A Study of Low Voltage PFC Emissions at Dubal

Zarouni, Abdalla; Reverdy, Michel; Zarouni, Ali Al; Venkatasubramaniam, K. G.

doi:10.1007/978-3-319-65136-1_146

Cited by 16 publications

(13 citation statements)

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“…-A strongly renewed focus in recent years with several reports [3,[9][10][11][12][13][14][15]. -The emitted PFC gases are the same as during normal anode effects, namely CF4 and C2F6.…”

Section: The Effect Of Local Alumina Depletionmentioning

confidence: 99%

“…The PFC emission has for a long time been a concern of the aluminium industry, and considerable efforts have been spent on this problem [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. However, one should be aware of "similar" electrolytic processes that apply carbon anodes in fluoride melts may have related problems.…”

Section: Low Voltage Non-propagating Aementioning

confidence: 99%

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Low Voltage PFC Emission from Aluminium Cells

Thonstad¹,

Rolseth²,

Тонстэд³

et al. 2017

J. Sib. Fed. Univ. Chem.

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It is well known that the perfluorocarbon (PFC) gases CF 4 and C 2 F 6 are being emitted during anode effects in aluminium cells. These PFC compounds are very strong greenhouse gases, and the aluminium industry has made great efforts to reduce these emissions. From 1990 to 2008 a 90% reduction in PFC emissions has been achieved. However, during the last few years we have received new alarming information, mainly from the Chinese aluminium industry, that there is an almost continuous emission of PFC gases from aluminium potlines even in the absence of anode effects, and it accounts for 10 to 90%of the total PFC emissions, the median being 70%. They named it "Non-anode effect PFC emissions". This information has later been confirmed from several sources, so it seems to be a universal problem. Ключевые слова: алюминиевый электролизер, анодный эффект, перфторулероды (ПФУ). IntroductionDuring the last 20 years strong efforts have been made in order to reduce the emission of PFC (perfluorocarbon) gases from the aluminium industry. These gases are being emitted during the so-called anode effect, which occurs when the concentration of dissolved alumina in the bath gets too low (< 0.5-2 wt%). The cell voltage then rises abruptly to 15-40 V, and an anode effect is on [1]. In order to extinguish anode effects, alumina is being fed, and the bath is being agitated in various ways, e.g. by inserting wooden poles or by repeatedly raising and lowering the anode beam.The PFC emissions from any given plant are being reported to the national environmental protection agency. It is being calculated by taking the time on anode effect multiplying it by an empirical factor, named "the slope". The units are ton CO 2 eq./ton Al. The time on anode effect is normally recorded as the time -32 -Jomar Thonstad and Sverre Rolseth. Low Voltage PFC Emission from Aluminium Cells above 8 V cell voltage. This data is being recorded due to the fact that the PFC gases, CF 4 and C 2 F 6 , are very potent greenhouse gases, contributing to global warming. CF 4 is 6500 times and C 2 F 6 is 9200 times stronger greenhouse gases than CO 2 . The initiative for this reporting comes from "The United Nations Intergovernmental Panel on Climate Change" (IPCC), and the data are being collected and reported by the International Aluminium Institute (IAI) in London. IAI has reported that the average PFC emissions have been reduced from close to 5 ton CO 2 eq./ton Al in 1990 down to 0.70 in 2010, and a goal of 0.34 in set for [2].This remarkable achievement is the result of impressive efforts made by the aluminium industry over the years by introducing new technology and improved cell control and cell operation. This is really a success story. But is it the whole story?Apparently it is not the whole story. In recent years there have been several reports [2][3][4][5] showing that under certain circumstances, PFC emissions are also being detected during normal operation when there is noongoing anode effect in thepotline. It has been named "non-anode effect PFC emission...

