JP2020117749A - Method for preparing ore slurry - Google Patents

Abstract

To provide a method capable of usually and stably manufacturing ore slurry without generating a problem on the transfer of the ore slurry.SOLUTION: A method for preparing ore slurry used as a raw material in a high pressure acid exudation method for collecting nickel and cobalt by subjecting a nickel oxide ore to acid exudation at a high temperature and a high pressure comprises: a pulverization and classification step S1 of uniforming the nickel oxide ore with a predetermined particle size; an ore slurry condensation step S2 of condensing the ore slurry obtained in the pulverization and classification step S1; and a slurry storing/sending step S3 of sending the slurry to the post step after storing the condensed ore slurry in a slurry storage tank once. After pressurizing the condensed ore slurry extracted from the bottom of the slurry storage tank by a circulating pump, the condensed ore slurry is self-circulated by returning the slurry to the slurry storage tank.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for treating an original ore of nickel oxide ore after mining to prepare an ore slurry, and in particular, to prepare an ore slurry in which a yield stress is suppressed so as to prevent the occurrence of problems such as blockage of a transfer pipe system. Regarding the method.

In the non-ferrous metal smelting, in recent years, a technology for recovering valuable metals such as nickel and cobalt from low-grade raw material ores has been required, and 1.0 to 2.0 mass% of nickel is contained in the entire ore raw material, As a hydrometallurgical method for efficiently recovering nickel and cobalt from a low-grade nickel oxide ore containing 0.1 to 0.5 mass% of cobalt, an HPAL method of acid leaching with sulfuric acid under high temperature and high pressure ( Attention has been focused on a high-pressure acid leaching method, which is also called High Pressure Acid Leaching.

In the HPAL method, for example, as described in Patent Document 1, an ore slurry prepared by adding water to a nickel oxide ore is leached with sulfuric acid under high temperature and high pressure, whereby nickel and cobalt other than valuable metals are added. A leaching step for obtaining a leaching solution containing an impurity element, and a pH of the leaching solution is adjusted to produce a neutralized precipitate composed mainly of iron among the impurity elements, and the neutralized precipitate is removed in the form of a concentrated slurry to obtain a purified solution. A neutralization step for obtaining a nickel recovery mother liquor, and a sulfurization step for producing a nickel-cobalt mixed sulfide by adding hydrogen sulfide gas to the nickel recovery mother liquor, and separating and recovering the nickel-cobalt mixed sulfide from the poor liquid have.

Among the above HPAL methods, in the leaching step, generally 90% or more of nickel and cobalt in the ore slurry can be leached, and the leachate separated from the leaching residue by solid-liquid separation is subjected to the next neutralization. In the step, impurities in the leachate are separated and removed by a neutralization method. The nickel-cobalt mixed sulfides recovered in the sulfurization step, which is the next step of the neutralization step, have a nickel grade of 55-60% and a cobalt grade of 3-6%, which is an intermediate level between nickel smelting and cobalt smelting. Used as a raw material.

By the way, the nickel oxide ore used as a raw material for the above HPAL method is generally prepared in the form of an ore slurry by undergoing an ore treatment step of performing various pretreatments on a raw ore obtained by mining a mine. To be done. In the ore processing step of this nickel oxide ore, a low grade nickel oxide ore with a nickel grade of about 1.0 to 2.0% is subjected to multi-stage classification (sieving) and pulverization to obtain a predetermined amount. An ore slurry containing an ore having a particle size at a predetermined concentration is prepared, and this is recovered and transferred to a leaching step. Since the ore slurry thus produced generally contains excess water, the ore slurry is concentrated before being transferred to the leaching step as described in Patent Document 2, for example. The excess water is removed in a thickener.

In the above thickener, the ratio and density of the solid content in the concentrated slurry obtained by sedimentation are controlled, and therefore the addition amount of the flocculant is adjusted according to the amount of ore charged. As a result, the ore component contained in the ore slurry per unit volume transferred to the leaching step increases, so that the operation efficiency of the entire plant can be improved. However, the viscosity of the slurry tends to increase as the proportion or density of the solid content in the slurry increases. Further, when a large amount of the aggregating agent is added, the viscosity of the slurry may become too high. As described above, when the viscosity of the slurry becomes too high, the problem that the transfer pipe of the slurry is frequently blocked tends to occur, and in some cases, the plant may be temporarily stopped, resulting in a significant decrease in operating efficiency. Become.

