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    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.  
    Abstract1847)      PDF (238KB)(2738)       Save
    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.
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    Progress of the Study on Bacillus thuringiensis as Biopesticides
    ZHU Wei;ZHAO Bing;WANG Xiao-dong;WANG Yu-chun
       2004, 4 (3): 282-288.  
    Abstract2611)      PDF (93KB)(2191)       Save
    Bacillus thuringiensis is one of the most effective and the most widely used microbial insecticides at present. The genetic bacterial strains, the fermentation process and the formulation of Bacillus thuringiensis as biopesticides are reviewed in this paper. The optimization of culture medium, operating conditions and type of fermentors are also addressed. Moreover, the existing problems and suggestions are discussed.
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    Kinetics on Chlorination Process of La2O3 and CeO2 by Ammonium Chloride
    SHI Wen-zhong;ZHANG Xin;ZHAO Yong-he;WANG Jing-yan;ZHU Guo-cai
       2005, 5 (1): 23-28.  
    Abstract2743)      PDF (101KB)(2088)       Save
    Using ammonium chloride (NH4Cl) as a chlorinating agent, the effects of chlorinating temperature, time and NH4Cl dosage on chlorination of La2O3 and CeO2, and the thermal decomposition of LaCl3 7H2O and CeCl3 7H2O were examined. The results show that NH4Cl directly participates the chlorination reaction, and HCl from pyrolysis of NH4Cl also contributes to the chlorination reaction. CeCl3 and LaCl3 can cause gas phase hydrosols formation or oxidation reaction which generates LaOCl, CeOCl and CeO2. The apparent activation energies of La2O3 and CeO2 chlorination reactions, Ea, are 43.73 and 140.67 kJ/mol respectively. The process is mainly controlled by the interfacial chemical reaction.
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    Phase Transition and Transition Temperature Hysteresis of VO2 Thin Film
    HU Zai-yong; XU Chu-shao; YANG Shao-li; CHEN Guang-bi
       2003, 3 (5): 0-0.  
    Abstract4211)      PDF (49KB)(2040)       Save
    The VO2 thin film was prepared by the colloid method with industrial V2O5 as raw material. The properties of the VO2 film such as resistance abrupt drop temperature, phase transotion temperature hysteresis are examined. The results show that the VO2 thin film phase transition temperature is 35oC. Preparation method and substrate show greater effect on resistance abrupt change order, which can reach 2~3 order if common glass or quartz glass were employed in underlay by H2 reduction process, while it can reach 1.5~2 order of magnitude by N2 thermal decomposition. The resistance abrupt change order of magnitude is larger for VO2 film with quartz glass as substrate, the transition temperature hysteresis is 1~6oC, and closely related with the resistance abrupt change order, underlay, substrate and preparation method.
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    Biosynthesis of Polyhydroxyalkanoates by Ralstonia eutropha with Short-chain-length Organic Acids
    YAN Qun; DU Guo-cheng; CHEN Jian
       2003, 3 (5): 0-0.  
    Abstract3829)      PDF (257KB)(1904)       Save
    Separation of dimethyl carbonate (DMC) and methanol (MeOH) is very difficult due to the azeotrope of DMC and MeOH, the pressure swing method is an effective method for separation of DMC and MeOH azeotrope. In this paper, a joint process of high-pressure distillation and atmospheric distillation was investigated. Binary interaction parameters of the UNQUAC model between MeOH and DMC were regressed against experimental data of vapor liquid equilibria of MeOH and DMC, the applicable range of the model is: pressure 0.1~1.5 MPa, temperature 337~440 K. Based on the thermodynamic model, the separation flowsheet, inclnding a high-pressure distillation column and an atmospheric distillation column in series, was simulated and analyzed. Sensitivity of operation factors was discussed and the optimum operation parameters were proposed. The optimal parameters of the high-pressure distillation column were as follows: stage number 40, feed stage 29, reflux ratio 7~10, operation pressure 1.0~1.5 MPa.
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    Leaching of a Low-grade Refractory Tantalum–Niobium Ore by KOH Sub-molten Salt
    ZHOU Hong-ming; ZHENG Shi-li; ZHANG Yi
       2003, 3 (5): 0-0.  
