CROSS-REFERENCE

This Application claims priority to US Provisional Patent Application No. 63/237,996 filed on August 27, 2021 (“PROCESSING HARD ROCK LITHIUM MINERALS OR OTHER MATERIALS TO PRODUCE BOTH LITHIUM CARBONATE AND LITHIUM HYDROXIDE”), which is entirely incorporated herein by reference.

FIELD

[0001] The present disclosure relates to methods for processing hard rock lithium minerals and other lithium containing materials to produce both lithium carbonate (Li2CO3) and lithium hydroxide monohydrate (LiOH-H2O).

BACKGROUND

[0002] Electrically-powered vehicles and other machines are increasing in popularity due to market demand, regulatory requirements, and political desire to reduce fossil fuel consumption and greenhouse gas emissions. This transition requires economical production of large volumes of lithium materials for batteries.

[0003] Lithium carbonate (Li2CO3, or LC) and lithium hydroxide monohydrate (LiOH- H2O, or LHM) are the two most important basic lithium materials for lithium battery production and for many other lithium related industries.

[0004] Lithium is extracted from two main lithium sources: liquid brine containing lithium; and hard rock deposits containing lithium such as spodumene. Spodumene is a pyroxene mineral consisting of lithium aluminum inosilicate (LiAl(SiCO3)2). The naturally-occurring low-temperature form a-spodumene is in the monoclinic system , and the high-temperature 0- spodumene crystallizes in the tetragonal system, a-spodumene converts to 0-spodumene at temperatures above 900 °C.

[0005] To produce U2CO3 and LiOH-HzO from hard rock, the sulfuric acid process is the most reliable technology, and is therefore the mostly used process in current lithium industry.

[0006] Fig. 1 shows a prior art method for processing a-spodumene concentrate to produce Li2CO3. Solid a-spodumene concentrate is converted to P-spodumene by kiln calcination. Then P-spodumene is mixed with H2SO4 and subjected to acid roasting. Then the acid-roasted material is mixed with water in leaching tanks, where lithium and other metal impurities are leached into solution. Limestone powder (CaCCh), lime (CaO) or hydrated lime (Ca(OH)2), NaOH, Na2CO3 or any other reagent which can precipitate the impurities may be added to the solution to change the pH and remove the impurities. By solid/liquid (S/L) separation, leaching residue and impurity residue are separated, and a pregnant leach solution (PLS) is obtained. If necessary, an ion exchange (IX) circuit is further used to remove Ca and Mg impurities. By this purification, clean PLS solution comprising Li2SO4 is obtained. The purified Li2SO4-PLS solution is reacted with Na2CO3 to precipitate Li2CO3. The precipitated L12CO3 is separated and dried as L12CO3 product. If battery-grade product is desired, the wetLi2CO3 cake obtained is re-dissolved and further purified by CO2 method as known in the art. The wet L12CO3 obtained after filtration is dried to produce a final battery-grade Li2CO3 product. Usually, before final packing, there are magnetic impurity removal steps in some parts of the process and a micronizing step to reduce the size of Li2CO3 particles to a desired size, as well as, some evaporation steps to increase concentration of main compositions. The mother liquor from Li2CO3 solid/liquid separation goes to a Na2SO4 crystallization circuit to get rid of Na2SO4 solid from the process. The mother liquor and condensed water after Na2SO4 crystallization can be recycled to the process for re-use.

[0007] Fig. 2 shows a prior art method for processing a-spodumene concentrate to produce lithium hydroxide monohydrate LiOH-H2O. The method is similar to the method of Fig. 1 for producing Li2CO3, with differences as follows. The purified Li2SO4-PLS is reacted with NaOH to produce mixed LiOH and Na2SO4 solution. By freezing treatment, a typical method used in current lithium industry and known in the art, Na2SO4 is separated from the solution in the form of Glauber's salt (Na2SO4-10 H2O). The Na2SO4-removed LiOH PLS solution is sent to crystallizer to produce a wet LiOH cake. The wet LiOH cake is dried to produce a final LiOH- H2O product. If battery-grade product is desired, the produced wet LiOH cake is re-dissolved and subjected to secondary or tertiary crystallization, as required. The mother liquor and condensed water of LiOH crystallization is recycled to the process for re-use. In another stream, the Glauber's salt separated from the PLS is re-dissolved and the resulting Na2SO4 solution is sent to an evaporator for Na2SO4 crystallization. The mother liquor and condensed water of Na2SO4 crystallization are recycled to the process for re-use.

[0008] The processes of Figs. 1 and 2 are directed to producing either Li2CCh or LiOH- H2O, but not both of them.

[0009] In general, the processes of Figs. 1 and 2 produce up to more than 2 tons of Na2SO4 for 1 ton of Li2CO3 or Li0H-H20. This is problematic for many reasons. First, the Na2SO4 byproduct needs a special production plant for its crystallization, which requires a high capital investment. For example, up to $15 million USD of capital investment is required for a typical Na2SO4 crystallizer plant for a 20 KT Lithium Carbonate Equivalent (LCE) chemical plant. This significantly increases capital expenditure, and significantly lowers production profit. Second, evaporating water from the very large volume of Na2SO4 solution consumes a large amount of energy. Third, NaOH or Na2CCh is consumed in the chemical conversion reaction from Li2SO4 solution to Na2SO4 byproduct. NaOH and Na2CO3 are higher value chemicals than Na2SO4, and therefore this impairs the economics of the process. Last, but not the least, the marketability of the Na2SO4 byproduct is limited. Use of Na2SO4 for the production of detergent powder accounts for more than 80% of the total market for Na2SO4, and this market is found mainly in Asian countries. This means that in countries outside of Asia, especially in North America and Europe, it will be economically prohibitive to produce lithium materials from hard rock with the conventional process as illustrated in Figs 1 and 2, despite the production of Na2$O4 as a byproduct and its transport to economically viable markets. Moreover, mining industries and many other industries also produce large volumes of Na2$O4, making for a supply-rich market of Na2$O4. [0010] The processes of Figs. 1 and 2 also produce CO2 emissions, as a result of combustion of fossil fuels to produce heat for the calcination and acid-roasting steps. These CO2 emissions may act as greenhouse gases that contribute to climate change.

