JP7220846B2 - Pretreatment method for nickel oxide ore used as raw material for hydrometallurgy - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pretreatment method for nickel oxide ore used as a raw material for hydrometallurgy, and more particularly to a nickel oxide ore pretreatment method for adjusting the slurry concentration by adjusting the amount of addition of a flocculant.

A hydrometallurgical process that includes a high-pressure acid leaching process, also called the HPAL (High Pressure Acid Leach) process, is known, in which nickel oxide ore as a raw material is subjected to a leaching treatment using sulfuric acid under high temperature and high pressure to generate a leachate. It is This hydrometallurgical method is different from the conventional pyrometallurgical method, which is a conventional method for smelting nickel oxide ore. In addition to being able to efficiently produce a mixed sulfide containing nickel and cobalt (hereinafter also referred to as a nickel-cobalt mixed sulfide), the treatment is performed by a consistent wet process without going through reduction and drying processes. It has the advantage of being advantageous in terms of energy and cost.

The hydrometallurgical process including the high-pressure acid leaching process includes an ore pretreatment process of pretreating a nickel oxide ore to prepare an ore slurry, and adding sulfuric acid to the ore slurry at high temperature and high pressure to obtain nickel, A leaching step of leaching valuable metals such as cobalt to obtain a leaching slurry, a solid-liquid separation step of separating a leaching solution containing impurity elements together with nickel and cobalt from the leaching residue while washing the leaching slurry in multiple stages, and a pH of the leaching solution. is adjusted and a part of the leaching residue and a coagulant are added to generate a neutralized sediment from impurity elements, which is separated and removed to obtain a final neutralization solution containing nickel and cobalt. a dezincing step of adding hydrogen sulfide gas to the neutralization final solution to form a mixed sulfide containing zinc and copper, which is separated and removed to obtain a dezincing final solution; It generally comprises a nickel recovery step in which a nickel-cobalt mixed sulfide is produced by adding hydrogen sulfide gas to the liquid and recovered by solid-liquid separation.

In the ore pretreatment step, nickel oxide ore as a raw material is first subjected to pulverization and crushing treatment, and then wet-classified by adding water to obtain nickel oxide ore having a predetermined particle size in the form of slurry. An additive is added to the obtained low-concentration ore slurry to concentrate it by sedimentation. In this way, a high-concentration ore slurry with an adjusted solid content concentration is produced. A thickener is generally used for this sedimentation concentration. The thickener consists of a cylindrical sedimentation separation tank with a bottom surface that slopes gradually toward the center, a rake that rotates slowly along the bottom of the tank, and ore in the center of the tank. A high-concentration ore slurry concentrated by sedimentation in the tank is extracted from the center of the bottom of the thickener.

In the thickener having the above structure, a flocculating agent is added as an additive to the ore slurry flowing through the feedwell to form flocs, as disclosed in Patent Document 1, thereby improving the sedimentation of the ore slurry. Techniques for improving are disclosed. Further, in Patent Document 2, in the ore pretreatment process, a neutralizing agent such as sulfuric acid or caustic soda is added to the ore slurry obtained by pulverization, crushing and wet classification to adjust the pH to the vicinity of the isoelectric point. discloses a technique for increasing the sedimentation separation performance in the subsequent thickener to increase the solid content concentration of the ore slurry.

Furthermore, in Patent Document 3, the level of the interface between the sedimentation concentration part and the supernatant liquid part formed in the sedimentation separation tank of the thickener (also referred to as a bed level) is measured with an ultrasonic level measurement device, and the sedimentation Techniques are disclosed for controlling thickener operations by continuously monitoring conditions. Further, in Patent Document 4, two thickeners are connected in series, and a concentrated slurry obtained by pre-concentrating the slurry in the upstream thickener is introduced into the downstream thickener, whereby A technique for increasing the sedimentation rate at 100 rpm and thereby efficiently obtaining an ore slurry with a high solids concentration is disclosed.

