Magnesium removal process

Abstract

A method for removing alkaline earth metals from a filtrate comprises a first crystallization step and a second crystallization step wherein the first crystallization step is a forced circulation crystallizer and wherein the second crystallization step is a draft tube crystallizer. Also included is a method for reducing magnesium in a chemical liquid, comprising crystallizing magnesium into magnesium sulfate hydrate in a first crystallization step, and precipitating magnesium by adding a caustic material in a chemical precipitation step.

Description

Technical Field

[0001] The present disclosure relates to the removal of alkali and alkaline earth metals from chemical processes. More particularly, the present disclosure relates to magnesium sulfate via crystallization. Background Art

[0002] Typical processes for purifying lithium typically require removing other impurities, such as magnesium, from the ore. Magnesium removal is generally necessary because, under normal circumstances, magnesium is significantly more abundant than lithium in various ores (up to about 20 times more abundant). Currently, chemical precipitation using quicklime or another caustic material is the preferred method, which has high operating costs. After mixing with quicklime, the slurry must be filtered to remove solids from the liquid. In the case of pure chemical precipitation, a large amount of filter cake is produced and is essentially waste that must be stored. Any brine contained in the filter cake can be recovered because it contains dissolved lithium. A typical approach is to try to "wash" the filter cake in a filter press; however, this is difficult, time-consuming, and may not be very effective using such materials. Typical crystallization methods may result in the formation of undesirable lithium-containing salts and product losses. Summary of the Invention

[0003] A method for removing alkaline earth metals from a filtrate is disclosed, comprising a first crystallization step and a second crystallization step, wherein the first crystallization step is a forced circulation crystallizer, and wherein the second crystallization step is a draft tube crystallizer.

[0004] Also disclosed is a method for reducing magnesium in a chemical liquor, comprising crystallizing magnesium as magnesium sulfate hydrate in a first crystallization step, and precipitating the magnesium by adding a caustic material in a chemical precipitation step.

[0005] Also disclosed is a method for reducing alkaline earth metals in solids, comprising acid leaching the solids to form an effluent slurry, neutralizing the effluent slurry to form a neutralized filtrate, concentrating the neutralized filtrate by heating a falling film evaporator with mechanical vapor recompression, crystallizing impurities in the neutralized filtrate in a first crystallization step in a forced circulation crystallization step, crystallizing impurities in the neutralized filtrate in a second crystallization step in a first draft tube crystallization step, crystallizing impurities in the neutralized filtrate in a third crystallization step in a second draft tube crystallization step, and precipitating remaining impurities by adding a caustic material.

[0006] The various embodiments described in the present disclosure may include additional systems, methods, features, and advantages that are not necessarily explicitly disclosed herein but will be apparent to one of ordinary skill in the art upon examination of the following detailed description and accompanying drawings. It is intended that all such systems, methods, features, and advantages be included within this disclosure and be protected by the following claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The features and components of the following drawings are shown to emphasize the general principles of the present disclosure. For consistency and clarity, corresponding features and components throughout the drawings may be designated by matching reference numeral characters.

[0008] Figure 1 It is a process of sequential crystallization steps.

[0009] Figure 2 It is a process in which a crystallization step precedes a precipitation step.

[0010] Figure 3 It is a process used to remove magnesium from lithium solids.

[0011] Figure 4a is a phase boundary diagram of magnesium, lithium and potassium sulfates at 75°C.

[0012] Figure 4b is a phase boundary diagram of magnesium, lithium and potassium sulfates at 50 °C.

[0013] Figure 4c is a phase boundary diagram of magnesium, lithium and potassium sulfates at 35 °C.

[0014] Figure 4d is the phase boundary diagram of magnesium, lithium and potassium sulfates at 25 °C.

[0015] Figure 4e is the phase boundary diagram of magnesium, lithium and potassium sulfate at 0 °C. DETAILED DESCRIPTION

[0016] A method for removing alkaline earth metals from a filtrate or solid, as well as related methods, systems, devices, and various apparatuses, is disclosed. The method includes the step of crystallizing the alkaline earth metals from the filtrate to better produce alkali metals, particularly lithium. The crystallization of magnesium occurs in the form of magnesium sulfate hydrates. These magnesium sulfate hydrates are advantageous due to their large crystal size and efficient washing. In addition, the crystallization of magnesium removes water from the process, which then does not have to be removed by evaporation later in the process. This water removal also concentrates the product in preparation for further processing, such as lithium carbonate production. Furthermore, because the concentration of magnesium in the remaining brine is known, as shown in Figures 4a, 4b, 4c, 4d, and 4e, it is easier to predict the amount of caustic material required to precipitate the remainder.

