makes it possible to significantly improve the extraction yield of cobalt, and that it also plays on the extraction yields of iron, nickel and copper.

Example 27

This example illustrates the carrying out of step d) of preparation of a manganous sulfate solution by treatment of the ground ore with sulfuric acid in the presence of sucrose.

After having ground a ton of nodules to a particle size of the order of 750 _w m, they are mixed with fresh water to form a pulp having a pulp ratio (mass of fresh water / mass of ground nodules) equal to 4. To this pulp is added 750 kg of sulfuric acid and 327 kg of sucrose, then the pulp is subjected to stirring. After two hours, the solid phase is separated from the liquid phase and the amounts of manganese, iron, nickel and cobalt present in the liquid phase are determined.

• - rendement d'extraction en Mn : 90 %,
• - rendement d'extraction en Fe : 3 %,
• - rendement d'extraction en Ni : 92 %,
• - rendement d'extraction en Cu : 90 %,
• - rendement d'extraction en Co : 80 %.

(Voir tableaux pages suivantes)

The results obtained are as follows:

• - Mn extraction yield: 90%,
• - Fe extraction yield: 3%,
• - Ni extraction yield: 92%,
• - Cu extraction yield: 90%,
• - Co extraction yield: 80%.

(See tables on the following pages)

Claims (15)

1. Process for the treatment of a complex manganese ore, characterized in that it comprises the following stages :

a) crushing the ore,

b) subdividing the crushed ore into a first part and a second part,

c) preparing the first pulp from the first part of the crushed ore,

d) reacting the first pulp with a reducing agent to obtain a manganous sulphate solution.

e) separating the liquid phase constituted by the thus obtained manganous sulphate solution from the solid phase of the thus treated first pulp,

f) preparing the second pulp from the second part of the crushed ore,

g) subjecting the second pulp to a solubilization treatment of the nickel, copper and cobalt by reacting it hot with sulphuric acid and the manganous sulphate solution obtained in stage e),

h) separating the liquid phase and the solid phase of the thus treated second pulp, and

i) recovering the nickel, copper and cobalt from the liquid phase separated in stage h).

2. Process according to claim 1, characterized in that the second part of the crushed ore is contacted with a manganous sulphate solution in order to fix to said crushed ore at least part of the manganese of said solution, so as to bring about a manganese enrichment of the crushed ore.

3. Process according to claim 1, characterized in that in stage i), the nickel, copper and cobalt are recovered by precipitating the corresponding sulphides by means of H₂S.

4. Process according to either of the claims 2 and 3, characterized in that there is a successive treatment of a first batch and a second batch of crushed ore and wherein the manganous sulphate solution used for the manganese enrichment of the second part of the crushed ore from the second ore batch is constituted by the solution obtained, following the recovery of the nickel, copper and cobalt, at the end of treatment stage i) of the first ore batch.

5. Process according to claim 1, characterized in that the second part of the crushed ore undergoes a washing stage using sulphuric acid at ambient temperature, in order to eliminate most of the alkaline and earth alkaline elements, that the solid phase is separated from the liquid washing phase and that the second pulp is prepared from the thus separated solid phase.

6. Process according to any one of the claims 1 to 5, characterized in that the manganous sulphate quantities present in solution in stage g) is 50 to 250 kg of MnS0₄ per tonne of ore subjected to solubilization treatment.

7. Process according to any one of the claims 1 to 6, characterized in that the solubilization treatment of stage g) is performed at a temperature between 150 and 200 °C.

8. Process according to any one of the claims 1 to 7, characterized in that the sulphuric acid quantity used in stage g) is 300 to 500 kg of sulphuric acid per tonne of ore subjected to the solubilization treatment.

9. Process according to any one of the claims 1 to 8, characterized in that the first part of the crushed ore represents 10 to 15 % by weight of the treated ore.

10. Process according to any one of the claims 1 to 9, characterized in that the reducing agent used in stage d) is sulphurous anhydride.

11. Process according to any one of the claims 1 to 9, characterized in that in stage d), the first pulse is reacted with sulphuric acid in the presence of an organic reducing agent.

12. Process according to claim 11, characterized in that the organic reducing agent is a carbohydrate or an alcohol.

13. Process according to claim 12, characterized in that the carbohydrate is saccharose.

14. Process according to claim 13, characterized in that the saccharose quantity used is 200 to 400 kg/tonne of ore subjected to the treatment.

15. Process according to any one of the claims 11 to 14, characterized in that the sulphuric acid quantity used is 700 to 850 kg/tonne of ore subjected to the treatment.

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