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Table of Content
05 December 2018, Volume 69 Issue 12
    Chemical looping technology for clean and highly efficient coal processes
    SHI Xiaofei, YANG Siyu, QIAN Yu
    2018, 69(12):  4931-4946.  doi:10.11949/j.issn.0438-1157.20180436
    Abstract ( 725 )   PDF (778KB) ( 463 )  
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    Chemical looping process is characteristic of a reaction loop consisting of several sub-reactions through the reaction and regeneration of looping materials, to realize efficient conversion of resources and low consumption of product separation. Used in clean coal utilization, chemical looping process may reduce exergy loss, achieve low CO2 capture consumption and suppress NOx production. It has great potential for oxygen production, hydrogen production, power generation, and chemical production processes. As the research progresses further, chemical looping technology will likely become an innovative technology with distinctive features in coal clean utilization.

    Photo-thermal synergistic catalysis for VOCs purification: current status and future perspectives
    RUI Zebao, YANG Xiaoqing, CHEN Junfei, JI Hongbing
    2018, 69(12):  4947-4958.  doi:10.11949/j.issn.0438-1157.20180520
    Abstract ( 552 )   PDF (780KB) ( 369 )  
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    Volatile organic compounds (VOCs) are an important class of air pollutants. Catalytic oxidation technology can convert VOCs into non-toxic CO2 and H2O, which is one of the effective treatment methods. In consideration with the high energy consumption of the traditional thermal catalysis and the low efficiency of the photocatalysis during the purification of VOCs, the coupling of photo catalysis and thermal catalysis for VOCs purification has received intense attention. The superior VOCs degradation performance by photo-thermal synergistic catalysis over the single thermal catalytic or photo catalytic process has been demonstrated. This work reviews the latest progress in the field of catalytic VOCs oxidation by photo-thermal synergistic catalysis with a special attention to the understanding of the synergetic mechanism and design of photo-thermal catalytic materials, including noble metal based and metal oxides based catalysts. Finally, future perspectives of photo-thermal catalytic technology for environmental application are provided.

    Effect of MgO and SiO2 nanoparticles on specific heat capacity of binary carbonate eutectic
    XIONG Yaxuan, WANG Zhenyu, XU Peng, WU Yuting, DING Yulong, MA Chongfang
    2018, 69(12):  4959-4965.  doi:10.11949/j.issn.0438-1157.20180564
    Abstract ( 394 )   PDF (1006KB) ( 164 )  
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    As a new type of heat storage and heat transfer medium, molten salt has been widely used in concentrating solar power (CSP) system due to its wide working temperature range, relatively high specific and strong heat storage capacity. Increasing the specific heat capacity of the molten salt can significantly increase its heat storage density. Nanofluids were synthesized by dispersing 20 nm SiO2 and MgO particles to binary carbonate eutectic (Li2CO3 and K2CO3). The specific heat capacity effect of nanoparticles on molten salt was characterized by DSC measurement. Results show that mass fraction of 20 nm nanoparticles significantly enhanced the specific heat of binary carbonate eutectic. Compared with the base salt, the average specific heat improved with 20 nm MgO and SiO2 nanoparticles was found to be 27.5%-34.1%, 11%-20.7%, respectively. The change rate of the specific heat values of the two nanofluids is lower than 4.31% after multiple solid-liquid cycles. The molten salt nanofluids showed good thermal stability. The microstructure of nanofluids was characterized by scanning electron microscopy (SEM). The images of nanofluids in solid state showed that special nanostructures were formed on the surface of molten salts.

    Numerical study of multi-pulsed cryogen spray cooling for laser lipolysis
    XIN Hui, CHEN Bin, ZHOU Zhifu, TIAN Jiameng
    2018, 69(12):  4966-4971.  doi:10.11949/j.issn.0438-1157.20180781
    Abstract ( 384 )   PDF (469KB) ( 154 )  
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    Noninvasive or minimally invasive laser lipolysis has great potential to reduce obesity, but the absorption of near infrared laser by water may cause thermal damage of dermis. At present, there is no effective cooling method to protect normal skin tissue from thermal injury, which restricts the development of laser lipolysis. A novel multi-pulsed cryogen spray cooling for laser lipolysis was proposed to protect epidermis and dermis. Numerical simulation based on multi-layer uniform skin tissue model and Pennes biological heat transfer equation was conducted to investigate the cooling effect of continuous and multi-pulsed R134a cryogen spray cooling. It was found that continuous spray cannot meet the requirement of laser lipolysis both in temperature and skin depth. Under the same accumulative spray time, the cooling depth of multi-pulsed spray is greater than that of continuous spray. The lowest temperature at 1 mm below skin surface after multi-pulsed cryogen spray can reach to 11℃ with pulse width of 10 ms, interval time of 2500 ms, spray times of 10 and duty cycle of 0.004, and the simulation cooling depth achieves 5000 μm, which can satisfy the cooling depth requirement of laser lipolysis.

    Experimental investigation on FDB starting point in three-side heating narrow rectangular channel
    ZHOU Yunlong, GUO Xintian, ZHANG Wenchao, CHEN Xu
    2018, 69(12):  4972-4978.  doi:10.11949/j.issn.0438-1157.20180475
    Abstract ( 293 )   PDF (580KB) ( 80 )  
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    The deionized water was used as the experimental medium, and the fully developed boiling (FDB) starting point of the three-sided heated narrow rectangular channel with a section of 3 mm×43 mm was studied. The influence of some thermal parameters on FDB starting point is analyzed. Empirical correlation of FDB's heat flux suitable for the three-side heating narrow rectangular channel was obtained by nonlinear regression analysis for experimental data of FDB starting location. The results show that the new empirical correlation can accurately predict heat flux of FDB in the three-side heating narrow rectangular channel. The relative error of predicting value is 15.17%. Besides, the simulation results of new empirical correlation are compared with some existing experimental data. The experimental data obtained from one-side heating narrow rectangular channel are in fairly agreement with new empirical correlation. This shows that new empirical correlation is well suited for one-side heating narrow rectangular channel.

    Flow boiling heat transfer and pressure drop characteristics in micro channel with micro pin fins
    DU Baozhou, LI Huijun, GUO Baocang, KONG Lingjian, LIU Zhigang
    2018, 69(12):  4979-4989.  doi:10.11949/j.issn.0438-1157.20180583
    Abstract ( 304 )   PDF (901KB) ( 382 )  
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    To explore the flow boiling heat transfer mechanism in the micro-rib array channel with different cross-sections, the deionized water is used as the working medium, the mass flow rate is 96-224 kg·m-2·s-1, and the effective heat flux density is 10-240 W·cm-2. The instability of flow boiling in microchannel was also analyzed in the experiment. The experimental results showed that the dominant heat transfer mechanism is nucleate boiling in the low heat flux region, while it is convective heat transfer of a thin liquid film evaporation in the medium and high heat flux regions. With the increase of heat flux and outlet quality, the boiling heat transfer coefficient decreases, but the two-phase pressure drop increases. The secondary channel width between the micro pin fins has a great influence on the heat transfer and the two-phase pressure drop. The wider the secondary channel is, the easier the bubble is to break out, the better the heat transfer effect, and the greater the pressure drop. The existence of micro fin inhibits the reverse flow of bubbles, which reduces the flow boiling instability and delays the occurrence of critical heat flux. The flow boiling stability of the elliptical micro pin fins is the best, while the flow boiling stability of the circular micro pin fins is the worst.

    Influence of channel height on resistance characteristics in triangular grooved channel by pulsating flow
    HUANG Qi, SI Chao, ZHAO Chuangyao, ZHONG Yingjie
    2018, 69(12):  4990-5000.  doi:10.11949/j.issn.0438-1157.20180473
    Abstract ( 285 )   PDF (798KB) ( 152 )  
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    The flow resistance characteristics of the pulsating flow in the triangular channel with different plate spacings were studied with water as the working fluid. Based on the force balance equation, a mathematical model suitable for the pulsating flow pressure drop of the triangular channel is established to theoretically analyze the influencing factors of the flow resistance. Mathematical model shows that flow resistance is mainly affected by channel height and enstrophy. Flow resistance increases as channel height reduces, but increases with enstrophy. In addition, experiment and numerical research have been conducted to investigate correlation among channel height, enstrophy and flow resistance. The experimental results show that flow resistance becomes large as the channel height becomes short. What's more, when the ratio of channel height and groove depth is less than 1.0, the sharp rise of flow resistance occurs. And flow resistance increases ten fold compared with the state that the ratio of channel height and groove depth is more than 1.0. Otherwise, no matter how the channel height changes, resistance also increases with pulsating amplitude, and there exists a Womersley number for the highest flow resistance. The numerical results indicate that the reason why flow resistance changes dramatically as the channel height decreases is because flow field changes with the channel height. When the ratio of channel height and groove depth is more than 1.0, vortex is mainly located inside the triangle groove. Thus the wall of mainstream can be rarely affected. However, when the ratio of channel height and groove depth is less than 1.0, vortex in the triangle groove expands and gradually affects the area of mainstream. Hence the flow separation occurs near the wall of mainstream, which causes wave flow and eddy coexisting.

