Half-batch method for oxidative leaching of nickel and cobalt

Abstract

The present invention provides a semi-batch method for preparing nickel sulfate or cobalt sulfate solutions, wherein sulfuric acid and hydrogen peroxide are periodically supplied to a reaction zone via a supply section, thereby circulating an acidic aqueous medium through the reactor until a predetermined concentration of nickel or cobalt is achieved in the nickel sulfate or cobalt sulfate solution, respectively.

Description

Technical Field

[0001] The present invention relates to a process for producing nickel sulfate and cobalt sulfate.

Background Art

[0002] Prior Art Secondary lithium-ion batteries (LIBs) have found extensive use in portable devices, electric vehicles, and special aviation applications. Important characteristics of reusable batteries include charge / discharge efficiency, cycle durability, energy density, and safety. Many developments have focused on improving the performance of the LIB cathode.

[0003] Lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate, lithium nickel manganese cobalt oxide ( "NMC", LiNi x Mn y Co z O2), and lithium nickel cobalt aluminum oxide ( "NCA", LiNi x Co y Al z O2) have received much attention due to their excellent performance. These can be easily obtained by mixing a suitable mixed metal precursor with a suitable lithium compound and then performing a heat treatment on the mixture. Further processing steps are widely reported for, for example, doping with additional elements, providing a surface coating, improving the crystallite size, etc.

[0004] The increasing demand for electric vehicles (EVs) has led to an increased demand for high-purity nickel and cobalt, particularly high-purity nickel sulfate and high-purity cobalt sulfate. In fact, nickel purification for preparing high-purity nickel is extremely important for the supply of battery materials in the next decade.

[0005] Such nickel refining needs to enable high-capacity and high-efficiency processes to obtain the desired nickel sulfate in the desired quantity and purity. Therefore, it is necessary to develop and optimize novel processes. Among other processes, oxidative leaching of nickel (Ni) from high-purity nickel metal is considered one of the more promising pathways.

[0006] The process for leaching Ni metal into sulfuric acid in the presence of hydrogen peroxide proceeds according to the reaction.

[0007] [ka]

[0008] This process is a highly exothermic (-423 kJ / mol) process, also known as the oxidative leaching of Ni metal. Similarly, the process for the leaching of Co metal in sulfuric acid in the presence of hydrogen peroxide proceeds according to the reaction.

[0009] [ka]

[0010] Similarly, it generates a lot of heat.

[0011] International Patent Publication No. 2021 / 105365 describes a method for producing nickel sulfate by leaching nickel-containing metal particles into an aqueous solution of nickel sulfate, the method comprising the steps of introducing metal particles into an aqueous solution of sulfuric acid and introducing an aqueous solution of hydrogen peroxide into the aqueous solution of sulfuric acid containing the metal particles, wherein the aqueous solution of hydrogen peroxide is introduced gradually into the aqueous solution of sulfuric acid containing the metal particles.

[0012] However, the novel method needs to address ease of operation, high throughput, optimization of reactant usage, and reduction of hydrogen peroxide consumption and H2 formation.

[0013] Japanese Patent Publication No. 2011-126757 describes a method for producing an aqueous nickel solution in a low-content free sulfuric acid. The method includes packing a metal dissolution column with a mass of metallic nickel, supplying heated sulfuric acid from the upper part of the metal dissolution column, and simultaneously supplying air or oxygen from the lower part of the metal dissolution column.

[0014] However, such batch methods may result in the contamination of the resulting process output with unreacted metal particles, and the equipment must withstand harsh chemical reaction conditions because a high initial H2SO4 acid concentration is required.

[0015] International Publication No. 2022 / 053448 describes a method for preparing battery-grade metal sulfate solutions. Battery-grade metal sulfate solutions are prepared directly from electrolytically produced metal objects, such as cathode plates, which are subjected to a continuous process at high temperature in a column with vigorous mixing into an aqueous leaching solution containing at least one acid leaching agent and a liquid oxidizing agent. However, such continuous processes typically operate at low acid content, as only low residual acid content is acceptable in the product flow. This limits the leaching rate and overall production capacity. Furthermore, such continuous processes are inflexible to changes in the reactivity or composition of the reagents and pose a risk of H2 formation when loading metal feedstocks into the column during operation. [Overview of the Initiative] [Problems that the invention aims to solve]

[0016] Therefore, an object of the present invention is to provide a new discontinuous method for preparing a metal sulfate solution with high productivity under safe conditions. The present invention provides a solution to at least one of the above problems by providing a method for oxidative leaching of each of nickel or cobalt in the presence of the acid and an oxidizing agent according to claim 1. Since the method and system of the present invention can be applied to oxidative leaching of nickel and oxidative leaching of cobalt, the method and system are described for both nickel and cobalt. When referring to nickel or cobalt in the following description, it should be understood that those skilled in the art will know from the context of the description whether nickel or cobalt is indicated.

[0017] The process is carried out at a controlled temperature and at a controlled injection rate of hydrogen peroxide (H2O2) and sulfuric acid (H2SO4).

[0018] The inventors have found that under such conditions, the conversion rate of nickel to nickel sulfate (NiSO4) and cobalt to cobalt sulfate (CoSO4) is optimized, and the formation of H2 is very limited. This optimizes process control and improves process safety.

[0019] The inventors have further found that the use of a column reactor helps to increase the batch size compared to a stirred tank. Furthermore, recirculation helps to maintain the heat balance at the start of a new cycle and throughout the process.

[0020] The inventors have further observed that no cooling and heating peaks occur throughout the process of the present invention.

[0021] The process of the present invention is schematically shown in FIG. 1.

Means for Solving the Problems

[0022] In a first aspect, the present invention provides a semi-batch process for the preparation of nickel sulfate or cobalt sulfate solutions within a column reactor (100) comprising a reaction zone (10), said process comprising the following steps: i. Supplying metal particles each containing nickel or cobalt to the reaction zone (10) of the column reactor (100); ii. Supplying an aqueous medium to the reaction zone (10); iii. Supplying sulfuric acid and hydrogen peroxide to the reaction zone (10) via a feed section, thereby contacting hydrogen peroxide with the metal particles containing nickel or cobalt in an acidic aqueous medium; iv. Simultaneously with step iii., circulating the acidic aqueous medium by discharging a fraction of the acidic aqueous medium from the column reactor (100) and recycling the discharged fraction back to the column reactor (100) until a concentration of at least 80 g / L of nickel or cobalt and a residual acid concentration of less than 20 g / L are achieved in each of the nickel sulfate or cobalt sulfate solutions; v. After step iv., discharging the nickel sulfate or cobalt sulfate solution from the column reactor (100). In this semi-batch process, during step iii., sulfuric acid and hydrogen peroxide reagents are added periodically or continuously, but when the desired batch volume, nickel or cobalt concentration, and residual acid concentration are reached, the process is interrupted to discharge the nickel sulfate and cobalt sulfate solutions.

[0023] The inventors have found that very high acidic conditions, such as those used in batch processes where all of the sulfuric acid is already present in the starting solution, are preferably avoided for reasons of avoiding severe conditions for the process equipment and for safety reasons in case of leaks or outflows.

[0024] In a preferred embodiment according to a first aspect of the present invention, the supply of sulfuric acid and hydrogen peroxide in step iii is as follows: a) A step of supplying sulfuric acid and hydrogen peroxide in a molar ratio of sulfuric acid to hydrogen peroxide of 0.9:1.0 to 1.1:1.0, b) The step of supplying hydrogen peroxide to further reduce the residual acid concentration of the nickel sulfate or cobalt sulfate solution.

[0025] The inventors have found that a semi-batch method using this sulfuric acid and hydrogen peroxide input strategy, combined with low residual acid content in the product solution, high hydrogen peroxide efficiency, and simple temperature control, enables rapid leaching at relatively high acid concentrations.

[0026] In another embodiment, the nickel concentration in the nickel sulfate product solution is 80 to 200 g Ni / L, preferably 90 to 175 g Ni / L, and more typically 100 to 150 g Ni / L.

[0027] In another embodiment, the cobalt concentration in the cobalt sulfate product solution is 80 to 200 gCo / L, preferably 90 to 175 gCo / L, and more preferably 100 to 150 gCo / L.

[0028] Another aspect of the present invention is a system for producing nickel sulfate or cobalt sulfate, • One or more reactors (100), preferably column reactors (100), are used to operate a process for preparing nickel sulfate or cobalt sulfate solutions, respectively, according to the present invention. The system comprises one or more buffer tanks, each configured to receive nickel sulfate or cobalt sulfate from the reactor (100).

[0029] Further guidance includes accompanying diagrams to better understand the teachings of the present invention.

[0030] The aforementioned figures are intended to aid in the explanation of the present invention and are not intended to be limitations of the inventions of this disclosure.

[0031] The figures and symbols contained herein have meanings that are generally understood by those skilled in the art in which this invention pertains. [Brief explanation of the drawing]

[0032] [Figure 1] Figure 1 schematically shows the process according to the present invention in a circulating reactor (100). [Figure 2] Figure 2 shows a cross-section of the circulating reactor (100) according to the present invention. [Figure 3] Figure 3 schematically shows the process according to Examples 4 and 5 of the present invention. [Modes for carrying out the invention]

[0033] Unless otherwise defined, all terms used to disclose this invention, including technical and scientific terms, have the meanings that are generally understood by one of the ordinary skills of the art to which this invention belongs.

