CIESC Journal

Multidiscipline and process integration of nonaqueous biocatalysis

WANG Zhilong

2005, 56(4): 563-569.

Abstract ( 617 )

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When compared to their chemical counterparts, the peculiar properties of biocatalysts, such as high selectivity, reaction under mild conditions and environmental benefit, have made biocatalysis a broad and growing field of biotechnology. It is often constrained by some obstacles, such as limited substrate accessibility to biocatalysts because of the low aqueous solubility of most organics, inhibition or toxicity of both substrate and product affecting the biocatalysts,and further degradation of products. Biocatalysis in nonaqueous solvent and in situ product removal are powerful tools to overcome these limits. The development of these techniques is reviewed. The microbial transformation of sterol in the cloud point system, a novel two-phase partitioning bioreactor developed recently by the authors,as an example of highly integrated process of biocatalysis in nonaqueous solvent and in situ product removal techniques is introduced.Based on the discussion of nonaqueous biocatalysis industry involving the characteristics of integrated process and multidisciplinary, nature of the development of nonaqueous biocatalysis industry is recommended.

Determination of heat capacity of deltamethrin at lowtemperature and its thermochemical properties

XUE Bin, WANG Jianya, TAN Zhicheng, WU Tonghao, ZHENG Zhuo, CHEN Huilin

2005, 56(4): 570-573.

Abstract ( 678 )

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The heat capacity of deltamethrin in the temperature range from 80 to 400 K was measured with a precise automatic adiabatic calorimeter.The sample was prepared with the purity of 0.9926 molar fraction. A solid-liquid fusion phase transition was observed in the experimental temperature range.The melting point, Tm, enthalpy and entropy of fusion, ΔfusHm,ΔfusSm, were determined as(372.15±0.02)K，(26.73±0.02)kJ·mol^-1，(71.81±0.06)J·K^-1·mol^-1 respectively.The thermodynamic functions data of deltamethrin,H_(T)-H_(298.15) ,S_(T) -S_(298.15) , and G_(T) -G_(298.15) , were reported with a temperature interval of 5 K in the temperature range of 298.15 to 400 K.The sample was measured with the DSC method and compared with the calorimetric method.The thermal decomposition of the sample was studied by TG analysis.The order of reaction n, pre-exponential factor A and activation energy E, were 1.78, 1.15×10⁹min^-1 and 603.8 kJ·mol^-1, respectively.

Note on mechanism of gas-liquid interfacial mass transfer of absorption processes

MA Youguang;YU Guocong

2005, 56(4): 574-578.

Abstract ( 748 )

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The concept of interfacial non-equilibrium during mass transfer between gas and liquid was presented to explain the mechanism of interfacial mass transfer in which the driving force of gas-liquid interphase mass transfer was considered coming from the non-equilibrium.Based on the general chemical potential driving force equation, a concentration corrrelation between two phases at interface was derived and solved at different bulk liquid concentrations in the absorption process.The computational results showed that the interfacial concentration of absorbed component on the liquid side was strongly affected by a dimensionless number Yo and was also dependent on bulk concentration.The CO₂ interfacial concentration on the liquid side in stationary absorption by pure methanol, ethanol and n-propanol absorbent respectively were measured by using micro laser holographic interference technique to validate the model proposed.The experimental values were in good agreement with the calculated ones.

Enhancement of gas-liquid mass transfer of reactive slurry

CAI Wangfeng, LI Xia, XU Chunjian, ZHOU Ming

2005, 56(4): 579-586.

Abstract ( 697 )

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The three-zone enhancement model, after investigating the enhancement of gas absorption on solid dissolution, was developed for the absorption systems with complex reactions between absorbed gas and dissolved particles existing in the liquid film zone. Enhancement of absorption rate was measured at different solid hold-up and stirring intensity in a batch stirred vessel for the SO₂-Mg(OH)₂ system.It was found that particle size, slurry hold-up, ‘inert zone’thickness, and partial pressure of transported gas showed major influences on the absorption enhancement.The model results with the consideration of ‘inert zone’ near gas-liquid interface and corrected by apparent viscosity agreed with experimental data well.