Therefore, in order to reduce the viscosity of the ore slurry, for example, Patent Document 3 discloses a technique for maintaining the solid content of the ore slurry at an optimum value of 40 to 45 mass %. Further, in Patent Document 4, when the particle size measured in the particle size measuring step is lower than a predetermined value, a part of the oversized ore particles removed in the crushing/classifying step is transferred to a solid-liquid separation device. A technique for suppressing an increase in the viscosity of the ore slurry by adding it is disclosed. On the other hand, in the above-mentioned Patent Document 4, as a measure for increasing the viscosity of the ore slurry, an effect of lowering the viscosity by using a “shear pump” for the ore slurry before transfer and applying a shearing force a plurality of times by this ( It is described that a shear thinning effect) can be obtained.

Further, in Patent Document 5, in order to prevent a transfer problem from occurring in the ore slurry in the concentration step of the ore slurry as a raw material for the high-pressure acid leaching method using a thickener, the molecular weight of the aggregating agent and its addition are added. A technique for producing an ore slurry whose concentration and viscosity are adjusted by specifying the dilution rate at the time, specifying the addition amount of the coagulant, and further specifying the temperature of the ore slurry after concentration It is disclosed. Further, in Patent Document 6, a sedimentation rate of an ore slurry is obtained by adding a neutralizing agent to an aqueous slurry of nickel oxide ore, which is a raw material for a high-pressure acid leaching method, to adjust the pH to near the isoelectric point. Alternatively, a technique for controlling the yield stress and thereby increasing the solid content concentration of the ore slurry is disclosed.

JP, 2005-350766, A JP, 2009-173967, A International Publication No. 2016/117051 JP, 2013-95998, A JP 2012-153922 A JP, 2008-189999, A

Although it is considered that the techniques disclosed in the above Patent Documents 1 to 4 can suppress the problem such as clogging that occurs when the ore slurry is transferred, the pipe may be clogged due to other disturbance factors. In particular, when the yield stress of the ore slurry increased to about 100 Pa or more, the slurry pipe was often blocked. For example, when a relatively inexpensive centrifugal pump that is generally used is used as a pump provided in a slurry transfer system, it is said that the yield stress of the slurry that can be sent is about 100 Pa. Therefore, when the slurry that exceeds the yield stress is sent, the pump may stop or the piping system may be blocked.

As a countermeasure against this, in the case of a slurry having a yield stress of more than 100 Pa, it may be possible to adjust the yield stress of the slurry to 100 Pa or less by performing dilution or the like. However, in this case, it is difficult to determine how much to dilute, and therefore it is uneconomical to dilute excessively for safety. Alternatively, it is conceivable to feed the slurry as it is by using a pump having a large power and a quantitative property or the above-mentioned shear pump without diluting, but these pumps are expensive, and especially the shear pump is used. In the case of (1), the structure becomes complicated, and the equipment cost and maintenance cost increase, which is not preferable.

Therefore, as described above, it is necessary to satisfy the contradictory requirements that the solid content ratio of the ore slurry is increased and the operating efficiency is improved, while the viscosity increase of the ore slurry, which is likely to occur along with this, is suppressed and the viscosity is kept low. become. The present invention has been made in view of the above circumstances, by reducing the yield stress of the ore slurry by a simple method, always stable ore slurry without causing problems in the transfer of the ore slurry It is an object of the present invention to provide a method capable of manufacturing

In order to achieve the above object, the method for preparing an ore slurry according to the present invention is an ore used as a raw material for a high pressure acid leaching method for recovering nickel and cobalt by subjecting a nickel oxide ore to an acid leaching treatment under high temperature and high pressure. A method for preparing a slurry, comprising a crushing/classifying step of aligning the nickel oxide ore to a predetermined particle size, an ore slurry concentrating step of concentrating the slurry-like ore slurry obtained in the crushing/classifying step, and the concentrated step. A method for preparing an ore slurry, comprising the step of temporarily storing the ore slurry in a liquid storage tank, and then sending the liquid to a subsequent step, wherein the concentrated ore extracted from the bottom of the liquid storage tank. It is characterized in that the concentrated ore slurry is self-circulated by returning the pressure to the storage tank after the pressure of the slurry is increased by a circulation pump.

