Mass spectrometric examination of anode gases from aluminum reduction cells

Henry, Jack L.; Holliday, R. D.

doi:10.1007/bf03398322

Cited by 14 publications

(8 citation statements)

References 2 publications

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“…Electrolytic aluminum production is known to entail emissions of CF4 and C2F6 (45). Formation of TFA or trifluoroacetyl fluoride was also considered possible, but analysis of a stackgas sample of an aluminum production site did not reveal any TFA.…”

Section: Discussionmentioning

confidence: 99%

Trifluoroacetate in the Environment. Evidence for Sources Other Than HFC/HCFCs

Jordan

Frank

1999

Environ. Sci. Technol.

129

119

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The partly halogenated C2-hydro(chloro)fluorocarbons (HFC, HCFC) 1,1,1-trifluoro-2,2-dichloroethane (HCFC-123), 1,1,1,2-tetrafluoro-2-chloroethane (HCFC-124), and 1,1,1,2-tetrafluoroethane (HFC-134a) are CFC substitutes found at increasing levels in the atmosphere. Trifluoroacetate (TFA) is an atmospheric degradation product of these compounds and due to its perstistence its potential accumulation in some aquatic ecosystems is a matter of environmental concern. The present study was undertaken to determine the present-days base level of environmental TFA and whether model calculations are in line with the actual data. Average levels of about 120 ng L-1 as predicted for the year 2010 are found in rain in Germany already now, slightly higher than in rain collected in Switzerland or Nevada. In the major rivers in Germany, TFA is present at average concentrations of 140 ng L-1. In air, levels of 45−60 pg m-3 have been found in Central Europe. Between March 1995 and September 1996, a period of substantial increase in atmospheric HFC-134a mixing ratio, the TFA concentrations in air and precipitation did not significantly increase. TFA is absent in old groundwater samples, and in river water from remote locations, concentrations are low. These data suggest that the total TFA in both compartments exceeds the formation potential of currently known sources, that TFA in atmosphere and rain is regionally associated with industrial or population density, and that other unresolved sources must contribute to the present concentrations.

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Section: Discussionmentioning

confidence: 99%

Trifluoroacetate in the Environment. Evidence for Sources Other Than HFC/HCFCs

Jordan

Frank

1999

Environ. Sci. Technol.

129

119

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“…Small amounts of other gases have been found in reduction cell gas but not in sufficient amount to affect the results presented here significantly. Hydrogen, hydrogen sulfide, and carbonyl sulfide have been found in concentrations of a few tenths of a per cent or less (3). Formation of fluorocarbons appears to be limited to periods of anode effect (3).…”

Section: Discussionmentioning

confidence: 99%

“…[2] and y Eq. [3]. (Note: y is the net number of CO~'s lost, i.e., y = Yl--Y~ since the reaction is reversible.)…”

Section: Journal Of the Electrochemical Societymentioning

confidence: 99%

The Relation of Gas Composition to Current Efficiency in an Aluminum Reduction Cell

