Table of Content

20 October 2013, Volume 13 Issue 5

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流动与传递

Optimal Selection of Numerical Simulation Methods for Flow Field in Cyclone Separator

CHEN Jian-lei HE Li-min LUO Xiao-ming WEI Yan-hai

. 2013, 13(5):  721-727. 

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In response to the study of cyclone separator with more and more complicated structural design, the computational fluid dynamics methods consisting of turbulence models, meshing schemes, governing equation discretization schemes and computation steps were analyzed. Comparison with experiments shows that Reynolds stress model can characterize Rankin vortex in tangential velocity field more suitably than RNG k-e model; The achieved prediction on unstructured hexahedron grids is more accurate; Simulation accuracy of the second order upwind is not worse than QUICK. In the case of complicated separator structure design and mesh generation, the second order upwind scheme is recommend. Under the condition of unsteady PISO algorithm, the residual error precision can reach over 10-6. The optimized numerical simulation methods can be used to analyze flow field in cyclone separator and conduct engineering design.

Simulation on Mixing Effect of Molten Steel in a 100 t LF Refining Furnace with Bottom-blown Argon

SUN Sai-yang SUN Yan-hui ZHAO Yong SUN Hua WU Jian-yong ZHU Shou-xin

. 2013, 13(5):  728-734. 

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On the basis of the similarity theory, a physical simulation system for 100 t cylinder ladle furnace (LF) of Nanjing Iron and Steel Company was established. Through changing the process parameters, the stirring effect of argon blowing from different positions in different flow rates was examined, the optimal bottom blowing positions and blowing rate were determined, and the numerical simulation was used to verify the optimized scheme. The results showed that the effects of prototypical single blowing and double plugs blowing are both relatively ideal, and two-hole (at the position of 0.57R with the angle of 84o) blowing effect is relatively better, and the optimal blowing rate is 350 L/min. After the implementation of the program, the desulfurization rate of LF was increased by 18.75%, and its working life was increased by 29.4%.

Evolution of Drop Formation Form in Another Liquid during Dispersive Liquid Atomization

LIANG Kun-feng WANG Lin RUO Chun-lei XU Bin

. 2013, 13(5):  735-741. 

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The evolution process of drop formation in another immiscible oil during dispersive liquid atomization is experimentally studied by image gathering and processing. The results show that there exist three typical dispersive liquid break-up forms related to drop formation, dripping, laminar jet and turbulent motion jet, with three different mechanisms. The variation of liquid-liquid atomization forms, jet break-up intensity, jet length fluctuation and drop size distribution with liquid Reynolds number (Re) and Weber number (We) show that jet break-up intensity is strengthened continually with increasing of Re and We, dispersive liquid break-up form is transformed from the dripping to laminar jet at Re=467 and We=8.6, and becomes finally the turbulent motion jet at Re=3169 and We=241, and the best spreading parameters of drop size distribution, the uniformity and least mean value of drops size, always appear in turbulent jetting form. Under the dripping form, emerging, developing and breaking away of liquid drops from the tip of nozzle are dominated by balanced-force mechanism. And under the laminar jetting form, the mechanism of dispersive liquid break-up is caused by interphase surface wave motion, and jet length fluctuation is characterized by random and no periodic ways. However, under the turbulent jetting form, coherent structure appears and acts on jet instability at the initial section of the jet, and a large number of finer drops form in the diffusion section.

Experimental Study on the Characteristics of Particles Dispersion and Adjusting for Concentrated Burner

AI Yuan-fang SUN Yan-wen TANG Cai-shuo CHEN Hong-rong LIU An-ming

. 2013, 13(5):  742-747. 

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A cold experimental model of concentrated burner with geometric similarity of 1:5 was built, the distribution uniformity of particles with varied dispersed cone, loading rate, process air and distribution air in a flash furnace were studied with the cold experimental methods of substituting sand for concentration, receiving and weighing particles, and the distribution nephograms of particles were drawn up with software Matlab. The results showed that the distribution uniformity of particles in the reaction tower could be adjusted. The dispersed cone and the loading rate had a small effect on the distribution uniformity of particles. The particles were concentrated on the central zone of tower, and the mass segregation function px of particles describing the distribution uniformity of particles inside the tower increased, when the loading rate increased, the flow rate of process air (Qpro) increased, or the flow rate of distribution air (Qdis) decreased. Qdis and Qpro could be expressed with the function of px within the experimental scope by the fitting relation of px=(-0.00025+0.3176/Qdis)Qpro-1.51, which accorded with operating parameters from references and smelting site.

