Patent Grant
11920211
This invention is related to the extraction and processing of natural brines that saturate the evaporitic sediments of chemical and clastic origin, which make up different types of aquifers developed in the salt bodies of, for example, the Argentine Puna, the Bolivian Altiplano and the Atacama Desert. In particular, it refers to a maximum recovery method and minimum environmental impact to obtain brines with a lithium ion concentration of approximately 80 g/dm3, with minimum impurity content, an attribute that becomes them chemically appropriate for obtaining high purity lithium compounds. More particularly, this invention also comprises a recovery method and minimum environmental impact to obtain other salts of interest for use in agriculture, livestock and industry.
In particular, salt flats and salt marshes of the Argentine Puna, Bolivian Altiplano and Atacama Desert are deposits that lie in endorheic basins that functioned as a receptacle of insoluble material inputs and liquids from the tectone-volcanic framework. These inputs accumulated as chemical evaporitic sediments and clastic sediments, where groundwater reservoirs are developed, consist of brine carrying a wide variety of ions. As a result of this accumulation process, a same salt body may contain one or more free, semi-confined and/or confined aquifers, which may or may not be interconnected and may also have different permeability for the liquid phase, i.e. interstitial brine, to circulate through them more or less easily.
Due to the accumulation of chemical sediments, these salt bodies carry important reserves of solid minerals of interest, such as ulexite, tincal, colemanite, mirabilite, thenardite, halite and others. In addition, the brine that occupies the interstitial space of aquifers, is a dense and virtually neutral and homogeneous sodium chloride solution, which may include other anions such as sulfate, borates, carbonate or bicarbonate and other cations such as potassium, lithium, magnesium, calcium, barium, strontium, iron, rubidium and caesium. The concentration of ions in the brine contained in the aquifers is the result of the balance between the recharge which was received and is received, and what is lost by evapotranspiration and/or discharges that occur with other types of higher or lower aquifers and/or drainage to other hydrogeological sub-basins. This explains the different chemism the aforementioned salt bodies have, which are clearly complex, dynamic and fragile hydrogeological systems.
As described, it is very important that the extraction and processing of brines contained in these salt bodies minimize the impact of the disturbances that will necessarily occur as a result of: (i) the extraction of brine by pumping; (ii) the use of reagents; and (iii) the handling and final disposal of effluents. Experience teaches that the processes that meet these requirements are those that aim to achieve maximum recovery with minimum environmental impact, giving priority to the natural separation of the chemical species of interest, minimizing the use of reagents and minimizing the use of primary non-renewable energy sources by giving priority to the use of renewable energy resources and available weather conditions where salt flats and salt marshes are located.
The mining resources contained in salt bodies are non-renewable natural resources because their natural availability, which is a measurable and quantifiable concept, decreases as their extraction evolves. Then, in addition to the extraction and processing process that is applied complies with what is specified in the previous paragraph, other necessary conditions must be met to ensure the sustainability of the operation over time. These other conditions are: giving priority to the use of Human Resources of populations close to the site of deposit and making the necessary forecasts for future generations to have the financial means to resolve the problems that may lead to the exploitation of non-renewable natural resources.
The current interest in obtaining lithium compounds has led to the start of several projects aimed at the extraction of lithium contained mainly in the salt flats and salt marshes of the Argentine Puna, Bolivian Altiplano and Atacama Desert in Chile. Among the main reasons for this interest in lithium, the following reasons are highlighted:
But lithium is not the only species of interest contained in natural brines. Depending on the chemical composition and the extraction and processing procedure that is applied, it is also possible to obtain the following products:
In general, the known processes for the extraction and processing of brines contained in the salt flats, initially aim to obtain lithium carbonate and/or lithium hydroxide and/or lithium chloride, as high purity solids. Lithium in brine is in the form of lithium ion [Li+], and the processes referred to may be identified as belonging to one of the following categories:
Processes similar to the scheme in
The processes shown in
In the case of
In the case of the process corresponding to
The processes in
Where the processes listed in
The O-P processes listed in
In addition, it is important to note that the investment corresponding to the S-O processes with no return of adulterated and/or depleted brine is always much greater than that corresponding to the O-P processes which are also with no return. It is clear that any process of separating lithium from a natural brine, in which this ion has a much lower concentration than almost all of the other ions that accompany it, is more onerous than the process of obtaining lithium carbonate from a concentrated and treated brine.
Processes with return of adulterated and/or depleted brine to the salt flat in
Finally, and as a summary, the procedures applied in prior art do not give priority to the necessary conditions to ensure that the activity is sustainable over time. None of them uses all the advantages offered by the weather conditions of high mountain. In addition, many of these procedures do not give priority to maximize the recovery degree and some of them only aim to obtain lithium compounds without taking into account the importance of the integral use of natural brines that are extracted from the aquifers contained in salt bodies.
The procedure object of this invention comprises an initial pre-concentration stage with fractional crystallization of natural brine in solar evaporation ponds, for the purposes of reaching the maximum lithium concentration in the liquid phase without crystallizing and precipitating salts that contain this element in their chemical formula. At this stage the first compounds of commercial interest, such as sodium chloride and potassium chloride, are separated and the volume of the liquid phase is significantly reduced. If the mass ratio of magnesium/lithium concentrations is less than a certain value in the liquid phase with initial pre-concentration, preferably approximately 2, the procedure continues to directly treat this liquid phase with lime and sodium sulfate, as described below. Otherwise, the procedure continues as described below. The concentration of sulfate anions in brine with initial pre-concentration depends on the room temperature and, consequently, varies throughout the year. When this concentration is approximately 20% higher than that corresponding to the equilibrium sulfate anion concentration in the liquid phase when it is cooled at approximately −7° C., the aforementioned reduction in the volume allows to face the next stage consisting of cooling this liquid phase to reach a temperature preferably between −6° C. and approximately −8° C. Under these conditions, sulfate anion-containing salts in their chemical formula crystallize by cooling, by substantially reducing the mass ratio of sulfate/lithium concentrations in the aforementioned liquid phase. Depending on the volume to be processed and the quantity and latent heat of the crystallizing salts, this cooling can be performed in natural crystallizers, taking advantage of the low temperatures of winter months, or in mechanical cooling crystallization equipment.
When the sulfate anion concentration in brine with initial pre-concentration, which varies depending on the room temperature, is preferably approximately 20% lower than that corresponding to the equilibrium concentration in the liquid phase when it is cooled at about −7° C., the cooling stage is not necessary. The procedure continues a stoichiometric chemical pre-treatment to the sulfate anion content of the post-cooling liquid phase with an aqueous calcium chloride or barium chloride solution. It is also possible to use calcium hydroxide, but as explained in the detailed description of the invention, this option is not convenient. Due to this reduction in the sulfate content it is possible to continue the pre-concentration of the pre-treated liquid phase until a new maximum possible lithium concentration value is reached, without crystallizing and precipitating lithium-containing salts in their chemical formula; this final pre-concentration is always performed in solar evaporation ponds. While the new maximum lithium concentration value depends on the evolution of lithium, magnesium and potassium concentrations in the final pre-concentration ponds, the mass ratio of magnesium/lithium concentrations in the liquid phase that delivers the final pre-concentration stage is always lower than that corresponding to pre-treated brine. When this new maximum lithium concentration value is such that the mass ratio of magnesium/lithium concentrations is not less than approximately 2, it is possible to continue the final pre-concentration process by adding the quantity of potassium chloride needed to avoid the crystallization of lithium-carnalite to the last ponds of this process. In any case, during this final pre-concentration stage the mass ratio of magnesium/lithium concentrations is significantly reduced by crystallization and precipitation of magnesium and potassium salts, and the liquid phase is able to undergo a chemical treatment with a minimum aggregate of reagents to reduce the contents of magnesium, calcium, sulfate and boron. This treatment is conducted at two stages: (i) a first stage in which calcium hydroxide is added, for example in the form of lime slurry, calculated stoichiometrically with respect to magnesium content, and an aqueous sulfate anion-containing solution, which is obtained by dissolution in water or in the recycling solution of precipitated salts at the cooling stage of anhydrous or decahydrated sodium sulfate, or a mixture of both, calculated stoichiometrically with respect to the calcium-ion content after precipitation of magnesium hydroxide; solid effluents obtained at this first stage of treatment are filtered and washed, by recycling the wash water for suspension and dissolution of reagents used at this same stage; and (ii) at the second stage, the liquid phase is treated with the necessary quantity of an aqueous sodium hydroxide solution to adjust pH and ensure a minimum magnesium content in the liquid phase, by then adding a stoichiometrically calculated aqueous sodium carbonate solution to separate the remaining calcium ions, and finally adding an aqueous barium chloride solution to separate the remaining sulfate ions. When the liquid phase obtained at the end of the final pre-concentration has a lithium concentration greater than approximately 35 g/dm3, it is diluted during treatment to minimize lithium loss in the solid effluents generated and, at the end of it, has a lithium content between approximately 10.5 g/dm3 and approximately 12 g/dm3. When the lithium concentration after final pre-concentration is low, as described in the example of the brine from the Rio Grande Salt flat, and it is not economically feasible to dispose of potassium chloride, the pre-concentrated brine is subjected to the chemical treatment as described by adding less water with reagents. In the latter case, the liquid phase obtained after treatment is concentrated in solar evaporation ponds to reach concentrations between approximately 65 g/dm3 and approximately 75 g/dm3. When pre-concentrated brine can reach a lithium concentration greater than 35 g/dm3, the liquid phase obtained after treatment can also be concentrated in solar evaporation ponds to reach concentrations between approximately 65 g/dm3 and approximately 75 g/dm3. This concentrated brine can be transported to sites with a good industrial infrastructure and has very low impurity content which facilitates operation and minimizes the cost of obtaining very pure lithium compounds. But, as showed in the detailed description of the invention and in the example of brine from the Pozuelos Salt flat, the alternative of transporting pre-concentrated brine with more than approximately 35 g/dm3 of lithium to places with an industrial infrastructure has important advantages from an economic technical viewpoint; in this case the chemical treatment is performed at the same plant where the final concentration process is performed in mechanical evaporation equipment, and the concentrated brine also reaches concentrations between approximately g/dm3 and approximately 75 g/dm3, has low impurity content and is obtained in less time. The procedure object of this invention allows selecting, for each case, the best alternative of application for the seven stages involved. For all possible alternatives, it has low mechanical and thermal energy requirement. In addition, avoiding the crystallization and precipitation of lithium-containing salts in their chemical formula in any of the stages, and by minimizing the use of reagents and an efficient system of separation and wash of crystallized and precipitated salts in the ponds and solid effluents generated in pre-treatment and treatment, the procedure has a recovery degree between approximately % and approximately 75%. Finally, the procedure object of this invention is applicable to an industrial scale and is a minimum environmental impact procedure, mainly because it is performed with no return of depleted and/or adulterated brine or any other liquid effluent to salt flat.
