Lithium-rich metallurgical slag

Abstract

The present invention concerns a slag composition having a high lithium content, suitable as additive in the manufacture of end-user products, or for the economic recovery of the contained lithium. The lithium concentration indeed compares favorably with that of spodumene, the classic mineral mined for lithium production. This slag is characterized by a composition according to: 3%<Li.sub.2O<20%; 1%<MnO<7%; 38%<Al.sub.2O.sub.3<65%; CaO<55%; and, SiO.sub.2<45%.

Claims

1. A Li.sub.2O bearing metallurgical slag comprising Al.sub.2O.sub.3, SiO.sub.2, CaO, and MnO, wherein the by-weight composition is as follows: 8%≤Li.sub.2O≤11.6%; 1.2%≤MnO≤6.7%; 39%≤Al.sub.2O.sub.3<55%; 2.5%≤CaO<25%; and 15%≤SiO.sub.2≤36.4%, wherein a total cobalt content in the Li.sub.2O bearing slag is 0.1%≤Co≤0.9%.

2. The Li.sub.2O bearing metallurgical slag of claim 1, wherein the SiO.sub.2 concentration is greater than or equal to 15% and lower than 25%.

3. The Li.sub.2O bearing metallurgical slag of claim 1, wherein the sum of the Al.sub.2O.sub.3, SiO.sub.2, CaO, MnO, and Li.sub.2O concentrations is higher than 80%.

4. The Li.sub.2O bearing metallurgical slag of claim 1, wherein the by-weight composition meets the following ranges: 8.2%≤Li.sub.2O≤11.6%, 39%<Al.sub.2O.sub.3<48.4%, 2.5%≤CaO<22.8%; and 18.9%≤SiO.sub.2<36.4%.

5. The Li.sub.2O bearing metallurgical slag of claim 1, wherein the by-weight composition is as follows: 8.1%≤Li.sub.2O≤11.6%; 1.2%≤MnO≤6.7%; 39%≤Al.sub.2O.sub.3<48.4%; 19.3%≤CaO<22.8%; and 21%≤SiO.sub.2≤36.4%, wherein a total cobalt content in the Li.sub.2O bearing slag is 0.1%≤Co≤0.9%.

6. A smelting process for recovering Li.sub.2O from spent lithium-bearing batteries, wherein the recovered Li.sub.2O is present in slag produced by the smelting process in an amount of at least 8 wt % of the metallurgical slag composition, the process comprising feeding spent lithium-bearing batteries, their components or their scraps to a smelter, the smelter containing a molten bath comprising a slag layer residing on top of a metal alloy layer; and introducing oxygen to the molten bath in an amount selected to influence the composition of the metal alloy and the slag, wherein the yield of Co in the metal alloy is at least 95% versus total elemental input to the smelter, the content of Co in the slag is less than 1 wt % of the total slag composition, and the contents of MnO, Al.sub.2O.sub.3, CaO, and SiO.sub.2 in the slag are as follows: 1.2%≤MnO≤6.7%; 39%≤Al.sub.2O.sub.3<55%; 2.5%≤CaO<25%; and 15%≤SiO.sub.2≤36.4%.

7. The process of claim 6, wherein the total cobalt content in the Li.sub.2O bearing slag is 0.1%≤Co≤0.5%.

8. The process of claim 6, wherein the aluminum content in the spent batteries is about 6%.

9. The process of claim 6, wherein the carbon content in the spent batteries is about 20% to 25%.

10. The process of claim 6, wherein more than 50% of the lithium reports to the slag.

11. The process of claim 6, wherein about 38 Nm.sup.3 O.sub.2 per ton of batteries is supplied to the furnace to provide heat to the furnace.

Description

(1) The different embodiments are illustrated with the following example.

(2) Use is made of an apparatus comprising a bath smelter equipped with a lance for blowing gasses directly into the slag layer residing on top of the molten metal alloy. A so-called starting bath of molten slag is provided, such as from a previous operation performed in similar conditions.

(3) Spent rechargeable lithium-ion batteries are fed to the furnace at a rate of 100 kg/h while limestone (CaCO.sub.3) and sand (SiO.sub.2) are simultaneously added at rates of 10 kg/h and 5.5 kg/h respectively. About 38 Nm.sup.3 O.sub.2 per ton batteries is supplied through the lance to provide heat to the furnace. This amount is chosen so as to guarantee strongly reducing conditions, i.e. leading to the formation of an alloy collecting copper, nickel, iron, and cobalt, each with yields of preferably more than 95% versus total elemental input.

(4) In this particular case, the process appears to be autogenous, as no additional fuel is needed. This is due to the relatively high amounts of reducing agents such as metallic aluminum (about 6%) and carbon (about 20 to 25%) in the spent batteries treated. A bath temperature between 1400° C. and 1700° C. is achieved, which is suitable to maintain both the slag and the alloy sufficiently fluid for easy tapping and handling. The produced alloy and slag are then tapped, either periodically or continuously.

(5) Table 1 shows the amounts and analyses of the input and output phases of the process, on an hourly basis. The figures between parentheses correspond to the elemental concentrations expressed as weight % of the main oxidized species assumed to prevail in the slag. Significantly more than 50% of the lithium reports to the slag, while a minor fraction escapes with the fumes. The slag is fluid and is free of metallic droplets.

(6) Table 2 illustrates other slag compositions that are obtained using a similar process. These slags correspond to the above-mentioned suitable Li.sub.2O bearing metallurgical slag, and/or according to said first or second preferred embodiments.

(7) TABLE-US-00001 TABLE 1 Input and output phases of the process on an hourly basis Composition (%) Mass Mn Al Si Li CaCO.sub.3 (kg) Cu Ni Fe Co (MnO) (Al.sub.2O.sub.3) (SiO.sub.2) (Li.sub.2O) (CaO) Input Batteries 100 10 4.0 14 10 2.0 6.0 1.5 Sand 5.5 (100) Limestone 10 100 Output Alloy 40 25 10 35 25 4.0 Slag 1 26 0.08 0.05 0.17 0.1 (2.1) (44.4)   (21.8) (8.4)  (22)

(8) TABLE-US-00002 TABLE 2 Composition of other slags produced Composition (%) Cu Ni Fe Co MnO Al.sub.2O.sub.3 SiO.sub.2 Li.sub.2O CaO Slag 2 0.60 0.20 1.60 0.90 2.6 44.2 30.0 9.0 11.4 Slag 3 0.10 0.06 0.40 0.25 1.3 48.0 36.4 11.6 2.5 Slag 4 0.30 0.10 1.00 0.20 3.9 39.1 25.7 8.1 8.0 Slag 5 0.18 0.07 0.46 0.35 2.5 47.6 21.1 9.0 16.6 Slag 6 0.09 0.02 0.36 0.21 1.2 48.4 18.9 9.8 22.8

(9) The described metallurgical slags are suitable as such with respect to the smelting process itself: they allow for the desired separation between more easily oxidized metals such as lithium, and less easily oxidized metals such as cobalt and nickel. The Li.sub.2O content of the slag may reach concentrations well above those found in minerals, making the slag an economical source for lithium recovery. The process also allows for the recovery of other valuable metals, in particular cobalt and nickel, which are concentrated in metallic form in the alloy.