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Bhattacharyay D.,University of Quebec at Chicoutimi | Kocaefe D.,University of Quebec at Chicoutimi | Kocaefe Y.,University of Quebec at Chicoutimi | Morais B.,Aluminerie Alouette Inc.
Neural Computing and Applications | Year: 2015

Carbon anode is one of the key components for the electrolytic production of aluminum. It is mainly composed of calcined petroleum coke, coal tar pitch, and recycled carbon materials. The impurities in the raw materials, which are mainly by-products of different industries, influence significantly the quality of anodes. Usually, no well-known mathematical relationship exists between the various physical and chemical properties of raw materials and the final anode properties. In such situations, the artificial neural network (ANN) methods can serve as a useful tool to predict anode properties. In this study, published data have been used to show the proficiency of different artificial neural networks using the MATLAB software. The average error between the predicted and experimental values is around 6 %. The artificial neural network was also used to identify the effect of impurities such as, vanadium, iron, sodium, and sulfur on the CO2 reactivity of anodes. ANN also showed the effect of pitch percentage and coke porosity on the CO2 reactivity of anodes. The effect of CO2 and air reactivities of coke on the CO2 reactivity of anode was also studied. The predictions were found to be in good agreement with the results of other studies in the literature. © 2015 The Natural Computing Applications Forum

Sarkar A.,University of Quebec at Chicoutimi | Kocaefe D.,University of Quebec at Chicoutimi | Kocaefe Y.,University of Quebec at Chicoutimi | Bhattacharyay D.,University of Quebec at Chicoutimi | And 2 more authors.
Energy and Fuels | Year: 2016

Undercalcined coke gained interest as raw material for anodes used in aluminum production since it is reported in the literature that anodes produced with this coke might have lower CO2 reactivity in the electrolytic cell. For any anode-grade coke, it is important to identify a suitable pitch which will bond well with that coke during baking and yield dense anodes. The wettability of petroleum coke by molten pitch indicates the quality of bonding between them and influences the final anode properties. In this study, the effect of coke crystallinity on its wettability by pitch has been studied using the sessile-drop test. Also, the chemical and physical properties of coke and pitch have been studied using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). It was found that the coke physical and chemical properties depend on its calcination temperature and, thereby, greatly affect the wetting properties. The study showed that the wettability of coke by pitch increases with decreasing crystalline length. The presence of porosity, C=C bonds, C=O, COO, and heteroatoms (O and N) are important factors which control the wetting of coke by pitch. © 2016 American Chemical Society.

Desmeules J.-F.,Dynamic Concept | Neron J.B.,Dynamic Concept | Tremblay M.,Aluminerie Alouette Inc.
TMS Light Metals | Year: 2016

In the aluminium electrolysis process, metal is retrieved from the cells using a tapping tube connected to a crucible in which vacuum is made to initiate and maintain molted metal flow. Care must be taken not to contaminate the aluminium with electrolyte during the tapping operation. Continuous improvement of cell performance, including reduction of the metal layer depth, increases the challenges related to the tapping operation. Reduction of the metal flow helps reducing the electrolyte quantity that is tapped, however this increases the duration of the operation and poses scheduling problems. A novel patent pending tapping control method and equipment have been designed and tested in the Alouette smelter, in order to minimize contamination while maintaining or reducing the tapping operation duration. Metal flow control is improved thanks to optimized software. Analysis of the process indicators show that a significant reduction in tapped electrolyte is obtained. The purpose of this paper is not to describe in detail the design and control algorithm of the control unit, which is proprietary, but rather to describe the results on various performance indicators. Some of these results were unexpected and in first appearance, showing downsides to the improved control. Further analysis shows that these apparent downsides are consequences of improved performance. Introduction.

Berends W.,Hatch Ltd. | Haley S.,Hatch Ltd. | Gagnon M.,Aluminerie Alouette Inc.
TMS Light Metals | Year: 2016

Anode assemblies suffer a significant electrical contact resistance across the cast iron to carbon interface that is inversely dependent on contact pressure and area. Industry efforts have incrementally reduced this electrical resistance by increasing stub diameter, changing iron chemistry and by improving the stubhole shape. The additional use of multiple steel conductors to bridge across the cast iron to carbon interface provides a means to further reduce the electrical resistance. The function of the conductors is independent of the iron to carbon contact pressure, the stub temperature, iron chemistry, and the stubhole shape. The steel conductors are tightly driven into the carbon anode at one end, with the other end bonded into the cast iron. This paper includes in-pot performance testing results which demonstrate the reduced resistance when using stubhole conductors. © Copyright 2016 by The Minerals, Metals & Materials Society.

Tremblay S.-O.,University of Quebec at Chicoutimi | Marceau D.,University of Quebec at Chicoutimi | Kocaefe D.,University of Quebec at Chicoutimi | Lagace C.-L.,Aluminerie Alouette Inc.
TMS Light Metals | Year: 2015

The electrical resistance of an electrolytic cell requires a voltage drop of about 4.5 V for a current of 300 kA of which 7% is attributable to the anode assembly. Reducing this voltage drop is one of the most challenging research topics for the aluminum industry. Over the past decades, there has been much research on the minimization of this loss using the same assembly configuration. In this work, a new approach, which consists of inserting elements into the carbon paste during the anode production, was developed. This approach would provide a significant reduction in the voltage drop mainly through the improvement of the contact quality at the anode connection and the current distribution in the anode. Laboratory tests simulating the baking as well as the operation of small-scale assembly were carried out to estimate the resistance. The results demonstrate that it is possible to decrease the resistance at the anode connection under the conditions similar to those used by industry.

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