Post processing in a system and process for extracting lithium enriched eluates from an untreated brine

Abstract

The present invention relates to a system (10) for extracting lithium or lithium salts from an untreated brine (30). The system comprises a feed unit (40) for receiving the untreated brine (30) and a direct lithium extraction unit (50) for extracting a lithium enriched eluate (60) from the untreated brine and a foreign ion removal unit (56) for removing foreign ions from the lithium enriched eluate (60). Additionally, a membrane purification unit (55) is arranged downstream between the direct lithium extraction unit (50) and the foreign ion removal unit (56), for increasing the concentration of the lithium or lithium salts in the lithium enriched eluate (60). The present invention further relates to a process for extracting lithium or lithium salts from an untreated brine (30).

Description

[0001] 30 April 2024

[0002] Vulcan Energie Ressourcen GmbH

[0003] Post processing in a system and process for extracting lithium enriched eluates from an untreated brine

[0004] The present invention relates to a system for extracting lithium or lithium salts from an untreated brine. The present invention further relates to a process for extracting lithium or lithium salts from an untreated brine.

[0005] Several brine sources exist naturally. For instance, brine sources include brine deposits like the Salar de Atacama in Chile, Silver Peak Nevada, Salar de Uyuni in Bolivia, or the Salar de Hombre Muerte in Argentina. Other common brine sources are geothermal, oilfield, Smackover, and relict hydrothermal brines. Processes for commercially exploiting these types of geothermal brines are described in US 9,644,126 B2.

[0006] Geothermal brines are of particular interest for a variety of reasons. First, geothermal brines provide a source of power due to the fact that hot geothermal pools are stored at high pressure underground, which, when released to atmospheric pressure, can provide a flash-steam. The flash-steam can be used, for example, to run a power plant. Additionally, geothermal brines contain useful elements, which can be recovered and utilized for secondary processes. In some geothermal waters and brines, binary processes for example organic rankine cycle processes, can be used to heat a second fluid to provide steam for the generation of electricity without the flashing of the geothermal brine.

[0007] Geothermal brines, in particular untreated brines, originating in the Upper Rhine Valley region typically exit a borehole at around 165°C, while geothermal brines originating in the Salton Sea area exit the borehole at around 350°C. Herein, geothermal brines exiting the borehole at more than 255°C are called high-energy brines and are sometimes referred to as Salton Sea or Salton Sea derived brines, while geothermal brines exiting the borehole at or below 255°C are called low-energy brines and are sometimes referred to as Upper Rhine Valley brines, or Upper Rhine Valley derived brines. The methods previously disclosed for the treatment and lithium extraction of high-energy brines, such as those found in the Salton Sea regions, are often not suitable for processing low-energy brines because of the differences in the mineral compositions resulting at least in part from the differences in temperature of the raw brines at the borehole. Because of the lower exit temperature, the low-energy brines do not have the high amounts of iron, manganese and zinc that cause the precipitation of silica components during the operation known as steam flashing. In the case of the low-energy brines, reducing the pressure of the raw brine either does not cause steam to flash off, or a reduced amount of steam is flashed off, and the dissolved solids in many cases tend to remain in solution, or are only partially precipitated.

[0008] One problem associated with extracting lithium from geothermal brines is that known processes require a costly and complex pre-treatment of the brines. Additionally, known processes are often time consuming.

[0009] Thus, novel processes are needed to allow for an improved processing, especially of low-energy brines, to allow for the improved extraction of valuable minerals such as lithium. In particular, it is desired to provide a simpler, cheaper and faster approach. Furthermore, it is desired to maintain the possibility to reinject the depleted geothermal brine into a geothermal reservoir after the lithium extraction. In view of the above, the invention is defined by the subject matter with the features of the independent claims.

[0010] A first aspect of the present invention relates to a system for extracting lithium or lithium salts from an untreated brine, comprising: a feed unit for receiving the untreated brine; a direct lithium extraction unit for extracting a lithium enriched eluate from the untreated brine; and a foreign ion removal unit for removing foreign ions and yielding a purified eluate comprising the lithium or lithium salts; wherein a membrane purification unit is arranged downstream between the direct lithium extraction unit and the foreign ion removal unit, for increasing the concentration of the lithium or lithium salts in the lithium enriched eluate.

[0011] Another aspect of the present invention relates to a process for extracting lithium or lithium salts from an untreated brine, comprising the steps of: providing a feed unit, a direct lithium extraction unit, a foreign ion removal unit and a membrane purification unit, wherein the membrane purification unit is arranged downstream between the direct lithium extraction unit and the foreign ion removal unit; receiving the untreated brine in the feed unit; extracting a lithium enriched eluate from the untreated brine via the direct lithium extraction unit; increasing the concentration of the lithium or lithium salts in the eluate via the membrane purification unit; and removing foreign ions and yielding a purified eluate comprising the lithium or lithium salts via the foreign ion removal unit.

[0012] A preferred aspect relates to a system for extracting lithium or lithium salts from an untreated brine, comprising: a feed unit for receiving the untreated brine; and a direct lithium extraction unit for extracting a lithium enriched eluate from the untreated brine; wherein a pressure control unit is arranged downstream between the feed unit and the direct lithium extraction unit and / or downstream of the direct lithium extraction unit for controlling the pressure in the direct lithium extraction unit.

[0013] Another preferred aspect relates to a process for extracting lithium or lithium salts from an untreated brine, comprising the steps of: providing a feed unit, a direct lithium extraction unit and a pressure control unit, arranged downstream between the feed unit and the direct lithium extraction unit and / or downstream of the direct lithium extraction unit; receiving the untreated brine in the feed unit; extracting a lithium enriched eluate from the untreated brine via the direct lithium extraction unit; and controlling a pressure in the direct lithium extraction unit via the pressure control unit.

