secondary production from geothermal fluids BRGM processes
BRGM A. F M.E. secondary production from geothermal fluids processes for Lithium recovery 2 nd progress report H. Pauwels C. Fouillac M. Brach Contract MAIM-OO23F(CD) Research funded in part by the Commission of the European Communities Non Nuclear R & D Programme (Geothermal Energy) mars 1989 89 SGN 229 EEE-IRG BUREAU DE RECHERCHES GÉOLOGIQUES ET MINIÈRES SERVICE GÉOLOGIQUE NATIONAL Département Eau - Environnement - Energie Institut Mixte de Recherches Géothermiques B.P. 6009 - 45060 ORLÉANS CEDEX 2 - France - Tél.: (33) 22.214.171.124
secondary production from geothermal fluids BRGM processes
1 - Lithium concentration as a function of the Na/Li ratio (for theabbreviations of samples see table 1)
2 - Schematic representation of different membrane-transportsystems
liste des tableaux
1 - Chemical composition of potential lithium sources
2 - Chemical composition and temperature of the fluids within theDogger rocks of the Paris Basin
3 - Chemical composition of fluids from Triassic rocks in France andEngland
4 - N a and Li contents of the water from two springs in the Massif
5 - Chemical composition of fluids from boreholes in Italy
6 - Acidity constants of selected chromogenic crown ether derivatives
Several types of water, from springs, of geothermal origin, or associated with hydrocarbondeposits, were investigated for their lithium potential. The water comes from Triassic andJurassic sedimentary formations that are in contact with crystalline-basement rocks, in France,the United Kingdom and Italy.
The water from Triassic rocks in Alsace and the Massif Central, and that issuing from thegeothermal field at Cesano, presents highly favourable characteristics for the extraction oflithium. Three extraction techniques can be envisaged, two of which are relatively standard andthe third being quite novel:
1 -Extraction on organic resins for fluids that have the highest Na/Li ratio.
2 -Extraction through carrying the lithium along during precipitation of an aluminiumcompound.
3 -Extraction by means of selective transport of lithium through a membrane .
A selective electrode with a plastic membrane, consisting of an ionophoric composite, wasdesigned for continuous measuring of the lithium content in solution extraction tests.
Lithium is present at various concentrations in natural geothermal fluids. Previoustechnical studies in U S A , Japan and N e w Zealand have shown the potential lithium exploitationin geothermal fluids, even in the case of low concentrations (10 to 20 p p m ) .
In the case of deep aquifers, lithium can be extracted from geothermal waters at marginalcost, the main investments (wells) being paid by the geothermal exploitation.
The present project consists of two main types of work:
- Firstly, a quantitative estimation of the lithium reserves in some French and Italiangeothermal aquifers.
- Secondly, a comparative laboratory study, concerning the efficiency and cost estimates oflithium extraction from selected geothermal waters in typical sites in France and Italy.
Conclusions will be drawn on the efficiency and operating costs for these methods whenapplied to the full range of variations in the "strategic" parameters concerning French and Italiangeothermal fluids (i.e. concentration in Li, p H , Na/Li ratio, fluid temperature, associated heatrecovery, etc.).
The final conclusions of the project will include the technical and economic description of areduced-scale pilot plant, a proposed site, selection of industrial partners and the programme forthe pilot plant.
A - LITHIUM PRODUCTION FROMNATURALLY-OCCURRING FLUIDS
I - POSSIBLE TYPES OF LITHIUM RESOURCES
The high lithium contents in certain waters have led several countries to studying thequantities of lithium metal that could be available. Table 1 shows the chemical analyses of typicallithium-rich waters found in the U S A , Mexico and Japan, which are brines, geothermal watersand sea water.
a - Non-geothermal brines
Except for the fluids shown in Table 1, certain other brines are also used for extractinglithium. For instance, lithium has been produced since many years at Silver Peak in Nevada (277to 416 m g Li/1), Searless Lake in California (70 m g Li/1), Great Salt Lake in Utah (55 m g Li/1), andfrom the Salar de Atacama in Chile. In general, lithium is extracted as lithium carbonate, afterevaporation of the solution and fractionated crystallization of other salts.
Saltón Sea 1
Saltón Sea 2
Table 1 - Chemical composition of potential lithium sources
The water from the Dead Sea in the Middle East, already exploited for its major alkalines,can be considered as a lithium source as well.