    Inverse modeling of EGS heat reservoir based on micro-seismic data and analysis of its heat recovery performance
    LI Tingliang, HUANG Wenbo, CAO Wenjiong, JIANG Fangming
    2018, 69(12):  5001-5010.  doi:10.11949/j.issn.0438-1157.20180769
    Abstract ( 227 )   PDF (1246KB) ( 112 )  
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    The characteristics of artificial heat reservoir have a decisive influence on the performance of enhanced geothermal systems (EGS). Accurately modeling of the structural characteristics of artificial heat reservoir is of great significance to the actual engineering of EGS. In this paper, we combine Habanero EGS geological information, micro-seismic data and other information, and reconstruct the spatial distribution of heat reservoir permeability and porosity. Based on the reconstructed heat reservoir, with an in-house three-dimensional dynamic simulation software developed previously, we further simulate the EGS heat extraction process and obtain the seepage field, temperature field and EGS heat extraction curve. When the fluid circulation rate is 15 kg/s, the production temperature of EGS with heterogeneous heat reservoir is 9.3℃ lower than that of the EGS with regional-homogeneous reservoir after 15 years of operation, and the total extracted heat of the former is 3.7% lower than that of the latter. These results reveal that the heterogeneity of the heat reservoir causes a significant decrease in the heat extraction performance of EGS.

    Numerical analysis of hollow oil droplet impact on rectangular groove surface
    ZHOU Jianhong, TONG Baohong, WANG Wei, LIU Kun, SU Jialei
    2018, 69(12):  5011-5023.  doi:10.11949/j.issn.0438-1157.20180620
    Abstract ( 275 )   PDF (4068KB) ( 159 )  
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    The behavior of the hollow oil droplets impinging on the rough surface often take place in the oil-gas lubricating system, which will affect the quality of the oil film formation on the surface of the friction pairs. The coupled level set and volume-of-fraction (CLSVOF) method is used to simulate this behavior. The formation mechanism of the central jet and the distribution of air entrainment are analyzed. And the effects of grooved width, grooved depth and impact position on the oil droplet spreading process are investigated. The results show that the central jet and air entrainment can be formed after the hollow oil droplet rectangular groove surface. The formation of the central jet originates from the velocity vortex at the bottom of impacting on the bubble. The position of air entrainment in the grooves is influenced by the spreading velocity of the hollow oil droplet. When the dimensionless grooved width Ag is less than 0.2 or equal to 0.4, the spreading coefficient of vertical grooves Dx of the hollow oil droplet is approximately same. However, when the dimensionless grooved width is equal to 0.3, the spreading coefficient of vertical grooves Dx increases rapidly in the later period of movement due to the formation of a neck jet on the grooved surface. In addition, the spreading coefficient of parallel grooves Dz increases with the increase of grooved width. The spreading height coefficient Dy of the oil droplet is consistent on each surface and is not affected by the grooved width. When the dimensionless grooved depth Hg ≤ 0.2, the spreading coefficient of vertical groove Dx decreases with the depth of groove increasing. When the dimensionless grooved depth Hg>0.2, the spreading coefficient of vertical grooves Dx is almost equal. However, with the increase of grooved depth, the spreading coefficient of parallel grooves Dz is decreased. The spreading height coefficient Dy of the hollow oil droplet decreases with the increase of the grooved depth, and the increase of the grooved depth can prevent the formation of the central jet. The effects of the impact position on the distribution of air entrainment are significant, while the movement of hollow oil droplet plays a negligible role in them.

    Resistance characteristics of supercritical CO2 in circular tube
    WU Xinming, ZHU Bingguo, ZHANG Liang, SUN Enhui, ZHANG Haisong, XU Jinliang
    2018, 69(12):  5024-5033.  doi:10.11949/j.issn.0438-1157.20180264
    Abstract ( 476 )   PDF (784KB) ( 192 )  
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    An experimental investigation of the pressure drop and friction factor of supercritical CO2 in circular tube is presented. Experimental length and inner diameter of the circular tube are 2000 mm and 10 mm. The experimental pressure ranges from 8 MPa to 16 MPa, mass flux ranges from 1000 kg·m-2·s-1 to 1525 kg·m-2·s-1, and heat flux on the inner wall ranges from 96.5 kW·m-2 to 283.2 kW·m-2. The variation of flow resistance was obtained and the effects of pressure, mass flux, heat flux and bulk fluid enthalpy on the frictional flow resistance coefficient of the circular tube were analyzed. The results showed that the frictional pressure drop increases significantly with increasing mass flux and pressure, particularly when the bulk enthalpy surpasses the pseudo-critical enthalpy, increased speed has become more intense, and meanwhile, it is found that the influence of heat flux on the friction pressure drop is not too great. The assessment of correlations demonstrated that constant-property-based correlations fail to predict the friction factor of supercritical CO2. Therefore, a new empirical correlation is proposed, and the experimental data accounts for 83.31% within the ±20% error band.

    Ash deposition characteristics of external surface of flue gas swept across tube bundles
    PENG Yan, ZHAO Qinxin, WANG Weishu
    2018, 69(12):  5034-5041.  doi:10.11949/j.issn.0438-1157.20180498
    Abstract ( 388 )   PDF (836KB) ( 78 )  
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    The problem of high exhaust temperature universally exists around the industrial boilers, which causes waste of energy. The surface of flue gas heat exchanger is easily to produce ash. To develop an efficient heat transfer element with self-cleaning function and extended heating surface, calcareous dust has the characteristic of high concentration. The characteristics of the physical, chemical and external working process of exhaust dust are studied. The physical and chemical properties of the particle size distribution, appearance and chemical composition of the ash are studied by using scanning electron microscopy, XRD and other instruments. Experimental research on the properties of heat transfer elements is carried out. The results indicated that the surface of lime dust ash have many holes with different sizes, and the particle structure is compact, it is easily to produce physical deposition to form loose ash. The increase of ash concentration will increase the amount of ash accumulation. The higher the ash concentration in the same time, the larger the ash content, and the sleek surface is more likely to be produced. When the flow velocity of flue gas is large, the amount of ash accumulation is quickly stable, and the increase of gas flow velocity will lead to the decrease of ash content in the windward area and the increase of the ash amount of the leeward area. There is the best flue gas flow velocity makes the minimum deposition of fly ash particles on the surface of the pipe. Increasing the lateral pitch and reducing the longitudinal pitch are beneficial to reduce the ash content.

    Mixing enhancement technique for laminar flow in stirred tank
    LIU Hailong, CAO Yu, DING Xuechong, MAO Baodong, WANG Yuerou, WANG Junfeng
    2018, 69(12):  5042-5048.  doi:10.11949/j.issn.0438-1157.20180552
    Abstract ( 388 )   PDF (1618KB) ( 157 )  
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    Mixing technology has a wide range of applications in chemical production, pharmaceutical and environmental protection. The mixing efficiency and flow field distribution are important indicators for measuring the quality of the mixing. However, in the laminar agitated flow field, the periodic disturbance of the agitating paddle creates an annular dynamic flow field resulting in the existence of a mixed isolation zone in the agitation tank. The existence of the isolation zone is the main obstacle to achieving efficient mixing. In this study, a planar laser induced fluorescence (PLIF) technology was employed to visualize the dynamic structure of mixing flow field. The post-image processing has been done with MATLAB and the custom-made functions was designed to evaluate the mixing efficiency. The effects of Reynolds number and the geometrical parameter of the stirred tank on the flow features were studied. The results show that the non-mixing zone always appears regardless of the mixing time, and it will not be broken down as the increase of Re in laminar mixing region. Different baffles are designed to destroy the symmetry of the flow field and thus substantial is increased the mixing efficiency. The results show that non-mixed regions of annular flow field can be almost completely removed if the baffle (ring baffles and cuboid baffles) structures are embedded in the specific position, and the mixing efficiency increased from 65% to 97% in 200 s.

