A green vapor suppressing agent for aqueous ammonia carbon dioxide capture solvent: Microcontactor mass transfer study

Highlights: • Ammonia-glycerol hybrid solvent evaluated for CO₂ capture. • Mass transfer performance of solvent assessed in T-shaped microchannel. • Box-Benhken method used to design the experiments and analysis of the results. • Higher K_Ga_V values in microchannel reactor compared to other operating units. Aqueous ammonia is a promising carbon dioxide capture solvent and has recently attracted significant attention, but its main problem is high evaporation rate of ammonia in the absorber. Glycerol, which is a by-product of biodiesel, has hydroxyl groups that bind to ammonia molecules. Hence, it can reduce the vaporization of ammonia as an additive and improve the CO₂ absorption properties. In this work, the mass transfer performance of glycerol, as an ammonia vaporization reduction additive, was investigated. Carbon dioxide absorption experiments using ammonia-glycerol hybrid solvent have been done in a T-shaped microchannel. The impact of process condition, including ammonia concentration (4–10 wt%), glycerol concentration (1–3 wt%), liquid flow rate (3–9 ml/min) and temperature (20–40 °C) was investigated on the volumetric overall mass transfer coefficient (K_Ga_V), absorption percentage (AP) and volumetric molar flux (N_Aa_V). According to the results, rising the glycerol concentration in the range of 2–3 wt% leads to an increase in K_Ga_V by 4.8%. Hence, the addition of glycerol to aqueous ammonia not only increases the mass transfer coefficient but also reduces the vapor pressure of ammonia as a green vapor suppressing agent and diminishes the ammonia loss in the absorption tower.