Injection Characteristics of Coal Powder by a New Type Swirling Oxygen-Coal Lance

ZHANG Zong-wang QIN Xue-gang

. 2013, 13(5):  748-753. 

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Injection characteristics of coal powder by a new type swirling oxygen-coal lance were studied in comparison with an ordinary single-tube one, and. the flow field, concentration field and pulverized coal combustion in the blowpipe examined. The results showed that the new lance generated a greater low velocity zone in the blowpipe, within 30 mm away from the outlet of the lance a clear recirculation zone formed, and within 200 mm away from that an oxygen enrichment zone with high pulverized coal concentration and strong turbulence formed. When the new swirling oxygen-coal lance was used, coal powder temperature was raised near 100 K, being beneficial to volatilization of volatiles in the coal, and its burnout rate was increased from 4.96% to 15.53%.

Numerical Simulation on Optimization of the Inlet Aspect Ratio in a Gas-Liquid Cyclone Separator

ZHOU Yun-long MI Lie-dong

. 2013, 13(5):  754-759. 

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The effects of inlet dimensions of a gas-liquid cyclone on its performance and flow field were investigated using the RSM and DPM models. The results show that the maximum tangential velocity in the cyclone increases with decreasing of the inlet dimensions, but the pressure drop is lowered. When the inlet width is wider than the gap between the cyclone barrel and vortex finder wall, part of the incoming flow will impact the vortex finder and affect the flow field. When the inlet width or height decreases, the pressure drop has no significant change. When the width is reduced, the separation efficiency of cyclone can be improved, but the height is the opposite. When the ratios of inlet height and width to cyclone diameter, a/D and b/D, are 0.2

Simulation on Large Eddy Turbulent Flow in a Circular-sectioned 90o Bend

GONG Bin LIU Xi-xing YANG Shuai ZHANG Jing DONG Xin

. 2013, 13(5):  760-765. 

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The flow field in a circular-sectioned 90o bending tube is numerically simulated by using four models with water as medium, and compared with the experimental values. The results show that the time average velocity and pressure drop of the large eddy simulation (LES) model in the curved section are consistent with experimental values when the Reynolds number (Re) ranges from 13000~60000. Using the LES model, the flow field characteristics on the cross section with different angles are analyzed in the curved section when Re=60000, two primary eddies in the secondary flow on the cross section are found, their positions change from the symmetric half section to the inside of bending tube, while horseshoe vortex is induced comprehensively by the bending tube wall and secondary flow in the tube. The distribution characteristics of static pressure in the curved section show that the pressure difference value of both bending tube inside and outside reaches the maximum on the 45o cross section. This angle is the critical angle when fluid flow separation occurs.

Axial Distribution of Solids Holdup of Burned Oil Sand Particles in the Riser of a Fluidized Bed

CAO Xin LU Chun-xi LIU Meng-xi LU Yuan-bao WANG Zhu-an

. 2013, 13(5):  766-770. 

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A large scale cold model apparatus of CFB riser reactor was established based on the method of directly fluidized coking oil sand. The measurement results of particle size indicate that the burned oil sand particles have wide size distribution (1~>2000 mm) with numerous fine particles. The axial distributions of pressure gradient and averaged cross-sectional solids holdup in the riser were measured by a multi-point pressure-fluctuation device. The results show that the latter increases with the increase of solid overall circulating flux and decreases with the increase of superficial gas velocity. The axial distribution of solids holdup in the riser is characterized by C type distribution with larger solid holdup values in the top and bottom sections, and smaller value in the middle section. The riser can be divided into three zones along the longitude based on the movement pattern of axial particles, i.e., accelerating zone (<4 m), full developing zone (4~12 m) and back-mixing zone (>12 m). Under the same operation conditions, the solids holdup of sand particles is much higher than that of FCC particles, the lengths of accelerating and back-mixing zones are both longer than that of FCC. Furthermore, an empirical model for estimating the axial distribution of averaged cross-sectional solids holdup was established based on the experimental data and theoretical analysis, respectively, which agreed with the experimental data.

