Abstract:
This invention relates to the separation of lithium from lithium-containing materials, primarily ores such as hectoritic montmorillonite, having about 0.1 to 1.0 percent lithium by weight. The process comprises reducing the particle size of the material to less than about 150 microns; mixing the material with a solid source of sulfates and carbonates at predetermined ratios; granulating the mix with an aqueous solvent in order to obtain granules of 1-10 mm; reacting the granules at temperatures of 950-1100° C.; slurrying the reaction products with an aqueous solution; heating the resulting slurry at about 50° to 100° C. for from about 0.3 to 2 hr; separating the solids and evaporating the solution to separate potassium and sodium salts; separating the liquid portion of the cooled brine, which is treated with sodium carbonate, potassium carbonate with heating to remove interfering alkaline earth metals, cooling and separating the aqueous phase followed by treatment with sufficient alkali carbonate to precipitate the lithium carbonate with filtering of the hot slurry to remove the lithium as solid lithium carbonate.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of priority of U.S. Provisional Application No. 61/358,324 filed Jun. 24, 2010, and U.S. Provisional Application No. 61/474,377 filed Apr. 12, 2011. Each of these provisional applications are incorporated in its entirety into this application. 
    
    
     FIELD 
     Lithium and potassium are metallic elements. They combine with certain substituent groups to form compounds with unique and desirable properties. These compounds include lithium carbonate, lithium hydroxide and potassium sulfate. The field of this application is the field of extracting these and related compounds from mineral deposits and other naturally-occurring sources of useful chemicals. 
     BACKGROUND 
     The lithium market is divided into two distinct parts: lithium chemical and lithium mineral. Lithium produced as a chemical is used as a feedstock to produce other lithium compounds and metal. The vast range of final applications for lithium chemical include the manufacture of lithium batteries—primary and secondary—greases, glass and ceramics production, aluminum smelting, air quality control, catalysts, pharmaceuticals, polymers, cements, and alloys. As a mineral, lithium concentrates are used in the specialty glass and ceramics industry. 
     Recent estimates tentatively put the world consumption of lithium at close to 113,000 tonnes lithium carbonate equivalent (LCE) or 21,230 tonnes lithium metal in 2008. Details on total consumption and breakdown by end-use markets are seldom published because of the high degree of concentration within the lithium industry. The outlook for lithium consumption nonetheless appears optimistic with an overall growth rate of 5.8% predicted between 2008 and 2013. Demand for lithium carbonate, lithium hydroxide and lithium salts is projected to rise by 15% pa over the same period, from 3,940 t Li in 2008 to 7,720 t Li in 2013. 
     The mass production of plug-in hybrid and electric vehicles present the most significant upside potential for lithium demand in this end use. Estimates vary widely as to the market penetration these vehicles will achieve and as such lithium consumption could be significantly higher or lower than this 15% per year forecast. High fuel prices may force the industry toward formulating a “greener” environment, which in-turn could make lithium a strategic element causing an escalating growth in its demand. 
     SQM and Rockwood have both increased capacity at their operations in Chile and plan to increase further capacity in 2013. Capacity at the salt lakes in Tibet and China could also rise to 16,000 tonnes/year, although projects in both areas have had problems and capacity has thus far been underutilized and slow to ramp up. Several development projects are in various stages of planning worldwide, which may have an impact on the supply of lithium to the market. 
     The price for lithium chemicals and lithium minerals has consistently risen for the past several years. United States pricing for lithium carbonate ranges from $2.80-$3 per lb and $6,160-$6,600 per ton when sold as part of a large contract. There is no spot market for lithium and the price is negotiated on a contract basis. 
     Potassium chloride is the most popular potassium fertilizer, followed in a distant second place by potassium sulfate and then by potassium magnesium sulfate, potassium nitrate, potassium phosphate, and solutions of potassium thiosulfate and potassium polysulfide. The dominant use of potassium sulfate is as a source of the nutrients potassium and sulfur in high-value crops such as berries, citrus, spinach, lettuce, grapes, and tomatoes. It is also used to fertilize turf grass for golf courses and other landscaped and high-traffic grounds. potassium sulfate&#39;s industrial applications include the production of rubber, medicines, firebrick, and various construction materials. 
     More than 90% of the world&#39;s agricultural potassium requirements are supplied by potassium chloride, since it is a high-concentration fertilizer (60% K2O nutrient) that can be produced and supplied relatively cheaply per unit of K2O from a variety of sources. Global consumption of about 55 million tonnes of product has increased in response to growing populations and reduced arable land per capita requiring improved crop yield efficiencies. The remaining supply of nutrient potash is in the form of premium potash fertilizers, of which potassium sulfate is the predominate form, with relatively minor quantities of sulphate of potash magnesia and nitrate of potash being produced. 
     Statistics for potassium sulfate (containing approximately 50% K2O) consumption are uncertain since such a large percentage is accounted for by China, and even in the United States potassium sulfate may be folded in with statistics for potassium chloride. This market is estimated at 5 million tonnes worldwide. For the United States market, Great Salt Lake Minerals (“GLUM”), North America&#39;s leading producer of potassium sulfate from its solar evaporation facility at the Great Salt Lake in Utah, publishes details of its sales broken down into domestic and exports and reports United States Census Bureau numbers modified by the USGS. Based on these numbers (with the trade data presented in short tons), the annual apparent consumption peaked at more than 400,000 tons in 2005 and dropped to 329,000 tons in 2008 as higher prices reduced demand. 
     The United States regional breakdown of consumption is based on the size of the agricultural industry and the type of crops grown. In particular, California and Florida are important areas for cultivating fruit and vegetables and account for the bulk of potassium sulfate demand. Both states have a relatively high percentage of soil testing low to medium in potassium). More than 60% of United States fruit and nut production is in California, Oregon, and Washington, all state that use potassium sulfate. In addition, tobacco grown in the southeastern United States (North Carolina, Tennessee, Kentucky, and Virginia) is an important but declining consumer of potassium sulfate. 
     The world&#39;s potassium sulfate supply is derived from more than twenty producing companies, plus another 40 to 50 within China, each with an annual output ranging from less than 10,000 tonnes to more than 500,000 tonnes. Global capacity has grown to approximately 4.9 million tonnes/year, with the main producers being Asia (mainly China) (53%), Western Europe (29%), and North America (10%) followed by Latin America (4%, all Chile), the Former Soviet Union (3%), and the Middle East and Africa with less than 1% each. Based on the size of the market and the types of crops requiring potassium sulfate, the three most likely targets for potassium sulfate sales are: 1) California/Washington, 2) Florida and parts of the southeast coastline, and 3) the Kentucky/Tennessee region. 
     Statistics released by GSLM indicate that the average selling price of potassium sulfate FOB Ogden, Utah, for fiscal year (FY) 2002 and 2003 was about $210 per ton based on sales of about 250,000 tons. In FY 2004, prices increased to an average of $227 per ton as sales jumped more than 50% to 386,000 tons through GSLM&#39;s acquisition of IMC Global&#39;s customer base. GSLM purchased IMC&#39;s potassium sulfate capacity at Carlsbad, N. Mex., which it closed, but continued to service the customer base from its source in Utah. In 2005 and 2006, sales were steady and the average price increased to almost $260 and then to $292 per ton. In 2007, the volume of sales increased to 423,000 tons and the average price was almost $322 per ton. Although the volume sold fell to below 400,000 tons in 2008, the average selling price increased to almost $596 per ton. This increase in the selling price per ton is well illustrated in the quarterly results, which show an average price of $752 per ton for Q3 2008 and $975 per ton for Q4 2008. These price levels are supported by the average value of imports from Germany at $934 per ton in 2008. Other values based on significant quantities include Canada at $551 per ton. 
     A wide variety of processes have been developed to produce potassium sulfate and similar compounds. One example is the process practiced at the Arad facility in the Negev desert in Israel. Brine is taken from the Dead Sea and heated to high temperatures in a fluidized bed. The brine decomposes, releasing HCl among other compounds. The HCl is used to make hydrochloric acid. This in turn is reacted with mined phosphate rock to form potassium sulfate. See also U.S. Pat. No. 5,552,126 to Efriam et al. Potassium sulfate may be made directly from brines. One example is the process described in U.S. Pat. No. 3,977,835 to Chemtob et al. Readily processable salt groupings were selectively crystallized out of a complex salt brine from Sealres Lake containing potassium, sodium, chloride, sulfate, carbonate and borate ions by cooling the brine in at least one artificial cooling stage to a temperature sufficiently low to at least crystallize mirabilite, evaporating the brine in a first solar evaporator to crystallize out halite, or halite and burkeite, free of potassium salt values, and then further concentrating the brine in a second solar evaporator to obtain a grouping of salts rich in potassium values. 
     The brine contained potassium ion in an amount up to about 3% by weight, preferably from about 0.5% to about 2% by weight, carbonate ion in an amount of from about 2.5% to about 4.5% by weight, sulfate ion in an amount of from about 3.0% to about 6.0% by weight, and borate ion in an amount of from about 0.6% to about 1.2% by weight, all based on the total weight of the brine, with the balance of the ionic species present being sodium ion and chloride ion. This brine could be artificially cooled to temperatures as low as about −20° C. without crystallization of potassium salts. 
     After artificial cooling to at least 20° C. to crystallize at least mirabilite, the resultant brine was processed in a solar-evaporation stage to crystallize halite or a mixture of halite and burkeite, again, without crystallization of potassium salts. After solar evaporation to crystallize sodium salts, the brine was passed to another solar-evaporation stage where the potassium salts were deposited along with borax and sodium salts. Depending on the degree of artificial cooling, the relative amounts of glaserite and sylvite deposited varied. Sylvite was the most desired form and a high degree of artificial cooling was preferred. Selective salt group crystallization using cooling in combination with solar evaporation allowed a total harvesting of all salts contained in a complex brine. 
     A wide variety of processes have been developed to produce lithium carbonate and similar compositions. As with potassium sulfate, lithium carbonate has been recovered directly from brines. One such process is disclosed in U.S. Pat. No. 4,287,163 to Garrett et al., which involved use of soluble sulfate salts as salting-out agents to precipitate lithium sulfate monohydrate. Magnesium sulfate was a preferred salting-out agent. Other sulfate salts found useful as salting-out agents were sodium sulfate and sulfuric acid, including any of their hydrates (including magnesium hydrates) or partially dehydrated salts. Process solutions were concentrated in solar ponds. 
     Lithium carbonate and similar compositions also can be produced directly from ore that is rich in convertible lithium compounds. One example is the experimental process developed by the United States Bureau of Mines (“USBM”) in 1988.  Lithium and Its Recovery from Low - grade Nevada Clays , USBM Bulletin 691 (1988). USBM worked with clays obtained from the McDermitt Caldera in Nevada, which contained lithium in the form of hectorite. 
     The experimental USBM process is depicted in  FIG. 1 . To convert the hectorite-bound lithium to lithium carbonate, the clay was mixed with limestone and gypsum and the mix was subjected to feed preparation  101  followed by roasting  102 . The clay was soft and friable and required no heavy crushing. However, it was air-dried and passed through a jaw crusher to produce a minus 10-mesh material before blending. The limestone and gypsum were treated similarly. Further feed preparation  101  entailed grinding and mixing the ingredients for 1 hour in a ball mill. The resultant mixture (80% finer than 200 mesh) was pelletized with water to produce nominal 6.5 mm diameter pellets. These pellets contained up to 20% moisture and were dried at 700° C. before roasting step  102 . 
     Objectives of roasting step  102  were to (1) generate calcined material for leaching  103 , purification, and product recovery studies, (2) determine optimum roasting conditions, and (3) determine typical gas emissions. Batch tests were conducted in the roaster to determine optimum retention time and roast temperature. Small charges (500 g) of pelletized 5:3:3 mix were roasted. The test results showed a 2 hour retention time and 9000 C to be optimum. This retention time was used throughout the roaster studies; the temperature was varied in a few tests in which the effect of temperature on lithium extraction was investigated. 
     To generate calcine for use in product-recovery solution studies an equivalent 5:3:3 mixture of clay, limestone, and gypsum was used; batch testing had established the 5:3:3 mix as optimum. The pelletized feed was charged to the roaster  102  in 600-g increments every 5 minutes to simulate continuous operation. Generally, each test produced 80 lb. of calcine in 6.5 hour operating time. 
     The final phase of the roast studies involved investigating the effects of charge composition and roast temperature on lithium extraction. A test series was conducted in which various mixes were roasted. Lithium extraction was determined by water-leaching  103  composite samples of the calcines. Lithium extractions of at least 80% were attained with a wide range of clay-limestone-gypsum ratios. Also, good lithium extraction was achieved over a temperature range of 850° C. to 975° C. The 5:2:2 mix was chosen for cost evaluation because this mix provided high extraction with a relatively low reagent addition. Emissions of SO 2  and fluorine were calculated from material balances. In a commercial operation, these off gases would require scrubbing before being vented to the atmosphere. 
     The objective of the leaching  103  tests was to determine the relationship between leach-system variables and optimal lithium extraction. The following variables were studied: 
     1. leach pulp percent solids, 
     2. wash water recycle, 
     3. calcine particle size, and 
     4. leach time. 
