煤气化多环芳烃初步研究

Preliminary study on PAHs emission from coal gasification

为了研究煤及其气化产物中多环芳烃的分布特征,在一台小型常压流化床气化炉上进行了以空气和水蒸气为气化剂的煤气化试验.经索氏萃取和KD浓缩后,采用带荧光检测器和二极管矩阵检测器的高效液相色谱仪对原煤、底渣、旋风焦、布袋焦和煤气中被USEPA列为优控污染物名单的16种多环芳烃进行了测定.试验结果表明煤气化前后多环芳烃质量分数和毒性当量质量分数的分布特征相似,但多环芳烃的组成和质量分数不同;煤化程度增加,原煤多环芳烃质量分数和毒性当量质量分数减小,煤气化多环芳烃质量分数先增后减,毒性当量质量分数与煤化程度呈线性关系;部分煤种气化多环芳烃的质量分数高于原煤多环芳烃质量分数,且煤气化多环芳烃的种类分为原煤未分解的多环芳烃、热解合成的多环芳烃、自由基高温缩合生成的多环芳烃.

To investigate the distribution and content of polycyclic aromatic hydrocarbons (PAHs) in raw coal and gasified products during coal gasification,the air and steam gasification of coal was tested in an atmospheric fluidized bed gasifier. After Soxhlet extraction and Kuderna-Danish (K-D) concentration, the content of 16 PAHs recommended by United States Environmental Protection Agency (US EPA) in raw coal, slag, bag house coke, cyclone coke and fuel gas, were analyzed by a high performance liquid chromatography (HPLC) coupled with fluorescence and diode-array detection. The experimental results show that the distributions of content and toxicity equivalent quantity (TEQ) of PAHs in raw coal are similar to coal gasification but this compositions and contents are different. The rise of coal rank leads to the decrease of the content and TEQ of PAHs in raw coal and the increase of TEQ during coal gasification, while the content of PAHs emission from coal gasification increases first and then decreases with the increase of coal rank. The total PAHs contents generated in coal gasification of some sorts of coals are higher than in raw coal. The types of PAHs formed in coal gasification include undecomposed PAHs in raw coal, pyrosysthensis PAHs, and radical polymerization PAHs at high temperature.