Physicochemical Processes in the Firing of Acid-Resistant Materials Based on Unenriched Kaolin and High-Alumina Ferrochrome Production Slag

It is established that acid-resistant tiles satisfying GOST (State Standard) requirements cannot be manufactured from unenriched kaolin clay containing less than 18% of Al₂O₃ even at a firing temperature of 1300°C. The addition of an optimal grog quantity (40%) to the ceramic mass makes it possible to manufacture acid-resistant tiles corresponding to GOST requirements at a firing temperature of 1300°C. The use of ferrochrome production slag with an increased content of alumina (Al₂O₃ > 50%), magnesia (MgO > 15%), chromia (Cr₂O₃ > 5%), and calcia (CaO > 12%) enables the manufacturing of products with high technical characteristics within a firing temperature range of 1250–1300°C. X-ray diffraction analysis shows that the introduction of ferrochrome production slags into ceramic masses promotes the appearance of new minerals in the X-ray diffraction pattern, such as magnesium chromite (MgCr₂O₄), chromite (FeCr₂O₄), forsterite (Mg₂SiO₄) and magnesia aluminum spinel (MgAl₂O₄), corundum (Аl₂О₃), bonite (CaO⋅6Al₂O₃), and chromia (Cr₂O₃), which substantially improve the technical characteristics of acid-resistant materials. The presence of the above-mentioned minerals in the samples is also confirmed by IR spectra. A Russian Federation Patent for the use of ferrochrome production slag has been obtained.