According to the present invention, the yield stress of the ore slurry can be reduced by a simple method, and thus the ore slurry is always stable without causing problems in the transfer of the ore slurry such as clogging of the piping system of the ore slurry. Can be manufactured.

It is process drawing of the preparation method of the ore slurry of embodiment of this invention. FIG. 2 is a schematic flow diagram of self-circulation of ore slurry that is performed in the storing/sending process of FIG. 1. It is a graph which shows the relationship between a self-circulation flow rate and a slurry yield stress. It is a process drawing of one specific example of the hydrometallurgical method of nickel oxide ore performed using the ore slurry prepared by the preparation method of the present invention as a raw material.

Hereinafter, an embodiment of a method for preparing an ore slurry of the present invention and a metal smelting method performed using an ore slurry prepared by the method as a raw material will be described in detail in the following order with reference to the drawings. To do. The present invention is not limited to the following embodiments, and includes various modifications and alternatives without departing from the scope of the present invention.
1. Preparation method of ore slurry 1-1. Overview 1-2. About each process 2. Metal smelting method (hydrometallurgical method of nickel oxide ore)

<1. Preparation method of ore slurry>
<1-1. Overview>
The method for preparing an ore slurry according to the embodiment of the present invention, for example, a raw material ore such as nickel oxide ore is subjected to acid leaching with sulfuric acid under high temperature and high pressure to recover valuable metals such as nickel and cobalt. Is a method for preparing an ore slurry used as a raw material in the non-ferrous metal hydrometallurgy, which comprises a crushing/classifying step S1, an ore slurry concentrating step S2, and a storing/sending step as shown in the process diagram of FIG. It consists of S3.

That is, first, in the crushing/classifying step S1, the raw ore is crushed, and then wet classification is performed by supplying the raw ore together with water to a sieve having a predetermined opening, whereby oversized ore particles and contaminants are removed from the sieve. Along with the removal, a coarse ore slurry containing undersized ore particles under the sieve is obtained. Next, in the ore slurry concentrating step S2, the crude ore slurry is charged into a solid-liquid separator such as a thickener, where a part of the water contained in the crude ore slurry is separated and removed to concentrate the ore components. Finally, in the storing/sending step S3, the concentrated ore slurry is once stored in the slurry storage tank, then withdrawn at a predetermined flow rate and sent to the next high temperature pressurized sulfuric acid leaching step.

The method for producing an ore slurry according to the embodiment of the present invention is characterized in that, in the storage/liquid feeding step S3, the ore slurry stored in the slurry storage tank is self-circulated by using a self-circulation pump. Is. Hereinafter, each step constituting the method for producing an ore slurry according to the embodiment of the present invention will be described along the step flow of FIG. 1.

<1-2. About each process>
(Crushing/classifying process)
First, in the crushing/classifying step S1, the raw ore is crushed by a crusher, and the oversized ore particles are removed by performing wet classification by supplying it to a grid or a sieve having a predetermined opening together with water to perform undersize. A crude ore slurry containing ore particles of is obtained. In this crushing/classifying step S1, it is possible to remove impurities such as pebbles and tree roots contained in the raw material ore, and the raw ore that is agglomerated into a lump is crushed to have a predetermined opening. And sieve. The raw material ore targeted by the method for producing an ore slurry according to the embodiment of the present invention is not particularly limited as long as it is an ore containing a metal, and any ore may be used. For example, nickel oxide ore containing nickel or cobalt, copper oxide ore containing copper, and the like can be given.

