JP2021008654A - Nickel oxide ore exudation treatment method and wet smelting method including the same - Google Patents

Abstract

To provide a method that minimizes an aluminium exudation rate even in the event of changes of Al quality and Mg quality of raw material ore.SOLUTION: An exudation treatment method includes adding water to nickel oxide ore containing aluminum and magnesium to prepare ore slurry, adding sulfuric acid to the prepared ore slurry, preferably, conducting a sulfuric acid exudation treatment in an autoclave at a high-temperature high-pressure condition of about 220-260°C, to produce exudation slurry comprising nickel-containing exudate and exudation residues. An amount of the added sulfuric acid is controlled so that a free sulfuric acid concentration of the exudate falls within a predetermined range according to the ratio of an aluminum content to a magnesium content of the nickel oxide ore.SELECTED DRAWING: Figure 3

Description

The present invention relates to a nickel oxide ore leaching treatment method performed by adding sulfuric acid under high temperature and high pressure and a hydrometallurgical method including the leaching method, and particularly, the aluminum leaching rate is controlled by adjusting the free sulfuric acid concentration. The present invention relates to a method for leaching nickel oxide ore and a hydrometallurgical method including the same.

As a method for recovering valuable metals such as nickel and cobalt from low-grade nickel oxide ore having low nickel grade, for example, hydrometallurgy by a high pressure acid leaching (HPAL) method as disclosed in Patent Document 1 The process is known. In this hydrometallurgy process, an ore slurry prepared by adding water to a low-grade nickel oxide ore as a raw material is leached with sulfuric acid under high temperature and high pressure, and then continuously wet-treated to sulfide the valuable metal. It is possible to efficiently recover valuable metals from low-grade raw material ores.

The hydrometallurgical process by the above-mentioned high-pressure acid leaching method is generally composed of the following series of wet treatment steps. That is, an ore preparation step of adjusting the nickel grade and particle size of low-grade nickel oxide ore as a raw material and adding water to prepare an ore slurry, and a reaction vessel for high-pressure reaction called autoclave with sulfuric acid. A leaching step in which nickel is leached under high temperature and pressure, and a pre-neutralization step in which free sulfuric acid remaining in the leaching slurry generated in the leaching step is neutralized with limestone, and the preliminary The solid-liquid separation step of solid-liquid separation of the leached slurry neutralized in the neutralization step to obtain a noble liquid (leachate) from which the leachation residue has been removed, and the solid-liquid separation step of neutralizing the noble liquid and mainly consisting of iron. A neutralization step of obtaining a neutralizing final solution by removing impurities, a purification step of obtaining a mother liquor for recovering nickel by removing impurities mainly composed of zinc contained in the neutralizing final solution, and a nickel recovery step. It is discharged from the sulphurization step of adding hydrogen sulfide gas to the mother liquor to recover nickel and cobalt in the form of mixed sulfide, and the poor liquid discharged during the recovery of the mixed sulfide and the solid-liquid separation step. It is mainly composed of a final neutralization step in which the leachate residue is neutralized before being sent to the tailing dam to remove heavy metals to a predetermined concentration.

In the above HPAL method, various techniques have been introduced in order to increase the processing capacity. For example, Patent Document 1 discloses a technique for adjusting the concentration of free sulfuric acid at the end of leaching treatment to 35 to 45 g / L, which improves the true density of leaching residue and thus produces a high-density leaching residue. It is described that it is stably produced, and as a result, the solid-liquid separability of the slurry containing the leaching residue can be improved. Further, Patent Document 2 discloses a technique for separating the leaching residue by sedimentation while performing multi-stage cleaning using a plurality of thickeners connected in series in the above-mentioned solid-liquid separation step. In Patent Document 2, the poor liquid discharged from the sulfurization step is used as the cleaning liquid for the multi-stage cleaning.

Further, Patent Document 3 discloses a technique for blending the grade of Mg + Al in the ore slurry so as to be about 1.5 to 4.5% in order to control the oxygen consumption in the high-pressure sulfuric acid leaching step. Further, in Patent Document 4, in order to reduce the amount of sulfuric acid used while maintaining a high nickel leaching rate, the concentration of free sulfuric acid in the leached slurry is adjusted to a predetermined concentration according to the Mg / Ni ratio in the ore slurry. A technique for adjusting the amount of sulfuric acid added is disclosed.

Japanese Unexamined Patent Publication No. 2005-350766 JP-A-2019-000834 Japanese Unexamined Patent Publication No. 2014-037632 Japanese Unexamined Patent Publication No. 2019-035113

By the way, the raw material nickel oxide ore contains aluminum (Al) and magnesium (Mg) as impurities, and when the grades of these fluctuate, the aluminum concentration and magnesium concentration in the leachate also fluctuate, and in some cases, the reserve In the neutralization step, the amount of starch composed of aluminum hydroxide increases, the load of solid-liquid separation in the subsequent step becomes overloaded, and the clarity of the liquid phase after the solid-liquid separation deteriorates. Problems could occur. Further, since the starch made of aluminum hydroxide has a small particle size and a light specific gravity, it is difficult to separate solid and liquid, and the clarity may be further deteriorated.

