Method for recovering lithium hydroxide

Patent metadata

Field	Value
Publication number	US-2021070622-A1
Application number	US-202016951066-A
Country	US
Kind code	A1
Filing date	Nov 18, 2020
Priority date	May 18, 2018
Publication date	Mar 11, 2021
Grant date	—

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

1 .- 83 . (canceled)

84 . 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.

85 . The method according to claim 84 , wherein the alkali metal carbonate used in the pulping step is selected from sodium and potassium carbonate, optionally being at least partly composed of sodium carbonate.

86 . The method according claim 84 , wherein the first leaching step is carried out at a temperature of 160 to 250° C., optionally at a temperature of 200 to 220° C., and typically at a pressure of 10 to 30 bar, optionally 15 to 25 bar.

87 . The method according to claim 84 , 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, optionally at least to the pulping step.

88 . The method according to claim 84 , wherein the alkali earth metal hydroxide used in the second leaching step is selected from calcium and barium hydroxide, optionally being calcium hydroxide.

89 . The method according to claim 84 , 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, optionally mixed with fresh alkali earth metal hydroxide prior to addition to the second leaching step, more optionally mixed with fresh alkali earth metal hydroxide in a separate slurrying step.

90 . The method according to claim 84 , wherein the second leaching step is carried out at a temperature of 10-100° C., optionally 20-60° C., and most suitably 20-40° C., and typically at atmospheric pressure.

91 . The method according to claim 84 , wherein the step of purifying the solution obtained from the third slurry includes a purification based on the purification of dissolved ions and components, optionally an ion exchange or a membrane separation, or both, more optionally by first performing a membrane separation, and by carrying the thus purified solution to an ion exchange step, for further purification.

92 . The method according to claim 84 , wherein at least a fraction of the solution separated from the crystallization step is recycled to the pulping step.

93 . The method according to claim 84 , wherein at least a fraction of the solution separated from the crystallization step is carried to a lithium precipitation step, which optionally 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.

94 . The method according to claim 84 , 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.

95 . An arrangement for recovering lithium hydroxide from a raw material containing lithium according to the method of claim 84 , which arrangement comprises
a pulping unit for pulping the raw material containing lithium in the presence of water and an alkali metal carbonate, a first leaching unit for leaching a first slurry containing lithium at an elevated temperature, a second leaching unit for leaching a second slurry containing lithium carbonate, or a fraction thereof, in the presence of water and an alkali earth metal hydroxide, a solid-liquid-separation unit for separating a third slurry containing lithium hydroxide into solids and a solution containing lithium hydroxide, a purification unit connected to the solid-liquid-separation unit, for purifying the solution obtained from said separation unit, and a crystallising unit for recovering lithium hydroxide monohydrate from a solution containing lithium, which further comprises a line for carrying a solution from the crystallizing unit to a point further upstream of the crystallization unit, or back to the crystallization unit, comprising a recycle line arranged between the crystallizing unit, and/or a liquid section of a solid-liquid separation unit connected to the crystallization unit, and the second leaching unit.

96 . The arrangement according to claim 95 , which includes a recycle line leading from the first leaching unit, or from the liquid section of a solid-liquid separation unit placed in connection with said first leaching unit, either as line to the pulping unit or as line to the first leaching unit, or a separate line and to each, optionally at least to the pulping unit.

97 . The arrangement according to claim 95 , wherein the second leaching unit is connected to a slurrying unit for mixing an alkali earth metal hydroxide into an aqueous slurry.

98 . The arrangement according to claim 95 , which purification unit includes an ion exchange unit or a membrane separation unit, optionally a cation exchange unit, particularly containing a selective cation exchange resin, and wherein the purification unit most suitably is a combination of a membrane separation unit and an ion exchange unit, wherein the membrane separation unit has an outlet that is connected to an inlet of the ion exchange unit.

99 . The arrangement according to claim 95 , wherein the crystallization unit, or a downstream purification unit is connected to the second leaching unit, or the downstream solid-liquid separation unit via liquid line.

100 . The arrangement according to claim 95 , which comprises a recycle line arranged between the crystallizing unit, and/or the liquid section of a solid-liquid separation unit connected to the crystallization unit, and an upstream unit.

101 . The arrangement according to claim 95 , which comprises a recycle line arranged between the crystallization unit, and/or the liquid section of a solid-liquid separation unit connected to the crystallization unit, and the pulping unit.

102 . The arrangement according to claim 95 , which comprises a lithium precipitation unit connected to the crystallization unit or the solid-liquid separation unit through a line, which unit in turn optionally includes a feed inlet for feeding carbon dioxide or an alkali metal carbonate to the unit.

Assignees

• Outotec Finland Oy

Inventors

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

Classifications

• Y02P10/20

  Recycling · CPC title

• C01D15/02 Primary

  Oxides; Hydroxides · CPC title

• C22B3/42

  by ion-exchange extraction · CPC title

• C22B3/12

  in inorganic alkaline solutions · CPC title

• C22B3/02

  Apparatus therefor · CPC title