Table of Content

20 October 2012, Volume 12 Issue 5

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流动与传递

Study on Flow Field of Molten Steel in Slab Continuous Casting Mold with EMBr

JIA Hao ZHANG Zhen-qiang WU Ji-wen CHANG Tong-xu DENG Kang REN Zhong-ming;

. 2012, 12(5):  721-727. 

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A physical model was developed with mercury to describe steel flow in a slab continuous casting mold with electromagnetic brake (EMBr). The velocity in it was measured by an ultrasonic Doppler velocimeter with different types of EMBr, immersion depths of submerged entry nozzle and mold widths. Variation of the jet, surface and vertical flows (near the narrow wall) with the EMBr process and slab continuous casting was studied. The results indicate that the "flow passage" formed near the narrow wall, which was unfavorable for the development of plug-like flow with EMBr; channel effect decreased when the ports approached to the down pair of magnetic poles or were covered by magnetic field; The impacting effect of "flow passage" decreased with increasing of the mold width; the velocity and turbulent intensity of surface flow were lower with flow control mold II than those with electromagnetic mold brake ruler [the maximum horizontal velocity of surface flow: 0.071 (Case 2) and 0.068 m/s (Case 3)], and increasing the immersion depth made the velocity impinging the narrow wall decrease [the maximum horizontal velocity: 0.071 (Case 2) and 0.068 m/s (Case 3)]. Variation of the mold width would not change the influencing rule of change of the immersion depth on the flow field in the mold.

Non-linearity of Scaling Law of Instantaneous Pressure Fluctuation Signals in a Circulating Jet Tank

YU Yan-fang WU Jian-hua MENG Hui-bo

. 2012, 12(5):  728-734. 

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In order to reveal the nonlinearity of fluid system in the mixing zones of a circulating jet tank, a high-speed acquisition system was employed to measure the instantaneous pressure fluctuation signals at different axial, radial and circumferential positions in turbulent flow region with a range of Re between 3660 and 32940. Both the amplitudes of fluctuation energy and scaling law of extended self-similarity for the structure function of pressure signals were evaluated. The initial parameters on sampling frequency and data length of pressure time series were optimized based on the recurrence rate and amplitudes of fluctuation energy. The experimental results indicated that the relative increasing ratios of amplitude of fluctuation energy were below 0.3% and a linear relationship between logarithm values of amplitude of fluctuation energy and Re existed when the date length was not less than 80000. The logarithm values between the qth- and third-order time structure functions of pressure signals were in accordance with a linear relationship. The scaling exponent x(q) of time structure function was smaller than relative scaling exponent x(q, 3). The profiles of relative scaling exponents x(1, 3) and x(5, 3) [or x(2, 3) and x(4, 3)] were symmetrically distributed about the profile of x(3, 3). The relative scaling exponent x(q, 3) was enlarged with the increase of qm when the order value of q was equal or greater than 4. But the distribution of x(q, 3) was contrary with the increase of polar angle q or r/R when the order value of q was less than 3.

Morphological Characteristics of Chaotic Attractor of Instantaneous Pressure Fluctuation Signals in a Kenics Static Mixer

YU Yan-fang XIONG Qiang MENG Hui-bo WANG Wei WU Jian-hua

. 2012, 12(5):  735-741. 

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In order to evaluate moment of attractor morphology in a Kenics static mixer (KSM), 360 groups of pressure fluctuation signals (PFS) in vertical upward flow were measured in the turbulent region with a Re range from 1756 to 3512. Reference sections were placed in the chaotic attractor field of pressure fluctuation signals based on the phase-space reconstruction theory. The relationship between chaotic attractor morphology and Re, radial and axial positions was investigated. The secondary flow in the cross-sections consisted of different scale free and forced vortices which formed the Rankine vortex. The slopes of chaotic attractor moment at rm/R≤0.3 and rm/R>0.8 decreased with the increase of Re. The slopes of moment in the bulk zones at 0.4≤rm/R≤0.8 first increased, then decreased, and finally increased with the increase of Re. The chaotic attractor morphology of PFS was sensitive to evaluation of topology structure, which was helpful to understanding the nonlinear dynamic mechanism of vertical upward flow.

Numerical Simulation on the Structure Selection of Oil-Water Pre-separation Zone in a Compact Flotation Unit

YU Jie-cheng CHEN Jia-qing WANG Chun-sheng ZHANG Ming WANG Jian-wen SHANG Chao

. 2012, 12(5):  742-747. 

