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05 May 2015, Volume 66 Issue 5
    CIESC Journal(HUAGONG XUEBAO)Vol.66 No.5 May 2015
    2015, 66(5):  0-0. 
    Abstract ( 98 )   PDF (1205KB) ( 262 )  
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    Vapor-liquid equilibrium simulation for crotonaldehyde and its mixture with ethanal
    YANG Huaming, ZHANG Minhua, MA Jing
    2015, 66(5):  1627-1632.  doi:10.11949/j.issn.0438-1157.20141624
    Abstract ( 395 )   PDF (576KB) ( 552 )  
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    Gibbs ensemble Monte Carlo method with TraPPE-UA force field was used to study the vapor-liquid phase equilibrium of systems containing crotonaldehyde. To lay the foundation for the vapor-liquid phase equilibrium simulation, quantum chemistry calculations with B3LYP 6-311G (d, p) and MP2 6-31G (d, p) basis sets were firstly performed to obtain the lacking bond parameters and torsional parameters for crotonaldehyde molecular. Based on these parameters, a new TraPPE-UA force field was developed. Vapor-liquid phase equilibrium data of pure crotonaldehyde and its mixture with ethanal were calculated using the new force field and compared with experiment data. The saturated liquid densities of pure crotonaldehyde predicted by the new force field were in close agreement with experimental results, with deviations from 0.28% to 1.23%. This demonstrated that the new TraPPE-UA force field manifested high simulation precision for crotonaldehyde. For the binary system consisting of crotonaldehyde and ethanal, the deviation between simulations and experiments increased with rising temperature, and the minimum and maximum values were 0.13% and 7.44%, respectively.
    Numerical simulation of droplet generation in crossing micro-channel
    WANG Weimeng, MA Yiping, CHEN Bin
    2015, 66(5):  1633-1641.  doi:10.11949/j.issn.0438-1157.20141899
    Abstract ( 347 )   PDF (2772KB) ( 707 )  
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    Micro-droplet formation in the crossing micro-channel was numerically simulated by the 3D VOF model. Three flow regimes to generate droplet with monodispersity (squeezing, dripping and jetting) and other regimes (turbulent jetting, nodular flow, tubular flow, slip flow) were obtained. The simulation results agreed well with experiment observations, which validated the numerical model. The flow regimes were mainly affected by flow rate, surface tension and viscosity of two phases. With increasing flow rate of the continuous phase, droplet size would decrease and generation frequency would increase, whereas the effect of flow rate of the disperse phase was the opposite. Surface tension and viscosity of the continuous phase played a leading role under the conditions of high and low Ca number of the continuous phase, respectively. When Ca number was low, droplet size decreased in the squeezing and dripping regimes and increased in the jetting regime with decreasing surface tension, while generation frequency shows the reverse changing tendency compared with droplet size. When Ca number of the continuous phase was high, however, droplet size decreased with increasing the viscosity of the continuous phase, while generation frequency changed inversely. In addition, contact angel had little effect on the squeezing regime, but droplet could not be generated in the dripping and jetting regimes when contact angel decreased.
    Effect of diameter and length of vortex finder in water-sparged aerocyclone reactor on its mass transfer performance in air stripping of ammonia
    CHENG Zhiliang, XU Fei, QUAN Xuejun, QIU Facheng, DAI Mingxing
    2015, 66(5):  1642-1648.  doi:10.11949/j.issn.0438-1157.20141651
    Abstract ( 202 )   PDF (836KB) ( 308 )  
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    Water-sparged aerocyclone (WSA) is a new gas-liquid mass transfer equipment, which takes the advantage of coupling effect of air cyclone and liquid jet fields. In order to improve its mass transfer performance and establish design principles, the effect of diameter (De) and length (S) of the vortex finder in the WSA on its mass transfer performance and air pressure drop in air stripping of ammonia was investigated and optimized. A new concept, mass transfer efficiency per gas pressure drop, ηp, and its calculation equation were put forward. The WSA with smaller De and longer S showed higher mass transfer efficiency than that with larger De and shorter S in air stripping of ammonia. However, this kind of WSA had higher air pressure drop, which would consume more energy. Calculation of ηp, which was a comprehensive indicator considering energy consumption and mass transfer efficiency, showed that it increased with the increase of De/D and S/H,but it deceased a little when S/H increased from 0.71 to 0.93. The optimal De/D and S/H should be 0.43 to 0.53 and 0.70, respectively. These results could be used as a guide for the design of WSA with good mass transfer performance.
    Analysis of influence factors for heat transfer and pressure drop characteristics of moist air in metal foams during dehumidifying process
    WENG Xiaomin, HU Haitao, ZHUANG Dawei, DING Guoliang, XU Xudong, YANG Huaiyi
    2015, 66(5):  1649-1655.  doi:10.11949/j.issn.0438-1157.20141657
    Abstract ( 212 )   PDF (1359KB) ( 544 )  
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    The heat transfer and pressure drop characteristics of moist air in metal foam during the flow and dehumidification process were investigated experimentally, and the influence of different factors was analyzed. Heat transfer rate and pressure drop increased with increasing relative humidity as a result of increasing condensate water. When relative humidity increased from 50% to 90%, heat transfer and pressure drop respectively increased by 67% and 62%. With the increase of inlet air temperature, heat transfer rate and pressure drop increased. Heat transfer rate and pressure drop decreased with increasing cooling water temperature, pressure drop increased with increasing pore density, while heat transfer at first decreased slightly and then increased because of the influence of condensate water. Heat transfer rate and pressure drop increased with the increase of windward height of copper foam.
    Influence of Venturi structure on flow characteristics and pressure drop of gas-coal mixture
    LIU Kai, LU Haifeng, GUO Xiaolei, LIU Yi, PAN Xiangming, GONG Xin
    2015, 66(5):  1656-1666.  doi:10.11949/j.issn.0438-1157.20141628
    Abstract ( 263 )   PDF (756KB) ( 612 )  
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    The flow characteristics and pressure drop of gas-coal mixtures under high pressure and concentration through a Venturi with different structures, including diameter ratio(0.44, 0.55, 0.7), convergence angle (2.5°, 5°, 9°), diffuser angle (2.5°, 8°, 13°) and throat length (23d, 43d, 80d) were investigated in the dense phase pneumatic conveying of pulverized coal system. A similar trend but a varied degree in non-dimensional pressure distribution for the gas-coal mixture through different Venturis was observed. The most remarkable influence parameter was diameter ratio, which had the greatest influence on pressure drop. The increase in pressure drop of the Venturi and remarkable increase in pressure drop in the diffuser were observed with the decrease of diameter ratio. The major role of other structural parameters was to change pressure distribution inside the Venturi, while having little influences on total pressure drop. The greatest convergence pressure drop for the convergence angle series occurred in the 2.5°. There was little difference of convergence pressure drop between 5° and 9° under high pressure and concentration. The greatest throat pressure drop for the throat length series occurred in the 80d. The least diffuser pressure drop for the diffuser angle series occurred in the 8°. By introducing solids momentum flux, an empirical equation of pressure drop of gas-coal mixture through the Venturi was established. It showed good prediction with deviations from most experimental value within 30%.
    Numerical analysis of coupled level set-VOF method on droplet impact on spherical concave surface
    ZHENG Zhiwei, LI Dashu, QIU Xingqi, ZHU Xiaoli, CUI Yunjing
    2015, 66(5):  1667-1675.  doi:10.11949/j.issn.0438-1157.20141116
    Abstract ( 279 )   PDF (3721KB) ( 672 )  
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    In order to explore the mechanism of droplet impact on a spherical concave surface, a numerical model using the coupled level set and volume of fluid method was developed. The mechanism of droplet impact and breakup during spreading was obtained. The impact characteristics were closely related to impact velocity. Droplet impact on a spherical concave surface showed a smaller spread factor, earlier time of central normal jet and larger jet velocity than the impact on a flat surface. The maximum spread factor and relative maximum spread velocity increased exponentially with Reynolds number. The maximum length of jet increased logarithmically with Reynolds number. The maximum jet velocity decreased exponentially with Reynolds number. Through comparison of theoretical analysis models of maximum spread factor, the development direction of analysis model of maximum spreading factor of droplet impact on a concave surface was presented.
