PROCESS FOR THE RECOVERY OF METALS FROM COBALT-BEARING MATERIALS

Abstract

A process is divulged for recovering metals from a metal-bearing material containing, in oxidized form, more than 1% of Co, a total of Co and Ni of more than 15%, and more than 1% Mg. comprising smelting said metal-bearing material in a bath furnace together with slag formers, thereby producing an alloy phase with more than 80% of the Co, and less than 1% of the Mg, and a slag phase, by applying reducing smelting conditions, and by selecting CaO, SiO.sub.2, and A1203 as slag .sup.-formers, in amounts to obtain a final slag composition according to the ratio's 0.25 <SiO.sub.2/Al.sub.2O.sub.3<2.5, 0.5 <SiO.sub.2/CaO<2.5, and MgO>10%; and separating the alloy phase from the slag phase. This process ensures quantitative recovery of Co in an alloy phase along with other metals such as Ni, while collecting Mg into a slag.

Claims

1-6. (canceled)

7. A process for recovering metals from a metal-bearing material comprising, in oxidized form, more than 1% Co, a total of Co and Ni of more than 15%, and more than 1% Mg, the process comprising the steps: smelting said metal-bearing material in a bath furnace together with slag formers, wherein smelting comprises applying reducing smelting conditions to produce an alloy phase and a slag phase, wherein the alloy phase comprises more than 80% of the Co and less than 1% of the Mg, and selecting CaO, SiO.sub.2, and Al.sub.2 as slag formers in amounts to obtain a final slag composition having the ratios: 0.25<SiO.sub.2/Al2O.sub.3<2.5, 0.5<SiO.sub.2/CaO<2.5, and MgO>10%; and separating the alloy phase from the slag phase.

8. The process according to claim 7, wherein the metal-bearing material comprises Mixed Hydroxide Precipitates (MHP).

9. The process according to claim 8, wherein the smelting step is the only smelting step of a complete Co valorization process starting from MHP.

10. The process according to claim 7, further comprising a step of granulation or atomization of the alloy phase.

11. The process according to claim 7, wherein the metal-bearing material is obtained according to a process comprising: feeding Co-bearing ores or concentrates to a leaching reactor; leaching the ores or the concentrates in acidic conditions, thereby obtaining a Co-bearing mother liquor; and precipitating Co from the mother liquor by using MgO, thereby obtaining a metal-bearing material containing, in oxidized form, more than 1% Co, and more than 1% Mg.

12. The process according to claim 10, further comprising: leaching the granulated or atomized alloy phase in acidic conditions, thereby obtaining a Co-bearing leach solution; purifying the leach solution by extracting or removing impurities from the solution, thereby obtaining a purified solution; and recovering Co from the purified solution.

13. The process according to claim 7, wherein the alloy phase comprises more than 90% of the Co.

Description

EXAMPLE

[0044] Mixed hydroxide precipitates (MHP) typically contain 50% or more of free moisture.

[0045] Partial drying is needed before feeding such materials to a smelting furnace. The MHP are thus first dried to a moisture content of about 20%. Drying to lower moisture levels is not recommended as this would render the product too dusty for safe handling.

[0046] The composition of the MHP used as a starting product is shown in Table 1. The composition is expressed w.r.t. to product dried at 120 C.

TABLE-US-00001 TABLE 1 Composition of MHP INPUT (wt. %) Al Si Ca Mg Fe Co Cu Ni MHP 0.02 1.2 0.0 4.6 0.0 40.2 0.7 0.1

[0047] A mixture is prepared consisting of 1000 g MHP, 360 g cokes, 400 g ferro slag, and 100 g Al.sub.2O.sub.3 as fluxing agent. No pretreatment such as agglomeration or the use of binders is involved. The ferro slag is of the commonly available type produced in the blast furnace of ironmaking processes.

[0048] The mixture is melted in a boron nitride coated alumina crucible with a volume of 1 L. A temperature of 1500 C. is maintained using an induction furnace. When melted, 4 stepwise additions of 100 g MHP are made to the crucible.

[0049] Once all material is added, a fixed oxygen partial pressure is enforced by blowing a mixture of 130 I/h of CO and 6 I/h for 1 h into the bath. This results in the establishment of a proper equilibrium redox potential (pO.sub.2). The skilled person will easily achieve the same redox potential at industrial scale using other commonly available reducing agents such as natural gas, oil, and coal.

[0050] After this, the melt is allowed to decant for 15 minutes. The good fluidity of the slag allows for an efficient decantation, i.e. without residual alloy droplets floating in the slag. After cooling, an alloy-slag phase separation is performed manually whereupon both phases are analyzed.

[0051] A detailed material balance is provided in Table 2.

TABLE-US-00002 TABLE 2 Detailed material balance of the smelting operation Mass (g) Al Si Ca Mg Fe Co Cu Ni Input (wt. %) MHP 1400.0 0.02 1.2 0.0 4.6 0.0 40.2 0.7 0.1 Slag 400.00 3.1 16.0 24.7 3.9 2.7 0.0 0.8 0.2 Al.sub.2O.sub.3 100.00 52.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Input (g) MHP 1400.0 0.2 16.2 0.0 64.1 0.6 562.3 9.9 1.1 Slag 400.0 12.2 64.0 98.6 15.6 10.9 0.0 3.2 0.8 Al.sub.2O.sub.3 100.0 52.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Total 1900.0 65.3 80.3 98.6 79.7 11.4 562.3 13.1 1.9 Output (wt. %) Alloy 650.0 0.0 0.0 0.0 0.0 1.1 93.5 1.9 0.3 Slag 660.0 10.0 12.1 15.1 11.0 0.5 1.1 0.0 0.0 Water 590.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Output (g) Alloy 650.0 0.0 0.2 0.0 0.0 7.2 607.8 12.4 2.0 Slag 660.0 66.0 79.9 99.7 72.6 3.3 7.3 0.3 0.0 Water 590.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Total 1900.0 66.0 80.0 99.7 72.6 10.5 615.0 12.6 2.0 Distribution (wt. %) Alloy 34.2 0.0 0.2 0.0 0.0 68.4 98.8 97.8 99.9 Slag 34.7 100.0 99.8 100.0 100.0 31.6 1.2 2.2 0.1 Total 68.9 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

[0052] The slag has a SiO.sub.2/Al.sub.2O.sub.3 ratio of 0.7, and a SiO.sub.2/CaO ratio of 1.2. The Mg and Ca concentrations of respectively 11% and 15% correspond to 18.2% of MgO and 21.1% of CaO.

[0053] The Co yield to the alloy amounts to 98.8%, while the Mg yield to the slag amounts to 100%. An Mg free alloy is thus obtained.