    Abstract3408)      PDF (197KB)(1763)       Save
    Production of lignin peroxidase (LiP) and manganese peroxidase (MnP) in three kinds of reactors (stirred tank reactor, bubble column reactor and aeration reactor) by Phanerochaete chrysosporium was studied. High activity of enzymes, especially for LiP, was obtained in the aeration reactor. The production of enzymes and decoloration of orange I were investigated in semi-continuous culture and continuous culture respectively. High activity of enzymes for a long period of time was detected in the semi-continuous culture, in which five batches of dye wastewater could be decolored to more than 90% and the specific decloration rate of orange I was above 46.7 g/(g×d) when the proportion of replacement was 1/2, while enzymes decayed rapidly and poor decoloration was gained in the continuous culture. The application of semi-continuous culture in the aeration reactor was tried for the decoloration of four batches of printing-wastewater, and the decelerations rate of the first three was all above 90%.
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    Self-assembly Mechanism and Defect Analysis of Colloidal Silica Photonic Crystals
    ZHAO Xiao-feng;ZHANG Hui;TANG Qing
       2003, 3 (5): 0-0.  
    Abstract3208)      PDF (167KB)(1753)       Save
    Colloidal silica photonic crystals were prepared by using ethanol as medium. Nanospheres with a mean diameter of 238 nm and standard deviation 5.7% were obtained under strictly controlled conditions by using the improved Stober method. In this method, ethanol was proved a better medium than water and the prepared photonic crystals had fewer defects. The diffraction to incident infrared light obeyed the Bragg equation. The formation mechanism and defect formation of colloidal photonic crystals were also discussed.
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    Treatment of Coking Wastewater Using the Micro-electrolysis-SBR Activated Sludge Process
    ZHANG Wen-yi
       2003, 3 (5): 0-0.  
    Abstract3303)      PDF (286KB)(1751)       Save
    Challenges and opportunities to antibiotics are reviewed. Antibiotics, which have greatly enhanced human health, now are facing the issue of drug resistance of pathogen microbes and newly found diseases. However, modern biotechnology, including genomics, proteomics, bioinformatics and bio-macromolecular crystallization, is providing new ideas and methodology for the research and development of new pharmaceuticals.
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    Pyrolysis of Straw Obtained from Stagewise Treatment
    YANG Chang-yan;YANG Xue-min;LV Xue-song;YAO Jian-zhong;LIN Wei-gang
       2005, 5 (4): 379-383.  
    Abstract2710)      PDF (236KB)(1736)       Save
    The pyrolysis characteristics of wheat straw with steam-explosion and solid fermentation treatment were investigated by the thermogravimetry coupled with the Fourier infrared spectroscopy to analyze the evolved gasses. The pyrolysis process with the increase of temperature from TG can be divided into four stages, including drying stage (30~150℃), transitional stage (150~200℃), pyrolysis stage (200~600℃), and carbonization stage (600~900℃). The results of pyrolysis from TG-FTIR show that the process can be divided into two steps: (1) splitting of hydroxide radicals, chain scissions and depolymerization, accompanied by evolution of water, acids, aldehydes, compounds containing C?O?C groups and CO, CO2, CH4, etc.; (2) aromatization and formation of graphite layers, accompanied in turn by evolution of CH4, CO2 and CO. The yields of uncondensable gases and carboxyl compounds decrease after steam explosion/solid fermentation treatment, but the yield of pyrolysis liquid increases by the stagewise treatment.
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    Simulation of Current Distribution in Manganese-Silicon Ferroalloy Smelting Arc Furnace with Coke Layer
    CHU Shao-jun LI Zhong-si HE Ri-fei
       2008, 8 (3): 449-452.  
