Abstract: Provided is a method for recovering scandium as scandium oxide that contains high-quality scandium and in which coarse particles having good handling properties are formed. This method for recovering scandium includes a step for carrying out an oxalate conversion process wherein oxalic acid is used in a solution containing scandium (scandium-containing solution) to generate a reaction in which the scandium is converted into an oxalate form, the method characterized in that the temperature of the reaction solution during the oxalate conversion process is 50° C. to 80° C.

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 are a sulfuric acid adding facility and an operation method therefor which enable an increase in the maximum capacity and the operation rate of a sulfuric acid supply pump provided in the sulfuric acid adding facility. In a sulfuric acid adding facility, sulfuric acid is added to an autoclave used in a leaching step of a high pressure acid leaching method for a nickel oxide ore. The sulfuric acid adding facility is provided with the same number (n+1) (n is an integer, at least 1) of each of the following: a plurality of sulfuric acid adding pipes for adding sulfuric acid into the autoclave; and a plurality of sulfuric acid supply pumps for supplying sulfuric acid to the sulfuric acid adding pipes. Each of the first through n+1th sulfuric acid supply pumps includes at least three diaphragms and discharge ports of the same number as that of the diaphragms.

Abstract: Provided is a hydrometallurgical process for nickel oxide ore effectively reducing the amount of sulfuric acid used in the leaching step and the amount of a neutralizer such as slaked lime used in the final neutralization step without reducing nickel yield. The present invention is a method for pre-treating ore slurry to be submitted for leaching treatment in a hydrometallurgical process for nickel oxide ore, the method comprising: a separating step for separating the ore slurry into a coarse particle fraction, in which particles having a particle diameter of less than 45 ?m are 30 mass % of the solids or less, and a fine particle fraction, and feeding said fine particle fraction to the leaching process; and a vibration sieving step for separating the separated coarse particle fraction into oversize particles and undersize particles using vibration sieving and feeding the ore slurry of said undersize particles to the leaching process.

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: In an autoclave in a high pressure acid leaching process in which starting material slurry and sulfuric acid are stirred by stirring machines in each compartment in the autoclave partitioned by partition walls to proceed leaching, and slurry is transferred from a compartment on an upstream side to a compartment on a downstream side to sequentially proceed leaching, wherein starting material slurry supply tubes having the starting material slurry discharge ports and sulfuric acid supply tubes having sulfuric acid discharge ports are alternately disposed on a perimeter of stirring blades of the stirring machine provided in the compartment at an upstream end, and the starting material slurry and sulfuric acid are added to the compartment at the upstream end from the starting material slurry discharge ports and the sulfuric acid discharge ports positioned higher than an uppermost part of the stirring blades and lower than a contained liquid surface.

Abstract: The present invention provides a hydrometallurgical method for nickel oxide ore, wherein the plant can be smoothly started up without imposing a load onto a filter cloth for a separation treatment of zinc sulfide, and the amount of residual zinc in a mother liquor for nickel recovery can be reduced to 1 mg/L. In the plant start-up after the completion of a periodic inspection, a post-neutralization solution is controlled to return to a neutralization reaction tank via circulation piping by adjustment of a switching valve in flow piping without sulfurizing post-neutralization solution. When the flow rate and/or the temperature of the post-neutralization solution circulated reaches a predetermined value, a sulfurization treatment is applied to the post-neutralization solution in the dezincification reaction tank to form zinc-sulfide-containing mother liquor for nickel recovery and adjust the switching valve.

Abstract: The present invention is such that, with H1 being the height from a slurry outlet to a control liquid level, H2 being the height from the control liquid level to the top of a flash vessel, and being the diameter of the flash vessel, 0.35D?H1?0.45D, and 0.75D?H2?0.85D, and at least one liquid level sensor detects a slurry liquid surface at a control liquid level; when the liquid level sensor detects a slurry liquid surface which has risen, a slurry discharge valve installed on a slurry discharge pipe derived from the flash vessel is opened; and when the liquid level sensor detects a slurry liquid surface which has fallen, the slurry discharge valve is closed, whereby opening and closing of the valve is appropriately controlled thereby to reduce troubles with a steam discharge pipe, the slurry discharge pipe, and the slurry discharge valve.

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 hydrometallurgical process for nickel oxide ore effectively reducing the amount of sulfuric acid used in the leaching step and the amount of a neutralizer such as slaked lime used in the final neutralization step without reducing nickel yield. The present invention is a method for pre-treating ore slurry to be submitted for leaching treatment in a hydrometallurgical process for nickel oxide ore, the method comprising: a separating step for separating the ore slurry into a coarse particle fraction, in which particles having a particle diameter of less than 45 ?m are 30 mass % of the solids or less, and a fine particle fraction, and feeding said fine particle fraction to the leaching process; and a vibration sieving step for separating the separated coarse particle fraction into oversize particles and undersize particles using vibration sieving and feeding the ore slurry of said undersize particles to the leaching process.

