Bauxite concentrate behaviour at the leaching stage in the Bayer process

The purpose of the paper is study of the behaviour of bauxite concentrate produced by the thermochemistry-Bayer method at the stage of pressure leaching; investigation of the effect of calcium oxide dosage supplied for bauxite concentrate pressure leaching in the Bayer process; determination of calcium oxide optimal dosage; development of methods to control bauxite concentrate opening using the chemical analysis of solid and liquid phases; production of thermoactivated product due to the roasting of initial bauxite at 1000 °C and its desiliconization with alkaline solutions, followed by bauxite concentrate leaching according to the Bayer method in autoclave conditions; complete silicate analysis of the solid phase (red mud) and determination of the content of general, caustic, carbonate alkali as well as Al₂O₃ and SiO₂ in the liquid phase. Thermal activation of bauxite allowed to obtain a product with a silicon module (μ_Si) that equals 11.6 from high-silica bauxite from one of the Russian deposits. The effect of CaO dosage on the opening of bauxite concentrate has been studied. The conducted analysis of solid and liquid phases has showed the possibility to determine bauxite concentrate opening at pressure leaching. The optimal dosage of calcium oxide has been determined. The conducted laboratory studies made it possible to find out that the firing temperature (1000 °C) followed by 1 hour exposure on the one hand ensures the obtaining of high-quality concentrate, and on the other, allows to achieve theoretically possible alumina extraction under further traditional hydrometallurgical processing. It has been estimated that the optimal dosage of calcium oxide for this type of bauxite concentrate is 2.5% of the concentrate weight. The chemical analysis of pressure leaching products has showed the possibility to determine alumina extraction from bauxite concentrate in the aluminate solution (by the composition of both solid and liquid phases). A methodology of rapid analysis based on the composition of the liquid phase has been developed. It enables determination of the production possibility of the bauxite concentrate with a high silicon module as well as estimate its opening at the leaching stage in the Bayer process.

alumina production, bauxites, thermochemical activation, bauxite concentrate, pressure leaching, calcium oxide