Table of Content

13 March 2015, Volume 15 Issue 1

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流动与传递

Analysis of Particles Movement in the Serial-hopper Bell-less Top of Blast Furnace with Discrete Element Method

LI Chao CHENG Shu-sen ZHAO Guo-lei YIN Yi-xin

. 2015, 15(1):  1-8. 

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A full model of serial-hopper bell-less type charging system of blast furnace was developed, and the movement of burden from conveyor to throat was calculated by discrete element method. Particle size segregation on the conveyor and in the upper and lower hoppers was studied, and the effects of installed stone box on burden distribution in the hopper, particle movement during charging and discharging and the size variation of discharged particles were analyzed. The results show that the small particles percolate into the lower material layer on the conveyor, which results in the average size of lower particles being smaller than that of the upper. Particle segregation exists in the vertical, circumferential and radial directions of upper hopper, and in the vertical and radial directions of lower hopper. However burden distribution in the circumferential direction of lower hopper is uniform, and the standard deviation of relative particle size is about 0.03. Installing stone box has little effect on burden distribution in the circumferential and vertical directions of hopper, however, the effect of stone box on burden distribution in the radial direction of hopper is large, since the small particles percolate near the stone box. The material surface is level and particles move in plug flow in the lower hopper with stone box, but burden surface forms heap tip and particles move in funnel flow without stone box. Change in mean size of discharged particles is affected by particle movement and burden distribution in the lower hopper. When stone box is not installed in hoppers, standard deviation of the size variation in discharging process is 7.15, and that is 10.42 with stone box and the change of discharged particle size is more obvious

Performance Optimization of Cyclone Separator Based on the Wear Structure

ZOU Kang AI Zhi-jiu HU Kun QIAN Hui-jie FU Bi-wei

. 2015, 15(1):  9-15. 

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Based on the theory of gas-solid two-phase flow and erosion, conventional Stairmand cyclone separator and the rule of erosion wear type cyclone separator were studied. The results show that conventional cyclone wall erosion wear rate decreases down from the top of the cylinder. In the region below the cylinder L1/H1=0.8, the wear rate remains basically unchanged. In the region above L1/H1=0.8, the erosion wear rate shows an increasing trend, its maximum value is 2.3′10-6 kg/(m2×s). In the region below the cone L2/H2=0.35, the wear rate decreases, and in the region above L2/H2=0.35 the wear rate shows a gradual increasing trend, at the top of the pyramid it has a maximum value of 2.0′10-7 kg/(m2×s). Wear type cyclone separator in the region above cylinder L1/H1=0.8 has the maximum wall corrosion rate of 0.5′10-6 kg/(m2×s) which is far less than that of conventional cyclone separator. In the cone upward from the cone bottom the erosion wear rate decreases gradually, and is 0.4′10-7 kg/(m2×s) at the top of the cone, which is less than that of conventional cyclone separator. In small particle size range, the separation efficiency increases linearly with the increase of particle size. When the particle size is greater than 4 mm, wear type cyclone separator has a higher separation efficiency. The pressure drop decreases with increasing of the wear plate height gradually. The type A3 wear separator has a pressure drop of 360 Pa, which is less than that of conventional separator 550 Pa. Therefore, in order to reduce the cyclone wall erosion wear and reduce outlet pressure drop loss, when the particles with the size greater than 4 mm are separated, the most reasonable wear B1 type separator should be chosen for improving the wear performance of cyclone separator and prolonging its service life.

Three-dimensional Numerical Simulation of the Feeding System in Twin-roll Thin Strip Casting Process

PAN Li-ping LI Bao-kuan HE Zhu

. 2015, 15(1):  16-22. 

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The numerical simulation software FLUENT was used to analyze the three-dimensional unsteady conservation equations for transport phenomena in the flow distribution system and pool region of twin-roll with 600 mm in diameter and 550 mm in width in thin strip casting process. The rationalization of structure design was validated through the simulation results, and the influences of rotational speed and pouring temperature on the flow field and temperature distribution were analyzed. The results show that three-dimensional numerical simulation is more accurate in description of temperature distribution and solidification region along the axial direction of rollers than two-dimensional simulation. Moreover the temperature distribution and the solidification zone of molten pool are more reasonable when the rotational speed is 60 m/min, and pouring temperature 1490℃.

