Processing method of nickel sulfide raw material and sulfur recovery method

Abstract

To provide a processing method of a nickel sulfide raw material capable of preventing a deterioration in solid-liquid separation properties of a chlorine leaching residue molten material obtained by heating a chlorine leaching residue generated in a process of chlorine leaching of the nickel sulfide raw material, so as to enable efficient recovery of sulfur from the chlorine leaching residue.SOLUTION: A processing method of a nickel sulfide raw material including iron and arsenic includes: a cementation step of mixing a nickel sulfide raw material with a copper-containing and iron-containing crude nickel chloride aqueous solution containing a bivalent copper ion, and substituting and leaching nickel in the nickel sulfide raw material to obtain a cementation final solution with the copper ion removed and a cementation residue; and a chlorine leaching step of blowing a chlorine gas into a cementation residue slurry obtained by re-pulping the cementation residue to generate a chlorine leaching slurry to obtain a chlorine leachate and a chlorine reaching residue. In the chlorine leaching step, a hydrochloric acid is added to adjust a hydrochloric acid concentration of the chlorine leachate to be generated to set a pH of the chlorine leachate as -0.1 or less.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for treating a nickel sulfide raw material that contains nickel, cobalt, copper, and sulfur, and also contains iron and arsenic as impurities, and that makes it possible to efficiently recover sulfur from a chlorine leaching residue generated in a chlorine leaching process in which nickel and cobalt are leached with chlorine using nickel sulfide as a raw material, and a sulfur recovery method for recovering sulfur from the chlorine leaching residue obtained through the treatment method. [Background technology]

[0002] In the nickel hydrometallurgy process (hereinafter also referred to as the "MCLE process"), the raw material nickel matte or nickel-cobalt mixed sulfide (MS: mixed sulfide) is leached with chlorine, and the resulting leachate (chlorine leachate) is subjected to a purification process to remove impurities, and nickel and cobalt are recovered in the form of electrolytic nickel and electrolytic cobalt in an electrolytic process. The technology of the MCLE process is disclosed in, for example, Patent Document 1 and Patent Document 2.

[0003] As shown in FIG. 1, the chlorine leaching solution obtained from the chlorine leaching process is subjected to removal of excess copper in the copper removal electrolysis process provided between the cementation process and the cementation process, and impurities such as iron and arsenic are removed in the iron removal process, and then the solution is sent to the cobalt solvent extraction process. In the cobalt solvent extraction process, nickel and cobalt are separated by solvent extraction to obtain a crude nickel chloride solution (NiCl2) and a crude cobalt chloride solution (CoCl2). The crude nickel chloride solution is further purified by removing impurities in the solution purification process and sent to the nickel electrolysis process. Then, in the nickel electrolysis process, electrolytic nickel is produced by electrolytic winning. Meanwhile, the crude cobalt chloride solution is also further purified by removing impurities in the solution purification process and sent to the cobalt electrolysis process, where electrolytic winning is produced.

[0004] The MCLE process also includes a cementation process to remove copper ions, which are impurities contained in the chlorine leachate (copper-containing nickel chloride aqueous solution) obtained by chlorine leaching. In the cementation process, the oxidizing power of the divalent copper ions contained in the chlorine leachate is used to leach nickel and cobalt from the nickel matte and MS (hereinafter, these may be collectively referred to as "nickel sulfide raw material"), and the reducing power of the nickel matte and MS is used to distribute the copper ions and silver ions contained in the chlorine leachate to the solid side and remove them.

[0005] Now, the chlorine leaching residue obtained by separating it from the chlorine leaching solution in the chlorine leaching process contains undissolved metal-containing components (such as nickel, cobalt, and copper sulfides), but is mainly composed of elemental sulfur. Therefore, the separated chlorine leaching residue is sent to a sulfur recovery process, where the sulfur contained in the chlorine leaching residue is recovered and treated as a by-product. Specifically, in the sulfur recovery process, taking advantage of the relatively low melting point of sulfur, the chlorine leaching residue is heated to a temperature at which only the sulfur contained in the chlorine leaching residue melts and becomes liquid sulfur, and the chlorine leaching residue is then melted and subjected to solid-liquid separation using a mesh filter dedicated to melts, whereby high-purity sulfur can be recovered.

[0006] At this time, the metal-containing components do not melt because their melting points are very high, but some of the metal-containing components may clog the mesh filter, significantly impairing the solid-liquid separation property (the permeability of liquid sulfur through the mesh filter). For this reason, it is preferable that the chlorine leaching residue contains a small amount of components that may impair the solid-liquid separation property. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2018-3104 A [Patent Document 2] JP 2019-81920 A Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, in order to prevent deterioration of liquid permeability due to a mesh filter in solid-liquid separation in the sulfur recovery process, it is necessary to suppress the content of components that deteriorate solid-liquid separability contained in the chlorine leaching residue, and a means for achieving this is being sought. Here, the mesh filter refers to a solid-liquid separation device whose filtering material is in the form of a wire mesh or a porous plate, and an example of this corresponds to a batch-type leaf-type filtering device.

[0009] In the solid-liquid separation process in the sulfur recovery process, unlike the filtering operation of a slurry which is a mixture of a normal aqueous solution and a solid, a filtering operation of a slurry which is a mixture of liquid sulfur and a solid, which is obtained by liquefying sulfur, which is solid at room temperature, by raising the temperature, is performed. Therefore, deterioration of the liquid permeability means a decrease in the amount of liquid sulfur passing through, and a decrease in the liquid temperature causes a further deterioration of the liquid permeability. Furthermore, it may even become impossible to pass the liquid through. To explain in more detail, although the shell side of the solid-liquid separation device, including the piping, is naturally insulated, the internal parts such as the filter plate are not heated or insulated. Therefore, when the amount of liquid passing through decreases, the sensible heat possessed by the chlorine leaching residue melt itself dissipates in no small amount, so the temperature of the chlorine leaching residue melt decreases and the viscosity increases. When the viscosity increases, the amount of liquid passing through decreases further and the temperature decreases. When the temperature decreases to below the melting point of sulfur, solid sulfur precipitates, and it may become impossible to pass the liquid through.

