Undesired mineral precipitation in technical plants is a widespread problem - especially in geothermal power plants. Due to the high salt concentrations in the geothermal fluids and the cooling and pressure relief during energy production, the supersaturation of the fluids on certain minerals such as silicates, carbonates and sulphates is likely. Especially the precipitation of silicates due to supersaturation is problematic, since amorphous silicate phases are characterized by a rapid growth rate. Mineral precipitations in the heat exchanger and other plant components reduce the efficiency of a geothermal power plant and cause downtimes for maintenance and cleaning work.
The BMBF-funded BrineMine project is investigating the use of geothermal fluids for drinking water production and raw material extraction by using membrane processes. The focus is on reverse osmosis and membrane distillation, which is used to concentrate the solids dissolved in water and separate the drinking water. To prevent scaling, a pre-treatment of the fluids by selective removal of potential scaling agents is necessary. The focus of this work is the removal of dissolved silica from a model solution whose composition was modelled on the chemical composition of a thermal spring in Chile.