Table of Content

20 August 2013, Volume 13 Issue 4

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流动与传递

Similarity Solution in Chemical Engineering Guided by Dimensional Analysis

MAO Zai-sha YANG Chao

. 2013, 13(4):  541-547. 

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Similarity solution is a classical topic in chemical engineering, frequently encountered in analysis of flow and transport phenomena in semi-infinite domains. In this article, dimensional analysis is applied to resolve systematically the conditions for the existence of similarity solutions and formulate a basic procedure to get such solutions. With several classic examples, the method for finding the suitable combination of independent variables from original ones is demonstrated, so that the original partial differential equation can be transformed into a simpler ordinary differential equation, through which the desired similarity solution is finally achieved. In-depth analysis of one-dimensional diffusion/reaction problems by dimensional analysis results in some new insights. The elaboration is significant for deep insight of similarity solution and its application in chemical engineering.

Mixing of Liquids with Different Viscosities and Densities in a Helical Ribbon Impeller Stirred Tank

HUANG Juan BAO Jie DAI Gan-ce

. 2013, 13(4):  548-554. 

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The mixing of liquid addition in a stirred tank installed with a helical ribbon impeller under laminar flow regimes during inoculation in the simultaneous saccharification and fermentation of lignocellulosic biomass at high solids loading was studied. The effects of impeller rotational speed, volume ratio of added liquid a to bulk liquid b, Va/Vb, and their viscosity and density on mixing time, tm, were examined. The results show that it takes longer time for the liquids with different viscosities and densities to get homogenization than that of similar property liquids when Va/Vb is above 1%. tm of the liquids with different properties is 2~5 times longer than that of similar property liquids at identical conditions. Va/Vb is the most important operating parameter, dimensionless mixing time, Ntm, first decreases and then increases with Va/Vb, there is a minimum value. When Va/Vb≥2% and Dr/rb>0.2, Ntm increases linearly with them. Liquid addition in the bulk has shorter mixing time than that of addition on the surface. The mixing regime in the tank can be classified into Re controlled (stirrer controlled) regime and Ri controlled (gravity controlled) regime at high Va/Vb (>2%).

Analyses on Turbulent Heat Transfer Performance and Entropy Generation of Fluid in the Inner Half Coiled Jacket

LI Ya-xia DONG Guo-xian WU Jian-hua ZHANg Xian-zhen

. 2013, 13(4):  555-561. 

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Fluid turbulent heat transfer in the inner half coiled jacket is numerically studied by using CFD software Fluent with the focus on the effects of Reynolds number Re and curvature ratio d on heat transfer characteristics. Jacket heat transfer is evaluated by entropy generation number based on the second law of thermodynamics. The results show that minimum dimensionless temperatures of the heated curved wall are near the two main primary secondary flow vortices. The maximum value is at the centre of the heated wall, where is the worst position for heat transfer. At the same d value, the secondary flow intensity and turbulent kinetic energy are both enhanced with the increase of Re, which promotes the comprehensive performance coefficient Num/f of jacket. At the same Re value, the increase of d makes the secondary flow intensity enhance but turbulent kinetic energy abate, which reduces Num/f value. Average Nusselt number of the heated wall Num for the inner half coiled jacket is 1.168~1.241 times and friction coefficient f 1.021~1.077 times of that for the outer half coiled jacket in the studied scope. There is an optimal Reynolds number Reop making the irreversible loss least in the inner half coiled jacket. Reop is enhanced with the increase of d. The important positions of useful energy loss in the inner half coiled jacket are near the two dead zones of semicircular cross section.

Flow Behavior of Asphalt Particles in a Fluidized Bed-Riser Coupled Reactor

QIN Xiao-gang YAN Zi-han ZHANG Guang-jie FAN Yi-ping LU Chun-xi

. 2013, 13(4):  562-567. 