This invention comprises a procedure for the extraction and processing of natural brines that aims to meet the necessary conditions from the viewpoint of the procedure, to be sustainable over time. For natural brines generally and particularly for those contained in any salt body of the Argentine Puna, Bolivian Altiplano, Atacama Desert or any evaporite, this is achieved on the basis of the following:
But, in addition, the application of the procedure object of this invention is sustainable over time because it enables the use of human resources that are available in populations close to the lay sites of salt deposits.
As described above, there are other necessary conditions, which do not depend on the procedure being applied and must be met in order for the extraction and processing of brines contained in the salt flats to be sustainable over time. As, for example, making the necessary forecasts for future generations of populations close to the lay site of the resource to have the economic means to solve the problems that may cause the exploitation of non-renewable natural resources.
The procedure object of this invention consists of a succession of stages that alternate pre-concentration processes with crystallization and precipitation of salts in solar evaporation ponds, with cooling processes, pre-treatment and treatment of pre-concentrated brine, to finish with a final concentration process of treated brine.
The procedure object of this invention gives priority to the maximization of the recovery degree by avoiding the crystallization and precipitation of lithium ion-containing salts in their chemical formula. This is met at all stages comprising the procedure.
The procedure described in this invention also gives priority to the maximization of the recovery degree, by minimizing the lithium content in the moisturizing solution that retains the crystals obtained after drainage and wash in the concentration and cooling processes, and optimizing the filtration and wash operations of solid effluents obtained in the pre-treatment and treatment processes of pre-concentrated brines.
In the aforementioned geographical region, there are a few salt flats that have ion ratios w/w with very high values relative to the average values. For example, the Incahuasi salt flat, located in the Catamarca Province, has the following values: magnesium/lithium=103, sulfate/lithium=173, boron/lithium=9 and potassium/lithium=38. For salt flats with similar characteristics to Incahuasi the procedure begins with:
The procedure then continues the cooling stage and the other stages described below, for the brines contained in most salt flats of Argentine Puna, Bolivian Altiplano, Atacama Desert, or any evaporite.
As shown in the Table below, the ion ratios w/w, corresponding to the brines contained in most salt flats, have magnesium/lithium values less than 20, sulfate/lithium less than 70, boron/lithium less than 1.5 and potassium/lithium less than 40.
Table of Ion Ratios w/w
In salt flats such as Laguna Verde in Catamarca, Argentina, and Maricunga in Chile, natural brine has a high calcium content and low sulfate content. In these cases it is necessary to reduce the calcium content by natural crystallization of any hydrate or by the addition of trona or coipa. It is also possible to reduce the calcium content by mixing, where possible, this brine with another one that has a high sulfate content and low calcium content, from another salt flat or another area of the same salt flat as is the case, for example, in the Atacama salt flat. The procedure then continues the pre-treatment stage and the other stages described below mainly for the brines contained in most salt flats of the Argentine Puna, Bolivian Altiplano and Atacama Desert.
For salt flats with brines that do not have a high calcium content, and that have mass ratio values of magnesium/lithium concentrations less than 25, sulfate/lithium less than 100, boron/lithium less than 2 and potassium/lithium less than 50, the procedure object of this invention consists of the performance of the following stages:
Before starting the description of the stages that define the procedure, it is important to clarify that the concentration and fractional crystallization processes could be performed in mechanical equipment employing mechanical compression, evaporation in multiple stages, flash evaporation or adiabatic cooling crystallization, depending on the availability and cost of thermal and mechanical energy at the site of the resource location. But, taking into account the significant quantity of water that needs to be evaporated at stages I and IV, and the weather conditions of the region where the salt flats are located where there is high solar radiation, low rainfall, strong winds and low relative humidity in room, it is convenient to perform this operation in solar evaporation ponds. These ponds are large vats of approximately 2.5 m deep, with waterproofed floors and walls naturally or artificially, for example, preferably with PVC or polyethylene HDPE membranes, minimizing the losses of brine contained therein. For example, for an HDPE membrane of approximately 2 mm thick, the loss is estimated at approximately 0.4% of the volume pumped into a pond operating with a height of liquid phase of approximately 0.45 m; when the thickness of the membrane increases up to approximately 2.5 mm, the loss is reduced at less than approximately 10% of that corresponding to the membrane of approximately 2 mm; for this reason, to achieve greater recovery, it is convenient that the ponds operating at a higher lithium concentration are waterproofed with thicker membranes. Before waterproofing, floors must be smoothed and leveled with the minimum slope needed to counteract the wind effects; the walls must also be smoothed and built with the maximum slope that allows the material available in the area for construction.
In the procedure object of this invention, the initial pre-concentration and final pre-concentration stages are concentration and fractional crystallization processes that use solar evaporation ponds. These stages may include one or more substages defined by the lithium concentration in the brine entering into the substage, and the lithium concentration of the brine coming out thereof. In turn, each substage can be performed with one or more ponds in accordance with the volume of natural brine being processed, the recommended size for the construction and operation of the ponds, and the need to optimize the periodic harvesting process of the crystals deposited at the bottom of them. The post-treatment and final concentration stages can also be performed using solar evaporation ponds, with the same considerations described for the initial and final pre-concentration stages; but if transport of the pre-concentrated or pre-treated brine to a place with a better industrial infrastructure is chosen, these stages will be performed in thermally assisted mechanical evaporative crystallizers.
Stage I begins by pumping natural brine to the pond(s) of its first substage. The lithium concentration in the pond(s) of the last substage of this stage is that corresponding to a considerable volume reduction, preferably a lithium concentration close to the possible maximum one of reaching without crystallizing and precipitating lithium-containing salts at this substage to the lithium in their chemical formula. Depending on the characteristics of the natural brine being processed, the volume of brine with initial pre-concentration coming out of stage I may result in a value between approximately 3% and approximately 20% of the natural brine volume pumped into the pond(s) of its first substage. This volume reduction allows: i) continuous obtaining and accumulation of brine with initial pre-concentration during the months of a higher evaporation rate than in the southern hemisphere and the aforementioned geographical area corresponds to the months of August to May, to then continue, when necessary, with the cooling stage during the months with a lower minimum temperature corresponding to the months of June and July if using the natural conditions is chosen; or ii) without the need to accumulate pre-concentrated brine during the months of a higher evaporation rate, perform the cooling process continuously, using mechanical cooling crystallization equipment. Stage I comprises the following periods:
Charging Period of the Pond System Included at the Stage.
When cooling is necessary and in the case of using natural conditions, it is appropriate that in the southern hemisphere this period ends between 1 June and 31 July of the year in which the following period begins, which corresponds to the period of obtaining brine with initial pre-concentration. This is thus to minimize the size of the specially built ponds for brine accumulation with initial pre-concentration. When mechanical cooling crystallization equipment is used, there are no conditions for the end date of this charging period. In any case, the duration of this period is a function of the lithium concentration at the beginning and end of the stage, the height of free brine specified for the operation of the ponds of each substage, the retention of brine in the crystal bed deposited at the bottom of each pond and the average evaporation rate during the charging period.
First Period of Obtaining and Accumulating Brine with Initial Pre-Concentration, without Harvesting Crystallized and Precipitated Salts in the Ponds.
During this period, each pond generates a concentrated liquid phase flow, which depends on the lithium concentration at which the pond operates, the flow and the lithium concentration that has the brine entering into it and the evaporation rate. But from this total flow, the ponds only deliver the flow corresponding to the free liquid phase, retaining the trapped flow in the effective porosity of the crystal bed and the flow corresponding to the moisturizing solution associated with the crystals. As the evaporation rate varies throughout the year, for the same lithium concentration in the brine entering into the pond, the flow of this brine must change to maintain a constant lithium concentration at which the pond operates. In the event that it is necessary to process a minimum flow with a constant lithium concentration, such as the existence of a free-flowing well, the pond system should be designed for the average evaporation rate of the months with lower values, and another source of brine must be available, e.g. pumping from a surface vat or from a deep well. In any of these cases, if the concentration and flow of brine delivered by the stage is to be kept constant, the liquid phase level of the ponds involved must be adequately modified. Only in the event that the cooling stage is necessary and natural conditions are chosen, this period should end between 15 and 31 May each year for the same region.
Cleaning Period of Initial Pre-Concentration Ponds.
When the quantity of salts deposited at the bottom of a pond reaches a certain height preferably not greater than one meter, the free liquid phase is pumped into an auxiliary pond with the capacity to also contain the brine drained from the crystal bed and wash water of the precipitated salts. Preferably, the area of auxiliary pond should be equal to the area of the pond that is in the cleaning process. Crystals are drained by trenching and the drained brine is also pumped into the auxiliary pond. If the liquid phase at which the pond operates in the washing process has a lithium ion concentration greater than approximately 1.5 mg/dm3, it is necessary to wash the crystals by immersion adding a volume of water, preferably fresh water, equivalent to the estimated volume for the effective porosity of the crystal bed after drainage. The post-washed crystals are drained again by trenching and all the wash water is pumped into the auxiliary pond. Post-drained and/or post-washed crystals are harvested and heaped up grains for threshing in an area specially intended for accumulation for later use. The brine contained in the auxiliary pond is pumped back to the pond that was cleaned, and the auxiliary pond is intended for the cleaning of another pond. It is clear that, immediately after charging, the free brine height in the clean pond is higher than the height during the first unharvested operating period and, although it has a lower lithium concentration by dilution with wash water, the total quantity of lithium contained in it is higher. For this reason, during the new unharvested operation, the pond will deliver a little less than the total concentrated brine flow, in comparison to that which is actually produced. This is because it delivers the free brine flow produced in the new unharvested operation, plus a fraction of the trapped flow in the porosity of the crystal bed during the previous unharvested operation, plus the moisturizing solution flow associated with the crystals deposited at the bottom of the pond during the previous unharvested operation, and less the quantity of equivalent moisturizing solution, quantity of brine with the same lithium concentration at which the pond operates, which retain the post-washed and drained crystals, obtained during the previous unharvested operation. In this case, if the flow and lithium concentration in the brine delivering the stage is to be kept constant, the liquid phase level of the ponds involved must be adequately modified. But in this new unharvested period, the flow delivering the stage will be greater than that delivered during the first unharvested period. At the end of this new unharvested period the free brine height will have the same value with which the pond operated throughout the first unharvested period.