    Radial differential pressure used in multiphase flow metering based on phase-isolation
    WANG Shuai, WANG Dong, DONG Baoguang, LI Ruihua
    2018, 69(12):  5049-5055.  doi:10.11949/j.issn.0438-1157.20180493
    Abstract ( 303 )   PDF (788KB) ( 174 )  
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    The phase-isolation technology of multiphase flow in-pipe is widely used in scientific research and engineering area. Based on the application of the phase-isolation technology on single-phase flow measurement, the mechanism of radial differential pressure used in multiphase flow measurement was studied by taking oil-water two-phase flow as an example, and the experimental verification was carried out. The theoretical analysis showed that the radial differential pressure between the pipe wall and pipe center of a cross section downstream of the swirler has a functional relationship between the mass flowrate and oil cut. Once measuring the radial differential pressure between the pipe wall and pipe center of a cross section downstream of the swirler, the mass flowrate and oil cut can be determined if either of the two parameters was known. The experimental results showed that the relative error of oil cut was less than 8.02% for the cross section of 0.075 m or 0.115 m downstream of the swirler, and mass flowrate was less than 1.44%, which provides a theoretical basis for further study of the two-parameter measurement of multiphase flow.

    Analysis and prediction of heat transfer deterioration of aviation kerosene under supercritical pressures
    WANG Yanhong, LI Sufen, ZHAO Xinghai
    2018, 69(12):  5056-5064.  doi:10.11949/j.issn.0438-1157.20180250
    Abstract ( 356 )   PDF (702KB) ( 154 )  
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    Experimental study on heat transfer deterioration of aviation kerosene in a vertical upward circular tube at supercritical pressures was conducted. The influence mechanisms of buoyancy and thermal acceleration on heat transfer were investigated. Based on the applicability analysis of determination criteria, the factors team which can better reflect the heat transfer deterioration were selected, and the reasonable critical values were obtained, thus the determination criteria for aviation kerosene was proposed. The prediction formula of critical heat flux of heat transfer deterioration was established based on the controllable parameters. The process of thermo-acoustic flow instability owing to heat transfer deterioration was analyzed. The heat transfer correlation was developed by the amendments of buoyancy and thermal acceleration factors. Results indicate that when the buoyancy factor Bu and the thermal acceleration factor Ac are higher than 1.57×10-5 and 4.92×10-6, respectively, the heat transfer deterioration appears due to the weakened shearing stress in the boundary layer. The quasi-boiling is also the reason for heat transfer deterioration and thermo-acoustic flow instability.

    Flow pattern recognition method of gas-liquid two-phase flow based on adaptive optimal kernel and convolution neural network
    WENG Runying, SUN Bin, ZHAO Yuxiao, ZHANG Jingyue, WEN Yingjie
    2018, 69(12):  5065-5072.  doi:10.11949/j.issn.0438-1157.20180198
    Abstract ( 364 )   PDF (2738KB) ( 229 )  
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    To study the dynamic characteristics of gas-liquid two-phase flow, and to solve the traditional problem that the eigenvalues extracted are so few that is not representative and result in low recognition rate, V-cone flow-meter and dynamic differential pressure sensor were used to obtain fluctuating signals of gas-liquid two-phase flow in different flow patterns, time-frequency analysis of obtained dynamic signals were performed by adaptive optimal kernel(AOK) algorithm, to convert the one-dimensional time-domain signals to three-dimensional time-frequency spectra so as to describe clearly the flow status of gas-liquid two-phase flow in the pipeline. Time-frequency spectra of different flow patterns were learned by the convolution neural network (CNN) to extract the corresponding eigenvalue automatically, then were practiced by Softmax classifier to achieve flow pattern recognition. By experiment and analysis for several common flow patterns, adopting time-frequency spectrum and deep learning method of convolution neural network was found to identify the gas-liquid two-phase flow pattern can overcome the shortcomings of the traditional flow pattern recognition method for few eigenvalue extracted, and describe appropriately the dynamic characteristics of gas-liquid two-phase flow. This method allows further investigation of more types of flow patterns as well as porosity and more.

    Unsteady engulfment flow regime in T-jets reactor
    XU Xinlei, YAN Jiawei, ZHANG Wei, LI Weifeng, ZHANG Jingwei, LIU Haifeng, WANG Fuchen
    2018, 69(12):  5073-5080.  doi:10.11949/j.issn.0438-1157.20180464
    Abstract ( 262 )   PDF (1622KB) ( 200 )  
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    Flow regimes in the T-jets reactor were studied by planar laser induced fluorescence (PLIF) technique and large-eddy simulation (LES). It was found that four different flow regimes, the separated flow (Re<120), steady engulfment flow (120 ≤ Re<190), unsteady engulfment flow (190 ≤ Re ≤ 300) and unsteady symmetric flow (Re>300) displayed in turns with the increase of Reynolds number. In particular, the characteristics of unsteady engulfment regime were investigated by LES. The results showed that eddies periodically merged in the impingement plan and the subsequent merged eddies passed through the chamber which caused self-sustained oscillation in the reactor. The pressure, velocity and vorticity in the impact zone also varied periodically, and the periods were consistent with that of eddy merging in unsteady engulfment regime. This oscillation of eddy merging and propagation is caused by the periodic variation of velocity and pressure in the impingement plane.

    Interaction between CeO2 and ZrO2 in HCl catalytic oxidation
    FEI Zhaoyang, LI Lei, CHENG Chao, LOU Jiawei, TANG Jihai, CHEN Xian, CUI Mifen, QIAO Xu
    2018, 69(12):  5081-5089.  doi:10.11949/j.issn.0438-1157.20180443
    Abstract ( 304 )   PDF (1192KB) ( 95 )  
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    ZrO2/CeO2 (xZr/Ce) and CeO2/ZrO2 (yCe/Zr) catalysts with different loading were prepared by wet impregnation method. XRD, Raman, N2-Sorption, TEM and H2-TPR were used to study the interaction between CeO2 and ZrO2 in the recycling of Cl2 from HCl oxidation. The results showed that the doping appropriate amount of zirconium species on the surface of CeO2 could increase the concentration of oxygen vacancy over xZr/Ce, which was in favor of enhancing the activity of HCl oxidation. When there were too many Zr4+ doping on the surface of CeO2, a part of Zr elements would be presented as ZrO2 over the surface of xZr/Ce and the oxygen vacancy was covered, which was unfavorable to the activity of HCl oxidation. For yCe/Zr catalyst, the dispersive CeO2 over ZrO2 was beneficial to the improvement of the catalytic activity, but the increase of catalytic activity would slow down when the loading of CeO2 exceed 10%. By comparing xZr/Ce with yCe/Zr catalysts, the oxygen vacancy of xZr/Ce was mainly formed by Ce-Zr solid solution, while the oxygen vacancy of yCe/Zr was formed by highly dispersive CeO2. It was found that the oxygen vacancy produced by different structure have different effects on the activity. The oxygen vacancies produced by Ce-Zr solid solution are more favorable to the activity enhancement. The ability of chlorine resistance of xZr/Ce and yCe/Zr catalysts behaved a superior stability in the long-term test compared to pure CeO2.

    Preparation and catalytic degradation property research of novel phthalocyanine
    YOU Donghui, CHENG Zhiliang, LI Gan, ZHANG Feng, LYU Fanglei, JIANG Guangbin, QUAN Xuejun, WEI Jianwei, YANG Lu, LI Shuo
    2018, 69(12):  5090-5099.  doi:10.11949/j.issn.0438-1157.20180407
    Abstract ( 350 )   PDF (985KB) ( 113 )  
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    Large scale degradation of dye wastewater under neutral conditions is one of key difficulties in dye wastewater disposal. A novel hydroxyl-substituted cobalt phthalocyanine (CoTHPc) catalyst was synthesized and characterized by NMR and high resolution mass spectrometry. The binding energies of CoTHPc and amino phthalocyanine cobalt compund (CoTAPc) with acid red G (AR1) were simulated by Siesta software. The results showed that the adsorption capacity of CoTHPc with AR1 was better than that of CoTAPc under neutral conditions. The binding ability of CoTAPc to AR1 is greatly enhanced within the existence of hydroxide radical. The effects on the performances of the CoTHPc/H2O2 and CoTAPc/H2O2 systems by different pH, temperature, oxidant concentration and isopropanol were investigated as well as the degradation mechanism. The results showed that the optimal catalytic conditions for CoTHPc were pH=7.0, T=343 K, and 20 mmol/(L H2O2), and the optimal catalytic conditions for CoTAPc were pH=10, T=354 K, and 50 mmol/(L H2O2). The results also released that isopropanol as a free radical inhibitor does not stop or inhibit the catalytic oxidation reaction, so both CoThPc/H2O2 and CoTAPc/H2O2 systems are non-hydroxyl radical mechanisms. In summary, the CoTHPc/H2O2 catalytic system is one of feasible solutions for the degradation of complex dye wastewater under neutral conditions and has a great application prospect for complex printing and dyeing wastewater.

