ROASTING OF ALUMINA-CONTAINING MATERIAL IN A ROTARY KILN

This study examines the dehydration and firing of kaolin clays in a rotary kiln to optimize aluminum oxide extraction during nitric acid leaching. Previous pilot-scale tests in a fluidized bed furnace achieved up to 87% acid-soluble aluminum oxide at 750°C, but required granulation and extensive dust collection. Large-scale experiments using a 12-meter rotary kiln with an external furnace were conducted on kaolin clay from the Angren deposit and substandard bauxite. The study investigated temperatures from 600 to 800°C and residence times of 1–2 hours. Results indicate that a firing temperature of 750°C for 2 hours is optimal, yielding 86.8% Al₂O₃ extraction with reduced dust removal (8.5–10%) compared to fluidized bed kilns. The findings confirm the feasibility of rotary kilns for efficient kaolin clay processing with lower dust emission and simpler dust collection requirements.