PROCESS FOR CO-PRODUCING LITHIUM, ALUMINUM, AND SILICON-OXYGEN (Si-O) MATERIALS

Abstract

The present invention relates generally to a process for co-producing lithium, aluminum, and silicon-oxygen (SiO) materials, and more particularly, to a process for co-producing lithium, aluminum, and SiO materials from a hard rock source in the form of a granular concentrate of one or more lithium-containing silicate minerals including spodumene. In particular, there is provided a process for co-producing Li, Al, and SiO materials from the beta (?) crystallographic form of the Li-containing silicate mineral spodumene, which in its purest state has the composition LiAlSi.sub.2O.sub.6.

Claims

1. A process for co-producing Li, Al, and SiO materials from a hard rock source in the form of a granular concentrate of one or more lithium-containing aluminosilicate minerals, including spodumene, comprising: providing a hard rock source in the form of a granular concentrate of one or more lithium-containing aluminosilicate minerals, including ?-spodumene (Step 1); calcining the granular concentrate at an elevated temperature to obtain a granular concentrate that includes ?-spodumene (Step 2); mixing the granular concentrate that includes ?-spodumene with an aqueous solution of nitric acid and then agitating or stirring the resulting acidic mixture in a first reactor at a temperature greater than or equal to (?) about 120? C. and at a pressure greater than or equal to (?) about 1 atm to effect leaching of Li and Al (Step 3); conveying the acidic mixture to a second reactor to extract NOH gas at a temperature greater than or equal to (?) about 120? C. to form a slurry from which NOH gas has been removed (Step 4); conveying the slurry from the second reactor through a cooling unit to a separator where it is divided into two fractions, one fraction rich in leached granular ?-spodumene, and the other fraction comprising an aqueous liquid that contains dissolved lithium nitrate (LiNO.sub.3) and dissolved aluminum nitrate (Al(NO.sub.3).sub.3), wherein the fraction rich in leached granular ?-spodumene contains some residual LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid formed during LiAl leaching (Steps 5 and 6); transferring the fraction comprising an aqueous liquid that contains dissolved LiNO.sub.3 and Al(NO.sub.3).sub.3 to a first liquid mixer (Steps 5, 6, and 8); mixing the leached granular ?-spodumene-rich fraction with water of sufficient purity, either prior to or after the leached granular ?-spodumene-rich fraction enters a mixer-washer, to form a water-slurried leached granular ?-spodumene-rich fraction, leading to mixing of the water of sufficient purity with the residual LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid formed during LiAl leaching, to form a wash water containing LiNO.sub.3 and Al(NO.sub.3).sub.3 (Steps 5-7); conveying the water-slurried leached granular ?-spodumene-rich fraction to a separator where the solids and liquid are divided into two fractions, one fraction comprising leached granular ?-spodumene, and the other fraction comprising the wash water containing LiNO.sub.3 and Al(NO.sub.3).sub.3 (Step 7); transferring the wash water to the first liquid mixer where it coalesces with the previously separated LiNO.sub.3- and Al(NO.sub.3).sub.3-containing liquid that enters said first liquid mixer to form a LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid (Step 8); optionally, sending the water-washed leached granular solids to an optional reactor where said water-washed leached granular solids are mixed with aqueous/crystalline sodium hydroxide (NaOH) and/or aqueous/crystalline potassium hydroxide (KOH) to produce a (Na and/or K,Li,Al,SiO)H.sub.2O liquid (Step 39); transferring the liquid in the first liquid mixer to a third reactor (Step 9a); and subjecting the LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid in the third reactor to treatment that results in formation of a H.sub.2O-containing aluminous precipitate (Al(OH).sub.3) that contains either amorphous AlOH solid material or amorphous AlOH solid material mixed with quasi-crystalline AlOH phases, that treatment comprising one or more of: (i) a heat treatment at a temperature sufficient to decompose the Al(NO.sub.3).sub.3 dissolved in the liquid (Step 9a); (ii) reaction with an aqueous liquid that contains dissolved NH.sub.4OH (Step 9b); (iii) contact with aqueous (NH.sub.4).sub.2CO.sub.3 (Step 9c); and (iv) contact with solid (NH.sub.4).sub.2CO.sub.3 (Step 9c).

2. The process according to claim 1, wherein the granular concentrate of one or more lithium-containing aluminosilicate minerals, including ?-spodumene, is calcined at a temperature within a range of about 900? C. to about 1200? C.

3. The process according to claim 1, wherein the ambient gas pressure in the second reactor, if greater than about 1 atm, is reduced to about 1 atm to form a slurry from which NOH has been removed.

4. The process according to claim 1, wherein the LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid in the third reactor is subjected to heat treatment (i) at a temperature of about 180? C. (Step 9a).