Optimization of Structural Parameters for the Pleated Filter Element of Cartridge Filters by Response Surface Methodology Based on the Resistance

ZHA Wen-juan QIAN Fu-ping LU Jin-li HAN Yun-long

. 2013, 13(5):  771-775. 

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A two-dimensional numerical model of pleated filter element on resistance was established by CFD method, and its gas flow field simulated. The simulated values and values in reference in the resistance were compared. On the basis of this numerical model, the effects of pleat height (h), pleat spacing (W), and filtration velocity (Vf) of the filter element on the resistance of V-pleated filter element were studied by response surface method, the quadratic polynomial prediction model on the three impact factors was also developed, and the structural parameters and operating condition were optimized. The results show that the simulated values of the resistance are basically the same as those in reference. h, W and Vf have effect on the resistance, but the effect of Vf is obviously more significant than that of W, and the effect of W more significant than that of h. The relationship between the resistance and Vf is approximately linear, and the resistance increases with the increase of Vf, the optimal values of W which minimize the resistance can be obtained when Vf is a given value, and the optimal value of W increases with the increase of h. Within the ranges of parameters in this study, the optimal values of structural parameters are h=25 mm, and W=10.899 mm, respectively, and the optimal value of operating condition is Vf=0.005 m/s.

Coalescence of Taylor Bubbles in Cryogenic Two-phase Flow

DAI Xin-yi LIU Yi-peng BAO Yi-ying WANG Jing WANG Ping-yang

. 2013, 13(5):  776-780. 

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The coalescence process of Taylor bubbles in cryogenic slug flow was obtained by high speed camera in 16 mm inner diameter tube at the inclination angle from 30o to 90o. The results show that the existing equations of Taylor bubble coalescence for normal atmospheric temperature liquid have large discrepancy with the present experimental results. The maximum error is larger than 14.6%. Thus the new equations for Taylor bubble coalescence in cryogenic two-phase flow have been established, and the maximum error is reduced to 4.7%. The present study provides reference for installation of cryogenic tube.

反应与分离

Leaching Performance of High Iron Gibbsite-type Bauxite in Sodium Aluminate Solution

GAO Yun-nan ZHANG Ying ZHENG Shi-li LI Meng WANG Xiao-hui GUO Fen WANG Shao-na

. 2013, 13(5):  781-787. 

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Based on the mineralogical characteristics of high iron gibbsite-type bauxite ore from Guangxi, its leaching performance in sodium aluminate solution without addition of calcium-bearing compound was studied, and the effects of caustic concentration, reaction temperature and reaction time on Al2O3 leaching rate were examined. The results showed that 70% of aluminum in the ore mainly existed in the form of gibbsite, being conjoint with hematite. The optimum leaching conditions of gibbsite were obtained as follows: Na2O concentration in sodium aluminate solution 150 g/L, molar ratio 3.0, temperature 100℃ and time 15 min. Under the conditions, the leaching rate of Al2O3 reached 72%. The leaching kinetic results of bauxite under the conditions of low temperature and low alkali concentration showed that the leaching process was controlled by internal diffusion, and the calculated apparent activation energy was 61.78 kJ/mol. The inconsistency between the control mode and the apparent activation energy value might be due to the diffusion mode.

Flowability and Desulfurization of High Alumina Blast Furnace Slag

WANG Ping LIU Xiang MENG Qing-min LI Jia-xin GUO Ze-hua

. 2013, 13(5):  788-794. 

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KTH viscosity model was applied to predict the viscosity of blast furnace slag with high content of alumina, and the viscosity measured by a viscosity meter. The relationship between flowability and chemical composition of the slag and temperature of molten iron was studied. Multiple linear regression analysis was conducted to demonstrate the effects of compositions of slag and molten iron on the desulfurization ability of slag. The results showed that a high proportion of Al2O3 in the slag reduced the flowability of slag. The content of Al2O3 should be controlled below 18.5%(w), or at least below 19.5%(w). A moderate content of MgO improved the flowability of slag. The mass ratio of (CaO+MgO) to (SiO2+Al2O3) in the slag should be controlled at above 0.92, while the mass ratio of CaO to SiO2 should be lower than 1.2. The mass ratio of MgO to Al2O3 should be higher than 0.48, while the MgO content was favorably less than 12.5%(w) in the slag. The temperature of molten iron and mass ratio of CaO to SiO2 in the slag were the main influential factors on the desulphurization ability of slag, by contrast, MgO content and other factors had little effect on it.

