Investigation of CO2 desorption kinetics in MDEA and MDEA+DEA rich amine solutions with thermo-gravimetric analysis method

Abstract

In this paper, by means of thermo-gravimetric analysis(TGA), the desorption kinetics of CO2 absorbed in two kinds of rich amine solutions, MDEA (3.25mol/L) and MDEA+DEA(3.25mol/L-0.3mol/L), were investigated under different heating rates(2.5℃/min, 5℃/min, 10℃/min and 20℃/min). The thermal analysis kinetics was applied to analyze the TG-DTG curves of two rich amine solutions so as to research CO2 desorption kinetics. In addition, the CO2 desorption kinetics parameters have been calculated with model-free method Flynn-Wall-Ozawa (FWO) and model-fitting method Coats-Redfern (CR). The results indicated that CO2 desorption process could be divided into two stages. The CO2 and H2O were released with non-uniform speed in the first stage and MDEA or DEA with higher boiling points were evaporated in the second stage. For MDEA solution the average activation energy E was 50.36kJ/mol, the pre-exponential factor A was 1.68×107, and the most probable integral mechanism function was Gα=α3/2. For MDEA+DEA solution the average activation energy E was 59.68kJ/mol, the pre-exponential factor A was 2.22×107, and the most probable integral mechanism function was Gα=[(1+α)1/3−1]2. The technical feasibility of CO2 desorption performance in rich amine solutions with thermo-gravimetric analysis method was demonstrated.