Management of ethanol waste from the solar distillation process: Experimental and theoretical studies

In this article, models for the management of the ethanol waste of a solar ethanol distillation system prototype have been proposed. The solar distillation system operates as a batch operation and consists of three stages of distillation, which increase the ethanol concentration from 8% to 80% (v/v). In each distillation stage, various volumes of ethanol solutions with different concentrations were obtained; three reuse scenarios (1, 2, and 3) have been proposed for extracting the ethanol solution from the distillation tank in order to increase the overall efficiency of the ethanol distillation system and reduce the amount of materials (cassava broth) fed into the distillation system. The most efficient distillation process, in terms of the final product volume and ethanol concentration in the product, was realized by using scenario 3, which involved recycling a mixture of the waste from the first stage and the second stage, for redistillation in the first stage and returning the waste obtained from the third stage for redistillation in the second stage than in scenarios 2 and 1 under the same condition, both quantitatively and qualitatively. In addition, by using scenario 3 for managing the ethanol waste, the amount of feedstock (cassava broth) annually fed to the system in the first stage could be reduced by 88–92% (96,522–100,073 L/year), compared to using the other two scenarios. Compared to a distillation process without recycling, the amount of cassava broth fed to the system can be reduced by over 180,000 L/year by using scenario 3.