Computational Fluid Dynamics (CFD) Modeling of Bubble Dynamics in the Aluminum Smelting Process

Abstract

This paper presents a microscale modeling approach for investigation of bubble dynamics in the aluminum smelting process. The motion of a single bubble has been studied through a computational fluid dynamics (CFD) model facilitated with the volume-of-fluid (VOF) method to capture the bubble shapes. Using a two-dimensional geometry of part of a real cell as the testing bed, the motion of different sized bubbles has been simulated in an air–water system and a CO2–cryolite system. Comparisons between the two systems are conducted through the three periods of bubble motion: bubble sliding under the anode, bubble releasing at the anode edge, and bubble rising in the side channel. It was found that both systems show similar trends in bubble dynamics, such as an increase in the bubble sliding velocity as the bubble size increases and the appearance of a thick head at large bubble sizes. Quantitatively, there are differences between the two systems, evidenced in terms of the detailed bubble dynamics at each period of bubble motion, such as the bubble morphology, the bubble sliding velocity, the bubble layer thickness, and the bubble-induced liquid flow. The detailed microscale modeling provides useful information for the development of a multiscale modeling methodology by building constitutive correlations to support the macro/process scale modeling.

Two-Phase CFD Model of the Bubble-Driven Flow in the Molten Electrolyte Layer of a Hall–Héroult Aluminum Cell

“…For example, little information exists on drag forces for highly flattened bubbles moving under a horizontal surface, nor are there predictive models for the size of such bubbles at each point on the lower surface of the anode. In future extensions of the model, available information [11,13,33] will be incorporated into the model. Bubbles that rise in the inter-anode gaps where break-up is suppressed are assumed to be the same size as those under the anode.…”

“…Finally, for bubble size and shape to be similar, kinematic surface tension (r/q) between gas and liquid is the critical parameter: this is indeed approximately the same for water/air and cryolite/CO 2 systems. [11,33] Geometric idealizations in the water model include square anode edges/corners and square profile side channel (i.e., no ledge). It is expected that these simplifications will not change the general nature of the flow pattern, so the experimental data are suitable for the purpose of validation of the CFD model; since the model is fundamentally based, it can then be used with confidence to simulate more realistic geometrical details and potential design modifications.…”

Bubble Evolution and Anode Surface Properties in Aluminium Electrolysis

“…Generally one bubble is assumed to nucleate per pore. Subsequent to nucleation, local bubble motion is thought to be controlled by many factors including anode shape, roughness, surface tension, bath (and metal) flow and the contact angle between anode and electrolyte [35]. In a study 5 by Peterson et al [22], small bubbles that detached rapidly from the anode were produced when the anode-electrolyte contact angle was small, achieved by using an inert anode material.…”

Hydrodynamics and Oxygen Bubble Characterization of Catalytic Cells Used in Artificial Photosynthesis by Means of CFD

“…This method has already been used to simulate photo-electrochemical reactors for hydrogen production [28], and other types of fuel cells, such as solid oxide [29] or redox cells [30]. Multiphase problems can also be dealt with in CFD simulations, and they allow bubbles inside a liquid medium to be simulated [31]. In this study, CFD simulations have been carried out to assess the most efficient design of a microfluidic PEC cell.…”