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    28 March 2024, Volume 24 Issue 3
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2024, 24(3):  0. 
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    Review
    Research progress on preparation of magnetic activated carbon and its application in water treatment
    Qianyu WANG Yuming ZHANG Yanbin CUI
    The Chinese Journal of Process Engineering. 2024, 24(3):  259-272.  DOI: 10.12034/j.issn.1009-606X.223228
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    Activated carbon (AC) has the characteristics of high specific surface area, porosity, abundant surface functional groups and chemical stability, and these advantages make it a widely used adsorbent in water treatment. After being exhausted (saturated adsorption contaminants), the spent AC needs to be separated from aquatic systems and regenerated which is conductive to materials recycling. However, it is difficult to efficiently separate the powder AC saturated adsorption contaminants from aquatic systems by traditional separation methods (gravitational sedimentation, centrifugation, filtration, and flotation), and the disadvantages for these methods root in many aspects including time-consuming, high-cost, and low separation efficiency. These limit the wide application of activated carbon in the field of water treatment to some extent. Magnetic modification treatment on AC can provide a magnetic activated carbon (MAC) which possesses better performances reflecting in higher adsorption capacity, and can be easier, rapid and efficient separation through external magnetic fields. At the same time, MAC has good catalytic activity, which is useful for enhancing the capability of advanced oxidation process to efficiently degrade organic pollutants in aquatic systems. Therefore, MAC has broad application prospects in the field of water treatment. This work mainly introduces the preparation methods (co-precipitation method, thermochemical method, and mechanical milling method), microstructure and physicochemical properties (specific surface area, pore structure, magnetism, crystal and chemical structure, surface charge) of MAC. The research progress of MAC in wastewater treatment in recent years is reviewed, consisting of organic pollutant removal, heavy metal removal and other applications. The adsorption characteristics (adsorption isotherms and adsorption dynamics) and corresponding influencing factors (adsorption temperature, solution pH, and coexisting ions) are summarized in details. And the regeneration methods of AC are investigated comprehensively. In the end, the development and prospect of the application of MAC in water treatment are also discussed.
    Research status and prospect of flash boiling spray
    Jian GAO Run HONG Wenlong DONG Nian XU Huaqiang CHU
    The Chinese Journal of Process Engineering. 2024, 24(3):  273-283.  DOI: 10.12034/j.issn.1009-606X.223157
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    The rapid boiling that occurs when high-temperature fuel is injected into a low-pressure environment is called flash boiling, reasonable use of flash boiling phenomenon can effectively improve the atomization effect of fuel spray and improve engine efficiency. The research on the flash boiling phenomenon can be traced back to more than 60 years ago. With the development of the research on the flash boiling spray, the focus of the spray-related research has gradually shifted to the spray collapse. The related theories of flash boiling spray are summarized in this review, and some visualization techniques commonly used in the observation of flash boiling spray are briefly introduced. The influence of different fuel characteristics on the flash-boiling spray is illustrated by comparing different fuel characteristics. The characteristics of flash boiling spray of multi-component fuel are summarized. The superheat index which can be used to measure the flash boiling spray of multi-component fuel are introduced. The collapse mechanism of non-flash boiling spray and flash boiling spray and the influencing factors of spray collapse are studied by comparing the research status of non-flash boiling spray and flash boiling spray. It is generally considered that the collapse mechanism of non-flash-boiling spray is jet-induced collapse, and flash-boiling spray seriously affects the experimental observation because of too many droplets. Therefore, the understanding of the collapse mechanism of the flash boiling spray is numerous but not certain. In addition, according to the above summary, several feasible research directions are put forward for the spray research: effect of different fuel properties on flash boiling spray, study of parameters to measure the degree of superheat of multi-component fuels, the study on the collapse mechanism of the flash-boiling spray and the study on the suppression of the collapse of the flash-boiling spray.
