基于超临界水氧化的生活垃圾渗滤液和焚烧飞灰协同无害化处理研究

MSW Leachate and MSW incineration fly ash is the inevitable secondary pollutants generated from disposal process of municipal solid waste. Leachate includes high concentrations contamination of organic pollution, inorganic nitrogen pollution and heavy metals, while the fly ash is rich in persistent organic pollutants like dioxin and heavy metals. It's very difficult for existing technology to dispose leachate and fly ash efficiently and environmental friendly. This project focuses on reaction mechanism and interacting factors during co- removal process of persistent organic pollutants and heavy metals from leachate and fly ash based on supercritical water oxidation. The influence of reaction parameters on degradation efficiency of dioxins in leachate and fly ash in in supercritical water oxidation is studied. Through analyzing the degradation products, the dechlorination process caused by free radical reaction in supercritical water oxidation is researched and degradation mechanism of dioxin is established. Additional, the catalytic effect of heavy metals in fly ash on degradation process of dioxins is investigated, along with content and morphology change of heavy metals in the leachate and fly ash before and after reaction. And the migration model of heavy metals in leachate and the change of characteristics of heavy metals in fly ash in the homogeneous supercritical water reaction system is studied. The basic theory on supercritical water oxidation of leachate and fly ash is acquired through experimental and theoretical studies, which provides a theoretical foundation and guiding for the design and development of this technology.

垃圾渗滤液和焚烧飞灰是垃圾在处置过程中产生的不可避免的二次污染物，渗滤液包括高浓度有机污染、无机氮污染和重金属污染，而焚烧飞灰富集二噁英等持久性有机污染物和重金属，现有技术对渗滤液和飞灰的高效无害化处置难度很大。本项目以渗滤液和飞灰为研究对象，探索超临界水氧化反应中持久性有机污染物和重金属协同去除的机理和相互影响因素。研究反应参数对渗滤液和飞灰中二噁英超临界水氧化降解效果的影响，通过分析降解产物，研究其在超临界水氧化反应中的自由基脱氯过程，建立二噁英降解反应机理；并考察飞灰中重金属对其催化降解作用，以及渗滤液和飞灰中重金属在反应前后含量和形态，建立渗滤液中重金属在均相超临界水反应体系中的迁移模型以及飞灰重金属特性变化。通过实验和理论研究，掌握超临界水氧化法共处置渗滤液和飞灰的原理,并为相应的技术开发提供依据。

垃圾渗滤液和焚烧飞灰是垃圾在处置过程中产生的不可避免的二次污染物，现有技术对渗滤液和飞灰的高效无害化处置难度很大。本项目主要以渗滤液和飞灰为研究对象，在间歇式反应器上探索超临界水氧化反应中持久性有机污染物和重金属协同去除的机理和影响因素，主要研究内容如下：.（1）开展了基于正交实验的超临界水氧化法处理垃圾渗滤液中有机污染物的研究。COD和NH4-N的最大去除率分别达到98.5%和76.2%。建立了适用于渗滤液中COD降解的一阶动力学方程，反应活化能为58kJ/mol，指前因子318S-1。.（2）研究了渗滤液中重金属向固相的迁移特性。经SCWO处理后，原始垃圾渗滤液中的重金属由于溶解性和反应转变行为而从体系中分离沉积，得以被有效去除。在正交试验条件下，Cu的去除率为75％到94％，而Mn和Zn的去除效率则高达98％至99％之间。此外进一步向渗滤液中添加高浓度重金属Cr、Pb、Cu硝酸盐研究迁移机理，对固体灰渣检测发现主要为金属氧化物和金属盐，通过一系列水解、脱水、分解和氧化过程而形成的。.（3）开展了基于超临界水氧化法的垃圾渗滤液和焚烧飞灰无害化共处置研究。在添加飞灰情况下渗滤液COD的去除率最大值达到99.2％，比未添加飞灰时要高，表明飞灰中重金属对有机物的降解有催化效果。经处理后飞灰中的 PCDD/Fs 质量浓度从初始的28.2ng 减少到只有2.79ng，质量降解率达到90％；飞灰氯化度的降低表明 PCDD/Fs 的降解伴随这脱氯反应。反应后飞灰重金属As，Cr，Pb 和Zn的浸出浓度均显著降低，满足填埋允许限值。.（4）以典型氯代持久性污染物十氯联苯为对象开展了试验和量子化学研究。在无碱性添加剂情况下，D10CB的降解产物主要是N9CB、O8CB和H7CB；NaOH能明显促进D10CB的脱氯降解，D10CB和整体PCBs的降解效率分别达到99.9%和99.2%，降解产物向低氯代同系物转移。.（5） 在水平管式连续超临界水反应装置上进行了垃圾渗滤液的 SCWO 处理研究，为工业应用提供指导依据。经SCWO处理后渗滤液中COD最大去除率达到95%，而NH4-N最高去除率仅51%。