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Table of Content
05 October 2016, Volume 67 Issue 10
    CIESC Journal(HUAGONG XUEBAO)Vol.67 No.10 July 2016
    2016, 67(10):  0-0. 
    Abstract ( 134 )   PDF (21860KB) ( 219 )  
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    Progress of research and application of P-graph theory in process network synthesis
    XIAO Wu, ZHANG Yi, LÜ Junfeng, LI Zhonghua, HE Gaohong
    2016, 67(10):  4029-4039.  doi:10.11949/j.issn.0438-1157.20160154
    Abstract ( 316 )   PDF (732KB) ( 257 )  
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    With upsizing, complexifying and unifying in modern petro-chemical systems, the combined complexity among streams of mass, energy and information as well as among unit operations keeps increasing exponentially. P-graph theory has found widespread applications by generation of rigorous superstructures as a result of axiom constraints which may reduce creation of redundant structures. This review on P-graph theory began with the mathematical definition, fundamental axioms, solution algorithms and workflow, and a case study to show the modeling framework and graphic representation. A literature study of past 20 years' publications systemically summarized application of P-graph theory in traditional process system engineering of separation network synthesis, reaction path synthesis and heat exchange synthesis, and recent expansion in new areas of process technology selection, supply chain and process optimization. The advantages and disadvantages of P-graph theory and mathematical programming were compared, and improving ideas were proposed to solve nonlinear problems with P-graph theory. The prospective research and application of P-graph theory were forecasted, including multi-objective optimization in consideration of economic and environmental factors,effective solution of large complex nonlinear programming problems by the combination of both P-graph and mathematical programming, and other potential applications.

    Structure, morphology and function of Anammox granular sludge
    KANG Da, ZHENG Ping, HU Qianyi
    2016, 67(10):  4040-4046.  doi:10.11949/j.issn.0438-1157.20160277
    Abstract ( 311 )   PDF (5568KB) ( 298 )  
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    Anammox process is a new biotechnology for nitrogen removal from wastewater. It has become one of the research hotspots and has been put into wide used in wastewater treatment engineering. Anammox reactor based on granular sludge bed is a high-rate bioreactor. The biophase in the form of granular sludge is the key factor that determines the reactor performance. It can be divided into three structures from macroscale to microscale:sludge bed, granular sludge and bacterial cell. The morphological and functional characteristics of three structures and their relation with reactor performance are reviewed so as to give guidance for online optimization and process control.

    Effect on self-pressurization characteristics and mass loss of thermodynamic vent system for refrigerant R141b by heat load
    CHEN Zhongcan, HUANG Yonghua, WANG Bin, LI Peng, SUN Peijie, WANG Tianxiang, CUI Jiaxun
    2016, 67(10):  4047-4054.  doi:10.11949/j.issn.0438-1157.20160613
    Abstract ( 240 )   PDF (1254KB) ( 218 )  
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    In order to study the fundamental problems involved in the storage of cryogens in space, the experimental investigation of tank pressure control was carried out on a simulator of thermodynamic vent system (TVS), which works at room temperature with refrigerant R141b as working fluid. The pressure control characteristics were obtained at heat load of 120, 160 and 200 W. The test results showed that the self-pressurization rate were 6.43, 12.92 and 18.05 kPa·h-1 respectively at those three different heat load. Mass loss as a result of tank pressure control was compared between TVS method and direct gas vent method. Taking the heat load of 120 W as an example, the mass loss can be reduced by 79.3%. Assuming the mixture vented directly at zero-gravity containing 40% liquid, the TVS method can reduce the mass loss even by up to 84.7%. It was proved that the TVS method cannot only control the tank pressure but also significantly reduce the loss of the storage fluid.

    Measurement using laser induced fluorescence technique for interfacial convection during water-CO2 absorption process
    LI Luxing, HU Nan, YUAN Xigang
    2016, 67(10):  4055-4063.  doi:10.11949/j.issn.0438-1157.20160455
    Abstract ( 243 )   PDF (5589KB) ( 455 )  
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    An experimental apparatus based on laser induced fluorescence (LIF) technique for measuring interfacial Rayleigh convection in process of water-CO2 absorption was established. By fluorescein sodium and a calibration process, the correlation between the fluorescent light intensity and the concentration of CO2 in water was obtained, and thus an LIF method of quantitative measurement of CO2 concentration in water was established. By established installation and method, the concentration distribution evolution for the Rayleigh convection developed near the surface of water in the water-CO2 absorption process was investigated. Validation of the measurement results was made by checking with the critical value of Rayleigh number reported in literature. The experimental results were also used to analyze the transition mass transfer regime from molecular diffusion to convective diffusion, and the enhancement effect of the interfacial Rayleigh convection on the mass transfer process.

    Surface heat transfer characteristics during transient cryogen spray cooling
    TIAN Jiameng, CHEN Bin, LI Dong, ZHOU Zhifu
    2016, 67(10):  4064-4071.  doi:10.11949/j.issn.0438-1157.20160509
    Abstract ( 370 )   PDF (594KB) ( 322 )  
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    Spray cooling is widely used in industry. Complicated surface heat transfer characteristics are needed to reveal the mechanism. In this work, the surface heat transfer experiments of cryogen spray cooling (CSC) with R134a, R407C and R404A were conducted. The spray Biot number was defined to represent the ratio between the internal thermal resistance of substrate and the resistance of surface convective heat transfer. Dimensionless Reynolds number Rel and Fourier number Fol were proposed to represent the maximum heat flux and the corresponding time, respectively. By coupling Jakob number with Rel number and droplet Weber number (We), dimensionless correlations of maximum heat flux and the corresponding time were constructed. The similarity of the transient spray cooling process with different cryogens was found and the dimensionless correlation of time-dependent heat flux was obtained. By using these correlations, the simulated transient surface temperature during cryogen spray cooling agreed well with the experiment data, which proved the accuracy of the correlations.

    Fouling characteristics of magnesia nanoparticles on rectangular wing vortex generator with hole punched at waist groove
    XU Zhiming, XIONG Qian, GENG Xiaoya, WANG Jingtao, HAN Zhimin
    2016, 67(10):  4072-4079.  doi:10.11949/j.issn.0438-1157.20160485
    Abstract ( 221 )   PDF (7200KB) ( 303 )  
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    In order to explore fouling mechanism of nanoparticles in hole-punched vortex generator, magnesia nanoparticles were used experimentally in rectangular wing vortex generator with hole-punched at waist groove, which factors of inlet temperature, concentration, flow velocity, longitudinal space and attacking angle of vortex generator were studied. The experimental results showed good anti-fouling performance of the waist-groove-punched rectangular wing vortex generator and its significant dependence on operating conditions. High flow velocity, low magnesia particle concentration, low inlet temperature and short longitudinal space could enhance anti-fouling capability. The best anti-fouling was at the attacking angle of 60°.

    Model for calculating water bridge volume retained between vertical fins
    ZHUANG Dawei, YANG Yifei, HU Haitao, DING Guoliang
    2016, 67(10):  4080-4085.  doi:10.11949/j.issn.0438-1157.20160411
    Abstract ( 226 )   PDF (1749KB) ( 301 )  
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    When a fin-and-tube heat exchanger worked as dehumidifier, lots of water bridges would form between vertical fins and the water volume of these bridges could affect discharge of water condensate. A model for the calculation of water bridge volume was established by integration of meniscus curve along triple contact line of the water bridge. An ellipse equation was used to simulate the triple contact line while a model of meniscus curve at the water-air interface was obtained from calculation results of the Young-Laplace equation. The model for calculating water bridge volume was validated by experimental study on triple contact lines and meniscus curves. The model predicted water volumes of these bridges 95% times aligned with the experimental data within the deviation limit of ±15%, which had a mean deviation of 7.12%.

    Operation parameters optimization of spacecraft thermal cycling test system based on temperature uniformity and entropy generation
    HUANG Yiye, YANG Guang, WU Jingyi
    2016, 67(10):  4086-4094.  doi:10.11949/j.issn.0438-1157.20160429
    Abstract ( 176 )   PDF (1014KB) ( 237 )  
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    The temperature uniformity and entropy generation due to heat transfer inside a thermal cycling test chamber are investigated numerically under various operating parameters. Boussinesq approximation and k-ω model are used in the simulation and the result is validated by previous experiment. The result shows that in the range of 4.3×103Re ≤ 8.6×105 and 4.62×1013Gr ≤ 1.38×1014, both forced convection and natural convection contribute to the fluid flow and heat transfer. Fluid close to the walls gets heated and rises along the walls due to the buoyancy force while that near the center line accelerates downward to the exit. The temperature at the given height always increases from the center line to the walls. From the top to bottom of the cycling chamber, the temperature increases around the center line while decreases near the walls. The dimensionless standard temperature deviation increases with Reynolds number and changes little with Grashof number. During the mixed convection, the entropy generation due to fluid friction is much smaller than that by heat transfer, and the latter increases with both Reynolds number and Grashof number. In addition, the expressions of wall Nusselt number, dimensionless average temperature, dimensionless temperature standard deviation and dimensionless entropy generation by heat transfer are also provided.

    Experimental study and numerical simulation on shell side fluid heat transfer in submerged combustion vaporizer
    HAN Changliang, REN Jingjie, DONG Wenping, ZHANG Kang, BI Mingshu
    2016, 67(10):  4095-4103.  doi:10.11949/j.issn.0438-1157.20160350
    Abstract ( 315 )   PDF (1675KB) ( 263 )  
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    Submerged combustion vaporizer (SCV) is frequently applied for peaking systems of LNG receiving terminals, which both liquid flow and heat transfer characteristics of water bath on shell side of a vaporizer are key factors to determine whether the SCV could achieve high heat transfer efficiency. Influences of initial water level, volumetric flow rate and inlet temperature of flue gas on heat transfer coefficient of the water bath were investigated by visualization experiments and numerical simulation. The water bath absorbed sensible heat of the flue gas and latent heat of the steam condensation so that the temperature of outlet flue gas almost equaled to the equilibrium temperature of the water bath. Under the inductive impact of a great deal of heat transfer-generated bubbles, cycling water flows, which were formed by weir overflow in the water bath, could effectively collide tubular wall, decrease thickness of boundary layer and enhance heat transfer. The initial water level in combination with volumetric flow rate of flue gas largely affected overflow in water bath so the water bath heat transfer coefficient increased dramatically upon the occurrence of overflow. The ratio of fuel and air flow rates mainly affected inlet temperature of flue gas and the turbulent kinetic energy of water bath. In the case of smaller turbulent kinetic energy, the water bath heat transfer coefficient deceased although the inlet temperature of flue gas increased. This study can provide some scientific guidance to the design of SCV.