Experimental Study and Large Eddy Simulation of Mixing in a Seed Precipitation Tank with

LU Yuan ZHOU Yong-jun LIANG Jia-yong ZHANG Wei-meng

. 2015, 15(1):  29-34. 

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The mixing process in a seed precipitation tank with double improved INTER-MIG impellers was studied by experiment of achromatic method and numerical simulation. The change of mixing process was recorded by a high speed camera. The tracer transfer process and turbulent flow field were calculated by large eddy simulation (LES) and dynamic Smagorinsky-Lilly model subgrid scale model. The results showed that the mixing process predicted by LES was consistent with the experiment when the tracer was added to the liquid surface, and it dispersed in spiral form, but the predicted mixing time was longer. The optimal injection point was located in the region near lower impeller, its mixing efficiency was higher than that at the liquid surface by 17.16%. The mixing time monitored in the central region of the tank was smaller than that at the top and bottom positions. The difficult mixing part was located in the bottom region of seed precipitation tank with improved INTER-MIG impeller.

Research on the Mass Transfer Characteristics of Gas Phase in a Novel Rotating Packed Bed

GU De-yin LIU You-zhi QI Gui-sheng ZHANG Fang-fang CHEN Xiao-yan

. 2015, 15(1):  35-39. 

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The gas phase mass transfer characteristics of a novel rotating packed bed (RPB) were studied experimentally, the interfacial area (a) was determined by chemical absorption in CO2-NaOH system under different conditions of liquid flux, ratio of gas to liquid and super gravity factor, and the gas volumetric mass transfer coefficient (kya) measured by the stripping ammonia-rich water in the novel RPB under the same operational conditions, then the gas mass transfer coefficient (ky) was obtained. The results showed that a increased with the increase of super gravity factor, liquid flux and ratio of gas to liquid, kya and ky increased with the increase of super gravity factor and ratio of gas to liquid, but decreased with the increase of liquid flux. The kya of novel RPB was 36% higher compared with that of a baffled rotating packed bed under the same operational conditions. Based on the experimental data, the empirical formulae of a, kya and ky were developed.

Effect of Ventilation Duct Structure on Deposition of Particles

HAN Yun-long YIN Chuan-hui HU Yong-mei

. 2015, 15(1):  40-44. 

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Numerical simulation of particles deposition onto the bend, bifurcating duct and reducer was carried out based on comparison of dimensionless deposition velocity with the previous experimental and simulation results in the straight ducts with rectangular cross section. The Reynolds stress transport model was adopted, and a Lagrangian stochastic method of random walk model used to describe motion of particles in a gas-solid phase flow regime. The results show that there exists a similar trend of dimensionless deposition velocity with the relevant research results. However, the dimensionless deposition velocity onto the vertical wall and the ceiling decreases when the dimensionless relaxation time is higher than 1 (i.e., about 10 mm). The deposition efficiency of particulate matter increases with Stokes number (St) in the bend, reducer and bifurcating duct. The deposition efficiency of particulate matter in the three kinds of duct components is small and almost the same for St<0.1. When St>0.1, the deposition efficiency of particulate matter in the bend is the highest one, followed by the bifurcating duct and reducer under the same St. The deposition of small particles (<10 mm) in the straight duct is controlled by the turbulent diffusion and the large particles are mainly affected by gravity deposition. For the bend, bifurcating duct and reducer, the deposition of particulate matter (St>0.1) is governed by inertia collision.

Flow Behavior and Heat Transfer of Liquid-Solid Flow in Tubes with Spiral Insert

PENG De-qi ZHANG Lang YU Tian-lan WU Shu-ying ZHI Xiao-heng CHEN Qian

. 2015, 15(1):  45-49. 

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Numerical simulation on flow and heat transfer of liquid-solid flow in the tubes with spiral insert was carried out with the Fluent-EDEM coupling method. The particles collision on heat transfer surface and the heat transfer enhancement were analyzed, which was induced by spiral insert. The experiments show that the deviation between the simulation and experimental data is small in the range of 6.3%~13.8%. The fluid flows spirally, and the volume fraction of particles close to wall is increased from 0.44% to 3.27%, induced by the spiral insert. The results indicate that Nu of the combination is greater than that of only two-phase flow without insert under the same Re. When Re is below 60000, the two-phase tube flow with spiral insert has greater comprehensive evaluation index PEC than liquid-solid flow without insert and spiral insert without particles, respectively. Therefore, this combination technology can be applied in prevention of fouling and enhancement of heat transfer under the condition of low Re condition.

