(406f) Desing and Rating of a Thermically Integrated Distillation System with Low Stillage Generation

Although ethanol is widely recognized as a renewable, sustainable, and secure alternative energy source in face of uncertaintites surrounding fossil fuels and imminent energy crisis, the substantial amount of ethanol produced in Brazil has resulted in a significant increase of stillage generated during the process. This poses a serious environmental issue due to its high pollution potential. Stillage is a rich mineral source and can be utilized as fertilizer in sugarcane fields, however, its limited storage lifespan at the mill and dosages restrictions led by environmental standards, transporting stillage across the field became costly beyond a certain distance from the distillery leding to a problem that industry urges to solve. Usually, stillage is produced in a quantity up to 12 times larger than ethanol, making it the most prevalent by-product of the process. To concentrate stillage, conventional mills requires specialized equipment which can account for up to 60% of the total capital expenditure of a distillery and often requires additional steam usage, which is not practical for the majority of the industry. The proposed solution employed heat integration techniques between multiple-effect stripping columns to effectively decrease the volume of stillage during the distillation process, rahter than after as emplyed today. Simulations using Aspen Plus indicated that the stillage/ethanol ratio dropped from 12:1 to 5:1 in volume without requiring extra steam or equipment. A subsequent rate-based simulation considering physical and hydraulic parameters was conducted to determine if these findings could be effectively translated in actual hardware with positive outcomes. These results regarding mass, energy and hydraulic balances are unprecedented and potentially groundbreaking in process engineering, leading to an innovative approach if the system could be built.