Design and Optimization of Lactic Acid Purification Process by Reactive Distillation with Isoamyl Alcohol

The purpose of this study was to investigate a continuous process for the recovery of lactic acid from fermentation broth. A reactive distillation process to purify lactic acid by esterification with isoamyl alcohol and hydrolysis was designed and simulated by Aspen. Five columns were included in the process: esterification column, purification column, hydrolysis column, dehydration column and recovery column. Effects of process parameters (operating pressure, feed composition, feed position, number of reaction and separation stages, and reboiler duty) of the esterification column on the yield and purity of lactic ester was evaluated. Further evaluation was carried out to reveal the effects of process parameters of the hydrolysis column on the yield and purity of lactic acid. The total annual cost of the whole process was calculated. Simulation studies are carried out using Aspen Plus RADFRAC module. It was shown that under the optimized condition, the concentration of lactic acid can reach up to 82.4 wt%, and the organic acid impurities were less than 3 ppm. Compared with the traditional usage of methanol and butanol, the isoamyl alcohol process can save about 20% of the total annual cost at the same output of lactic acid. Results obtained in this work can be used for scale-up study of an industrial reactive distillation operation as an efficient and economical alternative to recover lactic acid from fermentation broth.