Recovery of alkali and alumina from bauxite residue (red mud) and complete reuse of the treated residue

Dealkalization processes of bauxite residue: A comprehensive review

Calcification-carbonation method for red mud processing.

Utilization of steel slags to produce thermal conductive asphalt concretes for snow melting pavements

Increasing demands for environmental accountability and energy efficiency in industrial practice necessitates significant modification(s) of existing technologies and development of new ones to meet the stringent sustainability demands of the future. Generally, development of required new technologies and appropriate modifications of existing ones need to be premised on in-depth appreciation of existing technologies, their limitations, and desired ideal products or processes. In the light of these, published literature mostly in the past 30 years on the sealing process; the second highest energy consuming step in aluminum anodization and a step with significant environmental impacts has been critical reviewed in this systematic review. Emphasis have been placed on the need to reduce both the energy input in the anodization process and environmental implications. The implications of the nano-porous structure of the anodic oxide on mass transport and chemical reactivity of relevant species during the sealing process is highlighted with a focus on exploiting these peculiarities, in improving the quality of sealed products. In addition, perspective is provided on plausible approaches and important factors to be considered in developing sealing procedures that can minimize the energy input and environmental impact of the sealing step, and ensure a more sustainable aluminum anodization process/industry.

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The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

Aluminum industry is one of the most important industries in China’s nonferrous metal metallurgy industry. With the development of output in alumina and the improvement of its production technology, China’s high quality bauxite resources are difficult to meet. Under this condition, “Calcification-Carbonation Method” was put forward to deal with middle-low grade bauxite and red mud by Northeastern University, the main purpose of this method is to change the balance phase of red mud into 2CaO•SiO2 and CaCO3 with hydrometallurgical process. Through treatment by “Calcification-Carbonation Method”, A/S of the new structure red mud lowed below to 0.5 and the Na content lowed below to 0.3%, the red mud could be used in cement industry directly. This paper mainly introduced the technological idea and principle of new method, process comparison and typical experiment results is given as well.

Calcification‐Carbonation Method for Alumina Production by Using Low‐Grade Bauxite

With the rapid development of China’s aluminum industry, deficiency of high-quality bauxite reserves has become a bottleneck restricting for the healthy development of China’s aluminum industry According to these issues, “Calcification-Carbonization Method” was purposed by Northeastern University for alumina production by using low grade bauxite This paper researched on the transformation and separation performance in the new method The experiment results indicated that: Al, Fe, Si transformed into hydrated garnet at 180°C and 245 °C through calcification treatment, and silicon phase changed into 2CaO • SiO2 through carbonization treatment The settling performance of calcification slurry by using gibbsite is near to that of bayer process, when the settling performance by using diaspore get worse because of the solid content is higher than that of bayer process Under the pressure of 018MPa, the filter constant of calcinated slurry are 418 × 10-5m2/s and 115 × 10-4m2/s for diaspore and gibbsite

Research on the Phase Transformation and Separation Performance in Calcification-Carbonation Method for Alumina Production

Our group put forward a “Calcification-Carbonation” new process use of low grade bauxite to produce alumina based on the problem of bauxite grade are decreasing gradually in china. This paper studies the effect of reaction thermodynamics, kinetics and processing parameters in calcification process. The thermodynamics calculation results show that both calcification reactions of gibbsite and diaspore can proceed within their dissolution temperature range. The study of Non-isothermal kinetics by high-pressure DCS results show that the calcification reaction for gibbsite occur within the temperature range 231.7–248.2°C and 248.2–268.7°C, with an activation energy of 23.7kJ/mol and 18.0kJ/mol respectively; diaspore occur within the temperature range 236.7–255.6°C and 255.6–287.5°C, with an activation energy of 264.9kJ/mol and 118.5kJ/mol respectively. Experimental results show that the appropriate calcification temperature of diaspore and gibbsite are 245°C and 180°C, molar ratio of CaO to SiO2 is 4.69:1; under these condition, silicon phase in minerals transformed hydrogarnet completely.

Basic research on calcification transformation process of low grade bauxite

Aluminum industry is one of the most important industries in China’s nonferrous metallurgy industry. With the development of China’s alumina output, red mud emission get 50 million ton at 2011. Under this condition, “Calcification-Carbonation Method” was put forward to deal with red mud by Northeastern University, the main purpose of this method is to change the balance phase of red mud into 2CaO·SiO2 and CaCO3 with hydrometallurgical process. This paper mainly research on the effect of carbonation conditions and steps on alumina extraction and dealkalize efficiency. The results indicate that: through multi-steps carbonation treatment of calcified slag by the new method, A/S of the new structure red mud lowed below to 0.24 and the Na2O content lowed below to 0.26% at carbonation temperature 120°C, CO2 pressure of 1.2MPa with 5-steps carbonation treatment. The new structure red mud could be used in cement industry directly.

Multi-Steps Carbonation Treatment of Calcified Slag of Red Mud

Fly ash is a very important unconventional aluminum resource in which the alumina content comes up to 40 ~ 60% in part of China. It has great economic and environmental value to exploit the recycling method of fly ash and produce high value-added multi-alumina products. In this paper, preparation of pseudo-boehmite by using Inner Mongolia Datang fly ash sintering clinker has been investigated. After a series of processing under optimized conditions (dissolution at 80°C, 60min, liquid solid ratio 4:1, first stage desilication 120min, 170°C, sodium silicon slag 100 g/l, sec-stage desilication 120 min, 90°C, CaO content 15 g/l), the silica ratio of the solution reaches up to 838, which conforms to the requirement of the industry. The pore volume of the seed precipitation product reaches 0.8291cm3/g, which is almost the same with standard sample. The Na2O content of pseudo-boehmite prepared is below 0.3%, which can meet the sodium content requirements of general catalyst.

Lv Guozhi

Papers

Calcification‐Carbonation Method for Alumina Production by Using Low‐Grade Bauxite

Research on the Phase Transformation and Separation Performance in Calcification-Carbonation Method for Alumina Production

Basic research on calcification transformation process of low grade bauxite

Multi-Steps Carbonation Treatment of Calcified Slag of Red Mud

Preparation of Pseudo Boehmite by Using High‐Alumina Coal fly Ash