[0017] In the case of pure chemical precipitation without crystallization, a large amount of filter cake is produced and is a waste product. The brine must be removed from the filter cake by washing the filter cake and then discarded. The waste stream in each step can be recycled to wash in the countercurrent decantation (CCD) step and the filtration step to ensure that as little brine as possible remains in the filter cake. By crystallizing the impurities before precipitation, the amount of filter cake containing magnesium hydroxide is less, and the filter cake produced can be recycled in the neutralization step. In addition, the reagent consumption for precipitation is also reduced. After the magnesium precipitation, a second precipitation step of calcium can be added. The filtrate from the magnesium precipitation step can be mixed with a 25% by weight soda ash (Na2CO3) solution to precipitate calcium carbonate (CaCO3). Flocculants and coagulants can be added to promote solid sedimentation and removal. As an example, ferric sulfate can be added as a coagulant.

[0018] Those skilled in the art will appreciate that the disclosed methods have been described in only a few of many exemplary aspects.No specific term or description should be taken as limiting the scope of the disclosure or any claims derived therefrom.

[0019] exist Figure 1 One aspect of removing alkaline earth metals from filtrates is disclosed and described in.

[0020] Figure 1 Process 100 is shown with an influent stream of chemical filtrate 110. Chemical filtrate 110 can contain various desirable cations, such as alkali metal cations, particularly lithium, as well as various undesirable cations or impurities, such as calcium, magnesium, or potassium. In some aspects, magnesium can be present in an abundance up to 20 times greater than the desired lithium cation. Chemical filtrate 110 can comprise a sulfate solution. Chemical filtrate 110 can flow to a first crystallization step 120.

[0021] The first crystallization step 120 may include a forced circulation crystallizer 125. The forced circulation crystallizer 125 may operate in a temperature range of 75°C to 55°C, more specifically about 65°C. In the present aspect, "about" the temperature value is defined as a range of ±5°C. The forced circulation crystallizer 125 may be a mechanical vapor recompression ("MVR") heated forced circulation crystallizer operated under vacuum via a vacuum pump or by other vacuum control methods (including but not limited to an ejector / condenser set). The first crystallization step 120 may include a waste stream 130 and a filtrate stream 140 leaving the first crystallization step 120.

[0022] A forced circulation crystallizer can be a type of evaporative crystallizer implemented. The forced circulation crystallizer consists of a crystal chamber, a circulation pipe, a circulation pump and a heat exchanger. The crystallization chamber can discharge the slurry from the bottom, and the circular axial flow circulation pump heats it again into the crystallization chamber through a heat exchanger. The forced circulation crystallizer can be a mixed suspension, mixed discharge (MSMPR) crystallizer for continuous operation. The MSMPR crystallizer can also be a draft tube crystallizer or a draft tube baffle crystallizer. The draft tube crystallizer can include various elements, such as a crystallizer container, an impeller pump (to provide circulation along the draft tube), a circulation pump (to provide external circulation) and a heat exchanger (to provide heat energy for the required crystallization rate). The draft tube crystallizer can also include a baffle to become a draft tube baffle crystallizer, wherein the baffle controls the crystal group by separating fine crystals from coarse crystals.

[0023] Waste stream 130 may contain crystallized impurities such as MgSO4, CaSO4, K2SO4 or hydrates and mixtures thereof in the form of a slurry. The crystals in waste stream 130 may then be dehydrated and washed to produce a liquid which is then sent to the next crystallization step 150.

[0024] The filtrate stream 140 may contain a lower amount of impurities than the influent filtrate stream 110. The filtrate stream 140 may then flow to a second crystallization step 150. The second crystallization step 150 may include a first draft tube crystallizer 155. The second crystallization step 150 may operate at a temperature in the range of 30°C to 50°C, more specifically approximately 40°C. In the present aspect, "approximately" for the temperature values is defined as a range of ±5°C. Water vapor and non-condensable gases may be removed from the second crystallization step 150 via an ejector / barometric condenser system cooled by cooling tower water. The ejector condenser system may be a combination of an ejector to remove air and water vapor to maintain a constant pressure and a condenser to condense the spent steam. Vacuum control may also be achieved through other methods, including but not limited to a vacuum pump. The cooling tower water temperature may control the operating temperature of the second crystallization step 150. The second crystallization step 150 may include a waste stream 160 and a filtrate stream 170 exiting the second crystallization step 150.

