Thermodynamics of Halite Scaling in Superhot Geothermal Systems

Lodin Ellingsen () and Tore Haug-Warberg
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Lodin Ellingsen: Department of Chemical Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
Tore Haug-Warberg: Department of Chemical Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway

Energies, 2024, vol. 17, issue 12, 1-10

Abstract: Over the past decades, considerable research has been conducted on extracting energy from superhot geothermal reservoirs, where temperatures are higher than at the critical point of water. A major challenge when operating wells under such conditions is managing scaling in an effective manner. In this study, the thermodynamics of the precipitation and scaling of crystalline NaCl (halite) under superhot conditions is explored using the H 2 O – NaCl system as a proxy. Phase diagrams in pressure–enthalpy and pressure–entropy coordinates are used to illustrate how scaling occurs in idealized processes, such as the isenthalpic expansion of geothermal fluid to the wellhead or the isentropic power generation of a steam turbine. Particular emphasis is placed on explaining the non-trivial graphical composition of these phase diagrams in an accessible manner. A wellhead sample and an estimate of the downhole conditions are used as points of reference in the discussion of scaling. All thermodynamic properties, including the solubility of NaCl in water vapor, are calculated using a newly developed equation of state by the same authors as in this article.

Keywords: NaCl; brine; saline; salt; phase diagram; enthalpy; entropy; equation of state; solubility; precipitation; supercritical (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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