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The oil-water separation performance of 4 kinds of pre-separation zone structure of a compact flotation unit (CFU) was studied with computational fluid software Fluent. Based on the steady and reliable computational model, the de-oiling efficiency and oil-phase distribution of the 4 structural configurations were studied under the design flow rate and inlet oil content firstly, and the effects of flow rate and inlet oil content on the de-oiling efficiency of a CFU were examined. The numerical results show that for the same kind of pre-separation zone structural configuration, the de-oiling efficiency is relevant with the flow rate and inlet oil content, which increases with increasing of inlet oil content when the flow rate is given, and decreases with increasing of the flow rate when the inlet oil content is given. The comprehensive oil-water separation performance of cylinder with bell-mouth upward structure is the best under the conditions of designed flow rate of 4 m3/h and inlet oil content of 2000 mg/L, the oil-water separation efficiency is 87.13%, and this structure configuration has wide operating range.

Effect of Waved Baffle Panel on Mass Transfer and Mixing Performance of Flat Plate Photobioreactor

WANG Lin-lin YOU Xue-yi

. 2012, 12(5):  748-753. 

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The computational fluid dynamics was applied to simulate the flow field of a flat plate photobioreactor (PBR) with waved baffle panel. After the reliability of model was validated, the effects of two structural parameters of waved baffles, i.e. the ratio of waved baffles height to wave length (L/l) and ratio of wave amplitude to wave length (A/l) on the mass transfer and mixing performance were systematically analyzed. The results showed that when L/l=12, better mass transfer and mixing performance were obtained and those related parameters such as the liquid volumetric mass transfer coefficient (kLa), ratio of cycle time of the downcomer to that of PBR (q) and averaged turbulence kinetic energy (Em) were higher. Besides, the obtained liquid velocity was close to the optimum value being most favorable to microalgal growth. When L/l=12 and A/l=0.8, the mass transfer performance was the best and the value of kLa was increased by about 10% compared with that of bioreactor with flat baffles. As L/l=12 and A/l=0.4, the mixing performance of the reactor was the best and the value of Em was increased by 14.7% compared with that of bioreactor with flat baffles.

Laminar Flow Characteristics in Helical Duct with Right-angled Isosceles Triangle Cross Section

WANG Cui-Hua TANG Mi WU Jian-hua KOU Li-ping

. 2012, 12(5):  754-759. 

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Laminar flow characteristics of helical ducts with right-angled isosceles triangle cross section is investigated numerically with CFD software. The velocity fields of fully developed laminar flow are obtained. The effects of dimensionless curvature ratio d and dimensionless torsion l on the intensity of secondary flow and flow resistance are analyzed. The results indicate that the steady flow structure of secondary flow on the cross section perpendicular to helix has two vortexes within d=0.021~0.083 and Re=100~1000. Both the secondary flow intensity and flow resistance rise with increasing of Reynolds number and d. In the range of study, l has little effect on the intensity of secondary flow and the flow resistance. The flow resistance of the triangular helical duct is smaller than that of the half-coil helical duct when they have the same structural parameters and Reynolds number, and with increasing of Re, the difference between them increases as well. In the range of Re, the friction factor of triangular helical duct is 84.1%~99.5% as much as that of half-coil helical duct.

Preparation of Lactose Particles Using Side Spray Technology in a Fluidized Bed

ZONG Rui-xia JING Qiu-fang MA Xiao-si REN Fu-zheng

. 2012, 12(5):  760-764. 

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Preparation of lactose particles in a fluidized bed was investigated using side spray technology. The particle size distribution and flowability were selected to evaluate the granulation with hydroxypropyl methylcellulose K4M as binding agent. Over 85%(j) of the particles were in the range of 200~355 mm when optimum formulation and process parameters were chosen, including the concentration of binding agent 1.5%(w), its mass increment 2%, spray rate 14~18 g/min, and atomization pressure 1.5′105 Pa. The slope of repose of granules (<34o) and degree of compression (<10%) showed the good flowability of lactose particles. The particles had a spherical shape, when observed under an optical microscope. The preparation process was very stable and had a good repeatability.

Heat Transfer Parameters of Gas in Checker Bricks of Hot Stove

CHEN Chuan CHENG Shu-sen

. 2012, 12(5):  765-769. 

