The Chinese Journal of Process Engineering

Transient Numerical Simulation on the Billet Heating Process of a Regenerative Reheating Furnace

OU Jian-ping;ZHAN Shu-hua;MA Ai-chun;XIAO Ze-qiang

. 2007, 7(2): 209-215.

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Based on commercial software CFX4.3 and some self-programming codes, a three-dimensional CFD simulation system for simulating thermal process in a regenerative continuous heating furnace was developed. The entrancement, combustion and billet heating process in a 80 t/h regenerative reheating furnace of Xinyu Iron and Steel Company were analyzed numerically, and the computational results were compared with production records and onsite measurements, which verified the practicability of this CFD system. The results indicate that the flow pattern and distribution of temperature in the regenerative reheating furnace are favorable to satisfy the high quality requirements of reheating, where the terminal heating temperature of billets is more than 1460 K and the temperature difference between each node is not more than 10 K. But since the surface average temperature of billets leaving heating zone is only about 1350 K and continued heating is needed in soaking zone, the design and operation of current state are still necessarily optimized to improve the temperature schedule of billet heating.

Numerical Calculation and Experimentation of Permeating Depth of Power-law Printing Ink in Porous Paper Printing

LIU Fu-ping;QI Xiao-kun;WANG An-ling

. 2007, 7(2): 216-222.

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In printing, the permeating depth formulae of power-law printing ink have been derived from the flow fluid equations for porous paper, which vary with the printing pressure and printing velocity, and the permeating depths of power-law printing ink of a few kinds of standard paper have been measured by experiment. The ratios of permeability to porosity are calculated from the measured results according to the permeating depths equations of power-law printing ink. Using the ratios and changing the printing pressure and printing velocity, the permeating depths of power-law printing ink in porous papers are calculated. The results show that computed permeating depths of power-law printing ink are in good agreement with the measured permeating depths of that. This indicates that the computing method is feasible, so that one may apply the permeating depth equations of printing ink in printing preparation and research of permeability of power-law printing ink in porous paper.

The Minimum Fluidization Characteristics of Mixture of Sludge Pellets and River Sand in a Fluidized Bed

HOU Feng-yun;LU Qing-gang;JIAO Wei-hong;HE Jun

. 2007, 7(2): 223-228.

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The experimental study was carried out in a fluidized bed of 105 mm in diameter and 800 mm in height to determine the minimum fluidization velocity and mixing characteristics. The results show that the minimum fluidization velocities and mixing are affected by the mass fraction of sludge pellets and river sand. The more the sludge pellets in the bed, the greater the minimum fluidization velocity, the mixing is the best when the mass fraction of sludge pellets in the mixture is close to 1:1, the more the moisture in the sludge pellets, the greater the minimum fluidization velocity of mixture. Based on the experimental data, a correlation of the minimum fluidization velocity of the mixture of sludge pellets and river sand is proposed. The research results can be reference for the design of bubbling fluidized bed sludge dryers.

Dispersion and Phase Separation Characteristics of Liquid-Liquid-Liquid Systems

YU Qian;YU Geng-zhi;YANG Chao;MAO Zai-sha

. 2007, 7(2): 229-234.

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A liquid-liquid-liquid system of two oil phases and one aqueous phase was prepared. The dispersion and phase separation of the triple-liquid phase system in an agitated tank were recorded with a CCD camera system. The results show that different types of impeller have different dispersion abilities. Radial impeller is better in phase dispersion than that of axial impeller. For axial impeller, the dispersion ability of downward flow type is better than that of upward flow. The phase volume ratio has great influence on the dispersion pattern. The phase separation process of the triple-liquid phase system is classified into types A and B, based on the result of difference in the status of phase dispersion. A mathematic model is proposed to predict the type A phase separation process, and the results show that the prediction is consistent well with the experimental observation.

Numerical Simulation of Electrolyte Flow in Aluminum Reduction Cells

XIA Xiao-xia;WANG Zhi-qi;ZHOU Nai-jun

. 2007, 7(2): 235-240.

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Physical and numerical models of the electrolyte flow in aluminum reduction cells were established by means of appropriate simplification. Based on the commercial CFD software, the electrolyte flow was numerically simulated in three cases, i.e., the flow induced by electromagnetic force, the flow driven by anode gas, and the flow driven simultaneously by the above two forces, respectively. The results indicate that the electrolyte flow induced by electromagnetic force produces a large eddy pattern predominately in the horizontal direction. The electrolyte flow driven by anode gas is a local circulation around each anode. The electrolyte flow driven by the combination of the above two forces is similar to the sole anode gas driven case, which indicates that the electrolyte flow field is mainly determined by the anode gas.

Investigation of Macro-instability in a Stirred Vessel Using the Combined Approach of Power Spectral Density and Wavelet Analysis

JIN Zhe-shan;LI Zhi-peng;GAO Zheng-ming;HE You-jun

. 2007, 7(2): 241-245.

