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Evolution of Brine and Gas Chemistry Associated with Antimony-Bearing Scale Through Casa Diablo IV Geothermal Heat Exchangers, Mammoth, California USA
Derek CARO, Adam JOHNSON, Ed MROCZEK
[Ormat, USA]
The Casa Diablo IV (CDIV) Power Plant commenced operation in 2022. CDIV increased the overall Mammoth Lakes Geothermal Complex nameplate net generation from roughly 34MW to 66MW. The CDIV facility utilizes production and injection wells that operate independently from the other two power stations (G1, G2/G3). As of 2024, CDIV generates electricity from 4,144 kph of approximately 342°F, single-phase fluid from three production wells. Brine from production fluids undergo three levels of Ormat Energy Conversions (OEC’s), extracting heat and reducing temperatures to approximately 145°F, prior to 100% re-injection. Throughout the history of operation at the Mammoth Geothermal Complex, scale deposition within the OEC equipment has shown to be problematic, resulting in regular mechanical cleanouts and material disposal. While the scale materials have been broadly characterized as antimony sulfide, an in-depth analysis on the scale type, associated brine/gas chemistry, and the physiochemical mechanisms leading to scale deposition have not been well studied. This study includes geochemical analyses of scale samples collected at several locations within the OEC’s during a plant outage, as well as analyses of eight brine and gas samples collected at the inlet and outlet of each OEC unit during normal plant operations. As a result, the geochemical characteristics of the brine and gas were evaluated at temperatures ranging between 339-145°F and pressures ranging between 294-234 psig. These data provide insight to the mechanisms driving scale precipitation within the CDIV power plant and provide a foundation for additional studies including targeted treatment/cleanout programs and thermodynamic geochemical modeling of scale deposition.
Topic: Geochemistry