Study on Kinetic Parameters and Reductive Decomposition Characteristics of FGD Gypsum

Decomposition characteristics and kinetics of analytical gypsum (AG), dry flue gas desulphurization gypsum (DG) and wet FGD gypsum (WG) were studied by using thermal analyzer in a nitrogen atmosphere. Kinetic parameters (such as activation energy E and frequency factor A) of thermal decomposition of AG, DG and WG were calculated based on TG-DTA curves and Coast-Redfern method. The apparent activation energy of FGD gypsums was much lower than that of AG. The apparent activation energies of tested AG, DG and WG were 214.73, 128.54 and 111.12 kJ/mol, respectively. Reductive decomposition characteristics of analytical gypsum, dry FGD gypsum and wet FGD gypsum were studied by using thermal analyzer. The results indicated that the factors of the final reaction temperature and the reaction atmosphere have significant influences on the decomposition of gypsum, in the condition of 850–1,050°C, the total decomposition rate of three gypsums increases and the time-consumption of reaching decomposition equilibrium of three gypsums decreased with the increasing of the final reaction temperature; in the condition of 0–5% CO, the total decomposition rate of all three tested gypsums increases with increasing of CO volume fraction, and the time-consumption of reaching decomposition equilibrium of three gypsums is shortened with increasing of CO volume fraction; doping of Fe₂O₃ in the analytic gypsum not only increases the total decomposition rate, but also improves the reaction rate at reasonable doping amount. AG with 5% Fe₂O₃ doping is more effective based on the total decomposition rate; however, AG with 10% Fe₂O₃ doping is slightly better on the basis of the decomposition reaction rate.