The Experts below are selected from a list of 3129 Experts worldwide ranked by ideXlab platform
Barry J Welch - One of the best experts on this subject based on the ideXlab platform.
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Individual Anode current monitoring during aluminum reduction cell power reduction
2021Co-Authors: Yuchen Yao, Barry J Welch, Jie Bao, Maria Skyllaskazacos, Ali JassimAbstract:In this work, an Individual Anode current measurement system is installed to monitor the aluminum smelting process in a case study involving power reduction and restoration. In this study, Anode current signals, together with the line current and cell voltage, were obtained at a high sampling rate to ensure the dynamic features in the process are captured. It is observed that the cell exhibits “battery” behaviors on stopping the electrolysis process due to the Anodes having surface intermediates that have not been transformed into the final gaseous products. It is also found that the currents carried by Anodes after the experiment are different from the ones before due to the changed hydrodynamic forces. The analysis results provide more fundamental understandings of the aluminum reduction process and can aid the cell operations such as power modulation.
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fault detection and diagnosis of alumina feeding system using Individual Anode current measurement
2020Co-Authors: Yuchen Yao, Barry J Welch, Jie Bao, Maria Skyllaskazacos, Ali JassimAbstract:With the growth in sizes of the Hall-Heroult cells, the detection and diagnosis of faults in the Hall-Heroult process is becoming more difficult, as the information from the cell resistance, which is obtained from the line current and cell voltage, only indicates overall conditions of the cell. In order to achieve improved process efficiency, the measurement of Individual Anode current has been studied extensively in recent years. Unlike conventionally measured line current and cell voltage, Individual Anode currents provide information about the localized cell conditions. This paper presents a method to detect faults in the alumina feeding system in the Hall-Heroult cells from Individual Anode current measurement. It involves the dynamic estimation of the feeding system operating conditions by incorporating a mass balance model, without using physical sensors attached to the feeders. This method is shown to be effective in observing feeder failure, evaluating the seriousness of the fault and identifying failed feeder location.
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multivariable feeding control of aluminum reduction process using Individual Anode current measurement
IFAC-PapersOnLine, 2020Co-Authors: Jing Shi, Jie Bao, Yuchen Yao, Maria Skyllaskazacos, Barry J WelchAbstract:Abstract In the Hall-Heroult process, the alumina concentration and its distribution play an important role in determining the process efficiency, but it is difficult and costly to measure the concentration regularly. The recent advances in Individual Anode current measurement provide the possibilities to develop better control strategies and algorithms for alumina concentration. This paper presents a multivariable feeding control method, aiming to achieve a uniform distribution of alumina concentration, and hence improve cell operation. Also, the Extended Kalman Filter (EKF) is used to estimate the localized alumina concentration. The simulation results show that the proposed control strategy can significantly reduce the variations in alumina concentration compared to the traditional control method.
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fault detection and diagnosis in hall heroult cells based on Individual Anode current measurements using dynamic kernel pca
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2018Co-Authors: Yuchen Yao, Barry J Welch, Jie Bao, Maria Skyllaskazacos, Sergey AkhmetovAbstract:Individual Anode current signals in aluminum reduction cells provide localized cell conditions in the vicinity of each Anode, which contain more information than the conventionally measured cell voltage and line current. One common use of this measurement is to identify process faults that can cause significant changes in the Anode current signals. While this method is simple and direct, it ignores the interactions between Anode currents and other important process variables. This paper presents an approach that applies multivariate statistical analysis techniques to Individual Anode currents and other process operating data, for the detection and diagnosis of local process abnormalities in aluminum reduction cells. Specifically, since the Hall–Heroult process is time-varying with its process variables dynamically and nonlinearly correlated, dynamic kernel principal component analysis with moving windows is used. The cell is discretized into a number of subsystems, with each subsystem representing one Anode and cell conditions in its vicinity. The fault associated with each subsystem is identified based on multivariate statistical control charts. The results show that the proposed approach is able to not only effectively pinpoint the problematic areas in the cell, but also assess the effect of the fault on different parts of the cell.