    Recent progress of heterogeneous catalysts towards selective catalytic reduction of NO by CO under oxygen-rich conditions
    Yaqi LIU Yan LIU Ke WU Liwen XING Dianxing LIAN Mohaoyang CHEN Jianjun JI Yongjun JI
    The Chinese Journal of Process Engineering. 2024, 24(3):  284-296.  DOI: 10.12034/j.issn.1009-606X.223136
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    Nitrogen oxides (NOx), as one of the predominant atmospheric pollutants mainly derived from automobile exhaust and industrial waste gas, have played the role of an inevitable precursor that led to acid rain, photochemical smog, and other environmental contamination issues. In addition to atmospheric pollution, the growing emissions of NOx pollutants also give rise to a serious threat to agricultural production and human health. Thus, it is of urgent need to develop feasible NOx abatement strategies. Selective catalytic reduction of NO by CO (CO-SCR) is a very promising denitrification technology that can simultaneously remove harmful gases of NO and CO, making it one of the most ideal solutions for flue gas treatment. To promote its industrial applications, CO-SCR should have a low operating temperature ranging from 150℃ to 250℃ and superior resistance to oxygen poison. Therefore, there is an urgent need to develop efficient CO-SCR catalysts used under oxygen-rich conditions for abating severe environmental pollution problems. This work provides a comprehensive review of the research progress and latest research findings of CO-SCR under oxygen-containing conditions. The research advances of Pd, Ir, Rh, Mn, and Co-based heterogeneous catalysts were introduced, and the effects of active components, promoters, and supports on the catalytic performance of CO-SCR are described in detail. In this section, the preparation method, doping modification, and reaction conditions are analyzed. Meanwhile, the impact of O2, H2O, and SO2 on the catalytic activity of CO-SCR is discussed, in which the inhibition mechanism of O2 is summarized. Finally, the challenges and future developments of CO-SCR under oxygen-rich conditions are summarized and the corresponding coping solutions are proposed. We hope this review can provide an in-depth understanding and useful guidance for the rational design of efficient heterogeneous catalysts for the CO-SCR reaction in practical applications.
    Research Paper
    Fluid-particle and particle-particle drag forces in moderate-Reynolds-number bidisperse suspensions
    Fan DUAN Xuan HE Qiang ZHOU
    The Chinese Journal of Process Engineering. 2024, 24(3):  297-314.  DOI: 10.12034/j.issn.1009-606X.223212
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    A set of fully resolved numerical methods are employed to simulate the bidisperse suspensions where the particles are free to translate and rotate according to the effects of the surrounding fluid, and the fluid-particle and particle-particle drag relations in the literature are examined. Three overall solid volume fractions of 0.1, 0.2, and 0.3, two diameter ratios of 1.5 and 2, three small-particle-phase fractions of 0.1, 0.3, and 0.5, four particle-to-fluid density ratios of 10, 100, 500, and 1000, and three overall particle Reynolds numbers of 10, 20, and 50 are chosen. Simulation results show that, among the fluid-particle drag relations available in the literature, in terms of the model accuracy, the relations obtained from static homogeneous systems are the best, the next are those of dynamic suspensions, and the monodisperse drag extended relations are the worst. Based on the simulation data, a new fluid-particle drag relation that meets all physical requirements is proposed. Further analysis reveals that the fluid-particle drag of bidisperse suspensions is influenced by five factors, that is the local solid volume fraction, the slip velocity between different particle phases, the granular temperature, the particle Stokes number, and the particle microstructure. Under the action of these factors, the change of the fluid-particle drag is not significant as the particle-fluid density ratio varies, and the difference of the fluid-particle drag between small and large particle phases is smaller than that in static homogeneous systems. For the particle-particle drag, when the particle-fluid density ratio equals 10 or 100, the collision numbers are unevenly distributed between different particle pairs because of the lubrication force. This uneven distribution of the collision numbers leads to the invalid of the assumption of molecular chaos, and for this reason, the particle-particle drag is highly overestimated by the relation derived from the kinetic theory of granular flow.
    Numerical simulation of multiphase flow process and structural improvement measures in the quench chamber of a gasifier
    Bing YUAN Jinjun GUO Xiaofei LI Junhui LIANG Zhenxiang Li Xiaodong LONG Congbin JIANG
    The Chinese Journal of Process Engineering. 2024, 24(3):  315-325.  DOI: 10.12034/j.issn.1009-606X.223196
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    The entrained flow coal gasification technology is one of the important means for the clean utilization of coal. In the syngas cooling device, the quench chamber with riser-downcomer structure is widely used in the coal gasification device. There is a situation where synthetic gas escapes from the black water outlet in the quench chamber of this type of quench chamber, resulting in a waste of resources. In this work, the gas-liquid two phase flow in the quench chamber is stuided with the numerical simulation method. The causes of syngas escape problem from the black water outlet in the quench chamber are analyzed, and three improved structures for the quench chamber are proposed as follow: extending the black water outlet pipe (structure A), extending the riser pipe downwards (structure B), adding a baffle on the rising pipe near the black water outlet (structure C). The simulation results indicate that all three improvement schemes can avoid the problem of syngas escape. In addition, the liquid-solid two phase flow in the black pool with four structures (structures A, B, C, and the original structure) are simulated, and the carry-out rate of ash particles with different particle sizes under the same conditions are compared in different structures. The results show that the carry-out rate of ash particle in the improved structure C is the smallest, followed by the structure A. These two structural schemes are suitable for the situation where the residual carbon in the filter cake is not recycled, and the low carry-out rate of ash by black water is beneficial for improving the water quality of the water circulation system. Compared with the original structure, the structure B has a higher carry-out rate for particles size smaller than 20 μm, but a low carry-out rate for large particles, which is suitable for recycling the residual carbon in the filter cake.