[0034] Further guidance includes definitions of terms to better understand the teachings of the present invention. As used herein, the following terms have the following meanings:

[0035] As used herein, “A,” “an,” and “the” refer to both singular and plural references unless the context explicitly indicates otherwise. For example, “a compartment” refers to one or more compartments.

[0036] As used herein, “about” when referring to measurable values ​​such as parameters, quantities, and temporal durations means that such variation includes variation of + / -20%, preferably + / -10%, more preferably + / -5%, even more preferably + / -1%, and even more preferably + / -0.1% from a particular value, insofar as such variation is appropriate for carrying out the disclosed invention. However, it should be understood that the values ​​referred to by the modifier “about” are themselves specifically disclosed.

[0037] As used herein, “comprise,” “comprising,” and “comprises,” as well as “comprised,” are synonymous with “include,” “including,” “includes,” or “contain,” “containing,” and “contains,” and are comprehensive or open-ended terms that identify the presence of, for example, components, and do not exclude or preclude the presence of additional, unlisted components, features, elements, members, or steps that are publicly known in the art or disclosed in the art.

[0038] The enumeration of numerical ranges by endpoint includes all numbers and fractions contained within that range, as well as the enumerated endpoints.

[0039] All percentages should be understood as percentages by weight, unless otherwise defined or unless a different meaning is evident to those skilled in the art from their use, and in the context in which they are used, whether abbreviated as “percent by weight” or “percent by volume.”

[0040] In a first aspect, the present invention provides a half-batch method for preparing a nickel sulfate or cobalt sulfate solution in a column reactor (100) including a reaction zone (10), the method comprising the following steps: i. A step of supplying metal particles containing nickel or cobalt, respectively, to the reaction zone (10) of the column reactor (100), ii. A step of supplying an aqueous medium to the reaction zone (10), iii. The step of supplying sulfuric acid and hydrogen peroxide to the reaction zone (10) via the supply section, thereby bringing the hydrogen peroxide into contact with the metal particles containing nickel or cobalt in an acidic aqueous medium, iv. Simultaneously with step iii, the acidic aqueous medium is circulated by discharging the fraction of the acidic aqueous medium from the column reactor (100), and by recirculating the discharged fraction back into the column reactor (100) in the nickel sulfate or cobalt sulfate solution until a nickel concentration of at least 80 g / L or cobalt and a residual acid concentration of less than 20 g / L are achieved, respectively. v. The process includes the step of discharging the nickel sulfate or cobalt sulfate solution from the column reactor (100) after step iv.

[0041] In this semi-batch method, reagent sulfuric acid and hydrogen peroxide are added periodically or continuously during step iii., but the process is interrupted to drain the nickel sulfate and cobalt sulfate solution when the desired batch volume, nickel or cobalt concentration, and residual acid concentration are reached.

[0042] The inventors have found that extremely high acidic conditions, such as those used in batch methods where all sulfuric acid is already present in the starting solution, are preferably avoided for reasons of avoiding harsh conditions on the process equipment and for safety reasons in case of leakage or spillage. Furthermore, it has been found that high concentrations of acid result in a fast leaching reaction, but also result in the generation of a relatively large amount of heat, which is more difficult to control. Moreover, as a result of higher acid concentrations, higher leaching dynamics lead to higher temperatures, which may accelerate the decomposition of hydrogen peroxide. Therefore, the inventors have devised a method according to a first embodiment, by which a substantially continuous supply of hydrogen peroxide is provided to the reaction zone, while sulfuric acid is periodically supplied to the reaction zone, thereby allowing sulfuric acid to be consumed in the oxidative leaching of the metal before a new supply of sulfuric acid is introduced to the reaction zone.

[0043] The aqueous medium in step ii may be water, preferably demineralized water, or most preferably a diluted sulfuric acid solution. Using nickel sulfate or cobalt sulfate solution allows for a lower process volume, the use of a smaller reactor, or higher nickel or cobalt concentrations. In a preferred embodiment, the aqueous medium is circulated through the reactor zone in step ii.

[0044] In a preferred embodiment according to a first aspect of the present invention, the supply of sulfuric acid and hydrogen peroxide in step iii is performed in the following steps: a. A step of supplying sulfuric acid and hydrogen peroxide in a molar ratio of sulfuric acid to hydrogen peroxide of approximately 0.9:1.0 to 1.1:1.0, preferably 0.95:1.0 to 1.05:1.0, more preferably 0.97:1.0 to 1.03:1.0, and most preferably about 1:1. b. The step of supplying hydrogen peroxide to further reduce the residual acid concentration of the nickel sulfate or cobalt sulfate solution.

[0045] In step a, sulfuric acid and hydrogen peroxide may be supplied periodically or continuously. Preferably, in step a, sulfuric acid and hydrogen peroxide are supplied at a constant rate. The total amount of sulfuric acid required is calculated in advance based on the batch volume, desired metal content, and residual acid content. In step b, when the desired volume and metal content are reached in the nickel or cobalt solution, only hydrogen peroxide is supplied. In step b, hydrogen peroxide may be supplied periodically or continuously.

[0046] Preferably, in step b, hydrogen peroxide is supplied at a constant supply rate. In a preferred embodiment, the constant supply rate of hydrogen peroxide in step b is lower than that in step a, more preferably the supply rate of hydrogen peroxide in step b is 10-60%, even more preferably 20-50%, and most preferably 20-30% of the supply rate of hydrogen peroxide in step a.

[0047] We found that a semi-batch method using this sulfuric acid and hydrogen peroxide input strategy, combined with low residual acid levels in the product solution, high hydrogen peroxide efficiency, and simple temperature control, enables rapid leaching at relatively high acid concentrations compared to the corresponding continuous method.

[0048] In a preferred embodiment according to the first aspect of the present invention, in step iii.a, the sulfuric acid content of the acidic aqueous medium entering the lower part of the reaction zone (10) is 10 to 60 g / L, preferably 15 to 60 g / L, preferably 20 g / L to 55 g / L, more preferably 30 g / L to 50 g / L, and more preferably about 40 g / L.

[0049] Preferably, the present invention relates to a method according to a first aspect of the present invention, wherein in step iii.a, during the circulation of an aqueous sulfuric acid solution as described in step iv, the reaction zone has a sulfuric acid solution at its top having a concentration of 10 g / L to 30 g / L, preferably 15 g / L to 25 g / L.

[0050] In a preferred embodiment according to the first aspect of the present invention, in step iii.a, the hydrogen peroxide content of the acidic aqueous medium entering the lower part of the reaction zone (10) is 3 to 15 g / L, preferably 5 to 10 g / L, and more preferably 7.5 to 9 g / L.

[0051] In a preferred embodiment according to the first aspect of the present invention, in step iii.b, the hydrogen peroxide content of the acidic aqueous medium entering the lower part of the reaction zone (10) is 0.5 to 10 g / L, preferably 1 to 5 g / L, and more preferably 1.5 to 4 g / L.

[0052] In a preferred embodiment, the entire volume of the aqueous medium or acidic aqueous medium is circulated in countercurrent mode in steps ii., iii., and iv., thereby pre-loading nickel or cobalt into the reactor from the top, thereby supplying the aqueous medium or acidic aqueous medium to the bottom of the reactor.

[0053] In a preferred embodiment, the cumulative H2O2 efficiency for the whole-half-batch method is at least 80%, more preferably at least 85%, most preferably at least 92%, and most preferably at least 97%, thereby the cumulative hydrogen peroxide efficiency is determined as the total moles of nickel or cobalt consumed per total moles of hydrogen peroxide added during the whole-batch process.

[0054] By operating a half-batch method to obtain the amount of residual sulfuric acid in the target solution, it is ensured that all peroxides are completely consumed.

[0055] In a preferred embodiment according to the first aspect of the present invention, the residual amount of sulfuric acid in the nickel sulfate or cobalt sulfate solution discharged in step v. is 1 g / L to 20 g / L, preferably 2 g / L to 15 g / L, and more preferably 2 g / L to 10 g / L.

[0056] In preferred embodiments, the present invention provides a method according to a first aspect of the present invention, wherein the concentration of nickel or cobalt in the nickel sulfate or cobalt sulfate solution is 80 g / L to 200 g / L, preferably 90 g / L to 175 g / L, and more preferably 100 g / L to 150 g / L, respectively. Furthermore, it may be desirable to dilute the target solution to obtain a predetermined concentration of the metal in the target solution. Such methods are advantageous in that they allow processing in large-capacity reactors.

[0057] Furthermore, it is desirable that hydrogen peroxide remains present in the nickel sulfate or cobalt sulfate product. Therefore, any residual hydrogen peroxide after step iii can be removed by heating and / or circulation of the nickel sulfate or cobalt sulfate solution.

