Device and method for recovering lithium hydroxide

Abstract

The present invention relates to an apparatus and a method for recovering lithium hydroxide, in particular to an apparatus and a method for recovering lithium hydroxide from a fresh feed in combination with a recycled solution and / or slurry containing lithium, the fresh feed comprising a mineral raw material containing lithium or a raw material containing lithium carbonate or a mixture of these raw materials, slurrying the feed in the presence of water and an alkali metal carbonate, leaching the slurry obtained twice, first at elevated temperature and secondly in an aqueous solution containing an alkaline earth metal hydroxide, separating the slurry thus obtained into a discardable solid and a solution containing lithium hydroxide, whereby lithium hydroxide monohydrate can be recovered from the solution by crystallization, and finally separating the solution and / or slurry obtained during the crystallization from the process and recycling it to one or more preceding steps including a slurrying step and an optional first leaching step.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for recovering lithium hydroxide from lithium-containing minerals and lithium carbonate. Background Art

[0002] CN102115101 discloses a method for producing lithium carbonate from spodumene minerals by subjecting the process to sulfuric acid treatment to obtain lithium sulfate, followed by a step of preparing a lithium carbonate mother liquor from which the carbonate product can be separated, and finally obtaining lithium hydroxide from the mother liquor by causticizing the mother liquor by adding lime. Barium hydroxide is also said to be used as the causticizing hydroxide.

[0003] CN 100455512 C discloses a method for preparing lithium hydroxide monohydrate by adding sodium hydroxide to a lithium sulfate solution to obtain liquid lithium hydroxide, followed by cooling, filtering and separating the lithium hydroxide from the sodium sulfate, followed by a series of recrystallization steps to provide pure lithium hydroxide monohydrate.

[0004] A similar process is described in CN 1214981 C, in which a step of adding sodium hydroxide to a lithium sulfate solution is performed, followed by cooling and separation to obtain liquid lithium hydroxide. The lithium hydroxide solution is then concentrated and crystallized, whereby a crude lithium hydroxide monohydrate product can be isolated. In this publication, pure lithium hydroxide monohydrate is obtained by reacting the crude product with barium hydroxide, followed by concentration and crystallization.

[0005] However, these methods are all performed with lithium sulfate.

[0006] US 3343910 A describes a method for recovering lithium hydroxide from a mineral raw material (calcined spodumene concentrate): by decomposing the mineral at 200°C using sodium carbonate, leaching with calcium hydroxide at or near ambient temperature, and finally crystallizing LiOH. It is also mentioned that the common practice of causticizing the separated lithium carbonate is at about 85°C, otherwise the results will be poor and uneconomical. US 334910 also describes that the hot mother liquor from the decomposition step containing unspent sodium carbonate can be removed in order to recycle the sodium carbonate. Optionally, lithium compounds can be separated from the leaching reaction product, and the solution concentrated to the crystallization point, after which the mother liquor can be returned to the process. However, no specific recycling route is mentioned.

[0007] Without further purification and recycle, the process is not very efficient.

[0008] There remains a need therefore for a process which allows the use of mineral raw materials and which will utilise a recycle stream containing or forming lithium carbonate which would otherwise end up as a discarded portion in known processes. Summary of the invention

[0009] An object of the present invention is therefore to provide an apparatus and a method suitable for recovering lithium hydroxide from a feed comprising mineral raw materials in high yield and high purity (typically battery grade) without the need for multiple processing steps including precipitation and purification steps (followed by further solid-liquid separation).

[0010] In particular, it is an object of the present invention to provide an apparatus and a method for recovering lithium hydroxide using simple purification steps and by optimizing recycling.

[0011] Battery-grade lithium hydroxide herein means lithium hydroxide monohydrate crystals having a lithium hydroxide purity of 56.5% or more.

[0012] Furthermore, the process concept is free of sulfates and acids and no undesired crystalline by-products are formed. The objects of the invention are achieved by means of an apparatus and a method which are characterized by what is stated in the independent claims. Preferred embodiments of the invention are disclosed in the dependent claims.

[0013] The present invention relates to a device for recovering lithium hydroxide from a fresh feed in combination with a recycled solution and / or slurry, the fresh feed comprising a mineral raw material containing lithium or a raw material containing lithium carbonate or a mixture of these, the device comprising

[0014] - a slurrying unit 1 for slurrying the feed in the presence of water and an alkali metal carbonate so as to form a first slurry containing lithium,

[0015] a first leaching unit 2 for leaching said first slurry containing lithium, optionally in combination with a recycled solution and / or slurry, at an elevated temperature so as to form a second slurry containing lithium carbonate,

[0016] a second leaching unit 3 for leaching said second slurry containing lithium carbonate or a part thereof in the presence of water and an alkaline earth metal hydroxide so as to form a third slurry containing lithium hydroxide,

[0017] - a solid-liquid separation unit 31, for separating the third slurry containing lithium hydroxide into a discardable solid and a solution containing lithium hydroxide, and

[0018] - A crystallization unit 4 for recovering lithium hydroxide monohydrate from the solution containing lithium.

[0019] The crystallization unit 4 is also connected to:

[0020] One or more recirculation lines 403 , 414 , 421 , 422 are used to transport solution and / or slurry from the crystallization unit 4 to one or more upstream units including the pulping unit 1 and the optional first leaching unit 2 .

[0021] According to an embodiment of the present invention, the apparatus also comprises additional necessary pipelines for conveying solutions, solids or slurries to their intended units.

[0022] The present invention also relates to a process for recovering lithium hydroxide from a fresh feed in combination with a recycled solution and / or slurry, the fresh feed comprising a mineral raw material containing lithium or a raw material containing lithium carbonate or a mixture of these. The process comprises the following steps

[0023] - slurrying the feed in the presence of water and an alkali metal carbonate to produce a first slurry containing lithium,

[0024] - leaching a first slurry containing lithium, optionally in combination with a recycled solution and / or slurry, at elevated temperature in a first leaching step for producing a second slurry containing lithium carbonate,

[0025] - leaching the second slurry or a portion thereof in an aqueous solution containing an alkaline earth metal hydroxide in a second leaching step to produce a third slurry containing lithium hydroxide,

[0026] - separating the third slurry into a discardable solid and a solution containing lithium hydroxide by solid-liquid separation,

[0027] - recovering lithium hydroxide monohydrate by crystallization from a solution containing lithium hydroxide, and

[0028] - The solution and / or slurry remaining after crystallization is separated from the process and returned as recycle solution and / or slurry to one or more preceding process steps including the slurrying step and the optional first leaching step.

[0029] Typically, the lithium-containing mineral raw material is selected from spodumene, petalite, lepidolite, mica or clay, or mixtures thereof, most suitably from spodumene.

[0030] According to an embodiment of the present invention, the mineral raw material containing lithium is selected from minerals that have undergone thermal treatment, whereby a particularly preferred material is β-spodumene.

[0031] As described above, according to an alternative embodiment of the present invention, a recycled solution and / or slurry containing lithium carbonate can be used. Preferably, the recycled solution and / or slurry is recycled from a downstream unit of the device. Most suitably, the recycled solution and / or slurry is used in combination with fresh feed.

[0032] According to an embodiment of the invention, the first leach solution is separated from the solids after the first leaching step, whereby only the solids are conveyed to the second leaching step.

[0033] According to an embodiment of the invention, the first leach solution is separated from the solids after the first leaching step and returned as a recycle solution to the pulping step or the first leaching step, or a portion of each step.

[0034] According to an embodiment of the invention, the solution obtained from the solid / liquid separation step carried out after the second leaching is subjected to a purification step.

[0035] According to an embodiment of the invention, the solution and / or slurry (also referred to as bleed solution) obtained from the crystallization step or from the optional pre-concentration step (preferably performed as an evaporation step) is recovered and returned to one or more preceding process steps including the slurrying step, and possibly also to the first leaching step, the second leaching step and / or back to the crystallization step.

