Packed column modelling and experimental evaluation for CO2 absorption using MDEA solution at high pressure and high CO2 concentrations

Abstract

N-Methyl-diethanolamine (MDEA) is a potential solvent to capture CO2 at high-pressure and high CO2 concentration conditions due to its high CO2-loading capacity and the pressure-driven nature of CO2-MDEA reaction equilibrium. However, no studies have been reported on packed column modelling and experimental evaluation of CO2 absorption process using MDEA solvent for high pressure and high CO2 concentration conditions. Therefore, this study presents the experimental evaluation and modelling of CO2 absorption in the packed column using the MDEA solution at these extreme conditions. The effects of amine concentrations (0.83–3 M), liquid flowrates (3.61–5.42 m3/m2h) and feed CO2 concentrations (35–45%) have been studied on the CO2 removal efficiency at 40 bar total pressure and 1.8 kg/h gas flowrate. Highest CO2 removal efficiency is found to be 61.7% for 35% CO2 at 5.42 m3/m2h and 2 M MDEA solution. Further, a rate-based model is developed by accounting for sequential chemical reactions and associated mass transfer resistances occurring at low (<1 molCO2/molMDEA) and high CO2 (>1 molCO2/molMDEA) loadings. The developed model has been successfully validated with the experimental data. In a parity plot of CO2 concentration profiles along the column height, R2 is found to be 0.97. Further the model is applied to forecast CO2 absorption performance over the extended process conditions. It is found that 98.2% CO2 removal efficiency can be achieved for 40% CO2 at the conditions of 333.15 K temperature, 4 M MDEA concentration, and 5.42 m3/m2h liquid flowrates.