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Dissolution kinetics of hydrogen reduced DRI in iron based hot metal
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School of Chemical Engineering |
Master's thesis
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en
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110
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Abstract
Steel is an indispensable material in modern life. The majority of crude steel is produced by the blast furnace - basic oxygen furnace route, which emits approximately 2.32 tons of CO2 for each ton of crude steel produced. Steel production accounts for 7 - 9 % of global CO2 emissions. Consequently, to align with EU climate action 2050 - net zero greenhouse gas emission by 2050, processes and technologies focusing on the decarbonization of the steel industry are under the spotlight. The purpose of this thesis is to gain an understanding of the dissolution kinetics of hydrogen reduced DRI (H2-DRI) in hot metal. DRI stands for Direct Reduced Iron. The Production of H2-DRI cuts a major share of CO2 emissions since the byproduct of this process is water instead of CO2. However, the absence of carbon in H2-DRI poses additional challenges to the subsequent steelmaking processes in terms of productivity and profitability.
The literature review of this thesis introduces iron and steelmaking processes, associated reactions, process variables, emission intensity and existing knowledge of the melting behaviour of H2-DRI. In the experimental part, H2-DRI with 69.4%, 73.8% and 83.7% metallization were experimented to melt in liquid hot metals of 1, 2 and 3 wt% C at 1500°C. The off gas was analysed with a gas analyser that detected the evolution of CO during the reduction process. The rate of the reaction of C and FeO was calculated from the gas analysis data. The degree of reduction was calculated from the amount of CO gas evolved during the melting experiments and the amount of FeO that was present in the DRI before the experiments. It was found that the rate of reaction and the degree of reduction tend to increase with a decrease in metallization and an increase in carbon content of hot metal. The phase analysis of the tested samples revealed the presence of spinel, fayalite, glassy slag and aluminosilicate slags in iron. The knowledge obtained from this work can be used to optimise the steel production with H2-DRI for the EAF or smelting process.
In future research, a bigger sample size should be used to minimise the uncertainties related to homogeneity in chemical composition. Quenching the samples after melting and adding flux to the system should be tried. Also, the effect of temperature on the dissolution process can be studied. Furthermore, melting experiments with less than 1 wt% C hot metals can be carried out to emulate the EAF process.
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Lindberg, DanielThesis advisor
Sukhomlinov, DmitryJeon, Junmo