CIESC Journal

CAO Chengbo, YU Xueli, WANG Zhenfang, HAN Hongbin, HAN Nianfeng, LIU Zonglin

2005, 56(3): 375-381.

Abstract ( 634 )

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Polymeric fluorescent brighteners (PFBs) which are polymerized by fluorescent monomer and other monomers can solve poor photostability of traditional FBs.Classification of the PFBs is briefly introduced.The synthesis, structure, properties and application of stilbene, naphthalimide and pyrene FBs are discussed. The basic structure of chromogen in PFBs remains the same,so PFBs have fluorescent properties of traditional FBs.Covalent bonds between chromogen and macromolecule chains enhance their photochemical stability，increase their whitening performance and fluorescence quantum yield. PFBs can be used not only for textile, polymeric materials and detergents，but also for high technology fields，such as liquid crystal displays，fluorescent probes, etc.Developing environmentally friendly high performance new products, mixing different PFBs and polymerizing more monomers with different chromogens are likely to be new areas of research.

Applications of ionic liquids in biocatalysis

LIU Liying;CHEN Hongzhang

2005, 56(3): 382-386.

Abstract ( 644 )

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Over the past years, ionic liquids (ILs) have gained increasing attention as solvent or co-solvent for performing biocatalytic reactions with sometimes remarkable results because of its special advantages.Enzymes of widely different types are catalytically active in ionic liquids or aqueous biphasic ionic liquid systems.Lipases have been mainly studied.Some of them maintain their activity in anhydrous ionic liquid media and the (enantio) selectivity, yield and operational stability are often better than that in traditional media.Some proteinase could catalyze transesterification in ILs and showed improved stability.The application of ILs to whole-cell systems and β-galactosidase is also successful, but the activity of cellulase and some peroxidase decreases or is lost.So further study is needed to improve enzyme activity.

Phase diagram of K₂O-Nb₂O₅-H₂O ternary salt-water system

ZHOU Hongming, ZHANG Yi, ZHENG Shili

2005, 56(3): 387-391.

Abstract ( 614 )

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The solubilities of the K₂O-Nb₂O₅-H₂O ternary salt-water system were studied at 30 ℃ and 80 ℃ by isothermal method, and the corresponding equilibrium diagram was plotted.These results might be used as the basis of crystallizing separation of potassium hexaniobate and KOH involved in the disposal of low-grade refractory niobium-tantalum ore by the KOH sub-molten method in the clean metallurgy process.

Improved L-M algorithm for ANNs prediction of phase equilibrium in macromolecule system

HE Xuezhong, ZHANG Xiangping, ZHANG Suojiang, LI Chunshan, LIU Jindun

2005, 56(3): 392-399.

Abstract ( 841 )

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Error back propagation (EBP) is a widely used training algorithm for feedforward neural networks (FFNNs)，but low learning rate limits its applications in the networks with complex topology architecture and large patterns.In this work, two modifications on Levenberg-Marquardt algorithm for FFNNs were made.One modification was made on the objective function, while the other was the evaluation of the initial weights and biases.The modified algorithm gave a better convergence rate compared to the traditional EBP algorithm and it was less computationally intensive and required less memory.The performance of the algorithm was verified separately with polymer and protein systems.The results showed that the BP network based on modified Levenberg-Marquardt algorithm could be used to predict the binodal curve of H₂O/DMAc(N，N-dimethylacetamide)/PSf(polysulfone) system and lysozyme solubility in aqueous salt solution.

Numerical analysis of enhanced flow boiling heat transfer in vertical porous tube

YANG Dong;LI Bin;CHEN Tingkuan;XU Yongquan

2005, 56(3): 400-407.

Abstract ( 743 )

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A semi-analytical model was developed for the prediction of enhanced flow boiling heat transfer in vertical porous tubes.The model assumes that forced convection and nucleate boiling coexist in the annular flow regime.Conservations of mass, momentum, and energy are used to determine liquid film thickness and temperature. The heat flux due to nucleate boiling consists of those inside and outside micro-tunnels. A detailed analysis of various forces acting on the bubble is presented to predict its mean departure diameter. The active nucleation site density of porous layer is determined by correcting the pool boiling correlation with a suppression factor. The flow boiling heat transfer coefficients of high saturation temperature organic fluid (cumene) in a vertical plasma coated tube are studied numerically. It is shown that the present model can predict most of experimental values within ±20%. The numerical results also indicate that the nucleate boiling contribution to the overall heat transfer coefficient decreases from 50% to 15% with vapor quality increasing from 0.1 to 0.5.

