The Chinese Journal of Process Engineering

Holdups of Dispersed and Gas Phases in a Gas-agitated Sieve Plate Extraction Column

LU Shu-xiang;WANG Wei;LIU Jian-guo;WANG Ya-quan;MI Zhen-tao

. 2004, 4(3): 193-197.

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The hydrodynamic characteristics of the air-water-working solution (a mixture of anthraquinone derivatives, TOP and C9 aromatics, used for industrial production of hydrogen peroxide) three-phase system in a gas-agitated sieve plate extraction column were investigated. The holdups of the dispersed and gaseous phases were measured by the shut-off method, respectively. The effects of the superficial velocities of air, dispersed and continuous phases on the holdups of dispersed and gaseous phases were studied. Correlations for the prediction of holdups of dispersed and gaseous phases in the air-water-working solution three-phase system have been proposed. The comparison of the predicted data with correlations and experimental data shows quite satisfactory agreement and the average relative deviations are 7.3% for the dispersed phase holdup and 7.1% for the gas phase holdup, respectively.

Gas Turbulence Flow in the Cyclone Tube

WANG Jian-jun;JIN You-hai

. 2004, 4(3): 198-203.

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In order to improve the separation mechanism, LDV (Laser Doppler Velocimetry) was used to measure the characteristics of gas turbulence flow in the cyclone tube. The distribution of mean velocity, turbulence density, power spectrum and vortex microscale were presented, and the effect of gas turbulence on particle separation was analyzed. Some conclusions were drown: there were different sizes of vortex in the cyclone tube; in the inner vortex region the vortex microscal was small, and the energy dispersion rate was high.

Fluidization of Ultrafine CaCO3 Powder in a CFB with Conical Dipleg

TONG Hua;LI Hong-zhong

. 2004, 4(3): 204-209.

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Based on the fluidizing characteristics of cohesive powders, such as the formation of agglomerates with wide size distribution during fluidization, and partial defluidization due to disposition of large agglomerates, a novel design of CFB dipleg, the conical dipleg, was put forward for fluidizing ultrafine and cohesive powders. The conical dipleg consists of a conical dipleg and a V-valve with aeration of gas. Experiments on the conical dipleg showed that it can prevent the fluidized dipleg from disposition and defluidization of large agglomerates at the bottom of the bed and elutriation of smaller agglomerates at the top of the bed by providing variational superficial fluidizing gas velocity. The experiments also showed that the aeration gas is essential for V-valve to feed highly cohesive powders into riser smoothly. With the aid of the conical dipleg, stable circulation of highly cohesive ultrafine CaCO3 powder was achieved. Pictures taken from the inside of riser show that the ultrafine CaCO3 powders in the fluidized riser are in agglomerate form in spite of the high fluidizing gas velocity. The size of agglomerates is much smaller than that in conventional fluidized beds, and it has no significant variation along the riser height. Experiments also showed that the axial solids concentration in the riser is of S-shape distribution; and the lateral solids concentration displays a core-annulus structure. These phenomena are typical features of fast fluidization.

Experimental Study on VOCs Adsorption in a Two-stage Circulating Fluidized Bed

DUAN Wen-li;SONG Wen-li;LUO Ling-ai

. 2004, 4(3): 210-214.

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A two-stage circulating fluidized-bed adsorber has been developed for Volatile organic compounds(VOCs) adsorption. Experimental research was conducted using Ambersorb 600 as adsorbent and toluene as adsorbate. PGM-7600, a type of photo-ionization detector, was used to measure and record the concentration of toluene. The pressure drop, voidage distribution and concentration distribution along the CFB riser were obtained. The influences of inlet toluene concentration and air flow rate on the performance of the adsorber were discussed. The adsorption efficiency is between 95% and 98% under the experimental conditions.

Numerical Simulation on High Temperature and Diluted Air Characteristics of Regenerative Ladle Baker

OU Jian-ping;JIANG Shao-jian;MA Ai-chun;XIAO Ze-qiang

. 2004, 4(3): 215-220.

