Table of Content

20 October 2014, Volume 14 Issue 5

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流动与传递

Radial Distributions of Solids Hold-up and Particle Velocity in FCC Riser Feed Injection Zone with Catalyst-Feed Oil Countercurrent Contact

YAN Zi-han QIN Xiao-gang CHEN Sheng FAN Yi-ping LU Chun-xi

. 2014, 14(5):  721-729. 

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A new kind of feed injection scheme is put forward, in which the feed jets realize a countercurrent contact with the catalysts. The radial distributions of solids hold-up and particle velocity at different heights are investigated via a large-scale cold model. Moreover, the effects of pre-lift velocity and nozzle jet velocity on the flow features in the feed injection zone are analyzed. The feed injection zone can be further divided into three zones, the upstream transition zone (H=-0.675~-0.375 m), jet controlling zone (H=-0.375~0.375 m) and downstream transition zone (H=0.375~0.675 m). Compared with the conventional structure, the influencing region of jet is shortened obviously above the nozzles while extending below the nozzles. The radial concentration profile of the catalysts is more uniformly distributed in the initial contacting area of oil with catalyst. Then, empirical formulae for estimating the radial distributions of solids hold-up are set up based on the experimental data and theoretical analysis, the computed and experimental results are in good agreement.

Numerical Study on Solute Transport in Leaching Process of Rare Earth by Lattice Boltzmann Method

WU Cheng-you QIU Ting-sheng WANG Li-min

. 2014, 14(5):  730-736. 

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The solute transport in the leaching process of rare earth from weathered crust elution-deposited rare earth ore is investigated by a lattice Boltzmann method coupling with mass transfer. Both distributions of flow velocity and solute concentration at pore scale are obtained after the validation of the proposed model. Meanwhile, the effect of leaching velocity on the solute transport process is studied. The result shows that there exists an optimal leaching flow rate at 0.25~0.35 mm/s for achieving the best efficiency of solute transport. The long leaching time and large dosage of leaching agent are required when the leaching flow rate is less than 0.2 mm/s, while the leaching efficiency is reduced with the emergence of channeling phenomenon in the packed column when the leaching flow rate is greater than 0.4 mm/s. Moreover, the simulated result of Sherwood number as a function of Reynolds number fits well with the previous empirical correlation, which indicates that the proposed model can be used to predict the solute transport mechanism in the leaching process of rare earth ore.

Numerical Simulation on the Formation and Dripping of Melt Droplet in the Electroslag Remelting Process

LIU Shuang HE Zhu WANG Qiang XIA Tian LI Bao-kuan

. 2014, 14(5):  737-743. 

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Based on the magnetohydrodynamic module of the CFD FLUENT software, a three-dimensional mathematical model was developed to describe the multi-field coupling phenomenon in the electroslag remelting process. The model predicted values were in good agreement with the experimental measurements. The simulation results show that during the melt dripping process, the equivalent resistance of the slag decreases gradually, and the current is redistributed, which directly influences the energy consumption and production rate of the electroslag furnace. The maximum value of current density, electromagnetic force and velocity appears when the large melt droplet detaches. The maximum value of the current density is increased by almost one order of magnitude. And the maximum value of the electromagnetic force and velocity is increased by 2.5 and 4.7 times, respectively. The maximum value of Joule heat and temperature appears when the droplets fall into the slag-metal interface. The maximum value of the Joule heat and temperature is increased about 174.7% and 26.8%, compared with the moment of electrode started melting.

Numerical Simulation of Solid-Liquid Suspension Characteristics in a Stirred Tank with Improved INTER-MIG Impeller

ZHOU Yong-jun LU Yuan CHEN Ming-hao LIANG Jia-yong

. 2014, 14(5):  744-750. 

