WO2017110572A1 - 硫化剤の除去方法 - Google Patents
硫化剤の除去方法 Download PDFInfo
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- WO2017110572A1 WO2017110572A1 PCT/JP2016/086972 JP2016086972W WO2017110572A1 WO 2017110572 A1 WO2017110572 A1 WO 2017110572A1 JP 2016086972 W JP2016086972 W JP 2016086972W WO 2017110572 A1 WO2017110572 A1 WO 2017110572A1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
- C22B23/04—Obtaining nickel or cobalt by wet processes
- C22B23/0453—Treatment or purification of solutions, e.g. obtained by leaching
- C22B23/0461—Treatment or purification of solutions, e.g. obtained by leaching by chemical methods
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Definitions
- the present invention relates to a method for removing a sulfurizing agent, and more specifically, removes a sulfurizing agent such as hydrogen sulfide dissolved in a post-sulfurization solution obtained through a sulfurization step of a hydrometallurgical process of nickel oxide ore. Regarding the method.
- nickel sulfide ore is subjected to dry smelting in a high-temperature furnace to obtain a mat having a nickel quality of about 70% by weight, and then the mat is leached with chlorine to remove impurities.
- a method for producing electric nickel by electrowinning after the separation has been performed.
- the HPAL process does not require dry processes such as reduction and drying processes, and is composed of wet processes. Is advantageous in terms of cost and environment.
- a leaching solution containing nickel and cobalt and a leaching residue are obtained by acid leaching of nickel oxide ore under high temperature and high pressure. Since the obtained leachate contains impurities, neutralization is performed by adding a neutralizing agent to separate the impurities.
- a sulfidizing agent such as hydrogen sulfide gas is added to the leachate from which impurities have been separated and removed, and a nickel / cobalt mixed sulfide having a nickel or cobalt grade of about 50% by weight ( Hereinafter, it is also simply referred to as “nickel sulfide”), and is recovered by solid-liquid separation from a post-sulfurization liquid (poor liquid) having a low nickel quality.
- the recovered nickel sulfide can be made into a product in the form of electric nickel or the like by subjecting it to the same treatment as the above-described mat and performing electrolytic treatment or the like.
- the post-sulfurization solution after the dissolved hydrogen sulfide is removed by such treatment can also be used as washing water for the leaching residue produced in the leaching treatment of the HPAL process.
- the step of washing the leaching residue with washing water is called “leaching residue washing step”.
- the dissolved hydrogen sulfide in the solution after sulfidation is not fully decomposed and removed, but remains in the leaching residue washing step or the final neutralization step that performs the final neutralization treatment before discharging as waste water. If released, the odor of hydrogen sulfide is generated around the equipment, which is a problem in terms of safety and environment. Therefore, it is one of important treatments to sufficiently remove the dissolved hydrogen sulfide in the solution after sulfiding.
- Patent Document 1 trivalent iron hydroxide is added to a solution containing hydrogen sulfide to make the pH 3 or less
- a method is disclosed in which hydrogen sulfide dissolved in a solution is fixed in the form of sulfur by reacting hydrogen sulfide with trivalent iron at an oxidation-reduction potential (ORP) of 0 mV (Ag / AgCl electrode standard) or more.
- ORP oxidation-reduction potential
- the trivalent iron ion source is obtained through a final neutralization step in which an alkali is added to the leaching residue generated by the HPAL process and the acid adhering to the residue is neutralized. It is preferable to use those containing trivalent iron hydroxide.
- the starch obtained through the final neutralization step is trivalent iron hydroxide produced by adding limestone or slaked lime in the neutralization treatment in the final neutralization step, and impurities such as aluminum and magnesium Is a neutralized starch containing Therefore, when neutralized starch containing a large amount of such impurities is used to remove dissolved hydrogen sulfide, the starch of aluminum and magnesium in the starch is also dissolved. Is required. Furthermore, after removing dissolved hydrogen sulfide, it is necessary to add a neutralizing agent again in the final neutralization step to precipitate aluminum and magnesium, resulting in repeated neutralization and dissolution of impurities.
- the conventional methods have a problem that the amount of sulfuric acid and neutralizing agent increases unnecessarily, which contributes to pressure on processing costs.
