(96d) The Extraction of Ethanol in a Continuous Fermentation Process for Fuel-Grade Ethanol

Ethanol is being used in reformulated gasoline (RFG) and oxygenated gasoline to fulfill the requirements of the Clean Air Act. Currently, there are 56 ethanol production facilities in the United States, producing approximately 4 billion gallons of ethanol per year, with more under construction and expansion. Most of the ethanol is produced from the starches found in corn. Because ethanol poses no serious health risk to humans, it is the most likely replacement of methyl tertiary butyl ether (MTBE), the most common additive used in reformulated gasoline (RFG). MTBE has been ban in several states and in other states; its concentration is limited due to health risks related to MTBE found in drinking water. These starches are converted to sugar and the sugar is fermented into ethanol. Ethanol fermentation is an inhibited-product reaction, and inhibition limits productivity. Our focus is not necessarily the production of ethanol, but rather the productivity. If ethanol were extracted from the process as it is produced, it would reduce inhibition and increase productivity. This project involves two methods that are aimed at improving the productivity. One method uses a packed bed distillation column to absorb water and the other method uses a membrane contactor to extract the ethanol. The two methods will be analyzed and compared. The concepts, experiments, and ideas behind the two methods are discussed in subsequent sections.