AchèresAlfort-VilleAulnay 3Aulnay 4BeauvaisBondyCachan Sud 1Cachan Sud 2Cergy 2Chatenay MalChampignyClichy 1CoulommiersCourneuve SudCourneuve NordCreilCréteil 1Celle St CloudEpernay 1Epinay/SenartEvry 1FontainebleauGarges-les-GorgesHay les RosesIvry/SeineMaisons AlfortMeaux 0Meaux 1Meaux 6Meaux 7MelunMontgeronOrlylPorte St CloudRis-OrangisSevranSucy en BrieTremblayVaux le PenilVigneuxVilleneuve Ga . . .ViletteVilIiersleB....
Table 2 - Chemical composition and temperature of the fluids within theDogger rocks of the Paris Basin
b • Geothermal fluids
Geothermal waters are already used for extracting energy, but in tandem with such heatproduction it is envisaged to extract the metals from certain of such waters, as in the Saltón Seageothermal field (USA) . Furthermore, many of these waters are enriched in lithium, which hasgiven rise to several extraction projects; at Hatchobaru (Japan) for instance the annual lithiumproduction is estimated at 53 tonnes. Other production comes from Wairakei (New Zealand),Arima (Japan) and Cerro Prieto (Mexico).
c - Sea water
Extraction of lithium from sea water has also been studied, even though lithium contentsare m u c h lower than in the fluids and brines mentioned above. The Japanese seem to beparticularly interested in this concept. The total lithium content dissolved in sea water isestimated to be 2.5 x 10 1 4 kg, but the fraction that could be recovered is minimal.
II - POTENTIAL LITHIUM RESOURCESIN THE EUROPEAN COMMUNITY
W e have assembled data on the lithium contents in spring waters, geothermal waters andwaters found in oil and gas wells, this in France, the United Kingdom and Italy. To be of interestas a lithium source, such waters must present two essential characteristics, which are:
- a high lithium content,
- the lowest-possible Na/Li ratio, as sodium is a nuisance for most of the extractionmethods.
a • Sedimentary formations of France and the United Kingdom
Productive layers of lithium-rich waters are the calcareous sedimentary rocks of theDogger in France (Table 2) and the Triassic sandstones of France and England (Table 3). Thelithium concentrations of such waters vary from 2 X 1 O 4 to 2 x 1 O 2 moles/1 (1.4 to 140 mg/1),younger rocks generally having a lower Li content. For instance, the waters from the Doggerrocks in the Paris Basin have not only the lowest Li contents (1.3 to 3.0 x 10-4), but also have aNa/Li ratio of around 1 000 that hinders Li extraction.
The Triassic waters present, in general, much more interesting lithium contents, which aremostly higher than those of the solutions for which lithium extraction was studied, such as thoseof the Dead Sea and Wairakei.
In the Paris Basin, the waters from the Keuper show a lower Na/Li ratio than those fromthe Rhaetian. In England, the waters have generally interesting characteristics, someresembling Keuper water and others being rather like Rhaetian water. The richest waters fromAlsace contain as m u c h Li (3.2 X 10-2 mol/1 or 220 mg/1) as the richest waters for which metalextraction is planned, which are the Saltón Sea and Smackover. However, the Na/Li ratios of, theAlsatian waters, at 60 and 44, are m u c h more suitable for extraction than those of Saltón Sea andSmackover (figure 1).
France : Middle andUpper Trias
Achère 1Achère 2CergyMeilerayChemeryRomorantinChaunoyVert le G . . .Montargis 1Montargis 2Montargis 3Alsace 46-16Alsace GCR1
France : Rhaetien
CourdemangeGrand ville E .GrandvilleSt Jus Sauv.Soudron
England : Trias
Bushey Fa rmBournemouthChilworthCleethorpes SCleethorpes MCleethorpes FMarchwoodSouthampton
Table 3 - Chemical composition of fluids from Triassic rocks in France and England
- 1 . 5 -
- 2 -
- 2 . 5 -
- 3 -
- 3 . 5 -
- 4 . 5 -
• Trias du B.P.<> Trías anglais
log(Na/ü)+ Trias alsacienA Dogger du B.P.
Figure 1 - Lithium concentration as a function of the Na/Li ratio(for the abbreviations of samples see table 1)
The characteristics of the Keuper waters in the Paris Basin and Alsace merit a moredetailed discussion of the composition of these fluids and, in particular, of the behaviour oflithium, so as to be able to estimate the total Li content of this aquifer. The chemical data of fluidspresented here are complete, except for a certain number of oil and gas wells whose fluidchemistry is unknown. However, usually total salinity (TDS) and temperature data are availablefor such petroleum-exploration wells.
Lithium is a chemical element, whose grade in solution depends on certain physical andchemical parameters. For instance, its grade is known to be dependent upon temperature andsodium content (in itself related to total salinity) as was reported by, e.g., Fouillac and Michard(1981) and Kharaka et Mariner (1982).
