Thermal-shock-based pre-desilication method for low-grade bauxite

Abstract

China has about 98% of the diasporic bauxite ores, with around 70% being low-grade. These low-grade bauxites containing high silica pose significant challenges in alumina recovery, as their reaction with sodium aluminate in the Bayer process leads to alumina loss and increased caustic consumption. This study presents a novel, sustainable process for upgrading low-grade bauxite with an initial alumina-to-silica mass ratio (A/S) of 2.39. The process involves muffle furnace heating and water quenching, as well as fragmentation of bauxite. In this process, low-grade bauxite was first treated in a muffle furnace at 350°C for 50 min, using a particle size of 355–425 µm, and then suddenly cooled in cold water for fragmentation. Subsequently, a separation of the parts into smaller sizes is needed. The results demonstrate a 130% increase in the A/S mass ratio, with 67% concentrate recovery for alumina extraction. This method offers a promising solution for efficiently using low-grade bauxites without further treatments, contributing to more sustainable alumina production practices. The process is adaptable to different bauxite sources and could significantly impact alumina refineries’ economics and environmental footprint worldwide.

Keywords

low-grade bauxite / pre-desilication / thermal shock / fragmentation / concentrate / water quenching

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