[0010] The chlorine leaching residue obtained by chlorine leaching of nickel sulfide raw material or cementation residue has good filterability because non-leached components remain in a porous sponge-like state even if it is the residue of metal-containing components other than sulfur, based on the particle structure of each compound constituting the nickel sulfide raw material or cementation residue. However, it was found that the precipitates generated secondarily during the chlorine leaching reaction become fine particles and significantly deteriorate the filterability.

[0011] The present invention has been proposed in view of the above circumstances, and has an object to provide a method for treating a nickel sulfide raw material, which prevents deterioration of solid-liquid separability of a chlorine leaching residue molten product obtained by heating a chlorine leaching residue generated in a chlorine leaching step in which nickel and cobalt are leached with chlorine from nickel sulfide as a raw material, and enables efficient recovery of sulfur from the chlorine leaching residue. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, it was found that although iron and arsenic, which are impurities contained in the nickel sulfide raw material, are once dissolved into the liquid by chlorine leaching, a part of them forms a precipitate again and is distributed to the chlorine leaching residue, and becomes in the form of poorly soluble iron arsenate (FeAsO4) in the chlorine leaching residue, which causes clogging of the mesh filter in solid-liquid separation in the sulfur recovery process, thereby deteriorating solid-liquid separation. Therefore, it was found that the grade of iron and arsenic in the chlorine leaching residue can be reduced and the amount of FeAsO4, which is a poorly soluble substance, can be suppressed by adding hydrochloric acid to adjust the hydrochloric acid concentration of the chlorine leaching solution produced in the chlorine leaching step of the MCLE process to a pH of -0.1 or less, and thus the present invention was completed.

[0013] (1) The first invention of the present invention is a method for treating a nickel sulfide raw material containing iron and arsenic as impurities, comprising: a cementation step of mixing a copper-containing and ferrous crude nickel chloride aqueous solution containing divalent copper ions with a nickel sulfide raw material; and displacing and leaching nickel in the nickel sulfide raw material with the copper ions in the copper-containing and ferrous crude nickel chloride aqueous solution to generate a cementation slurry, which is a mixture of the iron-containing crude nickel chloride aqueous solution from which the copper ions have been removed and a precipitate containing copper sulfide; and separating the cementation slurry into a cementation final liquid and a cementation residue by solid-liquid separation; and separating the cementation residue into a leaching slurry. This is a method for treating a nickel sulfide raw material, comprising: a chlorine leaching step of pulping the cementation residue to form a cementation residue slurry, blowing chlorine gas into the cementation residue slurry to leach heavy metals in the cementation residue and produce a chlorine leach slurry, and separating the slurry into a chlorine leachate and a chlorine leach residue by solid-liquid separation; and repeating the chlorine leachate as the copper-containing, iron-containing crude nickel chloride aqueous solution, wherein in the chlorine leaching step, hydrochloric acid is added to adjust the hydrochloric acid concentration of the chlorine leachate produced, thereby making the pH of the chlorine leachate -0.1 or less.

[0014] (2) A second aspect of the present invention is a method for treating a nickel sulfide raw material according to the first aspect of the present invention, wherein the chlorine leaching residue obtained by separating the chlorine leaching slurry has an iron content of 0.3 mass% or less and an arsenic content of 0.2 mass% or less.

[0015] (3) A third aspect of the present invention is a method for treating a nickel sulfide raw material according to the first aspect of the present invention, further comprising a sulfur recovery step of heating the chlorine leaching residue in a melting tank to melt the sulfur content contained in the chlorine leaching residue to form a chlorine leaching residue molten material, and subjecting the chlorine leaching residue molten material to solid-liquid separation to obtain liquid sulfur and a molten residue, wherein in the solid-liquid separation treatment in the sulfur recovery step, the liquid permeability when filtered with a batch leaf-type filtration device is controlled.

[0016] (4) The fourth aspect of the present invention is the third aspect of the present invention, wherein the amount of sulfur recovered per unit filtration area is 40 kg / m as a liquid permeability when filtered with a batch leaf type filtration device in the solid-liquid separation process in the sulfur recovery step. 2 This completes the method for treating nickel sulfide raw material.

[0017] (5) The fifth invention of the present invention is a method for recovering sulfur from a chlorine leaching residue obtained by chlorine leaching a nickel sulfide raw material containing iron and arsenic as impurities, the method comprising: a cementation step of mixing a copper-containing and ferrous crude nickel chloride aqueous solution containing divalent copper ions with a nickel sulfide raw material; displacing and leaching nickel in the nickel sulfide raw material with the copper ions in the copper-containing and ferrous crude nickel chloride aqueous solution to generate a cementation slurry which is a mixture of the iron-containing crude nickel chloride aqueous solution from which the copper ions have been removed and a precipitate containing copper sulfide; and separating the cementation slurry into a cementation end liquid and a cementation residue by solid-liquid separation; and repulping the cementation residue to obtain a cementation residue slurry, and then separating the cementation residue from the cementation residue. The method includes a chlorine leaching step of injecting chlorine gas into a slurry to leach heavy metals in the cementation residue to produce a chlorine leaching slurry, and separating the slurry into a chlorine leaching solution and a chlorine leaching residue by solid-liquid separation. The chlorine leaching solution is repeatedly prepared as the copper-containing, iron-containing crude nickel chloride aqueous solution. The method further includes a sulfur recovery step of heating the chlorine leaching residue in a melting tank to melt the sulfur contained in the chlorine leaching residue to produce a chlorine leaching residue molten material, and subjecting the chlorine leaching residue molten material to solid-liquid separation to obtain liquid sulfur and a molten residue. In the chlorine leaching step, hydrochloric acid is added to adjust the hydrochloric acid concentration of the chlorine leaching solution produced, thereby setting the pH of the chlorine leaching solution to -0.1 or less. Effect of the Invention