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The solid-liquid suspension characteristics, critical suspension speed of impeller and power consumption of a stirred tank with dual improved INTER-MIG impeller were numerically simulated with the software Fluent 12.0 on a parallel computer workstation. The effects of rotation speed (n), impeller off-bottom clearance height (C1) and spacing between impellers (C2) on particles suspension characteristics in the stirred tank were analyzed under the particle volume fraction as at 30%. The results show that at a constant rotation speed and impeller diameter, local structure of flow field changes with C1 and C2, appropriate of C1 and C2 can make solid-liquid mixed more evenly and good for suspension of particles and the mass and heat transfer. The optimal value of C1/D is 0.36, D is the tank diameter, and the optimal value of C2/D 0.44. Under the optimum working conditions, the critical suspension speed of impeller, Njs is 118.3 r/min, and the optimum speed, n, 124 r/min, which ensures the solids just suspended off the bottom and the minimum consumption of power.

Study on Flow Characteristics of the Fluid in Low Speed Rotating Cavity

ZHANG Cui-cui ZHAO Pei-tao LI Yang GE Shi-fu

. 2014, 14(5):  751-757. 

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A particle image velocimetry (PIV) test setup was used to study the fluid flow characteristics of axial center cross-section in a low speed rotating cavity, and three-dimensional numerical simulation of flow field in low-speed rotating cavity was performed based on the Realizable k-e model. The results of simulation were consistent with those from experimental study with a maximum relative error less than 16.9%, indicating the validity of the simulation methods and model. Besides, the effects of number and length of deflector, Reynolds number () of cavity inlet and rotating Reynolds number on fluid flow in the rotating cavity were examined based on the model equation. The results show that Re of cavity inlet, number and relative length of deflector have obvious impact on volume-averaged relative velocity and vorticity in the cavity, when Re of cavity inlet varies from 17000 to 53000, volume-averaged relative velocity and vorticity increases 2.4 times and 1.6 times, respectively. When the number of deflector varies from 0 to 4, the growth rate of that is 62% and 30% respectively. When the relative length of deflector increases from 0.5 to 0.93, volume-averaged relative velocity and vorticity increases 114% and 58% respectively. Pressure loss in the cavity is affected mainly by Re of cavity inlet, when Re of cavity inlet varies from 17000 to 53000, pressure loss in the cavity increases 8 times, while with the increase of number and relative length of deflector, pressure loss increases less than 5%. Under the present investigation conditions, in order to improve fluid disturbance in the cavity and reduce fluid flow resistance, it would be better to select an appropriate inlet velocity of the cavity, install deflectors and increase its relative length.

Measurement of Flow State in a Tube Inserted with Rotors with PIV

HE Li-chen GUAN Chang-feng HE Jian-yun HE Chang-jiang YAN Hua YANG Wei-min

. 2014, 14(5):  758-762. 

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Particle image velocimetry was used to study the tube inserted with three-blade rotor, tube inserted with two-blade rotor and tube without rotor, and flow fields of these tubes were obtained. The results revealed that the difference of distribution of the axial velocity along the radius between the tubes inserted with three-blade rotor of small lead and two-blade rotor was not distinct, near M type distribution was demonstrated, but the distribution of radial velocity along the radius of the tube inserted with three-blade rotor was obviously higher than that of two-blade rotor, and so was the distribution of the turbulent kinetic energy along the radius. The attenuation length of turbulent kinetic energy was characterized as the quantity of action range of one rotor, when one rotor was placed into the tube, the turbulent kinetic energy decayed gradually and became stable at a constant value at a distance of 10 mm, so the length of action range of Jienengxin rotor was regarded as 10 mm, which could be instructive to industrial application.

反应与分离

Extraction of Vanadium from Vanadium-containing Slag by Roasting-Hydrothermal Alkali Leaching

LIU Ji-xin LI Lan-jie ZHENG Shi-li WANG Shao-na DU Hao XIE Hai-yun

. 2014, 14(5):  763-769. 

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The effects of vanadium slag roasting and NaOH solution of hydrothermal leaching on the leaching rate of vanadium were studied, the optimum parameters of the process were obtained, and the mechanism was analyzed. The results showed that when the roasting temperature reached over 700℃, the oxidative decomposition of vanadium iron spinel could be achieved, the optimum conditions for roasting process were roasting at 850℃ for 2 h. The optimum leaching conditions were obtained as leaching temperature of 180℃, vanadium slag particle size lass than 74 mm, leaching time 2 h, ratio of liquid to solid 5 L/g, concentration of NaOH 30%(w) and stirring speed 500 r/min. Under these conditions, the leaching rate of vanadium could reached 95%. No harmful gases were produced in the roasting and hydrothermal leaching of NaOH.

