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Table of Content
05 August 2017, Volume 68 Issue 8
    A review on development and prospect of water refrigerant and water vapor compressor
    WU Di, HU Bin, WANG Ruzhu, JIANG Nanshan, LI Ziliang
    2017, 68(8):  2959-2968.  doi:10.11949/j.issn.0438-1157.20170264
    Abstract ( 785 )   PDF (410KB) ( 814 )  
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    As a representative of the fourth generation refrigerant, water has numerous advantages, such as non-pollution (ODP=0, GWP<1), accessible, low-cost, secure, stable and large latent heat of vaporization, which can completely satisfy the requirements of the environment as a refrigerant. However, low molecular weight, large specific volume and high adiabatic index of water vapor determine that the water vapor systems have the characteristics of small differential pressure, large compression ratio, small unit volume capacity, large volume flow and high discharge temperature. It also puts forward higher requirements for water vapor compressors, which seriously limit the use and promotion of water as a refrigerant. Currently, the water vapor compressors mainly are centrifugal, screw and roots compressor. Centrifugal water vapor compressor has the advantage of large volume flow rate, but it has small single stage compression ratio, high discharge temperature and droplet sensitivity. At the same time, the blade and shell material of the centrifugal water vapor compressor are severe and expensive. Therefore the centrifugal water vapor compressor is suitable for the largest volume flow rate and smallest compression ratio system. Screw water vapor compressor has the advantages of good stability, large compression ratio and wet compression; however the volume flow rate is smaller. It is more suitable for the refrigeration system with small volume flow rate and large compression ratio. Roots water vapor compressor has the advantages of less vibration components and simple structure, however it also has small compression ratio, so it is usually used in the medium heating capacity and large temperature rise systems. In order to promote water refrigerant to be wildly used in production and livelihood field, researching and developing practicable compressors for different usage occasions and steam requirements is an interesting and significant research project in future.

    Key scientific problems for studying leakage mechanism of contact mechanical seal interface
    JI Zhengbo, SUN Jianjun, MA Chenbo, YU Qiuping, LU Jianhua
    2017, 68(8):  2969-2978.  doi:10.11949/j.issn.0438-1157.20170302
    Abstract ( 592 )   PDF (791KB) ( 786 )  
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    As one focal point for research and application of mechanical seals, leakage mechanism of seal interface involves characterizing leakage channels, modeling contact mechanics of rough surface, exploring morphological changes of seal interface and defining fluid flow resistance in leakage channels. The development of leakage channel models of contact mechanical seals in recent decades was reviewed. After analyzing contributions and problems of G-W, M-B, and Persson models of rough surface contact mechanics, a new percolation channel model was proposed. The effects of fractal parameters of seal interface, fluid flow resistance of channels, and limited size of seal interface on leakage characteristics were discussed. It was noteworthy to point out that leakage occurrence at seal interface was mainly due to pore connection across interface and low flow resistance of fluid through interface channels. Future studies on leakage mechanism will be formation of leakage channels and characteristics of fluid flow in these channels.

    Measurement of gas-liquid phase equilibrium for trans-1,3,3,3-tetrafluoropropene and squalane
    SUN Yanjun, WANG Xiaopo, LIU Zhigang, JIN Liwen
    2017, 68(8):  2979-2984.  doi:10.11949/j.issn.0438-1157.20170284
    Abstract ( 467 )   PDF (1246KB) ( 410 )  
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    The gas-liquid phase equilibrium experimental system based on the isochoric saturation method in the laboratory was improved. The visual equilibrium cell, thermostatic system and magnetic stirring system were modified. In order to check the reliability and accuracy of the new system, the phase equilibrium of carbon dioxide and pentaerythritol tetrahexanoate was measured at 303.15 K, the absolute average deviation was 0.95% and the maximum deviation was 2.01% compared with the reference data. The expanded uncertainties of temperature, pressure and mole fraction are 0.03 K, 2.0 kPa, and 3.0%, respectively. Phase equilibria behavior of trans-1,3,3,3-tetrafluoropropene and squalane was determined at temperature range from 283.15 K to 348.15 K. The experimental data were correlated with Peng-Robinson equation of state and van der Waals mixing rule using two interaction parameters. The absolute average deviation between experimental data and calculated values for pressure was 0.88%, and the maximum deviation was 3.80%. In addition, the immiscibility phenomenon for trans-1,3,3,3-tetrafluoropropene and squalane mixtures was found in the temperature range from 283.15 K to 333.15 K.

    Ba (OH)2·8H2O composite phase-change material and its heat release characteristics in solar photovoltaic/photo-thermal collectors
    JI Jun, LIU Yufei, REN Yinglei, HUA Weisan, ZHANG Xuelai
    2017, 68(8):  2985-2990.  doi:10.11949/j.issn.0438-1157.20161763
    Abstract ( 384 )   PDF (2842KB) ( 802 )  
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    A new barium hydroxide octahydrate composite phase-change material with melting point of 78℃ was developed, and its super cooling degree was reduced by 3-5℃ with the nucleating additive and its thermal conductivity can be enhanced by 11.7% combined with nanotechnology. Heat release characteristics of the new material were investigated on the experimental solar photovoltaic/photo-thermal (PV/T) collectors with cascade heat storage through paraffin wax, water and the new material. The system experimental results show that the new material has no super cooling and performs stable during phase-change. Under the circumstances that the water flow is 90 L·h-1 and the environment temperature is 20℃, the solar collecting system can effectively store solar energy and water temperature can be maintained above 50℃ for more than 60 min, and meanwhile in the first 20 min, the outlet hot water temperature is above 70℃. Thus, the solar energy storage system can reduce the solar cell temperature, and at the same time meet the requirements of daily life.

    Visualization of controlled cryogenic fluids' liquefaction and solidification by cryocooler
    ZHOU Shaohua, HUANG Yonghua, ZHUAN Rui, CHEN Hong, GAO Xu
    2017, 68(8):  2991-2997.  doi:10.11949/j.issn.0438-1157.20161715
    Abstract ( 346 )   PDF (12712KB) ( 175 )  
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    Liquefaction and solidification are two common phenomena in engineering fluid systems. The low temperatures of the boiling point and melting point of cryogenic fluids make it relatively difficult to observe the liquefaction and solidification processes under controlled conditions. An experimental setup for visualization of such processes has been designed and fabricated to capture the moments of the vapor-liquid and liquid-solid phase transition of nitrogen (44-80 K), argon (50-90 K) and oxygen (50-90 K), based on a G-M cryocooler as the cold source. The experimental results showed that these three cryogenic fluids behave considerably different during the solidification process.

    Establishment of bubble-based EMMS/PFB model and its application on dense section of pressurized fluidized-bed
    SONG Sufang, HAO Zhenhua, DONG Libo, LI Junguo, FANG Yitian
    2017, 68(8):  2998-3005.  doi:10.11949/j.issn.0438-1157.20170230
    Abstract ( 407 )   PDF (2668KB) ( 294 )  
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    An energy minimization and multi-scale model, bubble-based EMMS/PFB, was established for pressurized fluidized-bed, based on methods of multi-scale decomposition and energy consumption analysis in combination with bubble diameter correlation to conical distributor. The model was used to simulate a 2D pressurized jetting fluidized-bed and to study influence of operating parameters such as operating pressure, bubble location, porosity and residual velocity on heterogeneous index. Comparison of simulation results to experimental data, it was showed that the new model provided better accuracy than the Gidaspow model in prediction of solid particle concentration distribution and change of particle velocity adjacent to wall above the distributor. Dense section simulation of a pressurized fluidized-bed by the new drag model yielded prediction of instantaneous and time-averaged axial distributions of particle concentration and particle velocity distribution. The simulation could make it available to visualize gas-solid flow behavior at dense section and provide guidance for design and industrial scale-up of pressurized fluidized-beds.

