Biogas upgrading via CO2 absorption using monosodium glutamate-promoted potassium carbonate in packed absorption column: Design and performance assessment

Abstract

Biogas, an alternative energy source derived from organic materials, particularly POME, is produced through anaerobic digestion. The utilization of an UASB-HCPB fermenter has successfully yielded biogas with elevated methane content. However, the produced biogas still contained a moderate amount of CO₂, necessitating further purification to make the biogas suitable for engine fuel applications. The presence of CO₂ must be mitigated through an absorption method. The amount of CO₂ removed from biogas required an absorption system designed to utilize environmentally friendly solvents that can operate effectively at low pressures. The absorption design is important in designing absorber columns, particularly packed column types. It requires careful consideration of flow rates and absorbent concentrations to ensure optimal performance and suitability for industrial applications. This study aims to elaborate the design, fabrication, and performance of a packed absorption column for CO₂ removal utilizing K₂CO₃ as a solvent with MSG as a promoter. K₂CO₃ promoted with MSG represents an eco-friendly solvent with potential for biogas purification applications. The novelty of this study highlights a gap in integrating biogas production and purification design, wherein biogas generated from anaerobic digestion of POME undergoes purification via an absorption system. Experimental parameters included absorbent flow rates of 1, 1.5, and 2 L/min; a biogas flow rate of 20 L/min; promoter concentrations of 1, 3, and 5 %; temperatures of 35, 45, and 55 °C; and a contact time of 5 min. Results indicated that optimal CO₂ removal (47.38±1.58 %) was achieved with an absorbent flow rate of 2 L/min and MSG concentration of 5 %. Based on the calibration results, the distilled water, air, and CO₂ flowmeters have regression values (R²) of 0.9947, 1.0000, and 0.9253, respectively. The highest CO₂ removal was 94.44 % on CO₂ flow rate of 5 L/min, air flow rate of 20 L/min and absorbent flowrate of 1.8 L/min. Maximum CO₂ loading (0.0081 mol CO₂/mol K₂CO₃) was obtained at an absorbent flow rate of 1 L/min and MSG concentration of 5 %. Temperature effects revealed optimal CO₂ removal (63.32±0.42 %) at 55 °C, while peak CO₂ loading (0.00987 mol CO₂/mol K₂CO₃) occurred at 45 °C. At 55 °C, the final biogas composition achieved was 94.18 % CH₄, 5.81 % CO₂, and 0.01 % H₂S. These results indicate an increase in the effectiveness of CO₂ removal and high-purity biogas products. However, future research of synergistic study is needed on the regeneration capability of monosodium glutamate-activated K₂CO₃ for long-term CO₂ absorption. Futhermore, development of the absorption column design is also needed by considering the operating pressure. It is expected that this initial study on integrated biogas production and purification can be further developed and applied to the palm oil industry to support the implementation of sustainable zero waste technology.