Continuous nickel oxidation leaching process

Abstract

To provide a method for oxidative leaching of Ni.SOLUTION: The present invention provides a process for preparing a nickel sulphate solution in a column reactor, wherein metal particles containing nickel are reacted with an oxidising leaching solution comprising sulphuric acid and hydrogen peroxide in water, wherein the acid in the oxidising leaching solution is substantially depleted.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing nickel sulfate. [Background technology]

[0002] Secondary lithium-ion batteries (LIBs) have found widespread application in portable devices and electric vehicles, as well as specialized aerospace applications. Important properties of reusable batteries include charge / discharge efficiency, cycling durability, energy density, and safety. Much development has focused on improving the performance of LIB cathodes.

[0003] After 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 attracted much attention due to their excellent performance. They can be easily obtained by mixing a suitable mixed-metal precursor with a suitable lithium compound, followed by heat treatment of the mixture. Further processing steps, for example, to dope with additional elements, provide a surface coating, improve the crystallite size, etc., have been widely reported.

[0004] The growing demand for electric vehicles (EVs) is driving an increase in the demand for high-purity nickel, especially high-purity nickel sulfate. In fact, nickel refineries for preparing high-purity nickel are considered to be the most important for the supply of battery materials over the next decade. Such refineries must enable high-capacity, highly efficient processes for obtaining the desired nickel sulfate in the desired quantities and purity. Therefore, novel processes must be developed and optimized. Among other methods, oxidative leaching of Ni from high-purity nickel metal is considered one of the more promising avenues.

[0005] The process of leaching Ni metal in sulfuric acid in the presence of hydrogen peroxide proceeds according to the following reaction: Ni+H2O2+H2SO4→NiSO4+2H2O

[0006] This method, also known as oxidative leaching of Ni metal, is a highly exothermic (-423 kJ / mol) process.

[0007] WO 2021 / 105365 describes a method for producing nickel sulfate by leaching metal particles containing nickel in an aqueous sulfuric acid solution, the method comprising: introducing the metal particles into the aqueous sulfuric acid solution; and introducing an aqueous hydrogen peroxide solution into the aqueous sulfuric acid solution containing the metal particles, the aqueous hydrogen peroxide solution being gradually introduced into the aqueous sulfuric acid solution containing the metal particles. Furthermore, there is a need for new methods that offer ease of implementation, high throughput, and optimized use of reactants. WO 2011 / 126757 describes a method for producing an aqueous nickel sulfate solution with a low content of free sulfuric acid. The method involves filling a metal dissolving column with metallic nickel mass, supplying heated sulfuric acid from the top of the metal dissolving column, and simultaneously supplying air or oxygen from the bottom of the metal dissolving column. However, such methods can have the drawback of entraining unreacted metal particles in the resulting process product. Summary of the Invention

[0008] The present invention provides a solution to at least one of the above-mentioned problems by providing a method for oxidative leaching of Ni as set forth in claim 1. Preferably, the method is carried out in a column reactor under continuous flow conditions, in which the acid concentration in the oxidative leaching solution is substantially depleted. More specifically, the acid in the oxidative leaching solution is depleted to the extent that the temperature of the resulting nickel sulfate solution is increased to a temperature just below the boiling point of the solution. The inventors have found that under these conditions, the conversion of Ni to nickel sulfate is maximized, and correspondingly, the column capacity is maximized. The method of the present invention is shown schematically in Figure 1. [Brief explanation of the drawings]

[0009] For further guidance, drawings are included to provide a better understanding of the teachings of the present invention. The drawings are intended to aid in the explanation of the invention and are not intended to limit the invention of this disclosure.

[0010] The drawings and symbols contained therein have meanings commonly understood by those skilled in the art to which this invention pertains. [Figure 1] FIG. 1 shows a schematic representation of the process according to the invention in a column reactor. [Figure 2] FIG. 1 is a graph showing the rate of nickel dissolution (Y-axis, kg / h) in an oxidative leaching process according to the method of the present invention as a function of the average acid concentration (X-axis, g / L sulfuric acid, calculated as the average of CSA,i and CSA,o) at a constant volumetric flow rate through the column. DETAILED DESCRIPTION OF THE INVENTION

[0011] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art to which this invention belongs. As a further guide, term definitions are included to better understand the teachings of the present invention. As used herein, the following terms have the following meanings:

[0012] As used herein, "a," "an," and "the" refer to both the singular and the plural unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more compartments.

