Alumina and Bauxite: Bayer Process and Iron
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: James Vaughan, University Of Queensland
Tuesday 8:30 AM
February 25, 2020
Room: 2
Location: San Diego Convention Ctr
Session Chair: Hong Peng, University of Queensland
8:30 AM Introductory Comments
8:40 AM
Quantifying the Effect of Seeds on Gibbsite Crystallization – Mathematical Modelling of Particle Size Distribution: Thiago Franco1; Marcelo Seckler2; 1CBA; 2São Paulo University
An utmost important step of Bayer process is the crystallization of aluminium hydroxide (Al(OH)3) from caustic solution. Perform this step only by cooling of the solution, makes the process unworkable and so it is added crystallized particles, which act as sites for the crystal formation. Mathematical models are particularly useful in this context because they provide the particle evolution of the crystals as a function of time, together from the mass balances and reaction kinetics of crystallization.Therefore, this work presents the crystallization PSD simulation of Companhia Brasileira de Alumínio (CBA) alumina refinery, developed in order to study the seeds feed effects, assisting the optimization and maximization of the process yield and alumina quality.
9:00 AM
Application of Advanced Oxidative Process for Organic Compounds Removal from Bayer Liquor: Miguel Soplin1; Amilton Botelho Junior1; Jorge Tenorio1; Marcela Baltazar1; Denise Espinosa1; 1Universidade de Sao Paulo
One of the most problems in aluminum industry is the organic matter in Bayer liquor. It causes a decrease on alumina quality and an increase on process costs. It occurs due to the high organic matter content presented in bauxite. Among the technologies available to remove those compounds, the advanced oxidative processes (AOP) can be used. This technique consists of the degradation of recalcitrant compounds by the formation of radicals, such as the OH°. The ozonation involves the injection of O3 for the OH° generation. The process can be improved by adding H2O2, accelerating the kinetics reaction. The aim of this work was to remove the organic compounds present in Bayer liquor through the injection of O3 and O3/H2O2 in a batch reactor. The effect of reagents concentration and temperature were evaluated. Results showed that the increase of temperature raises the organic degradation in higher concentrations.
9:20 AM
Disc Magnetic Separator Applied to the Extraction of Magnetite in Bauxite Residue: Yoann Robert1; Guy Simard1; Sebastien Fortin2; 1Université du Quebec à Chicoutimi; 2Rio Tinto
The valorization of bauxite residue generated by the Bayer process is a major challenge for the alumina industry. Iron oxides, mainly goethite and hematite, represent 20 to 50% of the bauxite residue content. Many reports describe a reduction of these species to magnetic ones, followed by magnetic separation, but no commercial success has been reported to date. The initial steps of our study on such magnetic separation process, using a home-made lab-scale disc magnetic separator, allowed for the quantification of key parameters, such as solids concentration, feed flow rate, rotation velocity, etc. In order to properly evaluate the various parameters’ influence, and the efficiency of the separation process, an ideal mixture of magnetic and non magnetic material was prepared and submitted to the disc magnetic separator. The collected material is enriched to more than 90 wt.% magnetic content, from an initial 30 wt.%.
9:40 AM Cancelled
Experimental Study on Flow Field Characteristics in Seed Precipitation Tank and Influence on Physical Properties of Al(OH)3 Products: Xiangyu Zou1; Yan Liu1; Xiaolong Li1; Ting-an Zhang1; 1Northeastern University
Compared with the traditional air-mixing seed precipitation tank, the mechanical stirring seed precipitation tank has the characteristics of low energy consumption, less knot at the bottom of the tank, and uniform slurry mixing. In this paper, a new type of HSG/HQG combination impeller is used to study the liquid-solid two-phase mixing system in the mechanical stirring seed precipitation tank. The combination of PIV software technology and experimental tank test is used to study the internal flow of the stirred tank. The properties of the field and various types of agitator are tested, and the physical properties of the seed decomposition products are tested under different impeller types and speeds. The results show that under the same physical parameters, using HQG/HSG new impeller structure, the crystal morphology of the seed products is more perfect, the particle size distribution is more uniform, and the wear index and specific surface area are improved.
10:00 AM Break
10:20 AM
A Review of Comprehensive Utilization of High-iron Red Mud of China: Ting-an Zhang1; Kun Wang1; Yan Liu1; Guozhi Lv1; Xiaofei Li1; Xin Chen1; 1Northeastern University
With the increasing requirement of environmental protection, the treatment of red mud has become more and more important issue. Depending on the various iron contents, red mud can be divided into low-iron red mud and high-iron red mud. This paper reviews the comprehensive utilization of high-iron red mud of China. In particular, this paper reviews the methods for iron recovery from red mud: physical recovery, hydrometallurgical recovery and pyrometallurgical recovery. This paper then introduces a new technique proposed by Northeastern University of China which can achieve high iron recovery and additional values from the molten slag. It is much preferred over the current methods. This method eliminates the pelletizing and sintering processes in Blast Furnace ironmaking shortening the technological process and saves energy greatly. The information should help to improve the future large-scale, high-value and zero waste utilization of red mud.
10:40 AM
Conversion Behavior of Iron-containing Minerals in the Process of Dissolving High-iron Bauxite by Starch Hydrothermal Method: Yongfei He1; Yiyong Wang1; Jidong Li1; Xingyuan Wan1; Zhe Ning1; 1University of Science and Technology Liaoning
Abstract: In the process of hydrothermal dissolution of bauxite, reducing agent starch can simultaneously reduce and separate iron oxide. Thermodynamic calculations show that Fe2O3 can be converted to Fe3O4. Fe2O3 will dissolve in alkaline solution to form Fe(OH)4-. The starch can be decomposed under alkaline hydrothermal conditions and form a strong reduction system, and reduce Fe(OH)4- to Fe(OH)3- , Fe(OH)4- reacts with Fe(OH)3- to form Fe3O4, which realizes the directional transformation of hematite to magnetite. It is found that temperature and alkali concentration have a great influence on the hydrothermal reduction of Fe2O3, and the dissolution of aluminum and the reduction process of iron compounds promote each other. The dissolution rate of aluminum is 98.57%, the iron reduction rate is 98.41%, the magnetic separation rate is above 97.0%, and the iron grade is 73.5%.
11:00 AM
Recovery of Iron from High-iron Bayer Red Mud by Smelting Reduction: Kun Wang1; Yan Liu1; Guozhi Lv1; Xiaofei Li1; Xin Chen1; Ting-an Zhang1; 1Northeastern University
The high-iron Bayer red mud, which contains 30% to 50% iron, is regarded as low-grade iron ore. With the global scarcity of iron supply worldwide, how to effectively utilize the iron in high-iron red mud has attracted more and more attention in recent decades. In this paper, the technology of recovery of iron from high-iron red mud was developed with smelting reduction followed by rapid cooling to separate the metal from slag. The effects of various experiment parameters such as temperature, basicity and reduction time on iron recovery from red mud was studied in detail. The results showed that the separation between metal and slag was thorough. The content of iron in metal and iron recovery ratio were 94.06% and 80.16% with basicity of 0.9 smelting at 1600℃ for 30 min. The optimum experiment result were of great significance to achieve large-scale, high-value utilization of red mud.