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Fig. 3 | Geothermal Energy

Fig. 3

From: Scale-fragment formation impairing geothermal energy production: interacting H2S corrosion and CaCO3 crystal growth

Fig. 3

Mineralogical composition of typically dark-colored KIR and DUR scale-fragment samples collected from the heat exchangers (WT) after acid digestion of the carbonate matrix based on powder XRD spectra. The black residua are mainly composed of variable metal sulfide and silica contents of variable crystallinity, i.e., FeS (pyrrhotite), CuFeS2 (chalcopyrite), ZnS (sphalerite), NiS (millerite), and a SiO2 component (quartz or adsorbed silica). Minor contents of Fe3O4 (magnetite) might result from partial later stage oxidation of iron sulfide

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