Beschreibung:
In this work, the reaction characteristics of CaS with CO2 were investigated by three methods: experiments, isothermal kinetic analysis, and density functional theory (DFT) calculations. It was found that the reaction rate of CaS with CO2 accelerated with the increase of reaction temperature as well as CO2 concentration. When the reaction temperature t ≥ 1000℃, CaS was all converted to CaO. When the reaction temperature t < 1000℃, a small amount of CaSO4 is produced due to the disproportionation reaction of CaSO3. In addition, when CaS reacts in 20% CO2 + N2 atmosphere, the activation energy of CaS reaction with CO2 is about 95.54 kJ/mol, the pre-exponential factor A=0.76557s-1, and the reaction kinetic model is a phase boundary reaction model with a modified model function G(α)=1-(1-α)1/1.368. During the reaction of CaS with CO2, S2- on the CaS surface combines with an O atom in the CO2 molecule to form the CaSO structure, while generating CO. Subsequently, the CO on the CaSO surface desorbs to produce a stable CaSO surface. Further, CaSO is oxidized by CO2 molecules to form CaSO2 and CO, and CO is desorbed to produce the CaSO2 surface. During this reaction, CaSO undergoes a significant deformation and the O atoms in the [SO]2- are transferred to the inner surface layer while receiving O2- from CO2 to form the [SO2]2-. Finally, CaSO2 continues to be oxidized by CO2 to form CaSO3 and CO. This step has the highest activation energy barrier and is the rate-controlling step of the reaction. The generated CaSO3 is unstable at high temperature and easily decomposes to form CaO and SO2, thus achieving the conversion of CaS to CaO