[0058] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein, after step iii. is completed, the circulation of step iv. is continued until the hydrogen peroxide in the nickel sulfate or cobalt sulfate solution is substantially depleted. Preferably, the circulation is continued until the hydrogen peroxide concentration is less than 1 g / L, more preferably less than 0.1 g / L, and most preferably about 0 g / L.

[0059] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein the molar ratio of the total amount of hydrogen peroxide supplied in step iii. to the total amount of sulfuric acid supplied in steps ii. and iii. is greater than 0.9 and less than 1.1, preferably greater than 0.95 and less than 1.05, and most preferably 0.95 to 0.99.

[0060] In a preferred embodiment, according to a first aspect of the present invention, the half-batch method is interrupted and the nickel sulfate or cobalt sulfate solution is discharged before the nickel or cobalt-containing particles have completely reacted with the sulfuric acid and hydrogen peroxide. Preferably, when the half-batch method is interrupted and the nickel sulfate or cobalt sulfate solution is discharged, at least 1% by weight, more preferably at least 2% by weight, at least 5% by weight, at least 10% by weight, or at least 15% by weight, and even more preferably at least 20% by weight, of the initial amount of nickel or cobalt-containing particles introduced into the reactor has not reacted with the sulfuric acid and hydrogen peroxide. More preferably, when the half-batch method is interrupted and the nickel sulfate or cobalt sulfate solution is discharged, at least 25% by weight, more preferably at least 30% by weight, 40% by weight, 50% by weight, or even 60% by weight, of the initial amount of nickel or cobalt-containing particles introduced into the reactor has not reacted with the sulfuric acid and hydrogen peroxide. This is important because the inventors have found that the leaching dynamics are more favorable, in particular when it is permissible for a certain amount of starting material to remain in the reactor. In a particularly preferred embodiment, when the half-batch method is interrupted and the nickel sulfate or cobalt sulfate solution is discharged, at least 80% by weight, more preferably at least 90% by weight, 92% by weight, 94% by weight, or even 96% by weight of the initial amount of nickel or cobalt-containing particles introduced into the reactor have not reacted with sulfuric acid and hydrogen peroxide.

[0061] The aqueous medium is supplied to the reaction section (10) of the reactor (100) in step ii., before it is leached with peroxide in step iii. The aqueous medium is preferably water, preferably demineralized water, and most preferably a diluted sulfuric acid solution.

[0062] In a preferred embodiment according to a first aspect of the present invention, the aqueous medium supplied in step ii contains sulfuric acid at a concentration of 0 to 30 g / L, preferably 5 to 30 g / L, more preferably 10 to 20 g / L, and most preferably about 15 g / L. Supplying a diluted sulfuric acid solution in step ii ensures sufficient reactivity when leaching with hydrogen peroxide is initiated in step iii, thereby promoting a gradual temperature increase during startup.

[0063] In a preferred embodiment according to the first aspect of the present invention, the aqueous medium supplied in step ii contains sulfuric acid at a concentration of 0 to 30 g / L, preferably 5 to 30 g / L, more preferably 10 to 20 g / L, and most preferably about 15 g / L.

[0064] Preferably, the aqueous medium is preheated before use in step ii. Preferably, the reaction heat of the aforementioned half-batch reaction is used to preheat the aqueous medium.

[0065] Preferably, in step ii, the aqueous medium is supplied to the reaction zone at a temperature of 50°C to 80°C, preferably 70°C to 80°C, and more preferably 75°C to 80°C.

[0066] Preferably, in steps ii., iii., and iv., the aqueous medium entering the reaction zone (10) has a temperature of 50°C to 80°C, preferably 70°C to 80°C, and more preferably 75°C to 80°C.

[0067] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein the reaction temperature at the top of the reaction zone (10) is 80°C to the boiling point of the leaching solution, preferably 85°C to 99°C, and more preferably 92°C to 99°C.

[0068] The term "leaching solution" refers to an aqueous solution containing sulfuric acid and hydrogen peroxide in the reaction zone (10) of the circulating reactor (100).

[0069] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, thereby generating nickel or cobalt-containing metal particles electrolytically, preferably cut cathodes. The inventors have shown that electrolytically generated nickel or cobalt cathodes can be successfully leached using the method of the present invention.

[0070] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein the metal particles containing nickel or cobalt each contain at least 96% by weight, preferably at least 99% by weight, and more preferably at least 99.9% by weight of nickel or cobalt, based on the total weight of the metal particles.

[0071] In a preferred embodiment, the height h of the reaction zone (10) is at least 1 m, preferably 1 m to 12 m, and more preferably 3 m to 10 m. Alternatively, the height h of the reaction zone (10) is at least 1 m, preferably 1 m to 3 m, and more preferably 1.5 m to 2.5 m.

[0072] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein the column reactor (100) comprises an insulating jacket and / or a heating jacket (50).

[0073] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein the pressure in the headspace above the reaction zone (10) is atmospheric pressure or a reduced pressure of less than 0.2 atmospheres.

[0074] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein the column reactor (100) further comprises an H2 detector (40).

[0075] In preferred embodiments, the method of the present invention is a semi-batch method. This means that the reaction is stopped and the nickel sulfate or cobalt sulfate solution is discharged when the target nickel concentration, cobalt concentration, or density is reached, respectively. The reactants are added to the system continuously over a specific period, but the sampling of the solution is done in an individual manner. The semi-batch method has several advantages over a continuous process, including handling of supply or reagent variability (e.g., Ni metal reactivity or H2O2 quality), leaching, suppression of H2 formation during metal loading, increased throughput due to leaching at higher acid content, the possibility of lower residual acid content, and generally greater flexibility.

[0076] In one embodiment, the method of the present invention is a semi-batch, i.e., discontinuous method. The term “semi-batch method” is considered to be a process adapted to periodically add reactants and / or periodically remove products, and therefore the method does not have any continuous flow conditions. Specifically, in the context of the present invention, the term “semi-batch method” refers to a method in which a batch of solids is processed, thereby periodically introducing a liquid, or liquefiing reagent, into the reactor. As a result, the bed volume of metal particles containing nickel or cobalt decreases over the reaction time in the reaction zone (10) of the semi-batch reactor (100) until at least a portion of the nickel or cobalt-containing particles react with sulfuric acid and hydrogen peroxide.

[0077] In one embodiment, the half-batch method is stopped and the nickel sulfate or cobalt sulfate solution is discharged when the nickel or cobalt-containing particles have completely reacted with sulfuric acid and hydrogen peroxide.

[0078] In a preferred embodiment, the half-batch method is interrupted and the nickel sulfate or cobalt sulfate solution is discharged when it has the desired, i.e., predetermined nickel or cobalt content, respectively.

[0079] In a preferred embodiment, the half-batch method is interrupted and the nickel sulfate or cobalt sulfate solution is discharged when it has the desired, i.e., a predetermined nickel or cobalt content and a desired, i.e., a predetermined residual acid content, respectively.

[0080] In a preferred embodiment, the half-batch method is interrupted and the nickel sulfate or cobalt sulfate solution is discharged when it has the desired H2O2 content, i.e., a predetermined nickel or cobalt content and a desired residual sulfuric acid content, respectively, and no more H2O2 remaining.

[0081] In a preferred embodiment, the reaction is stopped and the material is discharged from the circulating reactor when the leaching rate is low.

[0082] In one embodiment, the method is not a continuous method. The term "continuous" means that a metallic sulfuric acid solution may be obtained by adding nickel or cobalt-containing particles, sulfuric acid, and hydrogen peroxide, and recovering them without interrupting the process.

[0083] Nickel or cobalt metal may be supplied in advance to the half-batch method. Preferably, nickel or cobalt is supplied in advance to the reaction zone (10) of the reactor (100).

[0084] In a preferred embodiment, Ni and Co are reloaded after draining the leaching solution from the first half-batch method, before starting the next half-batch method. By avoiding contact between the leaching solution and the fresh Ni metal, safety of the operation and process is maximized because there is no hot acid solution present when the reactor is opened. Furthermore, this limits the risk of reaction between the fresh metal supply and the leaching solution. Therefore, the risk of H2 formation when opening the reactor is limited.

[0085] In an alternative embodiment, the Ni and Co particles are reloaded after the addition of hydrogen peroxide and sulfuric acid is stopped and before the leaching solution is drained. In this way, Ni and Co are loaded into the reactor filled with the leaching solution. This reduces the downward velocity of the particles loaded from the top, thus limiting the impact of particle loading on the reactor wall and reducing the risk of particles damaging the surface.

[0086] The process may begin with a low-temperature bed of metal particles or a preheated bed of metal particles. In a preferred embodiment, preheating the bed of metal particles is achieved by heating the aqueous medium supplied to the reaction zone while circulating it over the bed until the aqueous medium has a temperature of 50°C to 80°C, preferably 70°C to 80°C, more preferably 75°C to 80°C, and similar temperatures at the reactor outlet.

[0087] In another preferred embodiment, the metal particle bed is not preheated, and the aqueous medium is heated to about 75°C in a circulation tank or buffer tank (200) before the circulation of the aqueous medium to the reactor bed is initiated.