    Abstract3023)      PDF (266KB)(1688)       Save
    A simulation device for investigating the behavior of current distribution was designed according to the structure characteristic of coke layer molten pool in manganese-silicon ferroalloy smelting arc furnace and similarity theory. NaCl solution with the specific conductance of 10.08~17.97 mS/cm and coke were used as the electric conduction phase to simulate the behavior of electric conduction in manganese-silicon submerged arc furnace. The current distribution relationship of the total current between coke layer and molten slag layer was measured in the molten pool. The results indicated that the relationships among the depth of coke layer, HC, the granularity of coke, DC, the conductivities of electric conduction phases (both in solid and liquid phases, rC and rL), the ratio of current through the bottom of molten pool Ib to total current It followed the following equation, i.e., Ib/It=4.36(rL/rC)1.523(DC/HC)0.186. When operational resistance of melting layer increased, Ib/It would decrease, which was in accordance with the actual process of manganese-silicon ferroalloy production.
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    Preparation of Mesopore Activated Carbon from Municipal Solid Organic Wastes
    XIE Li-ping; LIN Wei-gang; YANG Xue-min
       2003, 3 (5): 0-0.  
    Abstract4134)      PDF (346KB)(1669)       Save
    In gaseous products of biomass steam gasification, there exist a lot of CO, CH4 and other hydrocarbons that can be converted to hydrogen through steam reforming reactions. There exists potential hydrogen production from the raw gas of biomass steam gasification. In the present work, the characteristics of hydrogen production from biomass steam gasification were investigated in a small-scale fluidized bed. In these experiments, the gasifying agent (air) was supplied into the reactor from the bottom of the reactor and the steam was added into the reactor above biomass feeding location. The effects of reaction temperature, steam to biomass ratio, equivalence ratio (ER) and biomass particle size on hydrogen yield and hydrogen yield potential were investigated. The experimental results showed that higher reactor temperature, proper ER, proper steam to biomass ratio and smaller biomass particle size will contribute to more hydrogen and potential hydrogen yield.
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    Experimental Observation on Cellulosic Biodegradation in Solid State Fermentation
    ZHOU Xiao-hong; CHEN Hong-zhang; LI Zuo-huo
       2003, 3 (5): 0-0.  
    Abstract4284)      PDF (132KB)(1657)       Save
    Expression of human Pro-urokinase gene in Pichia pastoris and the influence of main variables on the production and expression of Pichia pastoris were investigated. pH in the growth phase was 5.6, pH in the expression phase was 6.0, and the temperature was always 28oC. It is found that there exists clear corresponding between the AOX and Pro-UK production in the fermentation process, and a new procedure by feeding methanol and glycerol alternatively was proved to be effective in improving the enzyme activity of Pro-UK in the fermentation broth.
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    Cultivation of Dunaliella salina in an Airlift Photobioreactor
    HAO Jian-xin; CONG Wei; KANG Rui-juan; CAI Zhao-ling
       2003, 3 (5): 0-0.  
    Abstract4279)      PDF (164KB)(1649)       Save
    The separation property of membrane is related to the aperture structure of the membrane. In this paper, the chitosan ultrafiltration (UF) membrane was immersed into a coagulation bath with proper concentration and temperature and its aperture structure was modified. The results showed that the retention rate of chitosan membranes increased by 83.7% after being treated by precipitation. The retention rate, flux and aperture structure of chitosan membranes were affected by temperature of the coagulation bath, concentration of gelating agents and time of immersion precipitation. It is necessary to select appropriate parameters to enhance the separation property of chitosan UF membrane.
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    Review on Facilitated Transport in Fixed Site Carrier Membranes
    SHI Wei; ZHANG Feng-bao; ZHANG Guo-liang; ZHANG Gang
       2003, 3 (5): 0-0.  
    Abstract4493)      PDF (236KB)(1640)       Save
    Facilitated transport membrane with fixed site carriers is an attractive topic in the separation of gas and liquid mixtures because it is capable of increasing permeability and permselectivity simultaneously. In this paper, the mechanism of facilitated transport in fixed carrier membranes is addressed, the methods of carriers fixation are discussed and the problems to the development of the membrane process are summarized. In addition, the prospect of facilitated transport in fixed carrier membranes is previewed.
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    Application of Experimental Design to Optimizing the Medium of Nuclease P1
    XU Zheng-jun; XIAO Lin-ping;LU Hao;XIE Ning-chang; YING Han-jie
       2003, 3 (5): 0-0.  