5. A process of co-producing Li, Al, and SiO materials from a granular concentrate including spodumene in its alpha (?) crystallographic form, comprising: providing a granular concentrate including spodumene in its alpha (?) crystallographic form (Step 1); calcining the concentrate at an elevated temperature to convert substantially all of the ?-spodumene to the beta (?) crystallographic form (Step 2); mixing the resulting ?-spodumene concentrate with an aqueous solution of nitric acid (HNO.sub.3) and/or a NOH gas plus water (H.sub.2O), at a temperature ?about 120? C., and at a pressure between about one atmosphere (1 atm) and about 10 atm, prior to, or after, entry into a first reactor to form an acidic mixture (Step 3); in the first reactor, stirring or agitating the contained acidic mixture for a period of time sufficient to effect leaching of Li and Al from the ?-spodumene at ?about 120? C., and at a pressure ?about 1 atm (Step 3); conveying the resulting acidic mixture to a second reactor to extract NOH gas, wherein, if necessary, ambient gas pressure is reduced to about 1 atm to form a substantially gas-depleted slurry (Steps 3 and 4); conveying the substantially gas-depleted slurry from the second reactor through a cooling unit to a separator, where it is divided into two fractions, one fraction being rich in leached granular ?-spodumene and the other fraction comprising an aqueous liquid that contains dissolved lithium nitrate (LiNO.sub.3) and dissolved aluminum nitrate (Al(NO.sub.3).sub.3) (Steps 4 and 5); transferring the LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid to a first liquid mixer (Step 6); mixing the leached granular ?-spodumene-rich fraction with water of sufficient purity, either prior to or after the leached granular ?-spodumene-rich fraction enters a mixer-washer, to form a water-slurried leached granular ?-spodumene-rich fraction, leading to mixing of the water of sufficient purity with the residual LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid formed during LiAl leaching, to form a wash water containing dissolved LiNO.sub.3 and Al(NO.sub.3).sub.3; (Steps 5-7); conveying the water-slurried leached granular ?-spodumene-rich fraction to a separator where the solids and liquid are divided into two fractions, one fraction comprising leached granular ?-spodumene and the other fraction comprising the wash water containing LiNO.sub.3 and Al(NO.sub.3).sub.3 (Step 7); transferring the wash water to the first liquid mixer where it coalesces with the previously separated LiNO.sub.3- and Al(NO.sub.3).sub.3-containing liquid that enters said first liquid mixer to form a LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid (Steps 7 and 8); optionally, sending the water-washed leached granular solids to a ninth reactor, where they are mixed with (i) aqueous and/or crystalline sodium hydroxide (NaOH) and/or (ii) aqueous and/or crystalline potassium hydroxide (KOH) to produce a (Na and/or K,Li,Al,SiO)H.sub.2O liquid (Step 39); transferring the liquid in the first liquid mixer to a third reactor (Step 8); subjecting the LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid in the third reactor to treatment that results in formation of a H.sub.2O-containing aluminous precipitate (Al(OH).sub.3) that contains amorphous AlOH solid material or amorphous AlOH solid material mixed with quasi-crystalline AlOH phases, that treatment comprising one or more of: (i) a heat treatment at a temperature sufficient to decompose the Al(NO.sub.3).sub.3 dissolved in the liquid (Step 9a); (ii) reaction with an aqueous liquid that contains dissolved ammonium hydroxide, NH.sub.4OH (Step 9b); (iii) contact with aqueous ammonium carbonate, (NH.sub.4).sub.2CO.sub.3 (Step 9c); and (iv) contact with solid (NH.sub.4).sub.2CO.sub.3 (Step 9c), with the proviso that when only treatment (i) is used, the process steps further include cooling the slurry flowing out of the third reactor (Step 10); transferring the slurry to a mixer-separator where it is sufficiently stirred and/or agitated and thereafter divided into two fractions, one fraction comprising the aluminous precipitate formed in the third reactor and the other fraction comprising an aqueous liquid that contains dissolved LiNO.sub.3 (Step 11); transferring the fraction comprising an aqueous liquid that contains dissolved LiNO.sub.3 from the separator to a second liquid mixer (Step 11); mixing the slurry containing Al(OH).sub.3 with water of sufficient purity and conveying the resulting slurry to a mixer-washer where it is stirred and/or agitated prior to being divided into two fractions, one fraction being rich in Al(OH).sub.3, and the other fraction comprising a wash water that contains dissolved LiNO.sub.3 (Steps 11 and 12); conveying the separated fraction comprising the wash water to the second liquid mixer where it coalesces with the previously separated LiNO.sub.3-containing aqueous liquid transferred to that liquid mixer (Step 12); converting the separated Al(OH).sub.3 to one or more AlOH solids (Step 13 and optional Step 14); transferring the coalesced LiNO.sub.3-containing aqueous liquid from the second liquid mixer to a fourth reactor (Step 15); combining the coalesced LiNO.sub.3-containing aqueous liquid in the fourth reactor with NH.sub.3CO.sub.2 gas and/or aqueous (NH.sub.4).sub.2CO.sub.3 and/or solid (NH.sub.4).sub.2CO.sub.3, thereby inducing precipitation of solid Li.sub.2CO.sub.3 with simultaneous formation of aqueous NH.sub.4NO.sub.3 to form a Li.sub.2CO.sub.3, NH.sub.4NO.sub.3, and (NH.sub.4).sub.2CO.sub.3-containing aqueous slurry (Step 16); transferring the Li.sub.2CO.sub.3, NH.sub.4NO.sub.3, and (NH.sub.4).sub.2CO.sub.3-containing aqueous slurry from the fourth reactor to a fifth reactor where heating to a temperature of about 100? C., and at a pressure of about 1 atm, results in the decomposition of substantially all remaining dissolved (NH.sub.4).sub.2CO.sub.3, as evidenced by production of a NH.sub.3CO.sub.2 off gas, to form a Li.sub.2CO.sub.3- and NH.sub.4NO.sub.3-containing slurry (Steps 16 and 17); cooling the Li.sub.2CO.sub.3- and NH.sub.4NO.sub.3-containing slurry flowing out of the fifth reactor, and then transferring it to a mixer-separator where it is stirred and/or agitated, and thereafter divided into two fractions, one fraction comprising the solid Li.sub.2CO.sub.3 formed in the fourth reactor and the other fraction comprising a NH.sub.4NO.sub.3-containing aqueous liquid (Steps 18 and 19); transferring the NH.sub.4NO.sub.3-containing aqueous liquid to a third liquid mixer, and mixing the fraction comprising the solid Li.sub.2CO.sub.3 with water of sufficient purity prior to sending it to a mixer-washer where it is stirred and/or agitated, the result being formation and separation, in a separator connected to the mixer-washer, of a wash water that contains dissolved NH.sub.4NO.sub.3 (Steps 19 and 20); transferring the NH.sub.4NO.sub.3-containing wash water to the third liquid mixer where it coalesces with the previously-separated NH.sub.4NO.sub.3-containing aqueous liquid that enters that liquid mixer (Step 20); optionally, conveying the moist Li.sub.2CO.sub.3 from the separator to a dryer, and optionally thereafter transferring the dried Li.sub.2CO.sub.3 to a chemical conversion system, or optionally transferring the moist Li.sub.2CO.sub.3 from the separator directly to the chemical conversion system where the chemical conversion system is used to convert or react Li.sub.2CO.sub.3 to produce aqueous LiOH and/or solid LiOH.Math.xH.sub.2O (x=1, 2, 3, or 6) (Steps 20-22); upon its exit from the third liquid mixer, optionally heating the NH.sub.4NO.sub.3-containing aqueous liquid to a temperature of about 120? C. as it flows toward an additional mixer where it is combined with an excess amount of solid magnesium oxide (MgO), the MgO optionally being preheated prior to its mixing with the NH.sub.4NO.sub.3-containing aqueous liquid, to form a multiphase material (Steps 23 and 24); conveying the multiphase material from the additional mixer to a sixth reactor where its temperature is maintained at about 120? C., which results in the formation of an aqueous slurry of magnesium nitrate (Mg(NO.sub.3).sub.2) and magnesium hydroxide (Mg(OH).sub.2), and NH.sub.3 gas (Steps 24 and 25); conveying the NH.sub.3 to a gas mixer where it is combined with both provided CO.sub.2 and the NH.sub.3CO.sub.2 gas produced in the fifth reactor (Steps 25 and 26); conveying the mixed NH.sub.3CO.sub.2 gas through a cooling unit, and thereafter recycling it back to precipitate additional Li.sub.2CO.sub.3 (Step 16), or optionally sending it to a seventh reactor where it is mixed with H.sub.2O to form aqueous (NH.sub.4).sub.2CO.sub.3, the resulting (NH.sub.4).sub.2CO.sub.3-containing aqueous liquid then being recycled back to precipitate additional Li.sub.2CO.sub.3 (Steps 26 and 27); transferring the aqueous slurry co-produced in the sixth reactorit comprising Mg(NO.sub.3).sub.2, Mg(OH).sub.2, and H.sub.2Oto a mixer where it is stirred and/or agitated and thereafter separated into two fractions, one fraction containing Mg(OH).sub.2-rich solids and the other fraction being an aqueous liquid that contains dissolved Mg(NO.sub.3).sub.2 (Steps 25 and 28); conveying the Mg(NO.sub.3).sub.2-containing aqueous liquid to a fourth liquid mixer (Step 28); mixing the Mg(OH).sub.2-rich solids with water, and then sending the resulting slurry to a mixer-washer where it is stirred and/or agitated, the result being formation of a wash water that contains dissolved Mg(NO.sub.3).sub.2 (Steps 28 and 29); transferring the Mg(OH).sub.2- and Mg(NO.sub.3).sub.2-containing aqueous slurry to a separator where it is divided into two fractions, one fraction comprising moist Mg(OH).sub.2 plus any residual MgO, and the other fraction being the Mg(NO.sub.3).sub.2-containing wash water formed in the mixer-washer (Step 29); transferring the Mg(NO.sub.3).sub.2-containing wash water to the fourth liquid mixer where it coalesces with the previously-separated Mg(NO.sub.3).sub.2-containing aqueous liquid which enters that liquid mixer (Step 29); transferring a portion of the moist Mg(OH).sub.2?MgO to a first furnace where it is heated to a maximum temperature of about 600? C., the result being production of MgO and water vapor, the MgO being recycled back to Step 24 (Steps 29 and 33); transferring the Mg(NO.sub.3).sub.2-containing aqueous liquid from the fourth liquid mixer to an evaporator where it is heated to a temperature of about 150? C., which initiates production of molten Mg(NO.sub.3).sub.2.Math.xH.sub.2O (x?6), water vapor, and any generated NOH gas (Steps 30 and 31); after exiting the evaporator, conveying the H.sub.2O-depleted Mg(NO.sub.3).sub.2.Math.xH.sub.2O liquid to a mixer where it is blended with a portion of the moist Mg(OH).sub.2?MgO produced previously (Step 29) (Steps 31 and 32); transferring the Mg(NO.sub.3).sub.2.Math.xH.sub.2OMg(OH).sub.2?MgO slurry from the mixer to a second furnace where it is heated up to a maximum temperature of about 600? C., the purpose being to form MgO plus solid impurities, along with a NO.sub.2- and O.sub.2-containing NOH gas (Steps 32 and 34); conveying the MgO+solid impurities to a mixer-washer where the solids are slurried with a liquid in which MgO is substantially insoluble, but also in which the solid impurities are substantially soluble (Steps 34 and 35); stirring or agitating the MgO-containing slurry prior to sending it to a separator where it is divided into two fractions, one fraction comprising MgO, which is recycled back to Step 24, and the other fraction being the liquid that is enriched in impurities (Step 35); optionally treating the liquid in a way that divides it into two fractions, one fraction being a purified liquid and the other fraction comprising the impurities present in the liquid fraction formed in the separator (Step 36); optionally recycling the purified liquid back to the earlier step wherein MgO+solid impurities was slurried with the originally provided liquid (Step 36); conveying (i) the NOH gas removed from the second and third reactors, and also (ii) the NOH gas produced in the evaporator (if any), and also (iii) the NO.sub.2-, O.sub.2- and H.sub.2O-containing NOH gas formed in the second furnace, to a gas mixer where the individual streams of gas intermingle (Step 37); conveying the NOH gas from the gas mixer back to the first reactor, and/or to an eighth reactor where it is mixed into H.sub.2O to produce aqueous HNO.sub.3 that is subsequently sent back to the first reactor (Step 38).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] FIGS. 1-5 illustrate a non-limiting embodiment of the invented physicochemical process, with the step numbers on each sheet being keyed to the corresponding enumerated steps in the Detailed Description below. It will be observed on FIG. 2 that although three potentially independent options are presented for converting aqueous Al(NO.sub.3).sub.3 to an aluminous precipitate (Al(OH).sub.3), for the sake of simplicity and brevity, the first option (i), a thermal treatment, is selected to exemplify that conversion.

