The Chinese Journal of Process Engineering

Numerical Simulation on Fluid Flow in a Thin Film Evaporator

HE Xiao-hua;TANG Ping;LI Jia;LU Xiao-hua

. 2005, 5(4): 357-363.

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The calculation model of thin film evaporator (TFE) was developed, the flow of water and viscous fluid was simulated using CFX 4.4 software and the velocity distribution was obtained. The results show that the rotor speed and feeding rate have great effects on the fluid flow of TFE. The material exchange between the fillet and film can be promoted by increasing the rotor speed. There is one common optimum feeding rate under different rotor speeds for different fluids. At this feeding rate, the mean velocity in the fillet section reaches the maximum value. For water, the ratio of flow boundary layer thickness to film thickness is the minimum under the optimum feeding rate. Difference exists for the axial velocity distribution between viscous fluid and water, and no obvious flow boundary layer forms for viscous fluid.

Numerical Simulation on the Temperature Field and Film Heat Transfer Coefficient of Thin Film Evaporator

HE Xiao-hua;LI Jia;LU Xiao-hua

. 2005, 5(4): 364-369.

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The heat transfer calculation model of water and viscous fluid in a thin film evaporator was developed using CFD software CFX4.4. The mean temperature distributions along axial and film thickness directions were obtained, and the film heat transfer coefficient a under different conditions was calculated. The results show that feeding rate and rotor speed have great influence on the film temperature distribution and the film heat transfer coefficient. There is one common optimum feeding rate under different operation conditions for different fluids. At this feeding rate, the mean velocity in fillet section reaches the maximum value and so does the film heat transfer coefficient a. For water, both the ratio of flow boundary layer thickness to film thickness and that of temperature boundary layer thickness to film thickness reach the minimum value under high rotor speed or the optimum feeding rate. There exists an inherent relation between the flow boundary layer and temperature boundary layer, and the film temperature distribution and heat transfer coefficient are affected seriously by the thickness of transfer boundary layers. For viscous fluid, no obvious temperature boundary layer forms under the parameter range considered in this work．

Numerical Simulation of the Two-phase Flow in a Swirling-reactor for Continuous Pretreament of Molten Metal

LIU Xiang-jun;SHI Hong-zhi;WEN Zhi;FENG Jun-xiao;LIU Shuang-ke;YIN Xiao-dong;WANG Yan

. 2005, 5(4): 370-374.

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A novel continuous molten-metal pretreament technology using swirling-reactors is recently proposed by Japanese Scientists. Reactor designing is a key problem for developing and applying this technology. Detailed information about the flow process in a reactor is then very necessory. In this paper, a mathematical model for numerically simulating two-phase molten-metal and particle flow is established. The models used include the k-e two-equation model for turbulent molten-metal flow and the random trajectory model for particle flow. The governing equations are solved by SIMPLER algorithm. The two-phase flow characteristics in a swirling-reactor are numerically studied. Detailed flow field of the molten metal and moving behavior of the particles in the reactor are obtained. Calculated results show that particles can be effectively dropped into molten metal flow using this type swirling-reactor. Particles and molten metal could be mixed well when adopting proper geometrical parameters and operating conditions. These results offer detailed scientific basis for designing and optimizing the hot metal pre-treatment technology.

Mass Transfer and Hydrodynamics of Rotating Packed Bed in Distillation

LI Xiu-ping;LIU You-zhi;YANG Ming

. 2005, 5(4): 375-378.

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An experimental system of rotating packed bed for distillation operation was set up for studying mass transfer efficiency and hydrodynamics with methanol/water solution at the atmospheric pressure and total reflux. The results showed that the number of theoretical trays of rotating packed bed attained the maximum value corresponding to the increase of F and b. The least height equivalent to a theoretical plate was 0.0109 m. Two correlations for the number of theoretical plate (Nmin) and gas pressure drop (Dp) were established with least square method based on the experimental data.

Pyrolysis of Straw Obtained from Stagewise Treatment

YANG Chang-yan;YANG Xue-min;LV Xue-song;YAO Jian-zhong;LIN Wei-gang

. 2005, 5(4): 379-383.

