粉煤灰提铝残渣低温碱溶过程工艺研究

循环流化床粉煤灰“一步酸溶法”提取氧化铝工艺过程中产生的尾渣主要成分为无定形二氧化硅,且具有较高的活性,是制备白炭黑、分子筛、硅酸钠水玻璃的理想原料。对该提铝残渣在氢氧化钠溶液中的溶出过程做了研究,探讨了液固比、碱浓度、溶出时间、溶出温度工艺条件对二氧化硅和氧化铝溶出效果的影响。研究结果表明：在氢氧化钠碱液的浓度为4 mol/L、反应温度为70 ℃、液固比为6、反应时间为4 h的条件下,二氧化硅的溶出率最高,达到93%。提铝残渣碱溶后固体渣经XRD分析,其无定形二氧化硅基本已溶出,剩余物主要为锐钛矿与莫来石等。

Study on alkali leaching process of aluminum extraction residue from fly ash at low temperature

Mainly composed by amorphous silica and having higher activity,the residue from circulating fluidized bed ash detached Al₂O₃ with one-step acid dissolution method is ideal raw materials for preparation of silica,molecular sieve and Na₂SiO₃.The dissolving process of residue of fly ash in sodium hydroxide solution was studied.The influence of liquid-solid ratio,alkali concentrations,dissolving time and dissolving temperature on dissolution rate of SiO₂ and Al₂O₃ was also discussed.The results showed that the dissolving ratio of silica in residue of fly ash could be more than 93%,when the concentration of sodium hydroxide was 4 mol/L,the reactive temperature was 70 ℃,the liquid-solid ratio was 6,and the reactive time was 4 h.The solid residue from alkali leaching process of aluminum extraction residue was analysized by XRD.Results showed that almost all of amorphous silica in the residue dissolved into the lye,and the alkali residue was comprised of anatase,mullite and so on.