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Table of Content
05 January 2019, Volume 70 Issue 1
    Reviews and monographs
    Similarity between fluidization and phase transition
    Wei CHEN, Ying REN
    2019, 70(1):  1-9.  doi:10.11949/j.issn.0438-1157.20180315
    Abstract ( 253 )   HTML ( 7)   PDF (661KB) ( 154 )  
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    Generally, single-component multiphase systems exhibit three different structures and properties in solid, liquid, and gaseous state with temperature changes. The multiphase system consisting of solid particles and fluids in a circulating fluidized bed also experiences three structures with the increase of gas flow velocity, namely, bubbling, turbulence and rapid flow. Although the two systems are quite different in structure and nature, using the concept of mesoscience to analyze the state of the system, the transitional parameter, the driving force for the system state evolution and the underlying mechanisms, the two systems turn to be quite similar in nature. Their physical roots are alike in all important essentials, which are the inevitable result of the compromise in competition between different dominant mechanisms in the complex systems. After comparing the fluidization and the phase transition, a new proposition based on the energy minimization multi-scale (EMMS) model is suggested to sufficiently characterize the real non-equilibrium kinetics of phase transition.

    Research progress in extraction and recovery of lithium from hard-rock ores
    Hui SU, Zhaowu ZHU, Lina WANG, Tao QI
    2019, 70(1):  10-23.  doi:10.11949/j.issn.0438-1157.20180465
    Abstract ( 237 )   HTML ( 8)   PDF (880KB) ( 165 )  
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    Lithium is widely used in new types of energy materials and the applications are growing fast. Lithium hard-rock ores are the main resources for lithium production. The trend of lithium recovery from the ores is to realize cleaning and effective production, and resource comprehensive utilizations. Based on the composition and structure analysis of various kinds of lithium ores, its recovery by a variety of methods, such as, typically, acidic, alkaline, salt were reviewed. Future development for the techniques of lithium recovery from ores was also discussed. It is shown that the lithium extraction by acidic methods was usually high. However, the composition of the acidic leachate was complex, resulting in a long process of purification of lithium. It also could cause environmental pollution by off-gas when processing the ores containing fluorine. Alkali and salt based processes had good lithium selectivity, but its extraction was low and the cost was high, and large amounts of solid wastes were generated difficult to store and re-use. Some other methods have both advantages and disadvantages, such as high-temperature chlorination method which has high metal recovery and ready solid residue utilization but has high corrosiveness to the equipment. Therefore, the development of new processes for extracting lithium from ore is focused on reducing the output of waste residue and achieving comprehensive recovery of associated resources.

    Thermodynamics
    Density measurements of endothermic hydrocarbon fuel using random temperature signal cross-correlation
    Chen GENG, Yajun GUO, Song FENG, Qincheng BI
    2019, 70(1):  24-31.  doi:10.11949/j.issn.0438-1157.20180970
    Abstract ( 130 )   HTML ( 3)   PDF (605KB) ( 62 )  
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    To measure the density of a new endothermic hydrocarbon fuel (EHF) at supercritical pressures, a new densimeter, which is based on the mass conservation equation and cross-correlation method, was designed and constructed. Two K-type thermocouples with the same thermoelectric characteristics were installed in the upstream and downstream of the test tube with distance of 148 mm as the cross-correlation sensor. The delay time was found using the cross-correlation between upstream and downstream signal which were measured by the thermocouples. High sampling rate and correlation coefficient were used to ensure the accuracy and similarity of the signals. So the mean flow velocity could be calculated by the delay time and distance. With the flow velocity and mass flow rate known, the density could be determined based on the mass conservation equation. The n-dodecane and the binary mixture of n-octane and n-heptane with mass ratio of 1∶1 were tested for the system calibration. According to error analysis, the maximum relative deviations were below ±1.2%, and the absolute average relative deviations were within 0.6%. On the basis of calibration experiments, this measurement covers the temperature range of 302.0—529.6 K under pressures from 3.0 MPa to 5.0 MPa. The application of this method provides a new thinking of the density on-line measurement of endothermic hydrocarbon fuel under supercritical pressures.

    Fluid dynamics and transport phenomena
    Comparison of macro-mixing characteristics of a stirred tank with different impellers
    Ting LI, Zhuotai JIA, Qinghua ZHANG, Chao YANG, Zaisha MAO
    2019, 70(1):  32-38.  doi:10.11949/j.issn.0438-1157.20180948
    Abstract ( 118 )   HTML ( 6)   PDF (588KB) ( 96 )  
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    In order to enrich the data of centripetal impeller performance, the macro-mixing characteristics of stirred tanks installed with centripetal impeller, Rushton impeller, three pitched blade impeller and punched blade impeller were systematically studied. The influence of impeller speed, impeller off-bottom clearance, impeller type on mixing time, power and mixing efficiency of the stirred tank was investigated. The results show that the mixing time of the four impellers are all decreased with increasing impeller speed, and the power are all increased. At the same impeller speed, the power of the Rushton impeller is the highest, and the three pitched blade impeller is the lowest. The power of centripetal impeller is only a little higher than that of the three pitched blade impeller. However, the macro-mixing time of the four impellers shows different trends with increasing the impeller off-bottom clearance. The importance of the factor affecting the macro-mixing efficiency is impeller speed >impeller type > impeller off-bottom clearance. Among the four impellers, the overall evaluation of the macro-mixing efficiency of the centripetal impeller is the highest. The research results of this paper can accumulate experimental data for the industrial application of new impellers such as centripetal impeller, and provide theoretical basis for its optimization design and scale-up.

    Effect of solid particles in evaporative hot water tower on bubble movement
    Chenhui HU, Yifei WANG, Zebin BAO, Guangsuo YU
    2019, 70(1):  39-48.  doi:10.11949/j.issn.0438-1157.20180697
    Abstract ( 114 )   HTML ( 3)   PDF (1020KB) ( 75 )  
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    The evaporative hot water tower was used as the research object for visualization experiments. The high-speed camera and image processing software were used to study the motion period and characteristics of a single bubble above the single-hole sieve tray in the hot water tower. The aperture was 3 mm. In the experiment process, non-condensable properties were added to the steam. A mixture of gaseous N2 and N2/solid particles was used to study the effect of solid particles on bubble formation, fragmentation and processes. The results show that the entire growth cycle of the bubble includes the formation zone, the rising zone and the crushing zone. The ratio of the bubble length to diameter decreases from large to small in the formation zone, increases first and then decreases in the rising zone, and increases in the crushing zone. The equivalent radius of the bubble increases throughout the entire cycle of motion, with the highest growth rate in the formation zone. The Y-movement rate of bubbles in the formation zone shows an increasing trend, and the rising rate of bubbles in the rising zone and the crushing zone fluctuates smoothly. When N2 was introduced into the pulverized coal particles, it was found that the proportion of the rise time of the bubbles was greatly reduced, and the proportion of the crushing zone increased significantly, which was conducive to the transfer of heat within the tower.

    Experimental study on temporal and spatial distribution of bubbles during initial stage of static flash of pure water
    Ting LIANG, Dan ZHANG, Qingzhong YANG, Junjie YAN
    2019, 70(1):  49-55.  doi:10.11949/j.issn.0438-1157.20180786
    Abstract ( 76 )   HTML ( 3)   PDF (876KB) ( 36 )  
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    Experimental study on temporal and spatial distribution of bubbles during initial stage of static flash of pure water was carried out with depressurization rates varying between 0.27 MPa·s-1 and 0.64 MPa·s-1, and the initial height of waterfilm at 0.2 m. The results indicated that bubbles appeared primarily within the stage of pressure’s rapid decline. In terms of temporal distribution, the faster the pressure dropped, the earlier the bubbles turned up, and the faster the number of bubbles increased with time, and also the earlier the bubble number reached its maximum value. In terms of spatial distribution, the number of bubbles grew in trend of “slow-quick-slow” with increasing depth. Small depressurization rate could narrow bubble distribution along depth. At the same depth, the faster the pressure dropped, the larger the bubble number was. At the end of pressure’s fast decline, the relative bubble number had a peak value with increasing depth. Finally, above experiment results were fitted into a pair of correlations for the temporal and spatial distribution of bubbles. Their calculation results matched well with experimental results.

