Prediction of water vapor sorption in the polymeric membranes using PHSC equation of state

Dehydration of gas streams such as natural gas, flue gas and compressed air is a major process which has applications in the industry. The most common method for the dehydration of gas streams is the sorption method. Recently attention has been given to the use of membranes for the adsorption of water vapor from gas streams. In this study, water vapor sorption in the polymeric membranes including PEBAX-1074, SPEEK, PEO-PBT, NTDA and Nafion-117 has been modeled by using a thermodynamic model named perturbed-hard-sphere-chain (PHSC) equation of state (EoS) at temperatures 20–70 °C. PHSC equation of state is the sum of a hard-sphere-chain term as a reference system and a van der Waals attractive term as a perturbation term. PHSC equation of state for the simple fluids and spherical molecules contains two parameters which are ε, the well depth in molecular potential energy function, and σ, separation distance between segment centers of molecules. While this equation is used for the chain molecules such as polymers, the parameter r, the number of effective hard spheres per molecule is also required. The equilibrium calculations have been performed and results have been compared with the experimental data showing an overall average absolute deviation equal 0.53.