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Table of Content
05 May 2018, Volume 69 Issue 5
    Research progress in CO2 capture technology using liquid-liquid biphasic solvents
    XU Mimi, WANG Shujuan
    2018, 69(5):  1809-1818.  doi:10.11949/j.issn.0438-1157.20171487
    Abstract ( 218 )   PDF (586KB) ( 269 )  
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    Chemical absorption is one of the most promising technologies for post-combustion CO2 capture. But the high energy consumption of solvent regeneration process will limit its further development. The liquid-liquid biphasic solvents have been widely concerned by researchers due to the potential of reducing the energy consumption of CO2 desorption process. This paper gives an overview of the development of liquid-liquid biphasic solvents. According to the solvents composition and the phase separation mechanism, the liquid-liquid biphasic solvents are divided into thermomorphic biphasic solvents, organic amine-low absorption rate amine solvents, chemical-physical solvents, and organic amine-ionic liquid solvents. The research progress of various solvents is introduced, including the absorption performance and the phase separation mechanism. The advantages and disadvantages of the solvents are analyzed. It can be concluded that liquid-liquid biphasic solvents have great potential for energy saving. The future research should focus on the design principle and the deep phase separation mechanism of liquid-liquid biphasic solvents.

    Progress on mechanism and catalysts of biomass syngas methanation
    LIN Jianghui, WANG Qiong, WANG Jie, WANG Hongtao, MA Guangyuan, XU Yanfei, DING Mingyue
    2018, 69(5):  1819-1828.  doi:10.11949/j.issn.0438-1157.20171405
    Abstract ( 164 )   PDF (504KB) ( 195 )  
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    The increasing supply and demand of natural gas prompt people to search new resources of producing natural gas. Biomass syngas converting to natural gas (Bio-SNG) has attracted more and more attention, in which the choice of syngas methanation catalysts is the key. This paper summarized the latest development on the research of syngas methanation mechanism and catalysts. Especially, CO methanation mechanism, CO2 methanation mechanism, and the effects of active metals, promoters and support materials on methanation performances were introduced detailed. In addition, the shortcoming of present research and outlook of future research were also pointed out.

    COSMO-SAC molecular screening method to analyze imidazole ionic liquids for toluene vapor absorption
    ZHANG Wenlin, YAN Jiawei, SUN Tengfei, ZHANG Bin, LAN Xiaoyan, LI Chunli
    2018, 69(5):  1829-1839.  doi:10.11949/j.issn.0438-1157.20171228
    Abstract ( 84 )   PDF (675KB) ( 90 )  
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    Imidazolium ionic liquids as toluene vapor absorbent were evaluated by a molecular screening method based on the COSMO-SAC model. A s-map was established for hundred common imidazolium ionic liquids composed of N,N'-dialkylimidazolium cation and an anion. Absorption potential of ionic liquids to toluene vapor at 303.15 K was calculated from the s-map and was used as thermodynamic evaluation criterion to screen absorbents. Experimental measurements on saturated absorption of toluene vapor in six ionic liquids showed consistent results with these of molecular screening, which verified reliability of this molecular screening method. Interaction energy of ionic liquid cation and toluene was calculated by Gaussian 09 software. Subsequently, effects of kinetic factors such as vapor inlet concentration and velocity were explored. An initial toluene absorption by ionic liquid reached to 96.2% under temperature of 303.15 K, inlet concentration of 10000 mg·m-3, and inlet velocity of 0.05 m3·h-1. Further study indicated that toluene absorption was almost not changed with increasing number of repeated use cycles of ionic liquid absorbents.

    Mechanism of Hg removal by gaseous advanced oxidation process with Fe3O4 and H2O2
    ZHOU Changsong, YANG Hongmin, SUN Jiaxing, QI Dongxu, MAO Lin, SONG Zijian, SUN Lushi
    2018, 69(5):  1840-1845.  doi:10.11949/j.issn.0438-1157.20171236
    Abstract ( 71 )   PDF (1325KB) ( 68 )  
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    The decomposition properties of H2O2 molecule over Fe3O4 (111), (110), and (001) surfaces were systematically investigated by using density functional theory (DFT) calculations. Hg adsorption and oxidation mechanisms over H2O2/Fe3O4 system were studied. Binding energies, optimized geometries, Mulliken population, and molecular orbital analysis of partial density of states (PDOS) between Hg and H2O2/Fe3O4 surfaces were proposed. The most favored configurations of H2O2 decomposition, which was associated with the generation mechanism of OH groups, as well as the intermediates of Hg species were discussed. The results showed that OH radicals were more likely produced on Fe3O4 (111), (001) A, and (110) A surfaces. The oxidative activity of OH produced on different surfaces varies a lot. In addition, Mulliken charge population revealed Hg0 oxidation when the systems were in equilibrium because a large number of electrons transferred from Hg0 to the surface hydroxyl. The calculated binding energies suggested that the process of HO-Hg-OH and Hg-OH generation were exothermic on Fe3O4 surface with H2O2. The desorption analysis showed that HO-Hg-OH and Hg-OH intermediates had a lower desorption energy when they detached from the surface.

    Thermodynamics analysis of in-container self-propagating high-temperature synthesis immobilization process using numerical simulation
    TAO Jun, ZHANG Jijun, MAO Xianhe, ZHAO Jianwei, ZHANG Dongliang, CAI Xinan
    2018, 69(5):  1846-1853.  doi:10.11949/j.issn.0438-1157.20171111
    Abstract ( 105 )   PDF (1306KB) ( 88 )  
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    Self-propagating high-temperature synthesis (SHS) is a high-efficiency and low-cost thermal technology that uses the energy released during exothermic oxidation-reduction reactions to immobilize solid radioactive wastes, such as high-level radioactive calcined ash and contaminated soil. It is effective to increase the product's density and control the diffusion of the hazardous aerosol by using SHS immobilization in a sealed container. By the analysis of the chemical reaction mechanism and process of the SHS immobilization, the numerical simulation model for the in-container treatment was established and the variation characteristics of the temperature and pressure during the immobilization were studied. By using the COMSOL finite element analysis software with the preset model size, unit type and boundary condition, the in-container temperature-time and pressure-time variation curves in 7200 s after SHS ignition were solved. The simulation is compared with the experiment data in the same in-container immobilization condition, and the results have strong consistency and show staged difference among ignition, burning, flameout and thermal insulation of the SHS immobilization process. The numerical simulation conclusion could act as the reference data for the container safety design.

    Numerical simulation of vortex-eliminating plates in super vortex quick separation system at end of catalytic cracking riser
    WANG Yingqi, LU Chunxi, E Chenglin
    2018, 69(5):  1854-1866.  doi:10.11949/j.issn.0438-1157.20180030
    Abstract ( 78 )   PDF (10338KB) ( 70 )  
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    Gas phase flow fields in the exit space at upper section of a f572 mm×3000 mm super vortex quick separation system (SVQS) were simulated with and without vortex-eliminating plates by using RNG k-ε turbulent model on the basis of experimental data on large scale cold equipment. The simulation results show that plates of two different structures can efficiently alleviate high speed vortexes near the wall. By comparison, it was found that wall-mounted vortex-eliminating plate could effectively reduce pressure drop and spiral degree of airflow above the plate. Straight vortex-eliminating plate had smaller pressure drop and better outcomes than bent counterpart.

    Simplified two-fluid model coupled with EMMS drag for simulating gas-solid flow
    QIU Xiaoping, WANG Limin, YANG Ning
    2018, 69(5):  1867-1872.  doi:10.11949/j.issn.0438-1157.20180065
    Abstract ( 64 )   PDF (1102KB) ( 87 )  
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    A simplified two-fluid model (STFM) combined with energy-minimization multi-scale (EMMS) drag was proposed for accurate and fast simulation of gas-solid flows. In this new approach, solid phase pressure was calculated by an empirical correlation without considering solid phase viscosity and interphase momentum transfer was calculated from EMMS drag model by taking into account of coupled effects of meso-scale structures. A lab-scale bubbling fluidized bed was successfully simulated in 3D by this approach. STFM coupled with EMMS drag had comparable simulation results to FTFM coupled with EMMS drag, and both agreed well with experimental data. Compared to FTFM, STFM doubled simulation speed and thus significantly reduced computational cost. The gas-solid simulation suggests that drag model has a primarily dominant effect, followed by solid phase stress. The model of STFM combined with EMMS drag has large potentials in rapid simulation of commercial gas-solid reactors.

    Pressure drop characteristics of dry gas purification process in a coupled apparatus of cyclone and granular bed filter/adsorber
    GAO Sihong, ZHANG Dandan, FAN Yiping, LU Chunxi
    2018, 69(5):  1873-1883.  doi:10.11949/j.issn.0438-1157.20180014
    Abstract ( 114 )   PDF (638KB) ( 120 )  
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    A coupled apparatus of cyclone and granular bed filter/adsorber for dry gas purification, which combined centrifugal separation, filtration and adsorption, was designed to use in a wide range of temperatures and to provide a new means for high temperature gas purification. The static pressure drop between inlet and outlet of the apparatus was measured and investigated on no dust added gas under different granular circulation rates and inlet gas velocities. The result shows that static pressure drop, which dimensionless standard deviation is maintained within 0.4%, has strong stability and predictability over the whole operation process. The static pressure drop is not influenced by granular circulation rate but has a good quadratic (parabola) relationship with inlet velocity. Actual pressure drop can be divided into five parts, namely, five friction losses caused by inlet pipeline, fittings between square and circle ducts, vortex motion, granular bed and outlet pipeline. Correlation equation between the vortex motion friction, the actual pressure drop, and the inlet velocity head was developed. Compared to common cyclone separator, this device has no significant increase in resistance coefficient. The vortex motion effect between cyclone and granular bed was confirmed through preliminary experimental data of operation with added dust, providing a foundation for further optimization.

    Multiscale entropy analysis of two-phase flow in inclined pipe under vibration condition
    ZHOU Yunlong, LI Shanshan
    2018, 69(5):  1884-1891.  doi:10.11949/j.issn.0438-1157.20171087
    Abstract ( 56 )   PDF (784KB) ( 61 )  
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    After combined vibration apparatus with experiment loop of two-phase flow, gas-liquid two-phase flow in inclined pipe was studied experimentally under fluctuant vibration. The flow patterns were recorded and pressure fluctuation signal was analyzed by multiscale entropy method. The results indicate that two new flow patterns of bead flow and fluctuant slug flow are created in inclined pipe under vibration condition. Multiscale entropy analyses were performed on pressure fluctuation signals of five typical flow patterns under 95 different flow conditions. Results show that entropy change rate of different flow patterns at low scale (first nine) is obviously different and entropy at high scale can reflect dynamic characteristics of different flow patterns.