Local flow and heat transfer characteristics among roughness ribs in rectangular channel

WEN Shaoyi;PENG Xiaofeng;WU Hailing;WANG Buxuan

2005, 56(3): 408-411.

Abstract ( 699 )

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The roughness was simulated by using regular transverse rectangle ribs on the bottom surface of a rectangular channel, and local flow and heat transfer characteristics among ribs along a roughened surface were numerically investigated.The results showed that various flow structures appeared in different rib spacing regions along the flow direction, according to which three flow regimes in the roughness section were generally classified into—entrance, middle and exit zone.In the entrance zone flow structures varied quickly, particularly vortex distributions close to the wall in the rib spacing region appeared quite different from each other.In the middle zone,the flow became relatively stable and the flow structure was a single vortex.Similar to the entrance zone, in the exit zone the flow experienced a significant change of flow structure.Flow resistance exhibited W-shape at the very beginning of the entrance zone, while it evolved into a kind of sine wave at the end of the roughness section.Generally, heat transfer coefficient tended to be high in the middle area of each rib spacing region. It was revealed that different characteristics of flow and heat transfer performance were determined by various flow structures in different rib spacing regions along the roughened surface.

Application of micro capillary groove evaporator to electronic chip cooling

HU Xuegong;YAN Xiaohong;ZHAO Yaohua

2005, 56(3): 412-416.

Abstract ( 890 )

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A novel micro capillary groove evaporator for electronic chip cooling by using the micro capillary groove heat sink technique was designed,and an experimental investigation on the influence of various factors on cooling performance of the evaporator was carried out. The experimental results showed that an appropriate vacuum degree and volume fraction of liquid should be chosen for maximizing the cooling capacity of the evaporator. Compared with a current fan-cooled radiator for CPU chip of Pentium 4, the micro capillary groove evaporator showed higher capacity when keeping the chip temperature below 100 ℃. It was suitable for cooling those electronic chips with high power and thermal sensitivity.

Numerical simulation of falling film absorption in swaying tube using TFE/NMP as working fluid

LIU Yanli;XU Shiming

2005, 56(3): 417-423.

Abstract ( 818 )

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Based on the features of the falling film absorption in the absorbers used on boats, a physical and mathematical model of momentum,heat and mass transfer of falling film absorption in a swaying tube using TFE/NMP （2，2，2-trifluoroethanol/N-methyl-2-pyrrolidone）as working fluid was presented.The effects of swaying additional inertia forces on the distributions of film thickness,velocity,temperature and concentration of falling film flow field were fully considered. A combination of integral and completely implicit finite volume numerical method was adopted to solve the governing equations.By analyzing the computation results, it could be found that the distributions of the parameters such as velocity and temperature and so on,took on the traits of periodicity and symmetry due to the existence of the swaying additional inertia forces during the falling film absorption in the swaying absorber with TFE/NMP solution.

Numerical analysis of heat and mass transfer process on metal fill surface for air conditioning

SUN Hejiang;YOU Shijun;ZHANG Huan;TU Guangbei

2005, 56(3): 424-429.

Abstract ( 601 )

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A planar model of air and water flow on metal fill surface was set up to investigate heat and mass transfer performance of air conditioner.Experiment was done and two equations about coefficients of heat transfer and mass transfer were developed by using the multiple linear regression method to process experimental data. Mathematical equations were set up by considering water and air mass changes during their flow through metal fill due to evaporation and condensation.Computational results agreed with experimental data well. By visualization of the field of key variables on metal fill surface, another way to know heat and mass transfer performance was given.By this means, engineers can design metal fill for air conditioning application more accurately according to given factors such as water temperature, air mass flow rate, water mass flow rate, etc.

Heat transfer between liquid and gas in multistage-spraying rotating packed bed

PAN Zhaoqun;DENG Xianhe;ZHANG Yajun

2005, 56(3): 430-434.

