(371e) Adsorption Equilibria and Kinetics of CO2, CO, CH4, N2, O2, and H2 on Silica-Based Adsorbents

Although various effluent gases have low heating values, they are used as heat sources and generate a large amount of CO₂ in industries. Therefore, the demands for carbon dioxide utilization (CCU) is rapidly increasing as a way for carbon mitigation. Especially, since an iron and steel industry, one of the highest carbon-intensive industries, accounting for 7-9 % of the worldwide CO₂ emissions, can supply various heat sources in processes, CCU applications are more suitable than other industries.

Adsorption technology is promising for CO₂ capture, but its efficiency is critically affected by a desorption energy. However, with respect to CCU in an iron and steel industry, high purity CO₂ capture does not require but CO₂ has to be concentrated to a desirable level from the effluent gases of various processes. Therefore, a weak adsorbent can be applicable for cyclic adsorption processes, considering energy-efficiency at a desorption step.

In this study, the adsorption behaviors of six components (CO₂, CO, CH₄, N₂, O₂, and H₂) on silica-based adsorbents are studied because these components are generally found in effluent gases from iron and steel industries. The adsorption isotherms of each pure gas are measured via a volumetric method at 293, 308, 323 K and pressure up to 1000 kPa. The experimental isotherms are well fitted with the Dual-Site Langmuir model and temperature-dependent Sips model. The isosteric heats of adsorption are calculated with the Clausius-Clapeyron equation. The adsorption kinetics of each component are also analyzed by a non-isothermal diffusional model. The results can contribute to designing efficient adsorption processes to concentrate CO₂ from the effluent gases in iron and steel industries.