For this reason we show the temperature and sodium-concentration data in Table 3 in orderto be able to test the relationships between N a , Li and T for the formation waters in Alsace andthe Paris Basin.
The Na/Li/T relationship of aqueous solutions under consideration is governed by thefollowing equation:
N a 2.61log — = 1 690 - p = 0.89
Li 273 + t
where concentrations are expressed in mols/1 and temperature in degrees °C.
This (linear) equation is different from that proposed by Fouillac and Michard (1981), forsolution with a high chlorinity and in contact with the crystalline basement. The equation is alsodifferent from that proposed by Kharaka et al. (1982) for solutions in contact with sedimentaryrocks. Apparently it is thus impossible to obtain a universal equation for the relation betweentemperature and the Na/Li ratio; other factors than temperature also influence this ratio. Suchfactors certainly include the chlorinity of the solutions and the mineralogical composition of thereservoir rock.
However, in our case the correlation is entirely satisfactory for the samples studied and wasestablished with sufficient precision to be significant. The equation should therefore be applicableto waters with an unknown lithium concentration, under the condition that they derive from thesame geological formations.
In view of the fact that in waters from Triassic rocks the ratio N a / T D S varies little and isequal to
Na= 0.30 ± 0.02
it is a variation law of lithium concentration, expressed in g/1 and based on T D S andtemperature (in °C)
1690log (Li) = log (TDS) + 1.57 -
273 + t
Later in this research programme, this equation will be used to obtain an estimate of thelithium concentrations in fluids, of which only total salinity and temperature are known.
b - Other formations in France
Except for the water from the Alsatian Trias, which presents highly favourablecharacteristics for lithium extraction, two springs in the Massif Central (France) appear to beequally favourable. Not only do they contain rather high lithium grades (11.7 x 10-3 mol/1 at LaCroix Neyrat and 3.8 X 1 O 3 mol/1 at Coren), but their Na/Li ratios are satisfactorily low,respectively 40 and 28 (Table 4).
Table 4 - N a and Li contents of the water from two springs inthe Massif Central, France
c - Geothermal brines from Italy
Several of the solutions sampled by Euromin were analysed (Table 5). Compared with otherEuropean sources, these Triassic formation waters have a relatively low lithium content and arelatively high Na/Li ratio. Even so, these fluids are as interesting for lithium production asJapanese geothermal fluids, whose production plans are in an advanced stage.
However, Italy also harbours the Cesano geothermal field, which presents very favourablecharacteristics for lithium production. The strongly-mineralized fluids are very rich in lithium(5 X 10-2 mol/1 or 350 mg/1) and a favourable Na/Li ratio at about 55.
Table 5 - Chemical composition of fluids from boreholes in Italy
B - LITHIUM EXTRACTION FROMGEOTHERMAL FLUIDS -EXPERIMENTAL STUDY
I - QUANTITATIVE LITHIUM ANALYSIS IN SOLUTIONSCONSTRUCTION OF AN ELECTRODE
For all lithium-extraction techniques that can be envisaged, the recovery rate (efficiency ofthe extraction) can be monitored by means of chemical analysis of the experimental fluid. In orderrapidly to obtain a large number of experimental results for a better interpretation of theextraction experiments, it is necessary to dispose over a quicker and more flexible analyticaltechnique than the standard A . A . S . or ionic chromotography.
Specific electrodes permit to obtain continuous results in real time during an experiment.In fact, numerous researchers have tried to develop this analytical technique for lithiummeasurements in h u m a n blood. The authors have used the properties of ionophore compounds forthe development of such specific electrodes, which are still poorly selective as regards lithiumversus sodium or hydrogen (H + ) ions.
For this reason, few people have tried to commercialize such products. The Li electrode soldby Philips is equally sensitive to Li+ ions and protons, and it also reacts strongly to N H 4 + andN a + ions.
Present research is focused on the composition of the sensitive membrane; it is thusnecessary to select:
- the correct Li + ionophore, and
- the correct solvent to be used.
A m o n g the m a n y membranes proposed, Kimura et al. (1987 a and b) designed one whoseNa-Li or H + -Li selectivity appears to be adequate for the analyses that we propose to carry out.
W e are presently engaged in the design of a specific electrode: on the body of a Philips IS561 electrode, a plastic membrane is fitted that is manufactured in our laboratory. The ionophoreused is a crown ether with 4 oxygen atoms (6.6 Dibenzyl-14-crown-4, sold by Fluka) and thesolvent used is nitro-phenyl-octyl-ether ( N P O E ) . The composition of the membrane is thus:
The various products are mixed and deposited on the bottom of a flask, whereafter they areleft to evaporate during a night.