DETAILED DESCRIPTION OF THE INVENTION

[0083] Illustrated by way of the attached figures, the present invention is directed toward a process for co-producing Li-, Al-, and SiO-containing materials from the ? crystallographic form of spodumene, which in its purest state has the composition LiAlSi.sub.2O.sub.6. The description below presents an exemplary non-limiting embodiment of the invention, while the appended claims define the scope of patent protection.

[0084] Throughout the text that follows, the words transferred, conveyed, separated, and impurities may be understood to mean the following.

[0085] In the case of the words transferred and conveyed, when used to indicate movement in the physical location of a liquid or slurry, the understanding can be that the material may be pumped mechanically or gravitationally, or by differential pressure.

[0086] In the case of the word separated, when used in reference to dividing a slurry into solid and liquid portions, the understanding can be that the segregation may be accomplished by centrifugation and/or filtration.

[0087] In the case of the word impurities, usage is inclusive of both mineralogical and chemical contaminants in the materials that enter into, move through, and ultimately exit, the processing circuit. Mineralogical impurities include quartz, feldspar, and other substantially lithium-free crystalline solids that can occur in a spodumene concentrate. Significantly, a spodumene concentrate may also contain subordinate amounts of lithium-containing minerals that differ from spodumenee.g., petalite, lepidolite and amblygoniteand it should be understood that the processing steps of the present invention are likely to have effects on them that are similar to the effects they have on spodumene. Nevertheless, herein, no further attention is given to any accessory granite pegmatite minerals that might be present in a spodumene concentrate.

[0088] Regarding chemical impurities, the only ones considered below are selected minor and trace elements that commonly occur crystallographically in spodumene-namely, iron, manganese, sodium, potassium, magnesium and calcium. It will be proposed that problems associated with these contaminants can be handled post-dissolution (in aqueous media) by: (i) using a caustic aqueous liquid (e.g., aqueous ammonium hydroxide, NH.sub.4OH) to induce precipitation of calcium hydroxide, magnesium hydroxide, and FeMn oxides and hydroxides; or (ii) using a bicarbonate/carbonate material (e.g., aqueous ammonium carbonate, (NH.sub.4).sub.2CO.sub.3, or solid (NH.sub.4).sub.2CO.sub.3) to induce precipitation of calcium carbonate and magnesium carbonate prior to converting LiNO.sub.3 to Li.sub.2CO.sub.3; and (iii) allowing solubilized alkali metals (most notably Na and K) to remain in solution until after all valuable Li, Al and SiO materials are formed and separated.

