Effect of slag composition on iron nuggets formation from carbon composite pellets

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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Evaluation of Carbonisation Gas from Coal and Woody Biomass and Reduction Rate of Carbon Composite Pellets

Advances in Materials Science and Engineering ◽

10.1155/2018/3807609 ◽

2018 ◽

Vol 2018 ◽

pp. 1-14 ◽

Cited By ~ 1

Author(s):

Tateo Usui ◽

Hirokazu Konishi ◽

Kazuhira Ichikawa ◽

Hideki Ono ◽

Hirotoshi Kawabata ◽

...

Keyword(s):

Particle Size ◽

Reduction Rate ◽

Woody Biomass ◽

Carbon Composite ◽

Volatile Matter ◽

Gas Release ◽

Starting Point ◽

Composite Pellets ◽

Heat Value ◽

Gas Volume

Carbon composite iron oxide pellets using semichar or semicharcoal were proposed from the measured results of the carbonisation gas release behaviour. The carbonisation was done under a rising temperature condition until arriving at a maximum carbonisation temperature Tc,max to release some volatile matter (VM). The starting point of reduction of carbon composite pellets using semicharcoal produced at Tc,max = 823 K under the rising temperature condition was observed at the reduction temperature TR = 833 K, only a little higher than Tc,max, which was the aimed phenomenon for semicharcoal composite pellets. As Tc,max increases, the emitted carbonisation gas volume increases, the residual VM decreases, and, as a whole, the total heat value of the carbonisation gas tends to increase monotonically. The effect of the particle size of the semicharcoal on the reduction rate was studied. When TR is higher than Tc,max, the reduction rate increases, as the particle size decreases. When TR is equal to Tc,max, there is no effect. With decreasing Tc,max, the activation energy Ea of semicharcoal decreases. The maximum carbonisation temperature Tc,max may be optimised for reactivity (1/Ea) of semicharcoal and the total carbonisation gas volume or the heat value.

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Effect of Carbon Addition on Direct Reduction Behavior of Low Quality Magnetite Ore by Reducing Gas Atmosphere

Metals ◽

10.3390/met11091404 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1404

Author(s):

Seongrim Song ◽

Youngjo Kang

Keyword(s):

Direct Reduction ◽

Reduction Process ◽

Hydrocarbon Fuel ◽

Carbon Composite ◽

Direct Reduced Iron ◽

Carbon Efficiency ◽

Reducing Gas ◽

Initial Reduction ◽

Coal Particles ◽

Composite Pellets

Recently, direct reduced iron (DRI) has been highlighted as a promising iron source for electric arc furnace (EAF)-based steelmaking. The two typical production methods for DRI are gas-based reduction and reduction using carbon composite pellets. While the gas-based reduction is strongly dependent on the reliable supply of hydrocarbon fuel, reduction using ore-coal composite pellets has relatively low productivity due to solid–solid reactions. To overcome the limitations of the above two processes, and to achieve a more efficient direct reduction process of iron ore, the possibility of combining these two methods was investigated. The experiments focused on performing an initial direct reduction using ore-coal composite pellets followed by a second stage gas reduction. It was assumed that the initial reduction of the carbon composite pellets would enhance the efficiency of the subsequent reduction by gas and the total reduction efficiency. The porosity, as well as the carbon efficiency for direct reduction, were measured to determine the optimal conditions for the initial reduction, such as the size ratio of ore and coal particles. Thereafter, further reduction by the reducing gas was carried out to verify the effect of the preliminary reduction. The reduction kinetics of the reducing gas was also discussed.

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