CE H2020 | GEOFLEXHeat: Reducing Geothermal Fouling to Enhance Efficiency and Flexibility
The GEOFLEXHeat project was launched with the goal of developing advanced solutions for managing the reinjection of high-temperature geothermal brine into wells, reducing mineral deposit formation and improving the efficiency of district heating systems. Silica removal becomes essential when the brine temperature is lowered to increase the extractable thermal energy: cooling leads the solution into a supersaturated state, promoting silica precipitation and causing severe scaling in pipes, heat exchangers, and mechanical components in contact with the fluid. At the Bagnore site in Tuscany, the presence of stibnite and silica represents a major challenge throughout all district heating lines, with direct impacts on heat exchangers, pipelines, and operational continuity..
A complex issue: stibnite and silica in geothermal fluids
The geothermal brine from the Bagnore wells reaches temperatures up to 200°C and contains dissolved antimony, sulfur, and silica. Cooling the fluid before reinjection induces supersaturation conditions that favor stibnite and silica precipitation, a phenomenon that narrows pipes, reduces heat exchanger efficiency, and increases maintenance frequency.
Spike’s contribution: designing the silica reduction system
Spike Renewables designed an integrated system consisting of a lime treatment stage for silica removal and a cyclone geometry filtration reactor. This approach relies on rapid and functional silica separation: lime is added after cooling to 80°C, an optimal condition to initiate the formation of calcium-silicate compounds necessary for quick silica removal (within minutes).
Operational sequence and design criteria
The Spike team developed the plant layout and process logic, defining injection points, induction times, and mixing requirements to ensure treatment effectiveness. The addition of inhibitors before brine cooling protects high-pressure heat exchangers, while the cyclone reactor enables fast and efficient lime mixing, reducing the time required for silica precipitation and stabilizing the removal process. This strategy is based on key parameters such as contact time, pH control, and treatment sequencing to avoid chemical interference between additives.
A solution to enhance efficiency and reliability of geothermal systems
Spike’s work in the GEOFLEXHeat project demonstrates how an integrated, scientifically rigorous approach can effectively address structural issues in high-temperature geothermal systems. The combination of chemical inhibition, lime treatment, and advanced filtration increases system efficiency, extends equipment lifespan, reduces maintenance costs, and improves operational stability of the entire reinjection system. Spike’s engineering contribution is central to the scaling mitigation strategy and represents a technological cornerstone of the project.