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“…-A strongly renewed focus in recent years with several reports [3,[9][10][11][12][13][14][15]. -The emitted PFC gases are the same as during normal anode effects, namely CF4 and C2F6.…”

Section: The Effect Of Local Alumina Depletionmentioning

confidence: 99%

Section: Low Voltage Non-propagating Aementioning

confidence: 99%

Low Voltage PFC Emission from Aluminium Cells

Thonstad¹,

Rolseth²,

Тонстэд³

et al. 2017

J. Sib. Fed. Univ. Chem.

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show abstract

“…Most authors 5,7,[10][11][12][16][17][18][19] agree that alumina concentration, anode current density and anodic overvoltage have a significant impact on the onset of low-voltage PFC emissions. All of these parameters are interrelated and will dictate if the localised overvoltage eventually exceeds the threshold necessary to generate PFC.…”

Section: State Of the Artmentioning

confidence: 99%

“…PFC emissions are frequently observed up to multiple hours after an anode change. 12,[16][17][18][19] This is due to the redistribution of current towards anodes that increases the current density locally. The nonuniformity of the current distribution can be amplified if the anode-cathode distance is reduced in order to operate with lower energy consumption.…”

Section: State Of the Artmentioning

confidence: 99%

Prediction of Low-Voltage Tetrafluoromethane Emissions Based on the Operating Conditions of an Aluminium Electrolysis Cell

Dion

Kiss

Poncsák

et al. 2016

JOM

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Greenhouse gas (GHG) generation is inherent in the production of aluminium by a technology that uses carbon anodes. Most of those GHG are composed of CO 2 produced by redox reaction that occurs in the cell. However, a significant fraction of the annual GHG production is composed of perfluorocarbons (PFC) resulting from anode effects (AE). Multiple investigations have shown that tetrafluoromethane (CF 4 ) can be generated under low-voltage conditions in the electrolysis cells, without global anode effect. The aim of this paper is to find a quantitative relationship between monitored cell parameters and the emissions of CF 4 . To achieve this goal, a predictive algorithm has been developed using seven cell indicators. These indicators are based on the cell voltage, the noise level and other parameters calculated from individual anode current monitoring. The predictive algorithm is structured into three different steps. The first two steps give qualitative information while the third one quantitatively describes the expected CF 4 concentration at the duct end of the electrolysis cells. Validations after each step are presented and discussed. Finally, a sensitivity analysis was performed to understand the effect of each indicator on the onset of low-voltage PFC emissions. The standard deviation of individual anode currents was found to be the dominant variable. Cell voltage, noise level, and maximum individual anode current also showed a significant correlation with the presence of CF 4 in the output gas of an electrolysis cell.

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“…These transient events are referred to as anode effects (AEs) [3]. Recent reports indicate that in addition to AEs, PFC generation may also occur during normal potroom activities that result in either (1) a localized increase in anode current density or (2) a localized deficiency in alumina concentration; PFCs emitted during these periods not associated with AEs have been referred to as low-voltage PFCs (LV-PFCs) [4][5][6].…”

Section: Speciesmentioning

confidence: 99%

Continuous Emission Monitoring of Tetrafluoromethane Using Quantum Cascade Lasers

et al. 2016

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Recent developments in quantum cascade lasers have enabled the development of new sensors for in-situ applications that have so far only been possible with extractive systems. In this work, a sensor is presented using a unique Wavelength Modulation Spectroscopy approach to measure tetrafluoromethane, a strong greenhouse gas. The sensor was characterized in a laboratory environment indicating a long-term detection limit of 20 ppb·m and a short-term value of well below 10 ppb·m. To demonstrate the feasibility of the sensor in a real-world environment, it was installed at an Alcoa aluminum smelter. A co-located Fourier Transform Infrared Spectrometer allowed direct comparison measurements of both systems. General agreement between the two methods was observed, leading to the conclusion that the developed in-situ quantum cascade laser based sensor has the potential to continuously measure tetrafluoromethane at aluminum smelters.

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A Study of Low Voltage PFC Emissions at Dubal

Cited by 16 publications

References 1 publication

Low Voltage PFC Emission from Aluminium Cells

Low Voltage PFC Emission from Aluminium Cells

Prediction of Low-Voltage Tetrafluoromethane Emissions Based on the Operating Conditions of an Aluminium Electrolysis Cell

Continuous Emission Monitoring of Tetrafluoromethane Using Quantum Cascade Lasers

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