Abstract ( 692 )

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Multistage-spraying rotating packed bed is a novel equipment with low pressure drop, high mass transfer coefficient, small volume, light weight and lower investment, in which rapid and highly efficient reaction can be carried out.It has been used in flue gas desulfurization.When the multistage-spraying rotating packed bed is used in boiler flue gas desulfurization, the cool absorber liquid contacts the hot gas in the spraying area.Gas temperature drops and its humidity increases, while the temperature of absorber liquid increases, during the heat transfer between the hot gas and the cool liquid. The whole process was modeled on the basis of the spray theory and the Lewis Equation. The parameters of the liquid and gas in the spraying area and the outlet could be calculated. The calculated result was verified by the experimental data.

Mass transfer model for liquid-liquid micromixing systems

XU Jianhong;LUO Guangsheng;CHEN Guiguang,SUN Yong;WANG Jiading

2005, 56(3): 435-440.

Abstract ( 727 )

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The effect of total flow rate on membrane dispersion extraction efficiency was studied for liquid-liquid micromixing systems.Mass transfer coefficient and mass transfer rate were obtained from the experimental results for the micromixing process. In order to predict mass transfer performance of the micromixing process, some traditional mathematical models were tested.Total and individual mass transfer coefficients were calculated, and compared with the experimental results. The results showed that main factors affecting mass transfer coefficients were residence time and droplets size, and mass transfer coefficients increased with the reduction of residence time.Mass transfer coefficients in the micromixing process could reach as much as 1.2×10^-4m•s^-1,which was about 10—100 times higher than that in a traditional column extraction process. The mass transfer performance in the micromixing process could be predicted neither with the model in which mass transfer resistance of any one phase was ignored, nor with the simplified average equations.So mass transfer performance in the micromixing process was much different from the traditional column extraction process.The authors’results showed that mass transfer coefficients could be predicted with the full traditional [JP2]two-phase resistance model by considering both steady and non-steady states, and the calculated values were in good agreement with the experimental values.

Non-equilibrium critical flow characteristics of trans-critical carbon dioxide in short tube

YANG Liang;ZHANG Chunlu

2005, 56(3): 441-445.

Abstract ( 657 )

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A two-fluid model and a homogeneous model for trans-critical carbon dioxide in a short tube were developed.Both inter-phase velocity slip and temperature difference were taken into account in the two-fluid model, but not in the homogeneous model. Experimental results on the mass flow rate were used to verify these two models.The results showed that for the two-fluid model the deviation of 90% model prediction was under ±20%.Furthermore it could give reasonable pressure distribution along the tube length.The homogeneous model could also give reasonable prediction results,and not seriously lower than measured results while disregarding the non-equilibrium characteristics.The non-equilibrium flow characteristics of trans-critical carbon dioxide in the short tube are not obvious which could also be verified by small inter-phase velocity slip and temperature difference.Finally, this phenomenon was given theoretical explanation.

Heat transfer performance of heat pipe type gas-liquid-solid three-phase fixed-bed bubble-column reactor

WANG Jun, ZHANG Hong, TAO Hanzhong, ZHUANG Jun

2005, 56(3): 446-449.

Abstract ( 719 )

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In order to study the heat transfer performance of heat pipe type gas-liquid-solid three-phase fixed-bed bubble-column reactor,heat transfer was investigated in a fixed-bed reactor with inner diameter of 50 mm and height of 800 mm， and filled with porous packing material inside the bed.A water-stainless steel heat pipe of φ16 mm×2 mm was inserted in the reactor and water and nitrogen flowed co-current upwards.The results showed that the amount of heat transferred increased with gas flow rate u_g, and heat transfer became less sensitive to the gas flow rate when gas flow rate reached a certain value.An empirical equation for heat transfer coefficient between the bed layer of fixed-bed bubble-column reactor and the pipe wall of the heating section of heat pipe under the testing conditions was obtained by fitting the data with the least square method. The obtained equation was verified by heating simulation test.

Approximate analytical results for two-fluid model of laminar bubbly flow

XU Zhaofeng;LUO Rui;YANG Xianyong

2005, 56(3): 450-454.

