Mark Cooksey

Development of Bubble Driven Flow CFD Model Applied for Aluminium Smelting Cells

This paper presents the development of a computational fluid dynamics (CFD) model for the study of bubble driven bath flow in aluminium reduction cells. For validation purposes, the model development was conducted using a full scale air-water model of part of an aluminium reduction cell as a test-bed. The bubble induced turbulence has been modelled by either modifying bubble induced turbulence viscosity directly or by modifying bubble induced turbulence kinetic energy in a standard k-ϵ turbulence model. The relative performance of the two modelling approaches has been examined through comparison with experimental data taken under similar conditions using Particle Image Velocimetry (PIV). Detailed comparison has been conducted by point-wise comparison of liquid velocities to quantify the level of agreement between CFD simulation and PIV measurement. Both models can capture the key flow patterns determined by PIV measurement, while the modified turbulence kinetic energy model gives better agreement with flo...

CFD Modelling of Alumina Mixing in Aluminium Reduction Cells

Aluminium reduction cells have been continuously improved to reduce energy consumption and increase metal production rates. One method of reducing energy consumption is to operate the cell at low anode-cathode distances (ACDs). Line currents have been increased to increase production rates, which often requires larger anodes to maintain an acceptable current density. These changes may have a significant impact on aspects of cell performance such as bath flow and alumina mixing.

Life Cycle Assessment of Rare Earth Production from Monazite

The environmental life cycle impacts of conceptual rare earth production processes were assessed. An average greenhouse gas emission of 65.4 kg CO2e/kg was estimated for the 15 rare earths produced from monazite, ranging from 21.3 kg CO2e/kg for europium to 197.9 kg CO2e/kg for yttrium. The average water consumption of rare earth production was 11,170 kg/kg ranging from 3,803 kg/kg for samarium and gadolinium to 29,902 kg/kg for yttrium. The average gross energy requirement for production was 917 MJ/kg, ranging from 311 MJ/kg for samarium and gadolinium to 3,401 MJ/kg for yttrium. Given the low concentration of HREE in monazite, the high impacts across all categories for yttrium and other HREE are not necessarily representative of HREE sourced from all rare earth resources. Further studies into other rare earth mineral resources (e.g. bastnasite and xenotime) are recommended to improve the overall understanding of environmental impacts from rare earth production.

Numerical Modeling of Flow Dynamics in The Aluminum Smelting Process: Comparison Between Air–Water and CO2–Cryolite Systems

Air–water models have been widely applied as substitutes for CO2–cryolite systems in the study of the complex bubble dynamics and bubble-driven flow that occurs in the molten electrolyte phase in the aluminum electrolytic process, but the detailed difference between the two systems has not been studied. This paper makes a numerical comparison between the bubble dynamics for the two systems. Simulations of both single bubble and continuous bubbling were conducted using a three-dimensional computational fluid dynamics (3D CFD) modeling approach with a volume of fluid (VOF) method to capture the phase interfaces. In the single bubble simulations, it was found that bubbles sliding under an anode in a CO2–cryolite system have a smaller bubble thickness and a higher sliding velocity than those in the air–water system for bubbles of the same volume. Dimensionless analysis and numerical simulation show that contact angle is the dominant factor producing these differences; the effects of kinematic viscosity, surface tension, and density are very small. In the continuous bubbling simulations, the continuous stream of air bubbles detaches from the anode sidewall after a period of climbing, just as it does in the single bubble simulation, but bubbles have less tendency to migrate away from the wall. Quasi-stable state flow characteristics, i.e., time-averaged bath flow pattern, turbulence kinetic energy, turbulence dissipation rate, and gas volume fraction, show a remarkable agreement between the two systems in terms of distribution and magnitude. From the current numerical comparisons, it is believed that the air–water model is a close substitutive model for studying bubble-driven bath flow in aluminum smelting processes. However, because of the difference in bubble morphologies between the two systems, and also the reactive generation and growth of bubbles in the real system, there will likely be some differences in bubble coverage of the anode in the anode–cathode gap.

Numerical Investigation of Bubble Dynamics in Aluminium Electrolytic Cells

Gas generated beneath anodes in aluminum electrolytic cells play an important role for the circulation of the bath, alumina mixing, and heat balance. Those bubbles cause an extra voltage drop, which is strongly affected by the amount and shape of the bubbles beneath anodes. Consequently, understanding the dynamic behavior of bubbles in aluminum electrolytic cells has been a major research focus worldwide in recent decades.