关键词: 磷石膏, 硫化钙, 氧化钙, 正交实验

Abstract: Phosphogypsum，waste slag derived from phosphate fertilizer industry doping with 5%（mass fraction） CaCl₂ was used as raw material，purged with N₂ and then calcined under the presence of high-sulfur coal as reductant to prepare CaS and CaO.The contents of CaS and CaO in the product were analyzed by iodine quantity method so as to investigate the reduction rate of calcium sulfate.The effects of raw material mix ratio，calcining time，calcining temperature，and particle size etc. on the reduction of phosphogypsum were studied.Based on these studies，orthogonal experiments were conducted to find out the optimum process conditions for obtaining CaS and CaO by reducing phosphogypsum，which are as follows：amount-of-substance ratio of CaSO₄ to C was 1∶1.3，calcining temperature was 900 ℃，and calcining time was 2.5 h. Under those conditions the reduction rate of CaSO₄ in phosphogypsum could reach more than 98%.The doping of 5% CaCl₂ could decline the reductive decomposition temperature of phosphogypsum.

Key words: phosphogypsum, CaS, CaO, orthogonal experiments