     The calcines leached in these leaching  103  tests were produced by roasting 5:3:3 mixtures of clay, limestone, and gypsum. Generally, 70 lb. of calcine was water-leached in each test. A slurry filter  104  recovered the leach solution. The filter cake from filter  104  was washed and discarded. 
     A series of 30-minute  103  leach tests was conducted at ambient temperature to study the effect of percent solids and wash water recycle on lithium extraction. The test results showed that the calcine was leached effectively at 40% solids with recycled wash water. At 50% solids, the lithium extraction decreased. Since the wash water was recycled to the leach step, the volume of wash water used was equal to the volume of makeup water required for the next leach. 
     The calcine pellets did not break apart during the leach step  103 . USBM concluded that if a coarse particle could be leached effectively, grinding requirements would be minimized. A test series was conducted to study the effect of calcine particle size on lithium extraction. The calcine was leached for 30 minutes at 40% solids using recycled wash water. Test results showed that the 30-minute leach  103  extracted the lithium equally well from all particle sizes tested. To determine the effect of leach time on lithium extraction, a test series was conducted with coarse-crushed and whole pellets. The pellets were leached at 40% solids in recycled wash water. 
     Test results showed that lithium was extracted from coarse-crushed pellets with a 5-minute leach; whole pellets were not effectively leached in 5 minutes. Although the pellets did not break apart during the leach, prolonged agitation generated fines which affected filtration rates. Filtrate rates decreased with increased leach time and increased particle size. For 30-minute leaches, the whole pellet slurry filtered slowly because the filter cloth was blinded with fines. As the calcine particle size decreased, the fines tended to remain on top of the filter cake, allowing faster filtration. Overall, the test results indicate that coarse-grinding the calcine and  103  leaching it for 5 minutes at 40% solids provided good extraction and high filtration rates. Under these conditions, lithium extractions of 82 to 84% could be expected; the leach solution generally contained 2.5 to 3.0 g/l lithium. 
     USBM evaporator  105  was fed with leach solution and solution recycled from the previous test. The recycled solution—mother liquor plus product wash—accounted for about 20% of the total volume in evaporator  105 . In addition to concentrating the solution, calcium as calcium carbonate was removed from the leach solution in this step of the process. The leach solution was saturated with calcium sulfate (about 0.6 g/l calcium ion). It was found that reducing the calcium ion concentration to about 0.015 g/l prevented calcium contamination of the product. The evaporation procedure involved the following steps: 
     1. The solution—leach plus recycle—was evaporated to about 50% of its original volume and then passed through filter  106  to remove calcium carbonate. Carbonate ion (approximately 15 g/l) present in the recycled solution precipitated over 99% of the calcium contained in the leach solution. 
     2. The filtrate was returned to evaporator  107 . Evaporation continued until the solution was reduced to 20% of its original volume. 
     3. The hot concentrated solution, containing 12 to 13 g/l lithium, was transferred to the product precipitation step  108 . Generally, this concentrated solution was cloudy because a small amount of lithium carbonate precipitated during evaporation. 
     Lithium recovery step  108  involved heating the concentrated solution to boiling and adding a stoichiometric amount of sodium carbonate to precipitate a lithium carbonate product. The objective of this step was to recover a product of at least 99% purity. Initially, the product was recovered from the hot solution by vacuum filtration and then dried. This procedure yielded a product of about 80% purity with the principal contaminants being sodium sulfate and potassium sulfate. 
     Numerous tests were conducted using leach solution to investigate product purification techniques. Test results were erratic because precise control of solution concentration was difficult and synthetic solutions were used to study operating variables. A series of laboratory tests was conducted using 1-liter batches of synthetic concentrated solution—made up with reagent chemicals—containing 97 g/l lithium sulfate, 158 g/l potassium sulfate, and 87 g/l sodium sulfate. Adding a stoichiometric amount of calcium carbonate to the hot solution precipitated lithium carbonate. 
     Product filtration and washing procedures were then studied. The following observations were made: 
     1. Pressure filtration  109  yielded a product of higher purity than vacuum filtration  109  by reducing the moisture content of the filter cake. 
     2. With pressure filtration  109 , 4 to 6 liter of wash water per kilogram of dry product was required to produce a 99% pure product. A much higher volume of water was needed to produce a comparable product by vacuum filtration  109 . 
     3. For pressure filtration  109 , wash water volumes above 6 l/kg of dry product did not further improve product purity. Also, single-stage washing was as effective as either multistage washing or product reslurry. 
     4. Adding calcium carbonate as a saturated solution, rather than as a dry powder, had little effect on product purity. However, this procedure generated a coarse grainy product, in contrast to the fine powdery product obtained by adding dry calcium carbonate. 
     The wash water and product filtrate recovered in these tests contained 14 to 16 g/l of lithium carbonate. The wash was recycled to the evaporator. After a crystallization step, the mother liquor was also recycled. 
     In addition to residual lithium carbonate, the product filtrate from filter  109  contained high concentrations of potassium sulfate and sodium sulfate (over 150 g/l of each), preventing effective recycling. Tests showed that the most effective method for reducing the sulfate concentration involved crystallizing the salts in crystallizer  110  by chilling the product filtrate to between 0° and −4° C.; below −4° C. the filtrate froze. The mother liquor, which contained 70 g/l sodium sulfate and 100 g/l of potassium sulfate, was recovered by either vacuum or pressure filtration. Pressure filtration tended to reduce lithium loss by decreasing the amount of mother liquor present in the filter cake. 
     The filter cake was a mixture of glaserite and glauber salt Laboratory tests showed that glaserite and glauber salt could be recovered separately by a two-step crystallization procedure. At product filtrate temperatures down to about 17° C., the glaserite crystallized. The salt was recovered by vacuum filtration and analyzed as 33 wt % potassium, 8 wt % sodium, and &lt;0.1 wt % lithium. Further cooling of the product filtrate (to as low as −4° C.) crystallized the glauber salt. The salt was recovered by pressure filtration and analyzed as 28 wt % sodium, 6 wt % potassium (a small amount of glaserite crystallized with the glauber salt), and 0.15 wt % lithium. 
     USBM roast-leach test results indicated 82% to 84% lithium extraction as optimum. Treating the leach solution by the methods specified resulted in 95% to 98% recovery of the contained lithium. Losses occurred in calcium carbonate filtration (0.5% loss) and in the crystallization step (2% to 5% loss, depending on the filtration method used to separate the mother liquor from the salts). Overall, 78 to 82% of the lithium contained in the clay was recovered as 99% pure lithium carbonate. 
     A material balance and a cost evaluation for a 5:3:3 ratio of clay-limestone-gypsum was prepared by USBM. The operating cost for this feed ratio was $2.12/1b lithium carbonate; this figure was revised to $2.27/lb. lithium carbonate as of May 1985. The cost evaluation showed raw materials (primarily limestone and gypsum) used in the process to be the most costly component. To lessen this expense, the evaluation recommended a reduction in the quantity of reagents used in the roast feed. The feed ratio could be reduced from 5:3:3 to 5:2:2 without affecting lithium extraction. 
     In May 1985, the USBM prepared a further cost evaluation. The evaluation estimated the operating cost of the process at $1.86/lb lithium carbonate produced. The evaluation was revised as of July 1987 and the updated operating cost was $2.02/lb lithium carbonate. The selling price of lithium carbonate as of July 1987 was $1.50/lb. As in the initial cost evaluation, a principal cost was the purchase of limestone and gypsum raw materials, which amounted to $0.39/lb. lithium carbonate. A high-cost section process section was evaporation, which, because of high fuel costs, added about $0.35/lb lithium carbonate produced. The capital cost was estimated to be about $105 million. No cost was allowed for land acquisition, mine development, and royalties on the ore. These costs would have to be considered before development of the resource could occur. 
     USBM concluded that for its process to be economical in the market of the time, the operating costs had to be reduced. The process unit operations that showed promise for cost reduction were identified as roasting  102 , leaching  103 , and evaporation  105 / 107 . Limited rotary roaster testing was conducted to determine if the reagent requirement for the roast could be further reduced. The testing involved recycling lithium carbonate product filtrate and product wash water, without salt removal, to the roast step. Test results indicated that the salts in the recycled solution improved lithium recovery for the 5:1.5:1.5 feed ratio by about 1%; recovery for a 5:2:2 mix was improved by 3% to 5%. 
     In the USBM&#39;s proposed modification, the recycled solution would be used in pelletizing the roast feed; thus, the water requirements for feed preparation, as well as evaporation load, would be decreased. To reduce the capital costs associated with agitation leaching, percolation leaching was investigated. Tests were conducted using calcine from a 5:2:2 roast. The calcine was leached in a series of four acrylic columns measuring 4 inches in diameter by 4 feet high. Preliminary test results indicated that lithium extraction was comparable to that achieved using agitation leaching. The percolation leach solution contained about 7 g/l lithium; leach solution obtained by agitation leaching generally contained 2.5 g/l to 3 g/l lithium. This increase in solution loading could significantly reduce the evaporation load. 
     USBM believed that a cost-saving alternative for the evaporation step  105 / 107  would involve the use of solar evaporation. Although solar evaporation tests were not conducted, this modification was considered by USBM to be a viable alternative because of the hot, dry Nevada climate. The potential process modifications would all require expanded investigation to determine if they were viable alternatives to established procedures. 
     SUMMARY 
     A continuous process for simultaneously producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions. 
     A continuous process for simultaneously producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. 
     A continuous process for simultaneously producing lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions. 
     A continuous process for simultaneously producing lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions. in which lithium hydroxide is extracted by membrane electrolysis. 
     A continuous process for simultaneously producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions. 
     A continuous process for simultaneously producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. 
     A continuous process for simultaneously producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium hydroxide is extracted by membrane electrolysis. 
     A continuous process for simultaneously producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. 
     A method for recovering lithium, potassium and sodium from a material containing a low concentration of lithium, which method comprises:
         (a) reducing the material to small particles having average diameter of about 150 microns or finer;   (b) mixing the material with a solid source of sulfates and carbonates at ratios 0.1:1 to 0.9:1   (c) granulating the mix with an aqueous solvent in order to obtain granules of 1-10 mm   (d) reacting the granules at temperatures of 950-1100 degrees C.   (e) slurrying the reaction products of step (d) with process water;   (f) heating the slurry of step (e) at about 50 degree. to 100 degree. C. for about between about 0.2 to 2 hr;   (g) separating the solids and liquid of step (f);   (h) evaporating the liquid of step (g) to a volume of about 30 to 50% of original and cooling to 0 degree to 35 degree C.;   (i) treating the evaporate in (h) to remove glaserite by filtering the cool suspension   (l) reacting of the liquid phase of step (i) with a sufficient aqueous alkali carbonate to precipitate lithium carbonate and heating to between about 60 degree. to 125 degree. C. for between about 0.5 and 10 hr;   (m) separating the hot slurry of step (l) to recover the lithium value as solid lithium carbonate.   (l) decomposing the glaserite of step (i) to produce solid potassium sulfate   (n) reacting the liquid of step (m) with sufficient amount acid to remove carbonates   (o) remove glauber salt by cooling crystallization   (p) recovering of lithium hydroxide from mother liquor in step (i) by electrolysis.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing of a prior-art process for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions (discussed in Background). 
         FIG. 2  is a schematic drawing of a continuous process for producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. 
         FIG. 3  is a detail drawing of a continuous process for purifying the leach liquor resulting from a continuous process for leaching lithium and potassium compositions from a calcined mineral source. 
         FIG. 4  is a detail drawing of a continuous process for concentrating the leach liquor resulting from a continuous process for leaching lithium and potassium compositions from a calcined mineral source. 
         FIG. 5  is a schematic drawing of another continuous process for producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. 
         FIG. 6  is a schematic drawing of a continuous process  600  for producing, lithium hydroxide from lithium carbonate and potassium sulfate from a mineral source of potassium compositions. 
         FIG. 7  is a schematic drawing of a further continuous process for producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. 
         FIG. 8  is a schematic drawing of one more continuous process for producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. 
         FIG. 9  is a schematic drawing of a continuous process for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. 
         FIG. 10  is a detail drawing of a continuous process for extracting lithium carbonate by crystallization from the concentrated leach liquor of a continuous process for leaching lithium and potassium compositions from a calcined mineral source. 
         FIG. 11  is a schematic drawing of a continuous process for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. 
         FIG. 12  is a schematic drawing of another continuous process for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. 
         FIG. 13  is a schematic drawing of yet another continuous process for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. 
         FIG. 14  is a schematic drawing of a further continuous process for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. 
     
