Absorption And Regeneration Performance Of Ionic Liquid Activated MDEA Solutions For CO₂ Capture

With the rapid development of human civilization and technology, excessive emissions of carbon dioxide has caused serious negative impact in global environment and human health. Thus, the research about decarbonization technology is urgent. In order to improve the absorption performance of traditional organic amine, amino acid ionic liquids activated organic amine is an effective method. This will not only give full play to the advantages of amino acid ionic liquids’high absorption efficiency and organic amine’s high absorption capacity, but also overcome the high viscosity and high cost of ionic liquids and high corrosion resistance and ease decomposition of organic amines.In order to discover the influence of temperature, solution composition and pressure on CO2 absorption in aqueous solutions of N-methyldiethanolamine (MDEA) and tetramethylammonium glycinate ([N1111][Gly]), this study carried out the equilibrium absorption under a wide range of pressure (0～300kPa) at three temperatures in a dual-vessel absorption equilibrium system. The impacts of MDEA or IL concentration on the physical properties and absorption performance of CO2 under three temperatures:298K,308K, and 318K are compared in five aqueous solutions. It is found that with the increase of IL or MDEA concentration, the solution density grows slightly, while the viscosity rises dramatically. When the equilibrium pressure is less than 60 kPa, CO2 loads increase greatly as the pressure grows while temperature has little influence on the absorption capacities for all the solutions. When the equilibrium pressure is over 100kPa, the absorption capacity increases gradually as the pressure grows and higher temperature leads to less CO2 load in the solution.The regeneration performance of amino acid ionic liquid activated MDEA solutions was investigated to evaluate the influence of solution composition, regeneration temperature on the regeneration efficiencies and absorption rate of renewed solutions. Three high concentrated aqueous solutions (15wt%[N1111][Gly]+ 30wt% MDEA,10wt%[N1111][Gly]+30wt% MDEA and 10wt%[N1111][Gly]+ 40wt% MDEA) were saturated and then regenerated under the regeneration temperature:363K,373K and 378K(boiling point), respectively. The results reveal that most of CO2 in the liquid phase is released through the thermal regeneration before solution boiling. Absorption of CO2 in the regenerated absorbents over a wide range of equilibrium pressure (0-300kPa) shows that under the same pressure, the higher regeneration temperature leads to the high CO2 absorption capacity of the regenerated solutions, and the absorption curves of the solutions regenerated at 378K are close to those of the fresh solutions. Considering the regeneration efficiency and absorption rate difference between regenerated solutions and the blank, it can be concluded that most IL which determines the absorption rated is renewed, while MDEA which dominates CO2 load is fully regenerated.This paper studied the various factors in absorption and regeneration process of amino acid ionic liquid activated MDEA solutions for CO2 capture, which provided basic data for the development of new absorbent into industrial applications.