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Experiments were carried out in a flat-bottom cylindrical stirred tank with 0.476 m in diameter. The digital-signal processing approaches for macro-instability were analyzed and the combined approach of power spectral density and wavelet analysis was proved to be suitable for analyzing one-dimensional low-frequency signal with noise and peak value. The torque of the impeller was measured by torque transducer and analyzed by using the combined approach. The results show that there are macro-instabilities in the stirred vessel. The dimensionless macro-instability frequency (f/N) obtained by the combined approach was in good agreement with those from the literature. The combined approach of power spectral density and wavelet analysis was proved to be a useful tool for the investigation of macro-instability phenomenon.

Experimental Investigation on Separation of Potassium Chromate from Its Aqueous Solution by Solventing-out Crystallization

WANG Jiong;XU Hong-bin;ZHANG Song-pei;ZHANG Yi

. 2007, 7(2): 246-251.

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The solubilities of potassium chromate in the mixed solvents of methanol and pure water as well as ethanol and pure water were initially determined. The results show that the mass ratio of solvents to water (CH3OH to H2O and/or C2H5OH to H2O) has great influence on the solubility of potassium chromate in the mixed solvents. The solubility of potassium chromate in water decreases remarkably with the increase in the mass ratio of solvents at fixed temperatures, but increases slightly with the increase in temperature for fixed mass ratio of solvents. A new separation process for potassium chromate was proposed by solventing-out crystallization with ethanol as the solventing-out agent. The effects of different operation parameters related to the separation efficiency of the solventing-out crystallization process were theoretically analyzed and experimentally investigated. The results in this work confirmed the feasibility of applying the solventing-out crystallization method to the separation of potassium chromate from its aqueous solution, thereby providing a new approach to achieving the highly efficient separation of potassium chromate in the clean process for producing chromium compounds by the potash sub-molten salt (SMS) method.

Study on Microwave Demulsifier

FAN Yong-ping;WANG Hua-jun;ZHANG Qiang

. 2007, 7(2): 252-257.

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The demulsification effect was studied experimentally using self-designed 800 W continuous tunnel-shaped box microwave demulsifier, and the influential factors on the demulsification were examined. The optimum conditions were obtained, which were emulsion flux 70 L/h and heating rate 16℃/min. Under these optimum operating conditions, the content of water in an emulsion could be reduced from 50.0% to 2.20% by microwave demulsification-centrifugation separation. The result of circulating demulsification experiments showed that the content of water in emulsion after demulsification tended to be stable with the effective residence time increasing, and multiple demulsifiers in series could make the demulsification better, and improve the processing ability as well. The experiment applied a computer to simulate the electric field, and the difference of electric field distribution for the cases with and without materiel was compared, the results may provide guidance to scale up design of microwave demulsifier.

Microwave Demulsification-Centrifugation Separation of Complicated Emulsion in the Middle Part of a Crude Tank

FAN Yong-ping;WANG Hua-jun;ZHANG Qiang

. 2007, 7(2): 258-262.

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Microwave demulsification-centrifugation separation of complicated emulsion in the middle part of a crude tank in Changqing oil field was studied. The influences of the microwave radiation time, microwave radiation intensity, heating rate, centrifugation time and rotation speed on the dehydration rate of the emulsion were investigated. The optimum conditions were obtained, microwave radiation intensity was 2 W/g, microwave radiation time 3 min, heating rate 8.3℃/min, centrifugation time 4 min, and rotation speed 2500 r/min. Under these optimum operating conditions, the content of water in the emulsion could be reduced from 45.1% to 2.10% by the microwave demulsification-centrifugation separation. Based on the measurements of Zeta potential, the mechanism of microwave demulsification was analyzed, which suggests that the microwave radiation decreased the Zeta potential of the interface between water and oil, and the emulsion beads losing the effect of Zeta potential collided and aggregated easily, leading to the separation of water and oil.

Enhancement of Entrainer on Supercritical CO2 Extraction of Solanesol from Tobacco

ZHAO Ya-mei;HU Xiao-ling;GUAN Ping;YANG Feng

. 2007, 7(2): 263-267.

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Entrainer enhancing technology can significantly improve the solanesol separation efficiency of supercritical CO2 extraction. Based on the principles of supercritical CO2 extraction and enhancing effects from entrainer, three influential factors of the solvents including the type, content and addition method on the extraction of solanesol are examined. How the solanesol and entrainer are selectively separated from the extractive is also discussed. By the orthogonal test of extracting solanesol with entrainer enhancing technology, the importance sequence and prominence are analyzed for the influential factors of entrainer content, pressure and temperature. The optimum conditions for the extraction process are obtained: 25 MPa, 40℃, 150 mL of 95% ethanol for 100 g tobacco. A mathematical model is established with which the yield of the optimum extraction rate of solanesol can be predicted in the present study. Under the optimum conditions of the process, the solanesol extraction rate by designed experiments, 81.5%, is consistant with the prediction value, 82.4%

Characteristics of Adsorbing Heavy Rare Earth Elements with Phosphinic (Phosphoric) Impregnated Resin

LIAO Chun-fa;JIAO Yun-fen;QIU Ding-fan

. 2007, 7(2): 268-272.