    Characteristics of dryout for CO2 flow boiling heat transfer in mini-channels
    WU Hao, LIU Jianhua, ZHANG Liang, JIANG Linlin, DING Yang, LIANG Yaying
    2015, 66(5):  1676-1682.  doi:10.11949/j.issn.0438-1157.20141500
    Abstract ( 264 )   PDF (4178KB) ( 297 )  
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    Experimental and theoretical researches were conducted to get the two-phase flow boiling heat transfer characteristics of carbon dioxide as refrigerant in horizontal mini-channels. Based on infrared thermal imaging tests and experimental study on heat transfer coefficients, heat transfer coefficients of carbon dioxide were analyzed qualitatively and quantitatively under following experimental conditions: heat flux 2—35 kW·m-2, saturation temperature -10—15℃, mini-channels inner diameter:1 mm, 2 mm or 3 mm. With the increase of mass flow rate, the value of vapor quality decreased gradually when dryout happened. When mass flow rate was below a critical value, heat transfer coefficient almost kept constant with the increase of mass flow rate after dryout. When mass flow rate was above the critical value, heat transfer coefficient gradually increased with the increase of mass flow rate after dryout. With the increase of tube diameter, mass flow rate decreased and the critical value of heat flux increased when dryout happened. With the decrease of tube diameter, coefficient of heat transfer increased.
    Molecular dynamics simulation of self-diffusion and structure in N-methylformamide
    FENG Huajie, NIE Jingjing, SUN Zhenfan, CHEN Liuping
    2015, 66(5):  1683-1689.  doi:10.11949/j.issn.0438-1157.20141541
    Abstract ( 193 )   PDF (653KB) ( 493 )  
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    Density, self-diffusion coefficients and structural properties of N-methylformamide were studied by molecular dynamics simulation over wide ranges of temperature and pressure. The simulation results agreed well with the experiment of diffusion, and the average relative deviation was 7.3%, which suggested that one can use the simulation method as a powerful tool to obtain self-diffusion coefficients over wide ranges of temperature and pressure, under which it was rather difficult for experiments. In N-methylformamide, oxygen and amino hydrogen formed strong hydrogen bond, while oxygen and carbonyl hydrogen formed weak interaction. The temperature effects were more pronounced than the pressure effects on self-diffusion coefficients and radial distribution functions.
    Estimation of pore size distribution of porous media based on percolation theory
    DING Binbin, LI Chaolin
    2015, 66(5):  1690-1696.  doi:10.11949/j.issn.0438-1157.20141546
    Abstract ( 219 )   PDF (1531KB) ( 434 )  
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    Based on percolation theory and network model, an equation describing the relationship between filtration coefficient and pore size distribution (PSD) of filter media was established. Using this equation, PSD parameters of the filter medium could be obtained from experimental data. Moreover, the result was also compared with PSD parameters estimated by other methods and other data in the literature. In order to validate this method, the obtained PSD parameters were used in the simulation of straining-dominant filtration, and the simulation result was consistent with experimental data. The filtration model based on percolation theory for PSD parameter estimation was relatively accurate and effective.
    Wavelet analysis of dynamic pressure in T-abrupt of CFB riser
    ZHOU Faqi, CHEN Yong, WEI Zhigang, YAN Chaoyu, SUN Guogang, WEI Yaodong
    2015, 66(5):  1697-1703.  doi:10.11949/j.issn.0438-1157.20141535
    Abstract ( 245 )   PDF (656KB) ( 349 )  
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    To investigate the characteristics of pressure fluctuations in the T-abrupt exit, the dynamic pressures of gas-solid two-phase flow in the T-abrupt exit of a CFB riser were measured in a circulating fluidized bed device with FCC catalyst by dynamic pressure sensors. The pressure fluctuations of the blind tube in T-abrupt exit were the strongest and the gas-solid two-phase flow in T-abrupt exit formed a new fluctuation source which was the result of the particles cluster turning back in the blind tube. Wavelet analysis revealed that pressure fluctuations in the T-abrupt exit mainly came from the fluctuation source in the blind tube constituting the main frequency, while the energy ratio of secondary frequency increased with increasing solids mass flux. The standard deviation of the dynamic pressures in the T-abrupt exit was linear with the solids mass flux, and in the inlet of the T-abrupt exit the linear relationship was well-defined. So the real-time solids mass flux could be characterized by the standard deviation of the dynamic pressures in the inlet of the T-abrupt exit.
    Flow characteristics of water in hydrophobic micro cylinders group with different contact angles
    JIANG Guilin, ZHANG Chengwu, GUAN Ning, QIU Delai, LIU Zhigang
    2015, 66(5):  1704-1709.  doi:10.11949/j.issn.0438-1157.20141799
    Abstract ( 262 )   PDF (3256KB) ( 296 )  
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    Hydrophobic solution was prepared by adding 2% perfluorinated octyl fluorine silane and micro-nano particles to modified silicone dilute solution. This hydrophobic solution could be solidified to obtain hydrophobic surfaces, and the contact angle of water on these surfaces could be adjusted by changing the content of micro-nano particles in hydrophobic solution. Using the method above, different micro cylinders groups with contact angles of 99.5°, 119.5° and 151.5° (de-ionized water) were prepared, respectively. Using de-ionized water as working fluid, the flow resistance and pressure drops in micro cylinders groups with different contact angles were measured. The value of friction factor of test section with hydrophobic layer was apparently lower than that without the layer at the same Reynolds number, and this was because the surface tension on hydrophobic interaction interface led to a reduction of friction resistance. The larger the contact angle, the smaller the distance between the micro/nano bumps on the double structure of hydrophobic layer at the same Re, meanwhile the ratio of liquid-air contact area to the total flow area became higher, thus flow resistance decreased. The drag reduction rates attributed to the three kinds of hydrophobic coatings on surfaces of micro pin fins decreased continuously with the increase of Re.
    Reaction kinetics of non-catalytic peroxidation of liquid phase isopropyl benzene
    LIU Mingxin, XU Zhimei, SUN Weizhen, ZHANG Minghua, ZHAO Ling
    2015, 66(5):  1710-1715.  doi:10.11949/j.issn.0438-1157.20141807
    Abstract ( 363 )   PDF (618KB) ( 413 )  
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    Both main and side reaction kinetics of non-catalytic peroxidation of liquid phase isopropyl benzene (IPB) were investigated, including byproduct formation such as α-methyl benzyl alchohol (MBA) and acetophenone (ACP), and decomposition pathway of ROOR (DCP). Based on free radical chain reaction mechanism, a kinetic model was developed, in which IPB hydroperoxide (IPBHP), MBA, ACP and DCP were considered. The prediction by this kinetic model is agreed well with the experimental data, if the rate constants were used which were obtained by fitting of the experimental data at 373—404 K. The activation energies estimated were larger for all side reactions than for the main reaction. DCP decomposition requires the presence of oxygen. These data obtained could be helpful for deep understand of the reaction mechanism of liquid phase of alkyl aromatics and could be used as the fundamental data for design and optimization of industrial liquid phase oxidation of IPB.
    Comparation of non-isothermal coal char gasification in micro fluidized bed and thermogravimetric analyzer
    WANG Fang, ZENG Xi, WANG Yonggang, YU Jian, YUE Junrong, ZHANG Jianling, XU Guangwen
    2015, 66(5):  1716-1722.  doi:10.11949/j.issn.0438-1157.20141677
    Abstract ( 231 )   PDF (619KB) ( 379 )  
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    The non-isothermal gasification behavior of coal char with CO2 was comparatively studied in the newly developed micro fluidized bed reaction analyzer (MFBRA) and a commercial thermogravimetric analyzer (TGA). The reaction kinetics data were calculated according to the methods of single heating rate and combination heating rate. The experimental data demonstrated that heating rate had obvious influence on coal char gasification. Increasing heating rate evidently increased reaction initiation temperature (Tx≈0), and reaction temperature corresponding to the maximum reaction rate (TRmax), but it gradually decreased char conversion at a given temperature and the activation energy estimated by the method of single heating rate. Comparing the results from TGA and MFBRA at the same heating rate clarified that both Tx≈0 and TRmax were relatively lower for MFBRA, and the higher the heating rate, the larger the difference between MFBRA and TGA. The measurement using MFBRA led to higher activation energy for char-CO2 gasification, no matter the adopted estimation method of single heating rate (≥5℃·min-1) or combination heating rate. The difference in kinetics data tested by TGA and MFBRA at higher heating rate (≥5℃·min-1) could be much related to better heat transfer and lower diffusion inhibition.
