Arrangement for the kinetic separation of magnesium salts from magnesium- and lithium-containing brines by means of multi-channel nozzles

Abstract

The present invention relates to an arrangement for the kinetic separation of magnesium salts from magnesium- and lithium-containing brines by means of multi-channel nozzles, and to the use of such an arrangement. Such separation is necessary because lithium can only be recovered economically from brines if there is a favourable magnesium-to-lithium ratio in the mixture. This means that the content of magnesium salts must be below a certain threshold concentration relative to the lithium content. In order to achieve this ratio even in the case of brines from salt lakes having a highly unfavourable magnesium-to-lithium ratio, it is necessary to remove as much magnesium as possible from the mixture, whilst simultaneously minimising the associated losses of lithium. According to the invention, nozzles having concentric liquid streams which permit contact times between the liquid streams in the range of a few milliseconds promote a faster reaction. When there is co-precipitation of lithium and magnesium, the faster reaction is the precipitation of magnesium. Precipitation using nozzles allows the magnesium to be selectively precipitated and removed from the system as a solid, whilst the majority of the lithium remains in the liquid.

Description

[0001] MEISSNER . i h. rt E

[0002] PO Box 860624

[0003] 81633 Munich

[0004] Dr. Rainer Pommersheim M / DRPH-034-PC Am Berstädter Grabenweg 4b WH / KR / ir 55252 Mainz-Kastel

[0005] Arrangement for the kinetic separation of magnesium salts from magnesium- and lithium-containing brines using multi-channel nozzles

[0006] Description

[0007] The present invention relates to an arrangement for separating magnesium salts from magnesium- and lithium-containing brines using multi-channel nozzles, and to the use of such an arrangement. Such separation is necessary because lithium can only be economically extracted from brines if a favorable magnesium / lithium ratio is present in the mixture. This means that the magnesium salt content must be below a certain threshold concentration relative to lithium. To achieve this even with brines from salt lakes that have a very unfavorable magnesium / lithium ratio, as much magnesium as possible must be removed from the mixture while simultaneously minimizing the associated lithium losses.

[0008] This process utilizes the fact that the reaction rates of magnesium and lithium precipitation from brines are very different. Special nozzles with concentric liquid flows, where contact times of the liquid flows are in the range of a few milliseconds, promote a faster reaction. In the case of co-precipitation of lithium and magnesium, the reaction is that of magnesium. Precipitation with nozzles selectively precipitates the magnesium and removes it from the system as a solid, while the majority of the lithium remains in liquid. This shifts the magnesium / lithium ratio in MEISSNER BOLTE M / DRPH-034-PC 2

[0009] Brine significantly favors lithium, making it possible to utilize lithium deposits that are not economically exploitable using conventional methods today.

[0010] Lithium is one of the key elements driving economic change in the coming years, not least because of its crucial role in the production of high-quality electric battery cells. Therefore, rising demand for lithium is expected in the coming years, while resources remain relatively limited.

[0011] Currently, lithium is primarily extracted from ores or brines. Extraction from ores is relatively simple. However, it involves very high chemical consumption, which has serious environmental consequences. Furthermore, the globally available deposits of lithium-containing ores are very limited.

[0012] A sustainable alternative is the extraction of lithium from brines, i.e., from natural salt lakes. Although there are numerous salt lakes worldwide with relatively high salt and lithium concentrations, lithium can only be extracted from certain lakes. This is due to the high magnesium content in these lakes compared to lithium, which necessitates complex separation processes, resulting in significant lithium loss and a large amount of solid waste. This is largely due to the nearly identical radii of the Li + and Mg ++ This process involves separating the ions, resulting in very similar physical and chemical properties and rendering conventional separation methods inefficient. This is further exacerbated by the enormous freshwater requirement of over 500 m³. 3 per ton of Li2COs, which often faces water scarcity in the affected regions.

[0013] This situation creates an urgent need for effective, economical and environmentally friendly methods to separate magnesium from the brines of natural salt lakes, while minimizing lithium losses.