[0018] According to the present invention, there can be provided a method for treating a nickel sulfide raw material, which prevents deterioration of solid-liquid separability of a chlorine leach residue molten product obtained by heating a chlorine leach residue generated in a chlorine leach step in which nickel and cobalt are leached with chlorine using nickel sulfide as a raw material, and enables efficient recovery of sulfur from the chlorine leach residue. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a process diagram showing a schematic flow of a nickel hydrometallurgical process (MCLE process). [Diagram 2] FIG. 1 is a process diagram showing an example of a flow when the nickel sulfide raw material processing method is applied to processing in an MCLE process. [Diagram 3] FIG. 1 shows the results of EDS analysis (A) and XRD analysis (B) of the solid components adhered to a mesh filter. [Figure 4] FIG. 1 is a graph showing the correlation between the pH of the chlorine leaching solution obtained in the chlorine leaching step and the iron content (A), arsenic content (B), and iron and arsenic content ratio (iron / arsenic) (C) in the chlorine leaching residue. [Diagram 5] 1 is a graph showing the relationship between the pH of the chlorine leaching solution obtained in the chlorine leaching step and the amount of sulfur recovered when sulfur recovery treatment is performed using the obtained chlorine leaching residue. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiment, and various modifications are possible without departing from the gist of the present invention.

[0021] ≪1. Nickel sulfide raw material processing method≫ The method for processing a nickel sulfide raw material according to the present embodiment is a method for processing a nickel sulfide raw material containing iron and arsenic as impurities.

[0022] For example, the nickel sulfide raw material may be a raw material used as a raw material in a nickel hydrometallurgical process (MCLE process). Therefore, as described in detail below, the processing method can be applied to processing in the MCLE process, which includes a cementation step and a chlorine leaching step.

[0023] 2 is a process diagram showing an example of a flow when this processing method is applied to processing in an MCLE process. Specifically, the processing method for nickel sulfide raw material according to this embodiment includes a cementation step S1 in which a copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions is mixed with a nickel sulfide raw material, and nickel in the nickel sulfide raw material is substituted and leached by the copper ions in the copper-containing, iron-containing crude nickel chloride aqueous solution to remove the copper ions in the aqueous solution, and a chlorine leaching step S2 in which the cementation residue is repulped to form a cementation residue slurry, and then chlorine gas is blown into the cementation residue slurry to leach heavy metals to obtain a chlorine leachate and a chlorine leachate residue, and the chlorine leachate is repeatedly converted into a copper-containing, iron-containing crude nickel chloride aqueous solution, which is a raw material processing process.

[0024] This treatment method is characterized in that in the chlorine leaching step, hydrochloric acid is added to adjust the hydrochloric acid concentration of the chlorine leaching solution produced through chlorine leaching, thereby making the pH of the chlorine leaching solution -0.1 or less.

[0025] According to such a method for treating a nickel sulfide raw material, it is possible to reduce the grades of iron and arsenic in the chlorine leaching residue produced by chlorine leaching, and to suppress the production of iron arsenate (FeAsO4), which is a sparingly soluble substance. As a result, when recovering sulfur contained in the chlorine leaching residue, it is possible to prevent deterioration of the solid-liquid separability of the chlorine leaching residue molten material obtained by heating the chlorine leaching residue, and to efficiently recover sulfur. From this, the method according to the present embodiment can also be defined as a method for recovering sulfur from the chlorine leaching residue obtained by chlorine leaching a nickel sulfide raw material (sulfur recovery method).

[0026] [1. Cementation process] In the cementation step S1, a copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions is mixed with a nickel sulfide raw material to fix and remove the copper ions in the copper-containing, iron-containing crude nickel chloride aqueous solution.

[0027] Nickel sulfide raw materials contain iron and arsenic as impurities, and examples of the nickel sulfide raw materials include mixed sulfide (MS) containing nickel and cobalt produced by a hydrometallurgical process using nickel oxide ore as a raw material, and nickel matte produced by a nickel pyrometallurgical process.

[0028] More specifically, in the cementation step S1, a nickel sulfide raw material containing iron and arsenic as impurities is mixed with a copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions, and the nickel in the nickel sulfide raw material is leached by substitution with the copper ions in the copper-containing, iron-containing crude nickel chloride aqueous solution, thereby immobilizing and removing the copper ions in the copper-containing, iron-containing crude nickel chloride aqueous solution. This cementation reaction produces a cementation slurry, which is a mixture of the iron-containing crude nickel chloride aqueous solution from which the copper ions have been removed and a precipitate containing copper sulfide produced by immobilizing the copper ions as sulfides.

[0029] The copper-containing, iron-containing crude nickel chloride aqueous solution containing divalent copper ions, which is mixed with the nickel sulfide raw material, is a chlorine leachate obtained through a chlorine leaching treatment in the chlorine leaching step S2 described below. Thus, the process in this treatment method is a raw material treatment process that is configured by repeatedly converting the chlorine leachate into a copper-containing, iron-containing crude nickel chloride aqueous solution.

[0030] In the cementation step S1, the produced cementation slurry is subjected to solid-liquid separation to obtain a cementation end liquid (iron-containing crude nickel chloride aqueous solution) and a cementation residue (a precipitate containing copper sulfide). The method of solid-liquid separation is not particularly limited, and can be performed by a well-known method such as a centrifuge or a filter press, and the precipitate of copper sulfide, which is the cementation residue, can be efficiently separated.

