Process for recovering nickel, cobalt and other metals from lateritic nickel ore

Abstract

To provide a method capable of extracting nickel, cobalt and other metals from Indonesian laterite nickel ore, at an economically practicable nickel recovery rate.SOLUTION: A method for extracting nickel, cobalt and other metals from laterite nickel ore includes the steps of: a) separating nickel laterite ore into Fe ore and Mg ore; b) uniformly mixing concentrated sulfuric acid solution and the Fe ore; c) mixing a mixture of the step b) and Mg ore to form a sufficiently mixed paste; d) curing the paste in a rotary dryer at 250-450°C to form cured granular solids; e) calcining the cured granular solids in a rotary kiln at 650-800°C for at least 4 minutes; f) pulverizing the calcined solids to obtain powder; and g) leaching out the powder with water, to obtain a mixture of nickel, cobalt and other metals and residues.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for extracting nickel, cobalt and other metals from nickel laterite ore. The present invention mainly relates to a method for extracting nickel, cobalt and other metals from nickel laterite ore by water leaching-sulfation roasting method. [Background technology]

[0002] While almost all natural resources of high-quality nickel laterite ore in Indonesia are jointly owned and controlled by nickel smelting companies producing NPI (nickel pig iron), it is well-known that the natural resources of nickel laterite ore, which generally have nickel content below 1.65%, remain untapped.Therefore, there remains a strong need for environmentally friendly and economically viable technologies to extract nickel, cobalt and other metals from the natural resources of Indonesian laterite nickel ore.

[0003] Nickel laterite ores can be processed by pyrometallurgical, hydrometallurgical or a combination of both processes. Pyrometallurgical processes include those that produce nickel-bearing crude iron (nickel pig iron, NPI), while hydrometallurgical processes include high pressure acid leaching (HPAL). A combination of the two processes includes ammonia reduction leaching and roasting (the Caron process).

[0004] Yet another technique for the extraction of nickel, cobalt and other metals from nickel laterite ores is the sulfation roasting-water leaching process, which involves the thermal decomposition of ferrous sulfate at a temperature of about 700°C to remove the iron and selectively convert metals such as nickel and cobalt to sulfates that can be leached with water. This technique is described in YV Swamy, BB Kar, and JK Mohanty, "Physico-chemical characterization and sulphatization roasting of low-grade nickeliferous laterites", Hydrometallurgy, vol. 69, no. 1-3, pp. 89-98, 2003. The process described by Swamy et al. involves a two-stage isothermal roasting suitable for Indian nickel laterite ores (containing 0.78% Ni, 37.0% Fe and 1.25% Mg) and provides 85% nickel recovery.

[0005] The method of Swamy et al. has several drawbacks. First, the long roasting time of 20 min at 450°C followed by 15 min at 700°C makes the method inefficient for production. Second, the highly diluted 25 wt% sulfuric acid solution (concentration: about 300 g / L) used in the method is too dilute for production. However, the use of highly concentrated sulfuric acid solution makes the method unsuitable for high-Mg nickel laterite ores. The magnesium percentage in Indonesian nickel laterite ores is usually higher than the nickel percentage. It is known that the high content of Mg in nickel laterite ores mixed with highly concentrated sulfuric acid solution may cause rapid hardening during the mixing stage, resulting in non-uniform mixing, while high nickel recovery is highly dependent on uniform mixing. Third, high nickel recovery in the method is achieved only when the two-stage roasting is performed under isothermal conditions, which is highly unlikely to occur in production. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] YVSwamy, BBKar, and JKMohanty, “Physico-chemical characterization and sulfatization roasting of low-grade nickeliferous laterites,” Hydrometallurgy, vol.69, no.1-3, pp.89-98, 2003 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to overcome the drawbacks and problems of the method of Swamy et al., it is necessary to improve the sulfation roasting-leaching method including the two-stage roasting. That is, the objective of the present invention is to provide a method for extracting nickel, cobalt, and other metals from Indonesian nickel laterite ore with a high nickel recovery rate that is economically feasible. [Means for solving the problem]

[0008] The inventors have found that the above-mentioned problems can be solved by the following method: separating Mg-based components from nickel laterite ore, first mixing the nickel laterite ore without Mg-containing components with concentrated sulfuric acid solution, and then mixing the resulting mixture with Mg-based components to form a homogeneous mixed paste without hardening. The homogeneous paste is hardened and roasted in a rotary dryer and a rotary kiln, respectively, in this order, under non-isothermal conditions. Hardening using a rotary dryer allows the hardened granular solid to be formed quickly in small size, and can be efficiently roasted in a uniform temperature range in the rotary kiln. Roasting of the hardened granular solid needs to be carried out in a uniform temperature range, because insufficient roasting increases the amount of soluble iron, while excessive roasting increases the amount of insoluble nickel, cobalt and other metals. Effect of the Invention

