Table of Content

20 August 2010, Volume 10 Issue 4

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流动与传递

Two-phase Mathematical Model of Oxygen Jet Impinging on Molten Steel Bath Surface in EAF

WANG Guang-lian; ZHU Rong; HE Chun-lai;

. 2010, 10(4):  625-31. 

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A mathematical model of three-dimensional and two-phase flow in the molten bath of EAF has been developed to clarify the transient phenomena of oxygen impingement on molten steel when the flow rate of a single lance is 3000 m3/h. The simulation result shows that vortexes in bath form under the impingement of supersonic jet, which promotes the circulating flow in bath. The center of vortexes is located at 0.3 m deep in bath and 1.6 m far away from the center of bath. The velocity of molten steel on the axis of lances and under the center of vortexes is in piecewise linear relationship with Z position. With 1 cm decrease in the value of vertical Z axis, the velocity magnitude decreases 0.0015~0.002 m/s in the middle-lower section o

Study on Flow Characteristics in a Stirred Vessel with Double Hydrofoil Impellers with PIV

GUO Xin LI Zhi-peng GAO Zheng-ming

. 2010, 10(4):  632-637. 

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The flow characteristics in a stirred vessel of diameter (T) 0.476 m agitated by double narrow blade hydrofoil CBY impellers were experimentally investigated by using particle image velocimetry (PIV). The effects of the spacing between the two impellers (H2), the submergence of the upper impeller below the liquid surface (H3), and the clearance of the lower impeller above the base of the vessel (H1) on the flow pattern were investigated. The PIV results show that when H2 is not more than 0.6T, a whole axial circulation forms in the vessel, when H2 is not less than 0.7T, the circulation is separated into two smaller ones. The submergence (H3) has little effect on the velocity near the impeller region. With decreasing of H1, the radial flow generated by the lower impeller, the axial flow generated by the upper impeller, and the axial flow of the main circulation increase.

Flow Characteristics of an Impinging Jet Mixer Using Particle Image Velocimetry

WANG Duan LI Zhi-peng GAO Zheng-ming HUANG Jia-qi

. 2010, 10(4):  638-643. 

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The flow characteristics in an impinging jet mixer were experimentally investigated by using particle image velocimetry (PIV). The inner diameters of two inlet jets and the mixing chamber were 3 and 16 mm, respectively. The effects of flow ratio and distance between the axis of jets and the top wall of the mixing chamber on the distribution of velocity and turbulent kinetic energy were investigated. The results show that the impingement point locates in the middle of the chamber, and normalized velocity and turbulent kinetic energy distribution are almost consistent when the flow rates of two jets are equal. The region with high turbulent kinetic energy is in the vicinity of impingement point, and the maximum normalized turbulent kinetic energy is about 3 times of that near the impeller region of a standard Rushton turbine stirred tank. Flow ratio has significant effect on the location of impingement point. When the distance between the axis of jets and the top wall of mixing chamber decreases, the region with high turbulent kinetic energy is enlarged, which is beneficial for mixing in the chamber. The results are of importance to the design and optimization of industrial impinging jet mixer.

Numerical Research on Fluid Turbulent Flow and Heat Transfer in the Half-coil Jackets

LI Ya-xia WU Jian-hua GONG Bin ZHAN Hong-ren

. 2010, 10(4):  644-649. 

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Based on the simplified physical models, fluid turbulent flow and heat transfer in the half-coil jackets were studied according to the numerical simulation by CFD software Fluent. The results indicate that on the cross perpendicular to helix, the contour shape of time average tangential velocity is saddle-backed and the velocity gradient near the outer curved wall is much greater than that near the inner straight wall. The steady flow structure of secondary flow is with two vortexes and the centers of the two-vortex locate near the sharp points of semicircular cross section. Affected by the secondary flow, the distribution of local Nusselt number is asymmetry on the heated straight wall with the minimum value locating at the center of heated wall and the maximum one locating at two sides of the center point. With the studied limit, the minimum is 0.8~0.85 and maximum 1.15~1.25 times of average value. The dimensionless pitch has a slight effect on the developed flow and heat transfer characteristic. With the increase of curvature, the heat transfer in the jacket is enhanced and the flow resistance increased at the same time.

Chaotic-speed Stirring Mixing and Experiment

CHU Shu-po ZHOU Shen-jie; LUAN De-yu LIU Xiao-xian

. 2010, 10(4):  650-654. 

