Patent Application
20240240280
This disclosure relates to solvent extraction for selective lithium recovery. More specifically, this disclosure relates to solvent extraction for selective lithium recovery from a monovalent sulfate brine.
Lithium is a valuable mineral, which is commonly used in the production of batteries, glasses and ceramics, greases, and various other products. The largest use is the production of lithium-ion batteries, which are commonly used in electric vehicles, power grid storage, and portable electronic devices. In particular, the compounds of lithium carbonate (Li2CO3) and lithium hydroxide (LiOH) are utilized in the manufacture of batteries, and the processes require that the compounds be of very high purity with no more than trace levels of contaminants.
The required level of purity is difficult to achieve due to the nature of the extraction process. Lithium naturally occurs only as a compound, rather than an element. Lithium deposits generally are found at low concentration within certain rock formations, clays, and brines. In the case of rock and clay deposits, the ore is often treated with an acid, such as sulfuric acid, to leach the lithium into solution; however, numerous additional elements are co-extracted, depending upon the source. For example, aluminum, calcium, iron, potassium, magnesium, and sodium are commonly co-extracted from clay into the liquid leach brine, along with the desired lithium. Where sulfuric acid is utilized, the brine also contains a high sulfate concentration.
The majority of the aluminum, calcium, iron, and magnesium is typically removed by a combination of chemical and physical precipitation techniques, and subsequent purification techniques, such as ion exchange, are utilized to reduce these elements to trace levels. However, the resulting brine carries a mixture of lithium, potassium, and sodium, which cannot be utilized to directly produce lithium carbonate suitable for battery manufacturing due to the level of impurities without multiple subsequent purification steps.
In common practice, multiple steps are needed during lithium carbonate production to ensure that final product quality is achieved. Additionally, a step to remove sodium and potassium must take place after lithium carbonate is produced. These extras steps add process complexity and require extra equipment to build. Additionally, these steps increase consumption of energy and chemical inputs and result in losses of lithium in sulfate salts produced during waste-salt separation, such as in a zero-liquid discharge unit.
It is to be understood that this summary is not an extensive overview of the disclosure. This summary is exemplary and not restrictive, and it is intended to neither identify key or critical elements of the disclosure nor delineate the scope thereof. The sole purpose of this summary is to explain and exemplify certain concepts of the disclosure as an introduction to the following complete and extensive detailed description.
Disclosed is a lithium extraction process comprising: a solvent extraction unit configured to receive an aqueous feed stream from an upstream flow path, the aqueous feed stream comprising lithium cations and at least one additional monovalent species of cation; a waste-salt separation unit configured to receive an aqueous waste-water stream from a first downstream flow path, the first downstream flow path connecting the waste-salt separation unit in fluid communication with the solvent extraction unit; and a lithium carbonate production unit configured to receive an aqueous lithium-rich stream from a second downstream flow path, the second downstream flow path connecting the lithium carbonate production unit in fluid communication with the solvent extraction unit.
Also disclosed is a method for extracting lithium, the method comprising: processing an aqueous feed stream comprising lithium cations and at least one additional monovalent species of cation with a solvent extraction unit, comprising: contacting the aqueous feed stream with an organic solvent stream comprising at least one extractant to: extract the lithium cations from the aqueous feed stream to the organic solvent stream; and create an aqueous waste-water stream from the aqueous feed stream comprising the at least one additional monovalent species of cation; stripping the lithium cations from the organic solvent stream to an aqueous acid stream to create an aqueous lithium-rich stream; and separating waste salts from the aqueous waste-water stream in a linear process, the waste salts comprising the at least one additional monovalent species of cation.
Various implementations described in the present disclosure may include additional systems, methods, features, and advantages, which may not necessarily be expressly disclosed herein but will be apparent to one of ordinary skill in the art upon examination of the following detailed description and accompanying drawings. It is intended that all such systems, methods, features, and advantages be included within the present disclosure and protected by the accompanying claims. The features and advantages of such implementations may be realized and obtained by means of the systems, methods, features particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of such exemplary implementations as set forth hereinafter.
The features and components of the following figures are illustrated to emphasize the general principles of the present disclosure. The drawings are not necessarily drawn to scale. Corresponding features and components throughout the figures may be designated by matching reference characters for the sake of consistency and clarity.
The present disclosure can be understood more readily by reference to the following detailed description, examples, drawings, and claims, and the previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this disclosure is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, and, as such, can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.
The following description is provided as an enabling teaching of the present devices, systems, and/or methods in its best, currently known aspect. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the present devices, systems, and/or methods described herein, while still obtaining the beneficial results of the present disclosure. It will also be apparent that some of the desired benefits of the present disclosure can be obtained by selecting some of the features of the present disclosure without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present disclosure are possible and can even be desirable in certain circumstances and are a part of the present disclosure. Thus, the following description is provided as illustrative of the principles of the present disclosure and not in limitation thereof.
As used throughout, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “an element” can include two or more such elements unless the context indicates otherwise.
Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
For purposes of the current disclosure, a material property or dimension measuring about X or substantially X on a particular measurement scale measures within a range between X plus an industry-standard upper tolerance for the specified measurement and X minus an industry-standard lower tolerance for the specified measurement. Because tolerances can vary between different materials, processes and between different models, the tolerance for a particular measurement of a particular component can fall within a range of tolerances.
As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.
The word “or” as used herein means any one member of a particular list and also includes any combination of members of that list. Further, one should note that conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain aspects include, while other aspects do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more particular aspects or that one or more particular aspects necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular aspect.
Disclosed are components that can be used to perform the disclosed methods and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed, that while specific reference of each various individual and collective combinations and permutations of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods and systems. This applies to all aspects of this application including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific aspect or combination of aspects of the disclosed methods.