[0013] As used herein, "about" in reference to a measurable value, e.g., a parameter, amount, duration, etc., is meant to encompass a variation of the specified value by no more than ±20%, preferably no more than ±10%, more preferably no more than ±5%, even more preferably no more than ±1%, and even more preferably no more than ±0.1%, to the extent that such variations are appropriate for practicing the disclosed invention. However, it should be understood that the value to which the modifier "about" refers is itself specifically disclosed.

[0014] As used herein, "comprise," "comprising," "comprises," and "comprised of" are synonymous with "include," "including," "includes," or "contain," "containing," or "contains," and are inclusive or open-ended terms that specify the presence of what follows, e.g., components, and do not exclude or preclude the presence of additional, unrecited components, features, elements, materials, steps that are known in the art or disclosed herein.

[0015] The recitation of numerical ranges by endpoints includes not only the recited endpoints but also all numbers and fractions subsumed within that range. All percentages shall be understood as weight percentages, abbreviated as "wt %," or volume percentages, abbreviated as "vol %," unless otherwise defined or a different meaning is apparent to one of ordinary skill in the art from their use and in the context in which they are used.

[0016] In the context of the present invention, the term "continuous process" shall be considered a process in which the solution produced has a substantially constant composition. Specifically, a continuous process is one in which the solution produced has a constant composition within what would be considered normal process variations. It is also assumed that the liquid reagents fed to the reactor have a fixed composition under normal process conditions. More specifically, the solution produced has a composition in which the concentration of each component is within ±20% or less of its average concentration, preferably ±10% or less, more preferably ±5% or less, and even more preferably ±3% or less. In a preferred embodiment, the present invention provides a continuous process operating under steady-state conditions.

[0017] Preferably, sulfuric acid and hydrogen peroxide are supplied to the process according to the invention at substantially constant concentrations and flow rates. Ni metal can be supplied to the process intermittently or gradually. Preferably, the present invention provides a process, preferably a continuous process, in which the bed volume of nickel-containing metal particles in a column reactor is controlled within ±20% or less of the average bed volume, preferably ±10% or less, more preferably ±5% or less, and even more preferably ±3% or less.

[0018] In the context of the present invention, the term "concentrated nickel sulfate solution" is considered to be synonymous with the term "nickel sulfate solution having a nickel content of at least 60 g Ni / L," optionally including further ingredients such as sulfuric acid in an amount of less than 30 g HSO, preferably less than 20 g / L, and more preferably less than 10 g / L. Preferably, the nickel sulfate solution has a nickel content of at least 60 g Ni / L, preferably at least 80 g Ni / L. The nickel sulfate solution preferably has a nickel sulfate content below the saturation point of nickel sulfate at the treatment temperature, i.e., a temperature of about 90°C or about 95°C. Preferably, the nickel sulfate solution has a Ni content of 80 to 200 g Ni / L, 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 110-140 g / L, more preferably 120-140 g / L, and most preferably, the nickel sulfate solution has a nickel content of about 130 g / L.

[0019] In a first aspect, the present invention provides a method for preparing a nickel sulfate solution by oxidative leaching of nickel-containing metal particles in a column reactor having a feed section at the bottom of the reactor, an outlet or overflow section at the top or apex of the reactor, and a reaction section between the feed section and the overflow section. The method comprises: i. feeding nickel-containing metal particles into the reaction section of the column reactor; ii. feeding an oxidizing leachate comprising sulfuric acid and hydrogen peroxide in water via a feed section to the reaction section, whereby the oxidizing leachate contacts the metal particles containing nickel in the reaction section, whereby a residual amount of sulfuric acid (C SA,o obtaining a nickel sulfate solution containing iii. Discharging the nickel sulfate solution from the overflow section of the column reactor.

[0020] Preferably, the process according to the first aspect of the present invention is a continuous process. Preferably, the process according to the first aspect of the present invention is applied to prepare a concentrated nickel sulfate solution. The process is typically carried out under continuous flow conditions in a column reactor, where the acid in the oxidation leach solution is substantially depleted after passing through the column reactor. Specifically, steps ii) and iii) are typically carried out under continuous flow conditions, while step i) can be carried out under continuous flow conditions, or gradually or intermittently. More specifically, the acid in the oxidation leach solution is depleted to the extent that the temperature of the resulting nickel sulfate solution is increased to a temperature just below the boiling point of the solution, ensuring that the column capacity is maximized for the target acid concentration in the nickel sulfate solution at the top of the reactor. The inventors have found that under these conditions, the conversion of Ni to nickel sulfate is maximized, and the column capacity is correspondingly maximized.

