CIESC Journal

Progress of thermodynamics and kinetics of gas hydrate formation

SUN Changyu;HUANG Qiang;CHEN Guangjin

2006, 57(5): 1031-1039.

Abstract ( 633 )

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Complex thermodynamics and kinetics problems are involved in the gas hydrate formationThis paper reviews the research progress of hydrate thermodynamic models and kinetics mechanisms.In the thermodynamic aspect, phase equilibrium models based on isothermal adsorption theory (van der Waals-Platteeuw model) and double-process hydrate growth mechanism(Chen-Guo model)are emphasized,and the research progress of the hydrate structure and its transition are presented.Kinetics mechanisms for hydrate nucleation, including cluster nucleation from liquid and interfacial nucleation, and hydrate growth after nucleation are also introduced.The measurement techniques for hydrate at microscopic, mesoscopic, and macroscopic level are provided which can be used to improve the development of thermodynamics and kinetics models and connect the microscopic with macroscopic domainsThe important aspects for future hydrate formation research are discussed.

Research advances in bioreactors and bioprocesses for biodesulfurization of petroleum

LI Yuguang, LI Wangliang, XING Jianmin, LI Xin, LIU Huizhou

2006, 57(5): 1040-1047.

Abstract ( 644 )

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The development of bioreactors and bioprocesses for biocatalytic desulfurization of petroleum distillates in recent years are reviewed.The progress of several bioreactors, including stirred-tank reactors, airlift reactors, emulsion-phase contactor and fluidized bed reactors is introduced in detailIn addition, the development trend of various bioreactors and processes for the biodesulfurization of fuels is briefly described.The commercialization of biodesulfurization，problems to be resolved and future research are forecasted.

Monte Carlo simulation of adsorption of random copolymers at solid-liquid interface

SUN Lei, PENG Changjun, LIU Honglai, HU Ying

2006, 57(5): 1048-1054.

Abstract ( 766 )

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The Monte Carlo simulation method was used to simulate the adsorption of random copolymers on the solid/liquid interface.The microstructure information of adsorbed layer, such as adsorbed segment profile and distribution of sizes of various adsorption configurations, and the macrostructure information, such as total segment and segment density profiles, bound fraction, surface coverage, adsorption amount and adsorption layer thickness were obtained.In this work, the effect of attractive segment content f and its energy was investigated.It was shown that there were mostly smaller trains and smaller loops near the interface, but the distribution of loops configuration was wider.Small loops increased rapidly with increasing attractive segment content, and the distribution of train configuration became wider.As f and adsorption energy increased,bound fraction, surface coverage and adsorption amount also increased, but the thickness of adsorbed layer decreased.

Predictions of thermodynamics parameters based on first-principle force field methods

SUN Huai, WU Chuanjie, LI Xiaofeng, DAI Jianxing

2006, 57(5): 1055-1063.

Abstract ( 656 )

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The feasibility of using all-atom, first-principle force fields to predict thermodynamic properties was discussed.A newly developed TEAM force field was used to calculate fluid densities, vaporization enthalpies, heats of mixing, Henry’s law constants, and vapor pressures for representative molecules in various thermodynamic states.The force field was validated by using the thermodynamic data of gas and liquid phases, and then used to make predictions without any empirical adjustment.Initial results indicated that predictions of liquid densities and vaporization enthalpies were successful.The results comparable with experimental measurements could be obtained at extended state points.The prediction of heats of mixing required very high accuracy in evaluating cohesive energies for pure fluids,and the calculation of Henry’s law constants was extreme sensitive to fluid densities.Both required high quality of the force fields parameters.In order to calculate the vapor pressures and liquid-vapor coexistence densities effectively with the all-atom force fields,a new iterative procedure based on integration of the Clausius-Clapeyron equation was proposed.

Analysis of thermodynamics in synthesis of methanol from biomass-derived syngas

FU Yan, LU Hao, CHANG Jie, WANG Junfeng

2006, 57(5): 1064-1068.

Abstract ( 830 )

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The synthesis of methanol from biomass-derived syngas is a complicated reaction system.The dependence of reaction heats and equilibrium constants of each reaction in the system on temperature were obtained.Biomass-derived syngas was simulated with the gas consisting of CO 21.5%, CO₂ 22.8%, H₂52.5%, and N₂ 3.2%.The equilibrium composition, carbon equilibrium conversion rate and methanol concentration were calculated at 473.15—553.15 K，3—6 MPa with the equilibrium constants methods.The computing results revealed that methanol was mainly produced from CO+H₂ in the system.Lower temperature and higher pressure favored the promotion of carbon equilibrium conversion rate and methanol concentration.Commercial catalyst C306 was used to verify the calculation result.Because the reaction was controlled by thermodynamics and kinetics, at 3 MPa carbon conversion rate reached the peak at 533.15 K and was close to the carbon equilibrium conversion rate.Space time yield (STY) of methanol and concentration of methanol in the liquid product increased with increasing pressure.

