No abstract

Biomass-based fuels are gaining importance for operating a compression ignition engine as they can curb greenhouse gases and are a key for addressing the energy security. Hydrotreated oil is considered to be a potential drop-in fuel for the compression ignition engine as its cetane number is higher than fossil diesel. In this study, hydrotreated waste cooking oil and its blends (10%, 20%, 30%, 40% and 50% by volume) with diesel were prepared. The ignition probability of the test fuel samples was found using a hot-plate test setup. The neat hydrotreated fuel has higher ignition probability at a particular temperature than the other test fuels. The Sauter mean diameter of the test fuels was also observed using a Malvern Spraytec test setup. The results reveal that the neat hydrotreated fuel has higher Sauter mean diameter due to its high viscosity. As the percentage of the hydrotreated fuel in the blend decreases, the Sauter mean diameter decreases and diesel has the lowest Sauter mean diameter. The test fuels were also used to run a compression ignition engine. The results reveal a decrease in brake thermal efficiency with the increase in the hydrotreated fuel share in the blend. The heat release for the blends starts earlier than diesel and the peak heat release is also lower than diesel. The HC, CO and smoke emissions for the test blends decreases up to 30% blend. When the percentage of the hydrotreated oil is further increased, the emissions starts increasing. The NO emissions were lower than diesel for all the test samples. As compared to diesel, the maximum reduction in NO (neat), HC (30% blend), CO (30% blend) and smoke emissions (30% blend) is 23.2%, 14.4%, 13.83% and 13.3%, respectively.

Abstract Hydrotreating process is an alternate approach for producing diesel hydrocarbons from the biomass-based oils. In the present study, used cooking oil was selected for the hydrotreating process due to its high abundance. A batch reactor was used for carrying out the experiments. To increase the reaction rate a manganese, cerium promoted ruthenium-based catalyst supported on Al2O3 was used. The design of experiments was used for optimizing the process parameters. The Taguchi method was selected as it reduces the number of experiments which saves time and money. The study was aimed at increasing the conversion percentage and diesel selectivity and reducing the naphtha selectivity. Since multi-objective optimization was required, fuzzy logic was incorporated which utilizes the human thought logic. The analysis of variance shows that the reaction temperature and reaction pressure significantly affect the output parameters. Higher temperature leads to cracking of the oil resulting in the formation of large amount of lower carbon chains. Moreover, high hydrogen pressure results in increase in the hydrogenation process, thereby increasing the diesel selectivity. The optimized parameters obtained from the study were 360 °C reaction temperature, 40-bar initial reaction pressure, and 200-min reaction time. Confirmation experiment was carried out using these parameters, and the conversion efficiency and diesel selectivity was 89.7% and 88.2%, respectively. The study shows that the combination of Taguchi and fuzzy logic is an effective method for optimizing the process parameters of the hydrotreating process.