Separation of Iron Oxide and Sodium-Silicon Residue in Fe-rich Red Mud

WANG Yue-jiao DING Jian MA Shu-hua ZHENG Shi-li WANG Shao-na

. 2013, 13(5):  795-800. 

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Fe-rich red mud was treated by wet method using alkaline medium, dealkalization process of the red mud and enrichment process of Fe2O3 were carried out simultaneously. The effects of reaction temperature, reaction time, initial concentration of sodium oxide, initial caustic ratio and ratio of liquid to solid on the final slag composition and phase were investigated. The optimal conditions were obtained as follows: reaction temperature 250℃, reaction time 30 min, initial concentration of sodium oxide 530 g/L, initial caustic ratio 15 and ratio of liquid to solid 6 mL/g. Under the optimal conditions, Fe2O3 content in the final slag was increased to 46.27% from 33.56%, Na2O content decreased to 0.87% from 4.99%. The main phases in the red mud were converted from sodalite and andradite to a single phase of andradite.

Effect of Sulfur Content on Evaporation Crystallization Precipitation of Salts in Sodium Aluminate Seeded Precipitation Mother Solution

JIA Yong-zhen WAMG Jia-wei LI Jun-qi LV Chang-sheng

. 2013, 13(5):  801-806. 

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The effect of sulfur on evaporation salt discharge in NaAl(OH)4 seeded precipitation mother solution of high sulfur bauxite in Bayer process was studied. The results showed that Na2CO3×H2O and NaAlO2×1.25H2O mainly existed in the discharged salt slag after deep evaporation of NaAl(OH)4 solution. Sodium carbonate was precipitated effectively without too much NaAlO2 when the elemental sulfur concentration was 300~310 g/L. In the evaporation process the sulfur content had a great influence on the precipitation of Na2CO3, sulfosalt and NaAlO2. Their precipitation rates increased with increasing of sulfur content, and the salt discharge rates were all above 60%. The effect of sodium sulfate was the largest, and the salt discharge rate reached 91.33% at the elemental sulfur concentration of 6 g/L. And sodium sulfite followed. The effect of sodium sulphide on the precipitation rate was the smallest, the salt discharge rate was only 68.49% at the elemental sulfur concentration of 6 g/L. Na2CO3×H2O, NaAlO2×1.25H2O, Na2CO3×Na2SO4 and other forms of double salts existed in the slag when the NaAl(OH)4 solution of elemental sulfur concentration 4.5 g/L was evaporated to the sodium hydroxide concentration of 310 g/L. There were some sulfocompounds in lower valence state oxidized in the evaporation. About 7% and 4% of sodium sulphide were oxidized to sodium thiosulfate and sodium sulfite, and about 7%~11% of sodium sulfite to sodium sulfate. So the salt discharge effect was influenced by the interaction of sodium carbonate and each valence state sulfocompounds.

Polymerization Behavior of Intermediates in the Preparation Process of Fine Chemicals with Metallurgical Solid Waste

SHEN Xing-mei LUO Tao AI Jin WU Xing-rong LV Hui-hong LI Liao-sha

. 2013, 13(5):  807-811. 

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Gelation time, polymerization rate of monosilicic acid, and growth of colloidal particles in the silicic acid systems with Mg2+ and Al3+ ions, which are intermediates in the preparation process of fine chemicals by metallurgical solid wastes, were investigated. The results showed that at pH<4, polymerization reaction in the systems was promoted by Mg2+ and Al3+. In the early stage, Al3+ obviously accelerated the polymerization reaction. Due to stronger ability to react with negative ions of silicic acid and OH-, the acceleration effect of Al3+ on polymerization reaction in the systems was stronger than that of Mg2+, and the effects of both Mg2+ and Al3+ were found in the range between that of Mg2+ and Al3+ ions existing itself alone. Growth of colloidal particles and silicon dioxide particles was also promoted by Mg2+ and Al3+, and Al3+ entered into the gel to replace Si forming tetrahedron. The obtained silicon dioxide particles were amorphous.

