Study On Kinetics Of Thermal Desorption Of Enriched Aqueous Amine Solutions Absorbing Carbon Dioxide

The absorption and desorption rate of gas can be studied by traditionalmethods which include gravimetric method, chromatographic method,concentration method and vascular unloading technique.In this dissertation, the thermal desorption of enriched aqueous aminesolutions which absorbed CO₂have been studied by the technique ofthermogravimetric （TGA） under the non-isothermal conditions. It has beenfound that the desorption of enriched aqueous amine solutions can be dividedinto two stages that the first stage is the desorption of CO₂and theevaporation of H2O, and the second stage is the evaporation/decomposition ofMDEA and other components which have higher boiling points than CO₂andH2O.The Arrhenius parameters and the most possible reaction mechanismfunctions of the thermal desorption process of enriched aqueous aminesolutions have been gotten by the model-free method FWO combined withCoats-Redfern method. The results are shown as follows:（1） the preexponential A of enriched aqueous solutions of MDEA is5.98×10⁶, the activation energy E is45.47kJ/mol, and the reactionmechanism function can be expressed asG（α）＝（1－α）^-1－1;（2） the preexponential A of enriched aqueous solutions of MDEA/DEA is8.65×10⁷, the activation energy E is53.25kJ/mol, and the reactionmechanism function can be expressed asG（α）＝α^3/2;（3） the preexponential A of enriched aqueous solutions of MDEA/PZ is1.59×10⁸, the activation energy E is54.97kJ/mol, and the reactionmechanism function can be expressed asG（α）＝α^3/2.The absorption rate of CO₂can be increased when adding activatorDEA and PZ into MDEA. Desorption is the reversal process of absorption,therefore the thermal desorption of enriched aqueous MDEA solutions whichhas the smallest activation energy E can happen more easily among the threeenriched aqueous amine solutions.Kinetics parameters of the thermal desorption of enriched aqueous aminesolutions can be related to the absorption amount of CO₂. The calculation of activation energy E which can be used as a new index for the selection ofaqueous amine solutions is more convinient than traditional methods.