[0025] Waste stream 160 may contain crystallized impurities such as MgSO4, CaSO4, K2SO4 or hydrates and mixtures thereof in the form of a slurry. The crystals in waste stream 160 may then be dehydrated and washed to produce a liquid which is then sent to the next crystallization step 180.

[0026] Filtrate stream 170 may contain a lower amount of impurities than filtrate streams 140 and 110. Filtrate stream 170 may then flow to a third crystallization step 180. Third crystallization step 180 may include a second draft tube crystallizer 185. Third crystallization step 180 may operate at a temperature range of 1°C to 20°C, more specifically approximately 10°C. In the present aspect, "approximately" for temperature values is defined as a range of ±5°C. Water vapor and non-condensable gases may be removed from third crystallization step 180 via an indirect condenser / ejector assembly cooled by cooling water. In some aspects, the cooling water may alternatively be ethylene glycol, propylene glycol, a water mixture with a glycol, or other suitable cooling liquid. The cooling water temperature may control the operating temperature of third crystallization step 180. Third crystallization step 180 may include a waste stream 190 and an effluent stream 200 exiting third crystallization step 180. The crystals in waste stream 190 may also be dehydrated and washed to produce a liquid, which is then recycled to the previous crystallization step.

[0027] Figure 2 Process 300 is shown with an influent stream of chemical liquid 310, at least a first crystallization step 320, and at least a precipitation step 380. Chemical liquid 310 may contain various desirable cations, such as alkali metal cations, particularly lithium, as well as various undesirable cations or impurities, such as calcium, magnesium, or potassium. In some cases, magnesium is up to 20 times more abundant than desirable lithium cations. Chemical liquid 310 may comprise a sulfate solution.

[0028] The chemical liquid 310 may first flow into the first crystallization step 320. The first crystallization step 320 may be an evaporative crystallization process. The evaporative crystallization may be an MVR heated forced circulation crystallizer operated under vacuum via a vacuum pump or by other vacuum control methods (including but not limited to an ejector / condenser group). The first crystallization step 320 may operate at a temperature range of 55°C to 35°C, more specifically approximately 40°C. In the present aspect, "approximately" for the temperature value is defined as a range of ±5°C. The first crystallization step 320 may include a waste stream 330 and a liquid stream 340 leaving the first crystallization step 320.

[0029] Waste stream 330 may contain crystallized impurities such as MgSO4, CaSO4, K2SO4 or hydrates and mixtures thereof in the form of a slurry. The crystals in waste stream 330 may then be dehydrated and washed to produce a liquid which is then sent to the next crystallization step 350.

[0030] Liquid stream 340 may contain a lower amount of impurities than the influent chemical liquid 310. Liquid stream 340 may then flow to a second crystallization step 350. Second crystallization step 350 may be a cooling crystallization process performed using a draft tube crystallizer. Second crystallization step 350 may operate at a temperature range of 15°C to 1°C, more specifically approximately 10°C. In the present aspect, "approximately" for temperature values is defined as a range of ±5°C. During cooling crystallization, no LiKSO4 is formed. Over 50% of the magnesium and over 20% of the potassium may be removed during the cooling crystallization step. During evaporative crystallization and cooling crystallization, magnesium crystallizes as MgSO4·6H2O, MgSO4·7H2O, other hydrates, or combinations thereof, depending on the temperature. During evaporative crystallization and cooling crystallization, potassium may also crystallize as potassium sulfate, potassium sulfate hydrate, magnesium potassium sulfate, magnesium potassium sulfate hydrate, magnesium potassium double salt, or combinations thereof. Second crystallization step 350 may include a waste stream 360 and a liquid stream 370 exiting the first crystallization step 350.

[0031] Waste stream 360 may contain crystallized impurities such as MgSO 4 , CaSO 4 , K 2 SO 4 or hydrates and mixtures thereof in the form of a slurry. The crystals in waste stream 360 may then be dehydrated and washed to produce a liquid which is then sent to precipitation step 380 .