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A two-dimensional mathematical model of checker bricks in hot stove was established. The influences of different types of checker brick on the heat transfer parameters of gas were studied. Efficient microporous checker brick can improve the heating area and heat convection coefficient. 37 hole checker brick has about 1.8 times of the average heat exchange of 19 hole checker brick, 19 hole checker brick about 1.6 times of the average heat exchange of 7 hole checker brick. As the hole diameter decreases, the pressure loss increases. When the hole diameter and void area are 30 mm and 0.36, respectively, the blast temperature can reach 1206℃ and the pressure loss is between drastic and gradual regions. A good thermotechnical index can be achieved by using 19 hole checker brick in the newly built and reconstructed hot stove.

反应与分离

Adsorption Properties of Polyamine-Diacetone Acrylamide Modified PVC Resin to 4-Chlorophenol

SUN Lin LIU Chun-ping QI Ming-yi LIU Jun-shen LIU Xi-guang CUI Zhen-zhong

. 2012, 12(5):  770-775. 

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Polyamine-diacetone acrylamide modified PVC resin was synthesized through amination and Michael addition reaction with PVC as support. Adsorption properties of the resin to 4-chlorophenol were studied. The experimental results showed that the adsorption isothermal process accorded with Freundlich model. Its adsorption kinetic curves obeyed a pseudo-second-order rate equation, the rate constant was 5.38 and 9.04 mg/(mg×min) at 25 and 30℃, respectively. The adsorption capacity was 45.2 mg/g at 25℃ and removal rate of the resin for 4-chlorophenol was more than 97%. 4-Chlorophenol adsorbed on the resin could be eluted with anhydrous alcohol and 4% NaOH solution.

Adsorption of Cu2+ from Aqueous Solution by Polyacid Modified Shaddock Shin

TANG Wen-qing ZENG Rong-ying FENG Yong-lan WU Wei WANG Xue-xin LI Xiao-ming

. 2012, 12(5):  776-780. 

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Adsorption of Cu2+ on the cellulose citric acid (Cell-CA) as the adsorbent was investigated by batch experiments. Key physico-chemical parameters such as the initial concentration of solution, particle size, pH value, contact time, and temperature of the solution were examined. The experimental results showed that the highest removal rate of Cu2+ could reach 92.4% and adsorption capacity was up to 18.54 mg/g at pH 5.5. The data were correlated by Freundlich and Langmuir equations under different temperatures. The Langmuir equation accorded with the static adsorption characteristic of adsorbent. The kinetic parameters of adsorption of Cu2+ on Cell-CA were determined. The pseudo-first order and pseudo-second order kinetic models best described the adsorption of Cu2+. The thermodynamic parameters indicated that the adsorption of Cu2+ on Cell-CA was endothermic.

Effect of Ag+ on Bioleaching of Arsenic-bearing Gold Concentrate

ZHANG Ming YANG Qiao-wen ZHANG Guang-ji YANG Chao

. 2012, 12(5):  781-784. 

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The effect of Ag+ on bioleaching of As-bearing gold concentrate was studied. The concentrations of Fe3+, Ag+ and As in the bioleaching solution were monitored during the leaching process. The effect of Ag+ on the bacterial density was investigated and the leaching residue was characterized by XRD and SEM. The experimental results show that Ag+ can enhance the bioleaching rate especially at the high concentration of Fe3+, but the growth of bacteria was restrained under at higher concentration of Ag+, leading to the decrease of leaching rate. Based on the leaching results and leaching residue analysis, the catalytic mechanism of Ag+ was that the arsenic on the surface of concentrate was displaced by Ag+, and Ag2S formed, which could be dissolved by Fe3+, releasing Ag+ again.

Adsorption Characteristics of Aniline in Wastewater with Carbonized Rice Husk

ZENG Rong-ying TANG Wen-qing FENG Yong-lan WANG Xue-xin WU An-fu LI Xiao-ming

. 2012, 12(5):  785-788. 

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Activated carbon prepared from rice husk with phosphoric acid as activator at 300 and 600℃ was utilized as adsorbent (samples CC1 and CC2) to remove aniline from aqueous solution. The carbonized husk was characterized by Brunauer-Emmett-Teller analysis. Batch experiments were conducted to study the effects of pH value and temperature (20 and 30℃) on aniline adsorption. The adsorption behaviour of aniline on carbonized rice husk was also evaluated. The results showed that the CC2 had greater adsorption efficiency than CC1. The Langmuir model was applied to describe the adsorption isotherms of aniline. Kinetic studies showed that the adsorption process followed pseudo-second-order kinetic model with the correlation coefficient of 0.999. The thermodynamic parameters of ΔGq, ΔHq and ΔSq were also calculated. The negative ΔGq values indicated that the adsorption process was spontaneous.

