Reaction Mechanism for Iron Catalyst in the Process of Phosphogypsum Decomposition

This paper proposes a catalyst to lower the decomposition temperature of phosphogypsum (PG) and investigates the reaction mechanism. PG is stable in the inert atmosphere, decomposed above 1100 °C, and unstable in the reducing atmosphere relatively. The PG decomposition temperature dropped to 800–1000 °C through previous study in a CO/coal reducing atmosphere, which is still high. The Ellingham diagram and FactSage6.1 were used as a guide to find catalyst to lower the PG decomposition temperature further and explore the reaction mechanism, respectively. The analysis of FactSage6.1 Reaction, Equilib, and Phase diagram module showed that Fe(+3) was reduced by CO and oxidized by S(+6) reacted in the molten state completely, which lowered the PG decomposition temperature significantly. PG powder was added to FeCl3 aqua and decomposed in a thermogravimetric analyzer (TGA). With different FeCl3 impregnation concentrations, CO flow rates, and heating rates, the decomposing properties of PG were investigated by th...