    Synthesis of 2,4-dichloro-5-fluoropyrimidine and recovery of DMA from waste water
    FU Yongfeng, GUO Ning, YUN Zhi, SUN Shanshan
    2015, 66(5):  1723-1729.  doi:10.11949/j.issn.0438-1157.20141261
    Abstract ( 331 )   PDF (609KB) ( 610 )  
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    2,4-Dichloro-5-fluoropyrimidine was prepared by reaction of 5-fluorouracil (5-FU) and phosphorus oxychloride in the presence of N,N-dimethylaniline (DMA) as acid acceptor. The effect of molar ratio of 5-FU to phosphorus oxychloride, molar ratio of 5-FU to N,N-dimethylaniline, reaction temperature and reaction time was investigated. Furthermore, reaction mechanism was discussed. 5-FU and POCl3 ratio 1:10, 5-FU and DMA ratio 1:1.5, reaction temperature 114℃, reaction time 2 h were the optimum process parameters of synthesizing 2,4-dichloro-5-fluoropyrimidine. Under this process condition, maximum yield of 92.2% of 2,4-dichloro-5-fluoropyrimidine could be obtained. The pH of waste water was then adjusted by adding sodium hydroxide, and the effect of pH on recovery of DMA and yield of by-product disodium hydrogen phosphate was studied. When pH was adjusted to 7, maximum recovery of DMA and maximum yield of by-product disodium hydrogen phosphate could be obtained.
    Density functional theory study on disproportionation reaction of methylchlorosilane azeotrope byproducts catalyzed by AlCl3
    TAN Jun, OUYANG Yuxia, SUN Ping, LIU Hui, CHEN Jie, WEI Xiaoyan
    2015, 66(5):  1730-1737.  doi:10.11949/j.issn.0438-1157.20141522
    Abstract ( 247 )   PDF (583KB) ( 481 )  
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    The disproportionation reaction between (CH3)3SiCl and SiCl4 catalyzed by AlCl3 involves three reactions; the reaction between (CH3)3SiCl and SiCl4 to form (CH3)2SiCl2 and CH3SiCl3 (R1), the reaction between (CH3)2SiCl2 and SiCl4 to form CH3SiCl3(R2) and the reaction between (CH3)3SiCl and CH3SiCl3 to form (CH3)2SiCl2(R3). Density functional theory was used to study these reactions. The possible catalytic mechanisms of AlCl3 were stepwise reaction pathway of forming intermediate CH3AlCl2 and co-adsorption pathway of two reactants on AlCl3. The co-adsorption mechanism was more likely for these three reactions. The energy barrier ranking of these reactions was R2 >R1 >R3. By analyzing the thermodynamics data of these reactions, the effect of temperature on the Gibbs reaction energy of R2 was almost negligible within a temperature range of 543.15 K to 593.15 K. However, the Gibbs reaction energy of R1 and R3 significantly decreased at 593.15 K. These studies indicated that through appropriate temperature regulation, the reactions of R1 and R3 could be the dominant reactions while R2 would be effectively suppressed, influencing product distribution and facilitating formation of (CH3)2SiCl2.
    Supported Au/MOF-5: a highly active catalyst for three-component coupling reactions
    LIU Lili, TAI Xishi, LIU Meifang, LI Yufeng, FENG Yimin, SUN Xiaori
    2015, 66(5):  1738-1747.  doi:10.11949/j.issn.0438-1157.20141894
    Abstract ( 360 )   PDF (1718KB) ( 662 )  
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    Gold was supported on a functionalized MOF-5 by impregnation method. The catalyst Au/MOF-5 was characterized by powder X-ray diffraction (XRD), N2 adsorption-desorption, infrared spectra (IR), thermogravimetric analysis and differential thermal analyses (TG-DTA), transmission electro microscopy (TEM), and inductivity coupled plasma (ICP). Its catalytic performance was examined in one-pot synthesis of structurally divergent propargylamines via three component coupling of aldehyde, alkyne, and amine (A3) in 1,4-dioxane. The results showed that the Au/MOF-5 catalyst displayed high activity (high aldehyde consumption rate and turn-over number at 120℃: 18.7 mmol·(g Au)-1·h-1 and 14.7, based on total gold content) and 100% selectivity for propargylamines. Various aromatic and aliphatic aldehydes were also able to undergo the A3 coupling on the catalyst Au/MOF-5. It was also found that the conversion of benzaldehyde was higher on the catalyst for aryl aldehydes with electron-withdrawing group bonded on benzene ring than for those with an electron-donating group. There was good conversion of benzaldehyde for secondary amines and N-alkyl aniline such as piperidine, pyrrolidine, morpholine, diethylamine, and N-methylaniline. It was also found that the conversion of benzaldehyde decreased with increasing chain length of straight-chain alkyl substituted phenylacetylene. Au/MOF-5 catalyst could be recycled at least three times, and the activity only decreased slightly.
    Simulation of absorption-hydration separation unit for gas mixture by non-equilibrium stage approach
    MA Qinglan, LEI Yahui, CHEN Guangjin
    2015, 66(5):  1748-1759.  doi:10.11949/j.issn.0438-1157.20141195
    Abstract ( 286 )   PDF (621KB) ( 386 )  
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    It has been accepted that separation of low boiling-point gas mixture via hydrate technology has the advantage of operating at around 0℃, and therefore can reduce the refrigerating energy consumption dramatically. It is necessary to study the simulation algorithm for the operation process because this separation technique is still at the stage of theoretical research and has not fulfilled practical industrial application. In this work, a process of hydration and absorption two-tower series operation was simulated by using the non-equilibrium stage approach, which involved hydrate formation kinetic model, hydrate dissociation kinetic model, and mass transfer kinetic model when gas was absorbed in water-in-oil emulsion. The effect of operation parameters of two series towers, such as temperature, pressure on separation efficiency was investigated. The calculation results are of significance for designing separation process for low boiling-point gas mixture via hydrate technology, and can also lay a theoretical foundation for industrial application of this separation technique.
    Falling film absorption of CO2 into ionic liquid-MEA mixed solutions with different flow patterns
    ZHANG Fangfang, DING Yudong, ZHU Xun, LIAO Qiang, WANG Hong, ZHAO Linlin
    2015, 66(5):  1760-1766.  doi:10.11949/j.issn.0438-1157.20141597
    Abstract ( 324 )   PDF (962KB) ( 375 )  
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    Carbon dioxide absorption into a mixed aqueous solution of functional ionic liquid, tetramethyl ammonium glycinate ([N1111][Gly]) and monoethanolamine (MEA) was performed in a plate falling film reactor with different flow patterns. The effect of countercurrent gas flow on flow pattern transition was investigated. Absorption of carbon dioxide into the mixed aqueous solution of MEA and [N1111][Gly] was studied with different liquid flow rates, liquid temperatures, gas flow rates and inlet carbon dioxide concentrations. Falling liquid film was found to take the patterns of corner rivulet flow, falling film flow with dry patches, and complete falling film flow depending on gas and liquid flow rates. Reduction of gas flow rate could lower critical flow rate of pattern transition. Absorption rate increased with increasing liquid flow rate with flow patterns of corner rivulet flow and falling film flow with dry patches, and then became unchanged with the pattern of complete falling film flow. CO2 absorption rate reached a maximum with the pattern of complete falling film flow, however, corner rivulet flow had the largest liquid phase mass transfer coefficient.
    Recovery of KCl crystalline product from highly concentrated KCl-MgCl2-H2O solution with membrane distillation crystallization
    GUAN Yunshan, WU Jing, CHENG Wenting, LI Jianfeng, CHENG Fangqin, WANG Xuming
    2015, 66(5):  1767-1776.  doi:10.11949/j.issn.0438-1157.20141598
    Abstract ( 328 )   PDF (2681KB) ( 563 )  
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    Highly concentrated KCl and MgCl2 solutions were treated with direct contact membrane distillation (DCMD). The effects of salt concentration (1.0—4.0 mol·L-1) and circulation velocity (0.1—0.5 m·s-1) on permeate flux were investigated. Permeate flux decreased with increasing concentration, which was attributed to vapor pressure reduction caused by decrease of water activity in the solution. Reversed flux occurred in the DCMD process of highly concentrated MgCl2 solution (>3.0 mol·L-1) under the test conditions, which was due to the combined effect of lower water activity and higher viscosity of the fluid. Permeate fluxes increased with increasing circulation velocity, which was more effective to reduce the negative effect of temperature and concentration polarization for MgCl2 solution with higher viscosity. Membrane distillation-crystallization (MDC) of a highly concentrated solution of KCl-MgCl2-H2O was investigated for recovery of KCl crystalline product and pure water with batch operation mode. The effect of way of cooling on supersaturation of solution, morphology, and crystal size distribution was studied. KCl crystalline product with regular shape, tidy surface and concentrated particle size distribution was obtained by natural cooling and maximum degree of supercooling generated under natural cooling was lower than under quick cooling, which was beneficial to control nucleation amount and growth rate of KCl.
