CO₂ Heat Of Absorption And Solubilities In Aqueous MDEA And MDEA-PZ Solutions:Experiment And Modeling

In the CO₂ washing process with amine,the research on the regeneration energy consumption of CO₂-rich aqueous amine solution is of great significance to the selection of solution and the optimization of process.This work conducts the calorimetric measurements on the CO₂ heat of absorption and solubilities on aqueous 30 wt%and 50 wt%MDEA solutions and 40+10 wt%MDEA-PZ solutions at different temperatures（323.15,353.15 K）and pressures（0.5,1.0,2.0,4.0 MPa）.Combined with literature data,the effects of CO₂ loading,temperature,pressure,amine concentration and addition of PZ on the absorption process are deduced.The experimental results show that for aqueous solution with high concentration of amine,the increase of pressure and the decrease of temperature lead to lower heat of absorption in the non-saturation zone of CO₂,while enhancing the heat in the saturation zone.The concentration of MDEA has no apparent effect on the heat of absorption,but the addition of PZ increases the overall heat curve,especially when CO₂ loading is low.The CO₂ solubilities determined by calorimetric measurement are consistent with the VLE experimental results,while pressure,temperature and MDEA concentration are all influential factors.However,the composition of MDEA/PZ shows no effect.The CO₂ absorption process is then simulated based on electrolyte NRTL model by Aspen Plus.It is found that the predicted heat of absorption is in good agreement with the experimental results,especially in the case of low pressure.According to the analysis on the speciation and the contribution of each reaction,it is found that the addition of PZ at low CO₂ loading inhibits the reaction between aqueous MDEA solution and CO₂.Finally,the influence of MDEA/PZ composition is studied,and the results show that the concentration of PZ has significant effect on the heat of absorption,while the MDEA concentration influences mainly the solubilities.