Gas Pressure Drop and Desulfurization Performance of a Rotating Packed Bed with Structured Wire Mesh Packing

ZHAO Zhi-qiang CHU Guang-wen LUO Yong ZOU Hai-hui XIANG Yang CHEN Jian-feng

. 2014, 14(5):  770-775. 

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Gas pressure drop of the rotating packed bed (RPB) with four structured wire mesh packings was studied using air-water as working system. The effects of operating parameters, such as rotational speed, gas flow rate, liquid flow rate, and characteristics of packing on gas pressure drop were investigated. Comparative experiments were conducted in the RPB with traditional stainless steel wire mesh packing. Experimental results showed that gas pressure drop of the RPB with the structured wire mesh packings was 35%~70% lower than that of the RPB with traditional wire mesh packing. Moreover, the desulfurization performance of the RPB equipped with the structured wire mesh packing which had a lower gas pressure drop was studied with (NH4)2SO3 as absorbent. Experimental results indicated that the SO2 removal efficiency increased with increasing of rotational speed and (NH4)2SO3 concentration, decreased with increasing of SO2 inlet concentration and ratio of gas to liquid. The SO2 removal efficiency could be up to 97% under the experimental conditions. The outlet SO2 concentration could meet the demand of the emission standard of pollutants for sulfuric acid industry.

Separation of Heavy Metals from Leaching Solution of Hospital Waste Incinerator Fly Ash by Electrodialysis

WEI Guo-xia LIU Han-qiao WU Zhen-hua WANG Cheng-zhi

. 2014, 14(5):  776-781. 

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The effects of electric current density, ratio of liquid to solid and treatment time on the removal of heavy metals from the leaching solution of hospital solid waste incineration (HSWI) fly ash by electrodialysis were studied. The characteristics of HSWI fly ash before and after electrodialysis were analyzed. The results show that 11.1% of Pb, 42.3% of Zn, 56.7% of Cd, 38.7% of Cu and 7.5% of Cr were removed from the raw fly ash by optimizing the electrodialytic parameters at the current density 0.8 mA/cm2, ratio of liquid to solid 10 and treatment time 14 d. Under these conditions, the chlorine level decreased from 20.43% in the raw fly ash to 0.78% in the residual ash, loss on ignition of fly ash increased from 11.1% to 34.3% due to the solubilization of soluble compounds like NaCl after electrodialysis. Although some initially existent heavy metals had been removed from the ash during the electrodialysis, the content of heavy metals actually increased due to mineral dissolution and adsorption of activated carbon powder. The exchangeable fraction and carbonate fraction of these heavy metals in the residual ash decreased, but their leaching concentration was above regulatory thresholds of waste landfill.

Recovery of Metals from Stainless Steel Pickling Sludge by Reduction and Magnetic Separation

ZHANG Jing SUN Ying LIU Xu-long LI Qiu-ju

. 2014, 14(5):  782-786. 

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The stainless steel pickling sludge was calcined with graphite powder as the reducing agent, and then separated by magnetic treatment for recovery of metals. The results showed that under the optimal conditions of reduction temperature 1350℃, holding time 300 min, and atomic ratio of C to O 1.2 (mass ratio of carbon to the sludge at 11.8:100), the recovery rates of Fe, Cr and Ni were 92.7%, 86.7% and 93.6%, respectively. After reduction-magnetic separation, the content of Cr and Ni was decreased down to 0.07% and 0.04%, respectively, which meets the national discharge standard.

Drying of Banana Peel and Its Adsorption to Rhodamine-B

GAN Lin-huo HE Xiao-ye CHEN Xiong

. 2014, 14(5):  787-791. 

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Using banana peel as raw material, the effects of three different drying methods on preparation of banana peel powder were investigated, and its adsorption performance to Rhodamine-B was examined. It was found that drying in microwave oven with the power of 800 W was the optimum method, and the dried banana peel powder possessing fast rate of water loss (90%), easy grinding and good maintaining of its original appearance and structure was obtained after 4 min, the adsorbed amount of Rhodamine-B on banana peel powder (>110 mg/g) was larger than that of other biosorbents, the carboxyl and hydroxyl groups in the structure of banana peel powder contributed to the adsorption of Rhodamine-B.