- the present invention has been proposed in view of such a situation, and in a method for removing a sulfurizing agent such as hydrogen sulfide dissolved in a post-sulfurizing solution generated in a hydrometallurgical process of nickel oxide ore, a sulfurizing agent dissolved It is an object of the present invention to provide a method for removing a sulfurizing agent that can reduce the amount of a chemical such as sulfuric acid and a neutralizing agent while effectively removing water.
- the inventors of the present invention have made extensive studies to solve the above-described problems. As a result, by adding the leaching residue obtained from the leaching step to the hydrometallurgical process as a trivalent iron ion source to the sulfidized solution, the amount of sulfuric acid used and the final neutralization treatment performed after the sulfidizing agent removal treatment The inventors have found that the amount of neutralizing agent used can be effectively reduced, and have completed the present invention.
- a nickel oxide ore is subjected to acid leaching using sulfuric acid under high temperature and high pressure to obtain a leachate containing nickel and cobalt and a leach residue.
- a method of removing a sulfurizing agent dissolved in a post-sulfurization solution obtained by solid-liquid separation after producing a sulfide of nickel and cobalt and a post-sulfurization solution by performing a treatment, the post-sulfurization solution On the other hand, by adding a post-cleaning leaching residue obtained by cleaning the leaching residue and a sulfuric acid solution, and fixing and recovering the sulfurizing agent contained in the post-sulfurizing solution as sulfur, is there.
- the second aspect of the present invention is the sulfiding agent according to the first aspect, wherein the sulfuric acid solution is added so that the pH of the post-sulfurized solution is in the range of more than 1.2 and not more than 1.5. This is a removal method.
- the third aspect of the present invention is the sulfiding agent according to the first or second aspect, wherein after the leaching residue after washing is added, air of 1.8 Nm 3 or more is blown per 1 m 3 of the post-sulfurized liquid slurry. This is a removal method.
- the trivalent iron ion is 0.05 or more in a molar ratio with respect to the sulfiding agent dissolved in the solution after sulfiding.
- the leaching residue is added after washing so that the sulfiding agent is removed.
- the fifth invention of the present invention is the method for removing a sulfurizing agent according to any one of the first to fourth inventions, wherein the sulfurizing agent is hydrogen sulfide gas.
- the amount of sulfuric acid and neutralizing agent used can be effectively reduced while effectively removing the sulfiding agent dissolved in the solution after sulfiding, and an efficient treatment can be performed.
- the method for removing a sulfurizing agent according to the present embodiment is a method for removing a sulfurizing agent such as dissolved hydrogen sulfide gas from a solution such as a sulfuric acid acidic solution.
- the leaching solution containing nickel and cobalt obtained by acid leaching of nickel oxide ore with sulfuric acid under high temperature and high pressure is subjected to sulfidation treatment with a sulfidizing agent.
- a method of removing the sulfurizing agent dissolved in the post-sulfurization liquid obtained by solid-liquid separation after the cobalt sulfide and the post-sulfurization liquid are produced.
- a leaching residue after washing obtained by washing a leaching residue generated by acid leaching treatment of nickel oxide ore with respect to a sulfidizing solution in which the sulfiding agent is dissolved, and a sulfuric acid solution
- the sulfiding agent contained in the solution after sulfiding is fixed and recovered as sulfur.
- the term “fixed” as used herein refers to converting a compound into a stable form.
- a sulfiding agent such as hydrogen sulfide dissolved in the solution after sulfiding is used.
- S sulfur
- the leaching residue after washing is used as described above, and the reaction shown in the following reaction formula is caused by trivalent iron (iron oxide) contained in the leaching residue.
- This reaction is an example when hydrogen sulfide gas is used as a sulfiding agent.
- the amount of sulfuric acid used for dissolving the trivalent iron ion source can be reduced, and an efficient treatment can be performed.
- the post-sulfurized solution after the removal treatment is subjected to final neutralization treatment and drained.
- the amount of the neutralizing agent used in the final neutralization treatment can be effectively reduced, and the entire HPAL process can be efficiently operated.
- FIG. 1 is a process diagram showing the flow of a hydrometallurgical process for nickel oxide ore.
