The Chinese Journal of Process Engineering

Numerical Simulation of Performance of Heat Exchangers with Quarter-ellipse Helical Baffles

WANG Chen;SANG Zhi-fu

. 2007, 7(3): 425-431.

Asbtract ( )

PDF (387KB) ( )

Related Articles | Metrics

According to the numerical simulation by the CFD software FLUENT, the pressure drop and heat transfer for the shell-and-tube heat exchanger with the quarter-ellipse helical baffles with different helix angles (25o, 30o, 35o, 40o, 45o, 50o) were investigated. The results indicate that the heat transfer rate and pressure drop both decrease when the helix angle is increased. And the heat exchanger has the best overall performance when the helix angle is 35o. Among the different baffles, the quarter-ellipse helical baffle has better overall performance, compared with the segmental baffle and the quarter-sector helical baffle with the same helix angle.

Discrete Particle Simulation of Bubbling Behavior in a Gas-Solid Fluidized Bed

WU Chun-liang;ZHAN Jie-min

. 2007, 7(3): 432-438.

Asbtract ( )

PDF (854KB) ( )

Related Articles | Metrics

The bubbling behavior in a two-dimensional fluidized bed is numerically studied using the discrete particle simulation model. Inter-particle interactions are taken into account, which are described by binary collisions in a hard-sphere model. The interactions between the particulate and continuous phases are modelled by the Gidaspow's drag formula. The particle momentum equations are solved simultaneously with the gas governing equations, and the void fraction is calculated in a particular way. The hash table is introduced to deal with collision events and shortens the computing time. The numerical results indicate that the bubble transverse movements are enhanced by the interaction among bubbles in the fluidized bed. The trajectories and shapes of bubbles are dependent on the static pressure distribution in the bed and bubbles move towards the area with lower pressure and a larger pressure drop. This phenomenon is similar to that in the gas-liquid separate flow.

Numerical Simulation of Critical Suspension Impeller Speed in a High Concentration Stirred Tank

ZHANG Feng-tao;LIU Fang;HUANG Xiong-bin

. 2007, 7(3): 439-444.

Asbtract ( )

PDF (267KB) ( )

Related Articles | Metrics

Based on the function provided by CFX5.5.1, the critical suspension impeller speed, Njs, was simulated. The investigation was carried out in a fully baffled, flat bottom, cylindrical vessel, with 476 mm diameter, equipped with CBY (long thin blade) impeller. The clearance between the impeller and the bottom of the tank was D/3. The glass beads of 15~150 mm were chosen as the dispersed phase. The particle volume fraction was from 15% to 50%. Two different criteria were used to determine Njs from the numerical results. The original criterion is to identify the critical suspension by a sudden velocity increase with the impeller speed at the bottom center. The modified criterion is by observation of the velocity increase at the point with the most difficulty in suspension, i.e., at the radial position about 50 mm off the bottom center. The CFD predictions by the modified criterion are in good agreement with experimental data. At the bottom of the tank, turbulence kinetic energy at the critical impeller speed was also discussed.

Experimental Study on the Solid Hold-up in the Fluidized Bed of a Riser-Fluidized Bed Combined Reactor

NIE Xiang-feng;LU Chun-xi;MA An;LONG Wen-zi;SHI Ming-xian

. 2007, 7(3): 445-450.

Asbtract ( )

PDF (302KB) ( )

Related Articles | Metrics

The radial distributions of solid hold-up are investigated in a cold model of a new type of liquid-solid fluidized bed reactor with 500 mm ID and 4000 mm in height of a riser-fluidized bed combined reactor. The influences of superficial liquid velocity and solids circulating rate on the radial hold-up distribution are also analyzed respectively, focusing on the most probably influential factors. The experimental results show that the whole bed can be divided into three distinct axial zones, distributor influencing zone, gradually developed zone and steadily fluidized zone. At the same time, in these three zones, the cross-sections of the liquid-solid fluidized bed can be characterized by two areas in radial direction, the central and annual areas. Moreover, the three-zone flow features of the liquid-solid fluidized bed and the spouted bed are also compared in detail.

Fluidizing Behavior in a Fluidized Bed Incinerator with Tubular Distributor

ZHAO Yun-hua;ZENG Ling-yan;CHEN Hui-lin;LIU Wen-tie

. 2007, 7(3): 451-456.

Asbtract ( )

PDF (306KB) ( )

Related Articles | Metrics

Flow behavior of gas and particles was numerically studied in a bubbling fluidized bed incinerator with tubular distributor. The distributions of instantaneous and time-averaged velocities of gas and particles phases, and particle concentration were obtained. Simulated results show that on the whole particles flowed up in the center, and down near the walls, and an inter-circulation of particles formed. The influences of jetting gas velocity and particle diameter on fluidization were analyzed. Numerical simulations indicate that the optimum spacing between air tubes is in the range of 1.5 to 1.75 in the present study.

High Speed Propagation of Premixed Flame in Swirling Flow-II. Ignition Position and Process of Combustion

XIA Liang;ZHAO Dai-qing;SHAN Xia-bo shi;WANG Xiao-han

. 2007, 7(3): 462-466.

