Please wait a minute...
Table of Content
05 November 2019, Volume 70 Issue 11
    Reviews and monographs
    Technical characteristics and development trend of printed circuit heat exchanger for FLNG
    Liyi XIE, Zhiqiang LI, Guoliang DING
    2019, 70(11):  4101-4112.  doi:10.11949/0438-1157.20190634
    Abstract ( 641 )   HTML ( 21)   PDF (1194KB) ( 208 )  
    Figures and Tables | References | Related Articles | Metrics

    The printed circuit heat exchanger (PCHE) is a compact, efficient, safe and reliable heat exchanger type with good application prospects in floating liquefied natural gas platform (FLNG). The research status of PCHE is reviewed, including the classification of PCHE structure, heat transfer characteristics and resistance characteristics. The application status of PCHE in FLNG is summarized. And prospects of PCHE in FLNG is analyzed, including the structure design criteria of PCHE, the influence mechanism of sloshing and measure to defeating sloshing in heat exchangers applied in FLNG. Theoretical basis and research ideas of PCHE designing in sloshing condition are provided.

    Thermodynamics
    Solubility determination and thermodynamic calculation of CO2in several ether esters
    Xueman XU, Xia GUI, Zhi YUN
    2019, 70(11):  4113-4122.  doi:10.11949/0438-1157.20190360
    Abstract ( 564 )   HTML ( 13)   PDF (657KB) ( 236 )  
    Figures and Tables | References | Related Articles | Metrics

    In this study, the solubility of CO2 in propylene glycol monomethyl ether acetate (PMA), di(propylene glycol) methyl ether acetate (DPMA), 2-butoxyethyl acetate (BAC) and acetic acid 2-phenoxyethyl ester (EPA) was measured at the temperature variations from 353.15 K to 373.15 K rang up to 11.73 MPa by the constant-volume method. Results showed that the solubility of CO2 in the ether esters solvents decreased with the increasing of temperature, increased with the increasing of pressure, and the solubility was PMA<EPA<BAC<DPMA, which was greatly affected by temperature and pressure. Meanwhile, thermodynamic properties of the Gibbs free energy Δsol G, enthalpy change Δsol H and entropy change Δsol S of CO2 + ether ester system at different temperatures were also calculated by transformed Clausius-Clapeyron equation, further explained the dissolution mechanism of CO2 from the perspective of macroscopic thermal motion, and provided theoretical support for the development of new CO2 physical absorbents.

    Solubility and thermodynamics of lithium carbonate in sodium carbonate solution
    Haiwen GE, Huaiyou WANG, Min WANG
    2019, 70(11):  4123-4130.  doi:10.11949/0438-1157.20190647
    Abstract ( 2212 )   HTML ( 23)   PDF (561KB) ( 1158 )  
    Figures and Tables | References | Related Articles | Metrics

    The isothermal dissolution equilibrium method was used to study the dissolution equilibrium of lithium carbonate in sodium carbonate solution (278.15—358.15 K), the lithium carbonate solubility and density were determined, and the experimental data of lithium carbonate solubility was correlated by E-DH equation, standard deviation of calculated is less than 0.1. The Connaughton equation is used to correlate the solution density data with a standard deviation of less than 2×10-3. The experimental and theoretical results show that the solubility of lithium carbonate decreases first and then extremely slow decreases with the increase of sodium carbonate concentration in the temperature range of 278.15—358.15 K. Under the synergistic effect of the same ion effect and salt effect, the solubility change point is at sodium carbonate concentration of about 0.1 mol·kg-1. The dissolution enthalpy (ΔHd), entropy (ΔSd) and Gibbs free energy (ΔGd) of lithium carbonate in aqueous sodium carbonate solution were obtained by dissolution thermodynamic calculation. The results show that the dissolution process is a non-spontaneous process of exotherm and entropy reduction. The dissolution enthalpy and entropy increase with increasing sodium carbonate concentration, Gibbs free energy shows a maximum at 0.6 mol·kg-1, and the dissolution process is an entropy controlled process. The research results will provide basic data for the design of lithium carbide precipitation process for brine.

    Volumetric and viscosity properties of binary mixtures containing asymmetrical Gemini ionic liquid
    Xuzhao YANG, Jun WANG, Yun FANG
    2019, 70(11):  4131-4142.  doi:10.11949/0438-1157.20190470
    Abstract ( 430 )   HTML ( 5)   PDF (851KB) ( 156 )  
    Figures and Tables | References | Related Articles | Metrics

    Densities and dynamic viscosities of binary solutions containing asymmetrical Gemini ionic liquid (GIL), 1-(3-(trimethylammonio)prop-1-yl)-3-methylimidazolium bis(dicyanamide) ([N111C3MIM][N(CN)2]2) with acetonitrile (MeCN), methanol (MeOH) or ethanol (EtOH) over the entire mole fraction range have been measured from 293.15 K to 333.15 K under atmospheric pressure. Excess molar volumes (VmE) and excess viscosities (Δη) of the solutions were calculated based on the experimental density andviscosityvalues of pure [N111C3MIM][N(CN)2]2, molecular solvents, and their binary mixtures. The values of VmE and Δη were fitted by using the Redlich–Kister equations and the optimal ?tting parameters were obtained. The results indicate thatthe values of VmE and Δη reveal negative deviations from ideal solutions. There exists a minimum excess values. Negative values of VmE and Δη for all the binary mixtures indicate, compared to pure [N111C3MIM][N(CN)2]2 and molecular solvents, stronger interactions between [N111C3MIM][N(CN)2]2 and MeCN, MeOH or EtOH. These negative values are also related to the difference in size and shape of the molecules studied. Moreover, the variation of VmE and Δη on temperature suggests that temperature has an enormous in?uence on the intermolecular interactions between [N111C3MIM][N(CN)2]2 and molecular solvents.

    Thermodynamic studies on behavior of newly formed metallic iron on surface of particles
    Zhan DU
    2019, 70(11):  4143-4152.  doi:10.11949/0438-1157.20190931
    Abstract ( 399 )   HTML ( 9)   PDF (2368KB) ( 164 )  
    Figures and Tables | References | Related Articles | Metrics

    The influence of reduction conditions on the morphology of newly formed metallic iron during high temperature gas-based reduction of iron ore are studied from the standpoint of thermodynamic analysis, and the solutions for controlling iron morphology through regulation of reduction conditions are proposed. Experimental results showed that addition of H2 in CO could not only accelerate the growth rate of iron grains, but also increase the amounts of iron nuclei, resulting in the transformation of fibrous iron into dense one, addition of CO2 in CO could transform the“sharp-pointed”iron whiskers into“cactus-like”ones, decrease of reduction temperature could lower the strength of fibrous iron.

    Determination of solubility and ternary phase diagram of lamotrigine-phthalimide pharmaceutical cocrystal in pure solvent
    Jinyan ZHANG, Wenjie KUANG, Shaochang JI, Xiaoxue CAO, Anping LIAO, Ping LAN
    2019, 70(11):  4153-4161.  doi:10.11949/0438-1157.20190712
    Abstract ( 296 )   HTML ( 5)   PDF (862KB) ( 188 )  
    Figures and Tables | References | Related Articles | Metrics

    The solubilities of lamotrigine in n-propanol, isopropanol, n-butanol, isobutanol, ethyl propionate, methyl acetate were determined by the static method at a temperature range of 283.15 K to 323.15 K and correlated by Apelblat equation and λh equation. The results showed that the solubility of lamotrigine increased with the increase of temperature, and the solubility of n-butyl alcohol > n-propyl alcohol > isobutanol > isopropanol, methyl acetate > ethyl propionate. Apelblat equation had better fitting effect, which can be used to predict the thermodynamic behavior of lamotrigine monomer. On this basis, the lamotrigine-phthalimide cocrystal was presented and the ternary phase diagram of lamotrigine- phthalimide - solvent was established in isobutanol and ethyl propionate at 298.15 K and 303.15 K.The results showed that with the increase of temperature, the stability region for the pure lamotrigine - phthalimide cocrystal was increased, and the ternary phase diagram was symmetrical in isobutanol, which was conducived to cocrystal formed.

