GeoSmart: Spike’s Demonstration Plant for Silica Control
In the European GeoSmart project, Spike is responsible for the design and construction of the demonstration system dedicated to reducing silica in geothermal brines. This plant enables reinjection temperatures to be lowered to 50 °C, overcoming one of the most significant limitations in extracting heat from geothermal wells. The need to prevent silica precipitation has historically required high reinjection temperatures, reducing the amount of recoverable useful energy. The system developed by Spike is specifically designed to control scaling phenomena and improve the overall efficiency of geothermal plants.
Plant Configuration: Scaling Reactor and Retention Tank
The GeoSmart demonstrator is based on a two-stage system designed to separately manage the two main mechanisms responsible for silica precipitation: surface deposition and polymerization in solution.
The first component is the scaling reactor, a 10 m³ rectangular reactor designed to promote silica deposition through a forced internal flow path, high flow turbulence, and pH control between 8 and 9. Here, silica intentionally precipitates onto internal plates specially designed to be removed, cleaned, and reinstalled.
The second component is the 10 m³ retention tank, where the flow is maintained in laminar regime and the pH is reduced to around 5 to promote polymerization of the remaining silica and prevent deposition in downstream lines.
Silica Extraction System: A Unique Design
One of the main innovations of the demonstrator is the silica extraction system integrated into the scaling reactor. The reactor is equipped with two large sliding “drawer doors,” each containing removable internal plates mounted on wheels that slide along internal and external rails. This solution allows operators to easily extract the panels where silica accumulates, simplifying cleaning and material recovery operations.
The design involved FEM analysis for dimensioning reinforcements and structural components, as well as CFD analysis to optimize flow paths and turbulence distribution inside the reactor.
Materials, Coatings, and Compatibility Testing
Material selection was driven by the need to ensure corrosion resistance and stability under the aggressive conditions of geothermal brine. The scaling reactor is made of AISI 304L stainless steel, while the retention tank uses SA516 Gr. 70 carbon steel. Both solutions were validated through a coupon testing campaign carried out in simulated geothermal fluids at pH 5 and 104 °C.
SEM/EDX analyses, corrosion tests, and optical profilometry confirmed the suitability of the alloys and the effectiveness of Belzona and Sakaphen coatings in reducing silica adhesion on the system’s internal surfaces.
Construction of the Plant and Delivery to the Demonstration Site
The construction of the two reactors took place in 2022 at workshops selected by Spike. The system was completed, mechanically tested, and packaged for transport to the demonstration site operated by Zorlu Energy in Kızıldere-II, Turkey. The Turkish site is one of the region’s most significant geothermal areas, with brines featuring high silica concentrations and operating conditions ideal for validating Spike’s system.
Toward Field Validation and Expected Benefits
The GeoSmart demonstrator will enable field verification of the system’s effectiveness in reducing silica, controlling fouling in reinjection wells, and improving overall plant efficiency. Preliminary simulations and tests indicate that the outlet concentration from the reactor can be reduced from 451 ppm to about 265 ppm, achieving an expected removal efficiency of around 69%.
This result would allow safe lowering of reinjection temperatures, recovery of more heat, and potentially enable the use of recovered silica in high-value industrial supply chains. The plant represents one of the major technological outcomes of the GeoSmart project and offers a replicable solution for other high-enthalpy geothermal settings.