[0014] According to the current state of the art, lithium is extracted from salt lakes in an evaporative precipitation process. For this purpose, the brine is first directed into a series of solar evaporation ponds to MEISSNER BOLTE M / DRPH-034-PC 3

[0015] Sodium and potassium are precipitated. Calcium oxide is added to the remaining brine in a further basin. This causes the magnesium to precipitate as a magnesium hydroxide solid, while the lithium salt remains in solution. However, the non-specific reaction in the basin leads to a very high loss of lithium, on the order of approximately 50%. The remaining Li +The liquid, rich in nitrates, is then diluted and transferred to another container. + / Mg ++ The solution is directed to a separation unit consisting of several adsorption and multi-stage nanofiltration processes. The brine is further purified and concentrated via a reverse osmosis stage followed by an evaporation stage, before the lithium is finally precipitated as lithium carbonate by the addition of NazCCh. It is obvious that with an unfavorable Mg concentration, the process will be more complex. ++ / Li + The high lithium losses in the original brine quickly make such a process uneconomical due to the high lithium ratio. Therefore, it would be essential to use Mg. ++ / Li + already in advance in favor of the Li + to change and at the same time the Li + To minimize losses during downstream separation.

[0016] The publication: Yong, M., Tang, M., Sun, L. et al. “Sustainable lithium recovery and magnesium hydroxide co-production from brines” Nature Sustainability 10 / 2024) describes a nanofiltration process using ethylenediaminetetraacetic acid (EDTA) for the direct and efficient extraction of lithium. + -Extraction as well as for effective Mg ++ Precipitation from brine. In the first step, the Mg is removed. ++ The solution was precipitated with EDTA, and the remaining brine was processed largely using conventional methods. While such a process would certainly work on a laboratory scale, it would likely be uneconomical on an industrial scale simply because of the relatively high quantities of EDTA required. Furthermore, the use of EDTA in the environment, as would be necessary for the pretreatment of water from natural lakes according to the publication, would lead to very high environmental impacts.

[0017] DE 10 2010 019 554 A1 describes a process for enriching lithium while simultaneously removing magnesium from solutions with a high chloride content. This is achieved by adding potassium chloride to the salt solutions, causing potassium carnallite (KMgCl3·6H2O), a potassium magnesium salt, to precipitate. This shifts the magnesium-to-lithium ratio in favor of lithium. Disadvantages include the large quantities of potassium chloride required and the energy expenditure needed to convert potassium carnallite back into potassium chloride. MEISSNER BOLTE M / DRPH-034-PC 4

[0018] to decompose and regenerate. This process is also based on purely chemical steps, where reaction kinetics play no role.

[0019] US Patent 8691169 describes how metallic lithium can be extracted from naturally occurring or industrial salt solutions. The process involves the following steps: (i) precipitation of magnesium with calcium hydroxide; (ii) removal of boron by solvent extraction; (iii) precipitation of lithium with sodium carbonate; (iv) conversion of lithium carbonate to lithium bicarbonate with carbonic acid; (v) decomposition of lithium bicarbonate to high-purity lithium carbonate by heating the solution. Since the precipitations are carried out in basins or tanks, differing reaction rates are not a concern. Therefore, high losses of lithium are not expected. + to be expected, since the reactions are very non-specific and involve significant amounts of Li + with failure.

[0020] US Patent 11634789 describes methods for the selective recovery of lithium from salt solutions using aqueous redox reactions. Lithium extraction is carried out via iron phosphate solids in the form of iron(III) heterosite or iron(III) phosphate in the presence of a lithium reducing agent. The separated, loaded lithium iron phosphate solids, in the form of lithium iron(II) triphyllite, are then treated with an oxidizing agent, which re-oxidizes the extracted lithium. This yields a pure lithium(I) solution. A disadvantage of this method is the necessity of using reducing and oxidizing agents for lithium separation, resulting in a very complex process with a high number of steps.

[0021] WO2016 / 193087 describes a process for producing small particles that are synthesized in a continuous process and whose size can be precisely controlled. This is achieved using special nozzles at the outlet of which two reactants are brought into contact in such a way as to form small particles. The particle size is primarily determined by the flow parameters of the liquids at the nozzle outlet. This invention focuses on achieving the largest possible quantities of particles with the smallest possible diameters (nanoparticles) and the narrowest possible size distribution.

