Simulation study of biomethane liquefaction followed by biogas upgrading using an imidazolium-based cationic ionic liquid

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>To satisfy the ever-increasing global energy demand, biomethane is considered a promising sustainable and renewable energy source. Biomethane can be transported either in the gaseous phase (through pipelines, over a small distance) or in the liquid phase (through shipping, over a long distance). For transportation over long distances, liquefaction is one of the most economic and feasible approaches so far. However, biomethane is obtained as a result of biogas upgrading, i.e., CO<SUB>2</SUB> removal from biogas. Conventionally, CO<SUB>2</SUB> is removed through amine-based absorption, which consumes large amounts of energy to regenerate the amine-based solvent. Liquefaction of methane (obtained either from fossil-based or renewable resources) has also been recognized as an energy-intensive process. Hence, the major issue associated with biogas upgrading and subsequent biomethane liquefaction is their high energy consumption, which ultimately affords a cost-intensive process. In this context, we propose a simulation based an economical and energy efficient process for biomethane liquefaction following biogas upgrading using an ionic liquid (1-butyl–3–methylimidazolium hexafluoro phosphate [Bmim][PF<SUB>6</SUB>]). As such, biogas can be upgraded at an energy expense of 1.1048 kWh/kmol, while 11.26 kWh/kmol of energy is used for biomethane liquefaction. The specific total annualized cost for the proposed integrated process was calculated as $519.3/kg-biogas.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An integrated process is developed to upgrade and liquefy the biogas. </LI> <LI> Biogas upgrading leads to biomethane with 99 wt% purity adopting [Bmim][PF<SUB>6</SUB>]. </LI> <LI> The upgraded biomethane is liquefied through nitrogen-methane expander process. </LI> <LI> Total annualized cost of biogas upgrading to liquefaction is $311.6 × 10<SUP>5</SUP>. </LI> <LI> Specific total annualized cost for integrated process is $519.3/kg-biogas. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>