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Carbon formation in direct reduced iron and hot briquetted iron
Godoy, Michelle P.
Godoy, Michelle P.
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2020
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2022-04-17
Abstract
Carbon formation in the MIDREX© reduction shaft at voestalpine Texas LLC was investigated with computational simulations and physical examination of hot briquetted iron and direct reduced iron. Simulations were carried out utilizing HSC thermodynamic software, ANSYS Fluent computational fluid dynamic software and a material balance analysis. The simulation provided the theoretical amounts of carbon formation possible in the reduction shaft along with temperature and gas distribution profiles. The computational results led to a focused analysis of the transition zone due to the lack of interference with the reduction process, the greater possible range in process condition changes and increased quality control. The physical analysis was carried out utilizing x-ray diffraction, Mössbauer spectroscopy, total carbon content analysis, metallography and TIMA mineralogy. Plant trials were conducted to determine the carbon formation at various operating ranges. Prior to the trials, baseline testing was conducted to determine carbon variance. Additionally, material was collected during a furnace discharge and it was estimated that the bustle region introduces 44% of the total carbon formation. The transition zone trial proved carbon formation could be altered by a change of flow rate. The carbon was positively impacted by a higher transition zone flow rate, specifically a + 20.2 relative carbon percent was experienced with a 1000 SCFM increase of transition zone flow. A temperature change of the discharge material was also experienced due to the endothermic nature of the cracking of methane. Increased temperatures were experienced at the low flow rate set point, which had a positive effect on the briquetting density. The density was closely correlated with briquetting temperature rather than carbon formation.
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