Asbtract ( )

PDF (492KB) ( )

Related Articles | Metrics

The previous research of vortex-bursting shows that in the swirling condition, premixed methane-air combustion can be stable in the high inlet velocity gas. Based on the investigation of both the combustion efficiency of swirling premixed combustor and the effect of distribution of inlet velocity on enhancement of combustion efficiency in the previous paper, the numerical research of ignition position effect on the flame stability is carried on in this work. It is found that inappropriate ignition position can affect the process of flame evolution. Under the same condition, development of combustion will evolve in different trends if the flame is ignited at different positions in the flow field. A non-dimensional parameter is put forward for describing the ignition position. When ignition position is located on the axis and low velocity area of tube, the resulting flame will be stable. Instead, when ignition position is in high velocity area, the flame is finally blown out. In this work, the useful theoretical and applicable results for enhancing stability of premixed combustion are achieved.

Constitutive Relation of Pseudo-fluid Granular Flow

BIAN Lin;WANG Li;LIU Chuan-ping

. 2007, 7(3): 467-471.

Asbtract ( )

PDF (222KB) ( )

Related Articles | Metrics

For the slow intensive granular flow, the method of describing the granular flow as a pseudo-fluid flow is employed in this work. By analogy with non-Newton fluid with yield stress, a constitutive equation is put forward for slow intensive granular flow, and a mathematical model of testing granular equivalent viscosity is presented. Based on the experiment of wheat granules flowing down a rough inclined chute, the yield stress and the key coefficients of constitutive equation of the wheat granule flow are calculated. From theoretical analysis of wheat granule chute flow using the coefficients of the constitutive relation from experiment, the relative error of the prediction of the volume flow rate compared with corresponding experimental data is less than 15%.

The Effect of Dividing Surface on Heat Transfer Characteristics of Dropwise Condensation

MA Xue-hu;SONG Tian-yi;LAN Zhong;ZHOU Xing-dong

. 2007, 7(3): 472-475.

Asbtract ( )

PDF (310KB) ( )

Related Articles | Metrics

The relations of water vapor condensation heat fluxes with surface subcoolings on coated surfaces were determined experimentally, and the experimental results with and without dividing surfaces with the ratio of 1:1 were also compared. It was observed that the heat fluxes of dropwise-filmwise coexisting condensations (DFC) on dividing surfaces were more than the mean fluxes of pure dropwise and filmwise condensations (MDF) on coated and bare surfaces, respectively, and the differences between them increased with increasing the contact angles on the coated surfaces. The phenomenon was explained from the point of view of interfacial energy effect of condensate and solid.

Dimethyl Carbonate Synthesis by Oxidative Carbonylation with CuBr3L2 Catalyst

YANG Yang;LIU Xiao-qin;LIU Ding-hua;YAO Hu-qing

. 2007, 7(3): 476-482.

Asbtract ( )

PDF (256KB) ( )

Related Articles | Metrics

A new type of CuBr3L2 complex catalyst for dimethyl carbonate (DMC) synthesis by oxidative carbonylation of methanol in liquid-phase was reported. The complex catalysts were characterized by means of XPS and EPR. The results showed that the introduction of complexing agent tetrabuthylammonium bromide (L) can promote the substantial formation of Cu(I) species for DMC synthesis. With the method of orthogonal experiment, the process conditions (temperature, concentration of catalyst, pressure and reaction time, etc.) were examined. The results indicated that under the optimum conditions (temperature 373~383 K, pressure 3.0~3.5 MPa, reaction time 4~6 h, concentration of catalyst in methanol 0.15~0.20 g/mL), the conversion rate of methanol could reach 23% and the selectivity of DMC could exceed 95%. The reaction kinetics with CuBr3L2 complex catalyst for DMC synthesis was investigated. The kinetic equation and parameters were obtained. The results showed that the reaction of methanol oxidative carbonylation to DMC by the catalyst was an second order reaction approximately. The reaction rate constant (Kp) was related to reaction temperature and mass concentration of catalyst, and Kp was directly proportional to the square of mass concentration of catalyst. It was indicated that high temperature and pressure were unfavorable to the main reaction and caused the decrease of DMC selectivity.

Absorption of Low Concentration Sulfur Dioxide Using Liquid-containing Microporous Membrane

XUE Juan-qin;LAN Xin-zhe;MENG Ling-ai;LI Wei-da

. 2007, 7(3): 483-489.

Asbtract ( )

PDF (160KB) ( )

Related Articles | Metrics

The absorption of low concentration SO2 in flue gas by using the module of liquid-containing microporous membrane which is made up of hollow fiber and citric acid-sodium citrate buffer solution was investigated. The absorption efficiency of hydrophilic and hydrophobic membranes by using the concept of dynamic contact angle was mainly studied. The influences on absorption efficiency from absorption time, flowrate of gas phase, SO2 concentration of gas phase, air pressure, citrate concentration, pH value of solution as well as the generation of sulfate radical in absorption solution were examined. The results indicate that the hydrophobic hollow fiber membrane is better than hydrophilic membrane, the absorption efficiency decreases with increasing absorption time, gas phase flowrate, gas phase SO2 concentration and air pressure, the absorption rate and capacity of SO2 can be improved by increasing the citrate concentration, the absorption efficiency can be improved by increasing the pH value of citrate solution, the concentration of SO42- in absorption solution increases linearly with the absorption time at a rate around 0.192 g/(L×h).

Ethanol Dehydration to Ethylene over HZSM-5 Catalyst Modified by Zn and Mn

PAN Feng;WU Yu-long;ZHANG Jian-an;YANG Ming-de;LIU De-hua;DONG Jun-mao

. 2007, 7(3): 490-495.

