Modeling of a Novel Approach to Water Recovery from Sugar Cane Vinasse: Optimization of Exergy Efficiency, Heat Exchange Area, and Thermal Performance Ratio Using Genetic Algorithm and TOPSIS

Abstract

Historically, multistage flash distillation (MSF) led potable water production. By 2019, emerging technologies largely replaced MSF; however, it remains attractive for its energy and exergetic efficiency due to its reliance on low-temperature heat sources, especially when cogeneration is involved. In contrast, the sugar-energy industry consumes around 0.7 m3of water per metric ton of sugar cane processed. Rising environmental, social, and corporate governance (ESG) concerns have intensified efforts to reduce water use. Accordingly, this study identified an optimal configuration for integrating a once-through MSF (MSF-OT) system with a sugar cane processing facility. The proposed system recovers water from vinasse, a byproduct of ethanol production, by using steam generated during the sugar cane juice concentration process as its energy source. The process was modeled in MATLAB using data from a Brazilian plant, and optimization was performed with a genetic algorithm targeting exergy efficiency, total heat exchange area, and thermal performance ratio. The Order Preference by Similarity to Ideal Solution (TOPSIS) method subsequently selected the best alternative from the Pareto Front. Results indicated that 58 flashing stages and a terminal temperature drop in the condenser of the first stage of 4.3 °C are the optimal configuration, producing 50,080 m3of distilled water per harvest.