[0032] The liquid stream 370 may contain a smaller amount of impurities than the liquid stream 340. The liquid stream 370 may then flow to a chemical precipitation step 380. The chemical precipitation step 380 may include mixing the liquid stream 370 with a caustic material (such as a 25% by weight slurry of milk of lime) to adjust the pH to approximately 11, thereby precipitating magnesium as magnesium hydroxide. In the present aspect, "approximately" for pH is defined as a range of ±0.5. Calcium may also be co-precipitated during the chemical precipitation step 380. Depending on the temperature, calcium may be co-precipitated as calcium sulfate or its calcium sulfate hydrate. Magnesium may be precipitated to approximately 5 ppm in a single stirred tank with a retention time of 1 hour. Calcium may be maintained at a saturation level. The chemical precipitation step 380 may include a waste stream 390 and an effluent stream 395 that exit the chemical precipitation step.

[0033] Table 1: Two-step crystallization and precipitation data

[0034]

[0035] Table 1 is from Figure 2Exemplary data of the bench test of the method in Figure 2, including the first crystallization stage (see evaporation precipitation %), the second crystallization stage (see cooling precipitation %). All tests except the fifth and seventh tests include a first evaporation crystallization stage at 45°C and a second cooling crystallization stage at 5°C. The fifth test is actually two tests and is an adiabatic process and includes a first evaporation crystallization stage at 45°C and a second cooling crystallization stage at 25°C or 5°C. The seventh test includes a first evaporation crystallization stage at 35°C and a second cooling crystallization stage at 5°C.

[0036] The first through fourth, sixth, and seventh tests targeted specific concentrations of lithium in the solution after evaporation, measured in parts per million (ppm). Test parameters included temperature, lithium concentration, pH, and K:Li ratio. As shown in Table 1, all tests resulted in essentially no lithium precipitation during evaporative crystallization. The Table 1 tests also showed high magnesium (over 50%) and potassium (over 20%) removal during cooling crystallization. Under these parameters, there was also essentially no formation of lithium-containing salts during cooling crystallization.

[0037] Figure 3 A process 400 is illustrated, comprising a solids influent stream 410, an acid leaching step 420, a neutralization step 450, a concentration step 470, a first crystallization step 490, a second crystallization step 520, a third crystallization step 550, and a precipitation step 580. These solids 410 may be clay, limestone, ore, or other lithium-containing materials. These solids 410 may also contain a number of undesirable impurities, such as potassium, magnesium, sodium, iron, boron, aluminum, or calcium. Solids 410 are first acid-leached in the acid leaching step 420. Due to this non-selective acid leaching, undesirable impurities may be leached into solution along with the lithium. The leaching temperature of 75-90°C can be managed by heat generated by the dilution of sulfuric acid and the acid-solids reaction. In some aspects, continuous leaching can be performed in three stirred tanks in series, with a leaching time of one hour per stirred tank. The acid addition may be 490 kg of 100% H2SO4 per ton of leach feed solids. An effluent slurry 430 is produced by the acid leaching step 420 with the addition of acid 425 (eg, H 2 SO 4 ).

[0038] The effluent slurry 430 is then neutralized in a neutralization step 450 to form a neutralized stream. A magnesium hydroxide stream 590 recycled from a downstream precipitation step 580 may be used to neutralize the slurry 430 to a pH of approximately 6.5. In the present aspect, "approximately" for pH is defined as a range of ±0.5.

[0039] In some aspects, a two-step neutralization is performed in stirred tanks, one for each step, with a retention time of 1.5 hours in the first tank and 1 hour in the second tank. In the first step, a 30-40% by weight slurry of limestone powder can be combined with an acidic slurry to increase the pH of the acidic slurry to a target pH, preferably less than or equal to 4. The first step neutralization can neutralize most of the residual acid from the acid leaching and precipitate most of the iron and aluminum. A magnesium hydroxide stream 590 recycled from the downstream precipitation step 580 can be used to neutralize the effluent slurry 430 to a pH of approximately 6.5. A stream 435 of limestone can be added to the magnesium hydroxide stream 590 to form a neutralized stream 440.