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estimation of spatial alumina concentration in an aluminum reduction cell using a multilevel state observer
Aiche Journal, 2017Co-Authors: Cheukyi Cheung, Barry J Welch, Maria Skyllaskazacos, Sergey AkhmetovAbstract:In the Hall-Heroult process, spatial variations in alumina concentration are very difficult to measure and impossible to estimate from the conventionally monitored line amperage and cell voltage. This paper presents an approach to estimate in real time the alumina concentration distribution in an aluminum reduction cell based on Individual Anode current measurements. One of the key difficulties is that the localized mass transfer rates are unknown. To overcome this issue, a multi-level state observer is developed based on the robust extended Kalman filter. The approach utilizes a dynamic model of a reduction cell that is discretized subsequently level by level, where the estimated variables at each level are used to estimate more detailed alumina concentration spatial distribution at the next level. The proposed approach is validated in an experimental study using an industrial cell. This article is protected by copyright. All rights reserved.
Charles-luc Lagacé - One of the best experts on this subject based on the ideXlab platform.
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preventive treatment of Anode effects using on line Individual Anode current monitoring
2017Co-Authors: Lukas Dion, Charles-luc Lagacé, László I. Kiss, Francois Laflamme, Antoine Godefroy, James Evans, Sandor PoncsakAbstract:Anode effects (AE) are considered a nuisance for aluminium production due to the numerous negative impacts that they generate in an electrolysis cell. Previously, great efforts have been deployed to minimize the occurrence of this event. Using online Anode current monitoring, Alouette introduced an algorithm to detect abnormalities prior to an AE, allowing sufficient time to apply a corrective action before its occurrence. Several sets of strategies were tested to evaluate the best approach to correct the situation without generating additional problems in the cells. Finally, Individual Anode currents measurements were connected to the cell control system of two pots to automatically launch preventive treatment of AE. A decrease in the total number of Anode effects along with an increased cell stability is noticeable. Other indicators, such as anodic incidents, alumina dosage and metal purity were also compared to make sure that no deterioration in the cell conditions occurred over time.
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Quantification of perfluorocarbons emissions during high voltage Anode effects using non-linear approach
Journal of Cleaner Production, 2017Co-Authors: Lukas Dion, László I. Kiss, Sandor Poncsak, Jerry Marks, Charles-luc LagacéAbstract:Abstract Significant amounts of greenhouses gases are produced annually by aluminium smelters around the globe. Most of these emissions are carbon dioxide but perfluorocarbons are nonetheless an essential part of GHG inventories for aluminium smelters. The total mass of perfluorocarbons declared is estimated using a linear relationship between some process parameters and a specific emission coefficient. However, this linear method does not accurately represent the observed behaviour of PFC emissions. Continuous gas measurements were performed using a Fourier-transformed infrared spectrometer connected to the gas treatment centre for several days. With the data collected from Individual high voltage Anode effects, four new models are proposed to estimate the emissions of tetrafluoromethane, along with three new models to estimate hexafluoroethane emissions. These non-linear models are compared to the existing methods and the overall accuracy of each model is calculated in comparison to in-situ measurements. The accuracy of each model to predict emissions associated to Individual Anode effects have been investigated as well and the results indicate that tetrafluoromethane emissions can be more accurately predicted by the proposed non-linear models. Models proposed to predict hexafluoroethane emissions are optimistic, but further refinements are necessary to optimise the accuracy of Individual predictions.
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recent on line measurements of Individual Anode currents atalouette
2016Co-Authors: James W Evens, Lukas Dion, Francois Laflamme, Charles-luc LagacéAbstract:Since early 2014, Alouette has used a system provided by Wireless Industrial Technologies (WIT) to measure Individual Anode currents on two pots. The system works by measuring the adjacent magnetic field generated by the current for each Anode hanger. This paper summarizes initial difficulties and how they have been overcome. Recent current measurements show good agreement with alternative methods for measuring currents (e.g. mV drop along Anode hangers). An algorithm has been developed for discerning an imminent Anode effect from changes in the measured magnetic fields due to changes in Anode currents. Practical reductions of Anode effect frequency, compared to cells of reference, have been achieved by using the results of this algorithm to trigger corrective action through the pot control computer. Some additional potential benefits of Anode current measurement are described in the paper.