    Online monitoring of CO2 capture process using monoethanolamine by pH meter
    ZHANG He, ZHANG Hui, LIU Yingshu, HAO Zhitian, JIAO Lulu, ZHAO Ziling
    2015, 66(5):  1777-1784.  doi:10.11949/j.issn.0438-1157.20141617
    Abstract ( 331 )   PDF (1633KB) ( 576 )  
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    Monoethanolamine (MEA) aqueous solution has remarkable absorption capability for acid gas such as CO2 and has a potential application prospect in the field of gas separation and purification. Absorption temperature, gas flow rate and MEA concentration were taken into account as influence factors on reaction rate by monitoring the variation of pH in MEA aqueous solution. A conception called specific activity describing the absorption performance of the solution was introduced. The descending rate of pH decreased, saturation time was extended and the pH of final saturation state increased with the increase of solution concentration. With increasing temperature, the descending rate of pH increased and saturation time was shortened, but both of them would maintain a relatively stable value when temperature was high enough. When gas flow rate of CO2 increased, the pH of solution was gradually reducing at a faster rate, and finally, remained stable. The pH of saturated solution reached the lowest level at the flow rate of 70 ml·min-1. The monitoring method was easy to operate and the result was highly accurate so that it could provide a reference for development of CO2 absorption solutions.
    Synthesis of carboxymethyl polyamines chitosan and its adsorption properties for Ni(Ⅱ)
    GUI Shan, LIU Gonggang, JIANG Heng, DAI Yanni, YE Hongqi
    2015, 66(5):  1785-1791.  doi:10.11949/j.issn.0438-1157.20141197
    Abstract ( 242 )   PDF (758KB) ( 334 )  
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    A novel amino acid functionalized polyamine carboxymethyl chitosan (CTGCS) was designed to improve adsorption ability of chitosan (CS) for heavy metals. Chitosan resin (GCS) was firstly obtained via cross-link reaction of chitosan and glutaraldehyde. After following modification by tetraethylenepentamine and chloroacetic acid, CTGCS was successfully synthesized. The samples at different reaction steps were characterized by using FTIR and XPS to understand reaction mechanism. Moreover, the adsorption ability of as-synthesized CTGCS for Ni2+ from aqueous solutions was investigated. The adsorption process conformed with the Freundlich isotherm model and could be fitted by the pseudo-second order kinetics model. The maximum adsorption capacity of CTGCS for Ni2+ was significantly improved up to 533.8 mg·g-1, about 1.5 times more than that of TGCS, indicating that CTGCS was a promising adsorbent for heavy metals.
    Operation properties of oriented grid packing extractor
    FAN Zhaoyun, CAI Weibin, YANG Yunhui, WANG Yuqi, WANG Yujun, ZHU Shenlin
    2015, 66(5):  1792-1797.  doi:10.11949/j.issn.0438-1157.20141489
    Abstract ( 227 )   PDF (1352KB) ( 249 )  
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    The hydraulic characteristics and mass transfer efficiency of a new kind of oriented grid packing extractor were investigated by experimental study. The throughput of the new extractor increased greatly than the traditional packed extractor. When velocity ratio LR (dispersed phase:continuous phase) equaled 1:5, flooding throughout reached 150 m3·m-2·h-1. The new packed extractor also exhibited good extraction efficiency, and thus could have excellent application prospects in many areas as solvent deasphalting in petroleum refining process, phenol removal from wastewater in coal chemical industry, etc.
    Fault detection method based on sparse non-negative matrix factorization
    WANG Fan, YANG Yawei, TAN Shuai, SHI Hongbo
    2015, 66(5):  1798-1805.  doi:10.11949/j.issn.0438-1157.20141660
    Abstract ( 300 )   PDF (538KB) ( 701 )  
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    In this paper, a novel fault detection method based on sparse non-negative matrix factorization (SNMF) is proposed. NMF (non-negative matrix factorization) is a new dimension reduction technique that can find a low-rank matrix approximation from the original data. In contrast to the conventional multivariate statistical process monitoring methods, for example PCA, NMF has no assumption about the nature of latent variables, except for non-negativity. Combining linear sparse coding and NMF, SNMF can learn much sparser representation via imposing sparseness constraints. During factorization, low-rank matrix is orthogonalized to remove redundant information and concentrate information on fewer directions of projection. Then, SNMF is used to extract the latent variables that drive a process and new statistical metrics are defined for fault detection. Kernel density estimation (KDE) is adopted to calculate the confidence limits of defined statistical metrics. Afterwards, the proposed method is applied to the Tennessee Eastman process to evaluate the monitoring performance, comparing with conventional NMF and PCA. The results from the experiment show the feasibility of the new method.
    Fault diagnosis based on current distribution estimation for copper electrolytic tank
    ZHAO Rentao, ZHANG Yu, LI Huade, GUO Caiqiao, TIE Jun
    2015, 66(5):  1806-1814.  doi:10.11949/j.issn.0438-1157.20141844
    Abstract ( 290 )   PDF (1929KB) ( 398 )  
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    In order to achieve automatic diagnosis of burning-plate fault on the cathode bar and real-time monitoring of current distribution in the process of copper electrolysis, based on the principle of infrared imaging, an infrared camera was used to shoot the image of copper electrolytic tank, and the gray value on the cathode bar in the processed image was extracted. A mathematical model between gray value and cathode bar temperature was developed on the basis of field tests, and the surface temperature of the cathode bar could be calculated. A partial least squares (PLS) method was used to develop a mathematical model between surface temperature and current value of the cathode bar. The square of current value after integration was found to be in quasi-linear relationship with surface temperature of the cathode bar, the coordinates of cathode bar and ambient temperature. Contrast between the current on the cathode bar derived from the model and the current measurement on the field showed that the current on the cathode bar could be accurately determined with this method, which realized real-time monitoring of current value in the copper electrolysis process. In addition, the cathode bar with burning-plate fault could be accurately and automatically diagnosed, and this fault could be predicted by monitoring the current value on the cathode bar, achieving automatic diagnosis of the fault in the copper electrolysis process, thereby reducing burning-plate fault on the cathode bar and resulting in good economic benefits.
    SVDD-based chiller sensor fault detection method and its detection efficiency
    LI Guannan, HU Yunpeng, CHEN Huanxin, LI Haorong, LI Jiong, HU Wenju
    2015, 66(5):  1815-1820.  doi:10.11949/j.issn.0438-1157.20141585
    Abstract ( 274 )   PDF (549KB) ( 387 )  
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    In the refrigeration and air conditioning system, sensors are independent component for physical data measuring and operating state monitoring. Sensor faults, especially sensor biases output will lead to incorrect measurement, inappropriate controlling strategy and further energy consumption rise. Based on the pattern recognition theory, the fault detection task could be considered as a one-class classification problem. Therefore, a powerful pattern recognition-based one-class classification algorithm, Support Vector Data Description (SVDD) was used to detect the sensor biases occurring in a chiller system. The practical fault-free data were used as training dataset to develop the SVDD model so as to detect the sensor faults. The method and its fault detection efficiency were validated by test dataset with different artificially introduced levels of sensor biases. The SVDD-based fault detection method worked well with chiller practical operating measurements, but the fault detection efficiencies of different sensors with different level faults were inconsistent.