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High temperature air combustion (HTAC) can increase the adiabatic flame temperature and enlarge the flame volume, which can strengthen the heating capability. Based on the technology of HTAC, the fuel in regenerative ladle baker can burn completely. The preheated temperature of inlet gases affects the combustion process greatly. With the aim to study the effect of preheated temperature on the combustion, a 3-D transient mathematical model of combustion combined with flow and heat transfer is established in this paper. Based on the commercial CFD soft CFX, using the method of Finite Difference and SIMPLEC, the characteristics of high temperature diluted air in the chamber under different preheating temperatures of inlet gases are analyzed numerically. Turbulence k-e model, Mixed Is Burnt model and Monte Carlo method are used. Results evidence that due to effects of jets, backflow and eddies are formed and the high temperature burned flue gas in the ladle can mix and dilute the fresh air. Higher temperature of inlet gases is favorable to the combustion process. Increasing the preheating temperature can increase the domain temperature and its uniformity and decrease the oxygen content of local flue in the chamber. The deviation of temperature between calculated results and test results is less than 30 K. The calculated results agree with the experimental observation and theoretical analysis well.

Numerical Simulation on Tube-type Ethylene Pyrolyzer

LAN Xing-ying;GAO Jin-sen;XU Chun-ming;ZHANG Hong-mei

. 2004, 4(3): 221-227.

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Numerical simulation on the USC tube-type ethylene pyrolyzer was carried out. Some detailed information about flow field, temperature field and concentration distribution was obtained, which revealed the basic characteristics of flow, heat transfer, mass transfer and reaction processes in the pyrolyzer. The results indicated that there were highly non-uniform distributions of flue-gas velocity, concentration and temperature in the furnace, which caused non-uniform distribution of tube skin temperature and heat flux of reactor tubes. On the other hand, the profiles of oil-gas velocity, pressure, temperature and components concentration along the vertical direction of reactor tubes were obtained. The steep velocity and temperature gradients along the radial position, and less obvious radial profiles of components concentration were also found.

Coupling Leaching of Sphalerite and Separation of Iron

WANG Xing-yao;KANG Xiao-hong;XIE Hui-qin;LU Li-zhu

. 2004, 4(3): 228-232.

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Coupling treatment of oxidation leaching and extraction separation of sphalerite has been put forward, and the mechanisms of leaching with oxidation reagents (H2SO4-HNO3-O2) and mixed extractive reagents of tetrachloroethylene and 2-ethylhexyl 2-ethylhexylphosphate are discussed. The results show that the process activation energy of coupling leaching is 19.6 kJ/mol and the extracted fraction of zinc is 0.946, which is much higher than that with common leaching. The separation of zinc, sulfur and iron (the iron was obtained in the form of Fe2O3 nano-powder) was completed in the coupled leaching process with Fe2O3 nano-powder obtained.

Preparation and Characterization of MnxFe1-xO4 Nanoparticles Coprecipitated with Forced Mixing

ZHU Yi-hua;HU Ying;LUO Mei-fang

. 2004, 4(3): 233-238.

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MnxFe1-xO4 nanoparticles were prepared by coprecipitation with forced mixing. The measurement of magnetic properties indicated that with increasing Mn concentration the specific saturation magnetization of the MnxFe1-xFe2O4 samples decreased at first, and then increased again. The variational trend was also found in estimating particle size. The observation of TEM showed that the size of MnFe2O4 particles was larger than that of Fe3O4 particles. The calculation of Rietveld refinement suggested that the cation distribution of the MnFe2O4 sample was Mn0.3Fe0.7[Mn0.7Fe1.3]O4, and the oxygen parameter and the tetrahedral interstices of the MnFe2O4 sample were larger than those of Fe3O4 sample. The crystallite size and the microstrain of the MnFe2O4 sample were also larger than those of Fe3O4 sample, probably due to its larger ion radius and the metastable cation distribution. The thermal analysis of sample oxidation showed that the temperature for weight gaining from oxidation of the MnFe2O4 sample was higher than that of Fe3O4 sample. The temperature for maximum increase in weight shown in DTG curves was 234.7℃ for Fe3O4 and 358.1℃ for MnFe2O4, respectively, indicating that the stability against oxidation of MnFe2O4 was improved.

Preparation of Tungsten Disulfide Nanofibers by Thermal Decomposition

MA Jiang-hong;ZHAI Yu-chun;LI Zai-yuan

. 2004, 4(3): 239-244.

