The Chinese Journal of Process Engineering

Distribution and Fluctuation of the Light Intensity in Two-dimensional Fluidized Bed Photoreactors

HAO Xiao-gang;Li Hong-hui;Yu Qiu-shuo;Zhang Zhong-lin;Fan Cai-mei;Sun Yan-ping

. 2005, 5(5): 473-478.

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The distribution and fluctuation of the light intensity in a liquid-solid and three-phase fluidized bed are influenced by the fluid flow under the illumination of external parallel light. The mathematical models of the light intensity distribution in liquid-solid and three-phase flat fluidized beds are established based on the Lambert-Beer law. The light intensity is attenuated along the lateral distance in the fluidized bed and the influence of the gas holdup, liquid holdup, the specific absorbance of gas and solid on the distribution of light intensity is analyzed. The light intensity signals are measured using a fiber sensor made in our laboratory and the calculation of the model is consistent with experimental results. The analysis about the fluctuating signals shows that the PSD (power spectral density) is attenuated regularly from the low frequency to the high frequency in the liquid-solid fluidized bed, the PSD undulates because of the bubbles in the three phase fluidized bed and the peaks occur at 5~12 Hz, which is coincident with the frequency of bubbles. The model can be easily extended to other light sources and other types of fluidized bed photoreactor.

Numerical Simulation of Burning Characteristics of the Novel Low-dust Slagging Combustor of Pulverized Coal

WANG Xiao-han;ZHAO Dai-qing;CHEN En-jian;HE Li-bo;CHEN Yong

. 2005, 5(5): 479-484.

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The technology of pulverized coal low-dust slagging combustion, which is most suitable to small industrial furnaces, was introduced. Numerical method was used to simulate the burning characteristics of a f400 mm combustor. In addition to selecting several proper models for gaseous flow, solid phase flow, coal combustion and NO emission, the behavior of coal particles near the wall was discussed. Based on these models, the two-phase flow and combustion characteristics in the combustor were analyzed in detail. The predicted temperatures and NO concentrations were compared with the experimental data from the combustor, and acceptable agreement was achieved. Based on the experimental data and computational analysis, the old slag combustor was modified because of some defects. The recent experimental results proved that the performance of the new combustor was much superior to old one at low stoichiometric ratio, offering the advantages of high carbon burning efficiency, not very high temperature at the rear of combustor, high slag-capturing efficiency and low NO emission. When stoichiometric ratio is about 0.8, NO concentration at the rear of combustor is about 400 mg/Nm3, which is much less than that in conventional cyclone combustors.

The Local Phase Holdups of Three-phase Loop Reactors

ZHANG Tong-wang;GAO Ji-xian;WANG Tie-feng;WANG Jin-fu

. 2005, 5(5): 485-489.

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Better understanding of the hydrodynamic behavior in three-phase airlift loop reactors (TPALRs) is important for their design and scale-up. In the present paper, combination of pressure difference method with gas-liquid inter-phase slip velocity was proposed to measure the phase holdups in TPALRs. The comparison between the measured axial-averaged solid holdups and those calculated from the solid loading shows that the used method is reliable. The gas holdup and solid holdup were experimentally studied with the proposed measuring method. The results show that the gas holdup increases with the increase in the superficial gas velocity, and increases along the axial position. Large particles can break bubbles and increase the gas holdup. The solid holdup decreases with the increase in the superficial gas velocity, and its variation along the axial position is more remarkable than that of the gas holdup. The solid holdup decreases with the increase in the superficial gas velocity. At high superficial gas velocities, the solid holdup has an S-type axial profile.

Numerical Simulation of Cooling Air Distribution of Bottom Cavity of the Regenerator in a Cowper Stove

HU Ri-jun;CHENG Su-sen

. 2005, 5(5): 490-494.

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Numerical simulation studies by application of CFX-4.3 computational fluid dynamics software and contrastive analysis were carried out on the distribution of cooling air of the bottom cavity of the regenerator in a Cowper stove. It was found that the distribution of cooling air in the cross section of regenerator without flow control plates was very un-uniform and the capacity of heat storage was reduced greatly. The application of the flow control plates may improve the uniformity of the cooling air distribution effectively.

