预脱硅-Na_2CO_3焙烧-酸浸工艺提取粉煤灰中的氧化铝

Extraction of Alumina from Coal Fly Ash by a Predesilication-Na_2CO_3 Sintering-Acid Leaching Process

通过"预脱硅-Na_2CO_3焙烧-酸浸"工艺实现从粉煤灰中高效回收氧化铝。按照1:2固液质量体积比(m/V)添加150 g×L^(-1)的NaOH溶液于130℃预脱硅1 h,粉煤灰脱硅效率可达30.0%。脱硅粉煤灰按照1:0.7的Na_2CO_3与SiO_2质量比与Na_2CO_3混合并于900℃焙烧2 h,焙烧熟料再经水洗和4 mol×L^(-1) H_2SO_4浸出1 h,Al的浸提效率可达93.1%,尾渣量仅为初始粉煤灰的20.4%。通过XRD谱图体现的粉煤灰矿相变化揭示了Al的可能浸提机理。相较于工业上应用的石灰石烧结和碱石灰烧结,以及在研究发展中的方法如加压酸浸法,该工艺焙烧温度低、尾渣量少、设备腐蚀小,因而具备实际工程化应用前景。

This study investigated efficient alumina recovery from coal fly ash via a ＂predesilication-Na2CO3sintering-acid leaching＂ process. Desilication efficiency of 30.0% can be achieved when adding 150 g×L^-1NaOH solution（solid to liquid volume ratio（m/V） 1：2） at 130℃ for 1 h. The desilicated ash was mixed with Na2CO3（Na2CO3 to SiO2 mass ratio 1： 0.7） and sintered at 900℃ for 2 h, which was then washed and leached by 4 mol×L^-1 H2SO4 for 1 h, and the alumina extraction efficiency was 93.1%. The leached residue mass was 20.4% of the original ash. XRD patterns show possible extraction mechanism by presenting the transformation of mineral phases in coal fly ash. Comparing with limestone and lime-soda sintering and other developing methods such as pressure acid leaching, this process operates at lower sintering temperature and generates less residue with less facility corrosion, which has potential applications in the industry.