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An effective approach of stirring mixing was developed by integrating chaotic mapping and pulse width modulation (PWM) scheme. The chaotic numerical sequence was gained from one-dimensional logistic mapping and then assigned to the PWM duty cycle. The chaotic PWM signal was, by a full bridge converter, transformed into the chaotic voltage which acted on a DC motor driving the agitator. Thus, the rotational speed of agitator was chaotic. Stirring mixing experiments were conducted utilizing the acid-alkali neutralization decolorization method, and glycerin was stirred. Experimental results with the same maximum speed revealed that conventional constant-speed agitation approximately needed 9 min to achieve complete homogeneity, whereas chaotic-speed agitation just needed 20 s to achieve the same homogeneity, 5% of the former.

Modeling Formation Mechanism of Vortex during Steel Casting in a 60 t Ladle

LIN Rui; YAN Zheng-guo; LIU Tao; YU Jing-kun

. 2010, 10(4):  655-659. 

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Based on analogy principle, vortex and slag entrapment in a 60 t steel ladle were studied during casting by water model experiments. The effects of initial liquid level, nozzle diameter, nozzle position and slag on critical height of vortex were investigated. The results show that the critical height of vortex will rise with increasing of nozzle diameter, but descend with increasing of eccentricity ratio of nozzle position, initial liquid level has little effect on it, slag inhibits the formation and development of vortex to some extent, but the effect of the thickness of slag layer on critical height of vortex is not obvious. The relationship between critical height of vortex (h) during casting and nozzle diameter of ladle (d), position of nozzle (e) is expressed as h=65.276+1.427d-76.778e.

反应与分离

Separation of Sodium Vanadate in Alkaline Multi-component System

ZHANG Yan WANG Shao-na ZOU Xing DU Hao ZHENG Shi-li WANG Shao-na

. 2010, 10(4):  660-666. 

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The phase equilibrium of sodium salts in the NaOH-NaNO3-Na3VO4-Na2CrO4-H2O systems was determined. Based on the solubility data, sodium vanadate can be separated by cooling from the solution. By examination of NaOH concentration, NaNO3 concentration, crystallization end temperature, cooling rate, stirring speed, and seeds on the crystallization of sodium vanadate from multi-component alkaline solutions, the optimal experimental conditions for separation of sodium vanadate were obtained as follows: NaOH concentration 200~250 g/L, NaNO3 concentration 200 g/L, stirring speed 200 r/min, temperature from 80℃ to 40℃ with natural cooling, and seed addition 1%(w). Under the optimal conditions, the sodium vanadate yield of 61% was obtained, and the purity of the crystal was about 95%. The obtained crystal particles with large size (147 mm) exhibited excellent sedimentation and separation property (sedimentation speed 10 min).

Separation of Chromium and Aluminum and Alkali Recirculation in Treatment of Laterite Nickel Ore Containing Chromium with NaOH Solution

LI Li QU Jing-kui QI Tao WANG Jing-gang LI Jie

. 2010, 10(4):  667-672. 

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The leaching solution of laterite nickel ore containing chromium treated with NaOH contains sodium hydroxide, sodium aluminate, sodium chromate, and sodium carbonate. In order to separate Cr and Al from the leaching solution, the separation behavior was investigated through evaporation crystallization, carbonization and causticization. The results show that there are most of sodium aluminum and a little sodium chromate in the crystal phase when the alkali concentration of the first evaporation crystallization is around 40%(w). The pure aluminum oxide can be obtained by carbonization, and the decomposition percentage is 90.8%. While most of sodium chromate and a little sodium carbonate are contained in the crystal phase over the secondary evaporation crystallization with the alkali concentration of 50%(w). Pure chromate oxide can be obtained through causticizing at 90℃ for 1 h, the mass ratio of calcium to theoretical amount is 1.2:1, the causticizing percentage can be up to 79.2%.

Influential Factors of Vanadium Extraction by Reburning and Dilute Sulfuric Acid Leaching of Ash of Stone Coal

YU De-qi SHI Zheng-lun XIAO Wen-ding LI Ge-yao LUO Zhong-yang CEN Ke-fa

. 2010, 10(4):  673-678. 

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In order to obtain the optimal conditions of vanadium extraction process by reburning and dilute sulfuric acid leaching of ash of stone coal, the factors affecting the vanadium leaching efficiency were experimentally studied. The results indicated that the reburning temperature, reburning time, particle size of clinker, leaching temperature and concentration of sulfuric acid have obvious influence on the vanadium leaching efficiency, and the ratio of liquid volume to solid mass (L/S) and leaching time affect less. The optimal conditions are obtained as follows: reburning temperature 850℃, reburning time 1 h, particle size of clinker less than 180 mm, leaching temperature 18℃ (room temperature), concentration of sulfuric acid 0.36 mol/L, L/S between 2~2.5 mL/g, and leaching time 15 min. At the conditions, the leaching efficiency of vanadium can reach more than 81%.

