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Table of Content
05 July 2018, Volume 69 Issue 7
    Energy drive and regeneration in biotransformation
    ZHANG Liang, LIU Xiaochen, LIU Guiyan, LÜ Bo, FENG Xudong, LI Chun
    2018, 69(7):  2807-2814.  doi:10.11949/j.issn.0438-1157.20171636
    Abstract ( 168 )   PDF (588KB) ( 143 )  
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    Biotransformation plays a crucial role in biochemical industry, and the biotransformation process is accompanied by energy consumption and release. Therefore, in the design and regulation of biological transformation process, the supply and the balance of energy is a very crucial factor. If the exogenous energy is supplied directly to drive the reaction, such as the addition of energetic cofactors, the reaction efficiency will be not satisfactory and the cost is high. To promote the efficiency of the catalytic reaction continuously, the introduction of energy recycling and energetic cofactors regeneration system is of great significance and necessity. The current research on three kinds of energy recycling system is reviewed, its development in the field of metabolic engineering is discussed, and its application in cell-free catalytic process is applying in the future.

    Contrastive analysis of exergy in carbon black process of plasma method and furnace method
    CUI Haichao, CHEN Xianhui, WANG Cheng, XIA Weidong
    2018, 69(7):  2815-2821.  doi:10.11949/j.issn.0438-1157.20171694
    Abstract ( 179 )   PDF (445KB) ( 185 )  
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    Traditional process of carbon black (CB) by furnace method suffers from some shortcomings such as low energy efficiency, amount of CO2 and NOx emissions, and low yield of carbon. The plasma method instead of furnace CB could improve energy efficiency greatly, and eliminate CO2 and NOx emissions produced by combustion, and the ideal conversion rate of carbon could reach 100%. This paper aims at analysis energy efficiency by the plasma method comparing to that by the furnace method for producing CB. The processes of two methods were simulated based on Aspen Plus software. The process exergy rates of furnace CB were calculated for five kinds of CB (N110, N220, N330, N440 and N550) respectively, and two feedstocks of methane and tar were calculated in plasma method. The contrastive analysis of the processes of two methods was made, including the yield of carbon, the exergy rate of input and output materials, the exergy efficiency of product and process. The results indicate that the carbon yield of the furnace method is between 47.6%-66.6%, which is significantly lower than 94% ideal carbon yield of the plasma method. The exergy efficiency of product and process of the plasma CB are higher than that of furnace CB when tar is used as a feedstock. The exergy efficiency of product using tar as a feedstock is higher than that using methane as a feedstock in plasma CB process.

    Vapor-liquid equilibrium data for α-pinene + β-pinene + p-cymene at reduced pressure
    SUN Lixia, LIAO Dankui, WANG Kun, SUN Jianhua, TONG Zhangfa
    2018, 69(7):  2822-2828.  doi:10.11949/j.issn.0438-1157.20171626
    Abstract ( 81 )   PDF (387KB) ( 59 )  
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    Vapor-liquid equilibrium (VLE) data for ternary system of α-pinene(1) + β-pinene(2)+ p-cymene(3) were measured at 53.3 kPa and 80.0 kPa using the modified Dvorak-Boublik equilibrium still. The experimental data of ternary systems were found to be thermodynamically consistent by the McDermott-Ellis method. The ternary system data at reduced pressure were predicted with the parameters of NRTL model obtained from the pertinent binary systems. The maximum absolute deviations in temperature at two pressures were 0.80 and 0.86 K respectively, average absolute deviations were 0.30 and 0.39 K respectively. The ternary absolute deviation and average absolute deviation in vapor-phase mole fraction of α-pinene were 0.0096 and 0.0033 respectively, and those of β-pinene were 0.0102 and 0.0028 respectively at 53.3 kPa. The max absolute deviation and average absolute deviations in vaporphase mole fraction of α-pinene were 0.0083 and 0.0049 respectively, and those of β-pinene were 0.0081 and 0.0025 respectively at 80.0 kPa. These results provide the basis data for the separation of main components of turpentine.

    Solubility determination of calcium sulfate dihydrate in ammonium sulfate solution
    GE Jing, ZHU Jiahua, XIA Sulan, LIU Shizhong
    2018, 69(7):  2829-2837.  doi:10.11949/j.issn.0438-1157.20171695
    Abstract ( 158 )   PDF (522KB) ( 131 )  
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    The effect of the concentration (0-2.5 mol·kg-1) of ammonium sulfate on the solubility of calcium sulfate dihydrate is measured in inductively coupled plasma-atomic emission spectrometry (ICP-AES) under the conditions of 298.15-348.15 K. The activity coefficient model of extended Debye-Hückel was applied to correlate the experimental data, and the averaged relative deviation were found at 2.81%. Meanwhile, the activity coefficient model of extended UNIQUAC-Debye-Hückel was applied to calculate the solubility of calcium sulfate dihydrate in ammonium sulfate solution, and the experimental data agreed well with the model prediction, with an averaged relative deviation of 4.13%. The theoretical and experimental results show that the solubility of calcium sulfate dihydrate can firstly decrease and then increase with the increasing of the concentration of ammonium sulfate under the conditions of 298.15-348.15 K. At the solubility mutation point the concentration of ammonium sulfate is 0.07-0.08 mol·kg-1 under the synergetic effect of common-ion effect and salt effect. There are strong effects of temperature on the solubility of calcium sulfate dihydrate under higher ammonium sulfate concentrations (0.3-2.5 mol·kg-1). The results provide better understanding and theoretical guidance for process design of CO2 mineralization with phosphogypsum.

    Phase equilibria in systems K+, NH4+//Cl-, SO42--H2O and K+, NH4+//Cl-, SO42--H2O at 313.15 K
    REN Yongsheng, HE Tingting, XIE Juan, CAI Chao
    2018, 69(7):  2838-2850.  doi:10.11949/j.issn.0438-1157.20171315
    Abstract ( 122 )   PDF (560KB) ( 114 )  
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    An experimental study on phase equilibria in the system (K+, NH4+//Cl-, SO42--H2O) and (K+, NH4+//Cl-, SO42--(CH2OH)2-H2O) is done by the method of isothermal solution saturation. In these systems, the initial mass fraction of ethylene glycol is 30% in the salt-free binary solvent water + ethylene glycol. The solubilities, densities, viscosities, and refractive indices of saturated solutions have been measured for the two systems. On the basis of the experimental data, corresponding phase diagrams and diagrams of physical properties versus composition were plotted. All the physical properties of both systems change regularly with concentration change of the liquid phase. The phase diagram of (K+, NH4+//Cl-, SO42--H2O) consists of one invariant point, four univariant curves, and four solid phase crystallization regions at 333.15 K. The phase diagram of (K+, NH4+//Cl-, SO42--(CH2OH)2-H2O) is similar to the previous one, which contains one invariant point, four univariant curves, and four solid phase crystallization regions at 333.15 K. Comparisons of the stable phase diagrams for (K+, NH4+//Cl-, SO42--H2O) and (K+, NH4+//Cl-, SO42--(CH2OH)2-H2O) at 333.15 K are shown that they all have four solid solutions[respectively (K, NH4)Cl, (NH4, K)Cl, (K, NH4)2SO4 and (NH4, K)2SO4)]. These changes between phase diagrams at different solvents will be very useful for extracting the salts. According to this work, the measured data and phase equilibrium diagrams can be used for a new technology to design and optimize the production of K2SO4, from mother liquor of calcium carbonate whiskers prepared by FGD gypsum. At the same time, it can provide fundamental data support for chemical industry development.

    Numerical simulation of gas-liquid interface evolution for flow and condensation in square microchannel
    WU Chunxu, LI Junming
    2018, 69(7):  2851-2859.  doi:10.11949/j.issn.0438-1157.20171309
    Abstract ( 115 )   PDF (1308KB) ( 139 )  
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    Based on the fluid volume approach, the gas-liquid interface evolution for R32 flow and condensation in a square microchannel with 50 μm hydraulic diameter is studied. Annular, injection flow, bubbly flow and shrinking bubbly flow are simulated successively. Because of the gas-liquid interface curvature variation along the circumferential direction of channel, the existing surface tension generated transverse pressure gradient in the condensate film, which forces the condensate towards the corners and thins the condensate film at the middle of the wall of channel. A mechanism for the occurrence of injection flow dominated by the surface tension force and interface viscous force is proposed based on the minimum potential energy theory. The interface fluctuations on the annular flow upstream are induced by injection flow at low mass flux, and grow up gradually under interface viscous force which is different from the mechanism of “flow pattern transition at high mass flux being induced by interface fluctuations which grow up while flowing downstream”.

    Preparation and performance of modified sodium acetate trihydrate composite phase change material for thermal energy storage
    WU Dongling, LI Tingxian, HE Feng, WANG Ruzhu
    2018, 69(7):  2860-2868.  doi:10.11949/j.issn.0438-1157.20171617
    Abstract ( 161 )   PDF (706KB) ( 256 )  
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    Phase separation and supercooling are common phenomenon of salt hydrates, which is a key problem affecting the thermal stability and thermal performance of phase change material. Sodium acetate trihydrate (SAT), as a low and medium temperature hydrate salt, is the main study object. Carboxyl methyl cellulose (CMC) and disodium hydrogen phosphate dodecahydrate (DHPD) were firstly used to modify SAT by melt blending method. A high-performance composite phase change material (PCM) was prepared by optimizing the ratio of the additives. The thermophysical properties and stable performance of different samples were tested by using differential scanning calorimetry (DSC) and a melting-freezing setup. The effects of the additives on phase change enthalpy, phase transition temperature, supercooling and phase separation were analyzed. Finally, a high-density heat reservoir was built by using the modified PCM and a latent heat storage water system was set up. The charging and discharging performance of the system under different working conditions were analyzed. The results showed that adding 0.5% CMC as the thickening agent and 2% DHPD as the nuclear agent could avoid phase separation and decrease supercooling degree. The phase change enthalpy and temperature range of modified SAT were 258 kJ·kg-1 and 57℃,respectively. The modified PCM had good cycling stability and its supercooling degree was smaller than 2℃. In addition, the output water temperature of the latent heat storage system under different cooling conditions can be heated up to over 50℃. The efficiency was higher than 90% and the heating power was as high as 10 kW. The heating power, energy storage capacity and thermal storage efficiency increased with the decrease of the inlet water temperature. The system has good charging and discharging performance and its volume heat storage density is 2.6 times as higher as traditional water tank.