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A large scale cold model device of a fluidized bed-riser coupled reactor was established according to the gasification technique for heavy oil residuum (asphalt particles). The axial distributions of the averaged cross-sectional density in the reactor were measured. The results show that the suitable operating conditions are to control the riser superficial gas velocity from 0.70 to 1.76 m/s. The behaviors of asphalt particles in the fluidized bed-riser coupled reactor present fairly different characteristics from those of the Geldart A particles. The reactor can be divided into six axial zones based on the distinct flow patterns, fluidized bed dense-phase zone, the riser sparse-phase zone, riser concentration recover zone, riser accelerating zone, riser fully developed zone and riser back-mixing zone. The averaged cross-sectional density in the coupled reactor increases with the increase of particle mass flow rate and decreases with the increase of superficial gas velocity. Furthermore, empirical equations for estimating the axial distributions of averaged cross-sectional solids volume fraction are established based on the experimental data and theoretical analysis. The model predictions are in good agreement with the experimental data.

Flow Characteristics and Stability of Lignite Powder with Different Moistures in Pneumatic Conveying

ZHANG Zhong-lin LIANG Cai

. 2013, 13(4):  568-573. 

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Pneumatic conveying experiments of lignite powder with various moisture contents using nitrogen were carried out with an experimental facility under high conveying pressure. The effects of moisture content on pressure drop, mass flow rate and stability were investigated. The wavelet theory was applied to analyze pressure drop signal of horizontal pipe. Fluctuation amplitude, energy and standard deviation of different frequency regions were extracted to distinguish the stability of conveying process with conveying characteristic and apparent morphology. Lignite powder mass flow rate and pressure drop decreases, conveying stability falls and pressure drop shows periodic fluctuation with the increase of moisture content. The transmission characteristic is good with moisture content below 5.36%, the instability appears when the moisture content between 5.36% and 8.56%, when the moisture content is greater than 8.56%, the flow in the pipe becomes very difficult and blockage often happens, the system stability falls down sharply and there are not stable delivery conditions. In the conveying process of lignite powder with various moisture contents, the process is stable when fluctuation, energy and standard deviation mainly distribute in low frequency regions. As those of characteristic parameters transfer to high frequency regions, the flow becomes unstable.

Motion Characteristics of the Particles in the Classification Chamber of a Classifier

TONG Cong LI Shuang-yue LI Xiang YANG Jun

. 2013, 13(4):  574-579. 

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Based on the analysis of structure and classification mechanism of SLK5500 classifier, its classification chamber model is built. According to the computational fluid dynamics, discrete particle model is used to simulate trajectory of particles with unsteady method. Motion characteristics of the particles in the classification chamber are shown, and velocity distribution of the classification chamber is studied. According to the particles trapping computation, the effects of air volume and rotator speed on fine particles productivity and 80 mm residue are obtained, and the simulation method is verified, its results agree with experimental results.

Simulation on Turbulent Flow and Heat Transfer in the Triangular Helical Jacket

WANG Cui-Hua WU Jian-hua LIU Sheng-ju ZHANG Li

. 2013, 13(4):  580-585. 

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Turbulent flow and heat transfer in the triangular helical jacket were simulated. The velocity field of fully developed turbulent flow with constant heat flux on heated wall was obtained. The effects of dimensionless curvature ratio (k) and Reynolds number (Re) on the characteristics of flow resistance and heat transfer were analyzed. The mean flow friction factor and mean Nusselt number were correlated based on the simulated data. The results indicate that the structure of secondary flow has two steady vortexes. Both the secondary flow intensity and turbulent kinetic energy are enhanced with increasing of Re. Due to the centrifugal force, the mean friction factor on the outer wall is far greater than that on the inner wall. The peaks of local Nusselt number (Nulocal) are located at the inner heated wall near the centers of secondary vortices. With the increase of Re and k, two peaks of Nulocal increase significantly, the mean Nusselt number of the inner heated wall and the coefficient of resistance increase as well. In the simulated range, the efficiency factor increases with the increase of Re and k, ranging from 3.7 to 4.2.

Enhanced Heat Transfer of Rotational Flow Containing Solid Particles

PENG De-qi YU Huan YU Tian-lan TIAN Qing WU Shu-ying HUANG Jun CHEN Qian

. 2013, 13(4):  586-590. 