Among the above nickel oxide ores, so-called laterite ores such as limonite ore and saprolite ore can be mainly mentioned. The laterite ore usually has a nickel content of 0.8 to 2.5 mass% and is contained as a hydroxide or a magnesia silicate (magnesium silicate) mineral. Further, the laterite ore has an iron content of 10 to 50 mass %, which mainly has a form of trivalent hydroxide (goethite), but a part thereof has a form of divalent iron. Included in the magnesia clay mineral. In addition to the above-mentioned laterite ores, oxide ores containing valuable metals such as nickel, cobalt, manganese, and copper such as manganese nodules existing in the deep sea floor may be used.

The crusher or crusher used for crushing or crushing the above raw material ore is not particularly limited, and a general ball mill, rod mill, SAG (Semi-Automatic Grinding) mill or the like can be used. Also, there is no particular limitation on the size of the crusher or crusher, the size of the crushing medium such as balls used in the ball mill, etc., for example, regarding the distribution of the particle size and hardness of the raw material ore to be crushed and crushed. Preliminary tests may be conducted and selected appropriately. The apparatus for classifying the raw ore after crushing or crushing is also not particularly limited as long as the raw ore can be satisfactorily classified to a desired particle size, and for example, a general grizzly or a vibrating sieve and the like The apparatus can be used in one stage or a plurality of stages, but it is preferable to use a Trommel type wet classifier that performs wet classification as at least the final classifier.

There is also no particular limitation on the classification point that becomes the boundary between the oversize and the undersize of the raw ore during the classification treatment with the above classification device, and it can be appropriately set from the particle size distribution required for the ore particles contained in the ore slurry. .. For example, in the case of producing an ore slurry composed of an ore raw material having a particle size of 1.4 mm or less, classification can be performed at a classification point of 1.4 mm by sieving using a sieve having an opening of 1.4 mm. In this case, the ore particles having a particle size larger than 1.4 mm remaining on the sieve are removed as oversized ore particles together with pebbles and tree roots.

The removed oversized ore particles may be separately collected and, if necessary, added to the solid-liquid separation device in the subsequent ore slurry concentration step. On the other hand, small ore particles under the sieve (under the net) having a particle diameter of 1.4 mm or less that have passed through a sieve with a mesh of 1.4 mm are recovered as undersized ore particles. As described above, at least in the final stage classifier, the raw ore is charged together with water so that the raw ore is classified by the wet method, so the undersized ore particles recovered with water under the sieve are in the form of coarse ore slurry in the next step. Be transferred to.

(Ore slurry concentration process)
In the ore slurry concentrating step S2, the crude ore slurry containing the ore particles classified at the predetermined classification point in the crushing/classifying step S1 is introduced into the solid-liquid separation device, and the moisture contained in the crude ore slurry is introduced therein. A part is separated and removed. As a result, an ore slurry in which the ore component is concentrated is obtained.

More specifically, in the ore slurry concentration step S2, the above-mentioned crude ore slurry is charged into a thickener that performs solid-liquid separation by gravity settling, for example, as a solid-liquid separator, and the supernatant water from which the solid content is removed is added. Is discharged from the upper portion of the thickener by overflow, and the solid content settled out is discharged from the bottom portion of the thickener in the form of a concentrated slurry. By this solid-liquid separation, for example, an ore slurry concentrated to a solid content concentration of about 40 mass% can be obtained.

In the ore slurry concentrating step S2, a flocculant may be added to the crude ore slurry charged into the solid-liquid separator, if necessary. The addition of this aggregating agent promotes agglomeration of solids contained in the crude ore slurry, so that sedimentation and separability can be enhanced. As the aggregating agent, for example, a polymer-type aggregating agent can be used, and the molecular weight thereof is not particularly limited and various molecular weights can be used. The form of the coagulant is not particularly limited, but it is preferable to add it after diluting it with a diluting liquid such as water, which allows the coagulant to be more homogeneously mixed with the coarse ore slurry. The effect of addition can be sufficiently exerted. Further, in order to bring the flocculant into contact with the coarse ore slurry sufficiently, it is preferable to add the diluted flocculant to the coarse ore slurry flowing in the feed well of the thickener, for example.

