Smart scale-up of micromixers for efficient continuous biodiesel synthesis: A numerical study for process intensification

Abstract

This study focuses on developing continuous processes for biodiesel synthesis, overcoming limitations of conventional batch reactions, such as biphasic reaction and thermodynamic equilibrium, and reducing production costs. While microreactors are promising for enhancing mixing and transfer rates at smaller scales, scaling up to larger channels results in decreased efficiency and product yield. Microfluidic devices, useful in continuous biodiesel production, lose mixing efficiency when scaled up, affecting product yield. The present study proposes a novel microreactor design with static elements, aiming to improve fluid mixing and reaction performance at higher volumes. The smart scale-up strategy includes an optimized micromixer design, enlarged channel cross-sectional area, and an additional obstacle-free channel. Using a Fractional Design followed by a Central Compound Rotational Design, optimal values for key design variables are identified. Computational tests show a high mixing index (M > 0.77) across a wide range of Reynolds numbers (Re = 0.1–100). Numerical simulations under optimal conditions indicate high conversions (>91 %) for residence times above 60 s. This design promises advancements in industrial-scale biodiesel production, with improved flow and reactant distribution, potentially reducing the number of micro/millidevices needed.