【作者】 石德智；

【导师】 陈英旭；

【作者基本信息】 浙江大学 ， 环境工程， 2009， 博士

【摘要】 随着城市化进程的加快和城市生活垃圾产生量的不断增加，城市生活垃圾造成的围城现象和环境污染日益突出。城市生活垃圾的处理已成为我国和世界各国面临的重大环境问题。焚烧处理法是目前世界各国最广泛采用的处理生活垃圾的有效有段之一。由于我国现有垃圾的收运管理体系相对落后，垃圾中大量的可回收利用物质被直接焚烧造成资源的损失，与建设“资源节约型”社会的目标相违背。另一方面，我国的焚烧技术起步晚，还缺乏针对我国国情下性质复杂的城市生活垃圾的高效安全的焚烧处理技术，垃圾焚烧造成的二次污染给环境带来了巨大的压力。本研究针对我国城市生活垃圾的性质和变化趋势，以资源回收和焚烧污染控制为目标，研究建立了新型的垃圾源头分类收集与转运系统，研究了垃圾分类收运与焚烧处理综合技术体系下，垃圾焚烧炉的系统运行调控、二噁英类和多环芳烃的形成与污染控制、重金属的迁移与转化以及焚烧灰渣的资源化，研究结果对我国城市生活垃圾分类收集管理体系和与焚烧处理污染物控制技术适配的完善具有重要现实意义。研究取得的主要结论有：（1）依据垃圾性质的变化趋势、资源回收优先、简单方便易行等原则，确立了将生活垃圾分为厨余垃圾、干垃圾和有害垃圾等三类的城市生活垃圾分类收集技术与管理体系。优化了分类收运系统，设计建设了以废物资源回收为目的的干垃圾中转站分拣回收体系，建立了“收运压缩+中转垂直压缩+堆酵脱水”的组合脱水预处理工艺，构建了管理保障体系。通过运行实施发现垃圾分类投放正确率显著提高，建立的垃圾分类收集方法切实可行。组分显著变化导致垃圾含水率和容重升高，但组合脱水工艺可实现垃圾水分的高效脱除，含水率降低14％以上。（2）垃圾源头分类收集与分拣回收使纸张、织物、塑料等组分的比例下降，尤其是塑料组分显著减少达50％，厨余垃圾成为垃圾的主要组成部分。塑料袋与PVC等塑料组分的大量去除以及厨余垃圾中可溶性无机氯盐类通过脱水去除，直接导致垃圾中Cl元素的显著降低。组合脱水处理技术使垃圾湿基低位热值显著增加至5000kJ／kg以上。新型的垃圾分类收运与焚烧处理综合技术体系下，垃圾焚烧炉的处理效率显著提高，在降低助燃系统能耗的同时可显著提升垃圾焚烧过程炉膛温度。随着余热锅炉热量系统热量回收效率显著增加，汽轮机—机组的热电转化效率显著提升。（3）对焚烧炉烟气和尾气中7种2,3,7,8位氯取代的二苯并二噁英PCDDs和10种2,3,7,8位氯取代的二苯并呋喃PCDFs同系物浓度与毒性当量的分布特征发现，烟气向尾气转变过程中PCDFs和PCDFs的分布特征发生了显著变化。PCDD／Fs浓度与半干式烟气处理系统中PCDD／Fs的吸附去除量之间存在线性关系，PCDD／Fs同系物的浓度分布和活性炭的吸收负荷是影响二噁英去除效率的关键因素。最高毒性的2,3,7,8-TCDD在布袋除尘器飞灰中富集。共平面PCBs毒性当量对二噁英类毒性当量的贡献率不足1％，PCDD／Fs毒性当量是影响飞灰二噁英类毒性当量的决定性因子。垃圾物料的理化性质与焚烧炉工况是影响垃圾焚烧过程二噁英产生的关键因素。PCDD／Fs的浓度随着焚烧烟气中O₂、CO、HCl的含量的降低而下降，呈现正相关。新型的垃圾分类收运与焚烧处理技术体系可减少垃圾焚烧过程二噁英的产生量和毒性当量，并使二噁英富集在飞灰中从而降低向大气排放，由于二噁英排放因子降低至338．92 ng I-TEQ／t MSW。（4）对16种多环芳烃PAHs及7种致癌性PAHs在焚烧炉底渣、余热锅炉飞灰、布袋除尘器飞灰中的分布规律研究发现，PAHs主要分布富集在焚烧炉底渣中。灰渣中PAHs总含量、致癌性PAHs总量、PAHs致癌性毒性当量B[a]P_eq的顺序均为：焚烧炉底渣＞余热锅炉飞灰＞布袋除尘器飞灰。焚烧炉底渣与余热锅炉飞灰中PAHs的组成特征相似。新型的垃圾分类收运与焚烧处理技术体系下，底渣与飞灰中PAHs致癌性毒性当量B[a]P_eq均显著降低。垃圾中的氯源是影响垃圾焚烧过程中PAHs生成的关键因素。垃圾分类收集回收去除塑料和金属、组合脱水是从源头着手减少焚烧过程PAHs生成的两个重要环节。焚烧炉膛温度的显著升高是PAHs生成减少的重要因素之一。垃圾焚烧灰渣中PAHs与CO呈现正相关，与过剩空气系数呈现负相关，以CO浓度降低和过剩空气系数升高为表征的垃圾燃烧效率提高，是垃圾焚烧灰渣中多环芳烃生成减少的重要因素。（5）低挥发性的Cu、Cr、Ni、Mn等主要分布在焚烧炉底渣中。Hg、Cd、Zn、Pb等挥发性重金属因蒸发并冷凝吸附主要富集在各种飞灰中。焚烧灰渣中重金属含量水平受垃圾组成、焚烧过程工况特别是温度等因素影响。底渣中重金属含量显著降低与分拣去除含重金属的组分有关。飞灰中重金属的含量升高与焚烧炉膛温度的升高、重金属向飞灰中迁移并富集的速率增加有关。垃圾焚烧灰渣中各重金属在“最不利”环境条件下的最大可浸出量与灰渣中该重金属的存在形态直接相关，与水溶态、Ca离子交换态、Ag离子交换态、酸溶态等四种易浸出形态之和存在正相关性。新型的垃圾分类收运与焚烧处理技术体系，有利于重金属在飞灰中的富集而减少向大气排放，同时能降低重金属易浸出形态含量从而减少焚烧飞灰作为危险废物安全处置时重金属浸出的环境风险。（6）相较于飞灰，焚烧炉底渣的火山灰活性符合作为水泥的人工火山灰质混合材料。通过对底渣中影响波特兰水泥性质的SiO₂、CaO、Al₂O₃等组分的分析、微粉添加对混凝土试件强度和水泥胶砂流动度的影响研究，垃圾焚烧炉底渣的抗折强度、抗压强度及活性指数显著增加，水泥胶砂的流动度显著降低，而且烧失量降低，易磨性能显著增加，与垃圾分类后组分变化及垃圾焚烧充分、有机物质分解彻底、灰渣颗粒粒径减少等因素直接相关。新型的垃圾分类收运与焚烧处理体系下，焚烧炉底渣符合国家标准对人工火山灰质混合材料的各项技术要求，可以直接用于水泥生产的掺和料而实现在水泥和建筑行业上的资源化利用。更多还原

【Abstract】 With rapid economic development and urbanization, the quantity of municipal solid waste （MSW） generated has increased quickly. Expanding MSW production could have a great effect on the environment and public health as the disposal of MSW has become a serious problem in China and other countries around the world. Thermal treatment using incineration technology has proven as an attractive method of MSW disposal for many years. Due to the limitation of MSW management system in China, many components in MSW which could be recycled as resource were loss during combustion. It goes against the goal for establishing "Recycking-based Society". On the other hand, MSW incineration in China is still in initial stage. Due to the complex characteristics of Chinses MSW, secondary pollution from MSW incineration has been a serious problem. In this research, a newly source-classication and transportation system was established. The operation MSW incineration, formation and pollution control of PCDD/Fs and PAHs, transfer and transformation of heavy metals during MSW incineration process were studied. Furthmeore, the ultilzaion of residues from combustion was also dicussed. Main conclusions were:（1） Based on the variation trend of MSW, recycling and ultization of waste, and feasibility of methods, MSW should be sorted as