Influence Of Carbon And Additives On The High-Temperature Decomposition Behavior Of Phosphogypsum

The influence of carbon and iron additives on the high-temperature decomposition behavior of phosphogypsum (PG) is systematically investigated using XRD, SEM and EDS. In the absence of carbon, a small amount of anhydrite phase is decomposed after sintering at 1200 degrees C for 2 h. However, the undesirable oldhamite phase is observed in RG/carbon50, PG/carbon/FeSO4 mixtures, PG/FeS2 mixtures embedded in carbon after sintering at 800 degrees C for 2 h, respectively, which implies a strong reducing atmosphere can promote oldhamite to generate. In the case of a PG/carbon 100 mixture, the diffraction peaks of anhydrite are not observed after sintering at 1100 degrees C for 2h. Moreover, the main phases in the mixture are found to be wollastonite-2M, larnite. calico-olivine, gehlenite and lime. Overall, the anhydrite decomposition to lime is mainly influenced by carbon and the sintering temperature.