Hybrid CFD and crunode meshwork method for estimating structured packing column efficiency

GU Fang;LIU Chunjiang;YUAN Xigang;YU Guocong

2005, 56(4): 587-592.

Abstract ( 705 )

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Misdistribution of gas and liquid flow is a familiar phenomenon occurred in structured packing columns and is the main reason for the decrease of mass transfer efficiency. But there is still no published research work in investigating this effect by numerical method. In this paper, a computational fluid dynamic (CFD) model for predicting the hydrodynamics of gas flow in the structured packing is presented, which associated with the boundary condition about the interface shear stress of gas and liquid. Combined the CFD model of gas phase, the crunode meshwork model of the liquid phase given in literature and some classical mass-transfer theories, a hybrid CFD method for predicting the mass transfer efficiency for metal sheet corrugation structured packing is presented. Comparing the simulated results with the experimental data, a good agreement is shown. The method presented in this paper provides a new notion for the quantitative research of mass transfer process for structured packing columns.

Hydrodynamic performance of trapezoidal-rectangular solid series mass-transfer tray

DU Peiheng;DONG Yanhe;WANG Rongliang;HUANG Jing

2005, 56(4): 593-597.

Abstract ( 650 )

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Based on the new-vertical-sieve-tray,some reform on tray structure was made to develop a new kind of apparatus-LLC-Tray.Some improvements in pressure drop of tray, operating flexibility, capacity of production, entrainment ，etc, were observed.The basic hydrodynamics of multi-cover system,such as dry-pressure-drop, wet-pressure-drop and entrainment were measured and relevant correlations were obtained.

Shell-side heat transfer and pressure drop of shell-and-tube heat exchangers with overlap helical baffles

WANG Qiuwang, LUO Laiqin, ZENG Min, WANG Liang, TAO Wenquan, HUANG Yanping

2005, 56(4): 598-601.

Abstract ( 594 )

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The shell-side pressure drop and heat transfer performance of shell-and-tube heat exchangers with overlap helical baffles were studied experimentally in comparison with those of traditional segmental baffles heat exchangers.The influences of inserted dummy tubes and helical angles were investigated in detail. It was found that the presence of dummy tubes deteriorated the overall heat transfer performance of heat exchangers with helical baffles.The shell-side pressure drop and heat transfer coefficient decreased with the increase of helical angle at indentical shell-side mass flow rate, and both of them were lower than those of the corresponding segmental-baffle heat exchangers. The shell-side heat transfer coefficients for the helical-baffle heat exchangers were higher than those of the segmental-baffle heat exchangers at the identical shell-side pressure drop.

Numerical simulation of irreversibility due to forced convection in entrance region of duct

WU Shuangying;LI Yourong;ZENG Danling

2005, 56(4): 602-607.

Abstract ( 792 )

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The irreversibility due to laminar forced convection in the entrance region of a duct was studied by means of numerical simulation.Local entropy generation distributions and total entropy generation were obtained based on the entropy generation equation. The effect of Reynolds number on the irreversibility was studied for constant wall temperature and heat flux.The results showed that the irreversibility in the entrance region was different from that in the fully developed region.Reynolds number had a strong effect on the irreversibility in the entrance region.The entropy generation caused by temperature difference was relatively dominant over that caused by viscous flow.The irreversibility at constant wall temperature was different from that at constant wall heat flux.

Continuous adsorption water chiller with novel design

LIU Yanling;WANG Ruzhu;XIA Zaizhong

2005, 56(4): 608-613.

Abstract ( 821 )

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The paper proposes an adsorption refrigeration system using silica gel and water as working pair with novel design. In this system, the adsorber, condenser and evaporator are housed in one vacuum chamber, forming an adsorption refrigeration unit. Two such units work alternatively to supply cooling continuously. The construction, parameters of the adsorber, condenser and evaporator and characteristics of the cycle are given.The experimental results demonstrate that the mass recovery process can significantly improve the cooling capacity and COP. The effects of evaporating temperature and cooling water inlet temperature on chiller performance are analyzed.Comparison of the novel system and conventional ones demonstrates that the novel system has a higher performance than the conventional ones with heat recovery process if the problem of cooling loss can be resolved.