JP 2012-153922 A JP 2008-189999 A JP 2013-154262 A JP 2015-086457 A

In the above hydrometallurgical method in which nickel is recovered from low-grade nickel oxide ore as a raw material through a high-pressure acid leaching process, depending on the nickel oxide ore species used as a raw material, the ore pretreatment process before the high-pressure acid leaching process is performed. It is believed that there is a difference in sedimentation behavior in the thickener. As a result, the solid content concentration of the high-concentration ore slurry extracted from the center of the bottom of the thickener may become unstable. Specifically, what mechanism does the nickel oxide ore seed affect the sedimentation behavior? is not clarified.

Therefore, conventionally, in the thickener operation of the ore pretreatment process, the bed level in the sedimentation tank is continuously monitored by a measuring device, or the operator periodically measures it using a bed level level measuring jig. By doing so, the state of aggregation and sedimentation in the thickener was confirmed, and the bed level in the sedimentation tank was controlled within an appropriate range. In addition, the low-concentration ore slurry flowing into the feedwell is periodically sampled to visually confirm the particle size, and based on the result, the amount of coagulant to be added is adjusted.

In the operation management based on the experience of the operator as described above, the operation of the thickener tends to be unstable, especially when changing the ore type of the raw material, the sedimentation behavior changes as described above, and the flocculant is insufficient and the flocculation is reduced. Conversely, excessive addition of the flocculant may cause an excessive increase in slurry viscosity. The present invention has been made in view of the problems of the ore pretreatment process of the conventional hydrometallurgical method described above, and even if the ore type and ore grade of the nickel oxide ore used as a raw material change, An object of the present invention is to provide a method capable of stably preparing a high-concentration ore slurry having a solid content concentration of

As a result of extensive studies on the ore pretreatment process of the above hydrometallurgical method, the present inventors have found that by controlling the operation of the thickener in the ore pretreatment process based on the Fe grade of the nickel oxide ore used as a raw material, , even if the kind of nickel oxide ore contained in the low-concentration ore slurry introduced into the thickener is changed, it was found that a high-concentration slurry having a stable solid content concentration can be prepared, and the present invention was completed.

That is, the method for pretreating nickel oxide ore of the present invention is a method for pretreating nickel oxide ore used as a raw material when producing nickel-cobalt mixed sulfide by hydrometallurgical method, wherein the ore raw material is pulverized and / or A sorting step in which water is added after crushing and wet classification is performed, and a low-concentration ore slurry containing nickel oxide ore having a predetermined particle size recovered on the lower side of the sieve of the wet classification is precipitated and concentrated to a high concentration. and a concentration step to obtain an ore slurry, wherein when the Fe grade of the nickel oxide ore is less than 50%, 110 to 130 g of a flocculant per ton of the nickel oxide ore is added to the low-concentration ore slurry. The amount of flocculant added is adjusted so that 160 to 170 g of flocculant per ton of nickel oxide ore is added to the low-concentration ore slurry when the Fe grade is 50% or more. and the flocculant is polyacrylamide with a molecular weight of 8×10 ⁶ to 20×10 ⁶ .

According to the present invention, it is possible to obtain a high-concentration ore slurry having a stable solid content concentration even if the grade of ore processed in the ore pretreatment step of the hydrometallurgical process changes.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a process flow diagram of a hydrometallurgical process including an embodiment of a nickel oxide ore pretreatment method of the present invention. In the nickel oxide ore pretreatment method of the embodiment of the present invention, when the nickel oxide ore is introduced into the thickener together with the flocculant and is sedimented and concentrated, the amount of the flocculant added and the solid content concentration of the high-concentration ore slurry It is a graph showing the relationship.