Subsequent Periods of Obtaining and Accumulating Initial Pre-Concentrated Brine, without Harvesting Crystallized and Precipitated Salts in the Ponds.
During these periods the ponds operate as described for the first unharvested period, and the only difference is a greater height of free brine, as expressed in the previous item. For cooling using natural conditions, these periods must end between 15 and 31 May each year.
Crystalized and precipitated salts in the first ponds of initial pre-concentration generally contain more than approximately 95% sodium chloride. Particularly those that crystallize and precipitate in the ponds that reach a lithium ion concentration less than approximately 2.5 g/dm3 are those used to produce salt for human consumption, salt for industrial use, salt breads for direct use in livestock and as raw material for the production of mineralized salt for use in livestock.
If the mass ratio of magnesium/lithium concentrations is less than a certain value in the liquid phase delivering stage I, preferably approximately 2, the procedure continues with stage V, treating this brine with initial pre-concentration directly as described below. Otherwise, the procedure continues as described below.
The sulfate concentration in the liquid phase delivered by stage I depends on the temperature of the liquid phase and, consequently, varies throughout the year. When this concentration is between approximately 10% and approximately 20% higher than the sulfate anion concentration that has this liquid phase after being cooled at approximately −7° C., it is necessary to perform stage II. Otherwise, stage II is not performed and the procedure continues with the performance of stage III.
Stage II consists of a cooling process of brine with initial pre-concentration. This cooling process can be performed continuously, using mechanical cooling crystallization equipment, decreasing the temperature of the pre-concentrated brine up to temperatures between approximately −8° C. and approximately −6° C. In this case, the solids separated from the liquid phase mechanically are washed with a freshwater mass approximately equal to 30% of mass of drained crystals. Wash water is mixed with the obtained liquid phase and pumped to stage III. The mechanically washed and drained crystals are heaped up grains for threshing, to be then used as a raw material for obtaining sodium sulfate and/or potassium sulfate and/or potassium chloride. Sodium sulfate is mainly used in the detergent industry and in the cellulose pulp industry. Potassium sulfate and potassium chloride are used as fertilizers in agriculture. Where economically appropriate, sodium sulfate obtained at this stage is used as a reagent in the treatment corresponding to stage V described below; if it is appropriate to sell this sodium sulfate, the sulfate anions required at stage V may come from mirabilite containing decahydrated sodium sulfate and/or thenardite containing anhydrous sodium sulfate, minerals available, for example, in the aforementioned geographic Region.
The cooling process comprising stage II can also be carried out taking advantage of the minimum low temperatures and minimum absolute temperatures less than approximately −10° C. and approximately −17° C., respectively, characteristics of the months of June and July in the high mountain range at more than 3,600 msnm, where more than 90% of the salt deposits in the Region are located. This operation is carried out in natural crystallizers consisting of large and shallow vats of approximately 0.50 m, with leveled floors and smoothed and waterproofed floors and walls naturally or artificially, for example, preferably with PVC or polyethylene HDPE membranes, minimizing the losses of brine contained therein. In these vats the brine is charged with initial pre-concentration and exposed to natural cold for a preferable range between approximately 7 and approximately 9 days. Under these conditions salts containing, among others, ions to sulfate anion crystallize and precipitate. The free liquid phase and that obtained by runoff are pumped to accumulation ponds from where the pre-treatment plant is powered. Drained crystals are washed by immersion adding a quantity of fresh water preferably equal to that estimated for the effective porosity of the precipitated crystal bed to the crystallizers. Wash water obtained by runoff is also pumped into the same accumulation ponds. Washed and drained crystals are harvested from the crystallizers and heaped up grains for threshing, to be then used as described for the use of mechanical cooling crystallization equipment.
The free liquid phase and that obtained at this stage have a mass ratio of sulfate/lithium concentrations, whose value is generally between approximately % and approximately 40% of the value corresponding to natural brine. In the same proportion, the required quantity of reagents and the quantity of solid effluents generated in pre-treatment are reduced if natural brine or brine were pre-treated with initial pre-concentration. This, in addition to reducing the environmental impact of the process, maximizes the recovery degree by minimizing the losses associated with the moisturizing solution of the solid effluents generated.
Stage III consists of the chemical pre-treatment of brine resulting from stage II, in order to further reduce the value of the mass ratio of sulfate/lithium concentrations. The brine is charged into a stirred reactor, and mixed with the stoichiometric quantity of cations associated with the sulfate ions forming an insoluble salt; these cations power to the reactor as an aqueous solution. Preferably, this pre-treatment is performed by adding stoichiometrically an aqueous calcium chloride solution or an aqueous barium chloride solution, in concentrations close to those corresponding to those of saturation, preferably approximately 90% of the value corresponding to those of saturation at room temperature; the solid and liquid phases of the heterogeneous mixture obtained are separated by centrifugation or filtration, washing the solid phase with a quantity of fresh water approximately equal to one third of the mass of the drained solid effluent generated. It is also possible to use calcium hydroxide added in the form of lime slurry as a source of calcium ions; in this case the quantity of solid effluent generated is greater because the crystallization and precipitation of magnesium hydroxide is added, and the separation of the solid and liquid phases is more operationally difficult, because the solid effluent retains greater moisturizing solution and wash is more difficult. On the other hand, by separating the magnesium ions from the liquid phase, the potassium concentration will continue to increase throughout the concentration process, reaching very high values in the final concentrated brine. The pre-treatment process comprising stage III can also be run on continuous reactors and continuous liquid-solid separation systems. The liquid phase and wash water are mixed and pumped into the pond(s) of the first substage of stage IV. Depending on the reagent used, the solid phase obtained from pre-treatment may be calcium sulfate that can be marketed as agricultural gypsum or barium sulfate that is used as filler material in rubber products, paints such as permanent white, linoleum and, among other applications, such as pharmacopoeia.
By performing stage IV it is possible to continue the concentration process and fractional crystallization in solar evaporation ponds, due to the reduction of the sulfate content of the pre-treated liquid phase. Depending on the chemical composition of the brine being processed, at the first substage of this stage, sodium chloride and potassium chloride can crystallize and precipitate; at the next stage the crystallization and precipitation of carnalite can be added and at the next stage if it is convenient one more substage, bischofite. The lithium concentration reached at this stage is the maximum possible one to reach without precipitating lithium-containing salts in their chemical formula. When for this new maximum lithium concentration value the mass ratio in magnesium/lithium concentration is not less than approximately 2, it is possible to continue the final pre-concentration stage by adding the quantity of potassium chloride needed to avoid crystallization of lithium-carnalite to the last ponds of this stage. The latter, when the availability of the required quantity of potassium chloride is feasible, as shown in the example of brine processing from the Pozuelos Salt flat; otherwise, the procedure continues, by treating the brine with the lowest possible mass ratio of magnesium/lithium concentrations to obtain without the addition of potassium chloride, as shown in the example of brine processing from the Rio Grande Salt flat. In any case, during this final pre-concentration stage the mass ratio of magnesium/lithium concentrations is significantly reduced by crystallization and precipitation of magnesium and potassium salts, and the liquid phase is able to undergo a chemical treatment with the minimum possible addition of reagents to reduce the contents of magnesium, calcium, sulfate and boron. As for the ponds covered by stage I, the ponds included at this stage also have a charging period, a first unharvested operating period and cleaning periods that alternate with subsequent unharvested periods.
If the pre-concentrated brine obtained at the end of stage IV has a higher lithium concentration of approximately 35 g/dm3, the procedure considers the alternative of transporting this brine to places with an industrial infrastructure, for example, locating the raw and purified plants in the vicinity of a power plant making possible cogeneration, where stages V, VII and VII will be performed more efficiently. In addition, this alternative has important advantages based on the considerations detailed below, when transporting a pre-concentrated brine with, for example, approximately 2.78% w/w lithium:
Stage V consists of the chemical treatment of brine obtained at the final pre-concentration stage. This treatment aims to reduce the contents of magnesium, calcium and sulfate at very low values, and also reduce the boron content. Stage V is performed at two substages. When the lithium concentration in the liquid phase that delivers stage IV is approximately 35 g/dm3 or greater, substage V.1 consists of charging the pre-concentrated brine to a reactor with very good stirring and, while maintaining stirring, first add a quantity of water to reduce the lithium concentration by approximately 50%, and then add a lime slurry containing a preferably calculated quantity of calcium hydroxide with approximately 10% in excess of the stoichiometric value to precipitate all magnesium ions. Immediately afterwards and maintaining stirring, add an aqueous solution containing a stoichiometrically calculated quantity of sulfate anions to precipitate the remaining calcium ions in the liquid phase, then to the calcium hydroxide aggregate. Calcium hydroxide is preferably added as a preferably prepared lime slurry by suspending a ton of solid in a volume between approximately 2.5 m3 and approximately 3 m3 of water, preferably fresh water, wash water of solid effluents or recycling mother water of “raw” and purified lithium carbonate plants. The sulfate anions are added as a prepared aqueous solution, for example, dissolving between approximately 0.300 tons and approximately 0.370 tons of anhydrous sodium sulfate in approximately one cubic meter of water, preferably fresh water, wash water of solid effluents or recycling mother water of “raw” and purified lithium carbonate plants.