    Evaluation research on boiling heat transfer model of CO2 in tube
    Zhongyan LIU, Dahan SUN, Xu JIN, Tianhao WANG, Yitai MA
    2019, 70(1):  56-64.  doi:10.11949/j.issn.0438-1157.20180487
    Abstract ( 91 )   HTML ( 3)   PDF (806KB) ( 75 )  
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    Due to good environmental characteristics and excellent thermodynamic properties, CO2 is considered as an ideal alternative refrigerant. Compared with the traditional refrigerant, CO2 flow boiling heat transfer characteristics is very different. However, the existing heat transfer correlations are based on their respective test data fitting, because the data points are too less and the range of variable parameters is limited, the predicted results are very different. To establish the CO2 tube flow boiling heat transfer in a more comprehensive database, compare and analyze different heat transfer models, it is of great significance for deep understanding of the boiling heat transfer characteristics of CO2 in tube and study more accurate heat transfer correlation. There are six correlations analyzed by using 4040 experimental data points of CO2 flow boiling heat transfer from 24 references, the study found that for Fang (2013) correlation minimum error is 10.6%, and draw the variation of gas and liquid Reynolds number with pipe diameter, and the change of gas and liquid Reynolds number scatter plot and the plot of Nusselt number change with Bond number, it can provide insight into the CO2 tube flow boiling heat transfer characteristics and the future research a new type of heat transfer correlations for more accurate to provide the reference.

    Influence of ethanol and n-butanol additives on spray cooling
    Hong LIU, Yang HE, Chang CAI, Jiuliang GAO, Hongchao YIN
    2019, 70(1):  65-71.  doi:10.11949/j.issn.0438-1157.20180755
    Abstract ( 104 )   HTML ( 4)   PDF (636KB) ( 32 )  
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    Spray cooling is the most promising cooling method in the field of high-power electronic device cooling. Different concentrations of low alcohols (ethanol and n-butanol) were added into deionized water to improve the heat transfer performance of spray cooling. The experimental system was established and the effect of concentration on heat transfer characteristics was investigated. The results reveal that an optimal concentration exists by adding low-alcohol additives into deionized water. The performance of spray cooling is gradually enhanced with increasing concentration before the optimum concentration. The optimum concentration of ethanol is 4% and the optimum concentration of n-butanol is 0.5%.

    Study of thermal-hydrologic-mechanical numerical simulation model on CO2 plume geothermal system
    Jingyan LI, Zhongliang LIU, Yu ZHOU, Yanxia LI
    2019, 70(1):  72-82.  doi:10.11949/j.issn.0438-1157.20180368
    Abstract ( 85 )   HTML ( 3)   PDF (1544KB) ( 68 )  
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    A thermal-hydrologic-mechanical (THM) coupling model during the carbon dioxide plume geothermal system (CPGS) heat exploitation process was established. An ideal geothermal reservoir geothermal exploitation process was studied numerically, which combined with five-spot well pattern and a three-dimensional multi-rock formation geometric model. The rock deformation performance of CPGS geothermal exploitation process and the influence of rock deformation and geothermal reservoir initial porosity to CPGS heat exploitation were studied. The results showed that the rock significantly shrinkages during the process of the CPGS operation, reduces the volume, and increases the porosity of the reservoir. The deformation also helps increasing the permeability of thermal reservoir, accelerating the rate of exploitation process, and thus enhancing the geothermal exploitation process. While the porosity was lower, the influence of rock deformation was more obvious. Under the consumption that the initial permeability is the same, the smaller the initial porosity, the greater the increase in permeability caused by rock deformation, and the faster the thermal recovery rate of the system.

    Experimental study of a novel solution regeneration system for heat-source tower under unsteady state
    Xiantai WEN, Jiao YU, Xianqi CAO, Pengfei YU, Ning CAI, Yifan MAO
    2019, 70(1):  83-90.  doi:10.11949/j.issn.0438-1157.20180419
    Abstract ( 63 )   HTML ( 2)   PDF (667KB) ( 26 )  
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    Based on the problem of moisture absorption in winter for heat source tower, a novel solution regeneration system is proposed in this paper. The corresponding test bench is constructed to carry out the relevant experimental tests. Considering with the balanced temperature field in the initial operation and the phenomenon of solution thicken with the water seperation from solutionin, the unsteady characteristics of the solution regeneration system during start-up are studied, and the variation of the operation parameters with the initial running times is obtained. Simultaneously the regularity of operation parameters with different concentration is studied. The results show that: with the increase of initial operation times, under the condition that the total running water quantity remains unchanged, the energy consumption for a single operation decreases, the condensate water rate increases, and finally the system tends to be stable. With the increase of solution concentration, the regeneration efficiency increases first and then reduces. When the solution concentration is 18.5%, the regeneration efficiency reaches the maximum. Simultaneously the regeneration efficiency is 4.28 kg/(kW·h), and the regeneration rate is 749 kg/d. The regeneration percentage is 14%. In the system, low pressure boiling process of the solution is combined with the condensation process, and the energy efficiency is great.

    Flow behaviors in bubble-driven liquid-solid fluidized-bed adopting binary particles
    Yingjie LIU, Jesse ZHU
    2019, 70(1):  91-98.  doi:10.11949/j.issn.0438-1157.20180812
    Abstract ( 100 )   HTML ( 5)   PDF (602KB) ( 41 )  
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    Adopting two kinds of particles whose density is a little higher and lighter than fluid, the fluid dynamics in a bubble-driven liquid-solid fluidized-bed was studied. Air was introduced into the bottom as driving force and the liquid was continuous phase at the stationary phase. Pressure drops were measured and the videos were taken between different heights to estimate the initial fluidization gas velocity Uin,g, solid holdup and gas holdup. The initial fluidization gas velocity of heavy particles could be obtained by the variation of pressure drops at the bottom of the bed near gas distributor. While that of the light particles was determined by observation. The results showed that Uin,g of both the heavy and the light particles increase with solids loadings. The increasing tendency of the heavy particles at higher loadings becomes steep while that of the light particles is gentle. After fully fluidization, the axial distribution of solids holdup of the heavy particles is non-uniform comparing to the uniform distribution of the light particle solids holdup. When using binary particles, the fluidization of the upper light particles is influenced by the lower heavy particles. However, the heavy particles are not affected by the light particles. Thus Uin,g and the axial solids holdup of the heavy particles changes with heavy particle loadings. The light particle Uin,g varies with the total amount of binary particles.

    Influence of circulating air quantity on cooling system and water producing performance of new household pure water machine
    Li WANG, Weidong WU, Kun HU
    2019, 70(1):  99-106.  doi:10.11949/j.issn.0438-1157.20180672
    Abstract ( 77 )   HTML ( 2)   PDF (671KB) ( 28 )  
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    In this paper, a novel household pure water production system was proposed and established by combining the principles of vapor compression refrigeration and air humidification-dehumidification. The effects of the circulating air quantity on some running and performance parameters were experimentally conducted. These parameters included operating conditions of the system, refrigerating capacity, power consumption, coefficient of performance (COP), and produced water quantity of unit time and unit energy consumption. The results showed that with the increase of circulating air quantity, system refrigerating capacity, power consumption and produced water quantity of unit time tended to rise, the COP showed a downward trend after rising first, and the maximum water production of the system under the conditions studied in this paper was 668 g/h. The system has an optimal circulating air volume of 110.2 m3/h, which maximizes the system s energy consumption per unit, which is 2067 g/(kW·h). The hygienic indicators (i.e. TDS less than 3) and daily production (above 12 L/d) of the water in the system can meet the requirements of the general household drinking and the system has a wide application prospect.

    Optimization design and experimental properties of high-temperature and high-capacity pulse tube cooler
    Weifeng DENG, Zhenhua JIANG, Shaoshuai LIU, Ankuo ZHANG, Yinong WU
    2019, 70(1):  107-115.  doi:10.11949/j.issn.0438-1157.20180307
    Abstract ( 67 )   HTML ( 3)   PDF (821KB) ( 21 )  
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    A high-capacity pulse tube cooler (PTC) with nominal cooling of 50 W/170 K is presented in this paper. It is driven by an opposed-piston dynamic magnetic linear compressor. The regenerator and pulse tube are arranged in coaxial. The inertance tube and reservoir are used as passive phase shifter of the PTC. Based on the principle of electrical-mechanical-acoustic coupling field, a dynamic model of the PTC is proposed and transient simulation was conducted on the characteristics of the compressor under load. The mass-spring system of the compressor is improved to make the PTC resonant. The mass of the PTC is less than 12 kg without electric control equipment. A performance of 50 W/170 K is achieved with 230 W electrical power while the motor efficiency and related Carnot efficiency are 92.7% and 16.5% respectively. The specific power (electrical power/cooling power) is less than 5 W/W at the temperature range of 150—200 K. Under the rated input power, the maximum cooling power reaches 90 W@200 K. The PTC can be used for space to cool down giant Infrared Focal Plane Array (IRFPA) and provide an alternative to domestic refrigerator as cold source at the temperature range of -60—-20℃ as well.

