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Table of Content
05 March 2023, Volume 74 Issue 3
    Reviews and monographs
    Research progress in chemical recovery technology of fiber-reinforced polymer composites
    Ruizhe CHEN, Leilei CHENG, Jing GU, Haoran YUAN, Yong CHEN
    2023, 74(3):  981-994.  doi:10.11949/0438-1157.20221489
    Abstract ( 715 )   HTML ( 60)   PDF (1477KB) ( 326 )  
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    Fiber-reinforced polymer composites (FRPC) which have excellent properties such as high strength, easy processing and low cost are the preferred structural materials for typical industrial products such as wind turbines and circuit boards. With the increase in FRPC production year by year and the arrival of decommissioning period of industrial products, the accumulation of discarded composite materials will lead to serious environmental pollution and waste of energy and resources, thus it is urgent to develop efficient and clean recycling technologies. Chemical recovery technology can not only recover high-quality fiber materials, but also realize the targeted conversion of resin into fuel and organic chemicals. Based on the analysis of composition characteristics of composites wasted and chemical recovery technologies, this article evaluates the application of recycled products, technical economy and environmental benefits. It is further proposed that based on the characteristics of the functional groups of organic resins, the non-destructive recycling of fiber materials can be realized while producing fine chemicals through directional depolymerization and upgrading cycle under mild conditions.

    Advances in heterogeneous visible light photocatalysis coupled with persulfate activation for water pollution control
    Yin XU, Jie CAI, Lu CHEN, Yu PENG, Fuzhen LIU, Hui ZHANG
    2023, 74(3):  995-1009.  doi:10.11949/0438-1157.20221448
    Abstract ( 599 )   HTML ( 49)   PDF (1545KB) ( 218 )  
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    In recent years, how to effectively remove refractory pollutants from water has become a key issue in water pollution control. Visible light catalysis coupled with persulfate activation technology is a new water treatment process, which is expected to become a new strategy for the efficient removal of refractory pollutants. In the photocatalysis/persulfate oxidation system, the synergistic effect among light radiation, catalyst and persulfate is exploited to the largest extent, which greatly improves the oxidation performance of the treatment process. In this paper, a variety of commonly used metal-based, carbon-based and composite photocatalysts are introduced, and the effects of photocatalyst type, element composition, and surface properties on photocatalytic activity and mechanism are analyzed. The main characterization methods of optical properties are also discussed. Meanwhile, the major reactive species participating in the oxidation process are summarized. Finally, the application of this process for organic contaminants elimination and bacteria inactivation is reviewed. As well, the opportunities and challenges for future research are prospected.

    Research progress of pretreatment technology for efficient utilization of coal ash
    Qian WANG, Shenyong LI, Shuai KANG, Wei PANG, Longlong HAO, Shenjun QIN
    2023, 74(3):  1010-1032.  doi:10.11949/0438-1157.20221350
    Abstract ( 519 )   HTML ( 36)   PDF (4197KB) ( 340 )  
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    As a typical bulk solid waste, fly ash has received extensive attention for its comprehensive and efficient utilization. In China, coal ash emissions are huge, but the utilization rate is low. How to realize the resource-utilization of coal ash through reducing its burden on ecological environment, the threat to human health and improving its economic benefit is a hot topic. The activity of fly ash is the key to improve the comprehensive utilization of fly ash. Pretreatment of fly ash can improve its activity. In this paper, the functions of roasting, grinding, microwave, ultrasonic, pressure, vacuum and surfactant pretreatment technologies in the comprehensive utilization of fly ash are reviewed, and the application of leaching and separation of valuable elements is emphasized. By comparing the application scope and effect of different pretreatment technologies, the advantages and disadvantages of each pretreatment technology are pointed out, so as to provide suitable pretreatment reference scheme for the effective and comprehensive utilization of fly ash.

    Estimation of SAFT-VR Mie equation of state parameters and thermodynamic properties of C6—C10 alcohols
    Yuanjing MAO, Zhi YANG, Songping MO, Hao GUO, Ying CHEN, Xianglong LUO, Jianyong CHEN, Yingzong LIANG
    2023, 74(3):  1033-1041.  doi:10.11949/0438-1157.20221438
    Abstract ( 260 )   HTML ( 14)   PDF (2319KB) ( 131 )  
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    The statistical associating fluid theory (SAFT) equation of state (EoS) is of great significance for the thermodynamic properties study of long-chain alcohols. The acquisition of SAFT-type EoS parameters is the basis for the thermodynamic properties study of fluids. The SAFT-VR Mie EoS parameters for C6—C10 alcohols were obtained by using a parametric regression strategy based on the Levenberg-Marquardt algorithm and combining phase equilibrium, condensed-liquid density, and speed of sound properties. The predictive performance of SAFT-VR Mie EoS based on the new parameters for phase equilibrium and thermodynamic derivative properties over a wide temperature and pressure range was further evaluated. The results show that SAFT-VR Mie EoS exhibits excellent prediction performance of saturated vapor pressure, saturated liquid phase density, enthalpy of vaporization, condensed-liquid density, isobaric specific heat capacity, and speed of sound for C6—C10 alcohols with average prediction deviations of 0.74%, 0.82%, 3.02%, 0.54%, 2.88%, and 2.31%, respectively. Meanwhile, SAFT-VR Mie EoS provides reliable extrapolation prediction capability, and its prediction results of speed of sound for high pressure show satisfactory agreement with experimental data. In addition, the unreasonable description of the pressure-density derivative by SAFT-VR Mie EoS is the primary reason for the deviations of speed of sound predictions. Improving the intermolecular monomer and association interactions can effectively improve the prediction accuracy of specific heat capacity, and provide a better theoretical correlation model for the prediction of thermodynamic properties of long-chain alcohols associating fluids.

    Fluid dynamics and transport phenomena
    Study on online detection method of particulate matter in natural gas pipeline based on microwave technology
    Junxian CHEN, Zhongli JI, Yu ZHAO, Qian ZHANG, Yan ZHOU, Meng LIU, Zhen LIU
    2023, 74(3):  1042-1053.  doi:10.11949/0438-1157.20221312
    Abstract ( 206 )   HTML ( 12)   PDF (4646KB) ( 273 )  
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    Aiming at the problem of difficult detection of particulate matter in natural gas pipeline, an online detection method for particulate matter in natural gas pipeline based on microwave technology was proposed. Firstly, the characteristics of particles in natural gas pipe network were analyzed, and based on the principle of microwave measurement, microwave transmission in the pipeline was realized by means of a sealed probe. Secondly, finite element simulation software was used to study the structure optimization of the sealing probe and pipe size (distance between two probes), and the current distribution and optimal structural parameters of the microwave measurement system were analyzed. Finally, an experimental platform was built to quantitatively analyze the influence law of the output voltage of the measuring system and the concentration of particulate matter under different working conditions. The results show that when the droplet concentration in the pipeline changes from 39 mg/m3 to 210 mg/m3, the relationship between the output voltage of the measurement system and the droplet concentration is fitted by quadratic function, and the coefficient of determination R2 is above 0.966. The average relative indication error of each signal sampling point fluctuates around 5.20%, and the repeatability of the measurement system varies within 0.24%. The research results have guiding significance for the realization of the long-term detection method of subsequent natural gas pipelines, and then ensuring the safe operation of the pipeline network.

