Simulation and optimization of simultaneous fermentation and separation of butanol using pervaporation technique

Abstract

Product inhibition continues to be one of the major problems impeding the continuous production of butanol by fermentation process. Although many techniques are available which could sort out the fore mentioned problem, pervaporation continues to be the front runner in terms of effectiveness and efficiency. Analysis of biochemistry of ABE fermentation leads us to the development of new solvent- producing strains and changes in the metabolic pathway which could lead to significant amount of solvents production without the product inhibition problem. In this project we select a well-defined model for the fermentation process and try to reproduce the results of the pervaporation process. The set of differential equations were analyzed for their consistency and were solved using ode45 solver in Matlab. For the process involving pervaporation, a pervaporation factor (rp) was taken into account. This factor was derived from the data of the fermentation process so that accurate representation is possible. There were several constraints in choosing this factor. The inherent factors of the system such as scaling up on the retentate side, which decreased the effective area available for pervaporation, were not considered. It was also found that the rp factor had a pronounced effect, when even changed slightly, on the substrate consumption rate and the biomass production. The butanol rate was ffected only when the factor was changed drastically. After several trial runs we are led to the conclusion that we should have different values for rp in the two systems so as to give a realistic representation of the model. The biomass production in both the systems reached the same maximum concentration, a fact supporting the model.