    Experiment and simulation analysis of special-shaped overall heat pipe radiator
    DONG Liang, XU Weiqiang, LI Qianqian
    2016, 67(10):  4104-4110.  doi:10.11949/j.issn.0438-1157.20160483
    Abstract ( 248 )   PDF (5540KB) ( 240 )  
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    A new structured heat pipe radiator was designed with integration of the evaporator of flat heat pipes and the condenser of finned cupper cylinders, in order to meet the new requirements of heat dissipation and uniform temperature of electrical and electronic equipment. Heat transfer experiments and simulation analysis were performed to study temperature distribution across the heat pipe under various conditions, factors influencing performance and heat transfer capacity. Results showed good temperature control across the heat pipe with difference in the range of 1.75℃. Heating power and convection heat dissipation had influence on starting performance, overall thermal resistance, equivalent thermal conductivity and heat transfer coefficient. With the increase of heating power and convection rate, both start-up time and thermal resistance were decreased whereas equivalent coefficient of thermal conductivity and coefficient of heat transfer were increased. The minimum thermal resistance and the optimal equivalent thermal conductivity of the heat pipe were 0.189℃·W-1 and 20964 W·m-1·K-1, respectively. Compared to traditional heat pipe of same dimensions, the new design had a reduction in thermal resistance by 37% and an increase in heat transfer coefficient by 15%.

    Effect of cold source temperature on power generation of small organic Rankine cycle system with low-grade waste heat
    XIE Feibo, ZHU Tong, GAO Naiping
    2016, 67(10):  4111-4117.  doi:10.11949/j.issn.0438-1157.20160631
    Abstract ( 233 )   PDF (4509KB) ( 297 )  
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    For a thermal power system, cold source temperature fluctuates throughout a year in many areas due to the change of ambient temperature. Therefore, off-design operation of an organic Rankine cycle (ORC) system is often unavoidable. The effect of cooling water temperature on ORC performance was studied by using R123 working fluid to generate power from low-grade waste heat. When the inlet temperature of cooling water in the condenser was increased but the hot source temperature was kept constantly, the condensation pressure was increased and the evaporation pressure was increased slightly, whereas the heat load of evaporator and condenser as well as the pressure difference and ratio between the inlet and outlet of scroll expander was decreased. Hence, the electric power output and thermal efficiency of the system were decreased. In the range of study that the cooling water temperature increased from 21.82℃ to 42.10℃, the electric power output declined from 2.357 kW to 1.535 kW, thermal efficiency declined from 7.25% to 5.76%, and the electric power output and thermal efficiency linearly decreased by 34.87% and 23.86%, respectively. Under these operating conditions, the electric power output decreased by 0.0411 kW and 1.74% at every 1℃ increase of cooling water temperature. Therefore, cold source temperature significantly affected the performance of an ORC system with low-grade waste heat, which could serve as important reference for designing cold source system and optimizing ORC system performance with consideration of local weather conditions.

    Frictional and local pressure drops in waste heat recovery boiler of split shell-tube structure
    SHAO Huaishuang, MA Haidong, CHEN Jie, SHI Mingwei, HU Tao, ZHAO Qinxin
    2016, 67(10):  4118-4125.  doi:10.11949/j.issn.0438-1157.20151891
    Abstract ( 276 )   PDF (7549KB) ( 143 )  
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    The calculation of frictional and local pressure drops inside lower shell tubes upon a vapor-liquid two-phase flow running through horizontal tube bundles was studied on a visualizable experimental platform of split shell-tube waste heat recovery boiler. PIV flow velocity measurement technique was combined with traditional differential pressure method to measure cross-sectional vapor fraction in vertical upward tubes. A new method for calculating cross-sectional vapor fraction was proposed according to the bubble flow pattern. A new bubble-slug flow pattern was defined with vapor mass fraction x=10-4 as the boundary condition to distinguish bubble flow and bubble-slug flow in vertical upward tubes. Based on the similarity of their occurrences under a circumstance of a vapor-liquid two-phase flow running through horizontal tube bundles, both frictional and local pressure drops were analyzed integrally. A new correlation equation to calculate frictional and local pressure drops was obtained after processed experimental data by the Chisholm method and studied calculation of frictional and local pressure drops. Validation of the correlation equation with experimental data showed an error within ±20%, indicating that the equation could meet the needs of engineering calculation.

    Drag reduction of superhydrophobic microchannels based on parabolic gas-liquid interfaces
    LI Chunxi, ZHANG Shuo, XUE Quanxi, YE Xuemin
    2016, 67(10):  4126-4134.  doi:10.11949/j.issn.0438-1157.20160629
    Abstract ( 219 )   PDF (1280KB) ( 288 )  
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    Based on the model of volume of fluid, two-dimensional fluid laminar flow in superhydrophobic microchannels was numerically simulated with given parabolic gas-liquid interfaces. The effects of several flow and structural parameters on fRe, the normalized slip length and pressure drop were investigated. The results show that superhydrophobic microchannels with rectangular microcavities exhibited significant drag reduction in a way that fRe increased slightly with increase of Reynolds number whereas normalized pressure drop decreased slightly with increase of inlet velocity. When the area ratio of microcavities was increased or the microchannel diameter was decreased, fRe was reduced but normalized pressure drop was enhanced. In case of small microchannel diameter, the area ratio of microcavities significantly affected fRe. With increase of the parabolic height, the ratio of normalized pressure drop and the normalized slip length decreased linearly, however fRe increased linearly. The impact of microcavities on the normalized slip length and the ratio of normalized pressure drop was minimal provided that the microcavity depth was greater than 40% of its width. The dovetail microcavities exhibited the greatest effect on drag reduction, followed by the rectangular, trapezoidal, triangular microcavities in the order of high to low.

    Vortex formation characteristics of flow liquid film on corrugated plate
    LIU Mei, LIU Qiusheng, WU Zhengren, WANG Songling, SONG Zhaoxia
    2016, 67(10):  4135-4145.  doi:10.11949/j.issn.0438-1157.20160571
    Abstract ( 237 )   PDF (2878KB) ( 240 )  
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    The liquid film flow on the corrugated plate is common in the industrial field. But the characteristics of liquid film flow on the corrugated plate are pretty complicated. Thus, based on the VOF method, the vortex characteristics of the three-dimensional liquid film flow on the inclined corrugated plate are simulated by using FLUENT software. The evolution of vortex structure with time is studied, and the influence of inlet Reynolds number, waviness, wall inclined angle, fluid viscosity and surface tension on the vortex structure in corrugated plate structure is investigated. The results show that the size and shape of vortex are constantly changing with the time evolution and ultimately achieve stability. The change of vortex structure has significant influence on the fluctuation of free surface. With smaller Re and waviness, the vortex is not easy to form in the corrugated structure. With the increase of Re and waviness, the vortex is produced and its size is increasing, and the morphology of the vortex is changed. Meanwhile, the position of the free surface is increased and there is a phase lag compared with the wave wall. When the wall inclination angle is altered, the vortex characteristics in the corrugated structure change greatly. But the phase of the free surface and the thickness of the liquid film vary slightly. Surface tension has a significant effect on the vortex structure, and it cannot be ignored in the numerical simulation of liquid film flow. Nevertheless, when the fluid viscosity is changed, there is no significant change in the size and shape of the vortex in the corrugated structure. But if the viscosity is small and the surface tension is neglected, the thickness of the liquid film becomes thin. These conclusions are very important to predict and understand the characteristics of liquid film flow in industrial field.

    Factors influencing energy recycle performance of pump-driven heat pipe loop device
    DUAN Wei, MA Guoyuan, ZHOU Feng
    2016, 67(10):  4146-4152.  doi:10.11949/j.issn.0438-1157.20160058
    Abstract ( 265 )   PDF (504KB) ( 272 )  
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    A pump-driven heat pipe loop device was proposed for recycling energy from exhaust air and reducing energy consumption of processing fresh air in air-conditioning systems of public buildings. An experimental setup was built to investigate performances of such device under summer and winter working conditions. Through the study on effect of mass flow rate, heat exchange area and headwind velocity to heat transfer rate, temperature efficiency and coefficient of performance (COP), the optimum mass flow rate, heat exchange area and headwind velocity were obtained. Under summer working condition, the device had achieved the heat transfer rate of 4.09 kW and the COP of 9.26 at the mass flow rate of 250 kg·h-1, the heat exchange area of 58.0 m2 and the headwind velocity of 1.8 m·s-1. Under winter working condition, the device had achieved the heat transfer rate of 6.63 kW and the COP of 14.20 at the mass flow rate of 300 kg·h-1, the heat exchange area of 58.0 m2 and the headwind velocity of 1.8 m·s-1.

    Role and influence of characteristic Jakob number in high-temperature and high-pressure flash evaporation process
    JI Can, WANG Naihua, CUI Zheng, CHENG Lin
    2016, 67(10):  4153-4159.  doi:10.11949/j.issn.0438-1157.20160545
    Abstract ( 411 )   PDF (561KB) ( 308 )  
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    The dimensionless Jakob number (Ja) as a ratio of sensible heat to latent heat of vaporization in a phase change process was chosen as the characteristic parameter for flash evaporation process. The evolution of flash efficiency versus Ja was studied on a newly-designed experimental system for high-temperature and high-pressure spray flash evaporation under different operating conditions. The experimental results showed that flash efficiency was higher and flash evaporation was more violent at larger Ja. The flash efficiency increased with the increase of initial liquid temperature but decreased with the increase of evaporation pressure, which was closely related to the physical meaning of Ja. Based on the fact that both flash efficiency and Ja were increasing functions of the degree of superheat, a combination of high initial temperature and evaporation pressure was beneficial for flash evaporation under the same degree of superheat. An empirical equation between flash efficiency and Ja was developed from the experimental data. The findings were considered universal in the field of flash evaporations at high-temperature and high-pressure and thus could be a useful reference for industrial application.