    Fluid dynamics and transport phenomena
    Distribution of liquid film thickness and wave parameters in horizontal annular flow
    Hongjun SUN, Wei WANG, Mingyang GUI
    2019, 70(11):  4162-4171.  doi:10.11949/j.issn.0438-1157.20190388
    Abstract ( 483 )   HTML ( 7)   PDF (1763KB) ( 191 )  
    Figures and Tables | References | Related Articles | Metrics

    Annular flow is a common type of gas-liquid two-phase flow. A dynamic measurement system for annular flow liquid film with double parallel conductance probes array sensor is designed. The experiments in horizontal annular flow with superficial gas velocity of 15-35 m/s and superficial liquid velocity of 0.1-0.4 m/s are carried out. And the distribution of liquid film thickness and phase interface wave parameters in horizontal annular flow is analyzed. The results show that the bottom liquid film thickness decreases with the increase of the superficial gas velocity, and increases with the increase of the superficial liquid velocity in the horizontal annular flow. But there is a saturated growth trend at high superficial liquid velocity. Meanwhile, the liquid film thickness at other circumferential positions increases continuously, especially at 45° position. And the distribution of liquid film tends to be uniform at the lower halve circumference. From the bottom to the top, the wave velocity and wave frequency of the circumferential liquid film decrease gradually, which is consistent with the distribution of the liquid film thickness. The large disturbance wave mainly distributes at the bottom. The wave velocity and wave frequency of the bottom liquid film increase with the increase of the superficial gas velocity. However, the influence of the superficial liquid velocity to wave velocity and wave frequency is different. With the increase of superficial liquid velocity, the wave velocity increases, but the wave frequency almost unchanged, and the wavelength increases correspondingly.

    Effect of adsorption process intensification for high-temperature steam generation in adsorption heat pump
    Linsheng ZHANG, Zhouming LIU, Guangyao LI, Tingting CHEN, Bing XUE
    2019, 70(11):  4172-4180.  doi:10.11949/0438-1157.20190378
    Abstract ( 411 )   HTML ( 7)   PDF (1769KB) ( 354 )  
    Figures and Tables | References | Related Articles | Metrics

    In the open adsorption heat pump system based on direct contact heat transfer method, a pre-adsorption process or a preset mass transfer channel is introduced to investigate its influence on steam generation and system performance. In this paper, experimental working principle of high-temperature steam generation from hot water is described as a comparison. Then cyclic test with pre-adsorption units (saturation temperature=74.0℃ and 89.2℃) and mass transfer channels (branch shape and coiler shape) are conducted. The results show that after adding the pre-adsorption process(saturation temperature=89.2℃), the average temperature of the generated steam is 203 ?C and GTL (gross temperature lift) of the system is 98.4 ?C. Steam generation time was 131 s earlier than the comparative experiment, effective time ratio for steam generation is elevated by 52.2% and mass of generated steam is raised by 27.0%. COPh (heating coefficient of performance) and SHPs (specific heating power for steam generation)are improved by 28.2% and 27.2%, respectively. When presetting branch shape channel inside the adsorption bed, effective time ratio for steam generation is elevated by 17.8% and mass of generated steam is raised by 8.75%. COPh and SHPs are increased by 8.16%and 9.05%,respectively.The pre-adsorption process allows the adsorption bed to reach the entire adsorption and thermal equilibrium faster. As a result, the generated high temperature steam arrives the top exit earlier. Besides, the local adsorption equilibrium is promoted on account of the mass transfer channel, which also reduces the local mass transfer resistance and makes a part of generated steam leave the pocked bed quickly. These results indicate that with the rapidly achievement of the entire and local adsorption equilibrium, the dynamic steam generation process is successfully intensified and the system performance is significantly improved.

    Resistance characteristics of bed packed with mono-size cylindrical particles
    Chengquan ZHANG, Jun GAO, Lipeng LYU, Lianjie HE
    2019, 70(11):  4181-4190.  doi:10.11949/0438-1157.20190457
    Abstract ( 268 )   HTML ( 4)   PDF (1374KB) ( 135 )  
    Figures and Tables | References | Related Articles | Metrics

    The effect of particle density on the porosity of packed bed was studied by the experiment of the resistance characteristics of packed bed with cylindrical particles of different lengths of 3 mm and 4 mm. According to the experimental results, the following conclusions can be drawn that the porosity of the packed bed of cylindrical particles is independent of the particle density and is only related to the aspect ratio of the cylindrical particles.The modified model of the porosity of cylindrical particles packed bed was developed to make the prediction more accurate at high sphericity. The existing research results still have contradictions in predicting the cylindrical particle packed bed under different L/D values. And the Nemec model has higher prediction accuracy than the Wu model. When dep is used as the equivalent diameter, the R2 of Ergun constants are 0.92(C1) and 0.98(C2), respectively, which is highest compared with that of other equivalent diameters.

    Influence analysis of insulation on performance of single well geothermal heating system
    Yunmin RAN, Xianbiao BU
    2019, 70(11):  4191-4198.  doi:10.11949/0438-1157.20190412
    Abstract ( 458 )   HTML ( 9)   PDF (1277KB) ( 206 )  
    Figures and Tables | References | Related Articles | Metrics

    The heat transfer mathematical model of single well geothermal is established and the heat transfer process of single well geothermal is simulated. The effects of different insulation materials and depth on the fluid outlet temperature and heating power are compared and analyzed. The results show that the thermal conductivity of insulation material and the depth of the insulation installation have great influence on the heating power of the system. When the thermal conductivity of material are 0.03 W/(m·K) and 0.5 W/(m·K), the average heating power are 732.08 kW and 640.98 kW, respectively. When the thermal conductivity is 0.03 W/(m·K) and the depth of insulation installation is 1000 m, the temperature difference between inlet and outlet is 10.33 K, when the depth of insulation installation is 2000 m, the temperature difference between inlet and outlet is 15.98 K and when the depth of insulation installation is 3000 m, the temperature difference between inlet and outlet is 17.93 K. In the actual project, the production wells can be insulated by means of various materials and installations. The heat preservation focus is on the small depth of the well, which can ensure the production water temperature and save costs.

    Simulation of sessile nanofluid droplet evaporation character
    Ming JIN, Dinghua HU, Qiang LI, Desong FAN
    2019, 70(11):  4199-4206.  doi:10.11949/0438-1157.20190476
    Abstract ( 562 )   HTML ( 16)   PDF (1046KB) ( 621 )  
    Figures and Tables | References | Related Articles | Metrics

    Nanofluid droplet evaporation has been widely used in many applications, such as cooling of electronic equipment, inkjet printing and medical testing. To study the evaporation characteristics of water-based Al2O3 nanofluid droplets, a two-dimensional transient model of nanofluid droplet evaporation was established, taking into account the effects of nanoparticle transport and internal droplet flow, and using arbitrary Lagrangian-Euler method (ALE) captures the gas-liquid motion interface. Based on the proposed model, the effects of Marangoni flow, substrate temperature and initial particle concentration on the evaporation of alumina nanofluid droplet were studied. The results showed that the gas-liquid interface temperature distribution and evaporationrate can be affected by Marangoni flow. The evaporation rate increases with the increase of the initial concentration of nanoparticle and the substrate temperature owing to the variation of nanoparticle concentration distribution and interface temperature during droplet evaporation.

    Effect of drag models on CFD simulations for homogeneous liquid-solid fluidization
    Yi ZHANG, Yulong BAI, Dingling LUO, Jianzhou LU, Yanjun GUAN, Kai ZHANG
    2019, 70(11):  4207-4215.  doi:10.11949/0438-1157.20190583
    Abstract ( 631 )   HTML ( 10)   PDF (1168KB) ( 302 )  
    Figures and Tables | References | Related Articles | Metrics

    Drag model plays one of important roles for CFD simulation of multiphase flows. Six drag models proposed by Gidaspow, Syamlal-O Brien, Di Felice, Gibilaro, Dallavalle and BVK are compared for predicting homogeneous liquid-solid fluidization in this study. CFD simulations are conducted based upon a simplified inviscid two-fluid model proposed by Brandani and Zhang in a commercial platform together with user-defined FORTRAN subroutines. Typical experimental data including a wide range of particle Reynolds numbers from reference literatures are employed to evaluate numerical simulation. The results show that either BVK model or Dallavalle model could predict the bed expansion and overall solids holdup very well. The radial profiles of solids holdup predicted by BVK, Syamlal-O Brien as well as Dallavalle model are more accurate, and that the BVK drag model provides better prediction for the radial profile of solids axial velocity. Generally, the BVK drag model demonstrates the best performance for modelling hydrodynamics in homogeneous liquid-solid fluidization as its mechanism is corresponding with the kinetic behavior of particles in liquid-solid system. Taking both prediction accuracy and model complexity into consideration, Dallavalle drag model seems to be the optimal choice among the rest of the drag models.

