Experimental Investigation of Deposition of Silica Nanocolloids by Depressurizing Supercritical Water Vapor

Silje Bordvik, Morten Tjelta and Erling Næss ()
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Silje Bordvik: Department of Energy and Process Technology, Norwegian University of Science and technology (NTNU), Kolbjørn Hejes vei 1D, 7034 Trondheim, Norway
Morten Tjelta: Corrosion Technology Department, Institute for Energy Technology (IFE), Instituttveien 18, 2007 Kjeller, Norway
Erling Næss: Department of Energy and Process Technology, Norwegian University of Science and technology (NTNU), Kolbjørn Hejes vei 1D, 7034 Trondheim, Norway

Energies, 2025, vol. 18, issue 4, 1-25

Abstract: This article presents the results of an experimental investigation of silica deposition from depressurized supercritical steam. The case investigated is relevant for supercritical geothermal reservoirs with high temperature and pressure, where silica content is significant and deposition occurs rapidly upon depressurization. The purpose of the presented experiments is to accurately measure the deposited mass in two different areas in a flow tube and mathematically relate the measurement to particle formation behavior. In addition, SEM analysis permits valuable insight into the morphology of the scale formed under these conditions. The measured deposition is caused by silica solids formed when depressurizing supercritical fluids from around 350 bar and 500 °C by an isenthalpic valve to a state of superheated steam and pressures ranging from 60 to 150 bar. A test rig was designed, fabricated, and used for this purpose. The deposition mechanisms differ from silica particle formation in the water phase and the limited experimental research for the investigated conditions makes the gathered data highly interesting. The measured results are compared to validated models for deposition in straight pipes. The knowledge obtained on silica solidification and deposition can be used to optimize steam treatment of high-temperature pressurized geothermal sources for maximum power utilization by aiding in the development of advanced prediction tools for scaling and mineral extraction.

Keywords: silica; precipitation; supercritical; superheated steam; nanocolloid; deposition; high supersaturation kinetics; high temperature geothermal; hydrothermal steam (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: 2025
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