Effects of Flocculants on Sedimentation of High-mud Copper Oxide Leaching Pulp

GUO Yan-hua Dai Hui-xin YANG Jun-long

. 2013, 13(5):  812-816. 

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In order to solve the problems of high mud content, slow sedimentation and solid-liquid separation difficulty of copper oxide leaching pulp, flocculation sedimentation experiments of the pulp were carried out with the pulp concentration at 28.73%, and the effects of type of flocculants, dosage of flocculants, and concentration of flocculants on the sedimentation examined respectively. The results show that alum, sodium dodecyl sulfonate, polyacrylamide, modified anionic polyacrylamide and modified cationic polyacrylamide cannot effectively improve the sedimentation speed. But the modified nonionic polyacrylamide can make the slurry sedimentation speed greatly accelerate, which is due to the adsorption bridging between the functional groups on the molecular chain of modified nonionic polyacrylamide and colloidal particles in the leaching liquid, leading to the particles size increasing gradually in flocculating sedimentation. Modified nonionic polyacrylamide has larger molecular weight, and fluid mechanics size or volume in water, so as to improving its ability for the flocculation, reducing the use of flocculant concentration effectively, and improving the flocculation efficiency. When the concentration of modified nonionic polyacrylamide is 0.1% and the dosage 0.067 g/L, the best sedimentation effect can be achieved.

Preparation of Silicon-doped Carbonate Hydroxylapatite and Its Adsorption Properties to Manganese Ion

ZENG Rong-ying TANG Wen-qing ZHANG Fu-xing GONG Dao-xin

. 2013, 13(5):  817-820. 

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Silicon-substituted carbonate hydroxylapatite (Si-CHAP) was successfully synthesized by hydrothermal method with abandoned eggshell as raw material, and characterized by FT-IR. Its adsorption equilibrium, kinetics and thermodynamics to Mn2+ were investigated under different temperatures. The results showed that the adsorption equilibrium well fitted to Langmuir equation, the maximum adsorption amount for Mn2+ onto Si-CHAP was 38.91 at 20, 41.49 at 30 and 43.10 mg/g at 40℃. The adsorption kinetics accorded with the pseudo second order kinetic equation with high correlation coefficient (R2>0.99). The thermodynamic parameters indicated that the adsorption was a spontaneous and endothermic process.

Adsorption Characteristics of Phenol on Carbonized Sesame Stalks

TANG Wen-qing ZENG Rong-ying FENG Yong-lan ZHANG Fu-xing

. 2013, 13(5):  821-824. 

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Carbonized sesame stalks prepared from sesame stalks using monopotassium phosphate as an activator at 300 and 600℃ were utilized as adsorbents (CSS1 and CSS2) to remove phenol from aqueous solution, and the effects of pH value, adsorption time, and temperature on the adsorption of phenol examined. The results showed that the CSS2 sample had greater adsorption efficiency than the CSS1. The Langmuir and Freundlich models were applied to describe the adsorption isotherms of the phenol on CSS. The Langmiur model fitted well the experimental data with the maximum adsorption capacity of 13.53, 18.42, and 21.32 mg/g on CSS2 at 20, 30 and 40℃. Their kinetic behaviors showed that the adsorption was fast, the adsorption reached equilibrium within 150 min, and the adsorption process followed a pseudo-second-order kinetic model. The calculated values of thermodynamic parameters DGq, DHq and DSq indicated that the adsorption process was spontaneous.

过程与工艺

Gasification Reactivity and Kinetic Model of High-ash Coal Char

HUI He-long WEI Yun-zhao LIU Shu-cheng LI Jun-wei LI Cheng

. 2013, 13(5):  825-830. 

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CO2 gasification experiments of Hexi coal char were carried out, and carbon crystalline structure of the coal char was analyzed. The results indicate that the graphitization degree of char samples is in the order of demineralized coal char (DC) > clean coal char (CC) > raw coal char (RC) > tailing coal char (TC) under the same coke making conditions, and the gasification activity of char samples in the order of TC > RC > CC correspondingly, showing that the existence of ash inhibits the char graphitization and enhances the gasification reactivity of coal char to some extent. High-ash coal char (ash≥48.47%) exhibits higher gasification reactivity in the initial stage, and the gasification reactivity index (Rs) of coal char is Rs(TC)=1.304Rs(RC)=2.421Rs(CC). In the later stage, the gasification reactivity of high-ash coal char decreases gradually with the increase of ash layer resistance. CO2 gasification reaction of high-ash coal char can be well described by 3-D diffusion model. However, the best kinetic model expressing the reactivity of low-ash coal char is shrinking core model with chemical reaction controlling.