Asbtract ( )

PDF (270KB) ( )

Related Articles | Metrics

Preparation of ethylene from ethanol dehydration catalyzed by HZSM-5 molecular sieve modified with Zn and Mn was studied. The effects of modified solution, Si/Al ratio of HZSM-5, and modified conditions, such as concentration of modified solution, modification reaction time and temperature, and calcination temperature, were investigated. The results showed that when the Si/Al ratio of ZSM-5 was 25, modification temperature was 40℃, the concentrations of Zn(NO3)2 and MnCl2 were 2% and 6% respectively, the modification time was 1 h, and the calcination temperature was 550℃, the catalytic activity of modified HZSM-5 was higher. The HZSM-5 and modified ZSM-5 were characterized by XRD, BET, SEM and FT-IR techniques. The result indicated that Zn2+ and Mn2+ were located in the zeolite frame, and the crystalline structure of the modified zeolites was not changed, in addition B acid sites were decreased slightly and L acid sites increased greatly, which were favorable to catalytic dehydration of ethanol to ethylene.

Separation of Hydrophilic Licorice Flavonoid by Solvent Extraction Method

TIAN Qing-lai;XIE Yu-chun;ZHANG Bo;LIU Hui-zhou

. 2007, 7(3): 496-500.

Asbtract ( )

PDF (213KB) ( )

Related Articles | Metrics

Using the mixture of trialkylphosphine oxide (TRPO) and petroleum ether as extractive organic phase, the extraction of hydrophilic flavonoid from the aqueous leaching solution of licorice was carried out. Orthogonal tests showed that the concentration of TRPO was the most remarkable factor for extracting hydrophilic flavonoid, then the phase ratio and the smallest was pH value. It was also found that the extraction rate of total flavonoid (TF) decreased with increasing pH value in the range from 5 to 8. The extraction rate of glycyrrhizic acid rapidly decreased with increasing pH value in the range from 5 to 6, and it almost approached zero above pH 6. The extraction rate of TF rapidly increased with the increase of the concentration of TRPO and decreased with the increase of phase volume ratio (A/O). It decreased with the increase of the system temperature, and the reaction of the extracting TF was exothermic. The ratio of TRPO to solute in extractive complex was 3. The separation between hydrophilic licorice flavonoids and glycyrrhizic acid in the aqueous leaching solution could be achieved by solvent extraction method.

Enhancement Effects of Mechanical Activation on Esterification of Cassava Starch

HUANG Zu-qiang;CHEN Yuan;QIAN Wei-jin;TONG Zhang-fa;LI Xuan-hai

. 2007, 7(3): 501-505.

Asbtract ( )

PDF (209KB) ( )

Related Articles | Metrics

Cassava starch was mechanically activated by a stirring-type ball mill. Using acetic anhydride as esterification agent and methanesulfonic acid as catalyst, starch acetate was synthesized from cassava starch with different activation times. The effects of mechanical activation time, reaction time, reaction temperature, catalyst amount and acetic anhydride amount on esterification of cassava starch were investigated respectively by using degree of substitution (DS) of starch acetate as evaluating parameter. The results indicated that mechanical activation considerably enhanced the esterification of cassava starch, the DS increased with increasing activation time. The reasons are due to that the crystal structure and compact granule surface of cassava starch were destroyed by mechanical activation, the crystallinity decreased and reagents were easier to diffuse into starch intra-molecules. Moreover, it was also found that other affecting factors had a certain influence upon esterification and were closely related to the activation time of cassava starch, and the effects of reaction temperature, catalyst and acetic anhydride concentrations on esterification were reduced with increasing activation time. Furthermore, the structures of native starch, activated starch and high DS starch acetate were further characterized by using FT-IR.

Desulfurization Process of Gasoline by Extraction with Ionic Liquid

ZENG Xiao-lan;LI Dan;ZHANG Xiang-ping;WANG lei;ZHANG Suo-jiang

. 2007, 7(3): 506-509.

Asbtract ( )

PDF (196KB) ( )

Related Articles | Metrics

As new and green solvents, ionic liquids have been proved to be effective in the gasoline extraction desulfurization. In this work, gasoline extraction desulfurization process with ionic liquids is studied in detail. The simulated gasoline is prepared by mixing pentane, toluene and thiophene, and the desulfurization solvent is defined as methylimidazolium ionic liquids with different carbon numbers. With orthogonal experiment design, four critical factors, i.e., temperature, desulfurization time, ratio of solvent to gasoline and carbon number of ionic liquids with 5 levels on desulfurization officiency are examined respectively. The optimal desulfurization conditions have been obtained: 40℃, ~50 min, ratio of solvent to gasoline 1:1, and 10 carbon number ionic liquid (1-decyl- 3-methylimidazolium hexafluorophosphate). The kinetic equation of extraction desulfurization is regressed.

Effects of Additives on Ultrasonic Desorption of Sulfur Dioxide in Citrate Solution

XUE Juan-qin;LAN Xin-zhe;MENG Ling-ai;LI Wei-da;LU Xi

. 2007, 7(3): 510-513.

