Assessing The Role of Smelter Grade Alumina Porosity in The HF Scrubbing Mechanism

Agbenyegah, Gordon E. K.; McIntosh, Grant J.; Hyland, Margaret; Metson, James B.

doi:10.1002/9781119274780.ch86

Cited by 2 publications

(2 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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: 77%

“…With e = 0, we are in a purely Knudsen regime. It is possible to demonstrate that Knudsen diffusion cannot accurately describe the time-dependent changes observed as alumina is dosed, 24,25 indicating that surface diffusion must be active. Further, the energy parameter e must be fine-tuned in order to describe the observed changes correctly, given the unreasonable PSD changes when the barrier is set too high (see e = 150 kJ mol À1 ; Fig.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

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.

show abstract