[0088] In a preferred embodiment, the aqueous medium is preheated. In a preferred embodiment, preheated water is circulated until the circulating reactor and the reaction zone (10) of the circulating reactor (100) have reached a desired temperature. This avoids preheating the circulating reactor (100) and increases reaction efficiency. In a preferred embodiment, the aqueous medium is preheated for the first cycle but not for subsequent cycles. In subsequent cycles, the temperature of the aqueous medium may be in the range of 50°C to 70°C. In a preferred embodiment, the aqueous medium is not preheated during subsequent cycles, i.e., after the nickel sulfate or cobalt sulfate solution has been discharged and then nickel or cobalt-containing particles have been supplied to the reaction zone (10).

[0089] The inventors have found that residual heat from a preceding cycle may be sufficient to initiate the leaching process in a subsequent cycle. In a preferred embodiment, the time between two consecutive cycles is short enough to avoid cooling of the reaction zone (10) below the threshold temperature for nickel or cobalt metal leaching-reaction.

[0090] The process of the present invention makes it possible to produce a “concentrated nickel sulfate solution.” This should be considered synonymous with the term “sulfuric acid solution having a nickel content of at least 60 g Ni / L,” which optionally includes further contents such as sulfuric acid in an amount of less than 30 g / L of H2SO4, preferably less than 20 g / L, and more preferably less than 10 g / L. Preferably, the nickel content of the nickel sulfate solution is at least 60 g Ni / L, and at least 80 g Ni / L. Preferably, the nickel sulfate solution has a nickel sulfate content below the saturation point of nickel sulfate at the processing temperature, i.e., at a temperature of about 90°C or about 95°C.

[0091] Preferably, the nickel content of the nickel sulfate solution is 80 to 200 g Ni / L, more preferably 90 to 175 g Ni / L, and more preferably 100 to 150 g Ni / L. Preferably, the nickel sulfate solution obtained from the oxidative leaching reaction has a nickel content of 110 to 140 g / L, more preferably 120 to 140 g / L, and most preferably about 130 g / L.

[0092] The half-batch method of the present invention makes it possible to produce a “concentrated cobalt sulfate solution.” This should be considered synonymous with the term “cobalt sulfate solution having a cobalt content of at least 60 g Co / L,” which optionally includes further contents such as sulfuric acid in an amount of less than 30 g / L H2SO4, preferably less than 20 g / L, and more preferably less than 10 g / L. Preferably, the cobalt content of the cobalt sulfate solution is at least 60 g Co / L, and at least 80 g Co / L.

[0093] Preferably, the cobalt sulfate solution has a cobalt content below the saturation point of cobalt sulfate at the processing temperature, i.e., a temperature of about 90°C or about 95°C. Preferably, the cobalt content of the cobalt sulfate solution is 80 to 200 g Co / L, preferably 90 to 175 g Co / L, and more preferably 100 to 150 g Co / L. Preferably, the cobalt sulfate solution obtained from the oxidative leaching reaction has a cobalt content of 110 to 140 g / L, more preferably 120 to 140 g / L, and most preferably about 130 g / L.

[0094] In a preferred embodiment, a nickel sulfate or cobalt sulfate solution is subjected to a purification step to reduce the concentration of one or more impurities, thereby comprising one or more impurities selected from the list including Cu, Zn, Co, Mn, Fe, Al, F, C, Ca, Si, P, As, Cd, Cr, Sb, and Mg, thereby further comprising Co in the case of a process for preparing a nickel sulfate solution, or further comprising Ni in the case of a process for preparing a cobalt sulfate solution.

[0095] In a preferred embodiment, before subjecting the nickel sulfate or cobalt sulfate solution to a further purification step, a base is added to the nickel sulfate or cobalt sulfate solution to react with the remaining amount of sulfuric acid present in the solution, thereby the base is selected from the group consisting of ammonium hydroxide, ammonium carbonate, potassium hydroxide, potassium carbonate, nickel hydroxide or cobalt hydroxide, nickel carbonate or cobalt carbonate, cobalt hydroxide, cobalt carbonate, manganese hydroxide, manganese carbonate, calcium hydroxide, calcium carbonate, sodium hydroxide, sodium carbonate, lithium hydroxide, lithium carbonate, magnesium oxide, magnesium hydroxide, magnesium carbonate, or a combination of two or more of the above.

[0096] Preferably, the base is added until the pH of the nickel sulfate or cobalt sulfate solution reaches 2 to 5, preferably 2.5 to 4.5, and more preferably 3.0 to 4.0.

[0097] In a preferred embodiment, the metal particles contain nickel or cobalt in an amount of at least 96% by weight, preferably 97% by weight, more preferably at least 98% by weight, and most preferably 99% by weight, relative to the total weight of the metal particles. Preferably, the metal particles contain Ni or Co in an amount of at least 99.5% by weight, more preferably 99.9% by weight.

[0098] The Ni metal particles may further contain Co in an amount of up to 1% by weight.

[0099] In the context of the present invention, the nickel or cobalt metal supply unit preferably comprises high-purity nickel or cobalt metal having a purity of 99.97+%, 99.98+%, or even 99.99+%.

[0100] Nickel or cobalt metal can be supplied to the reactor typically in the form of nickel or cobalt cut cathode metal, shredded or cut whole-plate cathode metal obtained from an electrosuccessful process, round forms of nickel or cobalt metal, or nickel or cobalt pellets, balls with a diameter of approximately 0.5 cm, having sizes of 1"xl", 2"x2", or 4"x4".

[0101] In preferred embodiments, the hydrogen peroxide used in the process is typically an aqueous solution having a hydrogen peroxide concentration of 30-60% by weight in water, for example, 35% or 50% by weight, and the sulfuric acid has a concentration of 76-98% by weight in water, preferably 98% by weight in water.

[0102] Any water used in the process can be desalinated water or highly purified water such as R.O. water.

[0103] In one embodiment, the present invention provides a method according to a first aspect, wherein the oxidative leaching solution contains hydrogen peroxide in an amount of 1 to 50 g / L, preferably 1 to 30 g / L, and more preferably 5 to 30 g / L.

[0104] More preferably, the oxidative leaching solution contains hydrogen peroxide in an amount of 5 to 20 g / L, more preferably about 5 to 12 g / L, and even more preferably about 7 to 10 g / L.

[0105] In a preferred embodiment, hydrogen peroxide is supplied to the reaction zone (10) at a constant supply rate.

[0106] In one embodiment, the hydrogen peroxide supply rate decreases at the end of the process.

[0107] The inventors found that supplying sulfuric acid at high concentrations results in a temperature increase and can therefore be used to replace or reduce the preheating of aqueous media.

[0108] In a preferred embodiment, the acidic aqueous medium is supplied to the reaction zone (10) at a temperature of 50°C to 80°C, preferably 70°C to 80°C, and more preferably 75°C to 80°C.

[0109] In a preferred embodiment, the reaction temperature at the top of the reaction zone (10) is greater than 80°C, preferably 85°C to 100°C, and more preferably 92°C to 99°C.

[0110] In a preferred embodiment, sulfuric acid is supplied at an acid concentration higher than the target concentration, and the acidity of the acidic aqueous medium is then reduced by supplying an aqueous medium, preferably water, or a nickel sulfate or cobalt sulfate solution, respectively.

[0111] In one embodiment, sulfuric acid is supplied at a constant rate until a sufficient amount of sulfate is present in the reactor to achieve a predetermined amount of nickel sulfate or cobalt sulfate, respectively. Then, hydrogen peroxide is added to achieve a desired level of metal leaching, thereby achieving a predetermined amount of metal sulfate in the solution.

[0112] In a preferred embodiment, the acidity of the acidic aqueous medium is reduced at the end of the process cycle, i.e., before the nickel sulfate or cobalt sulfate solution is discharged. In a preferred embodiment, the acidity of the acidic aqueous medium is reduced to 10 g / L or less before the nickel sulfate or cobalt sulfate solution is discharged.

[0113] The inventors further found that throughout the leaching process, a sulfuric acid concentration of approximately 20 g / L at the top of the reaction zone (10) ensures that the peroxide addition kinetically limits the reaction. The inventors observed that a lower residual hydrogen peroxide concentration in the nickel sulfate or cobalt sulfate solution allows for a higher peroxide yield in this case. This also improves the quality of the nickel sulfate or cobalt sulfate solution through less hydrogen peroxide.

[0114] Therefore, in a preferred embodiment, the sulfuric acid is reduced at the end of the leaching process.

[0115] In a preferred embodiment, the circulating reactor is controlled to ensure that the nickel sulfate or cobalt sulfate solution obtained from the reactor in step v. has a residual sulfuric acid content of 1 g / L to 20 g / L. A lower residual sulfuric acid content ensures that the sulfuric acid is used economically in the process. Preferably, the residual sulfuric acid in the nickel sulfate or cobalt sulfate solution is 2 g / L to 15 g / L, more preferably 2 g / L to 10 g / L, and most preferably, the residual sulfuric acid is about 2 g / L, 4 g / L, 6 g / L, 8 g / L, or 10 g / L, or any value in between.

[0116] In a preferred embodiment, a nickel sulfate or cobalt sulfate solution obtained from the reactor and having a residual sulfuric acid content is used for subsequent leaching of compressed metal waste in a leaching column.

