Experiments and simulations on separating a CO₂/CH₄ mixture using K-KFI at low and high pressures

Abstract

Separation of CO₂ from CH₄ is needed in order to use low-quality biogas or landfill gas and to reduce greenhouse gas emissions. To study the separation of a CO₂/CH₄ gas mixture, K-KFI (Si/Al = 4.59) sorbent was synthesized and pelletized. We performed breakthrough experiments at flow rates of 16.6 and 30 N mL/min under ambient temperature and pressure (298 K, 100 kPa). The breakthrough experiments results showed that K-KFI separated a 40%/60% mixture of CO₂/CH₄ better than a 50%/50% mixture. Furthermore, the separation performance of K-KFI is superior to that of commercial sorbents zeolite-5A and 13X under the same conditions. Simulations of the breakthrough of binary mixed gases CO₂/CH₄ = 40%/60%, yield results that are in good agreement with our experimental data. By performing breakthrough simulations at a total pressure of 2 MPa, we demonstrated that pure CH₄ can be separated from CO₂/CH₄ gas mixtures under high pressure and that pure CH₄ can be recovered in the initial stages of the breakthrough.