Alumina & Bauxite: Session II
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Errol Jaeger, The Business Consultants FZ-LLC; Stephan Broek, Kensington Technology Inc

Wednesday 8:30 AM
March 22, 2023
Room: 31B
Location: SDCC

Session Chair: Errol Jaeger, The Business Consultants FZ-LLC

8:30 AM
Improvement Seminars: Continuous Improvement and People´S Engagement to Support the Sustainability: Nathalia Cordeiro¹; Bruna Cabral¹; Renan Cruz¹; Raphael Costa¹; Silene Vendrasco¹; Jaise Carvallo¹; Gustavo Silva¹; Guilherme Silva¹; Karina Trindade¹; ¹Norsk Hydro Brasil
    A robust management system guarantees the stability and the predictability of a company's processes. The focus is on the continuous improvement, supported by people, in structured methodologies, through a recognition program to leverage initiatives to contribute to sustainable business. Coordinating different facets, integrating areas, evolving its structure, and using Lean principles, focusing on people makes the challenge even more complex. This project presents the technical evolution of a recognition and improvement program in the bauxite and alumina business in Pará, Brazil. In 2022, it had more than 600 improvement projects that generated an engagement of more than 670 people with proven gains in dimensions such as health, safety, environment, quality of life in the work environment, innovation, and actual income in the millions level (US$). It indicates a growing potential in the involvement of teams for the development of improvements. The consequence is sustainability in achieving the global company's goals.

8:55 AM
Turning Bauxite Residue to Metal Adsorption Materials through a Low-cost Approach: Hong (Marco) Peng¹; James Vaughan¹; Shengchun Ma¹; Sicheng Wang¹; Xinyu Tian¹; ¹University of Queensland
    A low-cost approach to bauxite residue (BR) utilization has not been achieved due to the complicated mineralogy. In this study, BR has been treated by dilute acid to reduce the alkalinity of residue by dissolving sodalite phase. The acid washed BR samples are of high iron grade (>80% Fe2O3) with low sodium content (<0.3% Na2O) which can be potentially used as ironmaking feed. The washed acid solution was treated by caustic NaOH to synthesise the zeolite-like adsorption materials. The materials have been used for adsorption of copper and lithium metal salts. The Cu adsorption performance of the synthesised product shows the exhibits fast loading kinetics as within 15 min over 99% of adsorption efficiency is observed, compared with commercial grade zeolite LTA.

9:20 AM
Hematite and Anatase Conversion to Magnetic Phases During Reductive Re-digestion of Gibbsitic Bauxite Residue: Paula Araújo¹; Andre do Carmo¹; Fernando Gomes¹; Raphael da Costa²; Marcelo Montini²; Adriano Lucheta¹; Patrícia Silva¹; ¹SENAI Innovation Institute for Mineral Technologies; ²Norsk Hydro Brasil
    Bauxite residue (BR) is a by-product of the Bayer process for alumina production. The physical and chemical characteristics of BR from gibbsitic bauxite, such as, the fine particle size distribution and hematite (paramagnetic behaviour) presence prevents iron magnetic recovery. An alternative to enable a magnetic concentration operation would be the minerals transformation to a higher magnetic susceptibility phase. A Brazilian BR obtained from gibbsitic bauxite, with 47.03% Fe₂O₃ and 5.45% TiO₂, was re-digested with iron(II) sulfate 7-hydrate (FeSO₄·7H₂O), at 230ºC and high caustic concentration (370 g/l Na₂CO₃). Magnetite, titanium-magnetite (ulvospinel) and cancrinite were obtained. The results demonstrated that this route may be promising for iron magnetic recovery from treated BR. For future studies, one should evaluate the threshold for the conversion when the severity of conditions were diminished, as well as, the assessment of magnetic properties and the evaluation of potential recovery of the magnetic product.

9:45 AM
Digestion Efficiency Improvement of Gibbsite-boehmite Bauxite: Fengqin Liu¹; Songqing Gu¹; Huaitao Zhang²; Michael Ren³; Zegang Wu¹; Han Lu¹; Mingzhuang Xie¹; ¹University of Science and Technology; ²Shandong Xinfa Aluminum Group; ³Sunlightmetal Consulting Inc.
    Bayer digestion performance of gibbsite-boehmite bauxite is studied. Chemical and mineral compositions of gibbsite-boehmite bauxite from Australia are analyzed and tested by XRF, XRD and SEM. Test results show bauxite contains > 50% of alumina (gibbsite and boehmite) and about 9% silica (kaolinite and quartz). Its digestion efficiency is studied in detail with various digestion conditions such as temperatures, holding times and additives. A medium-temperature digestion technology has been developed based on study results and industrial tests in Chinese refineries: boehmite in bauxite will be totally digested at 225-250℃ for just a few minutes with bits of lime addition for a high alumina recovery efficiency and most inert silica minerals in bauxite at a stable state so caustic consumption reduced by over 10%, alumina recovery efficiency increased by 2-3% compared with traditional digestion technologies. There is a greater application prospect with this medium temperature digestion technology for Australian bauxite.