    Experiments and simulation of a single droplet impacting on cold surfaces
    XU Qing, WANG Jin, LI Miaomiao, LI Zhanyong
    2016, 67(10):  4160-4168.  doi:10.11949/j.issn.0438-1157.20160158
    Abstract ( 318 )   PDF (8029KB) ( 269 )  
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    The impact spread and solidification of single distilled water droplet of 3.2 mm in diameter at 293 K on a cold plate with temperature below 273 K was studied by both experiment and simulation. The impact heights (100, 250, 500 mm), cold plate temperatures (253, 268 K), and cold plate inclined angles (0°, 30° and 60°) were assessed for effects on the spreading and solidifying process. The impact process of a pullulan solution droplet at a height of 100 mm on a cold plate at 253 K was simulated and compared to that of a distilled water droplet. The results showed that both impact height and horizontal cold plate temperature played an important role in the droplet spreading process whereas inclined angle of cold plate affected freezing deposition of the droplet. Droplet viscosity affected spreading rate and diameter of freezing deposition. Temperature was not a determinant factor for highly viscose materials. A good alignment between simulation and experimental results indicated that temperature change of the droplet in spreading and freezing process would help to directly explain droplet solidification.

    Characteristics of thermal conductivity and thermal diffusivity of carbon dioxide hydrate
    WAN Lihua, LIANG Deqing, LI Dongliang, GUAN Jin'an
    2016, 67(10):  4169-4175.  doi:10.11949/j.issn.0438-1157.20160384
    Abstract ( 335 )   PDF (544KB) ( 383 )  
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    Thermal conductivity and thermal diffusivity are two key basic factors of thermal property data that determine gas hydrate resource extraction. In this study, carbon dioxide hydrate sample was formed from a supersaturated carbon dioxide gas solution and layer by layer formed with the equal thickness in the reactor cell lined with fluorine plastics. The thermal conductivity and thermal diffusivity of carbon dioxide hydrate were in-situ measured by means of transient plane source technique. The measurements were performed at 264.68-282.04 K and 1.5-3 MPa. The measurements were also performed during self-preservation effect process at 268.05 K and 0.6 MPa. The characteristics of thermal conductivity and thermal diffusivity of carbon dioxide hydrate were obtained on crystalline state and during self-preservation effect process. The results of this paper can provide basic data and theoretical basis for the development and utilization of natural gas hydrate resources.

    Synthesis of mesoporous titanosilicates from industrial by-product hexafluosilicic acid and application for catalytic cyclohexene epoxidation
    JIN Fang, LIU Tieliang, WANG Xianqiao, WU Yuanxin
    2016, 67(10):  4176-4186.  doi:10.11949/j.issn.0438-1157.20160187
    Abstract ( 200 )   PDF (3539KB) ( 253 )  
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    The hexafluosilicic acid, a by-product in phosphate fertilizer industry, was used as the raw material for hydrothermal synthesis of mesoporous titanosilicates with cetyltrimethylammonium bromide (CTAB) as the cationic surfactant and ammonia as neutralization agent. The influence of synthesis conditions including hydrothermal time, the ratio of CTAB to silica, Si/Ti ratio, and surfactant removal methods on the structures and properties of mesoporous titanosilicates were investigated by characterization of the resulting product with techniques of X-ray diffraction (XRD), nitrogen adsorption/desorption, scanning electron microscopy (SEM), solid UV light scattering. At the optimized synthesis condition of the ratio of SiO2:CTAB:Ti(OC4H9)4:NH3:H2O=1:1.50:0.03:10:150 and the hydrothermal time of 5 h, mesoporous titanosilicate had specific surface area of 1116 m2·g-1 and porosity of 0.79 cm3·g-1. When used as catalyst for cyclohexene epoxidation. this mesoporous titanosilicate showed good catalytic activities with cyclohexene conversion of 68.10%, cyclohexene epoxide selectivity of 96.60%, and turnover frequencies of Ti active sites of 99.5 h-1. This new synthesis technique will greatly improve profit of phosphate fertilizer industry by utilizing the by-product hexafluosilicic acid for the production of value-added mesoporous titanosilicate.

    Coupling reaction of dimethyl succinate and ethylene carbonate using organotin catalyst
    TANG Wenqiang, LIU Shaoying, BAI Yuansheng, YAO Jie, ZHANG Hua, WANG Gongying
    2016, 67(10):  4187-4195.  doi:10.11949/j.issn.0438-1157.20160297
    Abstract ( 218 )   PDF (588KB) ( 125 )  
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    A simple and ecient route for simultaneously synthesis of poly(ethylene succinate) (PES) and dimethyl carbonate (DMC) from ethylene carbonate (EC) and dimethyl succinate (DMSu) has been demonstrated in the presence of organotin catalyst. The effect of reaction parameters such as catalyst dosage, n(EC)/n(DMSu), reaction time, etc, on synthesis of PES and DMC was investigated. A reaction mechanism has been discussed with organotin catalyst. The results showed that Bu2SnO exhibited higher activity when the reaction time, catalyst dosage, n(EC)/n(DMSu), reaction temperature were 4 h, 0.75%(mol), 1 and 230℃, respectively in the standard atmosphere pre-polymerization step, and reaction pressure and reaction temperature were ≤ 400 Pa and 210℃, respectively in the vacuum condensation step. The DMC yield was up to 70.08% and the intrinsic viscosity of PES was up to 0.622 dl·g-1.

    Hydrolysis-etching preparation of CuMnO2 nanoplate array films and their catalytic performance for oxidation of aqueous methylene blue
    ZHU Qian, LI Errui, ZHOU Chen, XU Yishu, ZHANG Yingmeng, WANG Kai, YANG Zeheng, ZHANG Weixin
    2016, 67(10):  4196-4202.  doi:10.11949/j.issn.0438-1157.20160470
    Abstract ( 202 )   PDF (1128KB) ( 234 )  
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    CuMnO2 nanoplate arrays on copper foil were successfully synthesized through hydrolysis-etching CuO nanosheet arrays in manganese chloride aqueous solution under hydrothermal conditions. The CuMnO2 nanoplate array films exhibited excellent catalytic performance for oxidation degradation of methylene blue (MB) dye aqueous solution in the presence of H2O2 due to the synergistic effect of catalytic active Cu(Ⅰ) and Mn(Ⅲ). Results of scale-up experiments showed that the CuMnO2 nanoplate array film catalysts possessed superior stability in catalytic activity. Moreover, the CuMnO2 nanoplate array catalysts on substrates may avoid problems associated with powder catalysts, such as agglomeration, difficulty in separation and possibly secondary pollution, and thus demonstrate great potential in dye wastewater treatment.

    Process of two-stage absorption column to strengthen water scrubbing technology to purify biogas
    DING Jian, REN Jiajia, LI Zheng, YANG Zhuhong, LU Xiaohua
    2016, 67(10):  4203-4210.  doi:10.11949/j.issn.0438-1157.20160608
    Abstract ( 269 )   PDF (618KB) ( 221 )  
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    Pressure water scrubbing technology has become one of the key technologies of biogas purification. This paper adopted a packed absorption column to study on carbon dioxide removal. The influences of absorption pressure, absorption temperature, carbon dioxide content on the product gas and height of packing layer on carbon dioxide removal rate as well as those of liquid/gas ratio and biogas flow on volumetric overall absorption coefficient were investigated. At the same time, the intensive tests used a two-stage absorption column combined with a packed column and a spray column for purification process of pressure water. It was shown from the results that the increased absorption pressure, liquid-gas ratio and height of packing layer and reduced absorption temperature were favorable of removing carbon dioxide. Besides, volumetric overall absorption coefficient rose with increasing liquid/gas ratio and biogas flow. Two-stage absorption column was able to improve the effect of carbon dioxide absorption. When the biogas flow was 10 L·min-1, the height of packing layer 100 cm and carbon dioxide content less than 3%, about 12% of the amount of absorption liquid can be reduced by two-stage absorption column compared with the traditional packed tower. Furthermore, when the two-stage absorption column of 110 cm was used, the optimum purification effect can be obtained and the carbon dioxide removal rate can reach 97.4%.

    High efficient recycling of titanium from waste residue of ilmenite by acid hydrolysis through DTB device
    XU Yanxia, SONG Xingfu, LI Zongyun, TANG Bo, YU Jianguo
    2016, 67(10):  4211-4218.  doi:10.11949/j.issn.0438-1157.20151997
    Abstract ( 240 )   PDF (1498KB) ( 189 )  
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    China is the world's largest producer of titanium dioxide by sulfuric acid, and currently accumulates over million tons of by-products as acid tailings. Those acid tailings caused waste of resources and serious environment pollution problems without utilization because there are lots of more than 25 μm particles of titanium ore in those tailings. On the sedimentation experiments, good settling properties of particles are found. The hindered settling velocity of the particles of 25 μm is 0.60 mm·s-1 based on equations of hindered settling velocity. The DTB (draft tube babbled) type separator has been designed to separate waste residue and recycle titanium, based on analysis of flow field, sedimentation and beneficiation. The separator structure and process operation parameters are also optimized. The results show that there are little more than 25 μm titanium ore in the overflow from vortex finder. The purity of titanium for recycling can reach 27%,and recovery rate of titanium is 73% under the optimal conditions. The results provide the basic data for the industrial recycling of titanium dioxide from acid tailings.

    Effect of underflow pipe diameter on performance of hydrocyclone anti-blockage device
    TIAN Jinyi, NI Long, ZHAO Jianing
    2016, 67(10):  4219-4224.  doi:10.11949/j.issn.0438-1157.20160622
    Abstract ( 274 )   PDF (1193KB) ( 148 )  
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    Separation performance of a sewage-hydrocyclone anti-blockage device consisting of a hydrocyclone and an ejector-reflux component was studied on sand-water and domestic sewage with various diameters of underflow pipe. Experimental results demonstrated that the hydrocyclone anti-blockage device with continuous underflow had higher separation efficiency but negligibly higher power consumption than conventional hydrocyclones with a closed "grit pot". Contrary to the Kelsall's conversion separation efficiency, a more comprehensive separation efficiency for the hydrocyclone anti-blockage device was proposed to include separation efficiency of the device and amount of available water for heat pump system. Under the optimum diameter of underflow pipe in the range of 5 mm and 10 mm, i.e., the optimum diameter ratio of the underflow pipe to the vortex finder between 12.5% and 25%, the sewage-hydrocyclone anti-blockage device had the separation efficiency of 92.6%-94.3% and the split ratio of 1.32%-2.54% for foulants of sizes < 4 mm in untreated domestic sewage. The split ratio was proportional to the underflow pipe diameter. Therefore, hydrocyclone separation could isolate foulants temporarily, clean water and recycle heat from sewage.