Synthesis of Long-chain Diesters and Their Physicochemical Properties

GAO Yong-jian YU De-jiang HAN Wei ZHANG Guang-jin

. 2013, 13(5):  831-835. 

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A series of long-chain diester were synthesized by using dicarboxylic acid as raw material and polyoxometalates as catalyst, and the influential factors on the synthesis reaction were studied. It is found that under the conditions of 160℃, molar ratio of alcohol to acid 3:1, 1% catalyst content and 10% dehydrator content, the yield of esterification can reach over 98%. The synthesized diesters exhibit excellent physicochemical properties. Their freezing point can reach -74℃, flash point 258℃, and viscosity index 187, which is much better than commercial lubricant base oil and close to the standard of aviation lubricant base oil. The effect of chain length on the physicochemical properties of the esters was studied. It is found that with the increase of the chain length, their viscosity is increased significantly. And the chain length on the alcohol part plays a key role in the final viscosity of the diesters.

Kinetic Modeling and Analysis of Biomass Gasification in a Dual Fluidized Bed

ZHU Lin FAN Jun-ming ZHANG Zheng JIANG Peng

. 2013, 13(5):  836-840. 

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In order to further study the distribution of synthesis gas concentration in the biomass gasifier of a dual fluidized bed, the two-phase modeling was developed by dividing the bubbling fluidized bed into bubble and emulsion phases, and the mass and heat balance for the two-phases were accounted based on the kinetic rate equations. The simulated values agreed with the experimental data. The effects of ratio of steam to biomass (S/B) and gasification temperature on the composition of synthesis gas were studied. The results showed that the CO content increased with the increase of gasification temperature, and H2 and CO2 contents decreased. The water-gas shift and reforming reactions were promoted to their positive direction with the increase of S/B, leading to more consumption of CO and CH4, and generation of H2 and CO2. When S/B was 0~1.2, the ratio of CO to H2 changed 44%, which indicated that the water-gas shift was the main reaction with the increase of S/B. The profiles of syngas composition along the gasifier height were further analyzed at the gasification temperature 870℃ and S/B 0.75. When the gasifier height was less than 0.5 m, the H2O content decreased sharply, and the molar concentration of H2 increased steeply, and the CO and CO2 contents increased gradually. When the gasifier height was more than 0.5 m, the gasification reactions were inclined to equilibrium.

Effect of Oxygen-enriched Transportation on Combustibility of Pulverized Coal

WANG Ping GUO Ze-hua LI Jia-xin LONG Hong-ming LIU Xiang

. 2013, 13(5):  841-845. 

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Pyrolysis characteristics of two kinds of pulverized coal in air and oxygen, and the effects of oxygen content in transportation media on explosiveness and burning rate were studied. The results show that the pyrolysis characteristics of the pulverized coal in oxygen is better than that in air. When the oxygen content in transportation media is less than 51%(j), the explosiveness can be ignored. When it is higher than 61%(j), the explosiveness is enhanced. Oxygen content in transportation media is helpful to improve the burning rate of pulverized coal, and 1.97% of it is increased with the increase of 10% oxygen content. The burning rate of pulverized coal is reduced with the increase of mass ratio of pulverized coal to iron, and the rate is reduced 1.13% with the increase of 10 kg/t.

Influence of the Particle Size of Fujian Anthracite Coal on Its Burnout in CFB Boiler

ZHUANG Huang-huang HE Hong-zhou LI Zhi-wei ZOU Zheng

. 2013, 13(5):  846-850. 