Model calculation and analysis of heat and mass transfer of air and water in direct contact counter flow

SONG Yaozhen

2005, 56(4): 614-619.

Abstract ( 648 )

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Based on reasonable model hypotheses and the energy analysis of heat and mass transfer of air and water in a direct contact counter flow, a set of general equations that can describe the internal relationship between the state parameters of air and water and dimensionless parameters of transfer process are given. A method utilizing MATLAB to solve these general equations is also proposed.Calculations and analysis with the model of a cooling- dehumidifying process give a consistent result with that of previous experiment.A new method for designing equipment such as evaporating cooler and cooling tower, and for analyzing experiment data of heat and mass transfer of air and water in a direct contact counter flow can be derived from this study.

Second-order moment two-phase turbulence model for dense gas-particle flows

YU Yong;CAI Feipeng;ZHOU Lixing;SHI Mingxian

2005, 56(4): 620-626.

Abstract ( 635 )

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A second-order moment two-phase turbulence model for dense gas-particle flows (USM-Θ model), combining the unified second-order moment two-phase turbulence model with the kinetic theory of particle collision, was proposed. The interaction between gas and particle turbulence was described by using the transport equation of two-phase velocity correlation.The proposed model was used to simulate gas-particle flows in a horizontal narrow channel.Simulation results and their comparison with the experimental results showed that the predictions accounting for both particle turbulence and particle-particle collision were obviously better than those accounting for only particle turbulence or only particle-particle collision.

Effect of liquid viscosity on hydrodynamic behavior in inverse three-phase turbulent bed

CAO Changqing;LIU Mingyan;WANG Yiping;QIN Xiuyun;HU Zongding

2005, 56(4): 627-631.

Abstract ( 633 )

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Local phase holdups in an inverse three-phase turbulent bed of 150 mm i.d. and 4350 mm height were measured simultaneously by micro-electrical conductivity probe technique in this study.The experiments were carried out with polyethylene particles (d_p=4.01 mm, ρ_s=926 kg•m^-3),air, and water［0.05%(mass)SCMC, 0.20%(mass)SCMC］ as solid phase,gas phase and liquid phase respectively.540 sets of experimental data of local phase holdups in radial direction were obtained under U_g=U_g3. It was found that the distribution of local solid holdup showed a maximum peak at r/R=(0.75—0.90). The range of maximum peaks was larger than that of conventional fluidized beds. The distribution of local gas holdup in radial direction showed a maximum value at the column center and a minimum value near the wall.Moreover,the non-homogeneous distribution of local gas holdup in radial directions was more evident than that of conventional fluidized beds.The different operation regimes as well as the corresponding three specific gas velocities (U_g1,U_g2 and U_g3) were obtained on the basis of the axial distribution characteristics of cross-sectional average solid holdups.The effect of the operating conditions (liquid viscosity, initial volume fraction of solids H_s0/H₀, initial liquid height H_l0) on the specific gas velocities was presented.

Numerical simulation and experimental study of flow field in axial flow fixed bed

ZHONG Siqing, CHEN Qingling, CHEN Zhiqiang, TONG Haiying, CHEN Yihua, XU Yihan

2005, 56(4): 632-636.

Abstract ( 536 )

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The computational fluid dynamics model with porosity and drag coefficient was used to describe fluid flow in an axial flow fixed bed according to the characteristics of fluid flow in the fixed-bed of the reactor. The commercial computational fluid dynamics (CFD) code CFX was used to simulate the flow field in the axial flow fixed bed.The simulation predictions are in good agreement with experimental results of a large cold model. The influence of gas distributor on the flow field in the axial flow fixed bed was studied. A suitable gas distributor was used to attain less than 0.06 kPa radial pressure difference and less than 5.2％ radial velocity difference in fixed bed.

Global kinetics of reaction accompanied by partial internal wetting of catalysts

ZHOU Zhiming;CHENG Zhenmin;LI Zhuo;YUAN Weikang

2005, 56(4): 637-641.