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The characteristics of five different phosphinic (phosphoric) impregnated resins adsorbing heavy rare earth elements in hydrochloric acid are studied by static method. The results indicate that the impregnated resin containing double extractants is better than the single one (Cyanex272) under the same conditions. The optimal proportions between Cyanex272 and P507, Cyanex302, Cyanex923, TBP are 1:1, 5:1, 1:1, 2:1. The better pH value is 3~4 and the time of adsorptive equilibrium 50 min. Temperature rising enhances the adsorption respectively. Under the same experimental conditions, the saturated adsorptive capabilities of five different phosphinic (phosphoric) impregnated resins (Cyanex272, Cyanex272-P507, Cyanex272-Cyanex302, Cyanex272-Cyanex923, Cyanex272-TBP) in heavy rare earth are 20.04, 25.37, 21.87, 22.16, 38.48 mg/g, respectively.

Recovery of Copper from Leaching Solution of Copper Smelting Ash

PENG Cui;ZHU Guo-cai;CHI Ru-an;ZHAO Yu-na;ZOU Yong-qian

. 2007, 7(2): 273-277.

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An efficient and reliable approach based on solvent extraction to selectively recover copper from leaching solution of Jinchuan copper smelting ash has been developed in this work. And the extraction isotherm of 50%(j) N902 with initial aqueous acidity of 19.6 g/L was determined at 25℃. The results show that the extractant, N902, has good selectivity to copper, and its saturated capacity of copper under the given conditions is over 23 g/L. The recovery rate of copper in the extraction is over 99%. And copper extraction equilibrium is reached in 90 s using 50% N902 with kerosene as the diluenting agent at an organic and aqueous volume phase ratio (O/A) of 1. Furthermore, over 99.5% of the loaded copper in the organic phase could be stripped by applying 196 g/L H2SO4 as the stripping agent.

Adsorption of Sulfosalicylic Acid on 717 Anion Exchange Resin

XIE Zu-fang;CHEN Yuan;DAI Yan-ju;TONG Zhang-fa

. 2007, 7(2): 278-282.

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The adsorption and elution of aqueous sulfosalicylic acid solution with 717 anion exchange resin were investigated by using dynamic and static methods. The experimental results show that the resin has high adsorption capacity and reusing ability. It can effectively adsorb sulfosalicylic acid in pH 2.2~12. The curve of adsorption obeys the Langmuir isotherm equation. The adsorption is a spontaneous, exothermal and entropy decreasing process. The adsorption kinetics is mainly affected by the intraparticle diffusion. The results indicate that the static saturated adsorption capacity is 508 mg/g (resin). The sulfosalicylic acid adsorbed in the resin can be eluted by 10%NaCl+2%NaOH solution quickly with elution rate reaching 99% at 315 K. The resin can be used in wastewater treatment and recovery of sulfosalicylic acid.

Comparison of Dissolved Air Flotation and Sedimentation in Treatment of Typical North China Source Water

LIU Shan-pei;WANG Qi-shan;HE Wen-jie;HAN Hong-da;FAN Xue-hong;GENG Tian-jia

. 2007, 7(2): 283-287.

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The treatment of typical north China water by dissolved air flotation (DAF) and sedimentation process was examined. A pilot plant with a water treatment capacity of 120 m3/d constructed in the Jieyuan Water Treatment Plant (JWTP) of Tianjin, China, was utilized for the comparison of the two processes. The results show that during the pilot test, DAF process can remove particles and organic mater more efficiently than sedimentation process. The removal rate for turbidity by DAF process is 5.5% higher than that by sedimentation in normal turbidity period, and 40% higher in low turbidity period, it is 5%~10% higher for removals of algae, total organic carbon (TOC), trihalomethane formation potential (THMFP) and bacteria in all periods. The removal rates for turbidity, TOC, THMFP, algae and bacteria by DAF process can reach 95%, 30%, 20%, 94% and 97% respectively. From the results of the pilot test, it can be concluded that DAF is a feasible clarification process, especially for source water with low turbidity and high algal blooming.

Reduction Kinetics of a-Fe2O3 Microspheres

WANG Jian-hua;SUI Zhi-chao;YANG Yong;CHANG Jie;XIANG Hong-wei;LI Yong-wang

. 2007, 7(2): 288-292.

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The spherical a-Fe2O3 particles were prepared by the combination of continuous co-precipitation and spray-drying technology. The sample particles exhibited good spherical morphology with average diameter of 15.3 mm. The kinetic parameters of isothermal reduction of a-Fe2O3 to Fe3O4 in 563~583 K were obtained by H2-thermogravimetric analysis according to Hancock-Sharp method. The results show that the reduction rate increases with increasing reduction temperature, and the reduction reaction is predominantly controlled by phase change reaction mechanism when the reduction degree is lower than 0.8, partial Fe3O4 will be reduced to a-Fe2O3 in the terminal stage of the reduction process as the reduction temperature is higher than 578 K. Within the reduction range controlled by the phase change model, the activation energy is 152.44 kJ/mol.

The Biodegradation Kinetic Model of Ethylbenzene Waste Gas in Biofilters

WANG Bao-qing;MA Guang-da

. 2007, 7(2): 293-297.