[0089] Another important point: to simplify discussions of certain key processing steps, and also the representations of those steps on FIGS. 1-5, impurities that occur in wash waters are ignored. While the wash waters formed according to the present invention will contain dissolved, suspended and/or entrained contaminants, the amounts of them are expected to be much smaller than their abundances in other liquids that form and evolve in the invented process and, therefore, typically, their presence will not detrimentally affect either the processing or the final products produced therefrom.

[0090] It should also be understood that, in the various presented chemical reactions, the abbreviations enclosed in parenthesesappended to the formulas for the chemical specieshave the following definitions: s=solid, liq=liquid, aq=in aqueous solution, and g=gas.

[0091] It is envisioned that, generally, the reactors referred to below may be continuous stirred-tank reactors that are very compact due to the rapid kinetics of the reactions that occur within them.

[0092] It is also envisioned that each cooling unit referred to below could be a heat exchanger, or could simply be a tube enveloped by a heat transfer fluid, thermostated or not.

[0093] It is also envisioned that satisfactory blending of liquids and gases in the invented process can, in many instances, be achieved in a static mixer.

[0094] Finally, after weighing the merits of the chemical technology disclosed in this Specification, it will be evident to those skilled in the art that the method can be applied at length scales ranging from the laboratory benchtop to the factory floor.

[0095] Now, referring to FIGS. 1-5, the physicochemical steps in the exemplary embodiment are listed and described, with sufficient detail provided to allow persons skilled in the art to make effective use of them.

[0096] Step 1: A granular spodumene concentrate, with the spodumene in it being predominantly in its ? crystallographic form, is provided.

[0097] Spodumene is a natural mineral with the ideal/pure/theoretical/end-member composition LiAlSi.sub.2O.sub.6. A spodumene concentrate is a granular mechanical mix of minerals formed by crushing and grinding rock excavated from a spodumene pegmatite formation, with the proportion of spodumene in the resulting granular solids typically being enhanced by at least one concentration method, such as dense medium separation and froth flotation.

[0098] Other lithium minerals, such as petalite (ideally LiAlSi.sub.4O.sub.10), lepidolite (ideally K(Li,Al).sub.3(Al,Si,Rb).sub.4O.sub.10(F,OH).sub.2), and amblygonite (ideally (Li,Na)AlPO.sub.4(F,OH)), may also be present in a spodumene concentrate, but always in subordinate amounts. Significantly, three other subordinate minerals commonly present in a spodumene concentratequartz (ideally SiO.sub.2), albite (ideally NaAlSi.sub.3O.sub.8), and microcline/orthoclase (ideally KAlSi.sub.3O.sub.8)contain only negligible amounts of lithium, and for this reason are hereafter referred to as mineral impurities to distinguish them from chemical impurities.

[0099] Supplies of spodumene concentrate sold commercially are usually graded according to their Li.sub.2O content. Pure spodumene contains 8.03 weight percent (wt. %) Li.sub.2O; a run-of-mine spodumene pegmatite ore ordinarily contains 1-2 wt. % Li.sub.2O; a spodumene concentratethe proportion of spodumene in it commonly being between 75 and 87% by weighta desirable attribute for use in Li compound manufacturingwill typically contain 6-7 wt. % Li.sub.2O. Spodumene concentrates containing at least 7.6 wt. % Li.sub.2O, and having a low iron content, are consumed in making ceramics, and in other specialty applications.

[0100] Step 2: The granular ?-spodumene concentrate provided in Step 1 is calcined at an elevated temperature, or over a range of temperatures, e.g., between about 900? C. and about 1,200? C., but more usually at a temperature, or over a range of temperatures, between about 950? C. and about 1100? C., the main purpose being to convert all ?-spodumene to ?-spodumene.

[0101] Step 3: An aqueous solution of HNO.sub.3 and/or a NOH gas+H.sub.2O is/are provided and mixed into the granular ?-spodumene concentrate immediately prior to, or shortly after, entry into a first reactor (Reactor #1 on FIG. 1).

[0102] If provided, the HNO.sub.3-containing aqueous solution could contain between about 20 wt. % and about 68 wt. % HNO.sub.3, the balance being mostly water. Most preferably for commercial applications, the aqueous solution would contain between about 40 wt. % and about 68 wt. % HNO.sub.3.

[0103] Both the aqueous HNO.sub.3 (if provided) and the NOH gas (if provided) could be preconditioned to about 25?T(? C.)?about 140, and to about 1?P(atm)?about 10, prior to being conveyed to the reactor. In any case, the final temperature of the resulting acidic slurry would advantageously be about 120?T(? C.)?about 140? C. Heating to a temperature as high as about 140? C. could be accomplished by flowing the multiphase material through one or more pipes immersed in a heat transfer liquid. As flow of the material occurs, the pressure and temperature of the entire amount of it could be maintained, or allowed to increase slightly.

[0104] During this step, leaching of the granular ?-spodumene commences, with at least a significant amount of the Li in the mineral, along with a lesser portion of the Al in it, becoming dissolved in the acidic aqueous liquid (see below). This is in direct contrast to the prior art reference's (US 2017/0175228 A1 (Hunwick)) description discussed above, in which the leaching conditions created are such that non-lithium values tend not to be leached from the silicate mineral. Indeed, one of the key features of the process according to the present invention is extraction of both Li and Al during nitric acid leaching of granular ?-spodumene.

[0105] Data obtained from bench-scale laboratory testing indicates that ?-spodumene contact with aqueous HNO.sub.3 at about 120? C. and 1 atm results in extensive leaching of Li, lesser (but still significant) leaching of Al, and negligible leaching of SiO materials. Therefore, rather than dividing ?-spodumene into discrete Li, Al, and SiO portions, which is the ultimate goal of the invented process, the currently available evidence, instead, indicates that the contact yields a partially leached solid material which: possibly contains a small amount of residual Li; likely contains a substantial amount of residual Al; and certainly contains most of the SiO material that was originally present in the ?-spodumene. Consequently, it is contemplated that final compositions for nitric acid-leached ?-spodumene may include LiAl.sub.3Si.sub.8O.sub.20(OH).sub.2, LiAl.sub.4Si.sub.32O.sub.70OH and/or Al.sub.4Si.sub.64O.sub.134-solid aluminosilicates with these compositions conceivably being formed by one or more reactions similar to Reaction 1 below, as well as the other two that immediately follow it:

##STR00001##

[0106] It will be understood that the calculated numbers above the species in Reaction 1, and in certain related reactions that follow in this disclosure, are tonne mass balance figures for the production of 1 tonne of LiOH.Math.H.sub.2O, assuming that (i) the LiOH.Math.H.sub.2O is produced according to Reaction 4 below and (ii) the ultimate source of the Li in the LiOH.Math.H.sub.2O is the LiAlSi.sub.2O.sub.6 in the ?-spodumene that reacts with aqueous HNO.sub.3 according to Reaction 1.