Abstract ( 639 )

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The global reaction rate of benzene hydrogenation to cyclohexane accompanied by partial internal wetting of catalyst pellets was measured by a new method, which investigated both adsorption and chemical reaction.The adsorption investigation was used to establish a relationship between the extent of liquid filling of the catalyst and the bulk conditions while the chemical reaction investigation was to study the effect of partial internal wetting of the catalyst on the global reaction rate.It was shown that the extent of liquid filling in the catalyst interior showed a significant effect on the global rate, and the current state of the catalyst depended on the history, i.e. whether it was a liquid evaporation process or a vapor condensation process, and two steady states were found under certain circumstances.A mathematical model was developed, which took multicomponent diffusion, chemical reaction, pore size distribution of the catalyst and capillary condensation of condensable components in the catalyst pellet into consideration.The predicted values were in good agreement with the experimental data.

Preparation and evaluation of desulfurization catalysts for homogeneous catalytic oxidation of straight-run diesel

TANG Xiaodong;LIU Liang;SHUI Leilei

2005, 56(4): 642-645.

Abstract ( 574 )

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Large investment, high operating cost and severe operation condition exist in the technology of diesel hydrodesulfurization,and the technology of H2O2 oxidative desulfurization of diesel has such problems as high oxidizer cost, oxidizer not regenerable, and treatment of sour water.A new catalytic oxidative desulfurization method for straight-run diesel is presented in this paper.In order to produce low-sulfur diesel, the sulfide in diesel oil was oxidized and converted into sulfone-polar sulfide with homogeneous catalysts and air oxidizer,and then removed by extractant.The homogenous catalysts were prepared by compound decomposition.The catalysts selected could dissolve in diesel at a given temperature and separate out at a lower temperature.The effects of catalytic oxidation of zinc benzoate, manganese benzoate and manganese phthalate were tested.The desulfurization effect of zinc benzoate and manganese benzoate was much better and the sulfur content of the desulfurized diesel met the standard of EuⅡdiesel (＜300μg•g^-1).

Fault detection and diagnosis in continuous dynamic multivariable processes using independent component analysis

HE Ning, XIE Lei, GUO Ming, WANG Shuqing

2005, 56(4): 646-652.

Abstract ( 604 )

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A chemical process has a large number of measured variables, which are usually driven by fewer latent variables. The latent variables are extracted by using independent component analysis (ICA) and monitored to detect the fault.According to the situation of alarm limit violations of independent components, the diagnosis of faults is reduced to a string matching problem. The proposed method is data driven and any training data or a process model is not required. It was evaluated by the application to the Tennessee Eastman challenge process and its effectiveness was demonstrated.

Modeling fermentation process based on hybrid support vector machines-kinetics mechanism

XU Guang;YU Huanjun;TAO Shaohui;CHEN Dezhao

2005, 56(4): 653-658.

Abstract ( 670 )

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Support vector machines(SVM) based on structural risk minimization（SRM）is used to model batch fermentation process by considering the complexity and the problem of severe non-linearity in fermentation process.The model based on SVM was featured by less complexity and better prediction ability than that based on artificial neural networks(ANN).The hybrid support vector machines(HSVM) model was proposed by combing SVM with fermentation kinetics mechanism in serial and serial-parallel approaches and used to predict the state of biomass in fermentation.The mechanism analysis and the simulation results showed higher prediction accuracy, more powerful generalization ability and better performance of these two kinds of HSVM in modeling than those based on black-box SVM, simple and approximate kinetics model and the corresponding hybrid ANN.

Fault isolation and identification approach in principal component subspace

WANG Haiqing, JIANG Ning

2005, 56(4): 659-663.

Abstract ( 764 )

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Principal component analysis (PCA) has found wide application in chemical process monitoring and product quality control as a data-driven modeling method.Based on the fault reconstruction technology, the fault isolation and identification issues were explored by using T² index, since some faults involving process fault and sensor fault that do not violate the dominant process relation described by the PCA statistical model could only be detected by T² index.The theoretical conditions of isolatability and identifiability were obtained.The acquired results were then illustrated and verified by monitoring a simulated double-effect evaporator (DEE) process, where 10 different faults were studied.

Sensor monitoring and online measurement correction in electric capacitance tomography system

ZHANG Huiliang ;RONG Gang

2005, 56(4): 664-667.

