Smelter Fluoride Balances: The Interplay Between Alumina Phases, Pore Size Distributions, and the Impacts of Weather

McIntosh, Grant J.; Metson, James B.; Niesenhaus, Thomas; Reek, Till; Perander, Linus

doi:10.1007/s11837-014-1189-3

Cited by 10 publications

(13 citation statements)

References 11 publications

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“…22 This may indicate that there may be two mechanisms operating. However, given the range of materials we have considered both here and in previous studies, [11][12][13][23][24][25] and the fact that models such as those shown in Fig. 5 do not, when examined in detail, demonstrate the sorts of shifts that Dando and Lindsay observe, 22 this suggests that it is also possible that the PSD changes they observe may be associated with a different deposition product.…”

Section: Psd Reconstruction Modelsmentioning

confidence: 78%

“…First, from data taken exclusively from an operating smelter, a pore diameter threshold of 3.5 nm is identified below which the pores are ineffective in fluoride return through HF capture. We have previously demonstrated that this affects the stack emissions, 13 and also influences the fluoride balance of the pot. We have also linked this to energy efficiency.…”

Section: Resultsmentioning

confidence: 98%

“…We have correlated several alumina properties with important parameters relevant to smelter operation such as HF generation, 13 current efficiency and energy consumption. 6 In these studies, data from a wide range of smelter parameters were assimilated into 572-point-long vectors, one vector for each parameter.…”

Section: The Impact Of Alumina Pore Size On Fluoride Balances In An Omentioning

confidence: 99%

“…Our alumina group within the Light Metals Research Centre has recently performed a number of studies examining the role of pore size on HF capture efficiency 11,12 and its role in fluoride return to the reduction cells. 13 In this work, we review key elements of these studies, and address the overall implications when these results are taken together. These are supplemented with preliminary results from a model we are currently developing to describe the aging of alumina porosity during reaction with HF.…”

Section: Introductionmentioning

confidence: 99%

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The Pivotal Role of Alumina Pore Structure in HF Capture and Fluoride Return in Aluminum Reduction

McIntosh

Agbenyegah

Hyland

et al. 2016

JOM

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Fluoride emissions during primary aluminum production are mitigated by dry scrubbing on alumina which, as the metal feedstock, also returns fluoride to the pots. This ensures stable pot operation and maintains process efficiency but requires careful optimization of alumina for both fluoride capture and solubility. The Brunauer-Emmett-Teller (BET) surface area of 70-80 m 2 g À1 is currently accepted. However, this does not account for pore accessibility. We demonstrate using industry-sourced data that pores <3.5 nm are not correlated with fluoride return. Reconstructing alumina pore size distributions (PSDs) following hydrogen fluoride (HF) adsorption shows surface area is not lost by pore diameter shrinkage, but by blocking the internal porosity. However, this alone cannot explain this 3.5 nm threshold. We show this is a consequence of surface diffusion-based inhibition with surface chemistry probably playing an integral role. We advocate new surface area estimates for alumina which account for pore accessibility by explicitly ignoring <3.5 nm pores.

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Section: Psd Reconstruction Modelsmentioning

confidence: 78%

Section: Resultsmentioning

confidence: 98%

Section: The Impact Of Alumina Pore Size On Fluoride Balances In An Omentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Pivotal Role of Alumina Pore Structure in HF Capture and Fluoride Return in Aluminum Reduction

McIntosh

Agbenyegah

Hyland

et al. 2016

JOM

Self Cite

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“…[7][8][9][10][11] However, by far the largest consumer is the primary aluminium production industry that, in addition to using alumina as the primary feedstock, employs it as the dry scrubbing agent for hydrogen fluoride generated in the reduction cell. [12][13][14] With many of alumina's applications crucially dependent on its surface chemistry, it is necessary to understand the evolution of these properties from the precursor to final product.…”

Section: Introductionmentioning

confidence: 99%

Probing hydrogen bonding interactions and impurity intercalation in gibbsite using experimental and theoretical XANES spectroscopy

McIntosh

Chan

2018

Phys. Chem. Chem. Phys.

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The Al and O K-edge XANES spectra of Bayer process gibbsite are examined, both experimentally and with plane wave density functional theory, and transition assignments are made. We confirm that the broad transitions in Al K-edge spectra are fundamentally the same as those in more ordered and well-studied corundum, and typical of octahedrally coordinated aluminium. Analysis of O K-edge spectra reveals that while much of the initial edge transition structure (535-548 eV) is due to O 2p hybridization with Al orbitals, the lowest energy region (∼535-539 eV) is particularly influenced by O-H states which are heavily perturbed by hydrogen bonding interactions. We therefore tentatively suggest that an unexplained structure at 539 eV in O K-edge spectra of corundum may be due to surface hydroxylation. Finally, we examined Na K-edge spectra, as sodium is the major impurity in these materials and implicated in perturbation of the evolution of materials properties with calcination through the transition aluminas. Density functional theory calculations find sodium replacement of in-sheet H-atoms is the most thermodynamically stable site for sodium inclusion. We subsequently confirm this assignment spectroscopically, explicitly demonstrating the precise location of Na+ impurities for the first time.

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The Impact of Alumina Quality on Current Efficiency and Energy Efficiency in Aluminum Reduction

McIntosh¹,

Metson²,

Lavoie³

et al. 2016

Light Metals 2016

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Smelter Fluoride Balances: The Interplay Between Alumina Phases, Pore Size Distributions, and the Impacts of Weather

Cited by 10 publications

References 11 publications

The Pivotal Role of Alumina Pore Structure in HF Capture and Fluoride Return in Aluminum Reduction

The Pivotal Role of Alumina Pore Structure in HF Capture and Fluoride Return in Aluminum Reduction

Probing hydrogen bonding interactions and impurity intercalation in gibbsite using experimental and theoretical XANES spectroscopy

The Impact of Alumina Quality on Current Efficiency and Energy Efficiency in Aluminum Reduction

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