过程与工艺

Study on Solution Loss Reaction Kinetics of Coke with H2O and CO2

ZHAO Qing-qing XUE Qing-guo SHE Xue-feng WANG Hong WANG Jing-song

. 2012, 12(5):  789-795. 

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The effects of CO2, H2O and their mixture on coke degradation were studied from 900℃ to 1100℃ by self-command continuous measurement device for high temperature gas-solid reaction. The results show that the solution loss rate of coke reacting with H2O is 2~5 times of that of the coke with CO2. Compared with the coke reacting with CO2, the chemical reaction of coke with H2O is much more intense in the periphery of coke, and it is not easy to generate big holes and cracks in its center part. The main gasification ways of coke beginning to react with CO2 and H2O are micro-hole formation and pore expansion respectively when the temperature is 900℃; that of coke beginning to react with CO2 and H2O are pore expansion and micro-hole formation respectively when the temperature is 1100℃. The solution loss rate of coke increases with increasing of H2O in gaseous mixture. The synergistic effect of coke and H2O-CO2 gaseous mixture is apparent when the ratio of H2O to CO2 in the mixture is 5/5 or 7/3 during the gasification process. The shrinking core model was used to describe the gasification results of coke reacting with H2O and CO2. Their activation energy is 154.47 and 214.77 kJ/mol respectively.

Reaction Mechanism of NO2 in NO Absorption into Alkaline Solution

GAO Fang LIU Fang ZHANG Jun-feng TONG Zhi-quan; YANG Liu-chun

. 2012, 12(5):  796-802. 

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The promoting effect of NO2 on NO absorbing into alkaline solution was studied in a bubble column reactor operated in continuous flow mode and the effects of different process variables such as concentration of alkaline solution, feed concentration of NOx, ratio of NO to NO2 and reaction temperature (283~358 K) were investigated. The results indicated that the absorption of NOx was increased observably in the presence of NO2 and the removal efficiency of NO was higher than that of NO2 when the feed concentration of NOx was above 600′10-6 and the volume ratio of NO/NO2 in the range from 0.5 to 2.0. Furthermore, the ion chromatography analysis on the products showed that there were some non-stationary intermediate species formed from NO absorption induced by NO2 and there may be some novel similar-catalysis mechanisms in the removal of NO by injecting NO2 into alkaline solution.

Numerical Simulation on Reduction of Zinc-containing Steel-making Dust Pellets in a Rotary Hearth Furnace

WU Yu-liang JIANG Ze-yi ZHANG Xin-xin SHE Xue-feng

. 2012, 12(5):  803-809. 

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Based on zinc-containing dust treatment by direct reduction process in a rotary hearth furnace (RHF) in a steel plant, mathematical models of thermal process with gas flow, combustion and heat transfer in furnace and heat transfer process with physical-chemical reactions inside carbon-based pellets are established. Direct reduction experiment of the pellets used in actual production is performed by an Si-Mo heating furnace to validate the models. Distributions of temperature, flow and pressure of furnace gas, pellets temperature and composition are obtained. Influences of major operating parameters of RHF on product index are also analyzed. The results show that flow velocity of furnace gas increases along flow direction, and the highest furnace temperature (nearly 1350℃) appears in the reduction section II. After reduction for 20 min, metallization degree of iron and zinc removal rate of pellets will reach 77.9% and 92.7%, respectively. And, if iron metallization target reaches 70%, C/O molar ratio of green pellets should be below 0.9, however, zinc removal index is slightly affected by carbon content. When coal gas supply is reduced by 1%, final metallization degree of iron and zinc removal will fall 0.8% and 1.3%, respectively, and metallization degree of iron and zinc removal will also decline 14% and 24% when secondary air supply is less 20% than needed. Reduced zinc vapor, after diffusing out of pellets, is re-oxidized in furnace gas, and zinc-enriched dust collected during flue gas treatment can be sent to nonferrous industry.

Effect of Waste Plastics Addition Ratio on Combustion of Pulverized Coal

ZHANG Jian-liang LIU Wei-jian REN Shan SONG Jian WEN Yong-cai

. 2012, 12(5):  810-815. 

