Study On Thermal Reaction Of Gypsum And Potash Feldspar

Potassium is one of the three major nutrient elements in dispensable for the growth of agriculture. The development of fertilizer industry is relatively slow for restraining resource in China. The situations have become increasingly prominent in soil which contains nitrogen-rich, phosphorus-lower and potassium-deficiency. Demanding of potash mainly rely on imports.Phosphorus Chemical is the pillar industry of Yunnan, and the emissions of phosphogypsum have passed15million tons per year but its utilization ratio does not reach10%. The issues of resource and environmental is extremely urgent to solve. Recycling of sulfur resources has been the focus in phosphogypsum research, but has not got breakthrough. At the same time, solubility potassium is grave insufficient in our country but the reserve of insoluble potassium is very rich, which is not fully utilized in fertilizer industry. In this context, the issue put forward the academic ideas that using phosphogypsum and potassium in Yunnan to prepare raw gas of sulfuric and potassium sulfate. The way has great economic value and social significance, not only solved the environment pollution of phosphogypsum but also relieved the pressure of importing potash.In the paper, potassium feldspar, phosphogypsum and coke are used as raw materials to obtain soluble salts of roasting sample through mechanical grinding, roasting activation and leaching. A study has been conducted on the factors that affect the leaching ratio of K2O of roasting samples. Influencing regularity of potassium feldspar structure under high temperature and additives has been discussed. It also investigates mechanism of potassium feldspar on high-temperature sintering. Conclusions can be listed as follows through the experiment:(1)Mechanical activation scattered the adhesive particle of potassium feldspar, improved its fineness, increased the surface area, destructed the ordered structure of the vitreous. And new surface are increased, it was benefit for external ions to destroy Al-Si-O structure of potassium feldspar.(2)The crystal structure of potassium feldspar has been changed after calcination. There are more loose and porous stats, and increased the number of broken bonds as well internal energy. The reactivity of potassium feldspar is further improved. (3)Thermodynamic software HSC Chemistry5was used to calculate the reductive reaction of potassium feldspar-phosphogypsum-coke system. Derivation and experimental resulta show that the reaction is most easily carried out when n(KAlSi3O8):n(CaSO4):n(C)=2:7:3, at this time, mol-rate of calcium and silicon is1.0approximately.(4)It studied the factors such as roasting temperature, roasting time and atmosphere, which influenced the calcination of reaction system. It determined the optimum parameters about activation process. It also investigated the factors that affect the leaching ratio of K2O of calcined samples, such as the type and concentration of leaching medium, temperature, time, liquid-solid ratio. The results show that the leaching rate of potassium dissolution reaches76%under the optimum conditions both roasting and leaching.(5)Contrasted the XRD patterns of potassium feldspar on different roasting temperature, it is known that potassium feldspar structure transforming from initial micro-plagioclase to orthoclase, then becoming into sanidine with increased temperature. At this time, the order degree of crystal structure was destroyed, and decreased stability, so reactivity was enhanced. The crystal structure of potassium feldspar has disappeared at1300℃.It is conducive to extract potassium salts further from K-feldspar.(6)Based on the changing structure of potassium feldspar in high-temperature, process of sintering potassium feldspar with CaSO·2H2O、CaO、CaS、CaSO、2H2O and CaO、CaSO4·2H2O and CaS were investigated individually. The result shows:the mixed additives of CaSO4·2H2O and CaO can promote the generation of soluble potassium salt.(7)Roasting reaction mechanism for testing system of potassium feldspar-phosphogypsum-coke was deduced, which laid a theoretical foundation to take potash from K-feldspar by high-temperature calcined.The study provide a theoretical basis of the utilization for insoluble potassium mineral resources as well as open up a new way for phosphogypsum. So the technology has a good prospect in future.