Encyclopedie de la recherche sur l'aluminium au Quebec - Edition 2014 | Page 43

Modeling PRODUCTION DE L’ALUMINIUM // ALUMINIUM PRODUCTION The Electrical Resistivity Of Anode 41 Modélisation de la résistivité MODÉLISATION électrique de l'anode DE LA RÉSISTIVITÉ ÉLECTRIQUE DE L'ANODE MODELING THE ELECTRICAL RESISTIVITY OF ANODE S.Yousefi1, H. Alamdari1 1Department of Mining, Metallurgy and Materials Engineering, 1065 Médecine avenue Université Laval, Québec, QC, G1V 0A6, Canada Anode surface image Problematic Anode performance is negatively affected by high electrical resistivity. The lower the current can pass through the anode by the means of higher electrical resistivity, the higher the energy would be lost. Considering the real image of anode surface, different phases can be distinguished; coke particles, binder matrix and porosity. The effective conductivity may be influenced not only by porosity, but also by the size (size distribution) and shape (shape distribution) of the pores as well as the other phases. Therefore, it is essential to understand the conduction mechanism of anode and to reveal the effect of anode microstructure on its electrical resistivity. A model, relating the microstructure of anode to its electrical resistivity may allow further improvement of anode recipe in order to decrease its resistivity. In addition, such a model could be used to characterize the microstructure of an anode using non-destructive electrical measurements. Coke particles Binder matrix Objective Modeling the electrical resistivity of anode with regards to electrical resistivity behavior of each phase; coke particles, binder matrix and porosities. Literature Samoue¨ lian et. al. [1] tried to find out the information about the presence, position, orientation and extension of cracks from the analysis of apparent resistivity obtained by a three-dimensional electrical survey. There are also destructive and non-destructive methods proposed in the literature in order to characterize the electrical resistivity of porous media such as soil. Serial sections, X-ray tomography (XRT) and electrical resistivity tomography (ERT) are three techniques that can be used to obtain a 3D description of multi phase media [2]. Séger et. al. [3] compared the photograph pixel values for each colour with the 2D electrical resistivity values of the 2D planes that were extracted by 3D inversion for the three levels. They tried to describe the 3D structure of a heterogeneous material using 3D electrical resistivity tomography (ERT). Yunus et. al. [4] applied dual-modality tomographyhas, a combination of ultrasonic transmission tomography (UTT) and electrical resistance tomography (ERT) for imaging two-phase, to improve the situation of potential distribution and current density in the medium of interest. Binary image of the top surface of the block showing the cracking network pattern after desiccation at the end of the experiment [1]. Potential distribution at xy-plane and yzplane obtained from ERT and UTT[4]. Hypothesis The hypothesis is to consider the anode, which is a multiple phase media, as a network of resistivities. Each one of the three phases in anode represents its own resistance in this network. X and Y are presenting the resistivities of coke particles and binder matrix, respectively while, Z stands for the resistivity of porosities, which tends to infinity. CT image of the anode core Resistance network in HSpice Somaiieh Yousefi Houshang Alamdari Département de génie des mines, de la métallurgie et des matériaux, Université Laval Methodology The 3-dimentional structural information of anode will be obtained from computed tomography (CT). CT data are the 3D images of consecutive cross sections of anode which produce a matrix of data in the form of intensities, each intensity being related to a specific voxel. The intensity is influenced by the attenuation coefficient of each phase, thus indicating the nature, to some extent, and the density of the region where the voxel is located. These voxels may thus be represent