    Heat transfer characteristics of salt-bath structure heat exchanger in ascension pipe of coke oven
    WU Daodong, LI Juxiang
    2018, 69(7):  2869-2877.  doi:10.11949/j.issn.0438-1157.20171667
    Abstract ( 79 )   PDF (876KB) ( 70 )  
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    The flow and temperature distributions of coke oven gas (COG) in the salt-bath structure heat exchanger were investigated by numerical simulation and actual dynamic test. The variations of the temperature in the heat exchanger and the velocity of COG were obtained. The results showed that the COG was in the entrance region of laminar flow. The temperature of COG decreased sharply near the inner cylinder wall and the straight fins which welded on the wall, and the temperature gradient was small in the center of the heat exchanger along the radial direction. The temperature of the straight fins presented the higher tendency at the bottom and lower at the upper part along the axial direction, higher at the fin-top and lower at the fin-root along the radial direction at the same height. The temperature of inner cylinder wall in the heat exchanger could be controlled during the test, which could avoid a large amount of condensation from tar vapor in COG.

    Influences of interstage height and superficial gas velocity in multistage internal airlift loop reactor on performance of mixing and mass transfer
    TAO Jinliang, HUANG Jiangang, XIAO Hang, YANG Chao, HUANG Qingshan
    2018, 69(7):  2878-2889.  doi:10.11949/j.issn.0438-1157.20171647
    Abstract ( 105 )   PDF (717KB) ( 139 )  
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    A simple multistage internal airlift loop reactor (MIALR), which has been widely employed in the chemical industry, was designed and investigated. The influences of interstage height and superficial gas velocity in the MIALR on the performance of the mixing and mass transfer were inspected. Three typical regimes, i.e., abnornal, transition and regular regimes, in the MIALR were observed and proposed in this work for the first time. There were two critical superficial gas velocities impacted by the interstage height in the MIALR for the flow regime transition, and two mathematical models were proposed here for the prediction of flow regimes. The results showed that a higher superficial gas velocity was desired for reaching a regular regime when the interstage height of the MIALR increased. In addition, the respective gas holdups in the riser and the downcomer would be promoted if there was an increment of the interstage height in the MIALR. The gas holdups in the riser and the downcomer at the third stage were the highest at the same conditions, and those at the first stage were the lowest among the three stages in the reactor. Moreover, the higher the interstage height, the higher the circulating liquid velocity in the downcomer was. The highest circulating velocity in the downcomer was measured at the first stage, and the lowest value was obtained at the third stage. Finally, a reduction of mixing time was gained when the interstage height increased, while an increase of volumetric mass transfer coefficient was obtained at the same conditions. Therefore, a guideline for the scientific design, scaling up and operating of this kind of industrial MIALRs was provided.

    Bubble departure in gradient metal foam under pool boiling conditions
    HUANG Ruilian, ZHAO Changying, XU Zhiguo
    2018, 69(7):  2890-2898.  doi:10.11949/j.issn.0438-1157.20171547
    Abstract ( 79 )   PDF (1374KB) ( 118 )  
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    Pool boiling is considered to be an effective method for cooling high heat-generating electronic components with less noise and equipment. Despite many studies on boiling, opinions about the process are still disputed and there is still scope to investigate the pool boiling heat transfer mechanism, especially bubble behavior in porous materials. In this experiment, by utilizing high speed camera, the bubble departure in gradient metal foam in saturated pure deionized water and n-heptanol solutions under pool boiling conditions was investigated. To form the gradient metal foam, the foam layers were sintered together by Ag-Cu alloy sheets in a high-temperature muffle furnace. The gradient metal foam consists of a 40 PPI nickel foam layer with 4 mm thickness and a 10 PPI copper foam layer with 4 mm thickness; the foam porosity is 0.98, and n-heptanol solutions concentration is 400 mg·L-1 and 800 mg·L-1. The results show that n-heptanol affects the bubble parameters, and the bubbles in n-heptanol solution are smaller in size and quantity than in pure water which adversely affects the boiling heat transfer. The bubble variation is not sensitive to an increase in n-heptanol concentration. At the heat flux of 6.6×104 W·m-2, two common phenomena occur in the gradient foam:bubbles escape from the metal skeletons without cracking and bubbles separate into two smaller bubbles. When heat flux increases to 1.0×105 W·m-2, two neighboring bubbles move upwards and are sucked into the metal foam due to coalescence, then the big coalescence bubble departs from the metal foam.

    Heat transfer performance of three-dimensional oscillating heat pipe with flat-plate evaporator
    QU Jian, PENG Youquan, SUN Qin
    2018, 69(7):  2899-2907.  doi:10.11949/j.issn.0438-1157.20171653
    Abstract ( 83 )   PDF (943KB) ( 79 )  
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    The heat transfer performance of a compact three-dimensional oscillating heat pipe (3D-OHP) was investigated at vertical, horizontal and side orientation modes. The evaporator section of the 3D-OHP was fabricated by a 40 mm×40 mm×3.5 mm copper plate with nine parallel circular channels inside, and the condenser section was made of copper capillary tubes with inner and outer diameters of 2 and 3 mm, respectively. The capillary tubes were connected with the plate to form the 3D structure. Ethanol and deionized water were used as the working fluid with volumetric filling ratios from 20% to 70%. Two heat blocks were mounted on the copper flat evaporator to provide heating power inputs ranging from around 10 to 100 W. The results show that the 3DOHP could start-up and work well at the filling ratio range of 30% to 70% and had the best heat transfer performance at 30% filling ratio. In addition, the 3D-OHP had the lowest start-up temperature at the vertical orientation and the start-up temperature increased with the increase of filling ratio. The 3D-OHP still functioned at the horizontal orientation but had lower heat transfer performance than at the vertical orientation, and the reduction in filling ratio enhanced the performance. Compared with ethanol, the 3D-OHP charged with water had lower evaporation temperatures, higher evaporator temperature uniformity as well as heat transfer performance.

    Evaporation characteristics of sessile ethanol-water mixture droplets
    JIN Yanyan, SHAN Yanguang
    2018, 69(7):  2908-2915.  doi:10.11949/j.issn.0438-1157.20171267
    Abstract ( 106 )   PDF (678KB) ( 95 )  
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    Droplets evaporation is a common phenomenon. It's necessary to keep studying on the evaporation mechanism of multi component droplets, which can promote the development of related industry and technologies, such as pesticide powder spraying, inkjet printing, industrial coating and rapid cooling technology. Based on silicon and PTFE films, the evaporation of water-ethanol mixed liquid drops are studied by using 10%, 20% and 30% concentrations of ethanol and pure water. The CCD camera is used to record the change of the appearance of sessile droplets. Then evaporation characteristics of mixed droplets are obtained by analyzing the contact angle and contact radius. It can be seen from the experiment that the evaporation time shortens obviously after adding ethanol. The evaporation of mixed droplets on silicon wafers consists of three evaporation stages as similar as pure water. But the evaporation time of the both first and second stages reduced. And there is a sudden increase in angle at second stage in the experiment of 10% and 20%. On the PTFE film, the pure water droplet has only constant contact radius and mix evaporation stage. When the ethanol content increased to 20%, the first stage turns to be the constant contact angle evaporation mode. As the concentration of ethanol increases, the rate of mix stage is mainly raised. Besides, from the angle of rate and capacity of evaporation, it was found that two liquids may evaporate at the same time. But when the concentration of ethanol is high, the ethanol evaporates faster than pure water. For droplets on the silicon, pure ethanol evaporates in the first stage when the concentration reaches 30%. On the surface of PTFE, the concentration threshold of the ethanol is 20%. Therefore, the concentration of ethanol which can change the order of evaporation varies with the kind of surface. In summary, the addition of ethanol will affect the droplet evaporation mode and the total duration.

    POD analysis of flow field in horizontal two-group nozzle impinging stream reactor
    ZHANG Jianwei, MA Fanrong, ZHANG Zhigang, FENG Ying
    2018, 69(7):  2916-2925.  doi:10.11949/j.issn.0438-1157.20171615
    Abstract ( 69 )   PDF (4189KB) ( 78 )  
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    Two-dimensional high-speed particle image velocimetry was used to study horizontal-confronted twogroup-layered impinging turbulent flow fields. Flow structures of two sets of nozzles were analyzed under conditions of different Re, nozzle diameter, upper and lower radial jets. The velocity field was decomposed by POD to extract large scale energy-carrying structure. The results show that low-order intrinsic mode features a large-scale vortex structure with obvious vortex structures in flow field and energy of transient flow field mainly concentrates in the first-order mode. Flow characteristics of whole flow field is easily described such that modal reconstruction of pulsating field could accurately reestablish vortex structures in the flow field. Under condition of L=3d, asymmetric flow field energy was higher than that of symmetric flow filed, low order modal energy was increased with increasing nozzle Re, but was first increased then decreased with the increase of nozzle diameter. Under condition of 10 mm diameter, first order mode energy was the highest and vorticity was the maximum.

