Methane/nitrogen separation through pressure swing adsorption process from nitrogen-rich streams

⬢Separation of N2/CH4 using PSA process.⬢Optimization of operational pressures to PSA separation.⬢Improve cryogenic distillation for N2/CH4 separation by PSA.

This work presents a novel approach for the treatment of nitrogen contaminated natural gas streams. Literature states that for small and medium scale production wells (<400 MNm3/day), such stream can be treated by PSA. For larger scale natural gas production, the only mature option available is cryogenic distillation. Computer simulations were performed to evaluate the usage of silicalite in a PSA process for the separation of a nitrogen rich N2/CH4 mixture. This unit is designed for coupling to a cryogenic distillation process. The differential algebraic equations system, composed of mass and energy balances as well as other constitutive equations, was solved in the spatial dimension using the finite volumes method. Numerical methods employed were analyzed for numerical dispersion and oscillation. In order to test the numerical approach, parameters and model, data from the literature was correlated. A Rotated Central Composite Design (RCCD) was performed in order to determine optimum operational pressures. In the chosen set of operational values, the process presented nitrogen purity greater than 96% and a recovery beyond 50%. The nitrogen rich outlet stream purity is specified for venting, while the methane rich stream is proper for recycling to the cryogenic process.