Micromixing Characteristics in a Stirred Tank with Multiple Impellers

MIN Jian;GAO Zheng-ming;JIANG Yong;SHI Li-tian

. 2005, 5(5): 495-498.

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The product distribution of competitive reactions in an agitated reactor is significantly affected by micromixing. A pair of competitive parallel test reactions were used to investigate the micromixing in a stirred tank of 0.476 m diameter with multiple impellers. One triple 3-narrow blade hydrofoil CBY impeller agitator and combination of one 6-hollow blade disk turbine HD-6 as bottom impeller with two CBY impellers were used in the experiments. The effects of feeding time, impeller speed, feeding location and agitator type on product distribution were systematically studied. For the multiple impeller systems, the product distribution is dominated by the impeller closest to the feeding location. The simplified micromixing model, the engulfment model, was used to predict the product distributions of triple CBY impellers. Good agreement can be found between the results predicted by the engulfment model and the experimental data. The results are of importance to the optimum design of multiple impeller industrial stirred reactors for fast complex reactions.

Recovery of Cyanide with 201′7 Strongly Basic Anion Exchange Resin

LIAO Zan;ZHU Guo-cai;LAN Xin-ze;WANG Wen-zhong

. 2005, 5(5): 499-503.

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The adsorption and elution performances of 201′7 strongly basic anion exchange resin for cyanide were studied, and the influences of pH value, temperature and concentration were also examined. The optimum conditions for cyanide adsorption were determined under pH value between 10 to 11, room temperature and batch-wise operation for 15 min. A neutral strippant NaCl was selected for NaCN elution. The results show that the capacity of batch saturated adsorption for cyanide is 25.39 mg/mL, and the dynamic saturation is 27.43 mg/mL. The thermodynamics and kinetics of 201′7 basic anion exchange resin for adsorption of cyanide were investigated. The rate constants of adsorption and elution are k=1.01′10-2 and k=2.12′10-2 s-1 respectively. And the adsorption process is consistent with the Freundli equation. The results illustrate that 201′7 basic anion exchange resin can be used for recovery and disposal of cyanide in waste water.

Structural Optimization of a Novel Gas-Solid Separator Incorporating Inertial and Centrifugal Separatio

LIU Xian-cheng;LU Chun-xi;SHI Ming-xian

. 2005, 5(5): 504-508.

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As the feed stuffs of fluid catalytic cracking (FCC) become increasingly heavier, a new regeneration technology combining post coke-burning riser and conventional turbulent bed regenerator has been developed in this study. One of the key components of this technology is the gas-solid separator located at the outlet of the riser regenerator, having the advantages such as simple structure, high separation efficiency, low pressure drop and flexible operation. To meet these requirements a novel gas-solid separator incorporating inertial and centrifugal separation was investigated in detail. Talcum powder was employed as solid medium. Separation efficiency and pressure drop were experimentally tested in nine separator configurations under the same gas velocity and particle concentration at the separator inlet. The results show that a reasonable scheme is as follows: no baffle to block the solid circulation, no hem at the slots to obstruct gas entering the centre pipe, and dimensionless radius of centre pipe between 0.50 and 0.55.

Application of Fly Ash in Stabilization of Excess Sewage Sludge from Antibiotic Wastewater Treatment

XIANG Hui-qiang;YANG Hong;ZHI Yan-sheng

. 2005, 5(5): 509-513.

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Stabilization of excess sewage sludge from antibiotic production wastewater treatment with fly ash was studied. Fly ash and excess sewage sludge were mixed in four different ratios and three mixing times. Toxicity characteristics leaching procedure (TCLP), equilibrium leaching test (ELT), and long-term leaching test (LTLT) were used to investigate the leachability of heavy metals. Taking heavy metal ion concentration and pathogens into account, the mixture may be qualified to be used as soil conditioner for soil improvement application. Surface complexation and deposition (silicate and hydrate deposition) were the main mechanisms of fixation of heavy metals by fly ash. Surface complexation and silicate deposition worked in a relatively wider pH range, especially low pH. Hydrate deposition worked at higher pH. It was found that the fixing capacity increased with the increase of the loading rate of fly ash. In the study, fly ash can remove at least 92.6% of microorganism, and the high pH condition was considered to be the predominant reason for killing pathogens.