    Vortex analysis in flow field of cyclone separator with single volute inlet
    GAO Zhuwei, WANG Jiangyun, WANG Juan, MAO Yu, WEI Yaodong
    2017, 68(8):  3006-3013.  doi:10.11949/j.issn.0438-1157.20170260
    Abstract ( 479 )   PDF (2268KB) ( 719 )  
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    To study vortex characteristics in cyclone separator, advanced RNG k-ε turbulence model was applied to numerical simulation of strongly rotational gas flow in cyclone separators with single volute inlet. In addition, Q criterion was used to identify vortex structure and to plot more obvious and highly detailed 3D iso-surface of vortex structure. The results showed that equivalent diameter of Q criterion iso-surface was large in upper cylinder and became smaller downward along the axis, indicating gradual decay of vortex-carrying energy. The vorticity iso-surface was not distributed regularly but distorted around central axis. Because of friction resistance, vorticity magnitude decreased sharply and energy lost rapidly near the wall. Furthermore, the deviation of vortex core center from geometric center exhibited a trending process of enlarging in the upper cyclone cylinder, decreasing downward along the axis gradually, and stabilizing eventually at the bottom of the cyclone cylinder. In this process, vortex developed rapidly, sometimes even ruptured, which caused loss of dynamic energy. Therefore, measures to enhance balance of vortex structure were conducive to reduce energy loss, to curb flow instability, and to increase separation efficiency.

    Effect and mechanism of BEM/PMSQ hybrid pour point depressant on Qinghai waxy crude oil
    SHI Xin, MA Xiaobin, YANG Fei, LI Chuanxian, YAO Bo, SUN Guangyu
    2017, 68(8):  3014-3022.  doi:10.11949/j.issn.0438-1157.20170249
    Abstract ( 372 )   PDF (2832KB) ( 242 )  
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    Based on the outstanding organic compatibility and the micro spherical morphology of polymethylsilsesquioxane (PMSQ) microspheres, BEM/PMSQ hybrid pour point depressant was prepared by melt blending method. Then, the effect of BEM/PMSQ hybrid pour point depressant on the pour point, viscoelasticity, viscosity and yield value of Qinghai waxy crude oil was evaluated by rheological experiment and the morphology of wax crystals was observed by the polarizing microscope. The results showed that the pour point of the undoped crude oil was 27.0℃; compared with the same dosage of the neat BEM (100 μg·g-1), BEM/PMSQ 2% hybrid pour point depressant has the best performance, which can further reduce the pour point of 6.0℃, the gelation point of 4.3℃, the apparent viscosity of 39.0% and G' of 62.0%. The dispersion state of PMSQ microspheres and BEM/PMSQ hybrid pour point depressant in the dodecane showed that BEM were adsorbed on the surface of PMSQ microspheres, and acted as the wax crystal nucleation templates in the crude oil, thus resulting in the formation of the compact wax crystal structure and coating with less liquid oil, so as to improve the rheology of crude oil.

    Rheological properties of flame retardent and antistatic polypropylene material
    WANG Shuai, WANG Kejian, MA Yi, ZHANG Yinling, LIANG Wenbin, WANG Xu, SHI Jiao, JIANG Zhuoyu
    2017, 68(8):  3023-3029.  doi:10.11949/j.issn.0438-1157.20170214
    Abstract ( 330 )   PDF (3973KB) ( 312 )  
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    The effects of brominated flame retardant and carbon black-filling on the extrusion distortion of PP melt and dynamic rheological properties were investigated by capillary rheometer and rotational rheometer. It was shown that the more filled resin exhibited higher critical shear rate for extrusion distortion corresponding to wider processing window in low filler content range. In dynamic rheometry, the higher filled resins behavior in shear thinning with higher complex viscosity,storage modulus and loss modulus instead of lower loss factor. Quantitative analyses were conducted using entanglement model and Cross model. Filler can absorb polymer chains to reduce wall adsorption dropping distortion and result in higher critical shear rate. Particle filled network increases in the plateau modulus and entanglement density shortening relaxation time for quicker recovering according to smaller extrusion swell ratio. Carbon black more than 3.5%(mass) in composite forms percolation network being characterized by higher zero shear viscosity and longer relaxation time where liquid-solid-like transition occurs. Simultaneously, the surface resistivity decreased obviously. The viscoelastic percolation value consistent with the electrical percolation value approximately.

    Pressure evolution and interface movement of slug flow during micro-channel modulation process
    CHEN Hongxia, HUANG Linbin, GONG Yifei
    2017, 68(8):  3030-3038.  doi:10.11949/j.issn.0438-1157.20170064
    Abstract ( 357 )   PDF (2073KB) ( 372 )  
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    Slug flow separation, a traditional process in biochemical and pharmaceutical industries, is a valid method to control two-phase flow patterns and enhance heat transfer. The fundamental to study evolution mechanism of two-phase flow patterns is to understand development rules of local parameters by numeric simulation of drainage on micro-channel walls and modulation process of slug flow. The VOF model coupling with dynamic grid adaption was chosen to precisely track gas liquid interface, to simulate movement of the interface at split, and to acquire hydrostatic and dynamic pressure evolution along axial direction and at wall. Results indicated that piston-like movement of bubbles at split was critical to slug flow separation in micro channels. Because of the presence of Laplacian pressure drop at the interface, pressure drop of slug flow was discontinuous with a periodic wavy variation following the interface piston-like movement. The overall pressure drop of slug flow was influenced by local pressure drop at liquid bridge region. Significant pressure drop near bubble head while minimal pressure drop near bubble tail where liquid flow rate was reduced. Such pressure drop characteristics of slug flow is distinguished from other two phase flows.

    Flow and thermodynamic properties of efficient gas wave refrigeration plant
    YU Yang, LIU Peiqi, WANG Yunlei, LENG Chuang, ZHAO Yiming, WANG Jingxian, HU Dapeng
    2017, 68(8):  3039-3048.  doi:10.11949/j.issn.0438-1157.20170267
    Abstract ( 378 )   PDF (3243KB) ( 429 )  
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    With the theory of aerodynamics, the efficient gas wave condensation graph was established. To optimize the gas wave condensation graph and estimate the internal structure parameters of the device, the two-dimensional periodic boundary model was adapted and the ideal gas as the medium was used to numerical simulate the flow and temperature field of the efficient gas wave condensation separator. The thermodynamic model of condensing system was established and its thermodynamic properties were analyzed. At the same time, the experimental platform was built, and the main parameters of the device were studied. The experimental results shows:by using the shock wave to recycle the pressure energy of the high pressure admission, the pressure energy of the drying gas can be highly recovered. By recycling the cooling capacity of the drying gas and pre-cooling the next high pressure admission circulation, the lower condensation temperature can be obtained. The refrigeration efficiency of this device exists the single-valued optimal point. The internal expansion efficiency of efficient gas wave condensation is about 63% and the maximum of the drying gas pressure can be recovered to 90%, which decreases with the increase of the pressure ratio.