Abstract ( 946 )

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The two-fluid model is usually taken to predict the bubbly flow.The direct numerical calculation is often used for it, because it can not get the analytical results.In this paper, the results in integration type (i.e. the approximate analytical results) of the most simple type of bubbly flow and fully developed laminar bubbly flow in vertical pipe, are derived by symbol integration of the two-fluid model.Then they are calculated in numerical integration and compared with the experimental data.The numerical results coincide with the experimental data.Though the integration type results are not the analytical results of two-fluid model of bubbly flow, they can show what influences the flow field of bubbly flow.So they are good approximation of analytical results and have an advantage over direct numerical calculation.

Hydrodynamics in high-density downer reactor

CHEN Hengzhi;LI Hongzhong

2005, 56(3): 455-461.

Abstract ( 599 )

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Experiments were carried out in a special circulating fluidized bed of 5.6 m in height, 0.08 m in ID downcomer.Glass beads(ρ_p=2480 kg•m^-3,d_p=131 μm),FCC catalyst particles (ρ_p=992 kg•m^-3,d_p=82 μm)and two kinds of silica gel (ρ_p=750 kg•m^-3,d_p=128 μm and 572 μm) were used.The maximum of the solids flux was 600 kg•m^-2•s^-1and a solids holdup as high as 0.14 was achieved.The results showed that the characteristics of the transient solids concentration at high-density operation were different from those at low-density operation. Under low-density operation, the probability density distribution (PDD)curves had one peak,but under high-density operation,there was a horizontal line around the top of the PDD curves. Solids concentration increased with increasing solids flux.Smaller and lighter particles could achieve higher solids concentration, while the good fluidity and heavier particles could achieve high solids flux.The pressure gradient was positive in the overall downer and the length of particles acceleration zone was about 1.5—2.0 m.Depending on the structure of the exit, the downer could be divided into two regions：particle acceleration region and developed region under low-density operation or three regions：particle acceleration region, developed region, and exit region with high-density operation.

CFD simulation of liquid film flow on inclined wavy plates surface

GU Fang;LIU Chunjiang;YUAN Xigang;YU Guocong

2005, 56(3): 462-467.

Abstract ( 783 )

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The liquid flow behavior on the structured packing sheet can be regarded as the liquid film flow on an inclined wavy plate.A better understanding of the hydrodynamics of this kind of flow enables development of optimal packing surface with good wetting ability for improving mass transfer efficiency.A two-phase flow CFD model using the volume of fluid (VOF) method was presented for predicting the hydrodynamics of the falling film flow on the inclined wavy plates, where two momentum source terms, surface tension and interface stress shear were considered.The simulated results agreed well with the experimental results from Ref［1］ and ［2］, which showed that the CFD model used was reliable. Using the proposed CFD model, the flow behavior of liquids with various properties on different wavy plates were investigated.It was shown that changing the microstructures of wavy plates or reducing liquid surface tension would improve the formation of a continuous liquid film，which was significative for improving the mass transfer efficiency between gas and liquid.

Methanol steam reforming in plate-fin reactor for fuel cell system

PAN Liwei;WANG Shudong

2005, 56(3): 468-473.

Abstract ( 647 )

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A compact plate-fin reactor consisting of closely spaced plate-fins, where endothermic and exothermic reactions took place in alternate chambers was studied.In the reactor the catalytic combustion of reforming gas that was used to simulate the fuel cell anode off gas (AOG) supplied the necessary heat for the reforming reaction.Hydrogen was produced in one reforming chamber.Two vaporization chambers and two combustion chambers were integrated in one unit of the reactor.The reactor was compact,facilitating mounting and scale up.The effects of the ratio of water/methanol on the reactor performance were investigated, and the distribution of temperature in different chambers was studied.Besides, the steady-state behavior of the plate-fin reactor was studied.Internal plate-fins and [JP2]external catalytic combustion were applied to enhance the heat transfer in the reactor, which ensured both high methanol conversion and low CO concentration.In addition, this fully integrated reactor showed good testing stability.

Synthesis experiment of 2,4-difluorobenzaldehyde

WANG Lihua, ZHAO Guozhi, ZHOU Fengjun

2005, 56(3): 474-476.

