ETHANOL DEHYDRATION IN A PRESSURE SWING ADSORPTION PROCESS USING CANOLA MEAL

Canola meal was used as an adsorbent in a pressure swing adsorption (PSA) apparatus for ethanol dehydration. The experiments were conducted at different pressures, temperatures, vapor superficial velocities, vapor concentrations and particle sizes. Adsorption experiments were performed at equilibrium and breakthrough points. The results demonstrated that canola meal can break the azeotropic point 95.6 wt% and produce over 99 wt% ethanol. At elevated temperature, feed water concentration, and vapor superficial velocity, it was found that the mass transfer rate increased. In addition, the mass transfer rate decreases when either the total pressure or the size of the adsorbent particles are increased. Breakthrough curves were simulated and the overall mass transfer resistance was evaluated at all experimental runs. The internal mass transfer resistance was identified as the relevant mass transfer mechanism. For canola meal, the equilibrium water/ethanol uptake was achieved at 100, 105, and 110˚C. The Frenkel-Halsey-Hill (FHH) and Guggenheim-Andrson-de-Boer (GAB) models perfectly simulated the water adsorption isotherms. By applying Dubinin-Polanyi model to the experimental data, canola meal was identified as a large pore (non-porous) material. The heat of adsorption on canola meal with particle size of 0.43-1.18 mm was determined to be -32.11 kJ/mol. The result confirms that the adsorption process is an exothermic phenomenon and is of physical type due to the fact that the value obtained as the heat of adsorption is negative and its magnitude is within the range 20–80 kJ/mol. The equilibrium water uptake on canola meal was similar to that reported for other starchy and cellulosic adsorbents, while the ethanol uptake was higher. Water saturated canola meal was successfully regenerated by passing nitrogen at 110˚C which is lower than that for molecular sieves commonly used in industry for bioethanol dehydration. The canola meal bio-adsorbent was re-used for more than 32 cycles and no significant change in adsorption capacity was observed

Water Removal from Ethanol Vapor by Adsorption on Canola Meal after Protein Extraction

In this paper, biosorbents based on canola meal obtained after protein extraction were developed to adsorb water from ethanol–water vapor mixture in a pressure swing adsorption (PSA) process. It was demonstrated that through the process over 99 wt % fuel grade ethanol was achieved from lower grade feeds containing 80–95 wt % ethanol at 90–110 °C and 136–243 kPa. The breakthrough curve technique was used to investigate the adsorption dynamics and equilibrium. The effects of temperature, pressure, vapor feed concentration, and adsorbent particle size on water and ethanol uptake and separation factor were examined. External water mass transfer coefficients were also calculated. The model based on Dubinin–Polanyi potential theory fit the water adsorption isotherms reasonably well. The mean free energy of water adsorption was calculated to be 0.04 kJ/mol, and heat of adsorption was −35.81 kJ/mol, which indicated the physical nature of the adsorption. Water saturated canola meal biosorbents were regenerated at 90 °C under vacuum and reused