Simulation and Analysis of Rotary Tube Coal Moisture Control Technology

ZHAO Kai WU Li-zhong GONG Xiao-ran HU Chang-qing SHI Xue-feng GAO Jian-jun

. 2015, 15(1):  50-54. 

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Based on Fluent simulation software, the model of Euler multi-phase flow was adopted to simulate the flow field distribution, humidity and temperature variation of flue gas (coke oven gas) and coal in a rotary tube dryer. The results showed that the maximum velocity of flue gas is 9.65 m/s at the entrance, the minimum velocity of flue gas is 3.22 m/s in the rotary pipe, flue gas gathers in the center pipe by turning on pipe bend with the velocity of about 6~7 m/s, the maximum velocity of coal appears near the rotary pipe, and the minimum velocity of coal far away from the rotary pipe. After separation of coal with water, coal content increases, under normal circumstances, the dehydration rate can reach about 7%. The distribution of pulverized coal form the peripheral to central part in the dryer becomes dilute. The gas and coal have temperature gradient distributions, the temperature difference of flue gas is about 65 K, and that of pulverized coal about 31 K.

反应与分离

Modeling and Optimization for HCl Oxidation Combining Fluidized Bed with Multi-stage Quenching Adiabatic Fixed Bed Reactor

CHEN Xian YUAN Jie FEI Zhao-yang TANG Ji-hai CUI Mi-fen QIAO Xu

. 2015, 15(1):  55-61. 

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A novel HCl oxidation technology combining fluidized bed reactor (FBR) with multi-stage adiabatic fixed bed reactor (MSAFBR) in series was proposed. The operational parameters of HCl oxidation process, such as variety and flow rate of quench gas between MSAFBR, molar ratio of HCl to O2 in feed gas and catalyst dosage, were optimized based on the mathematic one-dimensional model established on the mass, energy and momentum balances. The results showed that liquid oxygen was more suitable in this technology. With liquid oxygen as the quenching

Effect of Perovskite Content on the Properties of Vanadium-Titanium Magnetite Sinter

LIU Ran LIU Chao-qing LIU Xiao-jie QIE Na-ya LV Qing

. 2015, 15(1):  62-67. 

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The relationship between the formation of liquid and perovskite in vanadium-titanium magnetite sinter with temperature was studied by experiments and calculation with FactSage6.0 to verify the thermodynamic analysis data. The results show that the tumbler index of vanadium-titanium magnetite sinter is 55.2% and RDI only 25.92%. By XRD pattern and mineral phase structure analysis, the poor metallurgical properties of sinter is mainly due to the presence of perovskite undermining the role of liquid phase bonding, the skeletal structure and dendritic perovskite noticeably increase, which seriously aggravate the proliferation of crack, and result in significantly lower quality of sinter. Thermodynamic calculation shows that the low temperature is advantageous to the formation of liquid-phase calcium ferrite and calcium silicate, but the high temperature to the formation of perovskite. When the temperature is greater than 800℃, the content of perovskite is basically stable, but the content of calcium ferrite and calcium silicate decreases obviously.

Numerical Simulation on Removal of Non-metallic Inclusions in a Bottom-blown Argon Ladle Furnace

JU Jian-tao YAN Ben ZHAO Fu-cai SHE Yuan ZHANG Zhao-hui

. 2015, 15(1):  68-73. 

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The effects of plug slit size and number, and argon blowing flow rate on the inclusion removal were studied by numerical simulation in a 60 t bottom argon blowing ladle furnace. The results showed that there was an optimal blowing argon flow rate that was conducive to removal of inclusion for different size slits. When the slit size increased from 10 mm to 30 mm, the critical blowing argon rate increased from 125 L/min to 225 L/min, the removal rate of inclusion would increase from 65% to 76%. The removal of inclusion occurred mainly in the first 12 min of argon blowing, and the removal rate of inclusion reached a maximum value when the slit number was 16. But an excessive argon flow rate had negative effect on the removal of inclusion when the other conditions were fixed. The industrial practice showed that the mathematical model could simulate the removal of inclusion well.