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The effect of waste plastics addition on combustion characteristics of Chuanmei coal and Wuben coal was studied comparatively by thermogravimetry. The results show that adding waste plastics can increase the maximum weight loss rate, reduce the ignition temperature, decrease the burnout temperature and the temperature of the maximum weight loss speed of the pulverized coal, which effectively improves the combustion rate of pulverized coal; At the same waste plastics addition ratio, the combustion effect of low volatile pulverized coal is superior to that of high one, and the most obvious effect of combustion occurs in a relatively low temperature region (500℃); At different waste plastics ratios, when the addition is higher at about 20%, the combustion effect is most obvious; when the addition is lower at 0.5%, the combustion of pulverized coal is significantly improved.

Production of Iron Nuggets Using Iron-rich Red Mud by Direct Reduction

WANG Hong SHE Xue-feng ZHAO Qing-qing XUE Qing-guo WANG Jing-song

. 2012, 12(5):  816-821. 

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The experiments were conducted to study the production of iron nuggets with iron-rich red mud by direct reduction and melting, and the impacts of temperature, C/O and CaF2 content on the reduction and melting investigated. And kinetic analysis of the experimental results obtained at different temperatures was carried out. The results showed that temperature and CaF2 content were critical influential factors on the reduction and melting. Iron nuggets and slag can be separated well under the conditions of 1400℃, C/O=1.2, 2% CaF2 addition and 14 min heating time. The carbon and sulfur contents of nuggets were 2.72% and 0.48%. The kinetic analysis result showed that carbon gasification and gas diffusion were both the rate-controlling steps for the reduction of iron-rich red mud. The obtained iron nuggets were a kind of steelmaking feed, and the slag could be used to extract scandium.

生化工程专栏

Purification of Polysialic Acid by Anion Ion Exchange Chromatography

ZHOU Ya-juan WU Jian-rong ZHU Li ZHENG Zhi-yong ZHAN Xiao-bei; ZHOU Wen-chen

. 2012, 12(5):  822-827. 

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A crude product of polysialic acid produced by Escherichia coli was subjected to anion ion exchange chromatography for further refining. Based on the preliminary results of static adsorption and gradient elution, a Q-Sepharose FF was chosen for the chromatographic matrix. The ion exchange chromatography conditions for polysialic acid purification were optimized. The results showed that the optimal elution conditions for polysialic acid were as follows: pH 7.2 sodium chloride-0.02 mol/L sodium phosphate buffer, linear elution at CNaCl=0.0017VEluent, elution rate 0.8 mL/min, and maximum injection volume 4.0 mL in 46 mL column. The purity of polysialic acid product was achieved to 98%, the protein content was decreased from 1.9% to 0.04% and the recovery rate of polysialic acid was more than 86.0%. Analytical results of UV spectrometry and high performance gel filtration chromatography showed that the final polysialic acid product was homogeneous and had average molecular weight of 303 kDa.

Preparation of Anion-type Bifunctional Carrier with Epoxy Group and Its Immobilization of Horseradish Peroxidase

LEI Qing-juan GAO Bao-jiao ZHANG Zheng-guo

. 2012, 12(5):  828-833. 

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Glycidyl methacrylate (GMA) was graft-polymerized on micron-sized silica gel particles, obtaining the grafted particles PGMA/SiO2. The partial chain units of grafted macromolecule PGMA to produce ring-opening reaction of the epoxy groups with sodium 4-hydroxybenzenesulfonate (SHBS) as reagent were made, obtaining anion-type bifunctional composite carrier containing epoxy group, SHBS-PGMA/SiO2. With SHBS-PGMA/SiO2 as carrier, the immobilization of horseradish peroxidase (HRP) was carried out. The effect and mechanism of electrostatic interaction between the enzymic protein HRP and functional carrier on the enzyme immobilization were studied. The results show that the sulfonate anions on SHBS-PGMA/SiO2 particles enable the carrier particles to be negatively charged. As the pH value of the medium is 6.0, HRP molecules are positively charged, and the strong electrostatic interaction between the enzyme protein and the carrier will happen, which leads to strong physical adsorption of HRP on the carrier, and greatly promotes the chemical immobilization of HRP. For the carrier with an SHBS bonding rate of about 18%, there is the strongest electrostatic interaction between them, and the immobilized enzyme has the highest coupling rate and specific activity. The ionic strength affects HRP immobilization greatly. As electrolyte NaCl is added into the medium, the electrostatic interaction between them will be shielded, which makes the coupling rate and specific activity of immobilized enzyme decrease.