Leaching of Red Mud with Different Acids for Extraction of Vanadium

ZHU Xiao-bo LI Wang GUAN Xue-mao

. 2014, 14(5):  792-796. 

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Leaching of vanadium from red mud with different acids was carried out, and the effect of acid concentration on the recovery rate of vanadium studied. Furthermore, the red mud, leaching solution and leaching slag were analyzed, the thermodynamics of vanadium solution in sulfuric acid medium was analyzed under standard conditions, where the diagrams of concentration logarithm-pH value under different valence vanadium were drawn. The results show that sulfuric acid was more suitable for recovery of vanadium from red mud. The recovery rate of vanadium could reach 88% under the conditions of ratio liquid to solid of 5 mL/g, reaction temperature of 90℃, reaction time of 1 h and sulfuric acid concentration of 5.5 mol/L. The brookite, perovskite, dolomite, hematite and muscovite were dissolved at a certain degree and the anhydrite phase appeared after leaching of red mud with sulfuric acid. The results of pH value of 0.47, colour of blue, valence state of four and vanadium concentration of 0.006773 mol/L were obtained in the leaching system. VOSO4 was generated from V(IV) in sulfuric acid medium, which could increase the solubility of vanadium and broaden its stability range. Furthermore, VO2 was easier to dissolve and VOSO4 more stable with increasing of sulfuric acid concentration.

Extraction of Al and Fe from Bauxite by Sulfuric Acid Roasting and Water Leaching Processes

LIU Jia-nan JIA Zhi-liang ZHAI Yu-chun SHEN Xiao-yi

. 2014, 14(5):  797-801. 

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The effects of roasting temperature, roasting time and molar ratio of sulfuric acid to ore on the extracting rates of Al and Fe from bauxite by sulfuric acid roasting and water leaching were investigated through single-factor experiments and orthogonal experiments. The results showed that the optimum conditions were obtained as the molar ratio of sulfuric acid to ore of 3.75:1, roasting temperature of 325℃ and roasting time of 2.5 h. The extracting rate of Al was over 98% and that of Fe over 80% under the optimum conditions. The sequence of each factor affecting the extracting rates of Al and Fe is the molar ratio of sulfuric acid to ore > roasting temperature > roasting time. The process was proved to be significant with advantages of high extraction rates and low temperature.

过程与工艺

Continuous Synthesis of Ethylenediamine by Tubular Non-isothermal Reaction with a Static Mixer

FU Li GUO Wa-li LIU Xi-xing HAN Jun-tao SANG Guo-long

. 2014, 14(5):  802-808. 

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Ethylenediamine was continuously prepared by dichlorethane under variable temperature conditions in a static mixing way. The influential factors of reaction were analyzed by single factor experiments, and the effects of the concentration of ammonia, system pressure and molar ratio of ammonia to dichlorethane on the reaction were evaluated by response surface methodology. The quadratic fitting equation between the yield of ethylenediamine and the influential factors was obtained, and these technical parameters were optimized. The results show that the three factors have obvious effect on the reaction, and the influential order from strong to weak is the molar ratio of ammonia to dichlorethane, concentration of ammonia, and system pressure. The optimal conditions obtained are: the length ratio of the first section to second one of high temperature reactor 1:1, the first pipe 130℃, the second pipe 110℃, reaction time 7 min, system pressure 4.61 MPa, concentration of ammonia 48.04%(w) and molar ratio of ammonia to dichlorethane 25.22. Under these conditions the yield of ethylenediamine is 76.49%.

Effects of Additives on Properties of Molten Medium-titanium Slag

ZHANg Xu-sheng LV Qing LIU Xiao-jie QIE Na-ya

. 2014, 14(5):  809-815. 

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Based on the blast furnace slag from Chengde Iron and Steel Company in Hebei Iron and Steel Group, the slag samples were prepared with chemical reagents, and the effects of additives on the viscosity and melting temperature of medium-titanium blast furnace slag investigated. The results show that when the basicity of slag is 1.12, the content of CaF2 0.5%~2%, Fe2O3 about 5%, Al2O3 13.75%, MgO 13.95% and MnO 5%(w), it is conducive to improving the slag melting temperature and viscosity. Ce2O3 added to the slag makes melting temperature and viscosity increase, which is not conducive to the production.