    Investigation on effect of hydrophilicity and hydrophobicity of metal foam on phase separation characteristics of gas-liquid two-phase flow in T-junction
    Hongwei LI, Guobao WEI, Yacheng WANG, Dongwei FU
    2019, 70(11):  4216-4230.  doi:10.11949/0438-1157.20190481
    Abstract ( 437 )   HTML ( 3)   PDF (1966KB) ( 120 )  
    Figures and Tables | References | Related Articles | Metrics

    Filling foam metal with small channels has become a research hotspot in the direction of heat transfer in recent years. Use air and water as working medium, the foam metal with PPI of 10 and 20 is filled into a T-shaped small channel with a cross section of 2.5 mm × 2.5 mm respectively. Change the hydrophilicity and hydrophobicity of metal foam, then study the influence mechanism of gas-liquid two-phase superficial velocity and hydrophilicity as well as hydrophobicity on phase separation under the action of slug flow and annular flow. The separation characteristics of three foamed metals treated with hydrophilic treatment, hydrophobic treatment and untreated were compared: whether it is a slug flow or an annular flow, the best separation effect is the hydrophilic treated foam metal, then the untreated foam metal, and the hydrophobic treatment foam metal get the worst effect, phase separation effect of T-channels filled with metal foam is significantly better than unfilled channels. For hydrophilic treated and hydrophobic treated T-channels, whether it is a slug flow or an annular flow, the gas phase recovery fraction of the inner branch of the T-shaped small channel is dominant, the liquid phase recovery fraction decreases with the increase of superficial velocity of the liquid, but the superficial velocity of gas phase has little effect on the liquid fraction. However, the reduction of the foam metal PPI will reduce the gas phase recovery fraction, which makes the distribution effect closer to the uniform distribution line.

    Experimental research on reverse flow phenomenon in natural circulation with equal height difference under low flow rate
    Jianchuang SUN, Xiaxin CAO, Xu RAN, Zhuohua ZHANG, Zhengpeng MI, Ming DING
    2019, 70(11):  4231-4237.  doi:10.11949/0438-1157.20190407
    Abstract ( 431 )   HTML ( 1)   PDF (1889KB) ( 134 )  
    Figures and Tables | References | Related Articles | Metrics

    Natural circulation systems are widely used in nuclear power plants due to their inherent safety. Natural circulation system with equal height different is a special system, because its heating section and water tank are connected by upper and lower horizontal loops. However, the phenomenon that the water in water tank reversely flows to the upper horizontal loop will be occurred in this kind of natural circulation system under low flow rate conditions. The studies of this phenomenon are not common. The reverse flow characteristics of upper horizontal loop is researched by visualization experiments. The results show that the reverse flow length in the upper horizontal loop decreases with the increase of flow rate, and increases with the increase of temperature difference between the outlet fluid of heater and the reverse flow fluid form water tank. It is found that the reverse flow in the upper horizontal loop is mainly affected by the inertia force of the hot water and the buoyancy force formed by the hot water and the reverse flow fluid. In addition, the reverse flow phenomenon in the upper horizontal loop can be judged by Richardson number.

    Performance optimization of ORC steam generator based on the second law of thermodynamics
    Wei YU, Huitao WANG, Jianjun WANG, Daofei ZHU, Shuai TAO, Zhong GE, Jinglun HUANG, Lingling ZHAO
    2019, 70(11):  4238-4246.  doi:10.11949/0438-1157.20190272
    Abstract ( 425 )   HTML ( 3)   PDF (1342KB) ( 426 )  
    Figures and Tables | References | Related Articles | Metrics

    To study the design and optimization of the low temperature waste heat driven ORC system, the main thermal performance calculation model of the organic Rankine cycle steam generator was established. Based on the second law of thermodynamics, the exergy increase of unit heat transfer area in steam generator was proposed as optimization objective function. R245fa was selected as the working fluid. Under the condition of a given flue gas inlet temperature and ensuring the working fluid gets saturated at the steam generator exit, the optimal mass flow rate under different conditions are calculated, and the effects of inlet temperature of flue gas, inlet pressure of working fluid, convective heat transfer coefficient of outside pipe and the per tube mass flow of flue gas on objective function and optimal mass flow rate of working fluid are analyzed. The results show that the inlet pressure of the working fluid and the convective heat transfer coefficient outside the tube have a significant influence on the optimal mass flow rate, while the inlet temperature of the flue gas and the per tube mass flow of flue gas have little effect on the optimal mass flow rate. With the increase of the inlet pressure of the working fluid and the convective heat transfer coefficient outside the tube, the optimal mass flow rate increases.

    Experimental study on DBD discharge plasma for anti-icing and de-icing
    Miao TIAN, Huimin SONG, Hua LIANG, Biao WEI, Like XIE, Jie CHEN, Zhi SU
    2019, 70(11):  4247-4256.  doi:10.11949/0438-1157.20190304
    Abstract ( 481 )   HTML ( 10)   PDF (2313KB) ( 226 )  
    Figures and Tables | References | Related Articles | Metrics

    In this paper, AC dielectric barrier discharge (AC-DBD), nanosecond pulse dielectric barrier discharge (NS-DBD) and radio frequency dielectric barrier discharge (RF-DBD) plasma de-icing experiments were carried out in a windless environment. Using high-speed imaging technology and infrared temperature imaging technology to record the dynamic process of the phase transition of the dielectric layer, systematically analyze the advantages and disadvantages of the three and the heat transfer mechanism. The results show that when the power output of the static experiment is the same, the temperature rise of the AC-DBD plasma is rapid, and the de-icing experiment is the best. For the NS-DBD plasma, the low-pressure high-frequency de-icing performance is obviously better than the high-voltage low-frequency; For RF-DBD, the discharge of the plasma is mainly concentrated at the edge of the electrode strip, and the discharge is severe, but the temperature between the electrodes is low, resulting in poor overall deicing effect. Finally, experimental verification of AC-DBD plasma anti-icing was carried out in the icing wind tunnel. In the wind tunnel test, the AC-DBD plasma has a good anti-icing effect in the downstream of the airfoil, but the anti-icing effect is not good at the leading edge position. In the next step, it is necessary to optimize the leading edge actuator configuration and improve the airfoil leading edge anti-icing effect.

    Experimental study on pressure drop for subcooled water flow boiling under high heat fluxes
    Jianguo YAN, Pengcheng GUO, Jiaqi MA, Xingqi LUO, Qincheng BI
    2019, 70(11):  4257-4267.  doi:10.11949/0438-1157.20190163
    Abstract ( 416 )   HTML ( 3)   PDF (1436KB) ( 109 )  
    Figures and Tables | References | Related Articles | Metrics

    Subcooled boiling has been widely used in high heat flow cooling applications, such as fusion reactor divertor cooling and pressurized water reactor core cooling. In this paper, the pressure drop characteristics of subcooled water flowing in a vertical stainless circular tube are experimentally investigated under high heat fluxes condition. The test tube has an inner diameter of 6 mm and a length-to-diameter of 44.4. The operating parameters are as follows: heat flux q = 7.5—12.5 MW/m2, mass flux G = 6000—10000 kg/(m2?s), pressure p = 3—5 MPa, and inlet fluid temperature T b = 80—200℃. The effects of mass flux, heat flux, pressure, boiling number and Jacob number on subcooling boiling pressure drop were discussed. The results show that subcooled boiling pressure drop increases with increasing heat and mass fluxes but decreases with increasing pressure. The experimental data are compared with the available empirical correlations, and it is found that these correlations cannot well predict our data, which may be mainly due to the variations in operating parameters and working fluids. Moreover, it is observed that the subcooled boiling pressure drop is affected by diameter effect. Therefore, a new correlation is proposed based on our previous correlation, in which a correction term for diameter effect is added. The new correlation can capture the experimental data within ±18% error bands.