    Pressure-driven flow properties of fullerene nanofluid in graphene nanochannels
    LIU Zhen, ZHANG Zhongqiang
    2018, 69(5):  1892-1899.  doi:10.11949/j.issn.0438-1157.20171136
    Abstract ( 130 )   PDF (917KB) ( 149 )  
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    The pressure-driven flow properties of the fullerene-water nanofluids confined in graphene nanochannels are investigated by using classical molecular dynamics simulations. The influences of the driving force, the volume fraction, and the electrical field intensity on the motion behaviors and the boundary slip are explored with considering the dynamics and the accumulation of the fullerene within the nanofluids. The results show that the relatively large driving force can weaken the accumulation of the fullerenes. The increase in the volume fraction of the fullerene in nanofluids can enhance the shear viscosity, induce the accumulation of the fullerenes,and it can also increase the boundary slip velocity of the nanofluids in graphene channels. As the electric field intensity of the graphene channel increases, the boundary slip of fullerene nanofluids first increases to a maximum and then decreases gradually, attributed to a cooperative phenomenon of the three key factors which are the variation of the interfacial coupling strength, the formation of the hydrophobic water monolayer, and the motion of the fullerene clusters. The findings may be helpful to the design and fabrication of the low dimensional carbon materials-based nano-apparatus.

    Experimental investigation on inorganic salt solution's supercooling degree under porous spherical layer with different spherical diameters
    XU Xiaofeng, ZHANG Xuelai, CHEN Yue, CHEN Qiyang, LI Yuyang
    2018, 69(5):  1900-1905.  doi:10.11949/j.issn.0438-1157.20171063
    Abstract ( 72 )   PDF (545KB) ( 58 )  
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    The supercooling degree of inorganic salt solution has great effect on the characteristic of the phase change meterials in cool storage. Ammonium chloride solution was chosen as a kind of inorganic salt solution, the experimental system was built to study the influence on supercooling degree of inorganic salt solution under the effection of concentration and porous media. The method of heat transfer enhancement was studied by changing the concentration of inorganic salt solution and the diameter of balls which is constituting the porous media. The experimental results show that with the increase of concentration, the value of inorganic salt solution's supercooling degree and dispersion degree reduced, while the stability increased. Compared with the ammonium chloride solution at the concentration of 5%, the supercooling degree decreased 17.5% when the concentration of chloride solution reached 15%. With the decrease of the diameter of balls which is constituting the porous media, the average value of chloride solution's supercooling degree and dispersion degree decreased, while the stability increased. Compared with the ammonium chloride solution without porous media, the average value of chloride solution's supercooling degree decreased 21.7% when the diameter of balls was 5 mm.

    New efficient middle region damping cavity gas wave tube
    ZOU Jiupeng, LIU Xuewu, XU Weihua, DAI Yuqiang
    2018, 69(5):  1906-1914.  doi:10.11949/j.issn.0438-1157.20171181
    Abstract ( 69 )   PDF (702KB) ( 50 )  
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    The moving shock in gas wave tube of gas wave refrigerator was reflected back from closed end boundary of the tube. If the reflected shock wave was back to open mouth of the gas wave tube it will heat the expanded refrigeration gas at the open end, and reduce refrigeration efficiency severely. Analysis shown that pre-existing efficient tail end absorbing cavity type gas wave tube was not enough for attenuating and damping reflected shock, therefore a novel middle damping cavity type gas wave tube was put forward. By the contrastive analysis of motion wave train in both tubes,the comprehensive mechanism of the middle damping cavity were uncovered, those include damping reflected shock, turning back reflected shock to backend section of the tube, and converting part of the incoming shock wave to expansion wave which may counteract the reflected shock wave of escape from damping cavity. Computational fluid dynamics numerical simulation shows that the new type of gas wave tube could improve the refrigeration efficiency by 7%-11% relatively if the gas injection frequency higher than the second high efficient frequency, and trough efficiency about 18% relatively, so the refrigeration efficiency curve tends to smooth. The two cavities type gas wave tube combined by middle damping cavity and existing tail end absorbing cavity could improve the refrigeration efficiency corresponding to the low and medium frequency gas injection by 6%-8% relatively. The efficiency curve was more smooth. Refrigeration efficiency of three type gas wave tubes were measured and compared by the single gas wave tube model experiment. The performance of high efficiency and smooth efficiency curve of new type gas wave tube were proved. The amplitude contrast and trends of refrigeration efficiency of three type gas wave tubes and gas injection frequency corresponding to peak and trough points of efficiency, were in conformity with the simulation results.

    Frequency characteristics of disturbance wave at vertical gas-liquid annular flow interface
    SUN Hongjun, GUI Mingyang, ZHAO Ning
    2018, 69(5):  1915-1922.  doi:10.11949/j.issn.0438-1157.20171169
    Abstract ( 104 )   PDF (744KB) ( 145 )  
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    Annular flow of an inner gas core and an annular liquid film is one of the most important flow patterns in engineering application. A disturbance wave occurs at interface of liquid film and gas core, which wave frequency is a characteristic parameter for describing the disturbance wave at annular flow interface and for studying mass and heat transfer in annular flow. A near infrared (NIR) equipment was designed to measure liquid film thickness. Non-contact thickness measurement of partial liquid film in annular flow was achieved by vertical optical path and inserted light guide tube to cover one side of liquid film and liquid droplet in gas core. Then frequency of interface disturbance wave was estimated by power spectral density. Quantitative study on annular flow in 50-mm-diametered vertical tube obtained wave frequencies at 70 different flow conditions with pressure ranging from 0.1 to 0.8 MPa, liquid volume flux ranging from 1.2 to 2.5 m3·h−1, and gas volume flux of 90 and 110 m3·h−1. These experimental results were used to verify current models, and a St-Fr model was established to predict disturbance wave frequency from flow parameters, which the Strouhal number was to describe influence of liquid phase and the Froude number was to describe influence of gas phase. The mean absolute error (MAE) of the St-Fr model prediction to experimental results is 11.42%.

    Experimental investigation on particle flow characteristics in spouted bed with longitudinal vortex generator
    SHANG Lingyi, WU Feng, MA Xiaoxun
    2018, 69(5):  1923-1930.  doi:10.11949/j.issn.0438-1157.20171705
    Abstract ( 77 )   PDF (1297KB) ( 53 )  
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    Longitudinal vortex effect was created by attaching a longitudinal vortex generator to spouted bed so as to improve radial and axial motions of particles in conventional spouted bed. Particle image velocimetry (PIV) was applied to explore effects of longitudinal vortex flow and particle physical properties on radial velocity of particles in injection and annular zones of a 152-mm-diametered spouted bed. The results show that a lot of secondary vortexes appear in the cross section above flow disturbance element of the vortex generator and particle radial velocity is significantly intensified when compared to conventional spouted bed, indicating that the longitudinal vortex generator can enhance radial movement of particle phase in both injection and annular zones. Within the range of stable injection, smaller diameter and lower density of particles have better intensification effect of longitudinal vortex on radial motion of particles.

    Effects of inlet distributor on particle flow characteristics in 18 m circulating fluidized bed riser
    MAO Xiaoyang, WANG Chengxiu, LAN Xingying, GAO Jinsen
    2018, 69(5):  1931-1937.  doi:10.11949/j.issn.0438-1157.20180016
    Abstract ( 97 )   PDF (554KB) ( 105 )  
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    Three kinds of riser inlet distributors were designed to investigate their effects on particle flow characteristics in a CFB riser with 18 m in height and 80 mm in diameter. The results show that inlet distributors have significant impact on particle hydrodynamics at the bottom region of the riser and different inlet distributors have different effects as indicated by characteristic length of the developing section. At the same operating condition, multiple tube inlet had uniform radial distribution of solid holdup and particle movement reached fully-developed state at about 9 m in axial direction, whereas perforated plate inlet had large concentration difference at bottom and particle movement developed slowly in axial direction requiring about 11 m in length to reach fully-developed state. On the other hand, single tube inlet had radial solid holdup and axial development region somewhere between those of the other two inlets. The single tube inlet had non-uniform radial solid holdup distribution of dilute center and dense side at the bottom of the riser and required 10 m axial length to reach fully-development state.

    Establishment and verification of a two-phase flow distribution model in a parallel flow heat exchanger
    XU Xiaoxiao, XIAO Jiumin, CHEN Long, LIU Chao
    2018, 69(5):  1938-1945.  doi:10.11949/j.issn.0438-1157.20171192
    Abstract ( 101 )   PDF (496KB) ( 98 )  
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    The flow mal-distribution of the refrigerant will have great influence on the heat transfer performance of parallel flow heat exchanger. This paper presents a new two-phase flow distribution model for parallel flow heat exchanger based on the combination of T-junction model of T-tube, mass equation and pressure equation along the flow path as well as an appropriate algorithm to predict the distribution of parallel flow heat exchanger. The validity of the model is verified by the experimental data. It can provide a reasonable basis for the design of parallel flow heat exchanger. This paper calculates and analyzes the effect of quality and mass flow rate on the distribution of parallel flow heat exchanger. The results show that the quality has little influence on the distribution, and the flow distribution can be improved by increasing mass flow rate.

    Experimental research and numerical analysis of heat collector performance for waste heat recovery
    DU Wenjing, SUN Huimin, CHENG Lin
    2018, 69(5):  1946-1955.  doi:10.11949/j.issn.0438-1157.20171001
    Abstract ( 118 )   PDF (662KB) ( 74 )  
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    The research object is a novel heat collector installed on the surface of the rotary kiln, which is used for waste heat recovery from the kiln. The experimental and numerical calculation methods are used to analyze the flow and heat transfer characteristics of this equipment. In the process of experimental research, one radiant type heat collector and two coupled type heat collectors are investigated to study the influence between the variation of outlet water temperature, outlet pressure and flow mass on the performance of the collector. Numerical calculations are also performed to obtain working performances of the heat collector using Matlab software. Both numerical and experimental results are compared to verify the accuracy of numerical calculations. The changes of the inlet air temperature, inlet air flow rate and kiln body temperature are numerically analyzed. Related results provide data support for the optimization design of the collector and the selection of the online operating parameters.