[0117] In preferred embodiments, the present invention provides a process according to a first aspect of the present invention, wherein the molar ratio of the total consumption of hydrogen peroxide to the total consumption of sulfuric acid for leaching one batch of metal particles is greater than 0.9 and less than 1.1, preferably greater than 0.95 and less than 1.00. In other words, after step iv., the ratio of the consumption of hydrogen peroxide to the consumption of sulfuric acid is greater than 0.9 and less than 1.1, preferably greater than 0.95 and less than 1.00.

[0118] In a preferred embodiment, the present invention provides a process according to a first aspect of the present invention, wherein sulfuric acid and hydrogen peroxide are supplied in step iii. in a molar ratio of 1.5:1.0 to 0.6:1.0. Preferably, sulfuric acid and hydrogen peroxide are supplied in step iii. in a molar ratio of 1.2:1:0 to 0.8:1.0, and more preferably, in a molar ratio of 1.1:1.0 to 0.9:1:0. Preferably, in the stage prior to step iii., sulfuric acid is supplied in excess of the amount of hydrogen peroxide supplied to the reactor. In other words, in the initial stage of step iii., sulfuric acid is present in excess of the amount of hydrogen peroxide present in the reaction zone (10). By using a larger amount of sulfuric acid in the stage prior to the process, good leaching dynamics in the stage prior to the process are ensured. Preferably, in the stage later than step iii., sulfuric acid is supplied in a substoichiometric amount relative to the amount of hydrogen peroxide supplied to the reactor. In other words, in the later stages of step iii, sulfuric acid is supplied in a substoichiometric amount relative to the amount of hydrogen peroxide present in the reaction zone (10). Supplying a smaller amount of sulfuric acid at the end of the process avoids high residual sulfuric acid in the target nickel sulfate or cobalt sulfate solution.

[0119] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein in the initial stage of step iii, the molar ratio of sulfuric acid to hydrogen peroxide in the reaction zone (10) is 2.50:1.00 to 1.01:1.00, preferably 2.00:1.00 to 1.01:1.00, and thereby in the later stage of step iii, the molar ratio of sulfuric acid to hydrogen peroxide in the reaction zone (10) is 0.60:1:00 to 0.99:1.00.

[0120] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, thereby keeping the concentration of hydrogen peroxide in the supply to the reactor zone (10) substantially constant in step iii, and preferably substantially constant in the first part of step iv. The inventors believe that a hydrogen peroxide concentration in the surrounding reaction zone of a predetermined concentration during oxidative leaching promotes good leaching dynamics, and thereafter, stopping or reducing the peroxide supply while supplying sulfuric acid ensures that all peroxide is completely consumed, provided that metal particles are still present in the reaction zone, which is economically desirable.

[0121] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein sulfuric acid is supplied at a constant rate until a sufficient amount of sulfate is present in the reactor to achieve a predetermined amount of nickel sulfate or cobalt sulfate, respectively, and then hydrogen peroxide is added to achieve a desired degree of metal leaching to achieve a predetermined amount of metal sulfate in the solution.

[0122] In a preferred embodiment, the present invention provides a method according to a first aspect, wherein the ratio of the sulfuric acid concentration (Csa,o) of the nickel sulfate or cobalt sulfate solution obtained from the column reactor to the sulfuric acid concentration (Csa,i) of the oxidative leaching solution supplied to the column reactor is less than 0.70, less than 0.65, less than 0.60, less than 0.55, or less than 0.50.

[0123] Preferably, the ratio is between 0.5 and 0.1. Preferably, the ratio is lower than 0.45, and even lower than 0.40. Preferably, the ratio is higher than 0.05. Most preferably, the ratio is about 0.10, about 0.15, about 0.20, about 0.25, 0.30, about 0.35, or any value in between.

[0124] In a preferred embodiment, the present invention provides a method according to a first aspect, wherein the difference Δac between the acid concentrations Csaj and Csa,o is at least 5 g / L of sulfuric acid, and at most 80 g / L of sulfuric acid, preferably at least 10 g / L of sulfuric acid, and at most 70 g / L of sulfuric acid.

[0125] Preferably, the difference Δac in acid concentration is at least 15 g / L, and preferably at least 20 g / L.

[0126] Preferably, the difference Δac in acid concentration is at most 60 g / L, or at most 50 g / L, and more preferably at most 45 g / L.

[0127] Most preferably, the difference Δac of the acid concentration is approximately 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, or 45 g / L, or any value in between.

[0128] In a preferred embodiment, the supply of hydrogen peroxide and sulfuric acid is stopped, while the circulation of the leachate is maintained until the residual peroxide is consumed.

[0129] In a preferred embodiment, the supply of hydrogen peroxide and sulfuric acid is stopped, while the circulation of the leaching solution is maintained until a predetermined residual sulfuric acid concentration is reached in the nickel sulfate or cobalt sulfate solution.

[0130] In a first embodiment, the present invention provides a method according to a first aspect, wherein sulfuric acid and hydrogen peroxide are supplied in stoichiometric amounts to the oxidative leaching solution. Preferably, the molar ratio of sulfuric acid to hydrogen peroxide is 1:1 to 1:1.2, more preferably 1.0:1.0 to 1:1.1.

[0131] In a second alternative embodiment, the present invention provides a method according to the first embodiment, wherein hydrogen peroxide is supplied to an oxidative leaching solution, which is supplied to a circulating reactor in a substoichiometric amount relative to the amount of sulfuric acid present in the oxidative leaching solution. For example, the oxidative leaching solution may contain 0.4 mol / L hydrogen peroxide and 0.5 mol / L sulfuric acid.

[0132] At the start of the half-batch method, the molar ratio of hydrogen peroxide to sulfuric acid in the oxidative leaching solution supplied to the circulating reactor is preferably 0.6 to 1.0, preferably 0.8 to 1.0, and more preferably about 0.9.

[0133] The method according to the present invention allows operation with a substoichiometric amount of hydrogen peroxide, thereby allowing for a residual amount of sulfuric acid in the resulting nickel sulfate or cobalt sulfate solution.

[0134] Excessive hydrogen peroxide leads to further depletion of sulfuric acid.

[0135] Excessive hydrogen peroxide ensures that it is not a process rate limiter.

[0136] Excess hydrogen peroxide can be recovered from the effluent of the circulating reactor.

[0137] In another preferred embodiment, the present invention provides a method according to the first aspect, wherein the gaseous atmosphere in the overflow zone (20) is treated in a scraper to remove water and any hydrogen that may be formed.

[0138] In a preferred embodiment, the present invention provides a method according to a first aspect, wherein the oxidative leaching solution comes into contact with the metal particles at atmospheric pressure in the headspace of a circulating reactor above the reaction zone, i.e., 1 bar, or less than 0.5 bar, preferably less than 0.2 bar, more preferably less than 0.1 bar, under reduced pressure.

[0139] Preferably, the oxidative leaching solution is brought into contact with the metal particles in an atmosphere of oxygen, air, or oxygen-concentrated air.

[0140] In another preferred embodiment, the gaseous atmosphere within the overflow zone (20) is flushed with a vapor or an inert gas such as N2. This allows for easy removal of hydrogen gas if it forms in the circulating reactor.

[0141] In a preferred embodiment, the present invention provides a method according to a first aspect, wherein the floor volume of the metal particles in the circulating reactor has a diameter Db and a height Hb, wherein the height-to-diameter ratio Hb:Db is 0.8 to 15, preferably 0.9 to 10, and more preferably 1 to 5.

[0142] Preferably, the height and diameter of the floor volume are kept substantially constant throughout the process.

[0143] The process of the present invention proceeds in a column. In the context of the present invention, the term “column” is considered equivalent to the terms “circulating reactor,” “packed bed,” or “packed bed reactor,” the term “tower,” or “tower reactor,” and refers to a circulating reactor having a substantially cylindrical shape with an inner diameter D and a height H.

[0144] The circulating reactor (100) consists of a vertically arranged cylindrical column and is configured to operate without mechanical stirring, preferably in upflow mode, i.e., with a fluid flow from the bottom to the top of the column.

[0145] The circulating reactor (100) is • A supply section at the bottom of the cylindrical reactor for supplying liquid reagents such as aqueous solutions, sulfuric acid, and hydrogen peroxide, - A section, or overflow zone (20), located at the upper portion or upper end of the circulating reactor, opposite the supply section, and characterized by effluent, for collecting the overflow nickel sulfate or cobalt sulfate solution, The further feature is that the cylindrical reactor comprises an intermediate section or reaction section (10) in the central part, on which the leaching reaction proceeds.

[0146] Optionally, the circulating reactor (100) includes a condensing section (30).

[0147] Figure 2 shows an exemplary cross-section of a circulating reactor (100) comprising an insulating and / or heating jacket (50), columns and coatings (60), and a rubber layer (70).

[0148] Metal particles, preferably containing nickel or cobalt, are supplied to the top of the reactor and gradually or intermittently added to form a bed of metal particles on the support within the circulating reactor.

[0149] The circulating reactor preferably includes a support above the supply section for supporting a solid reagent, such as nickel or cobalt metal.

[0150] The support consists of a grid for supporting nickel or cobalt metal.