    Catalysis, kinetics and reactors
    Study on ethane dehydrogenation over PtSn-Mg(Zn)AlO catalyst
    Xiaoping WU, Chenguang WANG, Qi ZHANG, Qiying LIU, Xinghua ZHANG, Longlong MA
    2019, 70(11):  4268-4277.  doi:10.11949/j.issn.0438-1157.20190569
    Abstract ( 568 )   HTML ( 5)   PDF (2924KB) ( 267 )  
    Figures and Tables | References | Related Articles | Metrics

    A series of PtSn-Mg(Zn)AlO catalysts with different Zn and Pt contents were synthesized by anion exchange method for ethane dehydrogenation. The experimental results show that the doping of a small amount of Zn in the hydrotalcite precursor has a significant effect on the performance of ethane dehydrogenation. When the Zn content is 2% (mass), the Pt-based catalyst exhibits the best performance with an initial ethane conversion of 27.1% and an average ethane conversion of 21.6% for a period of 2 h at 550℃. To study the effect of Zn doping on the performance of ethane dehydrogenation and the structure of catalyst, the prepared catalysts were characterized by XRD, BET, SEM and TEM. The BET and SEM results show that the PtSn-Mg(Zn)AlO catalyst has larger specific surface area than the PtSn-MgAlO catalyst. The TEM results show that the average diameter of the PtSn-Mg(Zn)AlO catalyst and the PtSn-MgAlO catalyst are (1.49 ± 0.31) nm and (2.0 ± 0.23) nm, respectively, which shows that the doping of Zn changes the structure of the catalyst to some extent, and better disperse Pt particles, thereby improving the catalyst reaction performance. Furthermore, the effect of temperature and Pt loading on the performance of ethane dehydrogenation were investigated. It was found that the ethane initial conversion was higher at higher temperatures, but the catalyst was more susceptible to deactivation. The effect of Pt loading on the dehydrogenation performance of ethane was investigated. It was found that increasing the Pt content did not increase the ethane conversion rate by a corresponding multiple, that is, increasing the Pt content reduced the utilization rate of Pt. Therefore, proper reduction of Pt content in Pt-based catalyst has far-reaching significance for studying the ethane dehydrogenation reaction.

    Effect of Pt precursor on structure and performance of Pt/CeO2 catalysts
    Kang XI, Yong WANG, Jing XIE, Ning WANG, Ying ZHOU, Qiulian ZHU, Hanfeng LU
    2019, 70(11):  4278-4288.  doi:10.11949/0438-1157.20190468
    Abstract ( 648 )   HTML ( 12)   PDF (2276KB) ( 393 )  
    Figures and Tables | References | Related Articles | Metrics

    The interaction between Pt and the carrier affects the catalytic activity of the intrinsic Pt nanoparticles. Herein, Pt/CeO2 catalyst was successfully prepared via a facile Pt colloidal particle deposition method, and its physicochemical properties and catalytic performance in CO oxidation and toluene combustion were investigated. XRD, TEM, XPS and H2-TPR were used to identify the states of Pt particles on the support surface, as well as their effect on the performance of the catalysts. Formation of metallic Pt0 which provided the active sites for CO oxidation and toluene combustion is one of the factors controlling catalyst activity. Pt/CeO2 catalyst prepared by colloidal particle deposition was found to be more advantageous than conventional impregnation and impregnation-reduction in producing very finely dispersed metallic Pt0 that did not noticeably agglomerate even after thermal treatment at 400℃ for longer duration. The CO oxidation and toluene combustion activity additionally demonstrate that the sample shows a remarkably better performance as compared to its impregnated counterparts. By contrast, all of Pt atoms were anchored with the surface oxygen of CeO2 by forming Pt-O-Ce bond during the oxidative treatment in impregnation method, resulting in the absence of metallic Pt0. This change is evidence of the appearance of Pt2+ species, which is supported by the H2-TPR and XPS data, and could be the main reason behind the deactivation of the Pt/CeO2 catalyst. Compared with impregnation method, the dispersion of metallic Pt0 rised while less Pt-O-Ce bonds existed on the support surface, and a higher Pt0/Pt2+ ratio could be maintained even under the high thermal treatment in impregnation reduction method. The catalytic activity test of CO oxidation and toluene combustion show that the sample exhibits the better catalytic performance due to the increase of surface metallic Pt0,but it is unavoidable for the sample to show a decline in catalytic activity compared with its colloidal particle depositional counterpart. Hence, it is concluded that the state and the dispersion of Pt nanoparticles on the support surface depended on the prepared method, and they are the decisive factors to promote the catalytic activity of Pt/CeO2 upon the oxidative treatment, especially the abundant surface metallic Pt0. Based on characterization results, the colloidal particle deposition method is proposed to realize the direct load of metallic Pt0 and gives the homogeneous dispersion of Pt nanoparticles, possessing a superiority in improving the catalytic performance.

    Catalytic conversion of palm oil to aromatics on Zn/HZSM-5 zeolites
    Zhiyuan AN, Chao ZHU, Yibin LIU, Xiang FENG, Xin JIN, Xiaobo CHEN, Chaohe YANG
    2019, 70(11):  4289-4297.  doi:10.11949/0438-1157.20190424
    Abstract ( 511 )   HTML ( 12)   PDF (1084KB) ( 412 )  
    Figures and Tables | References | Related Articles | Metrics

    HZSM-5 zeolite can be used in the process of catalytic conversion of fatty acid esters to produce aromatic hydrocarbons and low-carbon olefins. However, the yield of aromatics over untreated HZSM-5 zeolite is low. Modification of HZSM-5 zeolite with transition metal can optimize the acidity and greatly increase the yield of aromatics. A series of Zn/HZSM-5 zeolites with different zinc content were prepared by equal volume impregnation, and the modified zeolites were characterized by XRD, XRF, XPS, NH3-TPD, SEM, TEM, Py-IR, and N2 physical adsorption-desorption. The results showed that the crystal structure of Zn/HZSM-5 was not changed, and the zinc was uniformly distributed on the surface and pores of HZSM-5 zeolites. Catalytic conversion of palm oil on Zn/HZSM-5 zeolite with Zn content of 3% (mass) showed the best catalytic performance. The content of aromatics in the obtained liquid hydrocarbons was as high as 87.92% (mass), and the yield of aromatics reached 59.44% (mass).

    High-energy chemical laser multiphysics coupling numerical simulation
    Ying HUAI, Shuqin JIA, Kenan WU, Xi CHEN
    2019, 70(11):  4298-4305.  doi:10.11949/0438-1157.20190344
    Abstract ( 453 )   HTML ( 6)   PDF (1397KB) ( 132 )  
    Figures and Tables | References | Related Articles | Metrics

    High-energy chemical laser is a phenomenon that uses a large amount of chemical atomic stimulated radiation to generate luminescence. To analyze this process, a multi-physical coupling calculation is constructed. The numerical platform consists of chemical flow, optical and thermal-structural calculation. However, the characteristic time difference of the three physical processes will make it difficult to decide the time scale for the coupled simulation. Therefore, an asynchronous multi-time scale coupling strategy is proposed. Three-dimensional, high resolution and large-scale chemical laser numerical simulations have been performed. In this paper, a chemical oxygen-iodine laser simulation is carried out. The flow field, optical field and the cavity mirrors of the laser are numerically analyzed. The calculation can evaluate the most important parameters of the laser, including power and beam quality. The constructed numerical method is an important tool to investigate and optimize chemical lasers.

    Process system engineering
    Modification of molecular descriptor and modeling for boiling point prediction of aromatic hydrocarbons
    Xiangcheng MA, Wei QIN, Qinglin CHEN, Bingjian ZHANG
    2019, 70(11):  4306-4314.  doi:10.11949/0438-1157.20190425
    Abstract ( 490 )   HTML ( 10)   PDF (665KB) ( 184 )  
    Figures and Tables | References | Related Articles | Metrics

    According to the differences of chemical environment of carbon atoms in aromatic hydrocarbons, the carbon atom branching degree index δi in the Randi? connectivity index is modified, and a new molecular descriptor Modran is presented. Comparative analysis shows that the descriptor Modran has better selectivity for the chemical structure of aromatic molecules. Through analyzing the factors influencing the boiling points of aromatic hydrocarbons and using the best subset selection method, it is found that the combination of four molecular descriptors, such as Modran first-order and second-order branching index, molecular polarizability and aromatic ring carbon atom ratio, has good predictive ability for aromatics boiling point, and then linear combination model and neural network model including the four descriptors are established. Compared with the Marrero-Pardillo group contribution method, the neural network model of the four-molecule descriptor reduces the average absolute error of the boiling point prediction of aromatics from 12.26 K to 4.56 K.