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A simplified heat transfer and combustion model for the combustion of fine anthracite coal particles in a circulating fluidized bed (CFB) boiler was established. The burnout time and residence time (one time through furnace) of a single fine coal particle in the CFB boiler were calculated, and the effects of particle sizes of Fujian anthracite on both of time at different combustion temperatures and flue gas velocities examined. Besides, industrial combustion experiments of Fujian anthracite were conducted in a 35 t/h CFB boiler to test the effect of coal particle size on the carbon content of fly ash. It is shown that the particle size has a significant effect on the burnout of coal in the boiler. With rising of the coal particle size, both the burnout time and residence time increase, but the former increases more faster than the latter, the critical particle size of Fujian anthracite in burnout, which is burnt out once through the furnace, is about 0.15 mm. As the particles are coarser, their residence time is more sensitive to the flue gas velocity, while their burnout time to the combustion temperature. For those CFB boilers with small capacity for combustion of Fujian anthracite, in order to reduce the carbon content in fly ash, using the coarse coal particles with the sizes of 3~8 mm is suitable.

Synthesis of n-Butyl Acetate with Modified Resin Catalysts in a Slurry Bubble Column Reactor

YU Hai-shen

. 2013, 13(5):  851-854. 

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n-butyl acetate was synthesized with n-butanol and glacial acetic acid as raw materials in a slurry bubble column reactor by modified D001 cationic exchange resin catalyst. The technological advances of column reactor and characteristics of the catalyst were examined, and the effects of catalyst type, content, and used life time on the synthesis investigated. The results showed that under the optimized conditions of molar ratio of n-butanol to acetic acid 1.2:1, amount of catalyst 40% to that of the acetic acid, reaction temperature 110℃, and reaction time 75 min, the yield and purity of n-butyl acetate were 98% and 99.5%, respectively. By washing, activation and regeneration, the catalyst could be reused 6 times.

系统与集成

Multi-scale Simulation of the Reactive Characteristics in a Porous Packed Bed with Gas Solid Reactions

LI Ming-chun ZHAO Zhong-liang WU Yu-sheng QU Yan-ping

. 2013, 13(5):  855-861. 

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A mathematical model describing the coupled interaction of meso-level pore structure, micro gas-solid chemical reactions and macro transfer processes in a porous packed bed of pellets was established by applying pore network method. Taking the indirect reduction of iron ore as a case, the effects of pore structure pattern of the bed and structure variation of the pellets on the reaction characteristics and transfer in the bed were analyzed. The results show that the pore structure pattern of the bed has obvious effect on the gas concentration felid and the solid fractional conversion rate. For the normal distribution of pore structure, the average solid conversion rate on each cross section of the bed is the highest when the pore size decreases along the direction of gas flow. The maximum relative error between the average solid conversion rate calculated under the conditions of normal and uniform distributions is 29.5%. The actual normal distribution of commonly particulate materials screened narrowly could be approximate with uniform pore size distribution in the calculation. The maximum relative error of the solid conversion rate caused by the pore structure change of solid particles is demonstrated numerically to increase gradually with the reaction time, which reaches 14.6% at the solid conversion rate of 0.5.

生化工程专栏

Preparation of Triptorelin Acetate-loaded PLGA Microspheres by Premix Membrane Emulsification

WANG Ning WANG Yu-xia QIN Pei-yong WEI Yi MA Guang-hui

. 2013, 13(5):  862-869. 

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Triptorelin acetate loaded biodegradable poly(lactic-co-glycolic acid) (PLGA) uniform-sized microspheres were prepared by a method combining premix membrane emulsification and solvent evaporation with high concentration (160 g/L) gelatin as water phase and methylene chloride containing high concentration (500 g/L) PLGA as oil phase. It was possible for the drug completely entrapped by the PLGA microcapsules. The mean diameter of PLGA microspheres was about 30 mm, the encapsulation efficiency of triptorelin acetate 80.12%, and Span (coefficient of size distribution) value less than 0.8. Subsequently, the cumulative release rate of PLGA microspheres loading triptorelin in vitro for 36 d was 72.60%. Furthermore, the release profile of the drug in vitro was well for controlled release.

Preparation of mPEG-PLGA Porous Microspheres and Their Adsorption to Salcatonin

ZHANG Hui-xia WANG Yu-xia WEI Yi RUAN Yan-ye MA Guang-hui

. 2013, 13(5):  870-876. 

