Farm Ethanol Dewatering: Detailed Design Of Distillation Unit

Abstract

Sweet sorghum offers a range of advantages due to its low water input, high carbohydrate yield and drought tolerant characteristics. The team at the School of Bio-systems & Agricultural Engineering at Oklahoma State University has demonstrated the ability to harvest, express, and ferment sweet sorghum on-farm. The fermentation product is an aqueous 6 - 10 wt % ethanol product. The high concentration of water (90+ wt %) in the fermentation product provides a strong incentive to perform on-farm dewatering to replace high costs for transportation to a central processing facility. Furthermore, to ensure successful recovery of the ethanol obtained from fermenting sweet sorghum on farm, a small scale dewatering facility needs to be established. Rigorous, first-principles simulations have been created to provide the material and energy balances required for equipment design. Based on the findings from the simulations, the detailed design of a two-column dewatering system capable of producing a 190 proof ethanol product was completed. The design addresses contemporary issues of water requirements and waste disposal. The proposed design eliminates the need for well water make-up, required for cooling or steam generation, with air-cooling and reboiler substitutes. The system is designed to process approximately 250 gph of fermentation product in two 12-inch diameter columns, the smallest practical size that can be implemented on a farm. With a state-of-the-art demonstration unit future studies can be geared towards data generation and analysis required for economic and technical optimization of an on-farm ethanol production facility. Results from this work could have significant economic impact on agriculture. The role of the farmer will expand from feedstock supplier to that of fuel producer and increase the economic opportunities for local communities.