Process for Smelting Lithium-Ion Batteries

Abstract

The invention concerns a process for the separation of cobalt from lithium present in a charge comprising lithium-ion batteries or related products, comprising the steps of: smelting the charge using a bath furnace equipped with a submerged air-fed plasma torch for injecting plasma gas into the melt; defining and maintaining a bath redox potential where cobalt is reduced to the metallic state and reporting to an alloy phase, and whereby lithium is oxidized as Li.sub.2O and reporting to the slag phase; decanting and separating the phases. It is characterized in that the reduction and oxidizing steps are performed simultaneously. A suitably low cobalt concentration is obtained in the slag.

Claims

1-6. (canceled)

7. A process for separating cobalt from lithium present in a charge comprising lithium-ion batteries or battery scrap, comprising: smelting the charge using a bath furnace comprising a submerged plasma torch for injecting an oxygen-bearing plasma gas into the melt; defining and maintaining a bath oxygen partial pressure whereby cobalt is reduced to the metallic state and reporting to an alloy phase, and whereby lithium is oxidized and reporting to a slag phase; and decanting and separating the alloy phase and the slag phase; wherein the reduction and oxidizing steps are performed simultaneously.

8. The process according to claim 7, wherein said bath furnace further comprises a submerged injector for injecting an O.sub.2-bearing gas into the melt.

9. The process according to claim 7, further comprising adjusting electric power to the plasma torch to maintain a target bath temperature of between 1450 and 1650 ° C.

10. The process according to claim 7, further comprising adjusting oxygen input to the melt to maintain a target bath oxygen partial pressure between 10.sup.−18 and 10.sup.−14 atm.

11. The process according to claim 7, wherein the lithium-ion batteries or their scrap represent more than 80% of the total metallurgical charge, slag formers excluded.

12. A bath furnace for performing the process according to claim 8, wherein the bath furnace is configured to contain a molten bath up to a defined level, the furnace comprising a plasma torch for injecting an oxygen-bearing plasma gas into the melt through a first injection point, and an injector for injecting an O.sub.2-bearing gas into the melt through a second injection point, wherein the first injection point and the second injection point are located below said defined level.

Description

EXAMPLE

[0024] The invention is illustrated with the following example. The apparatus comprises a bath furnace equipped with a submerged electric plasma torch for injecting hot gases, and with a submerged nozzle for injecting pure oxygen-bearing.

[0025] Spent portable rechargeable Li-ion batteries (PRB) are fed to the top of the melt a rate of 1 ton/h. Together with the batteries, fluxes are needed to maintain the slag liquid even though the aluminum from the batteries is being slagged as Al.sub.2O.sub.3. To this end, 150 kg/h sand and 300 kg/h limestone are added, corresponding to a suitable CaO to SiO.sub.2 ratio of about 1. Since the reduction of cobalt to sub-percentage levels in the slag requires a very low oxygen partial pressure of about 10.sup.−14 atm, only a limited amount of oxygen can be injected. We have observed that for this particular lot, 235 Nm.sup.3 O.sub.2 per ton batteries fulfills this PO.sub.2 criterion. Since the heat balance of the furnace is negative at 1 ton/h PRB and 235 Nm.sup.3/h, an additional energy source is required. Therefore, a submerged electric plasma torch is operated at 500 Nm.sup.3/h air as plasma gas, generating about 1.3 MW of net enthalpy. A separate tuyère provides 130 Nm.sup.3/h oxygen into the bath, which, added to the oxygen in the plasma gas adds up to the required total of 235 Nm.sup.3/h. The temperature of the bath is controlled between 1450 to 1650° C. by adjusting the electric power of the plasma torch. At regular intervals, the alloy and slag are tapped after a decanting step of about 5 minutes.

[0026] Table 1 shows the material balance of the process. A suitably low cobalt concentration is obtained in the slag while lithium and aluminum are completely oxidized and slagged.

TABLE-US-00001 TABLE 1 Input and output phases of the process on an hourly basis Mass Cu Ni Fe Co Al.sub.2O.sub.3 SiO.sub.2 CaO (kg) (%) (%) (%) (%) (%) (%) (%) Input Batteries 1000 8 4 11 12 9 Sand 150 100 Limestone 300 56 Output Alloy 364 22 11 28 33 Slag 586 <0.05 <0.05 0.9 <0.05 29 30 28