    Onset of nucleate boiling characteristics of subcooled flow in vertical and horizontal helically-coiled tubes
    KONG Lingjian, HAN Jitian, CHEN Changnian, LIU Zhigang
    2018, 69(5):  1956-1963.  doi:10.11949/j.issn.0438-1157.20171075
    Abstract ( 72 )   PDF (631KB) ( 73 )  
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    An experimental study has been carried out to investigate the onset of nucleate boiling (ONB) characteristics of R134a in vertical and horizontal helically-coiled tubes. The experiments are carried out in a range of pressure from 412 to 850 kPa, inlet subcooling from 4.7 to 15.0℃, heat flux from 0.11 to 10.90 kW·m-2 and mass flux from 147.5 to 443.7 kg·m-2·s-1. The subcooled flow boiling curves of the vertical and horizontal helically-coiled tubes are analyzed from single-phase forced convection to ONB. A parametric study is explored to investigate the effects of the experimental parameters on ONB. The results indicate that the wall superheat and temperature undershoot at ONB in vertical coil are smaller than that in horizontal coil. The heat flux and wall superheat of the ONB increase with the increase of the mass flux and inlet subcooling but decrease with the increase of the system pressure and helical diameter for both vertical and horizontal helically-coiled tubes. Furthermore, the dimensionless parameters are introduced to develop a new correlation for predicting the heat flux at ONB in helically-coiled tube. It is shown that 95.8% of the experimental data of the heat flux at ONB are within 20% of that calculated from the new correlation.

    Cooling performance of cylindrical battery pack based on thermal management system with heat pipe
    GAN Yunhua, WANG Jianqin, LIANG Jialin
    2018, 69(5):  1964-1971.  doi:10.11949/j.issn.0438-1157.20171141
    Abstract ( 94 )   PDF (608KB) ( 167 )  
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    The reasonable design of a thermal management system is a key to improve the battery cooling performance. A battery thermal management system based on the combination of heat pipe and conduction element is proposed for a cylindrical battery pack. A numerical model is developed and validated with experimental results. The effect of conduction element on the thermal performance of the proposed thermal management system is numerically investigated. The results show that the conduction element significantly improves the thermal performance of the proposed thermal management system due to the increase of the contact area between conduction elements and batteries. The thermal performance can be improved by increasing the circumference angle between conduction elements and batteries to enlarge the contact area. But this improvement effect is slight when the circumference angle is greater than 95°. Its temperature can be slightly decreased by increasing the thickness of conduction element, and it is suggested that the thickness should be within 4 mm.

    Flow regimes of gas-liquid two phase flow in a U-bend unit and characteristics of pressure drop fluctuations
    MA Xiaoxu, TIAN Maocheng
    2018, 69(5):  1972-1981.  doi:10.11949/j.issn.0438-1157.20171148
    Abstract ( 81 )   PDF (994KB) ( 115 )  
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    Flow regimes of air-water two-phase flow were experimentally studied in a horizontal upward U-bend unit with an inner diameter of 16 mm and a radius of curvature as 100 mm. Visualization technique on flow observation and analysis of corresponding pressure drop fluctuations were used to objectively identify flow regimes. The fluctuation characteristics of pressure drops at various flow regimes were summarized and a new method for recognizing flow regimes quantitatively was proposed. A total of five flow regimes, i.e., stratified-churn, plug-bubble, slug-wavy, annular-wavy and annular-dispersed flows were identified within the scope of experiment. They are different from flow regimes in a horizontal or vertical straight tube. Compared to standard deviation of pressure drop signals, power spectral density (PSD) distributions can better reflect evolution characteristics and dynamic properties of different flow regimes in the U-bend unit. Combination of skewness or kurtosis of PSD distributions and ratio of gas-liquid superficial velocities could objectively and quantitatively identify flow regimes in the U-bend unit. Flow regime transition occurs at ratios of gas-liquid superficial velocities as 1 and 13.

    Effect of lubricating oil on convective heat transfer characteristics of supercritical carbon dioxide
    XU Wenjie, LI Minxia, GUO Qiang
    2018, 69(5):  1982-1988.  doi:10.11949/j.issn.0438-1157.20170993
    Abstract ( 110 )   PDF (532KB) ( 138 )  
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    To obtain the effect of lubricating oil on the heat transfer characteristics of supercritical carbon dioxide under heating conditions, the flow and heat-transfer model of CO2/lubricating oil two-phase mixture was established by using Fluent software. The model was used to analyze the heat transfer characteristics in detail at different oil concentrations, mass fluxes, heat fluxes and operation pressures. The results show that the presence of lubricating oil significantly weakened the convective heat transfer process of supercritical carbon dioxide. With the increase of lubricating oil concentration, the convective heat transfer was further deteriorated. The concentration of lubricating oil had a marked impact on the heating characteristics of supercritical carbon dioxide. When the oil concentration was less than 1%, the change trend of heat transfer coefficient was not affected. When the oil concentration exceeded 3% and the temperature was higher than the pseudo critical temperature of carbon dioxide, the degree of heat transfer deterioration decreased. The increase of heat flux made the convective heat transfer worse, but increasing the mass flux can effectively improve the phenomenon of heat transfer deterioration. The solubility of carbon dioxide in lubricating oil directly affected the convective heat transfer process. The increase of operating pressure can enhance the solubility of carbon dioxide in lubricating oil which contributed to reducing the degree of heat transfer deterioration under high lubricating oil concentration.

    Critical heat flux characteristics during flow boiling in a micro channel with micro pin fins
    DU Baozhou, KONG Lingjian, GUO Baocang, LI Huijun, LIU Zhigang, LÜ Mingming
    2018, 69(5):  1989-1998.  doi:10.11949/j.issn.0438-1157.20171013
    Abstract ( 76 )   PDF (894KB) ( 120 )  
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    Experiments were carried out to investigate the critical heat flux characteristics during flow boiling of deionized water in a micro channel with micro pin fins in the shape of circular, diamond, and ellipse, respectively. In the experiments, the mass flux ranges from 96 to 224 kg·m-2·s-1, the inlet subcooling ranges from 20 to 50℃, and the effective heat flux ranges from 10 to 240 W·cm-2. CHF is caused by dryout at the wall near the outlet of the microchannels, which in turn is attributed to the flow reversal upstream of the microchannels. The occurrence of CHF is marked by an abrupt increase in wall temperature near the outlet and an abrupt decrease in pressure drop across the microchannels. In addition, it is found that the experimental parameters such as mass flux, inlet subcooling, and the shape of micro fins also have a great influence on CHF. The experimental results show that the critical heat flux with micro channel of micro pin fins is higher than that of a smooth channel and the existence of micro fin greatly reduces flow reversal and subsequent instabilities in flow boiling. The CHF of the elliptical micro pin fins is the largest, and the circular micro pin fins is the smallest. The CHF increases with the increase of mass flux and inlet subcooling, but decreases with the increase of outlet quality. The experimental data are compared with the correlation proposed by Kosar et al. The results show that the experimental data are in good agreement with the correlation.

    Numerical simulation of macroscopic instability induced by 6PBT impeller in a stirred tank with pseudoplastic fluid
    LUAN Deyu, WEI Xing, CHEN Yiming
    2018, 69(5):  1999-2006.  doi:10.11949/j.issn.0438-1157.20171185
    Abstract ( 66 )   PDF (1153KB) ( 105 )  
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    The flow field structure and macroscopic instability (MI) in a stirred tank equipped with the perturbed six-bent-bladed turbine (6PBT) were numerically simulated by using CFD combined with the detached eddy model. The test fluids used were tap water and xanthan gum solution with different quality fraction, respectively. The numerical results of water velocity distributions were compared with the experimental data obtained by particle image velocimetry (PIV). The distributions of the MI frequency in stirring xanthan gum solution were analyzed by programming combined with the software MATLAB. The results show that the flow field structure and calculated values of the velocity components are in good agreement with the PIV measured data, which validates the detached eddy model. The peak value of MI frequency increases with the increase of the speed, which means the high pulse intensity of flow field. As the speed climes to 225 r·min-1, the peak characteristics of MI frequency disappear and a multi-scale wavelet structure appears, which characterizes that the flow field enters chaos. Moreover, the fluid rheology has less effect on MI frequency, which indicates that the MI phenomenon is a common feature of fluid flow.

    Experiment on heat absorption efficiency of non-packed heat source tower
    ZHANG Nan, LI Nianping, CUI Haijiao, LI Shengbing
    2018, 69(5):  2007-2013.  doi:10.11949/j.issn.0438-1157.20170422
    Abstract ( 72 )   PDF (515KB) ( 104 )  
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    An experimental system was established for non-packed heat source tower system. The heat absorption efficiency of the heat source tower was studied under the different air inlet positions, spray nozzle positions, air dry-bulb temperatures, relative humidity, air flow rates, and solution inlet temperatures. The results show that the position of air inlet and spray nozzle has obvious impact on heat absorption efficiency. The heat absorption efficiency of down-spray heat source tower is better than that of the up-spray tower. There was no significant correlation between heat absorption efficiency and dry-bulb temperature, while with the air dry-bulb temperature increases the total amount of heat absorbed from the air increases. The heat absorption efficiency increases with the air flow rate and relative humidity increase. With the inlet solution temperature increasing, the heat absorption efficiency is obviously improved. Compared with other parameters, the inlet solution temperature has the greatest impact on heat absorption efficiency.

    Liquid film flow and heat transfer model under spray impact
    QI Hang, ZHANG Wei, GONG Liang
    2018, 69(5):  2014-2022.  doi:10.11949/j.issn.0438-1157.20171067
    Abstract ( 87 )   PDF (602KB) ( 229 )  
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    Aiming at the shortcomings of the existing calculation model in spray cooling, based on mass, momentum and energy conservation equations, the liquid film flow and heat transfer equations of spray cooling in non-boiling region are established,and magnitude analysis method is applied to simplify equations, and numerical method is used to solve the model. Based on the given values of droplet velocity and temperature, the film thickness, average heat flux and liquid outflow temperature are solved by the model, then the calculated results are compared with the experimental results. The comparison results show that the liquid film thickness difference is less than 6%. The difference of average heat flux and final liquid temperature is less than 10%, and the results that difference less than 5% account for more than 60%. The excellent agreement between simulation and experiment confirms that this model can reasonably reflect flow and heat transfer in spray cooling. The calculated results of film thickness and temperature can deepen the understanding of spray cooling heat transfer mechanism.

    Subsequent development of collided droplets in impinging streams
    DU Min, HUANG Bin, LU Qicheng, GONG Jun, LUO Ming, WANG Zhuliang
    2018, 69(5):  2023-2031.  doi:10.11949/j.issn.0438-1157.20171225
    Abstract ( 85 )   PDF (547KB) ( 183 )  
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    In order to study subsequent development of collided droplets in impinging streams, a high-speed digital camera system, consisting of laser point source and high-speed digital camera, and a gas-liquid two-phase experimental platform was designed. The high-speed digital camera system was used to record droplet coalescence or secondary atomization caused by collisions in coaxially opposite gas-liquid two-phase impinging streams. Images of droplet movement were processed to analyze influence of droplet size, velocity, viscosity, and impact angle on collision outcomes. The results showed that droplets would be busted upon collision with unlimited increase in size and velocity. As surface tension was increased but viscosity and Ohnesorge number were decreased, inlet droplets were more inclined to break. Under experimental conditions, droplets upon collision were coalesced when moved coaxially in the same direction, were stretchily separated when moved in a certain angle, and were reflexively separated or busted moved coaxially in the opposite direction.