[0021] The depletion of sulfuric acid throughout the column reactor is controlled by the sulfuric acid concentration (C SA,o ) of the sulfuric acid concentration (C SA,i ) in the context of the present invention, the inventors recommend that this ratio be maintained at a value between 0.90 and 0.01, preferably between 0.80 and 0.01, and more preferably between 0.70 and 0.02. In the context of the present invention, this ratio is called the "acid ratio".

[0022] FIG. 1 shows a schematic representation of the process according to the invention in a column reactor.

[0023] The inventors have found that the desired, i.e., sufficiently low, acid ratio can be managed by maintaining a sufficiently low flow rate of oxidized leachate through the column reactor.

[0024] The inventors have found that the lower the flow rate of the oxidized leachate through the column reactor, the easier it is to control the column reactor process. By maintaining the flow rate of the oxidized leachate low enough, the sulfuric acid is depleted at the top of the column reactor. Also, by maintaining the flow rate of the oxidized leachate to the column reactor low enough, the leaching reaction can be controlled so that the temperature of the nickel sulfate solution at the top of the column reactor remains below the boiling point of the solution, allowing the inlet temperature to be kept at a moderate to low temperature. A sufficiently low flow rate can control the progress of the leaching reaction to ensure complete consumption of the oxidant, and preferably a sufficiently low flow rate is managed so that the temperature at the top of the column is just below the boiling point of the solution. Importantly, the inventors have recognized that operating the column reactor process at a sufficiently low flow rate results in a higher average acid concentration in the column reactor, resulting in a faster conversion of Ni metal to NiSO4.

[0025] FIG. 2 shows the nickel dissolution rate (Y-axis, kg / h) in an oxidative leaching process according to the method of the present invention as a function of the average acid concentration (X-axis, g / L sulfuric acid, C) at a constant volumetric flow rate through the column. SA,i and C SA,o The results show that the higher the average acid concentration in the column, the higher the nickel dissolution rate. The maximum capacity of the continuous process can be obtained when the acid consumption through the column is maximized, provided that the temperature at the top of the column reactor is controlled below the boiling point of the nickel sulfate solution.

[0026] On the other hand, processes carried out at higher ratios of sulfuric acid concentration in the nickel sulfate solution obtained in step ii. to that in the oxidized leachate, such as a ratio of 0.95 to 1.0, require higher flow rates and therefore lower average acid concentrations in the reaction zone. Therefore, such processes slow the conversion of Ni metal to NiSO4 and reduce capacity.

[0027] In a preferred embodiment, the present invention provides a method according to the first aspect, wherein on a macroscopic scale, a 1D flow profile is maintained throughout the column.

[0028] In a preferred embodiment, the present invention provides a method for adjusting the acid ratio, i.e., the sulfuric acid concentration (C SA,o ) of the sulfuric acid concentration (C SA,i The method according to the first aspect further provides a method in which the ratio of (i) to (ii) is less than 0.70, less than 0.65, less than 0.60, less than 0.55, or even less than 0.50. Preferably, the ratio is between 0.5 and 0.1. Preferably, the ratio is less than 0.45, or even less than 0.40. Preferably, the ratio is greater 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 therebetween.

[0029] In a preferred embodiment, the present invention provides a method for treating a microbial cell comprising: SA,i and C SA,o Difference Δ ac is at least 5 g / L and at most 80 g / L sulfuric acid, preferably at least 10 g / L and at most 70 g / L sulfuric acid. ac is at least 15 g / L, more preferably at least 20 g / L. ac is at most 60 g / L or at most 50 g / L, more preferably at most 45 g / L. Most preferably, the difference in acid concentration Δ ac is about 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 therebetween.

[0030] In a preferred embodiment, the oxidative leaching method, i.e., the column reactor, is controlled so that the nickel sulfate solution obtained from the column reactor has a residual sulfuric acid content (C SA,oLeaching with a low residual sulfuric acid content ensures that sulfuric acid is used economically in the process. Preferably, the residual amount of sulfuric acid in the nickel sulfate solution is between 2 g / L and 15 g / L, more preferably between 2 g / L and 10 g / L, and most preferably, the residual amount of sulfuric acid is about 2 g / L, 4 g / L, 6 g / L, 8 g / L, or 10 g / L, or any value therebetween.