    Assessing mixing uniformity of bubbles in direct-contact boiling heat transfer process
    XIAO Qingtai, HUANG Junwei, PAN Jianxin, LIU Yun, XU Jianxin, WANG Hua
    2017, 68(8):  3049-3055.  doi:10.11949/j.issn.0438-1157.20161643
    Abstract ( 349 )   PDF (1255KB) ( 769 )  
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    In order to assess the mixing performance of multiphase flow disturbed by bubble swarms in direct-contact boiling heat transfer process, a novel technique based on image processing technique and pixel discrepancy theory was proposed to test and measure the mixing uniformity of complex fluids. The gray scale matrix of bubbles RGB image was used to calculate discrepancy. The mixed state of gas-liquid in direct-contact heat transfer was characterized accurately and quantitatively. The values reflect the distribution status of bubbles swarm. Different mixing uniformity of multiphase flow systems have different mixing time. Pixel discrepancy time series were employed for normality test and chaotic detection. It is found that the data is approximate normal distribution and the whole mixing processes are chaotic. A simple method was used to solve a complicated problem that the quantification and characterization of bubbles behavior under the complicated condition. The alternative route brings new insights to study multiphase flow identification and can act as a guide to enhancing the chaotic behavior of systems.

    Simultaneous determination of CoO and MoO3 in catalyst impregnation solutions by flow injection spectrophotometry
    ZENG Mingguo, LI Yongsheng, ZHAO Yang, DU Xin
    2017, 68(8):  3056-3063.  doi:10.11949/j.issn.0438-1157.20170123
    Abstract ( 333 )   PDF (880KB) ( 350 )  
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    Based on flow-injection analysis (FIA) and reaction systems of Mo(Ⅵ)-ascorbic acid and Co(Ⅱ)-KSCN, a new FIA system was proposed for simultaneous determination of high-concentration CoO/MoO3 in impregnation solutions. It was found that reaction products of Co(Ⅱ) and KSCN were K2Co(SCN)4 and K4Co(SCN)6, which the latter can be used to quantitate Co(Ⅱ). Co(Ⅱ) inhibitory effect on reaction system of Mo(Ⅵ)-ascorbic acid interfered with the determination of Mo(Ⅵ). Such Co(Ⅱ) interference was resolved by adding cobalt nitrate in the chromogenic agent for Mo(Ⅵ) measurement. In addition, testing conditions were optimized for various factors such as constituents and concentrations in chromogenic reagents for determining Co(Ⅱ) or Mo(Ⅵ), sampling volume and reaction temperature. The chromogenic agents for testing Mo(Ⅵ) were consisted of 15% (mass) ascorbic acid, 10 g·L-1 cobalt nitrate (calculated by CoO) and 0.1 mol·L-1 sulfuric acid, whereas those for testing Co(Ⅱ) were consisted of 37.5% (mass) KSCN and 0.1 mol·L-1 NaAc-HAc (pH 5.8). The detection ranges of MoO3 and CoO were in 10-100 g·L-1 and 5-50 g·L-1, and the detection limits for MoO3 and CoO were 2.1 g·L-1 and 1.3 g·L-1, respectively. Relative standard deviation was less than 1.2% (n=11), recovery was in range 98%-104%, and the analysis rate was 20 samples per hour.

    Effect of Ag loading on soot oxidation for Ag/Ce0.75Zr0.25O2 catalysts
    DENG Xiangling, YE Songshou, CAO Zhikai, ZHANG Nuowei, ZHENG Jinbao, CHEN Binghui
    2017, 68(8):  3064-3070.  doi:10.11949/j.issn.0438-1157.20161683
    Abstract ( 466 )   PDF (1135KB) ( 581 )  
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    It is still important to develop soot oxidation catalysts with excellent activity under low temperature. Ag/Ce0.75Zr0.25O2 was synthesized via coprecipitation method for soot oxidation. Compared with the catalytic performance of Ce0.75Zr0.25O2, the introduction of Ag can lead to the decrease of soot-ignition temperature. Moreover, there is an optimal Ag loading. Subsequently, several methods such as XRD, in-situ XRD, BET, TPR were used to characterize the physicochemical properties of Ag-based catalysts. The results showed that the introduction of Ag resulted in decreasing the reduction temperature of surface oxygen species, being due to the interaction of Ag and Ce. The interaction also brings about the occurrence of Ag+ nature. And the feature is linked with the outstanding activity of soot oxidation for Ag-based catalyst. Furthermore, the Ag-based catalyst possessed fairly good stability in soot oxidation.

    Non-isothermal crystallization kinetics of dynamic ice slurry production by vacuum method
    LIU Xi, ZHUANG Kunyu, HUANG Cheng, LI Xuelai
    2017, 68(8):  3071-3081.  doi:10.11949/j.issn.0438-1157.20170336
    Abstract ( 335 )   PDF (820KB) ( 518 )  
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    Ice slurry treated with sodium chloride was produced by vacuum method. The feasibility of describing the crystallization behaviors of ice slurry based on the non-isothermal crystallization kinetic model, Jeziorny and Mo method, was theoretically proved. The relationships between the crystallization time and the ice packing fraction (IPF) were measured and the non-isothermal crystallization kinetic equations were developed. Experimental results indicated that the non-isothermal crystallization kinetics of ice slurry formation fit the Jeziorny and Mo model very well. The values of the Jeziorny exponent n were between 0.473 and 0.525, indicating that the crystallization mechanisms were almost the same for different experimental conditions and the growth pattern of ice crystals was flake thickening. The change trends of the crystallization kinetic parameters, Kc, the crystallization time, t0.25, and the cooling rate function, F(T), revealed that high cooling rate was beneficial to promote the formation of ice slurry and sodium chloride inhibited the growth of ice crystals.

    Preparation and performance evaluation of Ni2P/SiO2 catalysts for acetic acid hydrogenation to produce ethanol
    REN Jie, HU Wangwei, YUAN Haikuan, SHEN Lian
    2017, 68(8):  3082-3088.  doi:10.11949/j.issn.0438-1157.20170109
    Abstract ( 368 )   PDF (489KB) ( 556 )  
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    A series of silica supported transition metal phosphide catalysts were prepared through isovolumetric impregnation and heat treatment under N2 protection. Their catalytic performances were evaluated by ethanol yield and reaction kinetics of acetic acid hydrogenation. Results showed that both conversion of acetic acid and ethanol selectivity were gradually increased with reaction temperature increasing from 280℃ to 340℃. With P/Ni molar ratio for catalyst preparation was increased from 2:1 to 4:1, the obtained catalysts exhibited first increase and then decrease in activity and selectivity with optimal performance at P/Ni=3:1. The catalyst prepared by heat treatment at 250℃ had better catalytic performances than those at 200℃ and 300℃. The activity and ethanol selectivity of Ni2P/SiO2 catalysts were higher than that of Co2P/SiO2 catalysts. Catalysts using sodium hypophosphite as phosphorus supplement had better performance than those of potassium hypophosphite. Under temperature at 340℃, pressure at 2.0 MPa, molar ratio of hydrogen to acetic acid at 10:1, and WHSV at 0.4 h-1, acetic acid hydrogenation over Ni2P/SiO2 prepared in better conditions showed 100% conversion of acetic acid and 74.56% selectivity of ethanol. In addition, ethanol selectivity could be further improved by appropriate increase of reaction temperature.

