Table of Content

20 December 2006, Volume 6 Issue 6

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流动与传递

Numerical Simulation of Macroscopic Mixing in a Rushton Impeller Stirred Tank

WANG Zheng;MAO Zai-sha;SHEN Xiang-qian

. 2006, 6(6):  857-863. 

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The macroscopic mixing in a stirred tank with different tracer injection locations, impeller speeds and impeller positions is simulated numerically by solving the transport equation of the tracer based on the whole flow field in the baffled tank with a Rushton disk turbine numerically resolved using the improved inner-outer iterative procedure. Predicted mixing time is compared well with the literature correlations. The predicted residence time distribution of the stirred tank is very close to the present experimental results. The effect of the installation of a draft tube on the mixing time and residence time distributions is addressed.

Influence of V-shaped Gas Distributor on Flow in a Gas-Solid Jet Fluidized Bed

HONG Ruo-yu

. 2006, 6(6):  864-871. 

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The governing equations of multiphase hydrodynamics for describing dense gas-solid two-phase flow in a jet fluidized bed with conical gas distributors were provided. The numerical simulations were based on two-dimensional (2-D) general orthogonal grid. The numerical meshes were obtained by solving two Laplace equations iteratively. The improved IPSA algorithm was employed to solve the governing equations on the generated numerical meshes. A general-purpose CFD computer for 2-D simulations was developed. The post-processing was performed using Tecplot. For a typical case, the computed results were consistent with the experimental measurements. The angle of conical gas distributor, nozzle diameter, bed height, aperture distribution of holes in gas distributor, jet velocity and superficial gas velocity in bed were varied in the numerical simulation to study the flow patterns, the jet penetration heights and the solid particle circulation.

Effects of Operating Conditions on Pressure Drops in a Dual-loop Circulating Fluidized Bed

WANG Xiang-hui;GAO Shi-qiu;Song-wen-li;XU You-hao;ZHANG Jiu-shun

. 2006, 6(6):  872-877. 

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A riser with varying diameter and dual-loop is set up to study the fluid catalytic cracking (FCC) process of maximizing iso-paraffins (MIP). The riser is composed of a bottom pneumatic transport region with smaller diameter and higher gas velocity and a top fast fluidization region with larger diameter and lower gas velocity. Particles are added to the riser at both the bottom and the middle positions, and two solids circulating loops named main-loop and sub-loop are formed. The pressure balance of the two solids circulating loops and the effects of operating conditions on pressure drops of the riser were investigated in experiment. The pressure drops of both main-loop and sub-loop of the riser decrease with increasing gas velocity. The total solids circulating rate and the pressure drop of the two solids circulating loops increase with increase in the either solids circulating rate, although the increase of one solids circulating rate leads to the decrease of the other. Two circulating loops are influenced by each other, and the prerequisite for normal operation is that pressure balances of both loops are maintained and the pressure of downcomer side is higher than that of riser side at each solids circulating rate control valve. The increase in inventory, downcomer diameter and downcomer height is helpful to maintain the normal operation of system.

Statistical and Frequency Analysis of Pressure Fluctuations in Liquid-Solid Exterior Circulating Fluidized Bed

ZHANG Shao-feng;WANG Qi;GAO Chuan-bo;LIU Yan

. 2006, 6(6):  878-883. 

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The pressure fluctuation is important information that can be used to indicate the dynamic characteristics of the fluidized bed. In order to find out the flow characteristics of the liquid-solid exterior circulating fluidized bed, the time-domain analysis, frequency-domain analysis and correlation analysis were carried out with the wall pressure fluctuations in the liquid-solid exterior circulating fluidized bed. It was found that the pressure fluctuations at different positions were the same in the steady fluidization segment, the power distribution frequency ranges generated by the liquid flow and the motion of the particles concentrated in 0~10 Hz and 30~40 Hz. The probability density function was close to the normal distribution, and the pressure fluctuations signal existed between the periodic and random signals.

An Approximate Model of a High Viscosity Liquid Flowing inside a Wavy Plate Duct

SHI Jin-sheng

. 2006, 6(6):  884-888. 