[0014] Preferred embodiments of the invention are defined in the dependent claims. It shall be understood that the claimed process has similar and / or identical preferred embodiments as the claimed system, in particular as defined in the dependent claims and as disclosed herein.

[0015] The present invention is in particular based on the idea of directly injecting the untreated brine, preferably a geothermal brine, more preferably a low-energy geothermal brine, into the direct lithium extraction unit. Favourably, the untreated brine is provided to the direct lithium extraction unit without employing a pre-treatment circuit. Advantageously, the untreated brine is explicitly differentiated from a pre-treated brine.

[0016] The untreated brine is received via the feed unit, which can particularly be suitable for receiving the untreated brine from a geothermal reservoir. Preferably, the untreated brine is received from a geothermal power plant.

[0017] The term “lithium” particularly comprises lithium species, such as for example lithium cations, which may be for example dissolved in an aqueous solution or adsorbed to a sorbent material. The term “lithium salts” particularly comprises lithium chloride, preferably dissolved in the aqueous solution, but alternatively also solid lithium chloride and other combinations of lithium cations with anions. The term “foreign ions” particularly comprises non-lithium species, such as cations other than lithium cations and / or anions.

[0018] Advantageously, the lithium enriched eluate undergoes further purification steps, which lead to a higher concentration of lithium species and / or a higher purity, meaning a lower amount of non-lithium impurities in the lithium enriched eluate, such as foreign ions. In other words, the lithium enriched eluate is not limited to the aqueous solution comprising lithium species after the direct lithium extraction, but may also include eluates comprising lithium species after posttreatment steps. Therefore, the lithium enriched eluate of an upstream treatment step may be the feed for a subsequent downstream treatment step. The lithium enriched eluate forms the basis for extracting lithium or lithium salts. The lithium extraction unit may be realized as a lithium extraction circuit.

[0019] In comparison to previous approaches for extracting lithium or lithium salts from a brine, the approach of the present invention allows a more efficient and faster processing of low-energy brines at reduced costs. Additionally, it becomes possible to efficiently extract lithium or lithium salts at low environmental impact. The amount of energy consumption and waste is reduced since the pre-treat- ment of the brine is no longer required. It is to the contrary of previous research findings that the pre-treatment of the brine can be avoided. Nevertheless, in order to facilitate the downstream processing of the lithium enriched eluate for selectively isolating and purifying the desired lithium or lithium salts a specialized and tailored system and process is required. Advantageously, the combination of the membrane purification unit and ion removal unit, wherein the membrane purification unit is arranged downstream between the direct lithium extraction unit and the foreign ion removal unit, allows for enhancing the efficiency of the purification and the resulting purity of the lithium enriched eluate. Additionally, this setup allows for minimizing waste and promoting a more sustainable and resource-efficient approach to lithium extraction.

[0020] In a preferred embodiment a pressure control unit for controlling the pressure in the direct lithium extraction unit is comprised. Favourably, the pressure control unit is arranged downstream between the feed unit and the direct lithium extraction unit and / or downstream of the direct lithium extraction unit. Importantly, the pressure control unit allows for a more homogeneous and reproducible flow of the untreated brine through the direct lithium extraction unit, thereby resulting in a more efficient direct lithium extraction process so that higher yields can be achieved and costs can be reduced. In particular, a gas pressure, more particular a CO2 pressure, is not released from the untreated brine but instead reinjected into the depleted geothermal brine.

[0021] In particular, the pressure control unit is directly arranged downstream between the feed unit and the direct lithium extraction unit and / or directly downstream of the direct lithium extraction unit, rather than being arranged upstream before the feed unit. Favourably, the pressure control unit comprises a first pressure control unit, which is arranged between the feed unit and the direct lithium extraction unit and a second pressure control unit, which is arranged downstream of the direct lithium extraction unit. The second pressure control unit is favourably configured for regulating the pressure after the lithium extraction unit. The second pressure control unit may be used as an additional repressurization unit for repressurizing the lithium enriched eluate and / or the depleted geothermal brine. However, preferably an additional production pressure control unit is comprised by the system, wherein said production pressure control unit is more preferably arranged upstream before the feed unit, in particular inside the borehole.

[0022] In a preferred embodiment, the pressure control unit includes or consist of a pump. The pump is advantageously a low pulsation pump. Particularly, the pump is a centrifugal pump or a progressive cavity pump. Alternatively, or additionally, the pressure control unit comprises or consists of a conduit pressurized by a geodetic height difference and / or a pressure control tank. In particular, the pressure control unit includes a pressure reducing valve and a downstream pressure regulating valve. The pressure control unit advantageously allows modifying the pressure of the untreated brine for adjusting the pressure to optimal lithium extraction parameters. The first pressure control unit and the second pressure control unit may be constructed identically or different from each other. For example, the first pressure control unit may be a low pulsation pump and the first pressure control unit may be a downstream pressure regulating valve. The first pressure control unit and the second pressure control unit are preferably constructed as separate units, comprised by the system. The first pressure control unit and the second pressure control unit are favourably configured to operate independently of one another or dependent from each other, for controlling the pressure.

[0023] Preferably, the feed unit is configured to receive the untreated brine at a temperature of 65°C to 85°C and at a pressure of 15-30 bar. In particular, the feed unit can be configured to receive a geothermal brine from the geothermal power plant.

