Investigation of polycyclic aromatic hydrocarbons in fly ash from fluidized bed combustion systems
Investigation of polycyclic aromatic hydrocarbons in fly ash from fluidized bed combustion systems
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DOI：
10.1021/es990944s
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发表时间：
2000-06-01
影响因子：
11.4
通讯作者：
Riley, JT
中科院分区：
文献类型：
--
作者：
Liu, KL;Xie, W;Riley, JT
采用实验室规模的流化床反应器和0.1MWth流化床燃烧器研究了操作条件对流化床燃烧系统飞灰中多环芳烃（PAHs）生成的影响。以高挥发分烟煤为研究对象，研究了其热解富氧燃烧过程中多环芳烃的排放规律。在实验期间，流化床反应器在700 ° C至900 ° C的温度下操作，而过量空气比从0变化至1.3。在这项研究中使用的多环芳烃的提取和GC/MS分析。在测试过程中确定了大约40种不同的多环芳烃，其中只有少数是由美国环保署指定的。实验结果表明，虽然流化床燃烧系统具有高效的固气混合过程和相对较长的停留时间，但固相（床层和飞灰）中的多环芳烃主要来自于流化床燃烧和/或热解过程中的分解反应。飞灰中多环芳烃的总量远高于原煤和气相中多环芳烃的总量。三，四环芳香族化合物是主要的多环芳烃从热解条件下，而萘（二环）是富氧燃烧条件下收集的床灰中的主导化合物。在流化床燃烧系统中，仅在床灰中检测到萘。高速二次空气（空气分级）注入到流化床系统的超高是一种有效的方法，以减少PAH的排放，沿着的其他好处，包括减少NOx和SOx的排放。
A laboratory scale fluidized bed reactor and a bench scale 0.1 MWth fluidized bed combustor were used to study the effect of operating conditions on the formation of Polycyclic Aromatic Hydrocarbons (PAHs) in fly ash from fluidized bed combustion systems. A high volatile bituminous coal was chosen to investigate PAH emissions during the entire pyrolysis to oxygen-rich combustion process. During the experiments, the fluidized bed reactor was operated at temperatures between 700 degrees C and 900 degrees C, while the excess air ratio was varied from 0 to 1.3. An extraction and GC/MS analysis of PAHs was used in this study. Approximately 40 different PAHs were identified during the tests, of which only a few are specified by the U.S. EPA. The experimental results indicate the majority of the PAHs in the solid phase (bed and fly ash) are derived from the breakdown reactions during the processes of combustion and/or pyrolysis in a Fluidized Bed Combustion (FBC) system, although FBC systems have an efficient solid-gas mixing process and relatively long residence time. The total amount of PAHs in the fly ash was much higher than that in the raw coal and in the gas phase. Three and four-ring aromatic compounds were the major PAHs from pyrolysis conditions, while naphthalene (two-rings) is the dominant compound in bed ash collected from oxygen-rich combustion conditions. Only naphthalene was detected in the bed ash in the FBC system. High-speed secondary air (air staging) injected into the freeboard of the FBC system is an effective method for minimizing PAH emissions, along with the other benefits including minimizing NOx and SOx emissions.