垃圾焚烧飞灰水洗脱氯及重金属浸出特性研究

系统研究了机械炉排炉垃圾焚烧飞灰水洗过程中氯化物和重金属的浸出特性,并采用Visual MINTEQ模拟分析水洗液中重金属的存在形态。结果表明：飞灰中的氯主要以可溶性氯化钠（NaCl）、氯化钾（KCl）、氯化钙（CaCl₂）、碱式氯化钙（CaClOH）的形式存在,飞灰水洗浸出成分97%以上为氯离子（Cl^-）、钠（Na）、钾（K）、钙（Ca）,其中氯离子占比高达60%;重金属及其他成分的浸出量很少,不足1%。水洗对氯离子的去除效果非常明显,可达92%以上,但是重金属的浸出量极低。飞灰单次水洗最佳条件：液固体积质量比为6 mL/g,洗涤时间为10 min。Visual MINTEQ模型分析表明,pH是控制飞灰水洗液中铅（Pb）、铜（Cu）、锌（Zn）、镉（Cd）形态的重要因素,氯离子（Cl^-）对镉的形态分布也有着重要的影响。飞灰水洗液电导率与氯离子质量浓度具有极好的线性相关性,其可作为监测滤液中氯离子质量浓度变化的有效间接指标。

Study on dechlorination and heavy metal leaching characteristics of MSWI fly ash during water-washing

The leaching characteristics of chloride and heavy metals in the washing process of waste incineration fly ash from mechanical grate furnace were systematically studied,and the existing forms of heavy metals in the washing solution were simulated and analyzed by Visual MINTEQ.The results showed that the chlorine state in fly ash mainly existed in the form of soluble sodium chloride(NaCl),potassium chloride(KCl),calcium chloride(CaCl2)and basic calcium chloride(CaClOH).More than 97%of the leaching components of fly ash were Cl^-,Na,K and Ca,of which Cl^-accounts for 60%.The leaching amount of heavy metals and other components was very small,less than 1%.The removal effect of water washing on chloride ion was very obvious,up to more than 92%,but the leaching amount of heavy metals in the process of water washing was very low.The optimum conditions for single water washing of fly ash:the volume mass ratio of liquid to solid was 6 mL/g and the washing time was 10 min.The analysis of visual MINTEQ model showed that pH was an important factor to control the forms of lead(Pb),copper(Cu),zinc(Zn)and cadmium(Cd)in fly ash washing solution,and chloride ion(Cl^-)also had an important influence on the form distribution of cadmium.There was an excellent linear correlation between the conductivity of fly ash washing solution and the mass concentration of chloride ion,which could be used as an effective indirect index to monitor the change of mass concentration of chloride ion in leachate.