[0151] Furthermore, the circulating reactor (100) preferably includes means for supplying a solid reagent, such as nickel or cobalt metal, to the reaction zone (10) of the circulating reactor.

[0152] Furthermore, the circulating reactor (100) also preferably includes means for radially and uniformly distributing the oxidizing leaching solution to the supply section of the circulating reactor (100).

[0153] Solid reagents can be introduced onto the support by introducing nickel or cobalt metal at the top of the reactor or at any position above the support. The overflow zone (20) is provided with an overflow outlet and an overflow conductor (21) for receiving nickel sulfate or cobalt sulfate solution via an overflow mechanism.

[0154] In a preferred embodiment, the overflow conductor (21) preferably includes a filter for filtering out metal particles.

[0155] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein the liquid volume of the oxidative leaching solution in the circulating reactor (100) has a diameter Dl and a height Hl, wherein the ratio Hl:Dl of the height to the diameter is 1.0 to 10.0, preferably 1.5 to 8.0, more preferably 2.0 to 5.0, most preferably about 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, or any value in between.

[0156] The appropriate geometric shape of the liquid volume within the circulating reactor (100), and especially a sufficiently high Hl:Dl ratio, ensures that a one-dimensional flow is obtained throughout the column, and that small metal particles resulting from the reacted metal feed particles are not entrained upward into the nickel sulfate or cobalt sulfate solution resulting from the oxidative leaching reaction, thereby preventing the introduction of unreacted metal particles that contaminate the resulting nickel sulfate or cobalt sulfate and reduce the efficiency of the process.

[0157] In a preferred embodiment, the circulating reactor (100) is cylindrical in shape and has an inner diameter D and a height H, wherein the ratio of the height H to the diameter D is significantly higher than 1, for example, 1.0 to 10.0, preferably 1.5 to 8.0, more preferably 2.0 to 5.0, most preferably about 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0, or any value in between.

[0158] The appropriate shape of the circulating reactor (100), particularly a sufficiently high H:D ratio, ensures that a one-dimensional flow can be obtained throughout the column.

[0159] In a preferred embodiment, the reaction column further includes an H2 detector.

[0160] The use of a circulating reactor helps increase batch size. Furthermore, recirculation helps maintain thermal balance at the start of a new cycle.

[0161] In a preferred embodiment, mixing of the reactants within the reaction zone (10) is achieved by circulating an aqueous leachate. In this regard, a predetermined volume of the acidic aqueous medium, or leachate, is continuously discharged and recirculated to the supply section of the circulating reactor (100).

[0162] In the semi-batch method, the entire solution is circulated until the process stops and the product solution is drained.

[0163] In the context of this invention, the terms “circulate” or “to circulate” and “recirculate” or “to recirculate” are used interchangeably.

[0164] Recirculation is particularly advantageous when the fluidity of particles containing nickel or cobalt is reduced, such as nickel or cobalt cathodes.

[0165] In a preferred embodiment, the circulating leaching solution passes through a heat exchanger for cooling or heating before re-entering the column reactor to control the system's thermal balance and maximize the leaching rate and volume.

[0166] In a preferred embodiment, the heat recovered from the circulating leachate is used in another parallel process. The batch process according to the present invention allows the process to operate based on the actual need for energy recovery.

[0167] In a preferred embodiment according to a first aspect of the present invention, an acidic aqueous medium is circulated in a countercurrent mode, thereby loading nickel or cobalt into the reactor from the top, thereby supplying the leaching solution to the bottom of the reactor.

[0168] Countercurrent means that the solution is removed from the top of the reaction zone (10) and returns to the bottom of the circulating reactor (100) in the opposite direction to the direction in which the metal particles were added.

[0169] In a preferred embodiment, the acidic aqueous medium is circulated countercurrently, and Ni or Co particles are loaded from the top of the column reactor (100). Countercurrent circulation combined with nickel loading from the top has the advantage that fine particles accumulate in the lower region of the reaction zone (10). The remainder of the bed is advantageous in limiting particle contamination because it acts as a filter, and the smallest particles accumulate at the bottom near the solution inlet, leading to a further concentration reaction.

[0170] The latter maximizes the temperature rise, which is beneficial for leaching out the remaining metal particles within the column reactor.

[0171] In a preferred embodiment, the height h of the reaction zone (10) is at least 1 m, and can be higher, for example, 1 m to 3 m, preferably 1.5 m to 2.5 m. The inventors have shown that a floor height of 1 m doubled the leaching rate compared to a floor height of 50 cm. Therefore, in a preferred embodiment, the initial floor height of the nickel or cobalt-containing particles is at least 1 m, and can be higher, for example, 1 m to 3 m, preferably 1.5 m to 2.5 m. In another embodiment, the height h of the reaction zone (10) is at least 1 m, preferably 1 m to 12 m, and more preferably 3 m to 10 m.

[0172] However, the overall leaching capacity is generally limited by cooling needs and heat capacity.

[0173] In a preferred embodiment, the present invention provides a method according to a first aspect of the present invention, wherein the oxidative leaching solution comprising sulfuric acid and hydrogen peroxide is optionally supplied in water to the reaction section via the lower part of the circulating reactor (100), thereby the nickel sulfate or cobalt sulfate solution is discharged from the reaction section via the upper part of the circulating reactor (100) in step iii.

[0174] Preferably, the metal particles are supplied to the reaction zone (10) via the top of the column reactor. In one embodiment, the metal particles may be supplied in a single batch at the start of the half-batch reaction or after the completion of the half-batch reaction. The metal particles may be supplied continuously or intermittently, preferably intermittently.

[0175] In a preferred embodiment, the reaction zone (10) may also incorporate a mechanical impeller, i.e., an impeller attached to a motor by a rod, simply for the purpose of mixing liquid reagents. Alternatively, a static mixer may be used.

[0176] In a preferred embodiment, the reaction zone (10) comprises a plurality of vertical baffles positioned between the inlet nozzle and the impeller, such that they are arranged opposite each other and at least one baffle is positioned on the oppositely facing end of the reactor wall. In this embodiment, the impeller and vertical baffles assist in the microlevel mixing of the reactants. The impeller improves the reactor dynamics. The vertical baffles contribute to ensuring maximum mixing of the reactants within the reaction zone (10). The arrangement of the vertical baffles ensures that the reaction is confined to the reaction zone (10) and does not extend into zones above the reaction zone (10).

[0177] Preferably, the reactor has a sedation zone above the reaction zone (10). The sedation zone has a tubular structure with a constant cross-section, preferably a cross-section equal to the cross-section of the reaction zone (10), or an enlarged cross-section whose diameter is larger than that of the reaction zone (10). The sedation zone is in fluid communication with the reaction zone (10), with the reaction zone (10) at its distal end and an overflow zone (20) at its proximal end.

[0178] The function of the sedation zone is to achieve a non-turbulent liquid flow that adapts to a non-flowing state for unreacted metal particles. This allows unreacted or insufficiently reacted metal particles to return to the reaction zone (10).

[0179] The sedation zone may include a plurality of horizontal baffles positioned in the central, proximal, and distal portions of the sedation zone. In this embodiment, at least two of the provided horizontal baffles may be downward-facing baffles with a central flow opening, adapted to slow the rate of the reaction mixture.

[0180] In yet another embodiment, the central horizontal baffle provided is a conical baffle having an annular flow. In this embodiment, the arrangement of the horizontal baffle creates a curved flow path that allows larger particles to settle while simultaneously allowing the upward-flowing mixture to move smoothly within the overflow zone (20).

[0181] In a preferred embodiment, the overflow zone (20) has a tubular structure having the same cross-section as the sedation zone and reaction zone (10), and is located at the proximal end of the circulating reactor (100). The overflow zone (20) is provided with an outlet for receiving the formed nickel sulfate or cobalt sulfate solution.

[0182] In a preferred embodiment, the nickel sulfate or cobalt sulfate solution is drained when a predetermined acid ratio and / or nickel or cobalt concentration is obtained.

[0183] In one embodiment, the nickel sulfate or cobalt sulfate solution is discharged at the bottom of the reaction zone (10).

[0184] In a preferred embodiment, nickel or cobalt-containing particles are supplied while the nickel sulfate or cobalt sulfate solution is being discharged. The inventors found that supplying nickel or cobalt-containing particles while the circulating reactor (100) is open eliminates the risk of H2 formation.

[0185] In a preferred embodiment, water is added during the discharge of the nickel sulfate or cobalt sulfate solution. This further reduces residual sulfuric acid and residual hydrogen peroxide. This is particularly advantageous at higher nickel or cobalt concentrations. Higher nickel or cobalt concentrations in the nickel sulfate or cobalt sulfate solution increase the boiling point and therefore allow for a higher temperature difference (delta T). Higher nickel and cobalt concentrations also increase the capacity per batch. After discharge, safer loading is possible compared to a continuous process due to the elimination of H2 risk.

[0186] In a preferred embodiment, after draining the nickel sulfate or cobalt sulfate solution, a new cycle is started with the following process steps: Aqueous media, preferably water, hydrogen peroxide, and sulfuric acid, are supplied to the reaction zone (10) of the circulating reactor (100), preferably through the supply section at the bottom of the circulating reactor (100), with sulfuric acid and / or hydrogen peroxide supplied at high concentrations to obtain the resulting solution having a high nickel or cobalt concentration.

