关键词: 低Al2O3/SiO2质量比, 粉煤灰, 赤泥, Al2O3回收, 碱法工艺

Abstract: Based on the basic analysis on domestic Al2O3 industry and output of aluminosilicate residue, the potential value and necessity of Al2O3 recovery from aluminosilicate residue were evaluated. Si was the main impurity during Al2O3 recovery with alkali process, the mass ratio of Al2O3 to SiO2 (A/S) in aluminosilicate was generally about 1. The principle of alkali process was analyzed for low A/S materials and four novel alkali processes based on the improvement of Bayer process for Al2O3 recovery were introduced, hydrothermal process, hydro-chemical/sub-molten salt, sintering and pre-desilicating processes. The equilibrium phases in the hydrothermal and hydro-chemical/sub-molten salt processes turned into Fe-substituted hydro-grandite and NaCaHSiO4 respectively, which had low A/S, by changing reaction conditions. Si was fixed and amorphous SiO2 dissolved in the sintering and pre-desilicating processes respectively via pre-treatment of materials, leading to high A/S in material. Compared with Bayer process, the separation efficiency of Al with Si was promoted effectively in the four processes. Moreover, the contrastive analysis on their Al2O3 recovery rate, application field and industrial application status was done. Finally, in view of the research status of Al2O3 recovery, the further research direction in establishment of novel leaching system by adding new materials was pointed out.

Key words: low mass ratio of Al2O3 to SiO2, fly ash, red mud, alumina recovery, alkali process