Disclosed is an improved lithium extraction process and associated methods, systems, devices, and various apparatus. The improved lithium extraction process can comprise a solvent extraction unit. It would be understood by one of skill in the art that the disclosed improved lithium extraction process is described in but a few exemplary aspects among many. No particular terminology or description should be considered limiting on the disclosure or the scope of any claims issuing therefrom.
Turning to
In the present aspect, the main processing stream 197 can initially be a feed of lithium-containing solids, such as a clay for example and without limitation. The current process 100 can comprise a beneficiation unit 101, a leaching unit 103, a filtration unit 105, a divalent removal unit 107, a lithium carbonate production unit 109, a waste-salt separation unit 111, and an acid production unit 113. After passing through the leaching unit 103, the main processing stream 197 can be an aqueous sulfate brine; however, this chemical composition should not be viewed as limiting. The main processing stream 197 can be split into a separate lithium-rich stream 198 and a waste-water stream 199. This division of the main processing stream 197 can occur in the lithium carbonate production unit 109.
The beneficiation unit 101 can comprise multiple steps 102a-e. In step 102a, the lithium-bearing deposit can be mined to extract lithium-bearing material. The initially extracted materials can comprise desired lithium ores as well as waste materials, such as gangue, waste rock, clays, etc. In steps 102b-e, the extracted material can be physically broken down (comminution), sorted by size, and initially separated, or concentrated, to isolate and extract the lithium ore from the associated waste materials. For example, in step 102b, the extracted material can be fed through a feeder breaker, mineral sizer, and log washer, which can crush the material to smaller particle sizes and remove unwanted materials, such as non-lithium-bearing minerals. In step 102c, the material can be further broken down with an attrition scrubber and preliminarily sized via screening. In step 102c, waste rock can be sorted out from the main processing stream 197. In step 102d, the remaining material can be classified, such as by size, which can remove the course gangue from the main processing stream 197. Finally, the material can be mixed with water and flocculants to produce a lithium stream of high solids concentration.
In the leaching unit 103, the lithium ore can be subjected to an acid leaching step 104, wherein the lithium ore can be mixed with an acid from the acid production unit 113, which can extract lithium from the ore into solution. The acid leaching step 104 can result in various elements, such as aluminum, calcium, iron, potassium, lithium, magnesium, and sodium, for example and without limitation, being leached into solution. In the present example, the acid production unit 113 can generate sulfuric acid (H2SO4); however, a different acid can be utilized.
Following the leaching unit 103, the limestone can be fed into the main processing stream 197 in the filtration unit 105, wherein a neutralization and filtration step 106 can remove the aluminum and iron from the main processing stream 197.
The divalent removal unit 107 can remove magnesium and calcium from the main processing stream 197 through a variety of steps 108a-d. In step 108a, magnesium can be removed through evaporation and crystallization, such as in the form of magnesium sulfate (MgSO4). In step 108b, quicklime slurry can be added to the main processing stream 197 to further remove magnesium via precipitation and filtration of the magnesium precipitates. In step 108c, a flocculant, ferric sulfate, and soda ash solution (Na2CO3, also known as “sodium carbonate”) can be added to the main processing stream 197, and calcium can be removed with a reactor clarifier. In step 108d, remaining divalent ions can be removed with a chelating ion-exchanger. For example, a regeneratable resin can be utilized to extract the divalent ions from aqueous solution. The resin can be regenerated as needed with acid (such as sulfuric acid, for example and without limitation, from the acid production unit 113) and/or alkali/soluble base (such as sodium hydroxide, for example and without limitation) injected into the ion exchanger, which can release the divalent ions into an aqueous waste stream.
From the divalent removal unit 107, the main processing stream 197 can flow to the production circuit 115, which can comprise the lithium carbonate production unit 109 and the waste-salt separation unit 111.
The lithium carbonate production unit 109 can comprise multiple steps 110a-e. Steps 110a-c pertain to the production of the lithium carbonate compound, and here, the main processing stream 197 can be separated into the lithium-rich stream 198 and the waste-water stream 199. Step 110a is the first stage of lithium carbonate crystallization and centrifugation. In this stage, soda ash can be added to the main processing stream 197. The centrifugation can separate the solids from the liquid centrate. In this step, about 100% of the centrate can be directed to the waste-salt separation unit 111, discussed below, as shown by a flow path 117, which becomes part of the waste-water stream 199.
The lithium-rich stream 198 can carry solids from step 110a to a bicarbonation process in step 110b, wherein the lithium-rich stream 198 can be combined, or re-slurried, with treated water and intermixed with carbon dioxide. The lithium-rich stream 198 can then undergo a second stage of lithium carbonate crystallization and centrifugation, wherein the solid lithium carbonate can be separated in part from the liquid centrate. In step 110c, about 33% of the centrate can join the waste-water stream 199 directed to the waste-salt separation unit 111, as shown by a flow path 119. The remaining liquid and lithium carbonate solids of the lithium-rich stream 198 can be dried to remove the remaining water, cooled, and then stored in step 110d. The lithium carbonate can then be jet milled, magnetic filtered, and packaged in step 110e to produce the final salable product.
As noted above, the waste-salt separation unit 111 can receive centrate from steps 110a,c of the lithium carbonate production unit 109, which can form the waste-water stream 199. The waste-water stream 199 can have high concentrations of sodium and potassium; however, the waste-water stream 199 can also carry a portion of the desired lithium. The sodium and potassium must be removed from the main processing stream 197 to produce battery quality lithium product from the lithium carbonate production unit 109; however, the steps 110a-c can also result in undesirable removal of lithium from the main processing stream 197 to the waste-water stream 199.
In a step 112a of the waste-salt separation unit 111, the centrate can be treated with acid, such as sulfuric acid for example and without limitation, from the acid production unit 113, to decarbonate the centrate. Once decarbonated, the waste-water stream 199 can pass to a step 112b of the waste-salt separation unit 111, wherein the waste-water stream 199 can undergo a separation process, such as crystallization, evaporation, centrifugation, etc. The separation process can be a zero-liquid-process, which can yield solid sodium sulfate and potassium sulfate salts (and inadvertently, lithium sulfate salts). These salts can be separated for storage and/or removal from the mine.
