The feasibility of industrial waste fly ash as an alternative fluxing agent for silica in carbothermal reduction of medium-low-grade phosphate ore was studied in this paper. With a series of single-factor experiments, the reduction rate of phosphate rock under different reaction temperature, reaction time, particle size, carbon excess coefficient, and silicon–calcium molar ratio was investigated with silica and fly ash as fluxing agents. Higher reduction rates were obtained with fly ash fluxing instead of silica. The optimal conditions were derived as: reaction temperature 1,300°C, reaction time 75 min, particle size 48–75 µm, carbon excess coefficient 1.2, and silicon–calcium molar ratio 1.2. The optimized process condition was verified with other two different phosphate rocks and it was proved universally. The apparent kinetics analyses demonstrated that the activation energy of fly ash fluxing is reduced by 31.57 kJ/mol as compared with that of silica. The mechanism of better fluxing effect by fly ash may be ascribed to the fact that the products formed within fly ash increase the amount of liquid phase in the reaction system and promote reduction reaction. Preliminary feasibility about the recycling of industrial waste fly ash in thermal phosphoric acid industry was elucidated in the paper.

中文翻译：

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粉煤灰作为助熔剂在中低品位磷酸盐岩碳热还原中的可行性及反应动力学

研究了工业废粉煤灰作为二氧化硅替代助熔剂在中低品位磷酸盐矿碳热还原中的可行性。通过一系列的单因素实验，以二氧化硅和粉煤灰为助熔剂，研究了不同反应温度，反应时间，粒径，碳过量系数和硅钙摩尔比下磷矿石的还原率。用粉煤灰助熔剂代替二氧化硅可获得更高的还原率。最佳条件为：反应温度1,300°C，反应时间75分钟，粒径48-75 µm，碳过量系数1.2，硅钙摩尔比1.2。用其他两种不同的磷酸盐岩对优化的工艺条件进行了验证，并得到了普遍证明。表观动力学分析表明，与二氧化硅相比，粉煤灰助熔剂的活化能降低了31.57 kJ / mol。飞灰产生更好的助熔效果的机理可以归因于以下事实：飞灰内形成的产物增加了反应体系中液相的量并促进了还原反应。阐明了热磷酸工业中工业废粉煤灰的回收利用的初步可行性。