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The pyrolysis characteristics of wheat straw with steam-explosion and solid fermentation treatment were investigated by the thermogravimetry coupled with the Fourier infrared spectroscopy to analyze the evolved gasses. The pyrolysis process with the increase of temperature from TG can be divided into four stages, including drying stage (30~150℃), transitional stage (150~200℃), pyrolysis stage (200~600℃), and carbonization stage (600~900℃). The results of pyrolysis from TG-FTIR show that the process can be divided into two steps: (1) splitting of hydroxide radicals, chain scissions and depolymerization, accompanied by evolution of water, acids, aldehydes, compounds containing C?O?C groups and CO, CO2, CH4, etc.; (2) aromatization and formation of graphite layers, accompanied in turn by evolution of CH4, CO2 and CO. The yields of uncondensable gases and carboxyl compounds decrease after steam explosion/solid fermentation treatment, but the yield of pyrolysis liquid increases by the stagewise treatment.

Comparison of Bioleaching of Marmatite Flotation Concentrate with Acidithiobacillus ferrooxidans and a Moderately thermophlic Strain

SHI SHAO-yuan;FANG Zhao-heng

. 2005, 5(4): 384-388.

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The bioleaching of marmatite flotation concentrate by Acidithiobacillus ferrooxidans and Moderate thermophile (MLY) in the pure culture was carried out respectively, and the leaching effects with inoculation of different bacteria were examined. Experimental results showed that the adapted strains of two microorganisms could increase markedly the dissolution rate of marmatite, especially when inoculated with MLY strain. The mineralogyical analysis by scanning electron microscopy, X-ray diffraction and energy dispersive X-ray analysis indicated that the leached residues from the different bacteria had the similar morphological feature and chemical composition. It was demonstrated that the bioleaching of marmatite flotation concentrate by MLY was more effective when carried out under higher temperature and acidity, and would have better prospect industrial application than Acidithiobacillus ferrooxidans.

Ultrasonic Intensified Hydrometallurgical Process of Electro-oxidation for Molybdenum Concentrate

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. 2005, 5(4): 389-393.

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In order to promote current efficiency and decrease energy consumption in electro-oxidation process for molybdenite concentrate, ultrasonic wave was introduced to intensify the leaching process. Under the ultrasonic field leaching conditions can be ameliorated, surface superstralum of electrodes can be sharply reduced, and electrolytic current be increased remarkably. The results indicate suitable leaching conditions as follows: ultrasonification is eradiated 3 min per 15 min, cell potential is about 3.5 V, ratio of ore pulp liquid to solid (L/S) 10, anode current density 700 A/m2, original pH of pulp value 10, electrode spacing 13 mm. Under these conditions the current efficiency is above 100%.

Effect of Synthesis Method on Structure, Acidity and Catalytic Ability of Zeolite Beta

MA Jun;WANG Hai-yan;TIAN Yan-wen

. 2005, 5(4): 394-398.

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b-zeolite was synthesized by using tetraethylammonium hydroxide (TEAOH) as organic template, silicon gel as silicon source and sodium meta-aluminate as aluminum source, and adopting microwave radiation and hydrothermal method. The b-zeolite samples were characterized by IR, NH3-TPD and XRD. The effects of the different preparation conditions on relative crystallinity and surface acidity of b-zeolite were studied. The etherification test for fluidized catalytic cracking light gasoline was carried out in a fixed-bed reactor. The results showed that the amount of organic template in microwave radiation method was less 25%, crystallizing time shorter 36 h, and removing template time shorter 3.5 h than those in the conventional method of calcination. The b-zeolite with microwave radiation in synthesis and removing template had a higher total acid amount and an ideal distribution of Bronsted acid, and the optimum etherification activity.

Leaching Kinetics of Calcium Aluminate Slag

TOGN Zhi-fang;BI Shi-wen;LI Hui-li;YANG Yi-hong

. 2005, 5(4): 399-402.

