氢氧化钠循环母液杂质对高铝粉煤灰预脱硅过程的影响

Influence of Impurities in NaOH Solution on Pre-desilication of High Alumina Fly Ash

以高铝粉煤灰为原料进行预脱硅,在预脱硅过程中控制氢氧化钠循环母液中碳碱浓度和氧化铝浓度,研究两种杂质成分对预脱硅过程液相成分、液相黏度和脱硅粉煤灰铝硅比变化的影响。结果表明,随着循环母液中碳碱浓度的提升,液相中的氧化硅含量稍有下降,脱硅灰的铝硅比呈小幅下降趋势,循环母液中的碳碱浓度的提升会增大液相的黏度,对过滤过程不利,应将碳碱浓度控制在10g/L以下。循环母液中的氧化铝会与脱硅液中的氧化硅反应生成羟基方钠石等沸石类前驱体,从而降低脱硅液中的氧化硅浓度和脱硅灰的铝硅比,增加脱硅灰中化合碱含量,生产中循环母液中氧化铝浓度不应超过3g/L。

With high alumina fly ash as raw material for pre-desilication, and through controlling concentration of sodium carbonate and alumina in NaOH circulating mother liquor during pre desilication, the influence of two kinds of impurities on liquid composition, liquid phase viscosity and alumina silica ratio （A/S） of fly ash during pre desilication were investigated. The results show that content of silicon oxide in liquid phase and A/S of fly ash drop slightly with increase of concentration of sodium carbonate in sodium hydroxide solution. Increasing of concentration of sodium carbonate in sodium hydroxide solution will raise viscosity of liquid phase, which prohibites filtration process. Concentration of sodium carbonate should be controlled below 10 g/L. Alumina in sodium hydroxide solution reacts with silica in sodium silicate solution to produce zeolite precursor such as hydroxysodalite, which will reduce concentration of silicon oxide in sodium silicate solution and A/S of fly ash, and raise content of combined alkali in fly ash. Alumina concentration in sodium hydroxide solution during plant production should not exceed 3 g/L.