    Screening ionic liquids solvent for separation of oil and hydroxybenzene mixtures based on COSMO-RS model
    LIU Qian, ZHANG Xianglan, LI Wei
    2018, 69(12):  5100-5111.  doi:10.11949/j.issn.0438-1157.20180621
    Abstract ( 311 )   PDF (707KB) ( 185 )  
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    Phenolic compounds separation of low temperature coal tar (LTCT) is important for its effective utilization. Based on the COSMO-RS model, with m-cresol and cumene as model compounds, ionic liquids were used as extractants for the separation of the oil and phenol system. A s-profile database including 27 anions and 48 cations were established by Turbomole, screening the 1296 ionic liquids by COSMOtherm, the influences of cations and anions on the separation of the m-cresol and cumene were investigated and some of them were verified by liquid-liquid equilibrium (LLE) data of ternary system, which indicated that the selection method of ionic liquid solvents was effective. The results show that the influences of the anions on the separation were more than those of the cations, some ionic liquids were effective on separation, which contained Cl- or CH3COO- in anions, because of the stronger hydrogen bond interaction between these ILs and m-cresol. The increase of length of alkyl chain and the number of side chains could improve the separation effect of ionic liquid to m-cresol. The liquid-liquid equilibrium data of ternary system of bmimOAc-m-cresol-cumene, bmimCl-m-cresol-cumene, emimOAc-m-cresol-cumene and TPAC-m-cresol-cumene by experiment show that the four kinds of ionic liquids had greater distribution coefficient and selectivity for m-cresol, and the order of extraction separation effect was:emimOAc>bmimOAc> TPAC>bmimCl, which is consistent with the results obtained by COSMO-RS simulation screening, indicating that the screening has high accuracy.

    Absorption performance and stratification mechanism of biphasic CO2 absorbent[Bmim] [BF4]/MEA aqueous mixtures
    XU Lingjun, QI Yang, WANG Shujuan
    2018, 69(12):  5112-5119.  doi:10.11949/j.issn.0438-1157.20180687
    Abstract ( 286 )   PDF (574KB) ( 92 )  
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    The absorption performance of liquid-liquid biphasic CO2 absorbent aqueous mixture of 1-butyl-3-methylimidazoliumtetrafluoroborate ([Bmim] [BF4]) and monoethanolamine (MEA) was measured, and the effects of[Bmim] [BF4] on the absorption properties and stratification were investigated. The stratification mechanism and substance distribution were analyzed with quantitative13C nuclear magnetic resonance (NMR) method. The results showed that the liquid-liquid stratification would occur when loaded with CO2, which was accompanied with the enrichment of the reaction products of CO2. The cause of the liquid-liquid stratification is the increase of the concentration of carbamates. The absorption rates of absorbents increase first and then decrease with the increase of the mass fraction of[Bmim] [BF4]. H2O is mainly distributed in the rich phase after stratification, and[Bmim] [BF4] is mainly distributed in the lean liquid phase. The mass fraction of H2O directly affects the mass transfer performance of the rich liquid phase.

    Variation characteristics of shear force on membrane micro-interface of forward osmosis based on FBG sensing
    BAI Ruzhen, JIA Hui, ZHANG Cheng, WANG Jie, ZHANG Hongwei
    2018, 69(12):  5120-5129.  doi:10.11949/j.issn.0438-1157.20180879
    Abstract ( 314 )   PDF (775KB) ( 132 )  
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    A shear-force measurement method based on fiber Bragg grating (FBG) sensing technology is proposed to exert the real-time measurement of shear-force distribution on the membrane in forward osmosis (FO) process. The effects of different inlet flow rates on shear-force distribution, water flux and reverse salt flux (RSF) were investigated, and the hydraulic properties of membrane interface behavior were analyzed. The FBG results show that the FBG technique can better give the membrane shear-force shift in the FO module. The shear-force variation presented identical periodicity, and a non-uniform spatial variation of the shear-force distribution exists along the FO membrane surface, which directly leads to the change of water flux. Besides, the shear could be effectively improved at all locations on the membrane by increasing the inlet flow rate, but the larger flow should be applied to significantly improve the shear force farther from the inlet. The simultaneous increase of the shear force on both sides of the membrane module is beneficial to improve water flux, but simply increasing the shear force couldn't better reduce the concentration polarization (CP) and get higher flux.

    Quality-related process monitoring approach based on semi-supervised orthogonal factor analysis
    CUI Xiaohui, YANG Jian, SHI Hongbo
    2018, 69(12):  5130-5138.  doi:10.11949/j.issn.0438-1157.20180365
    Abstract ( 354 )   PDF (945KB) ( 164 )  
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    In the process of industry, the most of the observation samples are polluted by random noises, which makes the probability model owning assumption of noises has been widely used. However, the factors obtained from the model may contain quality-unrelated information in the process monitoring. It is hard to identify the happened fault influencing the quality of product or not for traditional methods which monitor the factors directly. Meanwhile, aiming at the problem previously mentioned and the situation of unequal sample sizes of quality variables and process variables, a semi-supervised orthogonal factor analysis (Semi-SOFA) model was proposed. Firstly, it is formulated by the complete data collected in different sampling rates. Then, apply quality-related orthogonal decomposition to the factors, and construct statistics T2. At the same time, calculate the corresponding statistics SPE according to whether the new sample is labeled by quality variables or not. The proposed Semi-SOFA can effectively identify the period of quality influenced by fault. Finally, numerical simulation and Tennessee Eastman (TE) process simulation demonstrated effectiveness of the proposed approach.

    Dynamic surface control of heat exchanger based on extended state observer
    WANG Suzhen, LIU Qinglong, SUN Guofa
    2018, 69(12):  5139-5145.  doi:10.11949/j.issn.0438-1157.20180539
    Abstract ( 252 )   PDF (570KB) ( 131 )  
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    For the temperature control problem with time delay and large inertia heat exchanger, the design is based on the extended state observer (ESO) dynamic surface controller. The heat exchanger temperature control is a nonlinear, time-varying and uncertain dynamic process. Firstly, an extended state observer is designed to obtain the immeasurable state and dynamics of the system in real time. Secondly, dynamic surface control is used to achieve accurate and fast tracking of temperature. Then Lyapunov function was used to prove the stability of the control system. Finally, the simulation results show that the dynamic surface control method based on ESO has superior control effect and robust performance by compared the classical PID control method and the dynamic matrix control method. The proposed method has better dynamic response performance when the controlled system set point and disturbances change.

    Fault detection based on IJB-PCA-ICA
    LIU Shurui, PENG Hui, LI Shuai, ZHOU Xiaofeng
    2018, 69(12):  5146-5154.  doi:10.11949/j.issn.0438-1157.20180643
    Abstract ( 310 )   PDF (695KB) ( 133 )  
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    In the view of the high dimensionality and the distribution complexity of modern industrial data, a fault detection method based on IJB-PCA-ICA (improved Jarque-Bera-principal component analysis-independent component analysis) is proposed. Through the method of Jarque-Bera test (J-B test), the original data are divided into Gaussian part, non-Gaussian part and semi-Gaussian part. The semi-Gaussian part divided from those variables with not obvious Gaussianity or non-Gaussianity is weighted to participate into Gaussian subspace and non-Gaussian subspace by the Gaussian confidence probability. After the partition by the correlation and principal component projection, the statistics of the Gaussian and non-Gaussian subspaces are obtained by PCA and ICA, respectively. Then the Bayesian inference is applied to obtain the comprehensive statistics for fault detection.

    Fault diagnosis of chillers using sparsely local embedding deep convolutional neural network
    LIU Xuting, LI Yiguo, SUN Shuanzhu, LIU Xichui, SHEN Jiong
    2018, 69(12):  5155-5163.  doi:10.11949/j.issn.0438-1157.20180704
    Abstract ( 255 )   PDF (611KB) ( 140 )  
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    A fault diagnosis method for chillers based on a sparsely local embedding deep convolutional neural network (sparsely local embedding network, SLENet) is proposed. The sparsely local embedding filters are adopted for feature selection in the first two layers of SLENet, as a result complicated training and adjusting process are avoided. In addition, the spatial pyramid max pooling layer is employed to construct the output layer of SLENet to reduce the output dimensions of the proposed network, and then alleviate the computationally burden of classification. The experimental data from ASHRAE RP-1043 are used to validate the fault diagnosis method. The results demonstrate that the method achieves high diagnostic accuracy compared to convolutional neural network (CNN) and support vector machine (SVM) methods.