[0036] Since the precipitate that may have formed in the pre-concentration step will most likely be formed from or at least contain lithium carbonate, such a slurry containing the precipitate will be highly suitable for recycling to said step.

[0037] Optionally, before it is returned to a previous process step, for example by using CO 2 The effluent solution obtained from the crystallization step is pretreated by carbonation to form a carbonate precipitate.

[0038] When an optional first solid-liquid separation is performed between the leaching steps, the solution used in the first leaching step (containing any excess leaching chemical, ie alkali metal carbonate) can be recovered and recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In the following reference will be made Figure 1 , 2 , 3, 4, 5 and 6 describe the present invention in more detail by way of preferred embodiments, wherein the accompanying drawings all show general flow charts and unit configurations of some embodiments of the present invention. DETAILED DESCRIPTION

[0040] like Figure 1 As schematically presented in , an embodiment of the present invention is an apparatus for recovering lithium hydroxide from a fresh feed in combination with a recycled solution and / or slurry containing lithium, the apparatus of this particular embodiment comprising a slurrying unit 1 for slurrying the feed in the presence of water and an alkali metal carbonate, leaching the obtained slurry optionally in combination with the recycled slurry or solution in a first leaching unit 2, followed by leaching in the presence of water and an alkaline earth metal hydroxide in a second leaching unit 3, after which the obtained slurry is separated in a solid-liquid separation unit 31 into a discardable solid and a solution containing lithium hydroxide, whereby the solution can be transported to a crystallization unit 4 for the production of high-purity lithium hydroxide. Figure 1In the embodiment of the present invention, the apparatus further comprises recycle lines 421, 422 for conveying solution and / or slurry from the crystallization unit 4 to one or more upstream units, which in this embodiment comprise a slurry unit 1 and an optional first leaching unit 2. However, as in Figures 2 to 6 As indicated in the claims, other recycling options are available.

[0041] exist Figures 2 to 6 Additional embodiments of the present invention are described in more detail below. These specific embodiments are described in more detail below.

[0042] Dashed lines in the drawings indicate that elements within those dashed lines may be combined in some embodiments of the invention.

[0043] In the present invention, the lithium-containing feed is typically selected from a fresh feed comprising a lithium-containing mineral raw material or a raw material containing lithium carbonate or a mixture of these raw materials in combination with a recycled solution and / or slurry containing lithium.

[0044] Preferably, the mineral raw material is selected from spodumene, petalite, lepidolite, mica or clay, or mixtures thereof. This mineral raw material is preferably a lithium-containing mineral in calcined form, more preferably obtained by heat treating the raw material, most suitably by using a temperature of 900-1200°C, in particular a temperature of 1000-1100°C.

[0045] A particularly preferred mineral is spodumene, which during the calcination step provides beta-spodumene.

[0046] In a preferred embodiment, the mineral raw material is used in combination with a slurry containing the lithium carbonate, preferably a slurry recycled from a subsequent step of the process.

[0047] The present invention therefore relates to an apparatus for recovering lithium hydroxide from a fresh feed comprising a lithium-containing mineral raw material or a raw material containing lithium carbonate or a mixture of these raw materials in combination with a recycled solution and / or slurry.

[0048] - a slurrying unit 1 for slurrying the feed in the presence of water and an alkali metal carbonate so as to form a first slurry containing lithium,

[0049] a first leaching unit 2 for leaching said first slurry containing lithium, optionally in combination with a recycled slurry or solution, at elevated temperature so as to form a second slurry containing lithium carbonate,

[0050] a second leaching unit 3 for leaching said second slurry containing lithium carbonate or a part thereof in the presence of water and an alkaline earth metal hydroxide so as to form a third slurry containing lithium hydroxide,

[0051] - a solid-liquid separation unit 31, used to separate the third slurry containing lithium hydroxide into a discardable solid and a solution containing lithium hydroxide,

[0052] - a crystallization unit 4 for recovering lithium hydroxide monohydrate from a solution containing lithium hydroxide,

[0053] o The apparatus further comprises one or more recirculation lines 403 , 414 , 421 , 422 for conveying solution and / or slurry from the crystallization unit 4 to one or more upstream units including the pulping unit 1 and the optional first leaching unit 2 .

[0054] In an embodiment of the invention, the apparatus further comprises a calcining unit for thermally treating the raw materials intended to be conveyed to the pulping unit 1 .

[0055] The slurry unit 1 preferably contains a feed inlet 101 for supplying raw material containing lithium to the unit 1 .

[0056] The first leaching unit 2 is preferably an autoclave.

[0057] In one embodiment, the first leaching unit 2 is connected to the pulping unit 1 via a slurry line 102 .

[0058] Both the pulping unit 1 and the first leaching unit 2 may comprise separate inlets for conveying recirculating solution, for example from recirculation lines 211 and 421 to the pulping unit 1 and from recirculation lines 212 and 422 to the first leaching unit 2 .

[0059] In one embodiment, a solid-liquid separation unit 21 is arranged between the first leaching unit 2 and the second leaching unit 3 .

[0060] Preferably, the recirculation lines 211, 212 lead from the first leaching unit 2 or from the liquid section of the solid-liquid separation unit 21 to a unit upstream of the first leaching unit 2. More preferably, the recirculation line leads from the first leaching unit 2 or from the liquid section of the solid-liquid separation unit 21 to the pulping unit 1 as line 211 or to the first leaching unit 2 as line 212, or to each unit as separate lines 211 and 212.

[0061] In an embodiment of the present invention, the second leaching unit 3 is a tank reactor, preferably a stirred tank reactor.

[0062] Preferably, the second leaching unit 3 comprises an inlet 303 for alkaline earth metal hydroxide or an aqueous slurry thereof.

[0063] Optionally, the second leaching unit 3 may be connected to a slurrying unit 30 for mixing the alkaline earth metal hydroxide into an aqueous slurry before conveying it to the second leaching unit 3 through the inlet 303 .

[0064] In addition, the second leaching unit 3 is typically connected to the first leaching unit 2 or the downstream solid-liquid separation unit 21 via a slurry line 203 .

[0065] Typically, the solution or slurry obtained from the liquid section of the solid-liquid separation unit 31 is conveyed to the crystallization unit 4 (see, e.g. Figure 3 ).

[0066] In an embodiment of the present invention (see Figure 4-6 ), the purification unit 32 is located between the solid-liquid separation unit 31 and the crystallization unit 4. Therefore, this optional purification unit 32 is used in the purification of the solution separated from the third slurry. The optional purification unit 32 preferably includes one or more of an ion exchange unit and a membrane separation unit, more preferably at least one or more ion exchange units, and most preferably a cation exchange unit (especially containing a selective cation exchange resin). Therefore, one option is to use a series of two or more ion exchange units, and possibly also a series of two or more regeneration units 33.

[0067] In the preferred embodiment where purification unit 32 is an ion exchange unit (see Figure 5 ), the purification unit 32 is connected to a regeneration unit 33 for regenerating the purification resin. This regenerated resin can then be fed back to the ion exchange unit 32 via a recycle line 332. However, it is also possible to carry out these purification and regeneration steps in a single unit 32 (see Figure 5 dotted lines around cells 32 and 33).

[0068] Such regeneration is not required when the purification unit 32 is a membrane separation unit. However, in the case where a membrane separation unit is used, the unit provides two streams, one being a purified solution which can be sent directly to the crystallization unit 4, and the other being a recycle stream suitable for sending to the second leaching unit 3, for example via a recycle line 323 (see Figure 6 ).

[0069] In another embodiment of the invention (see Figure 6 ), the device of the present invention may include an ion exchange unit 32a and a membrane separation unit 32b, and therefore also includes a regeneration unit 33. Due to the presence of the membrane separation unit 32b, a recycle stream can be provided, thereby transporting the recycle stream to the second leaching unit 3 through a pipeline 323.