    Visual experimental study on cavitation of R134a in micro clearance
    Shaohang YAN, Tianwei LAI, Yanwu WANG, Yu HOU, Shuangtao CHEN
    2023, 74(3):  1054-1061.  doi:10.11949/0438-1157.20221220
    Abstract ( 181 )   HTML ( 9)   PDF (3102KB) ( 67 )  
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    In order to study the cavitation characteristics of the working fluid in the confined space and high shear state, a visualization experiment platform for the cavitation evolution law of the micro-gap working fluid was designed and built. The cavitation characteristics of R134a in micro clearance were tested at different working conditions, including inlet and outlet pressure differences, subcooling degrees and inflow velocity. The evolution of the cavitation area was emphatically analyzed. The visualization experiment results show that the cavitation form is determined by the inlet flow velocity and cavitation number. According to the difference of the cavitation form, the process of cavitation in micro clearance can be divided into single-bubble cavitation pattern, multi-bubble cavitation pattern, gas-liquid mixing cavitation pattern and fog-core zone cavitation pattern. The single-bubble pattern and multi-bubble pattern appear randomly, which are related to the cavitation vapor nucleus in the medium during the experiment. The two patterns both occur in the case of low flow rate. The bubble area increases approximately exponentially in the single-bubble pattern. Gas-liquid mixing cavitation pattern and fog-core zone cavitation pattern mostly occur at higher flow rates and lower cavitation numbers, while the evolution of cavitation area follows a near-linear growth law. In each pattern, the generation of cavitation is promoted by the reduction of subcooling. In the multi-bubble mode, multiple independent tiny bubbles appear in the initial stage of cavitation. With the development of cavitation, the bubbles increase and interfere with each other. There is a phenomenon of fusion between the bubbles.

    Heat transfer characteristics of supercritical pressure CO2 in diverging/converging tube under cooling conditions
    Bingguo ZHU, Jixiang HE, Jinliang XU, Bin PENG
    2023, 74(3):  1062-1072.  doi:10.11949/0438-1157.20221426
    Abstract ( 201 )   HTML ( 11)   PDF (4089KB) ( 158 )  
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    Using the SST k-ω turbulence model, the heat transfer characteristics of supercritical carbon dioxide (SCO2) in three kinds of horizontal tubes (uniform cross-section tube, diverging tube and converging tube) were numerically calculated under cooling conditions, and different operating parameters were studied (pressure, mass flow and heat flux) on heat transfer performance. The computational results demonstrate that the diverging tube effectively strengthen heat transfer compared with the uniform cross-section tube. A maximum improvement of 47.98% in overall heat transfer coefficient can be observed with the employment of diverging tubes. However, the converging tube weakens the heat transfer. According to the distribution of quasi-liquid film and turbulent kinetic energy, the physical mechanism of heat transfer enhancement is clarified by the dual-effect of quasi-liquid film and turbulent kinetic energy on this account. Our work provides a new idea and theoretical guidance for the optimal design of SCO2 cooler.

    Numerical study on heat and mass transfer characteristics of straight slotted fins under wet conditions
    Yang HE, Senhu GAO, Qingyun WU, Mingli ZHANG, Tao LONG, Pei NIU, Jinghui GAO, Yingqi MENG
    2023, 74(3):  1073-1081.  doi:10.11949/0438-1157.20221440
    Abstract ( 184 )   HTML ( 11)   PDF (4914KB) ( 92 )  
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    In this paper, a new convection condensation heat transfer model and an analysis method of heat and mass transfer characteristics based on field synergy theory are established by using UDF in fluent, aiming at the lack of consideration of the influence on mass transfer in the calculation of mass transfer flux of existing condensation models. The flow, heat transfer and mass transfer characteristics of wet air side of straight slotted fin heat exchanger under dehumidification conditions are studied by using new condensation model and analysis method. The results show that the accuracy of condensation model considering convective mass transfer is improved. The amount of heat transfer and condensation decreases first and then increases with the increase of the slit height on the fin surface. The heat transfer and condensation of the upstream slotted fin tube are lower than those of the downstream slotted fin tube. Using the established analysis method, it is found that under the same boundary conditions, the synergistic angle αm and βm of the downstream slotted fin are smaller than those of the upstream slotted fin, which indicates that the downstream slotted fin has better synergy between the velocity field and the temperature gradient field, the velocity field and the concentration gradient field, and the heat and mass transfer capacity is stronger.

    Catalysis, kinetics and reactors
    Ethanol upgrading to higher alcohols over ordered mesoporous alumina supported Cu-based catalysts
    Jinfeng HE, Xiuzhen LI, Jianyao KOU, Tingjie TAO, Can YU, Huan LIU, Yongyuan CHEN, Haojian ZHAO, Dahao JIANG, Xiaonian LI
    2023, 74(3):  1082-1091.  doi:10.11949/0438-1157.20221517
    Abstract ( 237 )   HTML ( 15)   PDF (1756KB) ( 208 )  
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    In order to realize highly efficient conversion of ethanol to higher alcohols, a series of Cu-La2O3/OMA catalysts were prepared on the basis of ordered mesoporous alumina (OMA) synthesized by evaporation-induced self-assembly method, and their structure-activity relationships in higher alcohol synthesis reaction were studied in depth. The optimal Cu-La2O3/OMA (973) catalyst exhibited up to 55.5% ethanol conversion and 40.1% yield of higher alcohols under the reaction conditions of 533 K, 3 MPa, LHSV=2 ml/(g cat·h) and V(N2)/V(EtOH)=250∶1. Moreover, it showed excellent stability in 200 h on-stream evaluation. The highly dispersed Cu and La2O3 active components and OMA support afforded large amounts of metal and acid-base sites while OMA support also provided mesoporous channels with larger pore size to reduce the diffusion resistance of the reactants and products, thus resulting in higher ethanol conversion and selectivity to higher alcohols. Additionally, the penta-coordinated Al3+ on the surface of OMA anchored the Cu active species by formation of Cu-O-Al bonds, thus enhancing the stability of the Cu-based catalysts.

    Design of Ziegler-Natta catalyst modified with pore structure and preparation of UHMWPE with high impact resistance and low entanglement
    Qian LIU, Yu CAO, Qi ZHOU, Jingshan MU, Wei LI
    2023, 74(3):  1092-1101.  doi:10.11949/0438-1157.20221460
    Abstract ( 171 )   HTML ( 11)   PDF (3821KB) ( 112 )  
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    From the perspective of SiO2 carrier channel modification, polystyrene (PS) and polysilsesquioxane (POSS) were simultaneously introduced into the multi-level channel to form a functional composite carrier, which was used to load TiCl4 to prepare SiO2/PS/POSS/TiCl4 supported catalyst. Thermal gravimetric analysis, N2 isothermal adsorption and desorption, scanning electron microscopy, and diffuse reflectance infrared spectroscopy were used to characterize the structures of the catalysts before and after the modification. It was found that it was possible to use in-situ polymerization of styrene to introduce PS into SiO2 multistage pores, especially into the micropores, and that the swelling behavior of PS chain segments within the pores led to an increase in ethylene mass transfer resistance and a decrease in polymerization activity during polymerization. After introducing POSS into the SiO2 multistage pore channel, it could only enter the SiO2 macropores due to the sterichindrance of POSS molecules, where the reduction effect to the entanglenets of nascent of polyethylene was limited. A benign synergy for reducing the chain entanglements of nascent polyethylene was generated owing to the successive introduction of PS and POSS into the catalyst pores. The impact strength of the synthesized polyethylene was greatly enhanced. Finally, the catalyst active center was further diluted through reducing the loading of TiCl4 in the pore channel, where the untwining process of the propagated polyethylene chain was further strengthened. The optimum polymerization activity, the highest impact strength of the synthesized polyethylene were achieved when the titanium content was reduced to 2.65%.