    Catalysis, kinetics and reactors
    High-efficiency catalytic synthesis of polyoxymethoxy dimethylether from sulfolane-treated sulfonic acid resin
    Yan WANG, Lei SHI, Jiaqi FAN, Fei CHEN, Jie YAO, Guangwen XU
    2019, 70(1):  116-127.  doi:10.11949/j.issn.0438-1157.20180925
    Abstract ( 129 )   HTML ( 5)   PDF (648KB) ( 57 )  
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    Polymethoxy dimethylether (DMM3—7) as a diesel additive can improve diesel cetane number and fuel utilization rate, and has broad application prospects. For the synthesis of DMM3—7 from dimethoxymethane (DMM) and trioxymethylene(TOX), this work systematically studied the effects of different conditional parameters on the conversions and products selectivity with the sulfolane-treated sulfonic acid as the catalyst and the reaction routes were proposed according to the results of products analysis by GC-MS. It was observed that trace amounts (mg/kg level) of H2O left in the reaction system significantly influenced the reactants conversions and products selectivity. With raising H2O content, more white precipitation paraformaldehyde (PF) was gradually produced, while methanol was substantially generated to lower the selectivity of DMM3—7. The sulfolane-treated method was first proposed and sulfolane solvent was acted as dehydration and pore-forming reagent, that resulted in the absorbed H2O in the surface/pores of NKC-9sulfolane obvious decrease from 2154 mg/kg to 198 mg/kg. Meanwhile, 13X molecular sieve was applied to significantly reduce H2O content of DMM from 710 mg/kg to 54 mg/kg. When the reaction temperature is 313 K (40℃), the reaction is 2 h, the pressure is 1.0 MPa, and the mass ratio of DMM to TOX is 2/1, the DMM and TOX conversion rates and the DMM3-7 mass selectivity increase from 48.27%, 88.41% and 45.27% to 52.91%, 93.34% and 61.58%, respectively. Comparing to literatures reports, the mass selectivity to DMM3-7 was higher than 60% that makes it promising for industrial applications.

    Separation engineering
    Controllable crystallization of urea (520) crystal plane by molecular simulation
    Jingtao CAI, Daixi LI, Baolin LIU, Hansen LUAN, Baisong GUO, Dongqing WEI, Hao WANG
    2019, 70(1):  128-135.  doi:10.11949/j.issn.0438-1157.20180521
    Abstract ( 117 )   HTML ( 2)   PDF (907KB) ( 59 )  
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    Due to urea crystallization showing white needle, single crystal morphology and uncontrollable process of traditional crystallization, it seriously affects drug consistency evaluation. We adopt molecular dynamics simulation method to research regulating effect of different additives on urea crystal growth at molecular level, and reveal the regulation mechanism of additives on urea crystal growth. Finally, the experimental results show: ① At 101.325 kPa and 290 K, all 6 kinds of additives (trehalose, sucrose, glucose, sorbitol, lysine and arginine) can inhibit the growth of urea facet (520) to a certian extent. ② The more negative adsorption energy of the additive on the facet (520) lead to the better inhibition of crystal growth, and the trehalose is the best inhibit for the growth of facet (520). ③ The type and number of the polar group which is carried by additive determine the interactive strength between additive and crystal layer. In particular, trehalose and sucrose which contains 8 hydroxyl groups, have strong interaction with urea molecules on the urea layer,and they can form competitive adsorption with solutes in the solution layer. So they can better inhibit the growth of urea crystal facet (520).

    Research and optimization of separation technology of methanol to propylene
    Zizong WANG, Hongqian LIU, Jiming WANG
    2019, 70(1):  136-145.  doi:10.11949/j.issn.0438-1157.20171033
    Abstract ( 103 )   HTML ( 7)   PDF (737KB) ( 106 )  
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    Based on the actual equipment of 1.7 million tons/year methanol to propylene (MTP), this paper studies and optimizes the MTP separation process, draws on the experience of separation of naphtha ethylene unit, and optimizes the formation characteristics of MTP product gas. The process combination, process simulation and optimization of the separation technology are carried out together with de-methanizer tower and its exhaust gas recovery system, highly thermal coupling decarburization system (de-ethanizer and ethylene rectifying column), sorbent selection, and screen out a more suitable separation technology consisting of the following process unit: pre-cutting front-end deethanizer, recovery of de-methanizer tail gas by combination of intercooling oil absorption and throttle expansion, highly thermally coupled deethanizer system, take carbon four mixture as absorbing agent, etc.Assuming that there are no ethylene, carbon four and carbon five cycles back to the MTP reactor, the ethylene loss in the exhaust meets the design requirements, using the optimized separation technique, the dual power of the compressor and propylene compressor is 19.8 MW. The simulation results show that the optimized flow has a good application prospect.

    Screening of ionic liquids for separation of ethyl acetate-acetonitrile azeotrope based on COSMO-RS
    Zhigang ZHANG, Debiao ZHANG, Qinqin ZHANG, Tao ZHANG, Ru YANG, Wenxiu LI
    2019, 70(1):  146-153.  doi:10.11949/j.issn.0438-1157.20180911
    Abstract ( 120 )   HTML ( 1)   PDF (816KB) ( 58 )  
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    The application of different ionic liquids in the separation of acetate-acetonitrile azeotrope was investigated by COSMO-RS method. The accuracy of COSMO-thermX prediction of ionic liquid separation was verified by comparison between predicted and experimental values. The selectivity (based on acetonitrile) of 221 ionic liquids composed of 17 cations and 13 anions and the effect of ionic liquids on the relative volatility of ethyl acetate to acetonitrile near azeotropic point were calculated and analyzed. It was found that the ionic liquids containing [OAc]- and [Cl]- had a better promoting effect on the separation of ethyl acetate - acetonitrile mixture, while the difference in the promoting effect of cations on the separation of ethyl acetate - acetonitrile mixture was small. The effect of anions [OAc]- and [Cl]- on azeotrope was further studied by applying the surface charge density distribution (σ-profile), revealing that the order of influence of the anions [OAc]- and [Cl]- on the separation of ethyl acetate-acetonitrile was [OAc]->[Cl]-. The comprehensive prediction results show that ionic liquid [BMIM][OAc] is expected to be used as a highly efficient extractant in the separation of ethyl acetate-acetonitrile mixture.

    Structure optimization of cyclone based on response surface method
    Pan XIONG, Shuguang YAN, Weiyin LIU
    2019, 70(1):  154-160.  doi:10.11949/j.issn.0438-1157.20180557
    Abstract ( 155 )   HTML ( 5)   PDF (967KB) ( 106 )  
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    To optimize the separation efficiency and energy loss of the cyclone separator, the main structural parameters affecting the performance of the cyclone separator are determined. The response surface model and CFD numerical simulation are used to select the dust outlet diameter (Dd), exhaust port diameter (De), and inlet velocity (V), and the pressure drop and the total separation efficiency are used as the objective functions, and the three-factor optimization design analysis is performed. The results show that the diameter of the exhaust port has little effect on the pressure drop and the separation efficiency. The diameter and velocity of the exhaust port have significant effects on the pressure drop and the separation efficiency, and the interaction between the diameter of the exhaust port and the velocity is obvious. For the current 0.5—10 μm particle group, the optimal parameters are De/D=0.35,Dd/D=0.37,V=12 m/s. Compared with the experimental structure, in the case of similar separation efficiency, the pressure drop is reduced by half, effectively reducing the energy consumption. The established response surface model can accurately represent the relationship between design variables and objective functions. Optimization design method based on response surface model can be effectively applied to structural optimization of cyclone separator. And different particle size requirements can use different structures for dust removal. To achieve the separation requirements of the premise, the structure of the minimum pressure drop is used. This study provides a favorable basis for the separation of 0.5—10 μm particle size structure.

    Surface and interface engineering
    In-plant experimental study on desulfurized flue gas corrosion
    Peiyuan PAN, Heng CHEN, Jian JIAO, Zhiyuan LIANG, Qinxin ZHAO
    2019, 70(1):  161-169.  doi:10.11949/j.issn.0438-1157.20180328
    Abstract ( 118 )   HTML ( 3)   PDF (1177KB) ( 77 )  
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    Based on the need to increase the height of the exhaust plume and the whitening of the flue gas, the wet flue gas after the wet desulfurization of the flue gas of the coal-fired boiler must be properly disposed. However, the wet flue gas after wet desulfurization is very corrosive and will cause serious corrosion to downstream equipment. In this paper, in-plant corrosion tests were conducted in the flue after the wet desulphurization system in a 91 MW coal-fired travelling grate heating boiler. Five common corrosion-resistant steels including ND steel, 304 L, 316 L, 2205 and 2507 were tested and then evaluated. According to the results, surface temperature of the steel was the key factor in corrosion process. As the surface temperature increased, corrosion of the steels was first exacerbated due to the increase in Cl? concentration in the deposits and then mitigated due to the lack of the electrolyte.