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The method of preparing tungsten disulfide nanofibers by the thermal decomposition of ammonium tetrathiotungstate is reported, and TEM, HRTEM and XRD were employed to investigate the shape, structure and component of the product whose average diameter was less than 100 nm and the length longer than 10 mm. It is revealed that the product was dark-gray crystals with hexagonal lattice tungsten disulfide, a=0.3151 nm, c=1.271 nm, and quite pure. ED patterns show that the nanofibers were mono-crystal, highly crystallized, and the electron diffraction spots such as (100) and (002) were very clear. The factors such as the rate of raising temperature, cooling rate, atmosphere and reactant size were found to be dominating to the nanofibers growth.

Influence of Temperature, Nutrients and Light Intensity on the Growth of Nostoc flagelliforme

BI Yong-hong;HU Zheng-yu

. 2004, 4(3): 245-249.

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Nostoc flagelliforme is a terrestrial filamentous nitrogen-fixing cyanobacterium that has been used as a health food and herbal medicine by Chinese and other Asian populations over centuries. The commercial source of N. flagelliforme biomss is harvesting from natural aquatic environments. Mass culture of N. flagelliforme in an engineered system is sought but has not been available, due in large to the lack of understanding the growth physiology of the organism under changing environments. In this study, the effect of temperature, nutrients and light intensity on growth and biochemical composition of Nostoc flagelliforme were investigated. The results indicated that growth rate and biochemical composition were influenced by temperature, nutrients and light intensity. Specific growth rates under 25℃ and 45 mmol/(m2×s) were the most rapid than under other conditions. Growth rates in the culture medium lacking N, P and Ca were of significant difference from the control BG11 medium (p<0.05). No obvious growth difference existed between Medium lacking K, lacking micronutrient As and the control medium. Content of exopolysaccharides (EPS) decreased accompanied with increasing of temperature. Low and high light intensities were helpful to EPS producing. Nutrients starvation was a great disadvantage for algae to produce EPS. Protein content at 25℃ was the highest among all temperature experiments. It increased accompanied with increasing of light intensity but decreased when cultured in the modified BG11 medium (one of nutriment ingredient was deficient). It could be concluded that 25℃ and 45 mmol/(m2×s) were optimal culture conditions and N, P and Ca were necessary for this algal growth.

Improving the Acrylamide-tolerance of Nitrile Hydratase in Nocardia sp. by Extreme Cultivation

LIU Ming;LI Chun;HUANG Ye;GAO Yi

. 2004, 4(3): 250-255.

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The RS strain, Nocardia sp., was screened at extreme cultivation conditions to improve the acrylamide- tolerance of nitrile hydratase. Arylonitrile was fed periodically into the shaker containing the RS cells and medium to produce acrylamide by the cells. The extreme cultivation conditions were formed by gradual accumulation of acrylamide. The acrylamide-tolerance of cells was enhanced in the coupling process of cell growth, enzymatic catalysis and screening. The survival rate, specific death rate and nitrile hydratase activity of cells as the function of acrylamide concentration during the process were investigated. The amount of living cells decreased rapidly with the increase of acrylamide concentration and the survival cells were cultivated on solid medium to gain a new strain RS-1. The average reaction rate of acrylonitrile hydration catalyzed by the RS-1 cells was 30.8% higher than that by the RS cells within 0~400 g/L of acrylamide concentration. Accordingly, the acrylamide-tolerance of nitrile hydratase in the RS-1 cells was superior to that in RS cells. Under the same conditions, the hydration processes catalyzed by the RS and the RS-1 strain were compared. The final acrylamide concentration and percent conversion of acrylonitrile in the hydration catalyzed by the RS-1 strain were 587.1 g/L and 99.97% respectively, which were higher than those by the RS strain significantly. In the further study on acrylamide production catalyzed by the RS-1 strain, the final acrylamide concentration reached 641.4 g/L.

Preparation of Nano-Ce/TiO2 Inorganic Antibacterial Agent and Evaluation of Its Antibacterial Activities

LIU Xue-feng;ZHANG Li;TU Ming-jing

. 2004, 4(3): 256-260.

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With anatase nano-TiO2 and Ce(NO3)3 as raw materials, the nano-Ce/TiO2 inorganic antibacterial agent have been prepared by impregnation method. The antibacterial activities was evaluated with the halo method and the antibacterial mechanism was studied. The results show that the nano-Ce/TiO2 inorganic antibacterial agent has outstanding antibacterial activities and the antibacterial mechanism is of rare earth cerium ion dissolving.