    Catalytic nitrophenol degradation via peroxymonosulfate activation over Cu/Co doped porous carbon
    Xinlong YAN, Zhigang HUANG, Qingxun HU, Xin ZHANG, Xiaoyan HU
    2023, 74(3):  1102-1112.  doi:10.11949/0438-1157.20221442
    Abstract ( 224 )   HTML ( 13)   PDF (4537KB) ( 92 )  
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    Carbon-based catalysts with heteroatom doping and porous structures are desired for advanced oxidation processes (AOPs). Herein, Co and Cu co-doped porous carbon were developed by using metal-organic frameworks-74 (MOF-74) as self-sacrificial template and performing subsequent carbonization. The obtained samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), et al. The optimal composite catalyst (Cu1Co1-OC) exhibited excellent catalytic degradation performance toward 4-nitrophenol (4-NP). More than 98% of 4-NP (60 mg·L-1) could be removed within 15 min by 100 mg·L-1 of catalyst and 2 g·L-1 of peroxymonosulfate (PMS) at pH=6. Moreover, the catalyst showed good stability and reusability with about only 10% efficiency loss after 4 cycles. The effects of catalyst and PMS dose, pollutant concentration, pH and common anions were investigated, and reactive oxygen species (ROS) were studied by scavenger experiments and electron paramagnetic resonance (EPR) tests. Quenching experiments and electron paramagnetic resonance analysis showed that both free radicals (·SO4-, ·OH, ·O2-) and non-free radicals (1O2) participated in the degradation reaction. During the reaction process, the redox cycle of Co2+/Co3+ and Cu+/Cu2+ effectively activated PMS and promoted the generation of active oxide species, thereby improving the performance of the catalyst for the degradation of nitrophenols.

    Separation engineering
    Study on separation characteristics and membrane fouling mechanism of ceramic membrane for clarification of Eucommia ulmoides leaves extract
    Siqi WANG, Tianyu GU, Xianfu CHEN, Tong WANG, Jia LI, Wei KE, Xiaofeng LI, Yiqun FAN
    2023, 74(3):  1113-1125.  doi:10.11949/0438-1157.20221347
    Abstract ( 222 )   HTML ( 15)   PDF (3423KB) ( 96 )  
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    Eucommia ulmoides is a rare Chinese herbal medicine tree specie unique to China and is affluent in resources. Its leaves are rich in active substances such as chlorogenic acid and flavonoids. However, the content of gutta percha, protein, polysaccharide and other impurities in the extract of Eucommia ulmoides leaves is high. There is a lack of efficient separation technology for active substances. Ceramic membrane has been widely used in the clarification process of plant extract due to its advantages of high separation efficiency and good anti-pollution performance. At present, there are few reports on the application of ceramic membrane in the separation of Eucommia ulmoides leaf extract. It is of great application value to develop an efficient clarification technology of Eucommia ulmoides leaf extract by ceramic membrane. In this paper, the research was carried out from two aspects of membrane material and membrane process. The pore size of ceramic membrane was optimized. The effects of operating pressure, membrane surface velocity and temperature on the clarification process of ceramic membrane were systematically investigated. The membrane fouling mechanism was analyzed by Hermia model. The results showed that the ceramic microfiltration membrane with an average pore size of 100 nm had higher turbidity removal rate, active component transmittance and permeation flux, which was suitable for the clarification process of Eucommia ulmoides leaves extract. Under the optimized operating conditions, the stable flux of ceramic microfiltration membrane was about 58 L·m-2·h-1, the total transmittance of chlorogenic acid and flavonid was 75.3%, the turbidity removal rate was nearly 100%, and the flux recovery rate was over 85% after cleaning. Ceramic membrane separation technology has shown a good application prospect in the clarification process of Eucommia ulmoides leaves extract.

    Preparation and mass transfer efficiency of three-dimensional network extraction membrane
    Xiangshang CHEN, Zhenjie MA, Xihua REN, Yue JIA, Xiaolong LYU, Huayan CHEN
    2023, 74(3):  1126-1133.  doi:10.11949/0438-1157.20221622
    Abstract ( 209 )   HTML ( 9)   PDF (2306KB) ( 66 )  
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    The three-dimensional network extracting membrane (3D-NEM) was prepared by using hydrophilic polytetrafluoroethylene (PTFE) membrane as the support, vinyl triethoxysilane (VTES) as coupling agent, vinyl terminated polydimethylsiloxane (PDMS) and polymethylhydrosiloxane (PMHS) as grid locking extractant bis(2-ethychexyl)phosphate (D2EHPA). The designed 3D-NEM was tested for the extraction of nickel from heavy metal ion wastewater. The results showed that the surface treatment at 60℃ for 15 min would not destroy the membrane structure but only introduced hydroxyl groups on its surface successfully. Further, the 3D network composite layer could be anchored on the modified support surface. To treat the feed of 150 mg/L Ni2+, the 6 h average mass transfer flux of 3D-NEM prepared with 37%(mass) extractant content reached the highest value of 1560.28 mg∙m-2∙h-1. The cross-linked 3D grid structure effectively prevented the loss of extractants, and the flux attenuation was only 31.91% after 6 h of operation. Compared with the traditional support liquid membrane (SLM), the 3D-NEM prepared in this study anchored the ultra-thin extraction functional layer on the hydrophilic membrane surface, presenting dual advantages of reducing mass transfer resistance and improving operation stability.

    Research on performance of downhole oil-water separation hydrocyclone enhanced by inverted cone gas injection
    Xinya LI, Lei XING, Minghu JIANG, Lixin ZHAO
    2023, 74(3):  1134-1144.  doi:10.11949/0438-1157.20221516
    Abstract ( 205 )   HTML ( 9)   PDF (4396KB) ( 119 )  
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    In order to further improve the separation performance of downhole oil-water separation hydrocyclone, a structure of downhole oil-water separation hydrocyclone with inverted cone gas injection was proposed, and the influence of inverted cone gas injection on oil-water separation performance was studied. The distribution characteristics of flow field and oil-water separation efficiency of hydrocyclone under different gas injection rates, oil volume fractions, split ratios and inlet flow rates are analyzed via numerical simulation and experimental method. The results show that with the increase of gas injection rate, the separation efficiency increases at first and then decreases. When the gas injection rate is 2.034 m3/d, the separation efficiency reaches the maximum value 98.52%. When the inlet oil volume fraction of the hydrocyclone is 0.75%, the split ratio is 40%, and the inlet flow rate is 5.4 m3/h, the optimal separation efficiency of the hydrocyclone is 99.51%, which is 1.11% higher than that without gas injection. The separation performance experiments of downhole oil-water separation hydrocyclone are carried out. The numerical simulation results are in good agreement with the experimental results. The feasibility of improving separation performance of hydrocyclone by inverted cone gas injection and the accuracy of numerical simulation results are verified.

    Deep learning model of fixed bed adsorption breakthrough curve hybrid-driven by data and physical information
    Xuanjun WU, Chao WANG, Zijian CAO, Weiquan CAI
    2023, 74(3):  1145-1160.  doi:10.11949/0438-1157.20221609
    Abstract ( 368 )   HTML ( 25)   PDF (4615KB) ( 287 )  
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    A deep learning model of fixed bed adsorption breakthrough curve hybrid-driven by the data and physical information (PINN_MOD) was proposed in this work. A combined method of external data constraint enhanced by penalty factors and residual-based adaptive refinement strategy was adopted to gradually optimize the neural network parameters to approximate the solution of the partial differential equation (PDE) of the dynamic binary gas adsorption process of fixed bed by minimizing the loss function. The physics-informed neural network (PINN) model was generally used to solve the forward and inverse problem of the one-dimensional single-component convection-diffusion and fixed-bed adsorption PDE models with high fidelity. However, there are convergence difficulties when it is used to solve the one-dimensional binary fixed-bed adsorption PDE model on long-time scale. In this paper, the traditional finite differential method (FDM) was first used to solve the PDE problem of one-dimensional binary fixed bed adsorption, and then the component concentration data in the spatiotemporal region obtained by FDM simulations were adopted as an external constraint of the PINN model to solve the PDE of one-dimensional binary fixed bed adsorption. Taking the CO2/N2 mixture (molar ratio 30∶70) adsorption models in fixed bed packed with different MOFs (CALF-20 and UTSA-16) as an example, the PINN_MOD model was used to calculate the outlet CO2 breakthrough curve of fixed bed. The FDM calculation results can be well replicated, which proves that the model can effectively obtain high-fidelity PDE solutions only relying on a small amount of external data. It is confirmed that the PINN_MOD model could obtain the high fidelity solutions by relying on only a few external data. The proposed model is expected to play an important role in the development of novel metal-organic framework adsorbents for gas separation applications.