Measurement and correlation of solubility of 2-amylanthraquinone and 2-ethylanthraquinone in mixed solvents

LIU Chunxue, MI Zhentao, WANG Li, WANG Yaquan

2006, 57(5): 1069-1072.

Abstract ( 707 )

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solubility;solid-liquid equilibria;2-amylanthraquinone;2-ethylanthraquinone

Numerical simulation and research of fluid flow and heat transfer in the shellside of rod baffle heat exchanger with longitudinal flow of shellside fluid

DONG Qiwu, LIU Minshan, ZHAO Xiaodong

2006, 57(5): 1073-1078.

Abstract ( 615 )

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In the paper, the rod baffle heat exchanger with longitudinal flow of shellside fluid is simplified according to its structural characteristic and the periodic unit duct model is established.By employing commercial CFD software FLUENT, the numerical simulation of models for different media,at different Reynolds numbers and different rod-baffle pitches was carried out.The results were analyzed and compared to obtain the detailed characteristics of fluid flow and heat transfer in the duct and the optimal range of rod-baffle pitch values, which provides some reference for the research and application of heat exchanger with longitudinal flow of shellside fluid.

Coupled processes of chemical reaction, heat and mass transfer in non-thermal equilibrium porous medium

LI Mingchun, TIAN Yanwen, ZHAI Yuchun

2006, 57(5): 1079-1083.

Abstract ( 689 )

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A mathematical model describing the coupled processes of endothermic chemical reaction, heat transfer and mass transfer in porous media was established by using the assumption of local thermal non-equilibrium, which was required when the local thermal equilibrium between the fluid and solid phases broke down.The Ergun-Forchheimer-Brinkman model was used to represent the fluid flow within the porous media.An alternate dimension implicit method was adopted to solve this model numerically and the mathematical model was validated by comparing the numerical results with the experimental data in literature.The gas temperature fields, porous matrix temperature fields, the concentration fields of product gas as well as the distribution of the fractional conversion of solid reactant were obtained by changing various parameters.The results show that, the temperature difference between gas and porous matrix can not be neglected.The velocity in porous media at entrance,gas temperature at entrance and particle size were the important parameters which influenced significantly the reactive characteristics of the porous system.The results are useful in the conceptual design and operation of fixed reactor involving intense endothermic reactions.

Efficiency analysis of latent heat storage module with internal fluid flow

ZHANG Haifeng, GE Xinshi, YE Hong

2006, 57(5): 1084-1088.

Abstract ( 742 )

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Based on the analysis and mathematical solution of a latent heat storage module with internal fluid flow, several factors, including the dimensional characteristics of the module, the Peclet number, the Stefan number and the thermal conductivity of the phase change material (PCM), are investigated, and the ways to improve the systematic efficiency are also suggested.From the analysis of a typical module, in which water serves as the heat exchange medium and paraffin serves as the PCM respectively, the principal factor is to enhance the heat transfer inside the PCM.

Theoretical study of plate falling film absorber with film-inverting configuration

CUI Xiaoyu, LI Meiling

2006, 57(5): 1089-1094.

Abstract ( 618 )

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Plate falling film absorber with film-inverting configuration is a new kind of absorber that combines plate falling film absorption and film-inverting technique.By analyzing the fluid flow，heat and mass transfer processes in the absorber，a theoretical mathematical model was established.The control equation of the model was transformed by the flow function， discretized by the finite difference method， and used to numerically solve the case of lithium bromide solution falling film absorbed by using the TDMA algorithm.Comparison and analysis were made between the calculated result of the film-inverting plate falling film absorber and that of a same length vertical plate falling film absorber.It was shown that the newly developed absorber had better performance than the traditional plate falling film absorber under the same boundary and inlet conditions.

Influence of flute depth of spirally fluted tube on heat transfer and flow resistance performance of water cooler for turbo-generator stator

YUAN Yichao, MA Youfu, LIU Yuzheng, LI Jingfen

2006, 57(5): 1095-1101.

Abstract ( 663 )

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The characteristics of heat transfer and flow resistance of highly efficient water cooler which is composed of spirally fluted tubes and rod-baffles have close relation with its structure parameters.Experimental study on the influence of the flute depth of spirally fluted tube on heat transfer and flow resistance performance of the water cooler for turbo-generator stator was carried out.It was shown from the results that: the effect of shell side flow velocity on heat transfer coefficient was greater than that of tube side flow velocity, which meant that heat resistance on shell side was greater than that on the tube side.Hence, more attention should be paid to enhancement of heat transfer on the shell side in order to improve heat transfer performance of water cooler.Within the range of Reynolds number in this experiment, the flute depth of spirally fluted tube had a great effect on heat transfer coefficient of water cooler.A deeper flute led to higher heat transfer performance at the cost of increased flow resistance.At last, based on the experimental results, the correlations of heat transfer and flow resistance for water coolers with different structures were obtained.

CFD simulation of fluid flow and heat transfer in channels of plate-fin heat exchangers

ZHU Yinhai;LI Yanzhong

2006, 57(5): 1102-1106.