    Information increment matrix based quality prediction for multi-phase batch processes
    LI Zheng, WANG Pu, GAO Xuejin, QI Yongsheng, CHANG Peng
    2018, 69(12):  5164-5172.  doi:10.11949/j.issn.0438-1157.20180570
    Abstract ( 323 )   PDF (608KB) ( 124 )  
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    A sequential quality prediction algorithm based on information increment matrix is proposed for multi-phase batch processes. It can overcome the limits of some phase partition algorithms, which cannot cope with the sequence and dynamics of the processes and may inevitably divide the samples with discontinuous time sequence but similar characteristics into the same phase. First, the 3D data is transformed into 2D data by batch-wise unfolding and splitted into extended time slices that equipped with quality variables. Then a sliding window is used to divide the sub-phases according to information increment of extended time slices. PLS models of each sub-phase constitute the global quality prediction strategy. The proposed algorithm takes the correlations among variables into consideration and uses information increment to capture the dynamics. The feasibility and effectiveness of the proposed algorithm are illustrated by a penicillin simulation platform and an industrial application of E. coli fermentation, respectively.

    Experiment and numerical simulation of flow-accelerated corrosion of 90° elbow
    ZHANG Lingxiang, ZHOU Keyi, XU Qi, SI Xiaodong, LIN Tong
    2018, 69(12):  5173-5181.  doi:10.11949/j.issn.0438-1157.20180522
    Abstract ( 317 )   PDF (2149KB) ( 187 )  
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    Aiming at the flow-accelerated corrosion (FAC) problem in feed water system and drain system of supercritical boilers, a combination of experimental data and numerical simulation was used to analyze the corrosion of the 90° elbow. In the experiment, the FAC rate of elbows at different inlet velocities was measured by electrochemical method, and the experimental data were analyzed; the flow field of elbows at different inlet velocities was calculated by using numerical simulation methods; finally, based on the M.I.T model, the FAC model of the 90° elbow is simplified at room temperature, and the field synergy principle was used to analyze the characteristics and influencing factors of the FAC distribution at different positions of the elbow from the perspective of fluid dynamics. The analysis shows that along the flow direction, the higher the mass coefficient is, the higher the cross-section is; the greater the radial velocity of the center, the greater the rate of the bend FAC.

    Theoretical study on corrosion inhibition mechanism of six swallowtail perylene diimide gemini surfactants on alkaline zinc electrode
    WANG Hao, LIU Zheng, LIANG Qiuqun, ZHAO Yong, ZHANG Shufen
    2018, 69(12):  5182-5191.  doi:10.11949/j.issn.0438-1157.20180208
    Abstract ( 267 )   PDF (3924KB) ( 103 )  
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    To study the corrosion inhibition mechanism and adsorption behavior of perylene diimide gemini surfactants on alkaline zinc electrode, six swallowtail types were studied by density functional theory and molecular dynamics simulation. According to the calculations result of density functional theory, the frontier molecular orbital distribution is mainly located in the perylene diimide skeleton at the core of the molecule, and N atom in the perylene diimide skeleton is the reactive center of the molecule. It is shown in molecular dynamics simulations that six swallowtail perylene diimide surfactants can be interacted with the metal zinc surface in aqueous solution. N2 and P2 have a higher adsorption energy of -11315.868, -10785.698 kcal/mol and a higher diffusion coefficients in all gemini surfactants of 2.5, 1.32 respectively. The results show that gemini surface active agent layer formed by N2 and P2 can effectively prevent the corrosion particles of OH-. Besides, it can also play a role of excellent corrosion inhibition effect on the zinc metal surface.

    Optimized preparation and characterization of novel layered cross-linked enzyme aggregates of Candida sp. lipase
    YIN Chunhua, MA Yewei, ZHAO Zhimin, ZHANG Haiyang, YAN Hai
    2018, 69(12):  5192-5198.  doi:10.11949/j.issn.0438-1157.20180560
    Abstract ( 284 )   PDF (1038KB) ( 107 )  
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    A novel layered cross-linked enzyme aggregates (CLEAs) of Candida sp. lipase was developed. In the preparation of the novel enzyme aggregates, nano-ZnO particles were modified and cross-linked, which were used as the core of the immobilized lipase, then enzyme molecules were cross-linked on the surface of the nanoparticles, which formed a layered structure. The obtained results showed the bovine serum albumin (BSA) was the suitable agent to modify nano-ZnO particles among the test agents. The other factors affecting the activity of nano layered CLEAs (BSA-N-LCLEAs), such as ammonium sulfate saturation, concentration of glutaraldehyde, temperature and time for cross-linking reaction, were investigated. The optimum conditions were as follows:ammonium sulfate saturation 58%, glutaraldehyde concentration 3.5%, cross-linking temperature 0℃ and time 2 h. Compared with the traditional CLEAs, the recovered activity of BSA-N-LCLEAs increased about 196.5%. Scanning electron microscopy (SEM) characterization indicated that BSA-N-LCLEAs increased significantly compared to conventional CLEAs. Both pH stability and thermo stability of BSA-N-LCLEAs were improved. Furthermore, the layered CLEAs was used to synthesize astaxanthin succinate. The yields of astaxanthin were about 90%. The immobilized lipase could be reused for five batches, which indicated it had good operational stability.

    CO2 enrichment characteristics of coal/biomass fluidized oxy-fuel combustion
    LIU Qinwen, ZHONG Wenqi, LIU Xuejiao, LIU Qian, SHAO Yingjuan, YU Aibing
    2018, 69(12):  5199-5208.  doi:10.11949/j.issn.0438-1157.20180900
    Abstract ( 371 )   PDF (1142KB) ( 224 )  
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    Oxy-fuel combustion with fluidized bed is one of the most promising carbon capture technologies. The oxy-fuel combustion of coal/biomass was simulated in a micro-fluidized bed reactor (inner diameter is 10 mm, combustion temperature is 700-900℃) coupled with an online mass spectrometry, to deeply understand the oxy-fuel combustion behavior. Bituminous coal and rosewood were selected as the samples. The effects of oxygen concentration, combustion temperature and mass ratio of coal to biomass on the combustion characteristics, i.e. the total reaction time, the initial reaction time, CO2 concentration in flue gas and the generation rate of CO2 during particle combustion, were investigated. It was found that the increment of oxygen volume fraction lead to an increase of CO2 yield, the decrease of total reaction time and CO2 concentration in the flue gas. Increasing the combustion temperature could enhance the enrichment of CO2, as a result higher CO2 production by particle combustion and CO2 concentration in the flue gas were obtained. Higher ratio of biomass advanced the initial reaction time and shortened the total reaction time, which resulted in a decrease of CO2 concentration in the flue gas and CO2 production by particle combustion but the rate of CO2 formation is increased.

    Effects of component variation of natural gas on its premixed flame propagation characteristics
    ZHANG Zunhua, ZENG Xuan, LIANG Junjie, WANG Zhaojun, LI Gesheng
    2018, 69(12):  5209-5219.  doi:10.11949/j.issn.0438-1157.20180601
    Abstract ( 283 )   PDF (795KB) ( 463 )  
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    The constant-volume combustion vessel and CHEMKIN PRO software were employed to investigate the effect of component variation of natural gas on the laminar burning velocity and flame instability at the ambient temperature and pressure and stoichiometric ratio. The results show that the laminar burning velocity of natural gas rises with the increase of ethane content, propane content and n-butane content, and the effect of the variation of ethane content on the laminar burning velocity is the most obvious. The instabilities of natural gas-air flames are decreased with the increase of ethane content, propane content and n-butane content. For inhibiting the overall instabilities of natural gas-air flames, the ability of n-butane is approximately equal to the ability of propane, both of which are greater than that of ethane. The flame structure analysis shows that the variation of the peak value of mole fraction of the radical H is the most significant when the natural gas composition fluctuates. There is a strong correlation between the laminar burning velocity of natural gas and the maximum values of the sum of mole fractions of OH and H. The sensitivity analysis of the laminar burning velocity and the net reaction rate analysis show that the natural gas component variation affects the important elementary reactions. The competition between the elementary reactions with positive impacts and the ones with negative impacts varies the peak of H mole fraction and the variation of ethane content has the greatest effect on the mole fraction of H.

    Experimental research on new type of frost-free air source heat pump system in winter
    LI Weihao, QIU Junjun, ZHANG Xiaosong
    2018, 69(12):  5220-5228.  doi:10.11949/j.issn.0438-1157.20180636
    Abstract ( 319 )   PDF (700KB) ( 251 )  
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    This paper reports an experimental research of a new type of air source heat pump system in winter. This system can not only operate efficiently in winter, but also improve the performance in summer operation. Through constructing the heat pump system experimental platform, the effects of outdoor air dry bulb temperature, humidity, heat water temperature, heat water flow rate, solution flow rate, solution mass fraction and outdoor air flow rate in winter conditions on system supply heat model performance and the effects of solution flow rate, solution temperature and air flow rate in winter conditions on system regeneration model performance can be acquired. It is concluded that the supply heat model COP of air source heat pump air conditioning system increases with the decrease of heat water temperature, the increase of outdoor air dry bulb temperature, heat water flow rate, and solution flow rate. The effects of humidity and solution mass fraction on system supply heat model performance can be ignored. The regeneration model COP of air source heat pump air conditioning system increases with the decrease of solution temperature, the increase of air flow rate and solution flow rate. At the condition of experimental, the supply heat model COP of system can reach 3.11 and regeneration model COP can reach 4.03, more than the COP of traditional reverse cycle defrosting air source heat pump. The system heating integrated COP is improved in the test conditions compared with the reverse cycle defrosting system. The experiment proves that the system is suitable for low temperature and high humidity areas.

