Effects of static mixers on continuous methyl ester production: comparing four types of 3D-printed mixing elements

Abstract

Four types of 3D-printed mixing elements for static mixer reactors, namely, a twisted plate static mixer (TPSM), cross semi-elliptical static mixer (CSSM), X-grid static mixer (XGSM), and corrugated plate static mixer (CPSM), were evaluated for continuous biodiesel production from refined palm oil in terms of the methyl ester purity and the pressure drop across the reactor. The methanol content, potassium hydroxide loading, and static mixer length were optimized for each mixing element with respect to the methyl ester purity using the response surface methodology. The methyl ester conversion for the CPSM, with a short residence time of 132 s, surpassed those for the other three types of static mixers. The CPSM, XGSM, and CSSM reactors afforded methyl ester purities exceeding 99 wt% at reactor positions of 4, 6, and 10 m, respectively. The XGSM reactor was determined to be the preferred option among the four types of static mixers owing to its high reaction rate and low pressure drop during continuous biodiesel production. The CPSM reactor also displayed certain advantages, such as a small space requirement and short reaction time, although it required more pumping power than the XGSM reactor.