A Green Amino Acid-based Solvent Blended with Diethanolamine Solution for CO2 Capture Using Micro-contactor

Abstract

The core for carbon dioxide capture is the development of green solvents for absorption processes. The current research aims at the CO2 capture process from a gas stream in a micro-contactor using an amino acid-based green technology containing diethanolamine (DEA) and L-arginine (ARG) solutions. The gas-liquid mass transfer performance has been experimentally assessed in terms of CO2 absorption efficiency (%) and volumetric gas-phase mass transfer coefficient (KGaV). The measurements have been carried out under liquid flow rate (QL: 3.0–9.0 ml/min), gas flow rate (QG: 120.0-300.0 ml/min) at a constant temperature of 45°C, and atmospheric pressure. The aqueous composition of the blended solution was DEA ARG (35 0 wt%), DEA ARG (31 4 wt%), DEA ARG (27 8 wt%), and DEA ARG (23 12 wt%). It was found that an increase in the solvent flow rate from 3.0 to 9.0 ml/min enhanced the absorption efficiency, KGaV, and NGaV by 2.5%, 12.8%, and 2.6%, respectively. However, an increase in the gas flow rate from 120.0 to 300.0 ml/min reduced the efficiency by 6% but improved the KGaV and NGaV by 88% and 225%, respectively. Additionally, the KGaV values followed a declining trend as the contribution of the DEA in the blended solution increased. Based on RSM modeling, the correlations for predicting the KGaV and CO2 absorption efficiency into blended DEA-Arg were successfully established versus independent process variables. According to the optimization results, the maximum absorption efficiency and KGaV were attained at 92.93% and 69.40 kmol/m3.h.kPa for QL of 9.0 ml/min, QG of 263.4 ml/min, CDEA−ARG of (23 12 wt%). Comparing the gas-liquid mass transfer characteristics of the blended DEA-ARG with conventional secondary amine, DEA, in the T-shaped micro-contactor illustrated that presence of L-arginine amino acid with high concentrations of 12 wt%, as a promoter for CO2 capture, can boost the performance of CO2 absorption process.