    Synthetic process optimization of benzyl acrylate using fuzzy neural networks-genetic algorithms
    Zheng FAN, Panpan JI, Chao LI, Zhuang LIU, Yigang ZHAO, Xiaoyan JING
    2019, 70(11):  4315-4324.  doi:10.11949/0438-1157.20190268
    Abstract ( 489 )   HTML ( 5)   PDF (714KB) ( 449 )  
    Figures and Tables | References | Related Articles | Metrics

    Firstly, the effects of water-carrying agent dosage, reaction temperature, reaction vacuum degree, reaction time, acid-alcohol ratio on the mass fraction and yield of benzyl acrylate were investigated by multivariate analysis of variance. Then the Takagi-Sugeno fuzzy artificial neural networks was established with significant factors as input and comprehensive scores as output. Finally, the genetic algorithm was used to optimize the synthesis conditions of benzyl acrylate and the reliability was verified by t-test. The research demonstrated that all mentioned factors behaved extremely significant effects on the mass fraction and yield of benzyl acrylate synthesized products simultaneously. The prediction model was based on 5-15-243-1 network structure. After 36859 training iterations, the mean square error of the prediction model was less than the allowable convergence error limit 0.0050. The relationship between the output value and the expected value was approximately linear. The determination coefficient of training and testing stages were 0.9999 and 0.9998, respectively. The optimal control parameters including 53 ml water-carrying agent, 125℃ reaction temperature, 0.095 MPa reaction vacuum degree, 2.2 h reaction time and 1.4 acid-alcohol ratio were obtained by 149 evolutions of genetic algorithm. The mass fraction, yield and comprehensive scores of benzyl acrylate synthesis were 99.27%, 98.04% and 98.78% on the basis of the optimal process conditions. The prediction model was also proved to be reliable.

    Condition recognition based intelligent multi-objective optimal control for wastewater treatment
    Yongming LI, Xudong SHI, Weili XIONG
    2019, 70(11):  4325-4336.  doi:10.11949/0438-1157.20190453
    Abstract ( 445 )   HTML ( 9)   PDF (3157KB) ( 232 )  
    Figures and Tables | References | Related Articles | Metrics

    Aiming at the problems in wastewater treatment process, such as high energy consumption and penalty, a condition recognition based intelligent optimal control system for wastewater treatment is proposed. In order to ensure the accuracy and real-time performance of condition identification, the adaptive genetic algorithm is used to select reference variables from a variety of influent parameters, then based on the established historical knowledge base, identifies the real-time influent condition. Multi-objective optimization for energy consumption and penalty is guided by historical knowledge, and through the method of intelligent decision-making, the optimal preference solution is selected from pareto solution set, then update the knowledge base. The international benchmark simulation platform BSM1 is used to verify the results. The results show that the proposed method effectively utilizes the optimal solution information of historical conditions, improves the convergence of the algorithm, reduces the computational cost, and can control the energy consumption and fines at a lower level.

    Biochemical engineering and technology
    Molecular dynamics simulation of denaturation of DhaA induced by urea and dimethyl sulfoxide
    He ZHENG, Shengjiang YANG, Yongchao ZHENG, Yan CUI, Xuan GUO, Jinyi ZHONG, Jian ZHOU
    2019, 70(11):  4337-4345.  doi:10.11949/0438-1157.20190278
    Abstract ( 509 )   HTML ( 7)   PDF (2732KB) ( 408 )  
    Figures and Tables | References | Related Articles | Metrics

    DhaA can effectively degrade the chemical poison mustard gas, and poor environmental tolerance affects its application in military decontamination. However, the molecular denaturation processes of DhaA induced by urea and dimethyl sulfoxide (DMSO) remain unclear, although it is reported that directed evolution, chemical modification and immobilization were helpful to the stabilization of DhaA. In this study, molecular dynamics (MD) simulations are used to investigate the denaturation processes of DhaA in urea and DMSO solutions. The results show that urea molecules can replace water to form H-bonds with DhaA and its catalytic active sites, which made main tunnel lengthened, curvature enhanced and bottleneck radius reduced. Whereas DMSO molecules can enter into hydrophobic cavity of DhaA by van der Waals interaction, which made main tunnel shortened, bottleneck radius enlarged and conformation changed. These findings reveal the differences of molecular denaturation process of DhaA in two systems, which could provide theoretical guidance for the stabilization of DhaA.

    Energy and environmental engineering
    Experimental study on pollutant emission characteristics of lower-heat-value ethylene combustion in porous media
    Zhongqian LING, Chao ZHOU, Xianyang ZENG, Bo LING, Jiongjie QIAN
    2019, 70(11):  4346-4355.  doi:10.11949/0438-1157.20190405
    Abstract ( 371 )   HTML ( 4)   PDF (1933KB) ( 135 )  
    Figures and Tables | References | Related Articles | Metrics

    The use of low calorific value gas has slowly entered the public's field of vision in these years. In order to increase the utilization of low calorific value gas and achieve clean emission of low calorific value gas, a porous medium test bench was built to investigate the pollutant discharge law of premixed combustion of ethylene in freely stacked alumina pellets. This experiment analyzes the effect of equivalent ratio, flow rate and porosity on gas emissions and ethylene conversion with the data collection of the export flue gas under the different experimental conditions. It is found that the porous medium combustion technology is a kind of combustion method which can efficiently clean the calorific value gas. Under the better test conditions, the CO emission can be reduced to 125~187 mg/m3. The emission of NO is related to the equivalent ratio, and has little relationship with the flow rate and the diameter of the small sphere. The NO outlet concentration during the whole experiment is less than 16mg/m3.The conversion of ethylene is between 80% and 90% in the case of stable combustion. The experimental results have certain guiding significance for dealing with low calorific value gases.

    Lipids extraction of Nannochloropsis and hydrothermal liquefaction of defatted Nannochloropsis
    Xiaohan TANG, Xiaoyi YANG
    2019, 70(11):  4356-4362.  doi:10.11949/0438-1157.20190491
    Abstract ( 375 )   HTML ( 3)   PDF (505KB) ( 220 )  
    Figures and Tables | References | Related Articles | Metrics

    To improve the comprehensive utilization efficiency of microalgae, dry or wet Nannochloropsis were extracted with different solvent and hydrothermal liquefaction (HTL) experiments of defatted Nannochloropsis were carried out to explore the effects of defatted methods on HTL products. The solvent extraction results showed that polar solvent can extract 25.0% of lipids from microalgae without selectivity, which resulted in only 29.68% for the fatty acid methyl ester yield of the extracts; the fatty acid methyl ester recovery of mix solvent was 57.70%. For the HTL bio-crude of defatted Nannochloropsis, the yield was 27.7%—34.6%, nitrogen content was 5.29%—6.68%, mainly consisted of fatty acid, fatty acid esters, fatty acid amides, long-chain hydrocarbon, amines, oxygen-containing compounds and nitrogen-containing heterocyclic compounds. The yield of wet algae hydrothermal crude oil after methanol extraction was 34.6%, the nitrogen content was 5.44%, and the process energy consumption was low, indicating that methanol extraction wet algae combined with hydrothermal liquefaction has certain application prospects.

    Effect of salinity on fouling deposition characteristics in hyperhaline seawater
    Bing NI, Shengqiang SHEN, Yihao LI, Xiaohua LIU, Yiqiao LI, Shanlin LIU
    2019, 70(11):  4363-4369.  doi:10.11949/0438-1157.20190649
    Abstract ( 366 )   HTML ( 6)   PDF (971KB) ( 161 )  
    Figures and Tables | References | Related Articles | Metrics

    The process of fouling deposition is complicated. Factors such as the type of pipe, seawater composition, salinity and temperature can affect the deposition characteristics of the fouling. Deposition characteristics of fouling are studied on the surface of titanium tube and copper tube under static conditions with artificial seawater. The seawater temperature is 80℃ and seawater salinity is 6%, 8% and 10%, respectively. The results show that the deposition amount on the metallic surface achieves the highest value at the salinity of 8%. The major composition on the surface of titanium tube is flaky Mg(OH)2 and minor CaCO3. Mg(OH)2 is agglomerated on the surface of copper tube. Calcite CaCO3 andminor aragonite CaCO3 deposit on the surface of Mg(OH)2. The deposition trend of fouling on the surface of the two metals is different under the same salinity. CaSO4 crystals are not observed on the metallic surface.

