Conference Year
2016
Keywords
biogas, upgrading, exergy analysis, pinch analysis, refrigeration cascade
Abstract
Low temperature refrigeration system for biogas upgrading has been developed by the Cryo Pur company based on cooling biogas in three steps : removing most of the water content at -40°C, removing siloxanes and SVOCs (Sulfuric Volatile Organic Compounds) at -75°C and  frosting CO2  at temperatures varying from -90°C to -120°C. This process transforms typical biogas containing 35% CO2, 5% water vapor and pollutants in a bio-methane containing 2.5% of CO2. This paper studies how a single low temperature refrigeration system is able to cool biogas with an indirect system using low temperature heat transfer fluids. Exergy and energy analysis are used for comparison of several architectures. The exergy study defines the exergy losses and served as guidance for the energy/ pinch analysis which is used for the design of the series of heat exchangers and the appropriate heat recovery. An optimal system could save up to 40 % of the electric consumption of the refrigeration system.Â