Performance of Different Inert Gases in Production of Fuel Grade Ethanol by Diffusion Distillation

Performance of sulfur hexafluoride, nitrogen, argon, and helium inert gases was investigated in a view to produce fuel grade ethanol by diffusion distillation. Stefan–Maxwell equations based mathematical model was used for this study. Modeling results were also compared with the own experimental data. Shifting of azeotrope to different extents was observed by using different inert gases as selective filter. As the selected inert gas becomes lighter, narrow concentration range for positive selectivity was found. Sulfur hexafluoride was found to be the most suitable inert gas for ethanol dehydration by diffusion distillation, and quantity S_az(N_2/ . -0emN_1) , which represents the overall performance of any inert gas, was also found to be highest for this gas out of all the inert gases studied. Sulfur hexafluoride gas also allows to work at high vaporization temperature, which facilitates the high transfer efficiency. If light gases are to be used they should be used for high feed concentrations and at low vaporization temperatures to achieve the high degree of separation.