Optimization of mechanical oil extraction process of Nyamplung seeds (Calophyllum inophyllum L.) by flexible single screw extruder

Abstract

This research aims to investigate the potential of Nyamplung oil as a bio-based diesel engine fuel in outer islands and to achieve the optimum process of a mechanical oil extraction by using a flexible single screw extruder. Mechanical oil extraction process was selected because it has a cheaper operation cost and a green impact than a chemical extraction process. Nyamplung seeds were selected because this plant is easy to be growth in coastal areas, non-edible vegetable, and has a high fat content up to 75%. A flexible single screw extruder was selected to extract the seeds mechanically because it has simpler construction, cheaper production cost, and easier operation than a twin-screw extruder. Experiments to investigate the optimum process were conducted by varying screw configuration and operating condition. Ten screw configurations were examined to define the best performance of oil by evaluating the influence of operating conditions (barrel temperature and screw speed). The experiments to investigate the potential of Nyamplung oil as bio-based diesel engine fuel were conducted by testing its chemical properties and then comparing to diesel fuel. Generally, oil extraction yield is affected by the number, position, and pitch width of screw elements. Oil extraction yield increases as barrel temperature and screw speed are increased. It is observed that the highest oil extraction yield was 46.48%, which is obtained through screw configuration of T66/F16/I34/I34/I34/I34/F16/F10 with operating conditions of 105 °C, 25 rpm, 25 g/min while the seed moisture content was 1.67% and the average seed particle size was 5 mm. In these experiments, the chemical characteristics of Nyamplung oil before purification were 0.905 g/mL (density at 27°C), 94.128 cP (viscosity at 27 °C), 48.454 mg KOH/g of oil (acid value), 174.348 mg KOH/g of oil (saponification value), and 96.757 g I2/100 g of oil (iodine value), and the characteristics after purification were 0.879 g/mL (density at 27 °C), 55.278 cP (viscosity at 27 °C), 0.780 mg KOH/g of oil (acid value), 173.253 mg KOH/g of oil (saponification value), and 84.035 g I2/100 g of oil (iodine value). Based on the result, density, acid value, saponification value, and iodine value after purification had fulfilled biofuel requirements, but it was not for viscosity because it was more than 6 cP. Therefore, to reduce the viscosity, a preheater must be added to the diesel engine.