As discussed in greater detail below with respect to a ternary phase diagram for sulfates of sodium, potassium, and lithium, shown in
To avoid this loss of lithium, the crystallizer of step 112b can only perform partial separation of waste salts from the waste-water stream 199. Because the concentrations of sodium and potassium are much higher than the concentration of lithium in the waste-water stream 199, this partial separation only results in the production of sodium and potassium sulfate salts. The remaining liquid of the waste-water stream 199 (carrying the lithium portion and remaining sodium and potassium) can be sent back to step 110a of the lithium carbonate production unit 109 by a recycle loop 121.
The recycle loop 121 can be a substantial portion of the volume flow rate of the main processing stream 197. Recycling this volume through steps 110a-c of the lithium carbonate production unit 109 can increase the percentage of the lithium recovered by the current process 100, but at the expense of increased energy and reagent consumption, such as for soda ash and sulfuric acid. Recycling this volume always requires the equipment to be sized larger than would otherwise be necessary to accommodate larger flow rates.
The main processing stream 197, now stripped of divalent ions, can exit the ion exchange vessel 208 along a flow path 250, where the main processing stream 197 can be intermixed with soda ash, as demonstrated by a flow path 252, and the recycle loop 121 from the waste-salt separation unit 111. As similarly discussed above, the recycle loop 121 can return lithium ions and the remaining sodium and potassium ions that were not crystallized in the waste-salt separation unit 111. Notably, the soda ash can add additional sodium to the main processing stream 197.
The main processing stream 197 can then enter a first crystallizer 210a of the step 110a of the lithium carbonate production unit 109. The first crystallizer 210a can be a precipitator in some aspects. Here, the lithium cations (Li+) can react with the carbonate anions (CO32−) from the soda ash to form lithium carbonate crystals. The main processing stream 197 can proceed along a flow path 253 from the first crystallizer 210a to a centrifugal separator 210b of the step 110a of the lithium carbonate production unit 109. The centrifugal separator 210b can separate the solid lithium carbonate crystals from the liquid of the main processing stream 197. The lithium carbonate carried by the lithium-rich stream 198 can proceed along a flow path 254 to a bicarbonation vessel 210c of the step 110b of the lithium carbonate production unit 109.
The centrate from the centrifugal separator 210b can be directed along the flow path 117, where it can combine with a first portion 219a of the centrate discharged from a centrifugal separator 210f of the step 110c of the lithium carbonate production unit 109 along the flow path 119. Together, these streams can form the waste-water stream 199 that can be directed to the waste-salt separation unit 111, discussed in further detail below.
Returning to the bicarbonation vessel 210c, the lithium-rich stream 198 from the first crystallizer 210a can be rinsed with a second portion 219b of the centrate from the centrifugal separator 210f while carbon dioxide (CO2) can be injected into the bicarbonation vessel 210c along a flow path 255. Treated water can also be injected into the bicarbonation vessel 210c along a flow path 262. These steps can cause lithium carbonate solids to dissolve into solution as lithium bicarbonate (LiHCO3).
The lithium-rich stream 198 can proceed along a flow path 256 from the bicarbonation vessel 210c to a filter 210d of the lithium carbonate production unit 109, wherein waste solids and solid contaminants can be separated out from the lithium-rich stream 198 along a flow path 270. The lithium-rich stream 198 can flow along a flow path 257 to a second crystallizer 210e of the step 110c of the lithium carbonate production unit 109, where the dissolved lithium bicarbonate can be converted back to solid lithium carbonate crystals. In the present aspect, crystallization can be achieved through a precipitation process, such as a chemical crystallization process. In some aspects, crystallization can be achieved through a traditional crystallization process. By heating the lithium-rich stream 198, carbon dioxide can be removed, which can be recycled through the bicarbonation vessel 210c along the flow path 255. The bicarbonation and second crystallization steps can be required to achieve sufficient purity to produce battery-quality lithium carbonate.
The lithium-rich stream 198 can then flow along a flow path 258 to the centrifugal separator 210f of the step 110c of the lithium carbonate production unit 109, where the solid lithium carbonate crystals can be separated from the liquid as centrate. The lithium-rich stream 198, carrying the solid lithium carbonate, can proceed along a flow path 259 to be dried, sized, filtered, and packaged for sale (amongst other steps) as described above with respect to steps 110d, e of the production unit 109 in
The waste-water stream 199 can be a sulfate and carbonate brine containing large concentrations of sodium and potassium cations and a lesser concentration of lithium cations, amongst other aqueous ions. The waste-water stream 199 can pass through a decarbonation vessel 212a of the step 112a of the waste-salt separation unit 111. Here, an acid, such as sulfuric acid, can be injected into the decarbonation vessel 212a along a flow path 260, where the acid can react with the waste-water stream 199 to destroy all remaining carbonate anions (from the soda ash injected along flow path 252) and liberate carbon dioxide gas. This carbon dioxide gas can be collected and directed to the bicarbonation vessel 210c along the flow path 255. The addition of sulfuric acid to the waste-water stream 199 can lower the pH of the waste-water stream 199 and increase the concentration of sulfate anions in the chemical composition of the waste-water stream 199.
The waste-water stream 199 can then flow to a waste-salt separation unit, such as a zero-liquid-discharge (“ZLD”) unit 212b of the step 112b of the waste-salt separation unit 111. The aforementioned removal of remaining carbonate in step 112a can prevent the loss of lithium carbonate in the ZLD unit 212b. Referring to
Specifically, the ternary phase diagram defines three corners 300a,b,c and three sides 301a,b,c, each corresponding to the relative concentration ratios of lithium, sodium, and potassium sulfates, respectively. The relative concentration values of lithium, sodium, and potassium equal 100% when added together. The corners 300a,b,c respectively reflect 100% lithium sulfate, 100% sodium sulfate, and 100% potassium sulfate. For example, the corner 300a indicates that no sodium or potassium cations are present, only lithium cations (notably, the diagram is shown on a dry basis and omits the water in solution).
