In order to evaluate the feasibility of coal derived middle distil-lates as diesel-powered automobile fuels, mass emission of CO, HC, NOx and particulate matter, and content of soluble organic fraction (SOF) in the particulate matter were measured by operating two types of automobiles fueled with the middle distillate under 10 mode driving cycle, idle condition and constant speed conditions at 20, 40 and 60km/h. One (A) of the automobiles was conformed to Japanese emission standard for indirect injection type dieselpowered lightduty vehicle in 1988 and the other (B) to standard for dieselpowered passenger car in 1986 which required more stringent permissible limit for NOx. The middle distillate (BHD) was obtained from liquefaction of Battle River coal followed by catalytic hydrogenation and distillation ranged from 180 to 350°C. Test fuels BHD-10 and BHD-25 were prepared by mixing 10 and 25vol% of the distillate (BHD) with the gas oil (F), respectively, and test fuel (BHD-25D) by adding 0.5vol% of a cetane booster to the fuel BHD-25.
The mass emission of CO, HC and particulate matter emitted from the automobiles A and B increased with the increase of the middle distillate content in the test fuels, but the mass emission of NOx and the content of SOF did not correlate with the middle distillate content for either automobile. These results were almost the same as the results reported in a previous paper except for SOF. The emission from the automobile B showed stronger dependence on the middle distillate content than the other automobile, but the degree of dependence became very small compared with the previous results. Addition of the cetane booster to the mixed fuel improved the ignition quality, that is, the cetane number was raised from 44 to 53, and it decreased the mass emission of CO, HC and particulate matter in the case of automobile B.
Although exhaust emission characteristics of the mixed fuel containing the coal derived middle distillate were highly improved by adding the cetane booster and distilling the middle distillate between 180 to 350°C, the improvement of the middle distillate itself, such as lowering of aromaticity, is necessary to use it under more stringent emission standard.
