Dou Zhihe

Research on new type materials preparation for magnesium production by Silicothermic process

During the magnesium preparation process of the silicothermic process, dolomite was made into pellets after calcination process, about 5% fine materials would be produced which can’t be used and lead to high energy consumption and high-cost. Based on in-situ reduction of dolomite-based desulfurization theory, this paper proposed a new technology that dolomite was made into the pellets first and then was calcined to prepared the pellets with higher reactivity and stability. The results indicate that: In contrast with dolomite pellets prepared by single binder, dolomite pellets prepared by composite binder are dominant in functions without fine materials produced, the size of pellets is uniform, the falling strength can reach 2.5 times per 0.5 m, and the compressive strength gets 80N as well.

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.

A new green process to produce activated alumina by spray pyrolysis

Abstract A green process that uses the spray pyrolysis method to prepare activated alumina is proposed in this research. The effects of spray temperature, carrier gas pressure, and AlCl3 solution concentration are experimentally investigated using pure reagents. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and specific surface area (BET) analyses. The results indicate that the spray temperature is the most important factor on the conversion ratio of alumina during the spray pyrolysis process. The conversion ratio of alumina achieved over 99% at the following optimal conditions: temperature of 1000°C, pressure of 0.3 MPa, and AlCl3 solution concentration of 10 wt%. The activated alumina with 8–20 nm particle size (γ-Al2O3+α-Al2O3) was prepared using the same process, which well met the requirement of the catalyst carrier. The green utilization of high-alumina fly ash and acid recycling can be achieved by using this process.

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.

燃烧合成法制备NdB 6 超细粉体及反应机理

以B 2 O 3 、Nd 2 O 3 和Mg为原料, 采用燃烧合成法制备出NdB 6 超细粉体。考察了反应气氛、制样压力和物料配比对反应产物微观形貌和物相的影响。采用XRD、SEM对产物进行了表征, 结果表明: 燃烧产物由NdB 6 、MgO以及少量Mg 3 B 2 O 6 和Nd 2 B 2 O 6 组成, 稀硫酸处理去除可溶性成分后, 产物为单一的NdB 6 相, 纯度为99.1%。随着制样压力的增大, NdB 6 颗粒尺寸逐渐变小。制样压力为20 MPa时, 制备的NdB 6 粉末平均粒度小于500 nm。Mg-B 2 O 3 -Nd 2 O 3 三相反应历程: 首先Mg还原Nd 2 O 3 生成单质Nd和MgO, 然后引发Mg还原B 2 O 3 生成单质B和MgO, 同时生成的Nd和B反应得到NdB 6 , 反应的表观活化能为691.59 kJ/mol, 反应级数为3.2。

Effect of Combined Forms of Al and Si on the Acid Leaching Performance of Fly Ash

Research on the leaching performance of fly ash of Shanxi, Chongqing and Western Inner Mongolia. Analyze the existing forms, crystallinity and package situation of Al-Si phase in fly ash from different areas by using SEM and XRD. Effect of fractionation of Al-Si phase in fly ash on the leaching performance from the view of mechanism was investigated as well. Leaching experiments and analysis indicate that: the leaching rates of Al203 in fly ash from the there different areas are 97.41%, 68.94% and 23.61% respectively, under the conditions of solid-liquid ratio 1:20, rotary speed 500rpm, leaching time 120min, sulfate concentration 20%, particle sizes −74µm. Leaching performance of fly ash in Western Inner Mongolia is better than that in other two areas. The main reason for different leaching performance of fly ash from different areas is the difference in crystallinity, encapsulated glass phase of Al-Si phase in fly ash. The crystallinity for Western Inner Mongolia is 75.98%, while there is no non-crystalline phase in fly ash from other tow areas, The average FWHM of XRD diffraction peak of Al-Si phase are 0.641, 0.3324 and 0.1107, respectively. The crystallinity of fly ash in Western Inner Mongolia is worst among the there areas, and its content of glass phase is also lowest among them, so its activity is obviously higher than that of other two areas.

Effects of Roasting Pretreatment in Intense Magnetic Field on Digestion Performance of Diasporic Bauxite

This paper investigates the changes of phase and apparent morphology under the combined effects of an intense magnetic field and temperature field and the effect law of different roasting conditions on the digestion performance of roasted diaspore. The results indicated that roasting pretreatment under high magnetic fields can change the microstructure and improve the digestion properties of bauxite. The reasonable roasting conditions with intense magnetic field are as follows; the roasting temperature is 550°C, roasting time is 60min and the magnetic field intensity is 6T. The digestion rate of alumina of the roasted ore is 84.17% and the digesting liquid ratio is 1.39 while the digesting temperature is 190°C with the digestion time of 60mins. The digestion rate of alumina of the roasted ore increases to higher 52.85% than that of the raw ore, but the digesting liquid ratio is decreased to lower than 0.99 of the raw ore under the above roasting conditions. The digestion temperature of roasted ore decreases by 30°C compared to the raw ore.

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.