【作者】 李清海；

【导师】 陈昌和；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2007， 博士

【摘要】 焚烧是实现垃圾减量化、无害化和资源化的有效方法,研究其燃烧和污染物的排放特性具有重要意义。本文对层燃-流化复合垃圾焚烧炉的燃烧及排放进行了系统的实验和模型研究,取得了以下主要成果。通过对垃圾热值和燃烧温度的分析,指出对我国高水分、低热值的垃圾,采用层燃炉排预热干燥,进而使用循环流化床焚烧是独具优势的技术路线。对垃圾的干燥过程进行了实验和理论分析,得到了桔子皮等典型垃圾成分在不同干燥温度下的失水率和干燥的活化能等参数,得出了干燥床的优化结构和设计原则。利用TGA等分析手段,系统研究了多种垃圾组分的着火温度和燃烧过程中释放的气体成分,得到了热解产物烷烃、苯等随垃圾成分、加热温度的变化规律及着火温度,并得到了热解过程的活化能和指前因子等参数,为垃圾焚烧及排放模型的建立提供了基础。对单组分垃圾进行了燃烧实验,发现层燃条件下经过干燥后的垃圾在燃烧过程中CO、CxHy的峰值较大,必须注意二次风的配入;在流化床燃烧条件下,水分闪蒸和挥发分急剧释放会导致焚烧床内出现爆燃;二次风率增加,CO和NOx排放降低。分别在1MW垃圾焚烧实验台、150t/d和260t/d层燃-流化复合垃圾焚烧炉上进行了垃圾焚烧实验和热态工业测试,结果表明,沿炉膛高度CO和有机可燃气体的最大浓度和燃尽时间都明显大于燃煤锅炉,多级合理的配风是垃圾燃烬和降低污染物原始生成的决定因素;并表明垃圾在干燥床内预干燥,不仅有利于炉膛内燃烧稳定,降低掺煤比,还可以有效抑制爆燃和降低污染物的排放。提出了层燃-流化复合垃圾焚烧炉焚烧及排放的半经验计算模型,使用工业测试数据对计算结果进行了比较和验证。通过计算研究了过量空气系数、一次风率等运行参数对燃烧和污染物生成的影响。本模型对层燃-流化复合垃圾焚烧炉的设计改进和运行操作具有一定的指导意义。更多还原

【Abstract】 The incineration is an effective method to treat municipal solid waste (MSW) for its volume reduction, harmless treatment and energy recovery. It is important to study on the combustion process and pollutant emission in MSW incineration. The experiments and model simulating of MSW combustion and pollutant emission in a combined grate and circulating fluidized bed incinerator (grate-CFBI) have been performed. Through the study, following results are obtained.The analysis of low heating value and ignition temperature of MSW was carried out. The analysis results indicate that the technology of grate-CFBI, that is, to use at first the grate bed to dry out MSW and then to use the fluidized bed to incinerate MSW is very effective for MSW treatment. The drying process of MSW was experimentally investigated in test rigs and in a simulated grate bed respectively. The moisture loss rate and activation energy of typical waste at different temperature were obtained from the experiments. Based on the experimental and theoretical analysis results, the optimized structure of the grate bed of grate-CFBI and its design principle were proposed.The ignition temperature and evolved gas components of typical waste in drying, pyrolysis and oxidization process were experimentally studied by using the thermal gravimetric analysis (TGA). The changing trend of pyrolysis products including alkanes, benzene, et al. and the ignition temperature of MSW ware obtained. In addition, the activation energy and exponential factor of MSW in pyrolysis were analyzed. The obtained kinetic parameters of MSW pyrolysis and the ignition temperatures can be used as the data base in the model simulation of MSW incineration.The experiments of combustion of typical MSW components were performed in an experimental facility. It was found from the experiments that the peak values of CO and CxHy appeared in combustion process of post-drying waste at the grate bed were very high and the secondary air was required for their complete combustion. When MSW incinerated in fluidized bed, the flash vaporization of water and rapid release of volatile matter of MSW induced deflagration combustion, which lead to the pressure and temperature fluctuations in the furnace. With the increase of secondary air flow rate, the emission of CO and NOx decreased.The combustion experiment of raw MSW collected from community and the test carried out in the industrial grate-CFBI of 150t/d (ton per day) and 260t/d grate-CFBI were performed respectively. The results from both the experimental work and the industrial test showed that CO and other combustible gas concentrations along the height of the furnaces were higher and the burnout time of these gases were longer respectively than that in coal fired boilers. The multi-staging air supply was decisive to reduce the original pollutant formation. The experiment and the industrial test also indicated that the pre-drying of waste on the grate bed could not only maintain the stable combustion in furnace and reduce the supplement coal, but also inhibit the deflagration combustion and reduce pollutant emission.A semi-theoretical model for the simulation of MSW combustion and pollutant emission in the grate-CFBI was presented and verified by the experimental and industrial test data. The influence of operation parameters such as the excess air and primary air rate on combustion and pollutant formation was studied by the model simulation. This semi-theoretical simulation model is useful for the design and the operation of the grate-CFBI.更多还原