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Considering descaling, antiscaling and heat transfer problems in tubes, the widely used twisted and twisted tape inserted tubes were taken as object to study low concentration liquid-solid two-phase flow in rotational flow field on heat transfer. The results shows that the rotational flow field with particles can enhance the turbulence intensity of fluid, both twisted and twisted tape inserted tubes can achieve better rotational flow effect at the same Re, the heat exchange effect in twisted tube with particles is raised 18.7%~30.1% and the resistance coefficient 13.1%~181.8% compared with smooth circular tube, and its performance factor of combined evaluation is higher than the other heat transfer tubes over 15.5%. The heat exchange effect of twisted tape inserted tube with particles is raised 5.6%~32.9% over circular tube, and this tube has the highest resistance coefficient. Further experiment and optimization on the heat exchange effect of twisted tubes with particles show that the error range between the simulation and experimental results is 10.7%~12%. Rotational flow field can enhance the combined performance of liquid-solid two-phase flow, while increasing the flow rate will cause negative effect.

反应与分离

Investigation of Three-liquid-phase Extraction Systems for Simultaneous Separation of Emodin and Rhein

YANG Xing-fu LIANG Xiang-feng YANG Liang-rong LI Wen-song DENG Fu-li WANG Fu-chun LIU Hui-zhou

. 2013, 13(4):  591-599. 

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Several three-liquid-phase extraction systems comprised of organic extractant, polymer and salt aqueous solution were applied to isolate and purify simulated herbal extract containing emodin and rhein. Some influential factors on the partitioning behaviors were studied. The results revealed that extractant type and solution pH value were crucial factors for improving the separation performance. The optimal separation results were obtained at pH 8.00 with methyl isobutyl ketone as the extractant, 10%(w) polyethylene glycol with the molecular weight 4000 Da, and 10%(w) ammonium sulphate. Under the optimized conditions, 95% emodin and 97% rhein were simultaneously extracted into the organic phase and polymer-rich phase from simulated herbal solution with the initial concentration of 100′10-6(w), respectively, and their separation factor of over 10000 was achieved. By adjusting pH value, back extraction rate of both emodin and rhein could be up to about 99%. With the assistance of molecular simulation program XLOGP3 and molecular orbital package, the possible mechanism of extraction was analyzed, and hydrophobic interaction and hydrogen-bonding interaction might be the major driving forces affecting the partitioning behaviors of emodin and rhein.

Thermal Decomposition Characteristics and Kinetics of Burley Tobacco

ZHU Bao-zhong SUN Yun-lan SHI Shao-hui LI Hao HU Yong-hua

. 2013, 13(4):  600-607. 

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The thermal decomposition processes and combustion characteristics of burley tobacco samples from different habitats were studied by TG-DTG-DSC thermal analysis technique. Their thermal kinetics was also investigated. The results show that the thermal decomposition process of burley tobacco has four weight loss stages from room temperature to 800℃. The temperature range of four weight loss stages is different for different samples, and the mass change and heat release in different stages are different. The major reactions of burley tobacco occur in 138~583℃, that is volatilization and combustion stage, and coking combustion stage. The kinetic parameters in the four stages of burley tobacco from different habitats were calculated by Coats-Redfern method, and the reasonable mechanism function was selected by the Malek method. The results show that the first and second weight loss stages have the same mechanism function, the same to the third and fourth weight loss stages. The activation energy of burnout stage is higher than other stages in the four stages. The products in the four stages were collected by special collection device and the harmful products and aroma compositions analyzed. The results show that the quantities of harmful substances and aroma components are different in different weight loss stages for different burley tobacco samples in different growing areas, but most of harmful substances and aroma components are produced in the second weight loss stage, and the quantity of products is bigger than other weight loss stages.

Separation and Recovery of Ni and Cr from Ferronickel Slag of Nickel Laterite

ZHANG Pei-yu GUO Qiang SONG Yun-xia QU Jing-kui QI Tao

. 2013, 13(4):  608-614. 

