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Dynamic simulation of isothermal and non-isothermal reduction and oxidation reactions of iron oxide for a hydrogen storage process

  • This work aims first to develop a dynamic lumped model for the isothermal reactions of hydrogen/steam with a single iron oxide/iron pellet inside a tubular reactor and to validate the model results against the experimental reaction kinetic data with the help of our STA device. To describe the temporal change in mass, and consequently, the temporal heat of reaction, the shrinking core model, based on the geometrical contracting sphere, is applied. It turned out that, the simulation model can reproduce the experimental, temporal concentration and temperature-dependent conversion rates with a maximum deviation of 4.6% during the oxidation reactions and 3.1% during the reduction reactions. In addition, a measured isothermal storage process comprising one reduction and one oxidation phase with a holding phase in between on a single reacting pellet could be reproduced with a maximum absolute deviation in the conversion rate of 1.5%. Moreover, a lumped, non-isothermal simulation model for a pelletized tubular redox-reactor including 2kg of iron oxide pellets has been established, in which the heat of reaction, heat transfer to the ambient and heat transfer between the solid and gas phases are considered. The temporal courses of the outlet gas concentration as well as the temperatures of the gas stream and the solid material at a constant input gas flow rate and a constant reacting gas inlet concentration but different input gas temperatures are estimated. Because of the endothermic nature of the reduction reaction, the inlet reacting gas temperature shall be kept high to prevent the severe temperature drop in the solid phase and, consequently, the significant reduction of the reaction rate. Contrary to that, the oxidation process requires lower input gas temperatures to avoid the excessive overheating of the reaction mass and, consequently, the sintering of the reacting pellets. Finally, five of the previous reactors have been connected in series to explore the influence of the changing inlet gas temperatures and concentrations on the dynamic performance of each storage mass.

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Metadaten
Author:Bernd GamischORCiD, Stefan Ettengruber, Matthias Gaderer, Belal DawoudORCiDGND
DOI:https://doi.org/10.55092/rse20230004
Parent Title (English):Renewable and Sustainable Energy
Publisher:ELSP, International Open Science Platform
Document Type:Article
Language:English
Year of first Publication:2023
Release Date:2023/10/13
Tag:Aspen Custom Modeler; hydrogen storage; iron/iron oxide; isothermal reactions; kinetics of reactions; lumped model; non-isothermal reactions; redox reactions
Volume:1
Issue:1
Article Number:0004
Note:
Corresponding author: Belal Dawoud
Institutes:Fakultät Maschinenbau
Fakultät Maschinenbau / Labor Sorptionsprozesse
OpenAccess Publikationsweg:Gold Open Access- Erstveröffentlichung in einem/als Open-Access-Medium
research focus:Energie und Mobilität
Licence (German):Creative Commons - CC BY - Namensnennung 4.0 International