Numerical Validation of a Pressurized Batch Reactor for In-Situ Transesterification

Abstract

Subcritical in-situ transesterification is one of the more recently developed processes that consumes less energy and is more environmental friendly than conventional methods. Diving deeper into this process, the fluid dynamics of the liquid mixture is an area of interest not studied before due to the solid, thick metal enclosure of the reactor vessel. Previous studies observed that the mixing characteristics of the agitator being used influences biodiesel yield. As commercialization of this biofuel production process is of importance in order to contribute to biofuel demand in a nation-wide scale, this study considers a reactor vessel working volume of around 1.5L, which is relatively larger than typical laboratory batch-type sizes. A numerical validation study, through mesh analyses, was performed to produce a numerically accurate model for the study. Factoring in computational time and accuracy of the solution, a steady state, multiphase model running the standard k-∈ turbulence model was chosen. The Multiple Reference Frames approach was used for the steady state condition to be met. The validation model is of a 6.3L-volume cylinder with baffles. Glass beads served as the solids and water as the liquid in the system. The first mesh analysis was performed by comparing 11 unique mesh models. The model with a relevance of fine 30 was seen to have the closest data fit with the experimental data. It was seen that only when using the size function ‘proximity’ showed a slightly different velocity profile among the models. The second mesh analysis was conducted to check if the chosen mesh setting would affect this study’s smaller reactor geometry before the main study’s simulations are to be conducted. The model with baffle’s percent error at the specified point was at an acceptable 8.2%, and its resultant velocity profile’s is at 23.5% which is around the same range as that of the 1st mesh analysis’ models. With this, the numerical model developed was deemed to be applicable for the main study.