    Effects of negative electric field on C3H8/O2/Ar/CO2 flame characteristics under different CO2 blending concentrations
    MENG Xiangwen, LI Zhen, TANG Yuanzheng, HE Yan, WU Xiaomin
    2018, 69(12):  5229-5236.  doi:10.11949/j.issn.0438-1157.20180059
    Abstract ( 333 )   PDF (1200KB) ( 169 )  
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    To study the influence of the flame propagation speed on the electric field-flame effects, an experiment was conducted on the constant volume combustion bomb to investigate the effects of negative direct current electric field(U=0, -5, -10 kV) on the C3H8/O2/Ar/CO2 premixed flame with the different CO2 blending concentrations at equivalent fuel/air ratio of 1.0, room temperature and atmospheric pressure. The CO2 blending concentrations are 0, 10%, 15%, and 20%, respectively. Given applied electric field and mixture concentration, the flame propagation speed of C3H8/O2/Ar/CO2 flame decreases with the CO2 blending concentrations increasing, while both the normalized flame deformation ratio and the mean change rate of the flame propagation speed increase. When U=-10 kV and C3H8/O2/Ar/CO2 flames with the CO2 blending concentrations of 0, 10%, 15%, and 20%, the mean normalized flame deformation ratios are 1.01, 1.31, 1.80, and 3.12, respectively. The mean change rate of the flame propagation speeds are 10.87%, 17.87%, 19.16%, and 34.63%, respectively. The results show that the promoting effect of negative DC electric field on C3H8/O2/Ar/CO2 flame propagation is significantly enhanced with the decrease of flame propagation rate.

    Influence of Fe3O4 NPs heterogeneous Fenton-like pre-treatment on activated sludge technology for treatment amoxicillin wastewater
    SU Chengyuan, ZHENG Peng, LIAO Liming, DENG Qiujin, CHEN Menglin, HUANG Zhi
    2018, 69(12):  5237-5245.  doi:10.11949/j.issn.0438-1157.20180624
    Abstract ( 337 )   PDF (1912KB) ( 164 )  
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    Amoxicillin was used as the research object to investigate the effects of heterogeneous Fenton-like pre-treatment on the physicochemical properties and microbial community structure of activated sludge after different degrees of magnetic nano-iron (Fe3O4 NPs). The results showed that with increasing the pre-treatment degrees (without pre-treatment, with 40% H2O2 and 60% H2O2), the average COD removal rate increased from 81.5% to 89.1%, and the average ammonia nitrogen removal rate increased from 86.2% to 95.6% by the activated sludge. Meanwhile, the protease content increased from 0.13 mg·g-1 to 0.19 mg·g-1 in the activated sludge. With the increase of pre-treatment degrees, three-dimensional excitation emission matrix (EEM) spectra demonstrated that the absorption peaks of the fulvic acids and humic acids in the visible region were gradually decreased in the soluble microbial products (SMP) of the activated sludge. It was showed that the activated sludge had good activity. In addition, the abundance of Proteobacteria was 73.81%, 84.08%, 77.08%, and the abundance of Firmicutes was 0.6%, 0.82%, 0.78% at without pre-treatment, with 40% H2O2 and 60% H2O2 pre-treatment condition, respectively. Proteobacteria was the dominant bacteria species. Many nitrogen-fixing bacteria and phosphorus-accumulating bacteria belong to Proteobacteria. Meanwhile, Firmicutes could use hydrolytic enzymes to degrade proteins and sugars. The increase of the proportion of Proteobacteria and Firmicutes had provided a guarantee for the efficient removal of pollutants in the wastewater.

    Electrolytic preparation of sodium hypochlorite in undivided cell and its stability
    LIU Chunwei, FENG Li, FENG Yina
    2018, 69(12):  5246-5255.  doi:10.11949/j.issn.0438-1157.20180703
    Abstract ( 526 )   PDF (717KB) ( 220 )  
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    Disinfection is an essential part of drinking water treatment. The sodium hypochlorite disinfection gains a bright development prospect because of its effectiveness and safety. Preparation of sodium hypochlorite in an undivided cell offers several advantages as high current efficiency, low power consumption, simple operation and easy accessibility of raw electrolytic material, but its reaction mechanism still needs to be discussed and its poor stability is the main limitation for its broader application. The effect of temperature, PH, electrolyte type, electrolyte concentration, etc. on the current efficiency in an undivided cell was studied and an optimized electrolysis condition was acquired. Also, the electrolysis reaction order of n=4.38 was determined by differential method, the reaction rate constant of electrolysis was calculated and the kinetic equation was established to further determine the electrolysis mechanism. According to the concentration change of the available chlorine in sodium hypochlorite solution through time, the kinetic features of available chlorine attenuation was modeled by pseudo first-order and pseudo second-order equations to further adjust and control its stability.

    Evolution behavior on CO2 co-gasification of coal and cyanobacteria
    SHEN Tianxu, ZHANG Jiang, SHEN Laihong
    2018, 69(12):  5256-5265.  doi:10.11949/j.issn.0438-1157.20180709
    Abstract ( 399 )   PDF (739KB) ( 232 )  
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    The co-gasification of coal and cyanobacteria is an important approach to achieve the resource utilization of cyanobacteria. The TG-FTIR combined technology was used to explore the co-gasification characteristics of different blending ratio mixtures under CO2 atmosphere, which provided a theoretical basis for the application of chemical chain combustion technology. It is difficult to distinguish the drying stage and depolymerization stage in cyanobacteria, the polysaccharide of which was depolymerized in a low temperature of 100℃. During the pyrolysis stage, two weightlessness peaks were found in mixture samples corresponding to cyanobacteria and coal pyrolysis, respectively. The carbonyl and aromatics were the main gaseous products of cyanobacteria pyrolysis, and CO, CO2 and hydrocarbons were mainly produced from coal pyrolysis. The pyrolysis and carbonization stages can be described by the homogeneous model. The kinetic parameters of gasification stage were fitted well by the shrinking core model. The influence of synergy effect was found limited in pyrolysis stage. However, a significant synergistic effect was observed in char gasification. The reactive activity of coal gasification was intensified by blending cyanobacteria.

    Study on formation mechanism of akermanite in Zhundong coal ash
    ZHAI Zhongyuan, JIN Jing, WANG Yongzhen, HOU Fengxiao, YANG Haoran, LI Huanlong
    2018, 69(12):  5266-5275.  doi:10.11949/j.issn.0438-1157.20180751
    Abstract ( 354 )   PDF (1073KB) ( 171 )  
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    The formation mechanism of coal ash minerals in the three typical quasi-east coal processes of burning Tianchi South Mine, Wucaiwan and Yihua was studied at different temperatures by means of tubular furnace test bench. The mineral composition was analyzed by XRD. At 1100℃, there is a large amount of calcium, magnesium and feldspar formation, which is an important mineral in coal ash at 1100℃. The results show that the first step in the formation mechanism of akermanite is the generate of CaSiO3,then it react with MgO to form the akermanite.Based on the experimental results, the formation mechanism of akermanite was reserached by density functional theory at the B3LYP/6-311G++(d,p), and the kinetic analysis was studied.The results show that the second path during the formation of the wollastonite is easier to carry out,and the decisive step of this reaction is the O atom transfer step of SiO2 after CaO is bonded to SiO2. After that, CaSiO3 is complexed without barrier to form 2CaSiO3 and reactes with MgO, finally forming Ca2MgSi2O7, in this process, the maximum potential barrier occurs in the rotational step of the atoms after the bonding of 2CaSiO3 with MgO.