    Abstract4511)      PDF (65KB)(1600)       Save
    Experimental design was employed to study the effects of several factors on the production of nuclease P1 by Penicillium citrinum M02, such as carbon source, nitrogen source, phosphor source and corn steep liquor which acted as complementary nitrogen source. The results of two experiments showed that corn steep liquor could remarkably promote the production of nuclease P1. In addition, one model that can describe the fermentation perfectly was gained from these experiments. When nuclease P1 was produced on the optimized medium calculated from this model, its yield was 648.3 U/ml that is comparable with 661 U/ml from the model. And it is improved by 70% compared with the 380 U/ml, which was gained on the original medium at the same time. The possible reason for corn steep liquor promoting nuclease P1 fermentation is that corn steep liquor contains more useful amino acids such as glycin, alanine, serine and so on.
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    Characteristics and Formation Mechanism of Secondary Organic Aerosol
    BAI Zhi-peng;LI Wei-fang
       2008, 8 (1): 202-208.  
    Abstract3989)      PDF (237KB)(1524)       Save
    The formation of secondary organic aerosol (SOA) is one of the research focuses in atmospheric chemical process. In urban atmosphere, secondary organic carbon constitutes about 17%~65% of the total particulate organic carbon. Monoterpene and aromatics are the most important natural and anthropogenic precursors of SOA, respectively. The volatile precursors react with atmospheric oxidants such as hydroxyl (×OH), nitrate radical (NO3-) and O3 through multiple reaction pathways, producing semi-volatile secondary organics including diacids, multifunctional carbonyls and nitrate organics, etc. Theses compounds can distribute into particulate phase via adsorption and absorption processes, and will alter the property and environmental effects of ambient aerosols. Organic molecular markers are utilized to apportion the sources of atmospheric ambient aerosols, and organic diacids are potential tracers for SOA. In this article, the advances and problems in SOA research are reviewed, and future research recommendations are presented.
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    Production of Citric Acid from Apple Pomace Enzymolyzed by Cellulase
    SONG Ji-rong;HUANG Jie;XU Kang-zhen;ZHAO Qiao-yun
       2003, 3 (5): 0-0.  
    Abstract3334)      PDF (120KB)(1510)       Save
    Cellulase can evidently increase the content of glucose and has a significant effect on the production of citric acid from apple pomace by Aspergillus niger. Based on experiments, a cellulolytic enzyme named cellulase A6 was found able to produce about 170 g glucose from 1 kg dried apple pomace after 12 h reaction, with cellulase concentration of 20 U/g in the medium at 50oC, natural pH without pretreatment of alkali. Using the treated apple pomace as a liquid state substrate, Aspergillus niger-C selected out was able to produce about 256 g citric acid from 1 kg dried apple pomace at 35oC in 3 d or 30oC in 5 d with flask rotation speed of 210 r/min, and the conversion of citric acid could reach 80% based on the amount of sugar consumed.
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    Formate Dehydrogenase and Its Application in Cofactor NADH Regeneration
    HUANG Zhi-hua;LIU Ming;WANG Bao-guang;ZHANG Yan-ping;CAO Zhu-an
       2006, 6 (6): 1011-1016.  
    Abstract1886)      PDF (204KB)(1454)       Save
    NADH-dependent oxidoreductases are valuable tools for the biological synthesis of fine chemicals and chiral compounds. As the reducing equivalent, cofactor NADH plays a critical role in those reactions. Due to the high cost of the NADH cofactors, in situ NADH regeneration is required for preparative applications. NAD+-dependent formate dehydrogenase (FDH) is an abundant enzyme that plays an important role in energy supply of methylotrophic microorganisms. FDH captures increasing attention in recent years, and is widely used in enzymatic syntheses of chemical compounds as a versatile biocatalyst for NADH regeneration consumed in the main reactions. This review covers the latest developments in cloning genes of FDH from various sources, studies of its catalytic mechanism and physiological role, and its application for NADH regeneration from the following aspects: chemical stability, thermal stability and cost. Future development of FDH used as NADH regeneration platform is also illustrated.