    Decomposition behaviour of chromite in the HCl-HF system
    Hao CHEN, Yijuan TIAN, Xuejun QUAN, Ziwen JIANG, Gang LI
    2023, 74(3):  1161-1174.  doi:10.11949/0438-1157.20221479
    Abstract ( 185 )   HTML ( 4)   PDF (4132KB) ( 62 )  
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    The production of chromium salt by acid leaching and decomposition of chromite shows a great application prospect because the process can avoid the production of hexavalent chromium [Cr(‍Ⅵ)]. Using hydrochloric acid as the acid-leaching agent can take advantage of the difference in solubility of metal ions in hydrochloric acid, making the process characterized by easy recovery of residual acid and chromium salts. However, it also makes the leaching efficiency of chromite leaching by hydrochloric acid low because of the dissolution equilibrium. In this paper, a new process study of hydrofluoric acid (HF) enhanced chromite leaching by hydrochloric acid is proposed to improve the chromite leaching process’s efficiency. Based on the previous work, this paper investigates the laws, kinetics, and process mechanism of HF-enhanced chromite hydrochloric acid leaching. The results show that HF can significantly enhance the leaching rate of Cr and Fe in chromite, which increases with the increase of HF dosage, while the leaching rate of Al and Mg shows a trend of increasing and then decreasing with the rise of HF dosage. The other crystalline silicates enter the slag phase. This finding provides a basis for selecting appropriate leaching conditions to better separate Cr from impurities such as Al and Mg in the leachate. Cr, Fe, Al and Mg leaching rates can reach about 92%, 94%, 17%, and 14%, respectively, at higher HF dosages. HF dosage not only influences the control steps of the kinetics of the chromite hydrochloric acid leaching process but also plays an essential role in promoting the conversion of Al, Mg and Si-containing substances in the leachate to crystalline silicates.

    Process system engineering
    Research and construction of digital twin intelligent ethylene plant
    Zizong WANG, Hansheng SUO, Xueliang ZHAO
    2023, 74(3):  1175-1186.  doi:10.11949/0438-1157.20221473
    Abstract ( 326 )   HTML ( 24)   PDF (2214KB) ( 203 )  
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    Digital twin is considered to be an effective means to realize the interaction and integration of the information world and the physical world by practicing advanced concepts such as intelligent manufacturing and the industrial internet. It has attracted the attention of academic and business circles, especially the landing application of digital twin. Based on the research and construction work of Sinopec digital twin intelligent ethylene plant, this paper first described the definition and overall architecture of Sinopec digital twin intelligent plant. Secondly, based on the complete set of million-ton-level ethylene technology for complex raw materials, the research proposes a digital twin intelligent ethylene plant construction idea and corresponding key technologies that integrate and innovate “software of complete set of technical achievements, digitalization of engineering construction delivery, and intelligent operation of petrochemical plants”. The digital twin intelligent ethylene plant provided valuable experience for the construction of Sinopec’s intelligent plant 3.0, and lays a foundation for further extending ICT technology to the core devices of the aromatic hydrocarbon industry chain, coal chemical industry chain, and oil refining industry chain, and promoting high-quality development of petrochemical industry.

    Group2vec: group vector representation and its property prediction applications based on unsupervised machine learning
    Xinyuan WU, Qilei LIU, Boyuan CAO, Lei ZHANG, Jian DU
    2023, 74(3):  1187-1194.  doi:10.11949/0438-1157.20221216
    Abstract ( 249 )   HTML ( 18)   PDF (1049KB) ( 178 )  
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    Quantitative structure-property relationship models play an important role in chemical product design. The natural language processing-based deep learning modeling method is one of the effective methods to construct quantitative structure-property relationship models. A group embedding model (Group2vec)-based deep learning framework is proposed for property predictions. First, a pre-training database for the group embedding model and four property prediction databases are established. Second, the text-based SMILES strings in databases are converted to the group sequences by using the group division method. Third, the CBOW algorithm is used to pre-train the group sequences to obtain the group vectors containing similar structure information. Finally, a deep learning model including the attention mechanism is built based on group vectors, and the model is tested on different property databases. The comparison results show that the deep learning property prediction model based on Group2vec not only has high prediction accuracy and versatility, but also has a certain degree of interpretability.

    A multi-task learning approach for complex chemical processes based on manual predictive manipulating strategies
    Zhongqiu ZHANG, Hongguang LI, Yilin SHI
    2023, 74(3):  1195-1204.  doi:10.11949/0438-1157.20221340
    Abstract ( 206 )   HTML ( 9)   PDF (2916KB) ( 139 )  
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    PID feedback control has been considered as the primary control strategy for chemical production processes ever since. However, due to the large time-delay and nonlinearity of complex chemical processes, PID control usually suffers poor performances in controlling key process variables. For this reason, in actual engineering, it is usually the on-site operators who implement manual prediction and control based on their own experience. In order to effectively learn manual predictive regulation strategies from historical operating data, the paper proposes a multi-task learning cascade network (LSTM multi-task network cascades, LSTM-MNC). Therein, process prediction models that predict short-term changes and long-term trends are established based on different trends of process variables in the long and short term, and the causal relationship between estimated information of the process prediction model and manipulated variable sequences is extracted. Supported by predictions of controlled variable deviations, manipulated variable sequences are generated, achieving intelligent manipulations of production processes. Experiments were conducted on an industrial heat exchanger process simulation platform, leading to satisfactory results, which verify the effectiveness of the proposed method.

    Research on multi-parameter optimization method based on parallel EGO and surrogate-assisted model
    Xuerong GU, Shuoshi LIU, Siyu YANG
    2023, 74(3):  1205-1215.  doi:10.11949/0438-1157.20221345
    Abstract ( 229 )   HTML ( 11)   PDF (2154KB) ( 78 )  
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    Process simulation and optimization have the characteristics of high-dimensional and non-linear, which makes the simulation calculation difficult to converge. Excessive solution time is one of the bottlenecks during scheduling and operation optimization. Using surrogate models to replace mechanistic models is an effective way to reduce computational complexity and ensure the accuracy of results. Though the Kriging surrogate model has a stronger nonlinear approximation, it is still difficult to deal with high-dimensional problems. Therefore, this paper investigates the parallel EGO (efficient global optimization) algorithm integrated with the surrogate model and applies the model to typical chemical process. The parallel EGO algorithm is based on the prediction function and error function of the Kriging surrogate model. First, an analytical expression is derived from data sample combined by the probability density function and cumulative distribution function. Then the surrogate model is updated by new sample points obtained by PEI (pseudo expected improvement) criterion. Finally, combined with the improved differential evolution algorithm, the optimization parameters are searched globally. Under the premise of ensuring the accuracy of the results, the algorithm in this paper is compared with other optimization algorithms. Taking eight multi-peaked test functions as a test case, it is found that the convergence speed of the algorithm is improved by 85%. Then, it is applied to the study case of the two-stage ammonia absorption refrigeration process. The results show that the simulation error is less than 0.01%, and the optimization time is reduced from 9846 s to 3705 s.

