The iron and steel industry is a major CO₂ emitter and an important subject for the implementation of carbon emission reduction goals and tasks. Due to the complex ore composition and low iron grade, vanadium–bearing titanomagnetite smelting in a blast furnace consumes more coke and emits more carbon than in an ordinary blast furnace. Injecting hydrogen–rich gas into blast furnace can not only partially replace coke, but also reduce the carbon emission. Based on the whole furnace and zonal energy and mass balance of blast furnace, the operation window of the blast furnace smelting vanadium–bearing titanomagnetite is established in this study on the premise that the thermal state of the blast furnace is basically unchanged (raceway adiabatic flame temperature and top gas temperature). The effects of different injection amounts of hydrogen–rich gases (shale gas, coke oven gas, and hydrogen) on raceway adiabatic flame temperature and top gas temperature, and the influence of blast temperature and preheating temperature of hydrogen–rich gases on operation window are calculated and analyzed. This study provides a certain theoretical reference for the follow–up practice of hydrogen–rich smelting of vanadium–bearing titanomagnetite in blast furnace.

In this paper, the effect of titanium carbonitride (Ti(C,N)) on the viscosity of high-titanium-type blast furnace slags was investigated. The different Ti(C,N) contents were achieved by adjusting the reduction degree of TiO₂ to reflect the real characteristics of the high-titanium slag. The results show that the viscosity of the slag increased with the increasing Ti(C,N) content and decreased with the rising temperature. A deviation between the measured and the fitted viscosity appeared as the content of the Ti(C,N) was beyond 4 wt%. Furthermore, the apparent viscous flow activation energy of the slag ranged from 106.13 kJ/mol to 235.46 kJ/mol by varying the Ti(C,N) contents from 0 wt% to 4.97 wt%, which was evidently different from the results of previous studies. The optical microscope and energy dispersive X-ray spectroscopy (EDS) analysis show that numerous bubble cavities were embedded in the slags and the Ti(C,N) particles agglomerated in the solidified samples. This phenomenon further indicates that the high-titanium slag is a polyphase dispersion system, which consists of liquid slag, solid Ti(C,N) particles and bubbles.

Basicity of titanium bearing blast furnace (BF) slag is critical for its crystallization behavior. Thermodynamics calculation indicates that rutile is the main phase after crystallization (or at room temperature). It precipitates during the cooling when the basicity of the slag is lower than 0.7. With increasing basicity, perovskite appears and becomes the main phase instead which contains titanium. Crystallization temperature of perovskite is higher than that of rutile and the other phases. Namely, perovskite crystallizes firstly from the molten slag during decreasing temperature. XRD analysis shows that CaTi₂₁O₃₈ is the main phase with a basicity of 0.6. CaMg_0.39Al_0.87Ti_0.48Si_1.26O₆, CaTiSiO₅ and CaMgSi₂O₆ are the main crystallization phases with a basicity of 0.8. The difference between experimental and thermodynamics calculation is due to the complicate crystallization behavior of the multiple slag under super cooling rate. When the slag basicity increases to 1.1, the main precipitatied phase is perovskite, which agrees well with theory calculation. In addition, the crystal structure of the synthesized titanium bearing slag is basically similar regardless of the basicity.