Abstract: The present invention provides a chromium-containing water treatment method that allows treatment of water that contains chromium (chromium-containing water) at low cost. A chromium-containing water treatment method according to the present invention comprises: a reduction step in which chromium-containing water 11 and a liquid 12 containing 5-50 ppm of hydrogen sulfide are mixed, and the mixture is adjusted to pH 3.5 or lower and ORP 200-400 mV by adding an acid 13 thereto, so as to reduce chromium contained in the water; and a precipitation separation step in which a neutralizing agent is added to a solution 11? obtained via the reduction step so as to adjust the solution 11? to pH 8-9, thereby precipitating and separating, as a hydroxide, the reduced chromium contained in the solution.

Abstract: The present invention provides a chromium-containing water treatment method that allows treatment of water that contains chromium (chromium-containing water) at low cost. A chromium-containing water treatment method according to the present invention comprises: a reduction step in which chromium-containing water 11 and a liquid 12 containing 5-50 ppm of hydrogen sulfide are mixed, and the mixture is adjusted to pH 3.5 or lower and ORP 200-400 mV by adding an acid 13 thereto, so as to reduce chromium contained in the water; and a precipitation separation step in which a neutralizing agent is added to a solution 11? obtained via the reduction step so as to adjust the solution 11? to pH 8-9, thereby precipitating and separating, as a hydroxide, the reduced chromium contained in the solution.

Abstract: Provided is a method for producing nickel sulfide from an acidic sulfuric acid solution containing nickel, which is capable of suppressing particle diameters of nickel sulfide obtained thereby. The present invention is a method for producing nickel sulfide by causing a sulfurization reaction by blowing a hydrogen sulfide gas into an acidic sulfuric acid solution containing nickel, wherein: nickel sulfide having particle diameters of 5-20 ?m and serving as seed crystals is added into an acidic sulfuric acid solution having a nickel concentration of 0.5-5.0 g/L in an amount of 40-500% by mass relative to the amount of nickel contained in the acidic sulfuric acid solution; and a hydrogen sulfide gas is blown into the acidic sulfuric acid solution, into which the seed crystals have been added, while setting the amount of the hydrogen sulfide gas blown in to be within the range of 0.30-0.85 Nm3/kg-Ni.

Abstract: Provided is a method for producing nickel sulfide from an acidic sulfuric acid solution containing nickel, which is capable of suppressing particle diameters of nickel sulfide obtained thereby. The present invention is a method for producing nickel sulfide by causing a sulfurization reaction by blowing a hydrogen sulfide gas into an acidic sulfuric acid solution containing nickel, wherein: nickel sulfide having particle diameters of 5-20 ?m and serving as seed crystals is added into an acidic sulfuric acid solution having a nickel concentration of 0.5-5.0 g/L in an amount of 40-500% by mass relative to the amount of nickel contained in the acidic sulfuric acid solution; and a hydrogen sulfide gas is blown into the acidic sulfuric acid solution, into which the seed crystals have been added, while setting the amount of the hydrogen sulfide gas blown in to be within the range of 0.30-0.85 Nm3/kg-Ni.

Abstract: This invention provides a method for shortening operation shutdown time of high pressure acid leach equipment in a hydrometallurgical process, wherein the high pressure acid leach equipment comprises (i) means to transfer an ore slurry into the high pressure acid leach equipment;(ii) means to increase temperature and pressure of an ore slurry before leaching; (iii) means to add sulfuric acid into the high pressure acid leach equipment and to leach the ore slurry to obtain a leached slurry at high temperature under high pressure; (iv) means to adjust the pressure of the leached slurry; and (v) means to discharge the leached from the high pressure acid leach equipment; wherein, upon operation shutdown of the high pressure acid leach equipment, the leached slurry is subjected to self-circulation inside the high pressure acid leach equipment.

Abstract: The present invention aims at providing a method for effluent treatment, which enables the separation and recovery of a high-density and high-concentration aluminum sediment from waste water that is discharged in the smelting of a nickel oxide ore and contains aluminum ions. In the present invention, an alkali and an iron-containing solid are added to waste water containing aluminum ions to form a slurry, and the slurry is allowed to stand to perform solid-liquid separation, whereby an aluminum sediment and an effluent is formed.

Abstract: Disclosed is a method for producing an ore slurry that can suppress a rise in the viscosity of the ore slurry and consequently prevent a failure in transporting the slurry, and also to provide a metal refining method utilizing such a slurry producing method. The present invention includes: a pulverizing/classifying step of pulverizing raw material ores and classifying the resulting ores at a predetermined classifying point so that oversized ore particles are removed so as to obtain a coarse ore slurry composed of undersized ore particles; a grain size measuring step of measuring the grain size of the resulting coarse ore slurry; and an ore slurry condensing step of loading the coarse ore slurry to a solid-liquid separation device and separating and removing moisture contained in the coarse ore slurry therefrom so as to condense ore components.