[0022] EP2023 / 053468 describes a method and a technical process by which particles can be extracted from seawater, which MEISSNER BOLTE M / DRPH-034-PC 5

[0023] The particles must have a high magnesium content. Such particles can be, for example, magnesium hydroxide, or other water-insoluble magnesium salts such as magnesium sulfate, magnesium carbonate, etc. The particles are produced in a precipitation process using a suitable alkaline reagent. If this precipitation is carried out with the aid of a specially designed nozzle setup and / or the addition of auxiliary reagents, the size of the resulting particles and their yield can be influenced within certain limits. Here, too, the sole objective is the recovery of large quantities of particles (e.g., magnesium hydroxide). Achieving the highest possible concentrations of specific substances in the wastewater is not addressed here. Furthermore, there is no indication that the different rates of the reactions are intended to be used for the separation of specific substances from the mixture.

[0024] Based on the above, the object of the invention is to provide a further developed arrangement for separating magnesium salts from magnesium- and lithium-containing brines, which makes it possible to dispense with conventional, environmentally problematic separation methods.

[0025] The problem of the invention is solved by an arrangement according to the teaching of the independent claims and by the use of such an arrangement, wherein the dependent claims represent at least expedient embodiments and further developments.

[0026] The process according to the invention is based on the fundamental idea that the precipitation of magnesium and lithium salts from salt mixtures, such as those found in salt lakes, occurs at different rates. This effect is utilized by carrying out the precipitation with special nozzles. These are designed so that the reaction of the brine with the precipitation reagent does not take place throughout the entire liquid volume, but only at the interface of two concentric liquid streams. This results in a so-called interfacial reaction.

[0027] In a reaction that takes place throughout the entire volume, e.g., in a tank, the contact times of the reactants are very long. This allows both fast and slow reactions to occur. The situation is different with interfacial reactions. It is well-documented in the literature that precipitations occurring as interfacial reactions are very product-specific. This is due to the fact that the MEISSNER BOLTE M / DRPH-034-PC 6

[0028] The selectivity of the reaction is primarily based on kinetic parameters, since the contact times of the reactants can be kept very short in these reactions. This means that the product of the faster reaction is always formed. According to the invention, this enables a high selectivity of precipitation in favor of magnesium.

[0029] Unlike known devices for such interfacial precipitation, which all operate with parallel liquid channels, this device utilizes concentric liquid flows generated in a special nozzle. Devices with parallel liquid channels are found in so-called microreactors, which are unsuitable for high flow rates due to their high pressure losses. Concentric channels in the nozzles offer the advantage that, thanks to the inventive arrangement of the channels in the nozzle, very high flow rates with low pressure losses can be generated in a relatively simple design, making the nozzles suitable for large-scale industrial applications.

[0030] According to the invention, the flow velocities of the two liquid streams in the nozzle are selected such that the contact time is in the range of a few milliseconds, which promotes a faster reaction.

[0031] This involves the precipitation of magnesium, which can be separated as a solid and removed from the system, while most of the lithium remains in the liquid.

[0032] By shifting the magnesium / lithium ratio in the brines in favor of lithium, lithium deposits can be utilized that could not previously be economically exploited using conventional methods.

[0033] The design of the nozzles according to the invention also enables high flow rates of liquid of up to several hundred m³. 3 / h, with a simultaneous pressure drop caused by the nozzles of less than one bar to just a few bar, making the overall process suitable for large-scale industrial use. MEISSNER BOLTE M / DRPH-034-PC 7

[0034] According to the invention, the nozzles are built as multiple nozzle heads, which consist of several individual modules with, for example, 16 liquid channels each, as shown in principle in Figures 1 to 3.

[0035] Unlike known nozzle arrangements, these have been optimized for very high flow rates through a modification of the internal dimensions and geometries according to the invention. Furthermore, the multiple heads can be interconnected, which further increases the overall fluid throughput.

[0036] Each of the aforementioned modules is constructed as follows: At the center of several vertical, cylindrical channels are tubes a few millimeters long. The inner diameter of the tubes and the free cross-section of the cylindrical channels each have diameters of a few millimeters. Each tube and cylindrical channel is traversed by one of the reaction liquids (see Fig. 1 and Fig. 3).

[0037] Due to its design, the two fluid streams are prevented from coming into contact inside the nozzle, but only outside, at the nozzle outlet. This prevents the nozzle channels from becoming clogged.

[0038] Fig. 2 shows an example photograph of the use of a module as described above.

