Reaction characteristics and kinetics of phosphogypsum decomposition via synergistic reduction effect of composite reducing agent

Large-area stacking of solid waste phosphogypsum (PG) and coal gangue (CG) poses environmental contamination hazards. This work presents the reaction characteristics, thermal decomposition behavior and reaction kinetics of composite reducing agent on PG decomposition. The results show that the composite reducing agent of CG and coke can efficiently decompose PG. The optimal mass ratio is CG:coke:PG = 1:2:10, at which the decomposition rate reaches more than 99%, and the solid products are CaS, Ca2Al2SiO7, etc. The initial decomposition temperature of PG decomposition by composite reducing agent is 815 celcius, while it is 860 celcius by coke. The average apparent activation energy of PG decomposition with composite reducing agent is lower than that with coke, which was calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The synergistic effect of CG and coke clearly decrease the temperature and improve the reactivity of PG decomposition. This work provides an efficient method to cooperatively utilize of two kinds of industrial solid wastes via composite reducing agent decomposes PG.