    Interfacial disturbance wave velocity of gas-liquid two-phase annular flow in vertical pipe
    ZHAO Ning, WANG Peipei, GUO Suna, FANG Lide, WANG Dongxing, CHEN Xue
    2018, 69(7):  2926-2934.  doi:10.11949/j.issn.0438-1157.20171574
    Abstract ( 104 )   PDF (795KB) ( 71 )  
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    In two-phase annular flow, interfacial waves play a crucial role in mass, momentum and energy transfers between two phases. It is important to study characteristic parameters of the interfacial waves (wave velocity, wave frequency and amplitude). First, interfacial waves were classified and qualitatively described characteristics of every wave type. Then, interfacial wave velocity prediction model was developed on the basis of interfacial shear stress. With consideration of density increment of gas core caused by entrained droplets and effect of relative velocities between gas core and liquid film surface, a modified disturbance wave velocity prediction model was obtained for vertical two-phase annular flow. Interfacial wave velocity measurement sensor based on near infrared (NIR) absorption attenuation technology and cross-correlation principle was designed for high operating pressure in industrial process. Measurements of 154 different interfacial wave velocities under five system pressures of 0.2-0.9 MPa showed that the modified model had good prediction results with less than ±10% relative standard deviations and some extrapolation capability for different system pressure conditions.

    Enhancement on steam condensation heat transfer with hydrophilic/hydrophobic combination surfaces of PVDF hollow fiber heat exchange tubes
    JIA Wei, GAO Qijun, LÜ Xiaolong, CHEN Huayan, WANG Xuan, DONG Chang
    2018, 69(7):  2935-2943.  doi:10.11949/j.issn.0438-1157.20171639
    Abstract ( 73 )   PDF (1879KB) ( 82 )  
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    To solve the problem that plastic heat exchange tubes presented a low thermal conductivity, the surface hydrophilic(PVDF/SPES) and surface hydrophobic(PVDF) hollow fiber heat exchange tubes with dense/non-dense layer composite structure were prepared by controlling the content of sulfonated poly(ether sulfone)(SPES) in the casting solution during the course of non-solvent induced phase separation(NIPS). The outside surface contact angle of PVDF/SPES and PVDF tubes were 49.8° and 78.1°, respectively. The non-dense layer was filled with water to improve the thermal conductivity of heat exchange tubes. Single surface hydrophobic and hydrophilic heat exchange tube were weaved together to prepare tubular plastic heat exchanger. Thus, a hydrophilic/hydrophobic combination surface for steam condensation from outside surfaces of two tubes was built in the shell of heat exchanger. On this basis, the strengthening effect of steam condensation heat transfer on the combination surface was studied. The results showed that compared with the hydrophobic surface of dense PVDF heat exchange tubes prepared by melt-spinning method, the total steam condensation heat transfer coefficient on hydrophilic, hydrophobic and hydrophilic/hydrophobic combination surface prepared by NIPS method were improved by 46.6%, 56.5%, and 99.7%, respectively. Therefore, the hydrophilic/hydrophobic combination surface could strength obviously steam condensation heat transfer in comparison with single hydrophilic and hydrophobic surface.

    Pool boiling heat transfer and prediction of CuO/H2O nanofluids
    WANG Jiajun, LANG Zhongmin, YU Gewen, WU Gangqiang
    2018, 69(7):  2944-2955.  doi:10.11949/j.issn.0438-1157.20171621
    Abstract ( 69 )   PDF (1668KB) ( 93 )  
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    The CuO/H2O nanofluids performance of the nucleate boiling heat transfer was analyzed. The copper oxide nanoparticles were synthesized by complexation precipitation process. Firstly, the precursors of copper oxide were prepared by mixing copper nitrate and salicylicacid with stir continuously around 30 min. Sodium carbonate were dropped slowly in the solution as precipitant until the Cu(Ⅱ) precipitated completely, then the precipitate was centrifugal washed for more than three times. Finally, the precipitate was calcined at 500℃ to obtain copper oxide nanoparticles. The copper oxide particles size was observed by the scanning electron microscope (SEM), and the sizes of particles are in the range of 40-80 nm. The CuO/H2O nanofluid was prepared with the sodium dodecyl benzene sulfonate(SDBS) as the dispersant. The pool boiling heat transfer experiment was carried out to investigate the effect of thermal conductivity, contact angle and superficial particles deposition with different mass fractions on thermal performance of the nanofluid. The results have shown that the nanofluid can strengthen nucleate boiling heat transfer performance with CuO/H2O nanofluid as working fluid. The heat transfer coefficient increased 146.1% than deionized water with the mass fraction of 0.1%. The bubble behavior of 0.07% nanofluid was recorded by the high-speed CCD to verify the boiling mechanism. Bubble dynamics model were built to predict bubble diameter, departure frequency and nucleation sites as the heat flux within 25 kW·m-2 and 150 kW·m-2. The absolute value of relative deviation between the numerical results and experimental results were less than ±10%.

    Heat transfer performance of copper surface treatment MWCNTs/PA based on composites
    HUANG Jin, LI Xiaopeng, WANG Ting, HU Yanxin, SHENG Xinxin
    2018, 69(7):  2956-2963.  doi:10.11949/j.issn.0438-1157.20171514
    Abstract ( 69 )   PDF (750KB) ( 81 )  
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    Different coating treatments were carried out on the surface of copper plate from the point of view of corrosion and heat transfer of heat exchanger:polyacrylate (PA) single-sided and double-sided coating, MWCNTs/PA composite single-sided and double-sided coating, and noncoating copper plate. The heat transfer coefficient under different treatment conditions was studied by convective heat transfer experiment. The results show that the heat transfer coefficient of the copper plate is reduced by 21.91% and 40.00%, respectively, compared with the noncoating copper plate. The heat transfer coefficient of the copper plate treated with MWCNTs/PA composite material is improved, and the heat transfer coefficient of the copper plate treated with single and double sided MWCNTs/PA is improved by 16.74% and 27.49% respectively, compared with the noncoating copper plate.

    Analyze acoustic emission signals from moving bubbles by clustering method
    WANG Xin, LI Xiaolei, LI Meihui, SANG Xunyuan, WANG Taiyang
    2018, 69(7):  2964-2971.  doi:10.11949/j.issn.0438-1157.20171572
    Abstract ( 51 )   PDF (1485KB) ( 58 )  
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    A real time acquisition and processing program was developed to record acoustic emission (AE) signals, to extract AE wave packets, and to calculate AE parameters of continuous bubbles in their rising stages after released from a 3-mm-diametered nozzle. AE signal wave packets of 1.42 m/s gas velocity at orifice was classified by kmeans clustering analysis method. For each category, statistical characteristics of AE signal parameters was analyzed and time/frequency domains of AE signals were analyzed by fast Fourier transform and wavelet transform method. Identification of AE signals was effectively achieved with assistance of moving bubble images. Signal classification capability were further studied under different gas velocities. The results show that AE signals of all categories have somewhat similarity after processed by time frequency analysis and k-means clustering method, AE signals of moving bubbles in their rising stages can be efficiently studied in combination with high-speed image-capturing technique, and flow patterns of moving bubbles can be identified, including bubble oscillation, breakup, coalescence and so on.

    Synchronous thickness measurements of flowing liquid film on horizontal surface by ultrasonic pulse-echo and laser absorption spectroscopy methods
    SU Mingxu, MUHAMMAD Abdul Ahad, JIANG Yong, WU Wei, YANG Huinan
    2018, 69(7):  2972-2978.  doi:10.11949/j.issn.0438-1157.20171251
    Abstract ( 109 )   PDF (599KB) ( 64 )  
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    Because of common existence of liquid film flow in industrial processes, it's crucial to study methods for measuring thickness of moving liquid film. Measurement accuracy of both ultrasonic pulse-echo and laser absorption spectroscopy methods was validated by calibration standards of known film thicknesses (100-1000 μm). The coefficient of variation was 1.07% for ultrasonic pulse-echo method and 1.29% for laser absorption spectroscopy method. Then, thickness of flowing liquid film was measured by these two methods. The average film thicknesses were in good agreement for two methods when liquid film flow was at low/medium/high velocity. At three corresponding velocities, the difference of average film thicknesses between these two methods were 16.59, 16.26 and 13.36 μm, and the relative standard deviation of film thickness was 0.29%, 7.71% and 25.37%, respectively. Furthermore, both methods detected same number of fluctuations of liquid film within 1 s cycle at three different velocities.

    Character of sessile droplets evaporation on hydrophilic and hydrophobic heating surface with constant heat fluxes
    GAO Ming, KONG Peng, ZHANG Lixin
    2018, 69(7):  2979-2984.  doi:10.11949/j.issn.0438-1157.20171684
    Abstract ( 120 )   PDF (833KB) ( 87 )  
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    In previous researchers' studies, the evaporation of droplets were conducted on heating surfaces with constant wall temperature. However, no previous experiments were carried out on a constant heat flux heating surface. The evaporation of 3 μl sessile droplets on hydrophilic and hydrophobic heating surface with constant heat fluxes were observed and recorded by a high-speed photography. The evaporation time, dimensionless contact angle, dimensionless contact diameter and height were presented. The evaporation rate of the droplet on the hydrophilic surface was faster than that on the hydrophobic surface, and with the increase of the heat fluxes, the evaporation rate of the droplet increases. For both hydrophilic and hydrophobic surface, the evaporation mainly followed the CCR mode, and there was a mixed evaporation mode at the later stage of evaporation, but no CCA mode was found in the whole process.