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An experimental investigation on purification of ethylbenzene waste gas is conducted in a biofilter packed with ceramic pellets. The biofiltration model is derived from a mass balance based on diffusion and biodegradation reaction of ethylbenzene. The results show that the zero order biodegradation kinetic model in the case of diffusion limitation within the biofilm fits the experimental results well. The bQgCg,in1/2 is equal to a constant of 19.22 under the conditions of Staphylococcus as biodegradation bacteria, residence time more than 28.3 s, gas flowrate less than 1.0 m3/h, inlet concentration less than 6500 mg/m3. The value of b could be obtained from above equation if the values of Cg,in and Qg are given. Then Cg(h) could be calculated from the equation of Cg(h)=Cg,in(1-bh)2. Therefore, it is significant that the obtained equation can offer a reference for design of biofiter.

Kinetic Study on Carbochlorination of Bastnaesite Concentrate in the Presence of SiCl4

ZHANG Li-qing;WANG Zhi-chang;JIANG Lin-lin;WANG Xiao-huan;ZHAGN Feng-chun

. 2007, 7(2): 298-301.

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A carbochlorination process of bastnaesite concentrate was investigated by using activated carbon powder as reductant, Cl2 as chlorination agent and SiC14 as defluorination agent. The chlorination rate of bastnaesite concentrate was relatively low at the temperature below 500℃. When the temperature was raised and the amount of defluorrination agent increased, the rare earth chloride yield increased. But with the carbochlorination going on, the influence of temperature became weak. In the temperatures range from 450 to 650℃, and in the presence of SiCl4, the rare earth chloride yield increased from 36% to 98%. The carbochlorination of bastnaesite concentrate could be carried on at a low temperature in the presence of SiCl4. The carbochlorination followed the shrinking sphere model, and the model was expressed as a mathematical formula of kt=1-(1-X)1/3 and the apparent activation energy of the carbochlorination was 42.5 kJ/mol.

Separation of Solid from Petroleum Residue with a Hydrocyclone at High Temperature

GUO Chun-li

. 2007, 7(2): 302-305.

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Separation of solid from petroleum residue was carried out with a hydrocyclone at high temperature. And the influence on the separation efficiency of hydrocyclone was studied owing to the physical property and the petroleum chemical ingredient of the residue. The experimental results show that hygrocyclone can separate high-density particles in the residue effectively. And the density and viscosity of the flows before and after separation vary greatly. The separating efficiencies of toluene insoluble components, asphaltene and resin reach to 53.6%, 47.1% and 30.7% respectively under the temperature of 200℃ and the flow rate of 15 m3/h, which is mainly due to the combination and reuniting among particles and macromolecules. Moreover, calculation on cutting diameter was made according to the equilibrium orbit theory and testified to be consistent with the result of experiments.

Selection of Purification Solvent of D,L-lactide

HANG Ning;WANG Peng;ZHANG Ying-min;SHI Shu-jie

. 2007, 7(2): 306-309.

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Ethyl acetate and ethanol as two kinds of nontoxic solvent were studied in the process of purification of D,L-lactide. The effects of recrystallization temperature, time span and ratio of D,L-lactide to solvent on the yield of D,L-lactide were investigated, with the melting point as the designation of D,L-lactide purity. The results show that under different temperatures, different time spans and different ratios of D,L-lactide to solvent, the melting point of D,L-lactide purified three times with either solvent can meet the request for polymerization. The economic comparison of these two solvents indicates that ethanol is more suitable to be the solvent in the purification of D,L-lactide and the optimal conditions are obtained as recrystallization temperature 4℃ or lower, time span more than 1 h and dosage of ethanol 2.5 mL/g. The yield of D,L-lactide after 3 times purification with the optimal conditions is 63%. The product was characterized by elemental analysis, FT-IR and 1H-NMR, and the results demonstrated that it fit the cycle-structure of D,L-lactide.

A Novel Approach to Bioleach Soluble Phosphorus from Rock Phosphate

CHI Ru-an;XIAO Chun-qiao;HUANG Xiao-hui;WANG Cun-wen;WU Yuan-xin

. 2007, 7(2): 310-316.

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A novel approach to bioleach soluble phosphorus from rock phosphate, involving the bio-oxidation of pyrite by adaptated Acidithiobacillus ferrooxidans (At. f) and the product of sulfuric acid to dissolve rock phosphate, has been proposed in this paper. The soluble phosphorus could be leached more effectively in the presence of pyrite by At. f than that leached directly by sulfuric acid. The optimal technological parameters are presented. The highest phosphorus leaching rate is 9.00% when the culture substrate is the mixture of FeSO4·7H2O and pyrite, the phosphorus leaching rate is 8.00% when the initial pH and culture time are 2.5 and 5 d, respectively. The optimal rock phosphate particle size is 0.05 mm for the leaching of phosphorus. The bigger the grains of pyrite, the lower the phosphorus leaching rate. The bacterium At. f should be appropriately adaptated, which makes it easier to bioleach soluble phosphorus from rock phosphate.

Effects of Microwave Roasting on Leaching Behavior of Diaspore Ore

WABG Yi-yong;ZHANG Ting-an;CHEN Xia;BAO Li

. 2007, 7(2): 317-321.