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Prediction of Low-Voltage Tetrafluoromethane Emissions Based on the Operating Conditions of an Aluminium Electrolysis Cell
JOM, 2016Co-Authors: Lukas Dion, László I. Kiss, Sandor Poncsak, Charles-luc LagacéAbstract: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 CO2 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 (CF4) 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 CF4. 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 CF4 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 CF4 in the output gas of an electrolysis cell.
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on line monitoring of Individual Anode currents to understand and improve the process control at alouette
Light Metals, 2015Co-Authors: Lukas Dion, Charles-luc Lagacé, James W Evans, Ron Victor, László I. KissAbstract:In 2014, Alouette acquired a system to monitor the on-line Anode current on two pots. This system, developed and supplied by WIT, reports all Anodes current and the pot voltage for every second of operation. The following paper describes some of the resulting improvements that apply to the process control of the aluminum electrolysis cell.
Sergey Akhmetov - One of the best experts on this subject based on the ideXlab platform.
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fault detection and diagnosis in hall heroult cells based on Individual Anode current measurements using dynamic kernel pca
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2018Co-Authors: Yuchen Yao, Barry J Welch, Jie Bao, Maria Skyllaskazacos, Sergey AkhmetovAbstract:Individual Anode current signals in aluminum reduction cells provide localized cell conditions in the vicinity of each Anode, which contain more information than the conventionally measured cell voltage and line current. One common use of this measurement is to identify process faults that can cause significant changes in the Anode current signals. While this method is simple and direct, it ignores the interactions between Anode currents and other important process variables. This paper presents an approach that applies multivariate statistical analysis techniques to Individual Anode currents and other process operating data, for the detection and diagnosis of local process abnormalities in aluminum reduction cells. Specifically, since the Hall–Heroult process is time-varying with its process variables dynamically and nonlinearly correlated, dynamic kernel principal component analysis with moving windows is used. The cell is discretized into a number of subsystems, with each subsystem representing one Anode and cell conditions in its vicinity. The fault associated with each subsystem is identified based on multivariate statistical control charts. The results show that the proposed approach is able to not only effectively pinpoint the problematic areas in the cell, but also assess the effect of the fault on different parts of the cell.
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estimation of spatial alumina concentration in an aluminum reduction cell using a multilevel state observer
Aiche Journal, 2017Co-Authors: Cheukyi Cheung, Barry J Welch, Maria Skyllaskazacos, Sergey AkhmetovAbstract:In the Hall-Heroult process, spatial variations in alumina concentration are very difficult to measure and impossible to estimate from the conventionally monitored line amperage and cell voltage. This paper presents an approach to estimate in real time the alumina concentration distribution in an aluminum reduction cell based on Individual Anode current measurements. One of the key difficulties is that the localized mass transfer rates are unknown. To overcome this issue, a multi-level state observer is developed based on the robust extended Kalman filter. The approach utilizes a dynamic model of a reduction cell that is discretized subsequently level by level, where the estimated variables at each level are used to estimate more detailed alumina concentration spatial distribution at the next level. The proposed approach is validated in an experimental study using an industrial cell. This article is protected by copyright. All rights reserved.
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detection of local cell conditions based on Individual Anode current measurements
Light Metals, 2016Co-Authors: Yuchen Yao, Barry J Welch, Cheukyi Cheung, Jie Bao, Maria Skyllaskazacos, Sergey AkhmetovAbstract:The application of Individual Anode current measurements in the Hall-Heroult cells has been investigated to aid cell monitoring, in addition to the conventional use of cell voltage measurements. Its advantages are significant, especially in high amperage cells, where information from the voltage signal is heavily diluted. One common use of Individual Anode current measurements is to identify process faults that can cause a significant change in the local current flow paths between Anode busbar and the metal pad. While this detection is simple and direct, there are other consequential changes in cell conditions that impact the current distribution in the vicinity of a problem Anode. This paper presents a Moving Window Kernel PCA-based method to extract spatial information from the Individual Anode current signals by incorporating other known process variables.