    Effect of alkali about growth characteristics of CaCO3 on galvanized iron surface
    Huayi JIANG, Hanghang CAI, Aiguo LIANG, Dingzhou ZHANG, Nana SUN, Xinmin CHONG
    2019, 70(1):  170-178.  doi:10.11949/j.issn.0438-1157.20180884
    Abstract ( 85 )   HTML ( 4)   PDF (990KB) ( 54 )  
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    In order to solve the problem of pipeline blockage due to the water scaling, the key idea that the crystallization fouling process was changed from passive to active was proposed in this research. In view of the injected water form oil field, galvanized iron was selected as the substrate. The mechanisms of the influences of alkali types and concentrations on crystal growth were revealed using dynamic simulation experiments,SEM, EDS and liquid turbidity tests. These results were showed that: The effects of five kinds of alkalis (such as Na2CO3, NaHCO3, TEOA, Ca(OH)2 and CaO) on scale mass gains, calcium loss rate and scaling induction periods were different. Among them Na2CO3 has a significant effeet on the loss of calcium loss, while CaO has a significant effect on the rate of fouling. Secondly, the morphology of the crystal is correlated with the alkali types. If the surface of the material was capable of forming a blocky shape scale or a layered fouling, this material was beneficial for the aggregation and deposition of crystals. Finally, the alkali concentration played a twofold role in the growth of fouling, that was, to promote the aggregation of crystal and to inhibit the scale growth. In other words, there would be a preferred range of alkali concentrations.

    Biochemical engineering and technology
    Metabolic engineering of Saccharomyces cerevisiae for pinene production
    Tianhua CHEN, Ruosi ZHANG, Guozhen JIANG, Mingdong YAO, Hong LIU, Ying WANG, Wenhai XIAO, Yingjin YUAN
    2019, 70(1):  179-188.  doi:10.11949/j.issn.0438-1157.20180784
    Abstract ( 81 )   HTML ( 1)   PDF (759KB) ( 58 )  
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    The derivatives of pinene can be employed as high energy density fuels. However, the biosynthesis of pinene from single carbon sources has not been realized in yeast. As Saccharomyces cerevisiae has stronger ability on protein expression and post-translational modification as well as processes a maturity endomembrane system, it is more suitable for expressing complex proteins (e.g. cytochrome P450) by yeast than by prokaryotic hosts such as Escherichia coli. Therefore, it is crucial to engineer S. cerevisiae as the host cell to produce high energy density fuels (like “Crazy Carbon Ring”) based on the derivatization of pinene or other terpenes compounds. Here, in order to achieve pinene synthesis in yeast, endogenous farnesyl diphosphate synthase (ERG20) mutant ERG20ww and Pinus taeda pinene synthase (PtPS) were expressed in Saccharomyces cerevisiae strain, obtaining an initial pinene titer of 0.329 mg·L-1. N-terminus truncation (from 2A to 51P) of PtPS (obtaining tPtPS) improve the pinene production by 2.23-fold. The pinene titer was further enhanced by 5.16-fold by expression the fusion of ERG20ww/tPtPS on the basis of overexpression of isoprene pyrophosphate isomerase (IDI1) and the repressor of RNA polymerase III (MAF1). Replacing the promoter of gene ERG20 by a weaker promoter HXT1 down-regulated the transcription of ERG20. And correspondingly the pinene output was increased by 26.0%. Eventually, adjusting the pH of the fermentat-ion medium further increased the pinene production by 42.2% (to 11.7 mg·L-1). This titer was 34.5-fold higher than the initial one. This study is the first to achieve de novo synthesis of terpenes in Saccharomyces cerevisiae and to obtain the highest yield of known terpene shake flasks.

    Exploring the key structural properties affecting the function of multi-step phytoene dehydrogenase CrtI
    Chen CHEN, Ying WANG, Hong LIU, Yan CHEN, Mingdong YAO, Wenhai XIAO
    2019, 70(1):  189-198.  doi:10.11949/j.issn.0438-1157.20180813
    Abstract ( 79 )   HTML ( 3)   PDF (963KB) ( 54 )  
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    A kind of universal enzyme that catalyzes a multi-step continuous reaction in an organism plays an important role in the biological metabolic process. As a typical representative, phytoene dehydrogenase (CrtI) can catalyze multi-step continuous dehydrogenation to produce products of great value such as lycopene. Herein, the catalytic function of CrtI was studied in Saccharomyces cerevisiae. Firstly, by combining design and screening of three heterologous enzymes CrtE, CrtB and CrtI in the lycopene synthesis pathway, CrtI was confirmed as the main limiting factor, and CrtI from Blakeslea trispora exerted excellent catalytic function. Through bioinformatics and protein structural analysis the key residue S311 of BtCrtI was explored, which linked and maintained the key secondary structure of active center domain. Subsequently, the results of saturation mutation showed that the type of amino acid residue mutated at S311 had a significant effect on the structure and function of the active center domain. This provided a novel structural point for the design and modification of enzymes. Meanwhile, another interesting finding is that the various activity of CrtI mutants did not disturbing the carotenoid metabolic flow in our biosynthesis pathway. Therefore, CrtI is crucial to improve the yield and purity of lycopene.

    Energy and environmental engineering
    Relationship between pore structure and moisture reabsorption of lignite dewatered by high temperature drying process
    Yuanmo WU, Shouyu ZHANG, Hua ZHANG, Chen MU, Hao LI, Xiaobing SONG, Junfu LYU
    2019, 70(1):  199-206.  doi:10.11949/j.issn.0438-1157.20180822
    Abstract ( 68 )   HTML ( 2)   PDF (658KB) ( 36 )  
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    The coal samples dried at different temperatures were prepared by horizontal fixed bed experimental furnace. The specific surface area, pore volume and pore diameter distribution of the coal samples were determined using nitrogen adsorption isotherm (-196℃). The relationship between the pore structure and moisture reabsorption behavior of the lignite samples was investigated using a self-designed reabsorption device. The experimental results show that the N2 adsorption behavior of the semi-coke dried under different temperatures followed the type II adsorption isotherm, and the adsorption loops of the (raw coal and the semi-coke prepared under 600 and 700℃) belonged to type L1, while the adsorption loop of the semi-coke dried at 800℃ showed a transformation tendency from type L1 to type L2. With the increasing of drying temperature, the specific surface area of the dried semi-coke first increased slowly and then decreased and the pore diameter differential corresponded to the mesopore peak showed the same trend. Meanwhile, the pore diameter differential of the macropores remained unchanged. As the drying temperature increased, the fractal dimensions D1 and D2 changed in the opposite trends, and the value of D2 was higher than D1. The moisture reabsorption behaviors of the semi-coke followed the same trend, and the equilibrium moisture content decreased with the increasing drying temperature. The moisture reabsorption characteristics of the semi-coke were closely related to the pore structure, and the equilibrium moisture content had a good linear relationship with the pore volume.

    Treatment of acid red 73 by persulfate in the presence of rGO-Fe3O4 composite
    Fei YIN, Cui WANG, Shaoping TONG
    2019, 70(1):  207-213.  doi:10.11949/j.issn.0438-1157.20180918
    Abstract ( 113 )   HTML ( 1)   PDF (675KB) ( 46 )  
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    A reduced graphene oxide nanosheet-iron oxide composite (rGO-Fe3O4) was synthesized by using coprecipitation method, and characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The rGO-Fe3O4 composite was used as heterogeneous catalyst to activate persulfate (PS) to decolor acid red 73 (AR73). The effects of catalyst dosage, PS concentration, initial pH value and reaction temperature on the decolorization efficiency were investigated. The results showed that 50 mg/L AR73 was totally removed in 10 min at room temperature when the concentrations of rGO-Fe3O4 and PS were both 1.0 g/L. Singlet oxygen was confirmed to be the primary reactive oxygen species by quenching experiment. This study shows that the rGO-Fe3O4 composite is a promising catalyst for activating PS to treat wastewater due to its high activity and easy separation.