[0031] The cementation end solution obtained through the cementation step S1 is sent to a solution purification step including an iron removal step S3. As will be described later, in the iron removal step S3, iron, an impurity contained in the cementation end solution (iron-containing crude nickel chloride aqueous solution), is removed. Note that although the notation methods are different, Figures 1 and 2 are both flow diagrams of the electrolytic nickel production process (MCLE process), and the "iron removal step," "cobalt solvent extraction step," and "solution purification step" can all be considered as solution purification steps. For example, the "copper removal electrolysis step" shown in Figure 1 is omitted in Figure 2, and the "sulfur recovery step" shown in Figure 2 is omitted in Figure 1.

[0032] On the other hand, the cementation residue containing the copper sulfide immobilized in the cementation step S1 is sent again to the chlorine leaching step S2 and subjected to chlorine leaching treatment.

[0033] [2. Chlorine leaching process] In the chlorine leaching step S2, the cementation residue produced in the above-mentioned cementation step S1 is repulped to form a slurry (cementation residue slurry), and then chlorine gas is blown into the cementation residue slurry to perform chlorine leaching. By this chlorine leaching treatment, heavy metals such as nickel and copper in the cementation residue are leached into an aqueous solution.

[0034] In the chlorine leaching step S2, the chlorine leaching slurry produced through the chlorine leaching treatment is subjected to solid-liquid separation to obtain a chlorine leaching solution and a chlorine leaching residue. As described above, the obtained chlorine leaching solution is a solution obtained by leaching heavy metals such as nickel and copper contained in the cementation residue into an aqueous solution. The chlorine leaching solution also contains iron. Therefore, the chlorine leaching solution is an aqueous solution of crude nickel chloride containing copper and iron.

[0035] The chlorine leaching process will now be described more specifically. In the chlorine leaching step S2, for example, reactions shown in the following formulas [1] to [3] occur. Cl2+2Cu+ → 2Cl - +2Cu 2+ [1] NiS+2Cu 2+ → Ni 2+ +S 0 +2Cu + [2] Cu2S+2Cu 2+ → 4Cu + +S 0 [3]

[0036] That is, in the chlorine leaching step S2, when the cementation residue slurry is pumped, metal components such as nickel sulfide (NiS) and copper sulfide (Cu2S) contained in the cementation residue are oxidized and leached by "divalent copper ions" oxidized by chlorine gas. This produces a nickel chloride aqueous solution containing copper ions, which is the chlorine leaching solution. As shown in formula [1], it is estimated that oxidative leaching using divalent copper ions as electron carriers is carried out in the chlorine leaching step S2. In addition, NiS in formula [2] represents the main component of MS, and Cu2S in formula [3] represents the main component of cementation residue.

[0037] The chlorine leaching solution produced in the chlorine leaching step S2 is repeatedly used as an aqueous solution of copper-containing, iron-containing, nickel chloride containing divalent copper ions, and is sent to the cementation step S1 as described above, where it is mixed with the nickel sulfide raw material and treated to precipitate and remove the copper ions. 0 The chlorine leaching residue, mainly composed of, remains in the solid phase.

[0038] In addition, the elemental sulfur S produced by the reactions shown in the above formulas [2] and [3] 0 In the case of chlorine gas, a strong oxidation reaction occurs directly with chlorine gas, as shown in the following equation [4], producing sulfuric acid and hydrochloric acid. S 0 +3Cl2+4H2O → H2SO4+6HCl ···[4]

[0039] In chlorine leaching, the pH of the chlorine leaching solution decreases as these reactions proceed, but the final pH is essentially determined by the amount of sulfur contained in the nickel sulfide raw material and various other conditions.

[0040] On the other hand, as described above, the nickel sulfide raw material contains iron and arsenic as impurities, which are distributed to the chlorine leaching solution and chlorine leaching residue depending on the treatment conditions in the chlorine leaching step S2, etc. Regarding the behavior of iron and arsenic in chlorine leaching, when the pH is low, the distribution of both (iron, arsenic) into the chlorine leaching solution increases, but when the pH is high, the distribution into the chlorine leaching solution decreases, so that some of them remain as solids in the chlorine leaching residue.

[0041] As will be described in detail later, the chlorine leaching residue obtained by chlorine leaching is elemental sulfur S 0 Therefore, the chlorine leach residue separated from the chlorine leach solution is sent to a sulfur recovery process, where the sulfur contained in the chlorine leach residue is recovered and used as a by-product. In the sulfur recovery process, taking advantage of the relatively low melting point of sulfur, the temperature is raised to a temperature at which only the sulfur contained in the chlorine leach residue melts, turning it into liquid sulfur, and then the sulfur is recovered by performing solid-liquid separation using a mesh filter specifically for melts.

[0042] As described above, depending on the processing conditions in the chlorine leaching step S2, some of the iron and arsenic contained as impurities in the nickel sulfide raw material remain as solids in the chlorine leaching residue, but as a result of research by the present inventors, it was found that in the chlorine leaching residue in which iron and arsenic remain, poorly soluble iron arsenate (FeAsO4) is incorporated as a secondary precipitate. Specifically, the chlorine leaching residue is heated to a temperature at which only sulfur melts to make a chlorine leaching residue melt, and a solid-liquid separation process is performed by filtering using a leaf mesh filter. Then, an EDS analysis using an SEM device was performed on the solid components attached to the filter. As a result, it was confirmed that the arsenic content was the highest at 11.9 mass%, followed by the iron content at 8.6 mass%, as a component other than oxygen contained in the sulfur and oxide of the material to be recovered. In addition, a peak of FeAsO4, a poorly soluble substance, was observed in the XRD analysis of the solid components. Figure 3 shows the results of EDS analysis (A) and XRD analysis (B) of the solid components adhering to the leaf mesh filter.