In this way, if the aluminum grade or magnesium grade of the raw material ore fluctuates, the operation after the leaching process becomes unstable, and the processing capacity of the entire hydrometallurgy process may decrease. The present invention has been made in view of the above circumstances, and even if the Al grade or Mg grade of the nickel oxide ore used as a raw material for the sulfuric acid leaching treatment under high temperature and high pressure fluctuates, the sulfuric acid leaching treatment is carried out. The purpose is to provide a method for keeping the aluminum leaching rate low.

As a result of diligent studies to achieve the above object, the present inventors adjust the amount of sulfuric acid to be added according to the Al / Mg ratio of nickel oxide ore used as a raw material for sulfuric acid leaching treatment under high temperature and high pressure conditions. As a result, we have found that the aluminum leaching rate can be suppressed to a low level, and have completed the present invention.

That is, the method for leaching nickel oxide ore according to the present invention is to add sulfuric acid to an ore slurry prepared by adding water to nickel oxide ore containing aluminum and magnesium, and perform sulfuric acid leaching treatment under high temperature and high pressure conditions. A leaching treatment method for producing a leaching slurry composed of a leaching solution containing nickel and a leaching residue, wherein the free sulfuric acid concentration of the leaching solution is determined according to the ratio of the aluminum content to the magnesium content of the nickel oxide ore. It is characterized in that the amount of sulfuric acid added is adjusted so as to be within the range.

According to the present invention, since the aluminum leaching rate can be suppressed to a low level, it is possible to suppress a decrease in the processing capacity of the entire hydrometallurgical process.

It is a block flow figure of the wet smelting method which preferably includes the leaching treatment method of nickel oxide ore which concerns on this invention. It is a schematic process flow diagram of the continuous countercurrent washing method preferably performed in the solid-liquid separation step of the hydrometallurgical method of FIG. 1. It is a graph which shows the relationship between the Al / Mg ratio of the ore raw material used in the leaching treatment method of the Example of this invention, and the aluminum leaching rate at the time of their leaching treatment.

Hereinafter, embodiments of the nickel oxide ore leaching treatment method according to the present invention will be described with reference to the drawings. First, a wet smelting method including a series of wet treatment steps including a nickel oxide ore leaching treatment method according to the embodiment of the present invention will be described, and then the embodiment of the present invention included in the wet smelting method will be described. The leaching treatment method according to the above will be described.

1. 1. Hydrometallurgical method of nickel oxide ore The hydrometallurgical method of nickel oxide ore including the leaching treatment method according to the embodiment of the present invention is a high-pressure acid leaching method (HPAL) for an ore slurry containing nickel oxide ore as a raw material. After leaching nickel and cobalt by the method), the nickel and cobalt are recovered in the form of a mixed sulfide through a treatment for removing impurities such as iron and zinc contained in the obtained leachate.

Specifically, as shown in FIG. 1, in this wet smelting method for nickel oxide ore, a plurality of types of nickel oxide ore are mixed in order to adjust the nickel grade and the like, and water is added to classify them in a wet manner. The ore preparation step S1 for preparing the ore slurry, the high-pressure sulfuric acid leaching step S2 in which sulfuric acid is added to the obtained ore slurry and the leaching treatment is performed under high temperature and high pressure, and the leaching slurry obtained by the leaching treatment is neutralized. Pre-neutralization step S3 for adjusting the pH by adding the above, solid-liquid separation step S4 for separating and removing the leachation residue by solid-liquid separation while performing multi-stage washing of the pH-adjusted leaching slurry, and the leaching residue. By adding a neutralizing agent to the leachate containing an impurity element together with nickel and cobalt obtained by the separation and removal of the above, a neutralized starch containing the impurity element is produced, and this is separated and removed to contain zinc together with nickel and cobalt. Zinc sulfide is generated by adding a sulfide agent such as hydrogen sulfide gas to the neutralization final solution S5 for obtaining the neutralization final solution, and this is separated and removed to recover nickel containing nickel and cobalt. A purification step S6 for obtaining a mother liquor for use, a sulfide step S7 for producing a mixed sulfide containing nickel and cobalt by adding a sulfide agent to the mother liquor for recovering nickel, and recovering the mixed sulfide by solid-liquid separation. Neutralization treatment of the leachation residue containing free sulfuric acid separated and removed in the liquid separation step S4, and neutralization of the poor liquid containing impurities such as magnesium, aluminum and iron discharged during the solid-liquid separation in the sulfide step S7. It is mainly composed of the final neutralization step S8 for performing the treatment. Hereinafter, each of these series of wet treatment steps will be described in detail.

(1) Ore preparation step S1
In the ore preparation step S1, nickel oxide ore represented by so-called laterite ore such as limonite ore and saprolite ore is used as a raw material ore, and a plurality of types having different lots and the like so as to obtain a desired nickel grade and impurity grade. The nickel oxide ore is mixed and introduced into a crusher or a screen to have a certain particle size, and then introduced into a wet classifier together with water to remove oversized ore particles. As a result, the ore slurry containing nickel oxide ore having a predetermined particle size is recovered from the lower side of the sieve of the wet classifier.

