| 摘要: | 本研究選用甲基第三丁基醚(MTBE)、第三戊甲基醚(TAME)及乙醇三種含氧添加劑，各別添加3%及10%體積比於九二及九五無鉛基礎油中(92-3M、92-3E、92-3T、92-10M、92-10E、92-10T、95-3M、95-3E、95-3T、95-10M、95-10E、95-10T)，以及九二及九五無鉛基礎油(92-LFBG及95-LFBG)(不含MTBE)和市售之九二及九五無鉛汽油(92-LFG及95-LFG)作為燃料油品，以四行程機車汽油動力引擎，在不同行駛速度：怠速惰轉、30及50 km/hr操作條件下，針對每種燃料油之引擎排放廢氣中21種PAHs進行採樣及分析，分析儀器為GC/MS。
研究結果顯示，機車引擎排放之總PAHs濃度以92-M10為八種九二油品中最高者(19200 μg/Nm3)，分別為92-LFBG(18500 μg/Nm3)、92-LFG(14700 μg/Nm3)、92-M3(17900 μg/Nm3)、92-E3(8630 μg/Nm3)、92-E10(8690 μg/Nm3)、92-T3(15500 μg/Nm3)及92-T10(13400 μg/Nm3)之1.04、1.31、1.07、2.23、2.21、1.24及1.43倍；而九五油品中引擎排放之總PAHs濃度則以95-LFBG最高(24100 μg/Nm3)，分別為95-LFG(8850 μg/Nm3)、95-M3(14900 μg/Nm3)、95-M10(8910 μg/Nm3)、95-E3(10400 μg/Nm3)、95-E10(13000 μg/Nm3)、95-T3(10800 μg/Nm3)及95-T10(7970 μg/Nm3)之2.72、1.62、2.70、2.32、1.85、2.23及3.02倍。
比較九二及九五之引擎單位耗油量之總PAHs排放係數，九二無鉛汽油由高而低排序為92-T3>92-M3>92-LFBG>92-T10>92-M10>92-LFG>92-E10 >92-E3，而九五無鉛汽油中引擎單位耗油量之總PAHs排放係數則為95-LFBG>95-E10>95-E3>95-M10>95-M3>95-LFG>95-T3>95-T10。
不同燃料油品中，大多數之PAHs皆在引擎燃燒過程被分解。在機車引擎排放PAHs特徵之影響上，各別添加三種含氧添加劑(MTBE、乙醇及TAME)之九二及九五油品並沒有隨著添加量之增加削減率也相對增加之趨勢，但以九五油品之PAHs削減率較九二油品高出釵h。而PAHs排放係數之BaPeq以添加10 vol.% TAME之九二油品及市售之九五無鉛汽油具有相當高之削減率，進而對人體健康之危害風險也相對降低釵h。
Gasoline oxygenates, methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME) and ethanol, were used as additives in 95-leadfree base gasoline (95-LFBG) and 92-leadfree base gasoline (92-LFBG), respectively, to evaluate PAH emission from 4-stroke single spark engine under three cruising speeds. This engine was controlled by a dynamometer to simulate idling, 30 km/hr and 50 km/hr which were steady-state modes. PAH in engine exhaust, including particulate phase and gaseous phase were sampled for 3 times at individual mode and analyzed by GC/MS. The emission concentrations and factors of 21 PAHs and their total Benzo(a)pyrene equivalent values (BaPeq) were to compare the adding fraction of oxygenates in 92- and 95-LFBG.
The results of this study, the total PAH emission concentration from motor engine, reveals adding different oxygenates will change the PAH emission from motor exhaust. For 92-LFBG adding none, 3% and 10% alternative oxygenates, 92-M10 raises highest PAH concentration (19200 µg/Nm3) among eight 92 gasoline, 92-LFBG (18500 µg/Nm3), 92-LFG (14700 µg/Nm3), 92-M3(17900 µg/Nm3), 92-E3 (8630 µg/Nm3), 92-E10 (8690 µg/Nm3), 92-T3 (15500 µg/Nm3) and 92-T10 (13400 µg/Nm3). For 95-LFBG under same adding conditions, 95-LFBG has highest emission concentration (24100µg/Nm3), and the other 95- fuels are 95-LFG (8850 µg/Nm3), 95-M3 (14900 µg/Nm3), 95-M10 (8910 µg/Nm3), 95-E3 (10400 µg/Nm3), 95-E10 (13000 µg/Nm3), 95-T3 (10800 µg/Nm3), and 95-T10 (7970 µg/Nm3).
For the PAH emission factor (µg/L-fuel) of 92-, 95- fuels are 92-T3>92-M3>92-LFBG>92-T10>92-M10>92-LFG>92-E10>92-E3 and 95-LFBG>95-E10>95-E3>95-M10>95-M3> 95-LFG>95-T3>95-T10.
In this study, most original PAH in fuel was destroyed during internal combustion in motor engine. For these oxygenates, however, adding more additives, may or probably not increase the PAH depletion. It is worthy to concern is adding more ethanol in 92-LFBG will be more suitable than adding in 95-LFBG due to their total PAHs and BaPeq emission. |