It is important to note that the sulfate anion input can also be made partially or completely by adding: i) separate sodium sulfate at the cooling stage, either as anhydrous sodium sulfate or as decahydrated sodium sulfate, reducing the costs of reagents; ii) mirabilite, thenardite or a mixture of these minerals, if they do not contain water-soluble calcium, magnesium or boron compounds. The solid and liquid phases of the heterogeneous mixture obtained after treatment are separated by centrifugation or filtration, preferably using a filter press, washing the solid phase with a quantity of water, preferably fresh water, approximately equal to approximately 2 m3/t of dry solids obtained after treatment; wash water is used to dilute pre-concentrated brine and/or to add the reagents used at this substage V.1. The use of the filter press ensures that the loss of lithium in the post-washed solid effluent is less than approximately % of the dry solid effluent mass. This leads to a recovery degree at the treatment stage greater than approximately 95%. As a result of dilution to prevent salts that have lithium in their chemical formula from crystallizing and precipitating, the liquid phase obtained at substage V.1 has a lithium concentration preferably between approximately 11 g/dm3 and approximately 13 g/dm3. For some brines, the lithium concentration in the liquid phase that delivers stage IV may be less than approximately 35 g/dm3 and, in some cases, much less than in the case of brine from the Rio Grande Salt flat. In these cases it is convenient: i) not to dilute by adding fresh water; (ii) to add calcium hydroxide solidly not as lime slurry; and (iii) to use as little water as possible to add the sulfate anions. Known the resulting calcium, magnesium and sulfate concentrations in the liquid phase that delivers stage V.1, the procedure continues the performance of substage V.2. The process comprising this substage of the procedure consists of treating the brine obtained in V.1 in a stirred reactor to which the minimum quantity required of an aqueous sodium hydroxide solution with a low concentration, preferably less than approximately 150 g/dm3 is added to ensure its stability, in order to increase pH at approximately 11.2 and thus minimize the magnesium ion content in the liquid phase. Immediately afterwards, and maintaining stirring, an aqueous sodium carbonate solution is added, in order to minimize the calcium ion content in the liquid phase. The quantity of sodium carbonate is calculated stoichiometrically with respect to calcium ion content; the concentration of the aqueous sodium carbonate solution should preferably be equal to approximately 90% of the value corresponding to saturation at room temperature. Then, and maintaining the stirring, an aqueous barium chloride solution that preferably contains the stoichiometric quantity of reagent needed to precipitate all the sulfate anions contained in this brine is added; the concentration of the aqueous barium chloride solution should preferably be equal to approximately 90% of the value corresponding to saturation at room temperature. The heterogeneous mixture obtained is separated by centrifugation or filtration, washing the solid phase with a freshwater mass approximately equal to one third of the drained solid effluent mass generated. The processes at substages V.1 and V.2 of the procedure object of this invention can also be performed in continuous reactors and continuous liquid-solid separation systems.
In all cases studied, pre-concentrated and treated brine can be categorized as a brine with low impurity content considering that the mass ratios of ion/lithium concentrations are below the following values:
This brine is not saturated, has low density and low content of total dissolved solids (sólidos totales disueltos, STD).
When it is not possible to reach a lithium concentration greater than approximately 35 g/dm3 in the pre-concentrated brine without crystallizing lithium-containing salts in their chemical formula, the treatment plant must be located near the site where the ponds operate. In addition, if the brine entering into stage V is such that after treatment at the substages V.1 and V.2 has a lithium concentration greater than approximately 9 g/dm3, the procedure object of this invention offers as an alternative to obtain “raw” lithium carbonate from the pre-concentrated and treated brine obtained at stage V. In this case, and due to the low lithium concentration in the liquid phase delivered by stage V, the “raw” lithium carbonate plant will be located in the same place where the ponds and the treatment plant operate. The purification of this “raw” lithium by applying the carbon dioxide purification process, filtering the lithium bicarbonate solution obtained after the carbonation process and using ion exchange resins to reduce the calcium content in this solution will result in a high-purity product.
But, as demonstrated earlier, if the liquid phase that delivers stage IV has a higher lithium concentration of approximately 35 g/dm3, it is always better to transport pre-concentrated brine to sites with a better industrial infrastructure. In this case, after performing stage V, it is convenient to continue stages VI and VII to power the lithium carbonate plant with concentrated brine and with lower impurity content.
In the case of not transporting pre-concentrated brine due to the low lithium concentration in the brines delivered by the stage IV, if it is decided not to produce “raw” lithium carbonate from the liquid phase delivered by stage V, even if the lithium concentration in this brine is greater than approximately 9 g/dm3, the performance of stages VI and VII of final concentration is continued, until a lithium ion concentration between approximately 65 g/dm3 and 75 g/dm3 is reached in the brine. These stages can be performed in a solar pond system in which sodium chloride crystals will mainly be crystallized and precipitated. But, if in the vicinity of the site of the pre-concentration ponds and the treatment plant industrial infrastructure is available, taking into account that the contents of calcium, magnesium and sulfate are low in the liquid phase that delivers stage V, there are more advantages to perform these final concentration stages in thermally assisted evaporative crystallizers. In these cases, high-purity sodium chloride and distilled water, which is very useful considering that fresh water is a scarce resource in the Region of salt flats, will also be obtained as by-products.
As shown in the following Table, for the three Examples presented below in detail, as the process evolves through the stages involved, the mass ratios of ion/lithium concentration are reduced for impurities.
Table of Evolution of Brines of Each Salt Flat in Examples 1, 2 and 3 in Accordance with the Progress of the Procedure of the Invention.
S. Diablillos
S. Pozuelos
S. Rio Grande
When it is not possible to transport pre-concentrated brine to a site with an industrial infrastructure with more than approximately 35 g/dm3 of lithium, the possibility of obtaining a treated brine with a lithium concentration between approximately 65 g/dm3 and approximately 75 g/dm3 and with low impurity content, enables to transport it to places with a better infrastructure for the location of raw and purified lithium carbonate plants. While this has the disadvantage of increasing the transport cost of concentrated brine and recycling solution per ton of lithium carbonate produced, it has advantages that far outweigh this increase. The most important advantage is the reduction of the operating cost by the availability of thermal and electrical energy at lower costs, for example, by locating the plants of raw and purified products in the vicinity of a power plant and operating more efficiently without pressurized reactors, due to the fact that it is located at lower height above sea level. On the other hand, this alternative also provides the possibility of concentrating the recycle of plants of raw and purified products in such a way that it is possible to transport the same quantity of liquid that is transported to lithium carbonate plants to the pond sector; this optimizes the transport system between ponds and plants. This alternative also allows the possibility of purging and concentrating part of the recycle of raw reactor to obtain other chemical species present in natural brine such as rubidium and caesium.
The operating variables of each and all stages of the procedure object of this invention were determined based on the results obtained in a field and laboratory test (ensayo de campo y de laboratorio, ECL).
The volume required to initiate the ECL is calculated based on the lithium ion content of the natural brine to be processed, and the volume to be obtained from concentrated brine at approximately 75 g/dm3, at the end of the process. This final volume should be such that it is possible to verify the process of obtaining any of the pure lithium compounds, e.g. lithium carbonate. Preferably, this volume should be greater than approximately 3 dm3. Then, assuming a recovery level of approximately 70%, the initial volume for the field and laboratory test should be greater than:
For most brines contained, for example, in the salt flats from the Argentine Puna, Bolivian Altiplano and Atacama Desert, the lithium content is between approximately 350 mg/dm3 and approximately 1,500 mg/dm3. This determines that the initial volume for the ECL is generally between approximately 220 dm3 and approximately 920 dm3.
The operating variables that are measured during the execution of ECL, simulating the evolution of the stages that are performed in solar evaporation ponds such as those corresponding to stages I, IV, VI and VII, are:
With the information obtained from ECL and, in order to show that the procedure object of this invention is applicable on an industrial scale, for example, for 10,000 t of lithium carbonate per year, the operating variables that characterize the evolution of the ponds included at stages I, IV, VI and VII for the first period of unharvested operation and the following harvesting operating periods that alternate with the cleaning periods. Then, what aforementioned operating variables are indicated, and how the value corresponding to the default annual production is obtained.
Operating variables of stages II, cooling; Ill, pre-treatment; and V, treatment; they are also obtained by extrapolating the information obtained in the field and laboratory tests and from the annual volumes that deliver stages I and IV.
Three examples of field and laboratory tests and calculation of the operating variables that characterize the evolution of the seven stages of the procedure are described for brine from three salt flats. For the purpose of showing the different alternatives offered by the procedure, the following is considered:
By way of example, the results of field and laboratory tests and calculation of operating variables performed for brine contained in the Diablillos, Pozuelo y Río Grande salt flats are detailed below.
This Salt flat is a salt deposit located in the Region of Argentine Puna at more than 3,900 msnm.
Field and Laboratory Test
STAGE I: Initial Pre-Concentration
On day 1, at 4,050 msnm, three similar ponds with natural brine identified as 1FL (i) are charged to start the solar evaporation and fractional crystallization process.
1FL (i): Initial liquid phase of stage I
1V FL(i)=
5ρ (i)=
2A FL(i)=
3h FL(i)=
6T=
4STD FL(i)=
1V: Volume
2A: Area
3h: height
4STD: Total dissolved solids
5ρ: density
6T: Temperature
Initial Liquid Phase Chemistry (FL (i)):
Substage I.1
The brine (FL (I)) arranged in the three ponds is exposed to the solar evaporation process at 4,050 msnm for 10 days. On day 19 the precipitated crystals are separated from the liquid phase, and the following is obtained:
FL (I.1) which is arranged in two ponds to continue the solar evaporation process
Liquid phase chemistry (FL (I.1)):
B.1) Precipitated Solids (SP I.1))
Theoretical Calculation of the Precipitated Solid Mass SP(I.1):
Deviation 0.01
Total precipitated 7,349.9 g
Calculation of the Moisturizing Solution Volume (Vsm (I.1)):
Precipitated salts 105 moles of NaCl
Theoretical precipitated 10,041 g Deviation −0.039 mass
Harvested crystal mass 10,855 g
The specific quantity of good quality pond salt that can be obtained at this Substage is 5.5 t/t of CLE, wherein: CLE: equivalent lithium carbonate
Calculation of the Apparent Evaporation Rate (Tasa De Evaporación Aparente, TEA):
The brine FL (I.1) arranged in the two ponds is exposed to continue the solar evaporation process at 4,050 msnm during 23 days. On day 23 the precipitated crystals are separated from the liquid phase, and the following is obtained:
FL (I.2) that is transported to the laboratory is weighed, density is measured, volume is calculated and analyzed.
FL (I.2) Chemistry:
Deviation 0.002
B.2) Precipitated Solids (SP I.2))
Theoretical calculation of the precipitated solid mass SP (I.2) (it does not include the solids contained in the moisturizing solution volume).
Deviation 0.0040 g
Total precipitated: 64,222.6 g
Calculation of the Moisturizing Solution Volume (Vsm (1-2)):
Deviation −0.030
Calculation of the Apparent Evaporation Rate (TEA):
Precipitated solids SP (I.1) and SP (I.2) contain more than 90% NaCl, then solar evaporation processes (I.1) and (I.2) could be included in a single substage of the initial pre-concentration stage
STAGE II: Cooling
On day 25, the pre-concentrated brine FL (I.2) is cooled at −7° C. in a freezer located at 2,000 msnm, for a period of 3 days, and the following is obtained.
1FL (II) that is transported to the laboratory is weighed, density is measured, volume is calculated and analyzed.
During the separation process of the liquid phase FL (II) from the precipitated solids SP (II) 3.1 dm3 of the FL (II) was discarded to remove the sedimented clay at the bottom of the container during the cooling process.
