Adaptabilities of promoters in hydrate-based CO2 capture from simulated flue gases with high-temperature water vapor

Besides CO₂/N₂ mixed gases, actual flue gases also contain high-temperature water vapor exceeding 100 °C. For the hydrate-based CO₂ capture technology from flue gases, except for conventional hydrate formation promoter sodium dodecyl sulfate (SDS), another eco-friendly and high-efficient L-methionine (L-Met) recently emerges, both with great application potential. By using two liquid-injecting modes, three liquids with both 640 and 160 ml volumes of pure water and solutions of two promoters were heated to 110 °C and then injected inside a reactor containing mixed gases to form CO₂ hydrates. Specific adaptabilities and accelerating mechanisms of two promoters were then investigated under high-temperature water vapor scenario. The results indicate that both 0.1 and 1.0 wt% concentrations of promoters embody more significant accelerating effects on hydrate formation than pure water, and the promoter with a concentration of 0.1 wt% has a better effect. Considering the nozzle blockage and promotion efficiency, SDS is more suitable for 0.8 mm nozzles, and L-Met is more suitable for 0.1 mm nozzles. In terms of final averaged water conversion ratios to hydrate, 1.0 wt% SDS appears higher adaptability to 640 ml liquids and 0.1 wt% L-Met to 160 ml ones. The specific acting extent of SDS appears deeper than that of L-Met and the hydrate formed using SDS has coarse-grained morphology and that using L-Met the spherical one. This implies during hydrate formations by using SDS, some liquid water might be conserved inside the capillary pores acting as the water-source to foster continuous hydrate growth; for using L-Met, hydrate formation can absorb some liquid water from a relatively large distance through mobilization behavior of liquid water. This study provides some reference for future industrial-scale application of hydrate-based decarbonization technology from flue gases, especially under high-temperature water vapor scenario.