바이오가스 CO2 포집을 위한 습식 및 저온 증류 공정 최적화 설계

Abstract

Biogas, one of the renewable energy sources, is considered as a clean energy source to replace fossil fuels. Biogas produced through anaerobic digestion of organic waste generally contain a large amount of CO2, of which the cost-effective removal is essential for biogas upgrading processing to produce Bio-LNG. Aqueous amine-based CO2 capture and cryogenic distillation process are considered to remove carbon dioxide from biogas. In this study, a commercial simulator, Aspen HYSYS®, is used for process modeling and simulation of CO2 capture processes. For the amine-based capture process, MEA and MDEA solvents are used to minimize the solvent regeneration energy of the process, while two design options of structural modification as LVC (Lean Vapor Compression) and CSS (Cold Solvent Split), are considered for improving energy efficiency of CO2 capture process. The cryogenic distillation process consists of dual columns to obtain high purity bio-methane, which is designed to avoid freezing of CO2. External refrigeration cycles based on an cascade refrigeration cycle and a propane-precooled mixed refrigerant (C3MR) cycle are designed to be applicable for biogas upgrading. In the C3MR cycle, the composition of the mixed refrigerant and operating conditions of the cycle are simultaneously optimized using an in-built optimizer of Aspen HYSYS®. Through case studies, a biogas upgrading process is systematically designed to be sufficient for the quality of Bio-LNG, and the sensitivity analysis of key design variables allows to improve our conceptual understanding on the design and operation of CO2 capture processes.