Abstract: Provided are a sulfuric acid adding facility and an operation method therefor which enable an increase in the maximum capacity and the operation rate of a sulfuric acid supply pump provided in the sulfuric acid adding facility. In a sulfuric acid adding facility, sulfuric acid is added to an autoclave used in a leaching step of a high pressure acid leaching (HPAL) method for a nickel oxide ore. The sulfuric acid adding facility is provided with the same number (n+1) (n is an integer, at least 1) of each of the following: a plurality of sulfuric acid adding pipes for adding sulfuric acid into the autoclave; and a plurality of sulfuric acid supply pumps for supplying sulfuric acid to the sulfuric acid adding pipes. Each of the first through n+1th sulfuric acid supply pumps includes at least three diaphragms and discharge ports of the same number as that of the diaphragms.

Abstract: The wastewater treatment method is to obtain demanganized wastewater, through a step wherein an acid or an alkali is added to sulfuric acid acidified wastewater to adjust pH to not less than 4.0 and not more than 6.0, whereby the sulfuric acid acidified wastewater is separated into a dealuminized solution and an aluminum precipitate; a step wherein a slurrying solution is added to the aluminum precipitate to form a slurry, then an alkali is added to adjust pH to not less than 9.0 and not more than 9.5, whereby an pH-adjusted aluminum precipitate slurry is formed; a step wherein an alkali is added to the dealuminized solution to adjust pH to not less than 8.0 and not more than 9.0; and others.

Abstract: A method for improving the filterability in separating a zinc sulfide, produced by applying sulfurization treatment to a post-neutralization solution containing zinc together with nickel and cobalt in a dezincification step in a hydrometallurgical process for nickel oxide ore. The method includes a neutralization reaction step of neutralizing leachate in a neutralization tank, a separation step of separating neutralized slurry into a neutralized sediment and a post-neutralization solution by adding flocculant to the neutralized slurry, a measuring step of measuring the viscosity of the post-neutralization solution, a step of storing the post-neutralization solution in a storage tank, and a transfer step of transferring the stored post-neutralization solution to a dezincification reaction tank used in a dezincification step subsequent to a neutralization step.

Abstract: At the beginning of a dezincification plant used in a dezincification step in a hydrometallurgical method for nickel, a decrease throughout the dezincification plant is controlled to prevent a decrease in production volume and a cake layer is formed on a filter cloth provided to a filter device inside the dezincification plant. At the beginning of dezincification plant, a slurry containing a formed zinc sulfide is supplied to a filter for filtration and separation, an adjustment is performed in which the flow rate of the slurry is increased to reach a target flow rate in a time T2 which satisfies the following relational expression 3×T1?T2?5×T1, where T1 represents the time between starting a slurry supply and attaining the target flow rate in the case of transferring the slurry at the maximum liquid transfer capacity of a pump configured to transfer the slurry.

Abstract: Provided are a treatment method for a barren solution, and a treatment device for a barren solution, with which hydrogen sulfide can be efficiently removed from the barren solution. In an aeration tank provided with a vertical-type cylindrical reaction vessel, stirring blades arranged in the reaction vessel, and an annular aeration tube having a large number of air outlets, which is arranged to a bottom part of the reaction vessel, aeration is performed by blowing gas for aeration into the reaction vessel from a large number of air outlets of the aeration tube while stirring a liquid by rotation of the stirring blades.

Abstract: In an autoclave apparatus for a high-pressure acid leaching process which advances leaching by stirring heated and pressurized material slurry and sulfuric acid by stirrers in compartments in an autoclave main body of a plurality of compartments, transfers slurry from an upstream side compartment to a downstream one to advance leaching, liquid flow ports for slurry transfer that open and close by doors are provided on the partition walls, the liquid flow ports for slurry transfer are installed at positions where the heights from the lowermost portion the autoclave to the center of gravity are 0.1 to 0.3 times an autoclave diameter and distances from the center lines of the partition walls to the center of gravity are 0.05 to 0.25 times the autoclave diameter, and the liquid flow ports for slurry transfer have shapes which do not reach end portions of the partition walls.

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: A slurry-transporting facility equipped with a plurality of pump-equipment circuits, whereby a stop of slurry supply to a transport destination at the time of switchover between the pump-equipment circuits for use is prevented to make an efficient operation possible. The slurry-transporting facility includes: pipe arrangements which branch out from a feed tank into the plurality of circuits; a transport pump provided in each of the pipe arrangement; a first valve provided upstream from the transport pump; a second valve provided downstream from the transport pump; and a uniting pipe arrangement formed by joining of the pipe arrangements at a predetermined position and connected to a LT heater. The uniting pipe arrangement is provided with a third valve configured to control the transportation of ore slurry to the LT heater and a pressure gauge configured to measure a pressure in the uniting pipe arrangement.

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.