[0009] The present invention provides an economically viable method for extracting nickel, cobalt and other metals from nickel laterite ores with high nickel recovery. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 shows a flow diagram of a method for extracting nickel, cobalt and other metals from nickel laterite ore by the water leaching-sulfation roasting method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below. The method according to the invention is a method for extracting nickel, cobalt and other metals from nickel laterite ore, characterized in that it comprises the following steps: a) separating nickel laterite ore into Fe-bearing ore and Mg-bearing ore; b) homogeneously mixing the concentrated sulfuric acid solution with the Fe-based ore; c) mixing the mixture of step b) with Mg-based ore to form a well-mixed paste; d) hardening the paste of step c) in a rotary dryer at a temperature of 250-450°C to form a hardened granular solid; e) roasting the hardened granular solid material of step d) in a rotary kiln at a temperature of 650-800°C for at least 4 minutes; f) grinding the roasted solid of step e) to obtain a powder; and g) leaching the powder of step f) with water to obtain a mixed solution of nickel, cobalt and other metals and a residue.

[0012] The nickel laterite ore that can be used in the present invention is essentially composed of iron-based ore and magnesium-based ore. These two substances have very different reactivity when reacting with acid; Fe-based ore reacts poorly with acid, whereas Mg-based ore reacts easily with acid. These two types of ore can be easily separated using conventional techniques (step a)). In particular, the Fe-based ore and the Mg-based ore can be separated by crushing and sieving.

[0013] In the present invention, as a first step, Fe-based ore and sulfuric acid are mixed (step b)). These two substances react slowly during the mixing operation, and as a result, a homogeneous mixture is easily formed without hardening. Next, Mg-based ore is added to this mixture and mixing is continued to form a homogeneous mixture (paste), which is then allowed to stand (step c)). The concentration of the concentrated sulfuric acid solution is preferably in the range of 45% to 98%.

[0014] The Fe- and Mg-based ores are theoretically oxide ores and can react spontaneously with the acid releasing heat. The application of a small amount of external heat can further accelerate the reaction and the final mixture can harden rapidly (step d)).

[0015] The main reactant in the final mixture is iron(III). When this is hardened, the free acid is rapidly consumed to form iron sulfate. When the hardened granular solid containing iron sulfate is roasted, the iron(III) sulfate reacts with the nickel oxide and any insoluble nickel reacts to form nickel sulfate which dissolves (step e)). Fe2(SO4)3+ 3NiO = 3NiSO4+ Fe2O3

[0016] During the roasting operation, most of the iron(III) sulfate decomposes to sulfur trioxide, which is absorbed into sulfuric acid in the acid recovery unit (AR).

[0017] After roasting, nickel forms soluble sulfates together with cobalt, magnesium, manganese and other metals. The roasted solids containing the soluble sulfates are ground into powder (step f)). The soluble sulfates in the powder are easily leached by water to form a mixed solution, while the iron oxide, silica and other insoluble materials remain as a residue (step g)). This residue can be subsequently processed into slag bricks. Thus, the process is overall environmentally friendly.

[0018] The average Fe / Ni ratio of the mixed solution of step g) is preferably ≦2.0 and the average Ni recovery is preferably up to 95%. The mixed solution is usually converted to mixed hydroxides (MHP) by known procedures of iron removal, hydrolysis and precipitation. Magnesium sulfate remains in the waste water, but can then be evaporated and crystallized to hydrated magnesium salts, ultimately leaving no waste water. EXAMPLES

[0019] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0020] [Example 1] The raw material was a laterite ore containing 1.07% Ni, 0.1% Co, 42% Fe, and 2.0% Mg, and the following steps (1) to (8) were carried out.

[0021] (1) The ore samples were passed through a sieve with a mesh size of 1 x 1 cm. The ore that was retained on the sieve due to its large particle size was put into a crusher to be crushed into small particles with a maximum particle size of 1 cm. (2) The ore that passed through the mesh in step (1) was passed through a 16 mesh sieve (1.14 x 1.14 mm). The ore that remained on the sieve due to its large particle size was collected and mixed with the 1 cm particles from step (1), and the resulting granular ore was processed in the next step (3). Meanwhile, the ore that passed through the sieve was fed to a ball mill to produce 60 mesh Fe-based powder ore.

[0022] (3) The granular ores from step (1) and step (2) were fed into a ball mill to produce 60 mesh Mg-based ore powder. (4) In the mixing process, 18 kg of 60 mesh Fe ore was mixed uniformly with 600 g / L of high concentration sulfuric acid solution, the acid amount of which was controlled within the range of 13 ± 0.5 kg to make 98% acid. Then, 7 kg of Mg ore powder was added while stirring, and finally, a well-blended paste was obtained. This mixing process was repeated until more than 500 kg of paste was obtained.

[0023] (5) The burner output power was set at a low level. The rotation speed of the laboratory-scale rotary kiln was set at a high level so that the rotary kiln acted as a rotary dryer. The paste from step (4) was then passed through the kiln and cured at a temperature range of up to 450°C to continuously form a cured granular solid.