[0070] In the embodiment, it is particularly preferred to arrange the ion exchange unit 32a downstream of the membrane separation unit 32b.

[0071] In an embodiment of the invention, the apparatus comprises two or more crystallization units 4, which are preferably arranged in series.

[0072] Optionally, a separate pre-concentration unit, preferably in the form of an evaporation unit, may precede the crystallization unit (or units) 4, designed to provide a crystallization feed with an optimized concentration.

[0073] Typically, the apparatus comprises a solid-liquid separation unit 41 connected to the crystallization unit 4 for separating the crystals obtained in the crystallization unit 4 from the waste slurry.

[0074] Additionally, as noted above, one or more recycle lines 403, 414, 421, 422 are arranged between the liquid section of the crystallization unit 4 and / or the solid-liquid separation unit 41 and the upstream unit.

[0075] These recycling pipelines may include a recycling pipeline 403 arranged between the liquid section of the crystallization unit 4 or the solid-liquid separation unit 41 and the second leaching unit 3, a recycling pipeline 414 arranged between the liquid section of the crystallization unit 4 or the solid-liquid separation unit 41 and the inlet of the crystallization unit 4, a recycling pipeline 421 arranged between the liquid section of the crystallization unit 4 or the solid-liquid separation unit 41 and the pulping unit 1, and a recycling pipeline 422 arranged between the liquid section of the crystallization unit 4 or the solid-liquid separation unit 41 and the first leaching unit 2.

[0076] Among them, the recycle line 403 is intended for conveying soluble aluminum back to the second leaching unit 3, where it will then form a solid compound that can be discarded. In turn, the recycle line 414 is intended for providing means for reusing as quickly as possible in crystallization the solution and / or slurry separated from the crystals obtained in the crystallization unit 4, i.e. the crystallization mother liquor, which is a saturated solution containing lithium hydroxide.

[0077] However, preferred alternatives include recycle lines 421 and 422, with recycle line 421 being particularly preferred. These lines are intended to recycle and thus use the lithium hydroxide in the mother liquor that ultimately resides in the crystallization unit 4, while also preventing the accumulation of other salts in the crystallization unit 4.

[0078] In an embodiment of the present invention, the apparatus comprises a lithium precipitation unit 42 connected to a crystallization unit 4 or a solid-liquid separation unit 41 via a pipeline 423 .

[0079] One advantage of this precipitation unit 42 is that it provides means for reusing the solution recovered from the crystallization unit 4 (which is a strong alkaline concentrated solution carrying a large concentration of hydroxide ions). This concentration of hydroxide ions results from the fact that crystallization of lithium hydroxide can only be achieved from saturated solutions of lithium hydroxide (which are typically >12% solutions, depending on the temperature chosen).

[0080] On the other hand, the leaching units 2 and 3 are lower alkalinity environments, wherein the first leaching unit 2 forms a sodium carbonate environment and the second leaching unit 3 forms an environment with a lower concentration of lithium hydroxide solution, typically about 2-3.5%. Therefore, a large amount of strong alkali should be avoided in the leaching units 2 and 3.

[0081] As a result, it is necessary to neutralize a large portion of the hydroxide ions. Carbonation provides suitable neutralization of the hydroxide ions, as described below with reference to reaction (4).

[0082] Preferably, the lithium precipitation unit 42 comprises a feed inlet 424 for supplying carbon dioxide and optionally alkali metal carbonate to the unit 42 .

[0083] The precipitation reaction is preferably not carried out completely, whereby the slurry recycled through the recycle line 421a and / or 422a contains both lithium carbonate and lithium hydroxide. The advantages of using such a slurry containing both lithium carbonate and lithium hydroxide are explained above. For example, it is not necessary to completely convert the hydroxide to carbonate in the precipitation unit 42, as some carbonation will also occur in the pulping unit 1 or the first leaching unit 2.

[0084] According to one embodiment, the recycle lines 421 and / or 422 may be connected to this precipitation unit 42 instead of being connected directly to the liquid section of the crystallization unit 4 or the solid-liquid separation unit 41 as recycle lines 421a and / or 422a.

[0085] According to another embodiment, separate lines 421 and 421a and separate lines 422 and 422a are provided and there is no need to combine these recycled pulps and / or solutions before passing them to the pulping unit 1 or the first leaching unit 2, respectively.

[0086] It is particularly preferred to route the recirculation line 421 through the sedimentation unit 42, since carbonation will also take place in the pulping unit 1 to which the recirculation line 421 will lead.

[0087] Because the lithium hydroxide solution is a concentrated solution of a strong base, it provides a highly suitable solution for controlling the pH in the first leaching unit 2, which control is necessary in order to maintain suitable leaching conditions. When this solution is contacted with a sodium carbonate solution, such as in a pulping step, as described below, by reference to reaction equation (3), some poorly soluble lithium carbonate will be precipitated simultaneously. This reaction provides lithium carbonate for further lithium hydroxide recovery and sodium hydroxide for pH control.

[0088] Therefore, a particular feature of the present invention is that it provides means for supplying lithium carbonate already in line 102 leading to the first leaching unit 2, rather than forming lithium carbonate only in the first leaching unit 2.

[0089] In an embodiment of the present invention, the apparatus comprises a purification unit 43 connected to the crystallization unit 4 and / or to the solid-liquid separation unit 41, wherein the solid obtained in the crystallization step can be purified.

[0090] Preferably, the purification unit 43 comprises a feed inlet 431 for supplying a washing solution into the purification unit 43 .

[0091] In one embodiment, the apparatus includes a solid-liquid separation unit 44 connected to and downstream of the purification unit 43 for separating purified lithium hydroxide monohydrate crystals from spent washing solution.

[0092] Preferably, the purification unit 43 or the solid-liquid separation unit 44 connected to the purification unit 43 and downstream of the purification unit 43 is connected to the upstream purification unit 32 or the regeneration unit 33 through a recycling line 432 .

[0093] More preferably, the solid-liquid separation unit 44 connected to the purification unit 43 and downstream of the purification unit 43 is connected to the crystallization unit 4 through a recirculation line 444 .

[0094] Even more preferably, the solid-liquid separation unit 44 connected to the purification unit 43 downstream of the purification unit 43 is connected to the purification unit 43 via a recirculation line 445 .

[0095] In another alternative, the apparatus of the invention comprises combined purification units 41, 43, 44 for purifying the crystals obtained from the spent solution in the crystallization unit 4 and separating the purified crystals from the spent washing solution.

[0096] In this alternative, a recirculation line 414 connects the combined unit 41, 43, 44 with the crystallization unit. Likewise, a feed inlet 431 is connected to the combined purification unit 41, 43, 44. Additionally, a recirculation line 432 may connect the combined purification unit 41, 43, 44 with an upstream purification unit 32 or with a separate regeneration unit 33, and a recirculation line 444 may connect the combined purification unit 41, 43, 44 with the crystallization unit 4. Finally, a recirculation line 445 may connect the solid section of the combined purification unit 41, 43, 44 with the liquid section of the same combined unit 41, 43, 44.

[0097] In an embodiment of the present invention, the apparatus comprises a drying unit 45 connected to the crystallization unit 4 or to the solid section of the solid-liquid separation unit 41, 44 downstream of the crystallization unit 4, wherein the obtained lithium hydroxide monohydrate crystals can be dried.

[0098] Preferably, the drying unit 45 comprises a product outlet 451 through which the final battery-grade product can be recovered.

[0099] The present invention also comprises a process for recovering lithium hydroxide from a fresh feed comprising a lithium containing mineral raw material or a lithium carbonate containing raw material or a mixture of these in combination with a recirculating solution and / or slurry containing lithium.

[0100] The method of the invention comprises (with reference to the numbering used for the apparatus) slurrying 1 a feed containing lithium in the presence of water and an alkali metal carbonate for extracting lithium from the feed and producing a first slurry containing lithium.

