Influence of transient conditions on the methanisation of CO2 from Biogas with regenerative hydrogen in a wall-cooled fixed bed reactor

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Tauer, Georg ; Kern, Christoph ; Jess, Andreas:
Influence of transient conditions on the methanisation of CO2 from Biogas with regenerative hydrogen in a wall-cooled fixed bed reactor.
2016
Veranstaltung: DGMK Conference "Catalysis - Novel Aspects in Petrochemistry and Refining" , 26.-28.09.2016 , Berlin, Deutschland.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung , Poster )

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Abstract

The world’s energy consumption will increase from around 12000 Mt oil equivalent in 2006 to estimated 22000 Mt oil equivalent in 2050 [1]. Considering the increasing energy consumption, the limitation of fossil energy and the high market share of fossil energies (approx. 80 % in 2006) it is necessary to develop new strategies to get independent from fossil energy. Furthermore the burning of coal, natural gas and crude oil leads to an increasing concentration of the greenhouse gas CO2 in the atmosphere from around 280 ppm in 1800 to about ppm today. Beside nuclear power renewable energy sources like wind or solar power, biomass and hydropower are good alternatives for the future. The major task is to circumvent the disadvantages of the use of renewable energies. One of the main drawbacks of wind and solar power is that the amount of generated energy fluctuates and the storage capacity is quite low.
An often discussed approach for storage of renewable energy is the electrolysis of water to hydrogen and oxygen, but the storage and transport of compressed or liquefied hydrogen is expensive. A smart way for hydrogen storage is chemical storage. For this the Sabatier-reaction can be used. Here hydrogen reacts with CO2 to CH4 and water (CO2 + 4 H2 -> CH4 + 2 H2O) with a standard enthalpy of formation of ΔH = -165 kJ/mol. The source of CO2 can be biogas which consists of 1/3 CO2. Hereby excess electricity can be stored and biogas can be refined to synthetic natural gas (SNG). The big advantage of natural gas and SNG are the large existing storage facilities and many application possibilities.
Due to its high exothermicity the control of the Sabatier reaction is absolutely necessary. A model for a Wall-Cooled Fixed Bed Reactor in steady-state operation has already been developed in our group. Because of the fluctuation of the feed when renewable sources are used it is important to additionally know how the reactor acts under transient operation.
The aim of this work is thus to investigate the influence of transient conditions on the methanisation of CO2 in a Wall-Cooled Fixed Bed Reactor for modeling a non-steady-state methanisation process. For this a single-tube reactor with the length of 1 m and a diameter of 2 cm with a downstream gas analysis is used.
[1] Andreas Jess, Energy Policy 38 (2010) 4663-4678