ETHANOL DEHYDRATION WITH PROTEIN EXTRACTED CANOLA MEAL IN A PRESSURE SWING ADSORPTION PROCESS

Abstract

Bioethanol is the most widely used biofuel nowadays, which can be derived from renewable sources of energy and is also environmentally friendly. The resulting ethanol from biomass, however, is as a mixture containing 10-15 wt% ethanol mixed with water and other organics. In order to be used as a fuel, the mixture should be purified to at least 99.5 wt% ethanol. Among several processes which have been applied to obtain fuel grade ethanol, adsorption using bioadsorbents seems more appealing due to low operation costs and high efficiency. In this study, canola meal after protein extraction was chosen as the biosorbent to dehydrate ethanol in a Pressure Swing Adsorption (PSA) system. The breakthrough experiments were conducted to investigate the equilibrium and kinetics of the process. The effects of temperature, pressure, feed flow rate and vapor feed concentration as well as adsorbent particle size, on the adsorption process were examined. The experimental results were compared in terms of breakthrough time, selectivity of water over ethanol and the slope of the breakthrough curve which is an indication of the mass transfer rate. The Dubinin- Polanyi model which is based on the adsorption potential theory represented a reasonable fit with the equilibrium data. The mean free energy of the adsorption process was calculated to be 0.04 kJ/ mole, which indicated the physical nature of the adsorption process. It was demonstrated that over 99 wt% ethanol was achieved using protein extracted canola meal as the biosorbent in a pressure swing adsorption process. However, a significant amount of ethanol was also adsorbed along with water which led the selectivity of the biosorbent to adsorb water over ethanol to be less than 4.