Optimization of Energy and Water Consumption in Corn-Based Ethanol Plants

In this paper we study the simultaneous energy and water consumption in the conceptual design of corn-based ethanol plants. A major goal is to reduce the freshwater consumption and wastewater discharge. We consider the corn-based ethanol plant reported in Karuppiah, et al. AICHE J. 2008, 54, 1499-1525. We review the major alternatives in the optimization of energy consumption and its impact in water consumption. Next, for each of the alternatives we synthesize an integrated process water network. This requires closing the loops for process and cooling water and steam, and implementing the proper treatment for the water streams. We show that minimizing energy consumption leads to process water networks with minimum water consumption. As a result, freshwater use is reduced to 1.54 gal(water)/gal(ethanol), revealing that it is potentially possible to achieve levels of freshwater consumption that are significantly lower than the ones in current industrial operation and that wastewater discharged can also be reduced.