[0101] The alkali metal carbonate is preferably selected from sodium carbonate and potassium carbonate, most suitably at least partly consisting of sodium carbonate. Typically, the alkali metal carbonate is present in excess.

[0102] After slurrying, the first slurry containing lithium, optionally in combination with a recycled slurry or solution, is leached 2 at an elevated temperature for a first time to produce a second slurry containing lithium carbonate.

[0103] The presence of alkali metal carbonate and process conditions result in the formation of lithium carbonate and analcime solids which in the case of spodumene and sodium carbonate can be represented using the following formula (1).

[0104] 2 LiAl(SiO 3 ) 2 +Na 2 CO 3 =2NaAl(SiO 3 ) 2 +Li 2 CO 3 (1)

[0105] The first leaching 2 of the first slurry containing lithium is typically carried out in a suitable autoclave or a series of autoclaves.

[0106] In an embodiment of the present invention, the first leaching step is carried out at a temperature of 160 to 250° C., preferably at a temperature of 200 to 220° C. Likewise, the first leaching step is carried out at a pressure of 10 to 30 bar, preferably 15 to 25 bar. Suitable conditions for this step are typically achieved using high pressure steam.

[0107] Preferably, at least part of the water and alkali metal carbonate sent to the pulping step is obtained from a recycled aqueous solution containing said alkali metal carbonate and optionally lithium carbonate.

[0108] An optional solid-liquid separation step 21 may be performed, wherein the solution and solids may be separated after the first leaching step 2 and the solids may be conveyed to the second leaching step 3 .

[0109] In one embodiment, the solution separated from the solids in the optional separation step 21 is returned to one or more previous steps as a recycle solution.

[0110] Preferably, the solution is returned to the pulping step or the first leaching step, or a portion of each step. More preferably, the solution is returned to the pulping step.

[0111] In the second leaching step 3, the lithium-containing phase (here typically a solid or the entire second slurry) is leached 3 using a hydroxide reagent, i.e. an alkaline earth metal hydroxide, preferably in an aqueous solution of the hydroxide reagent, so as to form a third slurry containing lithium hydroxide. Subsequently, the solid is separated from the liquid by solid-liquid separation 31. This separation 31 results in the formation of a solid that can be discarded and a solution containing lithium hydroxide.

[0112] The alkaline earth metal hydroxide used in the second leaching step 3 is preferably selected from calcium hydroxide and barium hydroxide, more preferably calcium hydroxide, optionally prepared by reaction of calcium oxide (CaO) in aqueous solution.

[0113] In an embodiment of the invention, the alkaline earth metal hydroxide used in the second leaching step 3 is mixed with water or an aqueous solution before being added to the second leaching step 3. The hydroxide reagent may be obtained from a separate slurrying step 30, for example.

[0114] Preferably, at least a portion of the solution separated from the solids in the separation step 31, in particular containing lithium and sodium, is added to the second leaching step in the form of a recirculating solution, preferably mixed with fresh alkaline earth metal hydroxide before addition to the second leaching step, more preferably mixed with fresh alkaline earth metal hydroxide in a separate slurrying step 30.

[0115] The second leaching step 3 is typically carried out at a temperature of 10-100° C., preferably 20-60° C. and most suitably 20-40° C. The second leaching step 3 is typically carried out at atmospheric pressure.

[0116] The presence of an alkaline earth metal hydroxide and the process conditions lead to the formation of lithium hydroxide, which in the case of analcime, lithium carbonate and calcium hydroxide can be represented by the following formula (2).

[0117] 2NaAl(SiO 3 ) 2 +Li 2 CO 3 +Ca(OH) 2 =2NaAl(SiO 3 ) 2 +CaCO 3 +2LiOH (2)

[0118] All lithium carbonate is reacted under the conditions in this second leaching step 3. This includes lithium carbonate formed in the first leaching step 2 according to reaction (1), i.e. under high pressure conditions, and lithium carbonate precipitated in reactions (3) and (4) described below as well as lithium carbonate added as fresh feed.

[0119] After the two leaching steps 2, 3 have been carried out, the third slurry obtained containing lithium hydroxide is separated 31 into a solid phase and a solution. The solution contains at least a major part of the lithium hydroxide formed, whereby the solid phase can be discarded. The separation 31 can be achieved using any suitable solid-liquid separation method. For example, the third slurry can be sent to a thickener, from which the overflow can be sent directly to purification, and the underflow can be further filtered in order to recover all the lithium hydroxide present in the solution and separate it from the solid impurities, or simple filtering techniques can be used. Typically, all solid-liquid separations described herein require a supply of wash water for washing the solids (e.g. Figure 3-6 ). One reason for this optional solid washing step is to displace another portion of the solution that accompanies the solid as moisture. After washing, the spent wash water is typically returned to the previous step of the process as a recycle solution. If the used wash water is recycled, this washing step will also provide the additional benefit of recovering usable reagents.

[0120] The solids obtained from this separation of the third slurry into solids and solution typically consist of undesirable residues which may be discarded as tailings.

[0121] According to an embodiment of the invention, the third slurry separated from the second leaching step 3 is purified 32 before it is sent to the crystallization step. This optional purification step is preferably based on the purification of dissolved ions and components, and more preferably comprises an ion exchange or membrane separation step or both, most suitably by using a cation exchange resin, in particular a selective cation exchange resin.

[0122] Typically, purification by ion exchange is performed by using a cation exchange resin, wherein the cation exchange group is, for example, iminodiacetic acid (IDA) or aminophosphonic acid (APA).

[0123] Selective cation exchange resins typically have chelating functional groups attached to the resin matrix. These chelating functional groups generally have much higher selectivity for polyvalent metal cations (e.g., heavy metal cations and alkaline earth metal cations) than monovalent alkali metal cations (Li, Na, K). Suitable resin functional groups are, for example, the above-mentioned iminodiacetic acid esters and aminophosphonates. These chelating resins can be used to purify typical cationic impurities such as calcium ions (Ca 2+) from lithium hydroxide solutions. 2+ ).

[0124] In one embodiment, the step of purifying the solution obtained from the third slurry is performed at least in part using resin regenerated in a separate regeneration step.

[0125] Preferably, the regeneration step is carried out using a recirculating solution coming from a subsequent process step, more preferably a separated solution obtained during a crystallization process, optionally in purified form.

[0126] In a preferred embodiment, this regeneration is performed using at least an acidic solution for metal elution, preferably hydrochloric acid (HCl), and an alkaline solution for neutralization, preferably sodium hydroxide (NaOH) or an alkaline lithium hydroxide solution, more preferably a recycled solution containing lithium hydroxide. In addition, water may be supplied to the regeneration step. The regenerated resin may be supplied back to the ion exchange.

[0127] However, it is also possible to combine these purification and regeneration steps and carry out them in the same purification unit.

[0128] According to another alternative, the purification step can be carried out in a unit 32 comprising a series of two or more ion exchange units. Likewise, a series of two or more regeneration units 33 can be used.

[0129] Membrane separation can be performed using a semi-permeable membrane that separates ionic or other dissolved compounds from aqueous solutions. More specifically, membrane separation can be used to classify dissolved ions and compounds by their size (depending on the pore size of the membrane material) and / or their charge (depending on the surface charge of the membrane material). Positive surface charges repel cations (having a stronger repulsion effect on multivalent cations) and attract anions, and vice versa. These phenomena will be able to purify, for example, multivalent metal cations, complexing materials (such as aluminum hydroxide complexes), polymeric materials (such as dissolved silicon dioxide) and larger anions (such as sulfate and carbonate ions) from lithium hydroxide solutions. Using membrane separation, regeneration is not required.

[0130] Since lithium hydroxide is a strong base with a high hydroxide ion concentration, metals that are strongly complexed by hydroxide ions (e.g., aluminum ions Al) cannot be purified by the selective cation exchange resins mentioned above. 3+ ). Therefore, the recycling described herein is used to purify these ions.

