Recovery of nickel and cobalt from black mass

Abstract

The present invention lies in the field of pyrometallurgy and discloses a process and a slag suitable for the recovery of Ni and Co from Li-ion batteries or their waste, particularly from Black Mass. The slag composition is defined according to: 25%<MnO<70%; Al.sub.2O.sub.3+0.5 MnO<45% SiO.sub.2>5%; Li.sub.2O>1%; MnO+Li.sub.2O+Al.sub.2O.sub.3+CaO+SiO.sub.2+FeO+MgO+P.sub.2O.sub.5>90%; and, wherein (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.22.0. This composition is particularly adapted to limit or avoid the wear or corrosion of furnaces lined with magnesia-bearing refractory bricks.

Claims

1. Process for the recovery of Ni and Co from Li-ion batteries or their waste, comprising the steps: providing a furnace lined with magnesia-bearing refractory bricks; providing a charge comprising slag formers and Li-ion batteries or their waste, wherein the content of Al in the charge is less than 8%; and, smelting the charge in reducing conditions, thereby obtaining an alloy containing the major part of the Ni and Co, and a Li-containing slag, wherein the slag has a percent composition by weight according to: 25%<MnO<70%; Al.sub.2O.sub.3+0.5 MnO<45% SiO.sub.2>5%; Li.sub.2O>1%; MnO+Li.sub.2O+Al.sub.2O.sub.3+CaO+SiO.sub.2+FeO+MgO+P.sub.2O.sub.5>90%; and, wherein (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.22.0.

2. Process according to claim 1, wherein the content of MnO in the slag is 30% or more.

3. Process according to claim 1 or 2, wherein the content of Al.sub.2O.sub.3 in the slag is less than 30%.

4. Process according to claim 1, wherein Al.sub.2O.sub.3+0.5 MnO<30%.

5. Process according to claim 1, wherein the Li-ion batteries or their waste is Black Mass.

6. Process according to claim 1, wherein the content of CaO in the slag is 40% or less.

7. Process according to claim 1, wherein the slag formers contain no CaO.

8. Process according to claim 1, wherein the content of Li.sub.2O in the slag is 3% or more.

9. Process according to claim 1, wherein the content of cobalt oxide in the slag is 0.05%<CoO<1%.

10. Process according to claim 1, wherein the content of Fe in the slag is 25% or less.

11. Process according to claim 1, wherein the content of Fe in the charge is 5% or less.

12. Process according to claim 1, wherein the content of P.sub.2O.sub.5 in the slag is 0.5%<P.sub.2O.sub.5<10%.

13. Process according to claim 1, wherein the step of smelting the charge is performed at a temperature of at least 1400 C. and at most 300 C. above the liquidus point of the slag, thereby avoiding overheating.

14. Process according to claim 1, the smelting step comprising the further steps: sampling the slag; cooling down the slag sample and assessing its color; and, in case the slag sample is green, terminating the smelting step; or, in case the slag sample is not green, proceeding with the smelting step after adjusting the pO.sub.2-level to achieve more reducing conditions.

15. Process according to claim 1, wherein the pO.sub.2-level is adjusted to 10.sup.7>pO.sub.2>10.sup.12.

16. Process according to claim 14, wherein the color of the slag is green.

17. Process according to claim 1, wherein the furnace is an electric furnace.

18. Li-containing metallurgical slag having a percent composition by weight according to: 25%<MnO<70%; Al.sub.2O.sub.3+0.5 MnO<45% SiO.sub.2>5%; Li.sub.2O>3%; MnO+Li.sub.2O+Al.sub.2O.sub.3+CaO+SiO.sub.2+FeO+MgO+P.sub.2O.sub.5>90%; and, wherein (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.22.0.

19. Li-containing metallurgical slag according to claim 18, wherein the color of the slag is green.

20. Li-containing metallurgical slag according to claim 18 or 19, wherein the content of MnO in the slag is 30% or more.

21. Li-containing metallurgical slag according to claim 18, wherein the content of Al.sub.2O.sub.3 in the slag is less than 30%.

22. Li-containing metallurgical slag according to claim 18, wherein the content of CaO in the slag is 40% or less.

23. Li-containing metallurgical slag according to claim 18, wherein the content of Fe in the slag is 25% or less.

24. Slag former in a pyrometallurgical recycling process comprising the Li-containing metallurgical slag according to claim 18.