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Magnetic separation was used to treat the ferronickel slag derived from pyrometallurgy of nickel laterite. After magnetic separation, Ni was enriched in magnetic concentrate. The content of Ni in magnetic concentrate increased from 0.26% to 2.57%, and the content of Cr in non-magnetic tailing from 4.55% to 4.61%, respectively. Then, Ni was leached from the magnetic concentrate with H2SO4 at atmospheric pressure. Under the optimum leaching conditions of sulfuric acid concentration of 220 g/L, leaching temperature of 110℃, leaching time of 2 h, and mass ratio of liquid to solid of 5, 91.5% of Ni was leached out from the magnetic concentrate of ferronickel slag. The acid leaching kinetics of Ni from magnetic concentrate revealed that the apparent activation energy from 80 to 120℃ was 19.6 kJ/mol, which corresponds to a diffusion controlled process. The leaching of Cr from the non-magnetic tailing was carried out by alkali-roasting with Na2CO3 and then leaching with water, the optimum conditions were as follows: temperature of 1000℃, mass ratio of alkali to slag of 0.65, time of 1 h, and particle size of <74 mm. Under the optimum conditions, 94.1% of Cr was leached out from the non-magnetic tailing of ferronickel slag.

Leaching Process of Spent Lead Paste in Citric Acid-Sodium Citrate System

ZHU Xin-feng YANG Jia-kuan SUN Xiao-juan ZHANG Wei HU Yu-chen LI Lei GUO Yi-fei CHEN Song-tao

. 2013, 13(4):  615-620. 

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The leaching process of spent lead paste in citric acid and sodium citrate system was studied. During the leaching process, the variation of morphology and composition of reactants was investigated by SEM/EDX. The results show that PbO2 and PbO can be completely transformed into lead citrate within 1 h, while PbSO4 reacts relatively slowly with a desulfurization rate of 36.2% in 1 h and can be completely transformed in 8 h leaching. During the reaction process, the particle size of PbSO4 reduces continuously, which indicates that the leaching process of PbSO4 may comply with a core-shrinking model. And lead citrate, the leaching product with an initial morphology of flocculent, gradually grows up in the final plate structure.

Roasting Kinetics of Fly Ash and Ammonium Hydrogen Sulfate

WANG Ruo-chao ZHAI Yu-chun NING Zhi-qiang

. 2013, 13(4):  621-625. 

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A new method was used to prepare Al2O3 from fly ash by NH4HSO4 roasting process. The effects of roasting temperature and molar ratio of Al2O3 in fly ash to NH4HSO4 on Al reaction rate were studied. The results showed that the control step of roasting reaction was solid layer diffusion, the reaction rate constant 1.25′10-3, 1.56′10-3 and 1.89′10-3 min-1 at 300, 350 and 400℃, and the activation energy calculated as 17.19 kJ/mol. The general kinetic equation was expressed as 1-2/3a-(1-a)2/3=0.0422exp[-17190/(RT)]t. The main roasted products were NH4Al(SO4)2 and NH4Fe(SO4)2 in the reaction process. The Al reaction rate reached more than 90% under the optimized conditions of 400℃, molar ratio of Al2O3 in fly ash to NH4HSO4 1:8 and roasting time 60 min.

系统与集成

Process Simulation and Techno-economic Analysis on Hydration and Hydrogenation Technology of Acrolein for 1,3-Propanediol Production

ZENG Hong FANG Bai-shan QU Yin-di

. 2013, 13(4):  626-632. 

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Based on laboratory and pilot experiments of hydration and hydrogenation of acrolein for production of 1,3-propanediol (PDO), the Superpro Designer? emluator was applied to simulate the scale-up process for 10000 t/a PDO production, coupling with costing and economic evaluation on the flowsheet. Simulation results show that the process design is reasonable with main process data complying with experimental results. The economic analysis indicates that raw material cost shares 49% of operating cost, equipment purchase cost is about 22.42 million yuan and the total investment is of approximately 150.88 million yuan. The expected returns on investment reach 28.21% as the after-tax profit is about 42.56 million yuan annually.

Kinetic Model of Simultaneous Reactions in Multi-component System during Metallurgical Process and Its Application

CHEN Jian-bin HU Ji-ye SUN Ya-qin

. 2013, 13(4):  633-637. 

