Lithium: Solar Evaporation versus Thermal Evaporation
Aug 25, 2011
For the last 30 years or so extraction of lithium from brines has been based on solar evaporation. One problem with this kind of process is that it is rather time consuming; it lasts over 14 months. By the time the lithium race takes off in a few years, this method of production may have become obsolete. I have therefore suggested shifting part of Bolivia´s reserves of natural gas to use thermal evaporation in production of lithium carbonate and other evaporite resources in the Salar de Uyuni. Here I comment on a recent response from the manager of the lithium pilot plant to my proposal.
In a recent article published on Bolivian newspaper Pagina Siete, Luis Alberto Echazu, evaporite resources manager, insists, among other things, that the process of exploitation of lithium used in the pilot plant is not obsolete, and reveals for the first time some data about my suggestion to utilize our reserves of natural gas for the extraction of lithium in the Salar de Uyuni. Here, I present a preliminary analysis of the arguments by the aforementioned public official.
First, I maintain that the process used in the pilot project to extract lithium from Uyuni is an obsolete technology because its long cycle of production – of over 14 months - to obtain lithium chloride with 6 % of lithium content before moving on to the chemical plant where they finally produce lithium carbonate, does not appear to be related to the future prospects of the lithium market. Second, with the data provided by the manager of evaporite resources, we can in effect expect a $ 5,460 per ton cost, not of lithium carbonate (as claimed by Mr. Echazu), but of purification of brine (using thermal evaporation instead of solar evaporation) to obtain salts of lithium chloride. This would be the result of multiplying $ 0.021 (the cost of 2,100 BTUs per kg of evaporated water) by the 260,000 liters of water to be evaporated into the purification process of the brines. As indicated by the evaporite resources manager, this cost does not consider the use of other inputs. Here, I guess he refers to some calcium compounds used to mainly precipitate the magnesium, as well as the depreciation of the solar ponds, the labor costs, the laboratoy costs in the pilot plant, and so on. I reiterate that this cost would allow us to produce only the lithium chloride salts with 6% of lithium content and low percentages of magnesium and other elements. From there, we would have to cover the other costs related to the operation of the chemical plant and, most importantly, the use of sodium carbonate. Thus, the total cost of a ton of lithium carbonate would easily exceed $7,000, which would essentially leave us out of the lithium market. However, the data presented by Mr. Echazu uncovers a sad reality, namely that the use of water to purify the brine seems indeed excessive. We're talking nearly three times more water used in brine purification in Uyuni than in the Salar de Atacama by Sociedad Quimica de Minerales (SQM), the largest producer of lithium brines in the world. I imagine that the increase is mainly due to the greater complexity of the brines in Salar de Uyuni and in particular the high content of magnesium. If, however, we used in the calculation, for example, 147 (instead of 260) liters of water needed to purify a liter of brine, ie, a volume only 50% higher than that in Atacama in Chile, the result would be $3,087 per ton for brine purification, a much more reasonable figure. Also, something that the aforementioned public servant didn´t say is that the time of production of lithium carbonate will be reduced significantly: a few weeks rather than over 14 months, with the resulting monetary benefits, over which Mr. Echazu didn´t comment in his article. Third, I would like to remind him that in these calculations the income that could be obtained from potassium chloride and other derivatives of magnesium, sodium, boron, etc. in the form of byproducts throughout the production process of lithium carbonate should also be considered.
Fourth, I'm not so sure about the validity of the linear approach assumed by Mr. Echazu regarding the application of a thermal evaporation process in Uyuni. I just wonder if using natural gas the logic of solar evaporation in the process of brine purification should be maintained. Enough said on this point because it requires more analysis and research. Perhaps it would be good, however, that under the recent agreement with the Koreans, the evaporite resources manager ask them how this matter can be dealt with. I promise this time not say anything about the 100% state participation…
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