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A research of a high viscosity liquid flowing inside a wavy plate duct is carried out with a mathematic modeling. The governing equations with their boundary conditions are firstly non-dimensionalized. Then a dimensionless stream function is introduced. By perturbation expanding, an approximate model has been developed. Analytical expressions for stream function, velocity and pressure variations along the duct are obtained. The effects of the amplitude and wavelength of the wavy plate duct on the flow state are discussed. Meanwhile, a preliminary estimation based on analogy theorem of the heat transfer enhancement to the flow friction increase is made.

Enhancement of Heat Transfer and Scale Inhibition in Flow Subcooled Boiling System

XIE Yun-feng;REN Xiao-guang;SONG Yong-ji;WANG Meng-lu

. 2006, 6(6):  889-893. 

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In the experiment of flow boiling heat transfer, the effects of calcium carbonate scaling and various technologcial conditions on flow subcooled boiling heat transfer were studied experimentally. The investigated conditions include liquid flow rate, temperature, concentration of calcium carbonate solution and heat flux. The effect of different scale inhibitors [polyaspartic acid (PASP), 2-phosphono-1,2,4-tricarbocylic butane (PBTCA) and amino-trimethylene-phosphonic acid (ATMP)] on flow subcooled boiling heat transfer was also examined. The results show that all the scale inhibitors can suppress the formation of scaling and reduce the fouling resistance, and there exists an optimum range of scale inhibitor concentration. However, different scale inhibitors perform differently, and under the experimental conditions, ATMP has the best effect of reducing fouling, followed by PBTCA and PASP.

反应与分离

Primary and Deep Purification of Complex System of MeSO4

PENG Chang-hong;TANG Mo-tang;HUANG Hong

. 2006, 6(6):  894-898. 

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In the complex system of MeSO4, the removal of Ca2+ and Mg2+ by fluorination precipitation and double salt precipitation deep purification process was studied by single factor method. The experimental results of fluorination precipitation demonstrate that the optimized conditions of fluorination precipitation process are as follows: the excess amount of NH4F is 2.0 times as theoretic consumption, precipitation time 1.0 h, reactive temperature 90℃ and the pH value 3.5. Under these conditions, the average removal rates of Ca2+ and Mg2+ are 92.98% and 89.95%, respectively. The key factors of double salt precipitation process are the excess concentration of (NH4)2SO4 and pH value of the solution. The optimized conditions of double salt precipitation process are as follows: the value of pH is 1.5~2.5, the excess concentration of (NH4)2SO4 2.0~2.5 mol/L, the precipitation time 1.0~1.5 h and the reactive temperature room temperature. Under these optimized conditions, the precipitation rates of main elements of Fe, Mn and Zn are 69.94%, 86.52% and 96.88%, respectively. And the removal rate of Si is 54.85%.

The Limiting Current Density in the System of Ion-exchange Membrane and Ammonium Sulfate Solution

ZHANG Xiao-yan;LU Wen-hua;CONG Wei

. 2006, 6(6):  899-902. 

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Current-voltage curve of the system of ion-exchange membrane and ammonium sulfate solution was studied with the membrane stack of six-compartment cells. Three distinct regions were observed in the current-voltage curve of monopolar membrane and ammonium sulfate system, and the limiting current densities were obtained from the curve. The experimental results showed that the limiting current density was significantly improved with the increase of ammonium sulfate concentration, flow rate and temperature. The relationships among limiting current density, ammonium sulfate concentration and flow rate were described well by the revised Wilson formulae, ilim=17.647C0.4570V0.5725(JAM-15) and ilim=13.003C0.2918V0.3697(JCM-15), respectively.

Characterization of New Type Molecular Sieve for Potassium and Its Exchange Capability to K+

YUAN Jun-sheng;GUO Zhao-shou;ZHANG Lin-dong

. 2006, 6(6):  903-906. 

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The self-made molecular sieve for potassium was characterized by SEM, chemical composition analysis, XRD and TGA-DTA. And the exchange capacities of the molecular sieve to K+ in pure potassium solution and in seawater and the selectivity coefficients to K+ in seawater were determined respectively. The results showed that the molecular sieve is composed of the two components, 76.25% Na6Al6Si10O32×12H2O and 23.75% K2Al2Si3O10×3H2O, and the mole ratio of silicon to aluminum is 5.22, it is stable up to 350℃, but the internal structure is destroyed at the temperatures more than 350℃, the exchange capacities of the zeolite to K+ in pure potassium solution and seawater are 100.30 and 55.10 mg/g respectively, and the selectivity coefficient to K+ in seawater is 74.41, that is, compared with the modified natural clinoptilolite, the new type molecular sieve has an increase of 2 times in the exchange capacity to K+ in seawater and 3 times in the selectivity coefficient to K+ in seawater. Therefore, the molecular sieve has high selectivity to K+, and can be used to extract potash selectively from seawater and the brine containing potassium.

