On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage Process
This work aims at investigating the kinetic mechanisms of the reduction/oxidation (redox) reactions of iron oxide/iron pellets under different operating conditions. The reaction principle is the basis of a thermochemical hydrogen storage system. To simulate the charging phase, a single pellet consis...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2022-11-01
|
| Series: | Energies |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1996-1073/15/21/8322 |
| _version_ | 1797468392179892224 |
|---|---|
| author | Bernd Gamisch Lea Huber Matthias Gaderer Belal Dawoud |
| author_facet | Bernd Gamisch Lea Huber Matthias Gaderer Belal Dawoud |
| author_sort | Bernd Gamisch |
| collection | DOAJ |
| description | This work aims at investigating the kinetic mechanisms of the reduction/oxidation (redox) reactions of iron oxide/iron pellets under different operating conditions. The reaction principle is the basis of a thermochemical hydrogen storage system. To simulate the charging phase, a single pellet consisting of iron oxide (90% Fe<sub>2</sub>O<sub>3</sub>, 10% stabilising cement) is reduced with different hydrogen (H<sub>2</sub>) concentrations at temperatures between 600 and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>800</mn><mo> </mo><mo>°</mo><mrow><mi mathvariant="normal">C</mi></mrow></mrow></semantics></math></inline-formula>. The discharge phase is initiated by the oxidation of the previously reduced pellet by water vapour (H<sub>2</sub>O) at different concentrations in the same temperature range. In both reactions, nitrogen (N<sub>2</sub>) is used as a carrier gas. The redox reactions have been experimentally measured in a thermogravimetric analyser (TGA) at a flow rate of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>250</mn><mo> </mo><mrow><mo>m</mo><mo>L</mo><mo>/</mo><mo>m</mo><mo>i</mo><mo>n</mo></mrow></mrow></semantics></math></inline-formula>. An extensive literature review has been conducted on the existing reactions’ kinetic mechanisms along with their applicability to describe the obtained results. It turned out that the measured kinetic results can be excellently described with the so-called shrinking core model. Using the geometrical contracting sphere reaction mechanism model, the concentration- and temperature-dependent reduction and oxidation rates can be reproduced with a maximum deviation of less than 5%. In contrast to the reduction process, the temperature has a smaller effect on the oxidation reaction kinetics, which is attributed to 71% less activation energy (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>E</mi><mrow><mi mathvariant="normal">a</mi><mo>,</mo><mi>Re</mi></mrow></msub><mo>=</mo><mn>56.9</mn><mrow><mo> </mo><mi>kJ/mol</mi></mrow></mrow></semantics></math></inline-formula> versus <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>E</mi><mrow><mi mathvariant="normal">a</mi><mo>,</mo><mi>Ox</mi></mrow></msub><mo>=</mo><mn>16.0</mn><mrow><mo> </mo><mi>kJ/mol</mi></mrow></mrow></semantics></math></inline-formula>). The concentration of the reacting gas showed, however, an opposite trend: namely, to have an almost twofold impact on the oxidation reaction rate constant compared to the reduction rate constant. |
| first_indexed | 2024-03-09T19:06:48Z |
| format | Article |
| id | doaj.art-c805b1f9a0744c3a9ca4d65371ea3d17 |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-03-09T19:06:48Z |
| publishDate | 2022-11-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-c805b1f9a0744c3a9ca4d65371ea3d172023-11-24T04:35:19ZengMDPI AGEnergies1996-10732022-11-011521832210.3390/en15218322On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage ProcessBernd Gamisch0Lea Huber1Matthias Gaderer2Belal Dawoud3Laboratory of Sorption Processes, Technical University of Applied Sciences, OTH Regensburg, Galgenbergstraße 30, 93053 Regensburg, GermanyLaboratory of Sorption Processes, Technical University of Applied Sciences, OTH Regensburg, Galgenbergstraße 30, 93053 Regensburg, GermanyRegenerative Energy Systems, TUM Campus Straubing for Biotechnology and Sustainability, Technical University of Munich, Schulgasse 16, 94315 Straubing, GermanyLaboratory of Sorption