[0040] The neutralized stream can be subjected to solid / liquid separation, such as, but not limited to, filter pressing, to produce a neutralized filtrate 460 liquid stream and a solids-containing stream (not shown). The solids can be transported to a storage facility. Prior to solid / liquid separation, the slurry can undergo a brine recovery step, such as, but not limited to, countercurrent decantation washing. In another aspect of brine recovery, the slurry in the solid / liquid separator (e.g., a filter press) can be washed with another liquid (e.g., raw water or condensate) to displace the brine with the washing liquid and facilitate recovery of lithium from the brine solution.

[0041] Prior to crystallization, the neutralized filtrate 460 can be concentrated in a concentration step 470 using an MVR heated falling film evaporator. The MVR heated falling film evaporator can concentrate the filtrate by heating the filtrate as it flows down the walls of the tubular heat exchanger within it, where the filtrate forms a film along the tube walls. Concentration can be performed by evaporation. The lithium concentration can be maintained below the target concentration leaving the evaporator to avoid crystallization of lithium-potassium double salts. In this step, a seed crystal recirculation system can be used to minimize the amount of scaling, such as caused by gypsum precipitation. Other risks of the concentration step can include, for example, crusting caused by picromerite or leonite. The risk of scaling or crusting varies depending on the impurities and solid types used in the process. The concentration step 470 can be performed at a temperature between 95°C and 105°C. After the concentration step, the concentrated neutralized filtrate 480 can flow to the first crystallization step 490.

[0042] The first crystallization step 490 may include a forced circulation crystallizer 495. The forced circulation crystallizer 495 may operate in a temperature range of 75°C to 55°C, more specifically at about 65°C. In the present aspect, "approximately" for temperature values is defined as a range of ±5°C. The forced circulation crystallizer 495 may be an MVR heated forced circulation crystallizer operated under vacuum via a vacuum pump or by other vacuum control methods (including but not limited to an ejector / condenser group). The first crystallization step 490 may also include separating the filtrate from the solid by a centrifuge. The first crystallization step 490 may include a waste stream 500 and a filtrate stream 510 leaving the first crystallization step 490.

[0043] Waste stream 500 may contain crystallized impurities such as MgSO4, CaSO4, K2SO4, hydrates, or mixtures thereof in the form of a slurry. The crystals in waste stream 500 may then be dehydrated and washed to produce a liquid that may then be sent to the next crystallization step 520 or recycled to the concentration step 470.

[0044] The filtrate stream 510 may contain a lower amount of impurities than the influent stream of solids 410. The filtrate stream 510 may then flow to a second crystallization step 520. The second crystallization step 520 may comprise a first draft tube crystallizer 525. The second crystallization step 520 may operate in a temperature range of 30°C to 50°C, more specifically at approximately 40°C. In the present aspect, "approximately" for temperature values is defined as a range of ±5°C. Water vapor and non-condensable gases may be removed from the second crystallization step 520 by an ejector / barometric condenser set cooled by cooling tower water. The cooling tower water temperature may control the operating temperature of the second crystallization step 520. The second crystallization step 520 may also include separating the filtrate from the solids by a centrifuge. The second crystallization step 520 may include a waste stream 530 and a filtrate stream 540 exiting the second crystallization step 520.

[0045] Waste stream 530 may contain crystallized impurities such as MgSO4, CaSO4, K2SO4, hydrates, or mixtures thereof in the form of a slurry. The crystals in waste stream 530 may then be dehydrated and washed to produce a liquid that is then sent to the next crystallization step 550 or recycled to the concentration step 470.

[0046] Filtrate stream 540 may contain a lower amount of impurities than filtrate stream 510 or solids 410. Filtrate stream 540 may then flow to a third crystallization step 550. Third crystallization step 550 may include a second draft tube crystallizer 555. Third crystallization step 550 may operate at a temperature range of 1°C to 20°C, more specifically approximately 10°C. In the present aspect, "approximately" for temperature values is defined as a range of ±5°C. Water vapor and non-condensable gases may be removed from third crystallization step 550 via an indirect condenser / ejector system cooled by cooling water. The cooling water may also include a glycol mixture, such as ethylene glycol, propylene glycol, a mixture of water and glycol, or other suitable cooling liquid. The cooling water temperature may control the operating temperature of third crystallization step 550. Third crystallization step 550 may also include separating the filtrate from the solids by centrifuge. Third crystallization step 550 may include a waste stream 560 and an effluent stream 570 exiting third crystallization step 550. The crystals in waste stream 560 may then be dewatered and washed to produce a liquid that is then sent to the next chemical precipitation step 580 or recycled to the concentration step 470 .