Abstract ( 573 )

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The recalibration of electrical capacitance tomography (ECT) system is one of the key problems in keeping the system running steadily.However, for engineering application in solids/gas transport,online calibration can not be implemented and the data from this sensor may be unreliable due to the sensor pipe interior wall abrasion during pneumatic transport,so the solids concentration calculated from the reconstructed image based on these data will be highly inaccurate.The simulations show that, the inter-electrode relative capacitance variation of electrode pair spacing 1 is the most sensitive to the abrasion of sensor pipe interior wall, so this relative capacitance variation when the sensor is filled with air can be used as an indicator demanding offline system recalibration when the wall abrasion goes significant.Furthermore, while the pipe interior wall abrasion is not very serious, online correcting measured inter-electrode capacitance with wall capacitance variation can improve the accuracy of concentration calculation.

Evaluation of anti-fouling performance for ion-rod water treater with automatic dynamic simulator of fouling

SUN Lingfang, YANG Shanrang, QIN Yukun, XU Zhiming

2005, 56(4): 668-671.

Abstract ( 626 )

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The application of a novel Automatic Dynamic Simulator of Fouling (ADSF) to evaluate the effectiveness of ion-rod water treater is reported.The effects of some parameters of the water treater were studied with an ADSF made according to patented technology, and orthogonal experimental design was adopted with the use of artificial hard water.Experimental results validated that the ion-rod water treater could mitigate fouling，and the anti-fouling efficiency varies with the test conditions.The anti-fouling efficiency of treater increased with the increase of flow velocity in the range of 0.8—1.2 m•s^-1 and output voltage in the range of 7500—15000 V.The efficiency weat up initially, and then went down with the increase in hardness.The rough surface of ion-rod was superior to the smooth one.The order of influence on treater performance with respect to these factors was as follows: water hardness, roughness of surface, flow velocity and output voltage.The research also provided a guide to improving the performance of ion-rod water treater.

Purification and properties of chitinase from Metarhizium anisopliae

YANG Ge;CHEN Hongzhang;LI Zuohu

2005, 56(4): 672-676.

Abstract ( 832 )

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A fungium-producing chitinase was isolated from the dead body of Anisopliae. A chitinase was isolated from the culture of Metarhizium anisopliae and purified to electrophoretic homogeneity by the steps of ammonium sulfate precipitation,DEAE-cellulose and hydrophobic interaction column chromatography. Its molecular mass was estimated to be about 61.5 kD by SDS-PAGE,and 57.14 kD by mass spectroscopy.The isoelectric temperature and pH of the enzyme activity were 55 ℃ and 6.0 respectively.The isoelectric point was 4.02.Its N-terminal sequence was VIGPAAPL. The carbohydrate content was 56.2% by the phenol-sulfuric acid method. Michaelis constant of the enzyme was 14.5 μmol•L^-1.The enzyme activity was stable under 45 ℃ and in the pH range of 3.0—9.5. The activity was enhanced by Zn²⁺、Ca²⁺、Ba²⁺ and Mn²⁺,and was strongly inhibited by Hg²⁺、Co²⁺ and Fe²⁺.EDTA also inhibited the activity.Ser was the possible essential residue for enzyme activity.

Kinetics of non-catalyzed decomposition of fructose in high temperature liquid water

CAI Lei;LV Xiuyang;HE Long;XIA Wenli;REN Qilong

2005, 56(4): 677-680.

Abstract ( 956 )

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The kinetics of non-catalyzed decomposition of fructose in high temperature liquid water was studied at temperatures from 453.15 K to 493.15 K and under pressure at 10 MPa.The main products of fructose decomposition were glucose, formic acid, acetic acid, levulinic acid, furfural and 5-hydroxymethyl furfural,etc.The evaluated energy of activation of fructose decomposition was 126.16 kJ•mol^-1.In addition, the effects of temperature and reaction time on the yield distributions of 5-hydroxymethyl furfural were investigated.Selective decomposition of fructose in high temperature liquid water was possible.

Metabolic network modeling and metabolic flux analysis of production of novel bioflocculant REA-11

HE Ning;LI Yin;CHEN Jian

2005, 56(4): 681-688.