[0131] Selective cation exchange is preferably used in the polishing removal of polyvalent metal cations that form sparingly soluble hydroxide compounds (typically calcium hydroxide). In the solution to be crystallized, these metals (or metal cations) should be removed, or at least their concentration should be reduced to very low levels in order to prevent them from contaminating the crystallized lithium hydroxide monohydrate product. Removal of these metals is not efficient using membranes and is therefore preferably accomplished by ion exchange, particularly with selective cation exchange resins.

[0132] In case membrane separation is performed, alone or in combination with ion exchange, a recycle stream is provided from the membrane separation which is suitable for conveying to the second leaching step 3 .

[0133] In membrane separation, the retained ions and compounds will eventually become a concentrated fraction, typically called "retentate", which can be returned to the second leaching step as a recycle fraction as described above. The other fraction obtained is the permeated liquid fraction, the "permeate", which is optionally purified by ion exchange (if these purifications are combined) and fed to the crystallization.

[0134] The final fraction of each ion and compound in a membrane separation depends on their characteristics: for example their charge and size. This retention goal can be achieved based on the selection of the desired membrane type (based on surface charge and / or pore size).

[0135] In terms of charge, the target retention species will typically be a multivalent metal cation such as calcium (Ca 2+ ), magnesium ion (Mg 2+ ) relative to the permeation (or zero to negative retention) of monovalent alkali metal cations such as lithium ions (Li + ) or sodium ion (Na + ).

[0136] In terms of size, the retained species will typically be larger compounds such as polymeric species (e.g. dissolved silica), complex ions (e.g. aluminum hydroxide complexes), and the largest types of anions (e.g. carbonate CO 3 2- and sulfate SO 4 2- ), while the smallest type of anion (such as hydroxide OH - ) is permeable (or has zero or negative retention).

[0137] Based on the above, it is particularly preferred to combine membrane separation with ion exchange, and most suitably membrane separation is first performed, and then ion exchange is used for polishing to remove polyvalent metal cations.

[0138] In the final step of the process, lithium hydroxide monohydrate crystals are recovered from the optionally purified lithium-containing solution by crystallization 4. Crystallization is typically performed by heating the lithium-containing solution to a temperature about the boiling point of the solution thereby evaporating the liquid or by recrystallizing the monohydrate from a suitable solvent.

[0139] Optionally, a preconcentration, preferably as evaporation, can be carried out before the crystallization step.

[0140] In an embodiment of the invention, two or more crystallization units are used, which are preferably arranged sequentially.

[0141] The method of the present invention is capable of producing pure lithium hydroxide monohydrate with excellent yield and purity using a continuous and simple process, typically providing battery-grade lithium hydroxide monohydrate crystals with a lithium hydroxide purity of 56.5% or more.

[0142] In another embodiment, the purified lithium hydroxide-containing solution is mixed with one or more solutions recycled from subsequent steps of the process before being subjected to the crystallization step 4, or these solutions may be fed to the crystallization 4 separately.

[0143] Preferably, the solid-liquid separation step 41 is after the crystallization step 4 .

[0144] The effluent solution obtained when crystallizing 4 lithium hydroxide monohydrate can be recovered and recycled to one or more previous process steps, including the pulping step 1 and the optional first leaching step, the second leaching step 3 and / or back to the crystallization step 4.

[0145] It is particularly preferred to recycle at least a portion of the solution separated from the crystallization step to at least the pulping step 1 and the first leaching step 2 .

[0146] The solution separated from the crystallization step is a saturated solution containing a large concentration of lithium hydroxide to be recovered. In addition, it is a concentrated solution of a strong base. Therefore, it provides a highly suitable solution to be used for controlling the pH in the first leaching unit 2. Due to the recycle streams sent to the pulping step 1 and the first leaching step 2, the main one is the stream sent to the pulping step through the recycle pipeline 211, this pH control is necessary. For example, when this lithium hydroxide solution is contacted with a sodium carbonate solution in the pulping step, as represented by the following formula (3), some insoluble lithium carbonate will be precipitated at the same time:

[0147] LiOH(aq)+Na 2 CO 3 (aq)=Li 2 CO 3 (s)+NaOH(aq) (3)

[0148] This reaction provides lithium carbonate for further lithium hydroxide recovery and sodium hydroxide for pH control.

[0149] In addition, some impurities in the crystallization discharge solution (e.g., aluminum and silicon) have a solubility that increases with increasing alkalinity (e.g., caused by increasing lithium hydroxide concentration), and thus these alkali-soluble impurities can be removed by returning them in solution to a step with lower alkalinity, such as a pulping step or a first leaching step. In the lower alkalinity environment, these impurities form poorly soluble compounds (e.g., aluminum hydroxide) and can be discarded with the solids in the separation step 31. Carbonate ions can also be recovered and utilized in this way.

[0150] In an embodiment of the invention, a portion of the solution separated from the crystallization step is returned to the second leaching step as recirculation solution.

[0151] The advantage of these recycling options is that the soluble impurities (mainly sodium, potassium, aluminum and carbonate ions, as well as soluble silicon and silicates) remaining in the liquor after crystallization can be recycled upstream where they can be removed. In particular, in the leaching step, these impurities form poorly soluble compounds, which can be discarded as solids after the second leaching step. Without the recycling options mentioned herein, these impurities would concentrate in the crystallization step and contaminate the product.

[0152] In another embodiment, a portion of the solution separated from the crystallization step is returned to the crystallization step as a recycle solution. In a typical crystallization process, the crystallization slurry is kept in continuous circulation, from which product crystals are continuously separated, and recycling at least a portion of the remaining mother liquor has the advantage that it increases the yield of the process.

[0153] In another embodiment, at least a portion of the solution separated from the crystallization step is sent to a lithium precipitation step 42, which is preferably performed as a carbonation step, wherein the solution is reacted with either or both of carbon dioxide or an alkali metal carbonate, preferably at least with carbon dioxide, to form a lithium carbonate slurry, as represented by the following formula (4):

[0154] 2LiOH+CO 2 =Li 2 CO 3 +H 2 O (4)

[0155] This optional lithium precipitation step 42 has the advantage of reacting the lithium hydroxide contained in the crystallization discharge solution to the corresponding carbonate, which is highly suitable for return as recycle solution to the pulping step 1 or the first leaching step 2 of the process.

[0156] Lithium hydroxide crystallization can be achieved only from a saturated solution of lithium hydroxide (which is typically >12% solution, depending on the temperature selected). Therefore, the solution recovered from the crystallization step provides a strong base concentrated solution carrying a large concentration of hydroxide ions. On the other hand, the leaching steps (first and second) are lower alkalinity environments. The first leaching step is carried out in a sodium carbonate environment, and the second leaching step is carried out on a lower concentration lithium hydroxide solution (typically about 2-3.5%). Therefore, the need for strong base in the leaching steps is very small. As a result, it is necessary to neutralize most of the hydroxide ions, and carbonation provides such suitable neutralization.

[0157] When this optional precipitation step is used, the solution from the crystallization step 4 can be transported back to the pulping step 1 and the optional first leaching step 2 by this precipitation step, wherein the lithium hydroxide is converted into lithium carbonate. However, the reaction may not be complete, whereby at least trace amounts of lithium hydroxide will still be present in the lithium carbonate slurry to be recycled. As mentioned above, some conversion of lithium hydroxide to the corresponding carbonate will also occur in the pulping step, whereby complete carbonation in the precipitation step is unnecessary. However, some carbonates are also useful in these steps.

[0158] Whether or not a precipitation step is used, the solution and / or slurry returned from the crystallization step to the pulping step and optional first leaching step will therefore contain some lithium hydroxide. However, this lithium hydroxide will typically be converted to the corresponding sparingly soluble carbonate in the pulping or first leaching step.

[0159] In an embodiment of the present invention, the solid obtained in the crystallization step (containing lithium hydroxide monohydrate crystals) is purified using a wash solution before being recovered as a product.