1. Hydrometallurgical method First, the hydrometallurgical method including the pretreatment method for the nickel oxide ore slurry according to the embodiment of the present invention will be described by taking the hydrometallurgical method including the high-pressure acid leaching step shown in FIG. 1 as an example. do. The hydrometallurgical method shown in FIG. 1 includes an ore pretreatment step S0 for preparing an ore slurry containing nickel oxide ore having a predetermined particle size by pretreating nickel oxide ore as a raw material, and the ore slurry A leaching step S1 in which sulfuric acid is added to the leached slurry and subjected to leaching treatment under high temperature and high pressure to generate a leached slurry, and a preliminary neutralization step S2 in which a pH adjuster is added to the leached slurry to adjust the pH within a predetermined range. a solid-liquid separation step S3 for separating the leachate containing impurity elements together with nickel and cobalt from the leach residue by washing the pH-adjusted leach slurry in multiple stages; a neutralization step S4 of producing a neutralized precipitate containing and separating and removing it to obtain a final neutralization solution containing zinc together with nickel and cobalt; A dezincing step S5 in which a nickel recovery mother liquor containing nickel and cobalt is obtained by separating and removing this, and hydrogen sulfide and sodium hydrosulfide are added as sulfurizing agents to the nickel recovery mother liquor to remove nickel and nickel. After producing the NiCo mixed sulfide containing cobalt, a nickel recovery step S6 for recovering the NiCo mixed sulfide by solid-liquid separation; A sulfiding agent removal step S7 in which a predetermined amount of oxidizing slurry is added to the liquid to decompose the sulfiding agent, and the poor liquid discharged by the decomposition processing is detoxified together with the leaching residue discharged from the solid-liquid separation step S3. and a final neutralization step S8 for processing. The preparation method of the embodiment of the present invention relates to the ore pretreatment step S0 in the hydrometallurgical process including a series of steps from the ore pretreatment step S0 to the final neutralization step S8. The ore pretreatment step S0 will be described in detail below.

2. _Ore pretreatment step In the ore pretreatment step S0, the nickel oxide ore as a raw material is pulverized and crushed, and then water is added to wet classify. and a concentration step _S02 for obtaining a high-concentration ore slurry by sedimentation concentration of the ore slurry. Specifically, first, nickel oxide ores prepared as raw materials are quantitatively analyzed for Ni grade, Fe grade, etc., using, for example, a fluorescent X-ray analyzer, and ores suitable for raw materials are selected. As a result, ores containing almost no Ni and ores with impurity grades higher than the specified value are excluded. After the unsuitable ore has been removed, the appropriate ore is once put into a hopper and stored, and then a fixed sieve with an opening of about 100 mm is used to extract a certain amount from the bottom of the hopper, and large lumps are first filtered. It is passed through several stages of fixed sieves and vibrating sieves as necessary until it is finally sieved with a wet sieve having an opening of about 1 mm. As a result, a low-concentration ore slurry containing nickel oxide ore having a predetermined particle size and having a solid content concentration of about 10 to 20% by mass is recovered on the underside of the wet sieve.

Next, the specific gravity and solid content concentration of the resulting low-concentration ore slurry are measured, and the Ni and Fe grades of the low-concentration ore slurry are quantitatively analyzed using a fluorescent X-ray analyzer. Other impurity grades are also quantitatively analyzed. After that, the low-concentration ore slurry is introduced into the feedwell of the thickener via the slurry pump for sedimentation and concentration. A flocculant whose concentration is adjusted by diluting it with water is added to this low-concentration ore slurry using a flocculant pump. At that time, the coagulant is added while measuring the flow rate with a flow meter provided on the suction side or the discharge side of the coagulant pump so that the coagulant is supplied at a predetermined set flow rate.

The low-concentration ore slurry introduced together with the flocculant is concentrated by gravity sedimentation in the thickener sedimentation tank, collected in the center by a rake, and discharged from the center of the bottom as a concentrated high-concentration ore slurry. On the other hand, the supernatant liquid separated from this high-concentration ore slurry is discharged from the upper end of the sedimentation tank by overflow. The high-concentration ore slurry extracted from the center of the bottom in this manner is sampled periodically or as required, and its specific gravity and solid content concentration are measured.

Based on the operational state of sedimentation concentration in the thickener ascertained from the above measurement results, the set flow rate of the addition amount of the flocculant is changed. For example, if the solid content concentration of the low-concentration ore slurry does not fluctuate but the solid content concentration of the high-concentration ore slurry tends to decrease, control is performed by increasing the flow rate setting value of the flocculant. The amount of sulfuric acid to be added during the high-pressure acid leaching treatment in the subsequent leaching step S1 is determined based on the results of the Ni grade, Fe grade, and other impurity grades obtained by quantitative analysis using the X-ray fluorescence spectrometer. be done.