(Storage/liquid transfer process)
Next, in the storing/sending step S3, as shown in FIG. 2, the ore slurry concentrated in the ore slurry concentrating step S2 is received in the storage tank 1 and temporarily stored therein, and then the storage tank 1 is stored. The ore slurry is preferably withdrawn from the bottom of the tank at a constant flow rate, the pressure is increased by the liquid sending pump 2, and the solution is sent to the high temperature pressurized sulfuric acid leaching step of the next step. The liquid storage tank 1 is additionally provided with a circulation system 4 for extracting the ore slurry from the bottom thereof, pressurizing it with the circulation pump 3 and returning it to the upper part of the liquid storage tank 1. The circulation system 4 supplies the ore slurry. By self-circulating, a shear stress can be applied to the ore slurry, so that the yield stress can be reduced.

Specifically, the ore slurry in which the yield stress is suppressed to 100 Pa or less can be prepared by the self-circulation in the circulation system 4 described above. As a result, even if a general pump is used as the liquid feed pump 2 described above, the ore slurry can be satisfactorily used in the leaching step of the latter stage, for example, the HPAL method, without causing problems such as liquid feed failure such as clogging of the piping system. Can be transferred. The concentration of the ore slurry prepared by this ore slurry preparation method is not particularly limited, but it is preferably prepared so as to be 15 to 45 mass %.

The circulation pump 3 may be a centrifugal pump that feeds by centrifugal force generated by high-speed rotation of the impeller, and may be boosted by a single-stage pump, for example, a low pressure pump and a high pressure pump. It is preferable to boost the pressure with a continuous multistage pump. Further, the circulation flow rate of the ore slurry in the circulation system 4 is preferably 250 m ³ /h or more. Alternatively, the value obtained by dividing the effective volume of the liquid storage tank 1 by the circulation flow rate is preferably 8 hours or more and 14 hours or less, and more preferably 10 hours or more and 12 hours or less. When the circulation flow rate is 250 m ³ /h or more, it is possible to prevent the ore slurry from becoming a yield stress exceeding 100 Pa, which is a region where clogging is likely to occur in the piping system.

The upper limit value of the circulation flow rate is not particularly limited, but is preferably 550 m ³ /h or less from the economical point of view. Further, in the above circulation system 4, it is preferable to determine the pipe size so that the flow rate of the slurry is within the range of about 1.0 to 3.0 m/sec. Further, the method for measuring the yield stress of the ore slurry is not particularly limited, and it can be measured using, for example, a rheometer. Generally, a rotating body is rotated using a rotary viscometer with respect to a fluid sample to be measured for viscosity, and at that time, the resistance (viscous resistance) received by the rotating body from the fluid is read from a rotating torque or the like. Therefore, the yield stress can be measured.

<2. Metal smelting method (hydrometallurgical method of nickel oxide ore)>
Next, a hydrometallurgical method for recovering nickel and cobalt by a high pressure acid leaching method (HPAL method) using an ore slurry containing nickel oxide ore prepared by the above-described method for preparing an ore slurry as a raw material, with reference to FIG. explain.

The hydrometallurgical method for nickel oxide ore shown in FIG. 4 is a leaching step for leaching nickel and cobalt by subjecting the ore slurry prepared by the above-mentioned method for preparing ore slurry to leaching with sulfuric acid under high temperature and high pressure. S11, a solid-liquid separation step S12 in which the leaching slurry obtained in the leaching step S11 is subjected to solid-liquid separation into a leaching solution and a leaching residue, and the leaching solution is neutralized to form a neutralized precipitate, which is separated and removed. Neutralization step S13 for obtaining a mother liquor for recovering nickel consisting of an aqueous sulfuric acid solution containing a valuable metal such as nickel, and hydrogen sulfide gas is blown into the mother liquor to perform a sulfurization reaction to generate a sulfide containing nickel, And a sulfurization step S14 for separating and recovering this from the poor liquid. Hereinafter, each of these steps will be described more specifically.