    Simulation analysis of multi-physics coupling SOFC fueled nature gas in the way of internal reforming and external reforming
    Jing XIE, Mingyi XU, Shuai BAN, Hui SUN, Hongjun ZHOU
    2019, 70(1):  214-226.  doi:10.11949/j.issn.0438-1157.20180445
    Abstract ( 104 )   PDF (1350KB) ( 53 )  
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    Internal reforming (IR) and external reforming (ER) are two modes of operation when solid oxide fuel cells (SOFCs) are fueled by natural gas (NG). The performance and efficiency of batteries in different reforming modes are also different. 3D unit cell of ER-SOFC and IR-SOFC model fueled NG was designed which consist of Ni-YSZ//YSZ//LSCF-GDC based on multi-physics coupling software COMSOL Multiphysics? 5.2. The simulation results show that: the power density, fuel utilization and energy utilization of IR-SOFC are higher than ER-SOFC; methane steam reforming occurs mainly in the regions near fuel inlet of anode side; different from the reduction of concentration of H2 and CO in ER-SOFC, the concentration of H2 and CO rises first and then decreases in IR-SOFC; the temperature of IR-SOFC change dramatically more than ER-SOFC and the temperature gradient of IR-SOFC is highest at the anode inlet area; more closer of distance near the current collector, more higher ion current density on the surface between cathode and electrolyte; carbon deposition do not happen in ER-SOFC at anode side, whereas it take place as a result of CH4 thermal decomposition reaction in IR-SOFC which carbon activity was more than 270.

    Nutrient removal and biomass production from dairy farm liquid digestate treatment using microalga Chlorella vulgaris
    Siran FENG, Pingzhong FENG, Shunni ZHU, Zhongming WANG, Zhenhong YUAN
    2019, 70(1):  227-233.  doi:10.11949/j.issn.0438-1157.20180739
    Abstract ( 83 )   HTML ( 1)   PDF (708KB) ( 56 )  
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    In this study, the treatment performance of dairy farm liquid digestate by freshwater microalga Chlorella vulgaris NIES-227 was investigated and the potential of biomass utilization was evaluated. In column photobioreactors, Chlorella vulgaris was used to treat wastewaters containing unsterilized liquid digestate at concentrations of 25%, 50%, 75%, and 100%. The results showed that the removal of total nitrogen (TN), total phosphorus (TP) and COD were 36.0%—92.5%, 42.8%—100% and 6.9%—32.2%, respectively. The microalgae exhibited the maximum removal efficiencies of nitrogen and phosphorus in 25% liquid digestate, and the maximum removals of ammonia nitrogen (NH3-N), TN and TP were 99.9%, 91.0% and 100%, respectively. The microalgae grew well in low concentrations of liquid digestate (25%—50%), and the highest biomass productivity was obtained in 50% liquid digestate with the value of 393.6 mg/(L·d). However, microalgal growth was inhibited in higher concentrations of liquid digestate (75%—100%), which led to the decreases of the removal of nitrogen and phosphorus. The number of bacteria increased significantly during the cultivation among all the treatment groups, which was beneficial to the COD removal. The contents of total lipid, total sugar and protein in biomass harvested from different concentrations of liquid digestate were 13.2%—32.2%, 12.3%—27.6% and 16.2%—30.9%, respectively. The experimental data show that low-concentration biogas slurry can produce more high-energy components of biomass, which is suitable for biofuel development; high-concentration biogas slurry can produce biomass with more protein, which is more suitable for animal feed.

    Effect of prehydrolysis strength on properties of black liquor from kraft pulping of Acacia wood
    Miaofang ZHOU, Haiqiang SHI, Chengxiang LI, Leiming WANG, Mimi YUAN
    2019, 70(1):  234-241.  doi:10.11949/j.issn.0438-1157.20180710
    Abstract ( 91 )   HTML ( 3)   PDF (589KB) ( 69 )  
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    The lignocellulose is treated by hydrothermal prehydrolysis technology, and the main components of the wood chips are changed, which has an impact on the subsequent chemical pulping properties and the properties of the pulping black liquor. In this experiment, Acacia wood chips were treated with different prehydrolysis strength (P-factor), and their kraft pulping behavior and resulting black liquor properties were analyzed. The results show that the yield of final pulp is reduced with the increase of P-factor, while the kappa number of pulp is gradually increased. When the P-factor is less than 200, the solid content of the black liquor is increased from 138.48 g/L in the control group to 162.86 g/L, the lignin content is increased from 58.57 g/L to 72.68 g/L, and the residual alkalinity content is decreased from 4.37 g/L to 2.07 g/L. When the P-factor at 200—600, the solid content of black liquor is reduced from 162.86 g/L to 142.71 g/L, the lignin content is reduced from 72.41 g/L to 59.16 g/L, and the residual alkalinity content is reduced from 2.07 g/L to 1.26 g/L. When the P-factor is greater than 600, the solid content of the black liquor is increased from 142.71 g/L to 156.95 g/L, the lignin content is increased from 59.16 g/L to 62.16 g/L, and the residual alkali content is increased from 1.26 g/L to 1.37 g/L. Under different conditions, the content of inorganic substance in black liquor changed little, and the calorific value of solid substance in black liquor increased from 13.71 MJ/kg in control group to 14.63—15.09 MJ/kg.

    Electrical performance of MFC-MEC coupling system and treatment of heavy metal wastewater containing cadmium
    Lulu PAN, Danjing WU, Weiping LIU
    2019, 70(1):  242-250.  doi:10.11949/j.issn.0438-1157.20180663
    Abstract ( 78 )   HTML ( 3)   PDF (911KB) ( 53 )  
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    The MFC-MEC coupling system was constructed by using anaerobic activated sludge as the anode species, sodium acetate simulated wastewater as the anode substrate, copper sulfate and potassium dichromate solutions as the microbial fuel cell (MFC) catholyte, artificially simulate heavy metal wastewater containing cadmium as microbial electrolytic cell (MEC) catholyte. The MFC was used to drive the MEC to realize the removal of Cd2+ in heavy metal wastewater containing cadmium. The effects of the MFC reactor volume, MFC stack, MEC electrode material, MEC catholyte pH on the electrical properties of the MFC-MEC coupled system and the treatment of heavy metal wastewater containing cadmium were investigated. The results show that the enlargement of MFC reaction volume could improve the electricity production performance, but at the same time it would also increase the internal resistance of MFC. With the increase of MFC volume, the removal rate of Cd2+ in MEC increased gradually, but at the same time, the removal rate of Cr6+ in MFC cathode decreased gradually; MFC stack could increase the voltage, the maximum output voltage was 1509 mV in series, and the removal rate of Cd2+ was 69.3%; when the titanium plate was used as the MEC electrode, the microorganism could effectively adhere to the anode surface, the removal rate of COD of the MFC anode was 85%, the removal rate of Cd2+ in the MEC was 51.5%; when the pH of MEC catholyte was 3—5, it was beneficial to the treatment of heavy metal wastewater containing cadmium, and the removal rate of Cd2+ was over 80%. By XRD analysis, the cathode reduction product of MEC is CdCO3.

    Experimental study on foaming characteristics of CO2-crude oil mixture
    Cailin WANG, Shuaiwei GU, Yuxing LI, Qihui HU, Lin TENG, Jinghan WANG, Hongtao MA, Datong ZHANG
    2019, 70(1):  251-260.  doi:10.11949/j.issn.0438-1157.20180716
    Abstract ( 83 )   HTML ( 5)   PDF (1036KB) ( 73 )  
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    CO2 enhanced oil recovery (CO2-EOR) technique is a good choice that can not only limit global warming, but also cut the high cost of carbon capture and storage (CCS). CO2 flooding produced fluid contains large amounts of CO2 and a lot of foam will generate in the separation process due to decompression. To study the foaming characteristics of CO2-crude oil system in oilfield separators, an experimental system was designed to simulate the real environment. Depressurization method was used to study the foam behavior in the tests. The foaming process of dissolved crude oil could be divided into depressurization stage and stable working pressure stage. Foam evolution from generation to attenuation was recorded by high-speed camera, and foam behaviors at different stages were summarized and analyzed. Foaming process could be divided into five stages: bubble formation, arrangement with single layer, bubble coalescence, bubble breakage and multilayer stack. As pressure decreased, the diameters of stable bubbles increased and the foam position moved upwards, and foaming behavior became more violent. In addition, foam form in crude oil belonged to spherical foam and the Gibbs-Marangoni effect of foam was found in the tests. The attenuation mechanism and influencing factors of CO2 foam were analyzed and it was found that gas diffusion was the main mechanism for CO2 foam attenuation. Furthermore, the effects of depressurization rate and stirring rate on the properties of foam were studied. The results show that the increase in depressurization rate had no obvious effect on the foaming behavior in depressurization process while it would aggravate the foaming behavior under stable working pressure. When the rotation speed is less than or equal to 120 r/min, the increase of the stirring rate will aggravate the foaming behavior in the depressurization stage, but accelerate the foam decay under stable working pressure.