1FL (II): Liquid Phase of Stage II
Liquid Phase FL (II):
FL (II) Chemistry:
Precipitated Solids (SP (II)):
Theoretical calculation of the precipitated solid mass SP (II) (it does not include the solids contained in the moisturizing solution volume):
Deviation −0.01
Precipitated Salts:
Calculation of the Moisturizing Solution Volume (Vsm (II)):
Deviation −0.010
The specific quantity of potassium salts (chloride and sulfate) that can be obtained at this stage is greater than 3.5 t/t of Lithium Carbonate (CL). Evolution of ion ratios until this stage:
STAGE III: Pre-Treatment
1,171 g of CaCl2·2H2O (s) is added to the total cooled solution calculated as the stoichiometric quantity (plus 10%) to precipitate 11.781 g/dm3 of SO4
After adding and stirring, it is verified that sulfate content in the brine is equal to 7.290 g/dm3. Without separating the solid phase (CaSO4·2H2O) 1,284 g of BaCl2·2H2O (s) is added by calculating the stoichiometric quantity (plus 10%) necessary to precipitate the remaining 7.290 g/dm3 of sulfate in the liquid phase. After adding the reagent, 3.5 dm3 of water, stirring and separating the phases, it is verified that the sulfate content in the brine is stabilized at 2.768 g/dm3. It is clear that some of the precipitated calcium sulfate passed to barium sulfate, before phase separation, increasing the calcium ion content in the liquid phase.
Finally, 790 g of BaCl2·2H2O dissolved at 1.5 dm3 of water is added to the liquid phase. After adding the reagent, it is stirred, allowed to stand for 24 hours and then the Phases are separated, and the following is obtained:
Liquid phase FL (III) that is weighed, density is measured, volume is calculated and analyzed:
FL (III) Chemistry:
Precipitated Solids in Pre-Treatment (SP (III)):
Total mass SP (III)=4.900 kg; H=19.8%
Separate post-treatment solids contain:
If the solid phase after pre-treatment with calcium chloride is separated, the solid obtained after adding barium chloride, it is barium sulfate mixed with less than 10% of water-soluble substances. Barium sulfate is obtained as a by-product from SP (III).
Reagent Requirement in Pre-Treatment
Assuming that the lithium recovery referring to the content in FL(III) and until obtaining Lithium Carbonate is 82%, the specific requirement of each reagent used is:
Solid Effluent Generation in Pre-Treatment
Assuming that the lithium recovery referring to the content in FL(III) and until obtaining lithium carbonate is 82%, the solid effluent generation per final product unit is:
Specific quantity of possible by-products to be obtained from the t-generated equivalent lithium carbonate (CLE) solid effluent:
1CLE
STAGE IV: Final Pre-Concentration
Substage IV.1
FL (III) is transported to the Diablillos Salt flat on day 66 and at noon two plastic boxes of area equal to 0.33 cm×0.52 cm each are charged, to continue with the natural evaporation and fractional crystallization process.
During the transport of FL (III) to the Salt flat and then in the transport of FL (IV.1) to the laboratory the equivalent value to 1 dm3 of FL (IV.1) is lost.
On day 87 the precipitated crystals are separated from the liquid phase and the following is obtained.
FL (IV.1) that is transported to the laboratory is weighed, density is measured, volume is calculated and analyzed:
FL (IV.1) chemistry
Pre-Washed Precipitated Solids (SP (IV.1))
Theoretical calculation of the precipitated solid mass SP (IVA) (it does not include the solids contained in the moisturizing solution volume).
Deviation: −0.007
Total precipitated: 3,256.9 g
Calculation of the Moisturizing Solution Volume (Vsm (IV.1)):
Deviation 0.027
The obtained solids are washed with a water volume approximately equal to half of the volume that have post-filtering. Wash water is concentrated until the same lithium concentration of FL (IV.1) is reached. The resulting volume of FL (IV.1) is:
Post-Washed Precipitated Solids (SP (IV.1)):
On day 92 brine FL (IVA) arranged in two containers is exposed to continue the natural evaporation process in the laboratory. On day 102 the precipitated crystals are separated from the liquid phase, and the following is obtained:
The Liquid Phase FL (IV.2) that is Weighed, Density is Measured, Volume is Calculated and Analyzed:
FL (IV.2) Chemistry:
Pre-Washed Precipitated Solids (SP (IV.2))
Theoretical calculation of the precipitated solid mass SP (IV.2) (it does not include the solids contained in the moisturizing solution volume):
Deviation 0.013
Total precipitated: 4,551.1 g
Calculation of the pre-washed moisturizing solution volume (Vsm (IV.2)):
The obtained solids are washed with a water mass approximately equal to half of the mass that have post-filtering. Wash water is concentrated until the same lithium concentration of FL (IV.2) is reached.
The resulting volume of FL (IV.2) is: 35.32 dm3
Post-Washed Precipitated Solids (SP (IV.2)):
The precipitated solids contain 12% potassium chloride and 76% sodium chloride and 12% carnalite.
Substage IV.3
On day 103 the brine FL (IV.2) is poured into two trays and is exposed to continue the natural evaporation process in the laboratory. On day 108 the precipitated crystals are separated from the liquid phase, and the following is obtained:
The Liquid Phase FL (IV.3) that is Weighed, Density is Measured, Volume is Calculated and Analyzed:
FL (IV.3) Chemistry:
Pre-Washed Precipitated Solids (SP (IV.3))
Theoretical calculation of the pre-washed precipitated solid mass SP (IV.3) (it does not include the solids contained in the moisturizing solution volume):
Deviation 0.005
Crystallization water carnalite: 3,024 g
Calculation of the Moisturizing Solution Volume (Vsm (IV.3)):
The obtained solids are washed with a water mass approximately equal to half of the mass that have post-filtering. Wash water is concentrated until the same lithium concentration of FL (IV.3) is reached. The resulting volume of FL(IV.3) is:
On day 109 the brine FL (IV.3) is poured into a tray and is exposed to continue the natural evaporation process in the laboratory. On day 114 the precipitated crystals are separated from the liquid phase, and the following is obtained:
The liquid phase FL (IV.4) that is weighed, density is measured, volume is calculated and analyzed:
FL (IV.4) Chemistry:
Precipitated Solids (SP (IV.4))
Theoretical calculation of the precipitated solid mass SP (IV.4) (it does not include the solids contained in the moisturizing solution volume):
Deviation 0.012
Crystallization water: 1,188 g
Calculation of the moisturizing solution volume (Vsm (IV.4)):
Deviation 0.004
The obtained solids are washed with a water volume approximately equal to 60% of the volume that have post-filtering. Wash water is concentrated until the same lithium concentration of FL (IV.4) is reached. The resulting volume of FL(IV.4) is:
Brine FL (IV.4) undergoes a treatment to reduce magnesium, calcium and boron content.
7.536 dm3 obtained (FL (IV.4)) is placed in a plastic container with a capacity of 30 dm3. Firstly, brine is diluted with fresh water up to 31-32 g/dm3 of lithium. Then, stirring manually with a plastic shovel, a prepared calcium hydroxide suspension is added by suspending 1.058 kg in 2.650 dm3 of fresh water. Immediately afterwards, and continuing with stirring, a prepared aqueous solution is added by dissolving 2.028 kg of anhydrous sodium sulfate in 5.5 dm3 of fresh water at 35° C. Finally, 754 cm 3 of a sodium hydroxide solution 4 N is added, ensuring a pH value greater than 11.3.
The obtained post-treatment heterogeneous mixture is separated by centrifugation and the following is obtained.
The Liquid Phase FL (V.1) that is Weighed, Density is Measured, Volume is Calculated and Analyzed:
FL (V.1) Chemistry:
Pre-Washed Precipitated Solids (SP (IV.1)):
Theoretical calculation of the precipitated solid mass SP (V.1) (it does not include the solids contained in the moisturizing solution volume):
Total precipitated 3698.5 g
Deviation 0.013
Calculation of the pre-washed moisturizing solution volume (Vsm (V.1)):
Deviation 0.091
Obtained solids are centrifuged, washed by suspending them at 9.5 dm3 of fresh water and centrifuged again. Wash water is concentrated until the same lithium concentration of FL (V.1) is reached. The resulting volume of FL(V.1) is:
Solid effluents SP (V.1) contain 62% dihydrated calcium sulfate and 24% magnesium hydroxide. Leaching these solid effluents with sulfuric acid and separating the phases it is possible to obtain the following per ton of equivalent lithium carbonate:
The quantity of sulfate moles required for stage V.1 can be added in whole or in part as potassium sulfate and sodium sulfate obtained at stage II of cooling. For brine from the Diablillos salt flat, at the cooling stage 17 sulfate moles are obtained, and at the treatment stage it is necessary to add 14.3 sulfate moles which means that it is not necessary to incorporate sodium sulfate as a reagent.
Substage V.2
22.514 dm3 obtained (FL (V.1)) is placed in a plastic container with a capacity of 30 dm3. Stirring manually with a plastic shovel, a prepared aqueous solution is added dissolving 306 g of dihydrated barium chloride in 1.4 dm3 of fresh water. The heterogeneous mixture obtained is separated by filtration and wash, and the following is obtained.
Liquid phase FL (V.2) (it includes wash water) that is weighed, density is measured, volume is calculated and analyzed:
FL (V.2) Chemistry:
Precipitated Solids (SP (V.2)):
Solids precipitated by the addition of barium chloride are washed with 100 cm 3 of water. Wash water is concentrated until the lithium concentration in FL (V.2) is reached and mixed with the same.
Precipitated solids SP (V.2) contain more than 95% barium sulfate dihydrate.
STAGE VI: Post-Treatment Concentration
On day 116 brine FL (V.2) is poured into a plastic tray and exposed to restart the evaporation process in the laboratory, using forced ventilation. On day 119 precipitated crystals of the liquid phase are separated, and the following is obtained.
Liquid Phase FL (VI) that is Weighed, Density is Measured, Volume is Calculated and Analyzed:
FL (VI) Chemistry:
Precipitated Solids (SP (VI)):
Theoretical calculation of the precipitated solid mass SP (VI) (it does not include the solids contained in the moisturizing solution volume):
Total precipitated 1538.1 g
Deviation −0.0003
Calculation of the Moisturizing Solution Volume (Vsm (VI)):
Precipitated solids are washed with 400 cm 3 of water. Wash water is concentrated until the lithium concentration in FL (VII) is reached and mixed with the same. The resulting volume of FL(VI) is:
FL (VII) Chemistry:
Pre-Washed Precipitated Solids (SP (VII)):
Theoretical calculation of the precipitated solid mass SP (VII) (it does not include the solids contained in the moisturizing solution volume):
Deviation −0.023
Total precipitated 866.5 g
Calculation of the Moisturizing Solution Volume (Vsm (VII)):
Deviation 0.011
Precipitated solids are washed with 500 cm 3 of water. Wash water is concentrated until the lithium concentration in FL (VII) is reached and mixed with the same. The resulting volume of FL (VII) is:
The calculation of the operating variables for an annual production of 10,000 tons of equivalent lithium carbonate was carried out using brine from the Diablillos Salt flat, when the cooling process at stage II is carried out with a mechanical cooling crystallization equipment and stages VI and VII are carried out in solar evaporation ponds.