The sides 301a,b,c opposite from these points reflect an absence of that respective cation. For example, points along the side 301a, which is opposite from corner 300a, represent an absence of lithium cations (i.e. only sodium and potassium cations are present in the chemical composition). Similarly, points along the side 301b represent an absence of sodium cations, and points along the side 301c represent an absence of potassium cations.
The ternary diagram for lithium, sodium, and potassium sulfates has six regions A-F, which each signify the types of salts that will be formed when a solution with a particular ratio of lithium, sodium, and potassium concentrations undergoes a separation process.
For example, a solution with ratios of lithium, sodium, and potassium falling into region A will initially yield Na2SO4·Li2SO4, which is a lithium-containing double salt. Region A generally corresponds to solutions with little or no potassium, and lithium and sodium present in similar concentrations.
A solution falling into region B will initially yield Na2SO4, which is a single salt devoid of lithium. Region B generally corresponds to solutions with a very high sodium concentration, and little or no lithium and potassium present.
A solution falling into region C will initially yield LiKSO4, which is a lithium-containing double salt that also contains potassium. Region C generally corresponds to solutions with moderate, low, or no sodium, and lithium and potassium present in similar concentrations.
A solution falling into region D will initially yield Li2SO4·H2O, which is a lithium-containing hydrated salt. Region D generally corresponds to solutions with a very high lithium concentration, and little or no sodium and potassium present.
A solution falling into region E will initially yield K2SO4·KNaSO4, which is a double salt devoid of lithium. Region E generally corresponds to solutions with little or no lithium, and potassium and sodium present in similar concentrations.
A solution falling into region F will initially yield K2SO4, which is a single salt devoid of lithium. Region F generally corresponds to solutions with a very high potassium concentration, and little or no sodium and lithium present.
A solution falling into region G will initially yield 2Li2SO4·Na2SO4·K2SO4, which is a lithium-containing triple salt. Region G generally corresponds to solutions with moderate-to-low levels of potassium, and lithium and potassium present in a relatively wide range of concentrations.
As previously noted, the initial chemical composition of the waste-water stream 199 (shown in
As the separation process progresses, the concentrations of lithium, potassium, and sodium increase as solvent (water) is removed until the aforementioned salt crystals begin to form and drop out of solution. To use region B as an example, an initial chemical composition at the outset of the separation process that falls within the interior of region B will initially yield solid Na2SO4 crystals. The formation of these sodium salts has the effect of reducing the ratio of sodium in the waste-water stream 199, which in turn increases the ratio of lithium and potassium in the waste-water stream 199. Accordingly, the concentration of the waste-water stream 199 will move in a direction towards side 301b as Na2SO4 crystals form until the concentration reaches one of the boundary lines 302a-c that border region B.
Once the concentration reaches a ratio lying along one of the boundary lines 302a-c, the concentration will never cross the boundary line 302a-c as the separation process continues. This is because continued separation yields the salts corresponding to each region bordered by that boundary line 302a-c.
For example, if the concentration shifts to lie along boundary line 302a, continued separation will yield Na2SO4 crystals, as represented by Region B, and Na2SO4·Li2SO4 double-salt crystals, as represented by region A on the opposite side of the boundary line 302a. Similarly, if the concentration shifts to lie along boundary line 302b, continued separation will yield Na2SO4 crystals, as represented by Region B, and 2Li2SO4·Na2SO4·K2SO4 triple-salt crystals, as represented by region G on the opposite side of the boundary line 302b. If the concentration shifts to lie along boundary line 302c, continued separation will yield Na2SO4 crystals, as represented by Region B, and K2SO4·KNaSO4 double-salt crystals, as represented by region E on the opposite side of the boundary line 302c.
Once the concentration lies along a boundary line, continued separation will result in the concentration shifting along that respective boundary line until final equilibrium is reached at a ternary point 303a-d. Note, only the ternary points 303a-d have been labelled because these points border one of regions B, E, and F. The ternary points 303a-d each lie at the intersection of three boundary lines. The ternary point 303a lies at the intersection of boundary lines 302a,b,i. The ternary point 303b lies at the intersection of boundary lines 302b,c,d. The ternary point 303c lies at the intersection of boundary lines 302d,e,h. The ternary point 303d lies at the intersection of boundary lines 302e,f,g.
Initial chemical compositions for the waste-water stream 199 lying in region B will always reach final equilibrium at either ternary point 303a or ternary point 303b, depending on the ratio of potassium to lithium present. Initial chemical compositions for the waste-water stream 199 lying in region E will always reach final equilibrium at either ternary point 303b, ternary point 303c, or ternary point 303d, depending on the ratio of potassium to sodium present. Initial chemistries for the waste-water stream 199 lying in region F will always reach final equilibrium at ternary point 303d.
Once the concentration reaches final equilibrium at a ternary point 303a-d, continued separation will yield solid salt crystals corresponding to each adjacent region to that ternary point 303a-d until complete separation is achieved. For example, continuing the separation process at the ternary point 303a will yield the salts of regions A,B,G, and notably, regions A and G result in the production of lithium-containing double and triple salts, respectively. Continuing the separation process at the ternary point 303b will yield the salts of regions B,E,G, and notably, region G results in the production of lithium-containing triple salts. Continuing the separation process at the ternary point 303c will yield the salts of regions C,E,G, and notably, region G results in the production of lithium-containing triple salts while region C results in a single salt containing both lithium and potassium. Continuing the separation process at the ternary point 303a will yield the salts of regions C,E,F, and notably, region C results in a single salt containing both lithium and potassium.