    Mechanism of reactive adsorption desulfurization over NiO/ZnO-Al2O3-SiO2 adsorbents
    LI Kai, ZHAO Jigang, SHEN Benxian, LING Hao
    2017, 68(8):  3089-3099.  doi:10.11949/j.issn.0438-1157.20170097
    Abstract ( 491 )   PDF (1101KB) ( 423 )  
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    The reactive adsorption desulfurization (RADS) of a model gasoline was investigated over a NiO/ZnO-Al2O3-SiO2 adsorbent. N2 and H2 were used as carrier gases, and their desulfurization results were compared. Results showed that the adsorbent performed well when using N2 as the carrier gas. Carbon deposition on the surface is the main reason of the drop of desulfurization efficiency. This indicates that NiO could directly react with sulfur compounds in gasoline without the presence of H2. Results of XRD, H2-TPR, TOPT and XPS showed that NiO is hard to be reduced under conditions of RADS. RADS process mainly depends on the reaction of NiO and Ni to remove sulfur compounds. At last, a possible RADS mechanism was presented and discussed.

    Molecular simulation on separation of CO2/CH4 gas mixture in carbon membranes with defect pore structure
    HE Liu, ZHAO Haohan, LI Hua, ZHOU Zirui, WANG Tonghua, PAN Yanqiu
    2017, 68(8):  3100-3108.  doi:10.11949/j.issn.0438-1157.20161790
    Abstract ( 367 )   PDF (2321KB) ( 342 )  
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    Three kinds of defect micropore models, i.e., random defect, averaged defect and partial defect models, were established based on the defect-free zigzag pore model in carbon membrane. Adsorption and diffusion behaviors of equimolar CO2/CH4 gas mixture within pores of carbon membrane were investigated in an effort to discuss the influences of pore defect in carbon membranes on gas separation. Results showed that under the operating temperatures ranging from 273 to 348 K, both equilibrium adsorption capacities and diffusion coefficients of CO2 and CH4 in the defect pore models were smaller than those of the defect-free pore model. Total CO2/CH4 separation coefficient of the partial defect pore model was relatively low compared with the defect-free pore model and the other two defect pore models. When the temperature was less than 298 K, total separation coefficients of the random defect and averaged defect pore models were greater than the defect-free pore model, and the total separation coefficients of random defect pore model are beneficial to the averaged defect pore model. Random carbon atom deletion approach is more reasonable than average deletion and partial deletion. The results could provide a basis for the further study of gas permeation mechanism in carbon membranes.

    Adsorption characteristics of low concentration gaseous naphthalene on ordered mesoporous carbons
    MENG Miaomiao, LIU Yingshu, LI Ziyi, JIANG Lijun, YANG Xiong, LIU Wenhai
    2017, 68(8):  3109-3118.  doi:10.11949/j.issn.0438-1157.20170079
    Abstract ( 328 )   PDF (878KB) ( 486 )  
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    Three kinds of ordered mesoporous carbons (OMCs) were used to remove low concentration of polycyclic aromatic hydrocarbons (PAHs)-naphthalene (Nap), by dynamic adsorption experiments. The adsorption isotherms were fitted with isotherm models (Langmuir, Freundlich, and Sips) and kinetic model based on the assumption of constant concentration wave, respectively. The regeneration performance of the adsorbents were analyzed by means of mass loss curve based on the temperature programmed desorption analysis. The results indicated that the static adsorption behavior of Nap on OMCs can be well predicted by Langmuir and Sips isotherm models (R2 > 99%),and the adsorption capacity of CMK-5 (1.735 mol·kg-1) is better than that of CMK-3 and FDU-15. The constant-pattern wave propagation model was found to well fit the breakthrough curves. And the existence of mesoporous in the adsorbents facilitated the adsorption mass transfer. With transversal micropores, CMK-5 and FDU-15 showed better regenerabilities, and the desorption activation energy follows the order:CMK-3 > CMK-5 > FDU-15. Based on the analysis of absorption and desorption kinetics, CMK-5 shows better application potential in the three kinds of adsorbents.

    Adsorption and desorption of tungsten ions in water by morpholine chelate resin
    ZHU Qianqian, XIONG Chunhua, LI Jionghui, SHEN Chen, MA Zhigao, LI Zhuoli, LI Jiandan
    2017, 68(8):  3119-3125.  doi:10.11949/j.issn.0438-1157.20170163
    Abstract ( 346 )   PDF (1559KB) ( 352 )  
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    In this study, the adsorption and desorption properties of chelating resin for tungsten have been investigated, batch studies were carried out, and the FTIR, TGA, Zeta and SEM were characterized before and after adsorption. The results showed that the optimal adsorption condition was at pH 4.0, 308 K, the maximum saturated adsorption capacity of tungsten is 349.2 mg·g-1, with a high selectivity adsorption capacity. The adsorption kinetic and equilibrium data were fitted well with the pseudo-second-order model and the Langmuir isotherm model, respectively. Desorption studies revealed tungsten ion could be eluted effectively by using the 2%(mass) NaOH solution, the desorption efficiency was 100%. PS-MPL resin has the advantages of high selectivity, high adsorption, high elution rate and so on.

    Separation of vanillin from dilute aqueous solutions by pervaporation-crystallization coupling
    WANG Qian, ZHANG Xinru, WANG Yonghong, HOU Mengjie, ZHANG Tao, LI Long, LIU Chengcen
    2017, 68(8):  3126-3132.  doi:10.11949/j.issn.0438-1157.20161828
    Abstract ( 398 )   PDF (1412KB) ( 485 )  
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    The high performance poly(ether-block-amide) (PEBA2533) membrane was prepared by dry phase inversion method, and then used for separation of vanillin from dilute aqueous solutions in the pervaporation-crystallization coupling (PVCC) system. The structural morphology of PEBA2533 membranes were characterized by SEM. The effects of feed concentration and operating temperature on the pervaporation performances of membrane were investigated. The results showed that the swelling degree of PEBA2533 membrane increased with the increase of concentration. This indicated that PEBA2533 could preferentially adsorb vanillin. With the increase of the feed concentration, the flux of vanillin increased while the separation factor decreased slightly. The vanillin permeation flux and separation factor both increased as the operating temperature increased. The equation of Arrhenius indicated that vanillin was more sensitive to temperature than water. When the temperature of first condenser was controlled at 2℃ in the PVCC system, the flux of crystal vanillin in the first condenser was 39.52 g·m-2·h-1 and the purity was more than 99%.