food waste, dry waste and harmful waste by residents. The whole system including collection, transfert and ransportation were optimized. A transfer station was designed and constructed for MSW recycling, and the combined dewatering technology" vehicle compress dewatering +mechanical dewatering + stockpile dewatering" was established. A management system were founded as well. It was shown that the separeation methods was feasible, and the correctness rates of MSW separatione increased significantly. The components of MSW changed due to the classification and recycling. Although the moisture and bulk density increased, but with a higher dewatering efficiency （more than 14%） the moisture of the classified MSW reduced significantly.（2） Due to reduction in source classification and separation section, conten of paper, textile and plastics decreased, plastics signicifantly lessend by 50% in particular. Kichetn waste became the main component. Cl content was decreased, which was dierectly related with the removal of a large amount od plastic bags and PVC, and the reduction of soluble chloride contaning in food waste through dewatering. The lower heat value （LHV） of feeding waste was increased to more than 5000kJ/kg, resulted from combined dewatering. The treatment efficiency of incinerator was improved and the temperature of incinerator furnace was continuously higher during the combustion process. By the newly established MSW source-classified collection and incineration system, the net enery output of the waste heat boiler increased significantly. Therefore, the energy transformation efficiency between waste heat boiler and steam turbine generator improved.（3） The concentration distribution and toxic equivalent quantity （TEQ） of 7 kinds of 2,3,7,8-substituted PCDDs congeners and 10 kinds of 2,3,7,8-substituted PCDFs congeners in flue gases from incinerator and the stack flue gases were studied. The ratio of PCDDs and PCDFs changed in stack flue gas compared with flue gas. 2,3,4,7,8-PeCDF was the key factor affecting the TEQ. The correlation relationship between the PCDD/Fs concentrations in flue gas and the removal quantity of PCDD/Fs in the air pollution control devices （APCD） was observed, which proved that the PCDD/Fs concentration distribution and the absorption load of active carbon were the two key factors affecting the removal efficiency of PCDD/Fs. The most toxic congener 2,3,7,8-TCDD was condensed in fly ash from bag filter （FABF）. The proportion of coplanar PCBs TEQ /dioxin TEQ of FABF was less than 1%, which indicated that TEQ of PCDD/Fs was the dominant factor affecting the dioxin TEQ of FABF. The characteristcs of feeding waste and the incineration parameters principally influenced PCDD/Fs formation during combustion. Content of O₂、CO、HCl in flue gas were decreased. The correlation relationship between PCDD/Fs and content of O₂、CO、HCl in flue gas existed. These results demonstrated that PCDD/Fs formation in flue gas could be reduced, and concentrated in fly ash to lessen the emission to atmosphere with the foundation of the new MSW source-classified collection and incineration system. Furthermore, the emission factor of dioxin from the plant was reduced to 338.92 ng I-TEQ/t MSW.（4） Distributions of 16 PAHs and 7 carcinogenic PAHs among BA, FAB and FABF were studied. PAHs were mainly concentrated in BA. The concentrations of PAHs in fly ashes were relatively lower. The ranking of the total content of PAHs, the total content of carcinogenic PAHs and the toxic equivalency of PAHs (B[a]P_eq) all were: BA > FAB > FABF. The constitution of PAHs in FAB were the similar. The total content of PAHs and B[a]P_eq of bottom ash and fly ash from the classified MSW incineration were both decreased. Chlorine was the key factor that affecting PAHs formation during MSW