[0024] Preferably, a fluid tight transfer line is arranged downstream between the feed unit and the direct lithium extraction unit for directly transferring the untreated brine from the feed unit to the direct lithium extraction unit, more preferably without degassing. Advantageously, transferring the untreated brine without degassing enhances the efficiency of the direct lithium extraction unit, for example because the pressure and the temperature of the untreated brine are higher. By supplying the pressurized untreated brine into the direct lithium extraction unit, a more homogenous flow through the direct lithium extraction unit can be achieved. Moreover, costs for the otherwise necessary pre-treatment and posttreatment of the solids removed by the pre-treatment are saved, rendering the lithium extraction more economic. In addition, avoiding gas release, which mainly comprises CO2, avoids undesired greenhouse gas emissions.

[0025] In a preferred embodiment a heat exchanger, which is preferably configured for adjusting the temperature of the untreated brine in the feed unit before entering the direct lithium extraction unit and / or in the direct lithium extraction unit, is comprised. In particular, the heat exchanger is configured for adjusting the temperature of the untreated brine to a temperature from 20 °C to 90 °C, preferably from 50 °C to 80 °C. Advantageously, the heat exchanger allows for a homogeneous and reproducible temperature of the untreated brine before entering the direct lithium extraction unit, which is particularly important for controlling the solubility of salts and other dissolved species in the untreated brine in order to avoid undesired precipitation of solids in the direct lithium extraction unit, thereby minimizing maintenance costs and increasing performance. Additionally, controlling the temperature of the untreated brine allows to optimize the temperature parameter for the direct lithium extraction process, resulting in a more efficient process and leading to increased yields.

[0026] In a preferred embodiment the direct lithium extraction unit comprises a column for holding the sorbent material. It is preferred that a pressure at the column is from 1 bar to 40 bar, preferably from 15 bar to 30 bar, more preferably from 16 bar to 28 bar and / or a flowrate through the column is from 1 m3per hour to 500 m3per hour, preferably from 200 m3per hour to 350 m3per hour, more preferably from 280 m3per hour to 300 m3per hour, most preferably 293 m3per hour. Pressurizing the untreated brine onto the column in the aforementioned range or ranges advantageously increases the efficiency of the lithium extraction, for example leading to a more homogenous flow through the sorbent material. The selection of a flow rate in the aforementioned range allows for a particularly efficient lithium extraction, considering both yields and throughput.

[0027] Preferably, the sorbent material comprises a plurality of sorbent granules and particularly has a bed porosity of 0.35 to 0.4. In particular, the sorbent material is a lithium-aluminate-based sorbent such as VULSORB®. The direct lithium extraction unit can temporarily function as eluate extraction unit configured to remove the lithium or lithium salts from the sorbent material by contacting the sorbent material with water or water containing low levels of lithium chloride. In particular the sorbent material can be flushed so that the lithium or lithium salt is washed out. The lithium enriched eluate is thereby obtained.

[0028] In a preferred embodiment the lithium enriched eluate comprises more than 600 mg / L but less than 2500 mg / L lithium, in particular more than 1500 mg / L but less than 2500 mg / L lithium, more than 50 mg / L but less than 1200 mg / L sodium, more than 10 mg / L but less than 200 mg / L potassium, less than 200 mg / L magnesium, more than 100 mg / L but less than 600 mg / L calcium, more than 5 mg / L but less than 40 mg / L strontium, less than 10 mg / L boron, iron, manganese, and zinc, less than20 mg / L silica, more than 90 mg / L sulfate, less than 10 g / L total dissolved solids, and having an oxidation reduction potential of less than 0.

[0029] In a preferred embodiment a first filter unit for filtering the untreated brine, preferably before entering the pressure control unit, especially the first pressure control unit and / or the second pressure control unit, for removing solid particles is comprised. In particular, the first filter unit is comprising or consisting of a candle filter or an edge gap filter, preferably made from duplex steel or a polymer material. The first filter unit preferably has a mesh size from 1 pm to 200 pm, more preferably from 10 pm to 80 pm, most preferably 50 pm. Advantageously, removing of solid particles protects the pressure control unit from damages or malfunctions and thereby decreases the maintenance costs.

[0030] In a preferred embodiment a second filter unit, preferably for filtering the untreated brine before entering the direct lithium extraction unit, and / or after exiting the pressure control unit, in particular after exiting the first pressure control unit, for removing solid particles, is comprised. In particular, the second filter has a mesh size smaller than the average gap size of sorbent granules of the direct lithium extraction unit. The second filter unit preferably has a mesh size smaller than the mesh size of the first filter unit. The second filter unit preferably has a mesh size from 1 pm to 100 pm, more preferably from 50 pm to 100 pm. Advantageously, removing solid particles prevents sedimentation of the solid particles on the sorbent granules of the direct lithium extraction unit, thereby decreasing the maintenance costs.

[0031] In a preferred embodiment a dosing unit for supplying the untreated brine with corrosion inhibitors and / or scaling inhibitors and / or oxygen scavengers and / or a base for adjusting the pH of the untreated brine an / or an acid for adjusting the pH of the untreated brine is comprised. The dosing unit is preferably arranged between the feed unit and the direct lithium extraction unit, more preferably between the feed unit and the (first) pressure control unit. The scaling inhibitor is preferably selected from the list consisting of methyolenic phosphonic acid, hydrochloric acid, phosphorous acid or any combination thereof. The corrosion inhibitor is preferably ethylene glycol and / or a fatty acid. The oxygen scavenger is preferably sodium bisulfite. The base is preferably sodium hydroxide, NaOH. The acid is preferably hydrogen chloride, HCL The dosing unit favourably enhances the efficiency of extraction efficiency by further processing of the brine direct before lithium extraction.

[0032] In a preferred embodiment an oil removal unit for removing oil from the untreated brine is comprised. The oil removal unit is preferably arranged upstream of the direct lithium extraction unit, in particular the first pressure control unit, more preferably upstream of the pressure control unit and most preferably between the feed unit and the pressure control unit. The oil removal unit is particularly advantageous, if the untreated brine is contaminated with oil, for example by oil added during production in the geothermal power plant.