- This hydrometallurgical process includes a leaching step S11 in which nickel oxide ore is acid leached with sulfuric acid under high temperature and high pressure to obtain a leaching solution and a leaching residue, a neutralized starch containing impurities by adding a neutralizing agent to the leaching solution, A neutralization step S12 for obtaining a post-neutralization solution, and a sulfurization step S13 for obtaining a sulfide and a post-sulfurization solution by adding a sulfiding agent to the post-neutralization solution. Further, this hydrometallurgical process has a final neutralization step S14 for recovering and detoxifying the leaching residue produced in the leaching step S11 and the post-sulfurization liquid discharged in the sulfidation step S13.
- the sulfurized solution obtained by the hydrometallurgy process of nickel oxide ore is treated, and the sulfurized agent dissolved in the solution after the sulfurization is removed.
- Leaching step S11 for example, using a high-temperature pressure vessel (autoclave) or the like, sulfuric acid is added to a slurry of nickel oxide ore and stirring is performed at a temperature of 220 ° C. to 280 ° C. while applying pressure.
- This is a step of producing a leaching slurry comprising a leaching solution containing nickel and cobalt and a leaching residue.
- nickel oxide ore examples include so-called laterite ores such as limonite ore and saprolite ore.
- Laterite ore usually has a nickel content of 0.8 to 2.5% by weight and is contained as a hydroxide or siliceous clay (magnesium silicate) mineral.
- the leaching slurry composed of the obtained leaching solution and leaching residue is washed, and solid-liquid separation is performed into a leaching solution containing nickel and cobalt and a leaching residue that is hematite (Fe 2 O 3 ).
- the solid-liquid separation process for example, after the leaching slurry is mixed with a cleaning liquid, the solid-liquid separation process is performed by a solid-liquid separation facility such as a thickener using a flocculant supplied from a flocculant supply facility or the like. Specifically, the leaching slurry is first diluted with a cleaning liquid, and then the leaching residue in the slurry is concentrated as a thickener sediment.
- the leachate separated by the solid-liquid separation process for the leach slurry is transferred to the next neutralization step S12, while the leach residue is recovered from the bottom of the thickener.
- the recovered leaching residue is transferred to a leaching residue cleaning step and subjected to a cleaning process with cleaning water.
- Neutralization process S12 adjusts pH by adding a neutralizing agent to the leachate obtained by leaching process S11 mentioned above, and neutralized starch containing an impurity element and the liquid after neutralization It is a process to obtain.
- a neutralizing agent such as nickel and cobalt
- valuable metals such as nickel and cobalt are included in the post-neutralization solution, and most of impurities such as iron and aluminum become neutralized starch.
- neutralizing agent conventionally known neutralizing agents can be used, and examples thereof include calcium carbonate, slaked lime, and sodium hydroxide.
- the pH it is preferable to adjust the pH to the range of 1 to 4 while suppressing the oxidation of the separated leachate, and more preferably to the range of 1.5 to 2.5. preferable. If the pH is less than 1, neutralization may be insufficient and the neutralized starch and the neutralized solution may not be separated. On the other hand, when pH exceeds 4, not only impurities, such as aluminum, but valuable metals, such as nickel and cobalt, may be contained in neutralized starch.
- Sulfurization step Sulfurization step S13 is performed by adding a sulfidizing agent to the post-neutralization solution obtained in the above-described neutralization step S12 to obtain nickel and cobalt sulfide (nickel-cobalt mixed sulfide), post-sulfurization liquid, It is the process of obtaining.
- nickel, cobalt, zinc and the like become sulfides, and the others are contained in the post-sulfurization solution.
- a sulfidizing agent is added to the obtained post-neutralization solution to cause a sulfidation reaction in which nickel or cobalt contained in the post-neutralization solution is sulfidized into a sulfide form.
- a sulfide of nickel and cobalt with a small amount of impurity components and a post-sulfurization liquid (poor liquid) in which the nickel concentration is stabilized at a low level are generated.
- the sulfiding agent for example, hydrogen sulfide gas, sodium sulfide, sodium hydrosulfide, and the like can be used. Among them, it is particularly preferable to use hydrogen sulfide gas in view of ease of handling and cost.
- a nickel / cobalt mixed sulfide slurry is subjected to a sedimentation treatment using a sedimentation apparatus such as a thickener to separate and recover the nickel / cobalt mixed sulfide from the bottom of the thickener, while the aqueous solution is sulfide.
- the latter liquid is recovered by overflowing.