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    Adsorption of Methyl Orange on Modified Activated Carbon
    LIU Jian ZHU Qiu-xiang TAN Xiong-wen YAN Ying ZHANG Hui-ping
    Chin. J. Process Eng.    2016, 16 (2): 222-227.   DOI: 10.12034/j.issn.1009-606X.215334
    Abstract1423)      PDF (247KB)(1442)       Save
    Activated carbon was modified by hydrochloric acid and aqueous ammonia and used as adsorbent to remove methyl orange (MO) from wastewater. The effects of modification condition, shaking speed and temperature on its adsorption performance of MO were examined. The adsorption data were simulated by both adsorption isotherm and kinetic models, and the adsorption thermodynamics was also analyzed. The results showed that the adsorption capacity of hydrochloric acid modified activated carbon for MO was better than that of ammonia modified one. The adsorption equilibrium was achieved with the removal rate of MO 93.7% within 24 h under the conditions of initial MO concentration of 60 mg/L, solution volume of 50 mL, temperature of 20℃ and shaking speed of 100 r/min. The adsorption data of hydrochloric acid modified activated carbon for MO fitted well to Langmuir (RC2>0.95) and Freundlich (RC2>0.97) adsorption isotherm models, and its saturated adsorption capacity reached up to 112.7 mg/g. Thermodynamic parameters, such as DG0<0, and DH0>0, DS0>0, showed that the adsorption of MO on hydrochloric acid modified activated carbon was a spontaneous and endothermal reaction. The adsorption kinetics could be well described by pseudo-second-order kinetic model. The adsorption rate constant increased with the increase of shaking speed.
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    Numerical Simulation and Experimental Study on Mixing Characteristics of Stirred Bioreactor
    HONG Hou-sheng;ZHANG Qing-wen;WAN Hong-gui;OUYANG Ping-kai
       2005, 5 (2): 131-134.  
    Abstract2579)      PDF (420KB)(1434)       Save
    By commercial CFD package CFX-4.4, mixing characteristics of stirred bioreactor were simulated and the mixing time variation under various operation conditions was investigated. The liquid mixing time was measured by means of detecting the concentration variety of [H+] with a pH probe. The deviation between simulation and experiment becomes smaller as the bioreactor volume is increased, and the error for 25 m3 bioreactor is less than 11.6%.
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    Effects of He-Ne Laser Irradiation on the Mutagenesis of Beauveria bassiana
    YANG Ge; CHEN Hong-zhang; LI Zuo-hu
       2003, 3 (5): 0-0.  
    Abstract3064)      PDF (110KB)(1427)       Save
    CaCO3 uniform nanoparticles with particle size of 10~30 nm were synthesized in quaternary W/O microemulsion solution containing Triton X-100, cyclohexane and n-pentanol. The reaction conditions were optimized on the basis of investigation of the influence of the ratio of water to surfactant, the concentration of reactants and the ageing time on the products. Transmission electron microscopy (TEM) was utilized to characterize the shape and size of the obtained nanoparticle products.
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    Mass Transfer and Hydrodynamics of Rotating Packed Bed in Distillation
    LI Xiu-ping;LIU You-zhi;YANG Ming
       2005, 5 (4): 375-378.  
    Abstract2205)      PDF (183KB)(1426)       Save
    An experimental system of rotating packed bed for distillation operation was set up for studying mass transfer efficiency and hydrodynamics with methanol/water solution at the atmospheric pressure and total reflux. The results showed that the number of theoretical trays of rotating packed bed attained the maximum value corresponding to the increase of F and b. The least height equivalent to a theoretical plate was 0.0109 m. Two correlations for the number of theoretical plate (Nmin) and gas pressure drop (Dp) were established with least square method based on the experimental data.
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    Numerical Simulation on the Temperature Field and Film Heat Transfer Coefficient of Thin Film Evaporator
    HE Xiao-hua;LI Jia;LU Xiao-hua
       2005, 5 (4): 364-369.  