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Leaching calcium aluminate slag by Na2CO3 solution is solid-liquid reaction generating solid product. A study on the leaching kinetics of calcium aluminate slag was carried out. The effects of reaction temperature, concentration of reagents, particle size and agitation rate on the leaching rate were deterimined. The results show that the leaching process can be modeled with the shrinking core model of the first order reaction. An empirical equation for the leaching kinetics was established as 1+2(1-xB)-3(1-xB)2/3= 1.108exp(-1906/T)t. The apparent activation energy is 15.84 kJ/mol. The leaching rate is controlled by diffusion of reacting reagents in a porous solid product layer. The leaching mechanism is fairly explained by the model. A higher leaching rate of calcium aluminate slag is obtained by higher leaching temperature and/or with smaller particle size.

Preparation and Characterization of Ultrafine Crystal NaX Membrane

HAN Ling;WANG Jin-qu

. 2005, 5(4): 403-406.

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Continuous ultrafine crystal NaX membrane was synthesized hydrothermally on the outer surface of a-alumina tube support (12 mm o.d., 8 mm i.d.). Surface-modified tubes were seeded with ultrafine zeolite X crystals prior to the membrane synthesis. The molar composition of the starting gel of NaX membrane was SiO2:Al2O3=3.85~4.2, Na2O:SiO2=1.2~1.5, H2O:Na2O=40~60. The outer surface of the tube was completely covered with zeolite crystals, which were about 500~800 nm in size and about 10 mm in thickness of the membrane as judged by a scanning electron microscope (SEM). The tests on permeation of H2, N2 and C3H8 were carried out to get the ideal separation selectivity of H2/N2 and H2/C3H8 systems. The measured permeability of H2 was about 2.45′10-6 mol×m2/(s×Pa) and the ideal selectivity of H2/N2 and H2/C3H8 was 4.21 and 7.56, which are higher than the respective Knudsen diffusion ratios of 3.74 and 4.69.

Temperature Change during Oxidization of Titanium-bearing Slag Using Air

WANG Ming-yu;ZHANG Li;ZHANG Lin-nan;SUI Zhi-tong;TU Gan-feng

. 2005, 5(4): 407-410.

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Titanium-bearing slag is deoxidized slag, and Ti is dispersed in the slag. Based on the technology of selective precipitation, the slag is supposed to be oxidized so as to transform Ti3+ and Ti2+ into single Ti4+ state for further recovery and utilization. While the oxygen potential of slag is raised, the reduced components in slag will be oxidized and the released heat will raise the temperature of slag. In the present study, the modeling calculation on the temperature change in the oxidization process was carried out and the temperature change of actual titanium-bearing slag during oxidization was also measured. The comparison of results shows that the calculated trend of slag temperature is reasonably consistent with temperature measurements.

Modification of Bentonite by Microwave Irradiation and Its Mechanism

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. 2005, 5(4): 411-413.

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Na-bentonite and organic-bentonite were prepared by using microwave radiation in the half-dry process. A small amount of ethanol in which a modifier was dissolved was mixed with the raw material, bentonite. Then, the obtained half-dry mixture was heated by microwave irradiation. Finally, the modified bentonite was treated by washing, filtering and drying. Compared with the traditional wet process, the proposed method not only shortened the reaction time by 60~90 times but also improved productivity by 11.5%~16% because of easy washing and filtering after microwave radiation. The mechanism of microwave effect on the improved process was explored by analyzing reaction factors. It was considered that the microwave irradiation enhanced the rate of mass transfer which became faster than that of reaction, and overall process was controlled by reaction under the conditions of the bentonite particle size less than 355 mm and microwave-power greater than 50 W/g.

Production of Lignocellulolytic Enzymes and Rice Straw Biodegradation by Coriolus versicolor

SONG An-dong;ZHANG Bai-liang;WU Kun;HUANG Bao

. 2005, 5(4): 414-419.