[0107] A guiding principle in achieving satisfactory nitric acid LiAl leaching of ?-spodumene is that solid-liquid mixing would best be accomplished under physicochemical conditions that tend to sustain, or even increase, the wt. % concentration of aqueous HNO.sub.3, while at the same time precluding any significant loss of ?-spodumene. For example, to mitigate against the decrease in wt. % aqueous HNO.sub.3 that occurs during leaching of Li and Al from ?-spodumene: (i) the starting wt. % concentration of aqueous HNO.sub.3 might be higher than absolutely necessary, e.g., in the range 50-68 wt. %; and/or (ii) the initial aqueous HNO.sub.3 to ?-spodumene weight ratio might be set high enough, to ensure that the wt. % concentration of aqueous HNO.sub.3 remains high throughout the period of LiAl leaching. Additionally, or alternatively, the wt. % aqueous HNO.sub.3 might be kept high by NOH gas, the sustained presence of which would induce the reaction

##STR00002##

the result being that depletion of aqueous HNO.sub.3 by reaction with ?-spodumene would be counteracted by replenishment of aqueous HNO.sub.3 due to reaction between NO.sub.2, O.sub.2 and H.sub.2O.

[0108] Finally, at the conclusion of this step, the acidic aqueous slurry in the reactor, which would preferably contain between about 30 volume percent and about 70 volume percent solids, is transferred to a second reactor (Reactor #2 on FIG. 1).

[0109] Step 4: The ambient pressure in Reactor #2 is lowered to an extent necessary to convert most of the remaining aqueous HNO.sub.3 to NOH gas.

[0110] Gas pressure in Reactor #2 could be lowered to about 1 atm by creating a headspace wherein gas can enter from the heated aqueous slurry below, and from which gas can be extracted through the one or more sides of, and/or through the top of, the headspace, this facilitating degassing of the slurry. It is contemplated that the removed gas will contain NOH volatile speciese.g., HNO.sub.3, H.sub.2O, NO.sub.2, and O.sub.2.

[0111] Step 5: The aqueous HNO.sub.3-depleted slurry formed in Reactor #2 is conveyed to a cooling unit where its temperature is lowered to a level satisfactory for transfer to a separator.

[0112] Conveyance of the slurry might be driven, entirely or partially, by a gradient in fluid pressure.

[0113] Step 6: After cooling down to about 25?T(? C.)?about 60, the slurry is transferred to a separator where it is divided into two fractions, one fraction comprising substantially all of the leached granular ?-spodumene (accompanied by subordinate amounts of one or more accessory lithium pegmatite minerals), the other fraction being a LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid that contains minimally detrimental amounts of residual dissolved, suspended and/or entrained solids, a portion of them being impurities.

[0114] After separation, the reacted granular solids are slurried with water of sufficient purity and conveyed to a mixer-washer connected to a separator. Also, optionally, the liquid produced by separation is filtered prior to transfer to a first liquid mixer (Liquid mixer #1 on FIG. 1).

[0115] Step 7: The water-slurried granular solids sent to the mixer-washer are stirred and/or agitated prior to transfer to a separator, the LiNO.sub.3- and Al(NO.sub.3).sub.3-containing wash water thus produced then being sent to Liquid mixer #1 where it coalesces with the LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid formed in Step 6.

[0116] Preferably, the solids would be washed in a minimum amount of water of sufficient purity, and after separation of the solids could optionally be reacted with aqueous/crystalline NaOH and/or aqueous/crystalline KOH to produce a caustic (Na and/or K,Li,Al,SiO)H.sub.2O liquid (Step 39).

[0117] Step 8: The LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid in Liquid mixer #1 is conveyed to a third reactor (Reactor #3 on FIGS. 1 and 2).

[0118] (Important note: Steps 9a-c below describe three potentially independent means for producing a H.sub.2O-containing aluminous precipitate from a LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid. For the sake of simplicity and brevity, hereafter this precipitate is designated Al(OH).sub.3, with the understanding that, in reality, it is a water-rich substance that may contain abundant amorphous AlOH semi-solid (gelatinous) material, possibly intermixed one or more quasicrystalline AlOH phases.)

[0119] Step 9a: The LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid residing in Reactor #3 is heated to ?about 140? C. to decompose substantially all of the dissolved Al(NO.sub.3).sub.3, a key result being precipitation of Al(OH).sub.3. (As noted previously, in this invention disclosure a thermal treatment is the chosen exemplary treatment option for converting aqueous Al(NO.sub.3).sub.3 to Al(OH).sub.3. Steps 9b and 9c below are described solely to point out that there are alternative methods for inducing precipitation of Al(OH).sub.3 from a LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid.) It is contemplated that the aqueous Al(NO.sub.3).sub.3 will be decomposed by a reaction similar to this one:

##STR00003##

[0120] Step 9b: A liquid comprising NH.sub.4OH dissolved in water, and/or a gas containing a substantial amount of NH.sub.3, is provided and mixed with the liquid residing in the third reactor to precipitate Al(OH).sub.3. It is contemplated that one or both of these actions will reduce the amount of Al(NO.sub.3).sub.3 in the aqueous liquid by a reaction similar to this one:

##STR00004##

[0121] In commercial settings, precipitation of Al(OH).sub.3 by either action would preferably be accomplished at about 25?T(? C.)?about 60, and at about 1?P(atm)?about 10.

[0122] Step 9c: An aqueous liquid containing dissolved (NH.sub.4).sub.2CO.sub.3, and/or a material containing granular (NH.sub.4).sub.2CO.sub.3, and/or a gas containing substantial amounts of NH.sub.3 and CO.sub.2, is provided and mixed with the liquid residing in Reactor #3, the purpose being to precipitate Al(OH).sub.3.

[0123] Three possible reactions that relate to the use of (NH.sub.4).sub.2CO.sub.3 to induce the precipitation of Al(OH).sub.3 from a LiNO.sub.3- and Al(NO.sub.3).sub.3-containing aqueous liquid are

##STR00005##

[0124] It is contemplated that, with any of the above reactions, precipitation of Al(OH).sub.3 could be induced at about 25?T(? C.)?about 60, and at an ambient pressure of about 1 atm. To ensure optimal production of Al(OH).sub.3 in commercial settings: first, the amount of provided (NH.sub.4).sub.2CO.sub.3 should be close to the minimum amount required to react away nearly all of the aqueous Al(NO.sub.3).sub.3 present in the liquid; and second, the produced CO.sub.2?O.sub.2 gas should be removed from the reactor as it forms.

[0125] Step 10: The Al(OH).sub.3- and LiNO.sub.3-containing aqueous slurry formed in Step 9a is conveyed from Reactor #3 through a cooling unit into a mixer connected to a separator.