Comparative Study on the Precipitates of Chemical Leaching and Bacterial Leaching of Uranium Ore

LIU Yu-long DING De-xin LI Guang-yue HU Nan WANG Yong-dong HU Nan WANG Yong-dong;

. 2010, 10(4):  679-684. 

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In order to investigate the role of bacteria in the leaching of uranium ore and precipitates, four kinds of uranium ore leaching experiments, namely, chemical powder leaching with ferrous ion concentrations of 2.01 and 4.63 g/L, bacteria leaching of powder with ferrous ion concentrations of 2.01 and 4.63 g/L and leaching experiments of two uranium ore samples in chemical leaching and bacteria leaching with ferrous ion concentration of 4.63 g/L were conducted. The variations in the concentration of uranium ions, pH value and redox potential of the leaching solutions were monitored in the leaching systems of powder. The morphological feature, chemical composition and mineral composition of the precipitates from the two kinds of leaching were analyzed. The results indicate that the uranium leaching rate are 64.86%, 69.13%, 94.35% and 92.80% respectively under the conditions of the above four different leaching systems. For chemical leaching, the precipitates on the surface are mainly silicate minerals, while for bacterial leaching, jarosite minerals, and the addition of an appropriate amount of iron to the leaching system is an effective way to reduce precipitate and improve effectiveness of bacterial leaching of uranium.

Adsorption Behavior of Puerarin on Metal-doped TiO2 Mesoporous Material

FENG Qing-ge TANG Wen-hua LIU Shao-you WANG Xiang LONG Bu-ming;

. 2010, 10(4):  685-690. 

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The adsorption of puerarin on metal (Al, Ni, Zn)-doped TiO2 and bare TiO2 mesoporous materials was investigated at the pH value of 4.5, puerarin concentration of 8 mg/L, different temperatures and various times. The results showed that the adsorption kinetics of puerarin on these mesoporous materials was in better agreement with Freundlich isotherm model and ascribed to the monolayer adsorption. The pseudo-first-order adsorption rate constant k varied from 0.30′10-2 to 0.58′10-2 min-1 and decreased by the order of Zn-TiO2

Extraction of Nickel(II) from Acidic Leaching Solution of Laterite Ore with Emulsion Liquid Membrane

JIANG Cheng-zhi ZHAI Xiu-jing ZHANG Ting-an

. 2010, 10(4):  691-695. 

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The water-oil-water (W/O/W) double-phase emulsion was prepared with Span-80 as surfactant, TBP as oil membrane phase, NH3×H2O solution as internal aqueous phase and kerosene as diluting agent. The effects of various factors on the extractive result were examined. The suitable composition of liquid membrane was 5% Span-80, 4% TBP, 2% paraffin, 89%(j) kerosene. And technological operating conditions were determined as follows: the volume ratio of oil phase to the internal phase was 1:1, and the volume ratio of emulsion to the water phase 1:3. Under the optimal operation conditions, the secondary extraction rate of nickel(II) from acidic leaching solution of laterite ores was up to 80%. The extraction mechanism of nickel(II) with emulsion liquid membrane was discussed by differential method. The results indicated that concentration series (nC=1) was less than time series (nt=2.8). So chemical reaction was controlling step.

Reaction Rate of NaCO3-CO2-H2O System in Bubbling Column with Reciprocating Plate

AN Gang SUN Bo AN Yi-hong QIAN Mei-hua XU Qing

. 2010, 10(4):  696-700. 

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The reaction behavior of NaCO3-CO2-H2O system in bubbling column with reciprocating plates was investigated. The effects of reaction time on the concentration of sodium bicarbonate and NaHCO3 generating rate at different volumetric flow rates of CO2 gas, vibration amplitudes of sieve plates and vibration frequencies of sieve plates were discussed, and the reaction rates in the reciprocating plate column, bubbling column and sieve plate bubbling column were experimentally determined at the same conditions. The results show that the concentration of sodium bicarbonate obtained at a high volumetric rate of CO2 is about 1.39 times of that at a low one when the reaction proceeds for 20~25 min in the reciprocating plate column, NaHCO3 generating rate at a vibration amplitude of 0.5 cm is 1.76 times of that at 1.5 cm while the reaction has been carried out for 5 min, and NaHCO3 generating rate at a frequency amplitude of 120 min-1 is 1.46 times of that at 60 min-1. Compared with the sieve plate bubbl

Experimental Study on Decomposition of K-feldspar with CaCl2 and NaCl for Extraction of Potassium

HU Tian-xi YU Jian-guo;

. 2010, 10(4):  701-705. 

