Fixed beds of corn grits have been used to produce anhydrous fuel-grade ethanol in commercial scale ethanol industry over 20 years. Starch in the corn grits selectively adsorbs water by forming hydrogen bonds between free-OH groups on the glucose units of the starch and water molecules. The bed is regenerated by counter-currently flowing hot CO2 gas through the bed. The regenerating gas carries the desorbed water and ethanol left in the void volumes of the bed to a recycling system. An automated research scale corn grit adsorber was constructed for evaluating conditions for drying of an azeotropic ethanol/water mixture. We present results for breakthrough and cyclic operation of two different sizes of corn grits in terms of their adsorption capacities and product ethanol purity at conditions that simulate an industry scale operation. This paper also reports and compares general properties of fresh corn grits compared to corn grits that have been in operation for a year. Both were analyzed for changes in compositional and physical characteristics, which were found to be small. A fundamental understanding of the properties and characteristics of corn grits and their performance in a fixed bed mode provides knowledge for improving adsorbent lifetime and design of better-performing starch-based adsorbents.

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