Abstract ( 726 )

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A computational fluid dynamics (CFD) program FLUENT was used to predict the fluid flow and heat transfer in channels of the plate-fin heat exchangers with plain fins and serrated fins.The calculation results indicated that the local coefficients of heat transfer for both cold and hot fluids in the heat exchangers with either plain fins or serrated fins had the maximum values at the entrance.The local coefficients of heat transfer and local pressure values for both cold and hot fluids changed abruptly at each staggered face of serrated fins.The thickness of boundary layer on serrated fins was thinner than that on plain fins.Both the local coefficient of heat transfer and pressure drops of fluids in the heat exchanger with serrated fins were larger than those in the heat exchanger with plain fins.

Simulation of mass and heat transfer in new phosphoric acid tower with circular water wall（Ⅰ）Model development

LIU Baoqing;JIANG Jialing

2006, 57(5): 1107-1113.

Abstract ( 587 )

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To avoid the energy waste in the production of furnace grade phosphoric acid, a new phosphoric acid tower with circular water wall was designed, which could recover waste heat to produce superheated steam.A three dimensional mathematical model of phosphorus combustion in the new phosphoric acid tower was developed by incorporating the k-ε turbulence model, eddy dissipation turbulent combustion model and P-1 radiation heat transfer model.The streamline field distribution, temperature distribution and species concentration distribution were predicted by numerical simulation.The results showed that phosphorus combustion mainly took place in the injection zone of atomized phosphorus,and the maximum combustion temperature and exit temperature were 1790 K and 970 K respectively which conformed well to practical data.

Simulation of mass and heat transfer in new phosphoric acid tower with circular water wall（Ⅱ）Analysis of influence on heat transfer

LIU Baoqing;JIANG Jialing

2006, 57(5): 1114-1119.

Abstract ( 887 )

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The effects of parameters on maximum combustion temperature, smog exit temperature, maximum wall heat flux, averaged wall heat flux of a new phosphoric acid tower with circular water wall were discussed, including phosphorus consumption, excess-air coefficient, wall temperature and radiation absorption coefficient, with the mathematical model developed in Part Ⅰ.The predicted results showed that maximum combustion temperature, smog exit temperature, maximum wall heat flux and averaged wall heat flux would increase with increasing phosphorus mass flow rate when excess-air coefficient or air flow rate was constant.Under the condition of constant phosphorus mass flow rate, the smog exit temperature would increase slowly while other parameters would decrease with increasing excess air coefficient.Wall temperature had a remarkable effect on smog exit temperature, whereas its effect on other parameters was not obvious.In addition, radiation absorption coefficient had a remarkable effect on maximum combustion temperature and maximum wall heat flux in the new phosphoric acid tower.

Staggered oriented ridges micromixer based on chaotic advection

YANG Huayong, RUAN Xiaodong, FAN Yurun, LIU Sufen, FU Xin

2006, 57(5): 1120-1126.

Abstract ( 608 )

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A novel static micromixer was proposed which was designed according to the characteristics of mixing liquids on the micro-scale.The device was fabricated on glass substrates using wet-etching technique.By applying a steady axial pressure gradient, staggered oriented ridges arranged periodically in the microchannel could generate transverse and three dimensional flow.Chaotic advection was induced in the microchannel,and then stretched and folded material interface and enhanced fluid mixing.The computational fluid dynamics(CFD)method was used to analyze the chaotic mixing in the micromixer.Red dye mixing experiments were carried out to visualize the development of mixing process and the performance in the micromixer.Experimental investigation demonstrated that the design enhanced mixing at both low and high Reynolds number.

Influence of blood perfusion and metabolic heat generation on cryosurgery

HE Qiong;ZHAO Gang

2006, 57(5): 1127-1132.

Abstract ( 748 )

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The influences of blood perfusion and metabolic heat generation on the distributions of the temperature and the thermal gradient, and on the growth of the frozen region are studied by using the commercial FEA (finite element analysis) software-Ansys (Version 7.0).The target tissue is treated as non-ideal material freezing over a temperature range, and the thermophysical nonlinear problem is solved.The enthalpy method and the finite element scheme are applied to solve the multidimensional phase change problem in cryosurgery.The results indicate that, when the source term composed by blood perfusion and metabolic heat generation are taken into consideration, the temperature around the cryoprobe is apparently higher than that of the case without consideration of the source term at the corresponding time, and furthermore, the maximal radius of the ice ball during the whole process of cryosurgery is also markedly decreased.So the vitro experiments will do little to optimize the process of cryosurgery or the design of a cryoprobe, the corresponding vivo experiments should be performed instead.The results are very meaningful for controlling and optimizing the practical cryosurgery.

Attrition experiment and gray relational analysis of quartzite particles as medium material in fluidized bed

WANG Hui, JIANG Xiumin, LIU Jianguo, YUAN Dequan

2006, 57(5): 1133-1137.