combustion. Removal of metals and paper printed with heavy metal containing materials might reduce PAHs generation from MSW incineration. Therefore, sorting of plastics and metal, combined dewatering were the two important steps for reducing PAHs formation. Becasue PAHs are typical products of imcomplete combustion, and PAHs formation are sensitive to the combustion process. A negative correlation between the total PAHs and furnace temperature was observed, which proved that the increase of furnace temperature during the classified MSW incineration was one of important factors for reducing PAHs generation. Moreover, a positive correlation between the total PAHs and CO, a negative correlation between the total PAHs and excess air ratio were shown. The increase of combustion efficiency which was presented as decrease of CO and increase of excess air ratio, might significantly decrease the PAHs formation.（5） Transfer and distribution of heavy metals in bottom ash and fly ash during MSW incineration were studied. Low volatile metals such as Cu、Cr、Ni、Mn mainly exsited in bottom ash. On the other hand, some volatile metals such as Hg, Cd, Zn and Pb, would evaporate and would be adsorpt by granule of fly ash during condensation process. Therefore, these volatile metals became rich in fly ash. Levels of heavy metals in residues are affected by feeding waste and combustion history, especially incineration temperation. Concentations of heavy metals in bottom ash were lower, probably due to the reduction of metals, metal-containing newpaper and textile in feeding waste. Volatile metals are expected to have higher transfer rate to fly ash as furnace temperature increases. Owing to the continuously higher in the incinerator furnace during the incineration of classified MSW, heavy metals concentrations in fly ashes were higher. The maximum leachable abilities of heavy metals were related with chemical special distribution of heavy metals in residues. There was a linear relationship between the maximum leachable abilities and the total content of four leacheable chemical speciations, that were water soluble, Ca exchangeable, Ag exchangeable and acid soluble, respectively. Under the newly established MSW source-classified collection and incineration system, the enrichment of heavy metals in fly ash may be advantageous for emission decrease of heay metals to atmosphere. On the hand, the decrease of leacheable chemical speciations in fly ash could be beneficial to reduce the ecological risk of heavy metals leachting, where fly ash treated specilly as hazardous waste.（6） As the results of volcanic activities testing for bottom ashes and fly ashes from MSW incineration, BA might be able to be applied as pozzolanic material due to its qualified activity of volcanic ash. According to chemical component analysis of BA in oxide form, particularly the distribution of SiO₂、CaO、Al₂O₃ which primarily affected the characteristics of pozzolanic cement, and the effect of BA on strength of concrete and fluidity of cement mortar, it was shown that the rupture strength, compressive strength and activity index of C-BA increased, fluidity of cement mortar decreased. In addtion, loss in ignition of BA decreased but property of grindability was improved. These might be due to the change of component of feeding waste, much more complete decomposition of organic matter and decrease of size distribution for BA, which were directly releated to the higher furnace temperature of the classified MSW incineration process. The results indicated that the newly established MSW source-classified collection and incineration system could improve the pozzolanic characteristics of BA as pozzolanic materials used for cement production, and therefore it could be conducive to BA utilization in cement and construction industry.更多还原