Abstract ( 647 )

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Metabolic flux analysis (MFA) was used to study the relationships among different metabolic pathways in the fermentation of Corynebacterium glutamicum CCTCC M201005.Metabolic network models were established to study the fermentation behavior under different fermentation stages and different dissolved oxygen tension (DOT) levels in batch fermentation.The effects of metabolic node on REA-11 secretion were evaluated.In addition, the supply and consumption of energy and reducing equivalent in cell metabolism were analyzed as well.The results showed that the flux of Phosphate-pentose Pathway (PP) was maintained at a high level during the whole fermentation process, indicating PP played a key role in the metabolism of C. glutamicum CCTCC M201005. The flux of REA-11 decreased when DOT increased, whereas cell synthesis flux showed a reverse trend.Increase of ATP flux stimulated cell growth but decreased REA-11 production.

Effects of water content on simultaneous purification of PC and PE by alumina column chromatography

SI Chaoyong;WU Sufang;XU Haidan;LV Xiuyang

2005, 56(4): 689-693.

Abstract ( 696 )

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The effects of initial water content in alumina and water content of mobile phase on the simultaneous purification of phosphatidyl choline(PC) and phosphatidyl ethanolamine(PE) by alumina column chromatography were studied systematically.The results showed that the initial water content in alumina had great influence on the purification process, but only little changes could be seen for the water content of mobile phase within the experiment range.Baseline separation and higher recovery of PC could be reached at 8%(mass) initial water content in alumina and 0.1%—1.1%(vol) water content of mobile phase.The recovery of PC was more than 90% and the recovery of PE over 40%.Explanation and discussion of the results were given.In addition, reproducibility of the experiments was tested. Not only could the work give some guides in the preparation of high purity PC and PE, but also it would be very helpful in R&D of other natural products.

De-emulsion after diesel oil biodesulfurization

MA Ting, LEE Kyngho, WANG Renjing, LI Guoqiang, LIANG Fenglai, LIU Rulin

2005, 56(4): 694-698.

Abstract ( 704 )

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There exists three-phase (diesel oil/bacteria cell/aqueous phase)O/W emulsion after diesel oil biodesulfurization(BDS).For commercial application,the emulsion must be de-emulsified to yield diesel oil after BDS.In fact, this is the last process of BDS.Several de-emulsifiers applicable to this three-phase O/W emulsion,such as several typical water-soluble de-emulsifiers, methanol, ethanol, and the Rhodococcus sp. pellets which can desulfurize diesel oil were tested.Ethanol was the best, and the de-emulsification mechanism with different de-emulsifiers was discussed. 4% ethanol, as a de-emulsifier could separate oil by centrifuge because of its strong surfactivity, high hydrophilic property and appropriate density.The diesel oil recovery could be increased by centrifugal separation from 60% to almost 100%.GC-MS analysis showed ethanol addition for de-emulsification did not affect the composition of alkenes.It was also noted that the pellets of DS-3 centrifuged showed the same growth rate and dibenthiophene desulfurization activity as the original bacteria, so they could be re-used as desulfurization biocatalyst.

Nitrogen removal from high nitrogen soybean wastewater by simultaneous nitrification and denitrification via nitrite

GAO Dawen;PENG Yongzhen;WANG Shuying

2005, 56(4): 699-704.

Abstract ( 673 )

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An innovative technology for nutrient removal from high nitrogen soybean wastewater was developed by controlling dissolved oxygen(DO) concentration in sequencing batch reactor (SBR). The experimental results showed that when DO concentration was maintained at 0.5 mg•L^-1 during aeration， nitrosation rate (NO^-₂-N/NO^-_x-N) was always more than 93% during nitrification, and ammonia removal via simultaneous nitrification-denitrification was up to 87.6% when aeration was ended. So nitrification-denitrification via nitrite and simultaneous nitrification-denitrification (SND) were achieved in a single reactor by controlling DO concentration at 0.5 mg•L^-1. Based on theoretical analysis and calculations of the new technology, the specific growth rate of ammonium oxidizers was about 2.22—2.43 times than nitrite oxidizers at DO=0.5 mg•L^-1, and the anoxic area for denitrification was easily built in activated sludge in the DO condition.In conclusion,stable nitrogen removal from wastewater by simultaneous nitrification-denitrification via nitrite at normal temperature could be achieved so long as DO was controlled at 0.5 mg•L^-1.

