Thermal chemical enhancement and influence of fluid flow in transesterification of palm oil

ABSTRACT

This paper presents a model describing the effect of mixing intensity, temperature, and hydrodynamic behavior of transesterification process in a batch continuously stirred tank reactors (CSTR) by using computational fluid dynamics (CFD) and optimization by ASPEN PLUS. The effect of varying temperature from 50, 60 to 65°C and impeller speed ranging from 150, 350 to 700 revolutions per minute (rpm) were investigated using CFD within ANSYS Fluent 12.1. It was found that the mixing efficiency varies with impeller speed from 150 to 350 rpm for maximum biodiesel (BD) yield. Also, the concentration of BD is higher near the impeller due to high turbulence dissipation rate in the zone near the impellers. It was observed that high reactor temperature results in an increased rate of BD production. The optimal BD production was achieved at 60°C. The optimization shows that the BD purity as high as 96.7% was obtained with the molar ratio of methanol to palm oil of 6:1, catalyst amount 1.0 wt%, a reaction temperature of 333 K, and a reaction time of 100 min. The model results were validated against published literature data and good correlation between model results and experimental data was observed. The model can potentially be used as a tool for design and optimization of a batch CSTR in BD production.

KEYWORDS:

• ASPEN PLUS
• biodiesel
• CFD
• modeling
• transesterification

Acknowledgments

The author of this paper would like to acknowledge the Late Prof. Iddi N. Mkilaha for his great support. May his soul rest in peace, without forgetting Prof. Peter L. Mtui who helped me to understand the power of CFD.