[0043] In other words, the analysis results showed that FeAsO4, a sparingly soluble substance generated by iron and arsenic and distributed in the chlorine leaching residue, clogs the mesh filters during solid-liquid separation in the sulfur recovery process, causing a deterioration in solid-liquid separation.

[0044] On the other hand, the pH of the chlorine leachate is essentially left to its own devices as described above, but since the distribution of iron and arsenic to the chlorine leachate and chlorine leach residue depends on the pH, the distribution of iron and arsenic to the chlorine leachate and chlorine leach residue also is essentially left to its own devices.

[0045] Therefore, in the method for treating nickel sulfide raw material according to the present embodiment, hydrochloric acid is added in the chlorine leaching step S2 to adjust the hydrochloric acid concentration of the chlorine leaching solution produced through chlorine leaching so that the pH of the chlorine leaching solution is −0.1 or less.

[0046] Fig. 4 is a graph showing the correlation between the pH of the chlorine leaching solution obtained in the chlorine leaching step S2 and the iron content (A), arsenic content (B), and content ratio (iron / arsenic) (C) in the chlorine leaching residue obtained by dividing the iron content by the arsenic content in the chlorine leaching residue. As shown in each graph in Fig. 4, it can be seen that the distribution rate of iron and arsenic to the chlorine leaching residue increases as the pH of the chlorine leaching solution increases, and the distribution rate of iron and arsenic to the chlorine leaching residue decreases as the pH of the chlorine leaching solution decreases. It is expected that the production amount of FeAsO4, which is a sparingly soluble substance, also decreases when the content of iron and arsenic in the chlorine leaching residue decreases.

[0047] Fig. 5 is a graph showing the relationship between the pH of the chlorine leaching solution obtained in the chlorine leaching step S2 and the amount of sulfur recovered when sulfur recovery treatment was performed using the chlorine leaching residue obtained by the chlorine leaching. The sulfur recovery treatment was performed by raising the temperature of the chlorine leaching residue to a temperature at which only the sulfur contained in the residue melts to form a chlorine leaching residue molten material, and filtering the chlorine leaching residue molten material with a filter equipped with a mesh filter. The mesh filter used was a filter with a filtration area of ​​44 m2. 2 A batch leaf-type filtration apparatus of the above was used. As shown in FIG. 5, it is understood that there is a correlation between the pH of the chlorine leachate and the amount of sulfur recovered (amount of sulfur recovered per one operation of the filter). It is also understood that the amount of sulfur recovered increases when the pH of the chlorine leachate decreases, particularly when the pH becomes -0.1 or less. In other words, this means that it is possible to prevent deterioration of solid-liquid separation performance (permeability of liquid sulfur through the mesh filter) in the sulfur recovery process, maintain its performance, and recover liquid sulfur satisfactorily.

[0048] The pH of the chlorine leachate is more preferably −0.2 or less, and even more preferably −0.4 or less.

[0049] In this way, by adjusting the hydrochloric acid concentration of the chlorine leaching solution by adding hydrochloric acid in the chlorine leaching step S2 and setting the pH of the chlorine leaching solution to -0.1 or less, it is possible to suppress the distribution of iron and arsenic to the chlorine leaching residue and to lower the iron and arsenic contents in the chlorine leaching residue. Specifically, it is possible to control the iron content in the chlorine leaching residue to a low level of 0.3 mass% or less and the arsenic content to a low level of 0.2 mass% or less.

[0050] Furthermore, because the iron and arsenic contents in the chlorine leaching residue can be kept low in this way, it is possible to reduce the amount of FeAsO4, a poorly soluble substance, produced in the chlorine leaching residue. As a result, solid-liquid separation properties (the permeability of liquid sulfur through a mesh filter) can be maintained in a good state when recovering sulfur from the chlorine leaching residue.

[0051] In other words, by adjusting the hydrochloric acid concentration of the chlorine leaching solution in the chlorine leaching step S2 by adding hydrochloric acid, the pH of the chlorine leaching solution can be adjusted to -0.1 or less, thereby controlling the liquid permeability when filtered with a batch leaf-type filtration device in the solid-liquid separation process for sulfur recovery. Specifically, the filterability when filtered with a batch leaf-type filtration device is set to 40 kg / m of sulfur recovery per unit filtration area. 2 That's all.

[0052] Hydrochloric acid may be added to the aqueous solution (including the slurry) at any stage of the chlorine leaching treatment in the chlorine leaching step S2. For example, hydrochloric acid may be added to the cementation residue slurry to be subjected to the chlorine leaching step S2, or to the chlorine leaching slurry (slurry before solid-liquid separation) produced by chlorine leaching.

[0053] The chlorine leaching process in the chlorine leaching step S2 can be carried out using a chlorine leaching apparatus equipped with a plurality of reaction tanks (a total of n reaction tanks) connected in series. In this case, the adjustment of the hydrochloric acid concentration by adding hydrochloric acid to the chlorine leaching solution can be carried out by adding hydrochloric acid to the chlorine leaching slurry contained in the final (nth) reaction tank of the plurality of reaction tanks connected in series. As the chlorine leaching reaction proceeds, the pH of the chlorine leaching solution decreases, but the final pH of the chlorine leaching solution can be accurately adjusted by adjusting the hydrochloric acid concentration by adding hydrochloric acid to the chlorine leaching slurry contained in the final reaction tank of the plurality of reaction tanks.

[0054] [3. Iron removal process] As described above, the cementation end solution obtained through the cementation step S1 is sent to the iron removal step S3. The cementation end solution is an iron-containing crude nickel chloride aqueous solution from which copper ions have been removed in the cementation step S1, but is an aqueous nickel chloride solution containing iron ions and arsenic ions as impurities (iron-containing arsenic nickel chloride aqueous solution). The arsenic in the aqueous solution is converted into arsenate ions (AsO4 3- ), arsenite ion (AsO 2- ), arsenic ion (As 3+ ), but in this specification, ions of various valencies, including oxoacid ions, will be collectively referred to as "arsenic ions."

