High-purity hydrogen is required for clean energy and a variety of chemical technology processes. A considerable part of hydrogen is to be obtained by methane conversion and its separation from other hydrocarbon gases not involved in energy production. Different alloys, which may be well-suited for use in gas-separation plants, were investigated by measuring specific hydrogen permeability. One had to estimate the parameters of diffusion and sorption to numerically model the different scenarios and experimental conditions of the material usage (including extreme ones), and identify the limiting factors. This paper presents a nonlinear model of hydrogen permeability and its modifications in accordance with the specifics of the experiment, the difference scheme for the solution of the boundary-value problem, and the results of numerical modelling.