Abstract ( 654 )

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Referring to some problems in industrial devices,the attrition of quartzite particles at various operational parameters in a hot fluidized bed was investigated.The experiment was designed by using the orthogonal method and carried out with various initial average particle sizes,bed temperatures,fluidization numbers and bed material heights.The extent of influence of operational parameters on attrition was sequenced by means of gray relational analysis as follows: initial average particle size>bed temperature>fluidization number>bed material height.

Two-phase multipliers characteristics of slotted orifice

GENG Yanfeng, FENG Shuchu, ZHENG Jinwu

2006, 57(5): 1138-1142.

Abstract ( 699 )

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The metering principle of slotted orifice as a new type of flow sensor for gas-liquid two-phase flow is briefly introduced.The interaction mechanism between two-phase flow and slotted orifice was analyzed in detail.Various factors that affected the two-phase multipliers were investigated based on the theoretical model and experimental data.Based on the surface-fitting technique a precise correlation was obtained, which described the relationship among the two-phase multipliers, pressure, gas Froude number and Lockhart-Martinelli parameter.Such information is important for the development of condensate gas meter.

Spouted pressure drop of double nozzle rectangular draft tube spouted bed

ZHANG Shaofeng;WANG Shuhua;ZHAO Bin;LIU Yan;ZHAO Jianbo

2006, 57(5): 1143-1146.

Abstract ( 797 )

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Spouted pressure drop was one of important parameters in the design and application of spouted bed.In this paper spouted pressure drop of a new double nozzle rectangular draft tube spouted bed was studied.A 120 mm×240 mm cross section double nozzle rectangular stainless steel spouted bed was used to investigate the effects of flow rate,particle diameter,bed height,draft tube diameter and height of entrainment zone on maximum spouted pressure drop.Maximum spouted pressure drop increased with increasing flow rate, increasing particle diameter and increasing height of entrainment zone.Maximum spouted pressure drop increased and then decreased with increasing draft tube diameter.Maximum spouted pressure drop was hardly affected by bed height.By regression of experimental data,the correlation of maximum spouted pressure drop with the above parameters was obtained.

Self-diffusivity of benzene in zeolite Y:different jump diffusion mechanisms investigated by KMC simulations

ZHANG Zhou;LIU Hui;CHEN Biaohua

2006, 57(5): 1147-1152.

Abstract ( 747 )

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Kinetic Monte Carlo (KMC) simulations of self-diffusivities of benzene in zeolite Y were performed for three possible jump diffusion mechanisms of the diffusant, and the corresponding dependence of self-diffusivity on loadings and temperature was investigated.It was demonstrated that different jump mechanisms resulted in significantly different temperature and concentration dependence relationships of self-diffusivity in zeolite Y.It was found and verified by comparison with literature data that S_Ⅱ-W-S_Ⅱ cage to cage jump was the dominant mechanism for diffusion of benzene in zeolite Y, while W-W jump played no role in the process.In this case, simulated temperature and concentration dependence relationships were closer to the experimental results than that predicted by the other two mechanisms.

Experimental studies and modeling of kinetics for methane hydrate formation with THF promoter in bubble column

LUO Yantuo;ZHU Jianhua;CHEN Guangjin

2006, 57(5): 1153-1158.

Abstract ( 753 )

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The kinetics of CH₄ hydrate formation with the presence of hydrate promoter THF was studied in a transparent bubble column.The effects of gas flow rate, temperature, pressure and volume fraction of hydrate on formation rate were measured.Based on the Chen-Guo hydrate formation mechanism, by using the simplified Gibbs free energy change of quasi-chemical reaction to form basic hydrate,-ΔG/RT, as the driving force, a kinetic model which took account of system temperature, pressure and specific gas-liquid interfacial area was established.The model was used to calculate the consumption rate of CH₄and the predicted results were in agreement with the experimental data.The experimental results and the kinetic model in this work would be helpful to designing commercial hydration reactor and optimizing operation conditions.

Photocatalytic oxidation performance and kinetics of simulated organic wastewater in circulating slurry photocatalytic reactor

ZHANG Dongxiang;ZHANG Lingyun;LI Hansheng

2006, 57(5): 1159-1165.

Abstract ( 721 )

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The technique of photocatalytic oxidation was used in the treatment of simulated wastewater with benzamide as a model pollutant.The photocatalytic oxidation performance and kinetics of the simulated organic wastewater in a circulating slurry photocatalytic reactor was investigated.The effects of operation conditions, such as dosage of photocatalyst, illumination time, initial benzamide concentration, pH value, anions and cations in wastewater, on the photocatalytic oxidation performance were discussed.The results showed that the application of photocatalytic oxidation to the treatment of wastewater was feasible and efficient, but it was affected by the operation conditions.There existed optimum value of the dosage of catalyst, initial benzamide concentration and pH value for the photocatalytic oxidation performance.H₂PO^-₄,Cl^-, Cu²⁺ and Al³⁺ showed obvious inhibition to the photocatalytic oxidation.Compared with the results obtained from a stirred slurry reactor and a bubble column slurry reactor, the circulating slurry photocatalytic reactor provided not only excellent blend of catalysts and reactants, but also high efficiency of UV light.It could increase the throughtput of treatment and reduce the dosage of catalyst.The kinetics study of the photocatalytic oxidation with different photocatalyst loadings and initial concentrations showed that the photocatalytic degradation rate followed pseudo-first order kinetics with respect to benzamide concentration,and the surface reaction rate constant (k₀)and adsorption equilibrium constant(K_TiO2) of TiO₂ catalyst were 0.0279 min^-1 and 17.99 L•g^-1 respectively.

