汽车排气中PAHs之特性及其与排放微粒中碳成份关系之探讨.doc

汽車排氣中PAHs之特性及其與排放微粒中碳成份關係之探討Characteristics of PAHs from a Gasoline-Powered Engineand its Correlation with Carbon Content in Emitted Particles研究生:簡維政Jian, Wei-Jain指導教授：陳瑞仁S. J. Chen【摘要】多環芳香煙化合物(PAHs)為高致癌性及致突變性之化合物，主要為有機質不完全燃燒所產生 為瞭解汽車廢氣中PAHs之排放特性，本研究乃利用實際汽車引擎、馬力試驗機及煙道採樣器等儀 器，採集馬自達(Mazda)引擎尾氣之廢氣進行PAHs分析，以探討汽車排氣中PAHs總濃度、氣固相 分佈、排放係數及PAHs與碳含量之關係採得之樣本經萃取、濃縮、淨化及再濃縮後以GC進行 PAHs分析研究結果顯示：汽車無論有無加裝觸媒轉換器，排氣中之PAHs主要以氣相存在以九五無鉛 汽油為燃料，引擎總PAHs排放之濃度平均為高級汽油及九二無鉛汽油之1.29及1.33倍，顯示九 五無鉛汽油有較大之PAHs排放量加裝觸媒轉換器後，PAHs之排放濃度及排放係數至少降低85 %以上，顯示觸媒轉換器對汽車煙道PAHs之排放有顯著之削減作用。

煙道排氣中2~3環之PAHs 濃度佔總PAHs之70%以上，且幾乎以氣相存在燃燒高級汽油、九五無鉛汽油及九二無鉛汽油， 其排氣中微粒上總碳濃度分別為0.659g/g、0.764g/g及0.627g/g ；元素碳濃度為0.21也/g、0.i90g/g 及0.280g/g ；有機碳濃度為0.44lg/g > 0.574g/g及0.347g/g，可知汽車煙道所排出之微粒其主要組 成為碳成分，且有機碳濃度較高，其值約為元素碳之1.3〜3.()倍在個別PAHs與元素碳之相關方 面，於未加裝觸媒轉換器時，以高級汽油為燃料，其排氣微粒中元素碳成分與本研究所採用之二十 一種固相PAHs之間，發現BkF、CYC及BghiP在微粒上之含量皆隨元素碳含量增加而增加；九 五無鉛汽油以Ant、BkF、PER及BeP四種PAHs與元素碳之相關性最好；九二無鉛汽油則以Nap、 AcPy、Ant、CYC、BeP、BkF及PER為最佳另外探討微粒上致癌性較高之PAHs與元素碳之關 係，結果顯示：高級汽油以BkF+BghiP ；九五無鉛汽油以BkF+BaP、BkF+BbF、BbF+CHR等隨元 素碳含量增加而增加在PAHs排放係數方面，不論有無加裝觸媒轉換器，1500rpm時之排放係數 值最大。

由油料平衡試驗發現，未加裝觸媒轉換器在轉速分別為3000rpm、2200rpm、1500rpm及 lOOOrpm時，燃燒單位體積油品產生之PAHs量，高級汽油依序為6.58、12.4、10.6及14」mg/liter ； 九五無鉛汽油依序為10.5、11.5、15.2及21.7mg/liter ；而九二無鉛汽油依序為8.11、9.07、9.04及 20.9 mg/liter，每一種油品皆在10()0 rpm(即空轉)時有最大之PAHs排放量最後，由煙道微粒之 SEM、EDS及WDS分析結果顯示：汽車煙道所產生之微粒，其外觀形貌多為光滑之圓球形表面， 且粒徑多在O.lum以下；微粒上除碳成分外，其他元素含量相當少，由WDS做Mapping之結果得 知：碳成分密集的散佈在微粒中，此現象與藉由元素分析儀測知汽車排氣管排出之微粒，其主要組 成為碳成分之結果相符°關鍵字：多環芳香煙化合物 含碳微粒 引擎轉速 觸媒轉換器[Abstract!The results show that PAHs mostly exist as gaseous phase in the exhaust, no matter a catalyst converter is adapted or not. The PAHs concentration for using 95-unleaded gasoline is higher compared to 92-unleaded and premium gasoline and the concentration ratios are about 1.29 and 1.33 . When a catalyst converter is adapted,the PAHs concentrations and emission factors reduce at least 85% of the origi ns，More than 70% of the PAHs are 2-3 cyclical and almost all of them are gaseous. The total carb on concentrations in the emitted particles for premium, 95-unleaded, and 92-unleaded gasolines are 0.659g/g, 0.764g/g and 0.627g/g respectively ； the elemental carbon concentrations are 0.218 g/g, 0.190 g/g and 0.280 g/g respectively ； and the orga nic carb on concen tratio ns are 0.441 g/g, 0.574 g/g, and 0.347 g/g respective! y. It is clear that the major con stitue nt of particles is carb on, and the con centratio n of orga nic carb on is higher tha n element one by 1 ・3 to 3.0 times ・ The correlation between the carcinoge n PAHs and elemental carbon in particles shows that there are linear correlations in BkF+BghiP in premium gasoline and among BkF +BaP, BbF + CHR, BkF + BbF, in 95-unleaded gasoline. With or without catalyst converter, the PAHs emission factors are highest at 1500rpm. By fuel balance test without catalyst converter, it is found that the PAHs amounts per unit fuel volume for premium gasoline are 6.5& 12.4, 10.6, and 14.1 mg/liter at 3000, 2200, 1500 and lOOOipm respectively. Those for 95-unleaded gasoline are 10.5, 11.5, 15.2,and 21.7 mg/liter. And those for 92-unleaded gasoline are &11,9.07, 9.04, and 20.9 mg/liter. The maximum emission amounts of PAHs for all fuels take place at lOOOrpm, which means idle. The tailpipe particles are analyzed by Scanning Electron Microscope(SEM), Energy Dispersive Spectrometer (EDS), and Wavelength Dispersive X-ray Spectrometer (XDS). The results show that the emitte particles are of sphere and smooth surface・ They are dominated by submicrometered size・ The particles are primarily composed of carbon and hardly of other elements.From the results of WDX mappi ng, it is found that carbon is densely distributed in the particles. This phenomen on is consistent with the results as the particles are analyzed by elemental analyzer.Keywords: PAHs , Carbon Particles , Catalyst converter。