Removal of Fe3+ by Solvent Extraction with P204 from Bacterial Leaching Solution of Copper Concentrate Ore

XIE Hai-yun;LIU Zhong-hua;CHEN Wen;YIN Shu-biao

. 2005, 5(5): 514-516.

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Using solvent extraction to separate Fe3+ from the leaching solution of arsenic-bearing sulfide copper concentrate ore is an important step of the process for preparing copper arsenate. P204 can extract Fe3+ from sulphate solution selectively. Under the conditions of extraction temperature at 25℃, phase ratio at 1?, aqueous pH at 1, concentration of P204 in kerosene being 30% (j), and 3-stage extraction, Fe3+ is extracted up to 93%, Cu and As are hardly extracted, and the content of Fe3+ in raffinate is under 9 mg/L.

Synthesis of Solid Disinfectant Urea Peroxide by Hydro-processes

CAO Ji-lin;LI Meng-qing;TAN Zhao-yang;LU Yu-wei;GAO Jie

. 2005, 5(5): 517-520.

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By means of the study on the effects of molar ratio of hydrogen peroxide to urea, reaction temperature and time, type and quantity of stabilizing agent on preparation of urea peroxide by hydro-processes, the suitable synthesis conditions of urea peroxide have been determined. They are molar ratio of hydrogen peroxide to urea 1.1:1, reaction temperature below 30℃, reaction time 50 min, stabilizing agent salicylic acid and its quantity 0.5% of urea. Carrying out these conditions is easier than those reported in the literature, and the loss of hydrogen peroxide in the preparation process of urea peroxide is also lower. In accordance with the utilization of remaining solution containing hydrogen peroxide after preparing urea peroxide, a new technology, namely vacuum distillation process, is proposed to realize recycling utilization of remaining solution. On the basis of phase diagram analysis of urea-hydrogen-peroxide-water system, the new technology is further discussed.

Dispersion and Aqueous Suspension of Nanosized BaTiO3 Powders

FU Ji-wen;SONG Yuan-ling;LEI Ji-xia;LIU Xiao-lin;CHEN Jian-feng

. 2005, 5(5): 521-524.

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The rheological behavior of colloidal barium titanate suspension with PAA-NH4 as a dispersant to aid the powder dispersion was investigated. The nanosized barium titanate powder was synthesized by a continuous high-gravity reactive precipitation process, and then annealed at 900℃ for 2 h. By measuring the Zeta potential and the particle size distribution of BaTiO3 in an aqueous medium the optimum conditions for preparing suspension with low viscosity and high stability can be obtained. An isoelectric point at pH=2.8 is found. The Zeta potential decreases upon addition of PAA-NH4. Using the particle size distribution tests, it is found that the stabilization of suspensions is attained at pH greater than or equal to 10 and concentrations greater than or equal to 12 mg/g (dispersant/powder). FT-IR spectroscopy shows that polyelectrolytes are bound to the BaTiO3 surface via the carboxylic acid groups with physical and chemical adsorption. By rheological measurements, pseudoplastic behavior and thixotropy are observed in the suspensions. The maximum solid content attained during this work is 45%(j). The green density of BaTiO3 tape is up to 55.4% of the theoretical density after tape casting of the suspension.

The Applicability of Debye-Hückel Model in NaAl(OH)4-NaOH-H2O System

LI Xiao-bin;WU Wei-jun;FENG Gang-tao;LIU Gui-hua;PENG Zhi-hong;ZHOU Qiu-sheng;MENG Yun

. 2005, 5(5): 525-528.

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Focusing on the most important NaAl(OH)4-NaOH-H2O system in the industry of alumina production, the feasibility of establishing a calculation model of activity coefficients according to Debye-Hückel theory via the equilibrium solubility data of sodium aluminate solution is discussed in this paper. Firstly, the hypotheses for applying Debye-Hückel theory into NaAl(OH)4-NaOH-H2O system are involved and the values of parameters are determined. Then the applicability of Debye-Hückel model in NaAl(OH)4-NaOH-H2O system is testified. The results indicate that Debye-Hückel model is applicable to the establishment of calculation model of activity coefficients in NaAl(OH)4-NaOH-H2O system and the value of ?NaAl(OH)4 is estimated as 0.3595 nm.

