Lv Guozhi

φ-pH diagram of V-Ti-H2O system during pressure acid leaching of converter slag containing vanadium and titanium

Abstract To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H 2 O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 °C was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH 3+ , VO 2+ and VO 2 + exist in the stable region of TiO 2 . The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 °C of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15:1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.

The Most Probable Mechanism Function and Kinetic Parameters of Gibbsite Dissolution in NaOH

Determination of probable mechanism function and kinetic parameters is important to hydrometallurgical kinetics. In this work, the most probable mechanism function and kinetic parameters of gibbsite dissolution in NaOH solution are studied. The sample, the mixture of synthetic gibbsite and sodium hydroxide solution, was scanned in high-pressure differential scanning calorimetry (DSC) equipment with the heating rate of 10 K·min−1. Integral equation and differential equation of non-isothermal kinetics were solved to fit the data related to DSC curve. According to the calculation results, the most probable mechanism function for pure synthetic gibbsite dissolution in sodium hydroxide solution is presented based on the optimum procedure in the database of the mechanism function. The apparent activation energy obtained is (75±1) kJ·mol−1, the frequency factor is 108±1 mol·s−1, and the reaction is a second order reaction.

Thermodynamics study on leaching process of gibbsitic bauxite by hydrochloric acid

Abstract For the low-grade gibbsitic bauxite, the leaching rate of alumina is very low during the Bayer process. The acid leaching method is attracting more attention, and the hydrochloric acid leaching was developed rapidly. The mineral composition and chemical composition were investigated by X-ray diffraction analysis and semi-quantitative analysis. The thermodynamics of leaching process was analyzed. The results show that the major minerals in the bauxite are gibbsite, secondly goethite and quartz, anatase and so on. The acid leaching reactions of the bauxite would be thermodynamically easy and completed. Under the conditions that ore granularity is less than −55 μm, the L/S ratio is 100:7, and the leaching temperature is 373–383 K, the leaching time is 120 min and the concentration of HCl is 10%, both the leaching rates of Al and Fe are over 95%. The main composition of leaching slag is SiO 2 which is easy for comprehensive utilization.

Kinetics of AlOOH dissolving in caustic solution studied by high-pressure DSC

Mechanism functions and kinetic parameters of AlOOH (boehmite or diaspore) dissolving in sodium hydroxide solution were researched. The mixture of boehmite or diaspore and caustic solution was scanned by high-pressure differential scanning calorimetry (DSC) instrument with heating rate of 10℃/min, and differential equation method was used to analyse the DSC curves, combining with iterative method and linear least square method. The most probable mechanism functions for both boehmite or diaspore and caustic solution reactions were logically selected from 30 types of non-isothermal kinetics differential equations, according to the calculated results obtained by Matlab program. The most probable differential mechanism function of boehmite dissolving in caustic solution is f(α)=1-α, which reveals the first-order reaction with apparent activation energy of 79.178 kJ/mol and the preexponential constant 1.031×10^8 s^(-1). The function, f(α)=2(1-α)(superscript 3/2), can describe the dissolution of diaspore sample in sodium hydroxide solution. The calculated results of kinetic parameters are apparent activation energy of 73.858 kJ/mol, preexponential constant of 5.752×10^7 s^(-1) and reaction order of 1.5.

E-pH diagram of ZnS-H2O system during high pressure leaching of zinc sulfide

The values of G(superscript Θ), E(superscript Θ) or pH from 110 to 160 ℃ were calculated and the relevant potential expressions were obtained, E-pH diagrams of ZnS-H2O system at oxygen partial pressure of 0.8 MPa, ionic activity of 1.0 and different temperatures were drawn through thermodynamical calculation. With the temperature increasing, the stable regions of S and Zn(Ⅱ) in the E-pH diagrams become gradually larger, but the amplification decreases over 150℃. The impacts of leaching parameters, such as temperature, liquid to solid ratio, initial acidic concentration, leaching time, oxygen partial pressure and stirring speed on the leaching rate of Zn(Ⅱ) and conversion rate of S in the single factor of high pressure leaching experiment of ZnS in autoclave, were studied. The leaching residue was examined by X-ray fluorescence (XRF) chemical composition identification and X-ray diffraction (XRD) phase identification, and the content of the leaching solution was tested by inductively coupled plasma-atomic emission spectrometry (ICP). The experimental results indicate that the leaching rate of zinc increases from 60.05% to 97.85% and the conversion rate of sulfur increases from 38.90% to 80.92% with the temperature increasing from 110℃ to 150℃, 5:1 of liquid-to-solid ratio, 150 g/L of initial acidic concentration, 120 min of leaching time, 0.8 MPa of oxygen partial pressure, and 480 r/min of stirring speed, which tend to be stable over 150℃. The experimental results correspond with theoretical calculation.

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.

Fluidized-bed chlorination thermodynamics and kinetics of Kenya natural rutile ore

Natural rutile and gaseous chlorine with carbon as reductant were used to prepare titanium tetrachloride.1173Kesing C uctant, Thermodynamics and kinetics of chlorination of Kenya natural rutile particles in a batch-type fluidized bed were studied at 1173–1273 K. Thermodynamic analysis of this system revealed that the equation of producing CO was dominant at high temperatures. Based on the gas-solid multi-phase reaction theory and a two-phase model for the fluidized bed, the mathematical description for the chlorination reaction of rutile was proposed. The reaction parameters and the average concentration of gaseous chlorine in the emulsion phase were estimated. The average concentration of emulsion phase in the range of fluidized bed was calculated as 0.3 mol/m3. The results showed that the chlorination of natural rutile proceeded principally in the emulsion phase, and the reaction rate was mainly controlled by the surface reaction.

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.

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.