Effect of fine coke particles on rheological properties of the binder matrix of carbon anodes in aluminium production process

Mollaabbasi, Roozbeh; Hansen, Lene Jensberg; Grande, Tor; Taghavi, Seyed Mohammad; Alamdari, Houshang

doi:10.1002/cjce.24108

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“…The study of how cracks are generated in the anode and the parameters affecting it, both experimentally and numerically, has limitations. The dependence of the properties of the anode materials on temperature and the need to keep the temperature constant during the compaction process [ 8 ], as well as the opacity of the anode components [ 9 ], make the experimental study of anode paste quite challenging. In addition, numerical methods based on continuum mechanics, such as finite element methods, suffer from the lack of constitutive equations that are capable of modeling the granular behavior of anode paste [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Particle Size Distributions and Shapes on the Failure Behavior of Dry Coke Aggregates

Sadeghi-Chahardeh

Mollaabbasi

Picard³

et al. 2021

Materials

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Carbon anodes participate in chemical reactions to reduce alumina in the Hall–Héroult process, of which coke aggregates make up a major part. The failure analysis of coke aggregates not only leads to a better understanding of the deformation mechanisms of anode paste under compressive loading but also can identify potential causes of structural defects in carbon anodes, such as horizontal cracks. The coke aggregates are composed of particles with different size distributions and shapes, which may strongly affect the failure behavior of the anode during compaction. In this paper, the effects of particle size distributions and shapes on the mechanical behavior and the failure of coke aggregates are investigated using the discrete element method modeling technique. The numerical results reveal that, although the mechanical behavior of coke mixtures is generally dependent on larger particles, the presence of fine particles in the coke aggregates reduces fluctuations in the stress–strain diagram. In addition, the rolling resistance model is employed as a parameter representing the effect of particle shape. It is shown that the rolling resistance model can be an alternative to the overlapped spheres model, which has a higher computational cost than the rolling resistance model. The second-order work criterion is used to evaluate the stability of the coke aggregates, the results of which indicate that the addition of fine particles as well as increasing the rolling resistance between the particles increases the stability range of the coke aggregates. Moreover, by using the analysis of micro-strain contour evaluations during the compaction process, it is shown that, both by adding fine particles to the coke mixture and by increasing the rolling resistance between the particles, the possibility of creating a compression band in the coke aggregates is reduced. Since the presence of the compaction bands in the anode paste creates an area prone to horizontal crack generations, the results of this study could lead to the production of carbon anodes with fewer structural defects.

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Section: Introductionmentioning

confidence: 99%