2 - Enhanced distillation process intensification for the recovery of pure solvents in a hexane-ethanol-water mixture.

FLORENCIA BALAUDO; MARTÍN SEBASTIÁN GROSS

Buenos Aires

Congreso; 11th World Congress of Chemical Engineering; 2023

AAIQ

To increase the relative concentration of proteins in the soybean expeller, a second hydroalcoholic extraction is added to the conventional oil extraction with hexane to solubilize the carbohydrates. However, at the end of the process, the ternary mixture (hexane-ethanol-water) is difficult to separate and becomes a harmful pollutant for the environment and population. Therefore, by using an enhanced distillation process, it is intended to obtain its components with the highest possible purity to reuse them, with an emphasis on energy savings during the separation process. The study begins with an equilibrium analysis, assuming ideal gas behavior for the vapor phase, since distillation takes place at pressures close to ambient condition. The NRTL activity model was selected to predict the behavior of the liquid phase, considering that it can be reliably applied to many mixtures with different component properties and can predict the partial miscibility between the two liquid phases. Using experimental data from different bibliographies, the behavior with temperature was analyzed from binary equilibria. Then, by setting certain parameters according to the interaction nature between the components, with a program for numerical calculations (GNU Octave) the model parameters were obtained. The azeotropic behavior was studied and the residual curves were constructed using the Unisim Design and Thermo Workbench software. Once the equilibrium parameters were defined, the distillation columns were designed with emphasis on determining the number of theoretical stages, optimum feed plate and external reflux ratio to minimize the equipment volume without reducing process performance. For this, the software UniSim Design was used. Changing those parameters, heats involved at the top and bottom of the column were determined. Finally, the heating loads of the reboilers and cooling loads of the condensers were reduced to improve the energy recovery capacity of the system from the integration of heat between the hot and cold streams. This mainly reduces the kettle steam consumption in the reboilers and makes the process more sustainable.