Effects of reboiler duty on the conceptual design of reactive distillation for the purification of lactic acid produced by fermentation

Temperature affected both reaction and separation in a reactive distillation column. This research used Aspen Plus V.10 in the simulation of the reactive distillation to produce 88 wt. % lactic acid. The feed was the fermentation broth generated from the fermentation using corn stover as raw material. The objective was to know the effects of the reboiler duty of both the esterification column and hydrolysis column on the temperature profiles, the reactions, and the separation in the columns. The heat duty of the esterification column ranged from 385 to 405 kW, and the heat duty of the hydrolysis column varied from 260 to 310 kW. The simulation results indicated that the temperature had a larger impact on the reaction than the separation. Ethyl lactate formed in the upper section of the column resulted in the lowering of the temperature. The low temperature led to the reverse reaction of ethyl lactate to lactic acid. The heat duty ranging from 260 to 290 kW of the hydrolysis column provided the high conversion percentages of ethyl lactate. The highest production rate of lactic acid was obtained from the heat duty of 290 kW. Furthermore, this heat duty also resulted in high ethanol flow rates from the ethanol recovery column. As a result, the highest conversion percentage of lactic acid in the esterification column was achieved when the reboiler duty was 405 kW. Nevertheless, the high temperature either in the esterification or the hydrolysis column was responsible for the reaction of lactic acid to di-lactic acid.