Preliminary Assessment of CO2 Compression Behavior Modified by [BMIM][AlCl4] for Engineered Geothermal Working Fluids
Year: 2026
Type: article
Abstract: Closed-loop geothermal systems (CLGS) benefit from engineered working fluids, and supercritical CO 2 is a leading candidate due to its low viscosity and buoyancy-driven circulation. However, system performance depends sensitively on CO 2 compressibility and behavior near the critical region. Ionic fluids (IFs) offer a potential route to tuning these properties, yet their interaction with CO 2 under geothermal high-temperature, high-pressure (HTHP) conditions is not well understood. This study examines the mixing behavior of [BMIM][AlCl 4 ] with CO 2 using constant composition compression experiments at 30, 50 and 100 °C up to 25 MPa. The results show that [BMIM][AlCl 4 ] alters CO 2 thermodynamic response: mixtures retain substantially higher volume, near-critical compressibility peaks are strongly suppressed, and gas-like fluid-like crossover pressures shift upward. Volume-matching analysis reveals CO 2 dissolution into the IF and microstructural reorganization of the halometallate phase. These findings demonstrate that [BMIM][AlCl 4 ] acts as an active thermodynamic modifier rather than an inert additive. For geothermal applications, such IF-induced stiffening and fluctuation suppression could affect density control, circulation stability, and heat-extraction performance in CO 2 -based CLGS. The results provide foundational data for designing IF-CO 2 working fluids tailored for next-generation geothermal systems.
Source: Geothermics
Authors: Damian Janiga, Paweł Wojnarowski
Institution: AGH University of Krakow
Language: English
Subfield: Catalysis
Field: Chemical Engineering
Domain: Physical Sciences
SDG: Climate action
Open Access status: hybrid
Estimated APC paid: $3,220
Award: G1459185487
OpenAlex ID: W7166141991