Abstract:It is one of core technology for alkali dissolution-carbonation precipitation new process for producing alumina with bauxite leached by NaOH solution. Pre-desilication and high pressure digestion experiments were carried out using the existing productive equipments of Bayer process, and dissolution effects of different A/S diasporic bauxite leached by NaOH solution were investigated. The suitable technological conditions were determined, and dissolution effects and production efficiency were compared with evaporation mother liquor from Bayer process. The results show that actual digestion rate of Al2O3 dissolution rises with increase of A/S of bauxite, caustic soda mass concentration NK, proportioning molar ratio αk and digestion rate of proportioning dissolution, while actual rate of Al2O3 dissolution rises first then drops with increase of lime addition. Dissolution effects leached by NaOH solution and vaporation mother liquor from Bayer process are keeping the same level, but bauxite amount leached by NaOH solution is 1.71 times than the same volume of evaporation mother liquor from Bayer process, and cycle efficiency is 2.16 times than the same volume of evaporation mother liquor from Bayer process. Actual digestion rate of Al2O3 dissolution is 87.75% under the suitable conditions for pre-desilication and digestion of alkali dissolution-carbonation precipitation process including A/S of 8.65, pre-desilication temperature of 98 ℃, pre-desilication time of 6 h, NK of 200 g/L, lime addition of 11%, proportioning molar ratio of 1.3~1.5, proportioning dissolution rate of 90%, digestion temperature of 273 ℃, and digestion time of 40 min.