Mill scale as a potential additive to improve the quality of hematite ore pellet

Abstract

Hematite pellet is required to be indurated at very high temperature to achieve its good strength as there is no exothermic heat of oxidation unlike magnetite. As mill scale contains mainly FeO and Fe 3 O 4 , any minor amount of its addition in pellet can provide in situ heat and enhance diffusion bonding and sintering. In this study, the mill scale generated in steel plant is added as magnetite input in hematite pellet both in acidic and in basic condition. It has been found that in fluxed pellet, mill scale can improve the properties of pellet. In acidic pellet, the induration temperature has been reduced to a great extent (1250-1275°C) and all properties have been found to be improved due to the addition of 15% mill scale. Mill scale shows enough potential to eliminate the flux addition in producing blast furnace quality pellet from hematite ore. Thus, the flux free acidic pellet has been developed even at very low temperature (1275°C) of induration.

Cold sintering to form bulk maghemite for characterization beyond magnetic properties

“…While this poor densification can be attributed to the low temperature and thus low diffusion rate, in the past, cold sintering of other oxides has achieved higher relative densities with the temperatures lower than 130‐250°C: >90% (~100°C, 77‐387 MPa) for ZnO, and 77.5‐84.5% (30°C, 200‐500 MPa) for HBO 2 ‐II . Yet, our work uniquely provides decent densification (55.8‐64.2%) with lower temperature (~130‐250°C) when compared with previous sintering work of iron oxides: 55% (400‐500°C, 200 MPa, maghemite nanoparticles), and ~76% (1250°C, hematite pellets) . To improve densification, in the future, multiple steps or reactive transient liquid phases can be introduced to the sintering process, followed by postsintering treatments …”

“…41 Yet, our work uniquely provides decent densification (55.8-64.2%) with lower temperature (~130-250°C) when compared with previous sintering work of iron oxides: 55% (400-500°C, 200 MPa, maghemite nanoparticles), 12 and ~76% (1250°C, hematite pellets). 13 To improve densification, in the future, multiple steps 42,43 or reactive transient liquid phases 30,44,45 can be introduced to the sintering process, followed by postsintering treatments. 46…”

“…Bulk‐scale maghemite samples would be convenient for nonmagnetic property measurement, but the previous work has been mostly focused on nanoparticles. Fabrication of densified maghemite has been attempted with powder sintering, precipitation, or sol‐gel method, but resulted in contaminants, phase transformation (at >500°C), and porosity. Naturally available iron oxide minerals are not purely maghemite and contain other phase and elements …”

Development of hematite ore pellet utilizing mill scale and iron ore slime combination as additive

“…Flux free acidic hematite ore pellets have very high induration temperature because of absence of any oxidation reaction and limited amount of diffusion bonding at lower temperature [16]. Figure 4 [18] shows minimum RDI at 0.3 basicity and beyond that, both RDI and CCS increase and reducibility decreases with the increase in basicity. However, a very good CCS is observed at 0.3 basicity as well.…”

“…The addition of mill scale can reduce induration temperature and increase CCS of acidic hematite ore pellets. In a separate study [18], the effect of mill scale in hematite ore on pellet properties was studied. It was found that the use of 15 % mill scale in acidic pellet can reduce the induration temperature up to 1250 °C and improve pellet properties viz CCS, RI, RDI, and swelling index.…”