    Density functional theory study on chlorine corrosion of biomass furnace
    Zekang LYU, Shenwei LONG, Guanbing LI, Shengli NIU, Chunmei LU, Kuihua HAN, Yongzheng WANG
    2019, 70(11):  4370-4376.  doi:10.11949/0438-1157.20190487
    Abstract ( 428 )   HTML ( 3)   PDF (1407KB) ( 142 )  
    Figures and Tables | References | Related Articles | Metrics

    Activated oxidative corrosion of chlorine is one of the main causes of corrosion in biomass boiler superheaters. To investigate the reaction mechanism of FeCl2 and O2 in the activated oxidation corrosion cycle, the DMOl3 module in Material Studio was used to optimize the geometry of each reactant, product, intermediate and transition state based on density functional theory and transition state theory. The authenticity of the intermediates and transition states was confirmed by frequency analysis. The results show that three Cl2 molecules are successively formed during the reaction of FeCl2 with O2 to form Fe3O4. The third Cl2 escaping to form Fe3O4 needs to absorb up to 300.4 kJ/mol, which is the rate determining step of the reaction pathway.

    Study on treatment of biological catalytic filter and membrane fouling with bimetallic catalyst as filter media
    Songze HAO, Hongwei ZHANG, Yun WU, Jie WANG
    2019, 70(11):  4377-4386.  doi:10.11949/0438-1157.20190390
    Abstract ( 394 )   HTML ( 2)   PDF (1992KB) ( 137 )  
    Figures and Tables | References | Related Articles | Metrics

    As a pretreatment process of the ultrafiltration membrane system, the bimetal catalyst biological filter replaces the traditional biological filter, can improve the removal efficiency of tri-nitrogen, ensure the stability of water quality, significantly mitigate the ultrafiltration membrane foulling and extend the service life of the membrane. The catalytic reduction reaction in the biocatalytic filter promotes the denitrification system and ensures the decomposition and removal of nitrogen nitrate and nitrite in the water. The results showed that the removal rate of TOC was increased from 73.2% to 81.5% by the pretreatment of the biological catalytic filter compared with the conventional biological filter. In addition, the modified bimetal catalytic filter material increased the filtration accuracy of the filter, and the average particle size of the effluent colloid was significantly smaller than that of the conventional biological filter. The iron ions produced by catalytic reduction reaction flocculate in the environment of filtering turbulent flow, further remove the colloid and suspended matter in the micro-polluted water source, and mitigate ultrafiltration membrane foulling by the colloid particles . In addition to the biodegradation and filtration effects of conventional filters, the biological catalytic filter also has a combined effect of catalytic reduction and microflocculation, significantly improving the removal rate of organic pollutants and colloidal particles in water, and effectively reducing the pollution of ultrafiltration membrane.

    CFD simulation of low-temperature NO oxidation using ozone in sintering flue gas
    Jiangyuan QU, Xiaolong LIU, Yanjun GUAN, Nana QI, Yang TENG, Wenqing XU, Tingyu ZHU, Kai ZHANG
    2019, 70(11):  4387-4396.  doi:10.11949/0438-1157.20190418
    Abstract ( 489 )   HTML ( 3)   PDF (1217KB) ( 199 )  
    Figures and Tables | References | Related Articles | Metrics

    The flue gas from a 256 m2 sintering machine was selected to explore the characteristics of NO oxidized by ozone at low temperature. The flow characteristics of O3 injection gas and sintering flue gas and NO oxidation characteristics were investigated by CFD numerical simulation method. By compared with 76-step complex reaction mechanism, 11-step simplified mechanism was verified to be reasonable for the above process. The effects of process conditions, including reaction temperature, O3/NO molar ratio and O3 distribution, on the conversion rates of NO x with different chemical valences were examined. The results from the simulation for the reactor, which is simple in structure, show that NO2 and N2O5 are the main oxidation products in the flue gas, whilst NO3 is consumed due to its poor chemical stability. The oxidation efficiency of NO changes little with the increase of reaction temperature, the conversion rate of NO2 increases and performs more significant change at higher temperature. However, the conversion rate of N2O5 presents an opposite trend compared with that of NO2. With the raise of O3/NO molar ratio, the oxidation rate of NO increases slowly and that of NO2 increases firstly and then decreases when the molar ratio higher than 1.25, while N2O5 emerges in the condition even the O3/NO molar ratio less than 1.0 and the N2O5 production increases gradually, resulting from a higher O3/NO ratio in the injection core regions. Furthermore, the structural optimization for the ozone distributor could improve the homogeneity of O3 in the sintering flue gas. Afterwards the oxidation efficiency of NO increases by 12.8% approximately when the O3/NO molar ratio is 1.0 and the average residence time is 0.87 s, while the increase for N2O5 conversion rate of about 15.6% was obtained when the O3/NO molar ratio is 2.0 and the average residence time is 1.73 s.

    Kinetics and mechanism of mercury adsorption on fly ashes from pulverized coal boiler and circulating fluidized bed boiler
    Xiaohang LI, Honggang LIU, Jianzhou LU, Yang TENG, Kai ZHANG
    2019, 70(11):  4397-4409.  doi:10.11949/0438-1157.20190445
    Abstract ( 403 )   HTML ( 1)   PDF (2611KB) ( 815 )  
    Figures and Tables | References | Related Articles | Metrics

    Gas-phase zero-valent mercury adsorption experiments were carried out on two 300MW class coal-fired generating units circulating fluidized bed boilers and pulverized coal boiler fly ash samples in a fixed bed adsorption reactor. The effects of temperature, inlet mercury concentration and inlet gas flow on mercury adsorption efficiency of fly ash samples were explored. Weber and Morris diffusion model, pseudo-first and pseudo-second order kinetic models, and Elovich kinetic model were adopted to explore the mechanism of mercury adsorption on fly ash samples and the difference of adsorption kinetic between the circulating fluidized bed boiler fly ash and pulverized coal boiler fly ash. The results show that the penetration time and adsorption capacity of the circulating fluidized bed boiler fly ash are much higher than that of the pulverized coal boiler fly ash under the same condition. Adsorption capacity of fly ash samples is the highest at 150℃. Mercury adsorption on fly ash samples increases with an increase of initial mercury concentration due to the enhancement of mercury diffusion force onto the fly ash surface and reduce the external diffusion resistance. The pseudo-second order kinetic model and Elovich kinetic model are more applicable to reflect Hg adsorption on fly ash. The mercury adsorption on the fly ash was affected by external diffusion, internal diffusion and surface adsorption, in which surface chemical adsorption plays a key role. Under the same work condition, the particle internal diffusion coefficient, order kinetic constant and initial adsorption rate of the circulating fluidized bed boiler fly ash are all higher than those of the pulverized coal boiler fly ash.

    Effect of aeration intensity on simultaneous biological nitrogen removal and N2O release from SBBR
    Youkui GONG, Yongzhen PENG
    2019, 70(11):  4410-4419.  doi:10.11949/0438-1157.20190522
    Abstract ( 381 )   HTML ( 3)   PDF (1511KB) ( 137 )  
    Figures and Tables | References | Related Articles | Metrics

    Using domestic wastewater as influent and carbon fibre as biological carriers, the characteristics of SND(simultaneous nitrification and denitrification) process and N2O emission were studied under different aeration intensity (30,20,10 L/h), with the DO(dissolved oxygen) concentration controlled at 1.5 mg/L by adjusting the ratio of N2 and O2. Hetertrophic and nitrifying bacteria conexisted in the biofilm, which are located in the outer and inner layers of the biofilm, respectively. The decrease of aeration intensity was beneficial to the proliferation of the external heterotrophic bacteria. With the aeration intensity was controlled at 30 L/h and 10 L/h, the removal efficiency of NH4+-N in the SBBR system were more than 95% and 79.2%±1.6%, the SND efficiency was 46.2%±2.6% and 62.1%±2.3%, the N2O yield was 6.25%±0.6% and 2.93%±0.43%, respectively. During the anoxic phase, the denitrification process and the accumulation of PHA (poly-β-hydroxyalkanoate) occurred simultaneously. In the following aerobic process, the PHA increased first and then decreased, which indicated that PHA could be used as internal carbon sources in the following denitrification process. Both the aerobic denitrification process of AOB and the denitrification process of denitrifying bacteria at the presence of lower oxygen led to the emissions of N2O. The decrease of aeration intensity leads to a decrease in hydraulic shearing force, an increase in the anoxic range in the biofilm, and an increase in the N2O residence time in the anoxic zone, which is beneficial to the denitrification reduction. As the aeration intensity decreased from 30 L/h to 10 L/h, the extracellular polymer (EPS) secretion decreased, and the PS/PN (polysaccharide/protein) decreased from 8.59 mg/mg to 6.58 mg/mg, resulting the reduction of the biofilm density, which created the favorable conditions for N2O transferring into the biofilm to complete the reduction process.

