Pyrometallurgical process for recovering nickel, manganese, and cobalt

Abstract

A 2-step high temperature process for recovering Ni, Co, and Mn from various sources comprises preparing a metallurgical charge comprising materials containing Ni, Co, and Mn, and Si, Al, Ca and Mg as slag formers; smelting the charge with slag formers in first reducing conditions, thereby obtaining a NiCo alloy comprising a major part of at least one of Co and Ni, with Si<0.1%, and a first slag comprising the major part of the Mn; separation of the first slag from the alloy; and, smelting the first slag in second reducing conditions, more reducing than said first reducing conditions, thereby obtaining a SiMn alloy comprising the major part of the Mn, with Si>10%, and a second slag. A NiCo alloy is produced, and a SiMn alloy is produced. The second slag is essentially free of heavy metals and therefore suitable for reuse.

Claims

1. Process for the production of SiMn alloy from materials containing Ni, Mn and Co, comprising the steps: a) preparing a metallurgical charge comprising said materials, and Si, Al, Ca, and Mg as slag formers; b) smelting the charge in first reducing conditions, thereby obtaining a Ni-Co alloy and a first slag, wherein the Ni-Co alloy comprises a major part of at least one of Co and Ni and has a Si content <0.1 wt %, and wherein the first slag comprises a major part of the Mn; c) separation of the first slag from the Ni-Co alloy; and d) smelting the first slag in second reducing conditions, more reducing than said first reducing conditions, thereby obtaining a Si-Mn alloy and a second slag, wherein the Si-Mn alloy comprises a major part of the Mn and has a Si content >10 wt %.

2. Process according to claim 1, wherein the first slag has a composition according to: 0.25<SiO.sub.2/Al.sub.2O.sub.3<2.5; 0.5<SiO.sub.2/CaO<2.5; MnO>2.5 wt %; MgO>5 wt %; and, Co+Ni>0.1 wt %.

3. Process according to claim 1, further comprising the step of adding the SiMn alloy to an Fe-based molten phase, thereby obtaining SiMn steel.

Description

EXAMPLE

(1) Li-ion batteries are shredded prior to loading to the crucible to allow easier mixing. The composition of the batteries is given in Table 1.

(2) TABLE-US-00001 TABLE 1 Composition in wt. % of the batteries Al Mn Co Cu Ni Li C Batteries 10 4 6 9 4 2.5 40

(3) A metallurgical charge is prepared consisting of 500 g batteries. 175 g limestone, 100 g silica and 50 g magnesia are added as fluxing agent.

(4) The mixture is added to a boron nitride coated alumina crucible with a volume of 2 L. Prior to adding the mixture, the crucible was filled with 500 g of starting slag and was heated to 1500 C. in an induction furnace. This creates a liquid slag bath to which the feed can be added. The starting slag composition is given in Table 2. Once the starting slag is fully liquid at 1500 C. the metallurgical charge is fed continuously during 2 hours to the crucible. During this time oxygen is blown at a rate of 80 liter/hour above the bath to combust the metallic Al and carbon present in the batteries.

(5) After the final addition, a reducing environment is enforced by blowing a mixture of 120 L/h of CO and 8 L/h CO.sub.2 for 1 h into the bath. This results in the establishment of a proper redox potential (pO.sub.2).

(6) After this, the melt is decanted 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, the slag phase is separated from the alloy and both phases are analyzed. A detailed material balance is provided in Table 2.

(7) TABLE-US-00002 TABLE 2 Material balance of the first smelting step Al Si Ca Mg Mn Co Cu Ni Li C (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) Input Mass (g) Starting 500 12 13 15 6 6 0.5 0.1 0.2 3 slag Batteries 500 10 4 6 9 4 2.5 40 Limestone 175 2.2 38.0 11.7 SiO.sub.2 100 46.7 MgO 50 60 Output Mass (g) Slag 1 890 12.3 12.9 15.9 6.7 5.6 0.6 0.1 0.2 3.1 Ni-Co 95 0.0 0.0 0.0 0.0 0.2 31.4 46.4 22 0.0 alloy Yield Mass (%) Slag 1 90 100 100 100 100 99.6 8 3 0.5 100 Ni-Co 10 0 0 0 0 0.4 92 97 99.5 0 alloy

(8) After the first step, the slag is separated from the crucible and the alloy, crushed and mixed with cokes. 500 grams of the slag is mixed with 30 grams of cokes and melted in a boron nitride coated alumina crucible with a volume of 1 L. A temperature of 1700 C. is maintained using an induction furnace.

(9) An additional amount of 20 grams of cokes is added to the liquid bath. The slag is then allowed to react for 3 hours. After cooling, an alloy-slag phase separation is performed manually whereupon both phases are analyzed. A detailed material balance is provided in Table 3.

(10) From Table 2, it is observed that the NiCo alloy has a Si content of less than 0.1% of Si (0.0% is reported) and that it comprises a major part of the Co and Ni (yields of 92 and 99.5% are respectively reported).

(11) The first slag has a SiO.sub.2/Al.sub.2O.sub.3 ratio between 0.25 and 2.5 (a ratio of 12.9/12.3 is reported, corresponding to a SiO.sub.2/Al.sub.2O.sub.3 ratio of 1.2), and a SiO.sub.2/CaO ratio between 0.5 and 2.5 (a ratio of 12.9/15.9 is reported, corresponding to a SiO.sub.2/CaO ratio of 1.3). It has a MnO content of more than 2.5% (5.6% is reported, corresponding to 7.2% MnO), and an MgO content of more than 5% (6.7% is reported, corresponding to 11.2% MgO). It contains a major part of the Mn (a yield of 99.6% is reported).

(12) TABLE-US-00003 TABLE 3 Material balance of the second smelting step Al Si Ca Mg Mn Co Cu Ni Li (%) (%) (%) (%) (%) (%) (%) (%) (%) Input Mass (g) Slag 1 500 12.3 12.9 15.9 6.7 5.6 0.6 0.1 0.2 3.1 Output Mass (g) Slag 2 438 14.5 12.8 18.4 7.8 0.5 0 0 0 1.9 Si-Mn alloy 46 0 23.7 0 0 65.8 6.4 1.2 2.6 0 Yield Mass (%) Slag 2 90.6 100 35.1 100 100 0.8 0 0 0 100 Si-Mn alloy 9.4 0 64.9 0 0 99.2 100 100 100 0

(13) Table 3 shows that the SiMn alloy has a Si content of more than 10% (23.7% is reported), and that it comprises a major part of the Mn (a yield of 99.2% is reported).