循环流化床粉煤灰在碱液中硅、铝的溶出及聚合研究

Dissolution and polymerization of Si and Al in alkaline solution by circulating fluidized bed fly ash

为提升循环流化床粉煤灰的利用价值,研究了温度、碱浓度、时间、液固比对粉煤灰中硅、铝溶出率的影响,分析了溶出液中硅、铝的聚合行为。结果表明:温度、碱浓度、时间、液固比对煤灰中活性硅、铝的溶出影响显著;当碱浓度为9 mol/L、反应温度90℃、反应时间4 min、液固比为20时,硅的溶出率最大,达70%;当碱浓度为6 mol/L、反应温度75℃、反应时间16 min、液固比为20时,铝的溶出率最大,达82%;当溶出温度为90℃、溶出液中硅浓度>0.05 mol/L、铝浓度>0.07 mol/L时,硅、铝会相互聚合。聚合时,硅、铝首先形成硅铝酸盐胶体,随后聚集为硅铝酸盐溶胶,最后联结形成硅铝酸盐凝胶。

In order to increase the utilization rate of circulating fluidized bed fly ash,the effects of alkali concentration, temperature, reac- tion time,liquid-solid ratio on Si, A1 dissolution rate were studied. Results demonstrate that alkali concentration, temperature, time,liquid- solid ratio affect the dissolution of active Si and A1 in fly ash. When the alkali concentration is 9 mol/L, the reaction temperature is 90 ℃, the reaction time is 4 min and the liquid-solid ratio is 20, Si dissolution rate is 70%. When the concentration of alkali is 6 mol/L, the re- action temperature is 75℃ ,the reaction time is 16 min and the liquid-solid ratio is 20,A1 dissolution rate is 82%. When the dissolution temperature reaches 90℃ , Si and AI concentration are higher than 0.05 mol/L and 0.07 mol/L separately, Si and A1 in the solution will polymerized. With the concentration of Si and A1 increase, aluminosilicate colloids is formed first, then these colloids aggregates to form alu- minosilicate sol, finally aluminosilicate gel is formed.