In this study a modified solution for CAAM approach, originally presented in our previous work for simulation of binary gas mixture separation in nanometric tubular membranes, is presented by considering the permeate pressure drop along the permeator length. The accuracy of the modified CAAM method is verified by comparing the predicted results with the exact solution, experimental data and the original CAAM method results. Also, a detailed parametric analysis is done to determine the effects of different parameters (feed operational parameters and membrane physical and dimensional characteristics) on the permeate pressure drop along the permeator length. (c) 2006 Elsevier B.V. All rights reserved.