Salt effect in distillation: A literature review

Reducing the Energy Demand of Cellulosic Ethanol through Salt Extractive Distillation Enabled by Electrodialysis

“…Corrosion due to aqueous ethanolic salt solutions requires consideration in regards to materials of construction (56,68). Other issues are related to solids handling, feeding and dissolving salt in the reflux stream, potential decrease in plate efficiency, and foaming inside the column (52,54,57). In the study presented here, the possible benefit in terms of energy demand is established, demonstrating that the concept may be attractive enough to deal with the possible complications.…”

“…These energy saving techniques have been shown to significantly reduce the distillation energy demand for the water-ethanol system (40-51); for instance, distillation energy demand reduction on the order of 42% has been reported for doubleeffect distillation with split feed compared to conventional distillation with a single column for distilling 93 wt% ethanol from a feed containing 7 wt% ethanol (43). Conversely, the VLE of the water-ethanol system can be improved towards ethanol separation by dissolving a salt in the liquid phase to raise the equilibrium vapor ethanol content (52)(53)(54)(55). Since salt remains as a nonvolatile component, the VLE of the water-ethanol-salt system can be studied and depicted as a pseudo binary system considering the equilibrium liquid composition on a salt free basis as is commonly done in literature (54,(56)(57)(58)(59)(60).…”

“…Since salt remains as a nonvolatile component, the VLE of the water-ethanol-salt system can be studied and depicted as a pseudo binary system considering the equilibrium liquid composition on a salt free basis as is commonly done in literature (54,(56)(57)(58)(59)(60). In addition to "salting out" ethanol this may also break the azeotrope (52,54,57). For example, starting with 70 wt% ethanol in water, 99.6 wt % ethanol was distilled using potassium acetate as the salt requiring only a quarter of the energy needed to obtain an inferior 93 wt% ethanol by conventional distillation (61).…”

“…Moreover, the studies (40,52,54,56,60,(63)(64)(65) which include both steps of salt extractive distillation and salt recovery do not generally consider techniques other than evaporation and drying for salt recovery. Evaporative salt concentration/crystallization and solids drying techniques are energy intensive.…”

Effect of Salt Magnesium Chloride on Vapour - Liquid Equilibria of Binary Azeotropic Liquid Mixture: Ethyl Acetate – Ethanol

“…For acetone methanol system, L.Belcku studied the effect of calcium chloride, J. Proszt and G. Kollar also studied the effect of calcium-chloride and lithium-chloride. The isobaric vapour liquid equilibrium data of the same system by using six different salts KI, NaCl, MgCl 2 , CaCl 2 , LiCl and CaBr 2 was discussed by S Ohe, K Yokoyama and S Nakamura [8] The binary liquid mixture ethyl acetate-ethanol is observe to forms a minimum boiling azeotrope at 0.55 mole fraction of ethyl acetate at 71.7 K under the local atmospheric pressure 700 mm Hg. The system ethyl acetate -ethanol was studied and reported by Hashitani and Hirata with different salts, namely, zinc chloride, potassium acetate and calcium chloride [9].…”