[0047] The filtrate stream 570 can then flow to a chemical precipitation step 580. The chemical precipitation step 580 can include mixing the filtrate stream 570 with a caustic material stream 575 (such as a 25% by weight slurry of milk of lime) to adjust the pH to about 11, thereby precipitating magnesium as magnesium hydroxide while removing a corresponding amount of sulfate as co-precipitated calcium sulfate or its hydrate. In the present aspect, "about" for pH is defined as a range of ±0.5. Magnesium can be precipitated to about 5 ppm in a single stirred tank with a retention time of 1 hour. Calcium can be maintained at a gypsum saturation level. The slurry can undergo solid / liquid separation to produce a magnesium hydroxide stream 590, which can be a stream of solids that can be recycled from the downstream precipitation step to the neutralization step 450. The effluent solution 600 can contain significantly less magnesium and potassium than the incoming solids 410 while maintaining a lithium recovery rate of over 90%.

[0048] Figure 3 The process shown can result in over 90% recovery of the lithium from the solids, over 80% removal of the magnesium as magnesium sulfate, and over 30% removal of the potassium as potassium sulfate.

[0049] like Figure 1 、 Figure 2 and Figure 3 The process shown can include more crystallization steps to optimize process costs and obtain higher lithium recovery.

[0050] Figures 4a, 4b, 4c, 4d, and 4e are ternary phase diagrams for lithium sulfate, potassium sulfate, and magnesium sulfate at various temperatures. Specifically, the ternary phase diagrams are for neat salts in water. Actual diagrams for these salts in filtrates, brines, or other solutions with more impurities may vary. Specifically, these diagrams show the ratios at which sulfate solutions of these salts crystallize. Minor impurities, such as sodium, iron, or aluminum, may be present in the claimed process and affect the data.

[0051] In one exemplary aspect, a method for reducing alkaline earth metals in a chemical filtrate may include crystallizing alkaline earth cations in the chemical filtrate in a first crystallization step and crystallizing alkaline earth cations in the chemical filtrate in a second crystallization step. The first crystallization step may be performed in a forced circulation crystallizer, and the second crystallization step may be performed in a first draft tube crystallizer.

[0052] In a further exemplary aspect, the method for reducing alkaline earth metals in a chemical filtrate may further include crystallizing impurities in a third crystallization step. The third crystallization step may be performed in a second draft tube crystallizer. In a further exemplary aspect, the second crystallization step may be operated at a temperature range of 30°C to 50°C, and the third crystallization step may be operated at a temperature of 1°C to 20°C. In a further exemplary aspect, the second crystallization step may be operated at a temperature of approximately 40°C, and the third crystallization step may be operated at a temperature of approximately 10°C. In a further exemplary aspect, the first crystallization step may be operated at a temperature of approximately 65°C.

[0053] In another exemplary aspect, a method for reducing magnesium in a chemical liquor may include crystallizing magnesium as magnesium sulfate hydrate in a first crystallization step, and precipitating the magnesium by adding a caustic material in a chemical precipitation step.

[0054] In a further exemplary aspect, the method for reducing magnesium in a chemical liquid may further include crystallizing magnesium into magnesium sulfate hydrate in a second crystallization step, removing magnesium sulfate hydrate from the first and second crystallization steps, and precipitating magnesium into magnesium hydroxide in a chemical precipitation step by adding lime milk to adjust the pH of the chemical liquid to 10.5 to 11.5. In a further exemplary aspect, the first crystallization step may further include crystallizing potassium into potassium sulfate, potassium sulfate hydrate, magnesium potassium sulfate, magnesium potassium sulfate hydrate, magnesium potassium double salt, or a combination thereof, and the second crystallization step may further include crystallizing potassium into potassium sulfate, potassium sulfate hydrate, magnesium potassium sulfate, magnesium potassium sulfate hydrate, magnesium potassium double salt, or a combination thereof. In a further exemplary aspect, the first crystallization step may be operated at a temperature of approximately 40°C, and the second crystallization step may be operated at a temperature of approximately 10°C. In a further exemplary aspect, the first crystallization step may be performed in a forced circulation crystallizer, and the second crystallization step may be performed in a first draft tube crystallizer. In a further exemplary aspect, the first crystallization step may be performed via evaporative crystallization, and the second crystallization step may be performed via cooling crystallization.