[0033] In a preferred embodiment a nano filtration unit for removing silicon compounds and / or silicon species and / or doubly charged ions from the lithium enriched eluate is comprised. The nano filtration unit is preferably arranged downstream after the lithium extraction unit. The nano filtration unit is preferably comprised by the membrane purification unit. Advantageously, removing impurities such as for example silica species, magnesium species, calcium species and / or barium species drastically enhances the processability of the lithium enriched eluate.

[0034] In a preferred embodiment a reverse osmosis unit for removing water from the lithium enriched eluate is comprised. The reverse osmosis unit is preferably arranged downstream after the nano filtration unit and more preferably comprises a plurality of reverse osmosis modules, each equipped with at least one reverse osmosis membrane. The reverse osmosis unit is preferably comprised by the membrane purification unit. The reverse osmosis unit preferably operates at a temperature from 20 °C to 45 °C, more preferably from 25 °C to 35 °C and / or at a pressure from 90 bar to 180 bar, more preferably from 100 bar to 160 bar. Advantageously, applying reverse osmosis leads to increasing the concentration of all ions in the lithium enriched eluate, thereby preferably facilitating downstream processing. In particular, because water was removed by reverse osmosis, smaller scaled process equipment can be used. The system may comprise a plurality of reverse osmosis units, in particular for increasing the concentration of all ions stepwise. Before entering the reverse osmosis unit, the lithium enriched eluate may be first pre-cooled by a heat exchanger and subsequently transferred to a reverse osmosis feed tank. In the reverse osmosis feed tank, the lithium enriched eluate may be further cooled with cooling water via a tank cooler or a heat exchanger arranged inside or in thermal contact with an outlet line of the feed tank, through which the lithium enriched eluate exits the feed tank. Hydrochloric acid or sodium hydroxide may be dosed into the reverse osmosis feed tank to maintain a near-neutral pH level. Sodium bisulfite may be added to the reverse osmosis feed tank to remove oxygen from the lithium enriched eluate. Advantageously, removing oxygen prevents the precipitation of iron salts and manganese salts, in particular on the reverse osmosis membranes.

[0035] In a preferred embodiment a precipitation unit for precipitating impurities from the lithium enriched eluate is comprised. The precipitation unit is preferably arranged downstream after the reverse osmosis unit. Optionally, the foreign ion removal unit comprises the precipitation unit. Particularly, the precipitation unit is configured to add compounds such as slaked lime, Ca(OH)2, and / or sodium hydroxide, NaOH, and / or lithium hydroxide, LiOH, and / or sodium carbonate, Na2CO3, and / or sodium bicarbonate, NaHCOs, or any combination thereof, to the lithium enriched eluate, preferably as a suspension or a solution. Favourably said compounds are added until a pH between 9 and 11 , preferably a pH of 10 is reached. Advantageously, this leads to the precipitation of undesired impurities such as for example calcium silicates. Preferably, the precipitation unit comprises a precipitate filter for removing precipitates formed during the precipitation process after addition of the aforementioned compounds. The precipitate filter optionally includes a candle filter, in particular a self-cleaning candle filter. The use of a candle filter allows an efficient filtering of particles. The precipitate filter particularly comprises or consists of a micropore filter with a pore size from 0.5 pm to 2.5 pm, preferably from 1 pm to 2 pm. Advantageously, filtering off the calcium silicates avoids redissolving in subsequent downstream processing.

[0036] In a preferred additional and subsequent precipitation step Na2CC>3, preferably as a solution, is added after micropore filtration, in particular such, that a 1.2 molar excess of Na2CC>3with respect to the calcium concentration in the lithium enriched eluate is reached. Favourably, said additional precipitation step leads to precipitation of impurities such as for example calcium carbonate, CaCOs, which is removed by an additional precipitate filter such as a cake filter, with a pore size from 5 pm to 20 pm, preferably from 10 pm to 15 pm.

[0037] In a preferred embodiment the precipitation unit is configured for adding Na2CC>3, preferably as a solution, in a first step, in particular such, that a 1.2 molar excess of Na2CC>3with respect to the calcium concentration in the lithium enriched eluate is reached, advantageously leading to the precipitation of impurities such as for example calcium carbonate, CaCOs, and other carbonates, which are preferably removed micropore filtration or cake filtration, in particular with a pore size from 5 pm to 20 pm, preferably from 10 pm to 15 pm.

[0038] In a preferred embodiment the precipitation unit is configured to add magnesium chloride, MgCh, preferably as a solution, optionally in a second step, in particular such, that a 0.7 molar to 1.4 molar ratio of the magnesium concentration to silicon concentration is reached. Profitably, this precipitation step leads to precipitation of impurities such as for example magnesium silicates, MgOxSiO2, wherein x is an integer from 1 .4 to 4.

[0039] Preferably, during precipitation, the pH is held above 8, in particular by adding NaOH and / or LiOH. Further preferably, during precipitation, the temperature is held between 70 °C to 90 °C, more preferably at 80 °C. Thereby, divalent metal hydroxides such as for example Mg(OH)2 are favourably precipitated. The precipitate may be removed by micropore filtration or cake filtration, in particular with a pore size from 10 pm to 15 pm, preferably removing a combined precipitate formed after addition of Na2COs and the precipitate formed after addition of MgCh and more preferably also the precipitate formed after addition of NaOH and / or LiOH.

[0040] Optionally, the precipitation unit is configured for firstly adding NaOH and / or LiOH and subsequently Na2CO3. This favourably allows for the precipitation of calcium carbonate, CaCOs, and / or magnesium hydroxide, Mg(OH)2, and / or transition metal hydroxides. Preferably, magnesium chloride, MgCh, and / or iron trichloride, FeCh, and / or aluminium trichloride AICI3 are subsequently added. Thereby, silicon species can be precipitated for example in the form of magnesium silicates and removed by subsequent filtration.

