Kinetics of carburization and metal dusting in iron under CO-H2 atmospheres for Sustainable direct reduction processes

초록

Carburization of direct reduced iron (DRI) is a critical step in modern steelmaking to enhance energy efficiency and process stability by lowering the melting point of iron. This study investigates the carburization kinetics of solid iron under various CO-H2 gas mixtures at 1073 K, simulating conditions relevant to low-carbon hydrogenbased ironmaking. Using thermogravimetric analysis (TGA) with minimized mass transfer effects, we found that hydrogen significantly accelerates the carburization rate by enhancing surface oxygen removal. Kinetic modeling based on the ideal Langmuir isotherm reveals that the rate of oxygen removal by H2 is approximately 4.3 times faster than by CO. However, high hydrogen concentrations also promote metal dusting, a detrimental phenomenon where carbon supersaturation leads to the disintegration of the iron surface into fine particles and carbon dust. Through microstructural analysis using OM and AES, the reaction was characterized in two distinct stages: (1) the carburization stage governed by surface reactions and (2) the dusting stage leading to surface degradation. These results provide essential guidelines for optimizing the H2/CO ratio and reaction time in the direct reduction process, ensuring reactor integrity and maximizing the efficiency of carbon-neutral steel production.

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