    Effect of rice straw holocellulose on disintegration of aspirin tablets
    Shuangfeng LI, Huai WANG, Jiali CHEN, Risheng YAO, Huixia ZHU, Xiaojing MA
    2019, 70(11):  4420-4427.  doi:10.11949/0438-1157.20190466
    Abstract ( 341 )   HTML ( 3)   PDF (770KB) ( 119 )  
    Figures and Tables | References | Related Articles | Metrics

    Rice straw holocellulose, prepared from biomass rice straw by SO3 micro-thermal explore, degradation of lignin and bleaching, was used as tablet disintegrating agent. The performance was evaluated by using it as a tablet disintegrating agent. According to the relevant standards of Chinese Pharmacopoeia (2015 Edition), several characters of rice straw holocellulose, such as surface morphology, specific surface area, pH etc., were detected. Taking aspirin as model drug, the disintegration performance of rice straw holocellulose was determined and compared with commercial microcrystalline cellulose. The results showed that the quality of rice straw holocellulose was in accordance with the relevant regulations of Chinese Pharmacopoeia, and the disintegration of rice straw holocellulose was obviously superior to that of commercial microcrystalline cellulose. The same disintegration effect with 15%—20% microcrystalline cellulose can be attained by using only 3%—5% rice straw holocellulose. This result should be closely owed to the structure and semicellulose of rice straw holocellulose.

    Leaching of chromite ore processing residue from non-calcium roasting with hydrochloric acid
    Peng YE, Xuejun QUAN, Xianfeng QIN, Chengfei FENG, Gang LI, Cunfang LU, Xueqiang QI, Li JIANG
    2019, 70(11):  4428-4436.  doi:10.11949/0438-1157.20190353
    Abstract ( 502 )   HTML ( 5)   PDF (1700KB) ( 134 )  
    Figures and Tables | References | Related Articles | Metrics

    Chromite ore precessing residue is the remaining tailings of chromite produced by chromite. It is also a secondary resource because it contains a lot of ferrum, chromium, aluminum and magnesium. In this work, a hydrometallurgy process was introduced to recover chromium, ferrum, aluminum and magnesium by using hydrochloride acid as a lixiviant and three variables were studied namely, liquid-solid ratio, leaching temperature and period. The results indicated that chromium, ferrum, aluminum and magnesium can successfully be recovered from COPR and the optimum leaching conditions were at the liquid-solid ratio of 5.6 with 110℃ and 6 h period. Simultaneously, the leaching efficiencies of chromium, ferrum, aluminum and magnesium reached 67.76%, 89.89%, 93.99% and 95.21%, respectively. A shrinking core model with the surface chemical reaction control can be used to describe the leaching kinetics of chromium, ferrum, aluminum and magnesium from COPR in the concentrated hydrochloride acid solution at 90—110℃, where the apparent activation energy are 102.31, 78.10, 66.44 and 81.66 kJ·mol-1, respectively. The analysis of particle size distribution also showed a reduction in particle size, indicating the dissolution of the solid particles. The application of Toxic Leaching Characteristic Procedure (TLCP) showed nearly no Cr6+ in the effluent, indicating that the residue will not contaminate the environment through leaching, and can be used for load bearing or backfill material.

    Simulation study on flow field optimization of flow battery based on flow frame design
    Dongjiang YOU, Jianyun WEI, Xuejing LI, Jingyuan LOU
    2019, 70(11):  4437-4448.  doi:10.11949/0438-1157.20190558
    Abstract ( 483 )   HTML ( 11)   PDF (3570KB) ( 711 )  
    Figures and Tables | References | Related Articles | Metrics

    The flow battery usually adopts a diagonally pushing flow field, which will form an electrolyte retention zone, which causes a large concentration polarization of the battery, which affects the overall performance. In view of this, a flow field optimization method based on frame design is proposed. By designing the electrode frame, two kinds of flow fields,“serpentine flow path”and“parallel flow path”can be obtained. Taking vanadium redox flow battery as an example, the effects of different flow field structures and parameters on the flow characteristics, electrochemical reaction and temperature change characteristics in porous electrode were studied by mathematical modeling. The calculated results are in good agreement with the experimental results. The results show that the flow uniformity of the electrolyte in the“parallel flow field”is better than that in the“serpentine flow field”, and there is no stagnant zone, and in the“parallel flow field”the concentration polarization is also lower than the“serpentine flow field”; in addition, for the same electrode area, the more“parallel flow channels”inside the electrode, the more uniform the flow velocity distribution of the electrolyte, and the better the reaction characteristics.

    Material science and engineering, nanotechnology
    Synthesis and properties of epoxy resin crosslinked by dynamic boronic ester bonds
    Feng CHEN, Yukun HOU, Qian ZHAO
    2019, 70(11):  4449-4456.  doi:10.11949/0438-1157.20190503
    Abstract ( 572 )   HTML ( 21)   PDF (1449KB) ( 668 )  
    Figures and Tables | References | Related Articles | Metrics

    A series of dynamic covalent polymer networks providing various rheological properties and glass transition temperatures were prepared via firstly introducing a diol group into an epoxy molecule through a thiol-epoxy click reaction and secondly crosslinking the diol groups by dynamic borate bonds. Effect of formulation on the properties of the materials was investigated. The rheological properties of the materials can be adjusted by tuning the ratio of the crosslinking agents and the exchangeable borate bonds. Glass transition temperature of the polymer can be adjusted from 14.6℃ to 36.5℃ by changing the ratio of the fed soft and hard epoxy components. A composite material is prepared by introducing the dynamic network into an open porous melamine foam. Such a composite can be rapidly self-welded in a few seconds after it had been cut. The welding performance is found to retain 0.06 MPa after 20 disassembling-bonding cycles, showing a good repeatability.

    Preparation of mesoporous peat-based activated carbon with peak distribution of 2—5 nm pores
    Feng DENG, Qiang XIE, Deqian LIU, Chaoran WAN, Xiaoqing HUANG, Xuemei GU
    2019, 70(11):  4457-4468.  doi:10.11949/0438-1157.20190331
    Abstract ( 309 )   HTML ( 8)   PDF (2933KB) ( 136 )  
    Figures and Tables | References | Related Articles | Metrics

    Peat was sampled, crushed, ground, impregnated with H3PO4, briquetted and re-crushed, then a series of activated carbon samples were prepared by activation in tube furnace at different temperature and time. Thermogravimetric analysis of H3PO4 impregnated peat samples were performed in a nitrogen environment. The adsorption capacity indexes including iodine value, methylene blue value and caramel decolorization rate were determined, and pore structure, carbonaceous structure, surface chemistry and micro morphology of activated carbon samples were characterized by gas adsorption instrument, Raman spectroscopy, infrared spectrum and scanning electron microscope, respectively. The results show that peat is cross-linked during phosphoric acid activation, and the maximum mass-loss temperature of carbonization/activation drops from around 300℃ to ca. 200℃. With the increase of H3PO4 impregnation ratio and activation temperature, content of irregular graphitic layers in activated carbon increases, and hydroxyls groups on surface of activated carbon decreases. The increase of H3PO4 impregnation ratio results in gradual increase of pore development, absorption performance and volume of 2—5 nm pores. And the increase of activation temperature results in shrink firstly (at 400—550℃) and then destroy ( at 600℃) of pore structure , decrease of absorption performance and volume of 2—5 nm pores. With the increase of activation time, the content of hydroxyl groups on surface of activated carbon firstly reduces greatly (during 120—150 min) and then undergoes irregular changes, meanwhile, the pores firstly expand (during 120—180 min) and then shrink (>180 min), and the absorption performance reduce rapidly after 180 min, at the same time the carbon structure and the volume of 2—5 nm pore section don t show significant change. An activated carbon with a specific surface area of 678.52m2·g-1, volume of 2—5 nm pores of 0.1475 cm3·g-1, accounting for 31.04% of the total pore volume and 70.24% of the mesopore volume, can be derived under the conditions of H3PO4 impregnation ratio 1.5, activation temperature 500℃, and activation time 180 min.