[0055] Specifically, in the iron removal step S3, the cementation end liquid is oxidized and neutralized, so that the iron in the cementation end liquid is precipitated as a neutralized precipitate, and the iron-removed end liquid and the iron-removed precipitate are obtained by solid-liquid separation. The oxidation neutralization method utilizes the property that heavy metals such as iron, when they become highly oxidized ions, tend to become hydroxides in the low pH range.

[0056] In the iron removal step S3, the impurity iron is removed by the reaction of the following formula [5]. 2Fe 2+ +Cl2+3NiCO3+3H2O→ 2Fe(OH)3+3Ni 2++2Cl - +3CO2···[5]

[0057] As shown in equation [5], in the iron removal step S3, hydroxide precipitates of impurity elements such as iron to be removed are formed from the iron-containing arsenic nickel chloride aqueous solution, which is the cementation end liquid, to obtain a nickel chloride aqueous solution from which impurities have been removed (iron-removed end liquid).

[0058] In general, the chemicals used in the oxidation neutralization method include hypochlorous acid, oxygen, air, and the like as the oxidizing agent in addition to chlorine gas. Also, hydroxides such as caustic soda, ammonia, and the like as the neutralizing agent in addition to nickel carbonate. These chemicals are used in combinations suited to the process conditions, but in a wet smelting process using a nickel sulfide raw material, it is preferable to use chlorine gas as the oxidizing agent and nickel carbonate as the neutralizing agent. For example, chlorine gas is a strong oxidizing agent that is generated in the process and is easy to use. Also, the reason for using nickel carbonate as the neutralizing agent is that it can control the ion concentrations of nickel, sodium, sulfuric acid, and the like throughout the process, and has excellent reactivity during oxidation neutralization.

[0059] Here, the cementation end solution is an aqueous solution of iron-containing arsenic-nickel chloride that contains arsenic as well as iron as impurities. It is known that arsenic ions precipitate by coprecipitation with iron ions, and therefore the iron-arsenic ratio (iron / arsenic) obtained by dividing the iron concentration in the cementation end solution subjected to the oxidation neutralization reaction by the arsenic concentration is an extremely important reaction index. For example, although a larger iron-arsenic ratio (iron / arsenic) in the cementation end solution is advantageous for removing iron and arsenic, if the value range fluctuates, the oxidation neutralization reaction becomes unstable, and iron and arsenic may not be removed efficiently.

[0060] As described above, in the method for treating nickel sulfide raw material according to the present embodiment, in the chlorine leaching step S2, hydrochloric acid is added to adjust the hydrochloric acid concentration of the chlorine leaching solution to make the pH of the chlorine leaching solution -0.1 or less. This stabilizes the distribution behavior of iron and arsenic, and suppresses the distribution of iron and arsenic to the chlorine leaching residue. This means that the iron / arsenic ratio (iron / arsenic), obtained by dividing the iron concentration by the arsenic concentration in the cementation end solution obtained through the cementation step S1, in other words, the cementation end solution to be subjected to the iron removal step S3, can be stably adjusted to a predetermined range with reduced variation.

[0061] Therefore, the cementation final solution to be subjected to the iron removal step S3 can be easily adjusted to have a stably adjusted iron / arsenic ratio (iron / arsenic) within a predetermined range by adjusting the iron / arsenic ratio (iron / arsenic) brought in from the nickel sulfide raw material. As a result, iron ions and arsenic ions can be efficiently and effectively removed from the cementation final solution through oxidation and neutralization in the iron removal step S3. For example, the iron ions in the iron removal final solution can be efficiently reduced to a low concentration of 0.01 g / L or less, and the arsenic ions can be efficiently reduced to a low concentration of 0.001 g / L or less.

[0062] [4. Other processes] The iron-removal end liquid obtained by removing impurities such as iron in the iron-removal step S3 is then sent to a cobalt solvent extraction step S4. In the cobalt solvent extraction step S4, nickel and cobalt are separated from the iron-removal end liquid by solvent extraction to obtain a crude nickel chloride solution (NiCl2) and a crude cobalt chloride solution (CoCl2).

[0063] The obtained crude nickel chloride solution and crude cobalt chloride solution are respectively sent to a solution purification step S5, where impurity elements are removed to obtain a high-purity nickel chloride solution and a high-purity cobalt chloride solution. The solution purification step S5 can be configured by combining various impurity removal processes depending on the impurity composition of the solution. For example, a deleading process using an oxidation neutralization method under different conditions from the process in the above-mentioned iron removal step, a dezincing process using an ion exchange method, etc. can be combined.

[0064] The high-purity nickel chloride solution and cobalt chloride solution thus obtained are sent to the electrolysis step S6 (nickel electrolysis step, cobalt electrolysis step). In the electrolysis step S6, electrolytic nickel is produced from the nickel chloride solution by electrolytic winning, and electrolytic cobalt is produced from the cobalt chloride solution by electrolytic winning.

[0065] 2. Recovery of sulfur from chlorine leaching residue The chlorine leaching residue obtained from the chlorine leaching step S2 through the above-mentioned nickel sulfide raw material treatment method is mainly composed of elemental sulfur S 0 The sulfur can be recovered by a sulfur recovery process.

[0066] As one step in the above-mentioned method for treating the nickel sulfide raw material, a sulfur recovery step for recovering sulfur from the chlorine leaching residue can be provided (see the process diagram of FIG. 2). The sulfur recovery step S7 will be described in detail below.

