The distribution of burden layers in an ironmaking blast furnace strongly influences the conditions in the upper part of the process. The bed permeability largely depends on the distribution of ore and coke in the lumpy zone, which affects the radial gas flow distribution in the shaft. Along with the continuous advancement of technology, more information about the internal conditions of the blast furnace can be obtained through advanced measurement equipment, including 2D profiles and 3D surface maps of the top burden surface. However, the change of layer structure along with the burden descent cannot be directly measured. A mathematical model predicting the burden distribution and the internal layer structure during the descending process is established in this paper. The accuracy of the burden distribution model is verified by a comparison with experimental results. A sensitivity study was undertaken to clarify the role of some factors on the arising layer distribution, including the descent-rate distribution, the initial burden surface profile, and the charging direction through the charging matrix. The findings can be used as a theoretical basis to guide plant operations for optimizing the charging.

The blast furnace campaign length is today usually restricted by the hearth life, which is strongly related to the drainage and behavior of the coke bed in the hearth, usually referred to as the dead man. Because the hearth is inaccessible and the conditions are complex, knowledge and understanding of the state of the dead man are still limited compared to other parts of the blast furnace process. Since a number of publications have studied different aspects of the dead man in the literature, the purpose of the current review is to compile the findings and knowledge in a comprehensive document. We mainly focus on contributions with respect to the dead man state, and those assessing its influence on the hearth performance in terms of liquid flow patterns, lining wear and drainage behavior. A set of common modeling approaches in this specific furnace area is also briefly presented. The aim of the review is also to deepen the understanding and stimulate further research on open questions related to the dead man in the blast furnace hearth.

Given the urgent pursuit of carbon neutrality and stringent climate policies, the H₂ shaft furnace (H₂-SF) is starting to gain widespread attention in the steel industry. In this study, the performance of the H₂-SF under operation with a dual-row injection top gas recycling system was investigated by a one-dimensional mathematical model. The potential of microwave heating as a means to supply thermal energy in regions of energy deficit was also assessed briefly. The results showed that for scenarios without microwave heating, increasing the upper-row injection rate can improve the furnace performance, and increasing the distance of the upper-row injection level from the furnace top also has a positive effect. A high microwave heating efficiency is expected in regions above the upper-row injection level. For scenarios with microwave heating, a higher microwave power leads to a better furnace performance. Thus, a higher furnace productivity can be achieved by increasing either the upper-row injection rate or the microwave power. However, the latter seems more promising as it decreases the total energy demand due to a better utilization of thermal energy. Based on the comparison of two representative examples, the decrease in the total energy demand is about 0.2 GJ/t-Fe.

In order to explore technically feasible options for improving the performance of the H₂ shaft furnace (HSF), a previously built and validated computational fluid dynamics (CFD) model was employed in the current work to assess the potential of the operation based on a center gas distributor (CGD). A set of simulations was performed to mimic scenarios where different amounts of feed gas (0–30% of 1400 Nm³/t-pellet) are injected via the CGD located at the bottom of the HSF. The results showed that a relatively large stagnant zone (approximately 8.0-m in height and 0.3-m in diameter) exists in the furnace center where the gas flows are weak owing to an overly shortened penetration depth of the H₂ stream solely injected from the circumferentially installed bustle-pipe. When adopting the CGD operation, however, the center gas flows can be effectively enhanced, consequently squeezing the stagnant zone and thus leading to a better overall performance of the HSF. In particular, the uniformity of the final reduction degree (mean values ranging from 0.8846 to 0.8896) of the solid phase (i.e., pellets) is well improved under the investigated condition where the total gas feed rate is fixed at 1400 Nm³/t-pellet. As for the final mean reduction degree of solid and top gas utilization degree, the two performance indicators rise to maximal values when the CGD feed ratio is increased to 20% and then slightly drop with a further increase in the ratio.

A transient computational fluid dynamics (CFD) modelling approach was used to study the complex multi-phase flow in an argon-stirred industrial scale ladle with a nominal capacity of 150 tons. During the stirring process, when gas was injected through the porous plug from the bottom into the steel bath, it breaks up into bubbles and infringes the slag layer creating an open-eye. The volume of fluid model was used to investigate the open-eye formation process in the simulations. In the numerical simulations, the open-eye area changed from 0.7 to 2.24 m² with the increment of argon flow rate from 200 to 500 NL/min for slag layer thickness of 40 cm. Furthermore, the influence of slag layer height on the open-eye area was investigated. An argon flow rate of 200 NL/min was able to break the slag layer for slag layer height of 40 cm, and the open-eye formation was not possible for the same flow rate when the slag layer height was elevated from 40 to 55 cm. The numerical simulation results were validated against industrial measurements carried out at Outokumpu Stainless located in Tornio, Finland. The numerical simulation results of dynamics and time-averages of the slag area showed a good agreement when compared to the industrial measurements. To conclude, it is necessary to define gas flow rate based on the slag layer height to have an open-eye suitable for alloying.