Synthesis, Characterization and Surface Properties of Cross-linked Polyurethane Dispersions Modified by Organosiloxane

GAO Ming-zhi;XU Ge-wen

. 2006, 6(6):  907-911. 

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A series of cross-linked polyether-polyester polyurethane dispersions modified with organosiloxane were prepared based on hydroxyl-terminated polydimethylsiloxane (HTPS) as hydrophobic component and 3-aminopropyl-triethoxysilane (APTS) as cross-linker as well as a bridge between polyurethane (PU) and polysiloxane (PSIL). It was discovered that polydimethylsiloxane segments were incorporated into PU chains chemically and organosiloxane was preferentially oriented toward the surface layer of the film by making a comparison of attenuated total reflection (ATR) spectra between the copolymer and the blend of PU and PSIL, which was further confirmed by investigation of electron spectroscopy for chemical analysis (ESCA). The relationships between surface properties of the film formed from polyurethane dispersion and organosiloxane content were also studied. The results showed that water contact angle of the film increased with the increase of organosiloxane content. Interestingly, it was also found that water contact angle of PUS film increased firstly and then decreased when film-forming temperature varied from 25℃ to 55℃.

过程与工艺

Synthesis of New Water-soluble 10-Hydroxycamptothecin Derivative

YANG Liu;XU Chun-Yan;JIA Meng-Qiu

. 2006, 6(6):  912-916. 

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Water-soluble derivative with the lactone ring intact was synthesized by using 10-hydroxycamptothecin (HCPT) as raw material and pyridine as solvent through phosphorylation, esterification and hydrolysis. The optimal reaction conditions for the phosphorylation were determined as follows: n(POCl3):n(HCPT)=2:1 (based on 0.01 mol HCPT), the reaction temperature -10℃, and the reaction time 30 min under stirring, for the esterification they are: n(ethanol):n(HCPT)=6:1, the reaction temperature 10℃, and the reaction time 1.5 h under stirring, pH<5.0 in hydrolysis reaction. The product, 10-hydroxycamptothecin derivative, was separated by octodecyl silica gel preparative column. The total yield of the derivative was 30%.

Volatilization of Ludwigite in the Process of Carbothermal Reduction

LIU Ran;XUE Xiang-xin;JIANG Tao;DUAN Pei-ning;HUANG Da-wei;WANG Xing-juan

. 2006, 6(6):  917-921. 

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Based on thermodynamic analysis, the reduction and volatilization of B2O3 and magnesium in ludwigite were studied using carbothermal reduction method. The experimental results show that the mass loss rate of the sample increases with increasing temperature. The maximum mass loss rate of the sample is 61.8% from 1400 to 1450℃. B2O3 is continuously reduced and volatilized during the experimental process. From 1400 to 1450℃, the mass loss rate of B2O3 is 37.9%. The mass loss rate of MgO is 98.0%. The content of B2O3 in the deposite reached 12.49%, determined by chemical analysis. The result of study shows the volatilization of boron oxide and magnesia from ludwigite.

Ammoximation of Acetophenone Catalyzed by TS-1 Molecular Sieve

ZHANG Yong-jie;WANG Ya-quan;LIU Teng-fei;MI Zhen-tao;WU Wei;MIN En-ze;QI Tao

. 2006, 6(6):  922-925. 

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The ammoximation of acetophenone to acetophenone oxime with 28%(w) H2O2 over TS-1 molecular sieve catalyst was studied. The influences of various parameters such as solvent, temperature, auxiliary catalyst (alumina and ammonium acetate), molar ratios of NH3 to acetophenone and H2O2 to acetophenone on the reaction were investigated. The results show that the best solvent is ethanol and the optimal reaction temperature 80℃, and ammonium acetate can promote the formation of acetophenone oxime. In order to achieve the high yield, the molar ratios of NH3 to acetophenone and H2O2 to acetophenone should be kept above 2.00 and 1.27, respectively.