25. The process according to claim 1, wherein the slag former comprises a Li-containing metallurgical slag having a percent composition by weight according to: 25%<MnO<70%; Al.sub.2O.sub.3+0.5 MnO<45% SiO.sub.2>5%; Li.sub.2O>3%; MnO+Li.sub.2O+Al.sub.2O.sub.3+CaO+SiO.sub.2+FeO+MgO+P.sub.2O.sub.5>90%; and, wherein (CaO+2 Li.sub.2O+0.4 MnO)/SiO22.0.

26. Li-containing metallurgical slag according to claim 18, wherein the slag further contains cobalt.

Description

EXAMPLE 1

(1) The dissolution of MgO from the walls of magnesia-bearing crucibles was measured, when using several different slag compositions. Various compounds contained in Li-ion batteries or their waste, respectively their oxides such as FeO, Al.sub.2O.sub.3, Li.sub.2O, MnO, and P.sub.2O.sub.5 were melted together with CaO and SiO.sub.2 as fluxing agents in a 1 L MgO crucible. The total weight of added oxides was 1000 g.

(2) The crucibles were gradually heated at heating rate of 150 C./h using an induction furnace. When the slags were fully molten, crucibles were kept at temperatures of 1500 or 1650 C. After 2 h of heating, molten slags were taken out of the crucibles, and quenched with water. Table 1 lists the composition of the produced slags in this example.

(3) TABLE-US-00001 TABLE 1 Composition of the produced slags Temp. Composition (%) Slag C. SiO.sub.2 FeO Al.sub.2O.sub.3 CaO Li.sub.2O MgO MnO P.sub.2O.sub.5 1-1 1500 15.2 0.0 25.8 22.2 7.5 3.3 25.2 0.8 1-2 1500 19.8 1.0 17.3 10.4 11.9 3.0 34.5 2.0 1-3 1650 6.3 1.9 17.9 12.5 12.9 1.1 44.3 3.1 1-4 1650 6.8 2.7 18.9 11.3 2.8 1.4 51.7 4.3

(4) MgO concentrations in above slags were relatively low (from 0.3% to 3.0%). This result indicates that a dissolution of MgO from the wall of the crucible was well-suppressed under the chosen conditions.

(5) (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.2 was 2.9 in slag 1-1, 2.2 in slag 1-2, 9.0 in slag 1-3 and 5.5 in slag 1-4.

(6) The experiments were performed with slag compositions having no Ni, Co or Cu, since the amount of these metals in the final slags are typically very low and thus essentially do not influence the slag properties.

COMPARATIVE EXAMPLE 2

(7) The dissolution of MgO from the walls of magnesia-bearing crucibles was measured, when using different slag compositions. Various compounds contained in Li-ion batteries or their waste, respectively their oxides such as FeO, Al.sub.2O.sub.3, Li.sub.2O, MnO, and P.sub.2O.sub.5 were melted together with CaO and SiO.sub.2 as fluxing agents, in a 1 L MgO crucible. The total weight of added oxides was 1000 g.

(8) The crucibles were gradually heated at a heating rate of 150 C./h using an induction furnace. When the slags were fully molten, crucibles were kept at temperatures of 1500 C. for 2 h. After 2 h of heating, molten slags were taken out of the crucibles, and quenched with water. Table 2 lists the composition of the produced slags in this example.

(9) TABLE-US-00002 TABLE 2 Composition of the produced slags Temp. Composition (%) Slag C. SiO.sub.2 FeO Al.sub.2O.sub.3 CaO Li.sub.2O MgO MnO P.sub.2O.sub.5 2-1 1500 28.6 0.0 29.1 20.5 5.6 9.0 6.5 0.8 2-2 1500 31.6 0.0 22.6 15.8 9.0 15.7 4.5 0.8

(10) Compared to the slags 1-1 to 1-4 used in Example 1, here the MnO content in the slags was adjusted to be lower than 10%. (CaO+2 Li.sub.2O+0.4 MnO)/SiO.sub.2 was 1.2 in slag 2-1 and 1.1 in slag 2-2. Measured MgO concentrations in above slags were relatively high (from 9.0% to 15.7%), which indicates that relatively large quantities of MgO from the crucibles were dissolved in the respective slags. As in Example 1, the slags contained no Ni, Co or Cu.

