Effects of additives on continuous hydrate-based flue gas separation

Highlights: • Multiple stage continuous hydrate-based gas separation process was proposed. • Solution movement characters was observed and analyzed for experimental cycles. • Hydrate saturation for 5% TBAB + 5% THF was higher than that of 19% THF. • 80 min is the appropriate time for rapid hydrate formation process. CO₂ capture from fossil fuel power plants is the main method of CO₂ storage. Hydrate-based gas separation is regarded as a potential method for CO₂ capture from flue gas. In this study, hydrate-based gas separation (HBGS) was used to capture CO₂ from flue gas (19.96 mol% CO₂ and 80.04 mol% N₂), and the continuous experimental process was monitored using magnetic resonance imaging (MRI). The effects of two additives (5 wt% TBAB + 5 wt% THF and 19 wt% THF), two gas injection methods (constant pressure and constant flow rate processes), and of different pressures and flow rates on the hydrate saturation and solution movement were investigated. The results show that both additives effectively promote hydrate formation. The constant pressure process was superior to the constant flow rate process for hydrate formation. Furthermore, the flow rate had little influence on the hydrate saturation. The process was most efficient when a hydrate formation stage time of approximately 80 min was used. The solution movement resulting from the continuous multiple cycles tended to decrease during subsequent cycles. Moreover, the addition of 19 wt% THF had a more obvious effect on the solution movement than 5 wt% TBAB + 5 wt% THF. Solution concentration phenomena were observed in the presence of 19 wt% THF at 285.15 K; these phenomena may have been affected by the formation and dissociation of hydrates. Due to solution movement during the continuous industrial hydrate-based gas separation process, the solution might need to be replenished. Finally, in terms of the resulting the hydrate saturation, the use of 5 wt% TBAB + 5 wt% THF was found to be more suitable in this study, while the 19 wt% THF was more suitable for a higher experimental temperature.