系统与集成

Modeling of Phase Equilibrium in Ethylene Slurry Polymerization System

SHEN Hang;GU Xue-ping;FENG Lian-fang;TANG Zhi-wu;LIU Bo

. 2006, 6(6):  926-931. 

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In modeling and optimization of ethylene slurry polymerization process, the phase equilibrium computation accuracy has decided the polyethylene production quantity and the molecular weight simulation accuracy. The equation of state of perturbed-chain statistical associating fluid theory (PC-SAFT) was applied to predict thermodynamic properties and phase equilibrium data in ethylene slurry polymerization system through Polymers Plus software. The related parameters of pure components of ethylene, hydrogen, hexane, polyethylene and nitrogen were obtained based on literature data. The interaction parameters of binary systems between ethylene and hexane, hydrogen and hexane, ethylene and hydrogen, ethylene and polyethylene, hexane and polyethylene were regressed. Comparing the results from modeling and literatures, the reparameterized equation of state of PC-SAFT can exactly predict component thermodynamic properties and phase equilibrium of binary system. The predictions of the ratio between hydrogen and ethylene in molar fraction are in agreement with those from plant.

Combined Water-Oxygen Pinch Analysis with Mathematical Programming for Wastewater Treatment

SONG Li-li;DU Jian;CHAI Shao-bin;YAO Ping-jing

. 2006, 6(6):  932-936. 

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Water-oxygen pinch analysis is an effective method to decrease the wastewater quantity and improve the wastewater quality. But when multiple-contaminants are present, the method is difficult to be carried out. In this paper, the method that combines water-oxygen pinch analysis with mathematical programming is proposed. It obtains the general optimal solution and leads to the reuse stream that cannot be found only by pinch analysis. The new method is illustrated by an example, and the annual cost is reduced by 8.43% compared with the solution of literature.

Segmented Optimal Design Method for the Combined Drying System

WAGN Sheng-wei;HU Yang-dong;AN Wei-zhong;WU Lian-ying

. 2006, 6(6):  937-941. 

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A new design method?the segmented design method for drying system was put forward. The primary idea of this method is disassembling one task into several tasks, then designing them based on the different characteristics of each assignment. This method was studied by the optimal design of the drying process. The optimal design was aimed at the minimization of annual total cost, of which the drying process was expressed as a three-segment superstructure at most and two drying equipments could be chosen in each segment. The system models of each unit and process and the economic models were used in this method. The result showed that it was better to apply the two-segment method when the moisture of material was more than the critical moisture under the same condition, with the rotating-cylinder drier and the fluid-bed drier combined to drying; one-segment drying method with materials put into fluid-bed drier directly should be adopted when the moisture of material was less than the critical moisture under the same condition.

生化工程专栏

Effects of Light and Temperature on the Redifferentiation of Saussurea involucrata Callus Cultured in the Bioreactor

LEI Liang;WANG Xiao-dong;XU Chun-ming;ZHAO Bing;WANG Yu-chun

. 2006, 6(6):  942-947. 

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A series of experiments were carried out to study the effects of light quality, light time, temperature difference between day and night, and time of low temperature treatment on the redifferentiation of Saussurea involucrata callus after the callus culture in a bioreactor. Compared with short wavelength light, long wavelength light led to high redifferentiation. The redifferentiation frequency of callus increased with the lighting time. The maximal redifferentiation frequency was obtained with daily lighting 16 h/d. The temperature difference between day and night was negatively correlative to the callus redifferentiation. Low temperature treatment was not necessary to the redifferentiation. The peroxidase isoenzyme analysis indicated that the redifferentiation frequency of the callus was closely related to the quantity and kinds of the peroxidase isoenzymes.

Co-expression of D-Hydantoinase and N-Carbamoylase in Recombinant Escherichia coli

HU Xiao-jia;LI Qiang;CONG Jin-yang

. 2006, 6(6):  948-953. 