Abstract: The present invention aims at providing a method for effluent treatment, which enables the separation and recovery of a high-density and high-concentration aluminum sediment from waste water that is discharged in the smelting of a nickel oxide ore and contains aluminum ions. In the present invention, an alkali and an iron-containing solid are added to waste water containing aluminum ions to form a slurry, and the slurry is allowed to stand to perform solid-liquid separation, whereby an aluminum sediment and an effluent is formed.

Abstract: A hydrometallurgical plant for nickel laterite ore extraction having a plurality of treatment facility lines wherein the plant is capable of minimizing a decrease in throughput when line failure occurs and efficiently restoring normal operation status Each line of the treatment facility includes a pretreatment step, a leaching step, a solid-liquid separation step, a neutralization step, a zinc removal step, a sulfurization step and a detoxification step. The lines are coupled by pipelines, each having a valve, installed after the solid-liquid separation step for sending a liquid from the solid-liquid separation step to the neutralization step in each line and/or after the sulfurization step for sending a liquid from the sulfurization step to the detoxification step in each line.

Abstract: Provided is a method for producing ferronickel from a nickel sulfide or a mixed sulfide containing nickel and cobalt, obtained by hydrometallurgy of nickel oxide ore or obtained from scraps or products in process. The method for producing a ferronickel raw material is to form the ferronickel raw material from a nickel sulfide or a mixed sulfide containing nickel sulfide and cobalt sulfide, wherein treatments are performed through the following steps: (1) redissolution step, (2) deferrization step, (3) solvent extraction step, (4) hydroxylation step, (5) roasting step, and (6) washing and calcining step.

Abstract: Disclosed is a method for producing an ore slurry that can suppress a rise in the viscosity of the ore slurry and consequently prevent a failure in transporting the slurry, and also to provide a metal refining method utilizing such a slurry producing method. The present invention includes: a pulverizing/classifying step of pulverizing raw material ores and classifying the resulting ores at a predetermined classifying point so that oversized ore particles are removed so as to obtain a coarse ore slurry composed of undersized ore particles; a grain size measuring step of measuring the grain size of the resulting coarse ore slurry; and an ore slurry condensing step of loading the coarse ore slurry to a solid-liquid separation device and separating and removing moisture contained in the coarse ore slurry therefrom so as to condense ore components.

Abstract: A production process of a sulfide containing nickel and cobalt by adding a sulfurizing agent under pressurization into an aqueous solution of sulfuric acid containing nickel and cobalt, which is capable of recovering nickel and cobalt as a sulfide in high yield, as well as enhancing the utilization efficiency of hydrogen sulfide gas. A production process of a sulfide containing nickel and cobalt by adding a sulfurizing agent under pressurization into an aqueous solution of sulfuric acid containing nickel and cobalt, characterized by supplying, as the above sulfurizing agent, hydrogen sulfide gas into the vapor phase of inside of a reactor, as a major sulfurizing agent, as well as, by supplying an aqueous solution containing a sodium hydrosulfide, which is recovered by absorbing unreacted hydrogen sulfide gas, which is discharged from inside of the reactor in producing the above sulfide, with an aqueous solution of sodium hydroxide, into the liquid phase.

Abstract: This invention provides a method for shortening operation shutdown time of high pressure acid leach equipment in a hydrometallurgical process, wherein the high pressure acid leach equipment comprises (i) means to transfer an ore slurry into the high pressure acid leach equipment; (ii) means to increase temperature and pressure of an ore slurry before leaching; (iii) means to add sulfuric acid into the high pressure acid leach equipment and to leach the ore slurry to obtain a leached slurry at high temperature under high pressure; (iv) means to adjust the pressure of the leached slurry; and (v) means to discharge the leached from the high pressure acid leach equipment; wherein, upon operation shutdown of the high pressure acid leach equipment, the leached slurry is subjected to self-circulation inside the high pressure acid leach equipment.

Abstract: Provided is a method for producing ferronickel from a nickel sulfide or a mixed sulfide containing nickel and cobalt, obtained by hydrometallurgy of nickel oxide ore or obtained from scraps or products in process. The method for producing a ferronickel raw material is to form the ferronickel raw material from a nickel sulfide or a mixed sulfide containing nickel sulfide and cobalt sulfide, wherein treatments are performed through the following steps: (1) redissolution step, (2) deferrization step, (3) solvent extraction step, (4) hydroxylation step, (5) roasting step, and (6) washing and calcining step.

