热等离子体处理前后垃圾飞灰中重金属浸出浓度的变化及二恶英分布特性的差异

Leaching toxicity and dioxin distribution characteristics of MSW fly ash by thermal plasma melting

为探究热等离子体处理飞灰工艺工业应用的潜力,分析处理前后飞灰中9种重金属浸出浓度变化及二恶英的分布特性,基于处理量为5 t·d^(-1)的中试规模的热等离子体熔融系统,在1550℃的处理温度下进行了飞灰处理实验。结果表明,不宜使用硫酸硝酸法检测玻璃态渣中As浸出浓度,硫酸根离子会与As在熔融过程中形成的砷酸钙和亚砷酸钙中的钙离子结合,导致As的浸出浓度增加;熔融处理后,除As外的其他重金属的浸出浓度均降至国家标准浓度限值以下;就太原地区而言,其垃圾飞灰中PCDFs的含量高于PCDDs,且低氯代呋喃含量高于高氯代呋喃;熔融处理后的垃圾飞灰中,二恶英毒性当量减少率为99.96%,降至0.5466 ng·kg^(-1),远低于填埋标准中二恶英排放限值,说明该中试系统能够满足飞灰处理要求。该研究结果可为热等离子体熔融飞灰中试系统的工业应用提供参考。

In order to obtain reference data for industrial application of thermal plasma treatment of fly ash,and to study the leaching concentration changes of 9 heavy metals and the distribution characteristics of dioxins.The test was conducted by heating up to 1550℃through a thermal plasma melting system with a processing capacity of 5 t·d^(-1) on a pilot scale.The results show that it is not appropriate to use the sulfuric acid nitric acid method to detect the As leaching concentration in the glassy slag.Sulfate ions will combine with the calcium arsenate and calcium ions in the calcium arsenite formed during the melting of As,resulting in an increase in the leaching concentration of As;The leaching concentration of other heavy metals except As has fallen below the national standard concentration limit;the content of PCDFs in Taiyuan area is higher than that of PCDDs,and the content of low-chlorinated furans is higher than that of high-chlorinated furans;the reduction rate of dioxin equivalent after melting treatment 99.96%,down to 0.5466 ng·kg^(-1),which is far lower than the dioxin emission limit in the landfill standard,indicating that the pilot system can meet the requirements for fly ash treatment.The research results can provide data support for the industrial application of the thermal plasma melting fly ash pilot system.