    
    
     DETAILED DESCRIPTION 
     The physical and chemical processes employed in the inventions are sensitive to temperature. Certain preferred and highly preferred ranges (in oC) apply to various aspects of the processes of the inventions. Reference the following: 
     
       
         
               
               
               
               
             
           
               
                   
               
               
                 Parameter 
                 Example 
                 Preferred 
                 Most Preferred 
               
               
                   
               
             
             
               
                 leaching (20-65% solids) 
                 FIG. 9 ref. 902 
                    30 to 100 
                   45 to 85 
               
               
                 evaporation 
                 FIG. 9 ref. 906 
                    50 to 110 
                   65 to 95 
               
               
                 crystallization  
                 FIG. 9 ref. 908 
                 −10 to 50 
                  −5 to 30 
               
               
                 crystallization  
                 FIG. 9 ref. 918 
                 −15 to 25 
                 −10 to 15 
               
               
                 precipitation 
                 FIG. 9 ref. 930 
                   80 to 97 
                   84 to 94 
               
               
                 crystallization  
                 FIG. 9 ref. 942 
                  −5 to 15 
                  −4 to 10 
               
               
                 reaction 
                 FIG. 2 ref. 218 
                    5 to 40 
                   10 to 30 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 1 
       FIG. 2  is a schematic drawing of a continuous process  200  for producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. The mineral source is hectorite ore. Viewed broadly, the major process steps are ore size reduction, calcination, water leaching, lithium carbonate recovery, lithium hydroxide recovery and potassium sulfate recovery. 
     Ore Preparation 
     The ore is delivered from the mine by trucks and can be fed directly to the process or stored on the runoff-mine ore pad with capacity of 30 days of production. A front-end loader is provided for alternate means of ore delivery from ore pad to the process. 
     An impact crusher operating in a closed circuit with a vibrating screen reduces ore size to ˜12 mm, suitable for the downstream grinding operation. The fine ore is conveyed to a stock pile providing surge capacity between the crushing operation on 10 hours per day schedule and the downstream continuous operation. The crushed ore is advanced to the process by reclaim feeders and conveyors. The downstream plant is designed to process 5000 tons per day of the ore. 
     Ore Calcining 
     The anhydrite and dolomite reagents required for the calcining process are crushed to ˜12 mm size and stored in separate silos. In preparation for the calcining process, ore and the reagents are ground and well mixed to facilitate reactions. Reagents and ore are metered by weigh-belt feeders to a dry ball mill, operating in a closed circuit with cyclonic separator. The components are ground to ˜150 micron and then are advanced to a pelletizer and dried in a fluid bed dryer, which is heated by a split stream of the hot off-gas from the downstream calciner. Dust generated in the ball mill and calciner circuits is collected in a baghouse filter and added to the pelletizer feed stream. 
     A step in this process is a conversion of lithium (and other alkali metals) contained in the ore to water-soluble sulfates employing a high temperature (1000° C.) calciner. The hectorite clay is mixed with dolomite and anhydrite minerals, which are necessary for the conversion process. The primary reaction is between lithium (and potassium, sodium) silicates present in the clay and calcium sulfate (anhydrite), forming alkali (lithium, potassium, sodium) sulfates and free silica (Si0 2 ). The presence of the dolomite prevents reverse reaction of alkali sulfates by bonding with free silica and forming calcium silicate. The advantage of this process is that the impurities in the ore remain insoluble, thus simplifying downstream recovery and refining. The reported reaction kinetics are slow, thus requiring an extended (1 hour) residence time. 
     The hot calcine is cooled by ambient air in a fluidized bed cooler. To increase the thermal efficiency of the system, preheated air from the cooler is used as make-up air for the calciner. To further maximize the thermal efficiency of the system, remaining calciner off-gas is used in the waste heat boiler to produce steam required in the downstream lithium and potassium sulfate recovery processes. The calcine material is stored in a bin to provide surge capacity between calcining and leach sections of the process. 
     Calcine Leaching 
     The calcine material is leached with water at 95° C. for 30 minutes. Operation at this elevated temperature maximizes concentration of potassium sulfate in solution, thus reducing energy costs in the downstream evaporation process. Lithium and potassium recoveries in the leach are 92% and 90% respectively. 
     The leach slurry is advanced to an automated filter press. Since the alkali sulfates are in the filtrate, the filter cake is washed and air-blown to maximize lithium and potassium recoveries and minimize the residual sulfate content of the tailings. Filtrate is stored in a holding tank, providing surge capacity between leach and downstream evaporation and crystallization processing. A polishing filter is provided on the filtrate stream to prevent any solid contaminant carryover to crystallizer  203 . 
     The clarified leach filtrate contains traces of calcium. This can be removed in an ion exchange column located upstream of the evaporator  202 . Calcium might contaminate the lithium carbonate product and foul up the membrane in the membrane electrolysis process. 
     Evaporation 
     Leach filtrate is fed as evaporator feed  220  to an evaporator  202  where brine concentration is increased to near-saturation. The composition of the feed  220  to the evaporator is as follows: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Evaporator Feed 220 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0.00 
               