    Application analysis of low temperature heat pump heating during heat pump drying
    ZHOU Pengfei, ZHANG Zhentao, ZHANG Xuelai, YANG Luwei, WEI Juan, LIU Pengpeng
    2018, 69(5):  2032-2039.  doi:10.11949/j.issn.0438-1157.20171125
    Abstract ( 97 )   PDF (593KB) ( 130 )  
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    Pointing at the unfavorable conditions and improving the reliability of the drying system, a coupled application scheme of low-temperature heat pump(LTHP) and dry heat pump(DHP) is proposed, according to the principle of two stage compression refrigeration cycle. By using the exergy analysis model, the exergy loss of the heat, the mass diffusion of the drying medium and the dehumidification process were analyzed respectively to the drying system. With the LTHP at 20, 22, 24, 26, 28, 30℃ and closed, the experiment tests and calculates the exhaust temperature and energy consumption of the compressor of DHP, coefficient of performance and the thermodynamic perfect degrees. The drying time and energy consumption of the system were measured when the water content of wood was decreased by 1%, at different heating temperatures. The results show that:compared with shutting down the LTHP, the exhaust temperature of the drying heat pump is reduced by 16℃ at most, and all the performance coefficient of the heat pump is improved. By the increase of the temperature of the machine hall, the irreversibility of the system cycle increases, and the thermodynamic perfect degrees decreases gradually. After opening the LTHP, the maximum amount of heating load and the drying time of the DHP increases by 44% and decreases by 46%, respectively.

    Multi-objective optimization of Rankine cycle using R245fa/pentane based on liquid-vapor separation
    HUANG Renlong, LUO Xianglong, LIANG Zhihui, CHEN Ying
    2018, 69(5):  2040-2048.  doi:10.11949/j.issn.0438-1157.20171182
    Abstract ( 62 )   PDF (698KB) ( 105 )  
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    Organic Rankine cycle (ORC) is considered as a promising heat-to-power technology for low grade heat recovery. The thermal efficiency of ORC is low and investment cost of equipment is high as temperature of heat sources is low. Low thermal efficiency results in high investment cost of equipment. This work focuses on cutting costs and increasing power generation of ORC and proposes a liquid-separation condensation and two-stage evaporation zeotropic ORC system. Multi-objective optimization using NSGA-Ⅱ is conducted for the BORC, DSORC, STORC and TLORC using zeotropic (R245fa/pentane) or pure fluids (R245fa and pentane). The optimization results indicate that:the net power output of BZORC is 5.6% and 14.0% higher than that of R245fa and pentane when using LINMAP method optimization; LINMAP point shows that the net power output of DSORC is 1.2% and 6.3% higher than that of R245fa and pentane, respectively; Among these four cycle configurations, Pareto Front shows the SIC in TLORC using R245fa/pentane is the lowest, about lower by 5.4% than BORC, while the net power output is 4.86% higher than BZORC.

    Performance analysis on R744 direct contact condensation refrigeration cycle
    NING Jinghong, LIU Shengchun
    2018, 69(5):  2049-2056.  doi:10.11949/j.issn.0438-1157.20171246
    Abstract ( 69 )   PDF (472KB) ( 119 )  
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    The performances of R717/R744-DCC refrigeration cycle, the R744 gas discharged from R744 compressor contacts directly with the R744 super-cooled liquid provided auxiliary super cooling by R717 refrigeration cycle, are analyzed. The following conclusions are obtained. The optimum condensing temperatures of R744 main cycle exist in the R717/R744-DCC refrigeration cycle, and at the optimum condensation temperatures, the maximum coefficient of performance and minimum R717 condenser heat load are obtained. With the increasing of super cooling degree of R744 main cycle supercooled liquid, the maximum coefficient of performance reduces, the minimum R717 condenser heat load increases, the condensation temperatures of R744 main cycle increases, and the refrigerant mass flow rate of R744 evaporator decreases. Meanwhile, compared with that of R717/R744 cascade refrigeration cycle, at the same operating conditions and the optimum R744 main cycle condensing temperatures, the maximum coefficient of performance of R717/R744-DCC cycle increases 5.2%, and the minimum R717 condenser heat load reduces 1.6%. Furthermore, in the range of -10-8℃ condensation temperatures of R744 main cycle, the mass flow rate of R744 evaporator of R717/R744-DCC refrigeration cycle reduces 1.75%-2.61%,and the mass flow rate of R717 condenser of R717/R744-DCC refrigeration cycle reduces about 0.51%-0.82%.

    Multiphase reaction model based on bubble structures in bubbling bed
    LIU Cenfan, ZHANG Nan, WANG Wei
    2018, 69(5):  2057-2062.  doi:10.11949/j.issn.0438-1157.20180020
    Abstract ( 109 )   PDF (425KB) ( 64 )  
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    Gas-solid bubbling beds embrace complexity coupled by flow, heat/mass transfer and reactions over a wide range of spatial-temporal scales, which meso-scale flow structure, e.g., bubble, plays a critical role on gas-solid transfer. It is necessary to build meso-scale model on the basis of reasonable physical simplification of real processes, for accurate interpretation of heat/mass/momentum transfer and reaction in gas-solid flow systems. A multi-fluid reaction model from bubble structures was proposed with a consideration of effects of non-uniform meso-scale structure on gas-solid reaction in bubbling bed. Further, the mass transfer and reaction model in the two fluid model (TFM) was modified by a defined heterogeneity reaction index, which made the model easier to use. Model was validated through simulation of ozone catalytic decomposition in bubbling bed, showing good agreement with literature data.

    Catalytic activity and sulfur-resistance stability of Ni-Mo-based catalysts for syngas methanation
    WANG Yuhan, BAI Siyu, CUI Lijie, LIU Jiao, YU Jian, XU Guangwen
    2018, 69(5):  2063-2072.  doi:10.11949/j.issn.0438-1157.20171098
    Abstract ( 114 )   PDF (1004KB) ( 72 )  
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    A series of Ni-Mo-based catalysts, prepared by precipitation-impregnation method, were studied for catalytic activity and sulfur resistance in a fixed bed reactor. Different characterization techniques were carried out to interpret their reaction mechanisms. Compared to catalysts with supports of NaY, γ-Al2O3 and pseudoboehmite (PB), catalyst with MCM-41 support showed superior activity and stability. Characterization on catalysts before and after reaction showed that Ni-Mo interaction plays critical role in catalyst performance. In the catalyst supported with MCM-41, Ni-Mo interaction resulted in appropriate interaction between active species and support. Reduced active Ni was homogeneously dispersed on support surface, which enhanced sulfur-resistance stability and anti-carbon deposition. Different Ni/Mo ratios also affected Ni-Mo interaction in catalysts. It was found that the 20Ni-10Mo/MCM-41 catalysts exhibited the best performance.

    Preparation of modified MgFeMn-HTLcs and catalytic performance in CO hydrogenation
    ZHANG Jianli, WANG Xu, MA Liping, YU Xufei, MA Qingxiang, FAN Subing, ZHAO Tiansheng
    2018, 69(5):  2073-2080.  doi:10.11949/j.issn.0438-1157.20180019
    Abstract ( 69 )   PDF (822KB) ( 53 )  
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    A series of MgFeMn-HTLcs (hydrotalcite-like compounds) precursors with different Mg/Fe/Mn molar ratios were prepared by coprecipitation-hydrothermal method, which were then calcined and modified with K impregnation to be used as catalysts for light olefin synthesis from CO hydrogenation. The catalysts were characterized by XRD, SEM, TG, N2 adsorption-desorption, H2-TPR and XPS techniques. The results showed that MgFeMn-HTLcs precursors had typical layered structures of hydrotalcite and reduced crystallinity by Mn addition. After calcination, MgO was only detected from Mg-Fe precursors whereas Mg2MnO4, MgO and MgFe2O4 were co-existed from Mg-Fe-Mn precursors. After CO hydrogenation, main phases were MgCO3 and FeCO3, accompanied by formation of FeO-MnO and little FexCy. Mn addition further promoted Fe dispersion and increased reduction from Fe2O3 to Fe3O4, compared to those of K/Mg-Fe catalysts. With Mn increase and its electron donating effect, binding energies of Fe 2p were shifted to lower values. In CO hydrogenation, all prepared K/Mg-Fe-Mn catalysts showed high activity and C2=-C4= selectivity. O/P value of 5.20 and C2=-C4= fraction of 43.03% were achieved with low methane selectivity over K/3Mg-1Fe-2Mn catalyst.

    Influence of new outlet configurations with baffle on hydrocycloneon separation performance
    LIU Hongyan, HAN Tianlong, WANG Ya, HUANG Qingshan
    2018, 69(5):  2081-2088.  doi:10.11949/j.issn.0438-1157.20171066
    Abstract ( 132 )   PDF (1276KB) ( 202 )  
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    The influence of new outlet configurations, which are designed with different internal baffles in the vortex finder and the underflow pipe, on the separation performance is investigated experimentally in a small hydrocyclone with a diameter of 50 mm. It is indicated that the vortex finder with internal baffles is suitable for the working conditions of a high throughput. Compared with that of traditional vortex finders, the separation efficiency of vortex finders with internal baffles in the hydrocyclone decreased slightly, but the pressure drop reduced remarkably to 11.11% at high flow rates. Three pieces of narrow and short baffles, which are spaced at regular intervals around the inner wall of the vortex finder, are recommended. It is found that the cross-shaped internal baffles in the underflow pipe can stabilize the inner vortex flow therein, and the separation efficiency can be improved by 5.96%. If the vortex finder and the underflow pipe are designed with the optimized baffles, the separation efficiency can be enhanced and meanwhile the pressure drop can be decreased. In addition, it is observed that the vortex finder with the internal baffles can eliminate the air core inside the hydrocyclone. It is inferred that the air core is not produced by air, but it is a forced swirl vortex with a high turbulence formed in the central zone with a negative gauge pressure.