[0011] The processes of Figs. 1 and 2 also consume large amounts of NaOH and Na2CCh as main reagents, and this adds to overall cost of the process.

[0012] Nonetheless, the conventional processes of Figs. 1 and 2 are well proven and optimized for the production of U2CO3 and LiOH-FFO, by the conversion reaction of Li2SO4 with Na2CO3 or NaOH, respectively. It would therefore be desirable to maintain these conversion reactions, while improving upon the processes to address the aforementioned issues.

[0013] Accordingly, there is a need in the art for methods of processing spodumene or other lithium containing materials and solutions to produce both U2CO3 and Li0H-H20, and allow for selective control over the amount of each such lithium product that is produced. It would also be desirable if such methods were to avoid or reduce production of the Na2SO4 byproduct. It would be desirable for such methods to increase the recovery of lithium produced by the method, significantly reduce the amount of required main or primary reagent or replace the main reagent with a more economical reagent, reduce energy inputs, and reduce CO2 gas emissions relative to prior art methods. It would be desirable to use one reagent to produce both Li2CO3 and LiOH-H2O. It would also be desirable if CO2 from the flue gas from lithium plant can be utilized in the production of a lithium product.

SUMMARY

[0014] In accordance with a broad aspect of the present disclosure, there is provided a method of processing a lithium-containing material to produce a lithium product, the method comprising the steps of: preparing an aqueous feed solution comprising lithium sulfate by reacting the lithium-containing material with sulfuric acid; reacting the feed solution with sodium hydroxide to produce a first intermediate solution comprising lithium hydroxide and sodium sulfate; producing the lithium product, wherein producing the lithium product comprises the sub-step(s) of: (i) separating a primary lithium product comprising the lithium hydroxide from a first portion of the first intermediate solution; or reacting a second portion of the first intermediate solution with carbon dioxide to produce a secondary lithium product comprising lithium carbonate.

[0015] In embodiments, in accordance with another broad aspect, the method of processing a lithium-containing material to produce a lithium product may comprise the steps of subjecting the first intermediate solution comprising lithium hydroxide and sodium sulfate to freezing, thereby separating the lithium hydroxide from the sodium sulfate; and reacting the carbon dioxide with lithium hydroxide to produce the secondary lithium product comprising lithium carbonate.

[0016] In accordance with a further broad aspect of the present disclosure, there is provided a method of processing an aqueous feed solution comprising lithium sulfate to produce a lithium product, the method comprising the steps of: reacting the aqueous feed solution with sodium hydroxide to produce a first intermediate solution comprising lithium hydroxide and sodium sulfate; wherein producing the lithium product comprises the sub-step(s) of: (i) separating a primary lithium product comprising the lithium hydroxide from at least a first portion of the first intermediate solution; or reacting a second portion of the first intermediate solution with carbon dioxide to produce a secondary lithium product comprising lithium carbonate.

[0017] In embodiments, in accordance with another broad aspect, the method of processing an aqueous feed solution comprising lithium sulfate to produce a lithium product may comprise the steps of subjecting the first intermediate solution comprising lithium hydroxide and sodium sulfate to freezing, thereby separating the lithium hydroxide from the sodium sulfate; and reacting the carbon dioxide with lithium hydroxide to produce the secondary lithium product comprising lithium carbonate.

[0018] In embodiments, the method may comprise a step of producing a second intermediate solution comprising sodium sulfate from the first intermediate solution. [0019] In embodiments, the primary and secondary lithium products may be simultaneously produced.

[0020] In embodiments, the method may comprise a step of reacting the second intermediate solution comprising sodium sulfate with an alkali chemical to produce sodium hydroxide and a byproduct. In accordance with another broad aspect of the present disclosure, there is provided a method of processing a lithium-containing material to produce a first primary lithium product of lithium hydroxide and a secondary lithium product comprising lithium carbonate, the method comprising the steps of: preparing an aqueous feed solution comprising lithium sulfate by reacting the lithium-containing material with sulfuric acid; reacting the feed solution with sodium hydroxide to produce a first intermediate solution comprising lithium hydroxide and sodium sulfate; separating the primary lithium product comprising lithium hydroxide from a first portion of the first intermediate solution comprising lithium hydroxide and sodium sulfate; and reacting a second portion of the first intermediate solution with carbon dioxide to produce the secondary lithium product comprising lithium carbonate.

[0021] In embodiments, in accordance with another broad aspect, the method of processing a lithium-containing material to produce to produce a first primary lithium product of lithium hydroxide and a secondary lithium product comprising lithium carbonate may comprise the steps of subjecting the first intermediate solution comprising lithium hydroxide and sodium sulfate to freezing, thereby separating the lithium hydroxide from the sodium sulfate; and reacting the carbon dioxide with lithium hydroxide to produce the secondary lithium product comprising lithium carbonate.

[0022] In accordance with a further broad aspect of the present disclosure, there is provided a method of processing an aqueous feed solution comprising lithium sulfate to produce a first primary lithium product of lithium hydroxide and a secondary lithium product comprising lithium carbonate, the method comprising the steps of: reacting the feed solution with sodium hydroxide to produce a first intermediate solution comprising lithium hydroxide and sodium sulfate; separating the primary lithium product comprising lithium hydroxide from a first portion of the first intermediate solution comprising lithium hydroxide and sodium sulfate; and reacting a second portion of the first intermediate solution with carbon dioxide to produce the secondary lithium product comprising lithium carbonate.

