Purification of isopropanol-butanol-ethanol (IBE) from fermentation broth: process intensification and evaluation

Abstract Biofuels from biomass have attracted great attention due to the increasingly serious environmental problems and the increasing demand for fossil fuels. Butanol is considered as a promising alternative biofuel because of its favorable properties, and it can be produced by IBE fermentation broths. Moreover, the high-purity isopropanol-ethanol (IE) mixture produced by IBE fermentation can be used as a gasoline additive. However, the IBE purification process is hindered by its low concentration and energy-intensive separation from IBE fermentation broths. In this work, a novel 6-column distillation process for IBE purification is proposed to reduce the total energy consumption (TEC) and capital cost. Furthermore, for achieving further energy savings, the double-effect distillation (DED) and heat pump assisted distillation (HPAD) technologies are used as the process intensification methods. These processes are compared in terms of energy, economic and environmental impact. The results indicate that the total annual cost (TAC), TEC and gas emissions of the IBE purification process can be reduced effectively by the three intensification processes, among them, the process intensification with HPAD (PI-HPAD) process is the best one, which can achieve 46.72%, 26.96% and 30.52% savings of TEC, TAC and CO2 emission, respectively.