Effect of Extracellular Polymeric Substances on Membrane Fouling during Domestic Wastewater Treatment

MA Xing-guan JI Wen-juan SUN Jun-ping XUE Xiang-xin YANG He FU Jin-xiang

. 2012, 12(5):  834-838. 

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The effects of concentrations of protein and polysaccharide, concentration ratio of protein to polysaccharide (P/P) and total quantity of extracellular polymeric substances (EPS) on membrane fouling of a membrane bioreactor were studied by simulating domestic wastewater at room temperature. The relationships between these parameters and transmembrane pressure (Dp) were described by establishing binomial nonlinear regression equation and corresponding related coefficient (R2). The results showed that the concentration of protein and P/P exhibit obvious direct proportion to Dp with the higher value of R2 being 0.5367 and 0.4298, respectively. As a hydrophobe, protein is prone to sediment on the membrane surface, forming secondary adsorption and increasing Dp. There is no obvious relation between polysaccharide concentration and Dp, which may be ascribed to the high concentration of polysaccharide in simulative domestic wastewater and its sediment as well as physical adsorption. Based on the present result, the protein is taken as the most significant factor for the fouling, changing the interaction between protein and membrane can alleviate it.

Extraction Kinetics of Astragalus Polysaccharides by Cellulase-assisted Aqueous Extraction

WEI Feng-yu 康家胜 KANG Jia-Sheng ZHANG Yu

. 2012, 12(5):  839-843. 

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The extraction of astragalus polysaccharides (APS) was studied with cellulase-assisted aqueous extraction (CAE) and aqueous extraction (AE). The effects of temperature (T) and particle size (R0) on the kinetic characteristics of extraction process were examined, and the cell microstructures of the samples extracted by CAE and AE were observed by SEM. The results showed that the extraction process of APS followed Fick model. Cellulase did not change the mass transfer mechanism of APS, but destroyed the structure of cells, and then significantly improved the mass transfer rate and apparent diffusion constant D￠. The relationships of D′ with temperature and particle size were expressed as lnD￠=-9.30-926.7/T+1.76lnR0 for AE, and lnD￠=-10.56-491.4/T+1.75lnR0 for CAE, respectively.

Basic Electricity-producing Characteristics of Microbial Fuel Cell Using Supernatant Fluid of Heat Pretreated Sludge

SONG Tian-shun WU Xia-yuan FAN Ping ZHOU Chu-xin

. 2012, 12(5):  844-848. 

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Using a single-chamber air cathode microbial fuel cell (MFC) as experimental reactor, its electricity generation using sludge supernatant fluid with heat pretreatment was studied. The results showed that its maximum power density (Pmax) of MFC was highest (44.4 mW/m2), when it was heated for 3 h at 90℃, which was 105 times that of MFC without heat pretreatment. Absorbance of UV254 and A250/A365 manifested that the substrate composition of supernatant fluid was most conducive to anodic microbial metabolism in electricity. Pmax of MFC was only 5.8 mW/m2, when MFC used the sludge heat pretreated again as substrate. These results evidently demonstrated the advantages of heating pretreatment to sludge for enhancing MFC power and combing with existing process easily, it was close to actual application.

材料工程专栏

Preparation of TiFe Based Alloy Melted by CaZrO3 Crucible and Its Hydrogen Storage Properties

YANG Bo ZHU Kai-liang ZHEN Qiang LI Zhi-lin WU Zhu WU Guang-xing LI Chong-he

. 2012, 12(5):  849-856. 

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The carbon contamination of alloys melted by electro graphite crucible is impossible to endure owning to an inherit reaction between the melt and carbon. The TiFe-based alloy is prepared by vacuum induction melting (VIM) with CaZrO3 and electro graphite crucibles. The prepared samples are examined by optical microscope, SEM, XRD and EDS, and their PCT curves measured. The results show that the oxygen content of alloy by melted CaZrO3 crucible is almost equal to that by the graphite one, but without the carbon contamination, meanwhile the carbon content of alloy obtained by the latter is 0.220%(ω), which exceeds the tolerance of commercial alloy [0.1%(ω)]. The microstructure of alloy melted by CaZrO3 crucible is dendrite, but that by the graphite crucible is composed of the equiaxed crystal with lamellar structure and spherical TiC particles distributed along grain boundaries or within the grains. The maximum hydrogen absorption capacity of alloys melted by both crucibles is 1.832%(ω) and 1.823%(ω), respectively. The TiFe based hydrogen storage alloys can be produced by VIM with CaZrO3 crucible in place of electro graphite crucible.