[0023] In embodiments, in accordance with another broad aspect, the method of processing an aqueous feed solution comprising lithium sulfate to produce to produce a first primary lithium product of lithium hydroxide and a secondary lithium product comprising lithium carbonate may comprise the steps of subjecting the first intermediate solution comprising lithium hydroxide and sodium sulfate to freezing, thereby separating the lithium hydroxide from the sodium sulfate; and reacting the carbon dioxide with lithium hydroxide to produce the secondary lithium product comprising lithium carbonate.

[0024] In embodiments, the alkali chemical may comprise calcium hydroxide and the byproduct may comprise calcium sulfate; the alkali chemical may comprise ammonium hydroxide and the byproduct may comprise ammonium sulfate; the alkali chemical may comprise comprises barium hydroxide and the byproduct may comprise barium sulfate; or the alkali chemical may comprise potassium hydroxide and the byproduct may comprise potassium sulfate.

[0025] In embodiments, the method may comprise a step of producing the second intermediate solution, wherein the second intermediate solution may comprises the sub-steps of: separating decahydrate of sodium sulfate from the portion of the first intermediate solution; and dissolving the separated decahydrate of sodium sulfate in water to produce the second intermediate solution comprising sodium sulfate.

[0026] In embodiments, the carbon dioxide may be separated from a flue gas produced by combustion of a fossil fuel used to produce heat for sulfuric acid roasting of a mineral used to prepare the feed solution, or for a calcination process of a mineral used to prepare the feed solution, or for generating steam for use in the method. [0027] In embodiments, the lithium-containing material may comprise a mineral, such as spodumene, and reacting the lithium-containing material with sulfuric comprises may comprise sulfuric acid roasting the mineral to prepare an acid-roasted mineral.

[0028] In embodiments, before reacting the mineral with sulfuric acid, the method may comprise the step of subjecting the mineral to a calcination process for phase conversion of the mineral.

[0029] In embodiments, the lithium-containing material may comprise low grade lithium carbonate, other lithium containing hard rocks, non-hard rock lithium containing minerals, or material from lithium battery recycling.

[0030] Additional aspects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments which are exemplary and should not be interpreted as limiting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the drawings, like elements may be assigned like reference numerals. The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted are but one of a number of possible arrangements utilizing the fundamental concepts of the present invention.

[0032] Further features and advantages of the present disclosure will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0033] Fig. 1 is a flow chart for a prior art method for processing a-spodumene concentrate to produce a Li2CCh lithium product, and Na2SO4 byproduct.

[0034] Fig. 2 is a flow chart for a prior art method for processing a-spodumene concentrate to produce a LiOH-FFO lithium product, and Na2SO4 byproduct. [0035] Fig. 3 is a flow chart for an embodiment of a method of the present invention for processing a-spodumene concentrate and flue gas to produce a LiOH-FFO primary lithium product, a Li2CCh secondary lithium product, a CaSCh byproduct by reaction of a Na2SO4 intermediate product with an alkali chemical, and a NaOH reaction fluid that is circulated in the closed loop and re-used in the method.

[0036] Fig. 4 represents a flow chart for another embodiment of a method of the present invention for processing a-spodumene concentrate and use of flue gas to produce a LiOH-FFO primary lithium product, a Li2CCh secondary lithium product, a CaSCh byproduct by reaction of a Na2SO4 intermediate product with an alkali chemical, and a NaOH reaction fluid that is circulated in the closed loop and re-used in the method. Fig.4 is similar to Fig.3 in most parts except that no Na2SO4 mother liquor stream is produced in Li2CO3 circuit.

DETAILED DESCRIPTION OF EMBODIMENTS

[0037] Overview.

[0038] Example methods are described herein. It should be understood that the words “example” and “exemplary” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as being an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or features. The example embodiments described herein are not meant to be limiting. It will be readily understood that certain aspects of the disclosed methods can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

[0039] The disclosure relates to processing a lithium-containing materials such as hard rock to produce either lithium carbonate (Li2CCh) or lithium hydroxide monohydrate (LiOH), or both of them. Any term or expression not expressly defined herein shall have its commonly accepted definition understood by a person skilled in the art. [0040] The present disclosure provides a method of processing a material containing lithium, such as hard rock lithium minerals like a-spodumene, to produce a primary lithium product comprising lithium hydroxide monohydrate (LiOH-I O), a secondary lithium product comprising lithium carbonate (Li2CCh), and a sulfate byproduct such as calcium sulfate (CaSO-i) by the conversion of a sodium sulfate (Na2SO4) intermediate product in the presence of an alkali chemical. It will be understood that the terms "primary lithium product" and "secondary lithium product" are used for convenience to distinguish the products, and do not limit the present invention in terms of the relative amounts that are produced of each product, or the order by which they each can be produced. The amount of each product may be selectively varied.