- the method for removing the sulfiding agent in the method for removing the sulfiding agent according to the present embodiment, it is obtained by subjecting the post-sulfurization liquid obtained by the sulfidation process in the sulfidation step S13, that is, the solid-liquid separation process to the slurry after the sulfidation process.
- the liquid after sulfidation is treated.
- the discharge standard is set for the post-sulfurization solution generated in the above-described sulfurization step S13, that is, the post-sulfurization solution containing an impurity element such as iron, magnesium, manganese.
- a neutralization treatment (detoxification treatment) for adjusting to a predetermined pH range to be satisfied is performed.
- the neutralization treatment is performed on the post-sulfurization solution from which the sulfurization agent such as dissolved hydrogen sulfide has been removed through the removal treatment of the sulfurization agent on the post-sulfurization solution, which will be described in detail later.
- the method of detoxification treatment in the final neutralization step S14 is not particularly limited, but for example, by adding a neutralizing agent such as calcium carbonate (limestone) slurry or calcium hydroxide (slaked lime) slurry. It can be adjusted to a predetermined range.
- a neutralizing agent such as calcium carbonate (limestone) slurry or calcium hydroxide (slaked lime) slurry. It can be adjusted to a predetermined range.
- the 1st step neutralization process (1st final neutralization process) which used limestone as a neutralizing agent, and the 2nd which used slaked lime as a neutralizing agent
- a stepwise treatment comprising a step-wise neutralization treatment (second final neutralization step) can be performed.
- the recovered post-sulfurized solution is charged into a neutralization treatment tank, and limestone slurry is added to perform a stirring treatment.
- the pH of the post-sulfurized solution is adjusted to 4-5 by adding limestone slurry.
- slaked lime slurry is added to the solution that has been subjected to the neutralization treatment in the first stage by adding the limestone slurry, and subjected to a stirring treatment.
- the pH of the post-sulfurized solution is raised to 8-9 by adding slaked lime slurry.
- a neutralization residue (final neutralized starch) is generated and stored in the tailing dam (tailing residue).
- the neutralized solution (the neutralized solution) satisfies the discharge standard and is discharged out of the system.
- iron contained in the post-sulfurization solution is fixed and separated in the form of iron hydroxide (Fe (OH) 3 ).
- the amount of neutralizing agent such as slaked lime or limestone according to the amount of impurity element ions such as magnesium ions and manganese ions remaining in the solution after sulfidation. Is determined. Therefore, if the amount of impurities remaining in the sulfidized solution is large, the amount of neutralized soot used is also large.
- a treatment for removing the sulfiding agent dissolved in the post-sulfurization solution is performed on the post-sulfurization solution obtained from the sulfurization step S13.
- the sulfur removal agent removal treatment step S22 the leaching residue after washing is used as a trivalent iron ion source.
- a post-sulfurized solution having a low concentration of impurities such as iron, magnesium, manganese, aluminum and the like can be transferred, and as a result, used in the final neutralization step S14.
- the amount of neutralizing agent used can be effectively reduced. Details will be described later.
- a post-cleaning leaching residue obtained by cleaning the leaching residue generated by the acid leaching treatment of nickel oxide ore and a sulfuric acid solution are added to the post-sulfurizing solution in which the sulfiding agent is dissolved.
- the sulfurizing agent contained in the liquid after sulfiding is fixed as sulfur.
- the dissolved sulfiding agent such as hydrogen sulfide is recovered and removed from the solution after sulfiding in the form of solid sulfur.
- FIG. 2 is a process diagram showing a flow when the process of the hydrometallurgy process of nickel oxide ore is combined with the process of removing the sulfiding agent (sulfurizing agent removing process) from the sulfidized solution.
- sulfiding agent sulfurizing agent removing process
- the post-sulfurization solution after separating and recovering the nickel-cobalt mixed sulfide obtained in the sulfurization step S13 of the nickel oxide ore hydrometallurgical process has a nickel ion concentration of about 0.04 g / L to 0.10 g / L. It is a sulfuric acid acidic solution containing impurities such as iron, manganese, magnesium, aluminum, chromium and lead.
- the hydrogen sulfide used in the sulfiding treatment in the sulfiding step S13 is dissolved in the post-sulfurized solution at a concentration of about 10 mg / L to 150 mg / L.