Activity Interaction Coefficients in Fe-C-N, Fe-C-V and Fe-C-V-N Melts

CHEN Er-bao;WANG Shi-jun;ZHOU Yun;SONG Bao-guo

. 2005, 5(5): 529-531.

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The saturated solubility of carbon and nitrogen in Fe-C-N and Fe-C-V-N melts was measured experimentally at 1435℃. The purpose of present work is to obtain the activity interaction coefficients between solute components in these melts. The saturated solubility of carbon in Fe-C-V melt can be calculated with the following formula: XC=0.2043+0.8365XV or -lnXC-9.683XC=-11.96XV- 0.3916. The saturated solubility of carbon and nitrogen in Fe-C-V-N melt increases with increasing vanadium concentration. According to the thermodynamic properties of Fe-C melt, the activity interaction coefficients between carbon and nitrogen in Fe-C-N melt, the saturated solubility of carbon in Fe-C-V melt as well as the saturated solubility of carbon and nitrogen in Fe-C-N and Fe-C-V-N melts, by strictly thermodynamic derivation and calculation the activity interaction coefficients between carbon and nitrogen in Fe-C-N melt, between carbon and vanadium in Fe-C-V melt as well as between vanadium and nitrogen in Fe-C-V-N melt were obtained as follows: eCN=0.5016, eCV=-11.96, eCV=-0.2443 and eVN =-0.2379.

Morphologies of Cu Reduced by Two Kinds of Polyols under Hydrothermal Conditions

CHEN Qin-chun;DENG Hui-yu;LIU Xiao-dong

. 2005, 5(5): 532-534.

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Via characterization of XRD and SEM, the morphologies of Cu reduced by two kinds of polyols with different additions, D-sorbitol and adonitol, under 180℃ hydrothermal conditions were demonstrated, when CuSO4×5H2O and NaOH were taken as main sources and the ratio of [Cu2+]/[OH-] was 1:4. The results show that the reduced products are obviously different with addition of different polyols at both 0.100 g and 0.255 g weights. The reduced products are leaf-like Cu with addition of D-sorbitol and octahedrons with addition of adonitol, respectively. The mechanism is that the D-sorbitol is not only reductive, but also plays as an orientation cooperating with [Cu(OH)4]2- to decide the crystal growth, while the adonitol is only as reductive, when the ratio of [Cu2+]/[OH-] is 1:4.

Effect of Adjusting Methods on the Performance of Methanol Synthesis from Biomass Syngas

ZHANG Xi-tong;TAN Tian-wei;CHANG Jie;WANG Tie-jun;FU Yan

. 2005, 5(5): 535-539.

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The behavior of methanol synthesis from biomass syngas, industrial syngas, reformed biomass syngas and hydrogen added biomass syngas was studied. The results show that the order of the yield of methanol is industrial syngas>reformed biomass-gas> hydrogen added biomass-gas>biomass-gas, and the lower yield of methanol from biomass syngas mainly results from higher concentration of carbon dioxide. (H2-CO2)/(CO+CO2) ratio has no obvious influence on the selectivity of methanol in liquid products when the (H2-CO2)/(CO+CO2) ratio is between 1.5 and 2. High concentration of carbon dioxide results in reduction of selectivity of methanol in liquid products.

Effect of Alternative Aeration on Key Enzymes and Coenzymes in 1,3-Propanediol Production by Klebsiella pneumoniae

DU Chen-yu;LIU Ming;RAO Zhi;BAO Xiao-wei;SHEN Jin-yu;CAO Zhu-an

. 2005, 5(5): 540-544.

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The effect of air in alternative aeration model on 1,3-propandiol anaerobic biosynthesis was studied by examining the activities of key enzymes and coenzymes in Klebsiella pneumoniae. Aerating air in the fore stage (the 12 h) for 4 h, the activities of glycerol dehydrogenase and 1,3-PD oxidoreductase were 1.5 times and 18% higher than control respectively, and the concentration of 1,3-propanediol was 16% higher than control. Aerating air in the later stage (the 28 and the 48 h), the activity of glycerol dehydrogenase changed little, while the activity of 1,3-PD oxidoreductase and 1,3-PD concentration both declined. In the fore stage, the aeration had no effect on the concentrations of NAD and NADH, while in the later stage cell growth ceased, and the concentrations of NAD and NADH declined consequently.