[0041] In a broad aspect of the present disclosure, there is provided a method of processing a material containing lithium, such as hard rock lithium minerals like a-spodumene, to produce a primary lithium product comprising lithium hydroxide monohydrate (LiOH-I O), a secondary lithium product comprising lithium carbonate (Li2CO3), and a sulfate byproduct such as calcium sulfate (CaSO-i) by converting sodium sulfate (Na2SO4) as an intermediate product, the method comprising the steps of: (i) preparing and providing an aqueous feed solution comprising lithium sulfate (Li2SO4) by reacting the lithium- containing material with sulfuric acid (H2SO4); (ii) reacting the aqueous feed solution with some base reagents, such as, sodium hydroxide (NaOH), sodium carbonate (Na2CCh), limestone powder (CaCCh), lime (CaO), hydrated lime (Ca(OH)2), water or other suitable reagents, and subjecting the aqueous feed solution to a solid/liquid separation to obtain a purified feeding solution containing Li2SO4; (iii) reacting the purified feeding solution with NaOH to produce a first intermediate solution comprising lithium hydroxide (LiOH) and sodium sulfate (Na2SO4), wherein said first intermediate solution may be further divided into a first and a second portion; (iv) separating the primary lithium product comprising lithium hydroxide (LiOH) from the first portion of the first intermediate solution, and producing a second intermediate solution comprising sodium sulfate (Na2SO4) from the first portion of the first intermediate solution; or/and (v) alternatively or in parallel, reacting the second portion of the first intermediate solution with a secondary reagent comprising carbon dioxide (CO2) to produce a secondary lithium product comprising lithium carbonate (Li2CCh) and a third intermediate solution comprising sodium sulfate(Na2SO4); and (vi) reacting the second intermediate solution comprising sodium sulfate (Na2SO4), or the third intermediate solution comprising sodium sulfate (Na2SO4), or both of them, with an alkali chemical to produce sodium hydroxide (NaOH) and a byproduct such as calcium sulfate (CaSCh); or/and optionally (vii) repeating steps (ii) through (vi), wherein the sodium hydroxide (NaOH) produced in step (vi) is used and recycled when repeating step (ii).

[0042] In an embodiment, the U2SO4 feed solution is derived from low grade lithium carbonate product, which can be obtained from the brine lithium industry. The low grade lithium carbonate may be reacted with H2SO4 to produce a Li2SO4 feed solution.

[0043] In another embodiment, the U2SO4 feed solution is derived from used battery materials, which can be obtained from the battery recycling industry. The used battery materials may be reacted with H2SO4 and be leached to produce U2SO4 feed solution.

[0044] In another embodiment, the U2SO4 feed solution can be derived from lithium extracted from hard rock minerals, other than spodumene, such as petalite, lepidolite, zinnwaldite, amblygonite, and eucryptite, and non-hard rock minerals such as hectorite, lithium clays, jadarite and so on. Lithium can be extracted from these minerals using a H2SO4 acid process similar to extracting lithium from spodumene to produce the Li2SO4 feed solution. Depending on the mineral, calcination, i.e. phase conversion, and/or acid roasting at high temperatures of the mineral may or may not be required.

[0045] It will be understood that the methods may be performed on a batch basis (i.e., the steps are performed once in sequence for a batch of a-spodumene concentrate), or on a continuous basis (e.g., the steps are performed continuously and simultaneously as further a- spodumene concentrate is continuously processed to continuously produce further feed solution, to continuously produce further primary lithium product and secondary lithium product).

[0046] Fig.3 and Fig.4, as described below in more details, represent flow charts showing steps of different embodiments of the methods. With the benefit of such flow charts, the person skilled in the art will be able to carry out processes of the described method using equipment known in the art, such as rotary kilns, various reactors, tanks, thickener, centrifuge, various filters, various driers, ion exchange, water treatment equipment, crystallizers, and other separation equipment, heating equipment, and so forth, as may be needed.

[0047] The following examples provide an embodiment of the method of the present disclosure, as it may applied to processing a-spodumene concentrate, such examples are not limitative , and shall not be interpreted, as limiting the methods described herein.

[0048] Example no. 1: combined production of LiOH-HiO as primary lithium product, LizCCh as a secondary lithium product by capture and conversion or sequestration of CO2 from fine gas, as well as, the production of CaSC>4 byproduct by the reaction of an intermediate byproduct NaiSCh with an alkali chemical (Ca(OH)2), and a NaOH reaction fluid that may be recirculated in a closed-loop and re-used in the method as described herein.

[0049] Fig. 3 represents a flow chart of an embodiment of a method of the present invention for processing a-spodumene concentrate to produce a LiOH-FFO primary lithium product, and a Li2CO3 secondary lithium product by capturing and convertingor sequestring CO2 from a flue gas. In this example, second and third Na2SO4 intermediate solution is converted by a reaction with an alkali chemical of Ca(OH)2 to produce a final byproduct of solid CaSCh. and a solution of NaOH. The NaOH may be re-used as a "reaction fluid" that is circulated inside a closed-loop circuit of the present method for further production of the primary lithium product (LiOH-H2O) and the secondary lithium product (Li2CO3). The as illustrated may be continuously performed. The term "NaOH reaction fluid", as used herein, distinguishes the NaOH produced and re-used inside the closed-loop circuit from an initial input of NaOH that is used when the method is started. As the method is continuously performed, the NaOH reaction fluid is again regenerated, and circulated in the closed-loop circuit, thus reducing or avoiding the need for an input of additional NaOH during the continuous and further production of LiOH-H2O and Li2CO3. [0050] Although Ca(OH)2 is used as the alkali chemical in this example, it will be understood that other alkali chemicals of the group consisting of ammonium hydroxide (NH4OH), barium hydroxide (Ba(OH)2), potassium hydroxide (KOH) or mixtures of any of the foregoing, may be used instead of Ca(OH)2. [0051] The reaction of these other alkali chemicals with Na2SO4 will produce different byproducts, as noted in Table 1 below.

[0052] As shown in Fig. 3, in embodiments, the steps of the method may be conceptualized as being parts of a PLS circuit, a LiOH/Na2SO4 separation circuit, a LiOH circuit, a Na2SO4 conversion circuit, a Li2CCh circuit, and a CO2 circuit, as described below. [0053] Pregnant Leach Solution (PLS) Circuit.

[0054] A purpose of the PLS circuit may be to produce an intermediate solution comprising a mixture of LiOH and Na2SO4, denoted LiOH/Na2SO4, that is used in downstream steps of the method. In embodiments as illustrated in Fig. 3, the PLS circuit includes steps 300, 302, 304, and 406. [0055] At step 300, solid a-spodumene concentrate is converted to P-spodumene by calcination in a rotary kiln. Calcination is typically performed at temperatures of above 900 °C to convert a-spodumene to P-spodumene, but the present invention is not limited by a particular temperature.