[0039] The turbidity of the liquid jet indicates that the reaction, i.e., precipitation, only takes place outside the nozzle. The dimensions of the resulting cross-sections through which the liquids flow are comparable and chosen so that even with laminar flow, the throughput per channel is in the range of several tens of liters per minute. The individual cylindrical channels and the tubes inside them are interconnected within the nozzle by horizontal channels in such a way that the flow conditions in each channel and tube are largely identical. If the inlet pressure of both liquids flowing through such a nozzle is changed, the flow parameters also change, and in particular their flow velocity through the tubes and through the vertical, cylindrical channels. This allows not only the contact times but also the mixing ratios of the liquids to be adjusted. MEISSNER BOLTE M / DRPH-034-PC 8

[0040] Chemically speaking, the precipitation process carried out with the nozzle proceeds as follows. The reactions listed below are the main ones that take place. In all cases, brines containing both Mg are used. ++ as well as Li + The salts are present (below, represented by MgCl₂ and LiCl₂). Solutions of NaOH or Ca(OH)₂ or other alkaline reagents can be used as precipitating agents.

[0041] Example A: Using a NaOH solution as a precipitating reagent:

[0042] 1. MgCl2+ 2 NaOH

[0043]

[0044] Mg(OH)2+ 2 NaCl Rate Vi

[0045]

[0046] 2. LiCl + NaOH → LiOH + NaCl Velocity V2

[0047] Example B: Using a Ca(OH)2 solution as a precipitating reagent:

[0048] 1. MgCh + Ca(OH)2

[0049]

[0050] Mg(OH)2+ CaCl2Velocity i

[0051] 2.2 LiCl + Ca(OH)2

[0052]

[0053] 2 Li OH + CaCl2Velocity V2

[0054] In both cases, Vi > V2

[0055] Due to the low solubility of Ca(OH)2 in water and the associated lower pH value of the solution compared to NaOH, better results are achieved when using NaOH.

[0056] Both Mg(OH)₂ and LiOH are solids. However, the concentrations of the precipitation reagents and the flow rates in the nozzle are chosen such that the Mg precipitates. ++ Ions are always present in a slight excess within the system. This is due to the higher reaction rate of Mg precipitation. ++ compared to the precipitation of Li + The reaction with Mg ++ This means that the entire precipitating reagent is consumed. As a result, the reaction with Li cannot proceed. +It does not occur; it therefore remains in solution. The Mg ++ However, it precipitates as a solid, which can be removed from the system, for example, gravimetrically or by filtration. In this way, the remaining brine becomes enriched with Li. + instead, which can then be further processed using conventional methods.

[0057] If the process is carried out in such a way that a slight excess of precipitating reagent exists in the system, the Mg will ++ The result was almost quantitative. Since in the MEISSNER BOLTE M / DRPH-034-PC 9

[0058] If any unreacted precipitating reagent remains in the obtained suspension, this will form part of the Li + failures, resulting in losses of Li + This leads to losses. However, these losses can be minimized by precisely adjusting the reaction conditions to the stoichiometry.

[0059] Against this background, it is proposed that the methods shown here, or the use of the arrangement in the process for Li + Extraction is to be used at two points: At the beginning of the process with the precipitation reagent in deficiency (excess of Mg). ++ ) around the Mg ++ / Li + to favorably influence the ratio and in the process itself, after the elimination of the other salts, to additionally utilize the remaining Mg ++ to remove the losses in Li + In this case, the losses are significantly lower than those of the classical methods described in the introductory section, where the losses in Li + in the range of 50%. Therefore, the method described here will in any case yield significantly higher amounts of Li. + possible compared to classical methods.

[0060] To obtain even more quantities of Mg ++To precipitate, the remaining brine can be further treated with solutions of gelling agents, which form firm, separable gels with the Mg. ++ form and the Li + Leave in solution. Such gelling agents include, for example, substances from the class of polyanions, such as polysaccharides like carboxymethylcellulose, cellulose sulfate, alginate, pectin, etc., or also polyacrylic acids and similar reagents.

[0061] The resulting reaction takes the following form, for example:

[0062]

[0063] Carboxymethylcellulose, e.g., sodium salt, carboxymethylcellulose, Mg ++ -Complex (liquid) (Gel: water-insoluble)

[0064] Such gels can also be fixed to a support. They can usually be dissolved and recovered by adding large amounts of monovalent ion salts such as NaCl or by applying a high alkaline pH. MEISSNER BOLTE M / DRPH-034-PC 10

[0065] The following are two examples to illustrate the implementation.

[0066] Example 1:

[0067] Precipitation with NaOH:

[0068] A brine solution with the following composition is used, which corresponds to that of the water of a salt lake, with a Mg / Li molar ratio of approximately 18:1.