    Robust minimum covariance constrained control for C3 hydrogenation process and application
    Jianghuai ZHANG, Zhong ZHAO
    2023, 74(3):  1216-1227.  doi:10.11949/0438-1157.20221474
    Abstract ( 201 )   HTML ( 17)   PDF (4499KB) ( 215 )  
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    C3 hydrogenation process has variable operating regions and cascade reactions. The conventional manual hydrogen operation is prone to over-hydrogenation or alkyne leakage, resulting in large fluctuations in the outlet methylacetylene (MA) and propadiene (PD) concentrations and also affecting the catalyst selectivity and conversion ratio. Due to the nonlinear features and changeable operating regions of the C3 hydrogenation process, traditional model predictive controllers based on linear models have great limitations in industrial process control. The Hammerstein model is a nonlinear model containing a nonlinear steady-state part and a linear dynamic part, which is suited to describe nonlinear industrial processes. In this work, a robust minimum covariance constrained control method is proposed for C3 hydrogenation process control based on the Hammerstein model. The nonlinear steady-state part of Hammerstein model is approximated by WaveARX neural network with multiple operating region data and the linear dynamic part is identified according to the first principle analysis with the operation data. In this work, the nonlinear robust control problem is transformed into a linear model robust control and nonlinear model inversion problem. Based on the Hammerstein modeling bias, the upper bound limit of output bias covariance is calculated and minimized to get the sub-optimal state feedback control law, and then obtain the control input of the system according to the inverse model of the nonlinear part. The simulation and industrial application results have verified the feasibility and effectiveness of the proposed method.

    Surface and interface engineering
    Analysis of turbulence effect on face groove cooling performance of high-speed mechanical seals
    Weizheng ZHANG, Jijun ZHAO, Xuezhong MA, Qixuan ZHANG, Yixiang PANG, Juntao ZHANG
    2023, 74(3):  1228-1238.  doi:10.11949/0438-1157.20221377
    Abstract ( 211 )   HTML ( 13)   PDF (1990KB) ( 219 )  
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    Under high-speed conditions, the viscous heat generation of the fluid in the sealing gap is serious and the flow behavior is complex. The fluid flow state is one of the key factors affecting the fluid-solid heat transfer process and temperature distribution in the cross-scale clearance. A 3D thermo-hydrodynamic lubrication (THD) model of annular groove and spiral groove compound end configuration (ASG) is established by using ANSYS Fluent under turbulence and laminar flow computational models. The cooling performance difference of the spiral groove and the cooling effect of the annular groove under the two models are compared, thus the influence mechanism of the fluid flow state on the cooling effect of the end groove is revealed. The effects of groove geometric parameters on temperature field and sealing performance under the two models are analyzed. The results show that the large dead fluid zone in the deep spiral groove under the turbulence model hinders the cold fluid from entering the root of the groove, resulting in the attenuation of the cooling effect of the spiral groove on the high temperature fluid in the sealing clearance. Under the laminar flow model, the deep spiral groove is filled with more cold fluid, and the cooling effect is stronger. The annular groove has a significant cooling effect under the two models, and the cooling effect is enhanced with the appropriate increase of groove depth and width. The continuous increase of spiral groove depth can’t achieve the purpose of continuous cooling, and the predicted value of the peak temperature of liquid film under the turbulence model is 29—40 K higher than that of the laminar flow model.

    Biochemical engineering and technology
    Aqueous two-phase system based adherent droplet microfluidics for enhanced enzymatic reaction
    Lufan JIA, Yiying WANG, Yuman DONG, Qinyuan LI, Xin XIE, Hao YUAN, Tao MENG
    2023, 74(3):  1239-1246.  doi:10.11949/0438-1157.20221603
    Abstract ( 167 )   HTML ( 16)   PDF (2968KB) ( 68 )  
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    Utilizing the aqueous two-phase system (ATPS) based droplet microfluidics, a highly efficient enzymatic reaction platform has been developed that takes the advantage of the properties of the ATPS adherent droplet microfluidics including rapid mass transfer, efficient mixing, and reaction-separation coupling. The proposed platform utilizes droplet microfluidics, overcoming the limitation of low mass transfer rate and the high time/energy consumption of the traditional bulk ATPS. A wall-mounted droplet microreactor is established, further enhancing mass transfer due to the creation of a larger vortex flow. In addition, the ATPS droplet with the ability of molecular containing and selective enzyme and product partitioning are investigated. By comparing the enzymatic reaction effects of two types of droplet microreactors with and without microchannel walls, it is found that the conversion of droplet microreactors with microchannel walls can reach 40% in only 6 min. It is 9.4 times higher than that of the droplet microreactor not attached to the wall of the microchannel. Therefore, this study paves a new way to enhance the enzyme-catalyzed reaction processes at the microscale through the ATPS droplet microfluidic technique.

    The construction and application of biosensor based on gold nanoparticles loaded SiO2-nanoflowers
    Ruiqi LIU, Xitong ZHOU, Yue ZHANG, Ying HE, Jing GAO, Li MA
    2023, 74(3):  1247-1259.  doi:10.11949/0438-1157.20221413
    Abstract ( 178 )   HTML ( 12)   PDF (3220KB) ( 100 )  
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    Dispersed gold nanoparticles-modified amino-silica composites (Au@NH2-SiO2) were prepared by in situ reduction using wrinkled silica nanoflowers (SiO2 NFs). Au@NH2-SiO2 NFs nanomaterials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier-infrared spectroscopy (FT-IR) and elemental mapping. The AChE/Au@NH2-SiO2 NFs/GCE biosensor was constructed based on Au@NH2-SiO2 NFs composite material. The detection performance of biosensor was investigated by two organophosphorus pesticides, malathion and chlorpyrifos. Separately, the prepared biosensor exhibited wide linear ranges of (1.00×10-11)—(1.00×10-5) mol/L with the LOD of 2.92×10-12 mol/L for malathion and (1.00×10-13)—(1.00×10-7) mol/L with a LOD of 5.60×10-14 mol/L for chlorpyrifos. The AChE/Au@NH2-SiO2 NFs/GCE biosensor was also used to detect real samples getting the recovery rate of 90.7%—107.0%. The AChE/Au@NH2-SiO2 NFs/GCE biosensor has outstanding stability and sensitivity.

    Energy and environmental engineering
    Multi-objective optimization of high-efficiency solar water electrolysis hydrogen production system and its performance
    Sheng’an ZHANG, Guilian LIU
    2023, 74(3):  1260-1274.  doi:10.11949/0438-1157.20221595
    Abstract ( 760 )   HTML ( 72)   PDF (2347KB) ( 1154 )  
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    Given the growing demand for clean and sustainable production technologies of green hydrogen, an efficient solar-based system with power and hydrogen production integrated has been developed. The system consists of a tower solar power generation and thermal energy storage system, a proton exchange membrane (PEM) electrolysis water system, a reheated steam Rankine cycle with a regenerator and an organic Rankine cycle waste heat recovery subsystem with a regenerator. Energy cascade utilization can be realized. The integrated system is simulated in Aspen Plus software, and the mathematical models of the solar heliostat field and PEM electrolyzer are written in Fortran language and embedded. Based on the non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ) and the interaction between Aspen Plus and MATLAB software, the trade-off between maximum exergy efficiency, maximum output electrical energy per day, and minimum levelized cost of hydrogen (LCOH) is performed through multi-objective optimization. The Pareto frontier shows that the optimal exergy efficiency and output electrical energy per day are 52.19% and 247.352 MWh/d, increased by 3.00% and 31.14%, respectively; the LCOH is 6.05 USD/kg, decreased by 4.87%, and the optimal hydrogen production capacity is 4.796 t/d. This study has specific guiding significance for large-scale solar power generation and hydrogen production.

