China Nonferrous Metallurgy

In the process of producing alumina from lithium-rich bauxite, most of the lithium enters aluminum hydroxide during the sodium aluminate decomposition process, which affects the quality of alumina products and the subsequent electrolytic efficiency. This paper systematically studies the change behavior of lithium in the calcination process of lithium-containing aluminum hydroxide products. Through single-factor experiments, the influence of calcination process parameters on the weight loss rate and lithium loss rate of aluminum hydroxide products is investigated. Combined with the characterization and analysis of the calcination products and intermediate products of the samples, the change behavior of lithium is studied, and the following main conclusions are obtained. Single-factor experiments show that the calcination temperature, calcination time and heating rate are all positively correlated with the weight loss rate and lithium loss rate of aluminium hydroxide products. Under the optimized conditions of calcination temperature of 1150℃, calcination time of 30min and heating rate of 25℃/min, the weight loss rate of aluminium hydroxide products is 34.86% and the lithium loss rate is 14.82%. Lithium in the roasting products is enriched in the form of oxides in alumina. Cracks and pores appeared on the surface of the crystals after calcination, which was mainly caused by the precipitation of crystalline water in the aluminum hydroxide products and the transformation of the aluminum oxide lattice. Increasing the calcination time or extending the calcination temperature would both lead to the expansion of cracks on the grain surface and the increase of small depressions.