Triboelectric charging, resulting from repeated particle-particle (P-P) and particle-wall (P-W) interactions, critically affects process safety and efficiency, yet remains insufficiently understood. This study presents a numerical investigation of tribocharging in a horizontal-bend-vertical pipe using our recent combined Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model, which is capable of modeling impact and frictional charging for various particle shapes. Dense- and dilute-phase conveying of non-spherical particles is simulated to assess charge evolution, wall erosion, gas-solid flow behavior, and P-P/W contact information. Charge mitigation strategy is explored, and pipe erosion under various particle shapes is also evaluated. Results reveal strong shape-dependent charging characteristics. Prolate particles achieve the highest equilibrium charge due to their elongated shape, which enhances P-P charge transfer, while oblate particles charge rapidly via extensive wall contact. Charge accumulation is amplified at bends, where secondary flows increase collision frequency and intensity. Shape-dependent drag forces and flow patterns show that particle layering and suspension govern triboelectric behaviors. Numerical results further show that strategically placing discharge points upstream of bends in the dense phase and downstream of bends in the dilute phase can substantially mitigate charge buildup. Additionally, pipe erosion intensifies with the presence of non-spherical particles. Maximum erosion occurs in deeper bend areas with non-spherical particles in the dense phase, while erosion distributions become similar in the dilute phase. A single charging cycle has a negligible impact on tribocharging-induced pipe erosion. This study offers insights into complex bend phenomena that can facilitate industrial applications.

The use of hydrogen in blast furnace (BF) ironmaking offers a significant potential for reducing carbon footprint. This paper comprehensively studies preheated hydrogen injection into a 400-m3 BF via hearth tuyeres under different conditions using a BF process model. Two scenarios are first considered under fixed bosh gas volume, hot metal (HM) temperature, and flame temperature to ensure smooth operation and consistent HM quality: (1) injection of preheated hydrogen at varying hydrogen injection rates and a constant coal injection (PCI) rate and (2) interactions between hydrogen injection temperature (HIT) and PCI rate. The numerical results show that injecting hydrogen into a BF under a given HIT decreases the fuel rate, though excessive injection increases it. These results help identify the optimal hydrogen usage for minimizing fuel consumption. Increasing the HIT reduces the fuel rate and increases the optimal hydrogen injection. A detailed analysis of the BF's inner states reveals that the advantage of lifting HIT is its ability to prevent an increase in coke combustion. Moreover, the interaction between preheated hydrogen and PCI is demonstrated to be controllable, allowing for a significant reduction in the fuel rate. In addition, the pure injection of preheated hydrogen is compared to the optimal case identified at varying HITs and PCI rates and to the conventional base case under the same bosh gas volume and HM temperature. The pure injection can significantly reduce fuel consumption- about three times that of the optimal case. However, it requires an exceptionally high hydrogen temperature and cannot completely omit coke consumption by direct reduction. To evaluate BF performance, the concept of total energy consumption in a BF is introduced, considering the contributions of different thermal and chemical energy resources in a unified manner. It demonstrates that increasing HIT or the hydrogen injection rate reduces total energy consumption. The findings from this study provide some valuable guides for designing and controlling BF with hydrogen injections under different conditions.

Major iron and steel companies have identified the H2-based shaft furnace (SF) as a key decarbonization technology for future development. Its continued advancement aims to achieve full H2 operation and broaden the applicability of ores with different grades. However, published studies report contradictory trends in SF reduction performance with increasing H2 content, leading to significant confusion about the role of H2. The underlying causes remain unclear, and the influence of ore properties on SF performance has received limited investigation. In this work, using our recently developed CFD model for industrial SFs, the influence of ore properties on SF reduction behavior is investigated under various H2 contents. Differences in ore properties focus on thermodynamic equilibrium differences, as documented in two well-known databases, NIST and FactSage. The results show that thermodynamic equilibrium differences can modify the contributions of high- and low-temperature reduction, leading to inconsistent trends in metallization as H2 content increases. The gas flow rate is also a contributing factor, as it alters the H2:CO range in which the thermodynamic disadvantage of H2 reduction hinders reduction. These findings provide insight into how ore properties and the reducing gas flow rate modulate in-furnace H2 reduction and highlight the need for reliable ore characterization to properly assess H2-based SF performance.

