从高铝粉煤灰中提取非晶态SiO_2的实验研究

RESEARCH ON THE EXTRACTIONOF AMORPHOUS SiO_2 FROM HIGH-ALUMINIUM FLY ASH

为了有效提高高铝粉煤灰的Al/Si比,为提取氧化铝奠定基础,研究了用NaOH从高铝粉煤灰中提取非晶态SiO2的最佳工艺条件,并对提硅反应的机理进行了探讨。首先根据高铝粉煤灰的化学与物相组成特点,确立了利用NaOH提取非晶态SiO2的基本技术路线;然后用正交实验法确定了提硅的最佳条件:NaOH的浓度25%,灰碱质量比1∶0.5,反应温度95℃,反应时间4 h。经最佳条件反应之后,SiO2的提取率达到了41.8%,灰中Al2O3的含量由48.5%增加到了57.38%,Al2O3/SiO2质量比由1.29提高到了2.39。

In order to increase the Al/Si ratio of high-aluminium fly ash, so as to lay a foundation for the extraction of Al2O3, this paper focuses on how to effectively extract SiO2 from fly ash as well as on the reaction mechanism. Firsdy, according to the chemical and mineralogical composition of the fly ash, the technical route of extracting amorphous Si02 by NaOH was deteimined. Then, the optimum extraction conditions were determined by orthogonal experiments and necessary complementary experiments. The optimum conditions are presented as follows： concentrations of NaOH. 25% ; mass ratio of ash to alkali： 1 ： 0.5; reaction temperature： 95 ℃, and reaction time： 4 hours. After reaction under the optimum conditions, the extraction efficiency of SiO2 amounts to 41.8 %, the Al2O3 contents of the fly ash increase from 48.5 % to 57.38 % and Al2O3/SiO2 mass ratio increases from 1.29 to 2.39.