<p>There are light impurities in isotopes that may leak from the air or be generated by reactions in the pipelines. When separating isotopes, these light impurities will affect the quality of the isotopes. Using a rotating cylinder to separate isotopes and impurity gases with a mass number difference by inertial force is one of the green and environmentally friendly as well as effective ways. It is meaningful to obtain the working mechanism of gas purification by the rotating cylinder through numerical simulation and study the optimization direction of the performance of the rotating cylinder so as to make the purification of gases by the rotating cylinder more efficient. This study analyzes the separation characteristics of the gas mixture of C₇F₁₄ and N₂ in the rotating cylinder. A hydrodynamic model of the binary gas mixture with sources and sinks is constructed. By employing an iterative approach to simultaneously solve the flow equation and the diffusion equation under strong perturbation, the flow field and the concentration distribution of the binary gas mixture within the rotating cylinder can be obtained. This study explores the impact of various factors on the total separation factor of gas mixture with large mass difference. The numerical results demonstrate that the binary gas mixture with a large mass difference in the rotating cylinder will still exhibit the radial separation characteristics under the action of strong driving circulation under the condition of having mass sources and sinks. The driving amount and the size of the scoop inlet have a regular influence on the total separation factor of the gas mixture.</p>