    Separation of C2H5OH/C4H8O2-3/C4H8O-3 ternary mixture with azeotropes by pressure swing distillation and its parameter optimization
    HUANG Xu, LUO Yiqing, YUAN Xigang
    2018, 69(5):  2089-2099.  doi:10.11949/j.issn.0438-1157.20171668
    Abstract ( 102 )   PDF (717KB) ( 100 )  
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    In this paper, a pressure-swing distillation (PSD) process with two recycle streams for the separation of ternary mixture C2H5OH/C4H8O2-3/C4H8O-3 was proposed. According to the residual curve map (RCM) of the ternary mixture, each of the three pairs of components form a minimum-boiling azeotrope, and the composition of C2H5OH/C4H8O2-3 azeotrope changes significantly with pressure. Moreover, the coexistence of the three azeotropes results in a distillation boundary pinch, across which a practical distillation in normal pressure is impossible, and thus a traditional procedure to develop a PSD may be invalid. In this paper, such a difficulty was overcome by pressure optimization of the columns and a novel separation configuration was developed. Rigorous steady-state simulations of this process were carried out. Under six different pressures of the high-pressure column (column T1), a sequential iterative approach was adopted to optimize the stage numbers, feed stages, reflux ratios and other design variables in order to reduce energy and equipment costs. By comparing the economics of these six processes, the optimal pressure of the T1 column was obtained, and heat integration was applied resulting in 14.9% extra reduction in the total annual cost (TAC) for the optimal process.

    Desulfurized gypsum modification on solid amine adsorbents and CO2 adsorption in flue gas
    XU Jingwen, CHANG Jing, YUAN Fuqi, TIAN Hongjing, GUO Qingjie, WANG Kai
    2018, 69(5):  2100-2109.  doi:10.11949/j.issn.0438-1157.20180017
    Abstract ( 46 )   PDF (1069KB) ( 52 )  
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    Biochar (BC) obtained from durian shell carbonization was mixed with silicium-calcium slag particles as adsorbent carrier material. The mixture of BC and silicium-calcium slag particles was impregnated with pentaethylenehexamine (PEHA) liquid and then mixed with wet flue gas desulfurized gypsum (FGDG) slags to prepare wet amine functionalized CO2 solid adsorbents, which significantly improved adsorption activity than FGDG-free adsorbents. The adsorbents were characterized by FT-IR, TGA, SEM and N2 adsorption-desorption. Effect of FGDG slag content, adsorption temperature and CO2 concentration in flue gas on adsorption performance were studied in a fixed bed reactor. The results showed that moisture presence in FGDG slags changed reaction mechanisms between amino groups and CO2. Adsorbent with 30% FGDG had a maximum adsorption capacity of 2.33 mmol/g at temperature of 85℃ and its adsorption capacity decreased slightly by only 4.2% after 12 cycles of regeneration and reuse, showing a favorable adsorption stability. The isosteric heat of CO2 adsorption calculated with Clausius-Clapeyron equation was found between heats of physical and chemical adsorption, suggesting simultaneous occurrence of physical and chemical interactions in adsorption process. Fitting experimental data with kinetic models showed that pseudo-first-order and pseudo-second-order models did not fit accurately but Avrami model fitted well, which further indicated that CO2 adsorption process on BC/SCS-PEHA-30%FGDG is not a simple physical or chemical adsorption process, but a combination of these two adsorption processes.

    Phase change phenomenon and properties of double spiral groove liquid film seals
    CAO Hengchao, HAO Muming, YANG Wenjing, WANG Yanhong, LI Yongfan, XU Lushuai
    2018, 69(5):  2110-2119.  doi:10.11949/j.issn.0438-1157.20171155
    Abstract ( 56 )   PDF (1246KB) ( 74 )  
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    In order to investigate the influence of phase change on sealing performance, a liquid film seal phase change model has been established by simultaneous N-S equation and mass transport equation, the governing equations are discretized using a finite volume method, the phase change phenomenon of double spiral groove liquid film seal is simulated and the influence of structural parameters on the phase change region and sealing performance is analyzed. The result shows that the physical parameters change when the phase change occurred, and the flow field in the seal clearance and the pressure distribution at the end face changed obviously. The inner spiral groove can provide stable opening force and ensure the sealing end face to be in good lubrication state, but at the same time lead to the seal leakage increased. The sealing leakage can be reduced, and the sealing performance can be improved by reducing the ratio of groove width to face width, the ratio of groove width to dam width, spiral angle, and groove depth of outer spiral groove or increasing the groove number of outer spiral groove.

    Copper corrosion inhibition mechanism by combination of 2-mercaptobenzothiazole and magnetic treatment
    SUN Xuhui, QI Yuan, DONG Shuyu
    2018, 69(5):  2120-2126.  doi:10.11949/j.issn.0438-1157.20171062
    Abstract ( 72 )   PDF (767KB) ( 96 )  
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    In order to investigate whether magnetic treatment and 2-mercaptobenzothiazole (MBT) have synergistic effect on corrosion inhibition, corrosion rate of red copper was measured under different treatment conditions by weight loss method. The treatments included permanent magnetic field, alternative magnetic field, corrosion inhibitor MBT, and combination of MBT and magnetic field. Mechanism of corrosion inhibition was studied with assistance of SEM, XRD and ATR-FTIR. The results showed that permanent magnetic field had little effect on corrosion inhibition, but alternative magnetic field had some improvement on corrosion inhibition by forming compact oxide film on copper surface. Alternative magnetic field reduced water polarity and gave water molecules power and activity, which increased MBT solubility in water and adsorbance on copper surface. Therefore, combination of alternative magnetic field and MBT has synergistic effect on corrosion inhibition. To achieve same corrosion inhibition effect as MBT itself, synergistic effect could decrease MBT usage by 60%. Because MBT is dissolved in NaOH solution, less MBT will reduce alkali consumption and lower conductivity of cooling water in power generator.

    Scale/corrosion inhibition and biodegradation of lysine modified polyaspartic acid
    LIU Xinhua, ZHOU Kun, HAN Jie, CHEN Zhihui, LI Huijuan
    2018, 69(5):  2127-2136.  doi:10.11949/j.issn.0438-1157.20171199
    Abstract ( 78 )   PDF (1004KB) ( 59 )  
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    A poly-aspartic acid derivative (Lys-PASP) was synthesized by ammonia reaction of L-lysine. FTIR characterization of the polymer demonstrated that Lys-PASP contained carboxyl and amide groups. SEM study indicated that adding Lys-PASP changed growth process and morphology of CaCO3 and CaSO4 crystals such that loose and fine calcium scale could be formed, which prevented developing dense-structured calcium scale and achieved a good scale inhibition. The addition of Lys-PASP also caused lattice distortion of calcium scale crystals and inhibited surface pitting corrosion. Besides, a layer of adsorption film on surface by chemical and physical adsorption assisted to achieve a better corrosion inhibition effect. The scale inhibition efficiency of Lys-PASP graft copolymer to CaCO3 and CaSO4 was closely related to Lys-PASP dosage, Ca2+ concentration and system temperature. At 10 mg·L-1Lys-PASP, the CaCO3 scale inhibition efficiency was 98.7% and that of CaSO4 was close to 100%. Lys-PASP exhibited good scale inhibition at temperature 80℃and Ca2+ concentration at 500 mg·L-1 and 7000 mg·L-1. Furthermore, gravimetric study showed that corrosion inhibition efficiency of Lys-PASP is 13% higher than that of PASP when both Lys-PASP and PASP were 150 mg·L-1. Lys-PASP polymer is easily biodegradable per oscillating incubator study.

    Experimental study on thermal demanding and preparation of aromatics of mixed pyrolysis of Nannochloropsis sp./walnut shell
    MIAO Peng, CHANG Guozhang, YAN Ximin, HU Xiude, GUO Qingjie
    2018, 69(5):  2137-2148.  doi:10.11949/j.issn.0438-1157.20171298
    Abstract ( 110 )   PDF (659KB) ( 88 )  
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    In this study, Nannochloropsis sp. (NS) and walnut shell (WS) were used as raw materials for mixed pyrolysis, and the characteristics of thermal demanding during pyrolysis of NS, WS and NS/WS were initially investigated by a thermogravimetric analyzer and a fixed-bed reactor. Then the effects of mass ratio, reaction temperature, and catalysts on the preparation of aromatic hydrocarbons from NS/WS mixed pyrolysis were studied by a GC/MS method. Results showed that the two endothermic peaks were observed from WS pyrolysis at 180-270℃ and 380-485℃, the overall performance of WS pyrolysis took on the endothermic effect with thermal demanding values of 378.56-596.45 kJ·kg-1 under different heating rates. An endothermic peak was obtained from NS pyrolysis at 280-450℃, the overall performance of NS pyrolysis took on exothermic effect with thermal demanding values of -814.76——1191.52 kJ·kg-1. The pyrolysis of NS/WS presented low exothermic effect with thermal demanding values of -99.05——158.04 kJ·kg-1, indicating that the mixed pyrolysis achieved a certain degree of thermal coupling. The mixed pyrolysis of NS/WS demonstrated a synergistic effect in the preparation of aromatic hydrocarbons. The optimum condition for aromatics preparation with a value of 20.51% was achieved at a temperature of 600℃ and a NS/WS mass ratio of 1:1. By introducing Cu/HZSM-5 catalyst, the relative content of aromatics was further improved (35.74%). This study provided a new approach for high-value utilization of NS and WS.

    Microstructure evolution of procedural products during limestone simultaneous calcination/sulfation
    WANG Ziming, CHEN Liang, YUE Shuang, WANG Chunbo
    2018, 69(5):  2149-2157.  doi:10.11949/j.issn.0438-1157.20171167
    Abstract ( 78 )   PDF (671KB) ( 40 )  
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    The calcination kinetics and pore structure evolution of limestone in simultaneous calcination/sulfation was studied by a self-designed constant-temperature thermogravimetric reactor. Sulfation reaction took place to form CaSO4 simultaneously with limestone calcination as long as SO2 gas was present. The presence of SO2 reduced calcination rate of limestone. Compared to pure calcination, simultaneous calcination/sulfation had slower increase in specific surface area and specific pore volume, which both distribution curves were lower, and these two parameters of small pores with 2-8 nm in diameters decreased with time in the final calcination stage. A mechanism was proposed to describe pore microstructure evolution during simultaneous calcination and sulfation, that is, because limestone calcination occurs from surface to inner core, small amount of CaSO4 was formed on CaO surface with few plugged pores and CaSO4 had little effect on calcination rate and pore structure in initial reaction stage (0-75 s), continuous increase of CaSO4 thickness and coverage enlarged both volume of closed pore and CO2 diffusion resistance but declined calcination rate in the middle calcination stage (75-225 s), and further accumulation of CaSO4 accelerated plugging on pores especially smaller ones in the final stage (225-300 s). Calculation of volume of closed pores showed that pore plugging started in initial and middle calcination stages and intensified rapidly in final reaction stage, which validated the proposed mechanism.

