Reaction Characteristics of Calcination and Decomposition of Phosphogypsum in a Bubbling Fluidized Bed.

A bubbling fluidized bed reactor is designed to investigate the high-temperature calcination and decomposition characteristics of phosphogypsum (PG). The reactor employs electric heating, and a lifting discharge tube is installed in the middle of the air distributor to allow flexible switching between batch and continuous feeding modes. The batch test results show that the solid-phase bed materials with a PG particle size of 0.27-0.55 mm and a coal particle size of 0.55-0.83 mm are found to have uniformly mixed at a PG/coal mass ratio of 5:1 and calcined at a high temperature of 1100 °C for 30 min. PG completely decomposes to yield mainly CaS and a small amount of Ca(SiO) as the solid-phase products. For the above-mentioned optimal process parameters, a 120 min thermal-state continuous test is conducted. Feeding and discharging are performed at intervals of 30 min to maintain the stability of the static bed height inside the reactor. The results indicate that the PG decomposition rate is higher than 92% in the batch and continuous tests. However, the continuous decomposition of PG has significant process advantages, such as a higher CaS yield (71.20%) compared to that in the batch mode (64.49%). Furthermore, PG undergoes agglomeration and bonding within the particles when heated, intensifying the formation of a Ca(SiO) eutectic.