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Fully enzymatic synthesis process for the production of D-amino acids involves two enzymes, D-hydantoinase and N-carbamoylase. In an attempt to select more efficient biocatalysts, the hydantoinase and carbamoylase genes from A. radiobacter TH572 were cloned in Escherichia coli. The genes were assembled to give polycistronic structures, and under the control of a strong araBAD promoter, the recombinant strain TaraCRH was obtained. Expression of the two enzymes was tightly controlled by araBAD promoter, high level expression of both hydantoinase and carbamoylase was achieved with the induction of arabinose, but no activity could be detected in the absence of arabinose. The expression conditions were then optimized. The highest level of soluble expression was obtained at an induction temperature of 29℃ and arabinose concentration of 0.05 g/L. Furthermore, we tried to use corn steep liquor medium instead of LB medium for the culture of E. coli TaraCRH, the optimized corn steep liquor medium consisting of corn steep liquor (45 g/L), glycerol (3 g/L), NaCl (3 g/L), KH2PO4 (0.5 g/L), CoCl2 (0.2 g/L) was developed by using orthogonal experiments. After culturing and inducing E. coli TaraCRH in this optimized medium, the activities of hydantoinase and carbamoylase achieved 3.52 and 4.21 U/mL, respectively, which enabled efficient production of D-HPG from DL-HPH.

Modification of Poly(Glycidyl Methacrylate-Divinylbenzene) Porous Microspheres with Polyethylene Glycol and Their Use as HIC Medium for Protein Adsorption

ZHANG Ying;WANG Ren-wei;MA Guang-hui;TAN Tian-wei;SU Zhi-guo

. 2006, 6(6):  954-958. 

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Porous poly(glycidyl mathacrylate-divinylbenzene) [P(GMA-DVB)] microspheres containing epoxy groups were synthesized through suspension polymerization. In order to minimize non-reversible adsorption of proteins, polyethylene glycol (PEG) was coupled onto the microspheres via the reaction with epoxy groups. The reaction process was studied and optimized with respect to the amount of PEG coupling. The optimum temperature was 80℃. Bovine serum albumin (BSA) and trypsin were used as two model proteins to examine adsorption and desorption properties of the modified P(GMA-DVB) microspheres. The modified microspheres had little non-reversible adsorption for BSA and trypsin. The mass recovery rate and activity recovery rate were more than 97%. The adsorption of protein on the modified microspheres was reversible hydrophobic interaction. The modified microspheres can be used for hydrophobic interaction chromatography of proteins.

Preparation of Butyl-agarose Chromatography Media with Controlled Ligand Density through Direct Coupling Reaction

FENG Qing-zheng;MENG Qing-qiang;WANG Jia-xing;MA Guang-hui;MA Run-yu;SU Zhi-guo

. 2006, 6(6):  959-963. 

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Butyl-agarose chromatography media were prepared by direct coupling of butyl glycidyl ether (BGE) on agarose 4FF beads. The effects of various reaction parameters on the density of butyl group were investigated. The preparative conditions were optimized by orthogonal design of the experiments. The optimum conditions were found to be 0.02 mL/g (BF3×Et2O/gel), reaction time 45 min and reaction temperature 45℃. The ligand density could be controlled by the amount of BGE added to the reaction mixture. The mechanical stability, chemical stability and adsorption capability were also investigated. The results demonstrated that the butyl-agarose chromatography media with varied ligand density would be promising media for protein separation and purification.

Preparation and Release Behavior of Alginate Microspheres Containing BSA by Emulsification

ZHANG Jie;GUO Ni-ni;ZHANG Dai-jia;XIU Zhi-long

. 2006, 6(6):  964-968. 

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Alginate (ALG) microspheres containing bovine serum albumin (BSA) were prepared by an emulsification technique. Soybean salad oil used widely in food industry was chosen as an oil phase. Orthogonal experimental design was used to find the optimal preparation conditions by comparing the encapsulation efficiency of BSA, loading capability and average diameter of microspheres. The fine spherical alginate microspheres with an average diameter of 10 mm were obtained under the appropriate conditions. The encapsulation efficiency of BSA and the BSA loading capability were 70% and 4% (w), respectively. As the concentration of ALG increased and the amount of BSA decreased, the encapsulation efficiency of BSA increased, however, BSA loading capability decreased. The in vitro release profile showed a fast release rate of encapsulated BSA, particularly in phosphate buffered saline solution, owing to the excellent pH responsive properties of alginate microspheres. Finally, electrophoresis experiment illustrated that the process of encapsulation had no effect on the molecular weight of the entrapped protein.

Application of Sun-light Conversion Film on the Growth of Haematococcus pluvialis

WU Xia;KANG Rui-juan;CONG Wei;TAN Tian-wei

. 2006, 6(6):  969-972. 