    Preparation of free-standing graphene carbon membrane for gas separation
    ZHANG Shengyi, LI Lin, WANG Chunlei, ZHENG Tianfu, SUN Yaming, WANG Tonghua
    2016, 67(10):  4225-4230.  doi:10.11949/j.issn.0438-1157.20160591
    Abstract ( 254 )   PDF (4020KB) ( 356 )  
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    Free-standing graphene carbon membrane with conch nacre structure was prepared via carbonizing composite membrane of graphene oxide (GO) and polyamide acid (PAA) obtained by solvent evaporation method at 600℃. The morphology and structure were characterized by XRD and SEM. The permeation performance of CO2 and CH4 of free-standing graphene carbon membrane with different PAA solid content was investigated. The results indicated that GO was thermally reduced to graphene in graphene carbon membrane after carbonization, in which graphene layers were lamellar stacked and gaps between layers were filled with holes and carbon residue. Both CO2 permeability and ideal selectivity for the CO2/CH4 of graphene carbon membranes were enhanced with increasing PAA solid content. The CO2 flux of graphene carbon membrane was up to 824 barrer and the CO2/CH4 ideal selectivity reached 38.9 simultaneously. The gas permeation channels of graphene carbon membrane were attributed to the lamellar stacked of graphene and carbon molecule sieve in graphene carbon membrane. This study opened up new opportunities to prepare the flexible free-standing graphene carbon membrane for gas separation.

    Performance of polypropylene hollow fiber membrane module for dust removal
    HUANG Yiping, ZHANG Chunyao, GENG Hongxin, XU Yiming, WANG Juan, ZHAO Yajing, LI Yingdong, LI Pingli
    2016, 67(10):  4231-4239.  doi:10.11949/j.issn.0438-1157.20160225
    Abstract ( 179 )   PDF (6097KB) ( 292 )  
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    Poly propylene (PP) hollow fiber membrane with an average pore size of 0.22 μm was used to purify the dusty gas. Effects of operating conditions such as dust concentration, gas flow rate, the filling ratio of membrane module, membrane thickness on the performances of membrane module dust removal were investigated systematically. The results showed that membrane permeability had no obvious change with the concentration of dust in the gas, while rejection coefficient of dust removal increased with an increase in dust concentration, and decreased with an increase in gas flow rate. Both the membrane permeability and rejection coefficient increased with increase in membrane thickness, and decreased with the increase in filling ratio. The rejection coefficient of PP membrane could reach up to 99.9%. When the size of dust is above 0.3 μm, the rejection coefficient could reach 100%, and when it is below 0.3 μm, the rejection coefficient could also reach 99%.

    Removal of CO2 from natural gas by 2-methylimidazole/ethylene glycol system at room temperature
    TONG Xiongshi, PAN Yong, WANG Muyu, SHI Jialiang, CHEN Guangjin, LIU Bei
    2016, 67(10):  4240-4245.  doi:10.11949/j.issn.0438-1157.20160366
    Abstract ( 318 )   PDF (496KB) ( 264 )  
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    A binary liquid mixture system of 2-methylimidazole and ethylene glycol was used to remove carbon dioxide (CO2) from natural gas at room temperature. The measurement on absorption capacity of methane (CH4) and CO2 in this system shows the CO2 solubility about 0.87 mol·L-1 at 0.1 MPa, which is higher than that in most ionic liquids under the same condition, and the absorption capacity of CO2 was greater than that of CH4. Further experimental results demonstrate that the liquid mixture could effectively separate CO2/CH4 gas mixture and could be regenerated and reused. After several cycles of absorption/desorption operations, the absorption capability was found barely changed, indicating good stability and application prospective of this binary system.

    Synthesis and characterization of β-cyclodextrin polyurethane magnetic adsorbents and their adsorption on corilagin
    ZHAO Jun, MIN Shuxue, LIN Jiduan, CHEN Guo, WANG Xiaoqin
    2016, 67(10):  4246-4254.  doi:10.11949/j.issn.0438-1157.20160468
    Abstract ( 294 )   PDF (3048KB) ( 322 )  
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    Two magnetic adsorbents β-CDPU@Fe3O4 and β-CDPU@(SiO2/Fe3O4) were synthesized by encapsulating Fe3O4 and SiO2/Fe3O4 composite magnetic beads by β-cyclodextrin polyurethane polymer (β-CDPU), and adsorption and enrichment of polyphenolic natural product corilagin from Phyllanthus niruri L. herb plants by magnetic separation were studied. Both adsorbents were characterized by FTIR, XRD, SEM and TG/DTA techniques. The appearance of several new peaks in FTIR spectra around 1695, 1617, 1559, 1259 and 1033 cm-1 was attributed to urethane and β-CD moiety. The adsorbent polymeric surface was rough with many protuberant lumps, folds and pores as observed by SEM. Both adsorbents were thermostable below 200℃, indicating suitability for separation usage at room temperature. Polymer content of the two adsorbents reached as high as 41.5% and 36.5%, respectively, based on the mass loss at high temperature in TG/DTA analysis. XRD showed that the crystal structure of Fe3O4 in both adsorbents was nearly the same as that of Fe3O4 and SiO2/Fe3O4 composite beads. Hence, β-CDPU encapsulation did not alter crystal structure of Fe3O4. Adsorption of corilagin by both adsorbents followed Langmuir adsorption isotherm, which was expected from double adsorption sites in β-CDPU skeleton. But the special interaction between Fe3O4 magnetic-core and corilagin, probably due to the complex formation of Fe(Ⅲ) and phenolic hydroxyl groups in corilagin molecule, made it difficult to elute corilagin and resulted in low elution and recovery yield of corilagin at 17.0% and 10.5%, respectively. SiO2 modification on Fe3O4 magnetic core was able to hinder such interaction and the adsorbent β-CDPU@(SiO2/Fe3O4) exhibited more favorable performance for corilagin enrichment with the elution yield of 41.0% and recovery yield of 22.8%. The corilagin enrichment from Phyllanthus niruri L. showed the adsorbent β-CDPU@(SiO2/Fe3O4) would find commercial application for recovery and enrichment of specific natural products from plant materials.

    Performance and mechanisms of coal fly ash-derived C-S-H on adsorption of U(Ⅵ)
    QI Guangxia, LEI Xuefei, SUN Fangyan, SUN Yinglong, LI Lei, YUAN Chao, WANG Bangda, WANG Yi
    2016, 67(10):  4255-4263.  doi:10.11949/j.issn.0438-1157.20160343
    Abstract ( 238 )   PDF (1313KB) ( 255 )  
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    Taking the desilication liquor produced during the alumina recovery of coal fly ash as raw material, mesoporous C-S-H with large specific surface area (401 m2·g-1) was prepared by using the normal precipitation method, of which the molar ratio of calcium to silicon had been controlled. The effects of initial concentration, sorbent dosage, solution pH and ionic strength on the sorption of U(Ⅵ) by C-S-H were systematically investigated, and the sorption kinetics and thermodynamics were also studied. Moreover, the performance of C-S-H on the removal of toxic metals in actual uranium-containing wastewater was evaluated. The results indicated that the transformation of calcium silicate solid in low quality to high-value-added sorbent material had been realized by controlling the synthesis condition. C-S-H of 0.75 g·L-1 still had a high sorption capacity in equilibrium at pH 2 (qe=67.9 mg·g-1), while UO2(H2O)52+ transformed to UO2(CO3)34- in alkaline solution with high amount of CO32-, and it was not good for the sorption of U(Ⅵ) on the negative surface of C-S-H. When C-S-H dosage increased to 2-5 g·L-1, the removal efficiency of U(Ⅵ) by C-S-H could be maintained at a comparatively higher level (C[U(Ⅵ)]initial=500 mg·L-1, 88.3%-93.5%). The equilibrium of the adsorption could be reached within several hours, and the process followed the pseudo-second-order kinetic model and two-stage Weber-Morris equation model. The adsorption followed Langmuir isotherm model. Ion exchange (84.6%) and surface complexation were the main mechanisms accounting for the sorption. The material exhibited a great capacity to remove U, Zn, Hg, Mn and Cd in uranium-containing wastewater. Therefore, C-S-H had great potential to become a promising material to remove the toxic metals from wastewater.

    Effect of two-step pressurization with intermediate gas on rapid vacuum pressure swing adsorption process for oxygen generation
    ZHU Xianqiang, LIU Yingshu, YANG Xiong, LIU Wenhai, LI Yongling
    2016, 67(10):  4264-4272.  doi:10.11949/j.issn.0438-1157.20160191
    Abstract ( 258 )   PDF (774KB) ( 236 )  
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    An improved rapid vacuum pressure swing adsorption (RVPSA) process, namely, two-step pressurization with intermediate gas, was proposed to improve performance of miniature oxygen concentrators, which were based on rapid pressure swing adsorption (RPSA) technology. The experimental results on the new process show that pressurization with intermediate gas at the exhaust end could effectively improve oxygen purity and re-pressurization with intermediate gas at the feed end could improve recovery. The pressure and oxygen purity of intermediate gas at the exhaust end before pressurization as well as the bed pressure after re-pressurization of intermediate gas at the feed end were key parameters for improving oxygen purity and recovery of the production. At the adsorption pressure of 240 kPa and the desorption pressure of 60 kPa, the improved RVPSA process exhibited recovery of recycling oxygen up to 34.57% and the BSF at 61.18 kg·TPD-1 for producing a ton of oxygen per day.

    Selective recognition of cefalexin by magnetic molecularly imprinted polymers based on magnetic fly-ash-cenosphere
    MAO Yanli, LUO Shitian, WU Junfeng, LIU Biao, KANG Haiyan, ZHU Huijie, WANG Hongqiang, WANG Xiangwen
    2016, 67(10):  4273-4281.  doi:10.11949/j.issn.0438-1157.20160196
    Abstract ( 157 )   PDF (3030KB) ( 224 )  
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    Magnetic fly-ash-cenospheres (MFACs) were firstly prepared via an effective coprecipitation method, and then the surface of the MFACs was endowed with reactive vinyl groups through modification with 3-(methacryloyloxy)propyl trimethoxysilane (MPS). Based on the MFACs-MPS, the magnetic molecularly imprinted polymers (MMIPs) were further synthesized for the selective recognition of cefalexin (CFX). MMIPs were characterized by SEM, FT-IR, XRD, TGA and VSM, which indicated that the MMⅡPs exhibited magnetic sensitivity (Ms=12.155 emu·g-1), thermal stability and the larger specific surface area (123.65 m2·g-1). Batch mode adsorption studies were carried out to investigate adsorption equilibrium, kinetics and selective recognition. The Langmuir isotherm model was fitted well to the equilibrium data, and the monolayer adsorption capacity of the MMIPs was 69.55 mg·g-1 at 25℃. The selective recognition experiments demonstrated high affinity and selectivity towards CFX over structurally related antibiotic compounds. Combined with high performance liquid chromatographic analysis technology, the prepared MMⅡPs were successfully applied to the separation of CFX from environmental samples.

