Methods and systems useful for drying ethanol

Abstract

Mixtures of ethanol and water are dehydrated using starch pearls to adsorb and remove water. Vapor-phase adsorption equilibrium capacities of cassava starch pellets (tapioca pearls) having different particle sizes are disclosed, and tapioca pearl particles are shown to be surprisingly more effective for dehydrating 88 to 97% w/w feed ethanol than corn grits. The adsorption equilibrium curve and BET surface area measurement show that the adsorption capacity of tapioca pearls is a function of surface area available to water molecules. SEM images demonstrate that the particle architecture required for the adsorption and dehydration properties is that of a core-shell configuration with pre-gel starch acting as a central scaffold holding together other particles to the outer layer of the particle. The outer surface area of the pearls, populated with dry starch granules, is the main factor determining the adsorption capacity of the pearls. Tapioca pearls are shown to possess a surprisingly higher adsorption capacity than corn grits of the same particle size. Pearls of 2 mm size in diameter gave 34% higher linear adsorption equilibrium constant (K) than grits of 1.7 mm.