Stability of performance of ANAMMOX reactors and assessment criteria

JIN Rencun;HU Baolan;ZHENG Ping;CHEN Xuliang

2006, 57(5): 1166-1170.

Abstract ( 738 )

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The stability of performance of anaerobic ammonium oxidation (ANAMMOX) reactors was studied and the indices of performance stability were compared.The results showed that under different types of shock load, the reactors with different configurations displayed different stability.The biofilm reactor stood first in stability towards substrate shock load, followed by anaerobic sequencing batch reactor (SBR) and the granular sludge bed.And the biofilm reactor took the first place towards hydraulic shock load, followed by the granular sludge bed and SBR.The three ANAMMOX reactors were more tolerant to hydraulic shock load than to substrate shock load.When different kinds of stability assessment indices(i.e., sensitivity ratio, mean variance ratio and derivative regression function) were used, inconsistent assessment conclusions were reached.It was suggested that the mean deviation ratio and derivative regression function were more effective and universal.

Selective flotation mechanism sodium chloride particle with dodecylmorpholine

ZHANG Wanping;SONG Xingfu;LI Xiaosong;YU Jianguo

2006, 57(5): 1171-1176.

Abstract ( 606 )

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The flotation behavior of dodecylmorpholine for sodium chloride particles in saturated brine was investigated.The results showed that NaCl particles improved the flotation ability of dodecylmorpholine by increasing the stability of bubbles.The result of infrared spectroscopy showed that the interaction between DMP molecule and NaCl particle was physical adsorption.The adsorption behavior of DMP on NaCl particle surface and the contact angle of NaCl particle surface were investigated.The results showed that the flotation mechanism of DMP with NaCl particle was that the dodecylmorpholine molecules adsorbed on NaCl particle surface by hydrophobic force in saturated brine medium while did not adsorb on carnallite（KCl•MgCl₂•6H₂O）particle surface due to repulsive hydration.NaCl particle was floated selectively in froth flotation because bubbles were adhered on NaCl particle by hydrophobic force with DMP molecule adsorbed on the interface of bubble.

Determination of competitive adsorption isotherms of tryptophan enantiomers by inverse method

CHENG Ming;LI Shuang;ZHANG Fengbao;ZHANG Guoliang

2006, 57(5): 1177-1181.

Abstract ( 932 )

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Competitive adsorption isotherm data for two enantiomers of tryptophan, in which the stationary phase was silica-immobilized bovine serum albumin(BSA) and the mobile phase was a phosphate buffer,were measured by using the inverse method.The competitive bi-Langmuir isotherm model(Fisher coefficient is 1769.07, R²=0.9997) and equilibrium-dispersive model were selected by comparison of the experimental results and the interaction mechanism.The corresponding parameters were obtained by simulating the chromatogram of racemic mixture at 2×10^-4 mol•L^-1 and 10^-3 mol•L^-1.The results showed good agreement between the isotherm determined by the inverse method and the adsorption data (Fisher coefficient is 119.32, R²=0.9973) which confirmed the validity of the model selected.

Inactivation of E.coli in carbon dioxide under elevated pressure

WU Yin;YAO Shanjing;GUAN Yixin

2006, 57(5): 1182-1186.

Abstract ( 603 )

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E.coli cells were inactivated remarkably by carbon dioxide under elevated pressure.The process can be divided into two stages based on the rate of inactivation: the rate of inactivation was slow at the early stage and increased sharply at the latter stage.The dissolution of CO₂ in the aqueous solution and then diffusion into cells controlled the time and inactivation rate at the early stage.An increase of pressure and temperature enhanced the antimicrobial effect of CO₂ under pressure.Inactivation was accelerated by low pH in the initial environmental condition.Inactivation was affected by agitation and release of pressure, which suggested that the diffusion rate of CO₂ was the key factor dominating the antimicrobial effect of CO₂ under pressure.E.coli cells at the exponential phase were more susceptible to elevated pressure CO₂ treatment.

Optimization of P450 BM-3 activity produced by gene engineering strain by response surface methodology

LU Yan;MEI Lehe;LU Yuefei;SHENG Qing;YAO Shanjing

2006, 57(5): 1187-1192.

Abstract ( 641 )

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Factorial design and response surface techniques were used to design and optimize the process to increase P450 BM-3 activity produced by gene engineering strain.Initially, Plackett-Burman design was used to evaluate the process variables which were relevant to the production of P450 BM-3.Four statistically significant parameters for response were selected and utilized in order to optimize the process.With the 416C model of hybrid design, response surfaces were generated, and P450 BM-3 activity was increased to 57.9×10^-3Uml^-1 from 37.6×10^-3Uml^-1 by the best combination of the physicochemical parameters at optimal levels of 0.12 mgL^-1 FeCl₃, inoculum volume of 2.1%, induction at OD₅₇₈=1.1, and 6 h of induction.

