Design and Optimization of an Azeotropic Distillation Pilot Plant for the Production of Pure Ethanol

Abstract

This study aimed to design an azeotropic distillation plant using Aspen Plus® V10 software and determine optimal process conditions for producing pure ethanol greater than 95% from pre-concentrated near-azeotropic ethanol-water solution. The non-random two-liquid Redlich-Kwong thermodynamic model was the base method for property analysis and performance prediction. Modelling and simulation of the converged process were conducted for fixed column variables (R = 5, N = 12 and p = 1 atm). Plant operating parameters were varied in the range of 0 to 1 for the pre-heater vapour fraction, 2 to 10 for the column feed plates (N FP ), 2 to 6 for the recycle feed plate (N RFP ), 10 to 20 kmol/h feed flow rate (F AZ ) and 0.81 to 0.86 mol/mol ethanol concentration (X FAZ ). Results show that an increase in F AZ and X FAZ resulted in retrograde phenomena, which hinders plant performance while increasing energy requirements. Further, an increase in N FP and N RFP results in a decrease in dehydration plant performance from 99.84% to 97.5%. It was concluded that high energy efficiency and enhanced plant performance are obtained when the plant is operated with F AZ ranging from 18 to 20 kmol/h. The feed and recycle plates should be located closer to the top of the column, i.e., stage 4 for the feed, stage 2 for aqueous solution and stages 1-3 for the recycle streams. The study recommends a careful distillation synthesis followed by real plant monitoring to address the retrograde phenomena effect and improve the overall ethanol dehydration plant performance.