Abstract:

Insoluble potash ores of different types from fourteen representative localities are characterized by microcline as principal mineral phase enriched in potassium. By pretreating the ores with such a procedure as ore crushing, bed sorting, wet magnetic sorting, and so on, potassium feldspar powders with purities up to 75% to 95% are prepared first. And then, with sodium carbonate as an additive, the powders are sintered at intermediate temperature, or with alkalinelime as additive, the powders are hydrothermally treated, the both procedures lead to structural decomposition of potassium feldspar to form a mixture of sodium metasilicate and sodium (potassium) metaluminate. And further, the aluminosilicate mixtures are hydrolyzed to form liquors rich in K+, Na+, and ［SiO2(OH)2］2- ions. By introducing CO2 gas into the liquids, the liquors are then converted into watersalt solutions in the ternary system of NaHCO3KHCO3H2O. By evaporation, crystallization of NaHCO3, separation from the liquids, and then evaporating the residual liquors, and crystallization of KHCO3, owing to much smaller solubility of the former, both of precipitants are separated, and at last by calcinating the precipitants at 200 ℃ for 2 h, potassium carbonate, or potassium sulfate and potassium nitrate are easily prepared, by reacted respectively with sulphuric acid and nitric acid.   In such a way, the components of Al2O3, and more than 40% of SiO2 in potassium feldspar of the ores are also manufactured into valuable chemical products, i.e., various alumina and inorganic siliceous compounds, giving rise to nearly 100% output coefficient of the potassium feldspar resources, close to zero discharge of solid wastes, waste waters, and exhaust gases. The procedures are  of energy saving, high efficiency, and clean production. It is therefore feasible to be industrialized at large scale both in decreasing import volume of potash fertilizer and maintaining the safety of crop productions in China, as well as enhancing the selfsupply degree of soluble potassic resources.

Key words: insoluble potash ore deposit, potassium feldspar, potassium carbonate, potassium nitrate, potassium sulfate, potash fertilizer industry, clean production