    Abstract2617)      PDF (218KB)(1415)       Save
    The heat transfer calculation model of water and viscous fluid in a thin film evaporator was developed using CFD software CFX4.4. The mean temperature distributions along axial and film thickness directions were obtained, and the film heat transfer coefficient a under different conditions was calculated. The results show that feeding rate and rotor speed have great influence on the film temperature distribution and the film heat transfer coefficient. There is one common optimum feeding rate under different operation conditions for different fluids. At this feeding rate, the mean velocity in fillet section reaches the maximum value and so does the film heat transfer coefficient a. For water, both the ratio of flow boundary layer thickness to film thickness and that of temperature boundary layer thickness to film thickness reach the minimum value under high rotor speed or the optimum feeding rate. There exists an inherent relation between the flow boundary layer and temperature boundary layer, and the film temperature distribution and heat transfer coefficient are affected seriously by the thickness of transfer boundary layers. For viscous fluid, no obvious temperature boundary layer forms under the parameter range considered in this work.
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    Chromatographic Separation of Gamma-Aminobutyric Acid
    LANG Li JIANG Li-hua QIU Yong-jun ZHOU Jia-chun ZHAO Li-ming
    Chin. J. Process Eng.    2016, 16 (3): 418-423.   DOI: 10.12034/j.issn.1009-606X.215384
    Abstract1225)      PDF (497KB)(1394)       Save
    Eight resins were tested systematically to select the best one for the chromatography separation of gamma-aminobutyric acid (GABA) and monosodium glutamate (MSG). Then the influence of the ratio of length to diameter of column, flow rate of mobile phase and column temperature on the separation efficiency of GABA and MSG were investigated in terms of resolution and recovery. Finally, the separation efficiency of fermentation broth was concretely studied. The results showed that the resin QY-HG01 separated GABA and MSG well. The best separation efficiency was achieved under the operating conditions of ratio of length to diameter 25, flow rate of mobile phase 2.5 mL/min and column temperature 50℃ through the single factor experiments. Injected with the pretreated fermentation broth, it was found that GABA and MSG were separated well. The decolorization rate of the fermentation broth was 84.9%, and the desalinization rate was 99.2%. The purity of GABA increased from 24.9% in the broth to 80.4% in the eluent with a recovery yield of 89.3%.
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    Numerical Simulation on Fluid Flow in a Thin Film Evaporator
    HE Xiao-hua;TANG Ping;LI Jia;LU Xiao-hua
       2005, 5 (4): 357-363.  
    Abstract2454)      PDF (295KB)(1387)       Save
    The calculation model of thin film evaporator (TFE) was developed, the flow of water and viscous fluid was simulated using CFX 4.4 software and the velocity distribution was obtained. The results show that the rotor speed and feeding rate have great effects on the fluid flow of TFE. The material exchange between the fillet and film can be promoted by increasing the rotor speed. There is one common optimum feeding rate under different rotor speeds for different fluids. At this feeding rate, the mean velocity in the fillet section reaches the maximum value. For water, the ratio of flow boundary layer thickness to film thickness is the minimum under the optimum feeding rate. Difference exists for the axial velocity distribution between viscous fluid and water, and no obvious flow boundary layer forms for viscous fluid.
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    Research on the Flow Field in the Exit Tube and the Mechanism of Pressure Drop Reduction in a Cyclone Separator
    WANG Jian-jun;WANG Lian-ze;LIU Cheng-wen
       2005, 5 (3): 251-254.  
    Abstract2494)      PDF (861KB)(1363)       Save
    Laser Doppler Velocimetry (LDV) was used to measure the flow field in the exit tube of a cyclone separator. It was found that the high speed rotating flow, reverse flow region and turbulent fluctuation were contributed to the pressure loss in the exit tube. When a stick existed in the cyclone separator, the flow field in the exit tube changed, the tangential velocity turned smaller, the reverse flow region disappeared, and the turbulent fluctuation became weaker, so the pressure loss of the cyclone separator decreased. These changes were found to be related to the width and shape of the stick cross-section.
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    Propagation and Decay of Concentration Wave in the Liquid–Solid Pulsed Fluidized Beds
    JIN Guo-dong; LIU Da-you; SHU Chi-wang
       2003, 3 (5): 0-0.  