[0031] In a preferred embodiment, the present invention provides a process according to the first aspect, wherein the oxidative leachate is fed to the reactor, i.e., the column reactor, at a temperature above 20°C, preferably above 30°C, preferably above 40°C, and more preferably above 50°C. Specifically, the oxidative leachate is fed to the reactor at a temperature between 50°C and 85°C, preferably between 65°C and 85°C, and more preferably at about 75°C. Providing a lower temperature oxidative leachate to the column is advantageous, allowing for a higher acid concentration. Such a higher acid concentration can increase the Ni conversion rate and, therefore, the process capacity. However, the inventors have recognized that maintaining a sufficiently high temperature of the oxidative leach solution entering the column is appropriate to ensure a sufficiently fast kinetics of the oxidative leaching reaction. The desired temperature, e.g., 60°C, can be achieved by mixing room temperature sulfuric acid and / or hydrogen peroxide with a partially cooled fraction of the column effluent. Furthermore, maintaining a sufficiently high temperature allows for an efficient cooling operation of the effluent fraction. Feed of the oxidized leachate at a lower temperature also ensures that decomposition of hydrogen peroxide in the feed solution is suppressed.

[0032] In a preferred embodiment, the present invention provides a process according to the first aspect, wherein the nickel sulfate solution is removed from the reactor at a temperature below the boiling point of the nickel sulfate solution, preferably a temperature of 90° C. to 105° C., more preferably a temperature of 95° C. to 100° C. Preferably, the nickel sulfate solution discharged from the reactor has a temperature of 95° C. to 99° C., for example 96° C., 97° C., 98° C. or 99° C.

[0033] In a preferred embodiment, the present invention provides a process according to the first aspect, wherein a first fraction φ1 of the nickel sulfate solution is cooled from above 90°C to below 85°C, and the fraction φ1 is mixed with sulfuric acid and hydrogen peroxide in water to form an oxidized leachate before feeding the oxidized leachate to the reactor. Preferably, the first fraction φ1 is cooled to a temperature of above 95°C to below 85°C, preferably below 80°C, more preferably below 75°C, even more preferably below 70°C, more preferably from above 97°C to below 85°C. Advantageously, the first fraction φ1 is cooled to a temperature of above 50°C, preferably above 60°C, more preferably above 70°C.

[0034] Cooling can be carried out in a heat exchanger, such as a plate heat exchanger or a shell-and-tube heat exchanger, or in a reactor equipped with cooling means. Preferably, the heat exchanger consists of a reactor equipped with cooling means. Such a reactor can further buffer the volume of the first fraction φ1. Alternatively, sulfuric acid and / or hydrogen peroxide can be preheated with heat recovered from the heat exchanger. Advantageously, the process conditions of the process of the present invention ensure that a constant temperature of the nickel sulfate solution at the top of the column reactor is achieved, which simplifies the cooling process.

[0035] In a preferred embodiment, the present invention provides a method according to the first aspect, wherein a first fraction φ1 of the nickel sulfate solution is mixed with sulfuric acid and / or hydrogen peroxide to form an oxidized leachate, and then the oxidized leachate is fed to the reactor. In a preferred embodiment, the volume ratio of the first fraction φ1 to the total volume of the nickel sulfate solution is 0.70 to 0.98, preferably 0.75 to 0.95, more preferably 0.80 to 0.93, and most preferably equal to 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, or any value therebetween.

[0036] In a preferred embodiment, the present invention provides a process according to the first aspect, wherein the heat recovered from the cooling step of the first fraction φ1 is at least partly used to heat the oxidized leachate and / or the contents of the reactor. Preferably, the heat is used to heat the oxidized leachate and / or the contents of the reactor to a temperature of between 55°C and 85°C, preferably between 60°C and 85°C, more preferably between 65°C and 80°C, most preferably to a temperature of about 65°C.

[0037] In a preferred embodiment, the present invention provides a method according to the first aspect, wherein a second fraction φ2 of the nickel sulfate solution is subjected to a purification step to reduce the concentration of one or more impurities in the second fraction φ2, the impurities comprising one or more selected from the list comprising Cu, Zn, Co, Mn, Fe, Al, F, C, Ca, Si, P, As, Cd, Sb, and Mg. In a preferred embodiment, a base is added to the second fraction φ2 of the nickel sulfate solution to react with any residual amount of sulfuric acid present in the nickel sulfate solution before the second fraction is subjected to a further purification step, the base being selected from the group consisting of potassium hydroxide, potassium carbonate, nickel hydroxide, nickel 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 foregoing. Preferably, the base is added until the pH of the nickel sulfate solution reaches 2 to 5, preferably 2.5 to 4.5, more preferably 3.0 to 4.0.