(Leaching process)
In the leaching step S11, the ore slurry prepared by the ore slurry preparation method is charged into, for example, a high temperature pressure vessel called an autoclave, and sulfuric acid is added to the high temperature pressure vessel to obtain a high temperature of about 220 to 280°C. The leaching process is performed under stirring under the conditions. In this leaching process, a leaching reaction represented by the following formulas 1 to 3 and a high-temperature thermal hydrolysis reaction represented by formulas 4 to 5 occurred, and leaching as a sulfate such as nickel and cobalt and leaching were performed. Immobilization of iron sulfate as hematite is performed. As a result, a leaching slurry composed of the leaching liquid and the leaching residue is generated. However, since the fixation of iron ions does not proceed completely, the liquid portion of the obtained leaching slurry normally contains divalent and trivalent iron ions in addition to valuable metals such as nickel and cobalt.

[Formula 1]
MO+H ₂ SO ₄ → MSO ₄ +H ₂ O
(In the formula, M represents Ni, Co, Fe, Zn, Cu, Mg, Cr, Mn, etc.)
[Formula 2]
2Fe(OH) ₃ +3H ₂ SO ₄ →Fe ₂ (SO ₄ ) ₃ +6H ₂ O
[Formula 3]
FeO+H ₂ SO ₄ →FeSO ₄ +H ₂ O
[Formula 4]
2FeSO ₄ +H ₂ SO ₄ +1/2O ₂ →Fe ₂ (SO ₄ ) ₃ +H ₂ O
[Formula 5]
Fe ₂ (SO ₄ ) ₃ +3H ₂ O→Fe ₂ O ₃ +3H ₂ SO ₄

The amount of sulfuric acid added to the high temperature pressure vessel is not particularly limited, but generally, it is performed by adding an excessive amount over the stoichiometric amount so that iron in the ore is sufficiently leached. ing. Specifically, about 300 to 400 kg of sulfuric acid is added per ton of ore. If the amount of sulfuric acid added per ton of ore is less than 300 kg, the leaching process may be insufficient, and if it exceeds 400 kg, the cost of sulfuric acid is too high, which is not preferable.

(Solid-liquid separation process)
In the solid-liquid separation step S12, the leachate containing nickel and cobalt is separated from the leach residue by performing solid-liquid separation while washing the leach slurry generated in the leach step S11, preferably by a multi-step cleaning method. This multi-stage cleaning method is not particularly limited, but a CCD method (Counter Current) in which a plurality of thickeners are connected in series and the nickel-free cleaning liquid and the above-mentioned leached slurry are brought into contact with each other by flowing countercurrently to each other It is preferable to use a continuous countercurrent washing method also called Decantation). By using this continuous countercurrent cleaning method, the cleaning liquid newly introduced into the system can be reduced and the recovery rate of nickel and cobalt can be 95% or more.

(Neutralization process)
In the neutralization step S13, a neutralizing agent such as calcium carbonate is added to the leachate obtained in the solid-liquid separation step S12 in order to adjust its pH while suppressing oxidation. As a result, the acid added in excess in the leaching step S11 is neutralized, and at the same time neutralized precipitates are produced from impurities such as trivalent iron ions and aluminum ions remaining in the leaching solution. The neutralized precipitate is separated and removed to obtain a mother liquor for recovering nickel.

In the pH adjustment by adding the above-mentioned neutralizing agent, the pH of the leachate is preferably 4 or less, more preferably 3.2 to 3.8. If the pH of the leachate exceeds 4, the generation of nickel hydroxide will increase and, as a result, the nickel recovery rate will decrease, which is not preferable. Further, when removing the trivalent iron ions remaining in the leachate in the neutralization step S13, it is preferable not to oxidize the divalent iron ions present in the leachate. Therefore, it is preferable to prevent the air from being blown into the solution and prevent the solution from being oxidized as much as possible. As a result, it is possible to suppress an increase in the consumption of calcium carbonate due to the removal of divalent iron. Further, since it is possible to suppress an increase in the amount of the neutralized precipitate slurry produced, it is possible to suppress nickel loss due to the neutralized precipitate as a result.