The salts corresponding to regions A, C, and G each contain lithium and are not commercially viable products. Lithium produced in these forms is effectively lost for practical commercial purposes. Accordingly, in typical operation of the current process 100, the waste-water stream 199 generally exhibits an initial chemical composition lying within region B, region E, or region F, and the waste-water stream 199 can only undergo a partial separation process to produce Na2SO4, K2SO4·KNaSO4, and/or K2SO4 waste salts without producing any lithium-containing salts. In other words, the separation process can only progress to the extent that the chemical composition has not yet reached any of the boundary lines 302a-g or the ternary points 303a-d to avoid losing lithium. A substantial amount of solvent (water) can remain at this process-imposed separation limit.
Returning to
Beginning with
In the present aspect, the ion exchange vessel 208 can also receive a recycle loop 406 from a lithium carbonate production unit 409 of the improved production circuit 415, which can rejoin the main processing stream 197.
In the aspect of
Two-separate streams can emerge from the solvent extraction unit 480: the waste-water stream 199 and the lithium-rich stream 198. The waste-water stream 199 and the lithium-rich stream 198 can each be aqueous streams. The solvent extraction unit 480 can selectively extract 99% or more of the lithium from the main processing stream 197 while only a few percent of the sodium and potassium can be extracted with the lithium, thereby leaving the majority of the sodium and potassium remaining in the main processing stream 197. For example and without limitation, in some aspects, 2% or less of the sodium and/or potassium can be extracted with the lithium in the solvent extraction unit 480. The extracted lithium can then be concentrated into the lithium-rich stream 198. When optimized, as discussed in greater detail below, the solvent extraction unit 480 can concentrate roughly 100% of the lithium from the main processing stream 197 into the lithium-rich stream.
With virtually all of the lithium extracted from the main processing stream 197 but substantial concentrations of sodium and potassium remaining, the main processing stream 197 can become the waste-water stream 199 exiting the solvent extraction unit 480. The waste-water stream 199 can contain less than 1% of the lithium from the main processing stream 197. When optimized, the solvent extraction unit 480 can produce a waste-water stream 199 comprising less than 0.1% of the lithium from the main processing stream 197.
Because of the waste-water stream 199 can comprise little to no lithium, a separation process of the waste-water stream 199, beginning immediately downstream of the solvent extraction unit 480 and extending to achievement of complete separation, or removal, of all waste salts, can be a linear process. “Linear process” means a process lacking any recycle loop (such as the recycle loop 121). For example, the entire waste-water stream 199 can be directed through a waste-salt separation unit 411 of the improved production circuit 415 to achieve substantially complete separation of waste salts in a linear process, without recycling any of the waste-water stream 199.
In the present aspect, the waste-salt separation unit 411 can comprise the ZLD unit 412a and the centrifugal separator 412b. The waste-salt separation unit 411 can remove substantially all of the liquid from the waste-water stream 199, leaving behind only waste salts, such as various potassium and sodium salts, that are devoid of lithium. For example, in some aspects, less than 0.5% of the lithium from the main processing stream 197 can be produced in the waste salts. In some more preferred aspects, 0.2% or less of the lithium from the main processing stream 197 can be produced in the waste salts. Referring to the ternary phase diagram of
Returning to
In some aspects of the improved production circuit 415, the lithium-rich stream 198 from the centrifugal separator 410b can be directly prepared for sale, such as by being dried, cooled, stored, jet milled, magnetic filtered, and/or packaged, as similarly discussed with respect to steps 110d, e of the lithium carbonate production unit 109 (steps 110d,e and lithium carbonate production unit 109 shown in
When the exchange medium is regenerated, the calcium and magnesium divalent ions can be removed from the ion exchange vessel 208, as demonstrated by the flow path 251. The main processing stream 197, now stripped of divalent ions, can exit the ion exchange vessel 208 along the flow path 250, where the main processing stream 197 can be intermixed with soda ash, as demonstrated by the flow path 252.
Instead of the waste-water stream 199 flowing directly to a waste-salt separation unit 511 in the aspect of
Returning to the main processing stream 197, after exiting the ion exchange vessel 208 along the flow path 250, the main processing stream 197 can then enter a first crystallizer 510a of a lithium carbonate production unit 509. The lithium carbonate production unit 509 of the improved production circuit 515 can be similar to the lithium carbonate production unit 109 of the current process 100 of
The centrate from the centrifugal separator 510b can be directed along the flow path 117, where it can combine with the first portion 219a of the liquid, or centrate, discharged from a centrifugal separator 510f of the lithium carbonate production unit 509 along the flow path 119. Together, these streams can comprise the waste-water stream 199 that can be directed to the solvent extraction unit 480, discussed in further detail below.
Returning to the bicarbonation vessel 510c, the lithium-rich stream 198 from the first crystallizer 510a can be rinsed with the second portion 219b of the centrate from the centrifugal separator 510f while carbon dioxide can be injected into the bicarbonation vessel 510c along the flow path 255, and treated (deionized) water can be injected into the bicarbonation vessel 510c along the flow path 262. These steps can cause formation of soluble lithium bicarbonate from the lithium carbonate crystals reacting with the carbon dioxide.
The lithium-rich stream 198 can proceed along the flow path 256 from the bicarbonation vessel 510c to a filter 510d of the lithium carbonate production unit 509, wherein waste solids can be separated out from the lithium-rich stream 198 along the flow path 270. The lithium-rich stream 198 can travel along the flow path 257 to a second crystallizer 510e of the lithium carbonate production unit 509, where formation of lithium carbonate crystals can occur. This process can liberate carbon dioxide, which can be recycled to the bicarbonation vessel 510c along the flow path 255.