    Influence of feedwater quality on nanofiltration membrane softening efficiencies for brackish water in long-term operation
    SONG Yuefei, ZHAO Guo, LI Tiemei, QIN Wenbo
    2017, 68(8):  3133-3140.  doi:10.11949/j.issn.0438-1157.20161721
    Abstract ( 410 )   PDF (3556KB) ( 635 )  
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    Laboratory-scale experiments were conducted with two different commercial types of the nanofiltration (NF) membranes (DL and DK) to soften one brackish water in the Huanghuai region of China. The influences of feed pH (3-10), feed total dissolved solids (1317-5926 mg·L-1) and total organic carbon (2.72-12.24 mg·L-1) on both selected NF membranes separating efficiencies were evaluated. The experimental results indicated that with the increase of feed pH, both DL and DK nanofiltration membrane specific fluxes firstly increased, then decreased, and finally slowly declined. But it decreased all the time with the increase of feed TOC and TDS. The divalent ions (Mg2+ and Ca2+) rejection rates for candidate NF membranes were on the rise during the testing scope. DL nanofiltration membrane was selected to continue to carry out the long-term stability test. When the operating time was running to 267 h, the membrane specific flux decreased by more than 10%, and chemical cleaning was adopted immediately. After chemical acid cleaning, the membrane specific flux recovery rate reached 85.05%; and after the coupling acid cleaning and alkali cleaning, the value is as high as 97.2%. Combined with scanning electron microscope and atomic force microscope characterization images, it was clearly showed that the chemical cleaning has good removal effect for membrane fouling.

    Application of modified elitist teaching-learning-based optimization algorithm to process optimization of methanol synthesis
    WANG Ying, ZHANG Lingbo, GU Xingsheng
    2017, 68(8):  3141-3151.  doi:10.11949/j.issn.0438-1157.20170146
    Abstract ( 314 )   PDF (934KB) ( 459 )  
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    Elitist teaching-learning-based optimization (ETLBO) algorithm is inspired by practical teaching-learning process. A novel group search optimizer, modified elitist teaching-learning-based optimization (mETLBO), was proposed to improve low precision and poor stability of the ETLBO. First, an autonomous learning process was introduced to strengthen local search of high quality solution so as to improve algorithm's elite-searching speed. Second, differentiated support and self-adaptive strategy providing appropriate and flexible learning approach to students at various levels, were applied to offer desirable assistance and balance searching rate and accuracy of the algorithm. Third, global searching ability of the algorithm was enhanced by increasing communication frequency between students. Optimization results on standardized functions show that the proposed algorithm is obviously superior to the original one in performance and efficiency. Finally, satisfactory results were achieved by applying the improved algorithm to process optimization with mechanism model of methanol synthesis.

    Component concentration optimization analysis of cooling process and control strategy in auto-cascade refrigeration system
    PAN Yaochi, LIU Jinping, XU Xiongwen, FU Zhiming
    2017, 68(8):  3152-3160.  doi:10.11949/j.issn.0438-1157.20161610
    Abstract ( 431 )   PDF (1566KB) ( 386 )  
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    The energy efficiency ratio of mixed refrigerant cryogenic system is low. For the sake of improving cryogenic performance and reducing energy consumption in the auto-cascade refrigeration system, genetic algorithm and Aspen Plus were adopted to optimize the ACR system in this paper. The optimal cycle mixed refrigerant compositions under different working condition were got. The simulation results showed that with the reduction of evaporation temperature, the demand of high boiling components reduced gradually. Based on the analysis result, an effective solution was proposed to control the working fluid composition and a corresponding experiment was done. The results showed that the control solution can increase temperature reducing rate of system and reduce the total power consumption of the compressor. Moreover, pressure of system was controlled.

    Biogeography-based learning particle swarm optimization method for solving dynamic optimization problems in chemical processes
    CHEN Xu, MEI Congli, XU Bin, DING Yuhan, LIU Guohai
    2017, 68(8):  3161-3167.  doi:10.11949/j.issn.0438-1157.20161786
    Abstract ( 287 )   PDF (378KB) ( 241 )  
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    Intelligent optimization algorithms have been playing an increasing role in dynamic optimization, due to advantages of wide applicability and strong global searching capability. Biogeography-based learning particle swarm optimization (BLPSO) was proposed for dynamic optimization problems (DOPs) by hybridizing biogeography-based and particle swarm optimization. BLPSO employed a new biogeography-based learning approach for construction of learning examples by ranking of particles (i.e., the quality of particles) and dimension as unit, such that learning efficiency was enhanced. Control vector parameterization first converted DOPs into nonlinear programming problems which were then solved by BLPSO. The simulation results on typical DOPs with non-differentiable, multi-modal and multi-variable characteristics show that BLPSO has outstanding solution precision and convergence speed.

    Disturbance modeling and feedforwad control of flue gas denitration in coking reverse process
    LI Yaning, WANG Xuelei, TAN Jie, LIU Chengbao, BAI Xiwei
    2017, 68(8):  3168-3176.  doi:10.11949/j.issn.0438-1157.20170216
    Abstract ( 426 )   PDF (942KB) ( 291 )  
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    A large amount of energy is wasted in integrated desulfurization and denitration device of coking flue gas during coking reverse process. In order to solve this problem in the unique coking reverse process, causes to NOx concentration change in the process were thoroughly analyzed. A modeling method for NOx concentration disturbance at inlet and outlet in the reverse process was proposed by data driven identification. Verification was performed from actual data measurement on two 55-hole and 6-meter top charging coke ovens and the relationship model of NOx concentration loss at inlet and outlet was obtained. A feedforward control system was designed for feedforward control rates of O3 under different NOx concentration settings. Simulation results provided cost savings of power consumption, which indicates necessity of the work.

    Variable weighted principal component analysis algorithm and its application in fault detection
    LAN Ting, TONG Chudong, SHI Xuhua
    2017, 68(8):  3177-3182.  doi:10.11949/j.issn.0438-1157.20170281
    Abstract ( 352 )   PDF (1723KB) ( 574 )  
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    Traditional principal component analysis (PCA) algorithm, targeting to explore correlations among measured variables in training dataset, has been intensively investigated and applied to data-driven fault detection. However, all variables are considered equally important in modeling process of traditional PCA-based methods, the difference between variable correlations cannot be comprehensively described. A variable weighted PCA (VWPCA) algorithm was proposed and applied to fault detection. Weight calculations were performed on the training dataset so correlation differences among measured variables were fully reflected in the processed data and a distributed PCA-based fault detection model was constructed. When implemented in online fault detection, the Bayesian inference was used to combine multiple monitoring results into an ensemble of probability indices. VWPCA approach assigned different weights to different variables according to the correlation difference, thus PCA modeling took correlation difference into account and the models could completely describe characteristics of the training dataset. Finally, superiority of the proposed VWPCA method was validated by well-known TE process.

    Multi-evidence fusion decision-making method for detecting abnormal data of batch processes
    LIU Weimin, WANG Jianlin, QIU Kepeng, YU Tao, ZHAO Liqiang
    2017, 68(8):  3183-3189.  doi:10.11949/j.issn.0438-1157.20170117
    Abstract ( 410 )   PDF (442KB) ( 267 )  
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    High-dimensional, non-linear, and non-Gaussian distributions of measured data in batch processes directly influence accuracy of detecting abnormal data. In order to integrate information of multi-source abnormal detection and increase detection accuracy, a method was proposed on the basis of multi-evidence fusion decision. With introduction of the Dempster-Shafer evidence theory, the main focal element was used to identify fake evidence and to recompute weight of evidences. The re-calculation on weight of evidences improved handling conflict evidences, reduced influence of conflict evidences on multi-evidence fusion decision, and enhanced detection accuracy of abnormal measured data. Furthermore, an abnormal detection model was constructed from multi-evidence fusion decision and was applied to decision-making of abnormal data detection in batch processes. The experimental results show that the proposed method can combine multi-evidence information and analyze conflict evidence effectively. Thus abnormal data detection for batch processes is achieved with low false and missing detection rates.

