Zhang Ting’an

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.

Research on activated alumina obtained by spray pyrolysis method

Activated Alumina was prepared by directly spray pyrolysis AlCl3 solution. Batch experiments was performed to choose better reaction device among muffle furnace, propane graphite furnace and tubular resistance furnace. The alumina was characterized by XRD and SEM, and the specific surface area of the prepared alumina was also examined. The experiment results showed that using the tubular resistance furnace by spray pyrolysis AlCl3 solution could effectively improve the efficiency of the pyrolysis, obviously change the morphology of product and effectively increase the specific surface area of product granule. Compared with the muffle furnace roasting, the product index of spray pyrolysis by using tubular resistance furnace was better, and the products conformed to the requirements of the index of activated alumina. The present paper provided a new way of preparing activated alumina.

Preparation of Zeolite 4A by Using High-Alumina Coal Fly Ash

With the rapid development of the electric power industry in China, the amount of fly ash discharged is growing day by day, which brings great harm to the production industry and people’s living conditions. In this article, hydro-thermal method and alkali fusion -hydro-thermal method have been used to prepare 4A zeolite from coal fly ash. The results indicate that the optimum conditions (calcination temperature 850°C, ratio of silicon to aluminum in raw material 0.8, alkalinity of NaOH 2.5mol/L, the aging time 6h, crystal temperature 90°C and crystal time 24h), the specific surface area of the prepared zeolite is 605.6m2/g. The synthesized 4A zeolite has a uniform particle size with a narrow distribution. Its shape is cube and in rules, and all its properties are close to 4A zeolite purchased in the market.

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.

Characterization of Activated Alumina Production via Spray Pyrolysis

A novel method was developed to prepare activated alumina via spray pyrolysis of aluminum chloride solution. In this paper, activated alumina was obtained by spray pyrolysis in tube furnace with aluminum chloride solution as raw materials in different temperatures. X-ray diffraction (XRD), scanning electron microscope(SEM) and the specific surface area analysis were used to characterize the spray 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 5 μm under scanning electron microscope. With the activated alumina were examined by specific 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.

Study on effective extraction of Al and Fe from high-iron bauxite through “calcification-carbonization” method

With the rapid development of China alumina production, efficient utilization of plentiful low grade high-iron bauxite has received widespread attention in the aluminum industry. Based on this, “calcification-carbonization-direct reduction” method is proposed for extracting effectively valuable metals Al and Fe from high-iron bauxite. The research results indicate that: after the calcification-carbonization process for high-iron bauxite, leaching rate of Al2O3 can reach 83.67%, higher than extraction rate of Al2O3 through Bayer method. Then, direct reduction of calcification-carbonization residue is investigated. Metallization ratio of Fe is 80.5% when reduction temperature and time is 1050°C and 2h respectively. Moreover, metallization ratio of Fe can reach 93.6% with the addition of additive A. After the “calcification-carbonization-direct reduction” process, valuable metals Al and Fe can be extracted effectively from high-iron bauxite. The main component of final residue is CaCO3 and CaSiO3, which can be directly applicable to the cement industry.

Reaction behavior and conversion of anatase in alumina production process with calcification-carbonization method

The reaction behavior and conversion of anatase in the calcification-carbonization process were investigated experimentally in the pure substance systems of Na2O-Al2O3-CaO-TiO2-H2O and Na2O-Al2O3-SiO2-CaO-TiO2-H2O. The calcification experiments were conducted respectively in the digestion conditions of diaspore and gibbsite. In calcification process, with temperature increasing, anatase converts to firstly Ca3TiSi2(Al2Si0.5Ti0.5)O14 and then CaTiO3. The increase of sodium aluminate solution concentration and additive TiO2-SiO2 ratio can promote this conversion. In carbonization process, CO2 can’t make CaTiO3 decompose. CaTiO3 is the most stable titanate phase in calcification-carbonization process.

Preparation of Pseudo-Boehmite by Using High-Alumina Coal Fly Ash

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.

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.