Asbtract ( )

PDF (212KB) ( )

Related Articles | Metrics

Introducing ultrasonic wave as an external field into the process of desorbing sulfur dioxide in sodium citrate buffer solution is a new approach. In this work, based on the characteristics of ultrasonification and the solution properties, the desorption mechanism of sulfur dioxide and the influence of the additives (surfactants and inert gases) on ultrasonic desorption are investigated. Experiments are performed to verify the analytical results. The results show that lauryl sodium sulfate, sodium dodecyl benzene sulfonate and dodecyl trimethyl ammonium chloride can all significantly reduce the surface tension of sodium citrate solution, thus the desorption efficiency of sulfur dioxide can be improved. Among these three surfactants, lauryl sodium sulfate gives the best effect. However, when the surfactant concentration is over 0.1 g/L, the surface tension of citrate solution can be hardly decreased further and the desorption rate of sulfur dioxide increases very slowly. It is also found that adding inert gases in the desorption system can also increase the desorption efficiency of sulfur dioxide by as much as 20%.

Catalysis of Reforming Methanol Steam for Generation of Hydrogen over Au/La2O3/TiO2 Catalyst

XU Xin;LUO Guo-hua;CUI Bing-bing;CHEN De

. 2007, 7(3): 514-519.

Asbtract ( )

PDF (265KB) ( )

Related Articles | Metrics

Au/La2O3/TiO2 catalyst was prepared by the deposition-precipitation method and characterized by XRD and TEM. The influences of the preparation conditions and reaction conditions were investigated in details. The results show that La2O3 can enhance the catalytic activity of methanol steam reforming, and the addition of La2O3 can decrease the production of CO and CH4 evidently, and increase the hydrogen selectivity, when the H2O/CH3OH molar ratio is 1.0, WHSV reaches to 3.42 h-1 and reaction temperature is at 275℃, the production of hydrogen via steam reforming of methanol over Au/La2O3/TiO2 shows the optimal performance.

Thermodynamic Analysis of Production Technology of Electronic Grade Polycrystalline Silicon

LI Guo-dong;ZHANG Xiu-ling;HU Yang-dong

. 2007, 7(3): 520-525.

Asbtract ( )

PDF (213KB) ( )

Related Articles | Metrics

Chemical reaction equilibrium in three reaction subsystems of the closed loop process of electronic grade polycrystalline silicon with SiHCl3 method was computed based on the principle of Gibbs free energy minimization, respectively. Thermodynamic analysis was given emphatically to SiHCl3 reduction subsystem. The suitable operating conditions in SiHCl3 reduction system were 1323~1473 K, 0.1 MPa. It could contribute to producing polycrystalline silicon through reduction of SiHCl3 under the temperature above 1323 K, the H2/SiHCl3 molar ratio above 6.6:1 and low pressure. Electrical heat under high temperature for traditional SiHCl3 reduction system was difficult for process operation. Based on this, energy coupling achieved by adopting Cl2 partial oxidation in SiHCl3 reduction system was proposed, that is, polycrystalline silicon production process could be achieved without supplying exterior energy, and electricity consumption could be saved. At the same time it was also found that feed Cl2 could react completely at equilibrium, and subsequent process was not influenced. Increasing pressure and lowering H2/SiCl4 molar ratio were favorable for producing SiHCl3 in SiCl4 conversion system.

Preparation of Uniform-sized Porous PST-DVB Microspheres by Combining Membrane Emulsification with Suspension Polymerization

QIN Lu;LIN Hai;GONG Fang-ling;HAO Dong-xia;MA Guang-hui

. 2007, 7(3): 526-530.

Asbtract ( )

PDF (439KB) ( )

Related Articles | Metrics

Poly(styrene-divinylbenzene) (PST-DVB) microspheres were prepared by combining microporous membrane emulsification with suspension polymerization, using self-made apparatus of membrane emulsification. In this study some important influential factors on the size of microspheres, morphology of microspheres were investigated, such as the shearing force, the pipeline linear velocity and the pressure of membrane emulsification. The results showed that there was little effect of the shearing force on the particle size within a appropriate range, the morphology was fine and the particle size was uniform, when the pipeline linear velocity varied in the range of 14.38~26.49 m/min and the pressure of membrane emulsification 0.008~0.012 MPa. The pressure of membrane emulsification and shearing force are two functional elements to the dispersed phase velocity, the pressure of membrane emulsification is more important. The investigation into these elements may lead to the establishment of design guidance for enlarging such apparatus.

Preparation of ZnO Nanoparticles in a Reverse Micellar System and Their Application in Glucose Biosensor

GUO Wei-ling;REN Xiang-ling;TANG Fang-qiong;CHEN Dong;ZHANG Lin;LIU Feng-ling

. 2007, 7(3): 531-535.

Asbtract ( )

PDF (235KB) ( )

Related Articles | Metrics

ZnO nanoparticles are produced in sodium-bis-(2-ethylhexyl ) sulfosuccinate (AOT)/cyclohexane reverse micelle system and then used to immobilize glucose oxidase (GOD) to prepare enzyme electrode of biosensor. The experimental results show that ZnO nanoparticles can significantly enhance the catalytic activity of the immobilization enzyme, and the electrode has a very good response to the concentration of glucose solution. The linear range for glucose determination is from 1′10-5 to 3′10-3 mol/L, with a high sensitivity [6 mA/(cm2×mmol/L)] and the apparent Michaelis-Menten constant of 2.57 mmol/L. In addition, the effects of pH value and temperature of glucose solution on the amperometric response of the electrode are also investigated.

Effects of External Addition of Fe2+ and Inoculum on Bioleaching of Marmatite Flotation Concentrate

ZHANG Guang-ji;YUAN Qiu-hong;FANG Zhao-heng;YANG Chao

. 2007, 7(3): 536-540.