    Application of CFD to improve calculated process of methanation over plum-shaped catalyst
    ZHANG Jie, LI Tao
    2018, 69(7):  2985-2992.  doi:10.11949/j.issn.0438-1157.20180104
    Abstract ( 194 )   PDF (1554KB) ( 144 )  
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    The simulation of methanation process is studied by CFD, and makes reasonable improvement to the model. The three-dimensional model of methanation reaction on the plum-shaped catalyst was established and the validity of the model was verified. Due to strong diffusion limitations the CO concentration of catalyst particles has great difference between the internal and external. Inside the catalyst, reaction conditions are changed to be a high H/C value. The diffusion rate of H2 is larger than CO. A single kinetics can't describe the reaction accurately. The catalyst domain is divided into two parts according to the variety of CO concentration in catalyst, and different kinetics is applied into the corresponding domain. Under the control of two kinetics, the average reaction rate of methanation has been accelerated, which is closer to the actual process and show that the new model is more accurate.

    Influences of organic additives on inhibiting by-products in zinc-catalyzed synthesis of alkynylsilane
    HUANG Pan, LIU Zhen, SHAO Yunqi, DENG Shifeng, LIU Boping
    2018, 69(7):  2993-3000.  doi:10.11949/j.issn.0438-1157.20171603
    Abstract ( 103 )   PDF (539KB) ( 68 )  
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    Silylation of phenylacetylene with trimethylchlorosilane (TMCS) in the presence of zinc powder catalyst will produce around 33% alkene by-product. Different organic additives were used as H scavengers to reduce the production of styrene (ST). From the results via GC analysis, pyridine and 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU) were found to be effective to increase the selectivity but the conversion rate was decreased. The concentration of organic additives, reaction time and temperature were then optimized. The concentration optimization showed that 6 mol DBU was effective to decrease the generation of styrene but the yield of main product phenylethynyltrimethylchlorosilane (PT) dropped significantly. 6 mol pyridine was the optimal concentration for its relatively high conversion and selectivity. The yield of styrene decreased to around 13% while the yield of PT was 57%. The optimal reaction time was 20 h. Conversion and selectivity rarely changed with a longer reaction time. As for temperature, it was found that a higher temperature was beneficial to improve the conversion but unfavorable to selectivity. The results showed that the conversion was highest at 110℃ while the selectivity was best at 100℃ with 6 mol pyridine.

    Effect of ultrasonic alkali treatment on structural, acidic properties and performance of MOR catalyst
    HAN Haibo, WANG Youhe, LI Kang, LIU Danhe, HAO Daijun, YAN Zifeng
    2018, 69(7):  3001-3008.  doi:10.11949/j.issn.0438-1157.20171632
    Abstract ( 120 )   PDF (1028KB) ( 132 )  
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    MOR catalyst commonly suffers the poor stability in the catalytic synthesis of methyl acetate. It's difficulty to introduce the hierarchical pores by traditional alkali treatment. To overcome this drawback, an ultrasonic alkali treatment was utilized to generate hierarchical MOR via desilication. Multiple analyzing methods, such as XRD, SEM, TEM, pyridine IR and N2 adsorption-desorption, were used to characterize the catalyst structure and the influence of ultrasonic treatment under different alkali concentration on the MOR framework. Acidity, pore structure and catalytic properties were investigated. The results showed that a proper ultrasonic alkali treatment could significantly improve the number of acidic sites, mesopore volume, surface area, pore size distribution, catalytic activity and stability. The DME conversion increased from 35.3% to 44.8%, and the catalyst lifetime was greatly prolonged. However, an excessive alkali concentration seriously destroyed the MOR framework, leading to a rapid decrease on catalyst activity and stability.

    Effects of silylation and organic weak alkali modified Mo/HZSM-5 on catalytic performance in non-oxidative aromatization of methane reaction
    TIAN Haifeng, YAO Lu, GAO Jialiang, ZHA Fei, GUO Xiaojun
    2018, 69(7):  3009-3017.  doi:10.11949/j.issn.0438-1157.20171428
    Abstract ( 78 )   PDF (821KB) ( 105 )  
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    The morphology of catalysts and the assembly of catalysts particles have important influence on the catalytic performance. The core-shell composite materials with Mo/HZSM-5 as the core and silicalite-1 zeolite as shell were prepared by silylation. The hollow structure of Mo/HZSM-5 catalyst microspheres with rich silicon surface and hierarchical pore structure was prepared by the weak organic alkali etching method. The structure of Mo/HZSM-5 were characterized by XRD, TEM, N2-adsorption-desorption and NH3-TPD. The surface acidity of Mo/HZSM-5 catalysts was modulated by silylation or the weak organic alkali etching method. The crystallinity, mesoporous specific surface and pore volume of Mo/HZSM-5 catalyst increased by the weak organic alkali etching method. The catalytic performance of Mo/HZSM-5 catalysts via different post-treatment was investigated, the results show that the catalyst stability could be improved and the distribution of the product has a significant influence in non-oxidative aromatization of methane reaction.

    Optimization of recycling copper from copper oxide smelting slag by response surface methodology
    WANG Anqi, WANG Yongliang, YE Liping, LU Yonggang, QIAN Peng, YE Shufeng
    2018, 69(7):  3018-3028.  doi:10.11949/j.issn.0438-1157.20171609
    Abstract ( 144 )   PDF (2230KB) ( 170 )  
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    The copper smelting slag with high copper content from Jiangxi has high economic value. Due to the copper mineral in the copper slag is mainly oxidized ore and the surface of the sulfide ore is oxidized, the copper recovery rate is low and the economic efficiency is poor. In this study, the copper oxide is activated by the addition of activator. To optimize the process conditions, the reaction surface methodology and the center composite design principle are used to investigate the response of the calcium oxide, sodium sulfide and Z-200 collector. The results show that the amount of Z-200 is the main factor affecting the grade and recovery rate of concentrate, and there are interaction effects among the response factors. The flotation index of close circuit test was achieved under the optimum conditions:CaO of 25 g/t, Na2S of 500 g/t and Z-200 of 100 g/t. The average grade of Cu in flotation concentrate is 12%, and the copper recovery is 86.57%, which proved that the flotation optimized process can obtain better recovery effect.

    Effect of rotating magnetic field coupled with water volume on CaCO3 crystallization
    LUO Zhiqiang, YANG Qingfeng
    2018, 69(7):  3029-3037.  doi:10.11949/j.issn.0438-1157.20171676
    Abstract ( 101 )   PDF (1085KB) ( 68 )  
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    With environmental issue being increasingly emphasized, anti-scaling methods without chemical additives gradually raises more concern over researchers. Some researchers consider magnetic treatment as a physical anti-scaling method that has the advantages of non-pollution and low cost. However, its effectiveness and mechanism in industrial applications still remain controversial. Wide range and narrow range magnetic treatment devices are newly designed, taking calcium carbonate crystal system as research object, to study the coupling relationship between magnetic treatment effect and the volume of treating water which are both closely related to industrial application. The results show that when the amount of treating water is small, magnetic treatment can promote the homogeneous nucleation of calcium carbonate, resulting in more crystal particles with smaller size and greater total deposition. In a certain speed range, magnetic treatment effect is enhanced with the increasing speed of rotating magnetic field.There is a clear coupling relationship between the rotating magnetic field and water volume:when the magnetic treatment conditions remained unchanged and the amount of water to be treated increased,magnetic treatment effect would be weakened; when the water volume treated remained unchanged and magnetic treatment condition strengthens, magnetic treatment effect would be enhanced. Stepwise magnetic treatment experiment with a part of solution which is going through magnetic treatment first and then gradually adding more can improve the removal rate of calcium carbonate in a large amount of water, and make the magnetic treatment effect more obvious. At the same time, the importance that matching water volume with magnetic field was illustrated.

    Enhancing mass transfer efficiency and stability of nickel ion by extraction gel membrane process conditions
    REN Xiaoshi, JIA Yue, LÜ Xiaolong, MA Shiqi, SHI Tenghua, CHEN Huayan
    2018, 69(7):  3038-3049.  doi:10.11949/j.issn.0438-1157.20171589
    Abstract ( 95 )   PDF (1317KB) ( 49 )  
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    The novel extraction gel membrane (EGM) prepared from polydimethylsiloxane-tetraethyl orthosilicatedi(2-ethylhexyl) phosphoric acid (PDMS-TEOS-D2EHPA) was applied in extraction of Ni ion. The basic physical and chemical properties of EGM were analyzed. The influences of the concentrations and flow rates of the two aqueous phases, aqueous phase temperature, module packing density, the feed circulation mode on the operation stability and Ni(Ⅱ) mass transfer flux of the EGM were explored. The results from 9 h experiments show that the highest extraction efficiency and the stability of EGM at the aqueous phase temperature of 22℃ were achieved in the condition of feed phase flow rate of 1900 ml·min-1, stripping flow rate of 93 ml·min-1, module packing density of 14% and the feed phase circulating through shell side, respectively. Finally, the operation stability of the EGM process were investigated and compared to conventional supported liquid membrane (SLM) process based on data from 60 h continuous running experiments. The results show that the conventional SLM suffered 100% flux loss within only 35 h, while the flux attenuation of EGM was merely 27.1% at the end of 60 h. Simultaneously, a 6.8 times promotion in initial flux compared to the traditional SLM was obtained. The results show dual advantages in improving both mass transfer efficiency and long-term operation stability of the EGM.

