Optimization of Batch Reactive Distillation Process: Production of Lactic Acid

摘要

Lactic acid is widely used as a raw material for the production of biodegradable polymers, food, chemical and pharmaceutical industries. The global market for lactic acid is set to reach 259 thousand metric tons by year 2012. In this work, the performance of batch reactive distillation is evaluated to produce lactic acid by hydrolysis reaction of methyl lactate. Minimum time optimisation problem is developed incorporating a process model within gPROMS software for range lactic acid purity (from 80 % to 99 %) and the amount of product. For a given column the minimum operation time configuration is obtained by optimising the reflux ratio profile. The lactic acid being heaviest in the reaction mixture, reflux ratio policy plays an important role in removing the light product methanol from the system while ensuring the presence of both reactants in the reaction zone to maximise the conversion to lactic acid. Also unlike esterification reaction, total reflux operation is demanded at the end of the operation in the hydrolysis reaction to purify lactic acid to about 99 % by removing the remaining reactants from the reboiler.