Modification of Rheological Properties of Biofuels From Soybean Oil

In this paper, the influence of fuel additives on rheological properties of crude soybean oil was presented. The tests were performed for low shear rates (1.2 12.4 s) at a temperature range of 5 to 30C. The fuel mixtures were prepared in a proportion of 80% soybean oil to 20% diesel or 20% depressor. Flow curves, viscosity curves, flow index and consistency coefficients were determined. Diluting soybean oil with fuel additives caused a significant decrease in viscosity and changed the rheological character of the obtained oil biofuels. Diesel oil has reduced the viscosity of soybean oil more visibly than the depressor. Modification of soybean oil by fuel additives significantly reduces the viscosity of the obtained fuel blends and can contribute to the development of sustainable agriculture. INTRODUCTION Vegetable oils are renewable and clean energy source and can be a substitute to diesel fuel (Shay 1993; Altin et al., 2001) The vegetable oils can be produced from numerous oil seed crops and have high energy contents (Franco and Nguyen 2011). Biofuels from vegetable oils are biodegradable and nontoxic, have low emission profiles and so are environmentally beneficial (Ma and Hanna 1999). The added advantage of biofuels is that they can be used for their own use by small farms (Kobus at el., 2015), what is important for the development of sustainable agriculture. A major obstacle deterring their use in the direct-injection diesel engine is their high viscosities (Schwab et al., 1987; Mustafa and Gerpen 1999). The viscosity of the fuel is of great importance for the correct exploitation of the engine and fuel system. It determines the quality of spraying in the combustion chamber, the flow resistance of the fueled wires and filters, and affects the lubrication of the injection pumps (Baczewski and Kołduński 2005, Jakóbiec et al., 2011). One of the ways to improve selected properties of crude vegetable oils is to use common fuel additives (Shah and Ganesh 2016). These include conventional fuels (diesel) or cold starters (depressors). The aim of the study was to investigate the effect of different compounds on the rheological properties of soybean oil. MATERIAL AND METHODS The raw soybean oil obtained after screw pressing was used in the study. Diesel and depressor were used to modify the oil properties. In both cases, the fuel blend was prepared in the proportion of 80% soybean oil and 20% fuel additive. Rheological properties were measured using Brookfield viscometer (Brookfield Engineering Laboratories: model LVDV-II + PRO). A sample of 16 ml of oil was used in ULA-baker for all experiments. The temperature of sample was changed from 5 to 30°C and kept at constant value using water bath (Brookfield TC-502P). The computer software (Rheolac 3.1) was applied to control viscometer and data acquisition. All experiments were carried out in three replications.