Phase Equilibrium Measurement of n-Butane/Water/n-Butanol System for Development of an Energy-Saving Biobutanol Extraction Process

Hiroshi Machida, Akio Watan

Abstract

The application of biobutanol as an alternative fuel has numerous advantages compared to bioethanol, such as high heating value, low moisture absorption, and low corrosion, although biobutanol requires a high dehydration energy because of its low initial concentration (approximately 1-3 wt%). To develop energy-saving dehydration process using light hydrocarbon extraction, butane solvent was selected as a suitable solvent because of their properties like no azeotropic point or high butanol solubility. Phase equilibrium data of an n-butane/water/n-butanol system were determined using apparatus for high-pressure phase equilibrium measurements and NRTL model parameters were regressed. The proposed process for butanol dehydration consist the extraction column and distillation column. In the extraction column, butanol is concentrated to 90%, after which butane and butanol are separated in the distillation column. Vapor recompression system was introduced for heat recovery. Anhydrous butanol is recovered from the bottom of the distillation column. Energy consumption of a biobutanol dehydration process was evaluated using the developed model and shows 5 MJ/kg-biobutanol from the initial n-butanol concentration of 2 wt% to the final recovery of 99.9 wt% of biobutanol.