Carbon monoxide is the major hazardous component in flue gas exhausting from the iron ore sintering. This study aims to reduce the CO emission by changing the sinter parameters by sintering pot tests; specifically, the sinter quality, CO concentration, and total emission in sintering flue gas were analyzed in detail. The sinter strength properties, including the shatter index and the tumble index, are analyzed by the sintering pot test and the sintering flue gas discussion. The results show that the CO emission can be suppressed by modifying the sinter parameters, such as carbon content, coke breeze and coal breeze ratio, water addition, and sintering negative pressure. The good sinter parameters with the lower CO emission are 2.8% carbon content and 7.5% water in the sintering mixture. A higher coke breeze to coal breeze ratio, or only coke breeze fuel in the sinter mixture, is beneficial for the lower CO emission with a negative fan pressure of −12 kPa.

Zinc ash is a by-product of the hot-dip galvanizing process and the electrolytic zinc process, which is classified as a hazardous waste consisting predominately of zinc oxide that could be recovered as the useful main resource for ZnO preparation. In this work, in order to reduce the energy consumption of the direct reduction process and improve the resource-recovery rate. A new technology for zinc oxide production, by a carbothermal reduction of zinc ash, is proposed. This process includes two steps: high-temperature roasting of zinc ash for dechlorination and a carbothermal reduction of dechlorination ash. Zn in zinc ash is mainly presented in the form of zinc oxide (ZnO), basic zinc chloride (Zn₅(OH)₈Cl₂H₂O), and metallic zinc (Zn). Basic zinc chloride can be roasted and decomposed to reduce the chlorine content in zinc ash. The results of a chloride ion removal test show that the optimal roasting temperature is 1000 °C, with a holding time of 60 min. Under the modified conditions, the chloride content in the roasted zinc ash is reduced to 0.021 wt.%, and the dechlorination rate is more than 99.5%, which can meet the requirements of zinc oxide production. The best process conditions for zinc oxide production by carbothermic reduction are as follows: reduction temperature of 1250 °C, reduction time of 60 min, and reduction agent addition of 22 wt.%. Under the best reduction process, the purity of zinc oxide product is 99.5%, and the recovery of zinc is more than 99.25%. Needle-like zinc oxide obtained by carbothermic reduction has high purity and can replace zinc oxide produced by an indirect process.

Hydrogen-based direct reduction (H-DR) represents an environmentally benign and energy-efficient alternative in ironmaking that has significant industrial potential. This study reviews the current status of H-DR shaft furnaces and accompanying hydrogen-rich reforming technologies (steam and autothermal reforming), assessing the three dominant numerical frameworks used to analyze these processes: (i) porous medium continuum models, (ii) the Eulerian two-fluid model (TFMs), and (iii) coupled computational fluid dynamics (CFD)–discrete element method (DEM) models. The respective trade-offs in terms of computational cost and model accuracy are critically compared. Recent progress is evaluated from an engineering standpoint in four key areas: optimization of the pellet bed structure and gas distribution, thermal control of the reduction zone, sensitivity analysis of operating parameters, and industrial-scale model validation. Current limitations in predictive accuracy, computational efficiency, and plant-level transferability are identified, and possible mitigation strategies are discussed. Looking forward, high-fidelity multi-physics coupling, advanced mesoscale descriptions, AI-accelerated surrogate models, and rigorous uncertainty quantification can facilitate effective scalable and intelligent application of hydrogen-based shaft furnace simulations.

In order to analyse the feasibility of sintering for municipal sludge treatment, a sintering pot was used for the experiment. The results showed that the main effects of sludge addition on the sintering process and sinter quality come from the changes in the heat addition and moisture content of the granulated sinter. The addition of sludge could improve the granulation efficiency of the sinter mixture and the particle size composition of the sinter. When the proportion of sludge was 7%, the addition of sludge completely replaced the water required for mixing, and the overall sintering index was the best. In this case, after reducing fuel consumption by 10%, except for the content of P, the sinter quality and the sintering index could met the requirements of steel production. Finally, the use of fuel and raw materials with high P content needed to be reduced with the addition of sludge.

Hydrogen-based smelting reduction has received widespread attention as an important technology for realizing low-carbon development in hydrogen metallurgy. In this study, the thermodynamics of smelting reduction was firstly analyzed by using FactSage 8.1 thermodynamic software, on the basis of which smelting reduction experiments of iron oxides by using bottom-blown hydrogen were carried out. The experiments used oxidized pellets as experimental materials, and the effects of the reduction process were analyzed in terms of the reduction temperature, the reduction time, and the hydrogen flow rate. The experimental results show that under the experimental conditions of a temperature of 1550 °C and a hydrogen flow rate of 0.2 Nm³/h, the reduction rate of iron oxides in the process of reducing iron oxides by hydrogen is significantly faster in the first 10 min than after 10 min. The hydrogen utilization rate reached a maximum of 41.87%, then decreased continuously and finally maintained at about 20%. Using the method of model fitting, it was found that the hydrogen-based molten reduction conformed to the phase boundary reaction model ($G\left(\alpha \right)={1-(1-\alpha )}^{1/2}$), the corresponding mechanism function is $f\left(\alpha \right)={2(1-\alpha )}^{1/2}$, where α stands for the reduction conversion, and the reaction rate constant $k\left(T\right)$ is 2.37 × 10⁻⁴ s⁻¹ under the experimental conditions.