               
                   
                 liquid [tph] 
                 127.77 
               
               
                   
                 total [tph] 
                 127.77 
               
               
                   
                 total [m3/h] 
                 113.07 
               
               
                   
                 sp.gr. 
                 1.13 
               
               
                   
                 Li2CO3 [kg/h] 
                 0 
               
               
                   
                 Li2SO4 [kg/h] 
                 5,176 
               
               
                   
                 K2SO4 [kg/h] 
                 14,301 
               
               
                   
                 Na2SO4 [kg/h] 
                 5,976 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 25,453 
               
               
                   
                 water [tph] 
                 102.32 
               
               
                   
                 Li [g/l] 
                 5.78 
               
               
                   
                   
               
             
          
         
       
     
     Evaporator  202  is operated at elevated temperature to maximize concentration of potassium sulfate. As an added benefit, lithium concentration is increased, thus reducing the lithium load in the recycle stream. The evaporator  202  is heated by steam generated in the waste heat boiler. Concentrated sulfate solution leaving evaporator  202  is collected in a pregnant liquor tank, providing surge capacity between evaporator  202  and crystallization process  203 . The composition of the concentrated sulfate solution leaving evaporator  202  as evaporator product  221  is as follows: 
                                           Evaporator Product 221                                    solids [tph]   0.00           liquid [tph]   70.00           total [tph]   70.00           total [m3/h]   56.91           sp.gr.   1.23           Li2CO3 [kg/h]   0           Li2SO4 [kg/h]   5,176           K2SO4 [kg/h]   14,301           Na2SO4 [kg/h]   5,976           Alk. Sulf. [kg/h]   25,453           water [tph]   44.55           Li [g/l]   11.49                        
Glaserite Crystallization
 
     An objective of the sulfate crystallization step  203  is to recover potassium sulfate as a marketable product and advance lithium to the lithium recovery step. The sulfate crystallization step  203  involves preparation of crystalline glaserite (3 K 2 SO 4 .Na 2 SO 4 ) as an intermediate product, followed by crystallization and drying of potassium sulfate. The full composition of the product leaving crystallizer  203  as crystallizer product  222  is as follows: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Crystallizer Product 222 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 13.18 
               
               
                   
                 liquid [tph] 
                 56.82 
               
               
                   
                 total [tph] 
                 70.00 
               
               
                   
                 total [m3/h] 
                 56.91 
               
               
                   
                 sp.gr. 
                 1.23 
               
               
                   
                 Li2CO3 [kg/h] 
                 0 
               
               
                   
                 Li2SO4 [kg/h] 
                 5,176 
               
               
                   
                 K2SO4 [kg/h] 
                 14,301 
               
               
                   
                 Na2SO4 [kg/h] 
                 5,976 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 25,453 
               
               
                   
                 water [tph] 
                 31.37 
               
               
                   
                 Li [g/l] 
                 11.49 
               
               
                   
                   
               
             
          
         
       
     
     Crystallizer product  222  is directed to centrifuge  204 . The glaserite crystals are isolated and routed to a potassium sulfate recovery circuit. The composition of the glaserite product  231  is as follows 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Glaserite Crystals 231 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 13.18 
               
               
                   
                 liquid [tph] 
                 0.69 
               
               
                   
                 total [tph] 
                 13.88 
               
               
                   
                 total [m3/h] 
                   
               
               
                   
                 sp.gr. 
                   
               
               
                   
                 Li2CO3 [kg/h] 
                 0 
               
               
                   
                 Li2SO4 [kg/h] 
                 63 
               
               
                   
                 K2SO4 [kg/h] 
                 9,868 
               
               
                   
                 Na2SO4 [kg/h] 
                 2,681 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 12,612 
               
               
                   
                 water [tph] 
                 0.38 
               
               
                   
                 Li [g/l] 
               
               
                   
                   
               
             
          
         
       
     
     The glaserite mother liquor  223  that is generated by centrifuge  204  has the following composition: 
                                           Glaserite ML 223                                    solids [tph]   0.00           liquid [tph]   56.12           total [tph]   56.12           total [m3/h]   45.26           sp. gr.   1.24           Li2CO3 [kg/h]               Li2SO4 [kg/h]   5,113           K2SO4 [kg/h]   4,433           Na2SO4 [kg/h]   3,295           Alk. Sulf. [kg/h]   12,841           water [tph]   30.98           Li [g/l]   14.27                        
Lithium Carbonate Recovery
 
     Lithium carbonate is precipitated from the glaserite mother liquor  223  (containing mixed alkali sulfates) by addition of sodium carbonate, which is metered to lithium precipitation process  205 . The lithium carbonate is soluble in water and more soluble in the glaserite mother liquor. Because this solubility decreases with an increase in temperature, precipitation is conducted at approximately 95° C. Precipitated lithium carbonate is separated from potassium and sodium sulfates in filter press  206 , washed with hot water and dried. The composition of the lithium carbonate is as follows: 
                                           Li2CO3 Crystals                                    solids [tph]   2.64           liquid [tph]   0.14           total [tph]   2.78           total [m3/h]               sp. gr.               Li2CO3 [kg/h]   2,637           Li2SO4 [kg/h]               K2SO4 [kg/h]   0           Na2SO4 [kg/h]   0           Alk. Sulf. [kg/h]   0           water [tph]   0.14                        
Lithium Hydroxide Recovery
 
     The sulfate-containing lithium mother liquor  225  from filter press  206  has the following composition: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Li2CO3 ML 225 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0.00 
               
               
                   
                 liquid [tph] 
                 78.35 
               
               
                   
                 total [tph] 
                 78.35 
               
               
                   
                 total [m3/h] 
                 65.84 
               
               
                   
                 sp. gr. 
                 1.19 
               
               
                   
                 Li2CO3 [kg/h] 
                 801 
               
               
                   
                 Li2SO4 [kg/h] 
                 0 
               
               
                   
                 K2SO4 [kg/h] 
                 4,433 
               
               
                   
                 Na2SO4 [kg/h] 
                 9,902 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 14,335 
               
               
                   
                 water [tph] 
                 50.91 
               
               
                   
                 Li [g/l] 
               
               
                   
                   
               
             
          
         
       
     
     This mother liquor  225  is acidified in acidification step  210  and then fed to membrane electrolysis process  211 . The composition of this acidified mother liquor as the electrolysis feed  226  is as follows: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Electrolysis Feed 226 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0 
               
               
                   
                 liquid [tph] 
                 106.10 
               
               
                   
                 total [tph] 
                 106.10 
               
               
                   
                 total [m3/h] 
                 86.26 
               
               
                   
                 sp. gr. 
                 1.23 
               
               
                   
                 Li2SO4 [tph] 
                 1,192 
               
               
                   
                 K2SO4 [tph] 
                 4,433 
               
               
                   
                 Na2SO4 [tph] 
                 9,902 
               
               
                   
                 M2SO4 [tph] 
                 15,527 
               
               
                   
                 water [tph] 
                 90.57 
               
               
                   
                   
               
             
          
         
       
     
     Membrane electrolysis process  211  converts alkali sulfates to their respective hydroxides on the cathode side to form a caustic catholyte  227 , while sulfates are converted to sulfuric acid on the anode side to form an acidic anolyte  228 . The electrolysis process generates very pure hydrogen and oxygen streams. Hydrogen can be used as supplemental fuel in calcining or marketed as a pure product. 
     The acidic anolyte  228  is in part recycled to acidification process  210  and in part fed to reactor  212  for further processing. The composition of the acidic anolyte  228  is as follows: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Acidic Anolyte 228 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0 
               
               
                   
                 liquid [tph] 
                 270.16 
               
               
                   
                 total [tph] 
                 270.16 
               
               
                   
                 total [m3/h] 
                 259.77 
               
               
                   
                 sp. gr. 
                 1.04 
               
               
                   
                 Li2SO4 [kg/h] 
                   
               
               
                   
                 K2SO4 [kg/h] 
                   
               
               
                   
                 Na2SO4 [kg/h] 
                   
               
               
                   
                 H2SO4 [kg/h] 
                 10,390.61 
               
               
                   
                 water [tph] 
                 259.77 
               
               
                   
                   
               
             
          
         
       
     
     The caustic catholyte  227  has the following composition: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Caustic Catholyte 227 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0 
               
               
                   
                 liquid [tph] 
                 188.02 
               
               
                   
                 total [tph] 
                 188.02 
               
               
                   
                 total [m3/h] 
                 179.07 
               
               
                   
                 sp. gr. 
                 1.05 
               
               
                   
                 LiOH [kg/h] 
                 519 
               
               
                   
                 KOH [kg/h] 
                 2,855 
               
               
                   
                 NaOH [kg/h] 
                 5,579 
               
               
                   
                 MOH [kg/h] 
                 8,953 
               
               
                   
                 water [tph] 
                 179.07 
               
               
                   
                   
               
             
          
         
       
     
     The caustic catholyte is fed to evaporation process  207 , where it is concentrated. The lithium hydroxide in the caustic catholyte has significantly lower solubility than either sodium hydroxide or potassium hydroxide. As a consequence, it crystallizes out in evaporation process  207  as lithium hydroxide mono-hydrate and drops out further when evaporator  207  output is cooled down prior to entering separator  208 . 
     The lithium hydroxide is filtered and washed with a saturated aqueous solution of lithium hydroxide to remove entrained sodium and potassium. The washed product is dried and packaged under an inert atmosphere to avoid contact with carbon dioxide in air. 
     Potassium Sulfate Recovery 
     The liquor leaving separator  208  is a mixed-caustic solution  238  having the following composition: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Mixed-Caustic Solution 238 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0.00 
               
               
                   
                 liquid [tph] 
                 33.76 
               
               
                   
                 total [tph] 
                 33.76 
               
               
                   
                 total [m3/h] 
                 22.50 
               
               
                   
                 sp. gr. 
                 1.5 
               
               
                   
                 LiOH [kg/h] 
                 5 
               
               
                   
                 KOH [kg/h] 
                 2,855 
               
               
                   
                 NaOH [kg/h] 
                 5,579 
               
               
                   
                 MOH [kg/h] 
                 8,439 
               
               
                   
                 MOH gpl] 
                 16,879 
               
               
                   
                 water [tph] 
                 16.88 
               
               
                   
                   
               
             
          
         
       
