Modeling of ammonium lactate recovery and impurity removal from simulated fermentation broth by nanofiltration

A multistage version of nanofiltration (NF) model has been developed, which can predict the transient and steady-state behaviors of the process for lactate recovery from fermentation broth. The model parameters were estimated based on experimental data at various lactate concentrations and operating pressures with simulated fermentation broth containing impurities as well as lactate by using Spiegler–Kedem model and Teorell–Meyer–Sievers model. Continuous NF operations were carried out for various bleed ratios to investigate the effects of bleed on the lactate recovery and level of impurity represented by sulfate in this study. Time profiles of lactate and sulfate concentrations in the system and permeate predicted by the proposed model were in a good agreement with the experimental data. Also, the accuracy of the steady-state prediction by the model was experimentally proved. It was demonstrated that impurity concentration decreased as the bleed ratio was increased, while the lactate recovery decreased proportional to the bleed ratio as expected. The proposed model can be used for predicting the process behaviors during a start up period and at the steady state, providing a useful tool in process design and optimization.