Analysis of Soot Emissions from the Combustion of Diesel Blended with Biodiesel Toward Mitigating Environmental Pollution

Abstract

Abstract In the attempt to reduce environmental pollution caused by emissions from diesel engines, alternative fuels for diesel have been suggested in this work to be used in suitable combinations with it as blended fuel. These alternative fuels are oxygen-containing compounds, which emit less emissions when used in the engines either alone or in combination with diesel due to the presence of fuel-bound oxygen. This work studies the effect of the use of blends of diesel and biodiesel (derived from neem-oil), on engine emissions. The smoke point test for the blends of diesel with biodiesel in increasing blending proportions from 0 – 30 % was conducted experimentally, according to ASTM D1322 standard. Soot was also collected at heights above the smoke point for the fuel blends, and the changes in the nanostructure and the reactivity of the resulting soot particles, as compared to soot from petroleum diesel, was identified using suitable characterization techniques such as high resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) techniques. Expectedly, these blends provide a notable reduction in the type and nature of the emissions in comparison to those emitted from petroleum diesel. These emissions typically contain soot and an understanding of the changes in the morphology and physical characteristics of the soot formed from the blends in juxtaposition to that formed from the diesel fuel is of interest in observing the effectiveness of the use of these oxygenated compounds in combination with the fuel on the engine emissions. It was observed that the smoke point values increased with increasing percentage of biodiesel in the blend, which indicated a reduction in the sooting tendency of diesel due to the addition of biodiesel. In addition, the results of the characterizations, in addition to the observed reduction in the sooting tendency of the diesel fuel due to the addition of the biodiesel, indicated physical and chemical changes in the nanostructure of the soot particles. Furthermore, these observed changes in the nanostructure of the soot particles were related to the changes in its morphology and reactivity. The results from this work contribute to the understanding of the nature, physical nanostructure, chemical reactivity and morphology of soot particles resulting from diesel fuel used in engines, as well as changes in these properties when it is used in combination with its oxygenated alternatives. Therefore, it indicates a potential avenue for the reduction of the environmental pollution effects of the fuel.