| Abstract |
Geothermal sources are very aggressive natural environments and thus represent a major threat to the integrity of the various components of geothermal power plants including liners and well casings, wellheads, turbines, etc. Dissolved CO2, H2S, NH3 gases, sulfate and chloride ions are the dominant elements generating corrosion, heavily dependent on operational factors such as the pressure, temperature, flow rate, oxygen concentration, suspended solids, flow regime and pH level of the geothermal fluid. The materials currently used are either not always capable of performing in such harsh environments thus leading to a constant need for maintenance (e.g. carbon steel), or highly expensive (e.g. Ni-/Ti-based alloys). Therefore, the geothermal industry needs to improve plant capability to withstand this harsh environment, to maintain the equipment lifetime and generation efficiency. Additionally, there is the requirement to produce better geothermal power plant equipment protection design concepts through virtual prototyping to meet the increasing requirements for lifecycle costs, environmental impacts and end-of-life considerations. To this aim, the scope of the Geo-Coat project is threefold: (a) to develop and test in geothermal environments specialized corrosion- and erosion-resistant coatings, based on selected High Entropy Alloys (HEAs) and Ceramic/Metal mixtures (Cermets), to be applied through thermal powder coating techniques (High velocity oxygen fuel spray, Laser metal deposition, Electrospark deposition, Electroless plating), (b) to develop a multi-phase, multi-component, high-temperature and high-pressure fluid flow simulator software including corrosion, erosion and scaling formation models and (c) to integrate the simulator and the coatings experimental results, to provide a powerful decision-based system for geothermal power plant operators. Preliminary results demonstrated promising corrosion and tribological performances for some of the tested coatings in lab-based simulated geothermal environments. |