Journal of Bioprocessing & Biotechniques

Simulation with Computational Fluid Dynamics of Succinic Acid and Co-Product Biorefinery Process

Abstract

Pierre Wensel, Liang Yu and Shulin Chen

Succinic acid is a di-carboxylic acid with tremendous future market potential, and there is increasing interest to produce it from microorganisms using cheap renewable resources like biomass. However, commercialization of bio-succinic acid is currently challenged by limited profitability of processes devoted solely to succinic acid, high downstream process costs, and minimal available industrial-scale simulation. To address these limitations, a novel industrial-scale biorefinery process to convert corn-stover into succinic acid and co-products was simulated using an integrated mathematical model developed from reported laboratory-scale experimental data. The upstream section of the biorefinery featured handling, pre-treatment, conversion, and separation of corn stover feedstock into a liquid fraction for ethanol processing and a solids fraction containing mostly cellulose that was further hydrolyzed into glucose for succinic acid processing. Subsequent units of operation were then simulated for a baseline process: Microfiltration was used to remove residual insoluble lignin, and glucose was then continuously fermented by the strain M. Succiniciproducens MBEL55E to produce succinate and by-products acetate, lactate, and formate. Additional steps to recover and purify succinic acid included cell microfiltration for cell removal, moving-bed adsorption for sugar removal and decolorization, nanofiltration for separation of succinate primarily from other salts, ion exchange for acidification and purification, and finally crystallization. The finite volume method of Computational Fluid Dynamics (CFD) was coupled with kinetic, stochiometric, mass, and energy balance equations to simulate the effects of inlet temperature impeller speed, diameter, and spacing, as well as inlet temperature and fermentor volume, on fermentor cooling jacket heat transfer area. Predicted dissolved CO2 concentrations in the fermentor were in agreement with those in literature. The effects of microfiltration recirculation rate, microfiltration stage numbers, and adsorber sorbent particle diameter on dimensional requirements and power consumption were additionally evaluated. Yields and estimated volume and area requirements for units of operation were obtained for the baseline process and for those involving the simulated variable changes. This work represents the first reported industrial-scale bio-succinic acid process model.