A new PSA process called the Petlyuk PSA process, which consists of two pairs of adsorption columns, an intermediate feed inlet and a side stream outlet, is proposed by extending the concept of Petlyuk distillation. By a simulation of the process with a simple mathematical model, the enrichment of a dilute ternary mixture of CO2-CH4-N-2 on activated carbon was taken as an example to investigate the performance of this PSA process numerically. It was found that both CO2 and CH4 could apparently be enriched in the top and side stream products, while both CO2 and CH4 were greatly removed from the bottom gas product (N-2) Some comments concerning process control, feasible applications and future work on the proposed Petlyuk PSA process are also described. It can be concluded that this process, with the advantages of low capital investment, low energy consumption and wide applicability, is a promising candidate for the simultaneous separation of ternary gas mixtures.