EXPERIMENTAL STUDY ON DIOXINS CONTROL DURING LOW-TEMPERATURE PYROLYSIS OF DOMESTIC WASTE
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摘要: 针对垃圾热解烟气中二噁英排放不达标的现象,在分析垃圾热解机理及二噁英产生机制的基础上,提出了定量供氧、分层控制二噁英的方法;并采用数值分析和试验测试相结合的方法,对炉内气流组织及垃圾热解过程进行模拟分析。结果表明:热解炉内部气流整体分布较为均匀,能够保证垃圾稳定热解。热解炉沿轴向方向上存在温度分层,与理论分析结果一致,但燃烧层与热解层之间的过渡层存在二噁英合成气氛;热解炉温度实测结果与模拟结果整体吻合较好;空气过剩系数为0.3时热解炉运行情况更有利于减少二噁英的产生。现场试验发现,热解炉出口烟气中除颗粒物浓度超标外,其余常规污染物及二噁英排放浓度均满足GB 18485-2014《生活垃圾焚烧污染控制标准》;而市面上常见炉型二噁英出口浓度为0.44 ng-TEQ/m3,超过GB 18485-2014限值0.1 ng-TEQ/m3;2种炉型试验结果对比证明,在热解炉布气均匀的基础上,通过定量供氧、分层控制的方法可以有效抑制烟气中二噁英的生成。该成果可为生活垃圾低温热解过程二噁英的控制提供理论参考。Abstract: Based on the phenomenon of substandard dioxin emission from waste pyrolysis flue gas, this paper proposed a method of quantitative oxygen supply and stratified dioxin control based on the analysis of the waste pyrolysis and dioxin generation mechanism, used a combination of numerical analysis and experimental test to simulate the airflow organization inside the furnace and waste pyrolysis process, and discussed the effect of air supply on dioxin synthesis. The results showed that the overall distribution of airflow inside the pyrolysis furnace was relatively uniform, which ensured the stable pyrolysis of waste. The temperature stratification along the axial direction of the pyrolysis furnace was consistent with the theoretical analysis, but there was a dioxin synthesis atmosphere in the transition layer between the combustion layer and the pyrolysis layer; the measured results of the pyrolysis furnace temperature were in good agreement with the simulation results as a whole; a comprehensive comparison suggested that operation of the pyrolysis furnace with an air excess factor of 0.3 was more conducive to reducing dioxin generation, and the waste treatment capacity was 2.4 t/d. The field test result showed that, except for the particulate matter concentration exceeded the standard, the other conventional pollutants from pyrolysis furnace outlet flue gas and dioxin emission concentration met the Standard for Pollution Control of Domestic Waste Incineration (GB 18485-2014). The commercially available common furnace model dioxin outlet concentration was 0.44 ng-TEQ/m3, exceeding the national emission standard limit of 0.1 ng-TEQ/m3. The experimental results of the two furnace types proved that dioxin generation in the flue gas could be effectively suppressed by quantitative oxygen supply and stratified control on the basis of uniform gas distribution in the pyrolysis furnace. The study could provide a theoretical basis for the control of dioxins in low-temperature pyrolysis of domestic waste.
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