钾长石水热碱法制取硫酸钾反应原理与过程评价

摘要

To develop an efficient and clean technique for comprehensively utilizing potassic syenite resources exposed in the Eastern Qinling to Dabie area of China, a series of experiments were performed using a typical K-feldspar powder as raw material, with focus on the hydrothermal stability of microcline in KOH-H2O solution, reaction principle of preparing potassium sulfate, as well as processing by-products from alumina and silica residue. Microcline was easily transformed into kalsilite by dislodging 2/3 SiO2 of the K-feldspar in the solution, resulting in nearly hundred percent higher concentration of K2O in the solid product, from which nearly pure solution of potassium sulfate was then obtained by dissolution with sulfuric acid, and further potassium sulfate was crystallized by evaporation of the solution or by the alcohol precipitation method. The alkaline solution of mainly potassium silicate reacted with lime milk to precipitate calcium silicate hydrate, from which needle-shaped wollastonite powder was synthesized hydrothermally, and then by calcination. The alumina and silica residue were used to make calcined kaolin first by acidic washing, and then by calcination. The whole procedure developed in this research was simple and economical, with recovery ratio of K2O up to 94.0%. In such a way, the components of K2O, Al2O3, and SiO2 in K-feldspar of the ores were wholly transformed to valuable products, giving rise to maximum utilization of K-feldspar resources, and also minimum consumption of relevant mineral resources. The technique is noted for energy conservation, high efficiency and clean production.%针对东秦岭-大别地区富钾正长岩资源的高效清洁利用技术难题，以代表性产地的钾长石粉体为原料，研究了在 KOH-H2O 介质中钾长石的水热稳定性、水热碱法制取硫酸钾的反应原理，以及硅铝组分资源化利用关键技术。结果表明，钾长石在KOH碱液作用下极易脱去2/3的SiO2而转变为钾霞石相，使K2O富集约1倍；继而以硫酸溶解，可得近于纯净的硫酸钾近饱和溶液；经蒸发结晶或醇析法，即可制成农用硫酸钾优等品。脱硅碱液与石灰乳反应所得水合硅酸钙沉淀，经水热晶化及煅烧，产物为针状硅灰石。剩余铝硅尾渣经纯化处理和煅烧，即制成煅烧高岭土。整个工艺过程简捷高效，K2O回收率达94.0%以上，可实现资源利用率最大化，一次性资源消耗量最小化，且环境相容性良好。