    Physicochemical properties and VOCs molecular characteristics of liquid digestate from anaerobic digestion of putrescible waste
    Yulong HUANG, Fan LYU, Junjie QIU, Hua ZHANG, Pinjing HE
    2023, 74(3):  1275-1285.  doi:10.11949/0438-1157.20221599
    Abstract ( 160 )   HTML ( 4)   PDF (2768KB) ( 116 )  
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    This paper studied and analyzed the physicochemical properties, molecular characteristics and correlation of volatile organic compounds (VOCs) of liquid digestate of anaerobic digestion (ADLD) from putrescible waste, in order to provide basic properties for the utilization of ADLD resources. The study found that the seasonal differences of biogas slurry physical and chemical indicators were small, and the differences of each biogas slurry were large. Different ions existed in different forms in ADLD. The content of heavy metals in ADLD was much lower than the stipulated limits of heavy metals in the domestic and foreign standards. A total of 304 kinds of VOCs were detected in each ADLD sample, mainly including aromatic compounds (30%—83%) and olefins (5%—44%). There were differences in VOCs produced by different anaerobic digestion processes. The dry anaerobic digestion ADLD contained more aromatic VOCs (32%—83%), while the wet digester contained more alcohols (1%—20%) and others (1%—30%). 14 kinds of plant sensitive VOCs, such as methyl salicylate, 2-butanone and so on, were found in ADLD (0.05%—15.42%). These compounds could promote plant physiological activities. Common compounds (1.09%—41.54%) were found in the 19 VOCs samples, such as flavor additives and food flavor compounds that were not anaerobic degraded.

    Effect of purging conditions on the impedance relaxation phenomenon and low temperature start-up of PEMFC
    Zhiguang QIAN, Yue FAN, Shixue WANG, Like YUE, Jinshan WANG, Yu ZHU
    2023, 74(3):  1286-1293.  doi:10.11949/0438-1157.20221344
    Abstract ( 238 )   HTML ( 14)   PDF (2085KB) ( 238 )  
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    As a key process before starting at sub-zero temperature in a proton exchange membrane fuel cell (PEMFC), purging is effective in reducing the water content in the membrane electrode to improve the success rate of cold start. Shutdown purging, as a key process before sub-zero temperature start-up of proton exchange membrane fuel cell (PEMFC), can effectively reduce the water content of membrane electrode (MEA) before cold start, so as to improve the success rate of battery start-up. In order to investigate the impedance relaxation phenomenon of PEMFC after purging and how the purging conditions directly contribute to the low temperature start-up performance of PEMFC, an experimental study was conducted with a 25 cm2 single cell as the subject. The results under experimental conditions showed that the impedance relaxation became more obvious with the increase of gas flow rate and purging temperature; the purging flow rate and purging time had significant effects on the cold start performance of PEMFC. Under experimental conditions, the test cell performed best in low temperature by purging with dry N2 at 1500 ml/min for 15 min. The excessive or insufficient purge flow rate and purge time are not conducive to the low temperature start-up of PEMFC, and optimal purge conditions exist.

    Study on semi dry hydrolytic denitrification of aluminum ash
    Dingping LIU, Aihua CHEN, Xiangyang ZHANG, Wenhao HE, Hai WANG
    2023, 74(3):  1294-1302.  doi:10.11949/0438-1157.20221396
    Abstract ( 229 )   HTML ( 8)   PDF (5776KB) ( 78 )  
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    Aluminum ash is a hazardous waste, and it will seriously pollute the environment if it is not denitrified. Therefore, a new semi dry hydrolysis denitrogenation technology of aluminum ash was proposed to make aluminum ash in a semi dry alkaline state at high temperature during reaction. The effects of various factors on denitrogenation rate and reaction time were systematically investigated. The results showed that the denitrification effect was the best when the solid-liquid ratio was 1∶0.45. The denitrification rate could be improved by increasing the reaction quality of the sample. The alkaline reaction solution system could effectively shorten the induction period. Grinding pretreatment had a general effect on promoting the hydrolysis reaction. Therefore, the best reaction condition of aluminum ash semi dry hydrolysis denitrification technology was that the reaction solution system was 5%(mass) NaOH, the solid-liquid ratio was 1∶0.45, and the sample mass was greater than 250 g. At this time, the hydrolysis reaction time could be shortened to 50 min, and the denitrification effect was the best, which was obviously superior to the traditional wet denitrification technology, and could effectively solve the problem of aluminum ash waste pollution.

    Study on quantification methodology and analysis of chemical effects of combustion control based on fictitious species
    Jin YU, Binbin YU, Xinsheng JIANG
    2023, 74(3):  1303-1312.  doi:10.11949/0438-1157.20221428
    Abstract ( 157 )   HTML ( 5)   PDF (2603KB) ( 54 )  
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    Aiming at the problem that the quantification method of the combustion regulation chemical effect of additives that will undergo self-reaction is still not perfect, a new method for quantification and analysis of the combustion regulation chemical effect based on virtual components is proposed. The reaction-active radical effect and reaction heat-temperature effect have been defined and formulated. Based on the proposed new methodology, two typical cases of C6F12O (Novec 1230) and hydrogen added to methane fuel as additives are investigated respectively. It is observed that when C6F12O is added to methane, the reaction heat-temperature effect and reaction-radical effect are both negative when equivalence ratio φ=1.0. when φ=0.6, the reaction heat-temperature effect exhibit a very weak inhibition, while the reaction-radical effect appear to promote combustion. Proposed methodology is compared with one-step reaction methodology, the results show that the reaction-radical effect includes both the self-reaction of hydrogen and the chemical effect of its product, so that the quantified value is smaller than the self-reaction effect value quantified by the single-step reaction methodology. Besides, present methodology adopts a detailed mechanism, which can eliminate the error caused by fitting the reaction coefficient of the single-step reaction mechanism. Finally, based on sensitivity analysis, key reactions of reaction-active radical effect and reaction heat-temperature effect for C6F12O and hydrogen addition are analyzed. This study is expected to provide theoretical support for the quantitative analysis of chemical additive properties, screening and development of new additives.

    Kinetics of methane storage in the natural tobacco leaching filtrate in the hydrate form
    Han HU, Liang YANG, Chunxiao LI, Daoping LIU
    2023, 74(3):  1313-1321.  doi:10.11949/0438-1157.20221242
    Abstract ( 137 )   HTML ( 9)   PDF (3517KB) ( 143 )  
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    Hydrate storage of natural gas is recognized as a highly efficient gas storage technology with great potential. How to accelerate the formation of hydrates and ensure the environmental protection of hydration-promoting materials are the key to the practical application of hydration storage gas technology. In order to investigate the kinetics of methane hydrate formation in the natural tobacco leaching filtrate, the solutions by filtering tobacco shred/granule-water mixtures were used to store methane in hydrate under 8.0 MPa and 274.2 K. The experimental results showed that the solution with a water-tobacco mass ratio (liquid-solid ratio) of 5—100 had similar properties of surfactant, and its surface tension decreased by 36.7%—47.5% compared with pure water. Methane hydrate could be formed rapidly in active solutions. The content of active substance in tobacco shred leaching filtrate was significantly lower than that in tobacco granule leaching filtrate. When the liquid-solid ratio was low, tobacco shred leaching filtrate could store more gas in hydrate and had higher storage rate. When the liquid-solid ratio was high, tobacco granule leaching filtrate had better gas storage performance. Especially, the methane uptakes in tobacco granule leaching filtrate with liquid-solid ratio of 50 reached 118.5 mmol·mol-1, and the gas storage rate was up to 2.98 mmol·mol-1·min-1.