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The effects of microwave roasting pretreatment on leaching behavior of diaspore ore were investigated. The influences of microwave irradiation temperature and microwave irradiation time were studied. The mechanism of microwave roasting pretreatment was also studied. The results show that microwave roasting pretreatment can greatly improve the leaching efficiency of Al2O3, and decrease the mole fraction of digestion liquor. The optimal microwave roasting conditions are that the microwave irradiation temperature is 535℃, and the microwave irradiation time 5 min. The high microwave irradiation temperature can result in ore sintering, influencing the leaching effect. Prolonging microwave irradiation time has no obvious influence on leaching behavior.

Dissolution Behavior of Chromium Ore in CaO-SiO2-MgO-Al2O3 Slag System

LIU Yan;JIANG Mao-fa;XU Li-xian

. 2007, 7(2): 322-326.

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The dissolution behavior of compact chromium ore with definite shape in CaO-SiO2-MgO-Al2O3 slag system was studied, and the effect of different slag compositions on the dissolution amount and rate of chromium ore in slag was investigated. The dissolution mechanism of chromium ore in slag was also discussed. It was found that the dissolution rate of chromium ore in slag increased with slag basicity decreasing under the present experimental conditions. The dissolution amount and rate of chromium ore decreased with the increase of Al2O3 and MgO contents. In particular, they decreased with the former. Addition of CaF2 to the initial slag increased the dissolution rate markedly.

Effect of TiO2 Addition on Crystallization of Glass-ceramic Made from Blast Furnace Slag

YUE Qin-yan;ZHANG Sheng-xiao;YU Hui;GAO Bao-yu;WANG Xiao-na;XIE Jian-kun

. 2007, 7(2): 327-331.

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Glass-ceramic made from blast furnace slag was studied. Glass-ceramic samples were produced by changing the content of TiO2 as nucleation-agent in the parent glass, and the samples were analyzed by a differential thermal analyzer (DTA) at different heating rates. Based on heating rate and the peak crystallization temperatures from the DTA curves, three different methods were used to calculate crystallization activation energy of glass-ceramic samples. The results showed that as TiO2 content increased, the values of activation energy first decreased, then increased. When the content of TiO2 was 3.1%, the activation energy was the lowest, 135.7, 143.9, or 151.7 kJ/mol, as calculated by the three different methods. Infrared spectra showed that the crystallization was the easiest when the content of TiO2 was between 3% and 4%. X-ray diffraction analysis showed that when the content of TiO2 was between 3% and 4%, the formed glass-ceramic had the crystal phases of diopside as main phase and rutile as subordinate crystal phase.

Experimental Study on Melting of Hospital Waste Incineration Ash by Electric Arc Furnace

CAI Jiu-ju;LIU Han-qiao;QI Peng-fei;TIAN Dong-qing

. 2007, 7(2): 337-341.

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The pilot-scale melting experiment of hospital waste incineration ash using a 2 kg DC electric arc furnace was carried out. The melting characteristics of bottom ash alone, and a mixture of bottom ash with bag fly ash were examined in terms of chemical composition, mineralogy, morphology, leaching behavior and residual fraction of heavy metals. The experimental results indicate that the bottom ash mainly consists of silicates, and major crystalline phases of bag fly ash are CaSO4 and NaCl, two kinds of melted slag are single-phase amorphous, glassy product. Volume reductions of two slags in comparison to the bottom ash and mixed ash respectively reach 78% and 80.5%. The Pb, Cd and Zn leaching concentrations of bag fly ash far exceed the hazardous waste landfill regulatory thresholds, the obtained slag is environmentally acceptable, possibly because heavy metals in the slag are combined into the Si-O network by the melting process. Residual fractions of Pb, Cd and Zn in two slags are low, and residual fraction of heavy metals in sample SLAG2 is lower than that in sample SLAG1.

Synthesis and Characterization of TiO2 Particles and Their Application in the Field of Photocatalytic Degradation of Acid Red B

CUI Yu-min;SUN Wen-zhong

. 2007, 7(2): 342-346.

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TiO2 nanometer particles are prepared by a sol-gel process. XRD technique is used for the characterization of samples. The primary factors which influence the photocatalytic degradation of acid red B are discussed. The results show that the photodegradation rate of acid red B can reach 99.2% by using TiO2 powder calcined at 600℃ as photocatalyst under the conditions of TiO2 2.00 g, air flow rate 10.0 L/min, starting concentration of acid red B 80 mg/L, pH 6.5, and illumination time 140 min.

A Universal Thermodynamic Model of Calculating Mass Action Concentrations of Components in Strong Electrolyte Binary Aqueous Solutions

GUO Han-jie;ZHAO Wei-jie;LI Lin;YANG Xue-min

. 2007, 7(2): 347-353.