    Non-linear mapping and multi-objective optimization of leading flow structure in plate-fin heat exchanger
    LIU Jingcheng, ZHANG Shuyou, XU Jinghua, ZHOU Zhiyong, YI Guodong
    2015, 66(5):  1821-1830.  doi:10.11949/j.issn.0438-1157.20140907
    Abstract ( 237 )   PDF (1904KB) ( 309 )  
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    Flow maldistribution in the inlet of the plate-fin heat exchanger along the longitudinal direction affects heat transfer among different layers. Nowadays experimental methods are used to determine the parameters of the leading flow structure, however, optimization of these parameters has not been reported yet. A new multi-objective optimizing method was proposed based on traditional leading flow structure. Considering the factors influencing fluid distribution in the inlet of the plate-fin heat exchanger, including diameter, space and number of hole on the leading flow structure, fluid velocity, location of the leading flow structure in the inlet of the exchanger and inlet diameter of the exchanger, the multi-objective optimizing models of pressure drop and heat transfer per unit time were established. Orthogonal experiment was conducted to create the simulation model and deduce non-linear mapping equations of the leading flow structure. The leading flow structure was optimized using back propagation network (BP) combined with genetic algorithm and the final parameters of the structur were determined. Fluid flow and distribution in the inlet of the plate-fin heat exchanger before and after optimization were simulated using the commercial software, Fluent, and were compared with those without the leading flow structure. The leading flow structure after optimization could improve fluid distribution along the longitudinal direction obviously, and meanwhile, improve heat transfer and enhance performance of the exchanger.
    Sensor fault detection and diagnosis using MAF
    FU Kechang, YUAN Shihui, JIANG Shiqi, ZHU Ming, SHEN Yan
    2015, 66(5):  1831-1837.  doi:10.11949/j.issn.0438-1157.20141595
    Abstract ( 280 )   PDF (520KB) ( 548 )  
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    For industrial processes, there are not only correlations among variables, but also autocorrelation in temporal structure of these variables, therfore, a new sensor fault detection and diagnosis method based on min/max autocorrelation factors (MAF) was proposed in this work. Firstly, MAF analysis of historical normal data was made. Then, strong autocorrelation factors and weak autocorrelation factors were obtained. Based on these factors, the statistics for fault detection were constructed and corresponding contribution plots were derived. The proposed method was applied to the continuous stirred tank reactor (CSTR) and compared with the principal component analysis method. Simulation results demonstrated that the proposed method could detect sensor faults with slow variation more quickly with less false-alarm. The contribution plots based on MAF can explain complicated sensor fault more reasonably than principal component analysis (PCA), which is a classical multivariate statistical method for process monitoring.
    Optimization of a batch water network with multi-contaminants based on matrix encoding genetic algorithm
    YE Mengqing, XIE Xin'an, LI Lu, LI Yan
    2015, 66(5):  1838-1843.  doi:10.11949/j.issn.0438-1157.20141496
    Abstract ( 209 )   PDF (492KB) ( 540 )  
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    For the multi-contaminants batch water network optimization problem, a mixer-integer nonlinear programming model with the objective of minimum fresh water usage was established. Meanwhile, a solution strategy combined with matrix encoding genetic algorithm and trust region sequential quadratic programming(TRSQP)was proposed. In this paper, the matrix encoding method is easy to establish scheduling module, so the water reused relationship between the water units is more clearly defined.The integer variables was optimized by matrix encoding genetic algorithm and the continuous variables was optimized by TRSQP, the optimal strategy integrated the two methods to achieve the solution of MINLP model with the MATLAB software. The proposed method was used to solve two typical examples and the results obtained were superior to those in literature, which demonstrated that the approach introduced by this paper was effective.
    Friction and corrosion behavior of ceramic milling balls in milling-leaching combined digestion of ilmenites
    LUO Wenbo, YUAN Shaojun, WANG Xiaomei, TANG Siyang, LI Chun, YUE Hairong, LIANG Bin
    2015, 66(5):  1844-1853.  doi:10.11949/j.issn.0438-1157.20141717
    Abstract ( 292 )   PDF (6037KB) ( 537 )  
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    The corrosion and friction behavior of four kinds of ceramic grinding balls (zirconia, alumina, agate, silicon nitride) was investigated in a milling-leaching combined process for the acidolysis of Panzhihua ilmenite in sulfuric acid. The order of corrosion rates of the balls were: silicon nitride>alumina>zirconia>agate balls. Corrosion of zirconia mainly conformed to the mechanism of friction, while collision and surface cutting were responsible for corrosion of agate balls. Corrosion of alumina ball was due to abrasive wear, and presence of ilmenite significantly increased weight loss. Silicon nitride balls experienced obvious surface spalling abrasive wear. The weight loss rates of the four ceramic grinding balls were over 80% caused by physical abrasion, and the aluminum and silicon nitride balls suffered an obvious combined effect of corrosion and friction. The weight loss rates of alumina and silicon nitride ball were 1.76 and 14.52 mg·cm-2·d-1, respectively, which were much higher than those of zirconia and agate balls. The results provided good reference to chasing the grinding ball materials in the milling-leaching process for acidolysis of ilmenite.
    Steam explosion and esterification modification of rice straw for oil spill absorption material
    PENG Li, LIU Changjian, LIU Baijun, CHU Shengli, LUAN Guohua, PEI Yuqi
    2015, 66(5):  1854-1860.  doi:10.11949/j.issn.0438-1157.20141734
    Abstract ( 245 )   PDF (1139KB) ( 427 )  
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    A natural organic oil spill adsorption material was developed by steam explosion and esterification modification of rice straw. The oil-absorption capacity and water-absorption capacity of the raw rice straw were 5.66 g·g-1 and 7.59g·g-1, respectively. The conditions of esterification modification of rice straw were optimized. The optimal reaction temperature, catalyst concentration and reaction time were 80℃, 0.75%, 6 h, respectively. The oil-absorption capacity and water-absorption capacity of the modified rice straw were 8.54 g·g-1 and 0.10 g·g-1, respectively. Furthermore, the rice straw before and after modification were characterized by BET, XRD, FT-IR. The modified rice straw had larger pore diameter after steam explosion, appearance of non-crystallizing state and acetyl group of characteristic peak after esterification, which proved the feasibility of esterification modification of rice straw.
    Chemical structure analysis of oil shale kerogen
    WANG Qing, HUANG Zongyue, CHI Mingshu, SHI Juxin, WANG Zhichao, SUI Yi
    2015, 66(5):  1861-1866.  doi:10.11949/j.issn.0438-1157.20141798
    Abstract ( 306 )   PDF (525KB) ( 443 )  
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    Five different oil shale kerogens were analyzed with advanced testing techniques (XRD, 13C NMR and FT-IR) to obtain important structural information. The long-range disordered state of aggregation was also confirmed by XRD. Using 13C NMR spectroscopy, 18 characteristic parameters of carbon skeleton structure were obtained. Detailed information about the chemical structure of kerogen was obtained through verifying the results of 13C NMR experiments with the qualitative analysis of kerogen groups made by FT-IR technique. The aliphatic structure of oil shale kerogen was up to 60%—90%, with the methylene carbon occupying the dominant position of 77%—90%, and most of the aliphatic structure were straight-chain while less alicyclic or branched chain. In addition to Huadian oil shale with a monocyclic aromatic carbon structure, the other four oil shale kerogens were co-existing monocyclic and polycyclic rings, with the latter mainly peri-condensed. The oxygen structure was C-O (alcohol, phenol, ether) and C=O, and carboxyl class was more than carbonyl class C=O. More C=O in kerogen was due to a low degree of metamorphism, while a high degree of metamorphism resulted in more C-O.
    Growth mechanism of product layer in SO2 and NOx simultaneous removal by calcium-based sorbent
    CHEN Guoqing, GAO Jihui, GAO Jianmin, WU Shaohua, QIN Yukun
    2015, 66(5):  1867-1873.  doi:10.11949/j.issn.0438-1157.20141246
    Abstract ( 301 )   PDF (7327KB) ( 845 )  
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    In order to analyze the growth mechanism of product layer in SO2 and NOx removal by calcium-based sorbent, the single-crystal Ca(OH)2(0001) surface was used to simulate the pore wall and external surface of the sorbent. The growth of product layer was analyzed under different reaction environments. The growth mechanism of product layer in SO2 and NOx simultaneous removal by calcium-based sorbent was proposed, combining crystal growth theory and discrepancy between SO2 and NOx single removal. SO2 removal reaction firstly occurred in the local area of the single-crystal surface to result in expansion of surface and formation of convex structure. Subsequently, the reaction and expansion area gradually extended, which led to formation of the continuous dense product layer. Due to solubility and diffusion of NO2 removal product in the water film, NO2 reaction had an obvious etching effect on the sorbent surface. When SO2 removal reaction coexisted with NO2 removal reaction, the etching action of NO2 removal reaction could inhibit formation of the continuous dense SO2 removal product layer. Meanwhile, the presence of NO2 removal product could change the growth habit of the SO2 removal product. Therefore, the sorbent surface structure after simultaneously reacting with SO2 and NOx was loose.
