Apparatus for recovering lithium hydroxide

Abstract

An 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.

1 .- 83 . (canceled) 
     
     
         84 . An arrangement for recovering lithium hydroxide from a raw material containing lithium the arrangement comprising:
 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.   
     
     
         85 . The arrangement according to  claim 84 , 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. 
     
     
         86 . The arrangement according to  claim 84 , wherein the second leaching unit is connected to a slurrying unit for mixing an alkali earth metal hydroxide into an aqueous slurry. 
     
     
         87 . The arrangement according to  claim 84 , 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. 
     
     
         88 . The arrangement according to  claim 84 , wherein the crystallization unit, or a downstream purification unit, or a downstream regeneration unit is connected to the second leaching unit, or the downstream solid-liquid separation unit via liquid line. 
     
     
         89 . The arrangement according to  claim 84 , 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. 
     
     
         90 . The arrangement according to  claim 84 , which comprises a recycle further 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. 
     
     
         91 . The arrangement according to  claim 84 , 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. 
     
     
         92 . The arrangement according to  claim 84 , which includes a purification unit connected to the crystallization unit, and/or to a solid-liquid separation unit connected to the crystallization unit, wherein the solids obtained in the crystallization step can be purified. 
     
     
         93 . The arrangement according to  claim 84 , 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, to the pulping unit.