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Research on decomposing potassium feldspar to extract potassium by calcination with the composite additive made of CaCl2 and NaCl was carried out. The phase analysis of products and decomposition process were studied by means of XRD and TG-DSC. The results show that the composite additive can shorten the time to reach the reaction balance, and obtain higher extraction rate at a lower calcination temperature and shorter calcination time, and the lower the temperature or the shorter the time, the more obvious the effect. The extraction rate of potassium using the composite additive is 93.65%, 22.57% higher than using CaCl2 and 39.56% higher than using NaCl at the conditions of 800℃ and 60 min. When the temperature reaches 700℃, the reaction rate of the system becomes rapidly, and the composite additive can effectively decrease the decomposition temperature. The optimum calcination temperature range is 800~890℃.

过程与工艺

Analysis of Flakes Peeling on the Surface of Cold-rolled Strip Steel

ZHAO Xin-kai; SUN Ben-Liang LI Chang-you HAN Zhao-xia

. 2010, 10(4):  706-713. 

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SEM, EDS and metallographic microscope were been used to study flakes peel-like defects on the surface of cold-rolled strip steel combined with mathematical simulation. The analytical results show that the flakes peeling was induced by non-metallic inclusions and scales. Inclusions could be derived from steel de-oxidation or slag entrapment, and scales, initiating cracks inside billet, which could be exposed to the surface on cold-rolling process, were caused by de-carbonization because of improper heating mode or time. Numerical simulation shows that after pouring within the first 6 s, temperature dropped to 124.9℃/s and solidified shrinkage rate to 0.07 mm/s, that makes corner cracks. Crack index of solidified front increased up to 0.75 at the end of solidification, with formation of porosity and shrinkage cavity. Crack index was over 1 near the surface from the edge to 41 mm thickness, where middle cracks formed. Temperature rally in the secondary cooling zone II resulted in extension of middle cracks along columnar grain boundary.

Preparation of Epoxidized Soybean Oil by Catalysis of Small Amount of Sulfuric Acid

SUN Xiao-ying ZHAO Xue-bing DU Wei LIU De-hua

. 2010, 10(4):  714-719. 

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Epoxidized soybean oil (ESO) was prepared with formic acid as oxygen carrier in a solvent-free system. The optimal production conditions of formic acid ESO were determined through orthogonal experiments. To further enhance the oxirane content and shorten reaction time, a small amount of sulfuric acid was added as catalyst. The results showed that when the mass ratio of soybean oil, formic acid, 30% hydrogen peroxide and sulfuric acid was 1:0.13:0.7:0.004, the oxirane content of product was 6.2% and the residual iodine value (IV) less than 6.0% after 3 h reaction at 65℃. The FT-IR, 1H-NMR and 13C-NMR spectra of the product were recorded in order to further characterize its chemical structure.

Thermal Decomposition of Glucose and Sucrose by Kinetics Analysis

CHEN Ying-qin HE Han-bing LIU Chang LU Xiao-hua;

. 2010, 10(4):  720-725. 

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Thermal decomposition process of glucose and sucrose was studied by TG-DTA. The Kissinger, Friedman and non-linear regression methods were used to obtain the reaction decomposition mechanism and kinetic parameters. The results showed that the decomposition of glucose was much easier than that of sucrose. The orders of decomposition reaction for glucose in two stages were 2 and 1 respectively. However, for sucrose, the order of decomposition reaction in two stages was n and 1 respectively. Non-linear fitting of glucose and sucrose was given a complete thermal decomposition reaction pathways and kinetic parameters. The activation energy of glucose in three stages was respectively 132, 150 and 253 kJ/mol, and pre-exponential factor 11.6, 11.1 and 19.6 s-1, and activation energy of sucrose in two stages was 105 and 229 kJ/mol, and pre-exponential factor 8.2 and 18.6 s-1.

Influence of Pre-calcined Copper-containing Slag on Catalytic Pyrolysis Kinetics of Biomass

ZHAO Lu-mei HU Jian-hang WANG Hua LIU Hui-li QING Shan LI Lei

. 2010, 10(4):  726-731. 

