生活垃圾焚烧飞灰中钙的脱除与回收

RECOVERY OF CALCIUM CARBONATE AFTER EXTRACTING CALCIUM SALT FROM FLY ASH OF MUNICIPAL SOLID WASTE INCINERATION

采用氯化铵(NH_(4)Cl)溶液浸出生活垃圾焚烧飞灰中钙后,再用碳化法对其进行回收。通过单因素实验和响应面设计获取钙离子浸出的最佳条件为:NH_(4)Cl浓度为3.9 mol/L,反应时间为64 min,液固比为5.6 mL/g;3个因素对Ca^(2+)浸出的影响程度排序为液固比>NH_(4)Cl浓度>反应时间。飞灰残渣重金属毒性浸出结果表明:Pb、Cu、Zn、Cd、Ni浸出浓度分别为0.0929,0.0012,0.0054,0.0017,0.0002 mg/L,明显低于GB 8978—1996《污水综合排放标准》中规定的最高允许排放浓度限值,即飞灰残渣的重金属毒性浸出结果满足HJ 1134—2020《生活垃圾焚烧飞灰污染控制技术规范(试行)》中6.3条综合利用要求。采用自制的PAN-PEI吸附盐洗液中的重金属后,再回收的碳酸钙品质极佳,其主要晶型为球霰石,Pb、Cd、Fe含量分别为0.0009%、0.0002%、0.0103%,符合HG/T 2776—2010《工业细微沉淀碳酸钙和工业微细性沉淀碳酸钙》标准要求,具有广泛的应用潜力。

After leaching calcium from fly ash of municipal solid waste incineration with ammonium chloride solution,the carbonization method was used to recover calcium carbonate from the leaching solution.The optimal conditions for leaching calcium ion after single factor experiment and response surface design were as follows:ammonium chloride concentration=3.9 mol/L,reaction time=64 min,liquid-solid ratio=5.6 mL/g;the degree of influence of the three factors on the leaching of calcium ions was in the order of liquid-solid ratio>ammonium chloride concentration>reaction time.The results of metal toxicity leaching from fly ash residues showed that the leaching concentration of Pb、Cu、Zn、Cd、Ni were 0.0929,0.0012,0.0054,0.0017,0.0002 mg/L,respectively,which were significantly lower than the maximum permissible emission concentration limit stipulated in GB 8978—1996 Integrated Wastewater Discharge Standard.And the heavy metal toxicity leaching results of fly ash residues met the comprehensive utilization requirements of Term 6.3 in HJ 1134—2020 Technical Specification for Pollution Control of Fly-ash from Municipal Solid Waste Incineration.After using homemade PAN-PEI to adsorb heavy metals in the salt wash,the recycled calcium carbonate was of excellent quality.Its main crystal type is vaterite,and the contents of Pb,Cd,and Fe were 0.0009%,0.0002%,and 0.0103%,respectively,in line with HG/T 2776—2010 Fine Precipitated Calcium Carbonate and Fine Activated Precipitated Calcium Carbonate for Industrial Use standard requirements,showing a wide range of application potential.