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The simultaneous reactions in a multi-component system in ferrous metallurgy as a comprehensive reactions system were investigated. The interaction between the various components on reactions was considered. A kinetic model of simultaneous reactions in a multi-component metal-slag-gas reaction system was established using metallurgical thermodynamics and kinetics. A computer program was designed to obtain the variation curves of concentrations of components with reaction time. The simulation data were verified by experimental results. The results showed that the calculated data by the kinetic model of simultaneous reactions in the system were consistent with the experimental results of Fe-Cr-Mn-C system. This modeling method for predicting the concentration of each component in the metal-slag reaction system was feasible, and could well explain the phenomena and reveal the process mechanism.

生化工程专栏

Effect of PLGA Microsphere Size on Regulation of Immune Response for HPV L1 Capsomere-based Candidate Vaccine

JIA Cheng-cheng WANG Lian-yan; FANG Ying CHEN Jian-ping CAO Ke LIU Yong-jiang MA Guang-hui

. 2013, 13(4):  638-645. 

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Two-sized poly(lactic-co-glycolic acid) (PLGA) microspheres prepared by membrane emulsification technique were used as vaccine delivery and adjuvant system. The effect of particle size on enhancing HPV L1 specific immune responses was investigated. The results showed that HPV L1 pentamers encapsulated in large-sized PLGA (1.38 mm) microspheres could elicit significantly higher level of IgG binding antibodies (87771±24983.0) and neutralizing antibodies (30720±15863.7) than the counterparts with 0.43 mm (38400±14021.7) and (2480±3892.6) (P<0.05 and P<0.01). The similar trend was also found in cytokine secretion levels, and higher levels of IL-6 (4.7 times of the cytokines for small-sized microspheres) and IL-4 (1.5 times of the cytokines for small-sized microspheres) were observed in mice immunized with large-sized PLGA microspheres (1.38 mm) encapsulating HPV L1 pentamers. While small-sized PLGA microspheres (0.43 mm) encapsulating HPV L1 pentamers elicited significantly higher IFN-γ secretion levels (2.1 times of the cytokine for the large-sized microspheres) than large-sized PLGA microspheres (1.38 mm). Small-sized PLGA microspheres can enhance antigen specific cellular immune responses, which is suitable for therapeutic vaccine, while large-sized PLGA microspheres can elicit higher level of humoral immune responses, which is favorable for prophylactic HPV vaccine.

Adjuvant Activity of PLA Microspheres Regulated by Protamine Sulfate

LIU Yu-ying CHEN Xiao-ming WANG Lian-yan; YUAN Qi-peng MA Guang-hui

. 2013, 13(4):  646-653. 

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Polylactic acid (PLA) microspheres and protamine sulfate (PS) modified PLA microspheres were prepared with ethyl acetate (for 400 nm diameter) or dichloromethane (for 900 nm diameter) by premix membrane emulsification method. BALB/c mice were used to evaluate the adjuvanticity of as-prepared microparticles for HBsAg, and the effect of particles size on their adjuvanticity was investigated. The results indicated that PS modification significantly promoted the adsorption of HBsAg onto the microspheres, and the adsorption rate was increased to 8.16% from 2.07%. Compared with PLA microspheres, PS modified microspheres induced more potent immune response, the spot formation cells (SFCs) of IL-2 and IFN-g (Th1 type cytokine) were increased 261% and 139%, respectively. The SFCs of IL-4 secretion of Th2 type cytokine were also enhanced by 67%. Immune effect of different sizes of PLA-PS microspheres demonstrated that the secretion level of IL-2 for 400 nm microspheres was 1.68 times to the counterparts of 900 nm microspheres. Key words: polylactic acid microsphere; protamine sulfate; adjuvant; membrane emulsification

Chemo-enzymatic Synthesis of Lipopeptide Surfactants from Fish Scale Collagen and Their Application in Enhanced Oil Recovery

LIU Xiang-yu ZHANG Gui-feng ZHANG Yu-fei; WANG Ping; SU Zhi-guo MA Guang-hui ZHANG Song-ping

. 2013, 13(4):  654-661. 