Effects of Oxygen Concentration on Combustion Reactivity of Pulverized Coal and Graphite Catalyzed by K2CO3

CHENG Wei GONG Xu-zhong GUO Zhan-cheng;

. 2015, 15(1):  74-78. 

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The effects of oxygen concentration on catalytic combustion, catalytic combustion reactivity of anthracite and graphite with K2CO3 were examined using TGA. The results showed that K2CO3 improved the combustion reaction and oxygen diffusion rates with the increase of oxygen concentration, but the incremental degree of combustion reaction rate was bigger, resulting in prolonging the platform time of anthracite combustion process. When the oxygen concentration increased from 21% to 100%, the extension of decreasing ignition temperature of pulverized anthracite and graphite catalyzed by K2CO3 promoted from 37.7℃ to 78.1℃ and 204.8℃ to 233.6℃, respectively. The apparent activation energy was reduced by K2CO3 in the initial combustion stage of coal, when the oxygen concentration was over 40%, the control step of combustion process changed from oxygen diffusion to chemical reaction. However, the apparent activation energy was always lower than 40 kJ/mol with the increase of oxygen concentration, the combustion reaction was controlled by oxygen diffusion in the later combustion stage of coal. For graphite combustion, the apparent activation energy decreased in the initial stage with addition of K2CO3, but the chemical reaction was still the control step. In the later stage of graphite combustion in the presence of K2CO3, the reaction activation energy increased from 39 kJ/mol to 110 kJ/mol with the increase of oxygen concentration from 21% to 100%, resulting in that the control step of combustion process changing from chemical reaction to oxygen diffusion.

Effect of Ultrasonic Power on Distribution of Al2O3 Inclusions in ESR Ingots

CHANG Li-zhong SHI Xiao-fang WANG Jian-jun LI Tao ZHOU De-fu PENG Cheng-song

. 2015, 15(1):  79-83. 

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A new electrosalg furnace with ultrasonic vibration was designed, and the effects of ultrasonic power on removal and distribution of alumina inclusions in electroslag remelting (ESR) ingots were studied. The results showed that during ESR, the biggest inclusion size decreased gradually from 40 mm to 36 and 14 mm when the ultrasonic power increased from 0 to 400 and 700 W. But when the power increased to 1000 W, the biggest inclusion size increased to 36 mm instead. Without ultrasonic vibration in ESR process, the inclusions had a tendency to aggregate in the edge and center of ESR ingots, and the edge aggregation was more serious. When the ultrasonic power increased, the distribution of inclusions became more uniform gradually. These phenomena were due to the ultrasonic cavitation and acoustic streaming effects, which improved the dynamic conditions of metal-slag reaction and were conducive to the removal and uniform distribution of inclusions. However, the too high ultrasonic power would generate the strong cavitation and acoustic streaming effects which would reduce the reduction of reaction rate between the slag and liquid metal, cause the disturbance of molten pool and depress the refining capacity of electroslag remelting process.

Preparation of Porous FeNi Alloy Powder by Oxalate Thermal Decomposition and the Kinetics

YAO Yong-lin ZHANG Chuan-fu FAN You-qi ZHAN Jing

. 2015, 15(1):  84-88. 

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The porous FeNi alloy powder with a particle size of 1 mm and BCC structure was prepared by a thermal decomposition-reduction process of oxalate precursor, and the thermal decomposition process studied. The results showed that the precursor underwent two steps in the heating process, dehydration (217.5℃) and gas (CO and CO2) release (352.5℃), and the latter was the reason for the formation of porous structure. The thermal decomposition followed random nuclei production and nuclei growth model, the activation energy was 148.59 kJ/mol, the pre-exponential factor 1.25×107 and the kinetics function G(a)=[-ln(1-a)]0.44.

Study on Pyrolysis Kinetics of Bamboo

DONG Qing ZHANG Shu-ping ZHANG Li XIONG Yuan-quan

. 2015, 15(1):  89-93. 

