Aggregation kernel of globular inclusions in local shear flow: application to aggregation in a gas-stirred ladle

Abstract

The control of metal cleanliness has always been a concern for metallurgists since inclusions directly influence the mechanical properties of alloys. In most metallurgical routes, a refining treatment of the liquid alloy is performed, in particular with the aim of improving the metal cleanliness that is achieved via a better control of particle contents and particle size. Since the efficiencies of inclusion removal mechanisms increase with inclusion size, the turbulent aggregation process plays a major role in all refining treatments. Interaction between particles such as aggregation is usually modelled through kinetics kernels which may be difficult to estimate. This paper contributes to express turbulent aggregation kernel taking into account the hydrodynamic effects at the inclusion scale. The numerical approach combines three numerical techniques, a Lattice Boltzmann Method to resolve the flow, an immersed boundary method for the particle-fluid interactions and a Lagrangian tracking for the motion of individual particles. Deterministic simulations of spherical particle pair trajectories leading to collision or avoidance allow us to calculate statistical kernels in a shear flow. The results show a strong influence of the short distance hydrodynamic effects on the collision kernel, particularly when the diameter ratio of the two interacting particles is far from unity. An application of this new aggregation kernel is applied to simulate the time evolution of the particle size distribution in a typical steel gas-stirred ladle.

Multiscale Simulation of Non-Metallic Inclusion Aggregation in a Fully Resolved Bubble Swarm in Liquid Steel

“…Local shear is the only driving force in this study. Equation (17) shows that the contribution due to each shear rate is weighted by the shear rate value and the corresponding collision efficiency. Figure 10 shows the contribution of all shear rates to the overall collision rate in distribution form (∂ f /∂γ) and in cumulative form (partial integration for shears between 0 andγ).…”

“…The present work builds upon earlier work by the present authors [7,16,17] and develops a novel multiscale approach in which simulations are conducted both at inclusion scale and bubble swarm scale, coupled by a statistical model to derive process quantities that apply to liquid metal flotation processes.…”

Local behavior of inclusions in reactors metallurgical: Aggregation and deposition on the walls

“…En plus des valeurs globales, une telle approche permet aussi de quantifier les contributions des différentes régions du réacteur, associées à des taux de dissipation d'énergie différents. L'expression des contributions dérive de celle de la fréquence de collision, son calcul est détaillé dans Gisselbrecht et al (2019). Les contributions à l'agrégation d'inclusions de 10 µm sont illustrées en Figure 7.…”

Effect of Wettability, Number of Liquid Phases, and Agitation Procedure on Agglomeration/Breakup/Transfer of Fine Particles in Liquid

“…Fruengieri et al [17,18] simulated the aggregation and breakup of colloidal particles under the effect of a shear field by combining a Monte Carlo algorithm and the discrete element method (DEM). Gisselbrecht et al [19] calculated the time evolution of inclusion size distribution in a gas-stirred ladle by a population balance model after connecting three numerical techniques of a lattice Boltzmann method, immersed boundary method, and Lagrangian tracking.…”