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Fish scale collagen was hydrolyzed by alkaline protease Protex 6L or 6 mol/L HCl to obtain peptides with the hydrolysis rate of 0, 5%, 10% and 100%. The peptides were then acylated with oleoyl chloride, lauroyl chloride, decanoyl chloride or benzoyl chloride to prepare 16 lipopeptide surfactants with different hydrophilic and hydrophobic groups. The measured results of emulsion index (E24) showed that the synthesized surfactants had stronger emulsifying capacity, such that E24 of 500 mg/L oleoyl peptide (hydrolysis rate 5%) reached to 60%, while the maximal E24 value of chemical surfactant sodium dodecyl benzene sulfonate (SDBS) was only about 20%. Lipopeptides also showed much higher crude oil removal capacity than SDBS. Oleoyl peptide (hydrolysis rate 10%) and lauroyl peptide (hydrolysis rate 10%) of pH 11.0 could wash about 35% of crude oil from oil sand within 20 min at 40℃ and 150 r/min shaking, while the oil removal rate with SDBS was less than 10%. The results of sand pack column experiments showed that injection of oleoyl peptide (hydrolysis rate 10%) or lauroyl peptide (hydrolysis rate 10%) after water flooding could significantly enhance oil recovery, additional oil recovery rate after surfactant flooding reached 52.35% and 41.18%.

Preparation of Biodegradable Porous PELA Nanoparticles with Phase Separation and Solvent Extraction

SUN Chao NA Xiang-ming SU Zhi-guo MA Guang-hui WANG Qi-bao GAO Fei

. 2013, 13(4):  662-668. 

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Monomethoxy-poly(ethylene glycol)-b-poly-DL-lactide (PELA) nanoparticles were fabricated by phase separation and solvent extraction. The optimum particles were obtained by using ethanol and acetone as the oil phase and deionized water as the aqueous phase at PELA concentration in oil phase 6.5 g/L, ethanol concentration in oil 50(j), SDS concentration in water phase 10 g/L and volume ratio of oil to water 1:6, respectively. The average particle size was 78.48 nm. The forming mechanism of such nanoparticles was first discussed based on such a formation procedure. Porous nanoparticles were further prepared by solvent swelling and controlled evaporation. A hollow structure with single hole in the surface was obtained by toluene as the solvent, while that a multi-cell structure and porous surface by dichloromethane, the swelling time was 0.5 h. Besides PELA, poly(lactic acid) and poly(lactic-co-glycolic acid) nanoparticles with similar morphology were also prepared by similar procedures. The degradation performance of porous PELA nanoparticles with simulated body fluid showed that the adequate degradation was achieved after 30 d.

Regulating Effect of Coenzyme on Biosynthesis of Vincristine in Catharanthus roseus Cell Suspension Culture

CHEN Wen GUO Zhi-gang

. 2013, 13(4):  669-674. 

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To study the regulating effect of coenzyme on biosynthesis of antitumor alkaloid vincristine, five kinds of coenzyme were added at different concentrations. The regulating mechanism was analyzed. The results showed that adding different coenzymes independently resulted in the increase of vincristine biosynthesis. The optimal adding concentrations were confirmed. Based on the results of coenzyme one-factor experiments, five factors four levels orthogonal experiments were designed. The optimal concentration combination obtained was 1.0 mmol/L DL-thioctic acid, 1.5 mmol/L vitamin B1, 3.0 mmol/L flavin mononucleotide, 3.0 mmol/L adenosine triphosphate, and 3.0 mmol/L lysine. The highest vincristine accumulation reached 0.217 mg/g dry weight. It was the first time for successful biosynthesis of vincristine in Catharanthus roseus cell suspension culture.

Analysis of Metabolites from Direct Fermentation of D-Glucose to 2-Keto-L-Gulonic Acid by HPLC

WEI Piao-piao MI Yu-zhen LI Qiang

. 2013, 13(4):  675-680. 

