Exergy, economic, and environmental assessment of ethanol dehydration to diesel fuel additive diethyl ether

Abstract

Ethanol dehydration to diethyl ether makes it suitable for diesel engines by improving its cetane number, autoignition temperature, flammability limits, and petrodiesel miscibility. Therefore, the present investigation aimed at analyzing the ethanol dehydration process in a continuous reactor from thermodynamic, economic, and environmental perspectives. An integrated soft computing approach was also used to model and optimize the ethanol dehydration conditions. The effects of three reaction variables, i.e., weight hourly space velocity (WHSV), dehydration temperature, and dehydration pressure, were thoroughly analyzed on the exergy, exergoeconomic, and exergoenvironmental indicators. The WHSV was the most influential variable on the exergetic indicators investigated, while the studied indicators were hardly affected by the dehydration pressure. The optimal dehydration temperature, pressure, and WHSV were found to be 398 °C, 82.3 bar, and 2.96 1/h, respectively. At the selected optimal ethanol dehydration conditions, the process exergy efficiency was found to be 22.7%. The cost and environmental impact of unit product exergy at the optimal ethanol dehydration conditions were 95.0 USD/GJ and 85.7 mPts/GJ, respectively. Generally, it could be deduced that chemical biofuel plants could be well understood and optimized using the exergy-based approaches, particularly exergoeconomic and exergoenvironmental methods.