One of the newest membrane processes is the application of poly dimethyl siloxane in the field of heavy hydrocarbon recycling. The problems related to performing the experimental measures by the means of membrane, especially at the industrial and semi-industrial scale refer to applying the obtained great importance in the efficiency evaluation. In this paper, in order to obtain the dimensionless retentate component flow rate of three-component gas mixture, including propane, methane and hydrogen, the equations in which the diffusion and solubility coefficients related to the components in the poly-dimethyl siloxane membrane are considered as the functions of temperature, pressure and the composition of feed percentage in the constant feed flow rate (30 cm 3 /s) have been solved after presenting the features and properties of poly dimethyl siloxane membrane. The numerical solution method proposed with respect to the algebraic equations and the short solving time has been chosen in comparison with the existing methods to solve the differential equations such as the finite elements of the effective interpolation method by using orthogonal collocation approximates using the temperature, pressure and concentration effects at the various levels and the membrane surface area on the dimensionless retentate component flow rate have been surveyed of crosscurrent membrane model.
