Minerals and fresh water extraction from geothermal sources

The use of the very limited freshwater resources in northern Chile presents a very great potential for conflict between the indigenous population and, above all, the mining industry. In addition to their use as energy sources, the brines produced in Chile's extensive geothermal sources could also be used to produce fresh water, which could help defuse the growing conflicts over the use of water resources. In addition, these brines often contain recyclable materials. The extraction of minerals such as lithium, magnesium, potassium, boron or gold from geothermal brines is not easy from a technological standpoint, but still quite possible. In the future, this is likely to be economically viable under appropriate conditions.

BrineMine's goal is therefore to develop and test a multi-stage process that will allow geothermal brines to be concentrated to selectively separate minerals and extract fresh water. Most geothermal sources in Chile have so far been characterised only by their essential elements. Further exploration is therefore intended to provide detailed information on the mineral content of various sources and their intrinsic value, enabling an economic analysis of the new process.

Process development and initial implementation

The aim of the project is the development of a multi-stage process for the recovery of minerals from geothermal brines, which consists of a pre-treatment stage, a reverse osmosis stage and a membrane distillation stage. The innovative approach is primarily in the use of membrane distillation as a thermal separation process, which is very well suited for use at very high salt concentrations. The thermal energy requirement can be covered directly from geothermal energy.

Heat is first extracted from the geothermal brine. The then cooled and still relatively weakly concentrated fluid is then fed into a reverse osmosis process, where preconcentration takes place. At the same time, a significant portion of the fresh water is recovered here. The concentrate of the reverse osmosis process is then fed into the membrane distillation process for further concentration into the region of saturation. In the course of the project, methods for selective solids separation will be investigated.

The content of the project is divided into three phases: In the first phase, preliminary examinations are carried out in the field and in the laboratory. These include the sampling and analysis of various geothermal brines as well as experiments in the laboratory with artificial and real brines for the investigation of thermal and concentration-induced scaling. In the second phase, a demonstration plant will be developed and
 

built. For this purpose, potential demonstration sites are being explored and the engineering of the demonstration plant integration carried out. In addition, the process technology of the demonstration system will designed and, finally, the demonstration plant will be built. In the third phase, the demonstration plant will first be commissioned in a technical centre in Santiago and then transferred to the demonstration site and operated there. The operating results will be analysed and evaluated.

Throughout all three phases of the project, models for commercialisation will be developed on the basis of brine analyses, current and prospective raw material prices as well as planned investment and operating costs of the extraction plants.

Testing of feasibility and profitability analysis

The BrineMine project is intended to provide two essential insights: Firstly, the technical feasibility of the newly developed process will be tested, demonstrated and evaluated. Secondly, whether and under what technical and economic conditions the extraction of minerals from geothermal sources can be useful and to what extent it could supplement conventional mining in the future is to be clarified. The extraction of fresh water can also play an important role here. Furthermore, the project should initiate interdisciplinary and international cooperation between German and Chilean geohydrologens, process engineers, geothermal companies and plant builders as well as form the basis for long-term cooperation. An industrial workshop in Santiago after 18 months should present the initial results and arouse industry interest in BrineMine technology.