[0056] At step 302, the produced P-spodumene is mixed with sulfuric acid (H2SO4) and subjected to acid roasting. Roasting is typically performed at temperatures of about 250 °C to form water soluble lithium sulfate (Li2SO4), but the present invention is not limited by a particular temperature.

[0057] In the steps 300 and 302, the heat required by kiln calcination and acid roasting is produced by combustion of fossil fuels in the current lithium extraction industry. This produces flue gases, including CO2 gas, which may be diverted for use in the process as described below, rather than emitted into the atmosphere.

[0058] At step 304, the acid-roasted material is mixed with water in leaching tanks where lithium and other metal impurities are leached into solution. For solution purification, usually, limestone powder (CaCCh), lime (CaO) or hydrated lime (Ca(OH)2), NaOH, Na2CCh or any other reagent which can precipitate impurities is or are added into the solution to change the pH and remove impurities and the over dosed SO4 ² ' in acid roasting. By solid/liquid (S/L) separation, leaching residue and impurity residue are separated and PLS (pregnant leach solution) solution is obtained. If necessary, an ion exchange (IX) circuit is further used to remove Ca and Mg impurities. By this purification, clean PLS solution comprising Li2SO4 is obtained. Step 304 results in the production of aqueous solution comprising lithium sulfate (Li2SO4), which solution is considered to be an example of a "feed solution" in the present invention. Some evaporation steps to increase concentration of main compositions may be used during this feed solution making step, as required.

[0059] As step 406, NaOH is added to the PLS solution comprising Li2SO4. The Li2SO4 PLS reacts with NaOH to form a solution of a mixture of LiOH and Na2SO4, as shown below in Eqn. 1. The NaOH may be considered to be an example of a "reaction fluid" in the present invention, and the mixed Na2SO4 and LiOH solution may be considered to be a "first intermediate solution" in the present invention. L12SO4(aq) "I" 2 NaOH(aq) N<12SO4(aq) "I" 2 LlOH(aq) (Eqn. 1)

[0060] LiOH/NaiSCh Separation Circuit.

[0061] A purpose of the LiOH/Na2SO4 Separation Circuit is to process the mixed LiOH and Na4SO4 solution resulting from the PLS circuit to produce the LiOH PLS solution and separate Na2SO4 from the solution. In embodiments, and as illustrated in Pig. 3, the LiOH/Na2SO4 Separation Circuit includes step 408.

[0062] At step 408, the solution resulting from PLS circuit may be subjected to freezing treatment by lowering its temperature between 0°C to -15°C. The solubility of LiOH at freezing temperatures is greater than the solubility of Na2SO4 at freezing temperatures. Thus, as a result of the freezing treatment, Na2SO4 is separated from solution in the form of the decahydrate of sodium sulfate (Na2SO4-10 H2O), which is known in the art as a Glauber's salt.

[0063] LiOH Circuit.

[0064] A purpose of the LiOH circuit is to process the LiOH solution resulting from the LiOH/Na2SO4 Separation Circuit to produce the LiOH-H2O primary lithium product. In embodiments, as illustrated in Fig. 3, the LiOH Circuit includes step 410.

[0065] At step 410, the Na2SO4-removed LiOH PLS solution resulting from step 408 is subjected to crystallization to produce a wet LiOH cake.

[0066] The wet LiOH cake is dried to produce a final LiOH-H2O product. If battery-grade product is desired, the produced wet LiOH cake can be re-dissolved and subjected to secondary or tertiary crystallization, as required. Usually, magnetic impurity removal in some parts of process and/or micronizing before packaging may also be performed for battery grade product.

[0067] NaiSO4 Conversion Circuit.

[0068] A purpose of the Na2SO4 conversion circuit is to process the Glauber's salt separated from the LiOH solution in step 408, and the mother liquor comprising Na2SO4 separated from step of 307 in the Li2CO3 Circuit, to produce CaSO4 as a byproduct. Another purpose of the Na2SO4 conversion circuit is to produce further NaOH reaction fluid, which is used to repeatedly react with further Li2SO4 PLS in step 406 of the PLS circuit, as the method continues to be performed. In the method, the NaOH reaction fluid allows the LiOH conversion reaction in step 406 of the PLS Circuit to continue and NaOH is so recycled back into the processing method.

[0069] The skilled in the art would appreciate that, the initial input of NaOH to start the method is effectively not consumed, because it is regenerated in the Na2SO4 conversion Circuit as the NaOH reaction fluid.

[0070] In embodiment, as illustrated in Fig. 3, the Na2SO4 conversion circuit may include steps 412 and 600.

[0071] At step 412, the Glauber's salt that is produced from the freezing separation process of step 408 is re-dissolved in water to produce a solution of Na2SO4. This may be considered to be a "second intermediate solution" of the present invention.

[0072] At step 600, the solution of Na2SO4 resulting from step 412 or the “second intermediate solution” is mixed with an alkali chemical, for example, with hydrated lime Ca(OH)2 so that the dissolved Na2SO4 and the Ca(OH)2 react to convert the Na2SO4 to CaSCh and NaOH., as illustrated by the following equation:

[0073] As noted above with reference to Table 1, different alkali chemicals may be used instead of Ca(OH)2 to produce NaOH and other sulfate byproducts, such as, but not limited to ammonium sulfate ((NH4)2SO4), barium sulfate (BaSO4), calcium sulfate (CaSO4) and potassium sulfate (K2SO4).