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The effects of pre-calcined copper-containing slag on catalytic pyrolysis kinetics of biomass were investigated by a thermogravimetric analyzer. The results indicate that activation energy of biomass pyrolysis is reduced by using untreated and precalcined copper slag. Catalytic activity of the slag catalyst increases first and then decreases with the increase of calcination temperature and the prolongation of time at 1000℃. The mineralogical characterization of copper slag under different conditions was conducted with TG, XRD, and SEM/EDX. The analysis shows that the initial increase and later decrease of copper slag activity are caused by the oxidation of fayalite, sulfide and phosphorous compounds. The formation of Fe3O4 and a-Fe2O3 is due to the extrusion of iron from the fayalite in copper slag during pre-calcination, severe segregation of iron is found to be non-uniform. The characteristic peaks of fayalite is gradually weakened and then disappears, the characteristic peaks of hematite increased, while the characteristic peaks of magnetite present a trend that first increases and then decreases. The increase of catalytic activity of pre-calcined copper slag is due to the formation of Fe3O4.

Mineralogical Study of Water-quenched Slag from Copper Smelting Reverberatory Furnace

HUANG Zi-li TAO Qing-ying GENG Chen-chen MA Feng HE Tian-hui; LIU Yuan-yuan

. 2010, 10(4):  732-737. 

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The industrial mineralogy of copper-containing slag from copper smelting reverberatory furnace was studied using X-ray fluorescence spectrometer, X-ray diffractometer, scanning electron microscope coupled with energy dispersive spectroscope, M?ssbauer spectroscope and optical microscope. The slag contained 1.06% Cu and 36.41% Fe. Copper was mainly in the form of copper matte, and fayalite at 53.5% was the dominant iron phase. The microscopic analysis indicated the major copper, iron and silicon phases in the slag were unevenly distributed and in close paragenesis. Thermodynamic analysis demonstrated that fayalite tended to convert into magnetic iron oxides in the presence of CaO and O2. An efficient treatment of the slag was proposed using copper flotation, silica removal by smelting and subsequent magnetic separation. The copper recovery rate after flotation increased from 18.6% to 39.02% at a copper concentrate grade of 4.6% when the sample was ground from 75% to 95% passing 74 mm. Silica removal was conducted for 30 min smelting at a molar ratio of 0.9 for CaO/SiO2 in the charge and 1350℃. At a cooling rate of 10 K/min, the formed matte was then crushed and ground for subsequent magnetic separation of iron phases. An iron concentration of 62% was obtained at a recovery rate of 71%.

Measurement and Correlation of Solubility of Capsaicin in Different Solvents

LEI Chao CHANG Zhi-dong; LIU Hui-zhou

. 2010, 10(4):  738-742. 

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The capsaicin crystal (capsaicin 50.4%, dihydrocapsaicin 37.1%, nordihydrocapsaicin 7.9%) was used as raw material, its solubility in different solvents in the temperature range from 262 to 333 K were respectively determined with the equilibrium method. The experimental data were correlated with mathematical models such as the ideal solution, Apelblat and polynomial empirical equations. The results show that the solubility of capsaicin is elevated as the temperature increases, and the dissolving effect of n-butanol is the best, but the water the worst. The calculations show that ether is suitable to the cooling crystallization of capsaicin, its yield is 51.23%. The polynomial empirical equation is the best to fit in the experimental results.

生化工程专栏

Preparation of Electrospun Poly(styrene-co-maleic anhydride) Nanofibers and Their Use in Immobilization of b-D-Galactosidase

ZHENG Guo-jian; ZHANG Song-ping ZHANG Yu-fei;

. 2010, 10(4):  743-749. 

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Unique poly(styrene-co-maleic anhydride) nanofibers with a uniform diameter of about 300 nm were prepared by eletrospinning a solution containing 0.35 g/mL polymer, 25 cm gap between ejection needle tip and collector, flow rate of 250 L/h, and applied voltage of 21 kV. The electrospun nanofibers were applied subsequently for immobilization of b-D-galactosidase, an enzyme loading of (15.1±0.5) mg protein/g membrane was obtained. The immobilized enzyme demonstrated a Michealis constant (Km) of 2.7 mmol/L, slightly higher than that of the native enzyme (2.2 mmol/L). The maximum reaction velocity (Vmax) of the immobilized enzyme was found as 97.2 mol/(min×mg), 47.8% that of native enzyme. The immobilized enzyme showed an excellent reusability such that 21 reusing cycles only led to 15% loss of the enzyme activity. Furthermore, the immobilized b-D-galactosidase was suitable for hydrolysis of lactose in a continuous stirring tank reactor that was operated steadily for 17 d.

Effect of Rare Earth Elements on Fermentation Process of 2-Keto-L-gulonic Acid

ZHENG Qizo-shuang; ZHOU Ling-wen CHEN Fu-jiang; LIU Jie LI Zhen CHEN Jian;

. 2010, 10(4):  750-755. 