[0160] The purified lithium hydroxide monohydrate crystals are preferably separated from the wash solution, dried and subsequently recovered.

[0161] In turn, the spent wash solution is preferably separated from the purified lithium hydroxide monohydrate crystals and returned to the crystal washing step or to the step of regenerating the resin for conveyance to the purification step, or to the crystallization step, or a portion of the spent wash solution is returned as a recycle solution to two or all three of these steps.

[0162] It is particularly preferred to return at least a portion of this spent scrubbing solution (or crystallization mother liquor) to the regeneration step, since this solution is relatively pure and contains uncrystallized lithium hydroxide that should be reused, in particular, in a step upstream of crystallization or in crystallization. Therefore, regeneration 33 is an option for recycling.

[0163] Reference numerals

[0164] The following is shown as Figures 1 to 6Reference numerals according to embodiments of the present invention used in (some of these devices and lines are optional):

[0165] 1 Pulping unit

[0166] 101 Feed inlet for supplying fresh feed to pulping unit 1

[0167] 102 Slurry pipeline for transporting the first slurry from the pulping unit 1 to the first leaching unit 2

[0168] 2. The first leaching unit

[0169] 203 Slurry pipeline for transporting the second slurry from the first leaching unit 2 to the second leaching unit 3

[0170] 21 Solid-liquid separation unit

[0171] 211 Recirculation line from separation unit 21 to pulping unit 1

[0172] 212 Recirculation line from separation unit 21 to first leaching unit 2

[0173] 3. Second leaching unit

[0174] 30 Slurry unit for mixing alkaline earth metal hydroxide into aqueous slurry

[0175] 303 is used to supply alkaline earth metal hydroxide or its aqueous solution to the inlet of the second leaching unit 3

[0176] 304 Liquid pipeline for conveying the third slurry directly from the second leaching unit 3 or from the separation unit 31 to the crystallization unit 4 or conveying the third slurry to the purification unit 32 or the optional regeneration unit 33

[0177] 31 Solid-liquid separation unit

[0178] 313 Recirculation line for conveying the solution obtained from the separation unit 31 to the second leaching unit 3 or to the optional slurry unit 30

[0179] 32 Purification unit downstream of S / L separation unit 31 and upstream of crystallization unit 4

[0180] 323 Recycle line for conveying the recycle stream from the purification unit 32 to the second leaching unit 3

[0181] 33 Regeneration unit

[0182] 332 Recycle line for conveying the regeneration stream from the regeneration unit 33 to the purification unit 32

[0183] 4 Crystallization unit

[0184] 403 Recirculation line from the crystallization unit 4 or the separation unit 41 to the second leaching unit 3

[0185] 41 Solid-liquid separation unit

[0186] 414 A recycle line from a downstream point of the crystallization unit 4 or from the separation unit 41 back to the crystallization unit 4

[0187] 42 Lithium Precipitation Unit

[0188] 421 Recirculation line from crystallization unit 4, optionally via separation unit 41 or precipitation unit 42, to pulping unit 1

[0189] 421a Recirculation line from crystallization unit 4 through precipitation unit 42 to pulping unit 1

[0190] 422 Recirculation line from the crystallization unit 4, optionally via the separation unit 41 or the precipitation unit 42, to the first leaching unit 2

[0191] 422a Recirculation line from the crystallization unit 4 through the precipitation unit 42 to the first leaching unit 2

[0192] 423 Slurry pipeline for transporting the reaction slurry from the crystallization unit 4 or the separation unit 41 to the lithium precipitation unit 42

[0193] 424 Feed inlet for supplying carbon dioxide or alkali metal carbonate to precipitation unit 42

[0194] 43 Purification or washing unit

[0195] 431 Feed inlet for supplying washing solution to the purification or washing unit 43

[0196] 432 Recycle line for conveying spent scrubbing solution to upstream purification unit 32 or to optional regeneration unit 33

[0197] 44 Solid-liquid separation unit

[0198] 444 Recycle line for conveying the waste solution from the purification unit 43 or the separation unit 44 to the crystallization unit 4

[0199] 445 Recycle line for conveying waste solution from purification unit 43 or separation unit 44 to purification or washing unit 43

[0200] 45 Drying unit

[0201] 451 Product outlet for lithium hydroxide monohydrate for crystallization and optional purification and drying

[0202] It is obvious to a person skilled in the art that as technology advances, the inventive concept can be implemented in various ways.The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

[0203] Example

[0204] Example 1

[0205] Batch tests of leaching and recycling were conducted by adding solid lithium carbonate to the β-spodumene slurry and treating the obtained mixture in an autoclave leaching step, followed by a second leaching step, as follows:

[0206] A 700 g batch of calcined β-spodumene material with a 3.0% Li content, 178 g of sodium carbonate and another 7 g of solid lithium carbonate were mixed with water to form a slurry with a total volume of 2.8 liters. The slurry was added to a 1 gallon autoclave and treated at 220° C. for two hours. The autoclave contents were cooled and then the slurry was filtered. A portion of 225.93 g of pressure leached filter cake and 25 g of calcium oxide were slurried and mixed with 0.63 l of deionized water to form a slurry with a total volume of 0.75 l. The slurry was treated at ambient temperature for 1 h and finally separated from the solid and liquid by filtration, and the filter cake was washed with water. The contents of the solid and solution were analyzed. The solid residue contained 0.16% Li and the solution had a Li content of 6.7 g / l. The contents of the solution are described in detail in Table 1 below.

[0207] The lithium recovery / yield of the solution was excellent, approximately 93%, so recycling this solution to the early steps of the process is highly beneficial.

[0208] Based on these results it is also clear that further purification steps, for example by ion exchange, may be included in the process, particularly for the removal of impurity metals such as calcium.

[0209]

Claims

1. A device for recovering lithium hydroxide from a fresh feed in combination with a recirculating solution and / or slurry containing lithium, the fresh feed comprising a mineral raw material containing lithium or a raw material containing lithium carbonate or a mixture of these raw materials, the device comprising - a slurrying unit for slurrying the feed in the presence of water and an alkali metal carbonate so as to form a first slurry containing lithium, a first leaching unit for leaching said first slurry containing lithium, optionally in combination with a recycled solution and / or slurry, at an elevated temperature so as to form a second slurry containing lithium carbonate, - a second leaching unit for leaching said second slurry containing lithium carbonate or a portion thereof in the presence of water and an alkaline earth metal hydroxide so as to form a third slurry containing lithium hydroxide, - a first solid-liquid separation unit, used for separating the third slurry containing lithium hydroxide into a discardable solid and a solution containing lithium hydroxide, - a crystallization unit for recovering lithium hydroxide monohydrate from a solution containing lithium hydroxide, - a second solid-liquid separation unit connected to the crystallization unit, and - one or more first recirculation lines for conveying the solution and / or slurry from the crystallization unit to the slurry unit and optionally to the first leaching unit, and - a lithium precipitation unit connected to the liquid section of the second solid-liquid separation unit via a pipeline, wherein the liquid section of the second solid-liquid separation unit is connected to the crystallization unit, The one or more first recirculation lines are arranged between the lithium precipitation unit and the pulping unit and optionally between the lithium precipitation unit and the first leaching unit, a separate second recirculation line is provided which leads to the pulping unit via the precipitation unit, and optionally a separate third recirculation line is provided which leads to the first leaching unit via the precipitation unit.

2. The apparatus according to claim 1, further comprising a calcining unit for thermally treating the mineral raw material to be conveyed as at least part of the feed to the pulping unit.

3. The apparatus according to claim 1, wherein the first leaching unit is a pressure autoclave.

4. The apparatus according to claim 1, wherein the first leaching unit is connected to the pulping unit through a slurry pipeline.

5. The apparatus according to claim 1, wherein a third solid-liquid separation unit is arranged between the first leaching unit and the second leaching unit, and an optional washing unit or a washing section within the third solid-liquid separation unit is used to wash the solid separated from the liquid in the third solid-liquid separation unit.

