Combustion Behavior of Diesel and Biodiesel Blends Containing Waste Transformer Oil

Combustion characteristics are critical parameters for the evaluation and classification of fuel types. In this study, the combustion behaviors of waste transformer oil (WTO), diesel fuel, biodiesel, and their ternary blends, TFB1 (70% biodiesel, 20% WTO, 10% diesel) and TFB2 (30% biodiesel, 60% WTO, 10% diesel), were examined using thermogravimetric analysis (TGA/DTG) under four different heating rates (2.5, 5, 10, and 20°C/min). Kinetic and thermodynamic parameters were evaluated employing the Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Kissinger methods. Among the fuels, biodiesel exhibited the highest average activation energy (Ea), while diesel showed the lowest value. According to Kissinger analysis, diesel fuel had the lowest enthalpy change (∆H), entropy change (∆S), and Gibbs free energy (∆G); however, biodiesel exhibited the highest ∆H and ∆S values. The thermodynamic behavior of WTO was found to be comparable to that of diesel. In particular, TFB2 demonstrated lower activation energy and enthalpy values than TFB1, indicating its superior suitability as a combustion fuel. It is thought that the study represents one of the initial comprehensive assessments of the combustion characteristics of such specific ternary fuel blends.