Effect of potassium feldspar on the decomposition rate of phosphogypsum

Abstract

AbstractBackgroundPhosphogypsum (PG) is a solid waste from a wet process of phosphoric acid and its main component is CaSO4·2H2O. However, the temperature of PG decomposition is above 1200 °C. In this study, the decomposition temperature of PG was decreased using a small amount of coke as reducing agent, and the decomposition rate of PG can be further increased using potassium feldspar (K‐feldspar) as an additive to form a eutectic mixture with PG in nitrogen atmosphere.ResultsA high PG decomposition rate of 99.40% was obtained at 1150 °C for 25 min, when the mass ratio of coke to PG and K‐feldspar to PG was 0.07 and 0.43, respectively. Compared with the addition of coke alone (coke/PG = 0.07) as the reducing agent, the decomposition rate of PG was increased by 35.40%. The HSC Chemistry software 8 was used to calculate the equilibrium compositions of the PG @K‐feldspar @coke system, and the decomposition rate of 99.77% was obtained at 1150 °C by calculation. The experimental results are basically consistent with the thermodynamic equilibrium calculation.ConclusionThe PG and K‐feldspar are fully utilized by calcination. The decomposition reaction of PG can proceed via the continuous consumption of CaO and CaS by K‐feldspar, which increased the decomposition rate of PG. The thermodynamic calculation results showed a good agreement between the equilibrium value calculated and the experimental data obtained. Furthermore, the calcined products can be used as an agricultural potassium fertilizer. © 2020 Society of Chemical Industry (SCI)