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studies on Anode pre heating using Individual Anode signals in hall heroult reduction cells
2016Co-Authors: Ali Jassim, Barry J Welch, Jie Bao, Maria Skyllaskazacos, Sergey Akhmetov, Yuchen YaoAbstract:The proportional increase in modern cells’ amperage and Anode size while aiming for low energy input has resulted in slowing the process of Anode current pick-up rate. Changes in cell thermal and electrical balance due to Anode replacement (while a thick layer of frozen electrolyte is formed under a new Anode) causes a slower Anode current pick-up rate which may require 4 days to reach the target current. Variations in cell conditions following Anode replacement result in increasing cell magnetohydrodynamic instability and prolonged presence of low superheat zones. This increases the possibility of forming local abnormalities, such as Anode spikes. As part of a continuous enhancement programme, the latest developed Individual Anode current monitoring system in DUBAL (EGA Jebel Ali) was used to study the benefits of preheating Anodes up to 500 °C. The work includes studying the impact of Anode pre-heating on current pick-up rate while conducting operations such as Anode dressing.
Lukas Dion - One of the best experts on this subject based on the ideXlab platform.
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preventive treatment of Anode effects using on line Individual Anode current monitoring
2017Co-Authors: Lukas Dion, Charles-luc Lagacé, László I. Kiss, Francois Laflamme, Antoine Godefroy, James Evans, Sandor PoncsakAbstract:Anode effects (AE) are considered a nuisance for aluminium production due to the numerous negative impacts that they generate in an electrolysis cell. Previously, great efforts have been deployed to minimize the occurrence of this event. Using online Anode current monitoring, Alouette introduced an algorithm to detect abnormalities prior to an AE, allowing sufficient time to apply a corrective action before its occurrence. Several sets of strategies were tested to evaluate the best approach to correct the situation without generating additional problems in the cells. Finally, Individual Anode currents measurements were connected to the cell control system of two pots to automatically launch preventive treatment of AE. A decrease in the total number of Anode effects along with an increased cell stability is noticeable. Other indicators, such as anodic incidents, alumina dosage and metal purity were also compared to make sure that no deterioration in the cell conditions occurred over time.
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Quantification of perfluorocarbons emissions during high voltage Anode effects using non-linear approach
Journal of Cleaner Production, 2017Co-Authors: Lukas Dion, László I. Kiss, Sandor Poncsak, Jerry Marks, Charles-luc LagacéAbstract:Abstract Significant amounts of greenhouses gases are produced annually by aluminium smelters around the globe. Most of these emissions are carbon dioxide but perfluorocarbons are nonetheless an essential part of GHG inventories for aluminium smelters. The total mass of perfluorocarbons declared is estimated using a linear relationship between some process parameters and a specific emission coefficient. However, this linear method does not accurately represent the observed behaviour of PFC emissions. Continuous gas measurements were performed using a Fourier-transformed infrared spectrometer connected to the gas treatment centre for several days. With the data collected from Individual high voltage Anode effects, four new models are proposed to estimate the emissions of tetrafluoromethane, along with three new models to estimate hexafluoroethane emissions. These non-linear models are compared to the existing methods and the overall accuracy of each model is calculated in comparison to in-situ measurements. The accuracy of each model to predict emissions associated to Individual Anode effects have been investigated as well and the results indicate that tetrafluoromethane emissions can be more accurately predicted by the proposed non-linear models. Models proposed to predict hexafluoroethane emissions are optimistic, but further refinements are necessary to optimise the accuracy of Individual predictions.
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recent on line measurements of Individual Anode currents atalouette
2016Co-Authors: James W Evens, Lukas Dion, Francois Laflamme, Charles-luc LagacéAbstract:Since early 2014, Alouette has used a system provided by Wireless Industrial Technologies (WIT) to measure Individual Anode currents on two pots. The system works by measuring the adjacent magnetic field generated by the current for each Anode hanger. This paper summarizes initial difficulties and how they have been overcome. Recent current measurements show good agreement with alternative methods for measuring currents (e.g. mV drop along Anode hangers). An algorithm has been developed for discerning an imminent Anode effect from changes in the measured magnetic fields due to changes in Anode currents. Practical reductions of Anode effect frequency, compared to cells of reference, have been achieved by using the results of this algorithm to trigger corrective action through the pot control computer. Some additional potential benefits of Anode current measurement are described in the paper.