6. The apparatus according to claim 1 or 5, comprising a fourth recirculation line leading from the first leaching unit or from the liquid section of a third solid-liquid separation unit connected to the first leaching unit to a pulping unit upstream of the first leaching unit.

7. The apparatus according to claim 1 or 5, comprising a fourth recirculation line, which is connected to the first leaching unit or to the first leaching unit as a pipeline to the pulping unit or as a pipeline to the first leaching unit, or as a separate pipeline and to each of the pulping unit and the first leaching unit.

8. The apparatus according to claim 1 or 5, comprising a fourth recirculation line leading from the first leaching unit or from a liquid section of a third solid-liquid separation unit connected to the first leaching unit to the pulping unit.

9. The apparatus of claim 1, wherein the second leaching unit is a tank reactor.

10. The apparatus of claim 1, wherein the second leaching unit is a stirred tank reactor.

11. The apparatus of claim 1, wherein the second leaching unit comprises an inlet for an alkaline earth metal hydroxide or an aqueous slurry thereof.

12. The apparatus of claim 1, wherein the second leaching unit is connected to a slurrying unit for mixing the alkaline earth metal hydroxide into an aqueous slurry.

13. The apparatus according to claim 1 or 5, wherein the second leaching unit is connected to the first leaching unit or the downstream third solid-liquid separation unit through a slurry pipeline.

14. The apparatus according to claim 1, wherein the first solid-liquid separation unit located downstream of the second leaching unit is connected to the washing unit or includes a washing section in the first solid-liquid separation unit for washing the solid separated from the liquid in the first solid-liquid separation unit.

15. The apparatus according to claim 1, comprising a purification unit connected to the first solid-liquid separation unit, for purifying the solution obtained from the first solid-liquid separation unit.

16. The apparatus of claim 15, wherein the purification unit comprises one or more of an ion exchange unit and a membrane separation unit.

17. The apparatus of claim 15, wherein the purification unit comprises at least one or more ion exchange units.

18. The device of claim 15, wherein the purification unit comprises at least one or more cation exchange units.

19. The device of claim 18, wherein the one or more cation exchange units contain a selective cation exchange resin.

20. The apparatus of claim 15, wherein the purification unit is an ion exchange unit or a series of two or more ion exchange units and is connected to a regeneration unit or a series of two or more regeneration units for regenerating the purification resin, wherein a pipeline is connected between the purification unit and the regeneration unit for returning the regenerated resin to the ion exchange unit.

21. The apparatus according to claim 15, wherein the purification unit is a membrane separation unit connected to the crystallization unit by supplying the purification solution to the crystallization unit and connected to the second leaching unit through a fifth recycle line for returning the recycle stream to the leaching step.

22. The apparatus of claim 15, wherein the purification unit is a combination of a membrane separation unit and an ion exchange unit, wherein the membrane separation unit has an outlet connected to an inlet of the ion exchange unit.

23. The apparatus of claim 1 comprising two or more crystallization units.

24. The apparatus according to claim 23, wherein two or more crystallization units are arranged in series.

25. The apparatus according to claim 1, 15 or 20, wherein the crystallization unit or the downstream purification unit or the downstream regeneration unit is connected to the first solid-liquid separation unit located downstream of the second leaching unit via a liquid pipeline.

26. The apparatus of claim 1, wherein a pre-concentration unit precedes the crystallization unit and is designed to provide a crystallization feed having an optimized concentration.

27. The apparatus of claim 26, wherein the pre-concentration unit is in the form of an evaporation unit.

28. The apparatus according to claim 1, comprising a sixth recirculation line arranged between the crystallization unit and / or the liquid section of the second solid-liquid separation unit connected to the crystallization unit and the second leaching unit.

29. The apparatus of claim 1, wherein the lithium precipitation unit comprises a feed inlet for supplying carbon dioxide or alkali metal carbonate or a mixture of these to the unit.

30. The apparatus according to claim 1, wherein the liquid section of the second solid-liquid separation unit is connected to the crystallization unit via a first recycle line, optionally via a crystallization feed device, for recycling a portion of the waste solution separated from the crystallization step back to the crystallization unit.

31. The apparatus according to claim 1, comprising a product purification unit connected to the crystallization unit and / or to a second solid-liquid separation unit connected to the crystallization unit, wherein the solid obtained in the crystallization step can be purified.

32. The apparatus of claim 31 , wherein the product purification unit comprises a feed inlet for supplying a wash solution to the product purification unit.

33. The apparatus of claim 32, wherein the feed inlet is connected to a seventh recirculation line.

34. The apparatus of claim 31, comprising a fourth solid-liquid separation unit connected to and downstream of the product purification unit for separating purified lithium hydroxide monohydrate crystals from the spent scrubbing solution.

35. The apparatus according to claim 31 or 34, wherein the product purification unit or the fourth solid-liquid separation unit connected to the product purification unit and downstream of the product purification unit is connected to the upstream purification unit or to the optional regeneration unit connected to the upstream purification unit through an eighth recycle line.

36. The apparatus according to claim 31 or 34, wherein a fourth solid-liquid separation unit connected to and downstream of the product purification unit is connected to the crystallization unit via a ninth recycle line.

37. The apparatus according to claim 31 or 34, wherein a fourth solid-liquid separation unit connected to the product purification unit and downstream of the product purification unit is connected to the product purification unit through a seventh recirculation line.

38. The apparatus according to claim 1, comprising a combined product purification unit for purifying the crystals obtained from the spent solution in the crystallization unit and separating the purified crystals from the spent wash solution.

39. The apparatus according to claim 38, wherein the combined product purification unit is connected to the crystallization unit via a first recycle line for returning the spent solution separated from the crystallization step as a recycle solution to the crystallization unit.

40. The apparatus of claim 38, wherein the combined product purification unit comprises a feed inlet for supplying a wash solution to the unit.

41. The apparatus according to claim 38, wherein the combined product purification unit is connected to an upstream purification unit or to a separate regeneration unit via an eighth recycle line.

42. The apparatus of claim 38, wherein the combined product purification unit is connected to the crystallization unit via a ninth recycle line.

43. The apparatus of claim 38, wherein the solid section of a combined product purification unit is connected to the liquid section of the same combined unit via a tenth recycle line.

44. The apparatus according to claim 1, comprising a drying unit connected to the crystallization unit or to the solid section of the third solid-liquid separation unit or the fourth solid-liquid separation unit downstream of the crystallization unit or to the solid section of the combined product purification and separation unit downstream of the crystallization unit, wherein the obtained lithium hydroxide monohydrate crystals can be dried.

45. Apparatus according to claim 44, wherein the drying unit comprises a product outlet through which the final product can be recovered.

46. ​​A process for recovering lithium hydroxide from a fresh feed comprising a lithium-containing mineral raw material or a raw material containing lithium carbonate or a mixture of these in combination with a recirculating solution and / or slurry containing lithium, wherein the process comprises - slurrying a lithium-containing feed in the presence of water and an alkali metal carbonate for producing a first slurry containing lithium, - leaching a first slurry containing lithium, optionally in combination with a recycled solution and / or slurry, at elevated temperature in a first leaching step for producing a second slurry containing lithium carbonate, - leaching the second slurry or a portion thereof in an aqueous solution containing an alkaline earth metal hydroxide in a second leaching step to produce a third slurry containing lithium hydroxide, - separating the third slurry into a discardable solid and a solution containing lithium hydroxide by solid-liquid separation, - recovering lithium hydroxide monohydrate by crystallization from a solution containing lithium hydroxide, and - separating the solution and / or slurry obtained during the crystallization process from the crystallization process and returning it as a recirculating solution and / or slurry to the pulping step and optionally also to the first leaching step, wherein at least a portion of the solution separated from the crystallization step is conveyed to a lithium precipitation step, wherein the solution is reacted with carbon dioxide or a mixture of carbon dioxide and an alkali metal carbonate to form a lithium carbonate slurry, which is recycled to the pulping step and optionally to the first leaching step, and wherein the recycled slurry and / or solution is passed to the pulping step and optionally to the first leaching step via the precipitation step.

