Abstract: The high-alumina fly ash solid-phase change in the desilication and dealuminization reactions in alkaline solution was investigated by chemical analysis, XRF, XRD, laser particle sizer, SEM and FT-IR. The results showed that after the desilication and alkali dissolution reactions, the leaching rate of alumina reached up to 85%, Al2O3/SiO2 mass ratio decreased in the tailings, as a result the alumina and silica were selectively separated in the desilication reaction, mullite and corundum phases remained unchanged, meanwhile, amorphous aluminosilicate glass was transformed into sodalite phase Na8Al6Si6O24(OH)2(H2O)2, which adhered the ash particle surface, as a result the particle size increased and the particle surface became coarse. After alkali dissolution reaction, mullite and corundum phases were transformed to NaCaHSiO4 and 1.2Na2O×0.8CaO×Al2O3×2SiO2×H2O phases, the particle size decreased.

Key words: high-aluminum fly ash, desilication, alkali dissolution, digestion, alumina, phase change

摘要： 采用化学分析和XRF、XRD、激光粒度仪、SEM、FT-IR分析技术，研究了高铝粉煤灰预脱硅及浓碱液提铝过程中的固相变化规律. 结果表明，高铝粉煤灰经预脱硅及NaOH浓碱溶液溶出后，碱灰质量比大于6时，Al2O3的溶出率大于85%，尾灰中铝硅质量比降至0.21，铝硅选择性分离. 预脱硅过程中莫来石相和刚玉相未被破坏，而所含无定型铝硅酸盐溶解形成羟基方钠石Na8Al6Si6O24(OH)2(H2O)2，并附着于颗粒表面导致中值粒径略有增加；浓碱溶液提铝过程中，莫来石及刚玉相完全溶解，形成规则柱状或杆状的NaCaHSiO4及类沸石1.2Na2O×0.8CaO×Al2O3×2SiO2×H2O，中值粒径减小.

关键词: 高铝粉煤灰, 预脱硅, 浓碱溶液, 溶出, 氧化铝, 相变