[0074] At step 600, a second input stream of a mother liquor comprising Na2SO4 solution from step 307 of Li2COs circuit may also be mixed with hydrated lime, and converted to CaSO4 and NaOH, in accordance with Eqn. 2. [0075] In comparison with the prior art process shown in Fig.1 and Fig. 2, a skilled in the art would appreciate that the method as shown in Fig. 3 has several advantages, such as, but not limited to, a crystallization circuit for treating the Na2SO4 may be avoided or at least be reduced in capacity, thus reducing its associated capital and operating cost; in comparison with Na2SO4, CaSO4 typically has a higher market value and different industrial application; and also CaSO4 may be more conveniently handled than Na2SO4.

[0076] A portion or all of the NaOH may be sold to market as a product. In addition or in alternative, a portion or all of the NaOH may be re-introduced and recycled back into the process for use in the PLS purification process of step 304. In addition or in alternative, a portion or all of the NaOH may be re-introduced to the process and repeatedly used as "reaction fluid" in the LiOH /Na2SO4 Intermediate Solution making process of step 406. A skilled in the art would appreciate that this aspect is particularly significant because it means that only an initial amount of NaOH needs to be supplied as a reagent to start the process in the first instance for performing step 406. As step 406 is performed continuously, it is no longer necessary to supply additional NaOH. Rather, the NaOH can be sourced from step 600 and re-used or recycled back into the method. That is, while the NaOH is consumed in the PLS circuit (see Eqn. 1), it is regenerated in the Na2SO4 conversion circuit.

[0077] Li ₂ CO ₃ Circuit

[0078] A purpose of the Li2CO3 circuit is to process the mixed LiOH/Na2SO4 solution resulting from step 406 to produce the Li2CO3 secondary lithium product. In embodiments, as illustrated in Fig. 3, the Li2CO3 circuit includes steps 307 and 308.

[0079] At step 307, the LiOH solution resulting from step 406 is reacted with CO2 produced from the CO2 circuit (described below), as follows. The CO2 dissolves and reacts with the hydroxide ions (OH ) to produce bicarbonate ions (HCO3 ) in accordance with Eqn. 3a. The bicarbonate ions (HCO3 ) react with hydroxide ions (OH ) to produce carbonate ions (CO3 ² ) and water (H2O), in accordance with Eqn. 3b. The carbonate ions (CO3 ² ) react with lithium ions to produce the Li2CO3 as a lithium primary product, in accordance with Eqn. 3c.

[0080] Thus, the overall process of converting the LiOH to U2CO3 in accordance with step307 is as follows.

[0081] The sodium sulfate Na2SO4 solution resulting from step 307 may be considered a "third intermediate solution" of the present disclosure, and separated as a mother liquor from the precipitated Li2CO3. It will be understood that the term "third intermediate solution" is used for convenience to distinguish the sodium sulfate Na2SO4 solution resulting from step 307 from the sodium sulfate Na2SO4 solution resulting from step 412 previously referred to as the "second intermediate solution." However, it will also be understood that the sodium sulfate Na2SO4 solution resulting from steps 307 and 412 collectively may be referred to as the "second intermediate solution", for the purpose of conveniently distinguishing them collectively from the "first intermediate solution" resulting from step 406. Or, in embodiments of the disclosure where step 412 is not performed, the sodium sulfate Na2SO4 solution resulting from step 307 may be referred to as the "second intermediate solution" for the purpose of conveniently distinguishing it from the "first intermediate solution" resulting from step 406.

[0082] At step 308, if battery-grade product is desired, then the obtained wet Li2CO3 cake is re-dissolved and, at step 308, is further purified by the CO2 method as described in the prior art, namely, the aforementioned CO2 method involves reacting Li2CO3 product with CO2 to produce soluble LiHCCh. Insoluble impurities, such as iron, magnesium, and calcium are removed from the solution. The CO2 is then removed, such as by increasing the temperature of the solution, to precipitate pure Li2CO3.

[0083] After steps 308, the obtained wet Li2CO3 is dried. Magnetic impurity removal steps may be performed in some parts of the process to remove impurities from the Li2CO3. A micronizing step may be performed to reduce the Li2CCh product to a desired particle size before final packing.

[0084] CO ₂ Circuit.

[0085] A purpose of the CO2 circuit is to produce a CO2 gas that is separated from a clean mixed source gas comprising CO2 gas. The produced CO2 gas may be used for reaction with the LiOH solution in step 307.

[0086] In embodiments as illustrated in Fig. 3, in step 700, the source gas may be a flue gas that is directed from a flue gas stream produced by combustion of a fossil fuel in kiln used to produce heat for calcination of a-spodumene to produce P-spodumene in step 300.

[0087] In addition or in the alternative, a skilled in the art would appreciate that in step 702, the source gas is a flue gas directed from a flue gas stream produced by combustion of a fossil fuel in a burner or other heating equipment used to produce heat for acid roasting of the - spodumene in step 302. In addition or in the alternative, in step 704, the source gas is a flue gas produced by combustion of a fossil fuel for some other process, which may or may not be otherwise associated with the method for producing the lithium product. As a non-limiting example, the fossil filed may be combusted to produce heat to generate steam for use in the process. In addition or in the alternative, the source gas may be open air.

[0088] At step 706 of the CO2 circuit, the source gas may be processed to produce a gas stream that has a CO2 concentration that is higher than that of the source gas. In embodiments, the produced gas stream may be pure or substantially pure CO2 gas, but the present limitation is not limited by any particular purity or concentration of CO2 gas. Suitable equipment and processes are known in the art for separation of CO2 gas from flue gas. Non-limiting examples include physical or chemical absorption-based methods (e.g., using monoethanolamine (MEA) solvent, caustic, ammonia solution), physical or chemical adsorption-based methods (e.g. using molecular sieves, activated carbon, metallic oxides), cryogenic methods, and membranebased methods that rely on gas separation, or gas absorption phenomena, as known in the art. Non-CCh components of the flue gas may optionally be treated before being emitted to the atmosphere (as indicated by the label "To air" in Fig. 3), sequestered, or otherwise treated in some manner. The gas stream that is relatively high in CO2 concentration may be directed to Li2CO3 for reaction with the LiOH solution in step 307. In other words, the captured CO2 in step 706 from flue gas is converted or sequestered in lithium carbonate product in step 307.