Preparation of Heparin-Agarose Gel 6FF and Its Application in the Purification of Antithrombin III

MU Cheng-hua;YAO Hong-juan;MA Guang-hui;LIAN Bin

. 2005, 5(5): 545-549.

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The self-prepared bead-formed agarose gel was used as the affinity support, and heparin was employed as the ligand. Heparin was linked covalently to amino-agarose beads, which was prepared by amination of epoxy-agarose beads. The effects of operating conditions on the coupling reaction were investigated and optimized. The amount of heparin immobilized on the synthesized gel was 2.7 mg/mL medium. The synthesized affinity medium was used to isolate antithrombin III from human plasma. The recovery of antithrombin III activity was 31.76%, which was similar to that of Heparin-Sepharose CL-6B from Pharmacia, Sweden.

Improving Enantioselectivity of Candida parapsilosis for Deracemization of (R,S)-1-phenyl-1,2-ethanediol by Addition of Alcohols during Cell Cultivation

REN Yan-qiu;XU Yan;MU Xiao-qing;NIE Yao

. 2005, 5(5): 554-557.

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(R,S)-1-phenyl-1,2-ethanediol (PED) was deracemized to the corresponding (S)-enantiomer by using whole cells of the Candida parapsilosis as a biocatalytic system. To improve enantioselectivity of Candida parapsilosis, a new method was developed by the addition of alcohols or ketones during cell cultivation. The results showed that there were little effect caused by addition of diols, middle-chain alcohols and ketones, but there were increases in cell mass, enantiomeric excess and yield by addition of short-chain (C1~C4) alcohols such as ethanol (EtOH) especially. Effects of the phase and concentration of added ethanol during cell cultivation on enantioselectivity of the cells were also investigated. When cultivation continued for 16 h under the condition of 0.1% (j) ethanol, the cell mass increased by 10% and the relative enzyme activity increased by 30%. Meanwhile, the conversion of 105 mmol/L R,S-PED to S-PED with the cells cultured under this condition, an improvement of enantiomeric excess from 91% to 99% and a yield up to 92% were achieved.

Preparation and Evaluation of Bioadhesive Microspheres Drug Delivery System- I. Preparation of Bioadhesive Microspheres by Ionic Crosslinking and Prediction of Their Diameter

YANG Zhen-qiu;SONG Bao-zhen;LI Qiao-xia;FAN Hong-lei

. 2005, 5(5): 558-562.

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Interest in drug delivery to the gastrointestinal tract by means of chitosan has been increasing. In this study, with the sulfuric acid solution as the crosslinker, chitosan bioadhesive microspheres were prepared via ionic crosslinking. The microspheres with spherical shape could be kept in the artificial simulated intestinal juice for more than 24 h, and also had high mechanical strength and more compact surface, compared with the microspheres crosslinked by sulfate. The diameter of the microsphere is the principal factor influencing the kinetic parameters of drug delivery. With the experimental design, four-factor second order orthogonal regression composite design, the influences of the factors of chitosan concentration, crosslinker concentration, crosslinking time and agitation speed were investigated, the regression equation with high reliability was obtained.

Microstructrues and Properties of Superlight Mg-Li-Zn Wrought Alloys in Cold-rolling and Annealing States

LI Hong-bin;YAO Guang-chun;LI Hai-bin;LIU Yi-han

. 2005, 5(5): 563-567.

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Cold-rolling workability, heat treatment characteristics and mechanical properties of Mg-5%~22%Li-2%Zn wrought alloys were studied. Density of the studied alloys is in the range between 1.209 and 1.617 g/cm3. The limit of reduction for cold rolling of the b phase alloys with 16% and 22% Li exceeds 90% at room temperature. The properties and microstructures of Mg-Li-Zn system alloys were studied. The alloys were coldly rolled, then annealed at different temperatures. Recrystallization behaviors of the alloys were investigated through microstructure observing and hardness measuring. The results show that the cast billets are suitable for rolling after homogenization at 573 K for 12 h for Mg-9%Li-2%Zn-2%Ca alloy and at 523 K for 24 h for Mg-16%Li-2%Zn alloy. The rolled plates are completely recrystallized by annealing at 573 K for 1 h. It is beneficial to the next cold-rolling.