The neutralized starch slurry removed in the neutralization step S13 may be returned to the solid-liquid separation step S12 if necessary. As a result, nickel contained in the neutralized precipitate slurry can be effectively recovered. That is, by repeating the neutralized starch slurry in the solid-liquid separation step S12 of treating at a pH condition lower than the neutralization step S13, the leaching residue was washed and the nickel content adhering to the neutralized precipitate was included. Since the adhered water can be recovered and the nickel hydroxide generated by the local reaction on the surface portion of the neutralized precipitate can be promoted, the recovery loss of the nickel component can be reduced. In addition, since a part of iron hydroxide is also redissolved simultaneously with nickel, a neutralizing agent may be needed again for fixing the dissolved trivalent iron ions. From this point as well, it is desirable to reduce the amount of neutralized precipitate without oxidizing the divalent iron ion as described above.

The reaction temperature in the neutralization step S13 is preferably about 50 to 80°C. If the reaction temperature is less than 50° C., the neutralized starch containing trivalent iron ions produced becomes too fine, so that when the neutralized starch slurry is returned to the solid-liquid separation step S12 as described above, The solid-liquid separation step S12 may be adversely affected. On the other hand, when the reaction temperature exceeds 80° C., the material of the device is easily corroded and the energy consumption for heating increases, which increases the manufacturing cost.

(Sulfiding process)
In the sulfiding step S14, hydrogen sulfide gas is blown into the mother liquor for nickel recovery, which is formed of the sulfuric acid aqueous solution obtained in the neutralizing step S13, to cause a sulfidation reaction to generate nickel sulfide. This mother liquor was originally obtained by leaching the ore slurry with sulfuric acid in the leaching step S11 as described above, and although the pH was adjusted in the neutralization step S13, the pH was about 3.2 to 4.0. Aqueous solution of sulfuric acid having a nickel concentration of 2 to 5 g/L and a cobalt concentration of 0.1 to 1.0 g/L. Further, this mother liquor contains iron, magnesium, manganese and the like as impurity components.

The above-mentioned impurity components greatly vary depending on the redox potential during the leaching process in the leaching step S11, the operating conditions of the autoclave, and the ore grade, but generally, iron, magnesium, and manganese are each contained in the amount of several g/L. There is. As described above, the mother liquor contains a relatively large amount of impurity components with respect to nickel and cobalt which are recovery target substances, but these impurities have low stability as sulfides. Therefore, these alkaline earth metals such as iron, manganese, alkali metals, and magnesium are hardly distributed to the sulfides produced.

When zinc is contained in the mother liquor, it is preferable to perform a dezincification treatment for selectively separating zinc as a sulfide before generating nickel or the like as a sulfide by the sulfurization reaction in the sulfiding step S14. In this dezincification treatment, it is preferable to carry out the sulfidation treatment under a weak sulfidation reaction condition such as lowering the pressure in the reaction vessel than in the sulfidation step S14. This makes it possible to suppress the rate of the sulfurization reaction, and it is possible to selectively remove zinc while suppressing coprecipitation of nickel having a higher concentration than zinc.

The sulfide containing nickel having a low impurity content generated in the sulfiding step S14 can be recovered by solid-liquid separation from the poor liquid in which the nickel concentration is stabilized at a low level. For example, the sulfide slurry containing nickel is introduced into a sedimentation separation device such as a thickener, and is subjected to solid-liquid separation treatment by gravity sedimentation, whereby the sulfide is separated and recovered as a precipitate from the bottom of the thickener. The aqueous solution component from which the precipitate has been removed can be discharged by overflow as a poor liquid. The poor liquid has a pH of about 1 to 3, and impurity elements such as iron, magnesium, manganese, etc., which are not sulfurized by the sulfurating treatment, remain.

In this sulfurization step S14, a sulfide containing nickel as a seed crystal (nickel sulfide) is added to the mother liquor so that the average particle size of the sulfide containing nickel recovered above becomes a predetermined size or more. May be. With this, when the sulfide slurry is subjected to solid-liquid separation by the thickener or the like, it is possible to reduce the concentration of fine suspended solids containing nickel contained in the poor liquid discharged as an overflow liquid. Recovery loss can be reduced.

