Screws in COREX shaft furnace are used to discharge burdens to the latter processor -the melter gasifier. They play a very important role in the uniform drawdown pattern, which directly affects the uniform gas distribution and further the smooth operation in the COREX shaft furnace. Therefore, a three dimensional model is established based on the discrete element method (DEM) in the present work. The model is used to investigate the effect of the bottom diameter of COREX shaft furnace, the cylinder height and the screw flight diameter on particle descending velocity along the radius during discharging process. Results show that the descending velocity decreases along the radial direction. It is better to decrease the bottom diameter of COREX shaft furnace, or the screw flight diameter, or to increase the cylinder height in order to achieve a uniform descending velocity along the radius. An optimization model is also proposed for uniform drawdown pattern in the end.

The role of COREX shaft furnace plays is similar with that of lump zone in blast furnace, but there are still some differences existed between them, especially the burden distribution. However, the research on burden distribution in COREX shaft furnace is quite few. Therefore, a three dimensional model is established in present work based on Discrete Element Method (DEM), after validated by industrial experiments, the model is used to investigate the burden profiles and distribution along radius in the upper part of COREX shaft furnace, the studied parameters include the distributor angle, rotating speed and length, and the stock line. The results show that the distributor angle affects the burden profile most, stock line is next, while rotating speed and length of distributor are least. The small particles segregate more intensively than large and medium particles. Additionally, it is better to reduce the distributor length and stock line in order to obtain a stable burden distribution along radius.

The primary-slags formation behaviors of sinter, lump ores and integrated burdens were studied to explore the high temperature interaction between sinter and lump ores in blast furnace. The results showed that the softening and melting properties of lump ores, viscosity and fluidity index of primaryslags of lump ores would be improved by the high temperature interaction. Particularly, the high temperature interaction was influenced by the chemical composition and porosity of iron ore samples. The high temperature interaction between sinter and lump ore L-2 (a typical limonite lump ore from Australia) was much stronger. Though the high temperature properties of lump ore L-2 was much worse than lump ore L-1 (a typical hematite lump ore from South Africa), the high temperature properties of integrated burden B (consist of sinter and lump ore L-2) was not worse than that of integrated burden A (consist of sinter and lump ore L-1) due to the strong high temperature interaction. In addition, the suitable MgO/Al2O3 weight ratio was calculated based on the assumption that the only phases of slags were akermanite and gehlenite, which showed a decreasing tend with the increase of CaO/SiO2 weight ratio.

Numerical simulation is considered to be an important method to study the inner characteristics of metallurgical processes, thus providing effective strategies for practical smooth operations. A three-dimensional full scale mathematical model considering mass, momentum, energy transfers and chemical reactions under steady state is developed in the present work to describe the characteristics inside the pre-reduction shaft furnace of COREX smelting reduction ironmaking process. The uneven gas and solid flow distributions in both radial and axial directions not only restrain the gas utilization but also cause the difference in the solid metallization between the center and near wall to reach as high as 0.4. Predicted by the established model, the CO-CO2-H2-H2O reducing gas with the temperature 1 050-1 100 K, the volume fraction of CO+CO2 around 70%, the ratio of CO to CO2 5-7, as low as possible H2O content, and the reasonably matched burden solid charging rate to control the top gas consumption per ton burden solid (TGC) in the range of 800-1 000 Nm 3 /t, are the optimal operation conditions to further improve furnace efficiency.

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