    Optimization and experimental study of vertical double wall dividing-wall column for separating a quaternary system
    WANG HongHai, WANG Baozheng, LI Chunli, JI Pengyu
    2018, 69(7):  3050-3058.  doi:10.11949/j.issn.0438-1157.20171552
    Abstract ( 78 )   PDF (727KB) ( 101 )  
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    A vertical double wall divided-wall column separating four-component mixture was proposed. The structure design of the tower was introduced and explained in detail. According to the structure and separation principle of the new divided-wall column, the five-tower model was designed and a shortcut design calculation was conducted. For the complete thermal coupling process of the four components separation of the hydrocarbon system, the simulation optimization and energy analysis were carried out by using the chemical engineering process simulation software Aspen. Compared with the general sequence tower separation process, the energy saving of the new divided-wall column was up to 18.6% and energy saving effect was obvious. By using the process simulation, a small pilot study was conducted on the new trays by using pentane, hexane, heptane and octane as separators. The results show that the main factor affecting the temperature distribution of the new divided-wall column is the spilt liquid ratio. The temperature distribution in the main tower section two could be controlled by controlling the reflux of the overhead condenser in the main tower section two of the new divided-wall column. Through the research of this paper, the theoretical basis and design reference for the industrialization of the separation of the four-component mixture in the new divided-wall column are provided.

    Characteristics of p-nitrophenol removal by SAT system with iron oxide coated sands
    WEN Yujuan, YANG Yuesuo, SONG Xiaoming, ZHANG Xi, LI Huizhong
    2018, 69(7):  3059-3067.  doi:10.11949/j.issn.0438-1157.20171620
    Abstract ( 66 )   PDF (1348KB) ( 84 )  
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    The more and more nitro aromatic compounds have been detected in the environment, and one of the most popular compounds was p-nitrophenol. To improve the removal effect of p-nitrophenol using soil aquifer system (SAT), the system was innovated with iron-oxide coated sand as the aquifer media. Characterization of the iron coated SAT shows that surface of the oxidized iron film was flocculent or lamellar without fixed shape. Ironoxide coated sand has pore structure and makes the specific surface increased 2 times to 4 times. Study of absorption kinetics indicated that the absorption kinetics were governed by the Freundlich model of chemical adsorption, and the absorption capacity was much enhanced. The diffusion model study demonstrated the pore diffusion was higher than sufficient diffusion. The results of the mini-column break through show that the adsorption is closely related to the residence time of the solute in the medium, so the flow rate should be appropriately controlled during the SAT operation.

    Preparation and adsorption properties of magnesium oxide via spray drying
    YANG Bin, SU Qi, YANG Gaoling, KUANG Mengjie, ZHANG Lina, SHI Anhong, LIU Baixiong
    2018, 69(7):  3068-3075.  doi:10.11949/j.issn.0438-1157.20171401
    Abstract ( 92 )   PDF (781KB) ( 119 )  
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    The flower-like MgO was synthesized by spray drying combined with heat treatment. The surface morphology of MgO was controlled by adjusting the heat treatment temperature. The adsorption properties of MgO powder as sorbent to Congo red were studied. When the heat treatment temperature was 400℃, a flower-like MgO nano structure was obtained. The specific surface area was 140.5 m2·g-1, and the saturated adsorption capacity of Congo red solution was about 1480 mg·g-1. Furthermore, the adsorption model, adsorption kinetics and adsorption mechanism were explored. The results show that the adsorption process accords with Langmuir adsorption model and the adsorption process of the sample to Congo red solution can be described by pseudo-second-order kinetics. The high uptake capability of the as-prepared flower-like MgO made it a potentially attractive adsorbent for the removal of Congo red from water.

    Preparation and adsorption properties of spherical poly(tannin)-cellulose resin
    ZHOU Peng, YUAN Hua, PENG Pingying, YAO Jinxin, PENG Zhiyuan
    2018, 69(7):  3076-3082.  doi:10.11949/j.issn.0438-1157.20171494
    Abstract ( 189 )   PDF (595KB) ( 119 )  
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    Tannin was crosslinked with paraformaldehyde to prepare tannin-phenolic polymer. The spherical poly(tannin)-cellulose resin was synthesized by inversing suspension cross-linking reaction of tannin-phenolic polymer and cellulose with epichlorohydrin as crosslinking agent. The spherical poly(tannin)-cellulose resin was characterized by infrared spectrum(FTIR) and scanning electron microscopy(SEM), and the adsorption properties of spherical poly(tannin)-cellulose resin for berberine hydrochloride were evaluated. The spherical poly(tannin)-cellulose resin has a porous structure and a large amount of phenolic hydroxyl groups in polymer network. The spherical poly(tannin)-cellulose resin has high adsorption capacity for berberine hydrochloride, the maximum adsorption capacity of berberine hydrochloride on spherical poly(tannin)-cellulose resin was 245.92 mg·g-1 when the initial concentration of berberine hydrochloride was 600 mg·L-1 at 298 K. The adsorption isotherms and kinetics of spherical poly(tannin)-cellulose resin for berberine hydrochloride can be well fitted by the Langmuir equation and pseudo-second-order model, respectively. The data of thermodynamic analysis suggest that the adsorption for berberine hydrochloride on spherical poly(tannin)-cellulose resin was a spontaneous and exothermic physical adsorption process. The spherical poly(tannin)-cellulose resin has a potential application prospect in the field of the separation and purification of alkaloids.

    Fault classification based on semi-supervised dense ladder network
    SHI Fangyi, WANG Ziyang, LIANG Jun
    2018, 69(7):  3083-3091.  doi:10.11949/j.issn.0438-1157.20171488
    Abstract ( 52 )   PDF (575KB) ( 62 )  
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    To meet the needs of fault identification and imbalanced dataset in actual industrial processes, a semisupervised deep learning method was proposed for fault classification. The enhanced semi-supervised ladder network, i.e., semi-supervised dense ladder network, was developed by improving network architecture and loss function. Dense connection strategy was applied in the network architecture to maximize information flow between layers of the ladder network, such that features among layers could be transmitted and copied. Meanwhile, to ensure consistency between training target and prediction output, prediction output loss of corrupted encoder was added into original loss function. Experiment results illustrated the proposed method could achieve ideal classification in small ratio marked dataset in actual industrial process.

    Double-level local KPCA method for incipient fault detection in nonlinear process
    DENG Xiaogang, DENG Jiawei, CAO Yuping, WANG Lei
    2018, 69(7):  3092-3100.  doi:10.11949/j.issn.0438-1157.20171675
    Abstract ( 79 )   PDF (667KB) ( 94 )  
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    A new method of double-level local kernel principal component analysis (DLKPCA) was proposed to overcome challenges that traditional kernel principal component analysis (KPCA) method has encountered in incipient fault detection of nonlinear process. In this method, local information was obtained from data in variable-wise and sample-wise viewpoints to improve fault detection performance. First, all process variables were diced into several local variable blocks according to similarity of mutual information correlation among different variables and kernel principal components. Then, residual function was constructed from score vector and eigenvalue to mine local sample-wise information. Finally, the Bayesian fusion strategy was used to integrate results of each block. Simulation results on Tennessee Eastman standard process show that the proposed method can effectively detect incipient faults and has better fault detection performance than traditional KPCA method.

    A self-adaptive multi-output soft sensor modeling based on deep neural network
    QIU Yu, LIU Yiqi, WU Jing, HUANG Daoping
    2018, 69(7):  3101-3113.  doi:10.11949/j.issn.0438-1157.20171624
    Abstract ( 153 )   PDF (1000KB) ( 262 )  
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    In wastewater treatment process (WWTP), existence of several important but difficult-to-measure process variables hinders not only monitoring of the production process but also adjustment or optimization of process control strategies. Even though soft-sensor models are reasonably constructed, it will still suffer degradation problem and high maintenance cost in real-time operation. Additionally, selection of proper secondary variables directly affects subsequent modeling. Therefore, a self-adaptive multi-output soft sensor model based on deep neural network was proposed for simultaneous online prediction of multiple target variables in wastewater treatment. Deep neural network was constructed from a stacked auto-encoder, which had satisfactory performance of online prediction under extremely complex scenarios. In order to overcome degradation problem and select proper secondary variables, time difference modeling and VIP (variable importance in projection) methods were added. Finally, validation on a true WWTP process shows that the proposed soft-sensor model has good performance on multiple output prediction and satisfactory prediction on single target.

    Ensemble WELM method for imbalanced learning in fault diagnosis of wastewater treatment process
    XU Yuge, SUN Chengli, LAI Chunling, LUO Fei
    2018, 69(7):  3114-3124.  doi:10.11949/j.issn.0438-1157.20171365
    Abstract ( 63 )   PDF (929KB) ( 64 )  
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    Highly imbalanced data for fault diagnosis in wastewater treatment process seriously affects fault diagnosis performance, especially in identification of faulty classes. Reduced recognition accuracies of faulty classes may lead to occurrence of other issues, such as failure to reach quality standard of effluent water, high operation cost and secondary pollution. An ensemble weighted extreme learning machine method (WELM) for imbalanced learning was proposed for fault diagnosis modeling in wastewater treatment process. AdaBoost ensemble classification algorithm based on WELM base classifiers was integrated into assessment index G-mean of imbalanced classification. New updating rules for initial weight matrix in the base classifiers and ensemble weight formula were defined for iterative learning of the base classifiers. Simulation results show that this fault diagnosis model of wastewater treatment process can improve classification performance, such as G-mean value, overall classification precision, and recognition accuracy of faulty classes. The proposed method is effective in imbalanced fault diagnosis of wastewater treatment process.

