Comprehensive solubility of N2O and mass transfer studies on an effective reactive N,N-dimethylethanolamine (DMEA) solvent for post-combustion CO2 capture

Abstract

The physical solubility and mass transfer performance of CO2 absorption into aqueous N,N-dimethylethanolamine (DMEA) solution were comprehensively studied in the present work. The physical solubility (Henry’s law constant (He)) was measured using a stirred cell reactor for pure DMEA and aqueous DMEA at temperatures from 293.98 to 333.03 K. Then, the physical solubility of CO2 was obtained based on the “N2O analogy” method. Furthermore, He was correlated successfully by using an empirical polynomial model with an average absolute relative deviation (AARD) of 4.23%. The mass transfer performance was studied in a laboratory scale structured packing absorption column at DMEA concentration of 1–4 kmol/m3, liquid feed temperature of 293.15–333.15 K, liquid flow rate of 3.90–11.7 m3/m2-hr, CO2 partial pressure of 6–20 kPa, lean CO2 loading of 0.050–0.300 mol/mol, over the inert gas flow rate range of 26.11–43.52 kmol/m3-hr. Based on the experimental values of He for CO2 into aqueous DMEA solution, the effect of the gas concentration of A in gas-liquid equilibrium (yA∗) on gas phase volumetric overall mass transfer coefficient (KGav) was considered in this study, but found to be an insignificant influence that can be ignored. Analogously, an attempt to correlate the mass transfer coefficient KGav and outlet concentration of CO2 (yout) using semiempirical models as function of the mentioned operational parameters was conducted. The predictive correlations for KGav and yout of the DMEA-CO2-H2O system in structured packing column are KGav=L0.230.6144aeq-aC/pCO2+0.02327 and lnyout=lnyin-0.77PVGΩL0.230.6144aeq-aC/pCO2+0.02327, with acceptable AARDs of 4.59% and 1.48%, respectively.