    Effect of phase change on performance of spiral groove liquid film seals
    CAO Hengchao, HAO Muming, LI Zhentao, YANG Wenjing, SUN Zhen, WANG Yanhong, REN Fujun
    2017, 68(8):  3190-3201.  doi:10.11949/j.issn.0438-1157.20170299
    Abstract ( 336 )   PDF (4395KB) ( 484 )  
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    In order to investigate phase change effect of liquid film on sealing performance of spiral groove liquid film seals, phase change model of non-contacting liquid film seals was established on the basis of mass conservation and mass source from Hertz equation. By discretization of governing equations with finite volume method, the effect of liquid film phase change on sealing performance was analyzed. Results show that phase change on sealing performance is closely related to sealing effectiveness. Both groove position and phase distribution in dynamic pressure groove have significant influence on sealing performance and pressure distribution at end face. During phase change in liquid film, seal opening force was increased but leakage was decreased for downstream pump seal, whereas the effect was different for upstream pumping seal. If the slot was close to inner diameter, seal opening force of upstream pumping seal was first increased and then decreased, but leakage was first decreased and then increased and finally decreased. If the slot was close to outer diameter, seal opening force of upstream pumping seal was increased linearly but leakage was first decreased and then increased. Phase transition occurred in groove region could strongly weaken hydrodynamic effects and largely impact on pressure distribution at the end face.

    Corrosion behavior of In625 alloy and 316L stainless steel in NaCl-CaCl2-MgCl2 ternary eutectic molten salt
    LIU Bo, WEI Xiaolan, WANG Weilong, SONG Ming, DING Jing
    2017, 68(8):  3202-3210.  doi:10.11949/j.issn.0438-1157.20170131
    Abstract ( 299 )   PDF (5926KB) ( 431 )  
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    Isothermal corrosion of 316L stainless steel and nickel based Inconel 625 alloy was evaluated by total immersion in eutectic NaCl-CaCl2-MgCl2 molten salt at 500-700℃.The effect of chromium (Cr), air contact, and temperature on corrosion was studied. Corrosion dynamic and velocity curves of 316L and Inconel 625 alloy at 600℃ molten salt for 21 d were obtained. X-Ray diffraction (XRD), scanning electron microscope (SEM) and X-ray energy spectrometer (EDX) were used to analyze corrosion products and cross section morphologies. The results show that mass loss of the steel and alloy increases with the increase of air contact and corrosion temperature. Element and morphology of metal surface and cross section after 21 d immersion at 600℃ indicate that Cr has a preferential solubility to other elements, which Cr depletion region was observed across cross-section. The dense layer of corrosion products can reduce corrosion rate. Inconel 625 exhibits better corrosion resistance than austenitic stainless steel in NaCl-CaCl2-MgCl2 eutectic molten salt.

    Density functional theory analysis on four pyrazine corrosion inhibitors and their adsorption behavior on Cu (111) surface
    SHI Xin, JIANG Yunying, WANG Hongbo, HAO Yilei, CHEN Shenghui, LI Chunling, SUN Shuangqing, HU Songqing
    2017, 68(8):  3211-3217.  doi:10.11949/j.issn.0438-1157.20170151
    Abstract ( 384 )   PDF (4192KB) ( 377 )  
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    In order to explore pyrazine inhibition mechanism on copper, adsorption properties of four corrosion inhibitors were studied comparatively. Quantum chemical calculations based on density functional theory (DFT) were used to study reactivity of inhibitor molecules and their adsorption on Cu (111) surface. The results showed that frontier orbitals of these four corrosion inhibitor molecules were all distributed on the pyrazine ring with hetero N atoms as reactive sites. All four molecules could perpendicularly chemisorb on Cu surface by forming covalent bonds through N atom. The order of adsorption energy from high to low was 2-aminopyrazine (AP) > 2-amino-5-bromopyrazine (ABP) > 2-methylpyrazine (MP) > pyrazine (PY). Furthermore, these inhibitor molecules can also physisorb on Cu surface by electrostatic interaction.

    Tolerance mechanism of Aspergilus niger C2J6 to cyclohexanone
    SU Xuelin, ZHANG Zihan, LIU Ya
    2017, 68(8):  3218-3224.  doi:10.11949/j.issn.0438-1157.20170277
    Abstract ( 316 )   PDF (3018KB) ( 190 )  
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    The mycelium growth and enzyme activity of Aspergillus niger C2J6 in organic solvent are related to cell tolerance in the solvent. In order to reveal the regulation and mechanism of organic solvent tolerance, fifteen kinds of organic solvents were used to investigate the organic solvent tolerance of Aspergillus niger C2J6. Then the tolerance mechanism for cyclohexanone, which is a less hydrophobic solvent, was studied in the cellular level. The results indicate that Aspergillus niger C2J6 can grow in a variety of organic solvents for enzyme production. Organic solvents whose lgP are between -0.24 and 3.0 will inhibit the cell growth and enzyme production to different degrees, whereas organic solvents whose lgP are greater than 3.0 will promote the growth and production. Under the stress of cyclohexanone, the cell membrane is damaged. The intracellular organelles shrunk. The hydrophobicity of cell surface decreased. Extracellular nucleotide concentration increased. The content of unsaturated fatty acid decreased while the content of saturated fatty acid increased. These phenomena illustrate that cellular tolerance to cyclohexanone is influenced in many aspects, and there are variety of tolerance mechanisms working together which help to reduce the toxicity of cyclohexanone on the cells, so as to improve the tolerance of the microbes.

    Numerical simulation on formation of SO3 during SNCR process in pulverized coal-fired boiler
    SHEN Wenfeng, XIANG Baixiang, ZHANG Hai, ZHANG Yang, LÜ Junfu
    2017, 68(8):  3225-3231.  doi:10.11949/j.issn.0438-1157.20170095
    Abstract ( 334 )   PDF (618KB) ( 355 )  
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    A numerical investigation on the formation of SO3 during selective non-catalytic reduction (SNCR) process and the influences of the concentrations of SO2, NO, O2, and H2O were performed using the plug flow reactor of the CHEMKIN-PRO software with a detailed chemical kinetic mechanism. The simulation results showed that the presence of NH3 changed the formation mechanism and reaction pathway of SO3 and noticeably enhanced the formation of SO3. When the reaction temperature decreased from 1373 K to 573 K within 1.9 s residence time with inlet NH3 concentration being 300 μl·L-1 and inlet SO2 concentration being 2000 μl·L-1, the formation concentration of SO3 was above 10 μl·L-1. The SO3 concentration decreased while SO3/SO2 conversion ratio slightly increased with increasing inlet concentration of SO2. Meanwhile, SO3 concentration increased with increasing inlet concentrations of O2 and NO, and decreased with increasing H2O inlet concentration in the flue gas. Based on the study, the formation of SO3 during SNCR process should be paid attention when high sulfur coal was burned.