    Preparation of PAN-H1.6Mn1.6O4 membrane and its adsorption properties in brine
    WANG Jun, JIA Qingyuan, GUO Ruili, ZHANG Jianshu
    2016, 67(10):  4282-4289.  doi:10.11949/j.issn.0438-1157.20151871
    Abstract ( 243 )   PDF (6521KB) ( 299 )  
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    PAN-H1.6Mn1.6O4 lithium ion-sieve membrane was prepared by blend of lithium ion sieve (H1.6Mn1.6O4) with hydrophilic polymer poly(acrylonitrile) (PAN). The effects of adding amount of lithium ion sieve for PAN-H1.6Mn1.6O4 membrane structure and Li+ adsorption-desorption properties were investigated by SEM, Li+ static adsorption, (NH4)2S2O8 elution and adsorption experiments in brine. The results showed that the adsorption capacity of PAN-H1.6Mn1.6O4 membrane (17.45 mg·g-1) achieved to 88.0% of H1.6Mn1.6O4 powder when the concentration of PAN was 10% (mass) and the amount of loading of H1.6Mn1.6O4 was 50% (mass). In addition, when (NH4)2S2O8 solution was used as eluent with the eluent concentration, liquid-solid ratio and time of 0.3 mol·L-1, 600:1 and 12 h, respectively, the amount of lithium ion elution was 17.23 mg·g-1 and the manganese loss of ratio was only 1.14%. The PAN-H1.6Mn1.6O4 membrane showed good selectivity for Li+ in Lop Nor brine containing other cations such as Na+, K+, Mg2+ and Ca2+. After ten times adsorption-desorption cycles in brine, the adsorption capacity of lithium ion was lost only 6.0% (from 11.64 mg·g-1 to 10.94 mg·g-1). Overall results demonstrated that using hydrophilic PAN carrier material had little effect on the adsorption capacity of H1.6Mn1.6O4 for lithium ion, and the mild eluent was favorable to chemical stability of lithium-ion sieve membrane.

    Preparation and Pb2+/Cd2+ adsorption of encapsulated Fe3O4/sodium polyacrylate magnetic crosslinking polymer
    HE Shengfu, ZHANG Fan, CHENG Shenzhen, WANG Wei
    2016, 67(10):  4290-4299.  doi:10.11949/j.issn.0438-1157.20160259
    Abstract ( 211 )   PDF (1574KB) ( 538 )  
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    A magnetic crosslinking polymer, Fe3O4 encapsulated by sodium polyacrylate (CPAANa@Fe3O4), was prepared via dispersed solution polymerization followed by Ca2+ surface-crosslinking and characterized by techniques of XRD, FT-IR, SEM and TGA. Static adsorption of Pb2+ and Cd2+ ions to the polymer in aqueous solutions was investigated by varying solution pH, polymer adsorbent dosage, and initial concentration of heavy metal ions. The CPAANa@Fe3O4 magnetic crosslinking polymer showed good adsorption performance in solutions with pH in the range of 2-6. The maximum adsorptions for Pb2+ and Cd2+ were observed at adsorbent dosage of 1.0 and 1.6 g·L-1 for initial Pb2+ concentration of 200 mg·L-1 and initial Cd2+ concentration of 100 mg·L-1, respectively, such that the residual Pb2+ concentration could meet the standard for discharge (GB 8978-1996). The adsorption kinetics of both Pb2+ and Cd2+ on CPAANa@Fe3O4 polymer followed pseudo-second order model and their adsorption isotherms obeyed the Langmuir model. Maximum adsorption capacities of the polymer for Pb2+ and Cd2+ were 454.55 and 275.48 mg·g-1, respectively. The CPAANa@Fe3O4 polymer effectively removed Pb2+ and Cd2+ from complex electrolytic pulp wastewater, indicating its potential application advantages as an efficient adsorbent.

    Fault detection method based on variable sub-region PCA
    WANG Lei, DENG Xiaogang, XU Ying, ZHONG Na
    2016, 67(10):  4300-4308.  doi:10.11949/j.issn.0438-1157.20160217
    Abstract ( 211 )   PDF (628KB) ( 404 )  
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    Aiming at the problem that traditional principal component analysis (PCA) method can't highlight the local variable information in industrial process monitoring, this paper proposes a variable sub-region PCA (VSR-PCA) fault detection method. First, PCA is used to decompose original data space into principal component subspace (PCS) and residual subspace (RS), and mutual information between variables and PCS is calculated to measure their correlation which is utilized to obtain the variable sub-regions. Then, local T2 statistics and local SPE statistics are calculated in each variable sub-region. Bayesian inference is applied to integrate information in every sub-region to construct global statistics which are able to emphasize the local variable information while preserving the whole process information. Simulation results on the continuous stirred tank reactor (CSTR) system show that VSR-PCA method has better process monitoring performance.

    Simultaneous control of engine speed and evaporator superheat for gas engine-driven heat pump system
    WANG Mingtao, LIU Huanwei, ZHANG Baihao
    2016, 67(10):  4309-4316.  doi:10.11949/j.issn.0438-1157.20160605
    Abstract ( 292 )   PDF (2582KB) ( 192 )  
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    The complex gas engine-driven heat pump (GEHP) is composed of a gas engine, a heat pump as well as a data acquisition and control sub-system. Effective control of the gas engine speed and evaporator superheat is necessary for safe and highly efficient operation of a GEHP. Based on the characteristics of the gas engine and the heat pump, a simultaneous control strategy was developed with an expert PI controller for engine speed and gain-regulating controller for evaporator superheat. Simultaneous control studies were performed on a GEHP system over a wide range of engine speed and evaporator superheat. When the set point of evaporator superheat was changed, superheat overshoot was less than 1℃ and the engine speed control showed strong anti-interference. When the set point of engine speed was changed, the engine speed control showed a good performance with no overshoot and the superheat fluctuated within a range of less than 0.5℃. The experimental results also show that the simultaneous controller run well in terms of settling time and overshoot when the set points of engine speed and superheat were changed continuously. The research findings will provide technical support for design of automated GEHP control system.

    Fault detection by decentralized dynamic PCA algorithm on mutual information
    TONG Chudong, LAN Ting, SHI Xuhua
    2016, 67(10):  4317-4323.  doi:10.11949/j.issn.0438-1157.20160218
    Abstract ( 241 )   PDF (622KB) ( 329 )  
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    For modern large-scale complex dynamic processes, different measured variables have their own serial correlations and interactions among these variables show on different time points. A mutual information based dynamic fault detection method was proposed by an advantageously decentralized modeling strategy. After made multiple time-delayed observations on each variable, the relevant measurements for the variable were separated from all observations by utilizing mutual information and corresponding variable sub-blocks were created. This approach of variable grouping allowed each variable sub-block to capture sufficient information about its own self-and inter-correlations such that the dynamic characteristics of process data could be well analyzed. The principal component analysis (PCA) algorithm was employed to construct statistical modeling on each variable sub-block and a decentralized dynamic fault detection model for large-scale dynamic process. The feasibility and effectiveness of the proposed method on dynamic process modeling were validated by a case study of a chemical process.

    Regulate properties of glucose oxidase biosensors through pore sizes of TiO2 nanotube arrays
    RAO Chao, DONG Yihui, ZHUANG Wei, WU Xinbing, HONG Qiliang, LIU Chang, LU Xiaohua
    2016, 67(10):  4324-4333.  doi:10.11949/j.issn.0438-1157.20160181
    Abstract ( 223 )   PDF (1930KB) ( 294 )  
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    Highly ordered TiO2 nanotube arrays (TNA) with controlled pore sizes in a series of 21, 62, 83 and 102 nm were synthesized using constant current oxidization method. Glucose oxidases (GOx) were immobilized on TNA by physical adsorption, and the GOx activities on TNA were investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. All immobilized GOx had good oxidizing activities in glucose solution and GOx on 83 nm-pore-sized TNA showed the best sensibility of 27.2 μA·(mmol·L-1)-1·cm-2, which was probably due to a combination effect of reduced diffusion resistance and small Michaelis constant of the immobilized GOx. The experimental results had demonstrated that controlling pore sizes of TNA could effectively tune sensitivity of glucose biosensors.

    Influence of cavitation thermal effect on lubrication properties of upstream pumping mechanical seal
    CHEN Huilong, WANG Bin, REN Kunteng, LI Tong, ZHAO Binjuan
    2016, 67(10):  4334-4343.  doi:10.11949/j.issn.0438-1157.20160456
    Abstract ( 288 )   PDF (1897KB) ( 268 )  
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    Cavitation occurred at mechanical seal faces is an important factor affecting lubrication properties of the mechanical seal. A computational fluid dynamics model was established from Antoine equation with a consideration of cavitation thermal effect. The cavitation thermal effect on the sealing performance was analyzed and compared to results of commonly used model of viscosity-temperature effect of liquid film on seal faces. The results indicated that the influence of cavitation thermal effect was negligible at low rotating speed whereas weakened the capacity of forming high-pressure region in mechanical seal at high rotating speed, which reduced pumping rate and opening force. Both viscosity-temperature effect and cavitation thermal effect were needed to analyze seal failure mechanism at high rotating speed. The local temperature at the spiral groove was slightly higher from cavitation thermal effect than that from viscosity-temperature effect. With the cavitation thermal effect, degree of cavitation occurred most seriously in the rotating ring face and cavitation space became smaller with the smallest one in groove bottom from the rotating ring face to the stationary ring groove bottom, which was contrary to those by considering viscosity-temperature effect.

