Under normal temperature iron-bearing dust was mixed with coal and compacted to form pellets as per different ratio. After pellets were self-reduced in carbon tube furnace, the influence of C/O ratio, slag basicity, temperature on the separating behavior of metal phase from slag phase, metallization rate, dephosphorization and desulphurization rate was studied. The results indicate that self-reduced products can spontaneously separate when slag basicity is more than 1.8. The optimum inner ratio of C/O and slag basicity for complete separation of iron and slag is 1.1 and 2.0 respectively. Under those conditions and temperature at above 1350°C, such results that product can reach: iron yield is more than 95%, iron nuggets within size of 5~20mm is more than 80% and desulphurization rate is more than 85%.
In order to recover secondary iron-bearing dust, with converter sludge, mill scale, gravitational ash, casthouse ash as raw materials, high basicity carbon composite pellets are prepared to make iron nuggets through self-reduction at high temperature. The study demonstrates that: The effectively separation of iron and slag, naturally pulverization of the slag phase, and good surface quality of bigger, glosser and brighter iron nuggets can be obtained with reduction temperature 1400 °C,C/O molar ratio 1.1,as well as basicity above 1.8 in this process; The iron phase is not generated well and proportion of small size iron nuggets increases when C/O molar ratio is increased; With C/O molar ratio increases or temperature rises, CO generated increases in direct reduction, which strengthen the reducibility atmosphere in the pellets, beneficial to the processing of desulfuration and dephosphorization; Rising temperature accelerates the generation of molten iron, so that, the fixed carbon contacts with the molten iron longer, which increasing the carbon in iron nuggets. More carbon is provided for the carburizing reaction for the sake of increasing C/O molar ratio, as a result of making more carbon in iron nuggets.
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