As a promising low-carbon ironmaking technology, shaft furnace (SF) direct reduction using pure H2 is attracting significant attention from the steel industry. However, how SF performance evolves during the transition from H2-rich to pure H2 operation remains insufficiently understood, and how metallization under high H2 conditions can be improved remains unclear. A recently developed process model, further developed and validated to include both high- and low-temperature reduction steps, is applied to address these gaps. The comparative analysis highlights the importance of low-temperature reduction in the overall reduction process under high-H2 conditions. It also provides insight into the decline in reduction performance at a higher H2 content. Subsequently, systematic studies of gas-injection strategies are conducted to cover the effects of reducing gas temperature and flow rate, as well as N2 addition methods. The results identify feasible operational routes under pure H2 conditions, significantly increasing metallization while maintaining appreciable H2 utilization.

The metallurgical properties of raw materials—particularly their reactivities—can significantly influence blast furnace (BF) performance. However, due to variations in reactivity among different raw materials, it remains unclear whether existing reaction models can reliably describe each material. To address this, numerical models are developed to simulate laboratory-scale experiments measuring indirect reduction, coke reactivity, and softening–melting (S M) behavior. First, the reactivities of coke and individual iron-bearing materials, including sinter, pellets, and lump ore, are sequentially measured and evaluated. By combining numerical modeling with experimental measurements, widely used reaction models are modified to better capture the reactivity of each material. The reactivity of ore mixtures is further investigated, demonstrating that the indirect reducibility of mixed burden can be derived from the reactivities of its individual components. Subsequently, all the modified reaction models, together with the measured S M properties, are incorporated into simulations of the coke–ore coupled reaction–softening–melting process, and the results are validated against experimental data. In addition, the direct reduction model between melts and coke is verified under conditions of measured bed shrinkage. These results indicate that, while existing reaction models can qualitatively describe the reactivities of typical sinter, pellets, and lump ore, material-specific calibration is required for accurate quantitative predictions. The integration of lab-scale measurements with numerical modeling provides a robust framework for obtaining reliable calibrating parameters, which can be further extended to full-scale BF ironmaking applications.

The shaft furnace is a promising low-carbon ironmaking technology, but its complex internal processes pose challenges for efficient operation and control. Numerical simulation provides an effective method for revealing the internal states, whereas many existing models incorporate simplifications that limit prediction accuracy. This study presents a CFD model for industrial MIDREX shaft furnaces, incorporating major reactions, including CH4-related side reactions. An improved unreacted shrinking core model (USCM) is introduced for reduction based on the thermodynamic equilibrium diagram. It allows for the decoupling of reaction and diffusion layers, reducing the reaction layers and enabling variable diffusion structures. Consequently, the reaction model provides a more physically realistic and thermodynamically consistent representation of the multi-step reduction process, is valid for H-2-CO mixtures, and increases computational efficiency by 65-75 %. The model is validated using four sets of laboratory and industrial data, covering inner states and overall performance parameters. It also successfully captures the influence of CH4, an inevitable component arising from reforming. A high CH4 content causes substantial heat loss near the gas inlet and reduces metallization, primarily due to the combined effects of endothermic reduction and side reactions. Based on simulation results, an optimal CH4 level is identified to balance metallization, gas utilization, and energy efficiency. The model can serve as a valuable tool for analyzing shaft furnace performance and has the potential to support the evaluation of advanced decarbonization strategies such as high H-2 content operation.

New hydrocyclone designs can significantly enhance separation efficiency in applications such as water treatment and particle classification. Therefore, various hydrocyclone geometries with different inlet and cone configurations are explored through a validated mechanistic model, leading to a new cyclone design. The proposed design features a laminar spiral inlet and a straight-to-convex cone, achieving reductions of 44.2 % in separation sharpness and 58.4 % in water split. Its double-cone configuration reduces tangential velocities in the upper conical section, while the convex lower cone broadens the separation region, maintaining relatively high tangential velocities near the spigot. These effects reduce particle accumulation near the spigot and improve separation performance. Moreover, the laminar spiral inlet mitigates short-circuit flow near the vortex finder. To further enhance separation efficiency, the novel conical section is optimized by integrating mechanistic and data-driven models. Compared to the initial novel design, the optimized version exhibits an 18.2 % reduction in separation sharpness and a 16.2 % reduction in water split by optimizing four geometric variables characterizing the conical section. Internal flow field analysis confirms that the optimized configuration establishes favorable tangential velocities in the conical section, guiding fine and coarse particles along optimal paths and improving overall performance.