- the leaching residue generated in the leaching step S11 of the hydrometallurgical process is used as the trivalent iron ion source. More specifically, the leaching residue recovered by solid-liquid separation from the leaching step S11 is transferred to the leaching residue washing step S21, and the leaching residue after washing obtained by performing a washing process there is used.
- the leaching residue after washing is referred to as “leaching residue after washing”.
- the final neutralized starch produced in the final neutralization step S14 has been used as a trivalent iron ion source. Since the final neutralized starch contains a large amount of trivalent iron hydroxide, the removal reaction of hydrogen sulfide can proceed effectively. However, the final neutralized starch produced in the final neutralization step S14 contains a large amount of impurities such as magnesium, manganese and aluminum in addition to trivalent iron. When used for hydrogen removal treatment, sulfuric acid was used to dissolve these impurities, increasing the amount of sulfuric acid used and increasing the amount of neutralizing agent used in the subsequent neutralization treatment. .
- the amount of sulfuric acid used can be effectively reduced by using a leaching residue after washing as a trivalent iron ion source, which is efficient. Can be processed. Moreover, the usage-amount of the neutralizing agent in final neutralization process S14 can also be reduced effectively, and efficient operation can be performed as the whole hydrometallurgical process.
- the leaching residue cleaning step S21 the leaching residue collected from the leaching step S11 is subjected to a cleaning process using cleaning water, and impurities adhering to the leaching residue are removed.
- the washing water is not particularly limited, and for example, water can be used.
- the post-neutralization liquid is a liquid from which impurities have been removed in the neutralization process of the final neutralization step S14.
- the leaching residue used is mainly hematite (Fe 2 O 3 ), for example, trivalent compared to the final neutralized starch produced in the final neutralization step S14.
- Iron is difficult to dissolve.
- a sulfuric acid solution is added to the post-sulfurization solution so that the pH is 1.5 or less, and the reaction is carried out while maintaining the pH. It is preferable to make it occur. If the pH exceeds 1.5, the amount of sulfuric acid used will decrease, but the amount of hematite dissolved will also decrease. Therefore, the supply of trivalent iron will be insufficient and the amount of dissolved hydrogen sulfide will be reduced. There is a possibility that.
- the pH of the solution after sulfidation is preferably adjusted to exceed 1.2.
- the pH of the solution after sulfidation is 1.2 or less, the amount of trivalent iron dissolved increases, and the amount of leaching residue after washing is reduced, but magnesium, aluminum, etc. contained in the leaching residue are reduced. Impurities are also dissolved, increasing the amount of sulfuric acid used, and increasing the amount of neutralizing agent used in the neutralization treatment in the final neutralization step S14 after the hydrogen sulfide removal treatment.
- the pH of the post-sulfurized solution is preferably adjusted to a range of more than 1.2 and 1.5 or less, and more preferably adjusted to a range of 1.4 or more and 1.5 or less.
- the sulfuric acid solution it is considered preferable to use concentrated sulfuric acid having a high concentration, but the concentration is not particularly limited. However, in the case of an extremely low concentration sulfuric acid solution, the reaction time for immobilizing hydrogen sulfide as sulfur becomes longer. Further, when a low-concentration sulfuric acid solution is used, the amount of sulfuric acid to be added increases, and facilities such as a tank and a pump are inevitably increased. Therefore, it is preferable to use a sulfuric acid solution having a concentration of 0.05 N or more, for example.
- the removal treatment of hydrogen sulfide can be performed, for example, in a stirred reaction tank equipped with a stirring means.
- the stirred reaction tank contains the sulfidized liquid, and the washed leaching residue and the sulfuric acid solution are placed in the reaction tank. Added.
- the pH condition is set to a range exceeding 1.2 and 1.5 or less, and the ORP is set to 150 mV or more, and the reaction is caused while stirring the post-sulfurized solution.
- the reaction time (residence time) of the post-sulfurization solution is not particularly limited, but is preferably 30 minutes or longer, for example.
- the amount of sulfuric acid used for dissolving the trivalent iron ion source can be reduced, and an efficient treatment can be performed. it can.
- the post-sulfurized solution after the removal treatment is subjected to final neutralization treatment and drained.
- the amount of the neutralizing agent used in the final neutralization treatment can be effectively reduced, and the entire HPAL process can be efficiently operated.