    Pyrolysis study of bamboo Phyllostachys edulis pretreated with ionic liquids mixtures
    CHEN Qiyu, WANG Qingyue
    2015, 66(5):  1874-1882.  doi:10.11949/j.issn.0438-1157.20141494
    Abstract ( 319 )   PDF (4757KB) ( 360 )  
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    The pyrolysis study of the ionic liquid (IL)-H2O mixtures pretreated bamboo (Phyllostachys edulis) was investigated. 1-Butyl-3-methylimidazolium chloride ([Bmim]Cl)-H2O, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4)-H2O and 1-butyl-3-methyl pyrrolidinium chloride ([Bmpy]Cl)-H2O with or without solid acid catalyst (Nafion®NR50) were used in the pretreatment process. The composition analysis result of untreated bamboo and pretreated bamboo were compared. XRD and SEM result were analyzed to explain the effect of ILs mixture on cellulose crystalline structures and surface structures. According to the result of TG-DTA and GC-TCD, the sample pretreated with [Bmim]Cl-H2O mixture was used in the pyrolysis process to produce more gaseous products and low char. About 0.12 g gaseous products and 0.19 g char were produced from 1.0 g sample pretreated with [Bmim]Cl-H2O mixture and added solid acid catalyst, different from the result of untreated sample, 0.04 g gaseous products and 0.24 g char. The potential and problems of IL-H2O mixture pretreatment used in thermal chemical conversion methods were discussed.
    Absorption refrigeration cycle driven by waste heat using R124-DMAC as working fluids
    LI Xing, XU Shiming, LI Jianbo
    2015, 66(5):  1883-1890.  doi:10.11949/j.issn.0438-1157.20141333
    Abstract ( 262 )   PDF (1757KB) ( 551 )  
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    Energy saving and emission reduction technologies for vehicles have been paid more attention in recent years, and it is necessary to investigate how to efficiently recover and utilize the waste heat from vehicle engines to drive automotive air conditioning system. Based on that, a full air-cooled bubble absorption refrigeration test system with 3 kW cooling capacity driven by waste heat, using R124-DMAC as working fluids was designed and built. In the system, engine exhaust gas was simulated by heated air. Operating parameters were tested through changing heat source temperature, chilled water temperature and pump flow rate. The maximum COP of the system could reach 0.54 under the condition of generator temperature 100℃ and evaporating temperature -4℃. Heat source and chilled water temperatures had an important effect on cooling capacity and COP, and this system had good stability. However when evaporating temperature was below 5℃, a rectification unit should be considered in order to improve cooling effects. Additionally, this experiment proved that the air-cooled bubble absorber worked well, providing theoretical support for the refrigeration system driven by waste heat in vehicle air conditioning.
    Analysis and formation mechanism of condensates on surface of flue gas cooler of coal-fired power plant
    MA Haidong, WANG Yungang, ZHAO Qinxin, CHEN Heng, JIANG Weiwei
    2015, 66(5):  1891-1896.  doi:10.11949/j.issn.0438-1157.20141698
    Abstract ( 310 )   PDF (3962KB) ( 557 )  
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    Two kinds of important equipment i.e. selective catalytic reduction system (SCR) and flue gas cooler are applied in coal-fired power plant to achieve energy conservation and to reduce emission. However, few studies have been published on the influence of ammonia escaped from SCR system on flue gas cooler. In this study, the condensates deposited on the wall of the cooler at the downstream of SCR were analyzed by XRD, XRF, SEM and EDS. The results indicated that the white crystalline material in the condensates is mainly ammonium fluoroborate and some intermediates such as ammonium fluoride, boric acid and ammonium fluorosilicate. The formation of crystalline layer took place by coupling reaction between the ammonia escaped from SCR system and both fluorine element and boron element volatilized in combustion of coal. Although the deposition layer has only a limited thickness, it could be hamper directly for operation of flue gas cooler.
    Influence of hydraulic retention time on sludge characteristics of DC anaerobic reactor for treating traditional Chinese medicine wastewater
    SU Chengyuan, WANG Kaiyao, LI Weiguang
    2015, 66(5):  1897-1903.  doi:10.11949/j.issn.0438-1157.20141882
    Abstract ( 345 )   PDF (1098KB) ( 371 )  
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    The influence of hydraulic retention time (HRT, 24, 18, 15 and 12 h) on the performance of double circle (DC) anaerobic reactor for treating traditional Chinese medicine wastewater was investigated. Additionally, the characteristics of granular sludge were studied, including particle size distribution (PSD), extracellular polymeric substances (EPS), and distribution of microbial communities. When HRT was reduced from 24 h to 12 h, the DC anaerobic reactor demonstrated good COD removal of 90%. Although concentration of acetate increased to 339.69 mg·L-1, the process was operating favorably without acidification. But humic acid-like and fulvic acid-like absorption peaks were stronger and coenzyme F420 absorption was weaker in the EEM spectra of soluble microbial products (SMP) at HRT 12 h. It was not recommended to further reduce HRT. The contents of EPS, protein, and polysaccharide decreased in the sludge at HRT 12 h, and tyrosine played an important role in maintaining stability of the sludge. The phospholipid fatty acids analysis showed that reducing HRT affected significantly distribution of microbial community in the second reaction area of the DC anaerobic reactor. Gram-positive bacteria decreased from 44.24% to 32.69%, while gram-negative bacteria increased from 32.69% to 38.66%.
    Performance analysis of jacketed MVR heat pump evaporation concentration system
    LIU Jun, ZHANG Chong, YANG Luwei, ZHANG Zhentao, LI Bo, WU Yun
    2015, 66(5):  1904-1911.  doi:10.11949/j.issn.0438-1157.20141408
    Abstract ( 315 )   PDF (1645KB) ( 762 )  
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    In order to evaporate and concentrate the thermo-sensitive materials with properties of high viscosity, easy scaling and strong corrosion, a jacketed MVR (Mechanical Vapor Recompression) heat pump evaporation concentration system was designed. Water was used as the test medium for a series of experimental studies. Such parameters as temperature difference, compression ratio, evaporation capacity, coefficient of heat transfer, COP (Coefficient of Performance), SMER (Specific Moisture Extraction Rate), adiabatic efficiency and volumetric efficiency were influenced by operational and structural parameters like evaporating pressure, frequency of compressor and heat transfer area. The performance of the system when the compressor was running at afrequency of 50 Hz was much better than that under other conditions at a lower frequency. The most appropriate range of evaporating pressure was from 65 kPa to 85 kPa when a single evaporating kettle was running, and it was unnecessary to supplement external steam. Two evaporating kettles could be simultaneously used for industrial evaporation concentration by supplementing only a small quantity of external steam. Energy saving of both cases mentioned above was significant.
    Sulfidation performance of calcined limestone from CO2 capture cycles
    WU Shuimu, LI Yingjie, SUN Rongyue, LU Chunmei
    2015, 66(5):  1912-1918.  doi:10.11949/j.issn.0438-1157.20141700
    Abstract ( 248 )   PDF (1936KB) ( 546 )  
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    Zero emission coal (ZEC) process based on calcium looping in which CO2 is captured through a cyclic carbonation/calcination process is a promising technology for hydrogen production. In this process, H2S should be removed before raw gas flows into the downstream carbonator/reformer. In this work, the cycled CaO derived from limestone after multiple carbonation/calcination cycles for CO2 capture was used to remove H2S from raw gas. Cyclic carbonation/calcination of CaO was performed in a dual fixed-bed reactor and then the cycled CaO was sent to a sulfidation reactor for H2S removal. The effects of carbonation/calcination cycle number, sulfidation temperature, H2S concentration and CaO microstructure on sulfidation performance of the cycled CaO from CO2 capture cycles were investigated. The cycled CaO after the long-term carbonation/calcination cycles for CO2 capture still had high H2S removal capacity. Sulfidation conversion of CaO derived from limestone decreased rapidly with increasing number of carbonation/calcination cycles in the first 20 cycles, and then decreased slowly with further increasing cycle number. After sulfidation for 120 min, sulfidation conversion of the CaO after 0 cycle was nearly 100%. And sulfidation conversions of the cycled CaO after 1, 20 and 100 cycles were 94%, 81% and 74%, respectively. H2S concentration showed a great effect on H2S removal of the cycled CaO. Sulfidation temperature in the range of 800—1000℃ had a little effect on H2S removal of the cycled CaO, and the optimum sulfidation temperature was 900℃. As the cycle number increased, specific surface area of the cycled CaO dropped due to sintering. The pores 20—150 nm in diameter of the cycled CaO which were closely related with H2S adsorption also decreased. Thus, H2S removal capacity of the cycled CaO decayed with the number of cycles.