[0038] In a preferred embodiment, the present invention provides a method according to the first aspect, wherein the nickel-containing metal particles comprise nickel in an amount of at least 97 wt.%, preferably at least 98 wt.%, more preferably at least 99 wt.%, based on the total weight of the metal particles. The metal particles may further contain Co in an amount of up to 1 wt.%. Preferably, the metal particles contain Ni in an amount of at least 99.5 wt.%. In the context of the present invention, the Ni metal feed preferably comprises highly pure Ni metal, typically having a purity of 99.97+%, 99.98+%, or even 99.99+%. Ni metal can be fed to the reactor in the form of Ni cut cathode metal, i.e., chopped or chopped full-plate cathode metal obtained from an electrowinning process, typically having a size of 1 inch x 1 inch, 2 inches x 2 inches, or 4 inches x 4 inches; Ni metal rounds; or Ni pellets, i.e., balls having a diameter of about 0.5 cm. The hydrogen peroxide used in the present process is typically a 30-60% by weight, for example a 50% by weight, solution in water, and the sulfuric acid has a concentration of 78-98% by weight in water, preferably a concentration of 98% by weight in water. Any water used in the present process may be high purity water, such as demineralized water or RO water.

[0039] In a preferred embodiment, the present invention provides a method according to the first aspect, wherein the oxidized leachate comprises sulfuric acid in an amount of 10 to 150 g / L, preferably 15 to 100 g / L. Preferably, the oxidized leachate comprises sulfuric acid in an amount of 20 to 80 g / L, more preferably 20 to 60 g / L.

[0040] In a preferred embodiment, the present invention provides a method according to the first aspect, wherein the oxidized leachate comprises hydrogen peroxide in an amount of 1 to 50 g / L, preferably 1 to 30 g / L, more preferably 5 to 30 g / L. More preferably, the oxidized leachate comprises hydrogen peroxide in an amount of 5 to 20 g / L, more preferably about 5 to 12 g / L, even more preferably about 7 to 10 g / L.

[0041] In a first preferred embodiment, the present invention provides a method according to the first aspect, wherein hydrogen peroxide is present in the oxidized leachate fed to the column reactor in a substoichiometric amount relative to the amount of sulfuric acid present in the oxidized leachate. For example, the oxidized leachate may contain 0.4 mol / L hydrogen peroxide and 0.5 mol / L sulfuric acid. Preferably, the molar ratio of hydrogen peroxide to sulfuric acid in the oxidized leachate fed to the column reactor is between 0.6 and 1.0, preferably between 0.8 and 1.0, and more preferably about 0.9. The method according to the present invention can be carried out using a substoichiometric amount of hydrogen peroxide, thereby allowing for residual amounts of sulfuric acid in the formed nickel sulfate solution. In a second alternative embodiment, the present invention provides a method according to the first aspect, wherein sulfuric acid and hydrogen peroxide are present in the oxidized leachate in stoichiometric amounts. Preferably, the molar ratio of sulfuric acid to hydrogen peroxide is between 1:1 and 1:1.2, more preferably between 1.0:1.0 and 1:1.1. The excess hydrogen peroxide promotes further depletion of sulfuric acid. The excess hydrogen peroxide ensures that hydrogen peroxide does not become the rate limiting factor of the process. The excess hydrogen peroxide can be recovered from the column reactor effluent.

[0042] In a preferred embodiment, the present invention provides a method according to the first aspect, wherein the gas atmosphere in the overflow of the column reactor is circulated through a scrubber. Preferably, the scrubber is cooled. Preferably, the scrubber and the circulation reactor are integrated into one single unit. Preferably, the circulation reactor is maintained at a temperature of 50°C to 90°C, preferably at a temperature of about 65°C or about 85°C, more preferably at a temperature of about 75°C. A lower temperature is more favorable to the efficiency of the scrubbing operation.

[0043] In a preferred embodiment, the present invention provides a process according to the first aspect, wherein the oxidized leachate is contacted with the metal particles at atmospheric pressure, i.e., 1 bar, or under reduced pressure of less than 0.5 bar, preferably less than 0.2 bar, more preferably less than 0.1 bar. Preferably, the oxidized leachate is contacted with the metal particles in an atmosphere of oxygen, air or oxygen-enriched air. In another preferred embodiment, the gas atmosphere in the overflow is flushed with an inert gas, such as N2. This allows for easy removal of hydrogen gas if it is formed in the column reactor.

[0044] In another preferred embodiment, the present invention provides a method according to the first aspect, wherein the gas atmosphere in the overflow is treated in a scrubber to remove water and any hydrogen that may have formed.