     
     This mixed-caustic solution  238  is directed to reactor  212 . There it reacts with the acidic anolyte  228  generated during membrane electrolysis  211  to form an alkali-sulfate solution  239  that is rich in potassium sulfate and sodium sulfate: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Alkali-Sulfate Solution 239 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0 
               
               
                   
                 liquid [tph] 
                 267.85 
               
               
                   
                 total [tph] 
                 267.85 
               
               
                   
                 total [m3/h] 
                 255.10 
               
               
                   
                 sp. gr. 
                 1.05 
               
               
                   
                 Li2SO4 [kg/h] 
                 12 
               
               
                   
                 K2SO4 [kg/h] 
                 4,433 
               
               
                   
                 Na2SO4 [kg/h] 
                 9,902 
               
               
                   
                 H2SO4 [tph] 
                 0 
               
               
                   
                 water [tph] 
                 253.50 
               
               
                   
                 Li [g/l] 
               
               
                   
                   
               
             
          
         
       
     
     The glaserite crystals  231  isolated in centrifuge  204  are subjected to glaserite dissolution process  213  to produce the following potassium-sulfate crystallizer feed  232  for crystallizer  214 : 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 K2SO4 Cryst. Feed 232 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0.00 
               
               
                   
                 liquid [tph] 
                 61.67 
               
               
                   
                 total [tph] 
                 61.67 
               
               
                   
                 total [m3/h] 
                 51.39 
               
               
                   
                 sp. gr. 
                 1.2 
               
               
                   
                 Li2CO3 [kg/h] 
                   
               
               
                   
                 Li2SO4 [kg/h] 
                 0 
               
               
                   
                 K2SO4 [kg/h] 
                 9,868 
               
               
                   
                 Na2SO4 [kg/h] 
                 2,681 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 12,549 
               
               
                   
                 water [tph] 
                 49.12 
               
               
                   
                 Li [g/l] 
               
               
                   
                   
               
             
          
         
       
     
     The crystallizer product  233  of crystallizer  214  has the following composition: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Crystallizer Product 233 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0.00 
               
               
                   
                 liquid [tph] 
                 61.67 
               
               
                   
                 total [tph] 
                 61.67 
               
               
                   
                 total [m3/h] 
                 51.39 
               
               
                   
                 sp. gr. 
                 1.2 
               
               
                   
                 Li2CO3 [kg/h] 
                 0 
               
               
                   
                 Li2SO4 [kg/h] 
                 0 
               
               
                   
                 K2SO4 [kg/h] 
                 9,868 
               
               
                   
                 Na2SO4 [kg/h] 
                 2,681 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 12,549 
               
               
                   
                 water [tph] 
                 49.12 
               
               
                   
                 Li [g/l] 
                 0.00 
               
               
                   
                   
               
             
          
         
       
     
     The crystallizer product  233  of crystallizer  214  is separated into crystals and a mother liquor in centrifuge  213 . The crystals, which represent potassium sulfate product, have the following composition: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 K2SO4 Crystals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 4.83 
               
               
                   
                 liquid [tph] 
                 0.25 
               
               
                   
                 total [tph] 
                 5.09 
               
               
                   
                 total [m3/h] 
                   
               
               
                   
                 sp. gr. 
                   
               
               
                   
                 Li2CO3 [kg/h] 
                 0 
               
               
                   
                 Li2SO4 [kg/h] 
                 0 
               
               
                   
                 K2SO4 [kg/h] 
                 4,736 
               
               
                   
                 Na2SO4 [kg/h] 
                 97 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 4,833 
               
               
                   
                 water [tph] 
                 0.20 
               
               
                   
                 Li [g/l] 
               
               
                   
                   
               
             
          
         
       
     
     The potassium-sulfate mother liquor  234  from centrifuge  213  has the following composition: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 K2SO4 Crystallizer ML 234 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0.00 
               
               
                   
                 liquid [tph] 
                 61.42 
               
               
                   
                 total [tph] 
                 61.42 
               
               
                   
                 total [m3/h] 
                 49.53 
               
               
                   
                 sp. gr. 
                 1.24 
               
               
                   
                 Li2CO3 [kg/h] 
                 0 
               
               
                   
                 Li2SO4 [kg/h] 
                 0 
               
               
                   
                 K2SO4 [kg/h] 
                 5,131 
               
               
                   
                 Na2SO4 [kg/h] 
                 2,585 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 7,716 
               
               
                   
                 water [tph] 
                 48.92 
               
               
                   
                 Li [g/l] 
                 0.00 
               
               
                   
                   
               
             
          
         
       
     
     This potassium-sulfate mother liquor  234  is mixed with the output of reactor  212  in mixing process  216  to form a mixed-sulfate solution  235  having the following composition: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Mixed-Sulfate Solution 234 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 0.00 
               
               
                   
                 liquid [tph] 
                 324.49 
               
               
                   
                 total [tph] 
                 324.49 
               
               
                   
                 total [m3/h] 
                 304.68 
               
               
                   
                 sp. gr. 
                 1.065 
               
               
                   
                 Li2CO3 [kg/h] 
                 0 
               
               
                   
                 Li2SO4 [kg/h] 
                 12 
               
               
                   
                 K2SO4 [kg/h] 
                 9,565 
               
               
                   
                 Na2SO4 [kg/h] 
                 12,487 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 22,063 
               
               
                   
                 water [tph] 
                 302.42 
               
               
                   
                 Li [g/l] 
               
               
                   
                   
               
             
          
         
       
     
     This mixed-sulfate solution  235  is concentrated in evaporator  217  to arrive at the following evaporator product  236 : 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Evaporator Product 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 solids [tph] 
                 8.82 
               
               
                   
                 liquid [tph] 
                 74.49 
               
               
                   
                 total [tph] 
                 74.49 
               
               
                   
                 total [m3/h] 
                 57.30 
               
               
                   
                 sp. gr. 
                 1.3 
               
               
                   
                 Li2CO3 [kg/h] 
                 0 
               
               
                   
                 Li2SO4 [kg/h] 
                 12 
               
               
                   
                 K2SO4 [kg/h] 
                 9,565 
               
               
                   
                 Na2SO4 [kg/h] 
                 12,487 
               
               
                   
                 Alk. Sulf. [kg/h] 
                 22,063 
               
               
                   
                 water [tph] 
                 52.42 
               
               
                   
                 Li [g/l] 
               
               
                   
                   
               
             
          
         
       
     
     This evaporator product  236  is reacted with potassium chloride in reactor  218  to convert sodium sulfate into potassium sulfate, adding to the efficiency of the process overall in terms of recovery of potassium sulfate. The reactor output  237  is purified in purification step  219 . 
       FIG. 3  is a detail drawing of a continuous process for purifying the leach liquor resulting from a continuous process for leaching lithium and potassium compositions from a calcined mineral source. Calcine leach feed  303  is deposited in leach tanks  308 . Water is added. When leaching is complete, leach discharge pumps  310  convey the resulting slurry  311  to a slurry surge tank  312 . When appropriate, pressure filter feed pumps  313  take filter feed  314  from slurry surge tank  312  and convey it to belt filter  316 , which produces a filter cake  317  and a filtrate  319 . 
     The filter cake  317  is conveyed to a clay repulp tank  320 , where the filter cake  317  is agitated to form a clay  322 , which is pumped from the clay repulp tank  320  by clay tailings pump  321 . Filtrate  319  is conveyed to a filtrate tank  323 . From there, it is pumped by a filtrate pump  324  through a polishing filter  325 . The resulting leach filtrate  326  is conveyed to a downstream process evaporator. 
     The following table sets forth information about the various process streams shown on  FIG. 3 : 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                 Stream No. 
               
             
          
           
               
                   
                 303 
                 311 
                 314 
                 319 
                 326 
                 317 
                 327 
               
             
          
           
               
                   
                 Description 
               
             
          
           
               
                   
                 Calcine  
                 Slurry to 
                   
                   
                 Filtrate 
                   
                 Sulfate 
               
               
                   
                 to  
                 Surge 
                 Filter 
                   
                 to 
                 Filter 
                 Mother 
               
               
                   
                 leach 
                 Tank 
                 Feed 
                 Filtrate  
                 Evap. 
                 Cake 
                 Liquor 
               
               
                   
               
             
          
           
               
                 Solids 
                 tph 
                 149.9 
                 138.9 
                 138.9 
                 0.0 
                 0.0 
                 38.9 
                 0.00 
               
               
                 Liquid 
                 tph 
                 0.0 
                 208.3 
                 208.3 
                 99.3 
                 231.2 
                 34.7 
                 113.52 
               
               
                 TOTAL 
                 tph 
                 149.9 
                 347.1 
                 347.1 
                 99.3 
                 231.2 
                 173.6 
                 113.52 
               
               
                   
                 m3/h 
                 100.0 
                 252.7 
                 252.7 
                 80.8 
                 204.6 
                 86.1 
                 100.5 
               
               
                   
                 % solids 
                 100.0 
                 40.0 
                 40.0 
                 0.0 
                 0.0 
                 80.0 
                 0.0 
               
               
                   
                 sp. gr. 
                 2.70 
                 1.37 
                 1.37 
                 1.23 
                 1.13 
                 2.01 
                 1.13 
               
               
                 Li 
                 gpl, % 
                 0.418 
                 0.415 
                 0.415 
                 7.00 
                 4.85 
                 0 
                 1.41 
               
               
                 Li 
                 kg/h 
                 627.1 
                 576.9 
                 576.9 
                 565 
                 1251 
                 23 
                 141 
               
               
                 K 
                 gpl, % 
                 4.794 
                 .65 
                 4.65 
                 78.4 
                 78.4 
                 1.50 
                 35.8 
               
               
                 K 
                 kg/h 
                 7176 
                 6458 
                 6458 
                 6329 
                 10300 
                 129.2 
                 3599 
               
               
                 Na 
                 kg/h 
                 2492 
                 2243 
                 2243 
                 2198 
                 5234 
                 44.9 
                 2885 
               
               
                 Temp. 
                 deg. C 
                 60 
                   
                   
                   
                   
                   
                   
               
               
                   
               
             
          
         
       
     
       FIG. 4  is a detail drawing of a continuous process  400  for concentrating the leach liquor resulting from a continuous process for leaching lithium and potassium compositions from a calcined mineral source. Leach filtrate  405  is received from a process for purifying the leach liquor resulting from a continuous process for leaching lithium and potassium compositions from a calcined mineral source. Leach filtrate  405  is passed through ion exchange column  406  to remove calcium from solution. Cleaned filtrate  420  is heated in heat exchanger  409  and passed into evaporator  413 . 
     After sufficient residence time, concentrate  412  is pumped from evaporator  413  into pregnant liquor surge tank  415  by evaporator discharge pumps  411 . Crystallization feed pumps  416  pass concentrate from pregnant liquor surge tank  415  to downstream processes. 
     The following table sets forth information about the various process streams shown on  FIG. 4 : 
     
       
         
               
               
               
             
               
               
               
               
               
               
             
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                 Stream No. 
               
