Mathematical Model of Fluoride Evolution from Hall‐Héroult Cells

Haupin, Warren; Kvande, Halvor

doi:10.1002/9781118647851.ch133

Cited by 5 publications

(5 citation statements)

References 4 publications

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“…This equipment allowed for real-time sampling of 12 particle classes divided in the size ranges between 7nm and 10 µm. Results showed that larger number of particles were measured with the impactor equipment in the sub-micron range than were previously reported in a study using SEM for that purpose [22]. SEM images of the size-classified particulates revealed a change in agglomerate morphology for the different particle size classes.…”

Section: Chemical Composition Analysis By An Energy Dispersive Spectrmentioning

confidence: 51%

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: Chemical Composition Analysis By An Energy Dispersive Spectrmentioning

confidence: 51%

Enabling Efficient Heat Recovery from Aluminium Pot Gas

Clos

Andresen

Nekså

et al. 2017

The Minerals, Metals &Amp; Materials Series

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“…The electron microscopy approach to determine the particle distribution substantially underestimates the particle concentrations in the size range below 300 nm as shown elsewhere [13]. Compared to electron microscopy data published by Höflich [9], a significant higher number of smaller particles than 0.5 µm are observed with the present impactor method, making the method well suited for extracting on-line information on the state of the particulates in the off-gas from the cell and in the potroom air.…”

Section: Introductionmentioning

confidence: 55%

“… Vaporization of electrolyte and subsequent condensation as fine particles  Mechanical entrainment of liquid electrolyte or fines from crust cover material  HF generation due to reaction of electrolyte with hydrogen from the anodes, vapour or particulates with moisture from air and/or alumina Based on models assuming that particulates are mainly condensation and hydrolysis products from evaporated NaAlF 4 , according to Equation 1, different reactions are considered [9,10,11]. The gaseous NaAlF 4 may disproportionate to solid chiolite, Na 5 Al 3 F 14 , and AlF 3 according to Equation 2 and/or undergo hydrolysis as described in Equation 3.…”

Section: Introductionmentioning

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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“…The physisorbed moisture, called the moisture content of SGA, can be easily removed by drying at 110 • C for 24 h, and is usually quantitatively described with the value of moisture on ignition (MOI 25-300) between 25 • C and 300 • C. The physisorbed moisture influences the industrial aluminum electrolysis process in several respects. The SGA moisture is introduced to the molten fluoride electrolyte through alumina feeding and causes fluoride hydrolysis, contributing to nearly 10-25% of the total HF emission in the original cell fume [3,4]. Most of the physisorbed moisture is flashed off before reaching the high-temperature melt surface, increasing the relative humidity (RH) of the cell exhaust gas.…”

Section: Introductionmentioning

confidence: 99%

The Adsorption Behavior of Moisture on Smelter Grade Alumina during Transportation and Storage—for Primary Aluminum Production

Yang

Tao

Liu

et al. 2020

Metals

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Smelter grade alumina (SGA) plays multiple roles in the Hall–Héroult process for primary aluminum production. Given its very porous nature, one major role of SGA is to adsorb toxic hydrogen fluoride (HF) in the dry scrubber. However, also because of its porous nature, SGA inevitably adsorbs ambient moisture. This paper discusses the influence of alumina properties, including pore size distribution and specific surface area, on the physical adsorption of water vapor on SGA, as well as the adsorption kinetics. The result shows that the adsorption enthalpy of moisture on SGA is in the range of 4–13 kJ/mol. The adsorption capacity increases significantly with the particle specific surface area and total pore volume. A higher adsorption temperature indicates a much faster adsorption rate but corresponds to a lower equilibrium adsorption capacity.

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Mathematical Model of Fluoride Evolution from Hall‐Héroult Cells

Cited by 5 publications

References 4 publications

Enabling Efficient Heat Recovery from Aluminium Pot Gas

Enabling Efficient Heat Recovery from Aluminium Pot Gas

Particulate Emissions from Electrolysis Cells

The Adsorption Behavior of Moisture on Smelter Grade Alumina during Transportation and Storage—for Primary Aluminum Production

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