[0041] It is preferred that the precipitation unit comprises at least one precipitation tank, which is configured to receive the lithium enriched eluate and the added compounds and let rest for 30 minutes to 1 ,5 h, preferably 1 h, and / or includes a mixer for mixing the lithium enriched eluate with the compounds. The resting can be used alone or in combination with the use of a mixer, which allows for efficient precipitation. Also preferably, the precipitation unit comprises a first precipitation tank and a second precipitation tank, wherein more preferably the second precipitation tank is arranged downstream the first precipitation tank. In particular, in the first precipitation tank Na2COs and preferably NaOH and / or LiOH and in the second precipitation tank MgCh and preferably NaOH and / or LiOH, are added. Alternatively, in the first precipitation tank Ca(OH)2 and preferably NaOH and / or LiOH and in the second precipitation tank Na2CO3 and preferably NaOH and / or LiOH are added. Favourably, in the first precipitation tank and the second precipitation tank the lithium enriched eluate and the compounds are continuously fed and / or discharged.

[0042] Preferably, an additional ultra filtration unit is comprised, which is in particular configured to remove colloidal silicon species. The ultra filtration unit is favourably arranged downstream after the precipitate filter of the precipitation unit. The ultra filtration unit may be an integral part of the precipitation unit. Optionally, an adsorption unit is comprised, which is in particular configured to remove various types of silicon species. The adsorption unit is preferably arranged downstream after the reverse osmosis unit and / or after the precipitation unit. The adsorption unit may comprise a ferrous oxide-hydroxide, FeO- Fe(OH)3, containing adsorbent or an ion exchange adsorbent with an anion exchange resin, optionally operating at alkaline pH levels, preferably pH levels higher than pH 10. The ferrous oxide-hydroxide adsorbent may be a commercially available ferrous oxide-hydroxide adsorbent such as Bayoxide® E 33 HC. Additionally or alternatively, the adsorption unit may further comprise an aluminium oxide and / or an activated aluminium oxide. The precipitation unit advantageously allows to lower the concentration of impurities such as silicon and species, for example silicates, and phosphates below 1 ppm.

[0043] In a preferred embodiment an ion exchange unit for removing foreign ions from the lithium enriched eluate is comprised, preferably with an ion exchange resin. The ion exchange unit is preferably arranged downstream after the precipitation unit. Optionally, the foreign ion removal unit comprises the ion exchange unit. The ion exchange unit is favourably configured for removing Ca-ions, Mg-ions, B-ions, Ba-ions, Sr-ions or Mn-ions or any combination thereof. Profitably the ion exchange unit is reducing the amount of calcium species and magnesium species below 1 ppm, preferably below 8 ppb, more preferably below 7 ppb. The ion exchange unit preferably comprises a plurality of ion exchange subunits for removing different impurity foreign ions. In particular, in a first ion exchange subunit, Ca-ions and / or Mg-ions and / or Sr-ions and / or Ba-ions an / or other doubly charged cations are removed and in a second ion exchange subunit B-ions and / or As-ions are removed, in particular as anions. In the second ion exchange subunit a boron selective ion exchange resin may be employed.

[0044] The ion exchange unit and in particular the first ion exchange subunit and the second ion exchange subunit, may comprise a plurality of fixed bed ion exchange columns, preferably four fixed-bed columns with a lead-lag-lag-regen- eration configuration, wherein for example three columns are loading while the fourth column is either in regeneration or waiting to be placed in service. Before entering the column, the lithium enriched eluate may be passed through a guard filter to remove solid particles. A dilute hydrochloric acid solution may be added as a stripping solution and a dilute sodium hydroxide solution may be added as a regenerant solution for regeneration of the column’s ion exchange resin. An exemplary cycle of stripping and regeneration may be performed in the following sequence:

[0045] 1 ) Post-loading rinse. The column is firstly washed with water to displace any liquids in the column from previous steps.

[0046] 2) Elution: Dilute hydrochloric acid solution is fed to the column for removal of impurities from the ion exchange resin.

[0047] 3) Elution rinse: Water is fed to the column to remove residual acid from the column.

[0048] 4) Regeneration: Dilute sodium hydroxide solution is fed to the column to regenerate the ion exchange resin.

[0049] 5) Post-Regeneration Rinse: Water is fed to the column to remove the residual sodium hydroxide solution from the column.

[0050] On a periodic basis, the columns of the ion exchange unit may be backwashed with water to avoid compaction and to remove solids which may have accumulated in the ion exchange resin.

[0051] In a preferred embodiment an evaporation unit, in particular a lithium chloride evaporation unit, for removing water from the lithium enriched eluate is comprised. The evaporation unit is preferably arranged downstream after the ion exchange unit. In the evaporation unit, hydrochloric acid may be added in an agitated tank to decompose any residual carbonates. The CO2 gas generated therein may be vented to a CO2 scrubber. Before entering the evaporation unit, the pH of the lithium enriched eluate may be adjusted by adding NaOH and / or LiOH through an in-line mixer. Furthermore, before entering the evaporation unit, the lithium enriched eluate may pass a feed preheater, where it is heated. The evaporation unit preferably comprises a recirculation flow which is heated for example with steam and / or recompressed water vapor.