[0187] When the column begins to overflow and the circulating reactor (100) is filled, the oxidative leaching solution is recirculated, and in a preferred embodiment, the hydrogen peroxide and acid addition rates are constant over time, while in another embodiment, the hydrogen peroxide and acid addition rates are controlled by the acid consumption function.

[0188] Recirculation continues until the target nickel concentration, cobalt concentration, nickel density, or cobalt density is reached.

[0189] In a preferred embodiment according to a first aspect of the present invention, the leached aqueous solution is circulated from the top of the column reactor (100) to a buffer tank and from the buffer tank to the bottom of the column reactor (100). In this embodiment, the buffer tank is a circulation tank (200).

[0190] The circulation tank (200) may be equipped with a mechanical agitator. In a preferred embodiment according to the first aspect of the present invention, the circulation tank (200) does not have an agitator, and mixing in the reaction zone (10) and the circulation tank (200) is achieved by circulating the leachate solution.

[0191] In a second aspect, the present invention provides a system for producing nickel sulfate or cobalt sulfate, the system is The present invention provides for one or more circulating reactors (100), preferably column reactors, configured to operate a process for preparing sulfuric acid, nickel, or cobalt sulfate solutions. The circulating reactor (100) is equipped with one or more buffer tanks configured to receive nickel sulfate or cobalt sulfate solution.

[0192] One or more circulating reactors (100) are configured to operate a process for the preparation of a nickel sulfate or cobalt sulfate solution (N) within the circulating reactor (100), comprising a reaction zone (10) having a height h, an overflow zone (20), and optionally a condensation section (30), the process comprising the following steps: i. A step of supplying metal particles containing nickel or cobalt, respectively, to the reaction section (10) of the reactor (100), ii. A step of supplying an aqueous solution, preferably water, to the reaction section (10) via a supply section, thereby bringing the solution into contact with the metal particles containing nickel or cobalt in the reaction section (10), iii. Subsequently, hydrogen peroxide and sulfuric acid are supplied to the reaction section (10) to stimulate the leaching of the metal particles until the concentration or amount of sulfuric acid in the reactor falls below a predetermined value, iv. The step of oxidatively leaching metal particles containing nickel or cobalt into the reaction zone (10) to obtain a nickel sulfate solution or a cobalt sulfate solution, respectively. v. The step of discharging the nickel sulfate or cobalt sulfate solution from the reactor (100) after step iv.

[0193] In a preferred embodiment, one or more buffer tanks are in fluid communication with the circulating reactor (100) and, preferably, with the overflow zone (20) of the circulating reactor (100).

[0194] In a preferred embodiment, one or more buffer tanks are configured to receive nickel sulfate or cobalt sulfate solution from the circulating reactor (100).

[0195] In a preferred embodiment, the present invention provides a system according to a second aspect of the present invention, wherein the buffer tank comprises an outlet valve.

[0196] In a preferred embodiment, the buffer tank is configured to produce a constant outflow of nickel sulfate or cobalt sulfate solution. [Examples]

[0197] The following embodiments are intended to further clarify the present invention and are not intended in any way to limit its scope.

[0198] Example 1 - Circulating reaction column and supply Figure 1 schematically shows the process according to the present invention in a circulating reactor (100) with the following reference numerals.

[0199] 100 circulating reactors 10 reaction zones 20 Overflow Zones 21. Overflow conductors that optionally include filters. 30 Condensed Sections 40 H2 detector 50 Heating and / or insulating jacket (outer) 60 columns and coating layers 70 Rubber layer 200 Circulation or buffer tank The circulating reactor (100) comprises a reaction zone (10) having a height h, an overflow zone (20), an optional overflow conductor (21) containing a filter, means for discharging the acidic aqueous medium with a predetermined volume of the acidic aqueous medium, means for circulating the discharged acidic aqueous medium to a supply section of the circulating reactor (100), an optional condensation section (30), and an optional H2 measuring device (40).

[0200] Figure 2 shows an exemplary cross-section of a circulating reactor (100) comprising an insulating and / or heating jacket (50), columns and coatings (60), and a rubber layer (70).

[0201] The aqueous medium, and optionally the sulfuric acid solution inflow into the column, passes through a heat exchanger. This allows preheating without the need to preheat the entire circulation tank (200), and thus limits evaporation losses within the reactor.

[0202] Secondly, the column is encased in a heating insulation jacket (50) to allow for the introduction of additional heat. This enables preheating of the column and avoids heat loss through the walls.

[0203] In a particular, highly preferred embodiment, the method of the present invention involves the following steps: The steps include supplying nickel and water to the reaction zone (10) of the circulating reactor (100), The steps include partially draining the water and circulating it until the nickel bed in the reaction zone (10) reaches a high temperature, thereby heating the water and the reaction zone (10), The steps include supplying sulfuric acid and hydrogen peroxide (upward flow) while circulating over the floor, and in a preferred embodiment, the leaching is carried out in a countercurrent, and The process involves dissolving nickel until the target nickel concentration or nickel density is reached, The process includes the step of stopping the supply of hydrogen peroxide and sulfuric acid while maintaining circulation until all residual hydrogen peroxide is consumed and the level of residual sulfuric acid is sufficiently low.

[0204] If the nickel sulfate solution has a predetermined level of nickel and residual sulfuric acid, the nickel sulfate solution is discharged from the circulating reactor, and in a preferred embodiment, the nickel sulfate solution is discharged from the bottom of the circulating reactor (100).

[0205] • Optionally, new particles containing nickel are filled into the top of the floor.

[0206] In one preferred embodiment, the method includes the following further steps: The supply step involves supplying water, hydrogen peroxide, and sulfuric acid to the bottom of the reaction zone (10) with high concentrations of sulfuric acid and hydrogen peroxide, and in a preferred embodiment, supplying preheated water to the reaction zone (10) so that the leaching process can be started smoothly.

[0207] The step of stopping the water supply and recirculating the acidic aqueous medium after the column begins to overflow and the circulation tank (200) is (partially) filled.

[0208] • A step in which recirculation continues until the target nickel concentration or nickel density is reached.

[0209] • The step of stopping the supply of hydrogen peroxide and sulfuric acid.

[0210] • A step in which recirculation is continued until all residual hydrogen peroxide is consumed and the concentration of residual sulfuric acid is sufficiently low.

[0211] • Step of discharging the nickel sulfate solution.

[0212] • A step in which a new process is initiated, at the discretion of the user.

[0213] Example 2 - Reaction zone temperature during and between cycles Based on the pilot test in Example 1, the inventors observed that contact of nickel-containing particles with a high-temperature bed was sufficient to initiate a leaching reaction.

[0214] The inventors further observed that when the reaction bed is at the required temperature, the temperature of the liquid supply can be relatively low.

[0215] The inventors have further observed that if the reaction bed does not have the temperature necessary to initiate the leaching reaction, preheating of an aqueous medium, preferably water, is required.

[0216] Therefore, the inventors found that the time between two consecutive cycles should be kept short in order to ensure a sufficient temperature in the reaction zone (10).

[0217] Example 3 - Increase in sulfuric acid During the pilot test according to Example 1, the inventors observed a higher leaching rate when operating with 12 g / L acid compared to 10 g / L at the top of the reaction zone. The inventors believe that throughout the leaching process, a sulfuric acid concentration of 20 g / L at the top of the reaction zone (10) ensures that the supply of hydrogen peroxide kinetically limits the reaction.

[0218] As a result, the inventors believe there is no benefit to working with acid concentrations higher than 20 g / L. They further observed a significant difference in the results at 10 g / L.

[0219] Example 4 - Different stages of the half-batch method Figure 3 schematically shows the process according to the present invention in a column reactor. In a preferred embodiment, the half-batch method according to the first aspect of the present invention includes the following steps.

[0220] Stage 0: Load the column reactor and circulation tank. • Metal particles containing nickel or cobalt, and an aqueous medium are supplied to the reaction zone of the column reactor.

[0221] The aqueous medium and the reaction zone are heated by draining the aqueous medium from the top of the column reactor and circulating the aqueous medium until the nickel bed in the reaction zone reaches a high temperature.

[0222] Stage 1: Leakage In a preferred embodiment, sulfuric acid and hydrogen peroxide are continuously supplied (upward flow) while circulating over the floor, and leaching is carried out in the counterflow of the leaching solution in the direction to which the cathode was added.

[0223] • Dissolve nickel or cobalt-containing metal particles until the target nickel or cobalt concentration or nickel or cobalt density is reached.

[0224] Stage 2: Removal of residual acid If the leaching rate imposed during stage 1 is not fully reached, sulfuric acid and hydrogen peroxide will accumulate in the system.

[0225] The acid removal step is initiated by stopping the addition of sulfuric acid while the addition of hydrogen peroxide continues, but preferably at a reduced rate.

[0226] • If the acid concentration decreases, additional heating may be necessary.