[0055] In another exemplary aspect, a method for reducing alkaline earth metals in solids may include acid leaching the solids to form an effluent slurry, neutralizing the effluent slurry to form a neutralized filtrate, concentrating the neutralized filtrate by heating a falling film evaporator with mechanical vapor recompression, crystallizing impurities in the neutralized filtrate in a first crystallization step in a forced circulation crystallization step, crystallizing impurities in the neutralized filtrate in a second crystallization step in a first draft tube crystallization step, crystallizing impurities in the neutralized filtrate in a third crystallization step in a second draft tube crystallization step, and precipitating remaining impurities by adding a caustic material.

[0056] In a further exemplary aspect, the acid leaching of the solids may use sulfuric acid, and the acid leaching temperature of the solids may be between 75°C and 90°C. In a further exemplary aspect, the caustic material may be milk of lime, and the precipitated impurities may be magnesium hydroxide. In a further exemplary aspect, the magnesium hydroxide may be recycled to neutralize the effluent slurry. In a further exemplary aspect, the lithium concentration may be maintained below the target lithium concentration when the neutralized filtrate exits the mechanical vapor recompression heated falling film evaporator. In a further exemplary aspect, the mechanical vapor recompression heated falling film evaporator may evaporate the neutralized filtrate at approximately 105°C, the first crystallization step may be performed at approximately 65°C, the second crystallization step may be performed at approximately 40°C, and the first crystallization step may be performed at approximately 10°C. In a further exemplary aspect, the second crystallization step may be cooled by water from a cooling tower. In a further exemplary aspect, the third crystallization step may be cooled by a glycol-water mixture. In a further exemplary aspect, the glycol mixture may comprise ethylene glycol.

[0057] In another exemplary aspect, a method for reducing alkaline earth metals in a chemical filtrate may include crystallizing alkaline earth cations in the chemical filtrate in a first crystallization step and crystallizing alkaline earth cations in the chemical filtrate in a second crystallization step. The first crystallization step may be different from the second crystallization step.

[0058] It should be noted that, unless otherwise specifically stated or understood otherwise in the context of use, conditional language such as "can," "could," "might," or "may" is generally intended to convey that certain aspects include, while other aspects do not include, certain features, elements, and / or steps. Thus, such conditional language is generally not intended to imply that features, elements, and / or steps are in any way required for one or more particular aspects, or that one or more particular aspects necessarily include logic for determining, with or without user input or prompting, whether such features, elements, and / or steps are included or performed in any particular aspect.

[0059] It should be emphasized that the above aspects are merely possible implementation examples, which are provided only for the purpose of clearly understanding the principles of the present disclosure. Any process description or frame in the flow chart should be understood to represent a code module, segment or part comprising one or more executable instructions for implementing a specific logical function or step in the process, and include alternative implementations, wherein the function may not be included or executed at all, may be executed differently from the order shown or discussed, including substantially simultaneously or in reverse order, depending on the function involved, as will be understood by those skilled in the art of the present disclosure. Without substantially departing from the spirit and principles of the present disclosure, many changes and modifications may be made to the above aspects. In addition, the scope of the present disclosure is intended to cover any and all combinations and sub-combinations of all elements, features and aspects discussed above. All of these modifications and variations are intended to be included within the scope of the present disclosure, and all possible claims to the combination of various aspects or elements or steps are intended to be supported by the present disclosure.

Claims

1. A method for reducing alkaline earth metals in a chemical filtrate, comprising: crystallizing alkaline earth cations in the chemical filtrate in a first crystallization step; and crystallizing the alkaline earth cations in the chemical filtrate in a second crystallization step, wherein the first crystallization step is carried out in a forced circulation crystallizer, and The second crystallization step is carried out in the first draft tube crystallizer.

2. The method for reducing alkaline earth metals in a chemical filtrate according to claim 1, further comprising crystallizing impurities in a third crystallization step, wherein the third crystallization step is performed in a second draft tube crystallizer.

3. The method for reducing alkaline earth metals in a chemical filtrate according to claim 2, wherein the second crystallization step is operated at a temperature ranging from 30°C to 50°C, and wherein the third crystallization step is operated at a temperature ranging from 1°C to 20°C.

