Abstract:
Utilization of iron ore-carbon composite enables to play a significant role in reducing CO2 emission from the ironmaking process. However, its efficiency seems to be limited under the condition of the blast furnace. In this study, the effect of pressure from 0.1 to 8.0 MPa on the gasification and reduction of the composite was evaluated, and acceleration mechanism of reduction was discussed by mathematical simulation. The composite sample prepared using hematite reagent and graphite powder was heated up to different target temperatures at a heating rate of 0.167 ºC/s under different pressures. Under atmospheric pressure, reduction of composite sample started at approximately 900 ºC and completed at 1200 ºC. Starting temperature of reduction decreased with increasing pressure. At 1050 ºC, the effect of pressure on the reduction was most significant because gasification of graphite activated. To discuss the behavior, a mathematical simulation was carried out using Langmuir-Hinshelwood type gasification and unreacted-core models assuming that the temperature distribution in the composite sample can be neglected. Using the experimental data under atmospheric pressure, all parameters were decided, and the effect of pressure on the reduction was evaluated. Below 3.0 MPa, the calculated results were coincident with the measured one. It seems that reduction acceleration by increasing pressure is caused by an increase in the amount of adsorbed CO and O on carbon. Above 5.0 MPa and 1000 ºC, however, the latter was higher than the former. The reason may be that the temperature distribution cannot be neglected under higher pressure.
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