47. A method according to claim 46, wherein the mineral raw material used as at least part of the feed to the slurrying step is a lithium-containing mineral in calcined form.

48. The method according to claim 47, wherein the lithium-containing mineral in calcined form is obtained by heat treating the raw material using a temperature of 900-1200°C.

49. The method according to claim 47, wherein the lithium-containing mineral in calcined form is obtained by heat treating the raw material at a temperature of 1000-1100°C.

50. The method of claim 46, wherein the mineral raw material used in the pulping step is selected from spodumene, petalite, lepidolite, mica or clay, or mixtures thereof.

51. The method of claim 46, wherein the mineral raw material used in the pulping step is spodumene.

52. The method of claim 46, wherein the mineral raw material used in the pulping step is beta-spodumene.

53. A process according to claim 46, wherein the raw material containing lithium carbonate is newly added raw material or is recycled from a subsequent step of the process.

54. A process according to claim 53, wherein at least a portion of the raw material containing lithium carbonate is recycled from the crystallization step.

55. The method of claim 46, wherein at least a portion of the water and alkali metal carbonate sent to the pulping step is a recycled aqueous solution containing the alkali metal carbonate.

56. The method of claim 46, wherein the alkali metal carbonate used in the pulping step is selected from the group consisting of sodium carbonate and potassium carbonate.

57. The method of claim 46, wherein the alkali metal carbonate used in the pulping step consists at least in part of sodium carbonate.

58. The method of claim 46, wherein the first leaching step is performed at a temperature of 160 to 250°C.

59. The method of claim 46, wherein the first leaching step is performed at a temperature of 200 to 220°C.

60. The method of claim 46, wherein the first leaching step is performed at a pressure of 10 to 30 bar.

61. The method of claim 46, wherein the first leaching step is performed at a pressure of 15 to 25 bar.

62. A method according to any one of claims 46 or 58 to 61 wherein high pressure steam is used to achieve suitable conditions for the first leaching step.

63. The process of claim 46, wherein after the first leaching step the solution is separated from the solids in a separate solid-liquid separation step and the solids are conveyed to a second leaching step, optionally after washing the solids.

64. The method of claim 46, wherein the solution is separated from the solids after the first leaching step and the solution is returned as a recycle solution to the pulping step or the first leaching step, or a portion of each step.

65. The method of claim 64, wherein the solution is returned to the pulping step.

66. The process of claim 46, wherein the alkaline earth hydroxide used in the second leaching step is selected from calcium hydroxide and barium hydroxide.

67. The process of claim 46, wherein the alkaline earth metal hydroxide used in the second leaching step is calcium hydroxide.

68. The process of claim 46, wherein the alkaline earth metal hydroxide used in the second leaching step is mixed with water or an aqueous solution before being added to the second leaching step.

69. The method of claim 46, wherein at least a portion of the solution separated from the solids in the solid-liquid separation of the third slurry is added to the second leaching step in the form of a recycled solution.

70. The process of claim 69 wherein the recirculating solution is mixed with fresh alkaline earth metal hydroxide before being added to the second leaching step.

71. A process according to claim 70, wherein the recirculating solution is mixed with fresh alkaline earth metal hydroxide in a separate slurrying step.

72. The method of claim 46, wherein the solids obtained from the solid-liquid separation of the third slurry are washed.

73. The method of claim 72, wherein at least a portion of the spent wash solution is combined with solution separated from solids in the solid-liquid separation of the third slurry.

74. The method of claim 46, wherein the second leaching step is performed at a temperature of 10-100°C.

75. The process of claim 46, wherein the second leaching step is carried out at a temperature of 20-60°C.

76. The process of claim 46, wherein the second leaching step is carried out at a temperature of 20-40°C.

77. The method of claim 46, wherein the second leaching step is performed at atmospheric pressure.

78. The method of claim 46, wherein a step of purifying the solution obtained from the third slurry is performed, the step comprising purification based on purification of dissolved ions and components.

79. The method of claim 78, wherein the purification based on purification of dissolved ions and components is ion exchange or membrane separation or both.

80. The method of claim 46 or 78, wherein the step of purifying the solution obtained from the third slurry is performed by ion exchange.

81. The method of claim 80, wherein the ion exchange is performed by using a cation exchange resin.

82. The method of claim 80, wherein the ion exchange is performed by using a selective cation exchange resin.

83. The process of claim 80, wherein the ion exchange is performed at least partially using a purification resin that has been regenerated in a separate regeneration step, the regenerated resin being returned to the ion exchange.

84. The method of claim 83, wherein the regeneration step is performed using a recycled solution from a subsequent process step.

85. The process of claim 84, wherein the recycled solution is a separated solution obtained from a crystallization or from a subsequent washing step.

86. The process of claim 46 or 78, wherein the step of purifying the solution obtained from the third slurry is performed by membrane separation, whereby the membrane separation produces a purified stream that is sent to the crystallization step and a recycle stream.

87. The process of claim 86, wherein the recycle stream is sent to a second leaching step.

88. The method according to claim 46 or 78, wherein the step of purifying the solution obtained from the third slurry is carried out by first performing a membrane separation and by sending the thus purified solution to an ion exchange step for further purification.

89. The method of claim 46, wherein the crystallization of lithium hydroxide monohydrate is carried out by heating a solution containing lithium to a temperature at the boiling point of the solution.

90. The process of claim 46, wherein the pre-concentration step precedes the crystallization of lithium hydroxide monohydrate.

91. A method according to claim 90, wherein the pre-concentration step is performed as evaporation for dispersing excess liquid from the solution containing lithium.

92. The process of claim 46, wherein the crystallization of lithium hydroxide monohydrate is carried out in two or more crystallization units.

93. The method of claim 92, wherein the two or more crystallization units are arranged sequentially.

94. A process according to claim 46, wherein the solution containing lithium hydroxide is mixed with one or more solutions recycled from subsequent steps of the process before being sent to the crystallization step, or they are all fed separately to the crystallization step.

95. The process of claim 46, wherein at least a portion of the solution separated from the crystallization step is returned to the second leaching step as a recycle solution.

96. The method of claim 46, wherein at least a portion of the solution separated from the crystallization step is returned as a recycle solution to one or both of the pulping step and the first leaching step.

97. The method of claim 46, wherein the lithium precipitation step is performed by carbonation.

98. The method of claim 46, wherein the lithium precipitation step is carried out by reacting the solution sent to the lithium precipitation step with carbon dioxide or a mixture of carbon dioxide and an alkali metal carbonate to form a lithium carbonate slurry.

99. A process according to claim 97, wherein precipitation is carried out with carbonation in an incomplete reaction whereby at least trace amounts of lithium hydroxide will still be present in the lithium carbonate slurry.

100. A method according to claim 97 or 99, wherein the slurry comprising lithium carbonate is recycled to the slurrying step.

101. The process according to claim 46, wherein a portion of the solution separated from the crystals obtained after the crystallization step is returned to the crystallization step as a recirculation solution.

102. The process of claim 46, wherein the solid containing lithium hydroxide monohydrate crystals obtained in the crystallization step is purified using a washing solution before being recovered as a product.

103. The process of claim 102, wherein the purified lithium hydroxide monohydrate crystals are separated from the wash solution, dried and subsequently recovered.

104. A process according to claim 102, wherein the spent wash solution is separated from the purified lithium hydroxide monohydrate crystals and returned as a recycle solution to the crystal washing step or to the step of purifying the solution separated from the third slurry or to the regeneration step prior to said purification step or to the crystallization step, or a portion of the spent wash solution is returned to two or more of these steps.

105. The method of any one of claims 46 to 104, performed using the apparatus of any one of claims 1 to 45.

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