4. The method for reducing alkaline earth metals in a chemical filtrate according to claim 3, wherein the second crystallization step is operated at a temperature of about 40°C, and wherein the third crystallization step is operated at a temperature of about 10°C.

5. The method for reducing alkaline earth metals in a chemical filtrate according to claim 4, wherein the first crystallization step is operated at a temperature of about 65°C.

6. A method for reducing magnesium in a chemical liquid, comprising: crystallizing magnesium as magnesium sulfate hydrate in a first crystallization step; and The magnesium is precipitated in a chemical precipitation step by adding a caustic material.

7. The method for reducing magnesium in a chemical liquid according to claim 6, further comprising: crystallizing magnesium as magnesium sulfate hydrate in a second crystallization step; removing magnesium sulfate hydrate from the first and second crystallization steps; as well as Magnesium is precipitated as magnesium hydroxide in a chemical precipitation step by adding lime milk to adjust the pH of the chemical liquor to 10.5-11.

5.

8. The method for reducing magnesium in a chemical liquid according to claim 7, wherein the first crystallization step further comprises crystallizing potassium into potassium sulfate, potassium sulfate hydrate, magnesium potassium sulfate, magnesium potassium sulfate hydrate, magnesium potassium double salt, or a combination thereof, and wherein the second crystallization step further comprises crystallizing potassium into potassium sulfate, potassium sulfate hydrate, magnesium potassium sulfate, magnesium potassium sulfate hydrate, magnesium potassium double salt, or a combination thereof.

9. The method for reducing magnesium in a chemical liquid according to claim 7, wherein the first crystallization step is operated at a temperature of about 40°C, and the second crystallization step is operated at a temperature of about 10°C.

10. The method for reducing magnesium in a chemical liquid according to claim 9, wherein the first crystallization step is performed in a forced circulation crystallizer, and the second crystallization step is performed in a first draft tube crystallizer.

11. The method for reducing magnesium in a chemical liquid according to claim 9, wherein the first crystallization step is via evaporation crystallization, and wherein the second crystallization step is via cooling crystallization.

12. A method for reducing alkaline earth metals in a solid, comprising: acid leaching the solid to form an effluent slurry; neutralizing the effluent slurry to form a neutralized filtrate; concentrating the neutralized filtrate via a mechanical vapor recompression heated falling film evaporator; crystallizing impurities in the neutralized filtrate in a first crystallization step using a forced circulation crystallization step; crystallizing impurities in the neutralized filtrate in a second crystallization step using the first draft tube crystallization step; crystallizing impurities in the neutralized filtrate in a third crystallization step using a second draft tube crystallization step; and Remaining impurities are precipitated by adding caustic material.

13. The method for reducing alkaline earth metals in solids according to claim 12, wherein the acid leaching of the solid uses sulfuric acid, and wherein the temperature of the acid leaching of the solid is 75°C to 90°C.

14. A process for the reduction of alkaline earth metals in solids according to claim 13, wherein the caustic material is milk of lime and wherein the precipitated impurity is magnesium hydroxide.

15. The process for reducing alkaline earth metals in solids according to claim 14, wherein the magnesium hydroxide is recycled to neutralize the effluent slurry.

16. The method for reducing alkaline earth metals in solids according to claim 12, wherein the lithium concentration remains below a lithium target concentration when the neutralized filtrate exits the mechanical vapor recompression heated falling film evaporator.

17. The method for reducing alkaline earth metals in solids according to claim 12, wherein: The mechanical vapor recompression heated falling film evaporator evaporates the neutralized filtrate at about 105°C; The first crystallization step is carried out at about 65°C; The second crystallization step is carried out at about 40°C; and The first crystallization step is performed at about 10°C.

18. The method for reducing alkaline earth metals in solids according to claim 17, wherein the second crystallization step is cooled by water from a cooling tower.

19. The method for reducing alkaline earth metals in solids according to claim 18, wherein the third crystallization step is cooled with a glycol-water mixture.

20. The method for reducing alkaline earth metals in solids according to claim 19, wherein the glycol mixture comprises ethylene glycol.

21. A method for reducing alkaline earth metals in a chemical filtrate, comprising: crystallizing alkaline earth cations in the chemical filtrate in a first crystallization step; and crystallizing alkaline earth cations in the chemical filtrate in a second crystallization step; The first crystallization step is different from the second crystallization step.

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