    Degradation of methylparaben by UV/PMS, UV/PDS and UV/SPC process
    Qingyun YANG, Qingsong LI, Zeming CHEN, Jing DENG, Yuying LI, Fan YANG, Guoyuan CHEN, Guoxin LI
    2023, 74(3):  1322-1331.  doi:10.11949/0438-1157.20221522
    Abstract ( 246 )   HTML ( 7)   PDF (2780KB) ( 66 )  
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    The UV/PMS, UV/PDS和UV/SPC processes were employed to degrade MeP in aqueous solution. Different free radicals during the three processes were identified by electron paramagnetic resonance. The effects of different oxidant dosages, pH, anions, NH4+ and HA on MeP removal were investigated. The second-order rate constants of SO4-· with MeP and contributions of different free radicals on MeP removal were determined by competitive kinetics, and the economics of different oxidant dosages were evaluated. The mineralization rate, DBPs formation and the alteration of acute toxicity during the degradation of MeP were investigated. The results showed that the three oxidants had good synergistic performances with UV, the pseudo-first-order kinetic rate constants of UV/PMS, UV/PDS and UV/SPC processes under experimental conditions were 0.1615, 0.3868 and 0.0798 min-1, respectively. The second-order rate constants of SO4-· with MeP were determined to be 1.37×109 L·mol-1·s-1. The kobs of MeP during the three processes increased with the increasing of oxidant dosage and the economic benefit of UV/PDS was superior to the other two processes. The kobs of UV/PMS and UV/PDS for MeP increased slightly with the increasing of pH, while the kobs of UV/SPC for MeP had a tendency of increasing first and then decreasing. Among the three processes, NO3- and HCO3- promoted the kobs of UV/PMS, UV/PDS and UV/SPC for MeP in varying degrees, while NH4+ and HA did the opposite. Cl- had an inhibiting effect on UV/PDS process, but it had a dual effect on UV/PMS and UV/SPC processes. UV/PDS manifested the highest mineralization rate of MeP among the three processes, but also generated more disinfection by-products.

    Carbon release products and denitrification bioavailability from chemical components of woody biomass
    Lingxin ZU, Rongting HU, Xin LI, Yudao CHEN, Guanglin CHEN
    2023, 74(3):  1332-1342.  doi:10.11949/0438-1157.20221375
    Abstract ( 158 )   HTML ( 10)   PDF (3611KB) ( 119 )  
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    Woody biomass has complex chemical components and structures, and when it is used as a carbon source for nitrate pollution control, it often suffers from slow denitrification rate and residual organic matter. Woodchip was selected as raw material. It was used to remove the lignin (RL), and hemicellulose (AF) by chemical methods. The acquired compositions were used for carbon release experiment, and then carbon release solution was utilized for denitrification experiment. The kinetic characteristics of carbon release were fitted. The carbon and nitrogen indexes and spectral characteristics were measured during experiments. The results showed that the infrared absorption peak disappeared at 1732 and 1251 cm-1 after removing lignin. The carbon release rate reached 0.11 mg·g-1·d-1 for natural biomass (NW). Compared with NW, the rate for RL and AF was 1.8 and 1.2 times that of NW. Carbon release processes fitted with second-order reaction kinetics (R2>0.90) and Ritger-Peppas kinetics (R2>0.98). Utilization rates reached 26.5%—49.7% when using the carbon release products in denitrification, and the rate of NW was the lowest among the three groups. The C/N ratio reached 1.0—1.5 in the denitrification. The humification degree was low for residual organic matter, and it mainly was tyrosine.

    Material science and engineering, nanotechnology
    Preparation of high molecular weight polypropylene glycol in microchannel reactor
    Xueting ZHANG, Jijiang HU, Jing ZHAO, Bogeng LI
    2023, 74(3):  1343-1351.  doi:10.11949/0438-1157.20221630
    Abstract ( 280 )   HTML ( 20)   PDF (2485KB) ( 134 )  
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    High molecular weight polyether polyols are widely used. However, there is not only a large risk of reaction heat, but also a long reaction time in its traditional production process by using the semi-continuous reactor. The microchannel reactor (MCR) has the characteristics of high heat transfer efficiency and process safety, but the viscous material and high reaction heat release make it difficult to produce the high molecular weight polyether polyols. In this work, using double metal complex (DMC) as catalyst and n-hexane as solvent, the ring-opening polymerization of propylene oxide (PO) was carried out in MCR. Polypropylene glycol (PPG) with molecular weight ranging from 2000 to 8000 was prepared. Effects of reaction conditions, such as flow rate, channel length, reaction temperature and feed policy, were investigated. It has been found that when the residence time is long enough, the molecular weight of the produced PPG is basically equal to the theoretical molecular weight. When the flow rate of initiator is fixed, an increase in flow rate of monomer will result in the molecular weight distribution (MWD) first widened and then narrowed. If the tube length is longer, the molecular weight is larger and the MWD is wider. If the temperature increases, the induction period of the polymerization can be shortened. Using the segmented feed, it is easier to prepare high molecular weight PPG with higher conversion than using the single feed, but the MWD is wider. These rules can be explained from the mechanism of PO ring-opening polymerization catalyzed by DMC and micro-mixing strength of materials in MCR. The lower the micro-mixing strength, and the smaller the rate ratio of chain transfer to chain propagation in polymerization, the wider the molecular weight distribution is.

    Heat and moisture performance study of Cur-LiCl coated heat exchanger
    Yu PAN, Zihang WANG, Jiayun WANG, Ruzhu WANG, Hua ZHANG
    2023, 74(3):  1352-1359.  doi:10.11949/0438-1157.20221354
    Abstract ( 213 )   HTML ( 11)   PDF (3984KB) ( 117 )  
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    Desiccant-coated heat exchanger (DCHE) combines the heat exchanger with the solid desiccant, which can significantly improve the dehumidification efficiency of the air conditioning system. The adsorption characteristics of the desiccant have an important influence on the dehumidification performance of the desiccant-coated heat exchanger. In this paper, the curdlan-lithium chloride composite adsorbent was developed and analyzed by the ASAP Mike adsorption instrument and the STA synchronous thermal analyzer. The material components were optimized, and the optimized composite adsorbent was applied to the heat exchanger to verify the efficient deep dehumidification performance of the desiccant-coated heat exchanger. The experimental results show that the curdlan composite adsorbent has the ability of deep dehumidification, even under 30℃ and 30% relative humidity (RH), the saturated adsorption capacity can reach 2.65 g/g and the adsorption rate coefficient k was 2.1×10-4 s-1. The MRC of the prepared composite desiccant-coated heat exchanger is 3.78 g/kg. This study achieves the development of a new low-cost and high-performance desiccant-coated heat exchanger with good dehumidification and stable circulation performance, which provides a reference for the technology of deep dehumidification system.

    Synthesis and properties of phenylene-containing α,ω-hydroxy-terminated fluorosilicone polymers
    Runzhu LIU, Tiantian CHU, Xiaoa ZHANG, Chengzhong WANG, Junying ZHANG
    2023, 74(3):  1360-1369.  doi:10.11949/0438-1157.20221455
    Abstract ( 164 )   HTML ( 10)   PDF (3297KB) ( 95 )  
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    A series of phenylene-containing α,ω-hydroxy-terminated fluorosilicone polymers were synthesized by dehydration polycondensation in the presence of non-equilibrium catalyst from α,ω-hydroxy-terminated poly(methyltrifluoropropyl) siloxanes and phenylene-containing disilanol monomers. The effects of reaction time, catalyst dosage, reactant concentration, and monomer ratio on the appearance, intrinsic viscosity, molecular weight and distribution, and copolymer composition of the obtained polymers were studied. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), rheometer and thermal analysis were utilized to study their chemical structure, room temperature crosslinking reactivity, mechanical property, thermal resistance, and glass transition. The results show that the introduction of phenylene into the main chain not only significantly improves the high temperature resistance of the polymer, but also contributes to the improvement of the crosslinking reaction rate and mechanical properties, and when the phenylene content is lower than 30%(mol), it does not adversely affect the glass transition temperature (Tg) of the polymer. It is reasonable that the insertion of phenylene inhibits the cyclization degradation and simultaneously improves the stiffness of the siloxane chain, which is beneficial to thermal resistance. Besides, the terminal silanol is separated from bulky trifluoropropyl side groups by the insertion of phenylene, and thus their shielding effect is reduced, which is helpful to the crosslinking reactivity. Therefore, the polymers can be utilized to prepare fluorosilicone sealants which show good crosslinking property, physical property, and high and low temperature resistance.