    Thermal modeling of cylindrical lithium-ion battery module with micro-channel liquid cooling
    ZHAO Chunrong, CAO Wenjiong, DONG Ti, JIANG Fangming
    2017, 68(8):  3232-3241.  doi:10.11949/j.issn.0438-1157.20170278
    Abstract ( 542 )   PDF (1890KB) ( 747 )  
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    Considering the micro-channel liquid cooling thermal management system (TMS) of EV battery packs, a thermal model was established for a battery module consisting of 71 sections 18650 lithium-ion batteries. In this model, the thermal-lumped treatment was implemented for each single battery and the heat generation of a single battery was determined based on experimental measurements. In particular, heat conduction between neighboring batteries was considered. The battery module's thermal behavior, and investigated effects of the discharge C-rate, the liquid flow rate, the heat exchange area between neighboring batteries, and the interfacing area of the battery and the shell of micro-channel were numerically studied relying on the developed model. The simulated results corroborated the effectiveness of the micro-channel cooling system. It was found that:1) increasing the discharge C-rate led to higher temperature and worsened the temperature uniformity in the battery module; 2) increasing the liquid flow rate can significantly lower the maximum temperature and improve the temperature uniformity in the battery module; 3) increasing the exchange area between neighboring batteries slightly improved the temperature uniformity in the battery module, but only had limited effect at lowering the maximum temperature in the module; 4) increasing the interfacing area of the battery and the shell of micro-channel can significantly lower the maximum temperature in the battery module, but worsen the temperature uniformity in the module.

    Modeling and environmental applicability of solar solution grading collector/regenerator system with heat recovery
    PENG Donggen, LUO Danting, CHENG Xiaosong
    2017, 68(8):  3242-3249.  doi:10.11949/j.issn.0438-1157.20170033
    Abstract ( 389 )   PDF (644KB) ( 218 )  
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    To improve the collection and regeneration efficiency of strong solution under extreme conditions, this paper reveals a solar grading collector/regenerator method with inter-grade and same-grade heat exchangers. Based on heat and mass balance in the packed reservoir, a model of solar grading collector/regenerator system in which pre-dehumidification solution parameters could be adjusted is established. Numerical simulation shows that there are critical points in regeneration efficiency of grading regeneration under variety of outdoor situations compared with single-stage regeneration. Grading regeneration is preferable to single-stage regeneration while outdoor environmental temperature and relative humidity are above the critical points as well as sun radiation intensity is lower than the critical point. Finally, the applying ranges of grading collector/regenerator system on environmental parameters and solution concentration are comprehensively provided in this paper and it is found that the situations of lower radiation from sun and higher temperature and relatively humidity are beneficial to regenerate solution of high concentration by grading collector/regenerator system.

    Characteristics of NOx and SO2 emission from combustion of antibiotic mycelial residue with high water content in fluidized bed reactor
    GE Yaxin, ZHANG Guangyi, CUI Lijie, GAO Shiqiu
    2017, 68(8):  3250-3257.  doi:10.11949/j.issn.0438-1157.20170035
    Abstract ( 272 )   PDF (595KB) ( 356 )  
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    The characteristics of NOx and SO2 emission from combustion of antibiotic mycelial residue with high water content in a fluidized bed reactor were studied. The results showed that with the increase in excess air ratio, the NOx emission concentration increased while the SO2 emission concentration decreased. Enhancing the combustion temperature led to the increases in both the NOx and SO2 emission concentrations. With increasing fuel moisture content, both the NOx and SO2 emission concentrations first decreased and then increased. The air-staging combustion enabled good control of NOx emission. The NOx emission concentration was significantly lower with increasing the secondary air ratio. At the secondary air ratio 3/7, the air-staging combustion cut the NOx emission amount off by more than 50% compared to the traditional combustion. Desulfurization by adding CaCO3 into the furnace indicated that the SO2 emission concentration decreased with increasing molar ratio of calcium to sulfur (Ca/S), and when Ca/S 3, the SO2 emission concentration decreased to below 25 mg·m-3 and the sulfur removal efficiency surpassed 99%.

    Thermo-economic comparative analysis of different organic Rankine cycle system schemes for vehicle diesel engine waste heat recovery
    CHAI Junlin, TIAN Rui, YANG Fubin, ZHANG Hongguang
    2017, 68(8):  3258-3265.  doi:10.11949/j.issn.0438-1157.20170004
    Abstract ( 324 )   PDF (1307KB) ( 551 )  
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    In order to have a full recovery of the waste heat from a vehicle diesel engine, simple organic Rankine cycle (ORC) system and dual-loop organic Rankine cycle (ORC) system are compared and investigated. According to bench test results of a vehicle six-cylinder diesel engine, the thermodynamic models and economic models of both ORC systems are established, and the thermo-economic comparative analysis of both ORC systems are done on the basis of the study on waste heat characteristics under engine various operating conditions. The results show that, under engine entire operating conditions, net power output, augmentation proportion of power output and improvement of brake specific fuel consumption (BSFC) of the dual-loop ORC system are better than the simple ORC system, the maximum value are 24.38 kW、8.71% and 8.01% separately; Levelized Energy Cost (LEC) of the dual-loop ORC system is 0.8089 CNY·(kW·h)-1 and 19.26% lower than the simple ORC system.

    Controlling factors of excess sludge on adsorbing trace typical pharmaceuticals
    CAO Daqi, WANG Zhen, HAO Xiaodi, WANG Qunhui
    2017, 68(8):  3266-3274.  doi:10.11949/j.issn.0438-1157.20170137
    Abstract ( 356 )   PDF (705KB) ( 285 )  
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    Conventional biological systems in centralized wastewater treatment plants (WWTPs) are presently inefficient in the removal of pharmaceutical and personal care products (PPCPs), resulting in their ubiquitous presence in excess sludge by absorption. When the sludge is utilized in agricultural land, the absorbed PPCPs may be released and then water environment is contaminated. Therefore, it becomes a crucial issue to predict and assess the content of PPCPs in excess sludge, by revealing the controlling factors of PPCPs adsorption. The adsorption properties of three typical pharmaceuticals onto the sludge from a certain WWTP in Beijing, were investigated based on a trace concentration level using UPLC-MS-MS. The adsorption capacity of ciprofloxacin (CIP) and sulfamethoxazole (SMX) decreased, however, that of acetaminophen (ACP) increased with increasing pH; because the speciation of pharmaceuticals in aqueous solution and zeta potential of biosolid are as a function of pH. Extracellular polymeric substance (EPS) could enhance the adsorption of three typical pharmaceuticals onto the sludge, independent of pH; because the metal ions and organic substances contained in EPS determine the adsorption of pharmaceutical onto the sludge.

