Continuous biodiesel production in a helicoidal reactor using ultrasound-assisted transesterification reaction of waste cooking oil

Designing of a continuous biodiesel production system from waste cooking oil with ultrasonic homogenizer assistant through transesterification reaction was studied. Through some pre-tests based on cavitation phenomenon to accelerate the transesterification reaction, two types of reactors (batch and continuous) were used. GC–MS results showed the total content of 94.2 % of methyl esters derived from different fatty acids formed in a batch reactor using a magnetic stirrer and an electrical heater. These results were then compared to those of two ultrasonic homogenizers with low and high capacities of 400 and 1,500 W, which tested successfully under mild conditions. The results indicated the advantages of using ultrasonic homogenizer. The continuous system consisted of a 1,500 W ultrasonic homogenizer and glass helicoidal reactor with a tube length of 20 m. This set-up was kept submerged in a hot water bath. As a result, the reaction time decreased to 150 s, the methanol/oil molar ratio was 8.6 and the weight % of NaOH/oil was 0.5 %. After separation of undesired contents, the physical and chemical characteristics of the final product were measured according to ASTM standard methods. Study of performance of the system also showed a significant improvement in yield of the reaction (90 %) compared to prior studies.