Unraveling heat transfer dynamics in shaking solvent-aided crystallization: toward efficient glycerol separation from biodiesel

Abstract

Biodiesel purification from crude palm oil (CPO) is often hindered by residual glycerol and other impurities. This study investigates the role of heat transfer in a shaking solvent-aided crystallization (SAC) system to enhance the selective solidification of glycerol. By evaluating the effects of coolant temperature (8–16 °C), crystallization time (15–35 min), and shaking speed (11.05–31.85 cm/s), a comprehensive heat transfer model was constructed, segmenting the system into four thermal zones (coolant, vessel wall, solid glycerol, and biodiesel solution). Fourier’s law, Newton’s law of cooling, and latent heat balance equations were applied and refined based on zone-specific assumptions. Crucially, these models were related to practical outputs: the thickness of the glycerol layer, the rate of heat removal, and the predicted yield of solidified glycerol. The results showed that lower coolant temperatures and moderate agitation facilitate efficient glycerol crystallization, with deviations between theoretical and experimental yields remaining below 10 %. Key findings revealed that precise control of thermal gradients and solution movement significantly impacts glycerol layer thickness, influencing biodiesel purity. This study provides both a conceptual and practical framework for optimizing glycerol removal via crystallization and reinforces the SAC system’s potential for industrial-scale biodiesel purification.