On the effect of inert gases in breaking the formic acid-water azeotrope by gas-gap membrane distillation

The effect of inert gases, such as helium, air, and sulfur hexafluoride, in breaking the formic acid-water azeotrope by gas-gap membrane distillation process is theoretically investigated under the process relevant operating conditions. A Stefan-Maxwell-based mathematical model that includes all nec essary vapor-liquid equilibrium, heat, and mass relations is used for this purpose. According to the model predictions, heavy inert gases such as sulf ur hexafluoride help more in breaking the azeotrope than Lighter ones such as air and helium. This phenomenal behavior is discussed along with the eff ect of other associated process parameters. (C) 1999 Published by Elsevier Science S.A. All rights reserved.