    Abstract4085)      PDF (190KB)(1333)       Save
    The propagation and decay of concentration wave in liquid–solid pulsed fluidized beds is studied by numerical simulation and experimental validation. When the semi-on period and semi-off period are much longer than the particle relaxation time, the difference between the inertia forces of the two phases is small compared with the gravity of the solid phases except a short period in the order of the particle relaxation time after a sudden change of fluidizing velocity, the momentum equations of the two phases in pulsed fluidized beds can be simplified to a local equilibrium model. The simulation difficulty caused by the ill-posedness of the basic two-fluid model can be avoided using the concentration wave equation. The liquid–solid flow pulsation induced by the fluidizing fluid varying in both sinusoidal and step-wise patterns is simulated using the five order WENO scheme for spatial derivative and three order TVD Runge–Kutta method for time derivative. The front-fixing method is used to handle the moving upper boundary. The simulation result of fluidizing velocity varying in step-wise pattern is validated and matches the experimental data well. In the pulsed fluidization, the concentration wave decays due to the interaction between the concentration discontinuity and dilatation waves.
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    Numerical Simulation on Gas-Liquid Two Phase Flow in Continuous Casting Tundish with Bottom Gas Blowing
    Zhan Shu-hua;OU Jian-ping;Xiao Ze-qiang
       2005, 5 (3): 233-240.  
    Abstract2261)      PDF (748KB)(1321)       Save
    Gas-liquid two phase flow in a tundish has been studied with a water model, prototype of which is the one in Meishan Iron and Steel Corporation. Experimental results show that with bottom gas blowing, tiny, steady and uniformly distributed bubbles can be produced and bubbly flow pattern forms in the tundish, uprising bubbly flow can destroy the laminar-like flow in the tundish and enhance flow mixing, on the other hand, the uprising bubbles can form a baffle-like gas column, which is in favor of inclusion removal. Based on the experiments, an Eulerian multi-fluid model is used to simulate gas-liquid bubbly flow in the tundish, Sato model is incorporated to include bubble-induced turbulence, Grace model is used to model inter-phase drag force, buoyancy is considered with Boussinesq approximation, turbulence dispersion force is also included with the model of Lopez. Numerical results well agree with those from experiments.
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    The Effect of pH Value on Preparation of TiO2 Nanoparticles with Sol-Gel Method
    ZHOU Li-min;WANG Yi-ping;HUANG Qun-wu
       2007, 7 (3): 556-560.  
    Abstract1575)      PDF (332KB)(1286)       Save
    TiO2 nanoparticles were prepared with sol-gel method and characterized by transmission electron microscope (TEM) and X-ray diffraction (XRD). The composition changes of Ti4+-triethanolamine (Ti-TEOA) complex system with aging time and the effect of pH value on particles size, crystallization habit and yield of TiO2, and the stability of Ti-TEOA were investigated. The results showed that the synthesized product was anatase TiO2. Ti(OH)4 gel was totally converted into TiO2 after 10 h of aging at 140℃. The mean diameter of TiO2 particles was 5~22 nm and increased with increasing pH. However, the yield of TiO2 decreased dramatically at pH>10.6 and no TiO2 particles were found at pH 12. The crystallization habit of TiO2 was greatly changed with different pH values. Ti-TEOA complex system was stable at pH>6 and 25℃.
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    Investigation of Metabolic Routes to Poly(glutamic acid) by 13C-labeled Glucose as Medium Carbon Source
    SHI Ning-ning;XU Hong;YAO Jun;WANG Jun
       2007, 7 (1): 145-148.  
    Abstract1873)      PDF (255KB)(1286)       Save
    Bacillus subtilis NX-2 produce was used to g-poly(glutamic acid) (g-PGA) with glucose and glutamic acid as medium carbon sources. To clarify the role of these carbon sources in g-PGA synthesis, metabolic routes to g-poly glutamic acid were investigated using 13C-labeled glucose as medium carbon source by detecting 13C-NMR peak intensity. When the medium glucose concentration was 4%, the repeat units of g-PGA formed from glucose were approximately 9%. While the medium glucose concentration was 3%, the repeat units formed from glucose fell to 6%. Glucose was mainly used to form biomass and provide adenosine tri-phosphate (ATP) for g-PGA synthesis, while glutamic acid was the main source of g-PGA repeat units.
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