AN INDUSTRIAL ETHANOL AZEOTROPIC DISTILLATION PROCESS: MODELING, ANALYSIS, AND SIMULATION (THERMODYNAMICS, DEHYDRATION, GASOHOL, OPTIMIZATION, SEPARATION)

A steady state process simulator with extensive capabilities was developed for the simulation of process plants involving non-ideal multicomponent systems. A comprehensive stand alone program was developed to represent process systems encountering three phases. A computer program was also developed to handle simultaneous regression of vapor-liquid and liquid-liquid equilibria data to estimate the liquid phase activity coefficients via a global set of parameters for the ethanol azeotropic distillation process, using benzene as the entrainer.;In an extensive study on the azeotropic column, the optimum entrainer to binary feed ratio and the dry ethanol product rate have been established for aqueous ethanol feed concentration ranging from 70 to 89.4 mole % (ethanol). A multiple solution phenomena was investigated for the azeotropic column, and it was found to require a very stiff material balance to obtain the desired product split.;A global set of modified UNIQUAC interaction parameters has been determined using the regression program. This single set of parameters, obtained by simultaneous regression of binary isobaric vapor-liquid equilibria data and a single liquid-liquid tie line, has been established on the basis of its performance in the key units of the ethanol azeotropic distillation process.;Finally, twelve potential entrainers have been evaluated for the ethanol dehydration process using the UNIFAC activity coefficient equation. A set of suitable entrainers has also been prepared, based on extensive analysis using the model of the azeotropic distillation column to demonstrate production of marketable ethanol.;An industrial ethanol azeotropic distillation process has been simulated using the developed process simulator (PROSIM). A study of the azeotropic column's aqueous ethanol feed composition reveals 82.9 mole % (ethanol) as the optimum concentration. The complete process plant as well as the individual process units were found to operate under a very narrow range of operating conditions. A sensitivity study on the process plant was conducted with respect to the ethanol product specifications and benzene stripping column pressure.