New process for canthaxanthin synthesis

YANG Zehui;CHEN Xinzhi;QIAN Chao

2006, 57(5): 1193-1197.

Abstract ( 882 )

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A new process for selective catalytic oxidation of β-carotene was proposed.Optimum oxidation conditions were determined by uniform test design and simplex optimization.β-Carotene was synthesized from 3-methyl-5-(2,6,6-trimethyl-1-cycolhex-en-1-yl)-1,3-pentadienylphosphonates and 2,7-dimethyl-2,4,6-octatriene-1,8-dial with a yield of 68%.Proper catalytic oxidation conditions were: β-carotene 6.8 g, compounded catalyst 0.45 g, dichloromethane 250 ml, saturated sodium hypochlorite 50 ml and reaction temperature -5℃.Carbon dioxide was used to maintain a weak acidic system.The process was completed in 40 min.Purification of β-carotene and canthaxanthin was made by recrystallization.

Mechanism of microwave-enhanced extraction of dihydromyricetin from Ampelopsis grossedntata

ZHENG Cheng;YANG Ling;CHEN Jianhui

2006, 57(5): 1198-1203.

Abstract ( 836 )

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In this paper, the ultrastructure destruction of Ampelopsis grossedntata cell in the process of microwave-assisted solvent extraction was studied.In a series of conditions of differential microwave irradiation strengths and times through the MARS5, the cell wall of Ampelopsis grossedntata leaves were observed with transmission electron microscope.The results showed that with the increase of microwave output power and irradiation time,increasing disruption of cellular structures were found when irradiation time and microwave irradiation strength reached 5 min and 300 W respectively or microwave irradiation time and irradiation strength reached 2 min and 600 W respectively.This is the cause of enhancement of extraction of dihydromyricetin from Ampelopsis grossedntata by microwave.

Influence of microwave irradiation on structures of tapioca starch

XIONG Jian;YE Jun; WANG Qian

2006, 57(5): 1204-1208.

Abstract ( 669 )

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The time-temperature profiles of open or sealed tapioca starch systems with different moisture contents subjected to microwave processing were established and the multi-level structures of tapioca starch after irradiation were investigated.For both open and sealed systems, the lower the moisture content in tapioca starch,the faster the temperature rose, and isothermal transformation occurred in the starch samples.The time of isothermal transformation became longer with the rise of moisture content.Moreover, the interval lengths of isothermal transformation were also more obvious with the samples irradiated in open beakers as compared to those irradiated in sealed beakers.FTIR data suggested no new functional groups on the molecular chain of starch irradiated by microwave, only the infrared crystalline indices of the starch samples slightly decreasing.After irradiation, microscope (or polarizing microscope) data indicated that the crystal structure of the tapioca starch changed, but its morphologic structure remained unchanged.It was believed that tapioca starch food irradiated by microwave is safe for human being and other creatures.

Purification of soybean isoflavones from soybean whey with macroporous resin

JING Legang;ZHANG Yongzhong

2006, 57(5): 1209-1213.

Abstract ( 991 )

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In order to purify isoflavones by column chromatography from soybean whey，the discarded by-product in the production of soybean protein isolate,the adsorption and desorption characteristics of four kinds of macroporous resins for isoflavones were comparatively investigated.D4006 resin was chosen as the adsorbent.Before column chromatography, the soybean whey was ultrafiltrated and extracted with ethyl acetate to remove protein and other components.The sample containing isoflavones was passed through a column(φ30 mm×800 mm) packed with D4006 resin at the flow rate of 1 ml•min^-1 at 25℃.The concentration of isoflavones in the sample was 1 mg•ml^-1.The volume of the sample was 2.67 liters per liter resin.After adsorption, the resin was gradient-eluted by using aqueous ethanol solution (from 20% to 95% ethanol, by volume) at the flow rate of 1 ml•min^-1 at 75℃.The eluate was vacuum-distilled to remove ethanol and water, and then was vacuum-dried to obtain a solid product.Under these conditions, a product with 72.5% of soybean isoflavones determined by HPLC was obtained.

Formation of ozone and NO_x during corona discharge radical shower

WU Zuliang;GAO Xiang;LUO Zhongyang;NI Mingjiang;CEN Kefa

2006, 57(5): 1214-1219.

Abstract ( 746 )

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The formation of ozone and NO_x during corona discharge radical shower has important effect on NO oxidation and energy consumption.How the geometric structure,number and placement direction of nozzle electrode affected the formation of ozone and NO_x during corona discharge was studied.The results showed that increasing nozzle radius and number of nozzles could expand corona region and strengthen discharge intensity.Ozone concentration increased obviously with increasing nozzle radius and number of nozzles.However, overly-larger nozzle radius and too many nozzles might lead to corona shield phenomena, which decreased discharge current and ozone concentration.In this experiment φ3(14) nozzle electrode was considered the best.Increasing number of nozzles only increased maximum ozone concentration.However,the energy efficiency of NO conversion in the reactor would not be improved by increasing number of nozzles because NO conversion depended on ozone formation.Ozone was produced more with vertical nozzle electrode than with horizontal nozzle electrode.NO_x concentration was lower during corona discharge with different geometry nozzle electrodes, less than 15 μl•L^-1.

