Modelling the formation and dissolution behavior of alumina agglomerate in the cryolite--颗粒学报PARTICUOLOGY

Wang, J., Li, M., Cheng, B., & Li, H. (2024). Modelling the formation and dissolution behavior of alumina agglomerate in the cryolite. Particuology, 86, 211-222. https://doi.org/10.1016/j.partic.2023.06.014

Modelling the formation and dissolution behavior of alumina agglomerate in the cryolite

Jiaqi Wang, Mao Li ^*, Benjun Cheng, Hesong Li

School of Energy Science and Engineering, Central South University, Changsha, 410083, China

10.1016/j.partic.2023.06.014

Volume 86, March 2024, Pages 211-222

Received 20 January 2023, Revised 30 April 2023, Accepted 20 June 2023, Available online 7 July 2023, Version of Record 14 July 2023.

E-mail: lmao@csu.edu.cn; limao89@163.com

Highlights

• A semi-analytical mathematical model was established coupling heat and mass transfer.

• Formation, melting and dissolution process of alumina agglomerates were formulated.

• Penetration and solidification of cryolite were considered based on packing theory.

• Time duration for each stage and the maximum diameter of agglomerates were derived.

• Dimensionless method was employed to analyze the influence factors on dissolution.

Abstract

The presence of alumina agglomerates seriously affects the current efficiency of the aluminum electrolysis process. Clarify the dynamic dissolution process of agglomerates is essential to improve the current efficiency of aluminum electrolysis. A mathematical model is proposed to describe the different phenomena from the formation until complete dissolution of agglomerates. Considering permeation and solidification processes of cryolite, a semi-analytical mathematical model is developed to formulate the formation, melting and dissolution processes of agglomerates, and the time duration for each stage is deduced. Porosity and heat mass transfer of agglomerates are explored based on the packing theory and mechanism of heat mass transfer in wet porous media. Dimensionless approach is applied to investigate the main factors affecting the dissolution stages and porosity of agglomerates. The results show that the superheat has a great influence on the formation and melting stage, the diameter of agglomerates can reach 14.93 mm for 200 particles agglomerated. The density decreases with the increase of agglomerated particle number, which varies in the range of 2.27–2.28 g/cm³. The average dissolution rate of agglomerates is about 1.83*10^-5 - 2.95*10^-5 kg/s within the range of alumina concentration in this study.

Graphical abstract

Keywords

Mathematical model; Alumina agglomerate; Porous media; Packing theory; Heat and mass transfer

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