[0227] Stage 3: Hydrogen Peroxide Removal • While maintaining circulation, stop supplying hydrogen peroxide and sulfuric acid until all residual hydrogen peroxide is consumed and the level of residual sulfuric acid is sufficiently low.

[0228] Stage 4: Discharge from the system If the nickel sulfate solution has a predetermined level of nickel and residual sulfuric acid, the nickel sulfate solution is discharged from the column reactor, and in a preferred embodiment, the nickel sulfate solution is discharged from the bottom of the column reactor.

[0229] Optionally, new particles containing nickel or cobalt are filled onto the floor.

[0230] Example 5 - Leaching rate of the half-batch method The experimental setup used is shown in Figure 3. The column reactor is packed with 850 kg of nickel cut cathodes. Initially, these are 2 inches x 2 inches when supplied to the reactor, but most of the cut cathodes in the reactor have already been reduced in size by partial dissolution in a previous leaching operation. The reactor diameter is 35.5 cm, and the reactor is 4 m high from the bottom to the top overflow. The circulation tank is filled with 300 L of water, the mixer inside the circulation tank is activated (75 rpm), and the circulation pump is started at a flow rate of 900 L / hour. The solution is heated until the column inlet temperature is approximately 75°C and the outlet temperature is approximately 73°C, which means that the cathode bed in the column reactor is fully preheated. Sulfuric acid is then added to the solution until a concentration of 15 g / L of H2SO4 is obtained. Then, both H2SO4 and H2O2 are introduced into the system. These reagents are stoichiometrically (meaning 1 mole of H2SO4 per mole of H2O2) and are added at a constant rate of 23.8 kg / hour in a 78% H2SO4 aqueous solution, equivalent to 190 moles / hour of H2SO4, just before they enter the bottom of the reactor column.

[0231] Once the leaching reaction begins, the column outlet temperature gradually rises until it reaches a stable value of approximately 95-98°C. The leaching rate in the column reactor is 12.42 kg Ni / ton Ni / hour.

[0232] Water is added to compensate for evaporation. This phase is completed when the solution reaches a density of 1.37 g / mL, which corresponds to a Ni concentration of 150 g / L. The acid removal stage is initiated by stopping the H2SO4 addition while raising the column inlet temperature to 80°C. Peroxide addition during acid removal was reduced to 25% of the addition rate during the leaching stage.

[0233] When the free acid content inside the buffer container is 12 g / l H2SO4, the system is ready to proceed to the peroxide removal stage. The addition of H2O2 is completely stopped while the sampling method and the addition of water continue. The peroxide removal stage ends when the peroxide concentration approaches 0 g / l H2O2.

[0234] The final solution is discharged from the column towards the circulation tank by reversing the pump direction until a flow rate of approximately 700 L / hour is reached.

[0235] The overall cumulative peroxide efficiency was 97.3%. The residual acid concentration was 9.6 g / l H2SO4. The maximum concentration of H2SO4 reached by reactor overflow was 20.5 g / L. The maximum measured H2O2 concentration was 2.5 g / L. At the end of the batch, approximately 10% of the nickel in the column had reacted.

[0236] The leaching stage took approximately 8 hours, the acid removal step approximately 1 hour, and the peroxide removal step approximately 1 hour. The total time to complete the batch process was approximately 10 hours. This corresponds to an average leaching rate of 9.95 kg Ni / ton Ni per hour over the total duration of the half-batch method.

[0237] Comparative Example 6 - Leaching Rate in a Continuous Process The continuous process was carried out using the same column as in Example 5, with continuous input of acid, hydroxide peroxide, and Ni cut cathode. In this comparative example, the circulating reactor was packed with 300 L of nickel sulfate solution at a concentration of 120 g / L Ni. This solution was pumped into the reactor at a constant flow rate of 900 L / hour while heating to 80°C. After reaching a stable temperature, the input of acid and peroxide solution was started at a stoichiometric molar ratio of 1:1 and a very low rate of 50 mol H2SO4 / hour. Meanwhile, water was continuously added to the circulating reactor to maintain the solution concentration at approximately 120 g / L. Furthermore, a fraction of the solution from the column overflow was continuously withdrawn to maintain the system at a constant volume. This withdrawn fraction is the continuously collected product solution. Meanwhile, the elution of Ni in the product solution was compensated for by adding an additional cut cathode to the reactor.

[0238] Gradually increase the rate of addition of H2SO4 and H2O2 until the product solution reaches a free acid concentration of 10 g / l, comparable to the solution of Example 5.

[0239] In this way, it was found that a maximum leaching rate of 7.4 kg Ni / ton Ni per hour could be achieved without exceeding 10 g / L H2SO4 in the product solution. Further increases in the leaching rate would result in a more incomplete reaction and, consequently, more residual acid in the product solution. Therefore, the average leaching rate in Example 5 is 34% higher than that in the corresponding continuous process with similar yields on hydrogen peroxide. This is explained by the lower amount of free acid in the solution and thus less invasive leaching conditions that can be applied in a continuous process for similar product quality. [Explanation of symbols]

[0240] 100 circulating reactors 10 reaction zones 20 Overflow Zones 21. Overflow conductors that optionally include filters. 30 Condensed Sections 40 H2 detector 50 Heating and / or insulating jacket (outer) 60 columns and coating layers 70 Rubber layer 200 Circulation or buffer tank

Claims

1. A half-batch method for preparing a nickel sulfate or cobalt sulfate solution in a column reactor (100) equipped with a reaction zone (10), wherein the method comprises the following steps: i. A step of supplying metal particles containing nickel or cobalt, respectively, to the reaction zone (10) of the column reactor (100), ii. A step of supplying an aqueous medium to the reaction zone (10), iii. The step of supplying sulfuric acid and hydrogen peroxide to the reaction zone (10) via a supply section, thereby bringing the hydrogen peroxide into contact with the metal particles containing nickel or cobalt in an acidic aqueous medium, iv. Simultaneously with step iii, the acidic aqueous medium is circulated by discharging the fraction of the acidic aqueous medium from the reactor (100), and by recirculating the discharged fraction back into the reactor (100) in the nickel sulfate or cobalt sulfate solution until a nickel or cobalt concentration of at least 80 g / L and a residual acid concentration of less than 20 g / L are achieved, respectively. v. A method comprising the step of discharging the nickel sulfate or cobalt sulfate solution from the column reactor (100) after step iv.

2. In step iii, supplying sulfuric acid and hydrogen peroxide is the following step: a. A step of supplying sulfuric acid and hydrogen peroxide in a molar ratio of sulfuric acid to hydrogen peroxide of 0.9:1.0 to 1.1:1.0, b. The method according to claim 1, comprising the step of supplying hydrogen peroxide to further reduce the residual acid concentration of the nickel sulfate or cobalt sulfate solution.

3. The method according to claim 2, wherein in step iii. a., the sulfuric acid content in the acidic aqueous medium that enters the lower part of the reaction zone (10) is 15 g / L to 60 g / L.

4. The method according to any one of claims 1 to 3, wherein the residual amount of sulfuric acid in the nickel sulfate or cobalt sulfate solution discharged in step v. is 2 g / L to 15 g / L.

5. The method according to any one of claims 1 to 4, wherein the concentration of nickel or cobalt in the nickel sulfate or cobalt sulfate solution discharged in step v. is 80 g / L to 200 g / L, respectively.

6. The method according to any one of claims 1 to 5, wherein the cycle of step iv. is continued after step iii. is completed until the hydrogen peroxide in the nickel sulfate or cobalt sulfate solution is substantially consumed.

7. The method according to any one of claims 1 to 6, wherein the molar ratio of the total amount of hydrogen peroxide supplied in step iii to the total amount of sulfuric acid supplied in step ii and iii is greater than 0.9 and less than 1.

1.

8. The method according to any one of claims 1 to 7, wherein at least 80% by weight of the initial amount of nickel or cobalt-containing particles introduced into the column reactor has not reacted with the sulfuric acid and hydrogen peroxide when the method is interrupted and the nickel sulfate or cobalt sulfate solution is discharged.

9. The method according to any one of claims 1 to 8, wherein the aqueous medium supplied in step ii contains sulfuric acid at a concentration of 5 g / L to 30 g / L.

10. The method according to any one of claims 1 to 9, wherein in steps ii, iii, and iv, the aqueous medium entering the reaction zone (10) has a temperature of 50°C to 80°C, preferably 70°C to 80°C, and more preferably 75°C to 80°C.

11. The method according to any one of claims 1 to 10, wherein the reaction temperature at the top of the reaction zone (10) is 80°C to the boiling point of the leaching solution, preferably 85°C to 99°C.

12. The method according to any one of claims 1 to 11, wherein the metal particles containing nickel or cobalt are obtained electrolytically.

13. The method according to any one of claims 1 to 12, wherein the metal particles containing nickel or cobalt each contain nickel or cobalt in an amount of at least 96% by weight relative to the total weight of the metal particles.

14. The method according to any one of claims 1 to 13, wherein the column reactor (100) is equipped with an insulating jacket (50).

15. The method according to any one of claims 1 to 14, wherein the pressure in the headspace above the reaction zone (10) is atmospheric pressure or a reduced pressure of less than 0.2 atmospheres.

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