             
          
           
               
                   
                   
                 405 
                 412 
                 417 
                 419 
               
             
          
           
               
                   
                   
                 Description 
               
             
          
           
               
                   
                   
                   
                   
                   
                 Evaporator 
               
               
                   
                   
                 Filtrate to 
                 Evaporator 
                 To Li  
                 water to 
               
             
          
           
               
                   
                 Evap. 
                 Product 
                 Precip 
                 cooling tower 
               
               
                   
               
             
          
           
               
                 Solids 
                 tph 
                 0.0 
                 0.20 
                 0.0 
                 0.0 
               
               
                 Liquid 
                 tph 
                 316.4 
                 130.0 
                 129.9 
                 186.3 
               
               
                 TOTAL 
                 tph 
                 316.4 
                 130.2 
                 129.9 
                 186.3 
               
               
                   
                 m 3 /h 
                 280.0 
                 104.99 
                 104.8 
                 186.3 
               
               
                   
                 % solids 
                   
                 0.15 
                 0.0 
                 0.0 
               
               
                   
                 sp. gr. 
                 1.13 
                 1.24 
                 1.2 
                 1.00 
               
               
                 Li 
                 gpl, % 
                 4.85 
                 13.5 
                 7.1 
                 0 
               
               
                 Li 
                 kg/h 
                 1251 
                 1416.7 
                 747.2 
                 0 
               
               
                 K 
                 gpl, % 
                 39.1 
                 98.1 
                 96.9 
                 0 
               
               
                 K 
                 kg/h 
                 10300 
                 10300 
                 10159 
                 0 
               
               
                 Na 
                 kg/h 
                 5234 
                 5234 
                 5170 
                 0 
               