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The effects of different rare earth ions and coordination compounds on the synthesis of 2-keto-L-gulonic acid (2-KLG) by mixed culture of Bacillus megaterium and Ketogulonigenium vulgare were investigated in the two-step fermentation of vitamin C. The results indicated that the proper promotion concentrations of various rare earth ions were all about 5 mmol/L. Furthermore, the low concentration caused 2-KLG synthesis promotion while high concentration caused 2-KLG synthesis inhibition. EDTA-La and lanthanum citrate inhibited 2-KLG synthesis, but lanthanum oxalate promoted it at a concentration of 1 mmol/L and enhanced the final production of 2-KLG by 6.4%. The cell growth conditions at the mid- and late fermentation stages were remarkably improved with the addition of 5 mmol/L La3+. 2-KLG ultimate output was increased and the fermentation time reduced at the same time. When 5 mmol/L La3+ was fed to 3.6 L fermentor for batch fermentation, the L-sorbose consumption rate and 2-KLG productivity were increased by 12.4% and 14.8% compared with that of the control, respectively. And the fermentation time was declined by 11.1%.

Separation of Propionic Acid by Expanded Bed Adsorption Coupled with Vitamin B12 Fermentation

LI Ling-yun; WANG Peng WANG Yun-shan; MA Guang-hui; SU Zhi-guo

. 2010, 10(4):  762-766. 

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Using alkalescence anion exchange resin 330 to adsorb propionic acid from fermentation broth, the expanded bed adsorption and desorption process of propionic acid were investigated systematically with the selected resin, and the optimized operation conditions were obtained as follows: pH 5.0, concentration of propionic acid 10 g/L, resin humid volume 1/10 of the fermentation broth volume, 20 min and flow velocity 710 mL/min. Under above conditions, the dynamic adsorption capacity reached 57.73 mg/g. When the concentration of NaOH was 3 mol/L and flow velocity 1.32 mL/min, the desorption rate reached 93.2%, an coupled bioprocess for in situ recovery of propionic acid coupled with fermentation of vitamin B12 was established based on this technology. By decreasing the concentration of propionic acid, the inhibition of propionic acid to Propionibacterium freudenreichii was lightened dramatically. High density of cell and vitamin B12 were obtained compared with the Fed-batch fermentation, the yields of vitamin B12 and propionic acid increased 26.6% and 39.4%, respectively.

Optimization and Kinetics of the Fed-batch Bioconversion from L-phenylalanine to 2-Phenylethanol via Saccharomyces cerevisiae

WANG Hang DONG Qing-feng; MENG Chun SHI Xian-ai GUO Yang-hao

. 2010, 10(4):  767-771. 

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The carbon and nitrogen sources during the bioconversion from L-phenylalanine to 2-phenylethanol via Saccharomyces cerevisiae were optimized. In a 5-L fermentor, final 2-phenylethanol concentration of 4.39 g/L, space-time yield of 0.314 g/(L×h), molar yield of 0.8 and residual L-phenylalanine concentration of 0.634 g/L were achieved when respiratory quotient was controlled at 1.1±0.1 by feeding glucose, and 1 g/L urea and 8 g/L L-phenylalanine were selected as nitrogen source and precursor respectively.

Impact of Accumulated By-products during Distillage Recycling on Growth and Ethanol Fermentation of the Self-flocculating Yeast SPSC01

ZHANG Chun-ming; ZI Li-han; ZHAO Xin-qing; ZHAO Da-wei; BAI Feng-wu

. 2010, 10(4):  772-776. 

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Continuous ethanol fermentation coupled with the recycling of waste distillage was carried out in a single agitating bioreactor with the self-flocculating yeast and two-stage enzymatic hydrolysate of corn meal. The fermentation broth collected was distilled to separate ethanol and other volatile products in every 3 d, and the distillage was used to mix corn meal instead of fresh water. The fermentation system was run continuously for 25 d, and the accumulation of acetic acid, lactic acid, propionic acid, furfural and 2-phenyl-ethyl-alcohol, the byproducts that are inhibitory in the growth and ethanol fermentation of the self-flocculating yeast with their minimum inhibition concentrations of 3, 20, 1.5, 2 and 1.5 g/L, respectively, was monitored. It was found that propionic acid with its concentration of 2.7 g/L was the only byproduct accumulated to the level higher than its minimum inhibition concentration. And in the meantime, the synergistic effect of propionic acid and 2-phenyl-ethyl-alcohol as well as furfural and 2-phenyl-ethyl-alcohol were observed.

Synthesis of New Medical Textile Material Poly(g-glutamic acid) by Whole-cell Biocatalysis

YANG Ge; WANG Ning; ZHANG Chao;

. 2010, 10(4):  777-780. 

