Hard Gray Scale

Dando, Neal R.; Lindsay, Stephen J.

doi:10.1002/9781118647851.ch89

Cited by 4 publications

(4 citation statements)

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“…Results based on elemental composition showed that alumina, sodium and fluoride accounted for over 90% of the total mass of hard grey scale, which suggested that scrubber scale is formed principally from alumina and bath fines together with minor contributions from adsorbed fluoride and bath fumes (NaAlF4). Another study from 2013 [25] which investigated trace element concentration from pot exhaust and from depositions in fume treatment facilities agreed in the following result reported by the work on hard grey scale presented by Dando and Lindsay [24]. Both studies pointed out that the composition of particulate solids collected at the inlet of an injector scrubber shows similar chemical composition than the hard grey scale which deposits in scrubbers, despite the higher degree of crystallinity and higher carbon and sulphur content.…”

Section: Experimental Studies -Scale Formationsupporting

confidence: 71%

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Enabling Efficient Heat Recovery from Aluminium Pot Gas

Clos

Andresen

Nekså

et al. 2017

The Minerals, Metals &Amp; Materials Series

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In the present work, previous studies carried out by the Norwegian aluminium industry and research centres with the aim of recovering heat from aluminium production off-gas, are reviewed. The main challenge in improving heat recovery is the fouling phenomena, which is due to the presence of particulate matter and corrosive gases in the off-gas. Fouling can occur due to particle deposition, condensation of corrosive acids and scaling reactions, which in turn can build up hard layers, particularly, on heat exchanger surfaces. The review focuses primarily on fundamental studies (theoretical and experimental), which address off-gas composition characterization, particle size distribution and particle deposition phenomena in laboratory and industrial environments. Moreover, it presents commercial concepts already implemented in industry applications. Upcoming activities in regards to the scaling phenomena, which include the design of a cold-finger for laboratory and industrial measurements, as well as mathematical modelling using CFD, are also discussed.

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Section: Experimental Studies -Scale Formationsupporting

confidence: 71%

“…In 2008 Dando and Lindsay [24] presented a study aimed to define the chemistry and formation mechanism of HGS. Samples of HGS were collected from numerous Alcoa smelters worldwide and some pictures were presented which can be seen in Figure 4.…”

Section: Experimental Studies -Scale Formationmentioning

confidence: 99%

Enabling Efficient Heat Recovery from Aluminium Pot Gas

Clos

Andresen

Nekså

et al. 2017

The Minerals, Metals &Amp; Materials Series

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“…Dando and Lindsay [18] found that hard gray scale (HGS) in dry scrubbing consisted of an amorphous reaction product formed from the attrition-induced reaction of bath superfines, alumina fines and water. HGS could be artificially created by co-grinding these three components.…”

Section: Ductmentioning

confidence: 99%

Particulate Emissions from Electrolysis Cells

Gaertner¹,

Ratvik²,

Aarhaug

2011

Light Metals 2011

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In the dry cleaning of the exhaust gas from the aluminium cells impurities are accumulated in the finer fractions of secondary alumina from the dry scrubbers. The present work describes new methods for the determination of dust composition, aiming at increasing the understanding of the effect of cell operation on the amount and the composition of dust in the fume. New and advanced analysis methods are used to characterize a broad specter of emissions. An Electrical Low Pressure Impactor is used to sample and analyze the dust from the cells. The equipment enables real-time particle size distribution analysis of 12 particle classes in the range 30 nm-10 µm. The size classified samples are analyzed by means of SEM/EDS and XRD to determine the characteristic chemical composition of the different fractions. Understanding the evolution, evaporation, and condensation of particulates in the cell emissions under different operational conditions may facilitate new standards for environmental friendly and energy efficient high amperage electrolysis cells.

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“…In some cases, deposition layers keep growing until the pipeline is clogged, thus leading to system downtimes and loss of operational time. Aluminium production by the Hall-Héroult process is one example of an industrial application where scale formation is a significant challenge [4].…”

Section: Introductionmentioning

confidence: 99%