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Prediction of Low-Voltage Tetrafluoromethane Emissions Based on the Operating Conditions of an Aluminium Electrolysis Cell
JOM, 2016Co-Authors: Lukas Dion, László I. Kiss, Sandor Poncsak, Charles-luc LagacéAbstract: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 CO2 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 (CF4) 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 CF4. 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 CF4 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 CF4 in the output gas of an electrolysis cell.
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on line monitoring of Individual Anode currents to understand and improve the process control at alouette
Light Metals, 2015Co-Authors: Lukas Dion, Charles-luc Lagacé, James W Evans, Ron Victor, László I. KissAbstract:In 2014, Alouette acquired a system to monitor the on-line Anode current on two pots. This system, developed and supplied by WIT, reports all Anodes current and the pot voltage for every second of operation. The following paper describes some of the resulting improvements that apply to the process control of the aluminum electrolysis cell.
Cheukyi Cheung - One of the best experts on this subject based on the ideXlab platform.
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estimation of spatial alumina concentration in an aluminum reduction cell using a multilevel state observer
Aiche Journal, 2017Co-Authors: Cheukyi Cheung, Barry J Welch, Maria Skyllaskazacos, Sergey AkhmetovAbstract:In the Hall-Heroult process, spatial variations in alumina concentration are very difficult to measure and impossible to estimate from the conventionally monitored line amperage and cell voltage. This paper presents an approach to estimate in real time the alumina concentration distribution in an aluminum reduction cell based on Individual Anode current measurements. One of the key difficulties is that the localized mass transfer rates are unknown. To overcome this issue, a multi-level state observer is developed based on the robust extended Kalman filter. The approach utilizes a dynamic model of a reduction cell that is discretized subsequently level by level, where the estimated variables at each level are used to estimate more detailed alumina concentration spatial distribution at the next level. The proposed approach is validated in an experimental study using an industrial cell. This article is protected by copyright. All rights reserved.
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detection of local cell conditions based on Individual Anode current measurements
Light Metals, 2016Co-Authors: Yuchen Yao, Barry J Welch, Cheukyi Cheung, Jie Bao, Maria Skyllaskazacos, Sergey AkhmetovAbstract:The application of Individual Anode current measurements in the Hall-Heroult cells has been investigated to aid cell monitoring, in addition to the conventional use of cell voltage measurements. Its advantages are significant, especially in high amperage cells, where information from the voltage signal is heavily diluted. One common use of Individual Anode current measurements is to identify process faults that can cause a significant change in the local current flow paths between Anode busbar and the metal pad. While this detection is simple and direct, there are other consequential changes in cell conditions that impact the current distribution in the vicinity of a problem Anode. This paper presents a Moving Window Kernel PCA-based method to extract spatial information from the Individual Anode current signals by incorporating other known process variables.
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Characterization of Individual Anode Current Signals in Aluminum Reduction Cells
Industrial & Engineering Chemistry Research, 2013Co-Authors: Cheukyi Cheung, Jie Bao, Chris Menictas, Maria Skyllas-kazacos, Barry J WelchAbstract:Differing from cell voltage and line current, Anode current signals can provide an insight into the localized anodic dynamic behavior in an operating Hall–Heroult reduction cell, and can be used as an alternative in-depth method to study the process in the hostile industrial potline environment. This work involves further investigations on changes in the frequency response of Anode current signals (such as peaks and magnitudes) with Anode age and anodic reactions. Furthermore, two process abnormalities, Anode effect and Anode slippage, are studied. This study demonstrates that Anode current signals provide an earlier indication of an approaching Anode effect than the conventional cell voltage measurements. Frequency domain analysis has been found to be an additional identifier, in separating Anode effects from other abnormalities, that can also cause Anode current redistribution.