Selectivity tests, reaction time, and the various fields of use are presently being evaluatedfor fluids of the Cesano and Alsace types.
II - LITHIUM EXTRACTION - SELECTION OF TECHNIQUES
Various extraction techniques for lithium can be proposed. Most research concerned seawater, water from the Dead Sea, and geothermal waters (Table 1).
Certain techniques were only tested for extracting lithium from very simple solutions, suchas those that contain only one lithium salt. The major techniques presently known are:
- extraction by precipitation of aluminium,
- adsorption on mineral exchanger,
- extraction by organic solvents,
- extraction on classic resins.
The efficiency of each of these methods depends on the chemical composition andtemperature of the fluid, and certain methods were further studied in the framework of thesolutions w e proposed to study.
a - Extraction by precipitation of aluminium
This is one of the most commonly proposed techniques (Pelly, 1978. Epstein et al., 1981;Yaganase et al, 1983; Schultze, 1984; Rothbaum and Middendorf, 1986). The aim of the method isto carry along lithium during precipitation of an aluminium hydroxide. Lithium can then beeither coprecipitated or adsorbed. Experimental work was done on sea water, geothermal watersand brines. The recommended technique differs according to the fluid in question. In order for thetechnique to be economically viable, it must be possible to recycle the aluminium after extraction.
The aluminium is added to the solution either as AICI3.6H2O or as NaAlC>2, the lattercompound apparently being more efficient, especially when used as a solid.
The optimum extraction p H varies, according to author, from 7 to 12-13. Furthermore,certain chemical elements present in the solution can impede extraction:
- Silicium, which is abundantly present in geothermal fluids, causes aluminium toprecipitate as aluminosilicate, which does not carry lithium with it. However, whenworking at high p H levels, Si apparently does not hinder (Yaganase et ai, 1983).
- Calcium has an adverse effect on the extraction level of lithium, as was mentioned by theauthors that work at a basic p H . It seems that the presence of C a is better tolerated at p Hlevels around neutral. As the calcium must precipitate during the reaction, it isnecessary to remove it from the precipitate, in order to be able to recycle the aluminiumafter the manipulation.
- Magnesium, which has somewhat similar chemical characteristics to lithium, alsodisturbs the proper extraction process. Its presence, however, seems to affect themanipulations at very high basic p H , when it precipitates as a very insoluble hydroxidethat carries the lithium with it.
The various experiments agree on the point that the lithium-extraction rate depends on thetemperature with an inverse relationship. It seems, therefore, that the degree of crystallinity ofthe compound is of primary importance. Furthermore, the quantity of aluminium introduced inthe solution also seems to determine the quantity of lithium carried along during precipitation.
After separating the precipitate from the solution, the Al/Li separation can be effected by re-dissolution in acid of the solid and by using organic solvents.
This technique can be used on fluids that have high Li levels and it seems adequate for theAlsatian waters, which have a low Si content. Experimental work can thus take place at p H levelsclose to neutral, so as to avoid any problems posed by the presence of Ca and M g .
The same situation holds true for the Cesano fluids, which precipitate mineral phasesduring their rise and thus come to surface with low Si and C a contents. The M g content is alreadylow within the reservoir.
Experimental extraction by precipitation of aluminium is thus planned for both Alsatianand Cesano fluids. The research should cover both solid and liquid phases and is planned incollaboration with a C N R laboratory at R o m e .
b - Selective lithium transport through a membrane: the use of crowncompounds
Selective ion transfer through a membrane for extraction of a substance, rests on the sameprinciples as the transport through biological membranes. This technique was twice proposed inthe literature for lithium extraction by Jagur-Grodzinsky and Sheri (1985) and Sakamoto et al.(1987). A typical membrane system is in fact a modified version of the extraction-by-solventtechnique. It consists of a hydrophobic phase (the membrane) which separates two aqueousphases. Chemical elements can migrate from one phase to the other through the membrane ,consisting of a chemical compound that is capable of transmitting them (figure 2).
Based on the type of the compound that governs the metallic-ion transfer, two types oftransport can be described, passive and active.
Passive transport. Here the necessary energy for the separation process is provided by theconcentration gradient of the element to be transported between the two aqueous phases. Thecomplex of the required ion traverses the membrane by diffusion. During its extraction, the cationis accompanied by an anion.
The efficiency of the passive process depends on several factors that must be tested, such as:
- the concentration of the complexing agent in the membrane,
- the concentration gradient between the two aqueous phases,
- the lipophile nature of the anion that accompanies the cation,
- the temperature,
- the diffusion through the Nernst layer on either side of the membrane,
- agitation of the media.
