Method for recovering lithium hydroxide

Patent metadata

Field	Value
Publication number	US-11292725-B2
Application number	US-202016951066-A
Country	US
Kind code	B2
Filing date	Nov 18, 2020
Priority date	May 18, 2018
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

A method and arrangement for recovering lithium hydroxide from a mineral containing lithium, by pulping the raw material containing lithium in the presence of water and an alkali metal carbonate, leaching the obtained slurry twice, first at an elevated temperature, and secondly in an aqueous solution containing an alkali earth metal hydroxide, separating the thus obtained slurry into solids and a solution containing lithium hydroxide, the latter being purified, whereby lithium hydroxide monohydrate can be recovered from the purified solution by crystallising, and finally separating the solution obtained during the crystallization from the process and recycling it to one or more of the previous process steps.

First claim

The invention claimed is:

1. A method for recovering lithium hydroxide from a mineral containing lithium, selected from spodumene, petalite or lepidolite or mixtures thereof, wherein the method comprises:
pulping the raw material containing lithium in the presence of water and an alkali metal carbonate for producing a first slurry containing lithium,
leaching the first slurry containing lithium in a first leaching step at an elevated temperature for producing a second slurry containing lithium carbonate,
leaching the second slurry or a fraction thereof in a second leaching step in an aqueous solution containing an alkali earth metal hydroxide for producing a third slurry containing lithium hydroxide,
separating the third slurry into solids and a solution containing lithium hydroxide by solid-liquid separation and purifying the obtained solution, thus providing a purified solution containing lithium hydroxide, and
recovering lithium hydroxide monohydrate by crystallising from the purified solution containing lithium hydroxide, and
separating the solution obtained during the crystallization from the process, and recycling it to one or more of the previous process steps, or back to the crystallization, with at least a fraction of the solution being recycled to the second leaching step.

2. The method according to claim 1 , wherein the alkali metal carbonate used in the pulping step is selected from sodium and potassium carbonate.

3. The method according claim 1 , wherein the first leaching step is carried out at a temperature of 160 to 250° C. and at a pressure of 10 to 30 bar.

4. The method according to claim 1 , wherein the solution is separated from the solids after the first leaching step, and the solution is recycled either to the pulping step or to the first leaching step, or a fraction to each.

5. The method according to claim 1 , wherein the alkali earth metal hydroxide used in the second leaching step is selected from calcium and barium hydroxide.

6. The method according to claim 1 , wherein at least a fraction of the solution separated from the solids in the solid-liquid separation of the third slurry is added to said second leaching step in the form of a recycled solution, mixed with fresh alkali earth metal hydroxide prior to addition to the second leaching step, and mixed with fresh alkali earth metal hydroxide in a separate slurrying step.

7. The method according to claim 1 , wherein the second leaching step is carried out at a temperature of 10-100° C. and at atmospheric pressure.

8. The method according to claim 1 , wherein the step of purifying the solution obtained from the third slurry includes a purification based on the purification of dissolved ions and components, by first performing a membrane separation, and by carrying the thus purified solution to an ion exchange step, for further purification.

9. The method according to claim 1 , wherein at least a fraction of the solution separated from the crystallization step is recycled to the pulping step.

10. The method according to claim 1 , wherein at least a fraction of the solution separated from the crystallization step is carried to a lithium precipitation step, which is carried out as a carbonation, wherein the solution is reacted with either carbon dioxide or an alkali metal carbonate in order to form a lithium carbonate slurry.

11. The method according to claim 1 , wherein the solids obtained in the crystallization step, containing crystals of lithium hydroxide monohydrate, are purified using a washing solution before recovery as the product, and the spent washing solution is separated from the purified crystals of lithium hydroxide monohydrate, and is recycled to the crystal washing step or to the step of purifying the solution separated from the third slurry or to a regeneration step preceding said purification step, or to the crystallization step, or a fraction of the spent washing solution is recycled to two or more of these steps.

12. The method according to claim 1 , wherein the alkali metal carbonate used in the pulping step is at least partly composed of sodium carbonate.

13. The method according claim 1 , wherein the first leaching step is carried out at a temperature of 200 to 220° C., and at a pressure of 15 to 25 bar.

14. The method according to claim 1 , wherein the solution is separated from the solids after the first leaching step, and the solution is recycled at least to the pulping step.

15. The method according to claim 1 , wherein the alkali earth metal hydroxide used in the second leaching step is calcium hydroxide.

16. The method according to claim 1 , wherein the second leaching step is carried out at a temperature of 20-60° C., and at atmospheric pressure.

17. The method according to claim 1 , wherein the second leaching step is carried out at a temperature of 20-40° C., and at atmospheric pressure.

18. The method according to claim 1 , wherein the step of purifying the solution obtained from the third slurry includes a purification based on at least one of the purification of dissolved ions and components, an ion exchange, a membrane separation, or both, by first performing a membrane separation, and by carrying the thus purified solution to an ion exchange step, for further purification.

Assignees

• Outotec Finland Oy
• Metso Outotec Finland Oy

Inventors

• Tiihonen Marika
• Haavanlammi Liisa
• Kolehmainen Eero
• Kinnunen Sami
• Savikangas Juho

Classifications

• Y02P10/20

  Recycling · CPC title

• C22B3/22

  by physical processes, e.g. by filtration, by magnetic means {, or by thermal decomposition} (treatment or purification of solutions by liquid-liquid extraction C22B3/26) · CPC title

• C01P2006/80

  Compositional purity · CPC title

• B01D61/58

  Multistep processes · CPC title

• C01D1/30

  by crystallisation · CPC title