    Synergistic effects of electrokinetics process coupled with zero-valent iron permeable reaction barrier in remediation of arsenic-contaminated soil
    JI Dongli, ZHANG Jing, MENG Fansheng, WANG Yeyao
    2018, 69(12):  5276-5282.  doi:10.11949/j.issn.0438-1157.20180787
    Abstract ( 286 )   PDF (812KB) ( 348 )  
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    The remediation of arsenic polluted soil from a mining area in China using the electrokinetics process coupled with zero-valent iron permeable reaction barrier was researched. The influence of soil moisture content and enhancement reagents on arsenic removal was investigated. The changes of distribution and valence state of arsenic before and after the remediation were analyzed. In addition, surface features of the fresh and used zero-valent iron were characterized by X-ray photoelectron spectroscopy (XPS). Then synergistic effects of EK/PRB in the remediation of arsenic-contaminated soil was discussed. The results showed that in the EK/PRB remediation process, fraction of the EK removal mechanism was 22% to 43%, while fraction of the PRB removal mechanism was 52% to 71%, so the PRB process was dominate. When the enhancement reagents was absent, arsenic mainly tends to move toward the anolyte, which indicated the mainly removal mechanisms was electromigration. However, when the enhancement reagents was added, the proportion of arsenic collected from the cathode solution was significantly increased. After EK/PRB remediation, the percentage content of As(Ⅴ) and As (Ⅲ) in soil, electrode liquid and PRB had no substantial changes, only the content ratio of As(Ⅴ) raised slightly. Pentavalent arsenic will not be reduced into trivalent arsenic with higher toxicity. There were no As(0) but As(Ⅲ) and As(Ⅴ) on the surface of the used Fe0. Therefore, arsenic was removed in PRB only through adsorption of the iron surface oxides.

    Adsorption mechanism of nitrate on cotton template Zn/Ti/Fe layered double oxide in water
    CHENG Aihua, QIAN Dapeng
    2018, 69(12):  5283-5291.  doi:10.11949/j.issn.0438-1157.20180839
    Abstract ( 300 )   PDF (692KB) ( 153 )  
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    The cotton template Zn/Ti/Fe layered double oxide (YLDO) and Zn/Ti/Fe layered double oxide (NLDO) were prepared by coprecipitation-baking method. The adsorbents were characterized by SEM, N2 adsorption, FTIR and XRD. The adsorption mechanism of nitrate on YLDO and NLDO in water and the regeneration mechanism of ultraviolet photocatalytic were investigated. The results showed that using cotton as template, the specific surface area of YLDO increased to 74.8 m2·g-1, and the number of large pores increased. The C element is introduced into the chemical composition, which enhances the adsorption capacity. The magnetic materials are composed to magnetic separation. The equilibrium adsorption capacity of YLDO is 66.57 mg·g-1 at 298 K and pH of 7, which is 22.6% higher than that of NLDO. The adsorption isotherms of nitrate on YLDO and NLDO can be described better with Langmuir equation model than Freundlich model, and the pseudo-second-order kinetics equation fit well with the adsorption data. The adsorption process for nitrate on YLDO and NLDO are exothermic and spontaneous. The saturated YLDO and NLDO can be regenerated under ultraviolet light, which keep high adsorption capacity after five cycles for continuous adsorption and regeneration. YLDO can effectively remove nitrate from water by adsorption-magnetic separation-ultraviolet photocatalytic regeneration process without secondary pollution and has potential application prospects in nitrate wastewater treatment.

    Removal effect of different organic fractions from coking wastewater by nature magnetite/UV/S2O82- process
    CHEN Lirong, CHENG Lujiao, GU Zhenchao, FAN Jian, ZHANG Kai, ZHENG Chunli
    2018, 69(12):  5292-5300.  doi:10.11949/j.issn.0438-1157.20180798
    Abstract ( 347 )   PDF (926KB) ( 199 )  
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    Applying the native ore of Inner Mongolia Baiyun as the catalyst(C) and persulfate(PS) as the oxidant, three oxidation systems of C/PS, UV/PS and C/UV/PS were established to treat the bio-treated effluent of coking wastewater. Ultra-filtration and organic matter resin separation were used to analyze the relative molecular weight distribution (MW) and hydrophobicity-hydrophilicity of organic compounds in bio-treated effluent of coking wastewater. The results showed that,there exist more organic compounds of refractory aromatic organic matter and those are mainly organic matter of MW<1×103, the next is such organic matter of MW>100×103 and MW between 10×103-100×103. In the wastewater searched the types of organic matter of hydrophobic-acid fraction and hydrophobic-neotral fraction played a predominate role, its DOC accounts for 45.88% and 32.09% of the total DOC respectively. The optimal oxidation conditions determined in the three oxidation systems were:C/UV/PS system, initial pH, iron ore and PS investment of 3 g·L-1 and 2 g·L-1, ultraviolet irradiation power of 300 W. Under the optimal conditions, COD, UV254, DOC and color removal rate could reach 74.9%, 93.5%, 84.1% and 80.1% in 90 min. The results showed that C/UV/PS system was more effective in removing organics of MW>10×103, the share of MW<1×103 organics increased after treatment, C/UV/PS system was also effective in removing hydrophobic and transphilic fraction compounds, and the share of hydrophilic substances increased after treatment.

    Langmuir-Hinshelwood kinetic model study of bituminous coal char reaction mechanism in O2/CO2/H2O atmosphere
    BU Changsheng, WANG Wenkang, HAN Qijie, WANG Xinye, ZHANG Jubing, CHEN Dandan, PIAO Guilin, JIANG Yong
    2018, 69(12):  5301-5308.  doi:10.11949/j.issn.0438-1157.20180902
    Abstract ( 374 )   PDF (569KB) ( 133 )  
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    Wet-recycle oxy-fuel (O2/CO2/H2O) fluidized bed (FB) combustion shows high efficiency of the power plant and low emission of pollutants. In O2/CO2/H2O atmosphere, char-O2, char-CO2 and char-H2O reactions can occur at the same time. To reveal the mechanism of interaction among those reactions, macro-thermogravimetric analysis (TGA) experiments were carried out in mixture of O2, CO2 and H2O at temperature of 900℃ using a bituminous coal-char. The reaction kinetics of char-O2, char-CO2 and char-H2O reactions were obtained through Langmuir-Hinshelwood (LH) model fitting. Assumptions of separate active sites and common active sites were used to analyze the experimental data in O2/CO2, O2/H2O and CO2/H2O atmospheres, results show that H2O molecules have priority in taking active sites, following by O2, and finally is CO2. In O2/CO2/H2O atmosphere, partial competition among char-O2, char-CO2 and char-H2O reactions was experimentally observed, and neither conventional separate active sites nor common active sites models could describe the reaction rate of bituminous char. According to the theory of H2O molecules primarily and O2 molecules sub-primarily occupy active sites when O2, CO2 and H2O are present, a new L-H type model was built. The developed model was found to describe well with the measured reaction rate of bituminous char in mixture of O2, CO2, and H2O. The results of this work provide theoretical basis for analyzing of the oxy-fuel FB combustion characteristics of char and developing of reliable char combustion model.

    Curing characteristics of bio-oil starch adhesive
    ZHANG Jizong, CHANG Houchun, CHANG Jianmin, LONG Jinxing, LI Xuehui
    2018, 69(12):  5309-5315.  doi:10.11949/j.issn.0438-1157.20180529
    Abstract ( 289 )   PDF (508KB) ( 249 )  
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    Bio-based adhesives have environmentally friendly, recyclable properties and have broad application prospects. Hence, the thermal behavior, curing kinetics and curing technology of bio-oil starch adhesive were studied by Differential Thermal Analysis (DTA) to provide the data foundation for efficient optimization, forecast and control of bonding technology. Compare to the thermal behavior of single curing agent, that of bio-oil starch adhesive by the composite curing agent had greater heat of curing reaction and lower curing temperature, which indicated that the curing effect of the composite curing agent was better than the single curing agent. With the increase of bio-oil dosage, the curing temperature of bio-oil starch adhesive became lower and the heat of curing reaction became larger, illustrating that bio-oil played a positive role in the curing of starch adhesive.

    Regeneration of spent LiFePO4cathode materials using solid state method and electrochemical performance
    CHEN Yongzhen, LI Hualing, SONG Wenji, FENG Ziping
    2018, 69(12):  5316-5325.  doi:10.11949/j.issn.0438-1157.20180319
    Abstract ( 368 )   PDF (1113KB) ( 289 )  
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    The recycled cathode material was obtained after removing the binder of the scrap electrode by heat treatment. The regenerated materials were obtained by high temperature solid state method that adding different proportions of Li, Fe, and P element sources to the recycled material on the basis of quantitative analysis. In this paper, the influence of impurities on regenerated materials was investigated and the optimal proportion of regenerative reaction materials was obtained. The results showed that the Fe2P impurity occurred during the regeneration process. The diffraction characteristic peak of the Fe2P phase gradually declined with the increase of Li, Fe and P element sources. The presence of Fe2P phase decreases the specific capacity of the sample due to the low content of LiFePO4 active material. The morphology of regenerated materials tends to become densification as the proportion of Li, Fe and P element sources increases. The fine and close microstructure decreases the capacity and cycle performance of regenerated materials. The initial specific discharge capacities of the recycled material, stoichiometric regenerated material and excess element sources regenerated material were 103.4, 115.8 and 134.0 mA·h·g-1, respectively. Compared with that of the recycled material, the initial specific discharge capacity of the two regenerated materials was improved by 11.99% and 29.59%, respectively. The discharge capacities of the above three materials after 50 cycles are 100.9, 108.0 and 115.3 mA·h·g-1.