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Kinetic study on bamboo pyrolysis was conducted with a thermogravimetric analyzer under nitrogen condition. The effects of heating rate and particle size on the pyrolysis process were examined. The results showed that the pyrolysis process of bamboo included four stages, drying, pre-pyrolysis, rapid pyrolysis and slow pyrolysis. Heating rate had a significant effect on the bamboo pyrolysis. With the increase of heating rate from 40 to 100℃/min, both the maximum and average reaction rates increased, and the decomposition reaction was postponed to a higher temperature. The values of kinetic parameters calculated from the main reaction regimes decreased from 130.87 to 73.85 kJ/mol. A kinetic compensation effect was observed between the values of natural logarithm of frequency factor and activation energy. The pyrolysis process of bamboo was controlled by not only kinetics, but also heat and mass transfer within the particles with the sizes larger than 380 mm.

过程与工艺

Recovery of Indium and Preparation of High Quality Glass from Waste ITO Glass

WANG Yu-lin QI Sen HU Hai-juan CHEN Fang-qiu LIU Guang-fu

. 2015, 15(1):  94-99. 

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In order to recover indium and high-quality glass from liquid crystal display (LCD) panels, a recovery process was proposed. First, the pieces of indium tin oxide (ITO) glass substrate were leached with hydrofluoric acid to obtain indium-rich solution. After evaporating and concentrating of the solution, indium concentrate was obtained, then after four treatment steps of dissolution, aluminum replacement, melting and purification, crude indium was finally obtained. Meanwhile the glass substrate which was separated from the hydrofluoric acid was used for producing glass as batch. The results showed that the shattering process resulted in loss of indium. The indium could be extracted effectively in 8 mol/L hydrofluoric acid within 3 h, its purity was as high as 92.3% with the recovery rate of 89.2%. The mold temperature of recycled glass sample was 1462℃, thermal expansion coefficient 3.2′10-6/℃, average value of Vicker's hardness 584.9, density of the recycled glass sample 2.43097 g/cm3, and visible light transmittance 75.2. Despite of degradation of performances, the goal of recycling and reusing thin film transistor (TFT)-LCD glass substrate could be still realized by reducing appropriate amount of recycled glass in glass production.

Axial Desorption Characteristics of K+ in Continuous Packed Moving Bed Column under Countercurrent Operation

ZHAO Bin ZHANG Yu-long ZHANG Shao-feng WANG De-wu QIU Ya-juan

. 2015, 15(1):  100-105. 

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With 001′7 strong acid cationic resin with adsorbed K+ as solid medium and NaCl solution as desorbent, axial desorption characteristics of ion-exchange column to K+ in a packed moving bed under continuous liquid-solid countercurrent operation were studied in different operating conditions, and compared with a fixed bed. The results showed that in the moving bed, the cumulative desorption rate of unit resin increased gradually from top to bottom along the axial direction, which, especially, increased more rapidly in the lower 1/5 part of ion-exchange column, the full column resin cumulative desorption rate could reach over 90% under some conditions. The cumulative desorption rate of unit resin in each axial region increased when the initial concentration of desorbent increased in a certain range, but when the initial concentration of desorbent increased to a certain value, a phenomenon appeared in different axial regions of the ion exchange column that desorption and antiadsorption alternated in domination. With the increase of apparent velocity of the eluate in the ion exchange column and decrease of resin moving speed and original adsorption capacity, the cumulative desorption rate of unit resin in each axial region increased. The full column resin cumulative desorption rate and desorbed amount of K+ were higher in a continuous moving bed than in a fixed bed during the time of the eluate flowing through the ion exchange column in one-way.

Removal of Chloride Ion from Phosphoric Acid via Ozone Catalysis Oxidation

ZHANG Ren-yuan LIU Zhong-qing WANG Qin ZHANG Qiang MA Xue-xiang LIU Wei-zao LIANG Bin LI Chun

. 2015, 15(1):  106-110. 

