Analysis of Ionic Liquid Pretreated Low-Rank Coal via Equilibrium-Based Gasification Model

The utilization of vast coal deposits around the globe as an energy source is significantly limited in scope owing to environmental risks. In this context, ionic liquids (ILs) provide a novel solution as eco-friendly pretreatment agents. This work examined the effects of IL pretreatment on the gasification of low-grade coal using a simulation model in Aspen Plus®. Four ILs, ۱-butyl-۳-methylimidazolium chloride [Bmim][Cl], ۱-ethyl-۳-methylimidazolium chloride [Emim][Cl], trihexyltetradecylphosphonium chloride [P۶۶۶۱۴] [Cl], and tributylmethylammonium chloride [N۱۴۴۴] [Cl], were employed in this study. A comparative and sensitivity analysis was conducted on untreated and IL-pretreated coal samples using an equilibrium-based steam-O۲ gasification model designed in Aspen Plus®. The model was validated and utilized to vary the oxygen/fuel (O۲/F) ratio, steam/fuel (S/F) ratio, and temperature within the specified ranges (۷۰۰-۹۵۰°C, ۰.۱-۰.۶, and ۲-۴, respectively). The results showed that all the ILs increased CO and H۲, and decreased CO۲ and CH۴, in the syngas produced by coal gasification. The biggest change was affected by [P۶۶۶۱۴] [Cl], which increased CO and H۲ from ۱۲ mol% and ۴۲ mol % to ۱۶ mol% and ۵۰ mol %, respectively, and reduced CO۲ and CH۴ from ۳۵ mol% and ۳.۵ mol% to ۲۹ mol% and ۲ mol%, respectively. The lower heating value (LHV) of syngas was increased from ۷.۳۷ MJ/Nm۳ for untreated coal to ۷.۶۱, ۷.۵۶, ۸.۱, and ۷.۵۶ MJ/Nm۳ for coal treated by [Bmim][Cl], [Emim][Cl], [P۶۶۶۱۴] [Cl], and [N۱۴۴۴] [Cl], respectively. As opposed to raw coal, [Bmim][Cl] and [P۶۶۶۱۴] [Cl] generated more CGE, ENE, and EXE. The highest CGE, ENE, and EXE of ۱۹, ۱۳.۳, and ۳۸.۳% were achieved by [P۶۶۶۱۴] [Cl] treated coal. Syngas having higher H۲/CO ratio and LHV were produced at low temperatures, low O۲/F ratio, and high S/F ratio. The results of this investigation demonstrated that ILs composed of ammonium and phosphonium might be useful coal pretreatment agents in thermochemical conversion processes.

کلیدواژه ها:

Low-rank coal ، Ionic liquids ، Pretreatment ، Equilibrium model ، Aspen Plus ، Sensitivity analysis