Integrated processing for the separation of biobutanol. Part B: model-based process analysis

The biochemical production of butanol by fermentation is an interesting option for the sustainable production of a chemical that can be used as a fuel additive or solvent. However, butanol is toxic towards the production organisms, resulting in low concentrations of biobutanol in the aqueous fermentation broth. Therefore, conventional purification by distillation is very energy intensive. Extraction with ionic liquids and pervaporation as alternative separation technologies are two promising options for energy-efficient butanol recovery. These processes are analysed on detailed economics, including the influence of the uncertainty of the used model parameters and the sensitivity of the production costs to model parameters and design variables. It is shown that the costs for butanol purification by means of distillation are strongly dependent on the costs for thermal energy. For extractive recovery, the solubility of the extraction solvent in the raffinate is one of the main cost drivers as it affects the solvent loss. The costs of the pervaporation-based recovery mainly depend on the price for the membranes and are strongly dependent on the permeate fluxes. For all processes, the feed concentration has a noteworthy effect on the total downstream costs. This study allows not only an analysis of existing technologies but also helps to guide future research.