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Development of a fluid treatment strategy to enable combined raw material and freshwater recovery from geothermal fluids

The energy transition and the associated need for non-energy, mineral raw materials have prompted the German government to expand research and development activities along the entire value chain. It is well known that the highly mineralized thermal waters that circulate during the extraction of geothermal energy have, in some cases, significant enrichments of economically strategic elements such as lithium, rubidium, antimony or magnesium. The extraction of mineral resources from thermal waters is still challenging in terms of process technology, but new sustainable methods are paving the way for economic extraction as an alternative to conventional hard rock mining. Due to the overall high salt concentrations, selective separation of scale-forming minerals in a pretreatment stage is necessary to avoid scalings or membrane fouling in the later process steps. The focus of this study is on controlling silicate precipitation, which is expected to occur due to temperature changes and proceeding concentration cycles, which are required for raw material and freshwater extraction. The treatment and an associated precipitation process must be cost-effective, integrable into the power plant process, and selective for silica but must not affect the concentration of valuable elements. In a multi-step and interdisciplinary process, a treatment strategy was developed and implemented in a large-scale prototype. In this study, the development of the silica processing strategy from laboratory to prototype design is described. Finally, the construction and implementation of a large-scale prototype with promising field results are presented.


Valentin Goldberg1, Daniel Winter2, Fabian Nitschke1, Diego Morata3, Joachim Koschikowski2, Thomas Kohl1
1Karlsruhe Institute of Technology, Germany; 2Fraunhofer Institute for Solar Energy Systems ISE, Freiburg; 3Department of Geology and Andean Geothermal Center of Excellence (CEGA). Facultad de Ciencias Fisicas y Matemáticas, Universidad de Chile
GeoKarlsruhe 2021