Processes, Technical University of Applied Sciences, OTH Regensburg, Galgenbergstraße 30, 93053 Regensburg, GermanyThis work aims at investigating the kinetic mechanisms of the reduction/oxidation (redox) reactions of iron oxide/iron pellets under different operating conditions. The reaction principle is the basis of a thermochemical hydrogen storage system. To simulate the charging phase, a single pellet consisting of iron oxide (90% Fe<sub>2</sub>O<sub>3</sub>, 10% stabilising cement) is reduced with different hydrogen (H<sub>2</sub>) concentrations at temperatures between 600 and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>800</mn><mo> </mo><mo>°</mo><mrow><mi mathvariant="normal">C</mi></mrow></mrow></semantics></math></inline-formula>. The discharge phase is initiated by the oxidation of the previously reduced pellet by water vapour (H<sub>2</sub>O) at different concentrations in the same temperature range. In both reactions, nitrogen (N<sub>2</sub>) is used as a carrier gas. The redox reactions have been experimentally measured in a thermogravimetric analyser (TGA) at a flow rate of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>250</mn><mo> </mo><mrow><mo>m</mo><mo>L</mo><mo>/</mo><mo>m</mo><mo>i</mo><mo>n</mo></mrow></mrow></semantics></math></inline-formula>. An extensive literature review has been conducted on the existing reactions’ kinetic mechanisms along with their applicability to describe the obtained results. It turned out that the measured kinetic results can be excellently described with the so-called shrinking core model. Using the geometrical contracting sphere reaction mechanism model, the concentration- and temperature-dependent reduction and oxidation rates can be reproduced with a maximum deviation of less than 5%. In contrast to the reduction process, the temperature has a smaller effect on the oxidation reaction kinetics, which is attributed to 71% less activation energy (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>E</mi><mrow><mi mathvariant="normal">a</mi><mo>,</mo><mi>Re</mi></mrow></msub><mo>=</mo><mn>56.9</mn><mrow><mo> </mo><mi>kJ/mol</mi></mrow></mrow></semantics></math></inline-formula> versus <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>E</mi><mrow><mi mathvariant="normal">a</mi><mo>,</mo><mi>Ox</mi></mrow></msub><mo>=</mo><mn>16.0</mn><mrow><mo> </mo><mi>kJ/mol</mi></mrow></mrow></semantics></math></inline-formula>). The concentration of the reacting gas showed, however, an opposite trend: namely, to have an almost twofold impact on the oxidation reaction rate constant compared to the reduction rate constant.https://www.mdpi.com/1996-1073/15/21/8322thermochemical hydrogen storageiron/iron oxide redox reactionsreaction kineticsshrinking-core model |
| spellingShingle | Bernd Gamisch Lea Huber Matthias Gaderer Belal Dawoud On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage Process Energies thermochemical hydrogen storage iron/iron oxide redox reactions reaction kinetics shrinking-core model |
| title | On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage Process |
| title_full | On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage Process |
| title_fullStr | On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage Process |
| title_full_unstemmed | On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage Process |
| title_short | On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage Process |
| title_sort | on the kinetic mechanisms of the reduction and oxidation reactions of iron oxide iron pellets for a hydrogen storage process |
| topic | thermochemical hydrogen storage iron/iron oxide redox reactions reaction kinetics shrinking-core model |
| url | https://www.mdpi.com/1996-1073/15/21/8322 |
| work_keys_str_mv | AT berndgamisch onthekineticmechanismsofthereductionandoxidationreactionsofironoxideironpelletsforahydrogenstorageprocess AT leahuber onthekineticmechanismsofthereductionandoxidationreactionsofironoxideironpelletsforahydrogenstorageprocess AT matthiasgaderer onthekineticmechanismsofthereductionandoxidationreactionsofironoxideironpelletsforahydrogenstorageprocess AT belaldawoud onthekineticmechanismsofthereductionandoxidationreactionsofironoxideironpelletsforahydrogenstorageprocess |