Abstract
The Hall-Héroult process uses prebaked carbon anodes as electrodes. The anode’s quality plays a crucial role in the efficiency of the aluminium production process. During the baking process, the anode undergoes complex physicochemical transformations. Thus, the production of high-quality anodes depends, among others, on the efficient control of their baking process. This paper aims to investigate the evolution of some physical properties of the anode paste mixture during the baking process. These properties include the mass loss fraction, real and apparent densities, the ratio of apparent volume, the permeability, and porosities. For this purpose, experiments consisting of thermogravimetric analysis, dilatometry, air permeability, and helium-pycnometric measurements were carried out. The anode permeability at high temperatures was linked to the air permeability through a permeability correlator due to experimental limitations. Moreover, the real density at high temperatures was estimated by combining real densities of the coal tar pitch and coke aggregates. Different porosities, such as the open porosity and the closed porosity related to the pitch binder, were estimated by taking the permeability at high temperatures into account. In this context, the effect of the permeability correlator, which was introduced to link the permeability at high temperatures to the air permeability, was investigated through a sensitivity analysis. These results allow an estimation of the shrinking index, a new variable introduced to reflect the baking level of the anode mixture, which is linked to the volatile that is released in both open and closed pores. Afterwards, the pore pressure inside closed pores in the coal tar pitch was estimated. The obtained results highlight some new insights related to the baking process of the anode mixture. Moreover, they pave the way for better modeling of the thermo-chemo-mechanical behavior of anodes at high temperatures.
Highlights
IntroductionCarbon anodes are utilized as positive electrodes in the Hall-Héroult electrolysis process for the production of primary aluminium
The prebaked anode technology is often adopted in the aluminium production industry, because of its advantage in increasing the energy efficiency and reducing carbon consumption and emission of hazardous gases
polycyclic aromatic hydrocarbons (PAHs); Mv,i is the molecular weight of each PAH component; and, Pv,i is the concentration of each PAH component
Summary
Carbon anodes are utilized as positive electrodes in the Hall-Héroult electrolysis process for the production of primary aluminium. The prebaked anode technology is often adopted in the aluminium production industry, because of its advantage in increasing the energy efficiency and reducing carbon consumption and emission of hazardous gases. The prebaked anodes are highly consumable when compared with the other industrial carbonaceous materials utilized in the electrolysis cell [1]. High-quality anodes are required to maintain the sustainability of the operation, which substantially increases the efficiency of the electrolysis process. One of the most important solutions could be the control and improvement of the anode quality via its production process [2]. Available online: https://search-proquest-com.acces.bibl.ulaval.ca/docview/305088382?accountid=12008 (accessed on 18 December 2020)
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