Hydrogen reduction of iron oxides : Experimental study
Lillkaas, Nathalie (2022)
Lillkaas, Nathalie
2022
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2022070451039
https://urn.fi/URN:NBN:fi-fe2022070451039
Tiivistelmä
Steel is one of the modern world’s core pillars in engineering and construction materials, but the steel production causes large carbon dioxide emissions. The steel industry needs to reduce its carbon emissions to prevent global warming to exceed 2 °C. Today’s ironmaking mainly uses carbon monoxide to reduce the oxygen from iron ore. The product from the use of carbon monoxide in iron oxide reduction is carbon dioxide. Replacing carbon monoxide with hydrogen would fundamentally reduce the greenhouse gas emissions. Hydrogen has been an interesting gas in iron oxide reduction for some time and the reaction kinetics have some advantages over reduction by carbon monoxide. The gaseous product from iron ore reduction with hydrogen is water vapor.
The analysis of the reduction is often based on equilibrium considerations, since the termination of the reduction is expected to be achieved at a specified temperature in equilibrium state. From a thermodynamic point a higher temperature is better for the hydrogen reduction reactions. A high temperature is also beneficial in terms of the kinetics.
In this thesis, experimental studies of iron oxide reduction with hydrogen have been undertaken to obtain data for mathematical modeling of the reduction reactions. The experiments have been done at Åbo Akademi University. To obtain information for an evaluation for the modeling work, isothermal experiments with powder samples of both hematite and magnetite were undertaken at different temperatures and at different gas flow rates. Experiments without any sample were also done to achieve a better calibration of the data. The sample size was 100 to 200 mg and the temperature in the experiments was between 400 °C and 900 °C, while the flow of hydrogen was between 4 ml/min and 20 ml/min. Argon was used as an inert gas in the experiments.
It appears from the results of the experiments that the temperature is the main parameter that affects the reduction time, and that the concentration of hydrogen in the mass flow has a significant impact on the results. Previous studies have shown similar results as the ones found in this thesis. However, some odd results were obtained for gas of higher hydrogen concentration, and these were expected to be due to disturbances caused by water in the gas analyzed by a Mass Spectrometer. These problems should be solved in future work.
The aim of the experiments was to obtain data that could act as a starting point for a kinetic modeling of hydrogen reduction of hematite and magnetite. Despite the problems noted above, the experiments were reproducible and mostly successful, and the results have shed light on the reduction of iron oxide in hydrogen-containing gas mixtures.
The analysis of the reduction is often based on equilibrium considerations, since the termination of the reduction is expected to be achieved at a specified temperature in equilibrium state. From a thermodynamic point a higher temperature is better for the hydrogen reduction reactions. A high temperature is also beneficial in terms of the kinetics.
In this thesis, experimental studies of iron oxide reduction with hydrogen have been undertaken to obtain data for mathematical modeling of the reduction reactions. The experiments have been done at Åbo Akademi University. To obtain information for an evaluation for the modeling work, isothermal experiments with powder samples of both hematite and magnetite were undertaken at different temperatures and at different gas flow rates. Experiments without any sample were also done to achieve a better calibration of the data. The sample size was 100 to 200 mg and the temperature in the experiments was between 400 °C and 900 °C, while the flow of hydrogen was between 4 ml/min and 20 ml/min. Argon was used as an inert gas in the experiments.
It appears from the results of the experiments that the temperature is the main parameter that affects the reduction time, and that the concentration of hydrogen in the mass flow has a significant impact on the results. Previous studies have shown similar results as the ones found in this thesis. However, some odd results were obtained for gas of higher hydrogen concentration, and these were expected to be due to disturbances caused by water in the gas analyzed by a Mass Spectrometer. These problems should be solved in future work.
The aim of the experiments was to obtain data that could act as a starting point for a kinetic modeling of hydrogen reduction of hematite and magnetite. Despite the problems noted above, the experiments were reproducible and mostly successful, and the results have shed light on the reduction of iron oxide in hydrogen-containing gas mixtures.