[0052] In a preferred embodiment a crystallization unit for crystallizing impurities from the lithium enriched eluate is comprised. The crystallization unit is preferably arranged downstream after the evaporation unit. In particular the crystallization unit is configured for crystalizing and removing from the lithium enriched eluate sodium chloride, NaCI, and / or potassium chloride, KCI, and / or silicates and / or phosphates and / or sulfates, and / or other impurities and foreign ion salts. Preferably the crystallization unit comprises a vacuum pump, for example a liquidring compressor, and particularly operates under vacuum provided by the vacuum pump. The crystallization unit may comprise or consists of a steam-driven double-effect forced-circulation type crystallizer with a first-effect crystallizer recirculation loop, which may be heated by a first effect heater, for example by hot steam. For crystallization, the lithium enriched eluate preferably enters a first- effect crystallizer body where it is boiled at an eluate surface for concentrating the lithium enriched eluate and for producing crystals of impurities. The steam- driven double-effect forced-circulation type crystallizer may further comprise a second effect crystallizer with a second effect heater. After exiting the second- effect crystallizer, the lithium enriched eluate is further concentrated and thickened in a clarifier. The crystalized impurities are preferably removed from the lithium enriched eluate by centrifugation.

[0053] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. In the following drawings

[0054] Figure 1 shows a schematic illustration of a system for extracting lithium or lithium salts from a brine according to the present invention;

[0055] Figure 2 shows a schematic illustration of the lithium extraction with a pressure control unit; Figure 3 shows a schematic illustration of the lithium extraction with a precipitation unit;

[0056] Figure 4 shows a schematic illustration of the lithium extraction relating to post treatment aspects; and

[0057] Figure 5 shows a schematic illustration of an exemplary process for extracting a lithium enriched eluate from an untreated brine according to the present invention.

[0058] In Fig. 1 a system 10 for extracting lithium or lithium salts is schematically illustrated. The system 10 is employed to extract lithium or lithium salts originating from a geothermic power plant 20. In particular, the system 10 of the present invention is suitable for extracting lithium or lithium salts from a geothermal brine. The power plant 20 supplies an untreated brine 30 to a feed unit 40. For this, the feed unit 40 may be connected to the geothermal power plant 20.

[0059] The feed unit 40 directly transfers the untreated brine 30 to a direct lithium extraction unit 50, in particular without a pressure drop for avoiding degassing, in particular via a fluid tight transfer line 41 . The direct lithium extraction unit 50 is configured to extract a lithium enriched eluate 60. For this, the direct lithium extraction unit 50 may particularly include a column and function temporarily as eluate extraction unit. The column holds a sorbent material for extracting the lithium or lithium salts from the untreated brine 30. The eluate extraction unit then removes the lithium or lithium salts from the sorbent material. The resulting lithium enriched eluate 60 may comprise Li-concentrations up to 2500 mg / L. The lithium enriched eluate 60 is firstly transferred to a membrane purification unit 55, which is arranged downstream between the direct lithium extraction unit 50 and a foreign ion removal unit 56. The membrane purification unit 55 is configured for increasing the concentration of the lithium or lithium salts in the lithium enriched eluate 60. Subsequently, the lithium enriched eluate 60 enters the foreign ion removal unit 56. The foreign ion removal unit 56 is configured for removing foreign ions from the lithium enriched eluate 60.

[0060] Fig. 2 schematically illustrates the system and the process of the present invention in a preferred embodiment. The untreated brine 30 is received from the feed unit 40 and pressurized by a downstream pressure control unit 70. Before entering the pressure control unit 70, the untreated brine 30 passes through a first filter unit, which filters the untreated brine 30 before entering the pressure control unit 70 for removing solid particles. The pressure control unit 70 includes a pump, particularly, a centrifugal pump or a progressive cavity pump. Before entering the direct lithium extraction unit 50, the untreated brine 30 is passed through a second filter unit which filters off particles smaller than the average gap size of sorbent granules of the sorbent material in the direct lithium extraction unit 50. In another embodiment, which is not shown in the figures, the pressure control unit is arranged downstream of the direct lithium extraction unit 50, for example between the direct lithium extraction unit 50 and the membrane purification unit 55. In yet another embodiment, which is not shown in the figures, the pressure control unit comprises a first pressure control unit, which is arranged between the feed unit 40 and the direct lithium extraction unit 50 and a second pressure control unit, which is arranged downstream of the direct lithium extraction unit 50, for example between the direct lithium extraction unit 50 and the membrane purification unit 55.

[0061] The temperature of the pressurized brine is controlled by a heat exchanger 80. In particular, the heat exchanger 80, is configured for adjusting the temperature of the untreated brine 30 to a temperature from 50 °C to 80°C. The pressurized and temperature adjusted untreated brine 30 is then further processed in the direct lithium extraction unit 50 to obtain the lithium enriched eluate 60. By supplying the pressurized and temperature adjusted untreated brine 30 into the direct lithium extraction unit 50, a more homogenous flow and a more efficient extraction can be achieved, thereby increasing yields and lowering costs. The lithium enriched eluate 60 is transferred to the downstream membrane purification unit 55, which comprises a nano filtration unit 90. By applying nano filtration, silicon species and / or doubly charged ions are removed from the lithium enriched eluate 60. Subsequently, the lithium enriched eluate 60 is transferred to a downstream reverse osmosis unit 100, which is also comprised by the membrane purification unit 55. The reverse osmosis unit 100 is configured for removing water from the lithium enriched eluate 60 by reverse osmosis. The reverse osmosis unit 100 operates at a temperature from 25 °C to 45 °C and / or at a pressure from 100 bar to 160 bar.

