A cleaner and more sustainable decarbonation process via ionic-liquid absorption for natural gas with high carbon dioxide content

Ionic-liquids are considered alternatives to conventional aqueous-amines absorption solvents due to their carbon dioxide affinity, low vapor-pressure, high thermal stability and low heat-ratio. In this context, this work firstly approaches a new natural gas decarbonation process based on ionic-liquid [Bmim][NTf2] absorption and selective solute stripping at high-pressure and high-temperature (2-staged-stripping initiating at 50 bar and 250 degrees C) taking advantage of the high thermal resistance of halogenated ionic-liquids. Its strong points have to do with its high-pressure stripping (50 bar) which impressively lowers carbon dioxide compression power for enhanced oil recovery destinations. Consequently, such new process burns less fuel for power production and is a cleaner production alternative to traditional aqueous-amine-based decarbonation processes which strip carbon dioxide at only 1-2 bar. Secondly, the positive aspects of new ionic-liquid decarbonation process were confirmed in two new multi-criterial sustainability-related implemented procedures: (i) new ionic-liquid multi-criterial screening for natural gas decarbonation; and (ii) new multi-criterial sustainability assessment of natural gas decarbonation processes. The new multi-criterial screening confirmed the same [Bmim][NTf2] as the most suited ionic-liquid from environment/engineering relevant properties (e.g., carbon dioxide loading, absorption-related properties, toxicology and cost), while the multi-criterial sustainability assessment proved that the new [Bmim][NTf2] decarbonation process is five times cleaner and more sustainable than the amine-based counterpart, both respectively attaining sustainability degrees of 5.17 and 1.0. In this sustainability assessment, the two decarbonation processes were designed for cleaning natural gas with 45%mol carbon dioxide at 60 bar. Processes were scored in terms of compliance to qualitative heuristic criteria and quantitative sustainability metrics for environmental-economic-social aspects. Metrics were aggregated into one indicator, the sustainability degree, evoking a sustainability-based process ranking. (C) 2019 Elsevier Ltd. All rights reserved.