Kinetics, modeling, and simulation of carbon dioxide absorption into highly concentrated and loaded monoethanolamine solutions

Kinetics, modeling, and simulation studies were conducted for the absorption of carbon dioxide (CO₂) into highly concentrated and loaded monoethanolamine solutions (MEA). A new comprehensive absorption-rate/kinetics model was developed. The model takes into account the coupling between chemical equilibrium, mass transfer, and chemical kinetics of all possible chemical reactions. The mathematical model is capable of predicting gas absorption rates and enhancement factors from the system hydrodynamics and the physico-chemical properties, as well as predicting the kinetics of reaction from experimental absorption data. A rigorous numerical method to solve the system of unsteady-state partial differential equations was developed. The numerical scheme employed utilizes the Barakat-Clark method for solving diffusive differential equations. This explicit finite difference scheme was found to be very suitable because it is unconditionally stable and gives accurate predictions for concentration profiles as well as for absorption rates of gas into liquid. The model was validated by comparing its predictions with the experimental data of CO ₂ absorption into water and MEA solutions, as well as N₂O absorption into MEA solution.; There are two main experimental contributions. The first reports comprehensive data on the rates of CO₂ absorption into highly concentrated and loaded MEA solutions using both laminar jet absorber (laboratory scale) and packed columns (pilot plant scale). The concentration of MEA solutions ranged from 3.0 to 9.0M, CO₂ loading into solution ranged from 0.007 to 0.49 mol CO₂/mol MEA, and absorption experimental temperature ranged from 293 to 333K. The second recommends a new design for the nozzle of the laminar jet absorber that assisted to produce high quality absorption data without interfacial resistance and interfacial turbulence. The nozzle is a circular hole in a 0.07 ± 0.005 mm thick stainless-steel sheet and the inside diameter of this nozzle is between 0.50 to 0.65 mm. A very thin sheet is used in order to minimize the boundary-layer effects and to approach a flat velocity distribution at the charge point. The flat velocity profile is necessary to calculate the contact-time accurately.; Utilizing the experimental data obtained by the laminar jet absorber and the numerical absorption-rate model developed in this work, new kinetic data for the reaction of CO₂ with highly concentrated and loaded MEA solutions were obtained. (Abstract shortened by UMI.)...