[0126] Step 11: The slurry in the mixer is stirred and/or agitated prior to flow into a separator where it is divided into two fractions, one fraction being substantially Al(OH).sub.3, the other fraction a LiNO.sub.3-containing aqueous liquid.

[0127] After separation, the Al(OH).sub.3 is slurried with water and conveyed to a mixer-washer connected to a separator. Also, optionally, the LiNO.sub.3-containing aqueous liquid produced by separation is filtered prior to transfer to a second liquid mixer (Liquid mixer #2 on FIG. 2).

[0128] Step 12: The water-slurried Al(OH).sub.3 sent to the mixer-washer is stirred and/or agitated prior to being divided into Al(OH).sub.3-rich and wash water-rich fractions.

[0129] Preferably, after adding water to the Al(OH).sub.3 in Step 11, the resulting slurry in the mixer-washer will contain about 30-70 volume percent solids. The newly formed slurry is then stirred and/or agitated, and thereafter the Al(OH).sub.3 and wash water in it are separated, possibly by centrifugation and/or filtration. At the end of this step the wash water is sent to Liquid mixer #2 where it coalesces with the LiNO.sub.3-containing aqueous liquid formed in Step 11.

[0130] Step 13: The moist Al(OH).sub.3 produced in Step 12 may be heated to a temperature, or over a range of temperature, between about 100? C. and about 300? C., to dehydrate the material, this possibly leading to the production of one or more forms of crystalline Al(OH).sub.3 and/or crystalline Al.sub.2O.sub.3.

[0131] Step 14: Optionally, the AlOH solid(s) produced in Step 13 are processed further to produce one or more forms of high-quality Al.sub.2O.sub.3, and/or Al metal.

[0132] Step 15: The LiNO.sub.3-containing aqueous liquid in Liquid mixer #2 is transferred to a fourth reactor (Reactor #4 on FIGS. 2 and 3).

[0133] Step 16: The LiNO.sub.3H.sub.2O liquid in Reactor #4 is merged with either: (i) a mixed NH.sub.3CO.sub.2 gas having a composition previously shown to be suitable for converting aqueous LiNO.sub.3 to granular Li.sub.2CO.sub.3, the amount of NH.sub.3CO.sub.2 gas provided being sufficient to react away nearly all of the aqueous LiNO.sub.3; or (ii) an (NH.sub.4).sub.2CO.sub.3-containing aqueous liquid and/or granular (NH.sub.4).sub.2CO.sub.3, the amount of aqueous/solid (NH.sub.4).sub.2CO.sub.3 supplied being in excess of that required to react away substantially all of the aqueous LiNO.sub.3.

[0134] (Optionally, at the outset of this step, a small amount of NH.sub.3CO.sub.2 gas and/or aqueous/solid (NH.sub.4).sub.2CO.sub.3 is mixed into the LiNO.sub.3-containing aqueous liquid to induce precipitation of CaCO.sub.3- and MgCO.sub.3-containing solid material, the precipitate preferably being immediately separated from the enclosing liquid by filtration and/or centrifugation.)

[0135] In the case of merging the LiNO.sub.3H.sub.2O liquid with a sufficient amount of NH.sub.3CO.sub.2 gas of suitable composition, or range of compositions, it is contemplated that precipitation of granular Li.sub.2CO.sub.3 would occur mainly by the reaction

##STR00006##

[0136] In the case of merging the LiNO.sub.3H.sub.2O liquid with a sufficient amount of an (NH.sub.4).sub.2CO.sub.3-containing aqueous liquid and/or with granular (NH.sub.4).sub.2CO.sub.3the amount of (NH.sub.4).sub.2CO.sub.3 supplied being in excess of that required to react away substantially all of the aqueous LiNO.sub.3it is contemplated that precipitation of granular Li.sub.2CO.sub.3 would occur principally by the reaction

##STR00007##

[0137] In any case, in commercial settings this step would preferably be completed at about 25?T(? C.)?about 80, and at about 1?P(atm)?about 10and at its conclusion the produced Li.sub.2CO.sub.3, NH.sub.4NO.sub.3- and (NH.sub.4).sub.2CO.sub.3-containing aqueous slurry would be transferred to a fifth reactor (Reactor #5 on FIG. 3).

[0138] Step 17: The Li.sub.2CO.sub.3-, NH.sub.4NO.sub.3- and (NH.sub.4).sub.2CO.sub.3-containing aqueous slurry transferred to Reactor #5 is heated to decompose substantially all of the aqueous (NH.sub.4).sub.2CO.sub.3, this likely being the result of the reaction

##STR00008##

which in commercial settings would preferably be induced at about 60?T(? C.)?about 120, and at a pressure close to 1 atm. To ensure maximum decomposition of the residual aqueous (NH.sub.4).sub.2CO.sub.3, the produced NH.sub.3CO.sub.2 gas should be removed from the reactor as it forms.

[0139] Step 18: The Li.sub.2CO.sub.3- and NH.sub.4NO.sub.3-containing aqueous slurry produced in Reactor #5 is sent through a cooling unit into a mixer connected to a separator.

[0140] Step 19: The slurry in the mixer is stirred and/or agitated prior to flow into a separator where it is divided into two fractions, one fraction being substantially granular Li.sub.2CO.sub.3, the other fraction a NH.sub.4NO.sub.3-containing aqueous liquid.

[0141] After separation, the Li.sub.2CO.sub.3 is slurried with, preferably, 30-70 volume percent water, and subsequently conveyed to a mixer-washer connected to a separator. Also, optionally, the NH.sub.4NO.sub.3-containing aqueous liquid produced by separation is filtered prior to transfer to a third liquid mixer (Liquid mixer #3 on FIG. 3).

[0142] Step 20: The water-slurried granular Li.sub.2CO.sub.3 sent to the mixer-washer is stirred and/or agitated prior to being divided into Li.sub.2CO.sub.3-rich and wash water-rich fractions.

[0143] At the end of this step the wash water is sent to Liquid mixer #3 where it coalesces with the NH.sub.4NO.sub.3-containing aqueous liquid formed in Step 19.

[0144] Step 21: The moist Li.sub.2CO.sub.3 produced in Step 20 is optionally further processed to remove impuritiesand then optionally heated to a temperature, or over a range of temperature, between about 80? C. and about 120? C. to thoroughly dry the material.

[0145] Step 22: Optionally, the moist Li.sub.2CO.sub.3 produced in Step 20, or the Li.sub.2CO.sub.3 optionally purified and/or dried in Step 21, is converted to LiOH(aq) and/or solid LiOH.Math.xH.sub.2O (x=1, 2, 3, or 6).

[0146] Conversion of granular Li.sub.2CO.sub.3 to, for example, granular LiOH.Math.H.sub.2O can be achieved in several ways, a particularly well-known one being by the metathesis reaction

##STR00009##

followed by adjustment of the hydration state of the LiOH.Math.xH.sub.2O to produce LiOH.Math.H.sub.2O.