- Example 1 As shown in the hydrometallurgical process of nickel oxide ore shown in FIGS. 1 and 2, firstly, a slurry of nickel oxide ore is charged into an autoclave and leached using sulfuric acid under high temperature and high pressure, and leached liquid and leached. A leaching slurry containing the residue (hematite, Fe 2 O 3 ) was obtained (leaching step S11). Table 1 below shows the analysis results of the composition of the leach slurry.
- trivalent iron ions (3.6 kg as iron amount) are added to the post-sulfurization solution having a dissolved hydrogen sulfide concentration of 30 mg / L so that the molar ratio with respect to dissolved hydrogen sulfide is 0.05.
- the trivalent iron ion source the leaching residue mainly composed of hematite obtained in the leaching step S11 of the wet smelting process of nickel oxide ore is used, and the leaching residue is washed.
- the slurry of the leaching residue after washing obtained in (1) was supplied to the solution after sulfidation.
- a diluted sulfuric acid solution was added so that the pH of the solution after sulfidation was 1.5 and the oxidation-reduction potential (ORP) was 250 mV (silver / silver chloride electrode standard). Further, air of 1.8 Nm 3 or more per 1.0 m 3 of the post-sulfurized liquid slurry was blown into the slurry of the post-sulfurized liquid after the leaching residue was added. As a result, a reaction for fixing hydrogen sulfide dissolved in the liquid after sulfidation as sulfur was caused, and the hydrogen sulfide was removed.
- ORP oxidation-reduction potential
- the hydrogen sulfide concentration in the liquid after sulfidation after hydrogen sulfide removal was measured, and as a result, the analysis lower limit was less than 1 mg / L. Hydrogen sulfide was sufficiently removed.
- the supply amount of the post-cleaning leaching residue slurry used in the hydrogen sulfide removal treatment was 25.7 m 3 .
- Comparative Example 1 In Comparative Example 1, the final neutralized starch obtained from the final neutralization step S14 of the hydrometallurgical process was added to the post-sulfurization solution in the treatment for removing hydrogen sulfide dissolved in the post-sulfurization solution.
- trivalent iron ions (3.6 kg of iron amount) were added to the post-sulfurization solution having a dissolved hydrogen sulfide concentration of 30 mg / L so that the molar ratio with respect to dissolved hydrogen sulfide was 0.05.
- the trivalent iron ion source the final neutralized starch obtained in the final neutralization step S14 of the hydrometallurgical process of nickel oxide ore was used, and the slurry of the final neutralized starch was supplied to the sulfidized solution.
- Table 3 shows the analysis results of the composition of the post-neutralization slurry generated in the final neutralization step S14. As shown in Table 3, the final neutralized starch contained trivalent iron hydroxide and aluminum and magnesium hydroxides.
- a diluted sulfuric acid solution was added so that the pH of the solution after sulfiding was 1.7 and the ORP was 250 mV. Further, air of 1.8 Nm 3 or more per 1.0 m 3 of the post-sulfurized solution slurry was blown into the slurry of the post-sulfurized solution after the final neutralized starch was added.
- the hydrogen sulfide concentration in the liquid after sulfidation after hydrogen sulfide removal was measured, and as a result, the analysis lower limit was less than 1 mg / L. Hydrogen sulfide was sufficiently removed.
- the supply amount of the final neutralized starch slurry used in this hydrogen sulfide removal treatment was 10.8 m 3 .
- Comparative Example 2 In Comparative Example 2, in the removal treatment of hydrogen sulfide dissolved in the solution after sulfidation, the slurry of the leaching residue after washing was added to the solution after sulfidation in the same manner as in Example 1, but by adding the sulfuric acid solution, The pH was adjusted to 1.2.
- trivalent iron ions (3.6 kg of iron amount) were added to the post-sulfurization solution having a dissolved hydrogen sulfide concentration of 30 mg / L so that the molar ratio with respect to dissolved hydrogen sulfide was 0.05.
- the trivalent iron ion source the leaching residue after washing obtained by washing the leaching residue using the leaching residue mainly composed of hematite obtained in the leaching step S11 of the nickel oxide ore hydrometallurgical process. The slurry was fed to the liquid after sulfidation.
- the hydrogen sulfide concentration in the liquid after sulfidation after hydrogen sulfide removal was measured, and as a result, the analysis lower limit was less than 1 mg / L. Hydrogen sulfide was sufficiently removed.