[0062] Fig. 3 schematically illustrates the further processing of the lithium enriched eluate 60. After the reverse osmosis unit 100, the lithium enriched eluate 60 is transferred to the downstream foreign ion removal unit 56. The foreign ion removal unit 56 comprises a precipitation unit 110, which receives the lithium enriched eluate 60 from the reverse osmosis unit 100. The precipitation unit 110 is configured to perform a first precipitation process 111 and / or a second precipitation process 112. In the first precipitation process 111 Ca(OH)2 is added in a first precipitation tank 113 as a suspension to the lithium enriched eluate 60. Additionally, NaOH, and / or LiOH may be added until a pH of 10 is reached, leading to the precipitation of calcium silicates and other impurities, which are removed by subsequent filtration employing a precipitate filter 114 with a pore size from 1 pm to 2 pm. This precipitation step is performed preferably for 1 h in the first precipitation tank 113, which is comprised by the precipitation unit 110. After filtration, the lithium enriched eluate 60 is transferred to a second precipitation tank 115, wherein Na2COs is added as a solution such, that a 1.2 molar excess of Na2CC>3with respect to the calcium concentration in the eluate is reached. The calcium concentration in the lithium enriched eluate 60 has been preferably determined after passing the precipitate filter 114 and before adding Na2CC>3. Addition of Na2COs leads to the precipitation of impurities such as for example CaCOs, and other carbonates, which are preferably removed by a further filter 116, which may comprise a micropore filter or a candle filter or a multi-media filter, in particular with a pore size from 10 pm to 15 pm. According to the second precipitation process 112, firstly, in the first precipitation tank 113 Na2COs is added as a solution, such that a 1.2 molar excess of Na2CC>3with respect to the calcium concentration in the eluate is reached. This leads to the precipitation of impurities such as for example CaCOs, and other carbonates. After the addition of Na2CC>3, MgCl2 is added in the second precipitation tank 115 such, that a 0.7 molar to 1 .4 molar ratio of the magnesium concentration to silicon concentration is achieved. Preferably, the silicon concentration has been determined after adding Na2COs and before adding MgCL The addition of MgCh leads to the precipitation of impurities such as for MgOxSiO2, wherein x is an integer from 1.4 to 4. During the second precipitation process 112 the pH is held above 8 by adding NaOH and / or LiOH, to ensure that impurities such as divalent metal hydroxides for example Mg(OH)2 are also precipitated. The temperature is held at 80°C. Subsequently, all precipitates formed during the second precipitation process 112 are filtered off by a precipitate filter 117 with a pore size from 10 pm to 15 pm to remove all precipitates at once.

[0063] For both the first precipitation process 111 and the second precipitation process 112 the lithium enriched eluate 60 is continuously fed and / or discharged, while the resident time is 1 h for the first precipitation tank 113 and the second precipitation tank 115. However, the lithium enriched eluate 60 may still contain trace amounts of impurities, mainly the chlorides of Na, K, Ca, Mg and boron components, which are removed subsequently as follows.

[0064] Fig. 4 schematically illustrates the further processing of the lithium enriched eluate 60. After the precipitation unit 110, the lithium enriched eluate 60 is transferred to a downstream adsorption unit 120, which is also comprised by the foreign ion removal unit 56. The adsorption unit 120 comprises a Bayoxide® E 33 HC FeO-Fe(OH)3 and / or an active aluminium oxide containing adsorbent, through which the lithium enriched eluate 60 is passed. This removes silicates in an amount of approximately 10 g silica per liter Bayoxide® E 33 HC. Additionally, phosphates are removed as well. The adsorption unit 120 is thus employed for polishing after precipitation to further reducing silicon concentration in the lithium enriched eluate 60 down to less than 1 mg / L.

[0065] Subsequently, the lithium enriched eluate 60 is transferred to an ion exchange unit 130, which is arranged downstream after the adsorption unit 120. The ion exchange unit 130 is comprised by the foreign ion removal unit 56 and preferably comprises a plurality of ion exchange subunits for removing different impurities such as foreign ions. In a first ion exchange subunit, Ca-ions and Mg-ions are removed by adsorption. The lithium enriched eluate 60 is then transferred to a downstream second ion exchange subunit, wherein B-ions are removed.

[0066] After exiting the second ion exchange subunit, the lithium enriched eluate 60 is transferred to a lithium chloride evaporation unit 140, wherein water is removed from the lithium enriched eluate 60. Thereafter, the lithium enriched eluate 60 is supplied to a crystallization unit 150. In the crystallization unit 150 NaCI, KCI and other impurities such as sulfates are crystalized and removed from the lithium enriched eluate 60. In other words, the lithium chloride evaporation unit 140 pre-concentrates the lithium enriched eluate 60 while the crystallization unit 150 removes the impurities formed by crystallizing sodium, potassium, and sulfates.

[0067] Next, the lithium enriched eluate 60 is transferred to a debromination unit 160 for removing bromine anions and yielding ultra-pure aqueous lithium chloride solution. Subsequently, the ultra-pure lithium chloride is subjected to an electrolysis unit 170 for obtaining lithium hydroxide which can then be further used to produce batteries.

[0068] Fig. 5 shows a schematic illustration of an exemplary process for extracting lithium enriched eluates from an untreated brine according to the present invention. It is to be understood that the illustration represents an example. The skilled person can implement the different illustrated steps in corresponding units or circuits for carrying out the process. The skilled person may thereby also choose different arrangements or subset of the illustrated steps. The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. As will be understood by those skilled in the art, the present disclosure may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the de- scription is intended to be illustrative, but not limiting the scope of the disclosure, as well as other claims. The disclosure, including any readily discernible variants of the teachings herein, defines, in part, the scope of the foregoing claim terminology such that no inventive subject-matter is dedicated to the public.

[0069] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

Claims1 . System (10) for extracting lithium or lithium salts from an untreated brine (30), comprising: a feed unit (40) for receiving the untreated brine (30); and a direct lithium extraction unit (50) for extracting a lithium enriched eluate (60) from the untreated brine (30); a foreign ion removal unit (56) for removing foreign ions from the lithium enriched eluate (60); wherein a membrane purification unit (55) is arranged downstream between the direct lithium extraction unit (50) and the foreign ion removal unit (56), for increasing the concentration of the lithium or lithium salts in the lithium enriched eluate (60).