It is preferable to use polyacrylamide having a molecular weight of about 8×10 ⁶ to 20×10 ⁶ as the flocculant. If the molecular weight of this flocculant is less than 8×10 ⁶ , the effect of flocculation may be low, and the gravitational sedimentation in the thickener may take too long. Conversely, if this molecular weight exceeds 20×10 ⁶ , the effect of concentration by aggregation becomes too high, and there is a risk that the viscosity will not fall within the appropriate range.

Further, in the concentration adjustment by diluting the flocculant with water, the concentration of the flocculant is preferably adjusted to 0.010 to 0.050% by mass. If this concentration is less than 0.010% by mass, the total amount of liquid charged into the thickener sedimentation tank (low-concentration ore slurry + flocculant diluted with water) will be too large, and the residence time will be insufficient. You may not get it. Conversely, if the concentration is higher than 0.050% by mass, chances of contact between the nickel oxide ore particles contained in the low-concentration ore slurry and the flocculant are reduced, which is not preferable.

The Fe grade of the nickel oxide ore contained in the low-concentration ore slurry generally changes within the range of 48% or more and 53% or less. Therefore, in the ore pretreatment step S0 of the embodiment of the present invention, when the Fe grade of the nickel oxide ore is less than 50%, 110 to 130 g of a flocculant is added per ton of the nickel oxide ore, and the Fe grade is In the case of 50% or more, it is preferable to adjust the addition amount of the flocculant so that 160 to 170 g of the flocculant is added per ton of the nickel oxide ore. This makes it possible to further stabilize the solid content concentration of the high-concentration ore slurry extracted from the center of the bottom of the sedimentation tank of the thickener.

When the amount of the flocculant added exceeds 170 g/t-Ni oxide ore, the viscosity of the high-concentration ore slurry after concentration increases, for example, the yield stress becomes 100 Pa or more, and it is extracted from the center of the bottom of the sedimentation tank. There is a risk that the high-concentration ore slurry that is contained in the sedimentation tank will not be able to be sent satisfactorily by the slurry pump, or that the slurry extraction pipe at the center of the bottom of the sedimentation tank will become easily clogged. As described above, the reason why the cohesiveness of the nickel oxide ore particles contained in the low-concentration ore slurry varies depending on the Fe grade is that the higher the Fe grade, the more fine the ore is included. The inventor believes that this is because the

3. Leaching Step As described above, in the concentration step _S02 of the ore pretreatment step S0, the highly concentrated ore slurry extracted from the center of the bottom of the sedimentation tank is pressurized by a slurry pump and charged into a pressure vessel called an autoclave together with sulfuric acid. , the subsequent leaching step S1 is performed. Specifically, while being stirred in an autoclave, a high-pressure acid leaching treatment is performed under high-temperature and high-pressure conditions of about 3 to 4.5 MPaG and about 220 to 280° C. to produce a leaching slurry consisting of a leaching solution and a leaching residue. . Nickel-cobalt mixed sulfide is produced by subjecting the leached slurry obtained in the leaching step S1 to a series of wet treatments from the preliminary neutralization step S2 to the nickel recovery step S6 as described above.

As described above, in the production of nickel-cobalt mixed sulfides by hydrometallurgy, the solid content concentration of the high-concentration ore slurry prepared in the ore pretreatment step S0 affects the productivity and production cost of nickel-cobalt mixed sulfides. It is one of the important requirements because it influences. That is, the higher the solid content concentration of the high-concentration ore slurry, the more Ni can be charged into the autoclave in the leaching step S1, so the productivity of the nickel-cobalt mixed sulfide can be increased.

Generally, in the leaching step S1, it is preferable to set the free acid concentration in the ore slurry to a relatively high value, for example, about 30 to 60 g/L, so that valuable metals such as nickel can be efficiently leached. can. In this case, if the solid content concentration of the high-concentration ore slurry is high, it is possible to ensure a long residence time in the autoclave, so even if the free acid concentration is relatively low, the nickel leaching rate is improved. can be made However, if the solid content concentration of the high-concentration ore slurry is too high, it may become difficult to feed the high-concentration ore slurry charged into the autoclave with a slurry pump. Therefore, it is generally preferable that the solid content concentration of the high-concentration ore slurry is in the range of 40 to 50% by mass.