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An HPLC-based method for quantitative determination of the 4 metabolites of gluconic acid (GlcA), 2-keto-D-gluconic acid (2-KDG), 2,5-diketo-D-gluconic acid (2,5-DKG) and 2-keto-L-gulonic acid (2-KLG) from direct fermentation of D-glucose to 2-KLG by using HPLC was established. The optimum separation of the 4 substances could be achieved under the conditions of using Aminex HPX-87H column (size 300 mm ′7.8 mm) with the temperature of 30℃, sulfuric acid (50 mmol/L) as mobile phase at the flow rate of 0.2 mL/min, RID-10A detector, and malonic acid as internal standard. The analytical results show that the method has average analytical deviation of 1.53%, 0.89% and 1.84% on 2-KDG, 2,5-DKG and 2-KLG, respectively.

Enhanced Expression of D-Hydantoinase and N-Carbamoyl-D-Amino Acid Amidohydrolase in Sinorhizobium

CUI Ming-xin SUN Jia-jia LI Qiang

. 2013, 13(4):  681-686. 

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A recombinant plasmid pBBR1MCS-5-lac-CH was constructed based on pBBR1MCS-5 vector by combining the D-Hase and D-Case genes with a polycistronic structure under the control of lac promoter. After it was successfully transformed into the Sinorhizobium (Sino 416) and fermented for 24 h at 30℃, its total enzyme activity was increased about 2 times over the wild strains without induction. In order to reduce the glucose effect in Sino 416, the lac promoter was replaced by lacUV5, and the ribosome bind site optimized as well. The results show that the total enzyme activity could reach 0.5 U/mL by using of the recombinant plasmid, which is almost 4 times of that of the wild strains.

Isolation and Nitrogen Removal Characteristics of an Efficient Alkalophilic Aerobic Strain Denitrifier

GUO Yan ZHOU Xue-mei YANG Mao-hua LI Yu-guang YANg De-hui ZHOU Wei XING Jian-min;

. 2013, 13(4):  687-692. 

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An alkalophilic aerobic denitrification strain BMEN1 was screened from alkali plant sludge. According to the biochemical and physiological characteristics and sequence analysis of 16S rRNA gene, strain BMEN1 was identified as Pseudomonas stutzeri and named as P. stutzeri BMEN1. The aerobic denitrification-relevant genes napA, nirK, norB and nosZ were noted in P. stutzeri BMEN1. The optimal temperature and pH value for aerobic denitrification were 37℃ and 9.0, and the available carbon sources were sodium succinate, sodium acetate and glucose. Under the optimum conditions, nitrogen (NO3--N) removal rate of P. stutzeri BMEN1 reached up to 52.92 mg/(h×OD), and in the experiment of synthetic absorbed solution of flue gas, it could quickly remove away about NO3--N 140 mg/L and NO2--N 140 mg/L within 16 h. These results suggested that P. stutzeri BMEN1 was a potential efficient aerobic strain denitrifier.

Improvement on the Cheap Culture Medium for Scenedesmus dimorphus Based on Elemental Concentrations of Cell

WANG JIng-jing XUE Sheng-zhang CONG Wei ZHANG Xu

. 2013, 13(4):  693-697. 

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An elemental balance approach between culture medium and biomass composition is used to redesign BG11 culture medium, the main nutrients in the modified culture medium are KH2PO4 32 mg/L, MgSO4×7H2O 32 mg/L, (NH4)2SO4 22.4 mg/L, CaCl2×7H2O 8 mg/L, and FeSO4 2.6 mg/L. The results show that Scenedesmus dimorphus almost has the same initial growth curve in the modified and BG11 culture media, and the final volumetric yield of lipid is 0.407 and 0.403 g/L, respectively, in the case of reducing the cultivation cost to 33%~50%, Scenedesmus dimorphus in the modified and BG11 culture media almost obtains the same lipid yield.

材料工程专栏

Preparation and Characterization of PtNi-supported Graphene DMFC Cathode Electrocatalyst

ZHANG Dong-tang CHENG Chang WANG Xia-yan XIA Ding-guo

. 2013, 13(4):  698-703. 