Calculation and Analysis of the Standard Gibbs Free Energy of Formation for Ti-O Compounds

YANG Fan LI Fan YAO Chuan-hao YU Zhi-hui XIA Ding-guo

. 2012, 12(5):  857-863. 

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The rule of oxygen potential increasing with oxygen mole fraction in oxides and calculation with computer are applied to assess the data of standard Gibbs free energy of formation DfG0 for 24 types of Ti-O compounds obtained from literatures. The results show that the relationship of oxygen potential with the equilibrium reactions of Ti26O51 with Ti28O55 and Ti24O47 with Ti26O51 do not obey the rule of oxygen potential increasing at 1304 K. It is suspected that one of DfG0 data of Ti24O47, Ti26O51, and Ti28O55 is error. The methods of evaluating DfG0 by both the oxygen potential increasing and quasi-parabola rules are explained in detail. Then DfG0 data of Ti24O47, Ti26O51, and Ti28O55 are separately evaluated. The results obtained by the two different methods are the same. At 1304 K they are DfG0Ti24O47=-16785.366±0.011 kJ/mol, DfG0Ti26O51=-18202.261±0.021 kJ/mol, DfG0Ti28O55=-19619.080±0.008 kJ/mol. These results are analyzed, which shows that the original value in DfG0 of Ti26O51 is probably larger error. Based on the assessed data, Ti4O7 material is prepared from TiO2 by carbothermal and hydrogen reduction methods.

Performances of a Novel C/C-ZrB2-ZrC-SiC Composite with Ultra-high Temperature Ceramic Matrix

XIE Chang-ming QIAN Yang-bao WEI Xi GE min; ZHANG Wei-gang

. 2012, 12(5):  864-869. 

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C/C-ZrB2-ZrC-SiC composite was prepared by a combined process of chemical vapor infiltration of pyrocarbon and polymeric impregnant/pyrolysis of ceramics using a hybrid precursor of polycarbosilane, zirconium-carbon containing polymer and zirconium-boron-carbon containing co-polymer. The composition and microstructure of prepared composite was characterized. Its mechanical and ablation properties were also studied under high temperature oxidation. The formed ultra-high temperature ceramic matrix of ZrB2 and ZrC nanoparticles are homogeneously dispersed in the continuous SiC phase, these three phases form ZrB2-ZrC-SiC homogeneous ceramic matrix of the composite. Flexural strength and fracture toughness of the composite firstly increase and then decrease with increasing of pyrocarbon, and the composite with 22.3%(j) pyrocarbon exhibits the optimum mechanical properties of flexural strength of 127.9 MPa and fracture toughness of 6.23 MPa×m1/2 and pseudoplastic failure behavior. Its linear and mass ablation rates in plasma arc test at 1800~2200 °C for 1000 s are less than 1.67 mm/s and 1.66 mg/s, respectively.

Experimental Research on Online Determination Technology of Particles in High Pressure Natural Gas Pipeline

XU Qiao-qi JI Zhong-li LIU Gang CHEN Hong-hai XIONG Zhi-yi

. 2012, 12(5):  870-875. 

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Specific to the requirements for character assessment and model selection of filtration and separation facilities in high pressure natural gas pipeline transportation station, a particulate matter measurement device for natural gas pipeline is developed, and its characteristics tested. Concentration and particle size distribution of particulate matters in high pressure natural gas pipeline can be determined directly with the device under 12 MPa pressure without pressure reduction. Characteristics of particulate matters in the pipeline of a domestic natural gas station are measured under 6.3 MPa pressure by using online device and off-line isokinetic sampling methods. Analyzing the influences on on-line measurement results, a correction method is proposed based on off-line measurement results. After the correction of on-line detection, the particle size range is shifted from 0.65~9.5 mm to 0.55~7.2 mm. Before correction, online average concentration measurement with a result of 4.04 mg/m3 is obtained, offline average concentration measurement with a result of 2.76 mg/m3, there is about 46% deviation between them. After correction, the online measured average concentration is around 2.83 mg/m3, the deviation between off-line and on-line measurements is less than 5%.