Asbtract ( )

PDF (309KB) ( )

Related Articles | Metrics

Bioleaching of marmatite flotation concentrate by Acidithiobacillus ferrooxidans was carried out in a swing bed under 35℃. The effects of external addition of Fe2+ and the inoculum of the bacteria were studied, and a dissolved mechanism of the marmatite was proposed. The results showed that the improvement of Eh was very slow in the slurry absent of Fe2+, even though 40 mL inoculum was used. This suggests that the bacteria can hardly bioleach the mineral if there are not enough ferric ions in the slurry. With the addition of FeSO4×7H2O, the improvement of Eh was obvious and the leaching rate was enhanced with the improvement of the inoculum. These results indicated that the supplementary addition of ferrous iron as a source of ferric ion to be generated by the bacteria was necessary in the bioleaching of marmatite. The evolution of Eh and the concentration of total iron in the bioleaching indicated that Eh was more important than the concentration of Fe3+ in the dissolution of marmatite. On the other hand, it was found that the bioleaching of marmatite was a process with consumption of H+, as a result, the pH value of leaching solution increased continually.

Dispersion Behavior of TiO2 Nanoparticles in Refrigerant

BI Sheng-shan;SHI Lin;WANG Lei

. 2007, 7(3): 541-545.

Asbtract ( )

PDF (251KB) ( )

Related Articles | Metrics

TiO2 nanoparticles are easy to aggregate during the preparation and use because of their strong surface effects. It is a key problem for the application of TiO2 nanoparticles in refrigerating system. The stability of TiO2 nanoparticles in refrigerants was systemically investigated with sedimentation, light transmission ratio index measurement and means of particle size distribution measurement in this work. It has been revealed that the stability of TiO2 nanoparticles in refrigerant is better, and the polarity and dielectric constant of refrigerant are the main factors. Surfactant Span-80 might act as a dispersant in refrigerant. The effect of temperature on the stability was significant. The results will provide the basic data for the application of TiO2 nanoparticles in refrigerator.

Influential Factors in Preparation of Aluminum Silicate Nanoparticles

LI Liao-sha;LI Hong-hua;WANG Mei;ZHU Jing;DONG Yuan-chi

. 2007, 7(3): 546-550.

Asbtract ( )

PDF (429KB) ( )

Related Articles | Metrics

Aluminum silicate nanoparticles were prepared from aluminum-bearing waste liquids by controlling reaction conditions with addition of the surfactants as modifiers. The properties of the product were studied with chemical analysis, SEM, specific surface area measurement, spectrophotometric method, etc. The result showed that addition mode is a key influential factor for the performances of the product. When the waste liquid was added to the water glass, and the aging pH value of the solution was adjusted to 4.5, the product could reach up to the current enterprise standard of China, and the size distribution of particles became homogenous. Aggregation of the particles was effectively prohibited by adding polyethylene glycol and Tween-80 through steric stabilization function. But Tween-80 was more effective, and the suitable adding amount was around 0.9% (in mass percentage of the dry sample finally). The mean diameter of the products was about 40~50 nm, and the specific surface area was about 330 m2/g.

Preparation Conditions of Amorphous Ni(OH)2 Electrode Material

SHANG Wei;LIU Chang-jiu;WANG Hui-jing

. 2007, 7(3): 551-555.

Asbtract ( )

PDF (260KB) ( )

Related Articles | Metrics

Amorphous nickel hydroxide powder was prepared by the method of micro-emulsion deepfreezing deposition. By orthogonal tests of experimental conditions, the effects of pH, reaction temperature and time on the electrochemical activity of the amorphous Ni(OH)2 were examined. It was found that the main influential factor was pH value of solution, secondly reaction temperature and time. Amorphous nickel hydroxide powder was prepared in a TX-100/butanol/cyclohexane/water system under the optimal conditions of the volume ratio of TX-100 to butanol 1:15, mass ratio of water to surfactant 15.1 or so, pH of 12, reaction time 2 h at 50~60℃, the precipitate was then rapidly frozen at 0~5℃. Discharge specific capacity of the amorphous nickel hydroxide powder as electrode active material could reach as high as 333.22 mA×h/g. In addition, the mechanism of the method of micro-emulsion deepfreezing deposition was also discussed.

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.

Asbtract ( )

PDF (332KB) ( )

Related Articles | Metrics

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℃.

One-step Preparation Process of Magnesium Hydroxide Flame Retardant from Magnesium Sulfate

HU Zhang-wen;WANG Li-xiang;YANG Bao-jun;SHAN Cheng-xiang

. 2007, 7(3): 561-565.

Asbtract ( )

PDF (366KB) ( )

Related Articles | Metrics

The one-step process for preparing magnesium hydroxide flame retardant with the material of purified magnesium sulfate. The results of the single factor experiments show that the optimal technological conditions should be as follows: the addition of composite surface-active agent is [preparation 5 g Mg(OH)2] 5~10 mL, reaction treatment time 3.0~4.0 h, and aging time more than 4.0 h. The measurement results of XRD indicate that the diffraction intensity of (101) direction is higher than (001) direction, a strain in (101) direction is less than 3′10-3 and the specific surface area (BET) is not more than 20 m2/g. The shape of particles is acicular with a diameter of 25~50 nm, the ratio of length-to-diameter is 8~10, and their dispersive is good. The product quality has reached to the standard of magnesium hydroxide flame retardant. In a word, with mild technological conditions and lower equipment cost, the one-step preparation process is simple and reasonable.