    Emission characteristics of sulfurous pollutant from circulating fluidized bed boilers co-firing petroleum coke and coal
    CUI Jian, DUAN Lunbo, ZHAO Changsui
    2018, 69(5):  2158-2165.  doi:10.11949/j.issn.0438-1157.20171180
    Abstract ( 99 )   PDF (657KB) ( 109 )  
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    The emission characteristics and co-removal through air pollution control devices of sulfurous pollutant were conducted at three 410 t·h-1 circulating fluidized bed boilers equipped with in-situ desulfurization + electrostatic precipitator (ESP)/fabric filter (FF) + wet flue gas desulfurization (WFGD). The US EPA Method 8 was used for the sampling of various forms of sulfurous pollutant in flue gas. Concurrent with flue gas sampling, the feed fuel, limestone, bottom ash, fly ash, gypsum and wastewater were sampled. The results showed that particulate-bound sulfur and SO2 are the dominant species in the flue gas at the outlet of boilers, accounting for 48.94%-55.05% and 44.14%-49.07%, respectively. The removal efficiency of particulate-bound sulfur by ESP or FF is more than 95%. About 62.66%-67.82% of SO3/sulfuric acid mist and 53.06%-60.89% of particulate-bound sulfur in flue gas was removed by WFGD, respectively. The majority of sulfur in fuel was migrated into fly ash + bottom ash and gypsum + wastewater, accounting for 56.79%-70.12% and 29.25%-41.70%, respectively. Only 0.63%-1.51% of total output sulfur was emitted into atmosphere.

    Analysis of influencing factors on inhibition of lignite pulverization by liquefaction residue during co-pyrolysis in rotary kiln
    QU Yang, CHU Mo, ZHU Shuquan, ZHANG Chao, HAO Chengliang, XU Fang
    2018, 69(5):  2166-2174.  doi:10.11949/j.issn.0438-1157.20171114
    Abstract ( 89 )   PDF (965KB) ( 97 )  
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    The inhibitory effects of coal direct liquefaction residue (CDLR) on lignite pulverization were studied in a kilo rotary kiln during co-pyrolysis. Different CDLR to lignite quantity and particle size ratios were investigated in the study. The results showed that, with CDLR quantity ratio increased from 10% to 40% at 550℃, the co-pyrolysis char pulverization rate β was decreased from 7.55% to 1.98%, and the granulation rate λ was increased from 2.73% to 4.90%. Increasing CDLR quantity ratio effectively inhibited lignite pulverization and mixing granulation. Mixing 3-1 mm CDLR with 3-1 mm lignite reached the pulverization rate β of 2.82%, which is lower than the pulverization rate when mixing 6-3/13-6/25-13 mm CDLR with the same size lignite. Mixing 3-1 mm CDLR with 3-1 mm lignite reached the granulation rate λ of 24.99%, which was much higher than λ of mixing larger CDLR. Gray relational analysis indicated that the influence of CDLR size ratio on β and λ was greater than quantity ratio. A model of CDLR to lignite size and quantity ratio inhibiting lignite pulverization in rotary kiln during pyrolysis was constructed. The ratio factors affected pyrolysis along with other internal factors including strength of particle capturing, pore structure reinforcing and particle layer crossing behavior.

    Enhanced nitrobenzene removal by persulfate-assisted zerovalent iron
    FAN Peng, CHEN Jie, GUAN Xiaohong, QIAO Junlian
    2018, 69(5):  2175-2182.  doi:10.11949/j.issn.0438-1157.20171065
    Abstract ( 122 )   PDF (990KB) ( 141 )  
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    The removal of nitrobenzene in the zerovalent iron-persulfate (ZVI-PS) system was investigated in this study. During the process of nitrobenzene reduction by pristine ZVI, fast adsorption of nitrobenzene was observed at pHini 3.0 and the removal rate was accelerated with the decrease of initial pH values. The increase of ZVI dosage enhanced the removal effectively and PS added to the system significantly promoted the removal rate of nitrobenzene. The cost of PS added was far less than the increase of counterpart of ZVI dosage to achieve the same removal effect. By XRD characterization of the precipitates after reaction, PS was supposed to enhance nitrobenzene removal by promoting ZVI corrosion and transformation of ZVI corrosion products. By FTIR characterization, it was determined that PS accelerated the nitrobenzene reduction process only, but did not change its reduction pathway. GC-MS results verified that the main product of nitrobenzene reduction by ZVI/ZVI-PS was aniline.

    Crystallization behaviors of molten ash slag under different temperatures and cooling rates
    WANG Da, WANG Qian, ZHANG Jiansheng
    2018, 69(5):  2183-2190.  doi:10.11949/j.issn.0438-1157.20171157
    Abstract ( 179 )   PDF (1642KB) ( 174 )  
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    The single hot thermocouple technique (SHTT) and image analysis program were applied to study synthetic slag's crystallization behaviors under different temperatures and cooling rates. In order to get crystallization mechanism, the crystallization kinetics parameters in isothermal process were calculated. Crystalline phases also were predicted by FactSage. In isothermal process, as temperature decreases, crystallization time decreases at first and increases later, and the crystals get smaller. At the same time, crystallization proportion increases at first, keeps stable later and decreases finally. There is saltation of crystallization proportion because of different crystalline phases at different temperature ranges. With increase of cooling rates, initial crystallization temperature declines and crystal turn from bulks to grains. Crystallization proportion remains unchanged, then decreases. Several stable areas of crystallization proportion appear owing to different crystalline phases under changing cooling rates. There is no crystal when cooling rate is large enough, and slag is totally solidified in glassy state. The heat curve of slag's crystallization measured by DSC fits well with the result of SHTT.

    Silicon distribution in straw black liquor recovery process of pyrolysis and combustion
    YUAN Hongyou, WU Shubin, YIN Xiuli, HUANG Yanqin, LIU Huacai, WANG Guijin, ZHAN Hao, WU Chuangzhi
    2018, 69(5):  2191-2198.  doi:10.11949/j.issn.0438-1157.20171266
    Abstract ( 99 )   PDF (743KB) ( 75 )  
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    Pyrolysis technology is a widely utilized process in biomass energy production, and has potential to serve as an alternative for recovery of straw black liquor. A 10 kg·h-1 stirring type pyrolysis experimental apparatus was employed to prepare black liquor char (BLC) and fuel gas, aiming to analyze the differences of total alkali recovery and silicon distribution between BLC-leached and smelt-dissolved green liquor. The results showed that the total alkali in BLC-leached green liquor was equal to or a bit higher than that of smelt-dissolved green liquor. Around 30% to 40% of silicon retained in BLC-leached carbon powder as forms of insoluble silicates, which were mainly compound silicates of non-process elements such as Al, Ca, Fe and Mn. Because of the retention of a considerable part of silicon in leaching solid phase, the silicon concentration was lower in BLC-leached green liquor than that of smelt-dissolved green liquor, and the ratio of Na2CO3 to Na2SiO3 (or Na4SiO4) decreased to a large extent in the former green liquor compared to the latter. The findings indicate that chemical recovery using pyrolysis-leaching method is beneficial for decreasing the affects of silica problem especially improving the lime causticizing process.

    Ignition characteristics of methane/ethane and methane/propane mixed fuels
    ZHANG Zunhua, XU Li, LIANG Junjie, LI Jingrui, LI Gesheng
    2018, 69(5):  2199-2207.  doi:10.11949/j.issn.0438-1157.20170960
    Abstract ( 112 )   PDF (668KB) ( 123 )  
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    The effects of the mixing of ethane and propane on the ignition delay time of methane were studied through the shock tube and CHEMKIN software.The cause of these effects was analyzed from the perspective of chemical kinetics. The results show that the addition of ethane and propane can shorten the delay time of methane ignition, but this influence becomes smaller along with the increase of temperature. The sensitivity analysis suggests that H + O2=O + OH (R1) promotes ignition most both for the mixture fuels of methane/ethane and methane/propane, and the two elementary reactions of CH4 + H=CH3 + H2 (R128) and CH4 + OH=CH3 + H2O (R129) exert maximum inhibition for the ignition of methane/ethane and methane/propane blends. It is found that the increase of the ratio of ethane and propane in the mixed fuels of methane/ethane and methane/propane has little influence on the main reaction path of methane, but mainly affects the consumption rate of CH3.

    Macromolecular model construction and quantum chemical calculation of Ningdong Hongshiwan coal
    LI Zhuangmei, WANG Yanmei, LI Ping, LI Heping, BAI Hongcun, GUO Qingjie
    2018, 69(5):  2208-2216.  doi:10.11949/j.issn.0438-1157.20180013
    Abstract ( 96 )   PDF (689KB) ( 65 )  
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    Hongshiwan (HSW) coal from Ningdong China was characterized to determine key microstructural parameters of materials, such as elements, valence and chemical bonding, with proximate and ultimate analyses, solid state 13C nuclear magnetic resonance (13C NMR), X ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The results revealed that main structure of HSW coal was 75.96%(mass) aromatic skeleton and 0.315 ratio of aromatic bridge carbon to aromatic peripheral carbon, indicating more naphthalene than benzene and anthracene in coal. Oxygen predominantly presented in the form of ether (C-O), carbonyl (C=O) and carboxyl (-COO), which C-O was accounted for 53.57%. Nitrogen presented in the form of pyridine and pyrrole. Tri-and tetra-substituents were mainly located on benzene ring at 47.77% and 32.97%, respectively. Methyl (-CH3) group was predominant in cyclic and aliphatic hydrocarbons. Thus, coal molecular formula was defined as C221H148O28N2 with molecular weight of 3142.32. Based on these results, macromolecular 2D and 3D model of HSW coal was built with computer-aided modelling. The model was optimized and further verified by FT-IR and 13C NMR spectra simulation by quantum chemical calculations. Therefore, molecular microstructures of HSW coal have been depicted from both experimental and quantum chemical approaches.

    Wet process of elemental mercury removal using Ag@AgCl-BiOCl photocatalyst under fluorescent light irradiation
    LI Chengwei, LU Hao, ZHANG Anchao, XING Weibo, HU Song, XIANG Jun
    2018, 69(5):  2217-2225.  doi:10.11949/j.issn.0438-1157.20171235
    Abstract ( 84 )   PDF (844KB) ( 123 )  
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    A series of Ag@AgCl-BiOCl photocatalysts were synthesized by a coprecipitation-photoreduction method and characterized by N2 adsorption-desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) techniques to understand their physical-chemical structures. The effects of AgCl content, pH value, reaction temperature, SO2 and NO on the activities of elemental mercury (Hg0) removal were carried out in a wet Hg0 bubbling reactor under fluorescent light (FSL) irradiation. The results showed that a much higher Hg0 removal efficiency was obtained when the molar ratio of Ag to Bi was equal to 0.2 in the Ag@AgCl-BiOCl sample. With increasing pH value and reaction temperature, the Hg0 removal efficiency over Ag@AgCl(0.2)-BiOCl under FSL irradiation became gradually worse. Compared with SO2, NO showed a significant inhibitation on Hg0 removal. The mechanism analysis indicated that superoxide radicals (·O2-), holes (h+), hydroxyl radicals (·OH) and chlorine radicals (·Cl) could be reactive species in the photocatalytic process of Hg0 removal, and in particular the ·O2- played key role in Hg0 removal.

