Effect of recycle and feeding method on batch reactive recovery system of lactic acid

Reactive batch distillation coupling esterification and hydrolysis was studied for the recovery of lactic acid. The analysis of the dynamic behavior of the system showed drastic change of esterification reaction rate in the reboiler due to the difference of volatility and component boilup rate of each species. Methanol recycle and feeding method were investigated as the factors which could control the compoent boilup rate of each species and rate of esterification reaction. The flow rate and composistion of methanol recycle stream was controlled by the temperature of the partial condenser. A temperature slightly higher than the methanol boiling point is optimum as the temperature of the partial condenser. When the temperature of the partial condenser was increased in the initial part of whole batch time and decreased in the latter part, the performance of the system was enhanced, compared with when the partial condenser temperature remained constant. Semibatch operation was compared with batch operation. Continuous feeding of methanol enhanced the recovery system performance while continuous feeding of lactic acid aqueous solution deteriorated, compared with batch operation.