Zhao Qiuyue

Basic Research on Calcification Transformation Process of Low Grade Bauxite

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.

Multi-Steps Carbonation Treatment of Calcified Slag of Red Mud

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.

Dimensional Analysis in Cold Water Model Experiments of New Cathode Structure Aluminum Cell

Compared with the traditional cathode structure cell, the new cathode structure cell can restrain the level fluctuations of aluminum liquid, effectively reduce polar distance and decrease cell voltage, it makes greatly electricity saving into reality. In this paper, using cold water model experiment based on principle of similitude to study the level fluctuations by anode gas disturbance, and investigate the rules of level fluctuations in new cathode structure electrolytic cell. Numerical simulation of the anode structure with Fluent was also carried out. Simulation results are basically consistent with experimental results, which can verify possibilities of using Fluent to investigate fluctuations in the interface of cell. According to the analysis of experimental data, the empirical formula of amplitude are obtained by using dimensional analysis, which are associated to a variety of material factors, operating factors, equipment factors. After the theoretical analysis, Dimensionless equation is in good agreement with experimental results.

A Novel Self-Stirring Tubular Reactor Used in Bauxite Digestion Process

A novel self-stirring tubular reactor driven by pressure energy used in bauxite digestion process is presented originally in this paper. This reactor combines the advantages of autoclaves and conventional tubular digestion equipment, it can restrain scale at high temperature and high pressure and intensify mass and heat transfer. Stirring of the novel reactor only needs the pressure energy of the liquid. Performance of self-stirring reactor driven by pressure energy was studied in this paper. High-speed photography was adopted in the paper to research the effects of various factors on rotating speed in the self-stirring reactor driven by pressure energy. The results demonstrated that fluid pressure has the most outstanding effects on stirring speed of the novel reactor, and the effects of fluid density and viscosity on stirring speed are minor.

Economic Analysis of Producing Alumina with Low-Grade Bauxite (Red Mud) by Calcification-Carbonization Method

Calcification-carbonization is a new method of producing alumina with low-grade bauxite (red mud). Low-grade bauxite (red mud) are all converted into garnet hydration during calcification process, then garnet hydration are treated with CO2 and the new structure red mud are gained by digestion. Main components of the new sturcture red mud are CaSiO3 and CaCO3, it can be used directly for cement industry and Bauxite resource recycling is carried out. A series of experiments were done by our team and confirmed that the new method was feasible, A/S of new structure red mud dropped to 0.21 and the content of sodium is under 0.2%. Process calculation software METSIM was used to design and simulate the new process of producing alumina with low-grade bauxite (red mud) by calcification-carbonization method, and its economic with series process and bayer process was analyzed.

Physical Simulation on Mixing Uniformity in Seed Precipitation Tank

The suspension and dispersion of Al(OH)3 particles in seed precipitation tank, which may affect the quality and output of alumina besides the deposit on the bottom of the tank, is one of the key steps in Bayer process. In order to solve these problems, the solids concentration profiles of Al(OH)3 particles were investigated by cold water experiments under simulated industrial conditions. The results showed that, the mixing uniformity in the whole tank improved with the increase of impeller off-bottom clearance when used the impeller of small diameter (D / T ⩽ 0.6), and it deteriorated when enlarged the impeller (D / T = 0.65 ~ 0.7). The mixing effects can be improved by increasing the impeller diameter and stirring speed, meanwhile the influence of impeller off-bottom clearance was weakened. But the impeller diameter and stirring speed should be controlled in appropriate ranges for the consideration of power consumption and mixing efficiency.

Physical Simulation and Numerical Simulation of Mixing Performance in the Seed Precipitation Tank with a Improved Intermig Impeller

A PC6D fiber optic reflection probe was used to measure local solid concentrations distributions in the seed precipitation tank with a new-style Improved Intermig impeller, and the commercial software FLUENT 12.0 on parallel computing graphic workstation was used to simulate numerically its flow fields. The physical simulation results show that at high rotation and viscosity, high-speed particles are more conducive to uniform distribution. When η=3.50cp, n=172rpm, the multiple relationships of the average value of the experiment and theory is 1.011 times. The numerical simulation results show that the too long or too short impeller off-bottom clearance height(C) is not conducive to the suspension of Al(OH)3 particles. Enlarging the blade diameter is good for suspending of Al(OH)3 particles. The blade diameter has a big influence on the stirring power, and the longer blade diameter needs more power consumption, but the C has little effect on the stirring power, which can be ignored. The physical simulation results compare well with numerical simulation.