    Identification of linear parameter varying systems with variational Bayesian algorithm
    LI Hanshuang, ZHAO Zhonggai, LIU Fei
    2018, 69(7):  3125-3134.  doi:10.11949/j.issn.0438-1157.20171563
    Abstract ( 112 )   PDF (657KB) ( 181 )  
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    Linear parameter varying (LPV) method is an effective tool for nonlinear process modeling, which converts modeling of multi-stage nonlinear complex process into identification of multiple linear models. Various disturbance factors in industrial processes result in stochasticity of system modeling and uncertainty of model parameters. Identification of LPV models was studied under the variational Bayesian (VB) framework. After prior probability distributions were assigned to variables and parameters, posterior distributions of these variables and parameters were estimated by maximizing lower limits of objective functions. This full Bayesian system identification approach not only provided point estimates of parameters, but also quantified uncertainty of estimation. Numerical simulation on typical two-stage process and continuous stirred tank reactor (CSTR) demonstrated effectiveness and superiority of the proposed method.

    A structure evolution strategy motivated by large step size for optimization of heat exchanger network
    SUN Tao, CUI Guomin, CHEN Jiaxing
    2018, 69(7):  3135-3148.  doi:10.11949/j.issn.0438-1157.20171625
    Abstract ( 70 )   PDF (929KB) ( 50 )  
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    Random walk algorithm with compulsive evolution (RWCE) was an effective method for the optimization of heat exchanger network with the advantage of simple evolutionary strategy and less control parameters. The RWCE algorithm had the capacity to jump out of the local optimal through continuously accepting the imperfect solutions, but its jumping efficiency was often limited by the step size. The global search ability of the algorithm was reduced. Therefore, a novel combined step size generation method was established by studying the step size distribution of RWCE algorithm and analyzing the mechanism of large step size assisted to jump out of local optimal, then a structure evolution strategy motivated by large step size was proposed. Finally, the validity of the proposed structure evolution strategy was verified by three cases. Compared with the literature results, the results showed that the structure evolution strategy motivated by large step size had a strong global search ability.

    Coupled optimization modeling and application of fuel gas-steam-power system in integrated iron and steel works
    ZHANG Qi, MA Jialin, GAO Jintong, NI Tuanjie, LI Hui
    2018, 69(7):  3149-3158.  doi:10.11949/j.issn.0438-1157.20171700
    Abstract ( 97 )   PDF (608KB) ( 88 )  
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    Fuel gas, steam and power are important components of energy systems in integrated iron and steel works, which consists about 60% of total energy consumption. Reasonable development of energy output, fuel consumption and power purchase plan has very important significance in cost reduction and pollution control in integrated iron and steel works. Based on characteristics of fuel structure, equipment types and operating conditions, a coupled system optimization model was established to minimize both economic and environmental costs. With consideration of influencing factors, such as fluctuation of excess fuel gas, dynamic demand of steam and electricity, multi-fuel structure and external time-segmented price, the optimal scheduling plan for energy system was solved by GAMS software. The simulation results of the model applied to a large steel company show that the model can effectively provide a reasonable production plan of fuel gas-steam-power system, regulate excess fuel gas, efficient energy use, reduce operation cost, and increase economic and environmental benefits.

    DLNS-PCA-based fault detection for multimode batch process
    FENG Liwei, ZHANG Cheng, LI Yuan, XIE Yanhong
    2018, 69(7):  3159-3166.  doi:10.11949/j.issn.0438-1157.20171629
    Abstract ( 104 )   PDF (840KB) ( 85 )  
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    Modern industrial products often require multiple production stages, and the fault detection of multi-stage production process has become an important issue. Multi-stage process data have the characteristics of multi center, different structure of each stage and so on. Aiming at the characteristics, a fault detection method based on double local neighborhood standardization and principal component analysis (DLNS-PCA) is proposed. Firstly, the double local neighborhood set of the sample is found. Secondly, the standard samples are obtained by using the information of the double local neighborhood set. Finally, the PCA method is used to detect the fault on the standard sample set. The DLNS can move the data centers of each stage to the same point, and adjust the degrees of dispersion of data at each stage to make its approximately equal, then multi-stage process data is fused to a single modal data following multivariate Gauss distribution. A fault detection of penicillin simulation process was carried out. The results showed that DLNS-PCA has higher fault detection rate than PCA, KPCA and FD-kNN methods. DLNS-PCA method improves the efficiency of multi-stage process fault detection.

    Chiller fault diagnosis based on fusional Bayesian network
    WANG Zhanwei, WANG Lin, LIANG Kunfeng, YUAN Junfei, WANG Zhiwei
    2018, 69(7):  3167-3173.  doi:10.11949/j.issn.0438-1157.20180003
    Abstract ( 85 )   PDF (446KB) ( 101 )  
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    Based on a open network topology of Bayesian network (BN), on-site observed information is fused into BN to improve the fault diagnostic performances. A mechanism of distance rejection is introduced to determine the probability distribution of sensor measurement parameters. A chiller fault diagnosis method based on fusional BN is proposed. This method is able to detect new types of chiller fault and update its fault library dynamically. Use the experimental data from ASHRAE RP-1043 to evaluate the performances of the proposed method. The results show that the accuracy of the new type of fault (NF1) is 99.8%, and fusing on-site observed information increases the detection accuracies of the new types of fault (NF2) by 32.6% and the diagnostic accuracies of known fault rl and ro by 4.8% and 11.2% respectively.

    Simulation of fiber erosion on mold during filling process of fiber reinforced plastic injection molding
    JIANG Ben, ZHAI Ming, REN Jianxing, MA Shiheng, SHEN Changyu
    2018, 69(7):  3174-3180.  doi:10.11949/j.issn.0438-1157.20171673
    Abstract ( 92 )   PDF (1118KB) ( 41 )  
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    The surface erosion wear of plastic mold caused by the impact of glass fibers was studied. The finite element software ANSYS/LS-DYNA was employed to study the erosion process. A multi-particle erosion finite element model was established and a three-dimensional explicit impact dynamic scheme was carried out to analyze the erosion of the mold under different impacting velocities and incident angles to clarify the erosion mechanism. The results showed that the erosion of glass fibers to the mold was dominated by micro-cutting, and the erosion rate increased with the rising of impacting velocity and tended to rise and decline with the increasing of incident angle.

    Analysis of influencing factors of sealing face performance of mechanical seal coating
    LI Shuangxi, SUN Xiandong, ZHANG Peng
    2018, 69(7):  3181-3189.  doi:10.11949/j.issn.0438-1157.20171544
    Abstract ( 78 )   PDF (809KB) ( 69 )  
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    The application of sealing ring for mechanical coating, which combines the characteristics of wearresistant coating with the characteristics of the toughness base material, depends on experience. There is a lack of research on its performance. A thermal structural coupling model consisting of rotating seal ring, stationary seal ring and stationary ring seat was established by using ANSYS software. It considers the influence of the coating surface deformation, the liquid film reverse pressure and the temperature between the sealing rings. The correctness of the analytical model is validated by the experiment. The influence of coating structure and material on the product of seal face pressure and maximum velocity ((PbV)max), the seal face in the highest end temperature (Tmax), coatings on the surface of the maximum tensile stress (σmax), maximum shear stress of the main interface (τmax), the interface maximum side effect of shear stress (σcmax) and the maximum tensile stress (τcmax) was analyzed, and the coating structure and material were determined. The results show that the coating thickness, the coating and the substrate of the thermal expansion coefficient and elastic modulus ratio mainly affect the coating surface of the maximum tensile stress. For the coating surface design the thermal expansion coefficient of coating and substrate should be more than 0.5, the spraying angle should be 15°-30°, the elastic modulus ratio should be below 2.5, and the coating thickness should be 0.4-0.6 mm.

    Preparation of mixed-mode adsorbent and its application for removing Protein A from antibody
    YAN Jun, QIAN Yongchang, YAO Shanjing, LIN Dongqiang
    2018, 69(7):  3190-3197.  doi:10.11949/j.issn.0438-1157.20171564
    Abstract ( 89 )   PDF (670KB) ( 93 )  
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    A new mixed-mode chromatography (MMC) adsorbent, named Adhere NUPharose FF with functional ligand N-benzyl-N-merhylethanolamine was prepared and used for removing the leaked Protein A ligand while purifying antibody. The ligand presents hydrophobic, electrostatic and hydrogen bond interactions between Adhere NUPharose FF and adsorbate. The agarose beads were activated by allyl glycidyl ether and conditions of the activation and processes of ligand coupling on the agarose beads were optimized, leading to an activated density of 260 μmol·ml-1 and a ligand density of 120 μmol·ml-1. Meantime, the mixture of antibody and Protein A was used to test the ability of the prepared adsorbent to remove Protein A from antibody. The data showed that it could remove 83.1% Protein A from antibody preparation, and supply feasible method to remove Protein A from antibody product.