[0067] In the sulfur recovery step S7, sulfur is recovered from the chlorine leaching residue separated from the chlorine leaching solution in the chlorine leaching step S2 by using the chlorine leaching residue. Specifically, the chlorine leaching residue is charged into a melting tank and heated in the melting tank to melt the sulfur contained in the chlorine leaching residue to form a chlorine leaching residue melt, and then the chlorine leaching residue melt is separated into solid and liquid to obtain liquid sulfur (liquid phase) and molten residue (solid phase). The liquid sulfur obtained by heating the chlorine leaching residue is cooled to become product sulfur in the form of flakes or buttons, for example.

[0068] As mentioned above, the chlorine leaching residue is heated at a temperature at which the sulfur contained in the chlorine leaching residue melts. The main component of the chlorine leaching residue is elemental sulfur (S). 0However, it also contains nickel that was not leached by chlorine and remains, and impurities such as iron and arsenic. In the sulfur recovery process, the melting point of sulfur is lower than that of other components, so the sulfur is heated (heated) to a temperature at which only sulfur melts and becomes liquid sulfur, and made into a slurry. Specifically, it is sufficient to heat it to about 120 to 140°C, but it can be heated relatively easily by using steam as a heat source in an indirect heating device such as a coiled pipe.

[0069] In the sulfur recovery process, the chlorine leaching residue is converted into a chlorine leaching residue melt, and the chlorine leaching residue melt is subjected to solid-liquid separation using a filter equipped with a mesh filter or the like to obtain liquid sulfur in the liquid phase constituting the chlorine leaching residue melt and a solid-phase molten residue. Here, the mesh filter refers to a solid-liquid separation device having a wire mesh or porous plate-like filter material, and for example, a batch-type leaf-type filter corresponds to this.

[0070] Here, in the process of recovering sulfur from the chlorine leaching residue, the chlorine leaching residue is heated as described above, whereby the sulfur content melts to become liquid sulfur, while the other components remain as solids without melting because of their high melting points, resulting in a slurry consisting of liquid sulfur (liquid phase) and the other components as solids (solid phase). When such a slurry is filtered through a mesh filter to separate the solids from the liquid, the other components remaining as solids may cause the mesh filter to become clogged. In particular, nickel sulfide (nickel sulfide raw material), which is the raw material for the MCLE process, contains iron and arsenic as impurities, and it has been found that although the iron and arsenic are once dissolved into the liquid by chlorine leaching, a part of them forms a precipitate in the form of poorly soluble iron arsenate (FeAsO4) and is distributed and remains in the chlorine leaching residue.

[0071] In this regard, in the present embodiment, in the chlorine leaching step S2 in the nickel sulfide raw material treatment method, hydrochloric acid is added to adjust the hydrochloric acid concentration of the chlorine leaching solution to a pH of -0.1 or less, thereby suppressing the distribution of iron and arsenic to the chlorine leaching residue. Therefore, the generation amount of the sparingly soluble substance FeAsO4 can be suppressed, and the iron and arsenic contents in the obtained chlorine leaching residue can be reduced.

[0072] As a result, even when sulfur is recovered from the chlorine leaching residue, clogging of the mesh filter can be prevented, good liquid permeability can be maintained, and liquid sulfur (product sulfur) can be effectively recovered. EXAMPLES

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0074] Examples and Comparative Examples In the MCLE process using nickel sulfide as a raw material, the content (grade) of iron and arsenic in the chlorine leaching residue was investigated depending on whether or not hydrochloric acid was added in the chlorine leaching process. In addition, a process was performed to recover sulfur from the chlorine leaching residue obtained from the chlorine leaching process, and the amount of sulfur recovered and the permeability through a mesh filter were investigated.

[0075] In the process of recovering sulfur from the chlorine leaching residue, the chlorine leaching residue was charged into a melting tank and heated to a temperature at which the sulfur contained in the chlorine leaching residue melted to produce a chlorine leaching residue melt, which was then filtered using a filter equipped with a leaf mesh filter to separate the liquid sulfur (liquid phase) from the molten residue (solid phase). The mesh filter had a filtering area of ​​44 m2. 2 A batch-type leaf-type filtration device was used. The amount of sulfur recovered was the amount of sulfur recovered per operation of the filter (per batch). The liquid permeability of the mesh filter was evaluated in terms of the amount of sulfur recovered per unit filtration area.

[0076] [Comparative Example 1] In Comparative Example 1, in the chlorine leaching step, hydrochloric acid was not added to the chlorine leaching slurry in the final stage reaction tank of multiple reaction tanks connected in series, and the pH of the chlorine leaching solution in that reaction tank was left undisturbed.

[0077] As a result, the average pH value of the chlorine leaching solution was 0.3. The iron content in the obtained chlorine leaching residue was 0.8 mass%, the arsenic content was 1.5 mass%, and the iron / arsenic ratio (iron / arsenic) obtained by dividing the iron content by the arsenic content was 0.6, indicating that most of the iron and arsenic in the nickel sulfide raw material were distributed to the chlorine leaching residue.

[0078] Sulfur was recovered from the chlorine leaching residue thus obtained, and the amount of sulfur recovered was 1.43 t / batch. The liquid permeability through the mesh filter was 33 kg / m 2 It was.

[0079] [Comparative Example 2] In Comparative Example 2, in the chlorine leaching process, hydrochloric acid was added to the chlorine leaching slurry in the final stage reaction tank of multiple reaction tanks connected in series, and the hydrochloric acid concentration of the chlorine leaching solution was adjusted to maintain its pH at around 0.1.

[0080] As a result, there was almost no variation in the pH of the chlorine leaching solution. The iron content in the obtained chlorine leaching residue was 0.5 mass%, and the arsenic content was 0.5 mass%, which was lower than in Comparative Example 1, but it was found that some of the iron and arsenic in the nickel sulfide raw material were distributed to the chlorine leaching residue. The iron / arsenic ratio (iron / arsenic), obtained by dividing the iron concentration in the chlorine leaching residue by the arsenic concentration, was 1.0.