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The removal of chloride ion from phosphoric acid system by ozone catalyzing oxidation was experimentally studied with focus on the effects of phosphoric acid concentration, addition of transition metallic ions of Fe3+, Cu2+, and Co2+, and reaction temperature and time. The results indicated that the H+ dissociated from phosphoric acid could significantly catalyze the oxidation of chloride, resulting in Cl2 evolution, and the concentration of Cl- was decreased from 1000 to 5 mg/L at the concentration of phosphoric acid over 80%(w) and reaction temperature 70℃ for 1 h, which meets the quality requirements of technical-grade phosphoric acid Chinese national standard (GB/T 2092-2008) for chloride content. The oxidation could also be catalyzed by Fe3+, Cu2+ and Co2+ ions. With Fe3+ concentration ≥500 mg/L and under the otherwise same conditions, the phosphoric acid concentration required for chlorine ion to reach the standard could be reduced to 60%(w), while the acid concentration could be further reduced to 20%(w) upon using Co2+ concentration of 500 mg/L in the presence of Fe3+, thus the concentration section of phosphoric acid could be omitted. The results were further confirmed upon the application in removal of chloride ion from commercial wet process phosphoric acid.

生化工程专栏

Preparation and Properties of Dextran-grafted High Capacity Immobilized Metal Affinity Chromatography Media

ZHANG Jing-fei ZHAO Lan HUANG Yong-dong; ZHANG Zhi-gang MA Guang-hui SU Zhi-guo

. 2015, 15(1):  111-118. 

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Agarose microspheres were activated using allyl glycidyl ether, and further grafted with dextran molecules, and the effect of molecular weight of dextran on the grafting process was studied. Then iminodiacetic acid type immobilized metal affinity chromatography (IMAC) media were prepared using these dextran-grafted agarose microspheres as the matrix. The effects of dextran-grafting process on the pore structure, flow performance and capacity were examined. The results showed that dextran with molecular weight in the range of 20~500 kDa was evenly distributed inside agaroe microspheres, and the amount of dextran grafted increased with its molecular weight. The particle morphology, particle size and distribution of dextran-grafted IMAC media did not change obviously. However, dextran-grafted IMAC media possessed a better flow hydrodynamics property. Compared with the commercial chromatography media of Ni Sepharose 6FF, dextran-grafted IMAC media had a more abundant pore structure when the molecular weight of probe was between bovine serum albumin and ferritin. Binding capacity results indicated that its capacities for His-tagged lactate dehydrogenase and ciliary neurotrophic factor were 19 and 27 mg/mL, which were 26.6% and 42.0% higher than those of Ni Sepharose 6FF, respectively.

Intensification of the Bio-oxidation Process of Axi Refractory Gold Concentrate

WANG Guo-hua LU Ying LI Shou-peng XIE Jian-ping WU Hai-yan LIU Xin-xing

. 2015, 15(1):  119-125. 

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In order to enhance the efficiency of bio-oxidation of Axi gold concentrate, the effects of three mixed bacteria cultures and two-step treatment approach on the intensification of bio-oxidation were studied. The results revealed that the optimum mixed culture was moderate thermophiles, the oxidation rates declined drastically with increasing of pulp density. The extraction rates of iron and sulfur were 98.35% and 91.90% at 2% pulp density, when the pulp density was elevated to 15%, the extraction rates of iron and sulfur declined to 50.25% and 49.51%, respectively. The two-step treatment could further improve the efficiency of pretreatment with moderate thermophiles, the extraction rates of iron and sulfur boosted to 64.93% and 65.73% at 15% pulp density after the two-step treatment, which was equivalent to the result obtained at 10% pulp density with normal bio-oxidation process.

Analysis of Nutritive Elements and Optimization of Extraction Process of Protein from Scenedesmus dimorphus Residue

FAN Xing HUANG Yan-fei LIAO Yong-hong CONG Wei

. 2015, 15(1):  126-131. 

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The extraction process of protein from Scenedesmus dimorphus residue was optimized, and the obtained protein quality assessed. The effects of extracting solution pH value, ratio of solid to liquid, temperature and time on the extraction rate of the protein from Scenedesmus dimorphus residue were examined before the isoelectric point of the protein was determined. The optimum conditions of alkaline extraction were obtained by orthogonal experiments as follows: pH value of solution 12, ratio of liquid to solid 40 mL/g, and extraction at 45℃ for 140 min. Under these conditions, the extraction rate of protein was 40.13%. The ratio of essential to total amino acids in the protein was 44.3%. The essential amino acid index, amino acid score, chemical score, biological value, nutritional index and score of ratio coefficient of amino acid were 82.24, 63.32, 46.66, 77.94, 35.84 and 74.21, respectively.

Bioleaching of Copper from High Alkaline Copper Ore Tailings with Aspergillus niger

DIAO Ning-ning LI Guang-yue WANG Yong-dong DU Kang

. 2015, 15(1):  132-136. 