    A waste heat recovery power generation system combined with natural gas liquefaction and CO2 capture
    Li ZHANG, Wenwu WANG, Zhi’en ZHANG, Peisheng LIU, Jiangbo WEN, Liang DONG
    2019, 70(1):  261-270.  doi:10.11949/j.issn.0438-1157.20180567
    Abstract ( 95 )   HTML ( 1)   PDF (824KB) ( 70 )  
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    Aiming at the problem of waste heat recovery and energy utilization, LNG and heavy oil extraction exhaust gas are used as cold source and heat source respectively, and a waste heat recovery and utilization system combined with natural gas liquefaction and exhaust gas power generation and CO2 capture is proposed. The effect of key parameters on thermodynamic performance is evaluated. The results show that increasing the turbine inlet temperature, decreasing of turbine outlet pressure and in the compression ratio, have a positive effect on the organic Rankine cycle and refrigeration cycle. The maximum net output power and waste heat recovery efficiency are 454.9 kW and 34.2%, respectively. For the natural gas liquefaction system, the nonlinear optimization of natural gas liquefaction cycles was calculated by using C++. The total power consumption within the nitrogen expansion refrigeration compressors has been selected as the objective function. The nonlinear constrained optimization problem of the liquefaction process is constructed. The optimal total power consumption of the compressors is 101.54 kW. The gas peak load regulation can be taken by decreasing the natural gas compressor (K110) inlet temperature, nitrogen turbine (T3) outlet pressure and its mass flow rate; the maximum value is 378.8 kg/h. On the contrary, the volume of carbon dioxide captured can be increased by 28.6%.

    Material science and engineering, nanotechnology
    Computer simulations on switching effect of nanopores modified by dual-responsive block polymers
    Zheng CHEN, Li WANG, Jian ZHOU
    2019, 70(1):  271-279.  doi:10.11949/j.issn.0438-1157.20180596
    Abstract ( 88 )   HTML ( 2)   PDF (967KB) ( 62 )  
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    The switching effect of the dual-responsive block polymer modified nanopore was studied by computer simulation method (dissipative particle dynamics). The dual-responsive block polymers were grafted into nanopores with temperature responsive (N-isopropylacrylamide, PNIPAM) and pH responsive (acrylic acid, PAA).The effect of different block sequences (wall-PNIPAM-PAA or wall-PAA-PNIPAM) on the nanopore switching was studied. The results show that only the wall-PNIPAM-PAA block sequence can realize the different switching effects of nanopores under different conditions. Meanwhile, the effects of different grafting density, chain length and different block ratio on the nanopore switching effect were also investigated. The results show that different nanopores can be realized at the moderate to high grafting density, the suitable chain length and the medium block ratio, which can be used to control the size of the switch.

    Saturated adsorption capacities of graphene aerogels on organics
    Hui e LIU, Yangfan HUANG, Yanbing MA, Shuang CHEN
    2019, 70(1):  280-289.  doi:10.11949/j.issn.0438-1157.20180603
    Abstract ( 138 )   HTML ( 1)   PDF (728KB) ( 94 )  
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    Graphene aerogel (GA) was prepared through Pickering emulsion method. Pure organic compounds and oil emulsion in water were used as substances to be absorbed by GA. Saturated adsorption capacities were observed for the GA prepared in this work and for carbon aerogels from other researchers. It was found that the saturated adsorption capacities of almost all the carbon aerogels were directly proportional to densities of the organics, indicating constant adsorption volume of organics exists for certain carbon aerogel, independent of the kind of organics. It is expected that the adsorption of organics by carbon aerogels is a volume filling process, so that higher pore volume of aerogels favors the saturated adsorption abilities of organics. However, occupancy of pores, or the filling percent of pores by organics is also an important determining factor. The prepared GA has lower adsorption capacity for oil in water than its adsorption capacity for pure oil, and should be related to competitive adsorption of water and diffusion resistance of organic matter.

    Preparation and properties of decyl alcohol-palmitic acid/expanded graphite low temperature composite phase change material
    Sunxi ZHOU, Xuelai ZHANG, Sheng LIU, Qiyang CHEN, Xiaofeng XU, Yinghui WANG
    2019, 70(1):  290-297.  doi:10.11949/j.issn.0438-1157.20180646
    Abstract ( 82 )   HTML ( 4)   PDF (801KB) ( 55 )  
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    To find a low temperature phase change material with a temperature range of 2—3℃, a sterol-palmitic acid (DA-PA) binary composite phase change material was prepared by eutectic method based on theoretical calculation. To improve the thermal conductivity, the DA-PA/EG composite phase change material with the optimal mass ratio of 15:1 was obtained by using the porous characteristics of expanded graphite (EG). The structure and properties of the composite phase change material were studied by DSC, step cooling curve, FI-TR, SEM and high-low temperature cycle test. The results show that when the mass ratio of DA-PA was 97.8:2.2, the phase change temperature was 2.9℃ and the latent heat was 203.6 J·g-1. After vacuum adsorption, DA-PA was uniformly encapsulated in the porous network structure of EG. The phase change temperature of DA-PA/EG was 2.7℃, the latent heat was 193.9 J·g-1, and the thermal conductivity was 1.416W·(m·K)-1, which was 4.3 times higher than DA-PA. After 100 times of high-low temperature cycles, the thermal properties of DA-PA/EG did not change much and still maintained good stability. The results show that the DA-PA/EG composite phase change material has great application value in the cold chain logistics.

    Fabrication of PVDF-SiO2/PVSQ superhydrophobic compositemembrane via self-assembly with anti-fouling property for membrane distillation
    Kai WANG, Dewu WANG, Deyin HOU, Ziyi YUAN, Jun WANG
    2019, 70(1):  298-308.  doi:10.11949/j.issn.0438-1157.20180845
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    The SiO2 was hydrophobically modified by vinyltrimethoxysilane (VTMOS), and the modified SiO2 was grafted onto the surface of commercial PVDF (polyvinylidene fluoride) membrane by self-assembly method to make the surface superhydrophobic. The VTMOS not only modified the SiO2 particles changing from hydrophilic into hydrophobicity, but also produced highly monodisperse spherical polyvinylsilsesquioxane (PVSQ) particles by self-hydrolysis and condensation reaction. The achievement of the superhydrophobic membrane surface was attributable to the hierarchical micro/nano rough structure constructed by the random distribution of SiO2 particles and spherical PVSQ particles, which together with the hydrophobic groups like vinyl groups and methoxyl groups which had low surface tension distributed on the coating surface. The results showed that the maximum water of contact angle modified membrane surface was up to 159.5°, and the sliding angle could reach 8.1°. The anti-fouling properties of the commercial and modified membrane were investigated by direct contact membrane distillation (DCMD) experiments with feed solution containing NaCl, HA and CaCl2. The results indicated that the modified membrane with superhydrophobic surface was suitable.

    Influence of reduction temperature of graphene oxide on cross sensitivity between humidity and formaldehyde
    Dehui LEI, Tongjiang PENG, Hongjuan SUN, Guangping TANG, Jianzhao YANG, Yazhou REN, Lili WANG
    2019, 70(1):  309-318.  doi:10.11949/j.issn.0438-1157.20180681
    Abstract ( 58 )   HTML ( 1)   PDF (1003KB) ( 43 )  
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    As precursors, graphite oxide samples are exfoliated and used to prepare graphene oxide thin films by gas spin coating with Ag-Pd integrated electronic device (Ag-Pd IED). The graphene oxide thin films are annealed at 80—180℃ to obtain a series of reduced graphene oxide gas sensing element samples with different reduction degrees, and the layer structures, film thickness and functional groups change properties of all the samples are investigated by X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, Atomic force microscope and X-ray photoelectron spectroscopy. The prehumidification treatment with the relative humidity from 11.3% to 93.6%, the gas sensitivity tests are carried out to reduced graphene oxide thin film gas sensing element. Then the formaldehyde gas sensing measurement are also implemented. The results show that the structure of the graphene oxide samples are transformed to the graphitic structure after reduction at different thermal treatment temperatures. The oxygen functional groups on the surface of graphene oxide gradually pyrolyzed, the defects increase, the structure of graphene gradually changes to similar to graphite, and the resistance of the samples were significantly reduced in magnitude with 41 MΩ to 928 Ω. The samples with different relative humidity pretreated produced competitive adsorption of water molecules and formaldehyde molecules in formaldehyde atmosphere, leading to obvious changes in resistance. When exposed to the 10?4 formaldehyde gas at room temperature, unreduced or the reduced products at low temperature show good sensitivity of 69.1% to formaldehyde gas in high humidity environment. In medium humidity environment, the reduced products at medium temperature which exhibit a best sensitivity of 80.3% are suitable for the test of formaldehyde gas.