               
                 Temp. 
                 deg. C. 
                 20 
                   
                   
                 0 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 2 
       FIG. 5  is a schematic drawing of another continuous process  500  for producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. The evaporator is fed with a pregnant leach solution produced by calcining mineral bearing ore, hectorite being one such ore. 
     The pregnant leach solution from leach purification is concentrated by evaporation  501 . Lithium carbonate is precipitated in precipitator  502  by adding sodium carbonate to the concentrated pregnant leach solution. Precipitator  502  produces lithium carbonate crystals and a lithium-barren mother liquor. The lithium carbonate crystals are dried in dryer  511  to form lithium carbonate product. Optionally, some or all of the lithium carbonate crystals may be introduced into reactor  512  as a first step in converting them to lithium hydroxide. 
     The mother liquor is acidified in acidification process  503  and conveyed to precipitator  504 , where glaserite crystals are precipitated at 95° C., and then to precipitator  505 , where glaserite crystals are precipitated at 35° C. Separator  506  separates the precipitated glaserite from the glaserite mother liquor produced in the two precipitations. The mother liquor is subjected to another crystallization process  510  in which glauber salt is precipitated. The mother liquor from this process is recycled to evaporator  501 . 
     The glaserite obtained in crystallizations  504  and  505  is decomposed in process  507 . This is followed by another crystallization  508  in which potassium sulfate crystals are deposited. These are treated in dryer  509  to form potassium sulfate product. The mother liquor from crystallization  508  is recycled to crystallizer  505 . 
     When a lithium hydroxide product is desired, as noted, lithium carbonate crystals from precipitation  502  are introduced into reactor  512 , where they are acidified and solubilized by treatment with the acidic anolyte from the membrane electrolyzer  513 . The solution from reactor  512  is introduced into the membrane electrolyzer  513 . The catholyte (neg.) is rich in lithium hydroxide. It is concentrated in evaporator  514 , cooled and crystallized in process  515 , separated from its mother liquor in centrifuge  516 , and dried in dryer  517  to a lithium hydroxide product. 
     The mother liquor from centrifuge  516  is party recycled to evaporator  514  and partly carbonated with carbon dioxide from reactor  512  in carbonation process  518 . This forms soluble lithium bicarbonate. Impurities are filtered out in filter  519 , leaving solid lithium carbonate and an alkali carbonate recycle stream for insertion at the lithium carbonate precipitator  502 . The solid lithium carbonate can be recycled back to reactor  512  for a further pass through the conversion circuit. 
     EXAMPLE 3 
       FIG. 6  is a schematic drawing of a continuous process  600  for producing, lithium hydroxide from lithium carbonate and potassium sulfate from a mineral source of potassium compositions. The evaporator  601  is fed with a pregnant leach solution produced by calcining mineral bearing ore, hectorite being one such ore. 
     The pregnant leach solution from leach purification is purified in ion-exchange unit  620  before being concentrated by evaporator  601 . The concentrate is conveyed to precipitator  602 , where glaserite crystals are precipitated at 95° C., and then to precipitator  603 , where glaserite crystals are precipitated at 45° C. Separator  604  separates the precipitated glaserite from the glaserite mother liquor produced in the two precipitations. This is followed by a third glaserite crystallization  605  at 35° C., and the glaserite is separated from the glaserite mother liquor by separator  606 . 
     The glaserite mother liquor is subjected to another crystallization process  610  in which glauber salt is precipitated as a product. The mother liquor from this process  610  is recycled to evaporator  601 . The glaserite obtained in crystallizations  602 ,  603  and  605  is decomposed in decomposition process  607 . This is followed by another crystallization  608  in which potassium sulfate crystals are deposited. These are treated in dryer  609  to form potassium sulfate product. The mother liquor from crystallization  608  is recycled to glaserite crystallizer  605 . 
     Lithium carbonate is introduced into reactor  612 , where they are acidified and solubilized by treatment with the acidic anolyte from the membrane electrolyzer  613 . The solution from reactor  612  is introduced into the membrane electrolyzer  613 . The catholyte (neg.) is rich in lithium hydroxide. It is concentrated in evaporator  614 , cooled and crystallized in process  615 , separated from its mother liquor in centrifuge  616 , and dried in dryer  617  to a lithium hydroxide product. 
     The mother liquor from centrifuge  616  is party recycled to evaporator  614  and partly carbonated with carbon dioxide from reactor  612  in carbonation process  618 . This forms soluble lithium bicarbonate. Impurities are filtered out in filter  619 , leaving solid lithium carbonate and an alkali carbonate recycle stream for insertion in the potassium sulfate circuit. The solid lithium carbonate can be recycled back to reactor  612  for a further pass through the conversion circuit. 
     EXAMPLE 4 
       FIG. 7  is a schematic drawing of a continuous process  700  for producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. The evaporator  701  is fed with a pregnant leach solution produced by calcining mineral bearing ore, hectorite being one such ore. 
     The pregnant leach solution from leach purification is concentrated by evaporation  701 . Lithium carbonate is precipitated in precipitator  705  by adding sodium carbonate to the concentrated pregnant leach solution. Precipitator  705  produces lithium carbonate crystals and a lithium-barren mother liquor. The lithium carbonate crystals may be dried in to form lithium carbonate product. 
     The mother liquor is acidified in acidification process  706  and conveyed to precipitator  707 , where glaserite crystals are precipitated. Separator  708  separates the precipitated glaserite from the glaserite mother liquor produced in precipitation  707 . The mother liquor is subjected to another crystallization process  712  in which glauber salt is precipitated. The mother liquor from this process is recycled to evaporator  701 . 
     The glaserite obtained in crystallization  707  is decomposed in process  709 . This is followed by another crystallization  710  in which potassium sulfate crystals are deposited. These are treated in dryer  711  to form potassium sulfate product. The mother liquor from crystallization  710  is recycled to crystallizer  707 . 
     Lithium hydroxide product is obtained by taking concentrated leach solution from evaporator  701  and processing it in membrane electrolyzer  702 . The caustic catholyte is rich in lithium hydroxide, and lithium hydroxide product is produced in recovery unit  703 . The caustic mother liquor from recovery unit  703  is rich in hydroxide compounds of lithium, potassium and sodium. These are converted to sulfates in reactor  704 , where they are reacted with the acidic anolyte from membrane electrolyzer  702 . These converted sulfates are recycled to glaserite crystallizer  707 . 
     EXAMPLE 5 
       FIG. 8  is a schematic drawing of one more continuous process  800  for producing lithium carbonate, lithium hydroxide and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization and lithium hydroxide is extracted by membrane electrolysis. 
     Ore Crushing and Storage 
     Mined ore  801  bearing convertible lithium and potassium compounds is delivered from the mine by trucks and can be fed directly to the process or stored on the runoff-mine ore pad with capacity of 30 days of production. A front-end loader is provided for alternate means of ore delivery from ore pad to the process. 
     An impact crusher  802  operating in a closed circuit with a vibrating screen reduces ore size to ˜12 mm, suitable for the downstream grinding operation. The fine ore is conveyed to a stock pile providing surge capacity between the crushing operation on 10 hours per day schedule and the downstream continuous operation. The crushed ore is advanced to the process by reclaim feeders and conveyors. The downstream plant is designed to process 5000 tons per day of the ore. 
     Calcining 
     Calcium sulfate (anhydrite) and dolomite reagents are required for the calcining process  803 . They are crushed to ˜12 mm size and stored in separate silos. In preparation for the calcining process  803 , ore  801  and the reagents are ground and well mixed to facilitate reactions. Reagents and ore  801  are metered by weigh-belt feeders to a dry ball mill, operating in a closed circuit with cyclonic separator. The components are ground to ˜150 micron and then are advanced to a pelletizer and dried in a fluid bed dryer, which is heated by a split stream of the hot off-gas from the downstream calciner. Dust generated in the ball mill and calciner circuits is collected in a baghouse filter and added to the pelletizer feed stream. 
     Calcine process  803  involves a conversion of lithium and other alkali metals contained in the ore  801  (hectorite clay) to water-soluble sulfates employing a high temperature (approximately 1000° C.) calciner. The ore  801  is mixed with dolomite and anhydrite minerals because this is necessary for the conversion process. The primary reaction is between lithium, potassium and sodium silicates present in the ore  801  and calcium sulfate (anhydrite), forming lithium, potassium and sodium sulfates and free silica (Si0 2 ). The dolomite prevents reverse reaction of alkali sulfates by bonding with free silica and forming calcium silicate. The advantage of this calcining process  803  is that the impurities in the ore  801  remain insoluble, thus simplifying downstream recovery and refining. The reported reaction kinetics are slow, thus requiring an extended (approximately 1 hour) residence time. 
     The hot calcine is cooled by ambient air in a fluidized bed cooler. To increase the thermal efficiency of the system, preheated air from the cooler is used as make-up air for the calciner  803 . To further maximize the thermal efficiency of the system, remaining calciner off-gas is used in the waste heat boiler to produce steam required in the downstream lithium and potassium recovery processes. The calcine material is stored in a bin. This provides surge capacity between the calciner  803  and water-leach unit  805 . 
     Leaching 
     The calcine material is leached with water at 95° C. for 30 minutes in leach unit  805 . Operation at this elevated temperature maximizes concentration of potassium sulfate in solution, thus reducing energy costs in the downstream evaporation process. Lithium and potassium recoveries in the leach are 92% and 90% respectively. 
     The leach slurry is advanced to an automated filter press  806 . Since the alkali sulfates are in the filtrate, the filter cake is washed and air-blown to maximize lithium and potassium recoveries and minimize the residual sulfate content of the tailings. Filtrate is stored in a holding tank, providing surge capacity between leach  805  and downstream processing. A polishing filter is provided on the filtrate stream to prevent any solid contaminant carryover. 
     Evaporation 
     The clarified filtrate from filter press  806  contains traces of calcium. This has to be removed as it would contaminate the lithium carbonate product and foul up the membrane in the electrolytic process. One means of removal is an ion exchange column located upstream of the evaporator  807 . 
     Evaporator  807  receives filtrate from filter press  806  and a recycle stream from reactor  802  bearing potassium sulfate and sodium sulfate. Evaporator  807  increases concentration of these combined streams to near-saturation. The evaporator  807  is operating at elevated temperature to maximize concentration of potassium sulfate. As an added benefit, lithium concentration is increased, thus reducing the lithium load in the recycle stream. The evaporator  807  is heated by steam generated in the waste heat boiler. Concentrated sulfate solution is collected in a pregnant liquor tank, providing surge capacity between the evaporator  807  and downstream processes. 
     Sulfate Crystallization 
     Crystallization step  808  does not prepare potassium sulfate as a marketable product. Rather it prepares glaserite, an intermediate compound. The product of the crystallization is directed to separator  809 , which separates glaserite crystals from the glaserite mother liquor. The glaserite crystals are decomposed in decomposition step  810  and the resulting product is fed to crystallizer  811 , where potassium sulfate crystals are separated from a potassium-sulfate mother liquor rich in sodium sulfate. This mother liquor is subjected to a further crystallization step  813 , which yields crystalline glauber salt (sodium sulfate deca-hydrate) and a glauber-salt mother liquor that is recycled back into the glaserite crystallizer  808 . 
     An alternative to this process for recovering potassium sulfate would involve preparation of glaserite followed by crystallization to remove sodium sulfate as glauber salt. The glaserite would then be redissolved and a potassium chloride reagent added to convert the glaserite to potassium sulfate and sodium chloride. Crystallization of sodium chloride would be required to remove sodium from the circuit. The sodium chloride could be dried and marketed as a chemical product or deicing agent. Expanded production of potassium sulfate may be accomplished by converting the glauber salt with added potassium chloride. 
     Lithium Carbonate Recovery 
     Lithium carbonate is precipitated from a portion of the glaserite mother liquor resulting from separation process  809 . This is accomplished by addition to the mother liquor of sodium carbonate, which is metered to lithium precipitation tanks  814 . Lithium carbonate formed in the process is soluble in water and more soluble in the glaserite mother liquor. Because the solubility decreases with an increase in temperature, precipitation is conducted at 95° C. Precipitated lithium carbonate is separated in filter press  815  from a lithium mother liquor containing potassium sulfate and sodium sulfate, washed with hot water and dried in dryer  816 . The lithium mother liquor is acidified in acidification process  817  and recycled to the sulfate crystallization circuit. 
     Lithium Hydroxide Recovery 
     The feed to the membrane electrolysis process  818  can be an alkali sulfate stream or a stream based on lithium carbonate product. In  FIG. 8 , feed for the electrolysis process  818  is provided from a portion of the glaserite mother liquor resulting from separation process  809 , a process stream greatly depleted of potassium and sodium but containing a high concentration of lithium. 
     The membrane electrolysis process  818  converts alkali sulfates to their respective hydroxides on the cathode side. Similarly, it converts sulfates to sulfuric acid on the anode side. The electrolytic process  818  generates very pure hydrogen and oxygen streams. Hydrogen can be used as supplemental fuel in calcining or marketed as a pure product. 
     The catholyte is fed to a caustic evaporation/crystallization process  819 . As the lithium hydroxide has significantly lower solubility than either sodium hydroxide or potassium hydroxide, it crystallizes out in the evaporation process as lithium hydroxide mono-hydrate and drops out further when the evaporator is cooled down. The lithium hydroxide is filtered and washed with a saturated aqueous solution of lithium hydroxide to remove entrained sodium and potassium. The washed product is dried and packaged under an inert atmosphere to avoid contact with carbon dioxide in air. 
     The mixed-hydroxide mother liquor from evaporator/crystallizer  819  is combined in reactor  820  with a portion of the anolyte from electrolyzer  818 , which is highly acidic. This regenerates the corresponding alkali sulfates. The reaction liquor is recycled from reactor  820  to the sulfate crystallizer circuit to maximize recovery of potassium. The remainder of the anolyte is used to acidify lithium mother liquor in acidification process  817  to avoid precipitation of lithium carbonate in the sulfate crystallization circuit. 
     Tailings Disposal 
     There are two tailings streams generated by this process. The first tailings stream is leach residue, which contains 80% solids (inert calcined clay) and 20% residual moisture, mostly water with traces of potassium and sodium sulfates. This material is conveyed to tailings stockpiles located next to mined area. The second tailings stream is glauber salt slurry, basically sodium sulfate and water. This is deposited in a lined containment pond. 
     EXAMPLE 6 
       FIG. 9  is a schematic drawing of a continuous process  900  for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. No electrolysis recovery method is used in this Example. 
     Ore Crushing and Storage 
     Mined ore bearing convertible lithium and potassium compounds is delivered from the mine by trucks and can be fed directly to the process or stored on the runoff-mine ore pad with capacity of 30 days of production. A front-end loader is provided for alternate means of ore delivery from ore pad to the process. 
     An impact crusher operating in a closed circuit with a vibrating screen reduces ore size to ˜12 mm, suitable for the downstream grinding operation. The fine ore is conveyed to a stock pile providing surge capacity between the crushing operation on 10 hours per day schedule and the downstream continuous operation. The crushed ore is advanced to the process by reclaim feeders and conveyors. The downstream plant is designed to process 5000 tons per day of the ore. 
     Calcining 
     Calcium sulfate (anhydrite) and dolomite reagents are required for the calcining process. They are crushed to ˜12 mm size and stored in separate silos. In preparation for the calcining process, the ore and the reagents are ground and well mixed to facilitate reactions. Reagents and ore are metered by weigh-belt feeders to a dry ball mill, operating in a closed circuit with cyclonic separator. The components are ground to ˜150 micron and then are advanced to a pelletizer and dried in a fluid bed dryer, which is heated by a split stream of the hot off-gas from the downstream calciner. Dust generated in the ball mill and calciner circuits is collected in a baghouse filter and added to the pelletizer feed stream. 
     The calcine process involves a conversion of lithium and other alkali metals contained in the ore (hectorite clay) to water-soluble sulfates employing a high temperature (approximately 1000° C.) calciner. The ore is mixed with dolomite and anhydrite minerals because this is necessary for the conversion process. The primary reaction is between lithium, potassium and sodium silicates present in the ore and calcium sulfate (anhydrite), forming lithium, potassium and sodium sulfates and free silica (Si0 2 ). The dolomite prevents reverse reaction of alkali sulfates by bonding with free silica and forming calcium silicate. The advantage of this calcining process is that the impurities in the ore remain insoluble, thus simplifying downstream recovery and refining. The reported reaction kinetics are slow, thus requiring an extended (approximately 1 hour) residence time. 
     The hot calcine is cooled by ambient air in a fluidized bed cooler. To increase the thermal efficiency of the system, preheated air from the cooler is used as make-up air for the calciner. To further maximize the thermal efficiency of the system, remaining calciner off-gas is used in the waste heat boiler to produce steam required in the downstream lithium and potassium recovery processes. The calcine material is stored in a bin. This provides surge capacity between the calciner and water-leach unit  902 . 
     Leaching 
     The calcine material is leached with water at 95° C. for 30 minutes in leach unit  902 . Operation at this elevated temperature maximizes concentration of potassium sulfate in solution, thus reducing energy costs in the downstream evaporation process. Lithium and potassium recoveries in the leach are 92% and 90% respectively. 
     The leach slurry is advanced to an automated filter press. Since the alkali sulfates are in the filtrate, the filter cake is washed and air-blown to maximize lithium and potassium recoveries and minimize the residual sulfate content of the tailings. Filtrate is stored in a holding tank, providing surge capacity between leach  805  and downstream processing. A polishing filter is provided on the filtrate stream to prevent any solid contaminant carryover. 
     Evaporation 
     The clarified filtrate from the leach filter press contains traces of calcium. This has to be removed as it would contaminate the lithium carbonate product and foul up the membrane in the electrolytic process. One means of removal is an ion exchange column  904  located upstream of the evaporator  906 . Another means of removal  904  is to remove the calcium by precipitation from the leach filtrate. Yet another means of removal  904  is to concentrate the filtrate by evaporation and then remove the calcium by precipitation. 
     Evaporator  906  receives filtrate from filter press and a recycle stream from separator  944  bearing potassium sulfate and sodium sulfate. Evaporator  906  increases concentration of these combined streams to near-saturation. The evaporator  906  is operating at elevated temperature to maximize concentration of potassium sulfate. As an added benefit, lithium concentration is increased, thus reducing the lithium load in the recycle stream. The evaporator  906  is heated by steam generated in the waste heat boiler. Concentrated sulfate solution is collected in a pregnant liquor tank, providing surge capacity between the evaporator  906  and downstream processes. 
     Sulfate Crystallization 
     Crystallization step  908  does not prepare potassium sulfate as a marketable product. Rather it prepares glaserite, an intermediate compound. The product of the crystallization is directed to separator  910 , which separates glaserite crystals from the glaserite mother liquor. The glaserite crystals are decomposed in decomposition step  914  and the resulting product is fed to crystallizer  918 , where potassium sulfate crystals are separated from a potassium-sulfate mother liquor rich in potassium sulfate and sodium sulfate. This mother liquor recycled back into evaporator  906 . 
     An alternative to this process for recovering potassium sulfate would involve preparation of glaserite followed by crystallization to remove sodium sulfate as glauber salt. The glaserite would then be redissolved and a potassium chloride reagent added to convert the glaserite to potassium sulfate and sodium chloride. Crystallization of sodium chloride would be required to remove sodium from the circuit. The sodium chloride could be dried and marketed as a chemical product or deicing agent. Expanded production of potassium sulfate may be accomplished by converting the glauber salt with added potassium chloride. 
     Lithium Carbonate Recovery 
     Lithium carbonate is precipitated from the glaserite mother liquor resulting from separation process  910 . This is accomplished by addition to the mother liquor of sodium carbonate, which is metered to lithium precipitation tanks  930 . Lithium carbonate formed in the process is soluble in water and more soluble in the glaserite mother liquor. Because the solubility decreases with an increase in temperature, precipitation  930  is conducted at 95° C. Precipitated lithium carbonate is separated in filter press  932  from a lithium mother liquor containing potassium sulfate and sodium sulfate, washed with hot water and dried in dryer  936 . 
     Glauber Salt Recovery 
     The lithium mother liquor from filter press  932  is acidified in acidification process  938  and directed to crystallization process  942 , where glauber salt is precipitated in crystalline form. The glauber salt is separated from the glauber-salt mother liquor in separator  944 , which is recycled to evaporator  906 . The glauber salt is purified in purification process  948 . 
     Tailings Disposal 
     There are two tailings streams generated by this process. The first tailings stream is leach residue, which contains 80% solids (inert calcined clay) and 20% residual moisture, mostly water with traces of potassium and sodium sulfates. This material is conveyed to tailings stockpiles located next to mined area. The second tailings stream is glauber salt slurry, basically sodium sulfate and water. This is deposited in a lined containment pond. 
       FIG. 10  is a detail drawing of a continuous process  1000  for extracting lithium carbonate by crystallization from the concentrated leach liquor of a continuous process for leaching lithium and potassium compositions from a calcined mineral source. Soda ash  1001  is deposited in soda ash hopper  1006 . Weigh belt feeder  1007  meters soda ash  1001  into lithium precipitation tanks  1008 - 1010 , which are filled with lithium feed  1002 . 
     When precipitation is complete, lithium precipitation liquor  1011  is passed from lithium precipitation tank  1010  to lithium precipitation surge tank  1012 , which is agitated. Lithium filter feed  1013  is taken from lithium precipitation surge tank  1012  and passed into filter  1015 . The filtration process results in a lithium wash recycle  1016 , a filter leachate  1017  and a lithium product  1018 . The filter leachate  1017  is conveyed into a sulfate solution surge tank  1033 , and from there is pumped to downstream processes. 
     Lithium product  1018  is deposited on screw conveyor  1019  and dropped into dryer  1020 . Drying results in the production of lithium product and lithium fines  1027 . The fines are collected in baghouse filter  1032 . The very smallest fines  1030  are not collected and are conveyed for disposal to stack  1029  by ID fan  1031 . The collected fines  1026  are dropped on conveyor  1028  and then on bucket conveyor  1022 , which drops the fines  1026  into product bin  1024 . 
     The lithium product from dryer  1020  is passed through hammer mill  1021 . The milled lithium product is dropped onto bucket conveyor  1022 , which drops the lithium product in turn into product bin  1024  along with fines  1026 . Product bin  1024  feeds a drumming station  1025 , where lithium product is loaded for distribution. 
     The following table sets forth information about the various process streams shown on  FIG. 10 : 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                 Stream No. 
               
