北京市压缩天然气公交车的环境效果分析

经过对北京市2007年公交车队的详细技术构成与实际运营情况的调研,发现北京市公交车队的主力车型为国三和国四车辆,应用修正的COPERTIV模型计算出北京市各技术水平的汽油、柴油和压缩天然气(CNG)公交车的排放因子.2007年北京市国三CNG公交车PM2.5和NOx单车排放因子分别比国三柴油车削减了97%和30%,而公交车队中排放控制最为严格的EEV天然气公交车的PM2.5和NOx单车排放因子分别比国四柴油公交车削减了93%和69%.但由于CNG公交车的CH4排放水平较高,导致CNG公交车的总碳氢化合物(THC)单车排放因子显著高于相近控制水平的柴油公交车.在单车排放水平的基础上建立了北京市公交车排放清单,2007年北京市公交车排放的CO、NMHC、THC、NOx和PM2.5分别为9051t、955t、1222t、8553t和161t.与没有CNG公交车的对照情景进行比较,在使用了CNG公交车后,2007年北京市公交车CO、NMHC、NOx和PM2.5排放总量分别削减了293t、62t、775t和33t,削减比例分别为3.1%、6.1%、8.3%和17.2%.2007年北京市通过在公交车队中使用CNG车辆共减少了柴油消耗量约5.0×104t,相当于北京市各行业柴油总消耗量的2.6%.2007年北京市公交车尾气排放的温室气体的CO2当量为8.3×105t,比不使用CNG车辆的情景略微增加了2.4%.

Assessment of the environmental effects of the compressed natural gas bus fleet in Beijing

Based on the investigation of the bus fleet configuration and operation situation in Beijing in 2007, it has been identified that Euro III and Euro IV vehicles are the most common bus models. Modified COPERT IV has been used to estimate emission factors for gasoline, diesel and CNG buses of difference control level in Beijing. The PM2.5 and NOX emission factors of Euro III CNG bus has been reduced by 97% and 30% as compared to Euro III diesel bus. The PM2.5 and NOX emission factors of EEV CNG bus has been reduced by 93% and 69% as compared to Euro IV diesel bus. Because the CH4 emission factor of CNG bus is much higher than diesel bus, the THC emission factor of CNG bus is significantly higher than diesel bus of similar control standard. Bus emission inventory has been built on these emission factors. It has been found that the emission of buses in Beijing was 9051t, 955t, 1222t, 8553t and 161t for CO, NMHC, THC, NOX and PM2.5 in 2007, respectively. By using CNG buses, the emission of CO, NMHC, NOX and PM2.5 has been reduced by 293t, 62t, 775t and 33t for CO, NMHC, NOX and PM2.5, which was 3.1%, 6.1%, 8.3% and17.2% of total bus emissions. In 2007, the operation of CNG bus has saved diesel consumption by 5.0×104t , which was 2.6% of the total diesel consumption in Beijing. And CO2 equivalent of greenhouse gas emissions of Beijing buses in 2007 was 8.3×105t, which was 2.4% high than the scenario without CNG buses.