Design and Control of an Alternative Process for Biobutanol Purification from ABE Fermentation

There is an incremental demand for alternative biofuels because of the decreasing oil supply and increasing environmental concerns. In this respect, biobutanol production from acetone-butanol-ethanol (ABE) fermentation comes forward as a remarkable process alternative. However, the main drawback of this alternative is the production of dilute fermentation broth which results in very energy demanding separation steps. Thus, several hybrid separation techniques have been studied combining extraction and distillation technologies to develop energy efficient separation processes. Although these techniques solve the well-known drawbacks, they also bring their own disadvantages. In this study, an alternative separation process including reactive distillation columns is proposed to purify biobutanol from acetone-butanol-ethanol (ABE) fermentation. As a result of the reaction taking place in the process, ethylene glycol is obtained as an added-value coproduct besides the purification of butanol. The steady-state simulations using Aspen Plus indicate that the total annual cost (TAC) decreases significantly when compared with flowsheets given in the literature. In addition, effective control structures are designed using Aspen Dynamics, and their robustness is tested against two different types of load disturbances. It is seen that stable regulatory control is provided using the proposed control structures.