Development of lactic acid evaporation process model with multi effect evaporator and mechanical vapor recompression system

Lactic acid (LA) is a raw material for poly lactic acid, which is used in food, pharmaceutical, textile, and various chemical industries. Evaporation is an essential process to produce highly pure LA after the fermentation process. Notably, the evaporation process is energy intensive, and the energy consumption corresponds to approximately 50% of the total production cost. Consequently, the energy efficiency of the LA evaporation process must be enhanced. To this end, this study was aimed at establishing a process model based on a multi-effect evaporator (MEE) and mechanical vapor recompression (MVR) system. The MEE process model involved a distillation column, virtual reboiler, and flash drum. The steam consumption was reduced by recovering the latent heat of secondary vapor. Furthermore, the steam and condensate were recovered from the final evaporator. The MVR process model involved a compressor that substituted the steam consumed in the evaporation with electricity by recompressing the vapor in the evaporator. The energy efficiency of the two processes was analyzed by comparing the steam and electricity consumption values. The steam consumption decreased from 99.381 to 37.913 ton/h with the increase in the number of effects (from one to eight), and the electricity consumption of the MVR system was 31.32 kW.