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Relatively uniform size porous methoxy poly(ethylene glycol-L-lactic-co-glycolic acid) (mPEG-PLGA) microspheres were successfully prepared by premix membrane emulsification with solvent evaporate method. The effects of salcatonin concentration, salt concentration, pH value, adsorption temperature and time, and properties of microspheres on the adsorption capacity of salcatonin were investigated. The results showed that the adsorption capacity of porous microspheres reached 48.9 mg/g under the conditions of 1.0 mg/mL salcatonin concentration, pH value 7.4 of phosphate buffer, 0.2 mol/L NaCl concentration, 14℃ adsorption temperature and 8 h adsorption time. In addition, the adsorption capacity increased with the increase of specific surface area.

Preparation of Cefquinome Sulfate Liposome

LIU Meng-jiao FU Hua-lin FU Qiang ZHANG Yan-li LU Chao-cheng ZHOU Tao CAO Hang JIN Chao LUO Li ZHOuJian-yu

. 2013, 13(5):  877-881. 

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Cefquinome sulfate liposome was prepared by solid dispersion and effervescent techniques. The effects of decompression rotary evaporator temperature, volume of chloroform, mass ratios of soybean phosphatidylcholine (SPC) to cholesterol (CH), drug to lipid and citric acid to NaHCO3, and mass of Tween-80 on its visual form and entrapment efficiency were studied. Orthogonal design was adopted to optimize the formulation, and the formation mechanism of liposomes discussed. The optimized formulation parameters included the mass ratio of SPC/CH/tween-80/citric acid/NaHCO3 at 37:18:5:33:7, and drug/lipid 1:10. The received liposome prepared under the optimized conditions had a good appearance form and uniform size distribution of particles with the mean size of (203±5) nm, entrapment efficiency 55.17%±0.44%, and drug loading rate 5.04%±0.02%, respectively.

材料工程专栏

Preparation and Properties of Ca2+-doped Vanadium Bronze as Electrode Material of Supercapacitor

MU Xue-chao WANG Xin-ran ZHENG Shi-li WANG Shao-na GUO Fen DU Hao WANG Shao-na

. 2013, 13(5):  882-888. 

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Vanadium bronze was prepared by traditional acidification process with sodium vanadate as precursor, and its electrochemical capacitance quantitatively measured by cyclic voltammetry and galvanostatic charge-discharge methods in 1 mol/L NaNO3 solution. The effects of the precursor concentration, doping cation species and amount of doping cation on the performance of vanadium bronze were examined. Electrochemical investigation reveals that the product contains the optimal capacitance of 120 F/g when the concentration of Na3VO4 is 0.1 mol/L. The sample doped with 0.25 mol/L Ca2+ exhibits improved capacitance of 168 F/g in the initial circle and maintains 131 F/g capacitance after 100 circles. Its electrochemical properties are better than V2O5 and Na-doped vanadium oxide.

Synthesis and Characterization of Li4Ti5O12 Prepared by Microwave Hydrothermal Method

ZHANG Shou-quan CHEN Chun-hua

. 2013, 13(5):  889-892. 

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Lithium titanate Li4Ti5O12 as lithium ion battery cathode material was synthesized using hydrothermal and microwave hydrothermal methods, the influences of different methods on its electrochemical performance were examined, and its structure, morphology, constant current charge and discharge characterized. The results showed that Li4Ti5O12 could be synthesized by both methods, the latter could lead to better electrochemical properties of the sample in smaller and more uniform particle size and larger specific surface area, the first discharge capacity of 151.33 mA×h/g after 97 cycles was 140.94 mA×h/g, the capacity retention rate 93.14%, and the chemical impedance smaller.

综述

Research Advances in Safety of Nanometer Materials and Their Risk Assessment System

ZHANG Hao HUANG Xin-jie LIU Xiu-yu ZHU Qing-ming LIU Ying LIN Xiao-fei

. 2013, 13(5):  893-900. 

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The characteristics of nanometer materials and the importance of safety were summarized, and emphasis was put on the analysis of harm pathway of nanometer materials. The research status of nanometer materials safety in USA, EU, Japan and China was reviewed. According to the safety research status at home and abroad on nanometer materials, on the basis of hazard identification, exposure assessment, toxicity assessment, analysis of risk characteristics, and establishment of safety evaluation of nanometer materials frame were discussed. The steps of determining, safety evaluation of nanometer materials included exposed appraisal, exposure characteristics, hazard identification and characterization, and risk assessment. Meanwhile, outlook for the future research on safety of nanometer materials was given. The safety research of nanometer materials in the near future should consider how to make them safer.