    Preparation and mechanical properties of novel (C3H5O)1CB[7]/PAA hydrogel with high elasticity and self-healing properties
    YANG Qin, ZHAO Na, FANG Chunjuan, ZHAO Junkai, WANG Wendong
    2018, 69(12):  5326-5331.  doi:10.11949/j.issn.0438-1157.20180398
    Abstract ( 333 )   PDF (569KB) ( 219 )  
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    A novel type of propenyloxy cucurbituril [7]/polyacrylic hydrogel ((C3H5O)1CB [7]/PAA gel) with high elasticity and self-healing properties was fabricated by making use of propenyloxy cucurbituril [7] to replace N,N-methylene-bis-acrylamide (BIS), which is a traditional cross-linking agent. The structure of the hydrogel was characterized by IR and1H NMR. The swelling and mechanical properties of the hydrogel were studied, and the self-healing properties were observed macroscopically. The results show that multiple hydrogen bonds was considered as the mainly force in the formation of (C3H5O)1CB [7]/PAA gel's network. The hydrogel has excellent self-healing and mechanical properties in acrylic acid(AA 17.2%, water 82.1%, propenyloxy cucurbituril [7] ((C3H5O)1CB [7]) 0.33%, potassium persulfate(KPS) 0.33%. The maximum elongation of (C3H5O)1CB[7]/PAA gel is 105.6 cm (86 times the original length) and the elastic modulus is 0.39 kPa, and the equilibrium swelling ratio is 600%. (C3H5O)1CB[7]/PAA gel would be a potential bio-tissue engineering material.

    Electrochemical performance of Li3VO4 modified Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials
    SONG Liubin, TANG Fuli, XIAO Zhongliang
    2018, 69(12):  5332-5338.  doi:10.11949/j.issn.0438-1157.20180664
    Abstract ( 341 )   PDF (774KB) ( 178 )  
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    The Li3VO4 coated LiNi0.8Co0.1Mn0.1O2 cathode material was synthesized by wet fusion technology and high temperature solid phase method. The crystalline phase, morphology and microstructure of materials were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that Li3VO4 is evenly coated on the surface of LiNi0.8Co0.1Mn0.1O2 without changing the material structure and morphology of the raw materials. The coating thickness is 1-2 nm. The modification of LiNi0.8Co0.1Mn0.1O2 cathode material with different content of Li3VO4 shows that 3%(mass) Li3VO4 coated LiNi0.8Co0.1Mn0.1O2 has a capacity retention rate of 94.13% after 100 cycles under 1 C, which has the best multiplier performance and cycling performance. In addition, cyclic voltammetry (CV) and alternating current impedance (EIS) analysis show that Li3VO4 can increase Li+ conductivity, inhibit the side-effect between active material and electrolyte, and improve the electrochemical properties of materials.

    Preventing gas explosion by N2 in pipe with lateral venting
    LU Chang, LIU Yang, PAN Rongkun, WANG Hongbo, ZHANG Yunpeng, YU Minggao
    2018, 69(12):  5339-5347.  doi:10.11949/j.issn.0438-1157.20180479
    Abstract ( 483 )   PDF (1623KB) ( 165 )  
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    In the mine gas explosion, preventing the explosion by extinguishant will help to fundamentally eliminate the disastrous consequence of gas explosion. In this paper, we set up double nozzles on the explosion pipeline, and explore the discharge of N2 to achieve the explosion and extinguish the flame. For the straight pipe with surrounding sides inclosed, experiments are conducted with serial N2 pressures, but none of them can prevent the explosion from spreading along the pipe. Then, in this paper, an opening on lower surface of the pipe is set for venting. It can be observed in the explosion process that a large number of high-temperature air masses and premixed gas flow out from the opening, and continuously react outside the opening. Combined with lateral venting, when the left nozzle in the double nozzle does not spurt nitrogen, the explosions still can't be prevented no matter the right nozzle spurting N2 with various pressures. However, when the pressure of the left nozzle is 0.1 MPa and above, the explosions can be prevented. And the larger the N2 pressure, the more easily preventing the explosion and quenching the flame is. The first major reason for preventing explosion is to weaken the reaction in pipe by lateral venting. Also, lateral venting in the pipe to reduce the explosion speed of propagation, more nitrogen is ejected out and longer period of time is obtained to fully dilute the premixed gas. That is the second main reason for preventing the explosion and quenching the flame.

    Large eddy simulation of gasoline-air mixture explosion in closed narrow-long space
    LIU Chong, DU Yang, LI Guoqing, WANG Shimao, LI Meng
    2018, 69(12):  5348-5358.  doi:10.11949/j.issn.0438-1157.20180614
    Abstract ( 316 )   PDF (1963KB) ( 309 )  
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    Based on WALE model and Zimont premixed combustion model, a large eddy simulation(LES) had been applied to study the characteristics of flame of gasoline-air mixture explosions in a closed narrow-long space with an inner size of 0.187 m×0.187 m×2 m. The results of large eddy simulation and RNG k-e model were compared to experimental data and the comparisons confirmed that LES is capable to simulate gasoline-air mixture explosions in closed narrow-long space. The conclusions show that:(1) LES accurately reproduced the formations of flame structure throughout propagation. (2) Two kinds of symmetrical vortices in opposite direction were created in the burned region after the flame front. The kind of symmetrical vortices near the pipe surface contributes to the formation of Tulip flame and the opposite symmetrical vortices that come after the flame further propagation contributes to the collapse of Tulip flame. (3) At the normal concentration of gasoline-air mixture explosion, the gas flow remains positive in the unburned zone and the explosion overpressure, the flame propagation speed and the flame structure have significant coupling relation.

    Characteristics on methane explosion suppression by ultrafine water mist containing potassium oxalate
    YANG Ke, JI Hong, XING Zhixiang, HUANG Weiqiu, WANG Yu, ZHANG Ping
    2018, 69(12):  5359-5369.  doi:10.11949/j.issn.0438-1157.20180671
    Abstract ( 424 )   PDF (1285KB) ( 219 )  
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    To study the effect of ultra-fine water mist containing potassium oxalate on the effectiveness of suppressing methane explosion, a self-made semi-confined chamber was used for explosion suppression experiments to study the effect of changes in potassium oxalate concentration on the particle size of ultra-fine water mist and the performance of methane explosion suppression. The effects of explosion performance were analyzed. The parameters of flame propagation speed, explosion overpressure, average pressure increase rate and explosion power index were analyzed under different concentrations of potassium oxalate. The experimental results show that the addition of potassium oxalate has little effect on the particle size characteristics of ultra-fine water mist. Under the same spraying time, 2% potassium oxalate concentration shows the most significant explosion suppression performance for the 9.5% volume fraction of methane. Compared with the no spraying condition, the flame propagation velocity, maximum explosion overpressure, average pressure rise rate, and explosion power index decreased by 57.1%, 66.3%, 77.9%, and 91.5%, respectively; compared with pure water ultra-fine water mist suppressing the explosion, those parameters decreased by 43.1%, 61.3%, 75.3%, and 90.5%, respectively. The lower pyrolysis temperature of potassium oxalate can enhance the physical inserting of ultra-fine water mist and block the chemical chain reaction to suppress the explosion of methane effectively.

    Experimental and large eddy simulation study on gasoline-air mixture explosions in semi-confined pipe with 90° right-angle bend
    LI Meng, DU Yang, LI Guoqing, WANG Shimao, LIU Chong, WEI Shihao
    2018, 69(12):  5370-5378.  doi:10.11949/j.issn.0438-1157.20180519
    Abstract ( 353 )   PDF (1938KB) ( 147 )  
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    The characteristics of oil and gas pressure and explosion in a confined space with a 90° right-angle bend structure are studied. The pressure transient and flame morphology were collected by high-speed photography. At the same time, the large eddy simulation of the experiment is carried out. The overpressure, field structure and the shape of the flame passing through the pipe are accurately simulated, and the results are compared with the experimental results. The results showed that:(1) The bend has an effect on the flame structure during the explosion, and in the shape change. (2) The brush-like flame formed at the bend is caused by the vortex generated by the local pressure gradient of the bend. (3) The superposition of the local diffracted wave and the reflected wave in the bend have an enhanced effect on the peak value of the explosion overpressure. (4) During the explosion process, the peak value of explosion overpressure, flame speed and flame front area show significant coupling and close internal relationship. The three have strong consistency with time.