[0081] Sulfur was recovered from the chlorine leaching residue thus obtained, and the amount of sulfur recovered was 1.68 t / batch. The liquid permeability through the mesh filter was 38 kg / m 2 It was.

[0082] [Example 1] In Example 1, in the chlorine leaching process, hydrochloric acid was added to the chlorine leaching slurry in the final stage reaction tank of multiple reaction tanks connected in series, and the hydrochloric acid concentration of the chlorine leaching solution was adjusted so that its pH was maintained at around -0.1.

[0083] As a result, there was almost no variation in the pH of the chlorine leaching solution. The iron content in the obtained chlorine leaching residue was 0.3 mass%, and the arsenic content was 0.2 mass%, which enabled the distribution of iron and arsenic to the chlorine leaching residue to be reduced more than in Comparative Examples 1 and 2. The iron / arsenic ratio (iron / arsenic), calculated by dividing the iron concentration in the chlorine leaching residue by the arsenic concentration, was 1.4.

[0084] Sulfur was recovered from the chlorine leaching residue thus obtained, and the amount of sulfur recovered was 2.01 t / batch, which was higher than those in Comparative Examples 1 and 2. The liquid permeability through the mesh filter was also 46 kg / m 2 and good liquid permeability was maintained.

[0085] The results of Comparative Examples 1 and 2 and Example 1 are summarized in Table 1 below.

[0086] [Table 1]

[0087] From the above results, it was found that the distribution of iron and arsenic to the chlorine leaching residue can be suppressed by adding hydrochloric acid in the chlorine leaching process and adjusting the hydrochloric acid concentration of the chlorine leaching solution to make the pH of the chlorine leaching solution -0.1 or less, as in the treatment of Example 1. It was found that this can suppress the production amount of FeAsO4, which is a sparingly soluble substance, in the chlorine leaching process. As a result, it was found that it is possible to prevent clogging of the mesh filter and deterioration of the liquid permeability when recovering sulfur from the chlorine leaching residue.

Claims

1. A method for treating a nickel sulfide raw material containing iron and arsenic as impurities, comprising the steps of: a cementation step of mixing a copper-containing, ferrous, crude nickel chloride aqueous solution containing divalent copper ions with a nickel sulfide raw material, and displacing and leaching nickel in the nickel sulfide raw material with the copper ions in the copper-containing, ferrous, crude nickel chloride aqueous solution to generate a cementation slurry which is a mixture of the ferrous crude nickel chloride aqueous solution from which the copper ions have been removed and a precipitate containing copper sulfide, and separating the resulting cementation slurry into a cementation final liquid and a cementation residue by solid-liquid separation; a chlorine leaching step of repulping the cementation residue to prepare a cementation residue slurry, injecting chlorine gas into the cementation residue slurry to leach heavy metals in the cementation residue to produce a chlorine leached slurry, and separating the slurry into a chlorine leached solution and a chlorine leached residue by solid-liquid separation; The chlorine leachate is repeatedly used as the copper-containing, iron-containing crude nickel chloride aqueous solution, In the chlorine leaching step, hydrochloric acid is added to adjust the hydrochloric acid concentration of the chlorine leaching solution to a pH of −0.1 or less. Method for processing nickel sulfide raw materials.

2. The chlorine leaching residue obtained by separating the chlorine leaching slurry has an iron content of 0.3 mass% or less and an arsenic content of 0.2 mass% or less.

2. The method for treating nickel sulfide raw material according to claim 1.

3. The process further comprises a sulfur recovery step of heating the chlorine leaching residue in a melting tank to melt the sulfur content contained in the chlorine leaching residue to form a chlorine leaching residue molten product, and subjecting the chlorine leaching residue molten product to solid-liquid separation to obtain liquid sulfur and a molten residue, In the solid-liquid separation process in the sulfur recovery step, the liquid permeability when filtered using a batch leaf-type filtration device is controlled.

2. The method for treating nickel sulfide raw material according to claim 1.

4. In the solid-liquid separation process in the sulfur recovery step, the liquid permeability when filtered using a batch leaf-type filtration device is 40 kg / m of sulfur recovery per unit filtration area. ２ That's all. The method for treating nickel sulfide raw material according to claim 3.

5. A method for recovering sulfur from a chlorine leaching residue obtained by chlorine leaching a nickel sulfide raw material containing iron and arsenic as impurities, comprising the steps of: a cementation step of mixing a copper-containing, ferrous, crude nickel chloride aqueous solution containing divalent copper ions with a nickel sulfide raw material, and displacing and leaching nickel in the nickel sulfide raw material with the copper ions in the copper-containing, ferrous, crude nickel chloride aqueous solution to generate a cementation slurry which is a mixture of the ferrous crude nickel chloride aqueous solution from which the copper ions have been removed and a precipitate containing copper sulfide, and separating the resulting cementation slurry into a cementation final liquid and a cementation residue by solid-liquid separation; a chlorine leaching step of repulping the cementation residue to prepare a cementation residue slurry, injecting chlorine gas into the cementation residue slurry to leach heavy metals in the cementation residue to produce a chlorine leached slurry, and separating the slurry into a chlorine leached solution and a chlorine leached residue by solid-liquid separation; The chlorine leachate is repeatedly used as the copper-containing, iron-containing crude nickel chloride aqueous solution, The method further includes a sulfur recovery step of heating the chlorine leaching residue in a melting tank to melt the sulfur content contained in the chlorine leaching residue to form a chlorine leaching residue molten material, and subjecting the chlorine leaching residue molten material to solid-liquid separation to obtain liquid sulfur and a molten residue, In the chlorine leaching step, hydrochloric acid is added to adjust the hydrochloric acid concentration of the chlorine leaching solution to a pH of −0.1 or less. Sulfur recovery methods.

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