Thermodynamic investigation of SNG production based on dual fluidized bed gasification of biogenic residues
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ORIGINAL ARTICLE
Thermodynamic investigation of SNG production based on dual fluidized bed gasification of biogenic residues Alexander Bartik 1 & Florian Benedikt 1 Hermann Hofbauer 1
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Andreas Lunzer 2 & Constantin Walcher 2 & Stefan Müller 1,2
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Received: 3 April 2020 / Revised: 8 July 2020 / Accepted: 23 July 2020 # The Author(s) 2020
Abstract Natural gas is an important commodity in the European energy market. The gasification of biogenic residues and the further reaction to a methane-rich gas represent a promising concept for the production of synthetic natural gas on a fossil-free basis. This paper investigates the thermodynamics of methanation in a fluidized bed reactor for different product gas compositions of the dual fluidized bed gasification technology. The investigated product gases range from conventional steam gasification, over CO2 gasification, to product gases from the sorption enhanced reforming process. All investigated product gases from conventional steam gasification show an understoichiometric composition and therefore require a proper handling of carbon depositions and a CO2 separation unit downstream of the methanation reactor. The product gas from CO2 gasification is considered disadvantageous for the investigated process, because it only exhibits a carbon utilization efficiency of 23%. Due to the high flexibility of the sorption enhanced reforming process, a nearly complete methanation of the carbonaceous species is possible without the need for a CO2 separation step or the addition of steam upstream of the methanation reactor. Furthermore, the carbon utilization efficiency is found to be between 36 and 38%, similar to the results for conventional steam gasification. Temperature and pressure variations allow a thermodynamically optimized operation, which can increase the performance of the methanation and lower the extent of gas upgrading for grid feed-in. Additionally, if a higher hydrogen content in the natural gas grid would be allowed, the overall process chain could be further optimized and simplified. Keywords Thermodynamics . Fluidized bed methanation . Synthetic natural gas . Dual fluidized bed gasification . Biogenic residues
1 Introduction Increasing greenhouse gas emissions and the limited availability of primary energy carriers directed the energy policy of the European Union towards sustainable and innovative energy technologies [1]. Natural gas is one of the most important primary energy carriers in Europe, but its availability is heavily dependent on the non-European market. The production of synthetic natural gas (SNG) from biogenic residues offers a promising alternative to the utilization of fossil fuels and * Alexander Bartik [email protected] 1
Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Getreidemarkt 9/166, 1060 Vienna, Austria
2
Energy & Chemical Engineering GmbH, Waidhausenstraße 27/1/22, 1140 Vienna, Austria
represents a novel concept to support the current energy strategy of the European Union [1, 2]. One possi
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