    Synthesis of L-cysteine modified polyepoxysuccinic acid and evaluation of its inhibition on scale deposition and corrosion
    ZHANG Yijiang, LIU Xinhua, CHEN Zhihui, SUN Caiyun, WANG Qinghui, WU Weihua
    2016, 67(10):  4344-4355.  doi:10.11949/j.issn.0438-1157.20160167
    Abstract ( 348 )   PDF (6063KB) ( 408 )  
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    A polyepoxysuccinic acid derivative (LCY-PESA) was synthesized from polyepoxysuccinic acid (PESA) and L-cysteine (LCY) as well as characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The new LCY-PESA polymer was evaluated on inhibition of static and dynamic scale deposition, static corrosion inhibition, iron oxide dispersion, and biodegradation. The mechanism of corrosion inhibition was further explored theoretically by quantum chemistry modeling on molecular orbitals of the LCY-PESA polymer. In a medium containing Ca2+ at 400 mg·L-1 and HCO3- at 800 mg·L-1, the inhibition on static scale deposition reached up to 94.6% with addition of LCY-PESA at 6 mg·L-1. The minimum light transmittance was 61.5% when 15 mg·L-1 LCY-PESA was introduced to a clear medium of Ca2+ at 150 mg·L-1 and Fe2+ at 10 mg·L-1. The heat resistance of dynamic scale deposition decreased upon LCY-PESA addition to medium. At concentration of 1.0 mg·L-1, LCY-PESA had about 15% higher inhibition on dynamic scale deposition than PESA. Analysis on crystal structure of calcium carbonate scale deposits by infrared spectroscopy (IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) indicated that LCY-PESA could significantly distort calcium carbonate crystals such that the steady calcite was transformed to vaterite. Further experimental results showed that the new polymer had good scale dispersion and biodegradability. Molecular simulation showed that the sulfur and nitrogen atoms of LCY moiety strongly alter electron density of the highest occupied molecular orbital (HOMO) of the LCY-PESA molecule so that the energy gap (ΔE) between HOMO and LUMO (the lowest unoccupied molecular orbital) of LCY-PESA is less than that of PESA, which could improve corrosion inhibition of LCY-PESA polymer.

    Photo-electrochemical removal of graphene buffer layer on SiC substrate
    SUN Li, CHEN Xiufang, ZHANG Fusheng, YU Cancan, ZHAO Xian, XU Xiangang
    2016, 67(10):  4356-4362.  doi:10.11949/j.issn.0438-1157.20160583
    Abstract ( 298 )   PDF (5265KB) ( 450 )  
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    Monolayer graphene was fabricated on silicon carbide (SiC) (0001) face by thermal decomposition of SiC single crystal of 5 cm in diameter. The reaction of SiC substrate with aqueous potassium hydroxide (KOH) by photo-electrochemical etching reduced the interaction force between graphene and SiC substrate, and the quasi-free-standing bilayer graphene was obtained by removal of buffer layer between graphene and SiC substrate. Numerous conditions of current densities and illumination intensities were studied. The optimal condition to remove graphene buffer layer, which would synchronously obtain free standing graphene film in the highest quality, was estimated to be in the current intensity of 6 mA·cm-2 when samples held the distance of 3 cm to UV light source. Among three current densities of 3, 6 and 9 mA·cm-2, Raman spectra showed that the 6 mA·cm-2 current density was the most suitable for etching process. The decoupling effect of graphene buffer layer showed a positive correlation to UV light intensity in a certain range. Raman and XPS spectra on graphene film prepared under optimized condition showed broken bonds between SiC substrate and in-situ grown buffer layer and characteristics of free standing graphene film. The removal of graphene buffer layer was shown by disappearance of characteristic S1 and S2 peaks of buffer layer in XPS C1s spectra. The chemical reaction dynamics in etching process was proposed by analyzing electrochemical voltage-time curves.

    Preparation and electrochemical properties of graphene/nano-sulfur composite as cathode materials for lithium-sulfur batteries
    YANG Rong, WANG Liqing, LÜ Mengni, DENG Kunfa, YAN Yinglin, REN Bing, LI Lan
    2016, 67(10):  4363-4369.  doi:10.11949/j.issn.0438-1157.20160584
    Abstract ( 305 )   PDF (1067KB) ( 678 )  
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    A graphene/nano-sulfur (RGO/nano-S) cathode composites was prepared by chemical precipitation of nano-sulfur onto graphene sheets, which were synthesized by pyrolyzing reduction of graphene oxide from Hummers method. The microscopic structure and morphology of the composites were characterized by FT-IR, XRD, SEM, TEM and Raman, while the electrochemical properties were studied by galvanostatic charge-discharge measurements, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that wrinkled surface on the thermally reduced graphene created a space to accommodate sulfur and polysulfur ions, which helped to hinder dissolving of active cathode materials and suppress migration of polysulfide ions. A homogeneous distribution of nano-sulfur in the graphene conductive network significantly enhanced the effective contact with electrolyte and increased electrochemical reaction area, so that improved discharge capacity and cycle-life performance of the lithium-sulfur batteries.

    Performance comparison of self-pumping and spiral groove mechanical seals
    LU Jianhua, SUN Jianjun, CHEN Wei, MA Chenbo, YAN Yan
    2016, 67(10):  4370-4377.  doi:10.11949/j.issn.0438-1157.20160419
    Abstract ( 248 )   PDF (1744KB) ( 293 )  
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    3D flow field dynamics of two hydrodynamic mechanical seals of self-pumping and spiral groove, which were based on "pumping in" principle, were simulated by Fluent software. Sealing properties of opening force and leakage rate were compared on these two seals at various structural and operating parameters. The numerical simulation results showed that, at the same structure and operating condition, the spiral groove mechanical seal had higher hydrodynamic effect and leakage rate but lower ratio of opening force over leakage rate than self-pumping mechanical seal. In terms of seal performance of opening force and leakage rate, the impact of both transverse structure parameters and rotating speed were significant to spiral groove mechanical seal but insignificant to self-pumping mechanical seal. The performance of hydrodynamic mechanical seals is more dependent on dimensions for spiral groove mechanical seal than for self-pumping mechanical seal.

    Analysis of 2D flow chaotic mixing at cross section of tri-screw extruder by Lagrangian coherent structure
    TONG Ying, ZHU Xiangzhe, GAO He, HE Yandong
    2016, 67(10):  4378-4388.  doi:10.11949/j.issn.0438-1157.20160178
    Abstract ( 247 )   PDF (6915KB) ( 394 )  
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    As a novel equipment for polymer fluid processing, the tri-screw extruder has very complex mixing mechanism due to periodic change in geometrical structures and stresses at its unique center region. Chaotic mixing in tri-screw extruder was analyzed by Lagrangian system, which is much different from the traditional linear mixing analysis technique. With the finite-time Lyapunov exponent (FTLE), Lagrangian coherent structure (LCS), Poincaré section and particle visualization technology, mechanism of fluid transfer and chaotic mixing in 2D flow field as well as influence of dynamic structure characteristics at the center region to the FTLE's and LCS's distributions were studied in tri-screw extruder and compared to those in single-and twin-screw extruders. The results show that LCS divided the flow field in tri-screw extruder into three regions of different flow characteristics, namely, the near screw region, the far screw region and the center region, where a snarl is mass transfer bridge connecting these three regions. With the increase of mixing time, the degree of bending and folding in the snarls increased gradually, that enhanced chaotic mixing in flow field of tri-screw extruder by increasing transportation of polymer melt across three regions. Three hyperbolic fixing points near the kneading block indicated good mixing capability. The existence of elliptical cycle points in the Poincaré cross-sections implied the presence of non-chaotic spots in the center of flow field. Thus, mixing in the center region of tri-screw extruder was relatively poor.

    Chemical modification of oxalate decarboxylase with ethylenediaminetetraacetic dianhydride
    HE Junbin, LIN Rihui, LONG Han, WU Jia, CAI Xinghua, YANG Ying, CHEN Shengfeng
    2016, 67(10):  4389-4398.  doi:10.11949/j.issn.0438-1157.20160355
    Abstract ( 251 )   PDF (911KB) ( 200 )  
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    In order to improve the stability and application performance of oxalate decarboxylase (Oxdc) in the prevention and treatment of urinary calculi, chemical modification of Oxdc with ethylenediaminetetraacetic dianhydride (EDTAD) was investigated. The results of single-factor experiment showed that the extent of modification and the recovery rate of the enzymatic activity were 71.91% and 75.42%, respectively, when the reaction time was 8 h, the molar ratio of EDTAD/Oxdc was 50:1, pH 7.0, and the temperature was 37℃. The analysis results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS) indicated that Oxdc and EDTAD have been covalently bound. The ultraviolet-visible spectrum (UV) and circular dichroic (CD) measurement showed that the structure and conformation of Oxdc were tinily altered after modification by EDTAD. The enzymology changes of Oxdc were also analyzed, the results showed the optimum pH of EDTAD-modified Oxdc was shifted to the alkaline side about 1.5 unit and it had a higher thermostability. Moreover, through modification the adsorption capacity of Oxdc onto calcium oxalate monohydrate crystals was increased by 42.42%. These results suggested that the stability and application performance of Oxdc were significantly improved under this experiment.

    Reactions between P2O5 and calcium phosphate in kiln phosphoric acid
    LÜ Li, LIANG Bin, LIU Qiang, LIU Weizao, YANG Honghui, WU Pan, LI Chun
    2016, 67(10):  4399-4405.  doi:10.11949/j.issn.0438-1157.20160688
    Abstract ( 244 )   PDF (3915KB) ( 294 )  
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    Side reactions of gaseous product P2O5 with phosphate ores (so-called P2O5 back absorption) in rotary kiln produce large quantities of low melting point solid products, which could form a kiln ring, block material flow and cause unstable operation of the kiln. The back absorption of gaseous P2O5 with calcium phosphate was studied at different temperatures and the products were characterized for P2O5 content, morphology, phase composition, structure and thermal stability by chemical analysis and other techniques of SEM, XRD, IR, Raman, TG and DSC. The experimental results show that temperature significantly affected the back absorption, which was occurred above 500℃. Calcium metaphosphate was formed at 500-900℃ with almost pure calcium metaphosphate at 900℃. Calcium metaphosphate decomposed into calcium pyrophosphate and P2O5 at 1000-1300℃ with almost pure calcium pyrophosphate at 1300℃.