    Structure optimization and energy analysis of reverse electrodialysis to recover energy of oceanic salinity gradient
    DENG Huining, TIAN Ming, YANG Xiuli, HE Yunfei
    2015, 66(5):  1919-1924.  doi:10.11949/j.issn.0438-1157.20141805
    Abstract ( 375 )   PDF (735KB) ( 1078 )  
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    Salinity gradient power is a kind of chemical potential energy which exists between sea water and fresh water or water with different salt concentrations. Reverse electrodialysis (RED) is a process that transfers the salinity gradient to energy. Compared with other process, RED shows higher energy density. However, the studies on RED are limited to small membrane stacks. Experiments with a larger setup show that power density decreases significantly. Moreover, there is little research on the energy efficiency analysis of the RED process. In this paper, the energy transfer process of RED was simulated mathematically and the structure of the membrane stack was optimized. The power density and energy efficiency of RED at different structural parameters were also analyzed. Decreasing the thickness of the compartment could enhance both power density and energy efficiency greatly. Increasing flow length could result in higher energy efficiency, but average power density would decrease.
    Effect of C/N on performance of AAO-BAF process
    ZHANG Weitang, XUE Xiaofei, PANG Hongtao, ZHANG Jie, LI Dong, PENG Yongzhen
    2015, 66(5):  1925-1930.  doi:10.11949/j.issn.0438-1157.20141719
    Abstract ( 286 )   PDF (605KB) ( 372 )  
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    Combining anaerobic-anoxic-oxic reactor with an external nitrification biological aerated filter, the AAO-BAF process was used to treat domestic wastewater. Adjusting the influent COD concentration from 211 to 675 mg·L-1, the effect of carbon-nitrogen ratio (C/N) on the performance of the AAO-BAF process was investigated. A low or high influent organic concentration had significant effect on the nutrients removal efficiency due to the deficient phosphorus release or nitrate competition in the anoxic zones of the AAO reactor between DPAOs and ordinary heterotrophic organisms. When C/N was between 4 and 7,the average removal efficiencies of COD, TN and PO43- could reach more than 86%, 78% and 90% respectively. Large quantity of residual volatile fatty acid (VFA)would be transferred into the anoxic zones when C/N was very high (such as 9.5), which would cause rapid consumption of NO3- by ordinary heterotrophic organisms rather than denitrifying phosphorus accumulating organisms (DPAOs).
    Influence of shear history on morphology, microstructure and mechanical properties of micro injection molded parts
    WANG Jiajia, WANG Lixia, BIAN Ning, WANG Dongfang, WANG Yongzhen, ZHANG Yang, LI Qian, SHEN Changyu
    2015, 66(5):  1931-1938.  doi:10.11949/j.issn.0438-1157.20141661
    Abstract ( 283 )   PDF (3573KB) ( 343 )  
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    Micro injection molding experiments were conducted to investigate the influence of shear history on morphology, microstructure and mechanical properties of the micro-scale parts by changing injection speed based on the iPP parts with thickness of 0.2, 0.5 and 1 mm. Shear rate was analyzed with software Moldflow. Skin-core structure appeared in the thickness direction in both 0.5 mm and 1 mm parts, and imperfect shish-kebab structure appeared in the transition layer between skin layer and core layer of 0.5 mm and 1 mm parts, however, column crystal was shown in the transition layer of 0.2 mm parts. The whole shear level in shear history increased with increasing injection speed for all the parts with three thicknesses. The ratio of skin layer of 0.5 mm and 1 mm parts decreased with increasing injection speed, and yield stress, elongation at break, breaking strength and modulus decreased as the ratio of skin layer decreased. For 0.2 mm parts, the ratio of skin layer increased with increasing injection speed, and yield stress, breaking strength, modulus increased with increasing ratio of skin layer, while elongation at break decreased.
    Photocatalytic degradation of LDPE film with Fe-Sr2Bi2O5 photocatalyst under UV and visible light irradiation
    WU Pei, LUO Xuegang, LI Ke, ZHANG Sizhao
    2015, 66(5):  1939-1946.  doi:10.11949/j.issn.0438-1157.20141736
    Abstract ( 294 )   PDF (6836KB) ( 533 )  
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    A novel Fe-Sr2Bi2O5 photocatalyst was synthesized with the co-precipitation method and added into a low density polyethylene (LDPE) film. The solid-phase photocatalytic degradation behavior of LDPE composite film under UV and visible light irradiation at room temperature was investigated and compared with the pure LDPE film, CaCO3/PE,Sr2Bi2O5/PE and TiO2/PE composite films,and the obtained sample were characterized with contact angle, Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy (FESEM), including the analyses for the mechanical properties of reserved elongation at break and reserved tensile strength. Fe-Sr2Bi2O5 had a high photocatalytic activity in degrading LDPE under UV light and visible light irradiation. After UV light irradiation for 10 d, reserved elongation at break and reserved tensile strength were lower than 5% and 40%, respectively; while contact angle was reduced by 22.52°. At the same time, carbonyl groups were detected in LDPE composite films and there were holes on the surface of LDPE around Fe-Sr2Bi2O5. Fe-Sr2Bi2O5 made photodegradation of LDPE more effective compared with Sr2Bi2O5 and TiO2 under UV or visible light degradation. In conclusion, LDPE could be degraded obviously by Fe-Sr2Bi2O5 under UV and visible light irradiation at room temperature, and Fe-Sr2Bi2O5 could be a new photocatalyst for photocatalytic degradation of polyethylene film in the future.
    Process mineralogy analysis of waste residue from ilmenite by acid hydrolysis
    LI Zongyun, XU Yanxia, WANG Jin, SONG Xingfu, YU Jianguo
    2015, 66(5):  1947-1954.  doi:10.11949/j.issn.0438-1157.20141658
    Abstract ( 232 )   PDF (6603KB) ( 651 )  
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    Comprehensive process mineralogy analysis of waste residue from incomplete reaction of titanium concentrate and sulfuric acid in sulfate process of titanium dioxide industry was made with Mastersizer 2000, XRD, XRF, ICP-AES, SEM-EDS, specific gravity method and screening, to provide guidance to recycling ilmenite. The residue had wet surface with about 45%(mass) soluble substance, including 4.06%(mass)Ti ion which could be hydrolyzed easily. The insoluble particles with various appearances contained 17.14%(mass) TiO2, 10.78% (mass) Fe2O3, and 46.94%(mass) SiO2. Its particle size distribution was between 1 mm and 100 mm. Its density was 3.21 g·cm-3. From screening, there were different particle sizes and densities between ilmenite and other impurities. Particles above 120 mm with average density about 3.4 g·cm-3 were mainly anhydrite. Particles between 18 mm and 75 μm with average density greater than 3.5 g·cm-3 were mainly ilmenite. Particles below 18 mm with average density about 2.9 g·cm-3 mainly contained silicon sludge, and became viscous and difficult to separate in water.
    AB monomers of hydroxy modified PBO and its novel synthesis technology
    JIN Ningren, LI Chen, HU Xiaofeng, HU Yanhong, ZHANG Jianting
    2015, 66(5):  1955-1963.  doi:10.11949/j.issn.0438-1157.20141644
    Abstract ( 265 )   PDF (850KB) ( 591 )  
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    The molecular structure of a monohydroxy modified PBO and its AB monomer were proposed, and 2-hydroxy-4-(5-amino-6-hydroxybenzoxazole-2-yl) benzoic acid(HABA)was synthesized by the condensation-cyclization reaction of 4-amino-6-nitroresorcinol hydrochloride(ANR·HCl)and hydroxy terephthalic acid(HTA), then 2-hydroxy-4-(5-nitro-6-hydroxybenzoxazole-2-yl) benzoic acid(HNBA)was reduced to obtain the AB monomer (HABA). The precursor HNBA was one-pot prepared from ANR·HCl and HTA with a yield of 69.25% and purity of 96.81%, and the AB monomer HABA with a purity >98% was obtained by reducing HNBA, with a total yield of 58.38% from ANR·HCl. The novel synthesis technology had the characteristics of convenient source of raw materials,short reaction steps,mild conditions,excellent stability and equi-molar polycondensing group. HABA and HNBA were identified with FT-IR, MS and NMR.