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The bioleaching of high alkaline copper ore tailings from Hunan Province with Aspergillus niger was carried out in shake flasks. The effects of leaching time, potato and sucrose contents on the leaching rate of copper were examined. The results showed that the leaching rate of copper reached the maximum value in the leaching time of 7 d, and then begun to decline markedly with further leaching. The contents of potato and sucrose in PSA medium had a significant impact on copper leaching. When the contents of potato and sucrose were 200 g/L and 20 g/L, respectively, the highest leaching rate of copper was obtained. At an inoculum amount of 0.02%(j), pulp density 50 g/L, 30℃ temperature and 200 r/min rotating speed, the leaching rate of copper reached 79.03% in 7 d with the contents of potato 200 g/L and sucrose 20 g/L.

材料工程专栏

Preparation of Potassium Chloride and Spherical Calcium Carbonate Particles from Leaching Solution of Electrostatic Precipitator Dust of Iron Ore Sintering

PEI Bin ZHAN Guang CHEN Pan-ze GUO Zhan-cheng; GAO Jin-tao

. 2015, 15(1):  137-146. 

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Several physical and chemical analytical detection methods were used to study the basic properties of electrostatic precipitator (ESP) dust collected from Baogang Steel Corporation. The results showed that the major components in the dust were K, Na, Fe and Ca salts. Water leaching could be used for recovering the potassium salt. Massive soluble calcium sulfate existed in the leaching solution. In order to provide theoretical guidance to inhibition of the dissolution of calcium ion from the ESP dust, the water leaching experiment on ESP dust was performed, and the dissolution behaviors of CaSO4 in potassium chloride, sodium chloride, potassium sulfate and their mixed salt solutions were studied. The result showed that the solubility of calcium sulfate dihydrate increased sharply with increasing of concentrations of KCl and NaCl due to the salting-in effect of KCl and NaCl. A lower ratio of liquid to solid should be chosen in the leaching process to increase the concentration of SO42- and inhibit the dissolution of calcium sulfate dihydrate by using the common ion effect of SO42-. Using sodium carbonate solution as precipitating agent, the effect of Na2CO3 on the removal rate of calcium ion was studied. Na2CO3 was effective in removal of calcium ion. The effects of concentration of sodium carbonate solution, reaction temperature, and stirring speed on preparation of spherical calcium carbonate particles were studied. Spherical calcium carbonate particles of less than 10 μm with good dispersion and grain size distribution were obtained. Furthermore, a potassium recovery process with joint production of spherical calcium carbonate from ESP dust was designed, and the quality of KCl product was stable and met the requirements of national standard GB 20406-2006. This process had industrial application potential.

Synthesis of Lithium Metatitanate and Its Enrichment for Lithium by Ion Exchange

ZHU Xia-ping WANG Chang-fu LAI Yi ZHANG Huan WANG Yun ZHOU Li-min

. 2015, 15(1):  147-152. 

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The lithium metatitanate precursor was synthesized by alkoxide hydrolysis and sol-gel method with tetrabutyl titanate and lithium acetate as raw materials. The ion exchanger with selective enrichment property for lithium ion was prepared and further modified by acid treatment to extract lithium from lattice. The structure and ion enrichment of lithium metatitanate precursor and lithium metatitanate ion exchanger were examined. The results indicate that the ion exchanger has a high selective enrichment, and the maximum adsorption capacity of lithium ion is 33.5345 mg/g at pH 12.8 and 35℃ with initial lithium ion concentration 200 mg/L. The adsorption isotherms obey the Langmuir isotherm models. Thermodynamic data show that it is a spontaneous exothermic adsorption process of pseudo-second order kinetics.

Influences of Dispersants with Different Structures on the Dispersibility of Carbon Black

JIANG Dong WANQ Chao-sheng JIANG Zhen-lin ZHOU Wei ZHANG Fang

. 2015, 15(1):  153-158. 