With regard to the above-mentioned wet classifying device, oversized ore particles and impurities are removed by classifying the raw material nickel oxide ore at a predetermined classification point, and undersized ore particles are efficiently placed under the sieve together with water. There is no particular limitation as long as it can be recovered, and for example, a general wet vibrating sieve or a rotary wet sieve such as trommel can be preferably used. Further, the classification point adopted in this wet classification apparatus is not particularly limited, but it is appropriate so that the nickel oxide ore recovered under the sieve can be efficiently leached in the high-pressure sulfuric acid leaching step in the subsequent step. A sieve with a wide opening is selected.

(2) High-pressure sulfuric acid leaching step S2
In the high-pressure sulfuric acid leaching step S2, the ore slurry containing the nickel oxide ore prepared in the above ore preparation step S1 is introduced into the reaction vessel together with sulfuric acid, and the pressure is about 3.0 to 5.0 MPaG and the temperature is about 220 to 260 ° C. Leaching is performed under high temperature and high pressure conditions. As a result, a leaching reaction and a high-temperature thermal hydrolysis reaction occur, leaching of nickel, cobalt, etc. as sulfate and immobilization of leached iron sulfate as hematite are performed, and the leaching solution and leaching residue are formed. Leaching slurry is produced. As the above-mentioned reaction vessel, a pressure vessel for high-temperature and high-pressure reaction called a horizontal cylindrical autoclave whose inside is partitioned into a plurality of compartments by a weir is preferably used.

The amount of sulfuric acid added to the above ore slurry is excessively added so that iron in the nickel oxide ore is leached. At that time, in the high-pressure sulfuric acid leaching step S2, the pH of the leachate is set to 0.1 to 1.0 from the viewpoint of improving the solid-liquid separability of the leaching residue containing hematite in the solid-liquid separation step S4 of the subsequent step. It is preferable to adjust the amount of sulfuric acid added. Since the immobilization of iron ions does not proceed completely in this leaching treatment, the leaching solution contains valuable metals such as nickel and cobalt, as well as divalent and trivalent iron ions.

(3) Pre-neutralization step S3
In the preliminary neutralization step S3, a neutralizing agent is added to the leaching slurry obtained in the high-pressure sulfuric acid leaching step S2 to adjust the pH of the leaching slurry within a predetermined range. As described above, in the high-pressure sulfuric acid leaching step S2, in order to improve the leaching rate of the valuable metal, excess sulfuric acid is supplied to the autoclave, which is larger than the stoichiometric amount of sulfuric acid required for leaching the valuable metal. Therefore, the leaching slurry extracted from the autoclave after the leaching treatment contains excess sulfuric acid that was not involved in the leaching reaction, and its pH is very low. In order to neutralize the excess sulfuric acid and efficiently perform multi-stage washing in the solid-liquid separation step S4 of the next step, the pH of the leaching slurry is adjusted to a predetermined range in this preliminary neutralization step S3.

Specifically, it is preferable to adjust the pH so that the pH of the leaching slurry supplied to the solid-liquid separation step S4 is about 2 to 6. If this pH is lower than 2, a considerable cost is required to make the equipment in the subsequent process acid resistant. On the contrary, when this pH is higher than 6, the nickel leached in the leachate is precipitated in the process of the multi-stage washing and is removed together with the leaching residue, so that the recovery rate of nickel is lowered and the washing efficiency of the multi-step washing is lowered. There is a risk.

In the preliminary neutralization step S3, the leachate slurry supplied to the solid-liquid separation step S4 is supplied from the viewpoint of suppressing the pH fluctuation range in the subsequent neutralization step S5 and improving the reaction efficiency in the liquid purification step S6 and the sulfide step S7. It is preferable to set the pH value of. However, when the pH value of the leachate slurry becomes high, the amount of SS (suspended substance) due to the fine particle components contained in the leachate slurry increases, so that the sedimentation property deteriorates in the solid-liquid separation step S4 of the subsequent step and the solidity There may be a problem that the liquid separation becomes insufficient or the filter is easily clogged in the liquid purification step S6. In order to suppress this problem, in the preliminary neutralization step S3, it is more preferable to adjust the pH of the liquid phase portion of the leaching slurry supplied to the solid-liquid separation step S4 to be 2.5 to 3.4. .. The method for adjusting the pH is not particularly limited, but it can be suitably adjusted within the above pH range by adjusting the amount of a neutralizing agent added, for example, calcium carbonate slurry.

(4) Solid-liquid separation step S4
In the solid-liquid separation step S4, the leachate slurry whose pH has been adjusted in the pre-neutralization step S3 is washed in multiple stages and the leachate residue is separated and removed by gravity sedimentation to contain zinc as an impurity element in addition to nickel and cobalt. The exudate can be obtained. In this solid-liquid separation step S4, the leaching slurry is mixed with the cleaning liquid and then solid-liquid separated using a sedimentation separator such as a thickener, so that the leaching slurry is first diluted with the cleaning liquid and then separated into the leaching slurry by sedimentation separation. The leaching residue settles on the bottom of the thickener and is discharged in the form of a concentrated slurry. As a result, the nickel content adhering to the leaching residue can be reduced according to the degree of dilution thereof.

The solid-liquid separation by the thickener, such as shown in FIG. 2, is washed in multiple stages by introducing the above leach slurry and cleaning liquid to a plurality of thickener T ₁ through T _n which are connected in series each other become countercurrent It is preferable to use a continuous countercurrent cleaning method (CCD method: Counter Current Decantation method). That is, among the plurality of thickener T ₁ through T _n consecutive, the thickener T ₁ of the most upstream introduced leach slurry pH prepared in the preliminary neutralization step S3, the most downstream thickeners T _n introducing a cleaning fluid ..