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The photosynthetic microalga Haematococcus pluvialis, a potential source of astaxanthin, has been widely used in breeding of salmon. The influence of light quality on the growth of Haematococcus pluvialis was studied. The results showed that red light was beneficial to the growth and astaxanthin accumulation of H. pluvialis. By comparing the effects of sun-light conversion film (SCF) and PE film on H. pluvialis in a 2.5 L air-lift photobioreactor, it is concluded that the values of biomass, pigments and photosynthetic parameters under the SCF were all much higher than those under PE film. In the case of the air-lift photobioreactor, the concentration of astaxanthin and chlorophyll reached 3.57 and 12.42 mg/L respectively, and the dry weight increased 8.8% after 9 d.

材料工程专栏

Preparing Aluminum Foam Sandwich by the Roll-bonding-powder Metallurgy Foaming Technique

ZU Guo-yin;ZHANG Min;YAO Guang-chun;LI Hong-bin

. 2006, 6(6):  973-977. 

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The technique of roll-bonding was applied to prepare the foaming composite board in order to settle the main problem that exists in the preparation of aluminum foam sandwich in this work. The result shows that the preformed core powder cake can strongly integrate with the steel sheet after rolling. The tightness of rolled core powder is obviously higher than that of hot pressing composite board and the powder takes on the closely stratified structure, which creates the favorable condition for foaming. Considering integrated the factor such as bond strength, tightness of core powder and rolling defect, the best deformation rate should be controlled at 60%~70%. The composite board can obtain the perfect foam structure under proper foaming technological conditions: the best foaming temperature is 620~640℃ and foaming time 8~10 min. Intermetallic compound of FeAl3 and Fe/Al solid solution with about 10 mm thickness occur at the interface after foaming. Thus the interface leads to the perfect metallurgical bonding.

Evolution of Pore Morphology in Foam Aluminium

GUO Zhi-qiang;YAO Guang-chun;YU Hai-jun;LI Hong-bin

. 2006, 6(6):  978-982. 

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Two different kinds of pressing modes were applied in preparation of foam aluminium by powder metallurgy. It was found that the optimal structure of foam aluminium could be obtained by hot pressing mode. The evolution process of foam aluminium which was made by Al-Si-Ca alloy was studied at 680℃. It went through three stages: nucleation occurring in three different states, foam growth and collapse. The shape of foam also changed from round to polygon with the growth of foam. Finally the merging and porosity gradient of the foams which resulted from capillarity-driven and gravity-driven melt flowing within the melt foam column started, under the bottom of the foam, bubble-free layer appeared, the foam began to collapse.

Synthesis and Characteristics of Sn/Ni3Sn4 Alloy as Anode Material for Lithium Ion Batteries

YUAN Qing-feng;BU Dong-lei;WANG Wen-lu;CHEN Chun-hua

. 2006, 6(6):  983-986. 

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A dual-phase Sn/Ni3Sn4 alloy was synthesized by a method of wet chemical reduction followed by ball-milling. Its crystalline structure and powder morphology were characterized by XRD and SEM analyses. Cyclic voltammetry and galvanostic cell cycling were also used to characterize its electrochemical properties. The results showed that the Sn/Ni3Sn4 powder was mainly composed of 1~4 mm agglomerates and had 96.4% columbic efficiency and high specific charge-discharge capacity in the first cycle. The electrochemical cycling ability was very sensitive to the cutoff voltages of the charge-discharge process. Within the optimized voltage window of 0.3~1.0 V, the alloy showed a rather stable cycling performance.

Study on Ca0.6Mg0.4Zr4(PO4)6 Coating with Alkali Corrosion Resistance

ZHOU Jian-er;XU Ai-min;ZHANG Xiao-zhen;WANG Yan-xiang;WANG Yong-qing

. 2006, 6(6):  987-990. 

