2022 Volume 62 Issue 11 Pages 2225-2235
Flash ironmaking technology (FIT) is a potential alternative ironmaking process reducing energy consumption and environmental pollution. The newly proposed counter-current flash ironmaking process has a more reasonable temperature and concentration distribution, while the high dust rate cannot be avoided. In this study, a counter-current swirling configuration was introduced to improve the dust control performance. A comprehensive computational fluid dynamics (CFD) model, including gas-particle motion, chemical reactions, particle-wall sticking, slag movement, and wall reaction, was adopted to investigate the velocity vector, temperature, species distribution under the counter-current swirling flow. The effects of initial particle velocity (IPV) and swirl angle velocity (SAV) were analyzed as the crucial parameters. The results show that an annular updraft-center downdraft structure is formed by swirling flow, and the particles are pushed to the wall under the centrifugal force, adhere to the high-temperature wall, and flow down slowly with the molten slag. In the non-swirl cases, the increase of IPV can effectively inhibit the particles escaping ratio from 62.5% to 22.4% and increase the amount ratio of particles leaving the bottom directly with a lower reduction degree. Therefore, necessary swirling flow enhances the high probability of adhesion when the SAV over a varying critical value related to IPV. Also, the long residence time in the molten slag effectively increases the reduction degree of captured particles from 94.3% to 100%. The comprehensive reduction degree of particles increased from 83.3% to 87.3% in a single-cycle reaction.