    Controllable preparation of Co-Fe-Pd nanoparticles and their catalytic activities toward oxygen reduction
    Channa WANG, Ling LIU, Huihua WANG, Tianpeng QU, Jun TIAN, Deyong WANG, Zhenhui KANG
    2019, 70(1):  319-326.  doi:10.11949/j.issn.0438-1157.20180717
    Abstract ( 117 )   HTML ( 6)   PDF (1218KB) ( 74 )  
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    Co(FeOH)2, FeCl3 and PdCl2 were used as raw materials, citric acid was used as stabilizer, and ethanol was used as accelerator. Ultrasonic-assisted preparation of Co-Fe-Pd metal nanoparticles was carried out, and the oxygen reduction reaction (ORR) electrocatalytic performance was evaluated. The results show that the average size of Co-Fe-Pd nanoparticles prepared by ultrasonic method is about 3—5 nm, and only Pd diffraction peaks are detected for the Co-Pd,Fe-Pd and Co-Fe-Pd nanoparticles because of the dissolution of Co and Fe into the Pd lattice. Compared to Co, Co-Fe Fe-Pd and Co-Pd nanoparticles, the lattice contraction of Co-Fe-Pd nanoparticles exhibited as the wide peaks is remarkable, which leads to increasing lattice defects and subsequent enhanced catalytic activities. The onset potential of oxygen reduction and the slop of Tafel for the Co-Fe-Pd nanoparticles are 1.03 V(vs RHE) and -87 mV/dec, respectively. The values obtained here are comparable to those of commercial Pt/C catalyst. The transferred electron-number of Co-Fe-Pd nanoparticles is 3.80±0.04 during the oxygen reduction, which is dominated by a four-electron pathway. Furthermore, the peroxide percentage (H2O2) is about 10% from the results of RRDE.

    Effect of divinylbenzene-assisted maleic anhydride grafted poly(lactic acid) on properties of microcrystalline cellulose/poly(lactic acid) composites
    Fayang WANG, Jun DU, Lu DAI, Haichao WU, Youyong WANG, Yongming SONG
    2019, 70(1):  327-335.  doi:10.11949/j.issn.0438-1157.20180715
    Abstract ( 100 )   HTML ( 3)   PDF (1112KB) ( 39 )  
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    The effect of maleic anhydride (MAH)/divinylbenzene (DVB) grafted polylactic acid (PLA-g-DVB/MAH) on the properties of microcrystalline cellulose (MCC)/polylactic acid(PLA) composites was investigated. PLA-g-DVB/MAH graft polymer was synthesized by free-radical melt grafting using divinylbenzene(DVB) as a comonomer. MCC/PLA composites were prepared by injection molding using PLA-g-DVB/MAH as a compatibilizer. The molecular structure of PLA-g-St/MAH was characterized by FTIR and the influence of PLA-g-DVB/MAH on the rheological and mechanical properties of the MCC/PLA composites was also investigated. The results showed that MAH was grafted onto PLA and the graft copolymer of PLA-g-DVB/MAH was obtained successfully. Storage modulus, complex viscosity, equilibrium torque and shear heat increased with the addition of PLA-g-DVB/MA; The interfacial compatibility and the mechanical properties of MCC/PLA composites were significantly improved using PLA-g-DVB/MAH as a compatibilizer.

    Preparation and corrosion resistance of SiC membrane using for dust removal in high temperature
    Dongyan LI, Wei WEI, Feng HAN
    2019, 70(1):  336-344.  doi:10.11949/j.issn.0438-1157.20180960
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    Spray-coating was used to prepared silicon carbide (SiC) membranes on the surface of SiC supports, then the coated samples were sintered by switching sintering atmospheres (aerobic to argon) over different temperature ranges according to the oxidation characteristics of SiC, and the sintering cost of SiC ceramic membranes was reduced by optimizing the soaking time. The results revealed that the new sintering procedures can effectively control the oxidation of SiC in the aerobic sintering stage, and promoted its oxidation product silica (SiO2) reaction with the sintering aids such as zirconia (ZrO2) in the argon sintering stage. The average pore size of the prepared SiC ceramic membrane was 3.03 μm and the gas permeation was 175 m3·m-2·h-1·kPa-1. After etching for 6 h in 0.25 mol·L-1 H2SO4 solution and 0.25 mol·L-1 NaOH solution at 100℃, the surface morphology of the film has no obvious change and has strong corrosion resistance.

    Molecular dynamics simulations core-shell self-assembly from amphiphilic polymer and hydrophobic nanoparticle
    Wenjun XIANG, Zhaoju ZHU, Dan LIU, Lüshan ZHOU
    2019, 70(1):  345-354.  doi:10.11949/j.issn.0438-1157.20180942
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    Based on the Martini force field, the structure of Pluronic block copolymer on the hydrophobic nano-surface self-assembled film was studied by coarse-grained molecular dynamics simulation. The effect of structure of Pluronic copolymer on the self-assembled monolayer film structure is studied systematically. As simulation results show the core-shell structure of polymer-nanoparticle composites were formed whose core originates from nanoparticle while their shell is composed with Pluronic copolymer. The concentration and structure of Pluronic copolymers have a significant influence on the core-shell structure. At lower concentration, a completely covered film was observed with crimp configuration of ethylene oxide (EO) blocks, meanwhile layered film covered on the NP surface. With further rise in the concentration, star-shaped films with stretching configuration of EO blocks were formed. The thickness of shell-layer increases as increasing the relative molecular weights of polymers. Moreover, Pluronic copolymers revealed a special assembled pattern on a NP surface: transform from “S-shaped” to “W-shaped” or “U-shaped” as increasing the molar ratio of propylene oxide (PO). This result may be caused by the fact that limited hydrophobic NP surface can t provide enough adsorption sites as increasing the polymer concentration.

    Monte Carlo simulation of effect of MoO3 doping on Cu(Ⅱ) adsorption of silica
    Jiao WANG, Zhejunyu JIN, Kaining DING, Weiwei ZHAO, Xiaohua PU, Zongxiao LI
    2019, 70(1):  355-359.  doi:10.11949/j.issn.0438-1157.20180968
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    The adsorption behavior of Cu(Ⅱ) on silica and molybdenum doped silica was simulated by Monte Carlo method. The results show that Cu(Ⅱ) is adsorbed on the surface of the nanomaterial and the interatomic space. It is found that adding a small amount of molybdenum oxide to silica does not significantly change the adsorption capacity of Cu(Ⅱ). At the same time, the generalized gradient approximation (GGA) density functional theory (DFT) was used to verify the process, and the adsorption behavior of Cu(Ⅱ) in water by silica and molybdenum doped silica was verified by microcalorimetry. It was found that the adsorption process had ΔH<0, ΔS<0, van der Waals force as the adsorption driving force, and the molecular simulation was consistent with the experimental results.

    Preparation and application of graphene lubricant additive with extreme-pressure performance
    Yaqiang DUAN, Xianfeng HE, Tong WU, Yanping ZHANG, Zhiguo ZHAO
    2019, 70(1):  360-369.  doi:10.11949/j.issn.0438-1157.20181010
    Abstract ( 105 )   HTML ( 6)   PDF (2574KB) ( 72 )  
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    Since graphene was discovered, the application of graphene in the field of lubricants had been paid much attention originating from its excellent self-lubrication, mechanical and thermal properties. However, graphene had poor dispersion and easily reunited in oil, which is the key factor limiting the use of graphene in lubricants. To obtain the graphene lubricant additive (MGLOA) with excellent lubrication performance and stable dispersibility, long chain alkanes were grafted on the surfaces of graphene and the oleophilic modified graphene microchip (MGM) was obtained. Otherwise, the formula of lubricant additives (LOA) had been improved to strengthen the interaction between MGM and LOA, which was conducive to further promote the stable dispersion of MGM and showed synergistic lubrication with MGM. The results indicated that the use of MGM and/or LOA can fantastic increase the extreme-pressure lubrication performance of commercial lubricating oils and the optimal amount of MGM and LOA in other lubricants was 0.004 %(mass) and 5%(mass), respectively. The pressure lubrication performances of lubricating oils with 5%(mass) MGLOA-800 (MGM has a content of 0.08 %(mass) in LOA) were improved more than 11 times process. And in application, the process shows good cooling, noise reduction and vibration reduction.