[0045] In a preferred embodiment, the present invention provides a column reactor having a bed volume of the metal particles with a diameter D b and height H b and the ratio H of the height to the diameter b :D b is from 0.8 to 5, preferably from 1 to 5. Preferably, the height and diameter of the bed volume are maintained substantially constant throughout the process.

[0046] 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 "column reactor," "packed bed" or "packed bed reactor," "tower" or "tower reactor," and refers to a column reactor having a substantially cylindrical shape with an internal diameter D and a height H. A column reactor consists of a vertically arranged cylindrical column, arranged to operate without mechanical stirring, preferably in an upflow mode, i.e., with fluid flow from the bottom to the top of the column. A column reactor is further characterized by (i) a feed section at the bottom of the cylindrical reactor for feeding liquid reagents, such as an aqueous solution containing sulfuric acid and hydrogen peroxide; (ii) a top or overflow section at the top or end of the column reactor, opposite the feed section, characterized by an effluent for collecting the overflowing nickel sulfate solution; and (iii) a middle or reaction section in the middle of the cylindrical reactor, where the leaching reaction proceeds. Nickel-containing metal particles are preferably fed to the top of the reactor and can be gradually or intermittently added to form a bed of metal particles on a support in the column reactor. The column reactor preferably includes a support above the feed section for supporting a solid reagent, such as Ni metal. The support comprises a grid for supporting Ni metal. The column reactor further preferably includes a means for feeding a solid reagent, such as Ni metal, to the reaction zone of the column reactor. The column reactor further preferably includes a means for radially and uniformly distributing the oxidized leachate to the feed section of the column reactor. The solid reagent can be loaded onto the support by introducing Ni metal at the top of the reactor or any location above the support. The overflow zone is provided with an outlet for receiving nickel sulfate solution via an overflow mechanism.

[0047] In a preferred embodiment, the present invention provides a column reactor having a diameter D L and height H L and the ratio H of the height to the diameter L :D Lis between 1.0 and 10.0, preferably between 1.5 and 8.0, more preferably between 2.0 and 5.0, and most preferably about 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 or 5.0, or any value therebetween. L :D L The ratio ensures that one-dimensional flow can be obtained throughout the column and that small metallic particles resulting from the reacted metallic feed particles do not become entrained upward into the nickel sulfate solution resulting from the oxidation leaching reaction, thereby entraining unreacted metallic particles and thereby contaminating the resulting nickel sulfate solution and further reducing the efficiency of the process.

[0048] In a preferred embodiment, the column reactor is cylindrical and has an internal diameter D and a height H, with the ratio of the height H to the diameter D being 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 therebetween. An appropriate geometry of the column reactor, in particular a sufficiently high H:D ratio, ensures that one-dimensional flow can be obtained throughout the column.

[0049] In a preferred embodiment, the present invention provides a method according to the first aspect of the present invention, wherein in step ii., the oxidized leachate comprising sulfuric acid and hydrogen peroxide in water is fed to the reaction zone through the bottom of the column reactor, and in step iii., the nickel sulfate solution is discharged from the reaction zone through the top of the column reactor. Preferably, the metal particles are fed to the reaction zone through the top of the column reactor. The metal particles may be fed continuously or intermittently, preferably intermittently.

[0050] In a preferred embodiment, the reaction zone can also incorporate a mechanical impeller, i.e., an impeller attached to a motor by a rod, for simply mixing the liquid reagents. Alternatively, a static mixer is used. In a preferred embodiment, the reaction zone includes multiple vertical baffles, which are positioned diametrically opposite each other and located between the inlet nozzle and the impeller, with at least one baffle located at diametrically opposite ends of the reactor wall. In this embodiment, the impeller and vertical baffles aid in micro-level mixing of the reactants. The impeller improves the reaction rate of the reactor. The vertical baffles help ensure maximum mixing of the reactants within the reaction zone. The placement of the vertical baffles ensures that the reaction is confined to the reaction zone and does not extend beyond the reaction zone.

[0051] Preferably, the reactor has a calming zone above the reaction zone. The calming zone preferably has a tubular structure with a constant cross-section equal to the cross-section of the reaction zone, or a tubular structure with an enlarged cross-section whose diameter is greater than the cross-section of the reaction zone. The calming zone is in fluid communication with the reaction zone, with the reaction zone at its distal end and an overflow zone at its proximal end. The function of the calming zone is to achieve a non-turbulent liquid flow that allows unreacted metal particles to conform to a non-flowing state. This allows unreacted or insufficiently reacted metal particles to return to the reaction zone. The calming zone may include multiple horizontal baffles located in the central, proximal, and distal portions of the calming zone. In this embodiment, at least two of the horizontal baffles may be downward-facing baffles with a central flow opening adapted to slow the velocity of the reaction mixture. In yet another embodiment, the central horizontal baffle is a conical baffle with an annular flow. In this embodiment, the horizontal baffle arrangement creates a curved flow path that allows larger sized particles to settle while simultaneously allowing the upward flowing mixture to move smoothly into the overflow zone.

