Alumina & Bauxite: Bauxite Residues Technology
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Zhang Ting'an, Northeastern University
Tuesday 8:30 AM
February 28, 2017
Location: San Diego Convention Ctr
Session Chair: Guanghui Li, Central South University
8:30 AM Introductory Comments
Security Disposal and Comprehensive Utilization of Bauxite Residues: Songqing Gu1; Zhonglin Yin1; Lijuan Qi1; 1Chalco
Security disposal and comprehensive utilization of bauxite residues are of great significance to the world alumina industry due to environmental protection requirement and waste materials recovery. The security disposal and utilization technologies for bauxite residue will be shown and discussed in this paper. The dry stacking technology for Bayer residues by the drum or pressure filters has been applied widely in the Chinese refineries from 10 years ago. Magnetic separation dressing of high iron content red mud for iron ore concentrates has been put into industrial operations in China for more than 5 years. The residue from sintering process is able to be used for red mud pool dam construction and Soil Modifiers for high acidic soil areas for neutralizing and adsorbing the harmful heavy metal compounds in the soil. The high caustic Bayer residues could be applied for such construction materials as foamed ceramics and glass ceramics etc. The further utilization possibilities and potentials in the future are outlined in the steelmaking, construction, agriculture and environmental industry etc.
Application of Tricalcium Aluminate Instead of Lime for the Recovery of Aluminum in Middle-low Grade Bauxite in Calcification-Carbonization Process: Yanxiu Wang1; Zhang Ting'an1; Guozhi Lv1; Xiaofeng Zhu1; Weiguang Zhang1; Liqun Xie1; 1Northeastern University
In the process of calcification-carbonization, the alkali and aluminum in the mid-low grade bauxite and red mud can be regained effectively. Aluminum is obtained in the form of low-concentration sodium aluminate solution which is comparatively difficult to reuse. In this paper, the low-concentration sodium aluminate solution was reused to prepare tricalcium aluminate and went back to the calcification-carbonization process instead of lime. When processing gibbsite and diasporic bauxite with calcification-carbonization method, the effect of calcium aluminate on dealkalization and dealumination was investigated. The results show that the alumina-silica ratio of these two ores can be reduced to 0.70, and the sodium alkali content can be reduce to less than 0.50%. It indicates that it’s feasible to use calcium aluminate replacing lime. The proposal well solved the problem that aluminum is difficult to recycle at low concentrations and enhances the effectiveness and cleanness of calcification-carbonization process which has an extensive prospect.
Low Temperature Reduction of Hematite in Red-Mud to Magnetite: Sumedh Gostu1; 1Worcester Polytechnic Institute
Red-mud, the residue generated from the Bayers processing of bauxite ore in Jamaica was subjected to a low temperature reduction process. Hematite (~60 m%) was reduced to magnetite employing a gas based mixture of CO, CO2 and N2 as a diluent. Extensive thermodynamic study was conducted to identify the stability region for magnetite. ‘Optimal conditions’ for the gas-phase reduction were determined to be: a processing temperature of 540oC ± 10C , partial pressures CO(g) and CO2(g) each of 0.070atm (bar) ± 0.001atm.(bar)/ inert diluent-gas: N2(g), for a conversion-time of 30min. Frantz dry and Davis tube magnetic classification was tried on the magnetite product. The magnetic separation tests were not successful in achieving a high grade of magnetite in the magnetic fraction. This finding was subsequently attributed to the discovery, via STEM imaging, of nanometer length-scales associated with the nascent crystallites of the entities, which are intrinsic to Bayer-Process precipitate.
9:50 AM Break
Recovery of Iron-, Titanium-bearing Constituents from Bauxite Ore Residue via Magnetic Separation Followed by Sulfuric Acid Leaching: Guanghui Li1; Foquan Gu1; Jun Luo1; Bona Deng1; Zhiwei Peng1; Tao Jiang1; 1School of Minerals Processing and Bioengineering, Central South University
Bauxite ore residue is a hazardous byproduct derived from alumina production, containing iron, titanium, aluminum and other valuable metals. The feasibility of an integrated technological route for recovering titanium from bauxite ore residue was verified in this study. Titanium-bearing iron concentrate was first recycled through magnetic separation process, and titanium was further leached from the non-magnetic material derived from the upper-stream process by using sulfuric acid. The effects of magnetic intensity on the recovery of iron, and the effects of sulfric acid concentration, leaching temperature, leaching time and liquid to solid ratio on the leaching of titanium have been investigated. The results showed a magnetic concentrate with total iron grade of 56.39% and TiO2 content of 8.66% was obtained under a two-stage magnetic separation process (intensity: 0.8T and 0.2T, respectively), and magnetic recoveries of iron and titanium attained 55.79% and, 17.37% respectively. 96.36% TiO2 was subsequently leached from the non-magnetic material under the optimal conditions of sulfuric acid concentration of 8mol/L, leaching temperature of 70°C, leaching time of 120min, and liquid to solid ratio of 8.
Processing Diasporic Red Mud by the Calcification-carbonation Method: Xiaofeng Zhu1; Zhang Ting'an1; Guozhi Lv1; Fangfang Guo1; Weiguang Zhang1; Yanxiu Wang1; Liqun Xie1; Long Wang1; 1Northeastern University
The novel calcification-carbonation method was proposed to process the diasporic red mud discharged from Bayer process alumina plant. In this study, Batch experiments were performed to evaluate the potential effects of important parameters such as temperature, amount of CaO added, CO2 partial pressure and carbonation cycles on the recovery of alkali and alumina. The results showed that 99.8% alkali and 78.74% alumina were recovered from the diasporic red mud with decreases in the mass ratios of Na2O to SiO2 (N/S) and of Al2O3 to SiO2 (A/S) from 0.44 and 1.27 to 0.001 and 0.27, respectively. The Na2O content in the processed red mud was less than 0.1 wt%, and it can be used as a construction material.
Research of Flocculants and Dewatering Additives for Filtration of Red Mud: Cao Wenzhong1; Zheng Fuliang1; Tian Weiwei1; Zhong Hong1; 1Nanchang University
The polymer flocculants and dewatering additives have been applied to separation of Red Mud for thirty years.. In recent years, it is pointed out that the additives is related to the presence of other ions.. The experimental results show that the effect of mud dewatering and mud compaction will affect the production capacity and purity of product.. The potential of using water absorbing polymer or synthetic dispersant to change the rheological property of the slurry is also summarized in the end.. The combination of these effects, with the new bio polymer to improve the primary pour into the washing bath of the overflow liquid clarity and recovery of sodium hydroxide is also researched.
Characterization of Activated Alumina Production via Spray Pyrolysis: Long Wang1; Zhang Ting'an1; Guozhi Lv1; Xiaofeng Zhu1; Weiguang Zhang1; Sida Ma1; 1Northeastern University
A novel method was developed to prepare activated alumina via spray pyrolysis with aluminum chloride solution as raw materials. In this paper, activated alumina was obtained by spray pyrolysis in tube furnace with aluminum chloride solution as raw materials in different temperatures. XRD, SEM and the specific surface area analysis were used to characterize the pyrolysis products, respectively. XRD results showed that the crystal phase composition of activated alumina can be controlled through adjusting pyrolysis temperature. The crystal structure of γ-Al2O3 in the products conformed to the requirements of the index of activated alumina. Most of pyrolysis products were porous structure which the particle size was around 5μm under scanning electron microscope. With the activated alumina were examined byspecific surface area analysis, the products existed as inkbottle-shaped and parallel-plate pores. Pyrolysis products more conformed to the requirements of activated alumina after examined by XRD, SEM, and the specific surface area.