Influence of center gas supply device on gas–solid flow in COREX shaft furnace through DEM–CFD model

In order to develop the central gas flow in COREX shaft furnace, a new installment of center gas supply device (CGD) is designed. In this work, a coupled DEM–CFD model was employed to study the influence of CGD on gas–solid flow in COREX shaft furnace. The particle descending velocity, particle segregation behaviour, void distribution and gas distribution were investigated. The results show that the CGD affects the particles descending velocity remarkably as the burden falling down to the slot. Particle segregation can be observed under the inverse ‘V’ burden profile, and the influence of CGD on the particle segregation is unobvious on the whole, which causes the result that the voidage is slightly changed. Although the effect of CGD on solid flow is not significant, the gas flow in shaft furnace has an obvious change. Compared with the condition without CGD, in the case with CGD, the gas velocity is improved significantly, especially in the middle zone of the furnace, which further promotes the center gas distribution. Meanwhile, the pressure drop in the furnace with the installation of CGD is increased partly.

Influence of MgO on Low Temperature Reduction and Mineralogical Changes of Sinter in Simulated COREX Shaft Furnace Reducing Conditions

COREX (Coal-Reduction-Extreme) smelting reduction process provides a sustainable developing way for ironmaking industry, but the sources of iron ore materials restrict its development in China. Meanwhile, the application of sinter, which is marked by low manufacture cost and overcapacity in China, to COREX furnace faced proportion limitation due to its worse low temperature reduction degradation performance. This work explored the influence of MgO content on the low-temperature (550 °C) reduction of sinter in reducing conditions simulating COREX shaft furnace. The mineralogical change of sinter containing different content of MgO before and after reduction was analyzed by X-ray diffraction (XRD), optical microscopy, and scanning electron microscopy for revealing the action mechanism of MgO on the low-temperature-reduction of sinter. The results show that increasing MgO (1.36–3.10%) improved the low temperature reduction degradation performance of sinter, and decreased its reduction degree and reduction rate at low temperature. More MgO the sinter contained, less Fe2O3 and SFCA was observed in sinter. Meantime, less Fe2O3 was reduced and the generation of innerstress was restrained during reduction process. The improved RDI (reduction degradation index) in COREX process of sinter by increasing MgO content is a comprehensive result of lowering strength and inhibiting probable reduction of sinter.

Performance simulation and optimization of COREX shaft furnace with central gas distribution

To improve the distribution of the reducing gas inside the shaft furnace, recently, a central gas distribution (CGD) device is installed at the bottom of the shaft furnace in Bayi Steel. In this work, a two-dimensional steady-state mathematical model, including momentum, heat and mass transfers and chemical reaction, is developed to study the performance of the furnace with CGD. The model is validated by industrial production data of COREX-3000, and then it is used to study the detailed phenomena in the furnace with CGD. The results show that, compared with the traditional COREX shaft furnace without CGD, the CGD device has a positive effect on improving the solid metallization rate (MR) and gas utilization rate (UR). The solid metallization rate (MR) increases from 0.601 to 0.628, the gas utilization rate (UR) increases from 0.3437 to 0.3519 and the standard deviation (STDEV) of solid MR decreases from 0.0820 to 0.0037, which means that the MR of the DRI from the furnace with CGD is more uniform than that without CGD. In addition, the effects of operation conditions and the CGD design on the solid MR, gas UR and STDEV of MR are discussed and the optimized conditions are suggested.