In each of the plurality of thickeners T _{1 to} T _n , the concentrated slurry extracted from the bottom is transferred to the thickener on the downstream side immediately via the slurry pump P (the concentrated slurry of the most downstream thickener T _n is the final neutralization step. S8 is transferred to), while the clarified liquid overflows from the upper end portion is transferred immediately upstream thickener (most upstream thickener T ₁ of the clear solution is transferred to a neutralization step S5). As a result, the amount of soluble nickel and cobalt adhering to the residue contained in the leaching slurry can be reduced, so that the amount of cleaning liquid newly introduced into the system can be reduced and the recovery rate of nickel and cobalt can be improved. Can be done. It is preferable to add a flocculant to each thickener to coagulate the leaching residue, which can further improve the sedimentation separability.

The clear liquid overflowing from the upper end of the most upstream thickener T ₁ is sent as a noble liquid to the neutralization step S5 in the subsequent step. In the solid-liquid separation step S4, it is preferable to maintain high clarity of this noble liquid, whereby the solid-liquid separability of a solid-liquid separation device such as a filter used in the neutralization step S5 and the liquid purification step S6 of the subsequent step As a result, the productivity of the entire hydrometallurgy process is improved. That is, if the clarity of the noble liquid is low and a large number of suspended particles are contained, for example, in a filter, the pressure loss increases immediately and the flow rate of the liquid decreases at an early stage. It may become a bottleneck and reduce the processing capacity of the entire process.

As the cleaning liquid, it is preferable to use an aqueous solution having a low pH that contains almost no nickel and has almost no adverse effect on the reaction after the solid-liquid separation step S4, and it is more preferable to use an aqueous solution having a pH of about 1 to 3. .. If the pH of this cleaning liquid is higher than 3, a bulky aluminum hydroxide may be generated when aluminum is contained in the leaching liquid, which may cause poor sedimentation of the leaching residue in the above thickener. The cleaning liquid satisfying the above conditions is not limited, but for example, the poor liquid discharged from the sulfurization step S7 in the subsequent step has a pH of about 1 to 3, and it is preferable to use this repeatedly.

(5) Neutralization step S5
In the neutralization step S5, a neutralizing agent such as calcium carbonate is added to the noble liquid (leaching liquid) obtained by separating and removing the leachate residue in the solid-liquid separation step S4 to adjust the pH, whereby the noble liquid is adjusted. Neutralized starch is produced from the impurity elements contained in. This neutralized starch is separated and removed using a thickener or the like to recover the neutralized final solution containing zinc together with nickel and cobalt. In the above pH adjustment, the pH of the neutralized final solution is preferably 4 or less, more preferably 3.0 to 3.5, and most preferably 3.1 to 3 while suppressing the oxidation of the noble solution. The amount of the neutralizing agent added is adjusted to be .2. As a result, the sulfuric acid excessively added in the high-pressure sulfuric acid leaching step S2 is neutralized to generate a neutralized final solution which is a source of the mother liquor for recovering nickel, and trivalent iron ions and aluminum remaining in the leaching solution are produced. It is possible to remove impurities such as ions as a neutralized starch. The neutralized starch may be returned to the solid-liquid separation step S4 of the previous step.

(6) Purifying process S6
In the purification step S6, a sulfurizing agent such as hydrogen sulfide gas is added to the neutralizing final liquid generated in the neutralizing step S5 of the previous step to perform sulfurization treatment, and zinc sulfide produced thereby is separated and removed to nickel. And obtain a nickel recovery mother liquor (dezincification final solution) containing cobalt. The above-mentioned sulfurization treatment is preferably carried out, for example, by injecting the neutralizing final solution into a slightly pressurized low-pressure reaction vessel and blowing hydrogen sulfide gas into the gas phase portion of the low-pressure reaction vessel. As a result, zinc can be selectively sulfurized with respect to nickel and cobalt and removed as zinc sulfide, and a dezincinated final solution as a mother liquor for recovering nickel can be efficiently produced.

(7) Sulfurization step S7
In the sulfurization step S7, the dezincinated final solution produced in the purification step S6 is sulfurized as the starting solution for the sulfurization reaction to produce a mixed sulfide of nickel and cobalt having a small amount of impurity components. Specifically, the sulfur sulfide reaction starting liquid is charged into a pressurized sulfurization reaction tank, and hydrogen sulfide gas is blown into the gas phase portion in the sulfurization reaction tank to add hydrogen sulfide gas into the sulfurization reaction starting liquid. Dissolve. As a result, a sulfurization reaction is caused, and nickel and cobalt contained in the sulfurization reaction starting solution are immobilized as mixed sulfides. The mixed sulfide can be recovered by extracting the slurry containing the nickel and cobalt mixed sulfide from the sulfurization reaction tank and performing solid-liquid separation with a solid-liquid separation device such as a thickener.