Abstract ( 679 )

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2,4-Difluorobenzaldehyde was synthesized from 1,3-difluorobenzene and carbon monoxide with AlCl3 and HCl as catalyst in CO atmosphere at a pressure in the range of 1.5 MPa. Effects on the converting ratio and yield were investigated. The results showed that the optimum technological conditions should be that n（1,3-difluorobenzene）∶n（AlCl₃）=1.0∶1.0, the reaction temperature was 60℃, amount of HCl was 1.0% of total mass of reation mixture, and the reation time was 20 hours. The selectivity of 2,4-difluorobenzaldehyde from 1,3-difluorobenzene was up to the purity of the refined product w(2,4-difluorobenzaldehyde) ≥98.81%.

Simulation of novel process of distillation with heat integration and water integration for purification of synthetic methanol

WU Jia;CHEN Lu

2005, 56(3): 477-481.

Abstract ( 745 )

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A novel process of three-column distillation was proposed for the purification of synthetic methanol. In the new process with double-effect distillation to realize heat-integration, the feed to the lower-pressure column was a side-stream with moderate methanol concentration drawn from a stage of the higher-pressure column above its feed stage.A better balance of separation duty between the higher-and lower-pressure columns was achieved, which reduced further the total heat consumption of double-effect distillation process.The salt and base components from the pretreatment column were separated and concentrated to the bottom stream of the higher-pressure column so that the bottom stream of the lower-pressure column contained>99.9% water. Then the water was recycled to the pretreatment column as the extracting water, which realized water-integration within the process and reduced the consumption of fresh soft water of the process. A comparative case study by steady-state simulation was carried out between the traditional two-column process (A), the present three-column process (B) and the new process (C). The result showed that process (C) reduced the heat consumption by 49.2% of process (A) or by 24.7% of process (B) and reduced the soft-water consumption by 38.0% of both (A) and (B).

Fault diagnosis for batch processes based on MPCA-MDPLS

JIANG Liying;WANG Shuqing

2005, 56(3): 482-486.

Abstract ( 737 )

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In order to diagnose faults for batch processes, a novel method, MPCA-MDPLS model, is presented in this paper. The proposed method includes two models: MPCA (multiway principal component analysis) model and MDPLS (multiway discriminant partial least squares) model. Based on data collected from the plant during normal operation and specific faults, two models are constructed.The MPCA model can detect unknown faults.The faults，which are detected by using MPCA model as not unknown,are further diagnosed by the MDPLS model. If it is identified as unknown, the root cause is analyzed by using various methods. The unknown fault is then saved in the historical database in order to reconstruct the MPCA-MDPLS model. The method is proved to be feasible and effective by the application in diagnosing a multi-stage streptomycin fermentation process.

Estimation of kinetic parameters using hybrid ant colony system

HE Yijun, CHEN Dezhao, WU Xiaohua

2005, 56(3): 487-491.

Abstract ( 652 )

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A drawback of standard ant colony algorithm is not suitable for solving continuous optimization problems.A hybrid ant colony system (HACS), which was combined with the genetic algorithm and the Powell method,was proposed for solving continuous optimization problems.HACS, which included two kinds of ants: global ant and local ant, was built.The function of global ants was to explore the solution space, and that of local ants was to exploit the best solution. These two kinds of ants cooperated with each other in finishing the optimization task.The Powell method joined in local search, which was in favor of obtaining the accurate global optimal solution. The testing results indicated that the HACS showed better ability in finding global optimal solution than SGA.HACS was used to estimate the kinetic parameters of 2-chlorophenol oxidation in supercritical water.

PSO-based robust MPCA and its application to batch process monitoring

XIE Lei;WANG Shuqing;ZHANG Jianming

2005, 56(3): 492-498.

Abstract ( 668 )

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Batch processes are widely used in fine chemical and biochemical industries. The objective of batch processes is to produce high value-added products of high-quality. In order to reduce the variations of the product quality, multivariate statistical process control methods based on Multi-way Principal Component Analysis (MPCA) are used for on-line batch process monitoring. However, the MPCA and MPLS, based on the decomposition of relative covariance matrix, are strongly affected by outlying observations. In this paper, a PSO-based robust MPCA is proposed. How to construct the robust normal operating condition (NOC) model and robust control limits are discussed in detail. It is evaluated by monitoring an industrial streptomycin fermentation process and compared with the conventional MPCA. The results show that the robust MPCA is resistant to possible outliers and thus robust.

Cleaning strategy of membrane modules in reverse osmosis seawater desalination system

HU Yangdong;LU Yanyue;XU Dongmei;WU Lianying

2005, 56(3): 499-505.