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Graphene supported PtNi nanoparticles as DMFC cathode were fabricated by one-step approach with H2PtCl6 and NiCl2 as precursors in a microfluidic system assisted with ultrasonic irradiation, and characterized. PtNi nanoparticles were uniformly dispersed on the graphene sheet while polyvinylpyrrolidone (PVP) was used as capping agent, and ultrasonic irradiation applied. The anchored PtNi nanoparticles had a narrow size distribution and an average size of 2.1 nm. The content of Pt was 25.5%(w) which was measured by ICP-AES. The mass activity at 0.7 V (vs., NHE) of the prepared PtNi/graphene electrocatalyst was -107.6 mA/mg which was 2.8 times higher than the commercial Pt/C (-37.9 mA/mg), which indicated good electrocatalytic activity of PtNi/graphene toward oxygen reduction reaction.

Carbothermal Reduction and Nitridation Mechanism of VN Prepared by V2O5

WANG An-ren CHEN Li-ping ZHANg Qing-chun

. 2013, 13(4):  704-709. 

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The reduction and nitridation mechanism for preparation of VN with V2O5 as raw material and carbon powder as reductant was studied, the effects of mass ratio of C to V2O5 and temperature were examined, and the products analyzed. The results show that the reduction of V2O5 is successive, and indirect reduction occurs along with direct reduction. When the mass ratio of C/V2O5 is 28%, the nitrogen content in products is maximum. From 800 to 1000℃, carbonization reaction takes place, and the product is VC1-x. From 1000 to 1200℃, carbonization and nitridation reactions take place simultaneously, and the main phase is V(C,N). When the temperature is higher than 1300℃, V(C,N) is transformed gradually into VC1-x with the increase of temperature, the nitrogen content decreases and the vanadium content increases, the products will agglomerate even fuse each other and are composed of spherical particles with the average diameter of 1 mm. Using the above process to prepare VN, the nitrogen content of products can reach more than 17%, vanadium content more than 79%, and carbon content less than 2%, and the apparent density is about 3.5 g/cm3 which accords with national standard.

Mechano-chemical Synthesis and Catalytic Dehydrogenation Process of Ca(AlH4)2

GAO Chao QIAN Zhang-xin LIU Dong-ming

. 2013, 13(4):  710-714. 

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The reaction mechanism in mechano-chemical synthesis of Ca(AlH4)2 and the effects of F-containing compounds (K2TiF6, KBF4, TiF3 and NbF5) on the dehydrogenation process of Ca(AlH4)2 were investigated. It was found that the synthesis process of Ca(AlH4)2 from LiAlH4 and CaCl2 could be divided into two steps, LiAlH4 reacted with CaCl2 to form an intermediate phase LiCa(AlH4)3, and LiCa(AlH4)3 further reacted with CaCl2 to form Ca(AlH4)2. The addition of F-containing compounds could effectively improve its dehydrogenation property, and K2TiF6 exhibited the best catalytic effect, with the dehydrogenation temperatures in the first two steps of Ca(AlH4)2 reduced by 39 and 66℃, respectively. The F-containing additives could react with Ca(AlH4)2 during the ball-milling or subsequent heating process, and the generated substances improved the dehydrogenation property of Ca(AlH4)2.

综述

Advances in Methods for Enhancing Formation Process of Gas Hydrate

ZHANG Xue-Min LI Jin-ping WU Qing-bai WANG Chun-long JIAO Liang

. 2013, 13(4):  715-720. 

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Research advances in promotion technology of gas hydrate formation process are comprehensively reviewed, the status of reinforcing methods is summarized, and their relative merits are analyzed. The results show that the existing research of reinforcing methods was confined in hydration reaction process itself, and these methods such as stirring, bubbling and adding chemical additives could promote the formation process and shorten the induction time of hydrate formation. However, the formation process of hydrate is a complicated hydration reaction process with heat and mass transfer. The existing research has failed to accurately reveal the process mechanism. It is necessary to establish growth model of hydrate by putting the influential factors such as temperature, pressure, size of the object, state of water and degree of agitation into consideration, and accurately reveal the promoting mechanism of hydrate formation process. Finally, existing problems and future research direction in promotion of gas hydrate formation process are also pointed out.