Abstract
A high-temperature confocal scanning laser microscope and an online reduction–water quenching experiment system were used to systematically study the generation of iron whiskers during the reduction of hematite ore particles with CO/CO2 gas. The "blooming" phenomenon of the surface during the reduction of iron ore particles was found in this experiment. The orientation of the grain on the longitudinal section of an iron whisker was measured to be uniform by applying the electron back-scattered diffraction technique, which proved that the iron whiskers are most likely to exist in single crystal form. According to the in-situ online experimental video, the average diffusion flux of iron atoms when the layered iron completely covers the surface of the ore particle is about 0.0072 mol/(m2·s). While the iron atom diffusion flux at the root of the iron whisker during the pre-growth process is much larger than the flux when the layered iron is produced, which are defined to be 0.081 mol/(m2·s), 0.045 mol/(m2·s), 0.013 mol/(m2· s), and 0.0046 mol/(m2·s), respectively during the four stages of the growth of an iron whisker. The quantitative relationship between the chemical driving force and the whisker growth is established as Δ G θ + R T ln p CO 2 p CO + 2 n 0.056 r ρ E s T = 0 .
Highlights
With the gradual depletion of high-quality lump iron ore resources around the world, the efficient use of fine ore resources obtained after mineral processing has received wide attention in the iron-making industry [1,2,3,4]
Through systematic research on the gas-based reduction process of hematite ore fines and the mechanism of systematic metallic iron production, the followingreduction conclusions are drawn: Through research on the gas-based process of hematite ore fines and the mechanism of metallic iron production, the following conclusions are drawn: (1) The “blooming” phenomenon appearing on the surface of the iron ore particles during the reduction process is caused by the formation of layered iron
The average diffusion flux of iron atoms when the layered iron completely covers the surface of the ore particle is about 0.0072 mol/(m2·s)
Summary
With the gradual depletion of high-quality lump iron ore resources around the world, the efficient use of fine ore resources obtained after mineral processing has received wide attention in the iron-making industry [1,2,3,4]. According to previous studies [11], iron whiskers produced on the surface of the particles during the low-temperature gas-based reduction of iron ore fines cause the sticking problem of the material bed. In-depth analysis of iron whisker generation and the microscopic reduction process of iron ore particles has far-reaching significance for solving the problems of sticking and low efficiency during low-temperature gas-based reduction of iron ore fines. It can be found in electronic components [12] and it can be produced during vapor deposition [13], reduction of iron oxide [14], and cooling of wustite (Fe1-x O) [15]. Sometimes whiskers can cause problems, such as metal whiskers in electronic components can cause short circuit [12], iron whiskers produced during gas-based reduction of iron ore fines will cause the agglomeration of iron ore particles. Part of Krőger–Vink’s [25] mechanism was used to the theoretical derivation, and some insights on the mechanism of the nucleation of metallic iron and the generation of layered iron/iron whiskers are proposed
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