Potassium extraction by calcification and roasting of potassium feldspar-calcium oxide-calcium chloride system

With the mining of Baiyun Ebo iron ore, more than 2 million tons of potassium-rich slate are discarded every year, which are in the pile treatment without disposal, wasting a large amount of land resources. In order to realize the utilization of insoluble potassium salts, taking the potassium-rich slate as the object of research, we studied the potassium extraction process of the calcification roasting method in the potassium feldspar-calcium oxide-calcium chloride system. By analyzing the phase diagram of CaO-Al₂O₃-SiO₂ ternary system, the reaction generates Ca₂Al₂SiO₇ with a larger trend, Ca²⁺ in CaCl₂ can replace K⁺ in potassium feldspar, and the presence of CaO will combine with SiO₂ to promote Ca²⁺ replacement of K⁺. Therefore, orthogonal experiments and one-way analysis were used to investigate the CaO addition amount, CaCl₂ addition amount, roasting temperature, and roasting time on potassium extraction rate. The results showed that increasing the addition of CaO and CaCl₂, raising the roasting temperature and prolonging the roasting time were all favorable to the potassium extraction. Among them, the addition of CaCl₂ had the most significant effect on the potassium extraction rate, followed by the two factors of roasting temperature and roasting time, and the addition of calcium oxide had the weakest effect on the potassium extraction rate of the system. The system was suitable for the extraction of potassium by the volatilization method and the optimal process conditions were finally derived as m（potassium-rich slate） ∶m（CaO）∶m（ CaCl₂）=6∶5.4∶1.2, the roasting temperature is 1 573 K, the roasting time is 1 hour, at this time the potassium extraction rate can reach more than 95%.