Application of Multi-stream Heat Exchanger Network Synthesis Approach in Crude Oil Pre-heating System of Atmospheric and Vacuum Distillation

WEI Guan-feng;QIAN Yu;YAO Ping-jing

. 2007, 7(3): 566-573.

Asbtract ( )

PDF (329KB) ( )

Related Articles | Metrics

In this work multi-stream heat exchanger network (MSHEN) synthesis approach is applied to the crude oil pre-heating network reformation of atmospheric and vacuum distillation unit of a petrochemical company. Based on stage-wised superstructure of MSHEN, a more general and rigorous mathematical model eliminating the unreasonable hypothesis of isothermal mixing of stream splits by previous literatures is set up for MSHEN synthesis problem. A novel approach is put forward to convert the mathematical model formulated as a mixed integer nonlinear programming program (MINLP) to a nonlinear programming problem (NLP) through appropriately designing a valid solution generation method for MSHEN. The approach brings forth the advantage of shunning difficulty to solve the original MINLP problem. A genetic/simulated annealing hybrid algorithm is adopted to successively solve this problem. The comparison of the synthesis results obtained by the present mathematical model and optimization algorithm with those of commercial software HEXTRAN and the existing heat exchangers network indicates that the methodology proposed in this paper is quite effective, and MSHEN can be superior in industrial engineering as to economy and technical advantages.

Cloning and Effective Constitutive Expression of aspC Gene in Escherichia coli

GONG Chang-bin;XU Xian;HE Bing-fang;Bing-fang

. 2007, 7(3): 574-578.

Asbtract ( )

PDF (332KB) ( )

Related Articles | Metrics

L-phenylalanine (L-Phe) can be prepared from phenylpyruvate (PPA) via an amination reaction mediated by aspartate aminotransferase (encoded by aspC) as the key enzyme. In this study, the aspC gene was cloned into plasmid pUC18, pSE 380 and pET-22b to construct three kinds of constitutive vectors, which were then transferred into 6 strains of Escherichia coli, respectively, to over-produce aminotransferase. From the transformants, the E. coli strain BL21(DE3) harboring plasmid pET/P-aspC showing the highest activity was scored and designated BL21(pET/P-aspC). With L-Asp and PPA (20 g/L) as substrates, the conversion rate reached 80.1% after eight-hour reaction, approaching the theoretical yield. This system had good industrial prospects because no inducer or coenzyme was needed. Furthermore, the results showed the potential of gene engineering on strain selections.

Pretreatment of Chicken Egg White by Ultrasonic Wave Homogenization and Glucose Oxidase Desugarization

WANG Wen-jing;ZHOU Bei-hai;LI Wei-wei;CHEN Xiang-rong;MA Guang-hui;WANG Yin-hua

. 2007, 7(3): 579-583.

Asbtract ( )

PDF (205KB) ( )

Related Articles | Metrics

The effects of ultrasonic wave treatment and glucose oxidase (GOD) desugarization on the viscosity of chicken egg white (CEW), and the concentration and activity of lysozyme in the CEW were studied. The results showed that the viscosity of CEW could be lowered effectively by ultrasonic treatment and GOD desugarization, leading to the formation of uniform solution with low viscosity. However, the concentration and activity of lysozyme decreased with increasing ultrasonic power and the time of ultrasonic treatment. When GOD desugarrization was adopted, the activity of lysozyme decreased with increasing the addition of GOD, while the concentration of lysozyme increased with increasing GOD up to 30 mL/L and then decreased with further increase in GOD. The combination of ultrasonic treatment with GOD desugarization could further lower the viscosity of CEW, reaching 4.0 mPa×s, while the concentration and activity of lysozyme were declined by 19.48% and 19.13%, respectively.

Isolation and Cultivation of Acidithiobacillus ferrooxidans and Its Effects on Bioleaching of Phosphate Ore

GONG Wen-qi;CHEN Wei;ZHANG Xiao-zheng;BIAN-Xun;LIU Yan-ju;LIU Jun;HUANG Yong-bing;YANG Hong-gang

. 2007, 7(3): 584-588.

Asbtract ( )

PDF (312KB) ( )

Related Articles | Metrics

A strain of Acidithiobacillus ferrooxidans that can be used effectively in the leaching of low grade phosphate ore was isolated from acid mine drainage from a coal mine in Anhui Province in China. Its characteristics of morphology and growth were studied. Through the investigation of the effects of different solid culture medium components on the isolation and purification of Acidthiobacillus ferrooxidans, the optimum isolation conditions were determined as: the concentration of Fe2+ in 9K solid culture medium was 4.5 g/L. A double-layer plate, with heterotrophic microbe Rhodotorula sp. spreading onto the bottom layer and chemoautotrophic bacterium At. f spreading onto the upper layer, was used. The influential factors including culture media, energy source materials and the addition of surfactant on the leaching of phosphate ore with the cultivated At. f were studied. Through preliminary experiments, up to 48% of phosphate in the ore was leached out using the isolated At. f strain.

Catalytic Efficiency of Vanadyl Compound in a Microbial Fuel Cell Constructed with Rhodoferax ferrireducens

LI Shao-hua;DU Zhu-wei;ZHU Xue-yuan;LIU Wei;FU De-xian;LI Hao-ran

. 2007, 7(3): 589-593.