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A universal thermodynamic model which can be applied to calculate mass action concentrations of components in strong electrolyte aqueous solutions has been developed in this work based on the ion-molecule coexistence theory. To verify the new universal thermodynamic model, four binary systems, such as KCl-H2O, CsCl-H2O, NaCl-H2O and BaCl2-H2O, are chosen to calculate mass action concentrations of components in a concentration range from 0.2 mol/kg to saturation level at 298.15 K. The present calculated mass action concentrations are based on pure species as standard state and mole fraction as concentration unit. A transformation coefficient is provided to convert the reported activities based on infinite dilution as standard state and mass mole fraction as concentration unit, so that the comparison of the present model with the literature data can be conducted. The transformation coefficients change in a very narrow fluctuation range for each component. The mass action concentrations of components are in good agreement with those of reported activities. Hence, the newly developed universal thermodynamic model can be successfully applied to predict activities of components in other strong electrolyte aqueous solutions and to describe their structure characteristics in aqueous solutions.

Coupled Simulation of Multiple Physical Fields in a 300 kA Aluminum Electrolysis Cell

LI Mao;ZHOU Jie-min;WANG Chang-hong

. 2007, 7(2): 354-359.

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The method of nodal voltage analysis and magnetic scalar potential method were utilized to develop a customized program to model the coupled electromagnetic and flow fields in a 300 kA aluminum electrolysis cell, and the flow field was simulated with the derived electromagnetic forces. From the modeling it was shown that the asymmetry of the vertical magnetic component was obvious along the x and y axes while the horizontal current exerted significant effect on the magnetic fluid flow when interacting with the vertical magnetic field. There were four large vortexes in the liquid aluminum. The calculated results were compared with the measurements.

Fractal Geometry of Particle Aggregates Formed in Calcium Sulfite Slurry

NI Wei-min;WU Zhong-biao;GUAN Yu-hong;ZHAO Wei-rong;ZHENG Ping

. 2007, 7(2): 360-365.

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The solid-liquid separation is an important operation for the regenerated slurry of dual-alkali FGD system, and calcium sulfite could predominate in particle aggregates of the slurry. The settling velocity of calcium sulfite particles is a key parameter for the solid-liquid separation design. However, the settling velocity predicted by Stokes' Law could be suitable only for a spherical aggregate, but not for the irregular one. In this work, fractal geometry was introduced in order to characterize highly irregular geometric shapes. The sizes of calcium sulfite particle aggregates were analyzed using a metallographic phase microscope and image analysis. The results showed that particle aggregates had fractal features. The fractal dimensions could reveal the characteristics of the aggregates' geometry and aggregation process. An exponential relation between the fractal dimension D2 and the particle size l was determined as AμlD2. According to fractal theory, a parameter can be used to modify Stokes settling velocity close to actual settling velocity. The results could be valuable for the design of solid-liquid separation processes.

Prediction on Product Yields of Catalytic Reforming Unit by BPNN-PCA

GUO Yan;LI Chu-fu;HE Xiao-rong;GONG Zhen-zhi;CHEN Bo;ZHANG Qiu-yi

. 2007, 7(2): 366-369.

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An accurate prediction model of product yields of the catalytic reforming unit is important for keeping the production plan in optimal operation while the external factors are changing in a refinery. The prediction model based on back propagation-principal component analysis (BPNN-PCA) method was appended to the GIOPIMS (Graphic I/O Petro-chemical Industry Modeling System). In the actual production planning, the prediction results were accurate. The prediction model on product yields of the catalytic reforming unit can effectively assist the production planning.

Purification Process Design and Simulation of Enzyme-catalyzed Biodiesel Production Using Methyl Acetate as Acyl Acceptor

CHEN Jian;DU Wei;LIU De-hua

. 2007, 7(2): 370-374.

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Using methyl acetate as acyl acceptor instead of methanol, enzyme-catalyst was saved from the harm of methanol and glycerol. In this work, biodiesel purification process of methyl acetate reaction system was carried out. Moreover, feasible operation parameters and material balance were also obtained based on the results of purification experiments. The final end-product, refined biodiesel, could meet the strict criterion of DINE 51606. The vacuum rectification of crude biodiesel was analyzed by simulation software Pro/II to assess the influential factors on it. The computing results showed that the preferred operation parameters of the vacuum rectification column would be in the ranges of 9~11 pieces of theoretical trays, 133~1333 Pa at the top of distillation column and 1.5~3.0 of the reflux ratio.

Fed-batch Cultivation of Protocorm-like Bodies of Dendrobium huoshanense for Producing Polysaccharides in an Air-lift Bioreactor

WEI Ming;JIANG Shao-tong;LUO jian-ping

. 2007, 7(2): 375-379.

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The cultivation of protocorm-like bodies of Dendrbium huoshanense was carried out in a 10 L air-lift bioreactor. The effects of inoculum size, aeration rate, carbon, phosphate sources on the cell growth and accumulation of polysaccharides were investigated in suspension cultures of protocorm-like bodies from Dendrobium huoshanense. Thirty-day-old cells were transferred into liquid medium with the inoculum density of 100 g/L (fresh weight) cells and aeration rate of 0.5 L/min. The optimal concentrations of sucrose and phosphate in the medium for the cell growth were 30 g/L and 2.5 mmol/L, respectively. A total of 0.312 mmol/L of medium phosphate was better for the accumulation of polysaccharides. The results in two-step cultivation indicated that the maximum biomass and polysaccharides yield were 46.7 g/L (dry weight) and 8.15 g/L, which are 1.5 and 2.6 fold of those in one-step cultivation respectively.

