Optimization of productivity in a four-zone simulated moving bed process for separation of succinic acid and lactic acid

The necessity for separating a mixture of succinic acid and lactic acid, which was an outgrowth from the existing fermentation and nanofiltration processes in series, has been raised in the literature. To address this issue, the optimal design of the four-zone simulated moving bed (SMB) process for continuous separation of the two acids was carried out at the temperature of 30 °C in this study. First, a series of single-column experiments were performed to determine the mass-transfer parameters and to validate the adsorption isotherm and mass-transfer parameters at 30 °C. The detailed simulations based on such parameters were found to agree well with the experimental data from both the single-component and the mixture frontal tests. These validated parameters were then applied to the next stage of optimizing the SMB process of interest on the basis of standing wave design (SWD) principle. In this task, all the operating parameters and the column length were optimized to maximize productivity while taking into account the constraints on product purities, pressure drop, and switching time. Furthermore, the effect of feed concentration on the optimization results was also investigated. Finally, the simultaneous optimization of productivity and desorbent consumption was accomplished by using the optimization tool based on the SWD and elitist nondominated sorting genetic algorithm with jumping genes.