Existing and promising deep processing technologies for refractory potassium-containing aluminosilicate raw materials

Abstract

The paper outlines the specific concentration and processing features of refractory high-potassium aluminosilicate raw materials using the example of synnyrites and potassium feldspars. Synnyrite is an ultrapotassic rock (18–21 wt. % K2O), mainly composed of potassium feldspars (70–80 wt. %) and kalsilite (20–30 wt. %). The paper considers various deep processing scenarios for potassium aluminosilicate rocks based on alkaline and acidic methods with preliminary thermochemical or hydrochemical activation. It is shown that the nepheline method is ineffective for the processing of synnyrites due to an increase in limestone consumption, higher silica values in the raw material (over 50 wt. %) and, consequently, excessive solid waste generation. A combined technology based on sulfuric acid leaching with preliminary thermochemical activation of the original ore in the presence of magnesite or dolomite may be recommended as a promising technology for the complex processing of synnyrite. This approach reduces the sintering costs, recovers the magnesium additives consumed in the form of an additional finished product (magnesium sulfate hexahydrate MgSO4·6H2O), and minimizes waste generation. Two options have been proposed for processing synnyrite into final products: the traditional approach with the output of alumina Al2O3 and potassium sulfate K2SO4, and a new approach, allowing, for the first time, to produce the more scarce aluminium magnesium spinel MgAl2O4 and potassium magnesium sulfate K2Mg(SO4)2. The new processing method for the aluminium potassium sulphates KAl(SO4)2 obtained envisages their solid-phase interaction with potash K2CO3 and brucite Mg(OH)2 (or MgO) to form MgAl2O4 and K2Mg(SO4)2.