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Lignin biodegradation has important significance for environmental protection and resource usage. In the present work, Coriolus versicolor was cultivated in the solid media of rice straw supplemented with glucose and ammonium chloride. The activities of lignocellulolytic enzymes and the contents of main chemical constituents were determined during the process of culturing. The straw structure was determined through scanning electron microscope and Fourier-transform infrared spectroscopy. The results show that enzyme activity is affected by concentrations of carbon and nitrogen sources. The most suitable condition for production of cellulases, lignin peroxidases, manganese-dependent peroxidases, laccases is high carbon and low nitrogen (glucose 2%, ammonium chloride 0.03%), while the one of hemi-cellulases is low carbon and low nitrogen (glucose 0.15%, ammonium chloride 0.03%). The emzymes have crucial effect on the biodegradation, and the rate of biodegradation is directly influenced by the enzyme activities. Biodegradation of cellulose and hemi-cellulose significantly accelerates the biodegradation of lignin. 65.39% of cellulose, 45.11% of hemi-cellulose and 39.16% of lignin in rice straw are biodegradated after 32 d cultivation. Structure of rice straw has changed evidently after biodegradation.

Influence Mechanism of Metal Ions on ATP Production by the Cells of Saccharomyces cerevisiae

LIAO Xian-yan;WANG Bei;DU Guo-cheng;LI Yin;CHEN Jian

. 2005, 5(4): 420-424.

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ATP (adenosine 5￠-triphosphate) is very important in all lives as a carrier of energy. It can also be used as an energy supply for some enzymatic reaction systems. In this report the cells of Saccharomyces cerevisiae WSH-J701were used for the enzymatic production of ATP from glucose and adenosine. The influences of Mg2+, K+ and Na+ on ATP production were investigated. The results showed that Mg2+ greatly affected the synthesis of ATP. The highest ATP production (6.07 mmol/L) could be achieved at Mg2+ concentration of 40 mmol/L. High concentration of potassium phosphate buffer was not favorable for ATP production. At high levels of K+ concentration, ATP production was obviously inhibited, whereas adenosine could not be completely consumed in the absence of K+. Na+ promoted ATP production by stimulating the activity of adenylate kinase. In the meantime, the presence of Na+ resulted in the conversion of adenosine to inosine by stimulating the activity of adenine dehydrated ammonia enzyme.

Kinetic Analysis of Anaerobic Fermentation of 1,3-Propanediol by Klebsiella pneumoniae

CHEN Ke-ke;LIN Ri-hui;LIU Hong-juan;LIU De-hua

. 2005, 5(4): 425-429.

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The fermentation process of 1,3-propanediol by Klebsiella pneumoniae with glycerol as substrate was studied in batch system. A kinetic model was proposed based on the Logistic and Luedeking-Piret equations of cell growth, product formation and substrate consumption. With the evaluated model parameters, the model could provide reasonable description for the fermentation process under various conditions. Based on the model, a feeding strategy for glycerol was determined to maximize the final 1,3-propanediol concentration. The experimental results showed that the feeding mode with nonlinear optimization could improve the 1,3-propanediol productivity and concentration compared with other feeding strategies, such as pulse feeding and constant glycerol concentration feeding.

Kinetic Characteristics of Antibiotic Sisomicin in a Batch Fermentation Process

CHEN Jian-feng;ZHANG Yuan-xing;GUO Yang-hao;MENG Chun;SHI Xian-ai;CHEN Fan

. 2005, 5(4): 430-433.

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The sisomicin production was found to be non-associated with the cell growth of M. inyoensis F003. When starch was used as main carbon source, the maximal specific growth rate was 0.058 h-1, and the maximal specific sisomicin production rate was 0.0018 g/(g×h). The cells of M. inyoensis F003 grew well at 10.0~25.0 g/L maltose or 7.5~15.0 g/L glucose in fermentation broth. It was shown by HPLC analysis and enzymatic measurement that maltose was the main fermentable sugar during the fermentation, and sisomicin biosynthesis was limited when the level of fermentable sugar was below 10.2 g/L. The apparent activity of starch-hydrolytic enzymes in the batch fermentation of M. inyoensis F003 was 1/4 to 1/20 fold of the maximum value 0.84 g/(L×h) in sisomicin biosynthesis phase, its apparent activity, which would result in restriction to the sisomicin biosynthesis by the limitation of fermentable sugar in the broth. Sisomicin above 0.5 g/L was inhibitive to its biosynthesis.