The blast furnace bell-less top charging system involves multiple handling steps that affect burden distribution in the furnace throat. This study employs a GPU-DEM model to analyze particle motion and energy dissipation of burden materials from the belt conveyor to the furnace throat, providing insights into flow behavior, segregation, degradation, and erosion. Particle properties and size distributions strongly affect the flow structure. Pellets exhibit higher velocities than lumps, sinters, and coke, with differences decreasing in the rotating chute. Four regions of high energy dissipation were found, with coke and sinter degradation reaching 15 % of the feed and lump and pellet degradation remaining around 1 %. Wear intensifies with broader particle size distributions, driven by shear energy. Segregation before hopper filling is minimal, but in-hopper segregation significantly impacts in-furnace segregation, where larger particles accumulate at the periphery and top. Heap formation arises mainly from shifts between rolling and impact energy dissipation.

Degradation of the iron ore during handling and transportation results predominantly from impact from drops, such as the ship loading process. The lump ore degradation is directly related to the particle energy dissipation during impacting with wall or particles. In this work, graphical processing units (GPU) and message passing interface (MPI)-based discrete element method (DEM) is developed for the large-scale iron ore ship loading process to analysis the particle impact and energy dissipation. The effect of particle properties such as size distribution and shape, belt speed and dropping height on energy dissipation are studied. The results illustrate that Young's modulus has little effect on the energy dissipation under the same loading condition. Degradation varies with particle size, with coarser particles suffering a greater energy dissipation than finer ones. Particles with a size distribution provide a significant cushion effect on particle degradation, as demonstrated by an obvious smaller value in energy dissipation. This is explained by the inter-particle contact during the dynamic loading process. Belt speed has negligible effect on impact energy dissipation within the range considered. Dropping height, as expected, is the most significant factors affecting the impact energy dissipation. When the dropping height reduces from 10 m to 5 m, the dissipated energy by particle-particle impacts reduces more than half. Vogel and Peukert [1] particle breakage model is used to study the individual particle breakage probability under specific material properties. For the same energy input, smaller particles have lower breakage probability, indicating that larger particles are easier to break than smaller ones. (C) 2019 Published by Elsevier B.V.

Graphics processing unit (GPU)-based DEM combined with message passing interface (MPI) has been applied to large-scale handling and processing systems, including granular conveying, reclaiming, screening, ship loading, grab and screw unloading, and blast furnace top charging systems. The issues in terms of particle flow behaviour, particle-wall interaction/wall stress, particle energy dissipation, size segregation, and process efficiency, etc., are discussed. The results showed that for a belt conveying chute, wear became more severe at higher flow rates. In the reclaiming process, there was an increase in the digging resistance on the buckets with increasing bucket rotation speed. For the screening process, lower vibrating frequency lead to a higher screening efficiency, but also higher wall stresses. In a ship loading process, particle streams with a wide size distribution provided a significant cushioning effect on particle degradation, and when the dropping height reduces, the dissipated energy by particle-particle impacts greatly reduced. For a grab unloader, particle velocities became smaller with an increase in grab close time with tangential stresses only slightly reduced within the close time range considered. An increase of rotational speed of the bottom blades of a screw unloader indicated a higher unloading efficiency. A full blast furnace top charging process model was also developed. Size segregation was observed at different stages of the charging process. This paper demonstrated that GPU-based DEM can be successfully applied to the whole granular process chain of ironmaking related industries at different scales and provide guidelines for the key issues in different processes.

The discrete element method (DEM) based simulations were conducted to study the effects of particle-particle and particle-wall frictions on the compaction behaviour of wet particles. The results showed that in the die compaction the particle-wall friction had a minimum effect on the initial particle re-arrangement stage and mainly affected the particle deformation stage. The inter-particle friction, on the other hand, reduced the particle re-arrangement in the initial stage but had no significant effect on the deformation stage. This was attributed to their different roles in force transmission: while the particle-wall friction reduces the force transmission resulting in increased density/stress gradients in the compaction direction, the inter-particle friction enhances the vertical pressure transmission. Their different roles were also reflected in the unconfined axial compression: the compressive strength of compacts decreased with increasing particle-wall friction but increased with increasing inter-particle friction. It was also observed that the compact stiffness increased with inter-particle friction but showed no dependence on particle-wall friction. While the dominant failure mode did not vary with the frictional condition, larger particle-wall frictions caused smaller failure areas which were mainly localized at the bottom of the compacts.