A Continuous Biodiesel Production Process Using a Chaotic Mixer-Reactor

Abstract

A new transesterification reactor, operating in continuous mode, has been designed, made and tested experimentally in order to produce a biodiesel from rapeseed oil. This reactor is an alternative solution to the batch system existing in the industry. It is composed of three-dimensional serpentine geometry (S-3D). The flow in this geometry is laminar, Reynolds number is less than 360. However the particle trajectories are completely erratic due to the geometry perturbations. This type of flow is called chaotic flow. The reactor ensures the mixing of reagents by the effects of inertia of the movement created in the flow by the chaotic advection. The experiments were conducted with a methanol / oil molar ratio of 6:1 and a KOH concentration of 1 wt%. Four oil mass flow rates were tested (1, 2, 3 and 4 g/s) in combination with four temperature levels (40, 50, 60 and 70 °C). The results show a very high conversion of oil to biodiesel. The physical and chemical properties of biodiesel such as viscosity, flash point, and cetane number comply with the international standards (ASTM D6751 and EN 14214). In addition, despite its compactness, the reactor is capable of continuously producing 13.5 kg/h of biodiesel thanks to the use of a chaotic mixer-reactor. The reaction time was reduced from 2 h in the batch system to 6 min. Graphic Abstract: [Figure not available: see fulltext.]