Stage I: Initial Pre-Concentration Ponds
First Unharvested Period:
Stage I: Initial Pre-Concentration Ponds
Next Unharvested Periods:
Brackish water: water with density less than 1,100 g/dm3.
Auxiliary pond for stage I: 390,000 m2
Stage II: Cooling
This stage is performed in a mechanical cooling crystallization equipment and is detailed for the highest brine flow, i.e. the one corresponding to the post-harvest period for the pond system operation.
Brine to be Cooled
Specific heat: 0.85 kcal/kg ° C.
Salts that crystallize during cooling:
The cooling is executed with a pre-cooling stage, in which the cooled liquid phase with low sulfate anion content, which comes out of the cooling equipment at −7° C., interacts in a heat exchanger, with brine to be cooled that has an initial temperature of 16° C. As a result of this pre-cooling, brine to be cooled enters into the crystallization equipment by cooling at 0° C.
Under these conditions, it is easy to demonstrate that, for a performance coefficient of 60% of the ideal performance coefficient (Carnot), mechanical energy required per ton of lithium carbonate produced is less than 0.12 Mwh.
Liquid Phase Obtained after Cooling
Fresh water for crystal wash: 7,000 m3
Stage III: Pre-Treatment
Quantity of Reagents and Water Used Per Ton of Equivalent Lithium Carbonate
Stage IV: Final Pre-Concentration Ponds
Next Unharvested Periods
Stage V: Treatment
Substage V.1
Quantity of Reagents and Water Used Per Ton of Equivalent Lithium Carbonate
Ponds of Stages VI and VII
Next Unharvested Periods
Auxiliary Pond Area for Stages IV, VI and VII: 75,000 m2
Specific Water and Reagent Consumption of the Procedure Calculated Per Ton of Equivalent Lithium Carbonate
In this example, natural brine is not saturated and, consequently, the quantity of crystallized and precipitated solids at stage I is low. This has the following advantages: i) in the first unharvested period the recovery is greater than in the case of saturated brines, due to the lower quantity of trapped brine and ii) The cost of harvesting crystals per ton of equivalent lithium carbonate is lower. On the other hand, while in this example the lithium concentration reached at the initial pre-concentration stage is 4.7 g/dm3, it was subsequently verified that with this brine it is possible to reach values of 8 g/dm3. This substantially reduces the volume by reducing costs and facilitating the operation of stages II and III. It is also important to clarify that, although in this example the alternative of obtaining concentrated brine at the location of the pond system is chosen, with the lithium concentration reached at the final pre-concentration stage, it is convenient to transport the liquid phase that delivers stage IV to some site with an industrial infrastructure where stages V, VI and VII are performed.
This Salt flat is a salt deposit located in the Region of Argentine Puna at more than 3800 msnm.
Field and Laboratory Test
The lithium content in the natural brine with which ECL is performed is g/dm3 and the defined volume to start the test is 842 dm3.
On day 1 890 dm3 of natural brine is extracted by pumping from the Pozuelos Salt flat. This brine identified as FL(i) is transported to the experimental outdoor center located in the area of Tres Morros, Jujuy province, Argentina, and on the following day it is charged in three similar ponds with an area of about 1.5 m2. The average height of FL(i) in the ponds is approximately equal to 0.197 m.
Natural brine (FL(i)):
1ρ (FL (i))
2V (FL (i))
3STD (FL(i))
STAGE I: Initial Pre-Concentration
Substage I.1
The brine FL(i) is exposed to the solar evaporation process until day 50. That same day the crystals of the Liquid phase are separated, and the following is obtained:
Liquid phase FL (I.1):
FL (I.1) Chemistry:
Precipitated Solids at Substage I.1 (SP (I.1)):
2Total evaporated w at 105° C.=
3H=
1SP (I.1) = Precipitated solids at stage I.1
2Total evaporated w at 105° C. = Total evaporated water at 105° C.
3H=Humidity
Chemistry of Solids SP (I.1):
Theoretical Calculation of the Precipitated Solid Mass SP (I.1):
1Cryst. W
1Cryst. w NE: non-evaporated crystallization water
1SP (I.1)
Deviation 0.0000
Total precipitated 216,943 g
1SP (I.1): Precipitated solids
Calculation of SM Volume (Vsm (I.1))
1Vsm (I.1) =
2E crystallization w
Harvested crystals are washed with 144 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (I.1) is reached. Effective volume delivered by substage I.1:
Substage I.2
Brine FL (I.1) is charged into a pond and exposed to continue the solar evaporation process until day 78. That day the solids of the liquid phase are separated, and the following is obtained.
Liquid Phase FL (I.2):
FL (I.2) Chemistry:
Precipitated Solids at Substage I.2 (SP (I.2)):
Total mass SP (1.2)=53.1 kg; H=1.79%
Chemistry of Solids SP (I.2):
Theoretical calculation of the precipitated solid mass SP(I.2):
Deviation −0.0085
Total precipitated 52730 g
Calculation of the Moisturizing Solution Volume (Vsm (I.2))
Deviation 0.012
Effective volume delivered by the substage (1.2)=44.41 dm3
Harvested crystals are washed with 30 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (I.2) is reached.
STAGE II: Cooling
On day 85 FL (I.2) is transported to a laboratory where it is cooled at minus seven degrees Celsius (−7° C.) in a freezer for a period of 18 days, and the following is obtained.
Liquid Phase FL(II)
FL (II) Chemistry:
Precipitated Solids at Stage II (SP (II)):
1Total evaporated water.
Chemistry of Solids SP (II):
Theoretical Calculation of the Precipitated Solid Mass SP (II):
1Cryst. W
Deviation 0.0003
Total precipitated 2851 g
Precipitated Salts:
Deviation 0.035
Harvested crystals are washed with 1.5 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (II) is reached Effective volume delivered by Stage II=44.41 dm3
STAGE III: Pre-Treatment
1.875 kg of CaCl2·2H2O suspended at 2 dm3 of fresh water is added to total of FL (II). It is stirred for an hour and phases are separated, and the following is obtained:
Liquid Phase FL(III)
FL (III) Chemistry:
Precipitated Solids at Stage III (SP (III)):
Chemistry of Solids SP (III):
Theoretical Calculation of the Precipitated Solid Mass SP (II)):
This does not include:
Calculation of the Moisturizing Solution Volume (Vsm (III)):
Harvested crystals are washed with 1 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (III) is reached. Effective volume delivered by stage III (L)=42.4 dm3
STAGE IV: Final Pre-Concentration
On day 107 FL (III) is transported to the Experimental outdoor center located in the area of Tres Morros, Jujuy province, Argentina, and is exposed to solar evaporation.
Substage IV.1
On day 124 a sample of the liquid phase is taken. The lithium concentration in FL (IVA) is determined, and the value 16.856 g/dm3 is obtained. It is decided to continue the concentration process by solar evaporation.
Substage IV.2
The concentration process is continued by solar evaporation, and on day 129 the phases are separated, and the following is obtained:
Liquid Phase FL (IV.2):
FL (IV.2) Chemistry:
Precipitated Solids at Stage IV.2 (SP (IV.2):
Chemistry of Solids SP (IV.2):
Theoretical Calculation of the Precipitated Solid Mass SP (IV.2):
Deviation 0.0274
Total precipitated 11,795 g
Calculation of the Moisturizing Solution Volume (Vsm (IV.2)):
1E cryst w
Deviation 0.014
1E cryst w: evaporated crystallization water
Harvested crystals are washed with 8 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (IV.2) is reached.
Effective volume delivered by stage IV.2 (L)=13.2 dm3
Substage IV.2′
While during the evolution of stage IV.2 lithium-containing salts did not crystallize in their chemical formula, as evidenced by the low lithium content in the SP salts (IV.2), in the laboratory it was verified that when evaporating about 200 cm 3 of water, the lithium concentration in the liquid phase decreased by indicating the crystallization of lithium-carnalite, and the Mg/Li ratio also decreased, indicating the simultaneous bischofite crystallization. This occurs because of the low potassium concentration and the high magnesium concentration. It is then decided to add a prepared aqueous solution dissolving 1.169 kg of KCl at 4.136 dm3 of fresh water to FL (IV.2), and the following is obtained:
Liquid Phase FL (IV.2′)
FL (IV.2′) Chemistry:
Theoretical Calculation of the Precipitated Solid Mass SP (IV.2):
Crystallized Salts:
The heterogeneous mixture of FL (IV.2′) with the precipitated solids are exposed to solar evaporation on day 136.
On day 143 the solid and liquid phases are separated, and the following is obtained.
Liquid Phase FL (IV.3):
FL (IV.3) Chemistry:
Precipitated Solids at Stage IV.3 (SP (IV.3):
Chemistry of Solids SP (IV.3):
Theoretical Calculation of the Precipitated Solid Mass SP (IV.3):
Deviation −0.0080
Total precipitated 4.084 kg
Precipitated Salts:
Calculation of the Moisturizing Solution Volume (Vsm (IV.2)):
Deviation 0.001
Harvested crystals are washed with 4.6 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (IV.2) is reached.