Kinetics of graft copolymerization of acrylamide onto cassava starch in a five-component system of inverse emulsion

SHANG Xiaoqin, TONG Zhangfa, LIAO Dankui, HUANG Zuqiang, ZHANG Youquan, ZHENG Cheng

2006, 57(5): 1220-1224.

Abstract ( 567 )

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The kinetics of graft copolymerization in a five-component system of inverse emulsion, starch/monomer/emulsifier/water/oil, was investigated with cassava starch and acrylamide (AM) as the raw material, ammonium persulfate as the initiator and a mixture of two kinds of surfactants (Span-80 and OP-4) as the emulsifier.The rate orders of graft copolymerization with respect to the concentration of initiator, monomer, starch and emulsifier were determined.In the polymerization process,termination of fast chain and termination of slow chain existed at the same time.The effect of the concentration of the individual components in the polymerization system on conversion were investigated.The results showed that the dependence of the polymerization rate Rp on the concentration of components in the polymerization system could be expressed for all four components by the following equation: R_p∝［I］^0.93［M］^1.28［St］^1.47［E］^0.61.The overall activation energy for the polymerization process was 82.01 kJ•mol^-1 at 35—55℃.Based on the experimental results, some aspects of the polymerization mechanism were discussed.

Effect of hydrogen on mechanical properties and failure morphology for stainless steel weld overlay cladding

ZHONG Manying;XU Jian

2006, 57(5): 1225-1230.

Abstract ( 578 )

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The effect of high temperature and pressurized hydrogen on the mechanical properties and failure morphology for stainless steel weld overlay cladding of 309L and 347L，in the original specimens and the specimens thermally charged with hydrogen was investigated.The results of slow strain rate testing (SSRT) indicated that：ⅰ) Fracture stress and plasticity decreased obviously after thermal charging with hydrogen：ⅱ)For the original specimens the fracture of both smooth and notched specimens occurred in the 347L region (except the specimen with notch in 309L region)，but if the specimens were thermally charged with hydrogen the fracture occured in the 309L region (except the specimen with notch in the 347L region).After thermally charging with hydrogen the fracture stress dropped from 885MPa to 478MPa for 309L and from 799.9MPa to 564MPa for 347L respectively.The characteristics of low frequency fatigue with short-crack was also investigated.The propagation rates(da/dN) in three stages and the conditional threshold value (ΔJ_th) of the fatigue crack was calculated.The results showed that the ΔJ_th of specimen after thermally charging with hydrogen dropped obviously while the da/dN of specimen increased.In addition，the fracture morphology of SSRT and different crack propagation mechanism of low frequency fatigue in three propagation stages were observed with SEM.

Infrared spectrum of aluminate solutions with collector

YU Haiyan;BI Shiwen;ZHAI Xiujing;YANG Yihong;YAN Chuanwei

2006, 57(5): 1231-1235.

Abstract ( 775 )

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Organic constituents in the sodium aluminate solution，which is the important intermediate material of the Bayer process,change evidently because of trace amount long fatty acid collector adsorbed onto bauxite concentrates entering into the Bayer process.The effects of long fatty acid collector on the structure of sodium aluminate solution was studied with plastics sheets attached water as the background of infrared spectrum.The results showed that the characteristic peaks of sodium aluminate solution was distinct.The Al—O—Al bond peak intensity increased and the Al(OH)^-₄ bond peak intensity was constant with increasing content of the collector PS.The peak intensity of Al—O—Al vibration and AlOH antisymmetric vibration was stronger in α_k=1.56，ρ_Na2O=160 g•L^-1 solution than that in α_k=3.0，ρ_Na2O=220 g•L^-1 solution.

Data mining technology in novel method for synthesis of sodium aluminium carbonate hydroxide

WU Hongte;SONG Baoling;SUN Yabo;HUANG Zhongyang;WEI Yiping;LIAO Sen

2006, 57(5): 1236-1241.

Abstract ( 691 )

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A novel method for synthesis of sodium aluminium carbonate hydroxide was studied, and the target product was obtained with aluminium sulfate as aluminium source and PEG-400 as template via the one step low heat solid state reaction.Uniform experimental design and data mining technology were applied,and the synthesis tests were made with reference to the results of data mining technology.The characterization of XRD indicated that the product was NaAl(OH)₂CO₃ with size of 4.9 nm.The composition and the particle size of the prepared sodium aluminium carbonate hydroxide were optimized in the study at the same time to get the pure nano-crystals of sodium aluminium carbonate hydroxide.

