The Effect of Palm Oil Biodiesel-Neat Diesel (B10-B50) Mixing Ratio on Physical Mechanism of Fuel Deposits Developed on Heated Al Surface

To improve the physicochemical properties of biodiesel, researchers have been mixing pure biodiesel with neat diesel to produce blended fuels with certain blending ratios. However, one of the issues when combining ordinary diesel with biodiesel is the formation of deposits. In this study, the hot surface deposition test (HSDT) method was employed to investigate the effect of the mixing ratio on the deposition of diesel fuel (DF) and its blends with Malaysian palm oil biodiesel (B10-B50). The accumulated fuel deposits produced by the test fuels up to ND=16000 droplets were studied based on visual inspection and the use of a scanning electron microscope (SEM) to study the deposits’ composition. Generally, the higher the blend ratio, the more deposits were formed on the hot plate. Furthermore, a greater mass of deposits was produced during the wet condition (timp=3 seconds) test compared to that of the dry condition (timp=7 seconds) test. Deposits’ distribution area produced by the B30, B40, and B50 fuels were larger and appeared to be oily/greasy. Meanwhile, deposits produced by DF, B10, and B20 seem to be dry. The radius of the solid deposit was also larger during the wet condition test. For dry condition test at droplet ND=16000, the mass of deposit produced was 3.7mg (4mm radius) for DF, 3.9mg (5mm radius) for B10, 17.1mg (9mm radius) for B20, 24.0mg (9mm radius) for B30, 25.1mg (9mm radius) for B40, and 28.8mg (7mm radius) for B50. On the other hand, for the wet condition test, the mass of the deposit generated was 4.4mg (4mm radius) for DF, 8.9mg (7mm radius) for B10, 20.4mg (11mm radius) for B20, 31.1mg (13mm radius) for B30, 62.4mg (15mm radius) for B40, and 58.2mg (13mm radius) for B50, respectively. Additionally, the SEM analysis showed that the deposits’ composition for each test fuel primarily consists of carbon (>65%), with relatively lower oxygen concentration (<35%). The dry and wet condition also has a significant impact on the various deposits’ morphology.