    Process simulation and economic evaluation of monoclonal antibody production
    SHI Ce, YU Ji, GAO Dong, WANG Haibin, YAO Shanjing, LIN Dongqiang
    2018, 69(7):  3198-3207.  doi:10.11949/j.issn.0438-1157.20171645
    Abstract ( 136 )   PDF (818KB) ( 367 )  
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    Monoclonal antibody (mAb) is the most important biopharmaceuticals. With the continuous expansion of industrial-scale production and competition, the process rationality and economy have attracted more and more attention. In this paper, four scales of mAb manufacturing processes of 500, 2000, 5000 and 15000 L were established by using SuperPro Designer software, a bioprocess simulation software. Through the process analysis and cost evaluation, the economic 'hotspots' were determined and the optimization strategies were then proposed. The results showed that the scale effect on the production cost was obvious. With the increase of production scale, the cost would be significantly reduced, and the economic hotspots were transferred from equipment-dependent costs to raw materials and consumables, including serum-free medium and Protein A affinity resin. The key for upstream optimization was to increase the titer of mAb expression during cell culture. But when the titer was higher than 5 g/L, the effect of titer increasing on the cost was weakened and the cost was then mainly controlled by downstream process. The downstream optimization should focus on Protein A affinity resins, including capacity,price and the reuse cycles. The optimization of overall process would be the stagger mode with three main bioreactors corresponding one downstream line, for which the production scale and equipment cost were two key factors. The results demonstrated that with the aid of reasonable process simulation and economic evaluation, some hotspots of manufacture process could be identified and the appropriate optimization strategies would be proposed to improve the process efficiency and reduce the production cost.

    Migration and transformation of phosphorus during pyrolysis process of sewage sludge
    MENG Xiangdong, HUANG Qunxing, YAN Jianhua, GAO Huaping
    2018, 69(7):  3208-3215.  doi:10.11949/j.issn.0438-1157.20171509
    Abstract ( 155 )   PDF (705KB) ( 209 )  
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    The migration and transformation of phosphorus in sewage sludge during the pyrolysis process were studied based on standard measurement testing (SMT), analyzing the phosphorus in the treated sludge samples using nuclear magnetic spectrum and X-ray diffraction, and also the occurrence and distribution of phosphorus in the residue of the sewage sludge sample after pyrolysis. From the results obtained, with increasing heat treatment temperature, the organic phosphorus continuously transformed to inorganic phosphorus. Phosphorus was concentrated in the residue of the sludge after pyrolysis when the pyrolysis temperature was below 800℃. With increasing pyrolysis temperature, the content of total phosphorus (TP), inorganic phosphorus (IP), apatite phosphorus(AP) in the sludge showed a trend of gradual increases, while the non-apatite inorganic phosphorus (NAIP) content indicated a trend of fluctuation with an increase and then decreases. The increase of pyrolysis temperature led NAIP transform into AP, and AP content reached the maximum in 800℃. XRD results showed that the main forms of NAIP in the sludge were aluminum phosphate and ferric phosphate. The content of calcium phosphate in the sludge sample increased with increasing temperature. From the results of 31P NMR, the orthophosphoric acid monoester was converted to orthophosphate after heating, and orthophosphate was the most stable form of phosphorus. After the heat treatment, phosphorus was mainly in the form of orthophosphate. The new understanding on phosphorus migration and transformation in the process of sludge pyrolysis was discovered, and the theoretical support for the harmless, resource utilization and phosphorus pollution control technology of sludge was provided.

    Preparation of red mud/coal based material and its performance to remove Cr(Ⅵ) in waste water
    QIU Yali, LI Changming, WANG Deliang, LI Wensong, YU Jian, GAO Shiqiu, XU Guangwen
    2018, 69(7):  3216-3225.  doi:10.11949/j.issn.0438-1157.20171680
    Abstract ( 170 )   PDF (803KB) ( 178 )  
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    As the cheap substitution of commercial iron carbon microelectrolyte filler to remove Cr(Ⅵ) in waste water, the red mud/coal based material was prepared from the mixtures of red mud, pulverized lignite and sodium carboxymethyl cellulose via a carbothermal method. The different preparation parameters (carbonization temperature, carbonization time, mass ratio of red mud/coal) and adsorption conditions (solution pH, concentration) were investigated to improve the removal efficiency of Cr(Ⅵ). The results demonstrated that the red mud/coal based material carbonizated at 800℃ for 1 h with the mass ratio (red mud/coal) of 1/3 can reach the highest Cr(Ⅵ) removal capacity (4.03 mg·g-1), the lowest Fe dissolution ratio (< 0.19 mg·g-1) and the maximum adsorption capacity (12.97 mg·g-1, according to the Langmuir adsorption isotherm models). The adsorption isotherm of Cr(Ⅵ) on the red mud/coal based material was well consistent with Freundlich equation model, and its adsorption kinetics can be described by the pseudo-first-order or pseudo-second-order equation. The multiple characterization methods (XRD, XRF, BET, and SEM) further revealed that the red mud/coal based material had higher reduction degree of Fe element, bigger BET area and volume and better particle dispersion than the commercial iron carbon microelectrolyte filler, which accounted for its excellent removal efficiency of Cr(Ⅵ).

    Effect of exogenous H2 on biogas fermentation system
    DENG Xiaoning, YE Yuanyuan, ZHOU Xinkai, CHENG Yu'e, LIN Chunmian
    2018, 69(7):  3226-3233.  doi:10.11949/j.issn.0438-1157.20171533
    Abstract ( 109 )   PDF (705KB) ( 113 )  
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    The biogas fermentation was carried out in 30 L anaerobic stirred-tanks at 55℃ by using straw as substrate, in which the effect of exogenous H2 was particularly investigated. The results showed that the in-situ upgrading of biogas by means of introducing exogenous H2 was realized. At the stirring rate 100 r·min-1, the relative average volume of CH4 fraction increased from 69.6% to 94.4% while the relative average volume of CO2 fraction decreased from 30.4% to 5.6%. Compared with the bench-scale experiment without stirring, the utilization and conversion of the exogenous H2 increased from 91.0% to 93.1% and from 85.0% to 96.8%, respectively, at the stirring rate of 50 r·min-1. The introduction of exogenous H2 significantly promoted the degradation of propionic acid, butyric acid and isobutyric acid, which could effectively avoid the accumulation of volatile fatty acids in the fermentation process. At the same time, the strong agitation had an important influence on the decomposition of acetic acid and the consumption of CO2 in the biogas slurry. In addition, the introduction of exogenous H2 could change the proportion of the methanogenic microorganism in the fermentation system without obviously affecting the methanogenic microbial community.

    Experimental study of selective non-catalytic reduction process with methylamine as reducing agent
    PU Ge, DU Jiantai, ZHANG Zhang, ZHANG Dinghai, WU Bang, HUANG Beibei, ZHU Tuanhui
    2018, 69(7):  3234-3241.  doi:10.11949/j.issn.0438-1157.20171687
    Abstract ( 52 )   PDF (627KB) ( 58 )  
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    Selective non-catalytic reduction (SNCR) denitration efficiency is lower than the minimum designed requirement when the boiler is operating under low load. To improve the characteristics of such working conditions, the feature of selective non-catalytic reduction denitration with methylamine as reductants is studied and the reaction mechanism is analyzed in the tube furnace reaction system. The effect of oxygen content, NSR, initial concentration of NO, SO2 and water content on the denitrification properties of methylamine SNCR is discussed. The results show that:the relationship between denitration efficiency and temperature is bimodal, the inflection point temperature is 750℃, and the best temperature window for practical industrial application is 450-600℃. The NO reduction efficiency was increased with the increase of NSR, and the concentration of NO2 and N2O was also augmented. The maximum NO removal efficiency was 85.0%. The oxygen content has dual characteristics to SNCR denitrification reaction, the efficiency of NO reduction is the greatest under the condition of 3% oxygen content. The increase of the initial concentration of NO makes the material concentration of the simulated flue gas increase, the NO reduction efficiency and the by-product increase. The higher concentration of SO2, the greater the reduction of NO reduction efficiency. The increase of water content was beneficial to the denitrification reaction. The experimental conclusion of methylamine SNCR denitrification in this paper is helpful to the application of selective non-catalytic reduction process with methylamine as reducing agent to industrial furnace and to optimize the denitrification characteristics of the boiler at low load operation.

    Numerical simulation analysis of flow characteristics of suspended packing in biological contact oxidation tank
    WU Yun, DU Xiaolei, SONG Kai, LIU Hongyu, WANG Jie, WANG Erpo
    2018, 69(7):  3242-3248.  doi:10.11949/j.issn.0438-1157.20171511
    Abstract ( 99 )   PDF (984KB) ( 107 )  
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    A model was developed to simulate the flow properties of suspended packing materials in the biological contact oxidation tank according to the FLUENT multi-phase flow modeling. The distribution of suspended packing materials was improved by optimizing the oxidation tank structure and aeration intensity distribution. The results indicated that the ratio of length to width and aeration intensity distribution played the key role in uniform mixing of the packing materials in the oxidation tank. The tank was divided into four subsections using separation wall, which reduced the ratio of length to width from 7.1 to 1.8. Subsequently, instead of accumulating at the end zone of the oxidation tank, the biological packing materials could be evenly distributed in four subsections. When water body flew through the overflow hole, the flow rate instantaneously increased due to the narrowing cross section area. The water body at high flow rate collided with that at low flow rate at the surrounding area, resulting in the formation of huge vortex flow field. Thus, it mixed consistently the packing materials and enhanced the dispersion effect of the materials. However, the intersection between the separation wall and side wall of the oxidation tank was subjected to the formation of dead zone. It could be resolved by redistributing the aeration intensity of the subsections. The results suggested that uneven aeration could obviously optimize the flow field, which eliminated the accumulation of the packing materials at the side wall and end zone.