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The effects of reaction system conditions on poly(g-glutamic acid) production by immobilized Bacillus licheniformis WBL-3 in a 3.7 L stirred bioreactor were investigated. The results showed that total poly(g-glutamic acid) production was increased by lysine and L-glutamine, under the conditions of reaction system temperature 37℃, pH 7, amount of whole cell biocatalyst 4%(w), and agitation speed of 300 r/min, the cell metabolism and poly(g-glutamic acid) production are enhanced significantly, and the DO concentration is sufficient to satisfy the oxygen requirement during the reaction. To avoid the repression of poly(g-glutamic acid) expression caused by residual glutamic acid and ethanol accumulation due to overfeeding of glutamic acid, glutamic acid addition was controlled to produce continuous oscillations in dissolved oxygen, because the change of dissolved oxygen concentration could deliver the information of available carbon source in the reaction broth, optimum yield of poly(g-glutamic acid) reached 92.74%. The whole-cell biocatalyst showed a good catalytic capability for repeated use and the yield of poly(g-glutamic acid) could still maintain 81% after it was used for five times.

材料工程专栏

Study on Cu/MgO/ZnO Catalyst for Low-temperature Synthesis of Methanol

LI Yuan ZHANG Xiang-ping WANG Lei LI Chun-shan LIU Long ZHANG Tian-long ZHANG Suo-jiang

. 2010, 10(4):  781-787. 

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A series of Cu/MgO/ZnO catalysts with different Cu:(Mg+Zn) and Mg:Zn molar ratios were prepared by conventional co-precipitation method, which are used for low-temperature methanol synthesis. And Cu/ZnO and Cu/MgO catalysts were prepared as well. Comparison was made among them by characterization. Addition of MgO to Cu/ZnO catalyst could introduce more dispersed Cu+ sites, therefore the catalytic activity was promoted. At 443 K and 5.0 MPa, the activities of prepared catalysts were tested in a slurry reactor using liquid paraffin as solvent. The results indicated that the activity of Cu/MgO/ZnO catalyst was superior to that of Cu/ZnO and Cu/MgO, and when Cu:Mg:Zn=2:1:1, the catalyst had the highest activity: the conversion rate of CO was as high as 63.56%, and the selectivity and space time yield of methanol reached 99.09% and 5.413 mol/(kg×h) respectively. The deactivation phenomenon of Cu/MgO/ZnO catalyst was observed under high reaction temperature, and the characterization results indicated that it was due to the sintering of Cu particles.

Synthesis and Properties of 1-Methyl-3-Alkylimidazolium Tetrahalogenoferrate Magnetic Ionic Liquids

LI Xiao-hua YANG Fu-ming ZHOU Qing ZHANG Suo-jiang

. 2010, 10(4):  788-794. 

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Seven magnetic ionic liquids of 1-methyl-3-alkylimidazolium tetrachloroferrate [Cnmim]FeCl4 (n=2, 4, 6, 8) and 1-methyl-3-butylimidazolium tetrahalogenoferrate [C4mim]FeX4 (X=Cl, Br) were synthesized and verified with 1H-NMR, Raman and MS spectra. [Cnmim]FeCl4 and [C4mim]FeBr4 had single anions, but [C4mim]FeClBr3 and [C4mim]FeCl3Br had multi-anions, including FeBr4-, FeBr3Cl-, FeCl2Br2-, FeCl3Br- and FeCl4-. The density, viscosity and conductivity of magnetic ionic liquids were measured. It was found that their densities were bigger than those of traditional ionic liquids, 1.25~1.94 g/cm3 at 25℃; viscosities were lower, 21~65 mPa×s at 25℃; conductivities were higher, 0.23~1.37 S/m at 30℃. The influences of temperature and structure of cations and anions on the above properties were extensively investigated.

Controlling Mechanism of Specific Surface Area of Silica Nanoparticles in Carbonation Process

GU Ming-yuan; LIN Rong-yi; GUO Zhan-cheng;

. 2010, 10(4):  795-801. 