DISCUSSION OF EXAMPLES 1 AND 2

(11) The slags obtained in Example 1 contained less MgO than the slags obtained in Comparative Example 2. No visible degradation of the MgO crucible was observed under the conditions of Example 1, whereas the crucible walls became thinner under the conditions of Comparative Example 2. Slags containing relatively high concentrations of MnO suppressed the MgO dissolution, as demonstrated in Example 1. More specifically, the MgO dissolution into the slag was efficiently suppressed when the MnO concentration was 25% or higher.

EXAMPLE 3

(12) 500 kg of Black Mass was fed to a furnace with a diameter of 1 m, freshly lined with 200 mm chrome-magnesia refractory bricks. 40 kg of limestone and 20 kg of sand were added together with the Black Mass. A bath temperature of 1500-1550 C. was maintained, which is suitable to maintain both the slag and the alloy sufficiently fluid for easy tapping and handling. The heat was supplied by the oxidation of Al and C in the Black Mass, using submerged O.sub.2 injection. The injection rate was chosen to guarantee strongly reducing conditions, i.e. pO.sub.2 of 10.sup.9. Natural gas was added to compensate for heat losses in the furnace. After 1 h of heating, the produced alloy and slag were separated by tapping. Table 3 shows the analyses of the input and output phases of the process. During processing, small quantities of materials were captured as fume. Table 3 shows the complete material balance.

(13) TABLE-US-00003 TABLE 3 Input and output phases of the process Composition (%) Mass Al Li Mn P (kg) Ni Co Cu Fe SiO.sub.2 CaO (Al.sub.2O.sub.3) (Li.sub.2O) (MnO) (P.sub.2O.sub.5) C MgO Input Black 500 16.5 5.6 0.8 0.2 3.0 2.5 5.7 0.1 48.0 Mass Lime- 40 4.8 53.3 11.4 stone Silica 20 100 Output Alloy 119 69.1 23.2 3.3 0.8 3.4 0.2 Slag 128 0.1 0.3 0.1 0.2 17.0 16.5 (21.9) (16.5) (24.2) (0.9) 2.3

(14) During processing Black Mass, no visible degradation of the magnesia-bearing refractory bricks was observed. Concentration of MgO in the obtained slag was only 2.3%, equivalent to 2.9 kg loss of MgO from the refractory bricks, which is considered low. This slag thus efficiently suppressed the wear of the furnace walls.

EXAMPLE 4

(15) 500 kg of Black Mass was fed to a furnace with a diameter of 1 m, freshly lined with 200 mm chrome-magnesia refractory bricks. 135 kg of the slag produced in Example 3 was added together with the Li-ion batteries. A bath temperature of 1500-1550 C. was maintained, which is suitable to maintain both the slag and the alloy sufficiently fluid for easy tapping and handling. The heat was supplied by the oxidation of Al and C in the batteries, using submerged O.sub.2 injection. The injection rate was chosen to achieve strongly reducing conditions, i.e. in this case a pO.sub.2 of 10.sup.9. Natural gas was added to compensate for heat losses in the furnace. After 1 h of heating, the produced alloy and slag were separated by tapping. Table 6 shows the analyses of the input and output phases of the process.

(16) TABLE-US-00004 TABLE 4 Input and output phases of the process Composition (%) Mass Al Li Mn P (kg) Ni Co Cu Fe SiO.sub.2 CaO (Al.sub.2O.sub.3) (Li.sub.2O) (MnO) (P.sub.2O.sub.5) C MgO Input Black 500 16.5 5.6 0.8 0.2 3 2.5 5.7 0.1 48.0 Mass 2 Slag for- 128 0.1 0.3 0.1 0.2 17.0 16.5 (21.9) (16.5) (24.2) (0.9) 0.1 mer Output Alloy 119 69.1 23.2 3.2 0.9 3.6 0.3 Slag 208 0.1 0.3 0.1 0.2 10.4 10.0 (26.8) (20.1) (29.4) (0.9) 1.4

(17) During processing batteries, no visible degradation of the magnesia-bearing refractory bricks was observed. Concentration of MgO in the produced slag was only 1.4%, equivalent to 0.1 kg loss of MgO from the refractory bricks, which is an even smaller degradation than in Example 3, thanks to higher MnO content in the slag. This slag thus efficiently suppressed the wear of the furnace wall made of magnesia-bearing refractory bricks.

GENERAL CONCLUSION

(18) Metallurgical slags according to the present invention are suitable to recover valuable metals, such as Ni and Co, from Li-ion batteries or their waste, while minimizing degradation of the magnesia-bearing refractory bricks of the furnace.