Ethanol Dehydration in a Pressure Swing Adsorption Process Using Canola Meal

Abstract

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.iii ACKNOWLEDGEMENTS

Agricultural byproducts-based biosorbents for purification of bioalcohols: a review

“…It was the pioneering efforts of Ladisch and Dyck in Purdue University that opened up a new era-the use of biological materials as adsorbents for drying of ethanol using cracked corn, starch, and cellulose (Ladisch and Dyck 1979). Since then, extensive research has been carried out using a wide range of biomaterials such as corn grits, corn meal, canola meal, corn cobs, and barley straw for removal of water from alcohol and gases (Anderson et al 1996;Ladisch 1997;Chang et al 2006;Ranjbar et al 2013;Tajallipour et al 2013;Jayaprakash et al 2017;Dhabhai et al 2018;Hong et al 1982). The only biomaterial that was applied at an industrial scale is corn grits, which has been used since 1984 for drying methanol, ethanol, propanol, and tert-butanol vapors (Ladisch 1997;Beery et al 1998).…”

“…In addition, the production of biosorbents requires minimal processing and no chemical and thermal reactions like chemical adsorbents which often require high temperature activation. Moreover, the temperature of regeneration for biosorbents is much lower (< 110 °C) compared to commercial molecular sieves (> 190 °C) (Ranjbar et al 2013;Tajallipour et al 2013;Jayaprakash et al 2017). Even if regeneration is not possible with biosorbent, it can still be utilized as a raw material for the production of biofuels (Benson and George 2005).…”

“…In the literature, several biosorbents have been successfully employed for bioalcohols dehydration by vapor phase adsorption. The biggest advantage of vapor phase adsorption is that the process can be continuous and the biosorbent can be reused several times without deterioration as the liquid is not in direct contact with the adsorbents (Chang et al 2006;Ranjbar et al 2013;Tajallipour et al 2013;Jayaprakash et al 2017). Table 6 presents the compilation of literature for use of biosorbents in vapor phase adsorption.…”

Drying of nonpolar gas in a pressure swing adsorption process using canola meal biosorbents

“…Canola is abundantly cultivated in Canada and generates about $26.7 billion to the Canadian economy each year . This biosorbent, both before and after protein extraction, has a capability to selectively adsorb water, which has been explored in the recent past for ethanol drying . In other words, the functional groups on the biosorbent adsorbed more polar water molecules than less polar alcohol molecules.…”

“…16 This biosorbent, both before and after protein extraction, has a capability to selectively adsorb water, which has been explored in the recent past for ethanol drying. [17][18][19] In other words, the functional groups on the biosorbent adsorbed more polar water molecules than less polar alcohol molecules. Owing to the water selectivity and high wateradsorption capacity of CM, 17,20 it appears to be a suitable candidate to study water adsorption from wet nonpolar gases.…”