[0052] In a preferred embodiment, the overflow zone has a tubular structure, the cross section of which is equal to the cross sections of the settling zone and the reaction zone, and is located at the proximal end of the reactor, and is provided with an outlet for receiving the formed nickel sulfate solution. [Example]

[0053] The following examples are intended to further clarify the present invention, but are not intended to limit the scope of the invention.

[0054] Example 1 FIG. 1 shows a schematic representation of the process according to the invention in a column reactor.

[0055] An oxidized leachate is prepared by mixing an aqueous sulfuric acid solution A with a hydrogen peroxide solution P in water. The mixture is then mixed with a fraction φ1 of the effluent of the column reactor to prepare an oxidized leachate of about T i = 60°C. The column reactor has an internal diameter D and a height H, with a ratio H:D of about 2.35. Before mixing the fraction φ1 with sulfuric acid and hydrogen peroxide, the fraction φ1 is cooled from a temperature of about 98°C to a temperature of about 65°C. The oxidized leachate thus prepared has a temperature of about 60°C and a sulfuric acid content of about 45 g / L and is fed to the reaction zone of the column reactor via a feed.

[0056] The reaction zone includes a Ni metal cut cathode, the Ni metal cut cathode having dimensions of approximately 50 mm x 50 mm and a nickel content of 99.97%. Metal particles containing nickel are intermittently fed onto a support plate above the reactor feed. The metal particle feed is omitted from FIG. 1. The Ni metal is provided in a bed, the bed having a bed volume characterized by a height and a diameter, the ratio of the height to the diameter being approximately 3. Upon contact with sulfuric acid and hydrogen peroxide, a residual amount of sulfuric acid, C SA,o A nickel sulfate solution N is formed with a pH of about 7 g / L. The ratio of the sulfuric acid concentration in the effluent to that in the feed solution is about 0.15. Due to the exothermic nature of the reaction, the temperature T of the nickel sulfate solution N at the top of the columno is about 98°C.

[0057] A first fraction φ1 of the nickel sulfate solution N is cooled from a temperature of about 98°C to a temperature of about 65°C and then mixed with a mixture of sulfuric acid A and hydrogen peroxide P in water. A second fraction φ2 of the nickel sulfate solution N is further treated to a pH of about 3.5 and then treated to remove impurities. Any gases that may have formed in the atmosphere at the top of the column reactor are treated in a scrubbing unit.

[0058] Example 2 An oxidized leachate is prepared by mixing an aqueous sulfuric acid solution A with a hydrogen peroxide solution P in water. The mixture is then mixed with a fraction φ1 of the effluent of the column reactor to prepare an oxidized leachate of about T i = 75°C. The column reactor has an internal diameter D and a height H, with a ratio H:D of about 2.6. Before mixing the fraction φ1 with sulfuric acid and hydrogen peroxide, the fraction φ1 is cooled from a temperature of about 98°C to a temperature of about 75°C. The oxidized leachate thus prepared has a temperature of about 75°C and a sulfuric acid content of about 31 g / L and is fed to the reaction zone of the column reactor via a feed.

[0059] The reaction zone includes a Ni metal cut cathode, the Ni metal cut cathode having dimensions of approximately 50 mm x 50 mm and a thickness of 13 mm, and a nickel content of 99.97%. Nickel-containing metal particles are intermittently fed onto a support plate above the reactor feed. The metal particle feed is omitted from FIG. 1 . The Ni metal is provided in a bed, the bed having a bed volume characterized by a height and a diameter, the ratio of the height to the diameter being approximately 5. Upon contact with sulfuric acid and hydrogen peroxide, a residual amount of sulfuric acid, C SA,o A nickel sulfate solution N is formed with a sulfuric acid concentration of about 10 g / L. The ratio of the sulfuric acid concentration in the effluent to that in the feed solution is about 0.32. Due to the exothermic nature of the reaction, the temperature T of the nickel sulfate solution N at the top of the column o is about 98°C.