    Effects of graphene oxide on crystallization behavior of VS55 during cooling and warming
    Miaomiao LUO, Ning GUO, Yi XU, Daoping LIU
    2019, 70(1):  370-378.  doi:10.11949/j.issn.0438-1157.20180612
    Abstract ( 68 )   HTML ( 2)   PDF (1078KB) ( 30 )  
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    The effects of cooling and warming rates(5,10,25,50 and 100℃/min) as well as the concentration of graphene oxide(GO) (0.01,0.1,1 and 5 mg/ml)on the crystallization of VS55 were studied by differential scanning calorimetry (DSC) and Cryomicroscope during both cooling and warming process. The results showed that: (1) As cooling and warming rates rised, both the freezing crystallization enthalpy Hf and the recrystallization enthalpy HTd became smaller. (2) For the case of cooling 2.1 mol/L VS55, the larger the concentration of GO, the more the crystallization of the 2.1 mol/L VS55 solution was, and the initial freezing temperature of the solution was increased obviously. For 4.2 mol/L VS55, however, the crystallization enthalpy Hf presented a trend of first dropping then rising when increasing GO concentrations. And GO has little effect on both freezing crystallization during cooling and recrystallization during warming for 8.4 mol/L VS55. (3) For the cases of higher concentrations of GO as well as lower concentrations of VS55, the crystal growth inside VS55 was inhibited more significantly during warming. For example, when adding 5 mg/ml GO, the recrystallization enthalpy offrozen 2.1 mol/L VS55 reduced by 14.55 J/g, that of 4.2 mol/L VS55 reduced by 7.95 J/g, which was close to 6.91 J/g of 8.4 mol/L VS55. In general, GO and VS55 concentrations mainly affect the growth of ice crystals during the cooling process, but the main factors, which affects the devitrification or recrystallization during the rewarming process, include the concentration of VS55 and GO as well as the cooling and warming rates.

    Process safety
    Calculate time to maximum rate under adiabatic condition by numerical calculation method
    Yi ZHU, Hao WANG, Liping CHEN, Zichao GUO, Zhongqi HE, Wanghua CHEN
    2019, 70(1):  379-387.  doi:10.11949/j.issn.0438-1157.20180678
    Abstract ( 112 )   HTML ( 4)   PDF (780KB) ( 88 )  
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    The maximum reaction rate arrival time (TMRad) is a very important parameter in chemical process thermal risk assessment. The general method for calculation of TMRad is based on N-order model kinetic analysis. However, the chemical reaction process is so complicated that only do kinetic analysis based on N-order without consider the type of reaction may cause large deviation or even incorrect assessments. Therefore, this paper proposes to calculate TMRad and TD24 by numerical calculation methods based on reaction model. 20% DTBP toluene solution and CHP represent N-order reaction and autocatalytic reaction, respectively. The analysis of ARC test data of two substances shows this method can be used to calculate TMRad and TD24 of N-order reaction reliably, but the comparison of autocatalytic reaction with two methods shows that although the fitting effect is very good, the general method calculated result has a large deviation, because the kinetic parameters are different under two models, this paper also perform the deviation size analysis. Therefore, it can be seen that the numerical calculation method has wide-range applicability, and to an exothermal curve, it is necessary to use the method to evaluate the TMRad and TD24 based on the understanding of the reaction type, so that the evaluation result is more reliable and accurate.

    Risk evaluation model of deepwater drilling blowout accident based on risk entropy and complex network
    Xiangkun MENG, Guoming CHEN, Chunliang ZHENG, Xiangfei WU, Gaogeng ZHU
    2019, 70(1):  388-397.  doi:10.11949/j.issn.0438-1157.20180501
    Abstract ( 75 )   HTML ( 1)   PDF (1003KB) ( 45 )  
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    To control the cascading risk of deepwater blowout, a quantitative evaluation method associated with risk uncertainty and evolution of deepwater drilling system was proposed, based on risk entropy theory and complex network theory. The complicated accident scenario was converted into an intuitive network computing. Firstly, according to the drilling process, a complex network that includes 59 nodes and 102 edges was constructed to represent the accident scene and calculate the clustering coefficient. Secondly, referring to the Shannon entropy theory, the risk entropy was introduced to characterize the uncertainty of risk transmission, in view of its randomness and fuzziness. Finally, the shortest path formulation of the blowout network was described, and the formulation was then converted into a liner programming and a solution of the shortest path of every initial event was provided by utilizing the Dijkstra algorithm. The results show that the clustering coefficient of deepwater drilling blowout network is 0.132. The evolutional structure has the characteristics of small world with low aggregation but high evolutionary of nodes. In addition, shallow gas during drilling has the greatest influence on the blowout accident. The blowout accident has the greatest impact, but the risk of all initial events can be caused by a few steps to cause the blowout accident to verify the feasibility of the method in the quantitative risk assessment of complex process systems.

    Ignition delay measurements and analysis of kinetic mechanisms for gasoline-air explosion under different conditions
    Jiannan XU, Xinsheng JIANG, Changhua ZHANG, Yijun WANG, Dexiang ZHANG, Wei XIE
    2019, 70(1):  398-407.  doi:10.11949/j.issn.0438-1157.20180854
    Abstract ( 88 )   HTML ( 3)   PDF (1045KB) ( 56 )  
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    Ignition characteristics for RON92 gasoline/air were measured in a shock tube at temperatures ranging from 1200 to 1600 K at atmospheric pressure for the first time. Combustion of the mixture with different oil gas concentrations (CH%=1.0%,1.4%,1.65%,2.0%,2.4%, by volume) was investigated. The experiments were conducted to explore the ignition law of oil gas explosion. Based on experimental data, the variation of ignition delay time with temperature and concentration were analysed. The formula of ignition delay time with temperature under each concentration was fitted. In addition, seven reaction mechanism models were adopted to calculate ignition delay time and comparison was made with experimental results. According to the rate of production(ROP) of some main species simulated by the best model, the influence of concentration on ignition delay was researched. The present study shows that the ignition delay time of gasoline is in good exponential relation with the reciprocal of ignition temperature. And larger concentration leads to longer delay time at the same temperature, because larger oil gas concentration tends to promote the reaction between hydrocarbon molecules and H, which inhibits the reaction between H and O2 as a result. Among the seven validated mechanisms, Abhijeet Raj mechanism exhibits high accuracy in predicting gasoline ignition delay time over a wide range of concentration at low pressure, making it suitable for oil gas explosion simulation. This work should provide experimental data set for validation and refinement of gasoline combustion mechanism and contribute to a method for identifying application conditions of reaction mechanism.

    Effect of concentration and ignition position on characteristics of premixed hydrogen-air deflagration
    Ligang ZHENG, Xiaochao ZHU, Shuijun YU, Yalei WANG, Gang LI, Depeng DU, Zengguo DOU, Yang SU
    2019, 70(1):  408-416.  doi:10.11949/j.issn.0438-1157.20180726
    Abstract ( 85 )   HTML ( 1)   PDF (1187KB) ( 56 )  
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    To study the effect of the multiple concentrations and ignition locations on the characteristics of the premixed hydrogen-air deflagration, an experimental study is conducted in an elongated transparent square cross-section duct closed at one end and open at the opposite end. The results show that hydrogen concentration and ignition position exerted a great impact on the evolution of flame front structures. The reaction under each equivalence ratio proceeded most rapidly when the mixture was ignited at 100 mm from the closed end. The ignition position has a greater influence on flame development in very lean or rich fuel. The hydrogen concentration and ignition position simultaneously affected the pressure waveform. The overpressure waveform under different equivalence ratios presents complex changes when the ignition occurred in the left and right parts of the duct respectively, with the 300 mm from the closed end as the boundary of ignition position. The overpressure peak has a strong dependence on hydrogen concentration, and the effect of concentration on the overpressure peak is much greater than that of ignition location. The maximum overpressure peak was obtained in Φ = 1.25 at all ignition positions. the maximum overpressure corresponds to the ignition position which is depending on the equivalence ratio.

    ARC thermal inertia correction method based on C80 data merging
    Jiong DING, Qi CHEN, Qiyue XU, Suijun YANG, Shuliang YE
    2019, 70(1):  417-424.  doi:10.11949/j.issn.0438-1157.20180556
    Abstract ( 88 )   HTML ( 5)   PDF (862KB) ( 80 )  
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    Due to the limit of the principle of accelerating rate calorimeter, thermal inertia factor correction is necessary for kinetics computation. However, the existing correction methods are contrary to the fact that the thermal inertia factor is shifty during the reaction process. Actually, the specific heat of the reactant and the efficiency of temperature tracking change with the reaction process. This leads to the kinetic computation errors. In response to these deficiencies, a method is proposed that the dynamical thermal inertia factor correction based on differential scanning calorimeter (C80) and accelerating rate calorimeter (ARC) data merging. The details of the method are as followed. Firstly, according to the Friedman method, the non-model kinetics parameters are obtained with the C80 data. Secondly, the product of the heat capacity and the equivalent thermal inertia factor is got through using the non-model kinetics parameters to solve the accelerating rate calorimeter data. Third, with the replacement of constant thermal inertia factor and the specific heat by the product, the kinetics results of ARC data are calculated. To verify the validity of the proposed method, the experiments are performed by using di-tert-butyl peroxide (DTBP) and cumene hydroperoxide (CHP). The results show that the proposed methods can avoid the influence of the dynamical thermal inertia factor in kinetic computation. It is worth popularizing in the thermal safety evaluation of chemical process.