When the solid-liquid separator is a thickener, the mixed sulfide separated by gravity sedimentation is recovered from the bottom of the thickener in the form of a concentrated slurry. On the other hand, the supernatant from which the mixed sulfide is separated is discharged as a poor liquid from the upper end of the thickener by overflow. This poor liquid is an aqueous solution stabilized at an extremely low concentration of valuable metals such as nickel, but contains impurity elements such as iron, magnesium, and manganese that remain without being sulfurized. Therefore, this poor liquid is usually transferred to the final neutralization step S8 for detoxification treatment, but if necessary, at least a part thereof is returned to the solid-liquid separation step S4 and reused for nickel recovery. To.

(8) Final neutralization step S8
In the final neutralization step S8, when the leachate residue containing free sulfuric acid separated and removed in the solid-liquid separation step S4 and the mixed sulfide produced in the sulfurization step S7 are recovered by sedimentation separation, filtration, etc. A neutralizing agent is added to the poor liquid containing impurities such as magnesium, aluminum, and iron discharged to the phase side for neutralization treatment. This makes it possible to prevent the slurry, which poses an environmental problem, from being discarded outside the system from the present hydrometallurgy process. Specifically, the pH is adjusted to a predetermined pH range by adding a neutralizing agent to the above-mentioned leaching residue or poor liquid. As a result, the free sulfuric acid contained in the leaching residue is almost completely neutralized, and the impurities contained in the poor liquid are immobilized as hydroxides. The slurry containing the impurity hydroxide thus produced is transferred to the tailing dam (waste storage) as a waste slurry (tailing).

2. 2. Leaching Treatment Method for Slurry of Nickel Oxide Ore The leaching treatment method for nickel oxide ore according to the embodiment of the present invention is carried out in the high-pressure sulfuric acid leaching step S2 among the above hydrometallurgical methods. In this leaching treatment method, the nickel oxide ore containing aluminum and magnesium prepared in the ore preparation step S1 of the previous step is targeted for the leaching treatment. Further, as described above, in this leaching treatment method, the ore slurry containing the nickel oxide ore charged in the reaction vessel under high temperature and high pressure called an autoclave is leached with sulfuric acid. An leaching slurry composed of a leaching solution containing leaching liquid and a leaching residue can be produced extremely efficiently.

That is, in this leaching treatment, by adding sulfuric acid to the ore slurry under high temperature and high pressure, the leaching reaction represented by the following formulas i to iii and the high temperature thermal water addition represented by the following formulas iv to v A decomposition reaction occurs, which causes leaching of nickel, cobalt and the like as sulfates and immobilization of the leached iron sulfate as hematite. Since the immobilization of iron ions does not proceed completely, the liquid phase portion in the generated leaching slurry usually contains divalent and trivalent iron ions in addition to nickel and cobalt.

(Leaching reaction)
[Equation i]
MO + H ₂ SO ₄ → MSO ₄ + H ₂ O
(M in the formula represents Ni, Co, Fe, Zn, Cu, Mg, Cr, Mn, etc.)
[Equation ii]
2Fe (OH) ₃ + 3H ₂ SO ₄ → Fe ₂ (SO ₄ ) ₃ + 6H ₂ O
[Equation iii]
FeO + H ₂ SO ₄ → FeSO ₄ + H ₂ O

(High temperature thermal hydrolysis reaction)
[Equation iv]
2FeSO ₄ + H ₂ SO ₄ + 1 / 2O ₂ → Fe ₂ (SO ₄ ) ₃ + H ₂ O
[Expression v]
Fe ₂ (SO ₄ ) ₃ + 3H ₂ O → Fe ₂ O ₃ + 3H ₂ SO ₄

In order to efficiently carry out the above leaching reaction and fix most of the iron in the raw material ore as hematite, the reaction temperature is preferably maintained at about 220 to 260 ° C., more preferably about 240 to 255 ° C. in the autoclave. Leaching is performed. If the reaction temperature is less than 220 ° C., the rate of the high-temperature thermal hydrolysis reaction slows down, so that iron remains dissolved in the reaction solution, and the load of the purification step S6 in the subsequent step increases to remove the iron. It becomes difficult to separate from nickel. On the contrary, when this reaction temperature exceeds 260 ° C., the high temperature thermal hydrolysis reaction itself is promoted, but it becomes difficult to select the material of the autoclave for high temperature and high pressure leaching, and the thermal energy cost required for the temperature rise increases. To do.

The amount of sulfuric acid added to the ore slurry during the leaching treatment is generally in excess of the stoichiometric amount calculated from the formulas i to v, for example, 150 to 1 ton of ore. About 250 kg of sulfuric acid is added. However, the amount of sulfuric acid added is preferably as small as possible from the viewpoint of the cost of consuming sulfuric acid, and if the amount of sulfuric acid added per ton of ore exceeds 250 kg, the cost of sulfuric acid becomes too high, which is not preferable. On the contrary, if the amount of sulfuric acid added per ton of ore is less than 150 kg, the leaching of nickel may be insufficient.

The raw material nickel oxide ore to be leached is a so-called laterite ore represented by limonite ore and saprolite ore. This laterite ore usually contains nickel in a content of about 0.8 to 2.5% by mass as a hydroxide or a siliceous earth (magnesium silicate) mineral. In addition, this nickel oxide ore has an iron content of about 10 to 50% by mass, which mainly has the form of trivalent hydroxide (gesite), but some divalent iron is present. It is contained in Kay bitter mineral. In addition to the above-mentioned laterite ore, the raw material nickel oxide ore is an oxide ore containing valuable metals such as nickel, cobalt, manganese, and copper, for example, manganese aneurysm existing on the deep sea floor. There is.

