Pelletisation of canola meal by extrusion–spheronisation for ethanol dehydration

Abstract

Canola meal has been previously demonstrated to be an attractive biomaterial for dehydrating wet ethanol vapours in bioethanol manufacture. Extrusion–spheronisation was employed to prepare reasonably spherical pellets of canola meal for use in dehydration units. Canola meal pastes were prepared at water volume fractions of 57–70% and extruded through single and multi-holed dies with diameters 2, 3.5 and 4.5 mm. The pressure required to extrude the pastes, size and shape distribution of pellets and strength of dried pellets were measured. Formulations with a water volume fraction of 70% gave low extrusion pressures and highest pellet strength. Die land diameters of 2 mm gave the best combination of specific surface area, size and shape distribution, packing density and ethanol adsorption. Dehydration testing confirmed that the canola meal pellets could dehydrate water/ethanol vapour from an ethanol mass fraction of 92.5% (below the azeotrope at 1 bara) to 99%. The equilibrium water loading of 47.3 mg water per g adsorbent is larger than other biomass-based adsorbents reported for this application.