[0089] Inter-relationship of PLS Circuit, LiiCCh Circuit with LiOH Circuit LiOH/Na2SO4 Separation Circuit and NaiSO4 Conversion Circuit.

[0090] In embodiments, and as illustrated in Fig. 3, the skilled in the art would appreciate that the PLS Circuit, LiOH/Na2SO4 Separation Circuit, Li2CO3 circuit, LiOH circuit, and Na2SO4 conversion circuit are inter-related to each other in at least the following aspects.

[0091] First, the LiOH circuit and Li2CO3 circuit both process the LiOH/Na2SO4 mixed solution produced by step 406. Accordingly, the LiOH produced by step 406 maybe selectively directed (e.g., by use of appropriate process flow equipment such as piping and valves) between the LiOH circuit and Li2CO3 circuit, andselectively vary the amount of each lithium product that is produced. The LiOH circuit and the Li2CO3 circuit may be selectively sized for certain production capacities for these lithium products. For example, all of the LiOH/Na2SO4 mixed solution produced by step 406 may be directed exclusively to the Li2CO3 circuit to produce Li2CO3 as the only lithium product. Alternatively, all of the LiOH/Na2SO4 mixed solution produced by step 406 may be directed exclusively to the LiOH circuit to produce LiOH-H2O as the only lithium product. Alternatively, a first portion of the LiOH/Na2SO4 mixed solution produced by step 406 may be directed to the LiOH circuit to produce LiOH- H2O as a primary lithium product, while a second portion of the LiOH/Na2SO4 mixed solution produced by step 406 may be directed to the Li2CO3 circuit to produce Li2CO3 as a secondary lithium product.

[0092] Second, in step 307, precipitation of Li2CO3 from the mixed solution produces a mother liquor in the form of a Na2SO4 solution. In embodiments, this Na2SO4 solution may be directed to the process of step 600 whereby this Na2SO4 solution, and the Na2SO4 solution, resulting from step 412 if any, is mixed with Ca(OH)2 so that the Na2SO4 and the Ca(OH)2 react to convert the Na2SO4 to CaSCh and NaOH. As previously noted, step 600 regenerates the NaOH "reaction fluid" for repeated use in continued performance or for its recycling it back into step 406 of the method.

[0093] Third, as previously described, a portion or all of the NaOH produced by step 600 may be used to treat the feed solution in the PLS purification process of step 304, and/or reintroduced or recycled back into the process for use in the LiOH conversion process of step 406.

[0094] In comparison to the prior art processes that are illustrated in Figs. 1 and 2, a person skilled in the art would appreciate that, while having the benefit of the present disclosure, the method as shown in Fig. 3 has several advantages, such as, but not limited to the following:

[0095] First, the method may be capable of producing both Li2CCh and LiOH-H2O, or selectively one of Li2CCh or LiOH-H2O.

[0096] Second, by consuming CO2 emissions from flue gases, the method reduces CO2 emissions by effectively converting or sequestering them into the Li2CCh product, realizing a real on-site conversion or sequestration of CO2.

[0097] Third, by using CO2 gas as a reactant, the method avoids the use of or reduces the amount of Na2CCh reagent required for production of Li2CCh.

[0098] Fourth, by regenerating, re-using and re-cycling NaOH in a closed loop, the method reduces or even eliminate the amount of NaOH required for the production of LiOH. As noted above, only an initial amount of NaOH needs to be supplied as a reagent to start the process in the first instance of performing step 406.

[0099] Fifth, in comparison with known methods such as the one illustrated in Fig. 1, which uses Na2CO3 as a main reagent for Li2CO3 production and the method of Fig. 2, which uses NaOH as a main reagent for LiOH-H2O production, in the present disclosure, Ca(OH)2 effectively replaces both NaOH and Na2CO3 as the main reagent input for the combined production of both LiOH-H2O product and Li2CO3 product. [00100] Sixth, the method may also convert the relatively low value and low market demand intermediate product of Na2SO4 to a higher value and higher market demand byproduct such as Ca2SO4.

[00101] Seven, almost all of the Na2SO4 conversion reactions may be performed at room temperature and at ambient pressure and result in precipitation of a sulfate byproduct, thus reducing the need for expensive equipment, energy inputs for heating, or pressurization equipment, and other associated operating expenses. The reactions may be performed using low cost equipment, thus reducing capital expenses and operation cost.

[00102] Example No. 2: combined production of LiOH-HiO as primary lithium product, LiiCCh as a secondary lithium product by capture and conversion or sequestration of CO2 from flue gas, as well as, production of CaSC>4 as a byproduct by reacting an intermediate byproduct NaiSCh with an alkali chemical (Ca(OH)2), and wherein a NaOH reaction fluid that is circulated in a closed-loop and re-used in the method, and all Na2SC>4 is separated by the freezing separation method.

[00103] In this example, L12CO3 is produced by CO2 reacting with LiOH-PLS solution and in the absence of Na2SO4 mother liquor. All Na2SO4 is separated by freezing method.

[00104] In embodiments, and as illustrated in Fig. 4, there is provided a representation of a method of processing a material containing lithium, such as hard rock lithium minerals like a- spodumene, to produce a primary lithium product comprising lithium hydroxide monohydrate (LiOH-FLO), a secondary lithium product comprising lithium carbonate (Li2CO3), and a sulfate byproduct such as calcium sulfate (CaSCh). As with example 1 above, it will be understood that the terms "primary lithium product" and "secondary lithium product" are used for convenience to distinguish the products, and do not limit the present invention in terms of the relative amounts that are produced of each product, or the order by which they each can be produced. The amount of each product may be selectively varied.

