Calcium-based High-temperature CO _{2 Preparation And Performance Testing} Absorbent

With the development of industry, more and more CO2emissions to the atmosphere from human activities, CO2emission was recognized as the main reason for greenhouse effect. Reducing industrial CO2emissions is an effective means to mitigate the greenhouse effect. The calcium-based and the lithium-based sorbents are two major high temperature solid CO2sorbents. The calcium-based sorbents have higher absorption capacity, but the absorbing performance decreased quickly with increasing cycle number.In this study, using urea and calcium chloride as reactants, porous calcium-based sorbents were obtained through calcining CaCO3precursors prepared by hydrothermal and microwave-hydrothermal methods and the precursor preparation conditions were optimized using the response surface method. The results showed that the microwave intervening can greatly shorten the reaction time, and reduce the raw materials molar ratio. The as-prepared CaO sorbents with microwave hydrothermal method at the optimum conditions (the molar ratio of urea and calcium chloride was7, microwave hydrothermal for79min at the temperature of110℃) reached an absorption capacity of76.67%, and The absorption capacity of CaO sorbents with hydrothermal method at the optimum conditions(8.5molar ratio,110℃,1Oh) was only64.08%. This is resulted from the acicular porous morphologies.In addition, the doped with rare earth elements CaO-based sorbents were fabricated. Effects of doping kinds and content on CO2absorption properties were investigated. The results showed the doping CaO-based sorbents exhibited higher absorption capacity and better cycle durability. The most effective method was solid phase interaction; the most effective added content of rare earth elements were1.5%. Absorption capacity of those absorbents modified by La,Ce and Ywere67.05%respectively, higher than baseline value7.64%,10.83%,2.97%respectively, the modification effect of Ce was the most optimum. Cycle performance of absorbents were increased after doped with1.5%Ce, absorption capacity still hold at62.52%after16th cycles, cycle performance of absorbent decreased from98.2%to79.5%decreased by18.7%. The mechanism of rare earth elements modification was discussed in this work.In the meanwhile, the kinetics of absorbing CO2was investigated by a double exponential model. Compared the kinetic data about hydrothermal-CaCO3-CaO(E1,E283.28,69.2kJ/mol)and microwave hydrothermal-CaCO3-CaO (E1,E240.22,8.45kJ/mol). The result further proof willmigerl the function of microwave.