Study On Thermal Decomposition Kinetics Of Dolomite And Feasibility Analysis Of Ca_nO_n-1S Clusters Of Desulfurization Mechanism

Dolomite （CaMg（CO₃）₂） is the trigonal complex salt which is composed of calcite and magnesite. Its thermal decomposition way, thermal decomposition range, kinetic parameters are affected by different producer. CaO is one of thermal decomposition products of dolomite and has the excellent desulfurization capacity. Accordingly, exploring the thermal decomposition of dolomite and desulfurization process becomes very meaningful. By experiments, theoretical calculations and simulation of microscopic cluster structure, this paper analyzed thermal decomposition kinetics and studied the feasibility of the desulfurization products Ca_nO_n-1S clusters. The main contents and results are as follows:（1） By TG-DTG-DSC combined with thermal analysis, it preliminarily concluded that the thermal decomposition of dolomite is divided into two steps. When the decomposition temperature is low, it gradually decomposed into CaCO₃ and MgO. As the temperature increasing, CaCO₃ further broke down into CaO. These two steps correspond respectively to two temperature ranges, which are 680～810℃ and 810～920℃.（2） Using pattern matching method and isoconversional method to solve dolomite thermal decomposition’s three-factor of kinetics. Two-stage thermal decomposition activation energy were 209.68kJ/mol and 216.52 kJ/mol. According to kinetic compensation effect obtained pre-exponential factor A. Finally, by Satava law, determined the mechanism of function of first stage is g（α）=1-（1-α）^1/2 In second phase, its mechanism of function is g（α）=[1-1n（1-α）]^1/2（3） Using first-principles calculation method and comparing the difference between the free energy, the binding energy and electronic energy, the paper obtained Ca_nO_n-1S clusters is possible by the presence of CaO to CaS desulfurization process. Compared with the （CaO）_n clusters, Ca_nO_n-1S clusters is in the lower energy side and the reaction has a tendency to lower energy spontaneously. As an excessive state, Ca_nO_n-1S clusters forms before the nucleation CaS. According to analyze HOMO-LUMO energy difference, its chemical activity is higher than （CaO）_n.