Two-phase Beckmann Rearrangement of Cyclohexanone Oxime for Preparing e-Caprolactam in [bmim][BF4] Ionic Liquids Using PCl3 as Catalyst

ZHANG Wei;WU Wei;ZHANG Shu-zhong;MIN En-ze

. 2004, 4(3): 261-264.

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The Beckmann rearrangement of cyclohexanone oxime was effectively realized to prepare e-caprolactam by using phosphorous trichloride (PCl3) as catalyst in a two-phase system composed of 1-n-butyl-3- methylimidazolium tetrafluoroborate ([bmim][BF4]) ionic liquids and toluene. The system of two-phase facilitates the control of the reaction and the removal of reaction heat. The effects of the amount of cyclohexanone oxime and PCl3, reaction temperature and reaction time on the conversation of cyclohexanone oxime, selectivity of e-caprolactam and turnover numbers (TON) of PCl3 were studied. The optimized conditions were 2 ml [bmim][BF4], 5 ml toluene, 0.3 ml PCl3, 5.0 ml 2.0 mol/L cyclohexanone oxime, 90oC and 10~30 min. At the same time, the conversation of cyclohexanone oxime could reach 98.96%, the selectivity of e-caprolactam could reach 87.30% and the TON of PCl3 could reach 2.88. Most of the e-caprolactam (>90%) existed in the ionic liquid phase.

Photocatalytic Degradation of Methylene Blue

YANG He;XUE Xiang-xin;ZUO Liang;YANG Zhong-dong

. 2004, 4(3): 265-268.

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Experimental studies have been made on photocatalytic degradation of methylene blue in an aqueous solution by means of treated blast furnace slags containing TiO2. Dependences of photocatalytic degradation on pH of solution, strength of light, air flow rate were discussed in detail. The results indicate that the reaction rate was increased with increasing UV light intensity, advisable pH value and proportionate air flow rate. The degradation rate of dye by 254 nm UV light was dramatically higher than that by 365 nm UV light，and the best degradation effect was obtained after heat-treated at 600oC for slag.

Research Progress of Recycling Chlorine from Hydrogen Chloride

WU Yu-long;WEI Fei;HAN Ming-han;JIN Yong

. 2004, 4(3): 269-275.

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Recycling chlorine from hydrogen chloride is very useful in industry and environment protection. In this paper, the research progress of transfer of HCl to Cl2 in recent years was reviewed, and the main trends were pointed out, with main emphasis focused on the Deacon process, especially the newly developed two-stage Benson processprocess.

Progress in Preparation of High-purity Anhydrous Magnesium Chloride

ZHOU Huan;YUAN Jian-jun

. 2004, 4(3): 276-281.

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Anhydrous magnesium chloride is the raw material of electrolyzed metal magnesium and an important intermediate of some catalyzers or medicines. Anhydrous magnesium chloride may be prepared from materials containing magnesium chloride such as magnesium chloride hydrate, carnallite or bittern by different dehydrating methods of organic solvent distillation or molecular sieve absorption, gas protective heating, discomposing the MgCl2-NH3 complex that can be composed from high boiling-point polar-solvent system, water-ammonia system, low boiling-point mixed-solvent system. On the other hand, anhydrous magnesium chloride may also be prepared by chloridizing magnesium oxide, which converted from magnesite, brucite, or Mg(OH)2, in gaseous medium, or molten salt medium. For several decade innovation, some progress has been made for the anhydrous magnesium chloride preparation. However it still needs more deep study to change the traditional technology from complex process, high cost, serious pollution and grievous eroding, into the green technology with simple process, low cost, non-pollution and non-eroding.

Progress of the Study on Bacillus thuringiensis as Biopesticides

ZHU Wei;ZHAO Bing;WANG Xiao-dong;WANG Yu-chun

. 2004, 4(3): 282-288.

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Bacillus thuringiensis is one of the most effective and the most widely used microbial insecticides at present. The genetic bacterial strains, the fermentation process and the formulation of Bacillus thuringiensis as biopesticides are reviewed in this paper. The optimization of culture medium, operating conditions and type of fermentors are also addressed. Moreover, the existing problems and suggestions are discussed.

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