Induced Microbial Transglutaminase Accumulation by Streptomyces hygroscopicus due to Addition of Hydroxylamine

ZHANG Cheng-jie;DU Guo-cheng;LI Yin;CHEN Jian

. 2005, 5(4): 434-437.

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Effect of hydroxylamine addition on the accumulation of microbial transglutaminase (MTG) by Streptomyces hygroscopicus was investigated. The results showed that the addition of hydroxylamine induced MTG accumulation, and the optimum addition concentration and time of hydroxylamine were 0.5 mmol/L and after 38 h of fermentation, respectively. The maximum MTG activity in the culture broth was 5.3 U/mL and increased by 32.5% compared with the control. After the reaction between hydroxylamine and MTG, L-glutamic acid-g-monohydroxamate was produced, which was proved inhibiting MTG. The induced MTG accumulation was a balance process affected by positive action of hydroxylamine and negative action of L-glutamic acid-g-monohydroxamate.

A Preliminary Study of Improvement in Toxin Production of Alexandrium tamarense by Regulation of Nitrate Concentrations

HU Han-hua;SHI Yan-jun;CONG　Wei

. 2005, 5(4): 438-441.

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The influence of nitrate concentration on toxin content of Alexandrium tamarense was investigated, which gave rise to the supply of an appropriate nutrition condition and culture technique of increasing the toxin production of Alexandrium tamarense. Low nitrate level (88.2 mmol/L) resulted in higher specific growth rate, which was 1.2 times of that at high nitrate level (882 mmol/L). When cultures at low nitrate level were supplemented with nitrate at 793.8 mmol/L in late exponential growth phase, the highest cell density (48.5′103 mL-1) was drastically enhanced, which was 7.7 and 2.3 times of those under low (6.28′103 mL-1) and high (21′103 mL-1) nitrate conditions, meanwhile the highest toxin content and production were 1.26 pg/cell and 43.51 mg/L, which were 1.2 and 1.4 or 6.7 and 3.3 times of those under low and high nitrate conditions respectively. The results showed that toxin content of Alexandrium tamarense was enhanced at low nitrate and phosphate levels, and in particular toxin content increased significantly under limited-phosphate conditions. The supplementation of nitrate under low nitrate condition to maintain low level of nitrate contributed to the effective increase of toxin production of Alexandrium tamarense.

Adsorption of Kanamycin on Carboxylic Ion Exchange Fibers

LI Xia-lan;WENG Lian-jin;CHEN Pei-qin;CAI E-nuo

. 2005, 5(4): 442-445.

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Adsorption kinetics and isotherms of kanamycin on carboxylic ion exchange fibers were measured, and the effects of pH, NaCl concentration and temperature on the adsorption were investigated. Results show that the adsorption reaches equilibrium in 10 min and Langmuir isotherm can well describe the adsorption equilibrium. When pH is 7, their static ion-exchange capacity reaches the largest value of 5.6′104 U/g. It decreases sharply with NaCl concentration increase. Temperature has little effect on the adsorption. The dynamic ion-exchange capacity of adsorption of kanamycin fermentation filtrate on carboxylic ion exchange fibers is 5.16′104 U/g, whose 88.1% can be eluted.

Expression of Hblys in the E. coli High Cell Density Culture Using Lactose as an Inducer

LI Zhao-peng;ZHANG Xu;XU Bin;SONG Li-hua;TAN Tian-wei

. 2005, 5(4): 446-449.

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B lymphocyte stimulator (BLyS) is a recently identified member of the tumor necrosis factor (TNF) superfamily, which stimulates B lymphocyte's proliferation and differentiation. The process of expression of hBLyS (human B Lymphocyte cell stimulator) gene under the control of T7 promoter in Escherichia coli was investigated. Lactose was used as an inducer instead of the expensive nonmetabolizable analog of lactose, IPTG. IPTG is satisfactory for small-scale expressions, but not suitable for large-scale fermentations due to its high cost. It was found that lactose could induce foreign protein expression and enhance cell growth during the induction period. Through proper optimization of culture and induction conditions, an expression level near 14.3% of total cellular protein was achieved in the shake flask. This hBLyS expression level reached about 55% of the level (26%) with IPTG as inducer. And in 5 L fermentor, a high cell density OD600=62 and high expression level of hBLyS about16% of the total cell protein were obtained.