Pore Structure Characteristics and Effective Diffusion Coefficient of Limestone during Calcination

LI Ming-chun ZHANG Jin QU Yan-ping WU Yu-sheng

. 2014, 14(5):  816-822. 

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The evolution characteristics of pore structure and reaction mechanism of limestone during decomposition were experimentally studied with nitrogen adsorption method, field emission scanning electron microscope and thermal gravimetric analysis. A bimodal distribution of probability density function and mathematical model describing the effect of pore structure on the effective diffusion coefficient was established, and the simulation results validated with the experimental data. The results show that the pore size distributions of calcined limestone in different decomposition stages all have a characteristic of bimodal distribution. The number of mesopore near the main peak of pore sizes about 3 nm increases with the solid conversion ratio and has a step type growth when the solid conversion ratio achieves about 60%. As the solid conversion ratio increases from 50.41% to 68.27%, the effective diffusion coefficient decreases from 0.0162 to 0.0093 cm2/s at 1073 K, which leads to an increase in the pore diffusion resistance affecting the decomposition mechanism of limestone. The critical solid conversion ratio corresponding to the reaction rate controlled by the mass transfer is 60% and 75% at 1073 and 1223 K, respectively.

Direct Reduction of Polyethylene-added Carbon-containing Iron Ore Roasted Pellets

CHEN Wei-peng XIE Zhi-hui ZHANG Huan ZHAO Zeng-wu LI Bao-wei WU Wen-fei

. 2014, 14(5):  823-828. 

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Polyethylene particles were mixed with limonite powder and bentonite for producing carbon-containing iron ore roasted pellets in order to produce directly reduced iron by direct reduction in a muffle furnace. The effects of reduction temperature, time, molar ratio of carbon to oxygen (C/O) and content of polyethylene on reduction rate of carbon-containing iron ore roasted pellets were studied by orthogonal and single factor experiments. The results showed that the main influential factors include reduction temperature, reduction time, C/O and content of polyethylene. Under the optimum conditions of reduction time of 5 min, temperature of 1350℃, C/O of 1.2 and content of polyethylene of 4%(w), the reduction rate of pellets can reach up to 99.87%. In addition, the reduction time can be shortened, the reduction temperature reduced, and the reduction rate of the pellets improved by adding a certain proportion of polyethylene. Moreover, adding 2%(w) CaF2 in the balling process makes slag and iron separate apparently, and separated slag pulverize naturally. This is conducive to further screening for high-quality directly reduced iron.

Kinetics and Stratification of Hydrogen Reduction of Block Hematite

FANG Fei YANG Xiao-bo ZHOU Guo-zhi

. 2014, 14(5):  829-834. 

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The hydrogen reduction process of block hematite in 1073~1273 K was studied by using EPMA and metallographic analysis. The results showed that there were a staged character and stratification in the hydrogen reduction process of block hematite. The mechanism of the staged character and stratification was discussed based on the results of XRD and EPMA. Under the experimental conditions in this work, the reduction rate was controlled by gas diffusion and interfacial chemical reaction, and the apparent activation energy was 27.0±5.9 kJ/mol.

Effects of Additives on Release of Tar and CO in Flue Gas from Combustion of Flue-cured Tobacco

SUN Yun-lan LIU Yong-wu ZHU Bao-zhong HU Yong-hua

. 2014, 14(5):  835-840. 

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In order to find out the relationship between release stage of combustion pollutants such as tar and CO and its combustion kinetics for flue-cured tobacco, the method of cigarette suction combined with TG-DTG-DSC thermal analysis technology was applied to analyze the effects of KNO3 and KClO3 additives on combustion pollutants release and decomposition of flue-cured tobacco. The results show that both additives can reduce puff number, and release of CO and tar in different degrees. KNO3 has more obvious effect in reducing tar during flue-cured tobacco combustion than KClO3 due to the reduction of activation energy in the macromolecular volatile pyrolysis and combustion stage (504.15~696.15 K), and promotes this stage reaction. Although the promoting effect of KClO3 in carbon residue combustion stage (696.15~852.15 K) is slightly lower than that of KNO3, its promoting effect is remarkable in the pyrolysis volatilization stage of small molecule volatiles (407.15~504.15 K). Considering the comprehensive effect in the above two stages, reducing the release of CO with KClO3 is more obvious than that with KNO3. Moreover, the effects of additives on the reaction kinetics and reaction mechanism in different decomposition stages of flue-cured tobacco combustion are also studied.