Interfacial Structure and Mechanical Properties of Nano-CaCO3/PVC Composites Affected by CPE

SUN Shui-sheng;LI Chun-zhong;ZHANG Ling;CAO Hong-ming

. 2005, 5(5): 568-571.

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The effect of chlorinated polyethylene (CPE) elastomer on microstructure, mechanical properties and interfacial adhesion of PVC composites filled with nano-CaCO3 particles was investigated. The morphology of the fracture surfaces of the blends was observed by SEM. It was found that the dispersion and interfacial adhesion of nano-CaCO3 particles in PVC matrix were improved with the addition of CPE elastomer. The interfacial adhesion between nano-CaCO3 particles and PVC matrix was characterized by interfacial interaction parameter B quoted from TPT equation. It was found that the more the CPE elastomer added, the higher the interfacial adhesion reached. The effect of CPE on the mechanical properties of PVC filled with nano-CaCO3 particles and CPE was also investigated, and it revealed that compared to the case of only addition of nano-CaCO3 particles the impact strength of PVC composites increased more dramatically with the addition of CPE elastomer and nano-CaCO3 particles. The notched impact strength of nano-CaCO3/CPE/PVC could reach 25.2 kJ/m2 with the mass ratio of nano-CaCO3/CPE/PVC at 25/8/100, which was 5.6 times as high as that of pure PVC composites and 2 times of nano-CaCO3/PVC (25/100) composites.

Preparation and Characterization of Interfacial Properties of PVA/EC Alloy Membrane Material

GAO Su-lian;WANG Xiao-fei;ZHANG Xiu-zhen;LIU Jian-xin

. 2005, 5(5): 572-575.

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The polyvinyl alcohol/ethyl cellulose (PVA/EC) alloy was prepared by means of solution blending and liquid-solid phase inversion method. The HPLC method with PVA/EC alloy and EC as the column packing was employed to measure the retention values and equilibrium distribution coefficient of both inorganic solutes and organic solutes. The interfacial parameters and hydrophilicity were estimated from HPLC data, and the compatibility of alloy was also studied by means of viscometry, refractive index and IR. The experimental results show that PVA and EC have a good compatibility in PVA/EC alloy, and the alloy is superior to EC in separation efficiency for non-dissociable polar organic solutes.

Gas-phase Photocatalytic Activity of TiO2 Doped with Ag and Ni

SUN Xue-lian;ZHANG Guo-liang;ZHANG Feng-bao

. 2005, 5(5): 576-579.

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The Ag/TiO2 and Ni/TiO2 photocatalysts with variable Ag and Ni loadings were prepared by the sol-gel method, and their photocatalytic activities were tested by using gas-phase toluene degradation as the modal reaction. Two doped photocatalysts were characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD) and fluorescence spectra (FS). The results showed that a suitable metal ion loading could greatly enhance the TiO2 photocatalytic activity, and Ni/TiO2 was superior to Ag/TiO2. The optimal doping amount of two photocatalysts was 0.4%. At the same time, the effect of doped metal ion loadings on the photocatalytic activity was discussed.

Researches and Trend on Green Process Synthesis and Design

ZHANG Xiang-ping;ZHANG Suo-jiang;LI Chun-shan

. 2005, 5(5): 580-590.

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Rapid development of process industries has caused the severe environmental pollutions. Implementing cleaner processes that use or generate lower amounts of or less harmful pollutants will require systematic methodology of green process synthesis and design based on the principles of green chemistry. The current widely used environmental performance assessment criteria and methodologies are introduced and analyzed in this paper. The modeling and algorithms for green process synthesis and optimization design have been reviewed. Then, the principles, methods and developing trend of green process design are discussed and highlighted with two industrial cases. Combining the green chemistry with the methodology of process system engineering, we propose the green degree theory and methodology, and define the relevant research contents and application perspective. The basic methodologies of evaluating quantitatively the green degrees of material, energy, process and eco-system are established. Then, the green system integration procedures would be carried out with multi-objective optimization methodology and decision making strategy to reach the global sustainability of ecological, economic and social areas.

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