[0147] Step 23: After a sufficient residence time in Liquid mixer #3, the NH.sub.4NO.sub.3-containing aqueous liquid that exits from it is optionally heated to about 120? C. during flow toward a mixer (FIG. 4).

[0148] Step 24: After it reaches the mixer, the NH.sub.4NO.sub.3-containing aqueous liquid is contacted with an excess amount of granular MgO.

[0149] Optionally, the MgO is heated prior to entering the mixer, and at the end of this step the produced MgO?Mg(OH).sub.2- and NH.sub.4NO.sub.3-containing aqueous slurry is conveyed to a sixth reactor (Reactor #6 on FIG. 4).

[0150] (In the text that follows it is assumed that, in Step 23, the NH.sub.4NO.sub.3-containing aqueous liquid sent to the mixer is heated prior to its arrival there, and in Step 24, the heated NH.sub.4NO.sub.3-containing aqueous liquid is contacted with heated MgO.)

[0151] Step 25: The slurry in Reactor #6 is stirred and/or agitated at about 120? C. for a sufficient period of time to react away substantially all of the aqueous NH.sub.4NO.sub.3.

[0152] It is contemplated that aqueous NH.sub.4NO.sub.3 will disappear from the slurry by all three of the reactions below:

##STR00010##

[0153] Delivery of an excess amount of MgO to Reactor #6 is recommended for two reasons: first, the kinetics of Reaction 5a will slow down significantly if the amount of MgO present approaches zero; and second, some of the introduced MgO will combine with H.sub.2O to form Mg(OH).sub.2 (Reaction 5b), Mg(OH).sub.2 being less reactive with NH.sub.4NO.sub.3 than MgO because Mg(OH).sub.2 is stable in the presence of hot liquid H.sub.2O whereas MgO is not.

[0154] At the end of this step the produced Mg(NO.sub.3).sub.2- and Mg(OH).sub.2?MgO-containing aqueous slurry is transferred to a mixer connected to a separator (see Step 28).

[0155] Step 26: The NH.sub.3CO.sub.2 gas produced in Step 17, the NH.sub.3 gas that exits Reactor #6, and provided CO.sub.2 gas are combined in a gas mixer connected to a cooling unit.

[0156] To enhance processing effectiveness in the present invention, the composition of the NH.sub.3CO.sub.2 gas should be made suitable for consumption in either Step 16, or in the next step.

[0157] Step 27: Optionally, the mixed NH.sub.3CO.sub.2 gas exiting the cooling unit is transferred to a seventh reactor (Reactor #7 on FIG. 4) where it is contacted with water to produce a liquid that comprises (NH.sub.4).sub.2CO.sub.3 dissolved in water.

[0158] It is contemplated that aqueous (NH.sub.4).sub.2CO.sub.3 will be formed by the reaction

##STR00011##

at about 25?T(? C.)?about 80, and at about 1?P(atm)?about 10. Also, optionally (not shown on FIG. 4), after the (NH.sub.4).sub.2CO.sub.3-containing aqueous liquid has formed, most of the water in it may be removed from the (NH.sub.4).sub.2CO.sub.3-containing aqueous liquid to precipitate granular (NH.sub.4).sub.2CO.sub.3, which subsequently may be separated from any remaining liquid.

[0159] At the conclusion of this step the (NH.sub.4).sub.2CO.sub.3-containing aqueous liquid and/or granular (NH.sub.4).sub.2CO.sub.3 is sent back to Step 16.

[0160] Step 28: The Mg(NO.sub.3).sub.2- and Mg(OH).sub.2?MgO-containing aqueous slurry in the mixer immediately downstream from Reactor #6 is stirred and/or agitated prior to flow into a separator where it is divided into two fractions, one fraction being substantially fine-grained Mg(OH).sub.2?residual MgO, the other fraction being a Mg(NO.sub.3).sub.2-containing aqueous liquid.

[0161] At the end of this step: (i) the moist Mg(OH).sub.2?MgO is slurried with, preferably, about 30-70 volume percent water, and subsequently sent to a mixer-washer connected to a separator; and (ii) the Mg(NO.sub.3).sub.2-containing aqueous liquid is conveyed to a fourth liquid mixer (Liquid mixer #4 on FIG. 4).

[0162] Step 29: The aqueous Mg(OH).sub.2?MgO slurry in the mixer-washer is stirred and/or agitated prior to being divided into Mg(OH).sub.2?MgO-rich and wash water-rich fractions.

[0163] At the end of this step a portion of the moist Mg(OH).sub.2?MgO is conveyed to a first furnace (Furnace #1, see Step 33 on FIG. 5) while the Mg(NO.sub.3).sub.2-containing wash water is sent to Liquid mixer #4 where it coalesces with the Mg(NO.sub.3).sub.2-containing aqueous liquid formed in Step 28.

[0164] Step 30: The Mg(NO.sub.3).sub.2-containing aqueous liquid in Liquid mixer #4 is sent to an evaporator.

[0165] Step 31: The Mg(NO.sub.3).sub.2-containing aqueous liquid in the evaporator is heated to about 150? C., the result being production of molten Mg(NO.sub.3).sub.2.Math.xH.sub.2O and water vapor, and possibly also NOH gas.

[0166] The melting temperatures of Mg(NO.sub.3).sub.2.Math.6H.sub.2O and Mg(NO.sub.3).sub.2.Math.2H.sub.2O reported in the literature are 89? C. and 129? C., respectively. With increasing temperature above 129? C. the composition of a hydrous Mg(NO.sub.3).sub.2 melt can be represented by the formula Mg(NO.sub.3).sub.2.Math.xH.sub.2O, with x being <2.0 and the value of x steadily decreasing to <<2.0 with increasing temperature. Thus, it is contemplated that, with increasing temperature above about 129? C. to about 330? C. (the latter being the approximate upper thermal stability limit of anhydrous Mg(NO.sub.3).sub.2), molten Mg(NO.sub.3).sub.2.Math.H.sub.2O dehydrates by the reaction

##STR00012##

where 0?y<.sup.2.

[0167] At the conclusion of this step the produced NOH gas (if any) is transferred to a gas mixer (see Step 37 on FIG. 5), and the H.sub.2O-depleted molten Mg(NO.sub.3).sub.2.Math.xH.sub.2O is conveyed to a mixer (see Step 32).

[0168] Step 32: In the mixer (FIGS. 4 and 5) the Mg(NO.sub.3).sub.2.Math.xH.sub.2O (x<2) liquid is contacted with a portion of the moist Mg(OH).sub.2?MgO produced in Step 29, and after the two materials are mixed the resulting Mg(NO.sub.3).sub.2.Math.xH.sub.2O+Mg(OH).sub.2?MgO slurry is conveyed to a second furnace (Furnace #2, see Step 34 on FIG. 5).

