Abstract:
This study aims to identify a sustainable source of energy from natural and environment friendly resources. Karaya seeds were used as a biodiesel feedstock, and were collected form Al-Azaza Forest east of Al-Rusaires city in the Blue Nile State of Sudan. The oil from Karaya seeds was extracted using three techniques, chemical solvent soxhelet extraction, cold chemical solvent extraction and mechanical pressing. Percentage yields were 32.4%, 26.0 % and 18.2% respectively. Fatty Acids profile of Karaya oil shows that the oil contained, approximately, 97% saturated fatty acids palmitic, myristic and heptadecanoic, and 3% unsaturated fatty acids palmitoleic and linolenic. Free fatty acid, saponification number and iodine value were determined and found as 15.88 %FFA, 180.53 mg KOH/g and 50.91 gI2/100g respectively.
Biodiesel production was carried out using two steps, first step; acid catalysed esterification process to reduce high fatty acid content using HCl from 15.88% to 1.56%. Second step was Transesterified by alkali catalysed transesterification process using NaOH. Produced Biodiesel was identified using FTIR and GC-MS techniques which proved successful conversion to Biodiesel with a yield of 96.83%. Thermal stability of Karaya oil, Karaya biodiesel, Fossil diesel and B 20 blend was monitored and compared using thermo-gravimetric analysis and was found that the Karaya oil was more stable than the Karaya biodiesel and B 20 blend.
Physical and chemical properties of Karaya biodiesel was investigated according to ASTM D 6751 and had achieved the full requirements of the standard. Derivative Cetane Number of Karaya biodiesel was determined using Ignition Quality Tester and was obtained 97.3. B20 blend of biodiesel with Diesel was investigated
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according to ASTM D 7467 and had met the requirements of the method successfully. B 20 blend was run in 2L-T Toyota multi-cylinder diesel engine to investigate the gases emissions in comparison with fossil diesel, the results show that CO2, NO and NOx emissions were reduced by 27.5%, 27.4% and 28.5% respectively with the speed of 1500 rpm. Three Diesel-Biodiesel-Ethanol blends were prepared with different ratios, investigated and compared with standard method ASTM D 7467 and had met all standard requirements except for Flash point. The flash point of pure biodiesel was 158ºC, reduced to 70 ºC in the B20 blend and reduced to 14 ºC, 16 ºC and 18 ºC in D60 B20 E20, D80 B10 E10 and D80 B15 E5 respectively.