In the above leaching treatment, sulfuric acid is added to the ore slurry containing the nickel oxide ore prepared in the previous step to cause an leaching reaction. The ore slurry in the form of this slurry preferably has a solid content concentration (also referred to as slurry concentration) of about 15 to 45% by mass. If the slurry concentration is less than 15% by mass, an excessive autoclave is required to secure a desired residence time, and the amount of sulfuric acid added increases accordingly, which is not preferable. On the contrary, if the slurry concentration exceeds 45% by mass, the scale of the equipment can be reduced, but the transfer of the high-concentration slurry becomes difficult, the blockage occurs frequently in the transfer pipe, and excessive energy is required for the transfer. It is not preferable because it becomes.

By the way, the above nickel oxide ore contains aluminum and magnesium as impurities, and if these impurity grades fluctuate due to reasons such as switching of raw material lots, the operation after the solid-liquid separation step S4 becomes unstable. was there. Therefore, in the leaching treatment method of the embodiment of the present invention, the amount of sulfuric acid added to the ore slurry containing the nickel oxide ore is defined by the ratio of the aluminum content to the magnesium content of the nickel oxide ore. The amount is increased or decreased according to the reference Al / Mg ratio (hereinafter, also referred to as Al / Mg ratio), whereby the free sulfuric acid concentration of the leachate contained in the leachate slurry is adjusted within a predetermined range.

As a result, the aluminum leaching rate can be controlled, so that even if the Al / Mg ratio in the nickel oxide ore becomes higher than usual, the load of solid-liquid separation becomes too high in the solid-liquid separation step S4 of the subsequent step, or the load thereof becomes too high. It is possible to suppress the problem of deterioration of solid-liquid separability. The aluminum content and magnesium content can be determined, for example, by analyzing the raw material nickel oxide ore by ICP emission spectrometry. Further, the above-mentioned aluminum content and magnesium content may be referred to as an aluminum content ratio (or grade) and a magnesium content ratio (grade), respectively. Furthermore, since the ore slurry is produced by adding water to the raw material nickel oxide ore, the value of the Al / Mg ratio of the nickel oxide ore is basically the value of the Al / Mg ratio of the ore slurry containing the nickel oxide ore. Is the same.

Specifically, the aluminum content of nickel oxide ore such as laterite ore, which is a solid content in the ore slurry, is usually in the range of about 2.0 to 3.5% by mass, and the magnesium content is usually 0. It is in the range of about 8 to 1.8% by mass. Therefore, the Al / Mg ratio of the nickel oxide ore is in the range of about 1.1 to 4.4. When an ore slurry of nickel oxide ore containing aluminum and magnesium within the range of this degree of Al / Mg ratio is leached in the high pressure sulfuric acid leaching step S2, nickel, magnesium and aluminum are leached from the following formulas 1 to 3. It is leached by the reaction, and a part of the leached aluminum is immobilized by the hydrolysis reaction of the following formula 4.

[Equation 1]
NiO + H ₂ SO ₄ = NiSO ₄ + H ₂ O
[Equation 2]
MgO + H ₂ SO ₄ = sulfonyl ₄ + H ₂ O
[Equation 3]
2Al (OH) ₃ + 3H ₂ SO ₄ → Al ₂ (SO ₄ ) ₃ + 6H ₂ O
[Equation 4]
3Al ₂ (SO ₄ ) ₃ + 14H ₂ O →
2 (H ₃ O) Al ₃ (SO ₄ ) ₂ (OH) ₆ + 5H ₂ SO ₄

In the above leaching treatment, the aluminum leaching rate is preferably suppressed to 25.0% or less. If this aluminum leaching rate exceeds 25.0%, the aluminum concentration in the leachate becomes excessive, and the amount of starch composed of aluminum hydroxide becomes excessive in the preliminary neutralization step S3 of the subsequent step, resulting in a solid-liquid separation step. The load of S4 may become too high and the clarity of the noble liquid may deteriorate. Further, since the starch made of aluminum hydroxide has a small particle size and a light specific gravity, it is difficult to settle in the sedimentation separator of the thickener, and the clarity may be further deteriorated. As a result, the processing capacity of the entire hydrometallurgy process may be reduced. The aluminum leaching rate (Al leaching rate) can be defined by the following formula 5.

[Equation 5]
Al leachate = (amount of leachate produced per unit time x mass concentration of Al in leachate) ÷ (amount of nickel oxide ore treated per unit time x Al grade of nickel oxide ore) x 100

Therefore, in the leaching treatment method of the embodiment of the present invention, the sulfuric acid added to the autoclave is provided so that the free sulfuric acid concentration of the leachate falls within a predetermined range according to the Al / Mg ratio of the ore slurry charged in the autoclave. The amount of addition is adjusted. For example, when the Al / Mg ratio of the ore slurry charged into the autoclave tends to increase, the amount of sulfuric acid added is reduced so that the free sulfuric acid concentration of the leachate contained in the leachate slurry extracted from the autoclave is reduced. When the Al / Mg ratio of the ore slurry charged into the autoclave tends to decrease, the reverse operation is performed.