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Using sodium silicate as precursor, the controlling mechanism of specific surface area (SBET) of silica nanoparticles synthesized by carbonation process was investigated. The results of orthogonal experiments demonstrated that the order of factors affecting SBET was: sodium silicate concentration>added mass of PEG6000>reactive temperature>flow rate of CO2/N2 mixed gas. Under the optimal conditions of concentration of sodium silicate at 40 g/L, added mass of PEG6000 4 g/L, reactive temperature 80℃, and flow rate of CO2/N2 mixed gas 1.2 L/min, silica nanoparticles synthesized exhibited a high SBET of 318.9 m2/g. With the increase of concentration of sodium silicate, the size of primary particles increased, but SBET of silica particles decreased due to extension of Ostwald ripening process of SiO2 sol in the carbonation solution where pH>7. Due to the effect of temperature on the solubility and Brownian motion of SiO2 sol, the decrease of reaction temperature could accelerate the nucleation of silica and restrain the agglomeration of Si(OH)4 and ≡SiOSi(OH)3, therefore the SBET increased. The increase of SBET was facilitated by PEG6000 due to its steric hinderance effect. However, when PEG6000 in solution exceeded to 7 g/L, the precursor molecules entered into the PEG with tangled long chain, the SBET of synthesized silica nanoparticles would be decreased.

Anti-melting-loss Property of 8407 Steel with Surface Aluminization and Oxidation Treatment

SUN Jian; WANG Xiao-ming LIU Hong-hua

. 2010, 10(4):  802-808. 

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The 8407 steel specimen with Al coating obtained by cold spray of Al powder was diffused at 550℃ for 4 h, then room temperature hard anodic oxidation was executed at 2.5 A/dm2 for 60 min for formation of Fe3O4×Al2O3 film on its surface. The melting-loss properties of specimens with aluminization and oxidation treatment and without treatment in liquid aluminum alloy of ADC12 at 620℃ under settlement and rotation conditions were evaluated by weight loss method. The microstructures of cross sections were observed by optical microscope after melting-loss test. The microstructure and local composition of Fe-Al interface structure of surface untreated specimen melting-loss tested were examined by SEM to explore the melting-loss mechanism of 8407 steel. Finally, the anti-melting-loss mechanism of oxide film was discussed. The results show that the formed Fe3O4×Al2O3 film can improve melting-loss resistance especially under the dynamic condition by reducing the wettability between steel and molten aluminum because it isolates steel substrate from liquid aluminum.

Preparation of TiO2 Nanoparticles Coated Cotton Fibers at Low Temperature and Their Photocatalytic Activity

SHI Zhong-liang LU Chang-sui; WANG Hai-bo; PAN Yong-e; YAO Shu-hua

. 2010, 10(4):  809-814. 

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TiO2 nanoparticles coated cotton fiber composite was successfully prepared by using a sol-gel method at low temperature (about 100℃) using tetrabutyl-titanate [Ti(OBu)4] as raw material. The preparation of the TiO2 colloid and the composite were described. The properties of resulting materials were characterized by SEM and XRD, the photocatalytic degradation performance was tested using methylene blue (MB) as the target pollutant in aqueous solution. The results showed that the amorphous TiO2 nanoparticles were distributed evenly on the outer surfaces of cotton fibers, which shows efficient photocatalytic properties when exposed to UV light, the degradation rate of MB reached 95.35% under the conditions of catalyst dosage 2.5 g/L, MB concentration 50 mg/L, irradiation time 120 min, and pH 10, and the photocatalytic activity of TiO2/cotton fibers remained above 90% of its activity as-prepared after being used four times, the degradation rate of MB could reach 88.78% when irradiation time was 120 min. The photocatalytic degradation of MB could be properly described by the first-order kinetic law. By comparison of the removal rates of MB with and without UV light, it could be affirmed that the disappearance of MB was due to photodegradation rather than adsorption on cotton fibers.

综述

Advances in Preparation of Electrophoretic Particles for Electronic Paper Display

WEN Ting; MENG Xian-wei; REN Xiang-ling; TANG Fang-qion;g

. 2010, 10(4):  815-825. 

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To obtain excellent electrophoretic particles for E-paper, a number of techniques have been developed to modify the surfaces of particles for high surface charge density or decrease the particle densities, including mechanical, chemical and physicochemical methods. In this paper, these methods according to the applications in the preparations of white particles, black particles and chromatic particles have been separately summarized. Besides, the advantages or shortcomings of these methods utilized in electrophoretic particles preparations have been compared and elaborated. In particular, several different but valuable routes to prepare the white, black and chromatic electrophoretic particles based on the researches of our group are reported. At the end, the prospect of development and applications of electrophoretic particles is illustrated.

Progress in Electronic Paper Display and Its Assembly Process

LI Zheng-yuan; MENG Xian-wei; TANG Fang-qion;g

. 2010, 10(4):  826-832. 

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The development history of four types of electronic-paper display is summarized, and the assembly process of electrophoretic display introduced especially. Besides, the assembly techniques for reducing cost have been studied and improved. Photo-mask lithographic and ultraviolet curing methods have been introduced for the preparation of microcups and device assembly process. At the end, the prospect of development and applications of electrophoretic display is illustrated.