Measurement of the effective thermal conductivity of CO2 hydrate with additive cyclohexanone using the needle probe method

Abstract Using CO 2 hydrate formation and dissociation, CO 2 -hydrate-based techniques have been developed for carbon capture, CO 2 sequestration, gas separation, energy storage, desalination, and gas exchange for methane hydrate exploitation. Understanding the effect of additives is crucial for designing, developing, and simulating CO 2 -hydrate-based processes. This study aims to investigate the effect of the additive cyclohexanone on the effective thermal conductivity (ETC) of the CO 2 hydrate sample. A high-pressure apparatus and a needle probe were designed to generate CO 2 hydrate in situ and simultaneously determine the ETC. The performance of the designed needle probe was first validated by measuring the thermal conductivity of an ASTM-recommended reference material, glycerol. Subsequently, the ETC of the CO 2 hydrate sample was measured at different temperatures, pressures, and agitation speeds in the pure water system and compared accordingly. The measured ETC values for the pure water system ranged from 0.603 to 0.649 W m −1 K −1 . In contrast, adding cyclohexanone significantly decreased the measured ETC values, ranging from 0.419 to 0.338 W m −1 K −1 at additive concentrations of 1–10 mass%. By determining and comparing the induction times for systems with and without the additive, cyclohexanone was confirmed as an effective kinetic hydrate promoter for CO 2 hydrate nucleation. The shorter induction time and faster nucleation rate accelerated the formation of hydrate nuclei. The random packing of CO 2 hydrate crystals formed in a short period led to a loosely packed hydrate structure, resulting in a lower ETC in the system containing cyclohexanone.