Mass transfer coefficient of hybrid amines

https://doi.org/10.1039/C7RA01352C

“Usubharatana, et al.⁷⁴ have studied K_GCO2a_V for CO₂ absorption by using a hybrid solution containing MEA and methanol. Their experiments were carried out on a laboratory-scale absorption column with a 0.4 m packing height and a 0.034 m diameter, packed with DX-type structured packing with a specific surface area of around 900 m² m⁻³. They showed that by increasing the methanol concentration in the MEA solution, K_GCO2a_V increased. By increasing the liquid flow rate, K_GCO2a_V increased and led to a decrease of the methanol carryover because of its vaporization to the top of the absorber column. Fu, et al.⁶⁰ have obtained experimentally K_GCO2a_V by using a hybrid solution containing MEA and methanol. They performed the experiment on a structured absorber column (packing height 1.25 m; column diameter 0.028 m) packed with a DX packing. They reported the CO₂ concentration and temperature data along the height of the packed column (seven points along column) for 33 tested runs. The effects of key process parameters including the MEA concentration, CO₂ loading, amine flow rate and gas flow rate were investigated, and it was found that K_GCO2a_V decreased with increasing CO₂ loading, gas flow rate (in higher concentrations of the MEA solution), and CO₂ concentration in the inlet feed gas. The authors suggested using a high liquid-to-gas ratio and a low temperature of the feed gas and amine in the absorber column in order to prevent the vaporization of methanol at the top of the absorber column. Gao, et al.⁷⁵ have studied the effects of different process parameters on the K_GCO2a_V values using a hybrid solvent: MEA–methanol. The experiments performed on an absorber column (packing height 3 m; column diameter 0.15 m) packed with three different packing types including Sulzer BX500, Mellapale Y500, and Pall rings 16 × 16. Their results indicated that the Sulzer BX500 had higher K_GCO2a_V values than the Mellapale Y500. The reason for this was the good uniform distribution of gas and liquid on the packing surface. In addition, their results showed that (1) the K_GCO2a_V values increased as the CO₂ lean loading decreased and the hybrid solution temperature, hybrid solution flow rate and gas flow rate increased, (2) the optimal temperature for reducing methanol evaporation was 20 °C, and (3) operating at a high liquid-to-gas ratio led to a reduction of methanol evaporation as suggested by Fu, et al.⁶⁰ study.”