Reduction of iron oxides with hydrogen
Sundberg, Richard (2021)
Sundberg, Richard
2021
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2021061036482
https://urn.fi/URN:NBN:fi-fe2021061036482
Tiivistelmä
Iron is produced from iron ore in one of two ways, either through a blast furnace, where coke is used as fuel and reduction agent, or by a direct reduction process. The blast furnace is currently dominating iron production, although iron reduction processes are gaining traction. The increased demands for low CO2 emitting and environmentally friendly processes make the direct reduction process favorable compared to the blast furnace.
Direct reduction has been researched for a few decades, and there already exist several industrial implementations that can be considered state of the art. However, most implementations include the use of carbon monoxide (CO), or gas mixtures containing both CO and hydrogen (H2) in the reduction process. With requirements growing for the use of non-fossil and low carbon emitting processes, the aim is to phase out the use of CO and fully replace it with hydrogen produced, in the optimal case, by electrolysis of water by renewable electricity. Hydrogen has a few advantages over carbon monoxide. The by-product from reducing iron oxide with hydrogen is harmless water vapor, while reduction with carbon monoxide produces carbon dioxide, which contributes to climate change. Even though the reaction mechanisms and kinetics of the direct reduction of iron oxides have been reported in numerous publications, there exist significant discrepancies and gaps in the results. Moreover, the mathematical models developed for the kinetics are often very simplified and utilize lumped parameters. Moreover, the precisions of experimental data vary significantly. This has led to large discrepancies in the results, e.g., the values of reported activation energies can range between 26 to 250 kJ/mol.
The water gas shift reaction, which occurs in the typical reaction conditions and is catalyzed by iron compounds has often been overlooked when it comes to researching iron oxide reduction. Yet in some investigations, it has been shown that the reaction can have a significant impact on the reduction rate. Certain publications have shown that at lower temperatures, the water gas shift speeds up the reduction by producing hydrogen, as the reduction rate of hydrogen has been shown to be faster compared to carbon monoxide according to many publications.
The aim of this work is focused on literature review and analysis. Additionally, the aim was to develop a model in order to compare simulations with selected parameter values with literature data A three-interface shrinking core model was developed to analyze and predict the reduction process of a single ore particle. A few comparisons were made and found that the model looks promising, although some parameter values are currently very likely to be incorrect. Additional testing of the model with experimentally verified parameters should be performed to further evaluate it.
Direct reduction has been researched for a few decades, and there already exist several industrial implementations that can be considered state of the art. However, most implementations include the use of carbon monoxide (CO), or gas mixtures containing both CO and hydrogen (H2) in the reduction process. With requirements growing for the use of non-fossil and low carbon emitting processes, the aim is to phase out the use of CO and fully replace it with hydrogen produced, in the optimal case, by electrolysis of water by renewable electricity. Hydrogen has a few advantages over carbon monoxide. The by-product from reducing iron oxide with hydrogen is harmless water vapor, while reduction with carbon monoxide produces carbon dioxide, which contributes to climate change. Even though the reaction mechanisms and kinetics of the direct reduction of iron oxides have been reported in numerous publications, there exist significant discrepancies and gaps in the results. Moreover, the mathematical models developed for the kinetics are often very simplified and utilize lumped parameters. Moreover, the precisions of experimental data vary significantly. This has led to large discrepancies in the results, e.g., the values of reported activation energies can range between 26 to 250 kJ/mol.
The water gas shift reaction, which occurs in the typical reaction conditions and is catalyzed by iron compounds has often been overlooked when it comes to researching iron oxide reduction. Yet in some investigations, it has been shown that the reaction can have a significant impact on the reduction rate. Certain publications have shown that at lower temperatures, the water gas shift speeds up the reduction by producing hydrogen, as the reduction rate of hydrogen has been shown to be faster compared to carbon monoxide according to many publications.
The aim of this work is focused on literature review and analysis. Additionally, the aim was to develop a model in order to compare simulations with selected parameter values with literature data A three-interface shrinking core model was developed to analyze and predict the reduction process of a single ore particle. A few comparisons were made and found that the model looks promising, although some parameter values are currently very likely to be incorrect. Additional testing of the model with experimentally verified parameters should be performed to further evaluate it.