Asbtract ( )

PDF (593KB) ( )

Related Articles | Metrics

A rechargeable microbial fuel cell (MFC) was constructed with Rhodoferax ferrireducens, and catalytic efficiency of anodic catalyst NaVO3 and cathodic catalyst K3[VO(O2)2(OOC-COO)] (KVC) were studied in the present work. The highest current output of the MFC was 0.581 mA, which was 0.272 mA higher than that of the control experiment, with the anodic catalysis with NaVO3 at the concentration of 4 mmol/L and the external resistance of 510 W. KVC catalyst in the cathodic compartment also improved the performance of the MFC. The highest current of 0.949 mA could be achieved at the KVC concentration of 25 mmol/L. The current of the MFC was further enhanced to 1.06 mA whilst the NaVO3 and KVC catalysts were added to the anodic and cathodic compartments, respectively.

Construction of a Single-chamber Direct Microbial Fuel Cell and Preparation of Cathode Electrode

ZHU Xue-yuan;FENG Ya-li;LI Shao-hua;LI Hao-ran;DU Zhu-wei;LUO Xiao-bing

. 2007, 7(3): 594-597.

Asbtract ( )

PDF (416KB) ( )

Related Articles | Metrics

A new type of single-chamber direct microbial fuel cell was constructed successfully on the basis of studying the cathode electrode containing Fe3+. The electricity generation mechanism of the single-chamber microbial fuel cell and the effect of different Fe3+contents on cell voltage in the cathode electrode were studied through experiments. By analyzing the cell voltage measured by the acquisition system, it is proved that the single-chamber direct microbial fuel cell is feasible, microbial electricity generation is mainly attributed to the electrochemically and biologically active cells attached to the electrode. The use of an Fe3+-graphite cathode enhanced the oxidation-reduction efficiency. Electron transfer driving force was generated in coupling of Fe3+ reduction to Fe2+ on the cathode. The Fe2+ cations were subsequently oxidized by O2 in air. For this Fe3+ circular effect, the electron transfer and oxidation-reduction efficiency were enhanced. The power density of the single direct microbial fuel cell was up to 14.58 mW/m2.

Preparation and Properties of Epichlorohydrin-Dimethylamine Cationic Polymer/Bentonite Nano-composite

LI Qian;YUE Qin-yan;GAO Bao-yu

. 2007, 7(3): 598-603.

Asbtract ( )

PDF (315KB) ( )

Related Articles | Metrics

A new cationic polymer epichlorohydrin-dimethylamine (EPI-DMA) as intercalary reagent is used to prepare a series of cationic polymer/bentonite composites. The influences of the quantity of cationic polymer, reaction time, temperature and pH value on the formation of cationic polymer/bentonite are investigated. The optimum conditions for synthesis of the polymer/bentonite are also obtained, which are 7.0% initial polymer concentration, 2 h reaction time, 75℃ reaction temperature and system pH 7.0. This composite structure is characterized by specific surface area, z electric potential, XRD and TEM. The results indicate that the specific surface area of EPI-DMA/bentonite is increased, the bentonite surface charge is changed to positive, both the layer space and particle aggregation degree of the polymer/bentonite are enhanced. The decolorizing property of the cationic polymer/bentonite for orchil wastewater is also examined, indicating its excellent ability for dyeing water treatment.

Liquidus Temperature, Density and Electrical Conductivity of Electrolyte for Aluminum Electrolysis

KAN Hong-min;BAN Yun-gang;QIU Zhu-xian;WANG Zhao-wen

. 2007, 7(3): 604-609.

Asbtract ( )

PDF (211KB) ( )

Related Articles | Metrics

Liquidus temperature, density and electrical conductivity of the Na3AlF6-AlF3-Al2O3-CaF2-LiF-NaCl electrolyte system for aluminum electrolysis were measured. The effects of AlF3, Al2O3, LiF and NaCl concentrations on liquidus temperature, density and electrical conductivity of the electrolyte were analyzed in theory. Empirical equations for the concentration and temperature dependence of these parameters were developed on the basis of experimental data. The reliability of these equations was compared with regression equations published in the literature. The results showed that the liquidus temperature was reduced and the electrical conductivity was increased greatly by adding NaCl and LiF into the electrolyte. These data are useful for industry production of aluminum electrolysis, since they can provide a scientific basis for selecting suitable aluminum electrolyte composition.

Preparation and Microwave Properties of Ni0.5Zn0.5Fe2O4 Nanocrystalline Powder Prepared by Polyacrylamide Gel Process

MA Rui-ting;SHAO Zhong-cai;ZHANG Chun-li;LI Hong;TIAN Yan-wen

. 2007, 7(3): 610-614.

Asbtract ( )

PDF (381KB) ( )

Related Articles | Metrics

Nanocrystalline Ni0.5Zn0.5Fe2O4 powder was prepared using polyacrylamide gel method with acrylamide as monomer and N,N'-methylenediacrylamide as lattice agent. The analysis methods of Fourier transform infrared spectrometer (FI-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and wave-guide were used to characterize the gel and the products after calcining. The XRD study shows that the dried gel is amorphous, the spinel Ni0.5Zn0.5Fe2O4 forms at and above 400℃. The grain size and the M?O metal and oxygen characteristic absorption bonds are dependant on heat treatment temperature. When the calcining temperatures are 600 and 800℃, the grain sizes are 10 and 30 nm identified by TEM, respectively. The FT-IR spectra illustrate that the M?O characteristic absorption bonds shift from 590 to 613 cm-1 when the calcining temperature is shifted from 400 to 800℃. The nanocrystalline Ni0.5Zn0.5Fe2O4 has both dielectric loss and magnetic loss, while the complex permittivity and complex permeability of Ni0.5Zn0.5Fe2O4 increase with increasing the heat treatment temperature in the frequency range of measurement.