A Pretreatment Process for Hyaluronan Extraction Based on Characteristics of Fermentation Broth

DENG Yu;DU Guo-cheng;LI Xiu-fen;LIU Deng-ru;CHEN Jian

. 2007, 7(2): 380-384.

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To increase the quality and yield of hyaluronan, a novel pretreatment process aiming at removing microorganism and protein in fermentation broth was developed. The optimal conditions for pretreatment process were obtained as follows: the concentration of trichloracetic acid was 25 g/L, the mixed diatomite loading (ratio of coarse to small diatomite 1.5:1) was 1.2% of fermentation broth, the filtration temperature was 60℃, and pH value was 7.0. After pretreatment, the hyaluronan solution was treated by postprocessing of precipitation with ethanol, air flotation and granulation by ethonal. The relative molecular weight of hyaluronan product was up to 1.9 million. 46.39% glucuronic acid and only 0.047% protein were found in the end product of hyaluronan. The yield of HA reached up to 91.3%.

Effect of Electric Field on Cell Growth, Permeability and Extracellular Enzymatic Reactions of Phanerochaete chrysosporium

MIAO Fu-yuan;MIAO Chang-chun;HAN Hui-long;JIN Wen-biao;LIU Zheng

. 2007, 7(2): 385-389.

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The effect of electric field on the cell growth and permeability of Phanerochaete chrysosporium, and extracellular enzymatic activity of laccase, lignin peroxidase and manganese peroxidase, squeezed extracellularly out of Phanerochaete chrysosporium, was experimentally investigated, respectively. The application of 50 Hz alternating current of 50 mA enhanced the growth of Phanerochaete chrysosporium, giving a 1.72 fold increase in cell dry weight after 10 d culture. The cell permeability was also increased when exposed to either DC or AC. The enzymatic activity of laccase, lignin peroxidase and manganese peroxidase was firstly increased and then reduced when exposed to DC, and the suitable operation time was 10 h for DC of 10 mA.

Purification of Supercoiled Plasmid DNA by CTAB

XU Ying-qian;WU Lei;GAN Yi-ru

. 2007, 7(2): 390-394.

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A new non-chromatographic method for the large-scale purification of pharmaceutical-grade plasmid by CTAB was developed. Meanwhile the purification process was optimized. Firstly, large amount of impurities in the crude plasmid mixture had been reduced dramatically by a high purity filter medium?CelPure diatomite. Gradient concentrations of CTAB produced precipitation of plasmid variants. The selectivity mechanism is most likely based upon conformational differences among the several forms of DNA. The optimal concentration of CTAB to precipitate plasmid DNA is 2.0 g/L CTAB, and the optimal salt concentration for precipitating dissolution is 0.75 mol/L by using the plasmid pcDNA3 containing strain E. coli DH5a as a material. CTAB is effective for selective precipitation of plasmid DNA from proteins, RNA and the other relaxed and denatured forms of plasmid DNA. The final yield of supercoiled plasmid DNA is 78.94%, and the purity of the final concentrated solution is higher than 90% by this method. The result of plasmid DNA precipitation is related to initial plasmid concentration, and decline in concentration of supercoiled plasmid DNA is linear to CTAB increment. Supercoiled plasmid of molecular size is more important than purity. The molecular structure of Supercoiled plasmid is more important than molecular weight in the purification process.

Immobilization of Lipase by Sol-Gel Entrapment

GAO Yang;NIE Kai-li;WANG Fang;TAN Tian-wei

. 2007, 7(2): 395-398.

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Candida sp. 99-125 lipase was entrapped in organic-inorganic sol-gel powder prepared by polymerization of tetramethoxysilane (TMOS) and propyltrimethoxysilane (PTMS). PEG (MW=20000) and HCl were used as stabilizing additive and catalyst during the sol-gel process, respectively. The optimal preparation conditions were studied, which are PTMS/TMOS molar ratio at 4:1, water/silane molar ratio 20, enzyme loading 3.71% (w) of silane precursor and hydrolysis time of silane precursor for 35 min. The specific activity of immobilized lipase was 2.02 times higher than that of non-immobilized lipase under the optimal water content in esterification reaction system. The esterification activity of immobilized lipase retained 59.1% of the initial activity after 2 h incubation under 100℃, and the activity of immobilized lipase remained almost unchanged after 8 consecutive batches of each 12 h reaction.

Synthesis of 13X Zeolite and MCM-41 Mesoporous Materials and Treatment of Cd2+-containing Wastewater

YANG Jing;MA Xiao-guang;MA Hong-wen;Ray L. Frost

. 2007, 7(2): 399-403.