More specifically, it is determined whether the Al / Mg ratio of the ore slurry charged into the autoclave is higher or lower than the threshold value of 2.0, and when the Al / Mg ratio is 2.0 or more, it is determined. The amount of sulfuric acid added to the autoclave is adjusted so that the free sulfuric acid concentration of the leachate contained in the leachate slurry extracted from the autoclave is within the range of 32 g / L or more and 38 g / L or less.

By adjusting the free sulfuric acid concentration of the leachate within the above range, the aluminum leachation rate when the nickel oxide ore containing aluminum and magnesium is leached by the autoclave can be suppressed to a low level. That is, if the free sulfuric acid concentration exceeds 38 g / L, the aluminum leaching rate during the leaching treatment may become too high. On the contrary, if the free sulfuric acid concentration is less than 32 g / L, the nickel leaching rate when the nickel oxide ore is leached by the autoclave may not satisfy the desired conditions.

On the other hand, when the Al / Mg ratio in the ore slurry charged into the autoclave is less than 2.0, the concentration of free sulfuric acid in the leachate contained in the leach slurry extracted from the autoclave after being leached in the autoclave is high. The amount of sulfuric acid added to the autoclave is adjusted so as to be in the range of more than 38 g / L and 50 g / L or less, more preferably 40 g / L or more and 50 g / L or less.

As described above, the reason why the free sulfuric acid concentration is increased when the Al / Mg ratio of the ore slurry is less than 2.0 as compared with the case where the Al / Mg ratio is 2.0 or more is set in this free sulfuric acid concentration. When the Al / Mg ratio is lowered compared to the above case of 2.0 or more, the aluminum leaching rate is slightly lowered, but the magnesium grade in the ore slurry is higher than the case of the above Al / Mg ratio of 2.0 or more. This is because the added sulfuric acid is preferentially used for magnesium, and it becomes difficult to obtain the effect of reducing the aluminum leaching rate by lowering the free sulfuric acid concentration, and conversely, the nickel leaching rate is lowered.

That is, when the Al / Mg ratio of the nickel oxide ore treated in the above-mentioned high-pressure sulfuric acid leaching step S2 is low (this corresponds to the case where the magnesium grade is relatively high), the reaction of the above formula 2 is given priority. As it progresses, it inhibits the reaction of the above formula 3 and promotes the reaction of the above formula 4, so that the aluminum leaching rate tends to be low. On the other hand, when the Al / Mg ratio of the nickel oxide ore treated in the high-pressure sulfuric acid leaching step S2 is high (this corresponds to the case where the magnesium grade is relatively low), the leachate remains even if the above formula 2 proceeds. Since a sufficient free sulfuric acid concentration is maintained and the metal ion concentration of the leachate is low, the reaction of the above formula 3 is promoted or the reaction of the above formula 4 is inhibited, so that the aluminum leachation rate is high. Prone.

When the Al / Mg ratio of the raw material nickel oxide ore is high as in the latter case, the aluminum leaching rate tends to be high, so the control value of the free sulfuric acid concentration in the leachate is compared with the case where the Al / Mg ratio is low. And actively reduce it. As a result, the progress of the reaction of the above formula 3 can be suppressed and the progress of the reaction of the above formula 4 can be promoted, so that the aluminum leaching rate can be effectively suppressed as a result.

Although the method for leaching nickel oxide ore of the present invention has been described above based on the embodiment, the present invention is not limited to the above embodiment, and various alternative examples and various alternative examples are provided without departing from the gist of the present invention. It can include modified examples. That is, the scope of rights of the present invention extends to the scope of claims and the equivalent scope thereof. Next, the leaching treatment method of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

<Example>
Raw material ores of Samples 1 to 6 composed of laterite ore having different Al content and Mg content were prepared, and water was added to each of them to prepare an ore slurry having a solid content concentration of about 40% by mass. .. Each of the ore slurries of Samples 1 to 6 was continuously charged into the autoclave, and 98% sulfuric acid was continuously added with 200 kg per ton of ore as a guide, and the leaching temperature was about 253 ° C. and the leaching pressure was about. Sulfuric acid leaching treatment was performed under high temperature and high pressure conditions of 4500 kPaG to generate a leaching slurry.

At that time, the charging flow rate of the ore slurry was adjusted so that the residence time in the autoclave was 60 minutes. On the other hand, when the Al / Mg ratio of the raw material ore is less than 2.0, the free sulfuric acid concentration of the leachate contained in the leach slurry continuously discharged from the autoclave is 38 g / L or more and 50 g / L. Adjust so that it is within the following range, and when the Al / Mg ratio of the raw material ore is 2.0 or more, adjust so that the free sulfuric acid concentration of the leachate is within the range of 32 g / L or more and 38 g / L or less. did.

In this way, the leachate slurry obtained by sulfuric acid leaching treatment of the raw material ore of each sample is sampled, introduced into a nutche covered with filter paper to separate and remove the leachate residue, and contained in the leachate collected on the filtrate side. The concentration of aluminum was measured by ICP emission spectrometry. The obtained aluminum concentration (mass%) was substituted into the above-mentioned formula 5 to obtain the aluminum leaching rate. The results are shown in Table 1 below together with the Al content, Mg content, Al / Mg ratio, and free sulfuric acid concentration of the leachate of the raw material ore. In addition, the relationship between the Al / Mg ratio of the ore raw material and the aluminum leaching rate was plotted on the graph of FIG. The Al content and Mg content of the raw material ore were measured by ICP emission spectrometry, and the free sulfuric acid concentration of the leachate was measured by the neutralization titration method.