[0024] (6) The burner output power was set to a high level, and the furnace rotation speed was set to a low level. The hardened granular solid was then passed through a rotary kiln for roasting. The roasting temperature was controlled in the range of 650-800°C, and the granular solid was held in this temperature range for at least 4 minutes to obtain a roasted solid.

[0025] (7) The roasted solid from step (6) was pulverized into powder of 1×1 mm or less using a twin-shaft crusher (shredder). The powder was leached with water to obtain a mixed solution and a residue. The nickel and iron contents in this mixed solution were analyzed, and the Fe / Ni ratio was verified. As a result of calculation, the average Fe / Ni ratio was 2.0 or less. Next, the nickel content in the residue was analyzed, and the nickel recovery rate was calculated. As a result of calculation, the average nickel recovery rate was up to 95%.

[0026] (8) The residue from step (7) can be molded into slag bricks after adjusting the humidity and mixing with lime.

[0027] [Example 2] The raw material was a laterite ore containing Ni: 1.65%, C0: 0.05%, Fe: 24.5%, and Mg: 6.0%, and the following steps (1) to (8) were carried out.

[0028] (1) The ore samples were passed through a 1 x 1 cm mesh. The ore that was retained on the sieve due to its large particle size was fed into a crusher to be crushed into small particles with a maximum particle size of 1 cm. (2) The ore that passed through the mesh in step (1) was passed through a 16 mesh sieve (1.14 x 1.14 mm). The ore that remained on the sieve due to its large particle size was collected and mixed with the 1 cm particles from step (1), and the resulting granular ore was treated in the next step (3). Meanwhile, the ore that passed through the sieve was fed together with water to a ball mill to make a 60 mesh slurry. This slurry was passed through a compression filter to make an Fe-based filter cake.

[0029] (3) The granular ore from step (1) and step (2) was fed into a ball mill together with water to produce a 60 mesh slurry, which was then passed through a compression filter to produce a Mg-based filter cake.

[0030] (4) In the mixing step, first, the humidity of each filter precipitate was confirmed. Then, 12.5 kg of Fe-based filter precipitate was measured as a dry weight, and mixed with 9.0±0.2 kg of 98% sulfuric acid to obtain a mixed paste. Similarly, 12.5 kg of Mg-based filter precipitate was measured as a dry weight, and added and stirred to obtain a uniformly mixed final paste. This mixing step was repeated until more than 500 kg of paste was obtained.

[0031] (5) The burner output power was set at a low level, and the rotation speed of the laboratory-scale rotary kiln was set at a high level so that the rotary kiln acted as a rotary dryer. The final paste from step (4) was then passed through a furnace to continuously form a hardened granular solid at a temperature range of 240-330°C.

[0032] (6) The burner output power was set to a high level, and the furnace rotation speed was set to a low level. The hardened granular solid was then passed through a rotary kiln for roasting. The roasting temperature was controlled in the range of 650-750°C, and the granular solid was held in this temperature range for at least 4 minutes to obtain a roasted solid.

[0033] (7) The roasted solid from step (6) was pulverized into powder of 1×1 mm or less using a twin-shaft pulverizer. The powder was leached with water to obtain a mixed solution and a residue. The nickel and iron contents in the mixed solution were analyzed, and the Fe / Ni ratio was verified. As a result of calculation, the average Fe / Ni ratio was about 1.2. The nickel content in the residue was then analyzed, and the nickel recovery rate was calculated. As a result of calculation, the average nickel recovery rate was up to 93%.

[0034] (8) The residue from step (7) can be molded into slag bricks after adjusting the humidity and mixing with lime.

Claims

1. 1. A process for extracting nickel, cobalt and other metals from nickel laterite ore, comprising the steps of: a) separating nickel laterite ore into Fe- and Mg-based ores; b) homogeneously mixing the concentrated sulfuric acid solution with the Fe-based ore; c) mixing the mixture of step b) with Mg-based ore to form a well-mixed paste; d) curing the paste of step c) in a rotary dryer at a temperature of 250-450°C to form a hardened granular solid; e) roasting the hardened granular solid material of step d) in a rotary kiln at a temperature of 650-800°C for at least 4 minutes; f) pulverizing the roasted solid of step e) to obtain a powder; and g) leaching the powder of step f) with water to obtain a mixed solution of nickel, cobalt and other metals and a residue.

2. 2. The method according to claim 1, characterized in that the separation of the nickel laterite ore into Fe-bearing and Mg-bearing ores is carried out by crushing and sieving.

3. 3. The method according to claim 1 or 2, characterized in that the concentration of the concentrated sulfuric acid solution is in the range of 45% to 98%.

4. The method according to any one of claims 1 to 3, characterized in that the average Fe / Ni ratio of the mixed solution in step g) is less than or equal to 2.0 and the average Ni recovery rate is up to 95%.

5. The method according to any one of claims 1 to 4, characterized in that the residue of step g) is further processed into slag bricks.

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