[00105] In embodiments, as better seen in Fig. 4, Li2CCh is produced by CO2 reacting with LiOH PLS solution and in the absence of Na2SO4 mother liquor. Therefore, a person of ordinary skill in the art would understand that an embodiment as represented in Fig. 4 may include similar steps and circuits as those illustrated in Fig. 3 and explained in detail above, with the necessary adaptations, except that the Li2CCh circuit is different.

[00106] In the Li2CO3 circuit, instead of using a mixed solution of LiOH/Na2SO4 from a PLS Circuit as described in the Example No.1 and illustrated in Fig.3, the input stream is a LiOH PLS solution from the LiOH/Na2SO4 Separation Circuit. Furthermore, there is no Na2SO4 produced, since all of the Na2SO4 is separated in step 408 by a freezing separation method, which directs the Na2SO4 -10 FEO to a Na2SO4 conversion circuit as illustrated in steps 412 and 600.

[00107] In addition to the advantages with respect to Example No.1 and as illustrated in Fig. 3, a person skilled in the art would appreciate that, while having the benefit of the present disclosure, the method as shown in Fig. 3 has several other advantages, such as, but not limited to the following. In an embodiment, all of the Na2SO4 may be separated in one step and in the solid form of Glauber’s salt, thereby facilitating the process of producing the lithium product in accordance with the methods already described in detail. Moreover, the process is also simpler because no Na2SO4 is produced in the solution, given that the CO2 reacts with the LiOH to produce Li2CO3, Furthermore, there is only one stream for the separation of the Na2SO4, which facilitates the process overall. Finally, the recovery of Lithium is more efficient in the embodiment illustrated in Fig. 4.

[00108] Definitions.

[00109] References in the specification to "one embodiment", "an embodiment", etc., indicate that the embodiment described may include a particular aspect, feature, structure, or characteristic, but not every embodiment necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but do not necessarily, refer to the same embodiment referred to in other portions of the specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one skilled in the art to affect or connect such module, aspect, feature, structure, or characteristic with other embodiments, whether or not explicitly described. In other words, any module, element or feature may be combined with any other element or feature in different embodiments, unless there is an obvious or inherent incompatibility, or it is specifically excluded.

[00110] It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as "solely," "only," and the like, in connection with the recitation of claim elements or use of a "negative" limitation. The terms "preferably," "preferred," "prefer," "optionally," "may," and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

[00111] " Alkali chemical", as used herein, refers to a chemical selected from the group consisting of calcium hydroxide (Ca(OH)2), ammonium hydroxide (NH4OH), barium hydroxide (Ba(OH)2), potassium hydroxide (KOH), or mixtures of any of the foregoing.

[00112] " Flue gas", as used herein, refers to a gas comprising CO2 gas produced as an emission from the combustion of a fossil fuel. As non-limiting examples, flue gas may be CO2 gas mixed with non-CO2 gases such as water vapor, oxygen, carbon monoxide, nitrogen oxides, and sulfur oxide.

[00113] The expression "Feed solution", as used herein, refers to an aqueous solution comprising Li2SO4 is produced by leaching of material produced by acid-roasting of 0- spodumene, which is produced by calcination of a-spodumene concentrate. It will be understood that this is a non-limiting embodiment of how this "feed solution" may be produced, and that the present invention may be applied to such solutions formed by other processes, as described below.

[00114] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and/or" means any one of the items, any combination of the items, or all of the items with which this term is associated. The phrase "one or more" is readily understood by one of skill in the art, particularly when read in context of its usage. [00115] The term "about" can refer to a variation of ± 5%, ± 10%, ± 20%, or ± 25% of the value specified. For example, "about 50" percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term "about" can include one or two integers greater than and/or less than a recited integer at each end of the range. Unless indicated otherwise herein, the term "about" is intended to include values and ranges proximate to the recited range that are equivalent in terms of the functionality of the composition, or the embodiment.

[00116] As used herein, the term “comprising” is intended to mean that the list of elements following the word “comprising” are required or mandatory but that other elements are optional and may or may not be present. As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[00117] As used herein, the term “consisting of’ is intended to mean including and limited to whatever follows the phrase “consisting of’. Thus, the phrase “consisting of’ indicates that the listed elements are required or mandatory and that no other elements may be present.

[00118] It is noted that terms like “preferably”, “commonly”, ’’generally”, and “typically” are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that can or cannot be utilized in a particular embodiment of the present invention.

[00119] For the purposes of describing and defining the present invention it is noted that the term “substantially” is utilized herein to represent the inherent degree of uncertainty that can be attributed to any quantitative comparison, value, measurement, or other representation. The term “substantially” is also utilized herein to represent the degree by which a quantitative representation can vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[00120] The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims appended to this specification are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.

[00121] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges recited herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof, as well as the individual values making up the range, particularly integer values. A recited range includes each specific value, integer, decimal, or identity within the range. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc.

[00122] As will also be understood by one skilled in the art, all language such as "up to", "at least", "greater than", "less than", "more than", "or more", and the like, include the number recited and such terms refer to ranges that can be subsequently broken down into sub-ranges as discussed above. In the same manner, all ratios recited herein also include all sub-ratios falling within the broader ratio.

[00123] Features and advantages of the subject matter hereof will become more apparent in light of the following detailed description of selected embodiments, as illustrated in the accompanying figures. As will be realized, the subject matter disclosed and claimed is capable of modifications in various respects, all without departing from the scope of the claims. Accordingly, the drawings and the description are to be regarded as illustrative in nature, and not as restrictive and the full scope of the subject matter is set forth in the claims.