Characterization of the Mechanical Properties of Urea-Formaldehyde Microcapsules

. 2005, 5(4): 450-454.

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The mechanical properties of urea-formaldehyde (U-F) microcapsules were determined using a micromanipulation technique and a theoretical model. Loading-unloading, compressing and holding, and compressing to bursting tests at different speeds between two parallel plates for single microcapsules were carried out. It was found that the U-F microcapsules were visco-elastic (mainly elastic) at small compressive deformation, and plastic under large deformation. The transition point from elastic to plastic occurred at about (14±0.2)% compressive deformation. All the microcapsules would disrupt when compressed to about (17±0.2)% deformation, and the burst force increased linearly with their diameter. Compressing speed had no remarkable effect on both burst force and burst deformation. Liquid filled non-permeable and linear elastic spherical membrane model was used to simulate the uniaxial compression of single microcapsule, and its membrane modulus Eh was determined by fitting model prediction to experimental data. The average value of Eh was estimated to be (478±8) N/m.

Resisitivity and Electrochemical Property of Modified Composite Electrode for Vanadium Redox Battery

LUO Dong-mei;XU Qian;KANG Xiao-xue;LI Yan-dan;SUI Zhi-tong

. 2005, 5(4): 455-459.

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The composite electrode used in the vanadium redox battery was modified by adding titanate coupling agent in three ways: direct mixing with carbon-black, dissolving and mixing in ethanol, and dissolving in kerosene. The effect of titanate coupling agent on the resisitivity and electrochemical property of composite electrode was tested. It was observed that titanate coupling agent and carbon-black could not be mixed up uniformly neither by direct mixing nor by dissolving in ethanol. The results showed that the resistivity of composite electrode was reduced by adding titanate coupling agent dissolved in kerosene. This phenomenon was explained with the SEM microphotographs of the composite. The cyclic voltammograms of composite electrode demonstrate that titanate coupling agent in the composite electrode may introduce minor side-reaction in the electrode in vanadium redox battery.

Research on New Copper-Carbon Composite Pantograph Slide Plate

YANG Lian-wei;YAO Guang-chun;LU Yang

. 2005, 5(4): 460-463.

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In view of existing problems of current electric locomotive pantograph slide plate，a new pantograph slide plate was developed using powder metallurgy technology. The new pantograph slide plate consisted of copper, carbon fiber, graphite, etc., and the influences of pressure and sintering temperature on the performance of pantograph slide plate were evaluated based on the measurements of friction, abrasion and impact toughness of test samples. Performance of these pantograph slide plates was compared with other brands that are being used now. The results showed that the best plate was prepared with the conditions of the composition of copper 78%, carbon fiber 2%, graphite 15% and additive 5%, pressure 200 MPa and sintering temperature 880℃. Its performance in friction, abrasion and impact toughness, etc., was improved compared with current carbon slide plates: friction coefficient was reduced by 54.5%, abrasion rate decreased by 41%, impact toughness increased by 9.6 times and conductance increased by 87 times.

Multi-scale Approaches toward Sustainable Development

BI Xiao-tao;JIN Yong

. 2005, 5(4): 464-472.

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Approaches toward the sustainable development need integrated considerations of technical, economical, environmental/ecological and social issues. Current approaches from different disciplines can be grouped into at least three levels: micro-scale, meso-scale and macro-scale. At the micro-scale, green chemistry carries out chemical activities such as chemical design and synthesis so that environmentally benign chemicals can be synthesized without using and generating hazardous substances. Green engineering, at the meso-scale, develops green industrial processes or clean technologies via pollution prevention and cleaner production, which will cause minimal damages or dangers to the environment and ecosystems when the product is manufactured and used. Industrial ecology at the industrial complex or community level seeks to optimize energy and materials use and minimize waste generation in industrial systems or communities by promoting planned materials and energy exchanges. Incorporation of ecological principles with the life cycle thinking in the chemical pathway synthesis, product design, process development, and industrial system and community planning appears to be the most promising engineering approach in achieving sustainable industrial development.

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