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The 13X zeolite was synthesized hydrothermally by the calcined natural rocks, K-feldspar, from Jixian county, Tianjin, China. The ordered mesoporous molecular sieve material MCM-41 was synthesized by hydrothermal method using fumed silica, NaOH and CTAB. The synthesized 13X zeolite and MCM-41 samples were characterized by XRD, N2 adsorption, SEM and TEM methods. The results show that the MCM-41 has larger pore size (2~4 nm) and higher specific surface area than the microporous 13X zeolite. Moreover, the 13X zeolite and MCM-41 were used to treat Cd2+-containing wastewater. The amounts of Cd2+ adsorbed onto the 13X zeolite and MCM-41 were studied in different adsorbent amounts, pH values and mixing times. Theoretically, the adsorbed amount of Cd2+ onto MCM-41 should be much more than that of 13X-zeolite because of its higher specific surface area and larger pore size. However, it is shown that the 13X zeolite (with the pore size of about 0.7 nm) adsorbs much more Cd2+ than the MCM-41 sample in Cd2+ aqueous solution. The adsorption rate of the 13X zeolite is over 99%, and the adsorption rate is below 80% for the MCM-41. The 13X zeolite can be used for treating the wastewater containing Cd2+ more effectively than the MCM-41 mainly because of their different chemical compositions, pore structures and surface charges, and the 13X zeolite interaction with Cd2+ by ion exchange and the precipitation as well.

Preparation of Beta-zeolite/Carbon Nanocomposite Membrane

ZHOU Zhi-hui;SHAO Guo-lin;YANG JIan-hua;CHANG Li-feng;WANG Jin-qu

. 2007, 7(2): 404-408.

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A novel Beta-zeolite/carbon nanocomposite membrane has been prepared on a porous α-Al2O3 substrate by dip-coating. By single component gas experiments at room temperature, the Beta-zeolite/carbon nanocomposite membrane exhibits hydrogen permeations that are one order of magnitude higher than pure carbon membrane with comparable permselectivities. It shows that Beta-zeolite acts as high gas permeable phase in membranes. From the SEM images, when the amount of Beta-zeolite is increased, the thickness of nanocomposite membrane is reduced from 14 mm to 7 mm, which is helpful to decrease the resistance of gas permeance. Finally, the pathway through nanocomposite membrane is inferred by the experimental data and SEM images.

Effects of Applied Potential on the Growth Process of Porous Aluminum Oxide Membrane

JIANG Hai-bo;LI Chun-zhong;ZHAO Yin;HU Yan-jie

. 2007, 7(2): 409-413.

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Two-step electrochemical anodizing approach was introduced to prepare the porous aluminum oxide (AAO) membrane in oxalic acid solution. The dependence of morphology and growth process of AAO membrane on applied voltage was studied. It is found that current density, growth rate, pore diameters and pore distances of AAO membrane increase with the anodizing voltage increasing and the volume expansion factor varies linearly with the anodizing voltage. The porosity keeps a constant of 12%, which is independent of the applied voltage.

Thermal Stability of MC Nylon 6/ZnO Nanocomposite Based on Method of in situ XRD

ZHOU Li;TIAN Yan-wen;ZANG Shu-liang;ZHANG Jian-zhong

. 2007, 7(2): 414-418.

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MC nylon 6/ZnO nanocomposite was prepared by in situ polymerization method. Dynamic high temperature XRD patterns indicate that with the temperature increasing the α1 (200 lattice plane) of MC nylon 6 was shrunk, but the α2 (002+202 lattice plane) was expanded, the thermal expansion coefficients of the lattice planes of pure MC nylon 6 were aTα1=-8.8×10-5 ℃-1, and aTα2=1.6×10-4 ℃-1, the thermal expansion coefficients of MC nylon 6/ZnO nanocomposites were aTα1=-1.7×10-4 ℃-1, and aTα2=3.4×10-4 ℃-1 respectively. With the temperature increasing, the relative crystallinity of MC nylon 6/ZnO nanocomposite decreased, the crystal structure was almost destroyed at the temperature close to the melting temperature, and with the temperature decreasing from the tiptop, it recrystallized, the variation of crystalline morphology and relative crystallinity was almost reversible in the tested temperature range from 20 to 210℃. Along with the increase of the content of nanometer particles, the thermal stability of the composites showed a rising trend. The more evenly the particles distributed, the better the thermal stability was. Nano-ZnO addition made starting degradation temperature of MC nylon 6 increased by 1~9℃ and the maximal weight-losing rate temperature also increased.

Prospects of High-efficient Utilization of Biogas through Solid Oxide Fuel Cells

ZHU Qing-shan

. 2007, 7(2): 419-424.

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Biogas is readily available from various sources in large quantity. Large-scale utilization of biogas, which could effectively alleviate the energy shortage of China in the future, will be mainly dependent on the development of new technologies that could well be suitable to the characteristics of biogas, e.g. small scale, low net caloric value, frequent change of composition, etc. In the present paper, the status quo of biogas resources was investigated, and current status and future trends of biogas utilization were analyzed. Special focuses were put on analysis of technological and economic feasibility of biogas power generation via solid oxide fuel cells (SOFCs). It is demonstrated that SOFCs are highly adaptable to the characteristics of low net caloric value and frequent composition change of biogas. And, electrical generation through SOFCs is economically much superior as compared with conventional power generation techniques. Consequently, large-scale utilization of biogas via SOFCs will bring great economic, social and environmental benefits.

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