    Preparation and application of GO/PEDOT composite anode for MFC
    HUO Qingcheng, HUANG Renliang, QI Wei, SU Rongxin, HE Zhimin
    2016, 67(10):  4406-4412.  doi:10.11949/j.issn.0438-1157.20160595
    Abstract ( 266 )   PDF (6353KB) ( 502 )  
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    A microbial fuel cell (MFC) is an innovative power output device. The properties of the anode is a critical factor for improving the performance of MFC. In this study, a graphene oxide/poly(3,4-ethylenedioxythiophene) (GO/PEDOT) composite was prepared and used for modification of carbon felt (CF) via the electrodeposition with constant current. The cyclic voltammetry and electrochemical impedance characteristics of the electrode were evaluated. Furthermore, the as-prepared anode was applied in MFC and its electrogenesis capacity was investigated. The results showed that the GO/PEDOT-CF electrode had a large specific surface area and good electrochemical performance. When the GO/PEDOT-CF anode was used in MFC, the maximum power density and current density were up to 1.138 W·m-2 and 4.714 A·m-2, respectively, which were 4.80 times and 5.51 times higher than those of unmodified anodes. These results demonstrated that the GO/PEDOT composite is a kind of effective anode materials for improving electricity generation of MFC.

    Comparison of regeneration mechanism of Fe2+ in modified Fenton system
    ZHOU Wei, ZHAO Haiqian, GAO Jihui, WU Shaohua
    2016, 67(10):  4413-4421.  doi:10.11949/j.issn.0438-1157.20160446
    Abstract ( 248 )   PDF (939KB) ( 385 )  
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    The regeneration of Fe2+ can have a marked effect on·OH production in Fenton system. Hydroxylamine hydrochloride, hydroquinone, p-benzoquinone and sodium sulfite were used as typical additives. Different regeneration mechanisms of Fe2+ were revealed by analysis of Fe2+ concentration, H2O2 concentration and oxidation-reduction potential (ORP) as well. Furthermore, reactions between additives and H2O2 and·OH were also explored. Results demonstrated that Fe2+ was regenerated by hydroxylamine quickly, but concentration of Fe2+ gradually decreased with the consumption of hydroxylamine. Hydroquinone and p-benzoquinone exerted similar effect on Fenton system, resulting in enhanced regeneration of Fe2+. Quinone cycle could be built once they were added to Fenton system. Therefore, the concentration of Fe2+ could maintain a relatively high level in a long period. Quinone cycle can be established by one of the two substances or their mixture. Sodium sulfite reacted with·OH and H2O2, which contributed to a poor performance on Fe3+ reduction.

    Comparison of different carriers about ANAMMOX biofilm formation performance
    GAO Mengjia, WANG Shuying, WANG Shanyun, PENG Yongzhen, JIA Fangxu
    2016, 67(10):  4422-4430.  doi:10.11949/j.issn.0438-1157.20160563
    Abstract ( 395 )   PDF (5743KB) ( 380 )  
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    Filling carriers to anaerobic ammonium oxidation (ANAMMOX) reactor can improve Anammox biomass retention. But there are few researches about the influence of different characteristics of carriers on ANAMMOX biofilm growth. Two different suspending plastic carriers and two different sponge carriers were filled in the reactor to form ANAMMOX biofilm. The results showed that the NH4+ and NO2--N average removal rates of one sponge carrier were higher than one suspending plastic carrier on the whole. The EPS contents of sludge on sponge carriers and the speed of sponge carriers forming biofilm were higher than suspending plastic carriers. After biofilm forming for 30 days, the NH4+ and NO2--N removal rates of one sponge carrier with low density could be tested and the value of Δ(NO2--N)/(NH4+-N) was close to 1.32. After biofilm forming for 105 days, the NH4+ and NO2--N average removal rates of one sponge carrier with low density were 0.123 mg·L-1·h-1 and 0.160 mg·L-1·h-1, respectively. The value of Δ(NO2--N)/(NH4+-N) was 1.30, which was close to 1.32. The ANAMMOX activity of sludge on the sponge carrier with low density was the best. The abundance of anammox bacteria in the sludge on the sponge carrier with low density was the highest among the four types of carriers, which was 1.73×1010 copies·(g dry sludge)-1. The sponge carrier with low density had the best biofilm formation performance on the whole.

    Influence of pH on PHA production by halophilic sludge fermenting mixed VFAs substrate
    CUI Youwei, ZHANG Hongyu
    2016, 67(10):  4431-4438.  doi:10.11949/j.issn.0438-1157.20160085
    Abstract ( 237 )   PDF (633KB) ( 161 )  
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    Polyhydroxyalkanoates (PHA) production by halophilic mixed microbial cultures (MMCs) draw a lot of attention because of great advantages, such as free sterilization, easily extraction and high production. In this study, halophilic MMC was used to investigate the effect of pH on PHA production in the mixed VFAs fermentation process. The results indicated that there was no significant influence on PHA production in the pH range of 6.5-8.2. PHA production rate and substrate utilization rate would be inhibited in lower or higher pH conditions. PHA yield was influenced by pH in the systems, but different influencing mechanism existed in acidic condition and alkaline condition. Alkaline environment led to higher dissociation degree of VFAs. Then more energy needed as substrates being absorbed, which further led to the decrease of VFAs absorption rate. This affect was obvious when pH raised to 9.2. Molecular-state VFAs changed intracellular pH in the acidic condition. Then, the lower activity of related enzymes and protein resulted in slower substrate utilization. Energy consumption of substrate utilization and microbial metabolism reduced when pH=5.2, resulting in the decrease of intracellular PHA degradation and the increase of PHA yield. The pH value had little influence on PHA component. And HV accounted for 34.9%-38.3% of PHA weight when the initial pH between 5.2 and 10.2. This study would be a guide for PHA production using mixed VFAs as carbon source by halophilic MMCs.

    Effect of EPS on biological phosphorus removal in sludge shifting SBR process
    ZHOU Xiaohua, PAN Yang, CHEN Qianqian, DENG Meng, ZHENG Ying, XIA Jianwei
    2016, 67(10):  4439-4445.  doi:10.11949/j.issn.0438-1157.20160110
    Abstract ( 219 )   PDF (624KB) ( 157 )  
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    An updated enhanced biological phosphorus removal-sludge shifting SBR process was used for the treatment of synthetic wastewater. The role of extracellular polymeric substances (EPS) in the enhanced phosphorus removal process was investigated. As the sludge reflux ratios (characterized by sludge shifting volumes) was set as 0, 15% and 30%, the content of EPS in the sludge was (108.14±9.68) mg·(g MLSS)-1, (128.17±1.45) mg·(g MLSS)-1 and (123.35±22.98) mg·(g MLSS)-1, respectively. The total phosphorus removal efficiency in sludge (by sludge adsorption) was 82.14%±0.85%, 96.35%±1.25% and 98.99%±0.98%, respectively. Accordingly, the TP concentrations in the EPS at the end of the process accounted for 27.9%±2.55%, 57.23%±2.33% and 63.88%±2.87% of the TP concentrations in the sludge, respectively. In addition, the adsorption of phosphorus by EPS was (2.04±0.32) mg·(g MLSS)-1, (5.90±0.38) mg·(g MLSS)-1 and (6.00±0.52) mg·(g MLSS)-1, respectively, during the aerobic phosphorus adsorption process. In all the above cases, the EPS has contributed more than 90% of the phosphorus adsorption capacity of the sludge. The results indicated that in sludge shifting SBR process, the increase of the amount of sludge shifting improved phosphorus content in the EPS and corresponding phosphorus removal, showing that EPS played a major role in the phosphorus removal process. But sludge shifting had almost no impact on EPS content in the sludge.

    PM2.5 collection using surface-modified hydrophilic carbon steel collector
    XU Chunyan, CHANG Jingcai, WANG Xiang, ZHANG Jing, CUI Lin, ZHANG Bo, MA Chunyuan
    2016, 67(10):  4446-4454.  doi:10.11949/j.issn.0438-1157.20160150
    Abstract ( 245 )   PDF (2207KB) ( 179 )  
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    Fine particles with aerodynamic diameters of <2.5 μm (PM2.5) are significant pollution sources. Dust emission is restricted to less than 10 mg·m-3 under 6% oxygen in eastern China and wet electrostatic precipitators (ESPs) are encouraged for efficient removal of various fine particles in aerosol, especially in coal-fired power plant where strict air pollutant emission standards drive wide use of wet ESP as terminal control equipment. Previous studies showed wetting properties of a hydrophilically modified rigid collector and this study focused on fine particle collection performance of the modified collector at pilot scale. The characteristics of PM2.5 collection, mechanism of uniform water film and effect of main operation parameters on enhancement of particle collection efficiency were investigated. The results showed that the surface fiber layer of the modified rigid collectors reduced flue gas recoiling and particle electro-transportation resistance. A uniform and stable water film was maintained on surfaces of the modified rigid collectors at low washing water flowrate, which inhibited back corona occurrence and a secondary entrainment of dust as well as increased discharge current and flue gas humidity by evaporation of water film. The increase of particle charge number and electro-transportation speed enhanced the particle collection efficiency. With the increase of flue gas temperature, both discharge current and thermophoresis force gradually increased which could improve the particle collection efficiency. However, the increase of gas viscosity reduced the particles collection efficiency. The extension of residence time and the increase of applied voltage improved particle collection, whereas the inlet concentration of particles and the flushing water flowrate had little influence on particle collection. The wet ESPs of modified rigid collectors exhibited reduction of circulating water consumption per square meter by 86 percent and significant increase of particle collection efficiency for ultrafine particles with size of 0.04-0.48 μm as well as overall collection efficiency of all particles at low electric voltage. Hence, the modified rigid collectors had good potentials for application.

    Interaction effects of typical PPCPs and copper nanoparticles on physical-chemical properties
    MENG Di, CHEN Hong, XUE Gang
    2016, 67(10):  4455-4460.  doi:10.11949/j.issn.0438-1157.20160228
    Abstract ( 222 )   PDF (2185KB) ( 170 )  
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    When substances, such as pharmaceutical and personal care products (PPCPs) and metal nanoparticles (NPs) coexist in environment, their physical-chemical properties might be changed under the interaction process, which would result in their combined toxicity different from the single one. After the interactions of tetracycline and copper nanoparticles (CuNPs), triclosan and CuNPs in aqueous solution, and their physical-chemical property changes were investigated. The results indicated that the concentration of tetracycline decreasing mainly because of its degradation caused by CuNPs, and the adsorption of triclosan on CuNPs resulted in the triclosan concentration declining. In addition, the amount of dissolved Cu2+ from CuNPs was significantly increased probably due to its surface property change caused by tetracycline and triclosan. Thus, both the PPCPs and NPs had physical-chemical property changes in different type and various degrees under the interaction process.