Preparation of Aluminum Hydroxide from Industrial Residue of Aluminum Alloy Surface Treatment Process

WANG Xiao LIU Qing-fen WANG Ya-qi HUANG Xiao-zhu ZHANG Chao

. 2014, 14(5):  841-845. 

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Preparation of aluminum hydroxide from industrial residue of aluminum alloy surface treatment process was studied. The leaching process of Al from the industrial residue by NaOH solution and precipitation of Al(OH)3 from Al leaching solution by H2SO4 were explored. The effects of the concentration and dosage of alkali or acid, reaction temperature and time were examined. Process optimization was obtained by orthogonal experiments. The chemical composition, morphology and quality of Al(OH)3 product were examined as well. The results showed that the Al content in the dry residue was 28.7%, and Al existed as the form of Al(OH)3 crystal in the industrial residue. The optimum conditions of leaching process were the molar ratio of NaOH addition to Al(OH)3 in the industrial residue 2.88:1, reaction temperature 75℃, and reaction time 55 min. At these conditions, the maximum yield of aluminum in leaching process reached up to 97.5%. At the optimal conditions of precipitation process of Al(OH)3, such as the molar ratio of H2SO4 addition to AlO2- in leaching solution (0.95~1.10):1 and pH value 5.5, the precipitation yield of Al(OH)3 reached up to 89.2%, and the total recovery rate of aluminum was obtained by 87.1%. The Al(OH)3 product was amorphous with the diameter of particles of about 17 mm. The purity of Al(OH)3 in the product was up to 95.5%.

生化工程专栏

Expression and Fermentation Optimization of Urethanase in Bacillus subtilis

LV Si-yi FANG Fang DU GUo-cheng; CHEN Jian;

. 2014, 14(5):  846-852. 

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The gene encoding urethanase (UH) from Lysinibacillus fusiformis SC02 was firstly cloned and expressed in Bacillus subtilis WB600. Production of UH was optimized based on single factor experiments and response surface analysis at shake flask level, resulting in its yield of 14.20 U/mL. The composition of optimal culture medium was determined as: starch 10 g/L, K2HPO4 9 g/L, malt extract 25 g/L, MgS04 1 g/L and trypone 55 g/L. The optimal fermentation temperature and inoculum amount were 37℃ and 4%(j), respectively. Enzyme production of recombinant bacteria in a 3 L fermenter showed that after 16 h, enzyme activity reached the highest titer 18.03 U/mL.

Effects of Overexpression of Key Enzyme Genes Involved in the Purine Synthesis Pathway on cAMP Production with Recombinant Saccharomyces cerevisiae Strains

JI Xiao-bing WANG Kai CHEN Xun

. 2014, 14(5):  853-859. 

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The effects of overexpression of three key enzyme genes involved in the purine synthesis pathway on cAMP product with highly efficient cyclic adenosine monophosphate (cAMP)-producing Saccharomyces cerevisiae strains were studied. Saccharomyces cerevisae episomal plasmid YEplac195 and the promoter (PGK1p) and terminator (PGK1t) of phosphoglycerate kinase were used to construct single gene expression vectors containing PRS1, PRS3, ADE4 and ADK1, respectively, which were transferred to the cAMP-producing strain GA125. The recombinant strains generated with shake flask fermentation improved cAMP production performance with various degrees. With addition of adenine, the cAMP yield with PRS1, PRS3 and ADE4 was increased by 4.17%, 9.03% and 6.06%, respectively, but that with ADK1 decreased by 3.85%, compared with strain GA125.

