Abstract
In this study, the reduction characteristics of single magnetite particles with melting products at high temperature were investigated by using visualization and surface analytical techniques. The morphology evolution, product type, reduction degree, and reduction rate of single magnetite particles during the reduction process were analyzed and compared at different reduction temperatures. The results showed that the morphology of the product formed at the reduction temperature of 1300 °C was a mainly nodular structure. When the reduction temperature was above 1400 °C, the products were melted to liquid and flowed out of the particle to form a layered structure. The morphology of the melted products finally transformed to be root-like in structure on the plate around the unmelted core. Raman spectroscopy was used to determine the product types during the reduction process. Experiments studying the effects of gas flowrate and particle size on the reduction degree were carried out, and the results showed that both increasing the temperature and gas flowrate can increase the reduction degree. The internal/external diffusion influence can be ignored with a particle size smaller than 100 μm and a gas flowrate more than 200 mL/min. However, owing to the resistance of the melted products to gas diffusion, the reduction rates at 1400 and 1500 °C were reduced significantly when the reduction degree increased from 0.5 to 1.0. Conversely, the formation of the liquid enlarged the contact area of the reducing gas and solid–liquid and further increased the reduction degree. The kinetics parameters, including average activation energy and pre-exponential factor, were calculated from the experimental data. The reduction kinetics equation of the single magnetite particle, considering the effect of melted products is also given in this study.
Highlights
Introduction iationsIronmaking and steelmaking technologies are essential for the development of the infrastructure, industry, and economy of a country [1,2,3]
A schematic diagram of the flash ironmaking process is given in Figure 1, for which the detailed information can be found in Ref. [8]
The results showed that the total reduction time of a single magnetite particle was about 90 s at 1500 ◦ C while this time at 1300 and 1400 ◦ C was 210 and 150 s, respectively
Summary
Introduction iationsIronmaking and steelmaking technologies are essential for the development of the infrastructure, industry, and economy of a country [1,2,3]. The traditional ironmaking technology, such as the blast furnace, consumes a great deal of energy and produces abundant carbon dioxide To solve these issues, alternative and innovative ironmaking technologies have been developed, such as COREX, Midrex, FINEX, HIsarna, and flash ironmaking [4,5]. The novel flash ironmaking technology, which was conceived by Sohn et al from the University of Utah, has received much attention in recent years [6,7,8]. This technology can omit the complicated procedures, remove the energy consumption of the coking and sintering processes, and improve energy efficiency.
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