[0060] A first fraction φ1 of the nickel sulfate solution N is cooled from a temperature of about 98° C. to a temperature of about 75° C. and then mixed with a mixture of sulfuric acid A and hydrogen peroxide P in water. A second fraction φ2 of the nickel sulfate solution N is further treated to remove impurities. Gases that may have formed in the atmosphere at the top of the column reactor are treated in a scrubbing unit.

Claims

1. 1. A method for preparing a nickel sulfate solution (N) in a column reactor (R) by oxidative leaching of nickel-containing metal particles, comprising: i. feeding nickel-containing metal particles into a reaction section of the column reactor; ii. An oxidized leachate comprising sulfuric acid and hydrogen peroxide in water is supplied to the reaction zone via a supply zone, whereby the oxidized leachate is brought into contact with the metal particles containing nickel in the reaction zone, whereby a residual amount of sulfuric acid (C ＳＡ，ｏ obtaining a nickel sulfate solution containing iii. Discharging the nickel sulfate solution from the column reactor; The sulfuric acid concentration (C ＳＡ，ｏ ) the sulfuric acid concentration of the oxidized leachate (C ＳＡ，ｉ ) is 0.90 to 0.

01.

2. 2. The method of claim 1, wherein in step ii., the oxidized leachate comprising sulfuric acid and hydrogen peroxide in water is fed to the reaction section through the bottom of the column reactor, and in step iii., the nickel sulfate solution is discharged from the reaction section through the top of the column reactor.

3. The sulfuric acid concentration (C ＳＡ，ｏ ) the sulfuric acid concentration of the oxidized leachate (C ＳＡ，ｉ 2. The method of claim 1, wherein the ratio of 1 to 2 is from 0.70 to 0.

02.

4. The liquid volume of the oxidized leachate in the column reactor has a diameter D Ｌ and height H Ｌ and a ratio H of the height to the diameter. Ｌ :D Ｌ The method of claim 1, wherein the ρ is 1.0 to 10.0, or 1.5 to 8.

0.

5. 10. The method of claim 1, wherein the oxidized leachate is fed to the reactor at a temperature of from 50°C to 85°C.

6. 10. The method of claim 1, wherein the nickel sulfate solution is removed from the reactor at a temperature of from 90°C to 100°C.

7. A first fraction φ of the nickel sulfate solution １ is cooled from a temperature above 90°C to a temperature below 85°C, and the fraction φ １ is mixed with sulfuric acid and / or hydrogen peroxide to form an oxidized leachate before the oxidized leachate is fed to the reactor.

8. A first fraction φ of the nickel sulfate solution １ is mixed with sulfuric acid and / or hydrogen peroxide to form an oxidized leachate, and then the oxidized leachate is fed to the reactor, and the first fraction φ １ 2. The method of claim 1, wherein the volume ratio of the nickel sulfate solution to the total volume of the nickel sulfate solution is 0.70 to 0.

95.

9. The first fraction φ １ 9. The method of claim 7 or 8, wherein the heat recovered from the cooling step of step 1 above is used at least in part to heat the oxidized leachate and / or the contents of the reactor.

10. A second fraction φ of the nickel sulfate solution ２ is the second fraction φ ２ 2. The method of claim 1, wherein the sintered product is subjected to a purification step to reduce the concentration of one or more impurities in the sintered product, the impurities comprising one or more selected from the list comprising Cu, Zn, Co, Mn, Fe, Al, F, C, Ca, Si, P, As, Cd, Sb and Mg.

11. 10. The method of claim 1, wherein the nickel-containing metal particles comprise nickel in an amount of at least 96 wt. % based on the total weight of the metal particles.

12. 2. The method of claim 1, wherein the oxidized leachate comprises sulfuric acid in an amount of 20 to 100 g / L.

13. 10. The method of claim 1, wherein the oxidized leachate comprises hydrogen peroxide in an amount of 1.5 to 30 g / L.

14. 10. The method of claim 1, wherein hydrogen peroxide is present in the oxidized leachate fed to the column reactor in a sub-stoichiometric amount relative to the amount of sulfuric acid present in the oxidized leachate.

15. 10. The method of claim 1, wherein the gas atmosphere in the overflow section of the column reactor is circulated through a scrubber.

16. 10. The method of claim 1, wherein the oxidized leachate contacts the metal particles at atmospheric pressure or a reduced pressure of less than 0.2 atm.

17. The column reactor is controlled so that the nickel sulfate solution obtained from the column reactor has a residual sulfuric acid content (C ＳＡ，ｏ 2. The method of claim 1, wherein the method ensures that the .intg.

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