Penetration of Sodium and Electrolyte into Vibratory Compaction TiB2 Cathode

BAN Yun-gang;KAN Hong-min;REN Bi-jun;SHI Zhong-ning;WANG Zhao-wen

. 2007, 7(3): 615-619.

Asbtract ( )

PDF (473KB) ( )

Related Articles | Metrics

The penetration of sodium and electrolyte into the vibratory compaction TiB2 material and graphite material used as cathode of aluminum electrolysis was studied in this work. After 5 h electrolysis, the XRD analysis showed that NaF and Na3AlF6 existed in the graphite cathode, but NaF and Na3AlF6 were not found in the graphite of vibratory compaction TiB2 cathode. The SEM analysis showed that Na, F and Al penetrated slightly into the vibratory compaction TiB2 cathode, much less than that penetrated into the graphite cathode. Vibratory compaction TiB2 cathode can decrease sodium penetration effectively, but can not hinder sodium penetration thoroughly.

Preparation of Carbon Molecular Sieve Membrane

WEI Wei;HU Hao-quan;QIN Guo-tong;YOU Long-bo

. 2007, 7(3): 620-623.

Asbtract ( )

PDF (221KB) ( )

Related Articles | Metrics

The carbon molecule sieve membrane was prepared with coating solution of novolac phenol formaldehyde (PF) resin containing hexamine on the outer of green support from the same material. The top layer and green support were carbonized at one time. In this way, the cracks and pinholes of top layer can be eliminated effectively. The ideal selectivity of H2/CH4 and H2/N2 were 171 and 74 respectively. The obtained carbon membrane has smooth surface without pinholes judged by a scanning electron microscope. The coating solution, properties of support and soaking time have obvious effects on the properties of membrane. Molecular sieving appears to contribute to the gas permeation.

Preparation and Characterization of Superhydrophobic PTFE-PPS Composite Coating

WANG Hao;WANG Chang-song;CHEN Ying;FENG Xin;LU Xiao-hua

. 2007, 7(3): 624-627.

Asbtract ( )

PDF (577KB) ( )

Related Articles | Metrics

The superhydrophobic polytetrafluoroethylene-polyphenylene sulfide (PTFE-PPS) composite coating was prepared by spraying coating on the aluminum substrate. Scanning electron microscopy (SEM) investigation indicated that the composite coating had the similar surface structure to that of lotus leaf. The water contact angle on the coating surface was 155o and the sliding angle was 7o. Compared with the pure superhydrophobic PTFE coating on the aluminum substrate, the conglutination force of the composite coating was improved from grade 5 to grade 1, the pencil rigidity was increased from 4B to 4H, and the flexility of the composite coating was improved from (10±0.1) mm to (1±0.1) mm. The composite coating was sufficient to the requirements of industrial application.

Bending Properties of Novel Aluminum Foam Sandwich Panels

ZHANG Min;ZU Guo-yin;YAO Guang-chun

. 2007, 7(3): 628-631.

Asbtract ( )

PDF (443KB) ( )

Related Articles | Metrics

A sandwich rolling processing technique was proposed for preparation of aluminum alloy foam sandwich with a metallurgical bonding interface. The practical bonding property of the interface and the bending resistance were demonstrated using three-point bending tests carried out with the prepared aluminum alloy foam sandwich panel. By analyzing the load-deflection curve, deformation behavior of two kinds of porosity sandwich panels was discussed. The deformation behavior was obviously different between two kinds of porosity sandwich panels. Both bending strength and bending elastic modulus of low porosity (58.81%) sandwich panel were larger than those of high porosity (76.21%) one. Both fracture energy and fracture deflection of high porosity sandwich panel were higher than those of low porosity one. The experimental results can be technological guidance to the practical design of the foam aluminum sandwich in the industry.

Advances in Technologies for NOx Inhibiting and Removing during the Process of Coal Combustion

CHEN Yan-guang;WANG Zhi;GUO Zhan-cheng

. 2007, 7(3): 632-638.

Asbtract ( )

PDF (316KB) ( )

Related Articles | Metrics

According to the production mechanism and characteristic of NOx, the technologies of NOx inhibiting and removing in the process of coal combustion were classified into three kinds: nitrogen-free combustion, low NOx combustion and de-nitrification of flue gas. The present situation and characteristics of these ordinary de-nitrification technologies were reviewed and analyzed in this paper, and some new de-nitrification technologies developed in recent years were also described. The costs of operation in the technology of de-nitrification of flue gas and nitrogen-free combustion were higher, and the de-nitrification rate of the current low NOx combustion was lower. Thus new technologies of NOx inhibiting in the combustion should be developed to adapt to the current situation in China. A new method of controlling NOx generation in the process of sintering was proposed, which is based on the principle of coupling and decoupling combustion of coal by minimizing and controlling NOx contamination from its very beginning of generation.

Table of Content