Beck

1959

J. Electrochem. Soc.

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Experience with a 10,000-amp aluminum reduction cell indicates that the previously accepted equation relating current efficiency and cell gas CO~ concentration is an oversimplification. A modified equation, % CE ~ g[50 -t-u (% COs) ] --Z, fits the data more satisfactorily. The new terms, g and Z, respectively, account for: (a) less than 100% initial COs and/or reaction of CO~ with carbon, and (b) a certain percentage of current inefficiency by oxidation or loss of some cathode products without involvement of CO2. The experiments showed g to be somewhat larger than unity and to vary with the bake temperature of the anodes and Z to be somewhat larger than 3.5%.This paper describes work done on a 10,000-amp experimental aluminum reduction cell. The cell was established for studying process variables that could not be studied satisfactorily in any other way. It was of such a size that results could be scaled up to apply directly to the present commercial cells. Although it was only 1/6 to 1/10 the size of present commercial cells, it was comparable in size to the commercial cells of three decades ago (1). Because it was operated as an independent unit with its own power supply and was not tied to a production schedule, experiments and measurements could be made and an accuracy obtained that would be virtually impossible to attain under plant conditions. Significantly smaller self-sustaining cells operating at commercial current densities are difficult to operate because of proportionately higher heat losses for their greater surfaceto-volume ratio. Scale-up from still smaller externally heated bench scale cells to full scale plant cells is open to question.In construction and dimensions it was equivalent to placing the two ends of a commercial prebakedanode cell together after removing the center section. Dimensions of the cavity were approximately 43 in. x 65 in. cross section by 14 in. deep. Plant anodes and superstructure hardware were used. Anode dimensions were 151/2 in. x 19V2 in. cross section by 12 in. high.Early in the program a test was made to evaluate the effect of anode-bake temperature on carbon consumption. Routine cell gas analyses for CO2 and CO were made in order to determine what fraction of the carbon consumption could be attributed to the electrochemical reaction. Correlation of these gas analysis data with current efficiency was the basis for this paper.

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“…There have producible results were obtained for CF4 measurements, with been conflicting reports as to whether other sources are re-virtually no risk of contamination. A ¬-inch OD, 3-foot glass quired to account for the observed atmospheric concentra-column packed with 70-140 mesh Woeira Alumina GSC-120 tions [Henry and Holiday, 1957;$omiya and Konishi, 1971]. was used to separate the compounds of interest.…”

Section: Introduction 2 Experimentalmentioning

confidence: 99%

Atmospheric measurements of CF₄ and other fluorocarbons containing the CF₃ grouping

Penkett¹,

Prosser²,

Rasmussen³

et al. 1981

J. Geophys. Res.

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Careful measurements by GC/MS techniques on atmospheric carbon tetrafluoride confirm that itsconcentration in 1979 was constant at about 69.9 pptv (standard deviation is 7.2 pptv). It is almost certainly produced entirely by emissions from the aluminium industry. Other compounds in the atmosphere containing the CF3 group have been identified by GC/MS as C2F6, CF3CI, CF3Br, and C2FsCI. The concentrations of the first pair are about 4 pptv, and the latter two are about 0.7 pptv and 4 pptv, respectively. The C:F6 is produced simultaneously with CF4 in the manufacture of aluminium. CF3C1, CF3Br, and CeFsCI are probably produced by the chemical industry. The environmental importance of these compounds is discussed in the context of two papers on CF4 recently published by Cicerone (1979) and by Wang ½t al. (1980). power of the GC/MS combination to detect, identify, and strip chart recorder. quantify the concentration of low-level trace gases in the at-Because of the low boiling points of many of the commosphere. Information is also presented concerning the pos-pounds being measured and the likelihood of evaporation sible sources of these compounds.during the concentration procedure, the cryotrap efficiencies for CF4, C:F6, and CF3C1 were measured using standards. In

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Mass spectrometric examination of anode gases from aluminum reduction cells

Cited by 14 publications

References 2 publications

Trifluoroacetate in the Environment. Evidence for Sources Other Than HFC/HCFCs

Trifluoroacetate in the Environment. Evidence for Sources Other Than HFC/HCFCs

The Relation of Gas Composition to Current Efficiency in an Aluminum Reduction Cell

Atmospheric measurements of CF₄ and other fluorocarbons containing the CF₃ grouping

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Mass spectrometric examination of anode gases from aluminum reduction cells

Cited by 14 publications

References 2 publications

Trifluoroacetate in the Environment. Evidence for Sources Other Than HFC/HCFCs

Trifluoroacetate in the Environment. Evidence for Sources Other Than HFC/HCFCs

The Relation of Gas Composition to Current Efficiency in an Aluminum Reduction Cell

Atmospheric measurements of CF4 and other fluorocarbons containing the CF3 grouping

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Atmospheric measurements of CF₄ and other fluorocarbons containing the CF₃ grouping