材料工程专栏

Formation Process of Chromium-free Mn(VII)-Ti(IV) Chemical Conversion Film on Aluminum Alloy

HUANG Xiao-zhu LIU Qing-fen ZHANG Chao LIANG Xiang-feng LI Wang-liang LIU Hui-zhou

. 2014, 14(5):  860-866. 

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A novel formation process of chromium-free Mn(VII)-Ti(IV) conversion film on 6063 aluminum alloy was explored. Potassium permanganate and titanyl sulfate were used as main ingredients of the passivator. The parameters of film-forming process, such as temperature, reaction time, pH value and bath composition, were investigated, and the process was optimized by the orthogonal experiments. The surface morphology and element constituents of the chemical conversion film were analyzed, respectively, and its corrosion resistance was investigated by simply chemical analysis methods, such as the CuSO4 solution dripping and seawater corrosion tests. The optimum formulation was KMnO4 5 g/L, TiOSO4 2 g/L, NaF 0.05 g/L and ZnSO4 0.3 g/L, and the optimum conditions were temperature 50℃, reaction time 15 min and pH value 2.7. The results showed that a golden chemical conversion film with mass about 589 mg/m2 could be obtained. The main elemental constitutes of the conversion film were O, Mn, Al, Zn and Ti. The Mn(VII)-Ti(IV) conversion film had better corrosion resistance performance than hexavalent chromium conversion film in the CuSO4 solution dripping test, and had similar performance with hexavalent chromate conversion film in the seawater.

Cycle Performance of Cu-based Oxygen Carrier Based on a New Chemical-looping Combustion

ZHENG Xiao-ming SU Qing-quan MI Wan-liang SHI Yong

. 2014, 14(5):  867-873. 

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A metal oxide oxygen carrier of Cu-Ni/Al2O3 was prepared by a mechanical mixing method, and its cycle performance investigated in a fixed bed reactor based on a new chemical-looping combustion process. The results showed that the fresh Cu-Ni/Al2O3 exhibited an excellent performance. However, the oxidation rate of oxygen carrier decreased from 91.0% in the first cycle to 27.7% in the 120th cycle. In contrast, the reduction rate of oxygen carrier decreased mildly, and maintained 86.8% in the 120th cycle. According to the characterization of the degraded Cu-Ni/Al2O3, the main reason for the performance degradation of the oxygen carrier was speculated to be the powdering of Cu-Ni/Al2O3 particles and local aggregation of the powdered fine particles. Through re-granulating the degraded oxygen carrier, the performance of Cu-Ni/Al2O3 was recovered to a level close to the initial performance.

Preparation of Colloidal Pt/M(Co, Ni) Bimetallic Nanoparticles and Their Catalytic Activity for Hydrogen Generation

XIANG Sheng GU Ya-jun WANG Peng CHENG Jun KONG De-cheng ZHANG Hai-jun ZHANG Shao-wei

. 2014, 14(5):  874-879. 

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Polyvinylpyrrolidone stabilized Pt/M (M=Co or Ni) bimetallic nanosol was synthesized by a chemical co-reduction process, and its morphology, particle size, structure and composition were characterized by TEM and UV-Vis. The effects of composition on the hydrolysis of NaBH4 for hydrogen generation were also studied. The results indicate that the prepared Pt/M bimetallic nanosol particles have an average size of 2.0 nm. The catalytic activity of Pt/M bimetallic nanosol is superior to that of Pt, Co and Ni nanosols. The higher catalytic activity of Pt/M (M=Co or Ni) bimetallic nanosol over that of corresponding monometallic nanosol can be ascribed to electronic charge transfer effects. DFT calculations show that Pt atom is indeed negatively charged, while the Co or Ni atom has positive charge due to the electron donation from the Co or Ni atom to Pt atom. The positively charged Co or Ni atom and negatively charged Pt atom act as catalytic active sites for the hydrolysis reaction of alkaline NaBH4 solution for hydrogen generation.

Effect of Super-gravity Field on Solidification Structure of Al-6%Cu Alloy

JIA Shu-jian YU Bo SONG Gao-yang YANG Yu-hou Chuan-gen

. 2014, 14(5):  880-885. 