The amount of nickel sulfide added as the seed crystal is preferably 4 to 6 parts by mass of nickel with respect to 1 part by mass of nickel contained in the mother liquor. This makes it possible to suppress the adhesion of the produced sulfide to the inner surface of the reaction vessel in which the sulfurating treatment is performed, and to stabilize the nickel concentration in the poor liquid at a much lower level. As the nickel sulfide added as this seed crystal, it is preferable to partially extract and use the sulfide containing nickel recovered by the solid-liquid separation treatment such as the above thickener. It is preferable to classify the extracted sulfides by classifying them so that the average particle size becomes equal to or larger than a predetermined size. In addition, prior to the classification treatment, a treatment of pulverizing the sulfide may be performed if necessary. Next, examples of the present invention will be described, but the present invention is not limited to the following examples.

[Example]
The nickel oxide ore was processed according to the block flow shown in FIG. 1 to prepare an ore slurry. At that time, the crude ore slurry that has been settled and concentrated by the thickener in the ore slurry concentration step S2 is stored and fed in the storage step S3 as shown in FIG. 2 with an effective capacity of 3472 m ³ and a height of about 7 hours. It was continuously received in the 19.8 m storage tank 1. This crude ore slurry had a solid content concentration of 42 to 45 mass% and a density of 1.45 to 1.50 g/mL.

This crude ore slurry was self-circulated for one day using two continuous circulation pumps 3 and a circulation system 4 having a pipe diameter of 10 inches. At that time, the circulation flow rate was variously changed by adjusting the opening degree of the valve 4a on the discharge side of the circulation pump 3. To this crude ore slurry, 110 to 130 kg of a flocculant was added per ton of dry matter based on the above thickener. Further, as the circulation pump 3, a pump of model number 6E-AHF manufactured by Weir Minerals Australiaz Ltd. was used. While performing the self-circulation by the double circulation pump 3, the crude ore slurry was continuously fed to the next step by the triple liquid feeding pump 2.

FIG. 3 shows the relationship between the circulation flow rate of the self-circulation and the yield stress of the coarse ore slurry sampled from the liquid storage tank 1. From FIG. 3, it can be seen that the yield stress can be reduced by increasing the circulation flow rate. In particular, it can be seen that by setting the circulation flow rate to 250 m ³ /h or more, it is possible to maintain the value of the yield stress of 100 Pa or less, which is a threshold value at which the occurrence of pipe blockage easily occurs.

[Comparative example]
An ore slurry was prepared in the same manner as in the above example, except that the crude ore slurry received in the liquid storage tank 1 was continuously sent to the next step without self-circulation. As a result, when 110 to 120 kg of a flocculant was added per 1 ton of dry matter, the yield stress (Pa) of the coarse ore slurry sampled at random 5 times varied with 85, 88, 90, 100, and 100. Was there. When 120 to 130 kg of a flocculant was added, the yield stress (Pa) of the coarse ore slurry sampled at random 5 times varied to 98, 99, 100, 100, 123. As can be seen from these results, there was included a case where the yield stress exceeded 100 Pa, which is likely to cause pipe clogging.

1 Liquid storage tank 2 Liquid feed pump 3 Circulation pump 4 Circulation system 4a Valve S1 Grinding/classification process S2 Ore slurry concentration process S3 Storage/liquid transfer process S11 Leaching process S12 Solid-liquid separation process S13 Neutralization process S14 Sulfidation process

Claims (2)

A method for preparing an ore slurry used as a raw material for a high-pressure acid leaching method for recovering nickel and cobalt by subjecting a nickel oxide ore to acid leaching under high temperature and high pressure, wherein the nickel oxide ore is made to have a predetermined particle size. Crushing/classifying step, ore slurry concentrating step of concentrating the slurry ore slurry obtained in the crushing/classifying step, and once the concentrated ore slurry is stored in a liquid storage tank, then sent to a subsequent step A method for preparing an ore slurry including a storing/sending step, wherein the concentrated ore slurry extracted from the bottom of the liquid storage tank is pressurized by a circulation pump and then returned to the liquid storage tank. A method for preparing an ore slurry, which comprises self-circulating a concentrated ore slurry. The method for preparing an ore slurry according to claim 1, wherein the circulation flow rate of the self-circulation is 250 m ³ /h or more.

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