Investigation of the performance of high gravity rotating packed bed distillation for nitrogen removal

Abstract

The chemical industry faces increasing pressure to improve efficiency, reduce environmental impact, and enhance safety. Process Intensification (PI) offers a transformative approach to address these challenges by enabling the development of game-changing technologies with smaller equipment footprints and more economically attractive solutions. This work explores the potential of a novel Cryogenic Rotating Packed Bed (CryoRPB) system for enhanced nitrogen (N₂) removal from natural gas at industrially relevant pressures (12–15 bar). A systematic investigation is conducted to evaluate the impact of key operating parameters, including rotational speed, feed gas composition, reflux ratio, and mass flux, on nitrogen removal efficiency, Number of Transfer Units (NTU), and specific power consumption. Increased rotational speed enhanced product purity, while elevating pressure from 12 to 15 bar yielded only a marginal improvement. Nonetheless, lower pressures induced vapor–liquid equilibrium fluctuations, hindering separation. Higher rotational speeds (up to 600 rpm) and mass fluxes improved nitrogen removal, but excessive speeds (>700 rpm) reduced efficiency due to limited mass transfer contact time. Increased N₂ inlet concentration hindered separation and slightly increased specific power. NTU decreased with increasing reflux ratio, plateauing beyond 2.5. CryoRPB exhibited comparable NTU to carbon dioxide (CO₂) absorption in RPBs but higher value than simpler systems like alcohol/water separation while remained significantly lower NTU than conventional columns. This study highlights the potential of CryoRPB for challenging natural gas processing applications and underscores the need for future work on technology upscaling and de-risking for commercial deployment.