The lithium-rich stream 198 can then flow along a flow path 258 to the second centrifugal separator 510f of the lithium carbonate production unit 509, where the solid lithium carbonate crystals can be separated from the liquid as centrate. The lithium-rich stream 198, carrying the solid lithium carbonate crystals, can proceed along a flow path 259 to be dried, sized, filtered, and packaged for sale (amongst other steps) as described above with respect to steps 110d,e of the production unit 109 in
The waste-water stream 199 can contain large concentrations of sodium and potassium cations and a lesser concentration of lithium cations, amongst other aqueous ions. The waste-water stream 199 can enter the solvent extraction unit 480. The solvent extraction unit 480 can utilize numerous reagents. For example, the solvent extraction unit 480 can receive an acid, such as sulfuric acid for example and without limitation, along a flow path 501. The solvent extraction unit 480 can receive a caustic, or alkali, such as sodium hydroxide for example and without limitation, along a flow path 502. The solvent extraction unit 480 can receive one or more solvents along a flow path 503, such as one or more extractants, one or more diluents, or combinations thereof, for example and without limitation. In some aspects, the extractants can be reactive and can be dissolved in the diluent.
Two-separate streams can emerge from the solvent extraction unit 480: the waste-water stream 199 and a secondary lithium-rich stream 598. The waste-water stream 199 and the secondary lithium-rich stream 598 can each be aqueous streams. The solvent extraction unit 480 can selectively extract 99% or more of the lithium from the waste-water stream 199 while the majority of the sodium and potassium remain in the waste-water stream 199. The extracted lithium can then be concentrated into the secondary lithium-rich stream 598. When optimized, as discussed in greater detail below, the solvent extraction unit 480 can concentrate roughly 100% of the lithium from the waste-water stream 199 into the secondary lithium-rich stream 598.
With virtually all of the lithium extracted from the waste-water stream 199 but substantial concentrations of sodium and potassium remaining, the waste-water stream 199 can exit the solvent extraction unit 480 containing less than 1% of the lithium entering the solvent extraction unit 480 in the waste-water stream. In some aspects, 98% or more of the sodium and/or potassium can remain in the waste-water stream 199 while 0.5% or less of the lithium can remain in the waste-water stream 199, for example and without limitation. When optimized, the solvent extraction unit 480 can leave less than 0.1% of the lithium in the waste-water stream 199.
The waste-water stream 199 exiting the solvent extraction unit 480 can then flow to a ZLD unit 512a of a waste-salt separation unit 511 of the improved production circuit 515, and then to a centrifugal separator 512b of the waste-salt separation unit 511. In some aspects, a centrifuge, crystallizer, evaporator, or other type of separation equipment and/or a dryer can be used to completely separate waste salts from the waste-water stream 199. Notably, the waste-water stream 199 can be a linear process from immediately downstream of the solvent extraction unit 480 to complete separation of waste-salts from the waste-water stream 199, which is to say that the waste-water stream 199 can exclude a recycle loop (such as the recycle loop 121 of
With reference to the ternary phase diagram of
In the present aspect, the secondary lithium-rich stream 598 can follow a flow path 562 to a secondary crystallizer 530. Soda ash can be intermixed with the secondary lithium-rich stream 598, as shown by a flow path 563. The lithium of the secondary lithium-rich stream 598 and the soda ash can react within the secondary crystallizer 530 to form lithium carbonate crystals. The secondary lithium-rich stream 598 can exit the secondary crystallizer 530 and pass to a secondary centrifugal separator 532 along a flow path 564. The secondary centrifugal separator 532 can separate the lithium carbonate crystals from the liquid, or centrate. During the centrifugation stages, the lithium carbonate crystals can be washed to further remove contaminants. The lithium carbonate crystals can follow a flow path 565 to be prepared for sale, as similarly described above with respect to steps 110d,e of the carbonate production unit 109 of the current lithium extraction process 100 (shown in
The centrate can follow a flow path 566 to the lithium carbonate production unit 509. The centrate can carry the majority of the sodium added by the soda ash. In the present aspect, the flow path 566 can lead the centrate to the bicarbonation vessel 510c. In other aspects, the flow path 566 can lead to a different section of the lithium carbonate production unit 509, such as the first crystallizer 510a or the second crystallizer 510e.
In some aspects, rather than passing through the secondary crystallizer 530 and the secondary centrifugal separator 532, the secondary lithium-rich stream 598 can rejoin the main processing stream, such as by intermixing with flow path 250. Because the secondary lithium-rich stream 598 contains minimal amounts of sodium and potassium, intermixing of the secondary lithium-rich stream 598 can avoid substantially increasing the concentrations of these ions within the main processing stream 197.
The solvent extraction unit 480 can comprise an extraction circuit 681 and a stripping circuit 683. In the present aspect, the extraction circuit 681 can be a two-stage extraction process, though this should not be viewed as limiting. In various aspects, the extraction circuit 681 and/or the stripping circuit 683 can have greater or fewer than two stages. In the present aspect, the extraction circuit 681 and the stripping circuit 683 can be counter-flow circuits, although this should not be viewed as limiting.
As shown, an aqueous feed stream 600 can be supplied to the solvent extraction unit 480 along a flow path 601. In relation to the improved production circuit 415 of
An alkali 630, such as sodium hydroxide for example and without limitation, can be added to the aqueous feed stream 600 to control the pH of the aqueous feed stream 600, as demonstrated by a flow path 631 and a flow path 632a. In some aspects, the alkali 630 can be added to achieve a pH for the aqueous feed stream 600 of 10.0-12.5. In more preferable aspects, the alkali 630 can be added to achieve a pH for the aqueous feed stream 600 of 10.5-12.0. In most preferable aspects, the alkali 630 can be added to achieve a pH for the aqueous feed stream 600 of 11.0-11.5. In practice, an approximately stoichiometrically equivalent amount of alkali 630 can be added relative to the amount of aqueous lithium entering the solvent extraction unit 480 in the aqueous feed stream 600.