             
          
           
               
                   
                 1002 
                 1037 
                 1011 
                 1013 
                 1003 
                 1017 
                 1018 
                 1023 
                 1035 
               
             
          
           
               
                   
                 Description 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Sulfate 
               
               
                   
                   
                   
                 Li 
                   
                 Hot 
                   
                   
                 Li 
                 SoIn to 
               
               
                   
                 Filter 
                 Soda 
                 Precip 
                 Filter 
                 water 
                 Filter 
                   
                 Product 
                 Crystaliz- 
               
               
                   
                 Leachate 
                 Ash 
                 Liquor 
                 Feed 
                 Wash 
                 Leachate 
                 Li Product 
                 to Bin 
                 ation 
               
               
                   
               
             
          
           
               
                 Solids 
                 tph 
                 0 
                 3.42 
                 2.90 
                 2.90 
                 0 
                 0.00 
                 2.90 
                 2.90 
                 0.00 
               
               
                 Liquid 
                 tph 
                 129.9 
                 0 
                 130.5 
                 130.45 
                 17.53 
                 129 
                 1 
                 0.73 
                 129 
               
               
                 TOTAL 
                 tph 
                 129.9 
                 3.42 
                 133.4 
                 133.36 
                 17.53 
                 129 
                 3.63 
                 3.63 
                 129 
               
               
                   
                 m 3 /h 
                 104.8 
                   
                   
                   
                 17.53 
                   
                   
                   
                   
               
               
                   
                 % solids 
                 0 
                 100 
                 2.18 
                 2.18 
                 0 
                 0 
                 79.9 
                 79.9 
                 0 
               
               
                   
                 sp. gr 
                 1.24 
                   
                   
                   
                 1.0 
                   
                   
                   
                   
               
               
                 Li 
                 gpl, % 
                 7.13 
                 0 
                   
                   
                 0 
                   
                   
                   
                   
               
               
                 Li 
                 kg/h 
                 747 
                 0 
                 747 
                 747 
                 0 
                 162 
                 545.4 
                 545.4 
                 162 
               
               
                 K 
                 gpl, % 
                 96.9 
                 0 
                   
                   
                 0 
                   
                 0 
                 0 
                   
               
               
                 K 
                 kg/h 
                 10159 
                 0 
                 10159 
                 10159 
                 0 
                 9786 
                 0 
                 0 
                 9788 
               
               
                 Na 
                 kg/h 
                 5170 
                 0 
                 7044 
                 7044 
                 0 
                 5892 
                 0 
                 0 
                 5862 
               
               
                 Temp. 
                 deg. C. 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                   
               
             
          
         
       
     
     EXAMPLE 7 
       FIG. 11  is a schematic drawing of a continuous process  1100  for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. No electrolysis recovery method is used in this Example. The evaporator  1101  is fed with a pregnant leach solution produced by calcining mineral bearing ore, hectorite being one such ore. 
     The pregnant leach solution from leach purification is concentrated by evaporation  1101 . Lithium carbonate is precipitated in precipitator  1102  by adding sodium carbonate to the concentrated pregnant leach solution. Precipitator  1102  produces lithium carbonate crystals and a lithium-barren mother liquor. The lithium carbonate crystals are dried to form lithium carbonate product. 
     The mother liquor is acidified in acidification process  1103  and conveyed to precipitator  1104 , where glaserite crystals are precipitated at 95° C., and then to precipitator  1105 , where glaserite crystals are precipitated at 35° C. Separator  1106  separates the precipitated glaserite from the glaserite mother liquor produced in the two precipitations. The mother liquor is subjected to another crystallization process  1110  in which glauber salt is precipitated. The mother liquor from this process is recycled to evaporator  1101 . 
     The glaserite obtained in crystallizations  1104  and  1105  is decomposed in process  1107 . This is followed by another crystallization  1108  in which potassium sulfate crystals are deposited. These are treated in dryer  1109  to form potassium sulfate product. The mother liquor from crystallization  1108  is recycled to evaporator  1101 . 
     EXAMPLE 8 
       FIG. 12  is a schematic drawing of another continuous process  1200  for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. No electrolysis recovery method is used in this Example. The evaporator  1201  is fed with a pregnant leach solution produced by calcining mineral bearing ore, hectorite being one such ore. 
     The pregnant leach solution from leach purification is concentrated by evaporation  1201  and conveyed to precipitator  1202 , where glaserite crystals are precipitated at 95° C., and then to precipitator  1203 , where glaserite crystals are precipitated at 35° C. Separator  1204  separates the precipitated glaserite from the glaserite mother liquor produced in the two precipitations. The glaserite obtained in crystallizations  1202  and  1203  is decomposed in process  1205 . This is followed by another crystallization in precipitator  1206  in which potassium sulfate crystals are deposited. These are treated in dryer  1207  to form potassium sulfate product. The mother liquor from precipitator  1206  is recycled to precipitator  1202 . 
     The mother liquor from separator  1204  is subjected to another crystallization in precipitator  1208  in which lithium carbonate is precipitated in by adding sodium carbonate to the mother liquor. Precipitator  1208  produces lithium carbonate crystals and a lithium-barren mother liquor, which is acidified in acidification process  1209  and then treated in precipitator  1210  to precipitate glauber salt. The mother liquor from precipitator  1210  is recycled to precipitator  1202 . 
     EXAMPLE 9 
       FIG. 13  is a schematic drawing of yet another continuous process  1300  for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. No electrolysis recovery method is used in this Example. This drawing may be understood by reference to discussions of related processes in prior Examples, which use analogous process steps to arrive at the process as a whole. 
     EXAMPLE 10 
       FIG. 14  is a schematic drawing of a further continuous process  1400  for producing lithium carbonate and potassium sulfate from a mineral source of lithium and potassium compositions in which lithium carbonate is extracted by crystallization. No electrolysis recovery method is used in this Example. This drawing may be understood by reference to discussions of related processes in prior Examples, which use analogous process steps to arrive at the process as a whole.