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Ca0.6Mg0.4Zr4(PO4)6 coating on dense cordierite was prepared through sol-gel and dip-coating techniques. The phase composition and microstructures of coating surface and interface between coating and matrix were characterized by XRD and SEM. The results show that homogeneous, dense and crack-free Ca0.6Mg0.4Zr4(PO4)6 coating was successfully deposited on cordierite. The coating is single-phase Ca0.6Mg0.4Zr4(PO4)6 and composed of 2~3? mm spherical grains. SEM microstructural examination also revealed the excellent bonding between Ca0.6Mg0.4Zr4(PO4)6 coating and cordierite matrix. The assessment of coating alkali corrosion resistance was done through the measurements of weight loss and flexural strength degradation after 96 h alkali vapor corrosion at 1000℃, and the weight loss and flexural strength reduction are 0.9% and 10.2% respectively for the samples coated for three times, much less than those of uncoated cordierite, 8.2% and 87.2% respectively. The study shows that the Ca0.6Mg0.4Zr4(PO4)6 coating has good alkali corrosion resistance property and can greatly improve the high temperature alkali corrosion resistance of cordierite, and after 96 h alkali vapor attacking at 1000℃, the structure of the coating is almost not destroyed.

综述

Focus Attention on Structure, Interface and Multi-scale Issues to Open up New Mileage of Chemical Engineering

LI Hong-zhong

. 2006, 6(6):  991-996. 

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Since 1990s along with the fast development of the computer technology and measurement instruments，the research of chemical engineering has been pushed progressively from the level of judgment by empirical regulations to the level of quantitative analysis by computer simulations. The research range of chemical engineering is extended to cover from observation and prediction of the micro-scale structure and interface to the system integration of the macro-scale equipment and plant. The principles and knowledge of chemical engineering are applied to from chemical engineering to process engineering for chemical conversion and physical transform such as in metallurgy, materials, energy source, environment, bioengineering. The scientists and engineers in chemical engineering profession are seeking the third mileage of the chemical engineering after the first mileage, unit operations, and the second mileage, transport process and chemical reaction engineering. The methodology of averaging, which is popularly used in chemical engineering, but neglects the influences of the heterogeneous multi-scale structure and interface, is the main reason of the large prediction error and the overwhelming difficulty in effective design and operation of chemical equipment. We should focus our attention on the structure, interface, and multi-scale issues, study the quantitative prediction theory and optimum control method for the multi-scale structure and interface, and establish the modeling for predicting the relationships among the multi-scale structure and interface, momentum transfer, heat transfer, mass transfer and chemical reaction. These efforts, combined with advanced calculating methods, computational fluid dynamics and computer simulation, may well solve the difficult problems in optimum control and scale-up of chemical processes and equipment, and catalyze the birth of the new mileage of chemical engineering.

Progress of Gas Hydrate Studies in China

FAN Shuan-shi;WANG Ji-yang

. 2006, 6(6):  997-1003. 

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A brief overview is given on the gas hydrate-related research activities carried out by Chinese researchers in the past 15 years. The content involves: (1) Historical review. Introducing the gas hydrate research history in China; (2) Gas hydrate research groups in China. There are nearly 20 groups engaged in gas hydrate research now; (3) Present studies. Including fundamental studies, status of the exploration of natural gas hydrate resources in the South China Sea region, and development of hydrate-based new techniques; (4) Future development.

Investigation Progress on Release and Control of NOx and N2O during Coal Combustion in Circulating Fluidized Bed Combustor

ZHANG Lei;YANG Xue-min;XIE Jian-jun;DING Tong-li;YAO Jian-zhong;Song-wen-li;LIN Wei-gang

. 2006, 6(6):  1004-1010. 

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Circulating fluidized bed (CFB) coal combustion technology has been extensively applied in the past two decades due to its advantages, such as the adaptability to wide range of coal and low pollution emissions compared with other traditional coal combustion technologies. However, high N2O emission is a prominent disadvantage of CFB coal combustion. As the emission limits become more restrict in recent years all over the world, further lowering pollutant emissions in coal-fired CFB combustor is urgently needed. For this purpose, reviewing available knowledge on the emissions, especially NOx and N2O, in coal-fired CFB combustor is of essential importance. The mechanisms of formation and destruction of NOx and N2O homogeneously and heterogeneously in coal-fired CFB combustor were summarized in this work. The influences of operation parameters of coal-fired CFB combustor, such as bed temperature, excess air number, air staging and coal characteristics, on NOx and N2O emissions were discussed. Some common applied technologies of reducing NOx and N2O emissions in coal-fired combustor were also introduced. Two kinds of promising technologies, named as reversed air staging and CFB decoupling combustion were briefly described.

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. 

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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.