Preparation and photocatalytic performance of TiO₂-pillared montmorillonites treated by ultrasonic and pressure

NA Ping;ZHANG Haiyan

2006, 57(5): 1242-1246.

Abstract ( 633 )

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TiO₂-pillared montmorillonite catalysts were synthesized by the sol-gel method and then treated by ultrasonic and pressure.The catalysts were characterized by XRD，FT-IR and TEM，and the results indicated that all the TiO₂-pillared montmorillonite contained anatase-like TiO₂ particles between silicate layers of montmorillonite.The efficiency of phenol degradation under ultraviolet light with TiO₂-PILM were tested，and the effects of phenol initial concentration and pH value on the efficiency of photocatalytic degradation of phenol were studied.The results indicated that the catalyst treated by ultrasonic and pressure showed higher photocatalytic activity.The efficiency of phenol degradation was higher at initial phenol concentration of 10—20 mg•L^-1，TiO₂-PILM dosage of 1 g•L^-1 and pH value of 3—5.

Co-solubility of binary low-molecules in polyethylene

YAO Wenjuan;HU Xiaoping;YANG Yongrong

2006, 57(5): 1247-1250.

Abstract ( 847 )

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Solubility data for the ternary system ethylene/iso-pentane/PE and ethylene/n-hexane/PE were determined for PE crystallinity 48.6% at temperatures of 70—90℃ and pressures up to 2MPa with the partial pressures of iso-pentane 80—190 kPa and those of hexane 20—90 kPa.Compared with the solubility data of the binary system, the effects of the ternary system were discussed with respect to the partial pressure of the second component and temperature.It was shown that as the results of dilation and interaction between low-molecules, the presence of iso-pentane or n-hexane gave rise to an increase in the solubility of ethylene whereas the presence of ethylene decreased the solubility of iso-pentane or n-hexane.The higher the partial pressure of the second component, the more the impact on the solubility of the first one.The impact increased with decreasing temperature and increasing partial pressure of the first component.The solubility of ethylene in the ternary system could be described by Henry’s law whichwas similar to the binary system. Flory-Huggins model was satisfactory for fitting solubility data of both iso-pentane and n-hexane, especially the former.

Synthesis of trimethylsilyl methylcellulose and oxygen-enriching properties of membranes

ZHANG Ziyong;WU Xinhua

2006, 57(5): 1251-1254.

Abstract ( 731 )

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To improve oxygen-enriching properties of cellulose derivative membranes, trimethylsilyl methylcellulose (TMS-MC) with degree of substitution (DS) of 1.12 was synthesized by using methylcellulose with DS of 1.80 as raw material and hexamethyldisilazane as reactant in a homogeneous reactive system.The chemical structures of TMS-MC were characterized with FT-IR and ¹H NMR.The product samples were fairly soluble in ordinary organic solvents such as tetrahydrofuran, chloroform, xylene, toluene, and so on.The gas separation membranes were prepared by casting a xylene solution of TMS-MC on a sheet of PET.It was found that the oxygen permeation properties of the TMS-MC membrane were improved and an obvious increase in separation factor was obtained especially.Comparing with methylcellulose, for example, the permeability coefficient and separation factor of the TMS-MC membrane increased from 2.5 Barrer and 2.41 to 23.85 Barrer and 5.42 at 20℃, respectively.

Technique of saving oil and reducing exhaust emission by rare earth materials enhanced free radical

HUANG Lirong;JIN Zongzhe

2006, 57(5): 1255-1258.

Abstract ( 694 )

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The free radicals •H,•OH,•O are important active intermediates in catenarian oxidation reaction,which favor mixing and burning of fuel vapor, consequently fuel can be saved.After diesel oil was activated by rare earth materials, the signal of hydroxylic radical became stronger.The more electrons and negative ions were produced by rare earth materials, the stronger the signal of hydroxylic radical was.The test on diesel oil that activated by rare earth materials was conducted in an engine.The results showed that diesel oil consumption rate was reduced by 0—8%,and CO,NO₂, NO exhaust emission was reduced by 6%—30%.

ZnO and metal hydroxides as flame-retardants and smoke suppressants for flexible poly(vinyl chloride)

QU Hongqiang;WU Weihong;JIAO Yunhong;XU Jianzhong

2006, 57(5): 1259-1263.

Abstract ( 699 )

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ZnO and metal hydroxides as flame-retardants and smoke suppressants for flexible poly(vinyl chloride) were studied.The thermal degradation in air of flexible PVC treated with flame-retardants ZnO and metal hydroxides was studied with differential thermal analysis and thermogravimetry from ambient temperature to 1073 K.The kinetic parameters were obtained by using the equation of Kissinger, Broido and Vyazovkin.Their mechanisms were studied through comparing the thermal behavior with the flame retardant properties of the samples.The results showed that the flame retardant properties of the samples treated with ZnO and metal hydroxides were related to the thermal behavior of the samples.Metal hydroxides enhanced the activation energy of degradation and the flame retardant properties of the samples through endothermic dehydration.ZnO might act in the condensed phase as a Lewis acid.