Abstract ( 866 )

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In the reverse osmosis desalination process,regular cleaning is one of main measures to prevent and control membrane fouling and scaling. Cleaning can eliminate surface contamination of membrane and recover the water flux. On condition that the water production is ensured,optimal cleaning frequency and minimum cleaning cost could be obtained by choosing the appropriate cleaning strategy and time.This paper presents a new fouling model and the criterion of cleaning.The mathematical formulation of the optimum design is a mixed-integer non-linear programming (MINLP)problem, which targets at the minimum total operation cost during the whole projection period.One example is solved and the corresponding optimal time and cleaning strategy is obtained during the five-year projection period, which illustrates the effectiveness of the new method for the optimal maintenance of the 3—5 years life-span membrane modules.

Improved simulated annealing algorithm for synthesis of heat integrated distillation sequences

AN Weizhong;YUAN Xigang

2005, 56(3): 506-510.

Abstract ( 670 )

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A simulated annealing based approach was developed for the synthesis of large-scale heat integrated distillation sequences.The synthesis problem was formulated as a mixed integer nonlinear programming (MINLP) problem into which a more efficient representation of network structure and a more rigorous cost model were introduced. With the consideration of the characteristics of the studied problem,the simulated annealing algorithm was improved so that it could handle structural and parametric optimization simultaneously within the same annealing scheme, and could attain reasonable trade-off between computational accuracy and speed. The proposed approach was shown to be effective by the solution of larger-scale examples (the number of products≥10).

Acetyltransferase activity in Candida tropicalis and characteristics of CAT disruption recombinant

ZHANG Jian;GAO Hong;LI Chun;CAO Zhu’an

2005, 56(3): 511-517.

Abstract ( 643 )

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A rapid method of partially purifying carnitine acetyltransferase (CAT) from Candida tropicalis and determination of its enzyme activity was established.The characteristics of CAT-disruption recombinant of Candida tropicalis were also studied.It was confirmed that the specific activity of CAT of this recombinant was approximately half of that of its corresponding wild type. Therefore, the β-oxidation pathway of dicarboxylic acid was effectively suppressed. Correspondingly, the dicarboxylic acid productivity of this recombinant was increased by 11% and its alkane conversion rate was also increased by 12% in average.

Dynamic model of leaching Sanggenon from Sangbaipi

LU Xianghong, JI Jianbing, REN Qilong, WU Pingdong

2005, 56(3): 518-523.

Abstract ( 613 )

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The dynamics of leaching Sanggenon from Sangbaipi was studied, and the dynamic model describing leaching process, accounting to non-linear isotherm, was developed. The equilibrium equations of Sanggenon C and D between Sangbaipi and acetone, the intrapartical diffusion coefficient and the mass transfer coefficient in liquid film were obtained. The correlationships between the mass transfer coefficient in liquid film and the velocity were developed. The result that the dynamic curves calculated by the model were agreement with the experimental curves showed that the model can well express leaching process.

Mathematical model of 4-chlorophenol degradation in aqueous solution by pulsed high-voltage discharge (Ⅰ)Calculation of formation rate of ozone due to oxygen discharge

CHEN Yinsheng, ZHANG Xinsheng, LI Yunfei, DAI Yingchun, YUAN Weikang

2005, 56(3): 524-530.

Abstract ( 670 )

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The formation rate of ozone due to the point-to-plate pulsed high-voltage corona discharge was calculated with electronic collision theory. Investigation showed that the ozone formation rate was twice as that of the high-energy electron of higher than 6.0eV. The ozone formation rate increased linearly with increasing pulsed peak voltage and discharge frequency. The effect of the discharge electrode diameter on the ozone formation rate was greater than that of the point-to-plate distance of the two electrodes on the ozone formation rate.

Mathematical model of 4-chlorophenol degradation in aqueous solution by pulsed high-voltage discharge(Ⅱ)Relationship between enhancement factor of ozone mass transfer and 4-chlorophenol concentration

CHEN Yinsheng;ZHANG Xinsheng;DAI Yingchun;YUAN Weikang

2005, 56(3): 531-537.

