Continuous methyl ester production with low frequency ultrasound clamps on a tubular reactor

Abstract

A tubular reactor with ultrasound clamps (US reactor) was used to produce methyl ester from refined palm oil (RPO) as a continuous process. The US reactor had 16 units of ultrasound clamps attached to the tube wall. The clamps were operated at 20 kHz fixed frequency with maximally 400W power per clamp. The ultrasound clamps were fixed 100 mm apart along the length of the reactor. The effects of varying methanol content (5, 10, 15 or 20 vol.%) and KOH loading (4, 6, 8, 10 or 12 g L−1) on the purity of methyl ester were investigated. The results show that the lowest 5 vol.% methanol content tested was unable to convert the glycerides in RPO to over 64.2 wt.% methyl ester purity at any of the KOH loadings. The maximum 99.9 wt.% purity of methyl ester was achieved with 10 g L−1 KOH loading, 10 vol.% methanol, and 400 mm reactor tube length. However, the methyl ester reached its equilibrium level at 300 mm reactor length. Regarding the average energy consumption, 0.035 kW h L−1 was required to produce biodiesel when using ultrasound clamps on the tubular reactor.