    Influence mechanism of magnesium lignosulfonates on enzymatic hydrolysis of different cellulose materials
    REN Jiwei, LIU Lei, QIAN Zijun, ZHANG Yitong, OUYANG Jia
    2017, 68(8):  3275-3281.  doi:10.11949/j.issn.0438-1157.20170170
    Abstract ( 397 )   PDF (643KB) ( 292 )  
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    In order to investigate the influence mechanism of magnesium lignosulfonates as assisted additives on enzymatic of cellulose hydrolysis, two kinds of magnesium lignosulfonates from different materials were selected to study the fabric differences and influences on enzymatic hydrolysis of different lignocellulose materials. It could be found that commercial magnesium lignosulfonate had higher sulfonation degree than homemade magnesium lignosulfonate, but ML had higher total hydroxy related content. Both commercial magnesium lignosulfonate and homemade magnesium lignosulfonate could enhance the enzymatic hydrolysis of Avicel. For enzymatic hydrolysis of lignocellulose material, two kinds of lignosulfonates showed inhibit influences on wheat straw pretreated by liquid hot water pretreatment. Only low concentration homemade magnesium lignosulfonate indicated the positive influence on wheat straw pretreated by magnesium bisulfite pretreatment. This study provided the theoretical references for explanation on influence mechanism of magnesium lignosulfonates on enzymatic hydrolysis.

    Enhancing reactivity of zerovalent iron toward U (Ⅵ) by weak magnetic field
    CAO Bei, LI Jinxiang, GUAN Xiaohong
    2017, 68(8):  3282-3290.  doi:10.11949/j.issn.0438-1157.20170196
    Abstract ( 404 )   PDF (2236KB) ( 641 )  
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    The influence of weak magnetic field (WMF) on the process of U(Ⅵ) removing by zero valent iron (ZVI) was explored and the main mechanism was investigated. The weak magnetic field could obviously promote the U(Ⅵ) sequestration under the condition of different initial pH (pHini). The first-order kinetic rate constants of U(Ⅵ) removal by ZVI with WMF at pH 3.0-7.0 were about 0.7 to 11.2 fold greater than those without WMF. The removal capacity of zero-valent iron toward U(Ⅵ) was 1.7 g·g-1 with WMF at initial pH 4.0 and Fe 0.5 g·L-1, being of 0.3-fold higher than that without WMF. The weak magnetic field could promote the corrosion of the zero-valent iron, thereby increasing its removal of U(Ⅵ), which could be verified by SEM,[Fe2+] and pH variation. The main mechanism of U(Ⅵ) removal by zero valent iron was adsorption together with reduction. The application of WMF did not change the mechanisms but accelerated its adsorption and reduction toward U(Ⅵ). As a chemical-, energy-free and environmental-friendly method, improving the reactivity of ZVI by WMF superimposition was novel and promising in the prospect of U(Ⅵ) sequestration from water.

    Effects of demineralization methods on structure and reactivity of Zhundong subbituminous coal
    ZHANG Wenda, WANG Pengxiang, SUN Shaozeng, ZHAO Yijun, ZHAO Hongxiang, YAN Taisen, WU Jiangquan
    2017, 68(8):  3291-3300.  doi:10.11949/j.issn.0438-1157.20161821
    Abstract ( 396 )   PDF (769KB) ( 575 )  
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    It is critical for clean and efficient utilization to study the effects of the demineralization process on the chemical structure and reactivity of coals. In the study, Zhundong raw coal was processed using HCl-HF-HCl and HF-HNO3-HCl methods. The structures of both the raw coal and demineralized-coal were characterized by FT-IR, and their reactivities were analyzed by using a micro fluidized bed multistage gas-solid reaction analyzer. The results show that acid treatment is able to reduce the ash content of coal to the level under 0.2%. The intensity of absorption peaks near OH and COOH in demineralized coal was significantly enhanced. The aliphatic side chains and the substituent on aromatic ring became shorter. A huge amount of silicon and aluminum minerals were removed by the HF treatment process. HNO3 can react with organic matter in coal which leads to further increase in the content of oxygen functional groups. The combustion reactivity of demineralized coal is significantly lower than the raw coal at 600℃ and 700℃, but as the temperature rises to 800℃ and 900℃, the difference of combustion reactivity between the two kinds of demineralized coal and the raw coal becomes smaller.

    Eelectrochemical behaviors of ZnO in choline chloride-urea deep eutectic solvents
    LEI Zhen, XU Cunying, HUA Yixin, LI Jian, LU Donghui, KUANG Wenhao, ZHANG Zhen, GAO Xiaobing
    2017, 68(8):  3301-3309.  doi:10.11949/j.issn.0438-1157.20170084
    Abstract ( 399 )   PDF (2878KB) ( 784 )  
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    The effect of ZnO concentration on the electrochemical behaviors of ChCl-urea-ZnO deep eutectic solvents (DES) system were examined with electric conductivity tests and cyclic voltammetry. The results of electric conductivity tests indicate that the conductivity of ChCl-urea-ZnO DES increases with an increase in ZnO concentration as ZnO concentration is below 0.24 mol·L-1. When ZnO concentration exceeds 0.24 mol·L-1, the conductivity of ChCl-urea-ZnO DES tends to be roughly constant. The conductivity of ChCl-urea-ZnO DES increases with the increasing of temperature. The relation between conductivity and temperature is consistent with Kohlraush empirical formula. The results of voltammetry tests indicate that the reduction of Zn(Ⅱ) is a quasi-reversible process, which is controlled by diffusion step. The diffusion coefficient of zinc ion is about 1.2×10-7 cm2·s-1. Furthermore, with an increase in ZnO concentration, deposition potential of Zn shifts positively and reduction peak current increases gradually, indicating that the higher concentration of ZnO is helpful to the electrodeposition of zinc. In addition, the electrodeposition of Zn-ChCl-urea DES containing different concentration of ZnO was performed at 2.2 V and 343 K. The surface morphology and phase structure of Zn deposits were characterized by X-ray diffraction (XRD) and scanning electron microscopic (SEM), respectively. ZnO concentration is found to play central role on the morphology of deposited Zn. Different shapes of Zn deposits including rod-like and square, can be electrodeposited from ChCl-urea DES by controlling the ZnO concentration.

    Overpressure transients and flame behaviors of gasoline-air mixture deflagration in confined space with local opening
    WANG Shimao, DU Yang, LI Guoqing, QI Sheng, WANG Bo, LI Yangchao
    2017, 68(8):  3310-3318.  doi:10.11949/j.issn.0438-1157.20161640
    Abstract ( 300 )   PDF (2495KB) ( 469 )  
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    Experiments on gasoline-air mixture deflagration in the confined space with a local opening was carried out. Overpressure transients and flame behaviors under different concentration were acquired and the results showed that:there were two overpressure peaks inside the vessel but only one outside the vessel, and negative pressure zone was formed near the opening. The maximum value of internal and external overpressure were the same and both of them were caused by external deflagration. The value of overpressure peak showed the trend of first increasing and then decreasing with the increase of concentration, and the concentration corresponding to maximum overpressure peaks was 1.88%. The process of flame propagation could be divided into three stages, and the flame shape, color, duration of each stage, diameter of external fireball and average flame speed were dominated by initial concentration. With the increase of the concentration, the blue laminar flame with smooth front was changed into bright yellow flame with wrinkled front, and the duration of laminar propagating stage as well as accelerating and distorting stage showed the same trend of first increasing and then decreasing, but the duration of extinguishing stage showed a decreasing trend. The relationship between the diameter of fireball and concentration could be fitted by cubic polynomial, and the flame speed of 1st and 2nd stage could be fitted by quadratic polynomial. With the increase of opening ratio, the pressure peaks and flame speed of 2nd stage showed a decreasing trend, and the diameter of fireball showed a first increasing and then decreasing trend.