Characteristics and thermal behavior of fresh and waste oil blends as supplement in diesel engines

Abstract

This study deals with the combustion characteristics of base oil-based blends called number 10 lubes (NTLs), a blend of virgin/nonstandard base oils with low taxation petroleum products and/or wastes, used as diesel additive or substitute using thermogravimetric analysis with Fourier Transform Infrared Spectroscopy. Basic compositional analyses (i.e. elemental analysis, calorific value, sulfated ash) were also conducted with relevant methods in an accredited fuel analysis laboratory. In general, samples yielded exceptional characteristics in terms of sulfated ash content. Oxidation reactions were found to compose of one decomposition stage whilst up to three-stages were also observed outstandingly. Thermographs vary slightly in shape and position, similarly shaped to that for mineral oil, base oil or waste engine oil, and exhibited lower mass loss rates at low temperatures when compared to diesel. Quantitatively, combustion reactions occur between 236 ± 42.2 °C and 362 ± 39.0 °C yielding a maximum combustion rate and mass loss of 17.4 ± 3.87%/min and 98.4 ± 1.29%, respectively, on average, with major gases released carbon dioxide, water vapour, and the others complicating the interpretation of spectral bands. The combustion characteristic indices (ignition, flammability, burnout and comprehensive combustion index) also showed the combustion performance in favor of diesel > NTLs > mineral oil > waste engine oil > base oil > waste vegetable oil. Thus, this problem needs to be handled carefully via waste to fuel projects adopting the circular economy approach if sufficient knowledge on all of the technical and market aspects of such fuels would be obtained.