2. The system (10) according to claim 1 , comprising a fluid tight transfer line (41 ), which is arranged downstream between the feed unit (40) and the direct lithium extraction unit (50) for directly transferring the untreated brine (30) from the feed unit (40) to the direct lithium extraction unit (50), in particular without degassing.

3. The system (10) according to any previous claim, wherein the direct lithium extraction unit (50) comprises a column for holding a sorbent material and; wherein a pressure at the column is from 1 bar to 40 bar, preferably from 15 bar to 30 bar, more preferably from 16 bar to 28 bar; and / orwherein a flowrate through the column is preferably from 1 m3per hour to 500 m3per hour, more preferably from 200 m3per hour to 350 m3per hour, more preferably from 280 m3per hour to 300 m3per hour, most preferably 293 m3per hour.

4. The system (10) according to any previous claim, wherein the membrane purification unit (55) comprises a nano filtration unit (90) for removing silicon compounds and / or silicon species and / or doubly charged ions from the lithium enriched eluate (60); wherein the nano filtration unit (90) is preferably arranged downstream after the lithium extraction unit (50).

5. The system (10) according to any previous claim, wherein the membrane purification unit (55) comprises a reverse osmosis unit (100) for removing water from the lithium enriched eluate (60), wherein the reverse osmosis unit (100) is preferably arranged downstream after the nano filtration unit (90); and wherein the reverse osmosis unit (100) preferably operates at a temperature from 20 °C to 45 °C, more preferably from 25 °C to 35 °C and / or at a pressure from 90 bar to 180 bar, more preferably from 100 bar to 160 bar.

6. The system (10) according to any previous claim, wherein the foreign ion removal unit (56) comprises a precipitation unit (110) for precipitating impurities from the lithium enriched eluate (60), wherein the precipitation unit (110) is preferably arranged downstream after the reverse osmosis unit (100).

7. The system (10) according to any previous claim, wherein the foreign ion removal unit (56) comprises an ion exchange unit (130) for removing foreign ions from the lithium enriched eluate (60), wherein the ion exchange unit (130) is preferably arranged downstream after the precipitation unit (110); and / or an adsorption unit (120), which is configured to remove various types of silicon species, and which is more preferably arranged downstream after the reverse osmosis unit (100) and / or after the precipitation unit (110).

8. The system (10) according to any previous claim, comprising an evaporation unit (140) for removing water from the lithium enriched eluate (60), wherein the evaporation unit (140) is preferably arranged downstream after the ion exchange unit (130).

9. The system (10) according to any previous claim, comprising a crystallization unit (150) for crystallizing impurities from the lithium enriched eluate (60), wherein the crystallization unit (150) is preferably arranged downstream after the evaporation unit (140).

10. The system (10) according to any previous claim, comprising a pressure control unit (70) for controlling the pressure in the direct lithium extraction unit (50), wherein the pressure control unit (70) is particularly arranged downstream between the feed unit (40) and the direct lithium extraction unit (50) and / or downstream of the direct lithium extraction unit (50); wherein the pressure control unit (70) preferably comprises or consists of a pump, more preferably a low pulsation pump, most preferably a centrifugal pump or a progressive cavity pump.

11. The system (10) according to any previous claim, comprising a heat exchanger (80) for adjusting the temperature of the untreated brine (30) in the feed unit (40) before entering the direct lithium extraction unit (50) and / or in the direct lithium extraction unit (50); wherein the heat exchanger (80) is preferably configured for adjusting the temperature of the untreated brine (30) to a temperature from 20 °C to 90 °C, more preferably from 50 °C to 80 °C.

12. The system (10) according to any previous claim, comprising a first filter unit for filtering the untreated brine, preferably before entering the pressure control unit (70), for removing solid particles; and / or a second filter unit for filtering the untreated brine (30) before entering the direct lithium extraction unit (50) and / or after exiting the pressure control unit (70), for removing solid particles; wherein the first filter unit preferably has a mesh size from 1 pm to 200 pm, more preferably from 10 pm to 80 pm, most preferably 50 pm; and wherein the second filter unit preferably has a mesh size from 1 pm to 200 pm, more preferably from 5 pm to 80 pm, most preferably 10 pm.

13. The system (10) according to any previous claim, comprising a dosing unit for supplying the untreated brine (30) with corrosion inhibitors and / or scaling inhibitors and / or oxygen scavengers, wherein the dosing unit is preferably arranged between the feed unit (40) and the direct lithium extraction unit (50), more preferably between the feed unit (40) and the pressure control unit (70).

14. The system (10) according to any previous claim, comprising an oil removal unit for removing oil from the untreated brine (30);wherein the oil removal unit is preferably arranged upstream the direct lithium extraction unit (50), more preferably upstream the pressure control unit (70), most preferably between the feed unit (40) and the pressure control unit (70).

15. Process for extracting lithium or lithium salts from an untreated brine (30), comprising the steps of: providing a feed unit (40), a direct lithium extraction unit (50), a foreign ion removal unit (56) and a membrane purification unit (55), wherein the membrane purification unit (55) is arranged downstream between the direct lithium extraction unit (50) and the foreign ion removal unit (56); receiving the untreated brine (30) in the feed unit (40); extracting a lithium enriched eluate (60) from the untreated brine (30) via the direct lithium extraction unit (50); and increasing the concentration of the lithium or lithium salts in the lithium enriched eluate (60) via the membrane purification unit (55); and removing foreign ions from the lithium enriched eluate (60) via the foreign ion removal unit (56).

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