AT THE END OF THIS STUDY CONCLUSIONS WILL BE DRAWN ON THE EFFICIENCY AND OPERATING COSTS FOR THESE METHODS WHEN APPLIED TO THE FULL RANGE OF VARIATIONS IN THE "STRATEGIC" PARAMETERS CONCERNING FRENCH AND ITALIAN GEOTHERMAL FLUIDS (I.E.: CONCENTRATION IN LI, PH, NA/LI, RATIO, FLUID TEMPERATURE, ASSOCIATED HEAT RECOVERY, ETC...).
THE FINAL CONCLUSIONS WILL INCLUDE THE TECHNICAL AND ECONOMIC DESCRIPTION ON A REDUCED SCALE PILOT PLANT, A PROPOSED SITE, SELECTION OF INDUSTRIAL PARTNERS AND THE PROGRAM FOR THE PILOT PLANT.
The goals of this work were to study the potential for lithium production from geothermal fluids within territories of the European Community.
Data were collected on the lithium contained in geothermal waters, and in water from springs and boreholes, in France, the United Kingdom and Italy. For each of these fluids, the chemical composition was studied.
Estimates were made of the lithium reserves contained in 3 of the fluids. The 2 reservoirs in Italy (Cesano and Latera) contain, respectively, 7500 and 2000 tons of lithium. In northern Alsace, it is estimated that a 15 X 15 km block of Buntsandstein and Muschelkalk reservoirs contain about 200000 tons of lithium. However it is not possible to evaluate the amount of lithium that could in reality be mobilzed.
Tests to extract the lithium through the precipitation of aluminium, have given very encouraging results for the Cronenbourg and Cesano fluids. The lithium is adsorbed on amorphous aluminium trihydroxide; this adsorption is quite efficient at high temperatures and at a pH that is close to that of the original solutions. Moreover, quite modest amounts of aluminium are consumed. It is possible to eliminate all other elements that remain in contact with the precipitate by washing with distilled water, which leaves just the lithium and the aluminium in the solid phase. The presence of fluoride ions in the solution can hinder the lithium extraction, but the reverse of this medal is that the same fluorides can be used to desorb the lithium, in order to recover it after its extraction from the geothermal fluid.
THE STUDY CONSISTS OF TWO MAIN TYPES OF WORK :
- FIRSTLY, A QUANTITATIVE ESTIMATION OF THE RESERVES OF LITHIUM IN FRENCH AQUIFERS, USING THE ACTUAL DATA (ANALYSIS OF WATERS, PRODUCTIVITY, ETC...) AND NEW INFORMATION COLLECTED FROM MEASUREMENT, SAMPLING ANALYSIS AND LOG INTERPRETATIONS SPECIFICALLY MADE IN ORDER TO DETERMINE THE CONDITIONS FOR FURTHER EXPLOITATION.
THE STUDY WILL BE CONCENTRATED ON TRIASIC SANDSTONES IN PARISIAN BASIN AND ALSACE WHERE LITHIUM CONTENTS OF RESPECTIVELY 50 PPM OR 200 PPM HAVE BEEN OBSERVED.
IN ITALY, A COMPILATION OF EXISTING DATA FOR LITHIUM IN GEOTHERMAL DRILLHOLES WILL BE CONDUCTED. ADDITIONAL SAMPLING AND ANALYSIS ON SPRINGS AND DRILLHOLES WILL ALSO BE PERFORMED. FIELD SAMPLING, LITHIUM ANALYSIS, AND MAJOR ELEMENTS ANALYSIS FOR GEOTHERMAL FLUID CHARACTERIZATION, WILL BE CARRIED OUT BY EUROMIN.
- SECONDLY, A COMPARATIVE LABORATORY STUDY, CONCERNING THE EFFICIENCY AND COST ESTIMATE OF LITHIUM EXTRACTION FROM GEOTHERMAL WATERS SELECTED IN TYPICAL SITES IN FRANCE. SEVERAL METHODS ARE NEEDED FOR THIS :
1) TESTS IN ORDER TO PRODUCE ALUMINATE OF LITHIUM USING COPRECIPITATION WITH ALUMINIUM WILL BE CARRIED OUT ON WATERS FROM THE PARISIAN BASIN WHOSE NA/LI RATIO IS NOT FAVORABLE FOR THE DIRECT USE OF RESINS.
AL-LI SEPARATION WILL BE THEN CARRIED OUT USING DISSOLUTION IN HIGHLY BASIC OR ACID MEDIUM FOLLOWED BY LI FIXATION USING RESINS.
2) TESTS USING RESINS (AS AMBERLITE IR40B AND CHELEX 100) WILL BE CARRIED OUT DIRECTLY ON WATERS FROM ALSACE AND ITALY, AND ON CONCENTRATED ALUMINATE DISSOLUTION FROM THE COPRECIPITATION STEP DESCRIBED ABOVE.
3) A SPECIFIC INNOVATIVE WORK WILL BE PERFORMED IN ORDER TO SELECT AND TO EVALUATE SUBSTANCES WITH HIGH LITHIUM SELECTIVITY.
CHELATING FUNCTIONS, AND MORE SPECIFICALLY PROPERTIES OF CROWN ETHERS WILL BE EXAMINED.
THIS PART OF THE WORK WILL BE CARRIED OUT IN COOPERATION WITH C.N.R. (ISTITUTO TRATTAMENTO MINERALI).
Funding SchemeCSC - Cost-sharing contracts