Effects of cathode channel design on air-breathing PEMFC

WANG Ying;LI Xiangyi;KE Jian

2005, 56(4): 705-710.

Abstract ( 557 )

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With emphasis on the influence on the performance of air-breathing PEMFC (proton exchange membrane fuel cells) by various channel widths and rib widths, a coupled model was developed.In this model,natural convection in the channel and porous media was included, and concentration over potential was considered as a result of limited supply of oxygen in the catalyst layer.From the calculation, water and species distribution, temperature profile and polarization curves were simulated for the variation of cathode rib width and channel width. Results from the model indicated that concentration loss was more serious in natural convection than in forced convection, especially at a small channel opening size.The performance of air-breathing PEMFC could be improved by increasing channel opening size to some extent.Solid temperature, channel size and air flow rate interacted with each other, and the performance could not be improved infinitely by increasing channel size， and thus cathode flow field should be optimized.This work is useful for optimizing channel configuration.

Preparation and its properties of biodiesel by using solid base catalyst

LI Weimin, ZHENG Xiaolin, XU Chunming, XU Ge, WU Guoying

2005, 56(4): 711-716.

Abstract ( 662 )

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Hydrotalcite was prepared by co-precipitation of magnesium and aluminum nitrate solution.After calcination, the hydrotalcite was converted to Mg-Al composite oxides.The transesterification of rapeseed oil was carried out by using treated Mg-Al composite oxides as catalyst.Through orthogonal analysis, the optimum reaction conditions obtained for the transesterification were set at temperature 65 ℃, mole ratio of methanol to rapeseed oil 6∶1, reaction time 3 h, and catalyst dosage 2% (on rapeseed oil mass).The yield of fatty acid methyl ester (biodiesel fuel) was 95.7%.The fluidity of the biodiesel fuel at low temperature was much better than that of No.0 diesel fuel and the flash point was as high as 170 ℃ with a sound oxidation stability.Other principal physicochemical properties of the biodiesl fuel were similar to that of No.0 diesel fuel.The biodiesel fuel could be blended with No.0 diesel fuel at any ratio.

Effect of operation parameters on desulfurization rate of hydropyrolysis of high sulphur coal

ZHANG Guojie;ZHANG Yongfa;XIE Kechang

2005, 56(4): 717-719.

Abstract ( 583 )

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An orthogonal experiment design was adopted for studying the macroscopic reaction kinetics of sulfur removal of high sulphur coal hydropyrolysis.The experimental data of reaction desulfurization rate were analysed by margin and variance analyses.The optimal sulphur removal reaction conditions were recommended.

Surface character of pyrolytic carbon black

YANG Yongrong, WANG Jingdai, YAN Lihong

2005, 56(4): 720-726.

Abstract ( 720 )

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The recycled pyrolytic carbon black(PC) from used tyre was obtained by atmospheric pyrolysis with a small degree of aggregation,small surface area,and a lot of ashes and carbonaceous deposits. The PC was modified by a series of chemical treatment with nitric acid and nitric acid/stearic acid. Inverse gas chromatography was used to assess the consequence of the modifications. In particular, inverse gas chromatography at infinite dilution was shown to detect essentially the most active sites, and allows monitoring of the variation of surface properties upon chemical modifications of the PC. Inverse gas chromatography at finite concentration was used to characterize the surface energy site distribution.There are many structural defects on pyrolytic carbon black and the surface energy is heterogeneously distributed. In conclusion, nitric acid could decrease the surface carbonaceous deposits, and make more active sites. The retreatment of pyrolytic carbon black with stearic acid would, on one hand, diminish the particle-particle interactions and hence facilitate the dispersion of the filler in the natural rubber matrix and, on the other hand, enhance the compatibility between filler and matrix leading to better mechanical performance of the composite.

Affecting factors of shrinkage and warpage of thin-wall injection molding process

DONG Binbin;SHEN Changyu;LI Qian

2005, 56(4): 727-731.

