Thermodynamic Investigation of SNG Production Based on Dual Fluidized Bed Gasification of Biogenic Residues

Abstract

Natural gas is an important commodity in the European energy market. A promising concept for the production of synthetic natural gas on a carbon neutral basis is presented by the gasification of biogenic residues and the further reaction to a methane-rich gas. This paper investigates the thermodynamics of methanation for different product gas compositions of the dual fluidized bed gasification technology. A complete methanation of the carbon oxides is possible by the utilization of a product gas from the sorption enhanced reforming process. For product gases from conventional or carbon dioxide gasification, only partial methanation of carbon monoxide occurs. Additionally, proper handling of carbon depositions through adjustments of feed gas composition and operational parameters in the methanation reactor are essential. Temperature and pressure variations allow a thermodynamically optimized operation, which can reduce energy costs for compression or lower the amount of gas upgrading for grid feed-in. Vice versa, it is shown that the feed gas can be optimally adjusted to the operational parameters of the methanation via the sorption enhanced reforming process.