Experimental Study on Steam Gasification of Sawdust with High Temperature Copper-containing Slag

LI Juan-qin HU Jian-hang WANG Hua DENG Shuang-hui HU Wei

. 2012, 12(5):  876-881. 

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Experiment of sawdust steam gasification catalyzed by copper-containing slag was carried out using its waste heat as external heat source. Catalytic activity components of the slag were inferred and catalytic activity was evaluated by analysing its phase composition before and after the catalytic reaction by XRD and characterization of gas product. Sensible heat and utilization rate of waste heat of the slag were calculated by determining the temperatures of catalyzed copper slag before and after gasification. The results show that untreated copper slag presents characteristic peaks of Fe2O3 and the number of characteristic peaks of Fe2O3 and Fe3O4 is reduced and their strength weakened for calcined copper slag after catalytic gasification. Volume fraction of H2 significantly is increased and volume fractions of CH4 and C2H4 are significantly reduced after catalytic gasification. It is infered that catalytic components of the slag are Fe2O3 and Fe3O4 and its catalytic activity is determined by the content of Fe2O3 and Fe3O4. The higher the content of Fe2O3 and Fe3O4, the better the catalytic activity of the slag. The recycling sensible heat of the slag and utilization rate of waste heat are 151.89~237.48 kJ/kg and 18.49%~22.63% respectively for the temperature reduction of the slag by 130~240℃ within the gasification temperature range from 720 to 950℃.

Effect of Block Board Structure on Emission of Formaldehyde and Control

ZHANG Hao QIAN Fu-ping LIU Xiu-yu DING Hou-cheng

. 2012, 12(5):  882-887. 

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HJC-1 type environment testing chamber was used to simulate indoor environment with block board widely used in building adopted as the testing material. Formaldehyde concentrations in the chamber with different board structures in a certain period were measured. Activated carbon, formaldehyde sealing agent, photocatalyst and air catalyst were used to control its emission. The results indicate that the formaldehyde emission channels of block board are from the side surface, and if the inner structure of block board is loose, formaldehyde will release severely. Formaldehyde sealing agent and activated carbon adsorption control its emission in an ideal effect, their average efficiencies are 56.05% and 52.83% respectively. The concentration of formaldehyde in a short period of time is reduced to the levels below the class II (0.12 mg/m3) and class I (0.08 mg/m3) of civil engineering construction standard.

Characteristics of Activated Carbon Prepared with Anthracite for Separation of CH4 and N2 Mixture

ZHANG Bo GU Min XIAN Xue-fu

. 2012, 12(5):  888-892. 

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Granular activated carbon (GAC) was prepared by preoxidation-carbonization-vapor activation process using anthracite as raw material. The adsorption isotherms of CH4, N2 and CH4/N2 mixture were measured and the pore size distribution, surface functional group and crystal structure of GAC characterized. The results show that by a pressure swing adsorption process using single column and single cycle with the prepared GAC as adsorbent, the volume percentage of CH4 was increased by 30.7% maximally. The effective micropores for separation of CH4/N2 mixture occupied a great proportion. The oxygen-containing function groups on the surface of GAC were favorable for the separation of CH4/N2. The adsorption selective coefficient of CH4 on GAC was 3.4.

综述

Progress in the Application of Molten Salts for New Energy Production

YANG Wu-long JIANG Hong-tao WU Ye-ru FAN Hao HUA Wei WANG Hong-jun

. 2012, 12(5):  893-900. 

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The applications of molten salts in electrolyte cell (including fuel cell, lithium battery and thermal battery), solar thermal power generation and biomass pyrolysis are reviewed. The working characteristics, conversion efficiency and service life of fuel cells with molten salts are evaluated. It is also pointed out that the development of fuel cells will focus on molten carbonate fuel cells. Compared with the cathode material of lithium battery, prepared by high temperature solid phase method, the material by molten salt method is improved on crystalline structure and performance. And in solar thermal power generation field, high temperature molten salt as a low cost and high efficiency heat transfer and storage medium has been also applied. Furthermore, recent research progress in pyrolysis of biomass to bio-oil or hydrogen-rich gas in molten salt media is summarized. By examining molten salt composition and reaction temperature, and referring pyrolysis mechanism and kinetics, it is concluded that pyrolysis of biomass in molten salts is practicable. Finally, in order to enhance the development of molten salts application forward, problems to be solved are listed.