Abstract ( 963 )

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Communication and electronic products have been developing towards the design concept of being light, thin, short and small.To acquire the maximal internal space for parts to be packed closely into the product, one way is to reduce the wall thickness of the housing components.Therefore, the production technique of plastic injection molding of a part with a thin shell feature is becoming more important.Many factors lead to the defects of parts, such as warpage, shrinkage, residual stress, and so on. This research used the experimental design of the Taguchi method to determine the injection molding conditions, and the injection processes were simulated by using the integrated software packages Moldflow^TW.Both molding conditions and affecting factors were discussed regarding the degree of warpage of the shell of a mobile phone.The results showed that the melt and mold temperature had the greatest influence on shrinkage in X direction, the packing time had the greatest influence on shrinkage in Y direction and the packing pressure had the greatest influence on warpage of Z direction.However, the shrinkage and warpage were only slightly influenced by the gate dimension and the injection rate in the case of mobile phone. In addition, applying the experimental design of the Taguchi method is a quite effective method to deduce the optimum set of affecting factors in injection molding to produce plastic parts with minimum shrinkage and warpage.

Initial dehydration behavior of copolymer hydrogel for contact lens

LI Xinming, CUI Yingde, YIN Guoqiang, JIA Zhenyu

2005, 56(4): 732-737.

Abstract ( 626 )

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Hydrogel for contact lens was synthesized by copolymerization of N-vinylpyrrolidone, hydroxyethylmethacrylate, methylmethacrylate or ethylmethacrylate, butylmethacrylate.A dehydration model for hydrogel membrane was established.Initial dehydration behavior of the copolymer hydrogel was studied by the gravimetric and thermal mass loss analysis.The results showed that initial dehydration rate of hydrogel membrane was in inverse proportion with square crosslinking density.N-vinylpyrrolidone in the copolymer increased the dehydration rate, while methylmethacrylate, ethylmethacrylate or butylmethacrylate decreased the dehydration rate.In the initial dehydration stage,the dehydration behavior could be described by means of the first order reaction.

Membrane separation technique applied to improving extraction of lincomycin

LI Jiemei;ZHOU Peiyan;WANG Yaqing;ZHAO Renxing

2005, 56(4): 738-743.

Abstract ( 919 )

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Separation processes with ultrafiltration and nanofiltration were introduced to purify and concentrate the fiber-board filtered lincomycin broth in front of mixed-alcohol extraction.Bench scale test indicated that the application to the alkalized feed was superior to the non-alkalized feed.After comparing several membranes with different materials(PES,PS,PA) and molecular weight cutoffs,PES-10 and NF-270 were found to be the optimum UF and NF membranes.Successive extraction after UF-NF needed less extractant due to the reduced feed volume.Both the extraction efficiency and product yield were improved.For NF concentration multiple of 1.28,the mixed-alcohol once-extraction rate and the general product yield increased by 4.3% and 3.4% respectively.The color of extract phase was lighter than the ones without UF-NF.

Twisted strip with oblique teeth to efficiently remove fouling and enhance heat transfer at low flowing velocity

YU Xiumin, YU Tianlan, PENG Deqi, JIANG Shaoqing, LUO Jiankang

2005, 56(4): 744-747.

Abstract ( 827 )

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The plastic smooth twisted tape can not be used for heat exchangers with low fluid velocity of less than 1.0 m•s^-1 to prevent and remove fouling and it can not enhance heat transfer.A new twisted strip was proposed to enhance heat transfer.It was capable of being used in the circumstances with lower flow velocity of 0.5 m•s^-1.Oblique teeth were attached asymmetrically on both surfaces of the twisted strip at regular intervals.The fluid for heat transfer was directed by the teeth with asymmetrical reaction forces on the twisted strip to form an additional rotating moment.With this arrangement,total moment was increased by 75%～101% and heat transfer coefficient was raised by 171% as against that of the smooth twisted strip.Though the resistance coefficient of fluid flow became greater, the total flow resistance of the equipment was still within the permissible range of engineering application, e.g. for a heat exchanger of 4 tube circuits and 6 meter long tubes, the resistance was about 36000 Pa.The new twisted strip could be used to automatically remove fouling and enhance heat transfer with low flow velocity of 0.5—1.0 m•s^-1.