    Energy-saving analysis and experimental study of a new heat-source tower solution regeneration system
    WEN Xiantai, CAO Xianqi, YU Pengfei, YU Jiao
    2018, 69(5):  2226-2232.  doi:10.11949/j.issn.0438-1157.20171227
    Abstract ( 72 )   PDF (488KB) ( 86 )  
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    The heat-source tower heat pump system has the problem of solution dilution when it operates in winter. A solution regeneration design of heat-source tower based on vacuum boiling and condensation integration is proposed, and experimental tests are constructed. The results show that:with the increase of solution concentration, regeneration efficiency and regeneration rate have the trend of increasing first and then decreasing later, and have the best data at the ethylene glycol concentration of 26%. With the increase of vacuum value, regeneration efficiency and regeneration rate increase greatly, but the reliability of system can be decreased. With the inlet solution temperature of 36℃, and with electric heater outlet valve open time 12 s, regeneration efficiency and regeneration rate can be reached to the best. In the normal time, regeneration efficiency can be higher than 3.40 kg/(kW·h) and regeneration rate can be higher than 550 kg/d. Compared with traditional solution regeneration, the energy-saving potential is huge.

    Simulation and experimental study on smelter off-gas desulfurization using calcium-based desulfurizer
    CHANG Jing, HU Xiude, TIAN Hongjing, YUAN Fuqi, XU Jingwen, GUO Qingjie
    2018, 69(5):  2233-2241.  doi:10.11949/j.issn.0438-1157.20180048
    Abstract ( 93 )   PDF (791KB) ( 51 )  
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    A method was developed to recover elemental sulfur from smelter off-gas with high SO2 content. Based on thermodynamic simulation of reactions between some sulfides and SO2, calcium sulfide (CaS) was demonstrated to be a novel chemical desulfurizer. SO2 was reduced to elemental sulfur by reacting with CaS in temperature range from 400℃ to 650℃ and direct solid product was CaSO4 rather than CaO. The experimental desulfurization in a fixed bed reactor showed that reaction temperature had a strong effect on SO2 removal efficiency and sulfur recovery ratio. When temperature was increased within the range of 400℃ and 650℃, both SO2 removal efficiency and sulfur recovery ratio were raised gradually. When temperature was higher than 600℃, SO2 removal efficiency was approximately equal to sulfur recovery ratio. Increasing gas velocity reduced SO2 removal efficiency, sulfur recovery ratio, and difference between these two. SO2 removal efficiency remained at 99.8% at SO2 concentration below 1% but dropped sharply to 92.1% at SO2 concentration up to 3.45%. Average SO2 removal efficiency declined gradually when SO2 concentration was continuously increased. With increase of SO2 concentration, sulfur recovery ratio exhibited an optimal range. At late stage of desulfurization, large particle size of CaS decreased SO2 removal efficiency. SEM photos showed that desulfurizer particles agglomerated more obviously at increase of reaction temperature. XRD patterns verified sublimated elemental sulfur particles in the reduction of SO2 by CaS.

    Analysis of synergistic effects of process factors on energy distribution in MFCs
    CHENG Ben'ai, JIA Hui, YANG Guang, LIU Wenbin, ZHANG Hongwei, WANG Jie
    2018, 69(5):  2242-2249.  doi:10.11949/j.issn.0438-1157.20171073
    Abstract ( 54 )   PDF (593KB) ( 45 )  
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    Microbial fuel cell (MFC) is a novel energy conversion device which is able to convert chemical energy into electrical energy. In MFCs, organic matter was degraded in ways of microbial metabolism and bioelectricity conversion. According to the different allocation requirements of energy in the process of operation, the energy flow could be controlled by changing the operation parameters. In this study, MFCs factors, such as pH, organic load, dissolved oxygen, electrical conductance and external resistance, were applied by orthogonal design experiments to optimize parameters for regulation of energy flow. The results showed that the highest efficiency of electric energy conversion was 8.74% and the loads and resistances were significant factors. On the other hand, the highest efficiency of biological metabolism was 66.03% and the load and pH were significant factors. Therefore, when the system was under the same load condition, if the MFC were used as an electrical conversion units, the external resistances should be controlled, while if organic matter conversion capacity was required to be improved, the pH should be controlled.

    Main active substances and useless consumption path of free radicals in Fe (Ⅱ)/H2O2 system during NO oxidation process
    ZHAO Haiqian, LIU Chenghao, ZHOU Wei, WANG Zhonghua, QI Hanbing, GAO Jihui
    2018, 69(5):  2250-2254.  doi:10.11949/j.issn.0438-1157.20171274
    Abstract ( 93 )   PDF (463KB) ( 128 )  
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    Low utilization of H2O2 is a bottleneck in the application of Fe(Ⅱ)/H2O2 oxidation system. Free radicals useless consumption is one of the main reasons for the low utilization of H2O2. In this paper, the effect of H2O2 and various free radicals on oxidation of NO and the useless consumption pathways of the free radicals in Fe(Ⅱ)/H2O2 system were studied based on NO oxidation background. The results showed that the ability of directly oxidize NO by H2O2 was very weak. Although both ·OH and HO2· had the ability to oxidize NO, the oxidation ability of ·OH was greater than that of HO2·. In the process of NO oxidation, the vast majority of ·OH and HO2· was uselessly consumed through the rapid recombination of these two kinds of radicals, which seriously affected the utilization of H2O2. Therefore, simultaneous presence of both ·OH and HO2· radicals should be avoided when Fe(Ⅱ)/H2O2 system was adopted to degrade the pollutants.

    Chitin/polyethyleneimine composite as an adsorbent of aqueous Cr (Ⅵ)
    LIANG Xingtang, ZHONG Shuming, LIU Zijie, ZHENG Yunying, ZHANG Ruirui, JIAO Shufei, LIAO Riquan, WANG Yun, YIN Yanzhen
    2018, 69(5):  2255-2262.  doi:10.11949/j.issn.0438-1157.20171276
    Abstract ( 93 )   PDF (799KB) ( 147 )  
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    The polyethyleneimine (PEI) was homogeneously grafted onto the chitin (CT) with aid of epichlorohydrin to produce CT-based biosorbents (CTP) for removal of Cr(Ⅵ) from water. The structure and morphology of CTP were characterized by FT-IR, XRD, SEM, EDS and Zeta potential. The effects of pH value, contact time, initial Cr(Ⅵ) concentration, treatment temperature and coexisting ions on the Cr(Ⅵ) adsorption were investigated. The results showed that the CTP with a mass ratio of PEI:CT=4:1 (CTP4) presented a maximum adsorption capacity of 330.4 mg·g-1 according to the Langmuir isotherm at 25℃ and pH value 2.0. The adsorption was a spontaneous and endothermal process, which achieved the equilibrium within 60 min and followed the pseudo-second-order kinetic model. After six cycles of adsorption-desorption, the CTP4 remained 89.5% of its original adsorption capacity, suggesting its favorable reusability.

    Amidoxime modified polyacrylonitrile fiber based uranium chelation from wastewater containing uranium in presence of fluoride and chlorine with high concentration
    CHENG Yanxia, DONG Faqin, HE Ping, NIE Xiaoqin, CHENG Wencai, LI Caixia, DING Congcong, HUANG Wenbo, TAN Zhaoyi, XIAO Xiangzhu
    2018, 69(5):  2263-2271.  doi:10.11949/j.issn.0438-1157.20171175
    Abstract ( 128 )   PDF (751KB) ( 159 )  
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    Amidoxime modified polyacrylonitrile fiber (AO-PANF) was prepared by reacting polyacrylonitrile fiber (PANF) as fundamental materials with hydroxylamine hydrochloride. The chelation behavior of AO-PANF to uranium from wastewater containing uranium in the presence of fluoride and chlorine with high concentration was investigated by Scanning Electron Microscopy, Fourier Transform Infrared Spectra and batch adsorption. The results showed that nitrile groups were successfully transformed into amidoxime groups by the amidoximation reaction. The conversion rate of nitrile groups increased with the increasing concentration of hydroxylamine hydrochloride. The adsorption quantity of uranium reached up the largest value when the conversion rate of nitrile group was 22.34%. The adsorption quantity of AO-PANF to uranium increased and then decreased with increasing pH, and the maximum adsorption quantity was obtained at pH 5. The concentrations of both F- and Cl- have little effect on the adsorption quantity of AO-PANF to uranium. The maximum adsorption quantity of AO-PANF (22.34% conversion rate of nitrile groups) to uranium in 100 ml wastewater (100 mg·L-1 initial concentration of uranium) was 19.53 mg·g-1 under the condition of pH 5, 45℃ and 0.40 g adsorbent dose, and the adsorption experiment reached equilibrium after 3 h. AO-PANF adsorbed uranium through chelation between the -NH2 of amidoxime groups and UO2F42- of wastewater. The adsorption process conformed to Freundlich isothermal adsorption model and pseudo-second order kinetic equation. It was shown that AO-PANF can effectively extract uranium from wastewater containing uranium in the presence of fluoride and chlorine with high concentration, and has a promising application prospect.

    Preparation of mesoporous silica modified by zinc (Ⅱ) Schiff base complex and its adsorption and sustained release properties for chlorpyrifos
    ZHOU Hongjun, LIN Yueshun, LI Shujing, XU Hua, CHEN Huayao, ZHOU Xinhua
    2018, 69(5):  2272-2281.  doi:10.11949/j.issn.0438-1157.20171217
    Abstract ( 80 )   PDF (714KB) ( 81 )  
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    Zinc Schiff base modified MCM-41 (Zn-MCM-41) was prepared by co-condensation method, uses 3-aminopropyl triethoxysilane (APTES), salicylaldehyde and zinc ions as modifying agent. The chlorpyrifos/Zn-MCM-41 (CH-Zn-MCM-41) system was prepared by impregnation method, employing chlorpyrifos as a model drug. The structures and distribution form of chlorpyrifos of MCM-41, amino functionalized MCM-41 (NH2-MCM-41), salicylaldehyde Schiff base functionalized MCM-41 (SA-MCM-41) and Zn-MCM-41 were systematically characterized by X-ray diffraction assay(XRD), N2 adsorption-desorption, Fourier transform infrared spectroscopy(FTIR), differential scanning calorimeter(DSC) and X-ray photoelectron spectroscopy(XPS). The adsorption capacity of MCM-41 for chlorpyrifos before and after modification was discussed. The adsorption kinetics, adsorption thermodynamics and sustained release performance of as-synthesized system were also investigated. The results showed that the order structure of NH2-MCM-41 and SA-MCM-41 was still maintained by co-condensation method. After modification of MCM-41, the adsorption capacity of chlorpyrifos increased from 54 mg·g-1 to 186 mg·g-1, an increase of 244% due to the coordination effect between Zn-MCM-41 and chlorpyrifos. The adsorption kinetics and adsorption thermodynamics of MCM-41 on chlorpyrifos before and after modification were in accordance with pseudo-first-order kinetic model and Freundlich model, respectively. The releasing behavior of CH-Zn-MCM-41 could be described by Riger-Peppas equation which indicates that the chlorpyrifos release was controlled by Fick diffusion.