    Phase morphology and barrier performance of water-assisted injection-molded PP/EVOH blend parts
    ZHAO Junfeng, HUANG Hanxiong
    2015, 66(5):  1964-1969.  doi:10.11949/j.issn.0438-1157.20141480
    Abstract ( 322 )   PDF (5217KB) ( 498 )  
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    Three kinds of polypropylene (PP) with different viscosities were blended with poly(vinyl alcohol) (EVOH) to prepare 90/10 PP/EVOH blends, and the blends were then molded into hollow parts via water-assisted injection molding (WAIM). Samples were cut from locations near the gate (marked as 1#) and the end of flow channel (marked as 2#) of the WAIM blend parts, and the phase morphologies at three regions across the residual wall of the samples were observed with scanning electron microscope. The toluene permeabilities of the samples cut from the WAIM blend parts were measured. The phase morphologies at the three regions in the samples were interpreted with the aid of flow fields within the mold cavity under high-pressure water penetration during WAIM. Coarse fibers appeared in both outer and inner layers and droplets in the core layer for the sample taken from location 2# of the WAIM blend with high viscosity ratio, which resulted in modestly improved barrier performance of the sample compared with the WAIM corresponding PP sample (about 2.4 times). Slim fibers existed in the outer and inner layers and coarse and long fibers in the core layer for the samples taken from location 2# of the WAIM blends with low viscosity ratios, which resulted in greatly improved barrier performance of the samples compared with the WAIM correponding PP sample (about 9.8 times for the blend with the lowest viscosity ratio). Average diameters of dispersed fibers for the samples taken from location 1# of three WAIM parts were larger than those taken from location 2#, which resulted in lower barrier performance for the former samples.
    Dissolving polyacrylonitrile with twin-screw extruder
    ZHAO Shengyao, ZHU Bo
    2015, 66(5):  1970-1975.  doi:10.11949/j.issn.0438-1157.20141720
    Abstract ( 353 )   PDF (1113KB) ( 662 )  
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    In order to improve production efficiency, simplify procedure, and produce polyacrylonitrile (PAN) spinning dope, which is stable and has high viscosity-average molecular weight (Mη), a new PAN dissolution method with twin-screw extruder was developed. A mode of T-combination was used to frame the second order twin-screw and a filter was installed in the outlet port. A mixed solvent suitable for screw extruder based on PAN dissolution theory and dissolution ability of solvents was selected. The dissolved PAN was used in dry jet wet spinning and high strength fiber with low linear density was made. The twin screw method of dissolving PAN satisfied high performance fiber production requirement, and the solution quality was stable and more productive.
    Synthesis, properties and application of reactive nitrogen-phosphorus flame retardant
    HU Wentian, YANG Rong, XU Liang, SONG Yan, LI Jinchun
    2015, 66(5):  1976-1982.  doi:10.11949/j.issn.0438-1157.20141850
    Abstract ( 332 )   PDF (593KB) ( 680 )  
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    A novel reactive flame retardant named hexakis (4-diethyl phosphate hydroxymethyl phenoxy) cyclotriphosphazene (HPHPCP) was synthesized from hexachlorocyclotriphosphazene (HCCP), p-hydroxy benzaldehyde and diethyl phosphite. Chemical structures of intermediate and HPHPCP were characterized by Fourier-transform infrared spectroscopy (FTIR), proton and 31P nuclear magnetic resonance (NMR). Thermal stability of the HPHPCP was determined via thermogravimetric analysis (TGA). Halogen-free flame-retardant rigid polyurethane foams (RPU) were prepared by using HPHPCP as a reactive flame retardant. The effect of HPHPCP content on the thermal and flame-retardant properties of RPU was investigated with TGA, and limiting oxygen index (LOI). The temperatures of 5%(mass) loss (T5%) of HPHPCP in nitrogen and air were 162.7℃ and 153.0℃, and the residues at 800℃ of HPHPCP in nitrogen and air were 42.1% and 12.0%(mass), respectively. HPHPCP could enhance thermal stability of RPU. The T5% of RPU-20%HPHPCP was 193.9℃, 20℃ higher than pure RPU. Moreover, limiting oxygen index (LOI) of RPU increased with increasing HPHPCP, and LOI of RPU-30%HPHPCP was 27%.
    Effect of soluble phosphorus on high-strength α-hemihydrate gypsum prepared by atmospheric hydrothermal method
    RU Xiaohong, LI Haitao, ZHANG Xin'ai, MA Baoguo, LU Siwen
    2015, 66(5):  1983-1988.  doi:10.11949/j.issn.0438-1157.20141449
    Abstract ( 238 )   PDF (8293KB) ( 262 )  
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    The effect of soluble phosphorus on CaSO4·2H2O (DH) dehydration to α-calcium sulfate hemihydrate gypsum (α-HH) in hydrothermal CaCl2 solutions and the crystal shape regulation were investigated. The action mechanism of soluble phosphorus was studied by means of growth of hemihydrate crystal. The system pH was the main factor to determine whether DH could be dehydrated to α-HH in 24% CaCl2 solution at 98℃. Acicular a-HH crystal could be obtained when pH was less than 2.0. High-strength α-HH crystal with aspect ratios from 0.5 to 3.0 could be observed when polycarboxylic crystal habit modifier NS was added. The corresponding compressive strength was more than 20 MPa. The presence of soluble phosphorus was favorable for α-HH formation by lowering system pH, increasing supersaturation degree and reducing interfacial energy. On the other hand, acid radical ions affected α-HH crystallization behavior and adsorption results of medium crystal agent NS.
    Preparation and characterization of Li4Ti5O12/C anode material for lithium ion batteries
    ZHAO Xi, TIAN Yanhong, ZHANG Xuejun, CHEN Yong
    2015, 66(5):  1989-1995.  doi:10.11949/j.issn.0438-1157.20141179
    Abstract ( 260 )   PDF (6661KB) ( 678 )  
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    In order to enhance electrical conductivity and rate capability of Li4Ti5O12, the Li4Ti5O12/C powder was prepared by the sol-gel method, using PEG as carbon source. The performance of Li4Ti5O12/C coated by three different molecular weight carbon sources: PEG (400, 600, and 1000), was investigated with TG, XRD, SEM, TEM, constant current charge-discharge, rate discharge and EIS. The material obtained by using PEG1000 as carbon source had the best electrochemical performance. Initial discharge capacity was 143.5 mA·h·g-1 at 0.1C rate, and discharge capacity remained 105 mA·h·g-1 at 2C rate, capacity retention ratio was 73.17%, in addition, it had the smallest resistance.
    Influence of monoammonium phosphate on hazard characteristics of ammonium nitrate
    XU Sen, CHEN Xiang, TAN Liu, XIA Lianghong, LIU Dabin, PAN Feng
    2015, 66(5):  1996-2002.  doi:10.11949/j.issn.0438-1157.20141017
    Abstract ( 581 )   PDF (9979KB) ( 552 )  
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    Monoammonium phosphate (MAP) was mixed with ammonium nitrate (AN) by the mechanical mixing method (1) and the solution mixing method (2). The UN gap test and Koenen test of UN-Recommendations on the transport of dangerous goods, were used to determine the propagation of detonation and the effect of heating under confinement, and DSC was used to study the thermal decomposition characteristic. The results of UN gap test showed that samples with different mixing methods had the same result. When the MAP content reached 25%, the result was negative, i.e., the modified AN did not propagate detonation. In the Koenen test, when the MAP content in the modified AN-1 and modified AN-2 reached 30% and 25% respectively, the samples were not sensitive to intense heat under test confinement. The results of DSC showed that the Tonset of modified AN-1 was lower than AN, but the Tonset of modified AN-2 was higher than AN. The mechanical mixing method could improve the passivation effect of MAP on AN.