- the supply amount of the leach residue slurry used in the hydrogen sulfide removal treatment was 7.2 m 3 .
- Comparative Example 3 In Comparative Example 3, in the process of removing hydrogen sulfide dissolved in the liquid after sulfidation, the slurry of the leaching residue after washing was added to the liquid after sulfidation in the same manner as in Example 1. However, by adding the sulfuric acid solution, The pH was adjusted to 1.8.
- Example 1 Comparative Example 1 in which the final neutralized starch was added as a trivalent iron ion source by adding a leaching residue after washing to the post-sulfurization solution in which hydrogen sulfide was dissolved. It was found that the amount of sulfuric acid solution used can be greatly reduced compared to Moreover, it turned out that it can reduce significantly also about the usage-amount of the neutralizing agent (limestone and slaked lime) used by the final neutralization process after the removal of the hydrogen sulfide.
- the neutralizing agent limestone and slaked lime
- Example 1 In comparison between Example 1 and Comparative Example 1, as the reason that the amount of sulfuric acid solution used and the amount of neutralizing agent used increased in the treatment of Comparative Example 1, hematite was added to the final neutralized starch added. Along with the leaching residue as the main component, it is mentioned that a large amount of trivalent iron hydroxide produced in the final neutralization step, and hydroxides such as aluminum and magnesium are included, and the supply amount of trivalent iron ions is the same. Even so, it is considered that the necessary amount of the sulfuric acid solution used for the dissolution and the necessary amount of the neutralizing agent in the neutralization treatment increased as much as aluminum and magnesium exist.
- Example 2 In the comparison between Example 1 and Comparative Example 2, when the sulfuric acid solution was added and adjusted so that the pH of the post-sulfurized solution was 1.2 (Comparative Example 2), the required amount of the sulfuric acid solution increased. Along with this, the amount of neutralizing agent required for the neutralization treatment also increased. This means that when the pH is lowered to 1.2, the amount of trivalent iron dissolved increases and the required amount of leaching residue decreases, but the amount of impurities such as magnesium and aluminum contained in the leaching residue also decreases. Since it increased, it is thought that the required amount of the sulfuric acid solution and the required amount of the neutralizing agent (limestone, slaked lime) in the neutralization treatment increased.