A solvent stream 610, also referred to as an “organic solvent stream,” can be supplied to the solvent extraction unit 480, as shown by a flow path 611. This stream can comprise a solvent. The solvent can comprise at least one diluent and at least one extractant. The at least one diluent can comprise at least one organic diluent. The at least one extractant can be dissolved in the at least one diluent. The at least one diluent can carry the extractant(s) and facilitate contact between the extractant(s) and the sulfate aqueous brine. In some aspects, the solvent can further comprise at least one modifier. Addition of at least one modifier can increase efficiency of the solvent extraction unit 480 in some aspects. At least one modifier can be utilized for purposes such as, for example and without limitation, to help prevent unwanted phase formation, increase the solubility of the extractant in the diluent, or decrease extractant losses to the aqueous phase. During testing, organic solvent blends, such as Cyanex 923 (manufactured by Solvay S.A. of Brussels, Belgium) and Mextral 54-100 (manufactured by KopperChem of Chongqing, China) were tested. Cyanex 923 comprises a blend of compounds, such as trialkylphosphine oxides. Specifically, Cyanex 923 extractant can comprise a mixture of four trialkylphosphine oxides as follows: R3P(O) R2R′P(O) RR′2P(O) R′3P(0), where R=[CH3(CH2)7]-normal octyl, and R′=[CH3(CH2)7]-normal hexyl. Mextral 54-100 comprises a mixture of β-diketone 1-benzoyl-2-nonanone (as main ingredient), surfactant, modifier, stabilizer, and other compounds. In some aspects, these solvents were blended with a diluent, such as Exxsol D80 (manufactured by ExxonMobil of Irving, TX, USA). Exxsol D80 is a dearomatized hydrocarbon fluid. In practice, any organic solvent(s) (or blends thereof) suited for selectively binding lithium to remove it from the aqueous phase and into the organic phase in the presence of additional monovalent species, such as sodium and potassium for example and without limitation, can be utilized. In some aspects, the solvent can be paraffinic, as opposed to aromatic for example and without limitation.
The aqueous feed stream 600 and the solvent stream 610 can pass through a first extraction vessel 682a and a second extraction vessel 682b. In the present aspect, the aqueous feed stream 600 and the solvent stream 610 can pass through the first extraction vessel 682a and the second extraction vessel 682b in countercurrent flow. For example, the aqueous feed stream 600 can enter the first extraction vessel 682a along the flow path 601, exit the first extraction vessel 682a and then enter the second extraction vessel 682b along a flow path 602, and then exit the second extraction vessel 682b (and the solvent extraction unit 480) along a flow path 603. In some aspects, additional alkali 630 can be injected through flow path 632b into the flow path 602 to adjust the pH as needed. The aqueous feed stream 600 exiting along the flow path 603 can be depleted of lithium, such that the aqueous feed stream 600 becomes a waste-water stream.
With respect to the improved production circuit 415 of
By contrast, the solvent stream 610 can enter the second extraction vessel 682b along the flow path 611, exit the second extraction vessel 682b and then enter the first extraction vessel 682a along a flow path 612, and then exit the first extraction vessel 682a and being directed to the stripping circuit 683 along a flow path 613. The solvent stream 610 entering the stripping circuit 683 can carry substantially all of the lithium (dissolved in the organic phase) that entered the solvent extraction unit 480 in the aqueous feed stream 600 (dissolved in the aqueous phase). In some aspects, rather than passing the entire solvent stream 610 through both extraction vessels 682a,b, a first portion of the solvent stream 610 can be routed only through the first extraction vessel 682a and a second portion of the solvent stream 610 can be routed only through the second extraction vessel 682b. Each portion of the solvent stream 610 can then flow to the stripping circuit 683. In some aspects, the solvent stream 610 can first pass through the first extraction vessel 682a countercurrent to the aqueous feed stream 600 and then pass through the second extraction vessel 682b countercurrent to the aqueous feed stream.
The solvent stream 610 can selectively extract the lithium from the aqueous phase of the aqueous feed stream 600 and into the organic phase of the solvent stream 610. The volumetric ratio of the organic phase (the solvent stream 610) to the aqueous phase (the aqueous feed stream 600)(the “O/A ratio”) within the extraction circuit 681 can be from 5/1 to 1/5. Preferably, the O/A ratio can be from 1/2 to 1/1. Most preferably, the O/A ratio can be approximately 2/3. The O/A ratio in the extraction circuit 681 can affect the percentage of lithium extracted from the aqueous feed stream 600 to the solvent stream 610. In some aspects, 95% or more of the lithium can be absorbed from the aqueous phase to the organic phase, leaving 5% or less of the lithium in the aqueous feed stream 600 exiting along the flow path 603. In preferred aspects, 99% or more of the lithium can be extracted from the aqueous phase to the organic phase, leaving 1% or less of the lithium in the aqueous feed stream 600 exiting along the flow path 603. In most preferred aspects, 99.9% or more (roughly 100%) of the lithium can be extracted from the aqueous phase to the organic phase, leaving 0.1% or less of the lithium in the aqueous feed stream 600 exiting along the flow path 603. With an O/A ratio of 2/3, roughly 100% of the lithium can be extracted to the organic phase. In some aspects, the O/A ratio can affect the number of stages required for complete absorption of the lithium. For example and without limitation, with an O/A ratio of 2/3, two extraction stages may be required for roughly 100% extraction of lithium to the organic phase. For example and without limitation, with an O/A ratio of 1/2, three extraction stages may be required for roughly 100% absorption of lithium to the organic phase. The preferred O/A ratios can be affected over time by the relative costs of equipment and extractants. For example and without limitation, if extractant costs are high, it can be desirable to operate at a lower O/A ratio (i.e. lower extractant costs) with more stages (i.e. more equipment costs). For example and without limitation, if extractant costs are low, it can be desirable to operate at higher O/A ratios with fewer stages.