Abstract: A hydrometallurgical process for a nickel oxide ore comprising obtaining an aqueous solution of crude nickel sulfate by high pressure acid leaching of a nickel oxide ore; obtaining a zinc free final solution by sulfurization of the solution; obtaining a waste solution; and scrubbing hydrogen sulfide gas from an exhaust gas. The process is characterized by at least one of the following operations: Adjusting the total volume (m3) of a sulfurization reactor to a ratio of 0.2-0.9 (m3/kg/h) relative to the input mass (kg/h) of the nickel to be introduced to the reactor; and/or subjecting the waste solution and the exhaust gas to countercurrent contact, then introducing the exhaust gas back to the scrubber and charging the waste solution from the scrubber into the sulfurization reactor.

Abstract: In a hydrometallurgical plant of a nickel laterite ore having a plurality of lines of treatment facilities, the hydrometallurgical plant of the nickel laterite ore which is, even when a serious trouble will occur in said treatment facilities, capable of minimizing decrease in throughput caused by this, and restoring a normal operation state early, after eliminating the serious trouble, and an operation method thereof. A hydrometallurgical plant of a nickel laterite ore having a plurality of lines, as treatment facilities including a pretreatment step, a leaching step, a solid-liquid separation step, a neutralization step, a zinc removal step, a sulfurization step and a detoxification step as one line, wherein a coupling pipeline having a valve is installed between a liquid sending pipeline from the solid-liquid separation step to the neutralization step in each line and/or between a liquid sending pipeline from the sulfurization step to the detoxification step in each line.

Abstract: The separation method for zinc sulfide, in the hydrometallurgical process by a High Pressure Acid Leach for nickel oxide ore comprising leaching and solid/liquid separation step, neutralization step, zinc removal step, and nickel recovery step, which can inhibit clogging of a filter cloth and reduce a frequency of washing operation and replacement operation of a filter cloth by improving filtration performance of zinc sulfide, and inhibit decrease of nickel recovery ratio, in the zinc removal step in which zinc sulfide is formed by adding a sulfurizing agent to the neutralization final liquid containing zinc as well as nickel and cobalt and zinc sulfide is separated to obtain a mother liquid for nickel recovery containing nickel and cobalt. The separation method for zinc sulfide of the present invention is characterized in that in the above-described neutralization step, the leach residue is added to the leach liquor, and pH of the neutralization final liquid is adjusted so as to fall to the range from 3.

Abstract: A production process of a sulfide containing nickel and cobalt by adding a sulfurizing agent under pressurization into an aqueous solution of sulfuric acid containing nickel and cobalt, which is capable of recovering nickel and cobalt as a sulfide in high yield, as well as enhancing the utilization efficiency of hydrogen sulfide gas. A production process of a sulfide containing nickel and cobalt by adding a sulfurizing agent under pressurization into an aqueous solution of sulfuric acid containing nickel and cobalt, characterized by supplying, as the above sulfurizing agent, hydrogen sulfide gas into the vapor phase of inside of a reactor, as a major sulfurizing agent, as well as, by supplying an aqueous solution containing a sodium hydrosulfide, which is recovered by absorbing unreacted hydrogen sulfide gas, which is discharged from inside of the reactor in producing the above sulfide, with an aqueous solution of sodium hydroxide, into the liquid phase.

Abstract: The separation method for zinc sulfide, in the hydrometallurgical process by a High Pressure Acid Leach for nickel oxide ore comprising leaching and solid/liquid separation step, neutralization step, zinc removal step, and nickel recovery step, which can inhibit clogging of a filter cloth and reduce a frequency of washing operation and replacement operation of a filter cloth by improving filtration performance of zinc sulfide, and inhibit decrease of nickel recovery ratio, in the zinc removal step in which zinc sulfide is formed by adding a sulfurizing agent to the neutralization final liquid containing zinc as well as nickel and cobalt and zinc sulfide is separated to obtain a mother liquid for nickel recovery containing nickel and cobalt. The separation method for zinc sulfide of the present invention is characterized in that in the above-described neutralization step, the leach residue is added to the leach liquor, and pH of the neutralization final liquid is adjusted so as to fall to the range from 3.

Abstract: The hydrometallurgical Process for a nickel oxide ore, which is capable of preventing inevitable operation shutdown of a leaching step and maintaining high operation efficiency as a whole process, in a trouble of the steps other than the leaching step, in a hydrometallurgical Process for a nickel oxide ore using a High Pressure Acid Leach.