    Shape memory properties of mesogen-jacketed liquid crystalline polymers based on vinylterephthalic acid
    WU Nie, WAN Liying, LI Aimei, XIAO Chunping
    2018, 69(5):  2282-2289.  doi:10.11949/j.issn.0438-1157.20171089
    Abstract ( 90 )   PDF (729KB) ( 176 )  
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    Four kinds of mesogen-jacketed liquid crystalline polymers (PBPCS, PMPCS, PDCHVT, PbiPCS) based on vinylterephthalic acid have been synthesized via free radical polymerization. The results of TGA and DMA demonstrate that they all have good thermal stability, and the higher rigidity of the end group, and the greater rigidity of the corresponding polymer sheet in the temperature range of 30-80℃. Through shape memory angle recovery tests, the results indicate that all mesogen-jacketed liquid crystalline polymer sheets have good shape memory fixation ratios close to 100%. The shape memory recovery effect is related to the end group of polymer side chain. When the end groups of side chain are cyclohexyl and P-butoxy phenyl (corresponding polymers are PBPCS and PDCHVT), the polymer sheets demonstrate good shape memory properties, shape memory recovery ratios are 87% and 100%, respectively. PDCHVT fiber have been prepared by melt spinning, the shape memory properties of PDCHVT fiber have been analyzed by DMA shape memory cycle test, the results show that the fiber exhibits stable and excellent shape memory effect.

    Preparation of TiO2/attapulgite composite photocatalyst by supercritical fluid drying method
    ZHEN Wenyuan, LI Qing
    2018, 69(5):  2290-2298.  doi:10.11949/j.issn.0438-1157.20171153
    Abstract ( 75 )   PDF (934KB) ( 46 )  
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    TiO2/attapulgite nanocomposites were synthesized by the sol-gel method and supercritical fluid drying (SCFD) method using attapulgite as support and the aqueous solution of TiCl4 as raw material. The composition, morphological properties and catalytic performance of catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy(XPS), and nitrogen adsorption-desorption measurements. The results show that there are no phase transformation from anatase to rutile about samples, the specific surface area of materials was increased. The adsorption property of attapulgite is excellent, the quantity of active adsorption sites on the surface of the materials were increased. TiO2 calcined at different temperatures are all anatase, they have smaller particle size and short clavite structure. The photoactivity of the samples under UV light was evaluated by photocatalytic degradation of methylene blue in aqueous solution. The maximum photodegradation rate was obtained in the samples calcined at 400℃, it can reach 98.4% under the irradiation of ultraviolet light for 3 h.

    Preparation of attapulgite/polystyrene hybrid particles via simultaneous reverse and normal initiation atom transfer radical polymerization
    ZHANG Ao, YANG Haicun, MA Wenzhong, LI Yuxue, GONG Fanghong, TAO Guoliang, LIU Chunlin
    2018, 69(5):  2299-2308.  doi:10.11949/j.issn.0438-1157.20171203
    Abstract ( 82 )   PDF (1107KB) ( 68 )  
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    Attapulgite (ATP) hybrid particles were prepared via a simultaneous reverse and normal initiation atom transfer radical polymerization (SR&NI ATRP). ATP was first activated with hydrochloric acid to enhance the surface reactivity, and γ-aminopropyltriethoxysilane (APTES) was chemically bounded on the surface of ATP (ATP-APTES) via dealcoholization reaction. Then, ATP with ATRP initiating groups (ATP-Br) was prepared by amidation reaction between ATP-APTES and α-bromoisobutyryl bromide. Finally, SR&NI ATRP of styrene was conducted using copper bromide (CuBr2) complex tris(2-(dimethylamino)ethyl)amine (Me6-TREN) as the highly active catalytic system, initiated by 2,2-azobis(isobutyronitrile) (AIBN) and ATP-Br as a dual-component initiation system, and hybrid ATP particles grafted with polystyrene (ATP@PS) was obtained. The whole procedure was traced by gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), and X-ray photoelectron electron microscopy (TEM) in detail. The effects of different molar ratio of catalyst on the first-order kinetic behavior were investigated. The experimental results showed that polymerization of styrene under the AIBN-α-bromo amide initiation system and CuBr2/Me6-TREN catalyst displayed the living/controlled nature. As the increase of molar ratio of catalyst, the polymerization was deviated from the first-order kinetic prematurely, and the initiating efficiency was enhanced. When polymerization was performed at 80℃ under the ratio value of [St]/[CuBr2/Me6-TREN]/[AIBN]/[ATP-Br]=200/0.3/0.05/0.5, both of the molecular weight of grafted and free PS were grown in a controlled manner with a lower PDI (<1.54), and the difference of them was increased with conversion increasing. When proceeded SR&NI ATRP with 31.1% monomer conversion, the initiating efficiency was calculated to be 6.3%, and about 1.4 g·g-1 grafting ratio of hybrid particles was achieved. The thickness of grafted layer was attained to about 14 nm. Simultaneously, inhomogeneous distribution was observed, which resulted from the coupling termination between the surface-anchored and free active sites. The dispersion property of ATP@PS in PS matrix was improved obviously.

    Synthesis and characterization of poly (3, 4-ethylenedioxythiophene) aqueous dispersions with low molecular weight poly (sodium styrene sulfonate) as template
    TANG Baokun, LI Jian, REN Qiang, WANG Chenyi
    2018, 69(5):  2309-2317.  doi:10.11949/j.issn.0438-1157.20171044
    Abstract ( 106 )   PDF (700KB) ( 58 )  
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    Poly(sodium styrene sulfonate)s with low molecular weights were synthesized via reversible addition-fragmentation chain transfer polymerization(RAFT). Poly(3,4-ethylenedioxythiophene) aqueous dispersions were prepared with the low molecular weight PSS as the template. The structure and performance of PEDOT:PSS were investigated. The results from 1H nuclear magnetic resonance(1H NMR) showed that the PSS with molecular weight of 3900, 4900, 9600 and 18300 were successfully synthesized. Fluorescence spectrometry measurements showed that low molecular weight PSS prepared via RAFT can form micelles in water, and the critical micelle concentrations(cmc) were around 10-6g·ml-1. Four probe surface resistance tests showed that the conductivity of the PEDOT film were greatly improved when the low molecular weight poly (sodium styrene sulfonate) was used as the template, and the highest the conductivity of the PEDOT film was about 3 times of that of PEDOT film in which poly(sodium styrene sulfonate) produced via conventional free radical polymerization was used as the template. UV-vis spectra results illustrated that the transparency of PEDOT:PSS films decreased with the decrease of molecular weight of poly(sodium styrene sulfonate), and this is mainly due to the phase separation between the RAFT reagent segment and PEDOT:PSS. Thermal stability test showed that the low molecular weight PSS has no obvious effect on the thermal stability of PEDOT.

    Effects of carbon nanotubes mats structure on rejection performance of composite membranes
    ZHOU Feng, HUANG Huimin, QIAN Feiyue, SHEN Yaoliang, ZHOU Xiaoji, LI Xin, XIA Xue
    2018, 69(5):  2318-2326.  doi:10.11949/j.issn.0438-1157.20171317
    Abstract ( 100 )   PDF (2196KB) ( 188 )  
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    A novel composite membrane was prepared by loading multiwalled carbon nanotubes (MWCNTs) on the surface of existing aluminum oxide micro-filtration (MF) membrane using filtration-coating method. The effects of both loading dosages and dimensional sizes of MWCNTs on the surface mats structure were investigated, while the responses to the rejection performance of composite membranes were also established for improving the conventional MF process. The results showed that the effective dispersion of MWCNTs could be achieved by combining large molecular surfactant and ultrasonic technology, which was beneficial to form homogeneous carbon nanotubes mats on the surface of MF membranes. For the same type of MWCNTs, increasing MWCNTs loading dosage would have no significant effects on the pore size distribution and specific filtration resistance (rc) of carbon nanotubes mats. When the MWCNTs with low length-diameter (L/D) ratio was used, the smaller pore size on the surface mats resulted in the decrease of membranes permeability. On the contrary, a highly twining and fluffy mat structure was observed with the high L/D ratio of MWCNTs, corresponding to the lowest value of rc. In addition, the positive correlations between the rejection of composite membranes for small molecular fluvic acid and both loading dosages and specific surface area of MWCNTs were found, which was also related to the mats compactness based on the main mechanism of adsorption.

    Effects of obstacle position and gas concentration on gasoline-air explosion venting
    LI Guoqing, DU Yang, QI Sheng, WANG Shimao, ZHANG Peili, WEI Shihao, LI Meng
    2018, 69(5):  2327-2336.  doi:10.11949/j.issn.0438-1157.20171184
    Abstract ( 106 )   PDF (2099KB) ( 95 )  
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    To investigate the effect of obstacle position and oil-gas concentration on characteristics of gasoline-air mixture explosion, a series of contrast experiments were conducted under the condition of three different initial gasoline vapor concentrations (1.3%, 1.7% and 2.1%) and different obstacle positions. The main observed results are:(1) Three typical peak values are observed in gasoline-air mixture explosion. The peak value of pressure relief pv is independent of obstacle position, while the maximum absolute value of negative pressure peak pneg is obtained when the dimensionless distance between the obstacle and the igniter head Li/L=0.4. In the condition of 2.1% concentration, the peak value of maximum overpressure pmax is obtained at Li/L=0.4, while under the condition of 1.3% concentration, it is obtained at Li/L=0.6. (2) The maximum values of average pressure boost rate (dp/dt)ave, index of explosive power Emax, maximum pressure boost rate (dp/dt)max and maximum explosion index Kmax are all obtained at Li/L=0.4 under the condition of three initial concentrations. (3) During the initial flame propagation process, it presents a “finger-like” shape, while after disturbance by obstacles, the flame fronts produce irregular deformations, a mushroom like flame is formed outside the pipe. When Li/L=0.2, mushroom like flames are most pronounced. (4) The maximum flame propagation velocity Sfmax is obtained at Li/L=0.2 which monotonously decreases with the increase of Li/L from 0.2 to 0.8. Above observation results show that both location of obstacles and initial oil gas concentration have an influence on the characteristic parameters of the gas explosion in the pipeline with built-in obstacles.