Abstract ( 708 )

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The mass transfer of ozone from gas bubble to wastewater aqueous solution was improved by the reaction between the organic compound in the wastewater and ozone.The main reactions taking place in the acid aqueous solution were those between ozone and 4-chlorophenol and 4-chlorophenol salt ion. The reaction between •OH and the 4-chlorophenol could be neglected.

Modeling based on improved genetic algorithm for temperature model of PEMFC stack

WEI Dong, ZHU Xinjian, CAO Guangyi

2005, 56(3): 538-544.

Abstract ( 581 )

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The system of PEMFC stack is too complicated to model, and the parameters of the existing mathematical model are very different because the construction and materials used in the stack are different.There is no general model with high accuracy to describe all stacks and meet the need for designing the PEMFC control system. In this paper, the knowledge of heat transport and liquid kinetics is used to establish a stack model.Some parameters that have great influence on the accuracy of the model cannot be obtained from a simple experiment.Improved genetic algorithm proposed in the paper possesses excellent global and local searching capacity and is able to identify the parameters accurately.The results of simulation and experiment validate the practicability and reliability of the algorithm.

NO formation from coal char combustion in cement precalciner

HU Zhijuan, LIU Zhijiang, WANG Shijie

2005, 56(3): 545-550.

Abstract ( 563 )

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In a bench scale precalciner, the characteristics of NO release from coal char combustion were investigated in various conditions (different temperatures and presence of cement raw meal). The mechanism of NO formation was also discussed.The results indicated that the characteristics of NO emission from three kinds of chars were obviously different because of coal physical structure and chemical properties. The rate of NO formation increased with increasing temperature, however, sometimes the phenomenon was irregular. The rate and amount of NO formation clearly rose in the presence of cement raw meal, which suggested that cement raw meal showed distinct catalytic effect on NO formation.NO originated mainly from the oxidation of fuel nitrogen in the industrial precalciner. The conversion of char-N to NO was controlled by two competitive reactions: oxidation of fuel nitrogen and reduction of NO.

Synthesis of ZrO₂ nano-powders with pure tetragonal phase by low temperature hydrothermal method

GAO Longzhu;CHEN Hongling;XU Nanping

2005, 56(3): 551-554.

Abstract ( 743 )

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The ZrO₂ nano-powders were prepared from zirconium(Ⅳ) nitrate by the hydrothermal method at 180℃ for 18 h in reaction solution with different pH.The ZrO₂ powders were characterized by XRD and TEM.The ZrO₂powders of a mixture of m-ZrO₂ and t-ZrO₂ can be directly synthesized from zirconium(Ⅳ) nitrate by the low hydrothermal process in reaction solution with different pH. When the reaction solution was added with glycerin, it was found that ZrO₂ powders with pure tetragonal phase could be directly synthesized at 180℃ with certain pH.The proportion of glycerin and the pH value of reaction solution were interrelated to the crystallographic forms of the zirconia powders.The ZrO₂ powders with pure tetragonal phase are formed at 180℃ for 18 h when glycerin was added to the reaction solution with the ratio ［glycerin］∶［ Zr⁴⁺］ greater than 1∶1 and the pH 9—11, in other experiments mixtures of monoclinic and tetragonal phase ZrO₂ were formed. The ZrO2 powders with pure tetragonal phase were about 10nm and homogenous in size. Compared with the similar experiments without glycerin, addition of glycerin was important in synthesizing the tetragonal phase-ZrO₂ powders by the low temperature hydrothermal method.

Optimum conditions of grafting copolymerization ofpolypropylene fiber with acrylic acid

FENG Changgen;HU Xiufeng;ZENG Qingxuan;ZHOU Shaoji

2005, 56(3): 555-559.

Abstract ( 666 )

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The optimum conditions of grafting copolymerization reaction of acrylic acid(AA) onto polypropylene(PP) fiber was studied by using benzoyl peroxide(BPO) as initiator.The primary and secondary sequences of the grafting copolymerization reaction conditions was analysed. The results showed that grafting copolymerization reaction was greatly influenced by the temperature，reaction time, concentration of BPO and that of AA in the primary and secondary role as the above sequence. The optimum reaction conditions of gaining higher exchange capacity for the weak acidic cation-exchange fiber are as follows: the grafting temperature 80 ℃, the reaction time 7 h, the concentration of BPO 2% and AA 80%.