Predicting optimal temperature profiles in single-stage fixed-bed reactors for CO2-methanation
Date Issued
2015-05-14
Author(s)
Abstract
The catalytic conversion of carbon dioxide into methane, known as Sabatier process, is a promising option for chemical storage of excess renewable energy and greenhouse gas emission control. Typically externally cooled fixed-bed reactors (FBR) using supported nickel or ruthenium catalyst are applied. The Sabatier process, however, is strongly exothermic and leads to substantial hot spots within the reactor at stoichiometric feed ratios. Although high temperatures increase the reaction rate in general, they thermodynamically limit the achievable methane-yield in the Sabatier process. Here, we present an easy-to-use method based on a Semenov number optimization (SNO) to compute optimal axial temperature profiles in single-stage fixed-bed reactors that account for kinetic and thermodynamic limitations simultaneously, and thus result in maximized yield for a fixed reactor length. In a case study on CO2-methanation, these temperature profiles result in a twofold improvement of the methane-yield compared to isothermal and adiabatic operation, and thus demonstrate the high potential of thermal optimization that lies in the Sabatier process. The SNO-method provides a valuable tool to compute optimal temperature profiles, and allows intuitive insight into the key parameters for thermal process intensification. Further, it can readily be transferred to other processes that suffer from the dilemma between kinetic and thermodynamic limitations. Our findings illustrate the attractiveness of the SNO-method to compute optimal temperature profiles in fixed-bed reactors, and the need for catalyst supports with enhanced and tailorable heat transport properties.
Subjects
Methanation
;
Thermal optimization
;
Process intensification
;
Chemical energy storage
;
Semenov number
;
Mimenima
Publisher
Elsevier
Institution
Type
journal article
Journal/Edited collection
Band
132
Start page
59
End page
71
Secondary publication
Yes
Document version
Postprint
Language
English
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L. Kiewidt, J. Thöming, Predicting optimal temperature profiles in single-stage fixed-bed_2015_accepted version_Deckblatt_pdfa1.pdf
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Format
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