Effective volume delivered by stage IV.2 (L)=13.2 dm3
STAGE V
Treatment at Substage V.1
7.95 dm3 obtained (FL (IV.3)) is placed in a plastic container with a capacity of 30 dm3. Stirring manually with a plastic shovel, a prepared calcium hydroxide suspension is added by suspending 1.665 kg at 3.100 dm3 of fresh water. Immediately afterwards, and continuing with stirring, a prepared aqueous solution is added by dissolving 3.169 kg of anhydrous sodium sulfate at 6.3 dm3 of fresh water at 35° C. The heterogeneous mixture obtained after treatment is separated by centrifugation, and the following is obtained:
Liquid Phase FL (V.I):
FL (V.1) Chemistry:
Precipitated Solids at Stage V.1 (SP V.1):
Chemistry of Solids SP (V.1):
Theoretical Calculation of the Precipitated Solid Mass SP (V.1):
Total precipitated=5,035 g
Deviation 0.0136 Calculation of the moisturizing solution volume (Vsm (V.1)):
Deviation 0.018
Substage V.2
15.5 dm3 obtained (FL (V.1)) is placed in a plastic container with a capacity of 30 dm3. Stirring manually with a plastic shovel, 82 cm 3 of a 4 N solution (160 g/dm3) of sodium hydroxide is added, verifying that pH reaches 11.2. Immediately afterwards, and continuing with stirring, a prepared aqueous solution is added by dissolving 55 g of sodium carbonate at 190 cm 3 of fresh water. Then, and without suspending stirring, a prepared aqueous solution is added by dissolving 223 g of barium chloride dihydrate at 700 cm 3 of fresh water. The heterogeneous mixture is allowed to stand and then the precipitated solids are separated by vacuum filtration, and the following is obtained:
Liquid Phase FL (V.2):
FL (V.2) Chemistry:
Precipitated Solids at Stage V.2 (SP V.2):
Chemistry of Solids SP (V.2):
Theoretical Calculation of the Precipitated Solid Mass SP (V.1):
Deviation −0.0045
Total precipitated 258 g
Calculation of the Moisturizing Solution Volume (Vsm (IV.2)):
Deviation −0.010
STAGE VI: Post-Treatment Concentration
FL (V.2) is exposed to solar evaporation until a lithium concentration of 37 g/dm3 (3%) is reached, and the following is obtained:
Liquid Phase FL (VI):
FL (VI) Chemistry:
Precipitated Solids at Stage V.2 (SP VI):
Chemistry of Solids SP (VI):
Theoretical calculation of precipitated salt mass:
Deviation 0.0010
Total precipitated=1912 g
Calculation of the Moisturizing Solution Volume (Vsm (VI)):
Deviation −0.027
Harvested crystals are washed with 1.1 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (VI) is reached. Effective volume delivered by Stage VI: 7.05 dm3
STAGE VII: Final Concentration
FL (VI) is exposed to solar evaporation to reach a lithium concentration between 75 g/dm3 and 85 g/dm3. At this final concentration, phases are separated, and the following is obtained:
Liquid Phase FL (VII):
FL (VII) Chemistry:
Precipitated Solids at Stage VII (SP VII):
Chemistry of Solids SP (VII):
Theoretical calculation of the crystallized salt mass at the final concentration stage VII:
Deviation 0.0007
Total precipitated=636 g
Calculation of the Moisturizing Solution Volume (Vsm (VII)):
Deviation −0.022
Harvested crystals are washed with 40 cm 3 of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (VII) is reached. Effective volume delivered by Stage VII: 3.05 dm3
Calculation of Operating Variables
The calculation of the operating variables for an annual production of 10,000 tons of equivalent lithium carbonate was carried out using brine from the Pozuelos Salt flat, when the cooling process included at stage II is carried out with a mechanical cooling crystallization equipment and pre-concentrated brine and with more than 35 g/dm3 is transported to a site with an industrial infrastructure
Stage I: Initial Pre-Concentration Ponds
First Unharvested Period:
Stage I: Initial Ore-Concentration Ponds
Next Unharvested Periods:
This stage is performed in a mechanical cooling crystallization equipment and is detailed for the highest brine flow, i.e. the one corresponding to the post-harvest period for the pond system operation.
Brine to be Cooled
Specific heat: 0.85 kcal/kg ° C.
Salts that crystallize during cooling:
The cooling is executed with a pre-cooling stage, in which the cooled liquid phase with low sulfate anion content, which comes out of the cooling equipment at −7° C., interacts in a heat exchanger, with brine to be cooled that has an initial temperature of 16° C. As a result of this pre-cooling, brine to be cooled enters into the crystallization equipment by cooling at 0° C.
Under these conditions, it is easy to demonstrate that, for a performance coefficient of 60% of the ideal performance coefficient (Carnot), the mechanical energy required per ton of lithium carbonate produced is less than 0.09 Mwh.
Chemical composition of the liquid phase coming out of the cooling equipment:
Stage IV: Final Pre-Concentration Ponds
Next Unharvested Periods:
At the beginning of substage IV.3, 0.92 t of calcium chloride (KCl) is added per ton of equivalent lithium carbonate.
Brine with initial pre-concentration and with a lithium concentration equal to 35.364 g/dm3 is transported to a site with an industrial infrastructure where stages V, VI and VII are performed.
Making the same calculation as that indicated in the item detailed description of the invention when this pre-concentrated brine is transported to a site with an industrial infrastructure, in this case 0.430 t less material between the salt flat and the chosen site is transported (base transport of solids).
Stage V: Treatment
Substage V.1
Quantity of Reagents and Water Used Per Ton of Equivalent Lithium Carbonate
When transporting pre-concentrated brine to a site with a commercial infrastructure, it is convenient to execute stages VI and VII in thermally assisted evaporative crystallizers.
As the specific quantity of water to be evaporated at stages VI and VII is 8,622 kg per ton of equivalent lithium carbonate, using crystallization equipment with evaporation in multiple stages, the specific thermal energy requirement expressed in normal m3 of gas per ton of equivalent lithium carbonate is less than 280. The cost of this energy, coming from any primary source used, is fully offset by the operational advantages, the increased lithium recovery at stages VI and VII, and obtaining by-products such as 400 kg of high-purity sodium chloride per ton of equivalent lithium carbonate and 8,620 dm3 of distilled water per ton of equivalent lithium carbonate.
Specific Water and Reagent Consumption of the Procedure Calculated Per Ton of Equivalent Lithium Carbonate
In this example it is shown how the addition of potassium chloride at the last substage of stage IV allows reaching a higher lithium concentration in the liquid phase that delivers this stage. This not only reduces the reagent consumption at the treatment stage, but it also allows the transport of pre-concentrated brine to a site with an industrial infrastructure to perform stages V, VI and VII. In this example, transport up to a site with an industrial infrastructure, and it is showed that due to the quantity of water that is needed to evaporate at stages VI and VII it is feasible to use thermally assisted crystallization equipment with evaporation in multiple stages.
This Salt flat is a salt deposit located in the Region of Argentine Puna at more than 3,800 msnm.
Field and Laboratory Test
Lithium content in natural brine with which ECL is performed is 0.340 g/dm3 and the volume defined to start the test is 835 dm3. On day 1 840 dm3 of natural brine is extracted by pumping from an existing well in Rio Grande Salt flat. The well has an approximate depth of 30 m and the coordinates that define its location are:
This natural Brine identified as FL(i) is transported to the experimental outdoor center located in the area of Tres Morros, Jujuy province, Argentina, and on the following day it is charged in three similar ponds of about 1.5 m2 each. The average height in the ponds is approximately 0.186 m.
Natural Brine (FL(i))
1ρ (FL (i))
2V (FL (i))
3STD (FL(i))
1ρ (FL (i)): density of liquid phase at stage I
2V (FL (i)): volume of liquid phase at stage I
3STD (FL(i)): Total dissolved solids of liquid phase at stage I
FL (i) Chemistry:
STAGE I: Initial Pre-Concentration
Substage I.1
Brine FL(i) is exposed to the solar evaporation process during 43 days. On day 44, crystals of the Liquid Phase are separated, and the following is obtained.
Liquid Phase FL (I.1):
FL (I.1) Chemistry:
Precipitated Solids at Substage I.1 (SP (I.1))
Theoretical Calculation of the Precipitated Solid Mass SP (I.1):
Deviation 0.0010
Total precipitated 159502 g
Calculation of the Moisturizing Solution Volume (Vsm (I.1)):
Deviation 0.011
Harvested crystals are washed with 120 kg of fresh water. This water mass is approximately equal to half of harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (I.1) is reached. Effective volume delivered by substage I.1:
Brine FL (I.1) is charged into a pond and exposed to continue the solar evaporation process until day 58. That day the solids of the liquid phase are separated, and the following is obtained.
Liquid Phase FL (I.2):
FL (I.2) Chemistry:
Deviation=0.0092
Precipitated Solids at Substage I.2 (SP (I.2))
Total mass SP (I.2)=68.2 kg; H=3.27%
Chemistry of Solids SP (I.2):
Theoretical Calculation of the Precipitated Solid Mass SP(I.2):
1Cryst. W
1Cryst. w = crystallization water
Deviation −0.0165
Total precipitated 65,577 g
Calculation of the Moisturizing Solution Volume (Vsm (I.2)):
1Cryst. w [g]
Deviation 0.011
Harvested crystals are washed with 35 kg of fresh water. This water mass is approximately equal to half of harvested crystal mass.
Wash water is concentrated until the same lithium concentration that has FL (I.2) is reached.
Effective volume delivered by substage 1.2=139.9 dm3
STAGE II: Cooling
On day 68 FL (I.2) is transported to a laboratory where it is cooled at minus seven degrees Celsius (−7° C.) in a freezer for a period of 5 days, and the following is obtained.
Liquid Phase FL(II):
FL (II) Chemistry:
Precipitated Solids at Stage II (SP (II)):
Chemistry of Solids SP (II):
Theoretical Calculation of the Precipitated Solid Mass SP (II):
1Cryst. w
1Cryst. w NE = non-evaporated crystallization water
Deviation 0.0000
Total precipitated 37,384 g
1Cryst. w NE: non-evaporated crystallization water
Calculation of the Moisturizing Solution Volume (Vsm (II)):
Deviation 0.012
Harvested crystals are washed with 25 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass.
Wash water is concentrated until the same lithium concentration that has FL (II) is reached
4.144 kg of CaCl2·2H2O suspended at 4.425 dm3 of fresh water is added to total of FL (II). It is stirred for an hour and phases are separated, and the following is obtained:
Liquid Phase FL(III):
FL (III) Chemistry:
Deviation=−0.003
Precipitated Solids at Stage III (SP (III)):
Chemistry of Solids SP (III):
Theoretical Calculation of the Precipitated Solid Mass SP (III):
This does not include:
Total precipitated: 7,655 g
This does not include: Moisturizing solution.
Calculation of the Moisturizing Solution Volume (Vsm (III)):
Deviation=0.035
Harvested crystals are washed with 4.5 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass.
Wash water is concentrated until the same lithium concentration that has FL (III) is reached.
Effective volume delivered by stage III (L)=100 dm3
STAGE IV: Final Pre-Concentration
On day 79 FL (III) is transported to the experimental outdoor center located in the area of Tres Morros, Jujuy province, Argentina, and is exposed to solar evaporation. The concentration process is continued by solar evaporation, and on day 98 phases are separated by obtaining:
Liquid Phase FL (IV.1):
FL (IV.11 Chemistry:
Deviation=−0.004
Precipitated Solids at Stage IV.1 (SP (IV.1):
Chemistry of Solids SP (IV.1):
Theoretical Calculation of the Precipitated Solid Mass SP (IV.1):
Deviation=−0.0000
Total precipitated 17250 g
Calculation of the Moisturizing Solution Volume (Vsm (IV.2)):
1Evaporated cryst. w
1E cryst w: evaporated crystallization water
Deviation −0.016
Harvested crystals are washed with 14 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass.