[0069] Lithium chloride 1.28 g / L

[0070] Magnesium chloride hexahydrate 109.58 g / L

[0071] Calcium chloride 1.66 g / L

[0072] Potassium chloride 13.35 g / L

[0073] Sodium chloride 214.29 g / L

[0074] This brine is pumped through one channel of a nozzle as described. A NaOH solution is pumped through the second channel of the nozzle as a precipitation reagent. The resulting solid is separated. The ratio of the concentrations of Mg+ and Li+ in the native brine is determined, and subsequently in the brine obtained after the reaction.

[0075] Result:

[0076] The new Mg / Li ratio is now approximately 6:1. With simultaneous losses of Li + of less than one percent.

[0077] Example 2:

[0078] Precipitation with Ca(OH)2:

[0079] A brine solution with the following composition is used, which corresponds to that of the water of a salt lake, with a Mg / Li molar ratio of 18:1 MEISSNER BOLTE M / DRPH-034-PC 11

[0080] Lithium chloride 1.28 g / L

[0081] Magnesium chloride hexahydrate 109.58 g / L

[0082] Calcium chloride 1.66 g / L

[0083] Potassium chloride 13.35 g / L

[0084] Sodium chloride 214.29 g / L

[0085] This brine is pumped through one channel of a nozzle as described. A NaOH solution is pumped through the second channel of the nozzle as a precipitation reagent. The resulting solid is separated. The ratio of the Mg concentrations is determined. ++ and Li + determined in the native brine and subsequently in the brine obtained after the reaction.

[0086] Result:

[0087] The new Mg / Li ratio is now approximately 12:1. With simultaneous losses of Li + of approximately 4%.

[0088] In both cases, even better results can be achieved through further optimization. The results can also be improved by performing multiple passes through the nozzles.

[0089] Furthermore, by using suitable precipitating reagents, it is possible to remove the Li remaining in the system using the same method, i.e., with the aid of our nozzles. +e.g. as Li2COs or as another, water-insoluble Li + To precipitate a compound of high purity.

[0090] Figures 1 and 3 show a partial section and a complete section through a nozzle body with the feed openings for reactant 1 (RI) and reactant 2 (R2), the liquid channel (FK) for the precipitate (FP) and the respective centric tube (RC) within the respective liquid channel (FK).

[0091] Figure 2 is a photorealistic illustration of a nozzle module according to the invention, showing the actual reaction zone (RZ) outside the nozzle body.

Claims

MEISSNER . i h. rt E PO Box 860624 81633 Munich Dr. Rainer Pommersheim M / DRPH-034-PC Am Berstädter Grabenweg 4b WH / KR / ir 55252 Mainz-Kastel Arrangement for the kinetic separation of magnesium salts from magnesium- and lithium-containing brines using multi-channel nozzles Claims 1. Arrangement for the kinetic separation of magnesium salts from magnesium- and lithium-containing brines, in particular salt brines, by means of multi-channel nozzles by utilizing different reaction rates of the precipitation reactions of magnesium and lithium for the purpose of reducing the magnesium content in the brine in question, wherein the interfacial reaction at the contact surface of two liquid streams, formed from the brine and the precipitation reagent and short contact times, is used and furthermore the interfacial reaction is realized with a nozzle arrangement which provides concentric liquid streams.

2. Arrangement according to claim 1, characterized by the fact that The nozzles are designed in such a way that the reaction of the brine, especially salt brine, with the precipitation reagent takes place only in the contact area of ​​the concentric liquid flows.

3. Arrangement according to claim 1 or 2, characterized by the fact that the flow velocities of the liquid streams in the respective nozzle MEISSNER BOLTE M / DRPH-034-PC 2 provide a contact time of the currents in the range of a few milliseconds.

4. Arrangement according to one of the preceding claims, characterized in that The nozzles are implemented as multiple nozzle heads, consisting of several individual modules with a multitude of liquid channels (FK), whereby contact of the liquid flows only takes place outside the nozzles in a reaction zone (RZ).

5. Use of an arrangement according to the preceding claims in the process for obtaining Li + to reduce excess Mg ++ to reduce and in a subsequent step after eliminating further salts from the brine, in order to additionally reduce the remaining Mg ++ to remove almost completely, resulting in overall higher yields of Li + are reachable.

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