    Preparation and microwave absorption properties of light and thin carbon black coating
    Jin TANG, Bin LIN, Song BI, Zheng an SU, Genliang HOU, Chaohui LIU, Hao LI, Yangyang LIN
    2019, 70(11):  4469-4477.  doi:10.11949/0438-1157.20190393
    Abstract ( 580 )   HTML ( 21)   PDF (2218KB) ( 419 )  
    Figures and Tables | References | Related Articles | Metrics

    Carbon black (CB) was oxidized by using mixed acids, and CB coatings were prepared using silicone resin as the matrix. The microstructure and electromagnetic properties of the as-prepared coating samples with four different filler loadings were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vector network analysis (VNA). Microstructural analyses show that the size of CB particles is nano-scale, the diameter is about 60 nm, and the surface morphology after oxidation treatment is pleated. The prepared CB coatings possess a flat surface and uniform thickness, and the density is only 1.1 g/cm3. The coatings have both the lightweight and flexible characteristics. The microwave reflectance test results indicate that the coating samples exhibit excellent microwave absorption properties in the range of 8 to 18 GHz. When the filler loading is 3.7%, the coating with a thickness of only 1.6 mm has an effective absorbing bandwidth of 5.13 GHz and the absorbing intensity of -26.5 dB. When the filler loading is 2.3%, the effective absorbing bandwidth of the coating (1.9 mm) reaches the maximum value (5.44 GHz) and covers the entire Ku band, the effective absorbing bandwidth of the coating (2.5 mm) is 4.44 GHz and covers the entire X-band.

    Preparation and microwave absorbing performance of Al2O3/SiC, MoSi2/SiC porous composites
    Luping ZHANG, Xiaofeng YANG, Haikang ZHENG, Qian WANG, Zhenzhen MENG, Zhihong WU
    2019, 70(11):  4478-4485.  doi:10.11949/0438-1157.20190444
    Abstract ( 420 )   HTML ( 7)   PDF (4668KB) ( 376 )  
    Figures and Tables | References | Related Articles | Metrics

    Si, Al2O3, MoSi2 powder and biological bamboo were used to produce SiC porous ceramic, Al2O3/SiC and MoSi2/SiC porous composites by embedding and sintering method. The phase composition, microstructure and absorbing performance of the composites were measured by XRD, SEM and waveguide method, respectively. The results show that the MoSi2/SiC composite has obvious absorbing performance when the thickness is 2 mm. The effective absorption bandwidth is 2.75 GHz in the frequency range of 9.65—12.4 GHz in the X-band, and the minimum reflection loss is -38.27 dB. There are many SiC whiskers intermingled with Al2O3 in the pores of Al2O3/SiC composites, and a large number of electric dipole moments, generated dielectric loss. In addition to dielectric loss, MoSi2/SiC composites also have resistive losses, and the sponge structure of the metal Mo, Mo4.8Si3C0.6 and MoSi2 connecting rod formed in the tunnel constitutes a small conductive network to generate leakage loss to consume electromagnetic waves, so that the electromagnetic loss of the composite increases. So it will be more popular structural functional microwave absorbing materials in the future.

    Process safety
    Numerical simulation analysis of influence of filling amount and length of cylinder on resonance frequency of vehicle LNG cylinder
    Rui LIU, Zuzhi CHEN, Qianghua HUANG, Chunlin GU, Haiyang XU, Peiqi LIU
    2019, 70(11):  4486-4496.  doi:10.11949/0438-1157.20190432
    Abstract ( 450 )   HTML ( 7)   PDF (1934KB) ( 154 )  
    Figures and Tables | References | Related Articles | Metrics

    Taking the large-capacity liquefied natural gas (LNG) gas cylinder as the research object, the variation of the resonance frequency under different filling amount and different cylinder length with these two parameters is analyzed. When the length of the cylinder is constant, as the filling amount increases, the resonance frequency of the cylinder gradually decreases. When the maximum allowable filling rate is 90% according to the standard, the first-order resonance frequency of the cylinder has been reduced to below 40 Hz allowed by the national standard. When used, it is easy to cause axial collapse of the cylinder liner to fail. When the filling rate is 90%, the resonance frequency of the cylinder also decreases with the increase of the length of the cylinder. When the length of the cylinder is 0.8 times of the original length, the resonance frequency of the cylinder is lower than 40 Hz. As the length increases, it will be further reduced, and the possibility of resonance will increase, which does not meet the national requirements for the resonance frequency of the vehicle cylinder. The above results showed that the evaluation of the internal medium filling ratio should be considered when evaluating the anti-vibration performance of the cylinder. It is recommended to use a cylinder with a maximum filling rate of 90% as a condition for determining whether the resonance frequency of the cylinder is up to standard. On the other hand, when increasing the volume of the cylinder to increase the volume of the liquid, it is necessary to pay attention to the problem that the resonance frequency decreases with the length of the cylinder to avoid structural vibration damage.

    Influence of installation of perforated obstacles in pipelines on explosive characteristics of combustible gases
    Zengliang ZHANG, Xin WANG, Haoping WANG
    2019, 70(11):  4497-4503.  doi:10.11949/0438-1157.20190469
    Abstract ( 404 )   HTML ( 4)   PDF (612KB) ( 114 )  
    Figures and Tables | References | Related Articles | Metrics

    Using methane as a representative gas, the effects of different hole types and different sizes of perforated obstacles on the explosive flame and pressure propagation of combustible gas were studied in a closed conduit of 10% methane. The study found that when the obstacle partition is set, the explosion overpressure slowly grows in front of the obstacle, and continues to increase by the obstacle, and rapidly decreases before reaching the blind plate. The flame propagation rate increases slowly first and falls before passing through the obstacle partition, and rises sharply to the maximum after passing through the opening. As the opening area of the obstacle partition is reduced, the jetting effect caused by the airflow is obviously enhanced, and the influence caused by the negative pressure suction is increased, which leads to a more uneven distribution of the overpressure before and after the obstacle, and the obstacle is separated. The flame propagation speed in front of the plate decreases. Under the same opening area, the maximum overpressure and flame propagation speed are affected by different hole types. When the flame passes through the perforated obstacle partition, the circular opening is more in line with the flame shape than the square opening and the regular triangular opening. The law of development, the inner circular hole is smaller than the square hole, the flame is more affected, the turbulence is more obvious, and the flame speed and pressure rise are more obvious. The maximum overpressure relationship of different hole types is P triangle>P square>P round>P empty, flame propagation speed relationship is v triangle>v square>v round>v empty.

    Numerical simulation of oil vapor leakage and diffusion superposition effect of internal floating-roof tank group and experimental investigation on wind-tunnel
    Weiqiu HUANG, Jie FANG, Cheng LYU, Aihua LYU, Xianhang SUN
    2019, 70(11):  4504-4516.  doi:10.11949/0438-1157.20190338
    Abstract ( 413 )   HTML ( 4)   PDF (2714KB) ( 351 )  
    Figures and Tables | References | Related Articles | Metrics

    Oil vapor leakage from the internal floating-roof tank will bring potential hazards to the safety and environment of the oil depot. Based on CFD and its Realizable k-ε turbulence model, the numerical simulation method of the wind field and the oil vapor concentration field of the internal floating-roof tank was established, and its feasibility was verified by the wind tunnel experiments. After that, focus on the flow field and concentration field distribution in the case of single tank, double tank and four tank. The results show that the greatest concentration of the oil vapor is found near the rim gap of the floating deck, which will be prone to fire and other dangers. There is interaction between tank groups. Because of the blocking effect of the front tank, the wind speed in the rear tank is smaller, which is easy to produce the oil vapor superposition, resulting in the concentration of the oil vapor in the rear tank is higher than that in the front tank, so it is easier to reach the explosion limit. Whether in terms of safety, environmental protection or personnel health, appropriate measures should be taken to timely monitor and control.