- the required amount of the sulfuric acid solution and the required amount of the neutralizing agent limestone, slaked lime
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Abstract
Description
2Fe(OH)3+3H2SO4→Fe2(SO4)3+6H2O
Fe2(SO4)3+H2S→2FeSO4+H2SO4+S0
本実施の形態に係る硫化剤の除去方法は、硫酸酸性溶液等の溶液から、溶存している硫化水素ガス等の硫化剤を除去する方法である。
Fe2O3+3H2SO4→Fe2(SO4)3+3H2O
Fe2(SO4)3+H2S→2FeSO4+H2SO4+S0
先ず、硫化剤の除去方法のより具体的な説明に先立ち、ニッケル酸化鉱石の湿式製錬プロセス(以下、単に「湿式製錬プロセス」ともいう)について説明する。
浸出工程S11は、例えば高温加圧容器(オートクレーブ)等を用いて、ニッケル酸化鉱石のスラリーに硫酸を添加して220℃~280℃の温度下で、加圧しながら撹拌処理を施し、ニッケル及びコバルトを含有する浸出液と浸出残渣とからなる浸出スラリーを生成させる工程である。
中和工程S12は、上述した浸出工程S11により得られた浸出液に中和剤を添加してpHを調整し、不純物元素を含む中和澱物と中和後液とを得る工程である。この中和工程S12における中和処理により、ニッケルやコバルト等の有価金属は中和後液に含まれるようになり、鉄、アルミニウム等の不純物の大部分が中和澱物となる。
硫化工程S13は、上述した中和工程S12により得られた中和後液に硫化剤を添加してニッケル及びコバルトの硫化物(ニッケル・コバルト混合硫化物)と硫化後液とを得る工程である。この硫化工程S13における硫化処理により、ニッケル、コバルト、亜鉛等は硫化物となり、その他は硫化後液に含まれることになる。
最終中和工程S14では、上述した硫化工程S13にて生成した硫化後液、すなわち、鉄、マグネシウム、マンガン等の不純物元素を含む硫化後液に対して、排出基準を満たす所定のpH範囲に調整する中和処理(無害化処理)を施す。
さて、上述したニッケル酸化鉱石の湿式製錬プロセスにおいて、硫化工程S13での硫化処理を経て生成した硫化後液には、硫化反応を生じさせるために添加した硫化水素等の硫化剤が溶存していることがある。硫化処理で生成した硫化後液は、最終中和工程S14に移送されて、その溶液に対する無害化処理が施されることによってマグネシウム、マンガン等の成分が除去され、排水基準を満たした状態で系外に排出される。しかしながら、硫化後液に硫化剤が残存している場合には、その硫化剤についての除去処理を行わなければ、系外に放流することができない。
浸出残渣洗浄工程S21では、浸出工程S11から回収された浸出残渣に対して洗浄水を用いて洗浄処理を施し、その浸出残渣に付着する不純物を除去する。
硫化剤除去処理工程S22では、硫化水素が溶存する硫化後液に、上述した洗浄後浸出残渣を添加するとともに硫酸溶液を添加する。これにより、下記反応式に示す反応が生じて、硫化後液に溶存する硫化水素が酸化され、固体の硫黄として固定化される。
Fe2O3+3H2SO4→Fe2(SO4)3+3H2O
Fe2(SO4)3+H2S→2FeSO4+H2SO4+S0
[実施例1]
図1及び図2のニッケル酸化鉱石の湿式製錬プロセスに示すように、先ず、ニッケル酸化鉱石のスラリーをオートクレーブに装入し、高温高圧下で硫酸を用いて浸出処理を施すことによって浸出液と浸出残渣(ヘマタイト,Fe2O3)とを含有する浸出スラリーを得た(浸出工程S11)。下記表1に、浸出スラリーの組成の分析結果を示す。
比較例1では、硫化後液に溶存する硫化水素の除去処理において、湿式製錬プロセスの最終中和工程S14から得られる最終中和澱物を硫化後液中に添加した。
比較例2では、硫化後液に溶存する硫化水素の除去処理において、実施例1と同様に洗浄後浸出残渣のスラリーを硫化後液に添加したが、硫酸溶液の添加により、その硫化後液のpHが1.2となるように調整した。
比較例3では、硫化後液に溶存する硫化水素の除去処理において、実施例1と同様に洗浄後浸出残渣のスラリーを硫化後液に添加したが、硫酸溶液の添加により、その硫化後液のpHが1.8となるように調整した。
以上の結果から、実施例1のように、硫化水素が溶存した硫化後液に対して洗浄後浸出残渣を添加することにより、最終中和澱物を3価鉄イオン源として添加した比較例1に比べて、硫酸溶液の使用量を大幅に低減させることができることが分かった。また、その硫化水素の除去後に最終中和処理にて使用する中和剤(石灰石及び消石灰)の使用量についても、大幅に低減させることができることが分かった。
Claims (5)
- ニッケル酸化鉱石に硫酸を用いて高温高圧下で酸浸出してニッケル及びコバルトを含む浸出液と浸出残渣とを得て、該浸出液に対し硫化剤により硫化処理を施してニッケル及びコバルトの硫化物と硫化後液とを生成させた後、固液分離して得られた硫化後液中に溶存する硫化剤を除去する方法であって、
前記硫化後液に対して、前記浸出残渣を洗浄して得られる洗浄後浸出残渣と、硫酸溶液とを添加して、該硫化後液に含まれる硫化剤を硫黄として固定化し回収する
硫化剤の除去方法。 - 前記硫化後液のpHが1.2を超えて1.5以下の範囲となるように前記硫酸溶液を添加する
請求項1に記載の硫化剤の除去方法。 - 前記洗浄後浸出残渣を添加した後に、硫化後液スラリー1m3あたり1.8Nm3以上の空気を吹き込む
請求項1又は2に記載の硫化剤の除去方法。 - 3価の鉄イオンが、前記硫化後液中に溶存する硫化剤に対するモル比で0.05以上となるように前記洗浄後浸出残渣を添加する
請求項1乃至3のいずれか1項に記載の硫化剤の除去方法。 - 前記硫化剤は、硫化水素ガスである
請求項1乃至4のいずれか1項に記載の硫化剤の除去方法。
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