As can be seen from Table 1 and FIG. 3, the Al leaching rate is adjusted to 25 by adjusting the amount of sulfuric acid added so that the free sulfuric acid concentration of the leachate falls within a predetermined range according to the Al / Mg ratio of the raw material ore. It was able to be suppressed to 0.0% or less. It is considered that if the free sulfuric acid concentration is lowered even in the region where the Al / Mg ratio is less than 2.0, the aluminum leaching rate is considered to decrease slightly, but since the nickel leaching rate is greatly reduced by reducing the free sulfuric acid concentration, aluminum leaching is slightly performed. Lowering the free sulfuric acid concentration to lower the rate is generally unacceptable from an economic point of view.

<Comparison example>
Raw material ores of Samples 7 to 12 composed of laterite ores having different Al content and Mg content were prepared, and water was added to each of them in the same manner as in Examples to obtain a solid content concentration of about 40% by mass. An ore slurry was prepared. For each of the ore slurries of these samples 7 to 12, the free sulfuric acid concentration of the leachate is always within the range of 40 g / L or more and 50 g / L or less regardless of the value of the Al / Mg ratio of the raw material ore. The leaching treatment was carried out in the same manner as in the above-mentioned example except that the addition flow rate of sulfuric acid was adjusted. The results are shown in Table 2 below together with the Al content, Mg content, Al / Mg ratio, and free sulfuric acid concentration of the leachate of the raw material ore. In addition, the relationship between the Al / Mg ratio of the ore raw material and the aluminum leaching rate was plotted on the graph of FIG.

As can be seen from Table 2 and FIG. 3, even when the value of the Al / Mg ratio of the raw material ore is 2.0 or more, the free sulfuric acid concentration of the leachate is always within the range of 40 g / L or more and 50 g / L or less. Since the addition flow rate of sulfuric acid was adjusted so as to be, the Al leaching rate could not be suppressed to 25.0% or less.

From the results of the above Examples and Comparative Examples, it can be seen that the desired aluminum leaching rate can be obtained by adjusting the free sulfuric acid concentration according to the value of the Al / Mg ratio of the raw material ore. That is, it was found that the suitable free sulfuric acid concentration differs depending on the Al / Mg ratio of the raw material ore. For example, it was found that when the Al / Mg ratio of the raw material ore is 2.0 or more, the aluminum leachate rate can be reduced by reducing the amount of sulfuric acid added so as to reduce the free sulfuric acid concentration in the leachate. It is considered that this is due to the fact that the aluminum leaching reaction is inhibited by the decrease in the free sulfuric acid concentration, the hydrolysis reaction of aluminum sulfate is promoted, or both of them.

S1 Ore preparation process S2 High-pressure sulfuric acid leaching process S3 Pre-neutralization process S4 Solid-liquid separation process S5 Neutralization process S6 Purification process S7 Sulfurization process S8 Final neutralization process T _{1 to} T _n thickener P slurry pump

Claims (5)

Sulfuric acid is added to an ore slurry prepared by adding water to nickel oxide ore containing aluminum and magnesium, and sulfuric acid leaching treatment is performed under high temperature and high pressure conditions to generate a leachate slurry consisting of a leachate containing nickel and a leachate residue. It is a leaching method
The amount of the sulfuric acid added is adjusted so that the free sulfuric acid concentration of the leachate falls within a predetermined range according to the ratio of the aluminum content to the magnesium content of the nickel oxide ore. Leaching method. The nickel oxide ore leaching treatment according to claim 1, wherein when the ratio tends to increase, the amount of the sulfuric acid added is adjusted so that the concentration of the free sulfuric acid in the leachate tends to decrease. Method. When the ratio is 2.0 or more, the amount of sulfuric acid added is adjusted so that the free sulfuric acid concentration of the leachate is within the range of 32 g / L or more and 38 g / L or less, and the ratio is less than 2.0. The nickel oxidation according to claim 1 or 2, wherein the amount of the sulfuric acid added is adjusted so that the concentration of the free sulfuric acid in the leachate exceeds 38 g / L and is within the range of 50 g / L or less. Ore leaching method. The leaching of nickel oxide ore according to any one of claims 1 to 3, wherein the sulfuric acid leaching treatment is performed at a reaction temperature of 220 to 260 ° C. in an autoclave composed of a reaction vessel for a high-temperature and high-pressure reaction. Processing method. A high-pressure sulfuric acid leaching step of leaching an ore slurry prepared by adding water to the raw material nickel oxide ore using the nickel oxide ore leaching method according to any one of claims 1 to 4. A solid-liquid separation step of separating the leachate containing nickel produced by the leachate treatment from the leachate residue, and a neutralization step of adding a neutralizing agent to the leachate obtained in the solid-liquid separation step to remove impurities. A hydrometallurgical method for nickel oxide ore, which comprises a sulfurization step of adding a sulfurizing agent to the leachate from which impurities have been removed in the neutralization step and recovering the nickel in the form of a sulfide.

Images