粉煤灰转相焙烧过程铝硅碱溶活性探究

Study on Alkali-soluble Properties of Alumina Silicon in Coal Fly Ash Phase-transition Roasting Process

粉煤灰主要成分为氧化铝和二氧化硅,其铝硅比较低,传统拜耳法难以实现铝硅分离,在碱性体系下需对粉煤灰中的铝、硅组元进行改性与处理,提高其中铝、硅组元的碱溶活性差异,从而实现铝硅分离的目的。以内蒙古某地区高铝粉煤灰为研究对象,通过硫酸固相转化手段将铝硅酸盐解离,解离后的铝、硅组元混合相通过转相焙烧的方式进行碱溶活性调控,以实现铝、硅组元碱溶初步分离的目的。结果表明,随着焙烧温度的升高,焙砂中的非晶态氧化铝有向过渡相氧化铝转变的趋势,碱溶活性逐渐降低,非晶态二氧化硅的结构未有明显变化趋势,其碱溶活性也未发生明显变化;在焙烧温度950℃、焙烧时间60 min条件下和碱溶温度95℃、时间30 min、Na 2O浓度38.75 g/L、液固比10∶1的溶出条件下,二氧化硅溶出率达到73%以上,氧化铝溶出率不到2%。

The main components of coal fly ash are alumina and silica and the content of aluminum and silicon are relatively low.It is difficult to separate aluminum and silicon by traditional Bayer process.To achieve the extraction of alumina and silicon from coal fly ash in the alkaline system,the aluminum and silicon components in fly ash need to be modified.After this treatment,the difference of the alkali digestion property of the aluminum and silicon components is improved.Taking high-aluminum coal fly ash in a certain area of Inner Mongolia as the research object,the aluminosilicate was dissociated by the solid phase conversion method of sulfuric acid,and the dissociated aluminum and silicon component mixed phase was controlled by the phase transformation roasting.The results show that with the increase of roasting temperature,the amorphous alumina in the calcine has a tendency to transform to the transition phase alumina,the alkali digestion activity gradually decreases,the amorphous silicon dioxide with high alkali-soluble property has no obvious structure transition,and the alkali digestion activity does not change significantly.Under the phase transformation roasting conditions of temperature 950 ℃ and time 60 min,the alkali digestion temperature of 95℃,Na2 O concentration of 38.75 g/L,time of 30 min,and liquid-solid ratio of 10∶1,the digestion rate of silicon dioxide is above 73% and the dissolution rate of alumina is below 2%.