A numerical simulation procedure is proposed for analyzing the partial replacement of pulverized coal injection by hydrogen, oxygen, and blast furnace gas (BFG) injections mixed with pulverized coal (PCI) within the tuyeres of large blast furnaces. The massive use of hydrogen-rich gas is extremely interesting for ironmaking blast furnaces in the context of net-zero carbon hot metal production. Likewise, this new approach allows for increasing productivity and for reducing the specific emissions of carbon dioxide toward a net-zero carbon ironmaking technology. Nevertheless, the mixture of pulverized coal injection and gas injection is a complex technology. In addition to the impact on chemical reactions and energy exchange, the internal temperature and gas flow patterns can also change drastically. With a view to assessing the state of the furnace in this complex operation, a comprehensive mathematical model utilizing multiphase theory was developed. The model simultaneously handles bulk solids (sinter, pellets, small coke, granular coke, and also iron ore), gas, liquid metal and slag, and coal powder phases. The associated conservation equations take into account momentum, mass, chemical species, and energy while being discretized and solved using finite volume techniques. The numerical model was validated against the reference operating conditions using 220 kg per ton of pig iron (kg/t_HM) of pulverized coal. Therefore, the combined injection of different concentrations of fuel hydrogen, blast furnace gas, and oxygen was simulated for replacing 40, 60, and 80 kg/t_HM of coal injection. Theoretical analysis showed that the best scenario with stable operation conditions could be achieved with a productivity increase of 20% corresponding to a CO₂ reduction of 15% and 60 kg/t_HM of PCI replacement.

The shaft furnace knowed Midrex™ is used for the production of direct reduced iron with the use of reformed gas. Another process based on shaft reactors is the Tecnored process, which exhibits the great advantage of using self-reducing agglomerates. Therefore, it was proposed a combination of the shaft furnace for direct reduction with self-reducing pellet burden. In addition, with the aim of improving the furnace efficiency and reducing the need for reformed gas, the injection of natural gas and oxygen into the bustle region is proposed. Thus, it is possible exploit the advantages of direct reduction involving high amounts of hydrogen and faster reactions of the self-reducing process to decrease the CO2 emission, compared to that of blast furnace. The energy profile, productivity, and carbon emission of the traditional shaft furnace were compared with the simulated results after partial replacement of the burden with self-reducing pellets containing fines of elephant grass charcoal. The simulation results for a combination of 15% of self-reducing pellets in the burden with 2.5% oxygen and natural gas injection were the best among the scenarios simulated, with the productivity being 2.7 ton/m3 day and the decrease in the amount of reformed gas being 10%.

Welding is a widely used process that requires continuous developments to meet new application demands of mechanical projects under severe conditions. The homogeneity of metallurgical and mechanical properties in welded joints is the key factor for any welding process. The applications of external magnetic fields, mechanical vibration, and ultrasound are the fundamental steps to achieve success in improving these properties. The present work aimed at determining suitable processing conditions to achieve the desired balance between metallurgical and mechanical properties of 304L steel in TIG (Tungsten Inert Gas) welding under the application of an external magnetic field. The microstructural characteristics of the weld bead were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). In order to evaluate the mechanical properties of the welded specimen, its Vickers microhardness map and Charpy impact energy at −20 °C were obtained. In addition, corrosion tests were carried out in the saline medium to compare the corrosion resistance of the joint with that of the base metal and that without the magnetic field. It was found that the external magnetic field decreased the percentage of delta ferrite, improved the filling of the weld pool with the weld metal, and decreased the primary and secondary dendritic spacings. The Vickers microhardness value under the magnetic field was found to be lower than that without the magnetic field, and the Charpy test showed no significant variation in energy absorption. Moreover, the welded joint produced under the external magnetic field manifested less resistance to corrosion.

Unlike the available mineral resources, the steelmaking processes have demanded raw material with lower phosphorus content to decrease the costs, energy use, and the residue generated within the steel plant. One alternative is to develop pretreatment of the iron ore concentrates producing raw materials with lower phosphorus. Depending on the mineral structure, a heat treatment combined with leaching could be an efficient way to achieve concentrates with low phosphorus (less than 0.01%), suitable for steelmaking processes. A fast and efficient way of applying energy to iron ore particles is the use of microwave to heat the particles. Thus, we propose a treatment using microwave heating while mixing with a dilute aqueous solution of sulfuric acid, followed by quenching during leaching with water, as a feasible route for the phosphorus removal from iron ore particles. We performed a design of experiment (DOE) to investigate the optimal conditions of heating and leaching, which maximize the rate of phosphorus removal. The structure of the iron ore particles after their treatment with microwave energy was observed by scanning electron microscopy (SEM). Thus, we analyze the optimal conditions for heating and leaching, the structure of the iron ore particles and which mechanism and rate equations are controlling the phosphorus removal. The results indicated that the average heating time is 10 min, the size of the crack of the order of 20µm and a leaching time of 8 min are adequate to achieve less than 0.01% of phosphorus. We demonstrated that under the most favorable combination of conditions for heating followed by leaching proposed in this study, the removal of the phosphorus content in the iron ore samples could reach 100%.