    Facile preparation and properties of chemically modified galactomannan films via mild hydroxy-alkyne click reaction
    Haiqin LIU, Bowen LI, Zhe LING, Liang LIU, Juan YU, Yimin FAN, Qiang YONG
    2023, 74(3):  1370-1378.  doi:10.11949/0438-1157.20221588
    Abstract ( 164 )   HTML ( 7)   PDF (2416KB) ( 55 )  
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    Galactomannan (GM), an important plant polysaccharide, was successfully etherified via green hydroxyl-alkyne click reaction by using 1-phenyl-2-propyn-1-one (PPK) as etherification agent. The prepared galactomannan phenyl propylene ketone ether (GMPPK) films exhibited excellent mechanical property, hydrophobic property as well as UV-blocking property. The results showed that the hydroxyl-alkyne click chemistry can achieve efficient etherification of GM surface hydroxyl groups. Compared with the unmodified GM films, the GMPPK films exhibited new UV shielding (shielding 98.86% at 275 nm for GMPPK2), hydrophobicity (water contact angle increased from 74.9° to 96.5°). In addition, the mechanical performance of GMPPK films increased with the increase of molar ratio of —OH∶PPK, with the highest tensile stress of 44.7 MPa, the highest toughness of 1.7 MJ/m3, and Young’s modulus of 25.3 MPa, which were 2.2, 1.9, and 2.4 times of those for unmodified GM films, respectively. The research results lay a theoretical foundation for the development of high performance galactomannan packaging film materials.

    Preparation and electrochemical energy storage of polyaniline/manganese dioxide/polypyrrole composite nanospheres
    Dong XU, Du TIAN, Long CHEN, Yu ZHANG, Qingliang YOU, Chenglong HU, Shaoyun CHEN, Jian CHEN
    2023, 74(3):  1379-1389.  doi:10.11949/0438-1157.20221497
    Abstract ( 261 )   HTML ( 17)   PDF (6330KB) ( 210 )  
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    Polypyrrole (PPy) nanospheres with uniform size distribution were successfully prepared by chemical synthesis, and then KMnO4 was decomposed into MnO2 by acid hydrolysis. Finally, the polyaniline (PANI) in-situ grew on the surface of MnO2 by dilute solution synthesis to form PANI@MnO2@PPy ternary composite. Scanning electron microscope, transmission electron microscope, Raman spectroscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy confirmed that the PANI@MnO2@PPy was successfully synthesized. The PANI@MnO2@PPy ternary composite was prepared as electrode by solution coating and its electrochemical energy storage capacity was measured in 1 mol·L-1 Na2SO4 electrolyte solution. The specific capacitance of PANI@MnO2@PPy electrode was about 357 F·g-1 at a current density of 0.5 A·g-1, which was 1.96 times compare to the MnO2@PPy electrode. The capacitance loss of PANI@MnO2@PPy electrode was 26.9% when the current density increased from 0.5 A·g-1 to 5.0 A·g-1, indicating it had good rate capability. When the current density was 10.0 A·g-1, the capacitance retention rate of PPy, MnO2@PPy and PANI@MnO2@PPy electrodes were 45%, 70% and 76% respectively, after 1000 cycles of constant current charge and discharge, which showed that the chemical modification of PPy through PANI and MnO2 could effectively improve the long-life cycle stability of PANI@MnO2@PPy.

    Design, synthesis and anti-fungal activity of 1,2,4-oxadiazole derivatives
    Feng WANG, Yu CHEN, Hongyan PEI, Dongdong LIU, Jing ZHANG, Lixin ZHANG
    2023, 74(3):  1390-1398.  doi:10.11949/0438-1157.20221365
    Abstract ( 198 )   HTML ( 17)   PDF (2058KB) ( 66 )  
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    Soybean rust is one of the main fungal diseases affecting soybean production. To develop novel and highly effective fungicide, N-(4-(5-(trifluoromethyl)-1,2,4-oxadiazol-3-yl)phenyl)cyclopropanecarboxamide was used as the lead compound. Using the method of structural modification and introducing new substituents, 12 new 1,2,4-oxadiazole derivatives were designed, synthesized through oximation, ring closure, reduction and condensation reactions. Their chemical structures were characterized by 1H NMR and ESI-MS. The bioassay results showed that the inhibition rates of compounds 5b, 5d, 6a, 6e and 6g against soybean rust at the concentration of 3.125 mg/L were 60%, 65%, 100%, 98% and 95%, respectively. The activities were all better than that of control agent difenoconazole (50%). Compound 6a displayed prominent anti-fungal activity. When the mass concentration was 0.39125 mg/L, it still had 90% inhibition rate against soybean rust. The molecular docking results showed that compound 6a had various interactions with histone deacetylase 4(HDAC4) and histone deacetylase 7(HDAC7).

    Preparation and characterization of flame retardant bio-based polyols polyurethane foam
    Shuai WANG, Fukai YANG, Xinyu XU
    2023, 74(3):  1399-1408.  doi:10.11949/0438-1157.20221316
    Abstract ( 290 )   HTML ( 16)   PDF (4946KB) ( 231 )  
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    In this paper, two different soybean oil-based polyols (Polyol-E and Polyol-PPOA) were prepared by ring-opening reaction of epoxidized soybean oil with ethanol and phenylphosphoric acid, respectively. Rigid polyurethane foams of all bio-based polyols were prepared by combining them with isocyanate (PM200) according to different ratios. The cell structure, density, mechanical properties, and flame retardant properties of the prepared rigid polyurethane foams were tested and analyzed. The results of scanning electron microscopy showed that with the increase of the mass fraction of Polyol-PPOA, the number of cells in the samples first decreased and then increased, and when the content of Polyol-PPOA increased, the cell size first increased and then decreased. The density increased first and then decreased with the amount of Polyol-PPOA. The compressive strength showed a trend of first decreasing and then increasing. When the Polyol-PPOA was 70% (mass), the compressive strength reached 0.133 MPa, and the residual carbon rate reached 17.57% at 800℃. The limiting oxygen index also reached the highest at this time, which was 23.10%. Through experiments, it can be found that the rigid polyurethane foam material prepared by using mixed polyols can not only have a certain mechanical strength but also improve a certain flame retardant performance.

    Process safety
    Study on the effect of ignition mode on overpressure of underexpanded hydrogen jet explosion
    Zichao WU, Zhilei WANG, Rongye LI, Kexin LI, Min HUA, Xuhai PAN, Sanming WANG, Juncheng JIANG
    2023, 74(3):  1409-1418.  doi:10.11949/0438-1157.20221597
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    An experimental study was carried out on the variation of overpressure of underexpanded hydrogen jet ignition by spontaneous ignition and electric spark ignition. We measured the explosion overpressure and flame propagation rate of spontaneous ignition and electric spark ignition under different release pressures, we also analyzed the influence mechanism of initial pressure and ignition conditions on explosion overpressure. The experimental results show that under the same release conditions, the overpressure peak of spontaneous ignition is higher, the pressure rise rate is faster, and the development process of spontaneous ignition is more stable. With the release pressure of the buffer tank increasing from 6 MPa to 9 MPa, the explosion overpressure peak outside the spontaneous ignition tube first increases and then decreases. When the release pressure is 8 MPa, the explosion overpressure caused by spontaneous ignition reaches the maximum value of 15.97 kPa, while the explosion overpressure at the ignition source of electric spark decreases from 7.23 kPa to 3.17 kPa and then increases to 4.19 kPa with the increase of the release pressure. The spark ignition flame forms an irregularly shaped ignition core at the ignition source, and the flame propagation velocity is greater than the spontaneous combustion flame development velocity. This study has reference significance for the design of hydrogenation station and the risk assessment of ignition and explosion.