In the high-pressure acid leaching treatment in the leaching step S1, a leaching reaction and a high-temperature thermal hydrolysis reaction occur, and metal elements such as nickel and cobalt are leached from the nickel oxide ore as sulfates, and the leached iron sulfate is converted into Immobilization as hematite takes place. At that time, iron ions are not fixed completely, so that the liquid phase portion of the obtained leaching slurry usually contains divalent and trivalent iron ions in addition to nickel, cobalt, and the like.

Although the method for pretreating nickel oxide ore according to the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention. and alternatives. That is, the scope of rights of the present invention covers the claims and their equivalents. EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

Nickel oxide ores of various compositions were pretreated to prepare high-concentration ore slurries along the process flow of the ore pretreatment step in the hydrometallurgical process flow shown in FIG. Specifically, after pulverizing the raw material nickel oxide ore, water was added and the low-concentration ore slurry collected on the underside of the sieve by wet classification and the flocculant were introduced into a thickener, and sedimentation and concentration were performed. At that time, the addition amount of the flocculant was also changed variously. As the flocculant, a polymer flocculant having a molecular weight of 8×10 ⁶ to 20×10 ⁶ diluted with water to about 0.2 to 0.3 mass % was used. Further, the Fe grade of the nickel oxide ore constituting the solid content in the low-concentration ore slurry was measured with a fluorescent X-ray analyzer.

FIG. 1 shows the relationship between the solid concentration of the flocculant and the high-concentration ore slurry when pretreated under various conditions as described above. From FIG. 1, when the Fe grade of the nickel oxide ore is less than 50%, the solid content concentration of the high-concentration ore slurry is maximum when 110 to 130 g of the flocculant is added per 1 ton of the nickel oxide ore introduced into the thickener. I know it will be. Moreover, it can be seen that even if the amount of flocculant added exceeds 130 g per ton of the nickel oxide ore, the solid content concentration of the high-concentration ore slurry hardly increases.

On the other hand, when the Fe grade of nickel oxide ore is 50% or more, increasing the amount of flocculant added to 160 to 170 g per ton of nickel oxide ore introduced into the thickener increases the solid content concentration of the high-concentration ore slurry. I know it can be done. As described above, by changing the addition amount of the flocculant according to the Fe grade of the ore raw material to be used, it is possible to stably obtain a high-concentration ore slurry having a high solid content concentration.

S0 ₁ sorting step S0 ₂ concentration step S0 ore pretreatment step S1 leaching step S2 preliminary neutralization step S3 solid-liquid separation step S4 neutralization step S5 dezincification step S6 nickel recovery step S7 agent removal step S8 final neutralization step

Claims (4)

A pretreatment method for nickel oxide ore used as a raw material when producing nickel-cobalt mixed sulfide by hydrometallurgical method, which comprises a sorting step in which the ore raw material is pulverized and/or crushed and then wet-classified by adding water. and a concentration step of obtaining a high-concentration ore slurry by sedimentation and concentration of the low-concentration ore slurry containing the nickel oxide ore having a predetermined particle size recovered on the lower side of the sieve of the wet classification, wherein the nickel oxide ore When the Fe grade of is less than 50%, the amount of the flocculant added is adjusted so that 110 to 130 g of the flocculant per ton of the nickel oxide ore is added to the low-concentration ore slurry, and the Fe grade is 50%. % or more, the addition amount of the flocculant is adjusted so that 160 to 170 g of the flocculant per ton of the nickel oxide ore is added to the low-concentration ore slurry , and the flocculant has a molecular weight of 8×10 ⁶ to A pretreatment method for nickel oxide ore, characterized in that it is 20×10 ⁶ polyacrylamide . The hydrometallurgical method is characterized in that the high-concentration ore slurry is subjected to a high-pressure acid leaching treatment, and hydrogen sulfide is added to the obtained leachate to produce a nickel-cobalt mixed sulfide. , The pretreatment method for nickel oxide ore according to claim 1 . 3. The method for pretreating nickel oxide ore according to claim 1 , wherein the low-concentration ore slurry has a solid content concentration of 10 to 20% by mass. The pretreatment method for nickel oxide ore according to any one of claims 1 to 3 , wherein the flocculant is adjusted to a concentration of 0.010 to 0.050% by mass with water. .

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