PRODUCTION AND PERFORMANCE EVALUATION OF BLENDED BIODIESEL FROM RUBBER SEED OIL

Abstract

The global search for energy security and clean environment with minimal exhaust emissions have led to increased interest in recent years in the development of biodiesel as a renewable, sustainable and alternative energy source for diesel engines. The aim of the research is to produce and evaluate the performance of blended biodiesel from rubber seed oil. The objectives are to blend the rubber seed oil biodiesel with diesel at various ratios, characterize the blended biodiesel, evaluate the nature of chemical bonds, examine the engine performance and the exhaust emissions of the blended biodiesel and determine a suitable blend concentration. Rubber (Hevea brasiliensis) seed oil was extracted from rubber seeds using soxhlet extractor and normal hexane as extractant. The free fatty acid was determined by titration as 23.69% which was too high for alkaline transesterification. To reduce the amount of free fatty acid in the oil, it was esterified by adding sulphuric acid 1% by weight of the oil to a mixture of the oil and methanol at a molar ratio of 4:1 and stirred slowly at 600C for 30 minutes. This reduced the free fatty acid from 23.69% to 0.78%. The alkali-catalyzed transesterification synthesis of the esterified rubber seed oil was conducted at 6:1 molar ratio of methanol to oil in the presence of 2% sodium hydroxide catalyst by weight of the oil and stirred at 600C for one hour and at 300 rpm. The mixture was left overnight to reach equilibrium and the glycerol which was formed at the bottom layer was removed using a separatory funnel. The biodiesel was blended with diesel at 0%, 10%, 20%, 30%, 40% and 100% by volume according to engine manufacturers’ recommendation. The diesel, rubber seed oil, rubber seed oil biodiesel and its blends with diesel were characterized using standard methods of ASTM D6751 and EN 14214 for biodiesel. Fourier transform infrared spectroscopy test was carried out using Bruker spectrometer and the spectra of the samples obtained were interpreted to identify the structural features. Engine performance and exhaust emission tests were carried out on the biodiesel and its blends with diesel in a multi-cylinder Gardner model IL - 2 diesel engine which was connected to an eddy current dynamometer. The engine was operated at constant speed of 1800 rev/min while the engine load was increased. The experimental procedure was repeated at constant engine load and variable engine speed. The entropy method was used to compute the relative weights of the criteria while the technique for order preference by similarity to ideal solution method was applied in the final ranking of the alternative biodiesel blends. The results show that biodiesel blends contained alcohol at frequency band 3400 cm-1 to 3000 cm-1, alkane at 2990 cm-1 to 2800 cm-1, double bond aromatic carbon at 2360 cm-1 to 1800 cm-1, double bond ester carbonyl at 1760 cm-1 to 1700 cm-1, single bond ester carbonyl 1200 cm-1 to 1100 cm-1 and alkene functional group at 980 cm-1 to 600 cm-1. The biodiesel blend B10 and B20 showed a reduction in brake torque of 1.33% and 2.67% compared to conventional diesel whereas B30 and B40 show a reduction in brake torque of 4.00% and 7.33% compared to diesel at 1800 rpm. The biodiesel blends B10 and B20 give more power output of 54.31 kW and 54.48 kW than the other blends B30, B40 and B100. The fuel properties of biodiesel were improved by the blending of biodiesel and diesel fuel; the biodiesel – diesel blends showed improvement in engine performance and reduced exhaust gas emissions. The study established that blend B30 was the optimal blend concentration for operating diesel engines. It also provided a set of physicochemical and fuel properties of the blended biodiesel and data on performance and exhaust emission parameters.