Wash water is concentrated until the same lithium concentration that has FL (IV.1) is reached:
On day 99 FL (IVA) is transported to the experimental outdoor center located in the area of Tres Morros, Jujuy province, Argentina, and is exposed to solar evaporation. The concentration process is continued by solar evaporation, and on day 127 phases are separated by obtaining the following.
Liquid Phase FL (IV.2):
FL (IV.2) Chemistry:
Deviation=−0.007
Precipitated Solids at Stage (IV.2′):
Chemistry of Solids SP (IV.2):
Theoretical Calculation of the Precipitated Solid Mass SP (IV.2):
Deviation 0.0000
Total precipitated 2,352 g
Calculation of the Moisturizing Solution Volume (Vsm (IV.2)):
Deviation −0.031
Harvested crystals are washed with 2 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass. Wash water is concentrated until the same lithium concentration that has FL (IV.2) is reached Effective volume delivered by stage (IV.2)=20.1 dm3
STAGE V: Treatment
Substage V.1
20.1 dm3 obtained (FL (IV.2)) is placed in a plastic container with a capacity of 60 dm3. Stirring manually with a plastic shovel, 5.833 kg of calcium hydroxide is added at 7.95 dm3 as a solid. Immediately afterwards, and continuing with stirring, a prepared aqueous solution is added by dissolving 11.183 kg of anhydrous sodium sulfate at 28.14 dm3 of fresh water at 35° C. The heterogeneous mixture obtained after treatment is separated by centrifugation, and the following is obtained:
Liquid Phase FL (V.1):
FL (V.1) Chemistry:
Precipitated Solids at Stage V.1 (SP V.1):
Chemistry of Solids SP (V.1):
Theoretical Calculation of the Precipitated Solid Mass SP (V.1):
Deviation 0.1302
Total
precipitated: 18,663 g
Calculation of the Moisturizing Solution Volume (Vsm (V.1)):
Cryst. w (g)
Deviation 0.006
Drained solids are washed by suspending them at 68 dm3 of fresh water and centrifuged again. Wash water is concentrated until the same lithium concentration of FL (V.1) is reached. The resulting volume of FL (V.1) is:
45.6 dm3 obtained (FL (V.1)) is placed in a plastic container with a capacity of 60 dm3. Stirring manually with a plastic shovel, 300 cm 3 of a 4 N solution (160 g/dm3) of sodium hydroxide is added, verifying that pH reaches 11.2. Immediately afterwards, and continuing with stirring, a prepared aqueous solution is added by dissolving 141.4 g of sodium carbonate at 480 cm 3 of fresh water. Then, and without stopping to stir, a prepared aqueous solution is added by dissolving 1.497 kg of barium chloride dihydrate at 4.290 dm3 of fresh water. The heterogeneous mixture is allowed to stand and then the precipitated solids are separated by vacuum filtration, and the following is obtained:
Liquid Phase FL (V.2):
FL (V.2) Chemistry:
Precipitated Solids at Stage V.2 (SP V.2):
Chemistry of Solids SP (V.2):
Theoretical Calculation of the Precipitated Solid Mass SP (V.2):
Deviation −0.0042
Total precipitated=1,555 g
Calculation of the Moisturizing Solution Volume (Vsm (IV.2)):
Deviation −0.034
Drained solids are washed with 0.9 dm3 of fresh water and centrifuged again. Wash water is concentrated until the same lithium concentration of FL (V.2) is reached. The resulting volume of FL(V.3) is:
FL (V.2) is exposed to solar evaporation to reach a lithium concentration of 37 g/dm3 (3%) and the following is obtained:
Liquid Phase FL (VI):
FL (VI) Chemistry:
Deviation −0.003
Precipitated Solids at Stage VI (SP VI):
Chemistry of Solids SP (VI):
Theoretical Calculation of the Precipitated Solid Mass SP (VI):
Deviation 0.0286
Total
precipitated 8429 g
Calculation of the Moisturizing Solution Volume (Vsm (VI)):
135 moles NaCl
Deviation 0.026
Harvested crystals are washed with 5 kg of fresh water. This water mass is approximately equal to half of the harvested crystal mass.
Wash water is concentrated until the same lithium concentration that has FL (VI) is reached:
FL (VI) is exposed to solar evaporation to reach a lithium concentration between 75 g/dm3 and 85 g/dm3. At this final concentration, phases are separated, and the following is obtained:
Liquid Phase FL (VII):
FL (VII) Chemistry:
Precipitated Solids at Stage VII (SP VII):
Chemistry of Solids SP (VII):
Theoretical Calculation of the Precipitated Solid Mass SP VII:
Deviation 0.0007
Total precipitated=587 g
Calculation of the Moisturizing Solution Volume (Vsm (VII)):
9 moles NaCl
Deviation −0.023
Harvested crystals are washed with 40 cm 3 of fresh water. This water mass is approximately equal to half of the harvested crystal mass.
Wash water is concentrated until the same lithium concentration that has FL (VII) is reached:
The calculation of the operating variables for an annual production of 10,000 tons of equivalent lithium carbonate was carried out using brine from the Rio Grande Salt flat when the cooling process at stage II is carried out in natural crystallizers and stages VI and VII are carried out in solar evaporation ponds.
Stage I: Initial Pre-Concentration Ponds
First Unharvested Period
Stage I: Initial Pre-Concentration Ponds
Next Unharvested Periods
Stage IV: Final Ore-Concentration Ponds
Next Unharvested Periods:
Stage V: Treatment
Substage V.1
Quantity of Reagents and Water Used Per Ton of Equivalent Lithium Carbonate
Ponds of Stages VI and VII
Next Unharvested Periods:
This example shows the importance of the implementation of stage II of the procedure in obtaining more than 18 tons of anhydrous sodium sulfate per ton of equivalent lithium carbonate. In this case, the only option is natural cooling since because of the latent crystallization heat of sodium sulfate decahydrate, the mechanical energy consumption of a cooling crystallization equipment is very high. As is apparent from the results of the field and laboratory test for this example, without adding potassium chloride it is only possible to ensure that the magnesium/lithium mass ratio in the liquid phase only drops from 12.6 in natural brine to 7.3 in brine with final pre-concentration. The increased consumption of lime and anhydrous sodium sulfate required to treat a liquid phase with the referred magnesium/lithium ratio is largely compensated with the production of anhydrous sodium sulfate which is obtained. It is important to note that even when the reagent consumption at stage V is high, lithium recovery is 68% and the environmental impact resulting from the application of the procedure is minimum.
A natural brine from any evaporite is the initial liquid phase entering into stage I. As the procedure evolves, this liquid phase changes its chemical composition and physical properties. But also, when water evaporates from a liquid phase that is saturated, different salts crystallize and precipitate. Then, a safe way to measure the quantity of water that evaporates per time unit from a given area of a liquid phase exposed to solar evaporation is by mass difference. As one of the characteristics of the procedure object of this invention is that in none of the stages involved crystallize and precipitate lithium-containing salts in their chemical formula, the variation in the evaporation rate can be expressed based on lithium concentration, variable related to the physical and chemical properties of the evolving liquid phase.
In the Experimental outdoor center located in the area of Tres Morros, Jujuy province, Argentina, see
Measurements were made using plastic containers capable of containing around 20 dm3 of liquid phase each, making it easy to measure the area exposed to solar evaporation and the mass of each container. Each test began with 300 dm3 of liquid phase, contained in 15 plastic containers. The containers containing brine were initially weighed and exposed to the solar evaporation process. After a period of 4 to 6 days in summer and 15 to 20 days in winter, the containers were weighed again, precipitated solids were separated and drained and an aliquot of the liquid phase obtained to determine the lithium concentration was extracted. For each container, the evaporation rate associated with the corresponding lithium concentration range was determined. Averaging the obtained values, an average evaporation rate corresponding to the arithmetic mean of the average lithium concentration range was determined. The obtained liquid phase was charged into the required quantity of plastic containers, containing 20 dm3 each. The containers were weighed and the new liquid phase mass was exposed again to the solar evaporation process. This results in the evaporation rate corresponding to different lithium concentrations in the liquid phase. Tests are repeated throughout the year and with the obtained results the evaporation rate values are plotted as a function of lithium concentrations for the months of April, May, June, July, August and September (for the southern hemisphere), considered as months with a low evaporation rate; this results in functional dependence on the evaporation rate with the lithium concentration. The same is repeated with the values corresponding to the months of October, November, December, January, February and March (also for the southern hemisphere), considered as months with a high evaporation rate.
5 tests were carried out in the following periods:
Table 10 details the obtained results by expressing the lithium concentration at mg/dm3 and the evaporation rate at dm3/m2, which is equivalent to millimeters per day (mm/d).
Table of TE measurements based on Li concentrations:
TE: Evaporation Rate
These values obtain the functional dependence on the evaporation rate with the lithium concentration for the months with a low evaporation rate and for the months with a high evaporation rate. In this way it is possible to obtain the evaporation rate for any lithium concentration value within the range for which the tests were carried out. The average annual evaporation rate is obtained by averaging the corresponding rate values for the periods with a high and low evaporation rate. The evaporation rate for the operation of a pond with a given lithium concentration is estimated by multiplying the obtained value for the containers, by factor 0.7.
By way of example, Tables A and B below indicate the evaporation rate values for different lithium concentrations, for periods with a high evaporation rate, low evaporation rate and annual average values.
The procedure object of this invention has innovative advantages in relation to the known procedures that are applied and those that are intended to apply. The main advantages are detailed below:
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/ES2018/070460 | 6/27/2018 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/002653 | 1/3/2019 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4271131 | Brown | Jun 1981 | A |
| Number | Date | Country |
|---|---|---|
| 1398785 | Feb 2003 | CN |
| 102099296 | Jun 2011 | CN |
| 2013049952 | Apr 2013 | WO |
| 2014078908 | May 2014 | WO |
| Entry |
|---|
| International Search Report issued in corresponding International Application No. PCT/ES2018/070460 dated Nov. 6, 2018 (2 pages). |
| Written Opinion issued in corresponding International Application No. PCT/ES2018/070460 dated Nov. 6, 2018 (5 pages). |
| Office Action issued in corresponding CN Application No. 201880055506.9 with English translation dated Jan. 19, 2022 (18 pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20230313338 A1 | Oct 2023 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62525024 | Jun 2017 | US |
