A novel method for modeling the phase change of iron ore particles in the cohesive zone of a blast furnace

Cohesive zone plays a vital role in the stable operation of a blast furnace(BF),yet the complex phase change process of iron ore particles in this zone is still not well understood.In this study,a novel one-dimensional(1D)unsteady phase change model was developed to elucidate the heat transfer and melting mechanisms of iron ore particles.After model validation,the effects of several key operating parameters(e.g.,particle diameter,gas velocity,initial temperature)on the phase change behavior of iron ore particles were analyzed,and the joint effect of multiple parameters was discussed.The results show that larger-sized iron ore particles possess lower specific surface areas,which in turn reduces their convective heat absorption capacity.Consequently,the distance from the solid-liquid phase interface to the particle surface increases,thereby slowing down the movement of the phase interface and pro-longing the melting duration of the particles.Increasing the gas velocity and the initial temperature does not have a significant impact on reducing the duration of the complete melting process.Under the specified conditions,it is observed that increasing the gas velocity by 3-fold and 9-fold results in a reduction of the melting duration by 2.4%and 8.3%,respectively.Elevating the initial temperature of iron ore particles results in a decrease in the core-to-surface temperature difference,a slower heating rate,and a shorter duration to achieve melting.Among the factors affecting the melting process,the particle diameter is found to be the most significant in terms of the liquid phase precipitation,mushy zone thickness,and core-to-surface temperature difference of iron ore particles.

Niobium and phosphorus behavior during melting-separation process of pre-reduced niobium ore concentrate

The pre-reduced Bayan Obo ferroniobium（FeNb）ore concentrate block was taken as raw materials for studying the physical properties of niobium-enriched slag and changes in niobium recovery rate.In addition,the dephosphorization rate of the slag under different melting-separation conditions was investigated using the melting-separation test.The research results demonstrate that（i）the niobium recovery rate and dephosphorization rate of the slag decrease with the increase in melting-separation temperature;（ii）the niobium recovery rate of the slag initially increases and then decreases with increase in basicity and time;and（iii）the dephosphorization rate of the slag increases with the increase in basicity and time.When the test was performed under the conditions of basicity of 0.6-0.7,time of 7-10min,and temperature of 1400-1450°C,the niobium recovery rate and dephosphorization rate are over 96%and 95%,respectively.By scanning electron microscopy,it is observed that niobium mainly exists in the form of calcium and titanium silicate within the slag phase,with uneven distribution.