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The z potential of carbon black MA-100 adsorbed dispersants with different structures and its dispersing stability under different pH values were analyzed, and the storage stability and writing properties of gel ink that was prepared with carbon black paste were studied. The results show that the anionic polymer dispersant ammonium salt of styrene-maleate copolymer (SMA-NH4) has the best dispersing stability to carbon black MA-100 with the sedimentation rate of 17 mm/min, followed by the nonionic dispersant polyvinyl pyrrolidone with 30 mm/min, and the anionic dispersant methylenebis naphthalene sulfonate falls into the last position with 218 mm/min. In aqueous systems, pH value can change not only the ionization degree of SMA-NH4, but also the configuration of polymer chains on the carbon black surface. The z potential of carbon black is -45.7 mV at pH value of 8, so the molecular chains of the polymer fully stretch, leading to that improvement of SMA-NH4 steric resistance, the gel ink prepared with this dispersant shows good storage stability and writing properties.

Preparation and Photocatalytic Properties of Nanometer TiO2 Powder in Morpholine Ionic Liquid

ZHAO Jin-hua WANG Yu-song CHEN Wu-hua LAI Fei

. 2015, 15(1):  159-163. 

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The rutile nanometer TiO2 powder was prepared using self-made N-methy-N-nitrophenyl morpholine hydrochloride ionic liquid as the medium and TiOCl2 solution as the precursor by low temperature hydrolysis method. The results show that the prepared TiO2 particle size is 4.7 nm. The nanometer TiO2 was used in photocatalytic degradation of methyl orange. The results show that the degradation rate can reach 99.18% in 5 h, which shows that the prepared nanometer TiO2 has excellent photocatalytic performance.

Dynamic Photocatalytic Degradation of Toluene Gas in ACH/TiO2 Photocatalytic Network

YANG Fang XUAN Shao-feng MA Xin-sheng

. 2015, 15(1):  164-168. 

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TiO2 nano-particles were immobilized on activated carbon honeycomb (ACH) by impregnation method to prepare ACH/TiO2 photocatalyst. Experiments on dynamic photocatalytic degradation of toluene gas under UV excitation wavelength of 387 nm in a self-made photocatalytic reactor were carried out. The results indicated that ACH/TiO2 had a good synergistic effect, which could increase the degradation of initial concentration of toluene from 160 to 830 mg/m3. Moreover, the degradation rate of toluene could maintain the best level (90.0%) under the conditions of TiO2 in ACH/TiO2 12.5%±1%(w), initial concentration of toluene 410 mg/m3, relative humidity 30% and gas flow rate 1 L/min, respectively. Water vapor could affect the photocatalytic degradation of toluene gas. The degradation rate of toluene could be kept unchanged for 6 h under illumination with the flow stability.

Synthesis and Electrochemical Performance of Hollow ZnFe2O4 Microspheres

WANG Ya-lei ZHANG Li-xin

. 2015, 15(1):  169-173. 

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Hollow ZnFe2O4 microspheres were fabricated by one-step hydrothermal method with Zn(Ac)2×4H2O and FeCl3×6H2O as raw materials, and their crystalline phase, morphology and composition characterized. The results showed that the diameter of hollow ZnFe2O4 microspheres was about 300 nm with the shell thickness of 25 nm. When the composite was used as a cathode material for lithium ion batteries, the results displayed that the ZnFe2O4 sample exhibited the first discharge capacity of 1524 mA×h/g at a high current density of 100 mA/g, remained at 826 mA×h/g after 50 cycles and tended to be stable, reflecting excellent cycling performance.

综述

Research Progress in Aerobic Denitrifier and Its Removing Mechanism of Nitrite

HE Teng-xia LI Zhen-lun YANG Shan

. 2015, 15(1):  174-180. 

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The types and characteristics of aerobic denitrifiers are reviewed, and the mechanism and pathways in the nitrite removal process presented. The removing ways of nitrite with aerobic denitrifiers, including assimilation, enzymatic degradation, acid degradation and dissimilatory nitrite reduction to ammonium, are analyzed. Nitrite reduction by denitrifier is mainly enzyme-catalytic reaction that includes nitrite reductase, nitric oxide reductase and nitrous oxide reductase, which is a relayed relation in reduction of nitrite. The nitrite reductase is the reaction rate restriction enzyme. In the future, separation and screening of high efficient type of nitrite denitrifier, optimization of the enzymatic reaction technology and deep analysis of the influential factors of biological denitrification should be emphasized for improving the denitrification efficiency of denitrifiers in practical applications.