    Removal of marine diesel engine exhaust pollutants with DOC+SCR technologies
    WANG Zongyu, KUANG Hailang, ZHANG Jifeng, JI Yulong
    2018, 69(7):  3249-3256.  doi:10.11949/j.issn.0438-1157.20171600
    Abstract ( 86 )   PDF (534KB) ( 95 )  
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    The emission characteristics of DOC and SCR were tested by SMG 100 particle analyzer and Testo 350 flue gas analyzer on a diesel generator bench. Six working points were tested at rated speed. The effects of DOC on CO, NOx and PM were analyzed. The denitrification rates of SCR at different power points and urea injection were investigated. The results showed that DOC was greatly affected by temperature. CO removal rate was above 96% when the temperature was higher than 250℃. PM removal rate was above 76% at low or medium load. However, the PM removal rate was only 36% at full load because the PM concentration increased rapidly due to the rapid deterioration of diesel combustion. DOC could convert NO to NO2, but it had little effect on the total concentration of NOx. The denitrification rate of SCR was closely related to temperature and NH3/NOx ratio. It was almost 100% when the temperature was higher than 250℃ and NH3/NOx=1. Through the comparison with many articles, it may be more appropriate to use power/catalyst volume as the initial selection parameter for the vanadium-based SCR.

    Characteristics of dehydrated sludge based on chemical modification: low temperature hot-air drying
    LI Haiyan, LIU Huan, WANG Jiaxing, JIN Minghao, DENG Hongping, LU Geng, ZHANG Xiuju, YAO Hong
    2018, 69(7):  3257-3262.  doi:10.11949/j.issn.0438-1157.20171634
    Abstract ( 119 )   PDF (580KB) ( 111 )  
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    In China, the sludge production is gradually increasing recently, while most of disposal processes require a reduction in the water content of sludge to a certain extent. Low-temperature drying with heat pumps is an economical and efficient sludge drying technology, which is also free from geographical restrictions. Owing to the unclear characteristics of sludge drying at low temperature, influences of temperature and particle size on sludge drying rate were studied by controlling these two variables separately in constant temperature and humidity chamber. And visualized relationships among drying rate and two factors were obtained by applying curve fitting method. Moreover, moisture release characteristics of iron-calcium-carbon-based conditioning sludge in low-temperature drying and traditional drying cases were comparatively explored by using a self-designed vertical sludge drying system. The results indicated that even at 60-80℃, drying rate still significantly accelerated with temperature increasing. A decreasing quadratic fitting polynomial satisfied the relation between drying time reduction and temperature increment. An incremental cubic fitting polynomial is awfully appropriate for the connection between drying time and sludge particle mass in the cases of various kinds of sludge. It is remarkable that iron-calciumcarbon-based conditioner can dramatically improve the sludge drying performance, because CaO and rice husk can increase the porosity and thermal conductivity of sludge, and the latter has a more obvious effect on low-temperature drying in the early stage.

    Hydrothermal synthesis of reduced graphene oxide with tunable conductivity
    WENG Chengjie, SHI Yexun, HE Dafang, SHEN Liming, BAO Ningzhong
    2018, 69(7):  3263-3269.  doi:10.11949/j.issn.0438-1157.20171582
    Abstract ( 233 )   PDF (1001KB) ( 423 )  
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    Reduced graphene oxide (rGO) with tunable conductivity has great promise for potential applications in the fields of advanced structural-functional composites, new chemical materials and so on. In this research, environment-friendly hydrothermal method was applied to prepare rGO. The conductivity of the synthesized rGO can be controlled from 10-4 to 1 S·cm-1 by changing the hydrothermal reaction temperature and time. Various characterization techniques such as UV-vis, FT-IR, XPS, SEM, XRD, and Raman spectroscopy were used to analyze the composition and structure change of the rGO. The results showed that the oxygen contained functional groups on the rGO surface decomposed rapidly at ≥ 120℃, and the content of oxygen contained functional groups decreased drastically at ≥ 140℃. Meanwhile, the carbon sp2 region of the rGO was recovered gradually, which caused the conductivity increased to 1 S·cm-1 and the interlayer spacing decreased from 8.2 Å to 3.6 Å. Compared with thermal reduction method, hydrothermal method avoids the aggregation and stacking of the rGO, which has great significance in large-scale production of the rGO with tunable conductivity.

    Characteristics of solid-waste-based sulfoaluminate cementitious material being used in 3D printing and process simulation
    REN Changzai, WANG Wenlong, LI Guolin, WANG Biao
    2018, 69(7):  3270-3278.  doi:10.11949/j.issn.0438-1157.20171555
    Abstract ( 103 )   PDF (750KB) ( 127 )  
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    To obtain high performance, low cost and extend technology application, industrial solid wastes were used to prepare sulfoaluminate cementitious material (SCM), which was then processed into three-dimensional (3D) printing materials by using a suitable accelerator and retarder. Multidiscipline coupled-field analysis was used to determine the influence of slurry velocity and the quality that results from different water-cement ratios with the same nozzle diameter. It was proved that the SCM prepared from industrial solid wastes could meet the national standard GB-2007-R525. After improving their properties, the SCMs exhibit advantages of a controlled setting time of between 10 and 30 min, a rapid hardening and an early stable strength. The hydrated-specimen compressive strength reached 15-20 MPa after 2 h of curing. When the water-cement ratio of the 3D printing-material slurry exceeded 0.6, stacking and collapse phenomena might be resulted. When the water-cement ratio was below 0.4, the jetted slurry showed tailing phenomena that could affect the printing speed. A water-cement ratio of~0.5 with its corresponding nozzle size was most suitable for 3D printing applications.

    Microwave-induced imidazole poly(ionic liquid)/poly(vinyl alcohol) shape memory materials
    DU Haiyan, XU Yuyu, REN Zhe, YANG Huimin
    2018, 69(7):  3279-3285.  doi:10.11949/j.issn.0438-1157.20171539
    Abstract ( 85 )   PDF (729KB) ( 88 )  
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    The present work combines the microwave mechanism, the structure characteristic of poly(ionic liquids) and shape memory polymers to design and synthesize microwave induced shape memory polymer composites (SMPC) completely based on polymers. Ionic liquid (IL) monomer ethylene imidazole was synthesized initially, and then ILM was polymerized in poly(vinyl alcohol)/glutaric dialdehyde solution by using in suit polymerization to introduce PIL into PVA matrix, obtaining the PIL/PVA shape memory polymer composites (SMPC). 1H NMR was used to characterize the structure of ILM and PIL to prove the structural accuracy of the targeted compounds. Dielectric performance test results show PIL/PVA samples have high dielectric constant and dielectric loss. The dielectric loss factor of PIL/PVA composites gradually increase when the P[ViEtIm] [BF4] content increases from 0 to 30%, indicating PIL is one effective microwave absorption medium. The bending test results show the composites have good shape memory effect under microwave irradiation. For all samples, the shape fixity ratio nearly gets 100%, and the shape recovery ratio could over 80%. Moreover, the PIL content and the microwave output power have obvious effects on the shape recovery and recovery time. 140 W output power is enough to drive PIL/PVA to recover to its original shape, and the shape recovery could finish within 40 s under 280 W irradiation. When the output power increases to 420 W, SMPC could recover to its original shape within 20 s.

    Surface electrokinetic phenomenon of DK nanofiltration membrane under threshold concentration condition
    SONG Yuefei, QIN Wenbo, ZHANG Shan, HU Qihua, REN Ruiyi, XUE Shoucong
    2018, 69(7):  3286-3292.  doi:10.11949/j.issn.0438-1157.20171471
    Abstract ( 88 )   PDF (545KB) ( 69 )  
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    In the process when inlet bulk solution with low or medium concentration was involved, the scaling was apt to appeared on the nanofiltration (NF) membrane surface in the retentate side. Therefore, the study of surface electrokinetic phenomena of NF membrane termed as DK membrane under threshold concentration condition is very important. In this paper, the surface charge properties of DK nanofiltration membrane were studied using streaming potential method, and a series of two-component ternary electrolyte solutions (K2SO4+CaCl2) with the molar ratio of 1:1 were involved as the study objects. Using the home-made tangential streaming potential test device, DK membrane was characterized with streaming potential (Es), Zeta (ζ) potential and other measurements encountering with a wider scale-prone ionic concentration (0.5-18 mol·m-3), operating pressure (25-200 kPa) and feed pH (3.0-10.0). The results showed that at operating pressure of 180 kPa, with the scale-prone ionic concentration of feed solution ranged from 0.5 to 18 mol·m-3, it turned out Es and ζ -potential values increased from -87.37 and -59.13 mV to -3.41 and -36.34 mV, respectively. It becomes less negative and tends to be neutral due to electrostatic charge shielding and compression of the diffuse layer. But the calculated surface charge density (σ) value always increased from 13.94 to 34.86 mC·m-2 under the same operating conditions. It could be inferred that under the condition of non-alkaline sparingly soluble salt CaSO4 occurring in brine side, there are still some surface electrokinetic phenomena with low or medium level on NF membrane surface.

    Electrochemical properties of straw-based carbon materials in Li2SO4 electrolyte
    CHEN Zhanghao, MA Hongfang, ZHU Hanfei, WANG Xiaodan, LIU Xinxin, XU Zhaogui, YANG Juanjuan
    2018, 69(7):  3293-3299.  doi:10.11949/j.issn.0438-1157.20171622
    Abstract ( 102 )   PDF (677KB) ( 66 )  
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    The porous carbon materials were synthesized from the straw by hydrothermal method coupled with KOH activation, of which the structure and morphology were characterized. The electrochemical properties of the porous carbon materials were evaluated by the cyclic voltammetry, galvanostatic charge/discharge and AC impedance tests in Li2SO4 electrolyte with different concentrations using a three electrodes electrochemical system. The results showed that the porous carbon materials have the best electrochemical performances in 0.5 mol·L-1 Li2SO4 electrolyte. The specific capacitance of porous carbon materials can reach 224 F·g-1 at a current density of 0.5 A·g-1, with specific capacitance retention of over 94.1% after the 1500 charge/discharge cycles, which indicates a good cycle characteristics.