CE H2020 | GeoSmart: Spike’s System for Silica Reduction in Geothermal Fluids
GeoSmart is a European project dedicated to increasing the flexibility and efficiency of geothermal power plants through innovative thermal storage systems, ORC cycle management solutions, and technologies for fouling mitigation. Within this framework, Spike has developed and implemented an advanced system for reducing silica in geothermal brine, one of the main operational limitations for high-enthalpy plants.
Why Silica Is a Problem in Geothermal Processes
Geothermal brine contains high concentrations of dissolved silica, which remains stable under the high-temperature, high-pressure conditions in the reservoir. When the fluid is cooled to extract more heat, it becomes supersaturated, and silica tends to precipitate as polymers or amorphous deposits. This phenomenon causes scaling in reinjection wells, flow reduction, pipe damage, and efficiency losses in heat exchangers. The requirement to reinject the fluid at high temperatures (100–150 °C) is one of the most restrictive constraints on plant efficiency.
The Spike Solution: A Complete System for Silica Control and Reduction
Spike has developed an innovative treatment system based on three main components: an induction pipe, a scaling reactor, and a retention tank. This system leverages the induction time of silica—i.e., the natural delay between the moment the solution becomes supersaturated and the onset of precipitation—to control and guide polymer formation outside critical lines. The system is designed to cool the brine down to 50 °C while maintaining control over silica formation and preventing deposits in pipelines and reinjection wells.
From Modeling to Design: Chemical and Fluid-Dynamic Process Management
Spike’s approach integrates chemical modeling and process engineering. The combined effects of pH, supersaturation, flow rate, and salinity were analyzed to maximize silica polymerization under controlled conditions. The scaling reactor was designed to enhance contact between particles and surfaces, while the retention tank maintains laminar flow to minimize deposition risks and favor polymer growth in suspension. Test results indicate that under the operating conditions at Kizildere (brine at 451 ppm silica at 104 °C), the system can reduce silica concentration down to the solubility threshold at 50 °C, with an estimated efficiency of 69%.
Advanced Materials and Anti-Scaling Coatings
Spike also contributed to the selection and development of materials to minimize fouling on system surfaces. The use of carbon steel substrates with dedicated coatings—including fluoropolymer, epoxy, and amorphous sol-gel coatings—was validated during the project to reduce silica particle adhesion and ensure greater equipment durability. These coatings, tested in simulated geothermal environments, demonstrated significantly improved anti-scaling performance compared to traditional materials.
From Prototype to Plant: Toward Industrial Demonstration
The Spike system was installed and tested at the Kizildere II geothermal site in Turkey, a GeoSmart partner. The installation includes a 13 m³ reactor and a 7 m³ retention tank, capable of treating an initial flow of 5 t/h with retention times calibrated to the polymerization kinetics measured in the laboratory. Full-scale tests made it possible to verify system effectiveness and optimize operational parameters such as pH, inhibitor dosing, flow rate, and operating temperatures.
More Energy from Geothermal Fluid: A Technical and Economic Advantage
Reducing silica does not only prevent scaling: the ability to lower the reinjection temperature to 50 °C enables the extraction of much more usable energy from the fluid. Overcoming the silica constraint effectively doubles the recoverable heat, with direct impacts on thermal energy production and the feasibility of installing low-temperature ORC cycles.
Spike and GeoSmart: A Key Contribution to Geothermal Efficiency
The silica reduction system developed by Spike represents one of the technological pillars of the GeoSmart project, whose ambition is to enable European geothermal plants to operate more flexibly, efficiently, and in better integration with the energy networks of the future. The integration of chemical modeling, process engineering, and advanced materials highlights Spike’s ability to develop tailor-made solutions for complex geothermal contexts, making a concrete contribution to innovation in the sector.
100RES2020 – Applied Energy Simposium (ICAE): Design of a scaling reduction system for geothermal applications
100% RENEWABLES: Strategies, technologies and challenges for a fossil free future, Pisa, Italy, October 25th-30th 2020