In the stripping circuit 683, the lithium-loaded solvent stream 610 can be contacted with an aqueous acid stream 620, supplied by a flow path 621. In the present aspect, the aqueous acid stream 620 can comprise sulfuric acid. In the present aspect, the solvent stream 610 can be contacted with the aqueous acid stream 620 in a stripping vessel 684. In some aspects, the solvent stream 610 can be contacted with the aqueous acid stream 620 in multiple phases comprising multiple stripping vessels. In the present aspect, the solvent stream 610 can be contacted with the aqueous acid stream 620 in countercurrent flow.
The aqueous acid stream 620 can strip the lithium from the organic phase of the solvent stream 610 and re-claim the lithium into the aqueous phase of the aqueous acid stream 620 to create an aqueous lithium-rich stream 623. By supplying sulfuric acid at 100% the stoichiometric proportion to the amount of lithium in the solvent stream 610, roughly 100% of the lithium can be extracted into the aqueous acid stream 620. In practice, it can be desirable to supply 110% of the stoichiometric proportion to the amount of lithium in the solvent stream 610. The O/A ratio of the solvent stream 610 to the aqueous acid stream 620 within the stripping vessel 684 can be from 7/1 to 1/1. Preferably, the O/A ratio can be from 6/1 to 2/1. Most preferably, the O/A ratio can be approximately 4/1.
The aqueous lithium-rich stream 623 (carrying roughly 100% of the lithium initially introduced into the solvent extraction unit 480 in the aqueous feed stream 600) can exit the stripping vessel 684 and the solvent extraction unit 480 along a flow path 622. With regard to the improved production circuit 415 of
The solvent stream 610 can exit the stripping vessel 684 substantially devoid of lithium. The majority of the solvent stream 610 can be recycled, as shown by a flow path 614 wherein the solvent stream 610 can rejoin the flow path 611 after exiting the stripping vessel 684. A small portion of the solvent stream 610 can be lost in the process, which can be replenished by injection of additional extractant(s) and/or diluent(s) into the solvent extraction unit 480 along flow path 611. In some aspects, any organic components present in the aqueous waste stream can be subsequently removed. In some aspects, a technology such as an activated carbon filter, for example and without limitation, can be used to remove organics from an aqueous stream. This can be desirable in aspects wherein the presence of organics in an aqueous stream can cause issues in downstream processing steps (e.g. foaming, coloration, or other issues) and/or when required by applicable aqueous waste control standards from local or federal environmental protection regulations, for example and without limitation.
The table, below, contains one example of experimental results for the chemical compositions of the aqueous feed stream 600 and the aqueous lithium-rich stream 623:
In the example shown, the final concentration of lithium in the aqueous lithium-rich stream 623 can be 7.47× the initial concentration of lithium in the aqueous feed stream 600. The concentration factor can vary, such as depending upon the O/A ratios utilized in the extraction circuit 681 and the stripping circuit 683. In some aspects, the concentration factor for the lithium concentration can be greater than or equal to 3×. In preferred aspects, the concentration factor for the lithium concentration can be greater than or equal to 5×. In most preferred aspects, the concentration factor for the lithium concentration can be greater than or equal to 7×.
Notably, the concentration factors for the sodium concentration and potassium concentration can be less than 1, denoting a decrease in concentration for those respective cations from their initial concentrations in the aqueous feed stream 600 to their final concentration in the aqueous lithium-rich stream 623.
In some aspects, the concentration factor for the sodium concentration can be less than or equal to 0.5×. In preferred aspects, the concentration factor for the sodium concentration can be less than or equal to 0.35×. In most preferred examples, the concentration factor for the sodium concentration can be less than or equal to 0.10×.
In some aspects, the concentration factor for the potassium concentration can be less than or equal to 0.15×. In preferred aspects, the concentration factor for the potassium concentration can be less than or equal to 0.10×. In most preferred examples, the concentration factor for the potassium concentration can be less than or equal to 0.04×.
Because of the high purity of the chemical composition of the aqueous lithium-rich stream 623, the aqueous lithium-rich stream 623 can be suited for producing lithium-carbonate or lithium hydroxide of sufficient purity to meet criteria for battery applications. The improved lithium extraction process 400, 500 can also be utilized for producing salable lithium-carbonate or lithium hydroxide from brines containing other monovalent species of cations, such as rubidium and/or cesium.
As noted above, the waste-water stream 199 exiting the solvent extraction unit 480 along flow path 603 can be devoid of lithium, which allows waste-salts to be completely separated from the waste-water stream 199 in a linear process without the loss of more than trace amounts of lithium. By avoiding the need for a recycle loop in the treatment of the waste-water stream 199, resource consumption can be substantially reduced. For example, acid consumption, such as sulfuric acid consumption, can be reduced for a cost savings, or the saved acid can be repurposed for the acid leaching step 104, which can result in a 3-5% improvement in lithium recovery from the lithium ore. A loss of 2-3% of the lithium with the separation of sodium and potassium salts can also be avoided, thereby increasing production efficiency. Soda ash consumption can be reduced approximately 25-30%. Power consumption and overall cost of production can be reduced approximately 7% for the entire plant.
One should note that conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain aspects include, while other aspects do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more particular aspects or that one or more particular aspects necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular aspect.
It should be emphasized that the above-described aspects are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the present disclosure. Any process descriptions or blocks in flow diagrams should be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included in which functions may not be included or executed at all, may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present disclosure. Many variations and modifications may be made to the above-described aspect(s) without departing substantially from the spirit and principles of the present disclosure. Further, the scope of the present disclosure is intended to cover any and all combinations and sub-combinations of all elements, features, and aspects discussed above. All such modifications and variations are intended to be included herein within the scope of the present disclosure, and all possible claims to individual aspects or combinations of elements or steps are intended to be supported by the present disclosure.