    Effect of H2O2 oxidation on property of BFA compound snow-melting agent and its snow-melting mechanism
    HAN Yongping, GONG Ping, LIU Hongmei, ZHOU Wenping, HE Zhifu
    2016, 67(10):  4461-4467.  doi:10.11949/j.issn.0438-1157.20160408
    Abstract ( 244 )   PDF (1496KB) ( 278 )  
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    Biochemical fulvic (BFA) was degraded by hydrogen peroxide (H2O2) before it compounded with calcium salts to be the snow-melting agent. The effect of H2O2 concentration, temperature and pH on the freezing point of BFA compound was studied, and its snow-melting mechanism was analyzed by UV, FTIR and GPC. The optimal conditions in degradation were as follows:ratio of H2O2 to BFA was 1.5 ml/g, temperature 35℃ and pH 7.5, at which BFA had been degraded for 120 min and the freezing point of BFA compound reduced by about 27%. The results showed that H2O2 resulted in the ring opening of some complex aromatic hydrocarbon and oxidation of some unsaturated aliphatic hydrocarbons to produce lots of small-molecular carboxylic acid, alcohol, phenol and alkene arose, which formed some copolymer under Ca2+ complexation. They played the dominant role in ice or snow melting. The experiment results indicated that it was key in improving the property of BFA snow-melting agent and increasing the hydrophilic functional groups of carboxy (-COOH), hydroxyl (-OH) and phenolic hydroxyl (ph-OH) in BFA.

    Establishment of various char-RPM under O2/CO2 atmosphere
    QU Jian, LI Baowei, ZHENG Kuncan, WU Wenfei
    2016, 67(10):  4468-4476.  doi:10.11949/j.issn.0438-1157.20160532
    Abstract ( 179 )   PDF (649KB) ( 272 )  
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    The traditional random pore model is based on a simple one step reaction, which is not suitable to describe the complex gas-solid reaction of coke particles in O2/CO2 atmosphere. Based on the various carbons in coke and the characteristics of single char combustion in O2/CO2 atmosphere, the various char-RPM and the model of pore structure under the complex gas-solid reaction were established. The combustion process of char particles with a diameter of 100 μm in O2/CO2 atmosphere was simulated, and the results were calculated and analyzed by FORTRAN. The research showed that the particles in the early stage of combustion had a competitive effect and the gas concentration in the pore was fluctuated. The reason for fluctuation was the competition between chemical reaction and physical diffusion, which can be improved by increasing the O2 concentration or decreasing the particle size. The various char-RPM proposed in this work had a good adaptability to characterizing the combustion characteristics of char particles in O2/CO2 atmosphere.

    Experimental and modeling study on arsenic volatilization during co-combustion of high arsenic lignite and low arsenic bituminous coal
    LIU Huimin, WANG Chunbo, GUO Yongcheng, ZHANG Yue, HUANG Xingzhi, WANG Jiawei
    2016, 67(10):  4477-4484.  doi:10.11949/j.issn.0438-1157.20160530
    Abstract ( 245 )   PDF (689KB) ( 302 )  
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    Arsenic volatilization characteristics during co-combustion of high arsenic lignite and low arsenic bituminous coal were carried out on an isothermal experiment system from 600℃ to 1100℃ at different blending ratios (3:1, 1:1, 1:3). The results showed that with increasing temperature, the arsenic volatilization in single and mixed coals increased gradually. The volatilization ratios of arsenic in mixed coals at various blending ratios were between two single coals, while they were larger than the weighted average values. Combined with isothermal coal combustion curves, it was found that high volatile content in lignite affected the char combustion properties in blended coals, which in turn promoted the volatilization of arsenic. Considering the effects of temperature, coal blending and the difference of coal rank, the arsenic volatilization model during mixed coal combustion was proposed. The model results fit the experimental curves well, which provided a reference for the prediction of arsenic volatility characteristics of blended coals.

    Facile synthesis of MWCNT/SiO2 nano-composites as high-performance oil adsorbents
    HUANG Jiankun, LIU Hui'e, HUANG Yangfan, MA Yanbing, DING Chuanqin
    2016, 67(10):  4485-4492.  doi:10.11949/j.issn.0438-1157.20160148
    Abstract ( 341 )   PDF (2251KB) ( 390 )  
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    Multi-walled carbon nanotubes-silica (MWCNT/SiO2) nano-composites were prepared from carboxylated MWCNTs and silica sol-gel nanoparticles via one-step scalable precipitation. Structure and physical properties of the nano-composite were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and porous surface area and pore size distribution analysis (BET & BJH). Adsorption removal of oil was evaluated in diesel water on the nano-composite in comparison with SiO2 sol-gel nanoparticles, pristine MWCNTs, and activated carbon. The nano-composite improved MWCNT agglomeration after surface modification by silica nanoparticles and formed dual microporous and mesoporous structures. The diesel removal efficiency of the nano-composite could be up to 97.79% with adsorption equilibrium reached within 1 h. The adsorption process followed the pseudo second-order kinetics with the apparent activation energy at 11.37 kJ·mol-1 and the adsorption isotherms were fitted well with the Freundlich model. Overall, the nano-composite MWCNT/SiO2 showed stronger adsorption capacity than the other three adsorbents.

    Preparation and properties of iron doped TiO2 hollow microspheres
    LI Yabo, ZHENG Yuying, LIU Yanglong
    2016, 67(10):  4493-4499.  doi:10.11949/j.issn.0438-1157.20160443
    Abstract ( 249 )   PDF (8497KB) ( 281 )  
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    Iron-doped titanium dioxide hollow microspheres were prepared hydrothermally using titanium tetrafluoride and ferric nitrate nonahydrate in aqueous solution as starting materials, and were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), surface area (BET) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the microspheres was evaluated on photocatalytic degradation of aqueous methylene blue (MB). TiO2 in hollow microspheres created at 160℃ were anatase crystal and doping a relatively small amount of iron did not alter morphology and crystal structure of TiO2. Iron doping could significantly improve the photocatalytic activity of TiO2 hollow microspheres. The TiO2 hollow microspheres obtained at a condition of 160℃ for 12 h had optimal dimensional uniformity and photocatalytic activity, which the best photocatalytic effect were observed on hollow microspheres with a 1.5% ratio of iron over titanium because of the smallest size and the highest surface area.

    Preparation and properties of pH-responsive control release system of PAA/chlorpyrifos/amino functionalized mesoporous silica
    LIN Yueshun, ZHOU Hongjun, ZHOU Xinhua, GONG Sheng, XU Hua, CHEN Huayao
    2016, 67(10):  4500-4507.  doi:10.11949/j.issn.0438-1157.20160417
    Abstract ( 196 )   PDF (4501KB) ( 308 )  
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    A pH-responsive control release system of PAA/chlorpyrifos/mesoporous silica was prepared by using negative charged polyacrylic acid (PAA) to encapsulate amino functionalized mesoporous silica (NH2-MCM-41) with chlorpyrifos loaded in the pores. The PAA/chlorpyrifos/NH2-MCM-41 system were systematically characterized using X-ray diffraction (XRD), N2 adsorption-desorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Zeta potential and Fourier transform infrared spectroscopy (FTIR). The release behavior of chlorpyrifos was studied at various pH and temperature conditions. The experimental results showed that PAA was coated on the surface of chlorpyrifos/amino functionalized mesoporous silica as a result of electrostatic interaction. The chlorpyrifos release from the PAA/chlorpyrifos/NH2-MCM-41 system was inhibited mainly by PAA blockage with significant pH sensitivity, which increased with pH decrease at pH ≤ 7 and was slightly higher in weak base condition than that in neutral condition. The release also exhibited some temperature dependence and generally followed the Korsmeyer-Peppas kinetic model.

    Synthesis of core-shell epoxy/polyacrylate composite particle with high damping property
    DU Pengya, BIAN Feng, YAO Mengmeng, CHANG Da, TANG Erjun
    2016, 67(10):  4508-4513.  doi:10.11949/j.issn.0438-1157.20160131
    Abstract ( 228 )   PDF (653KB) ( 297 )  
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    An epoxy/polyacrylate (EP/PA) composite particles with core-shell structure was synthesized by two-stage emulsion polymerization. The high damping property was obtained by cross-linking reaction between core layer and shell layer. TEM showed that the composite particles had a spherical morphology with a core-shell structure 120nm size. Fourier transform infrared spectra (FTIR) indicated the cross-linking between EP groups in core and carboxyl groups in shell during film formation of composite particles. The cross-linking reaction improved the dynamic mechanical property by combining the core and shell polymers. DMA (dynamic mechanical analysis) results revealed that the coatings of composite latex presented a markedly loss factor (tanδ) and widen damping temperature range. The highest peak values of tanδ of the composite materials by heating formation film could reach 2.12, which exceeded the value of the traditional damping coatings. The damping temperature range (tan δ≥0.3) could reach to 40℃. It indicated that the composite material presented an obvious application potentials in the field of metal damping coatings.

    Optimization of hot press molding conditions for making PPy/CS composite electrodes
    ZHAO Chunxia, XUE Juanqin, ZHANG Yujie, LI Guoping, LUO Yao
    2016, 67(10):  4514-4520.  doi:10.11949/j.issn.0438-1157.20151833
    Abstract ( 211 )   PDF (2065KB) ( 213 )  
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    Electrodes using chitosan (CS) and polypyrrole (PPy) composites as active matrix were fabricated by hot press molding without application of bonding adhesive. The effect of conductive agents on mechanical properties and the influence of fabrication conditions such as hot pressing temperature, molding pressure, hot pressing time and types of activated carbon on electrochemical performances were studied.The experimental results show that high performance composite electrodes were manufactured by this technique. Compared to those of graphite and nano-silver as conductive agent, the electrodes of activated carbon as conductive agent had the best swelling and hydrophilic properties, which also exhibited enhancement in electrochemical performance with the increase of specific surface area of activated carbon. The optimal hot press molding conditions to prepare electrodes were pressing temperature of 150℃, molding pressure of 10 MPa and pressing time of 20 minutes.