[0169] Step 33: The moist Mg(OH).sub.2?MgO in Furnace #1 is heated to a temperature as high as about 600? C. at about 1-2 atm, the result being production of MgO and water vapor by the reaction

##STR00013##

[0170] At the conclusion of this step the produced MgO is recycled back to Step 24.

[0171] Step 34: The Mg(NO.sub.3).sub.2.Math.xH.sub.2O+Mg(OH).sub.2?MgO slurry in Furnace #2 is heated to a temperature as high as about 600? C. at about 1-2 atm, the result being production of MgO and a NO.sub.2-, O.sub.2- and H.sub.2O-containing NOH gas.

[0172] It is contemplated that the Mg(NO.sub.3).sub.2.Math.xH.sub.2O portion of the slurry would be decomposed by the reaction

##STR00014##

[0173] At the conclusion of this step: (i) produced MgO is slurried with a liquid and conveyed to a mixer-washer connected to a separator; and (ii) the co-produced NO.sub.2- and O.sub.2-containing NOH gas is transferred to a gas mixer (see Step 37). Preferably, the slurry sent to the mixer-washer would contain about 30-70 volume percent liquid. Also, the liquid in the slurry should be one in which MgO is substantially insoluble but impurities (e.g., alkali nitrates) are significantly soluble.

[0174] Step 35: The slurry in the mixer-washer is stirred and/or agitated prior to being divided into MgO-rich and liquid-rich fractions.

[0175] Optionally, the MgO formed in this step is further purified prior to being recycled back to Step 24.

[0176] Step 36: Optionally, the liquid+impurities formed in Step 35 is treated physically and/or chemically in a way that divides it into two fractions, one fraction being a liquid that contains very little dissolved, suspended and/or entrained solid material, the other fraction comprising mainly impurities that were held in the liquid prior to the physical and/or chemical treatment.

[0177] Optionally, the high-purity liquid is recycled back to Step 35.

[0178] Step 37: The NOH gas removed from Reactor #2 and Reactor #3 (Steps 4 and 9a), the NOH gas produced in the evaporator (if any) (Step 31), and the NO.sub.2-, O.sub.2- and H.sub.2O-containing NOH gas formed in Furnace #2 (Step 34, and subsequently cooled), are received by a gas mixer and intermingled there.

[0179] Optionally, some H.sub.2O may purposely be condensed from the mixed gas and separated for reuse in the processing circuit, and also optionally (i) some or all of the mixed gas is sent back to Step 3 to replenish a significant portion of the aqueous HNO.sub.3 that is consumed during that step, and/or (ii) some or all of the mixed gas is conveyed to an eighth reactor (Reactor #8 on FIG. 5).

[0180] Step 38: The NOH gas sent to Reactor #8 (if any) is mixed into H.sub.2O to produce aqueous HNO.sub.3, which is subsequently recycled back to Step 3 to replenish a significant portion of the aqueous HNO.sub.3 that is consumed during that step.

[0181] It is possible that mixing NO.sub.2- and O.sub.2-containing NOH gas with waterat one or more points in the processing circuitwill produce HNO.sub.3 in two stages, the first involving formation of a portion of HNO.sub.3 by the reaction

##STR00015##

the second featuring further HNO.sub.3 synthesis by the reaction

##STR00016##

[0182] In any event, the overall HNO.sub.3 regeneration reaction is expected to be

##STR00017##

[0183] Step 39: Optionally the water-washed leached granular solids produced in Step 7 are transferred to a ninth reactor (Step 39) where they are mixed with aqueous/crystalline NaOH and/or aqueous/crystalline KOH to produce a (Na and/or K,Li,Al,SiO)H.sub.2O liquid.

[0184] Table 1 below shows the calculated tonnes of each species consumed (C) and produced (P) in each of Reactions 1, 2a, 3b, 4, 5a, 5b, 6, 7, 8, and 9, in a hypothetical example where all ten reactions proceed to completion in the production of one tonne of LiOH.Math.H.sub.2O.

TABLE-US-00001 TABLE 1 Net Tonnes (consumed(?) Reaction Tonnes Tonnes vs. Species 1 2a 3b 4 5a 5b 6 7 8 9 consumed produced produced(+)) LiAlSi.sub.2O.sub.6(s) C 5.913 0.0 ?5.913 HNO.sub.3(aq) C P 3.003 3.003 0.0 LiAl.sub.3Si.sub.8O.sub.20(OH).sub.2(s) P 0.0 5.295 +5.295 LiNO.sub.3(aq) P C 1.643 1.643 0.0 Al(NO.sub.3).sub.3(aq) P C 1.692 1.692 0.0 H.sub.2O(liq, g) P C C P C C P C + P C 1.503 0.716 ?0.787 NO.sub.2(g) P P C 2.193 2.193 0.0 O.sub.2(g) P P C 0.381 0.381 0.0 (NH.sub.4).sub.2CO.sub.3(aq, s) C P 1.145 1.145 0.0 Al(OH).sub.3(s) P 0.0 0.620 +0.620 NH.sub.4NO.sub.3(aq) P C 1.907 1.907 0.0 CO.sub.2(g) C 0.524 0.0 ?0.524 Li.sub.2CO.sub.3(s) P C 0.880 0.880 0.0 Ca(OH).sub.2(s) C 0.883 0.0 ?0.883 LiOHH.sub.2O(s) P 0.0 1.000 +1.000 CaCO.sub.3(s) P 0.0 1.193 +1.193 MgO(s) C C P P 0.960 0.960 0.0 Mg(OH).sub.2(s) P C 0.695 0.695 0.0 Mg(NO.sub.3).sub.2(aq) P C 1.767 1.767 0.0 NH.sub.3(g) P C 0.406 0.406 0.0 Note: In Reaction 4, x is taken to be 1, and y is taken to be 0. Note: In Reaction 8, x is taken to be 2.

[0185] Table 2 below shows the calculated total amounts (tonnes) of the reactants and reaction products, mass balanced, for each of Reactions 1, 2a, 3b, 4, 5a., 5b, 6, 7, 8, and 9, in a hypothetical example where all ten reactions proceed to completion in the production of one tonne of LiOH.Math.H.sub.2O.

TABLE-US-00002 TABLE 2 Net tonnes Total tonnes, Total tonnes, (consumed(?) vs. Reaction reactants reaction products produced(+)) 1 8.916 8.916 0.0 2a 1.907 1.907 0.0 3b 2.788 2.788 0.0 4 2.193 2.193 0.0 5a 2.387 2.387 0.0 5b 0.695 0.695 0.0 6 1.145 1.145 0.0 7 0.695 0.695 0.0 8 1.767 1.767 0.0 9 3.003 3.003 0.0