Moreover, kinetic studies have shown that the formation velocity of the complex at the firstinterface and that of the ion liberation at the second, are two determinant factors. Moreover, thenewly-formed complex should not be too stable.
The drawback of passive transport is that the separation is controlled by the concentrationgradient, which means that the process comes to a a stand-still when the two concentrations havereached the same level. Also, in order to extract more than 50% of the lithium in the aqueoussource phase; the transported element must be constantly removed from the receiving phase.Such removal can take place with resins.
M e m b r a n e(lipophilicsolvent)
Li + ,
Figure 2 - Schematic representation of different membrane-transport systems
Active or coupled transport. In this case, transport through the membrane is possiblethanks to another process than that of the simple concentration gradient; such a process can bedriven by electrical or luminous energy, or by using a concentration gradient of another chemicalelement.
In this last case, one can move the ion of interest against its concentration gradient, fromlow to high concentration. Figure 2 illustrates such a case. The compound than can carrierlithium has acid-basic properties: at the first interface it captures the lithium ion, transports it tothe second interface, encounters a more acid solution, and liberates it in order to capture a protonthat it will liberate at the contact with the more-alkaline geothermal solution.
W e plan to adapt this process for the extraction of lithium from sodium-poor solutions, suchas the Alsatian water, as the compounds that can transport lithium can, to a lesser degree, alsotransport sodium. In this case, a membrane must be impregnated with a specific lithiumcompound that, like natural antibiotics, could be a crown compound.
The first crown ether was discovered in 1967 by Pedersen; this was a cyclic polyether(R-O-R), hence its name . This compound could capture in its centre such alkaline ions as were notaffected by traditional complexing agents. The size of the ring depends on the number of ethergroups; compounds with four oxygens (4 ether groups) are the most specific for lithium. Thesimplest of these is 12C4, where the number 12 indicates the number of atoms forming the ringand 4 the number of oxygen atoms.
Numerous derivations of this compound have been synthesized:
- the size of the ring (number of carbon atoms) could be increased;
- cyclical chains or compounds were grafted on to the carbon atoms of the crown;
- bicyclic compounds, called cryptands, were created;
- oxygen atoms were replaced by nitrogen atoms;
- the crowns were opened.
W e were able to draw up a list of 83 specific compounds for lithium, shown in annexe. Fromthis, not exhaustive, list several compounds must be selected for the experimental work, but onlyvery few of such products are commercially available. The choice must also bear in mind thephysical/chemical properties of such compounds. For this reason, w e have added to this list therelevant available data, including their selectivity coefficient compared to other ions. The valuesof the acidity constant when the compounds have acid-basic properties are shown in Table 6 of theannexe. It is important to note that the selectivity coefficients were determined during the use ofthese products for the manufacturing of a specific electrode. However, the crown compound is notthe only determinant factor in the selectivity; the solvent utilized is of equal importance. For thisreason it must be stressed that the values presented here only give an order of magnitude.
c - Extraction on an organic resin
Most classical cationic resins adsorb preferentially sodium and potassium, rather thanlithium. This is in fact one of the reasons that other extraction techniques were investigated.Various resins, commercially available, have however been proposed, such as Amberlite IR 120 Band Dowex 50 W - X 8 C R H . The nature of the eluant then becomes dominant for the Na/Li ratio.Furthermore, this technique can be used twice during this study:
1 - In view of the values of the Na/Li ratio in the waters from the Massif Central (40 at LaCroix Neyrat and 28 at Coren), we plan to adapt this technique to the direct extractionof lithium from these fluids.
2 - Extraction on resin can be used as extraction complement for the separation of lithiumfrom aluminium in the first technique proposed, or for abstracting the lithium from thereceiving solution, in case it is planned to adopt lithium extraction by the technique ofpassive transport through a membrane .
Several geothermal waters found in the European Community where classified as to theirlithium potential.
Lithium in waters from Triassic rocks below France shows a consistent behaviour that isgoverned by temperature and sodium concentration. This regularity made it possible to establisha variation law that will serve for estimating the lithium resources in this reservoir.
In view of their chemical composition and, especially, their advantageous Na/Li ratio,several fluids appear to be suitable for lithium production. These fluids are the geothermal watersat Cesano, Triassic water in Alsace, and certain waters in the Massif Central (Croix Neyrat andCoren).
For each of these waters, three possible extraction techniques for lithium were selected,which will be tested during the coming months. The techniques are:
- coprecipitation with aluminium,
- selective lithium transport through a membrane, and
- adsorption on organic resin.
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