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The effect of super-gravity on the refining of solidification structure and morphology of Al2Cu in Al-6%Cu alloy was studied by selecting the central part of the sample after processing by a centrifugal high temperature furnace. The results showed that the grains could be refined under super-gravity field. Al primary crystals in the alloy were the bulky equiaxed crystals with a diameter of 112 mm under the gravity coefficient G=1, and the grain diameter decreased to 85, 77, 70 and 63 mm as the gravity coefficient G increased to 100, 300, 500 and 700, respectively, indicating that the grain was remarkably refined as G increased. Moreover, super-gravity field could improve the morphology of Al2Cu precipitates and the properties. Al2Cu precipitates were bulky irregular block and the value of hardness was 59.9 MPa under G=1, and then they transformed into tiny lump and spheres gradually as G increased to 100, 300, 500 and 700, respectively. As a result, the value of hardness increased to 68.4, 73.2, 74.4 and 74.9 MPa, respectively. Smaller and denser Al2Cu precipitates formed as the super-gravity increased, which also improved the hardness of the alloy.

Combustion Synthesis and Electrochemical Properties of Li4Ti5O12 Cathode Material in LiNO3-TiO2-Urea System

CHANG Long-jiao LUO Shao-hua GUO Ke-shi LV Fang QI Xi-wei WANG Ying-ling ZHAI Yu-chun

. 2014, 14(5):  886-890. 

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Li4Ti5O12 was prepared by a combustion method using nano-TiO2 and LiNO3 as raw materials, and characterized by XRD, SEM, constant current charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that when the molar ratio of urea to lithium is 1:1, the preset temperature for muffle furnace 850℃ and calcination time 8 h, the obtained pure phase spinel Li4Ti5O12 with the average particle size of 500 nm has better electrochemical performance. The initial discharge specific capacity of the material is as high as 168 mA·h/g at the current density of 0.1 C (1 C=170 mA·h/g) with a single voltage plateaus at around 1.5 V. The capacity remains 162 mA·h/g after 100 cycles and the retention rate of charged capacity is 96.4%.

Optimization of Preparation Program for Cu-Ce/TiO2 Photocatalyst by Response Surface Method Based on the Photocatalytic Degradation Performance of Formaldehyde Solution

ZHANG Hao LIU Ying LIU Xiu-yu HUANG Xin-jie DU Xiao-yan TANG Gang

. 2014, 14(5):  891-895. 

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TiO2 was modified with transition metal Cu and rare earth metal Ce. The effects of Cu-Ce-doped loading, molar ratio of Cu to Ce and sintering temperature on photocatalytic performance of Cu-Ce/TiO2 were studied by response surface method, the quadratic polynomial prediction model on the three factors was also developed, the preparation program for Cu-Ce/TiO2 was optimized, and the optimal Cu-Ce/TiO2 property was characterized. The results show that the three factors affect the photocatalytic performance of Cu-Ce/TiO2, but the effect of sintering temperature is obviously more significant than that of Cu-Ce-doped loading, and the effect of Cu-Ce-doped loading more significant than that of molar ratio of Cu to Ce. The optimization program was Cu-Ce-doped loading 2.88%(mol), molar ratio of Cu to Ce 1.6364 and sintering temperature 544℃. Cu-Ce doping could effectively avoid dislocation of doped TiO2 crystal surface and near surface, generate more to suppress the lattice distortion increased, enhance the ability to induce TiO2 anatase crystal transformation to rutile crystal, and improve the uniformity and dispersion performance of particle size.

Performance Analysis of Semi-coke for Blast Furnace Injection

YANG Shuang-ping CAI Wen-miao ZHENG Hua-an LIANG Jie-qi ZHANG Sheng-jun XUE Qi-cai

. 2014, 14(5):  896-900. 

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Based on the physical and process properties of 2 kinds of pulverized coal and 3 kinds of semi-coke, including ash fusion point, grindability index, ignition point, explosibility and combustibility, all the properties of bituminite, anthracite and semi-coke are evaluated, and eventually reasonable solutions of coal blending are established. The results showed that pulverized coal injection with addition of semi-coke, the blended coal grindability increased, explosibility weakened, ignition point decreased, the ash fusion point rose and their combustion rates were both above 85%. Moreover when the semi-coke ratio reached 40%, the blended coal for blast furnace injection was viable and would obtain more excellent metallurgical properties.