    Numerical investigation on scale-up rule of circulating fluidized bed
    Jinchao XIE Nan ZHANG Tianbo FAN Xinhua LIU
    The Chinese Journal of Process Engineering. 2024, 24(3):  326-337.  DOI: 10.12034/j.issn.1009-606X.223135
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    Circulating fluidized beds have been widely used in industry, and scaling laws have been proposed during research and development from lab-scale units to industry plants. The particle diameter ratio has to be changed to keep the scale-up ratio, which may change the particle classification from Geldart A to Geldart B and even change the fluidization regime, thus limiting the utilization of these scale-up rules. A new scale-up rule, which can keep material properties or operating conditions unchanged, is thus proposed based on the Shi scale-up rule applicable for the same circulating fluidized bed and the Horio scale-up rule suitable for different circulating fluidized beds. The Euler-Lagrange model coupled with the EMMS drag coefficient was used to simulate the flow behavior in a circulating fluidized bed, and the rationality of the Shi scale-up rule was further verified by these simulations. The new scale-up rule proposed was then validated under the conditions of fixed superficial gas velocity, fixed superficial particle diameter and unrestricted combination of the gas velocity and the particle diameter in different circulating fluidized beds. The simulation results showed that the proposed scale-up rule can maintain similarities in the axial solid concentration, radial solid concentration and radial dimensionless velocity distribution. The mesoscopic characteristic distributions were further discussed through the analysis of pressure fluctuations in the time domain and frequency domain. The results showed that the mesoscopic characteristics were different to some extent, which meant that more work should be done to keep the similarities when considering heat and mass transfer in circulating fluidized beds.
    Prediction of vapor-liquid phase equilibrium of nicotine+alcohol binary system based on COSMO-SAC model
    Furong DENG Changzheng JI Yapeng NIU Xiaomin FENG Xiangshi MENG Mengwei ZHANG Changjun PENG
    The Chinese Journal of Process Engineering. 2024, 24(3):  338-345.  DOI: 10.12034/j.issn.1009-606X.223182
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    The phase equilibrium of the nicotine system holds great significance in guiding the separation and purification of nicotine, as well as exploring the release laws of nicotine and active ingredients in heated cigarettes. The conductor-like screening model-segment activity coefficient (COSMO-SAC) enables the prediction of phase equilibria and other properties through quantum chemical calculations. In this study, the vapor-liquid phase equilibria of nicotine with binary systems consisting of mono-alcohols (methanol, ethanol, n-propanol, isopropanol, butanol, pentanol, hexanol, heptanol, octanol) and poly-alcohols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, and glycerol) are predicted respectively using the COSMO-SAC model. The results show that alcohol molecules exhibit peaks in both the donor and acceptor regions of hydrogen bonds, whereas nicotine only exhibits a peak in the acceptor region. This suggests that nicotine can only act as a hydrogen bond acceptor to receive protons and form hydrogen bonds. The nicotine-alcohol binary systems are all positive deviation systems; specifically, the binary systems of mono-alcohols and nicotine exhibit general positive deviation systems and show a similar phase diagram profile, however, as the number of carbon chains of alcohols increases, the area of the gas-liquid coexistence region becomes smaller; the binary systems of poly-alcohols and nicotine exhibit the azeotropic phenomenon, which is a system with minimum azeotrope. As the temperature rises, the pressure and composition of the azeotrope increase accordingly. At 101.3 kPa, the temperature and composition of the azeotrope are 511.4 K and 0.261 for glycerol/nicotine, 459.5 K and 0.857 for 1,2-propanediol/nicotine, 483.0 K and 0.727 for 1,3-propanediol/nicotine, and 467.0 K and 0.889 for ethylene glycol/nicotine. These research results provide theoretical data to guide the purification and separation of nicotine and to understand the release law of nicotine.
    Study on the removal mechanism of Zn(II) and Pb(II) by magnetic flake nZVI-Fe3O4
    Shuxian WEI Canhua LI Wenqing MA Lanyue ZHANG Jiamao LI Aiqin MAO Chuan HE Minghui LI Weichang ZHU
    The Chinese Journal of Process Engineering. 2024, 24(3):  346-359.  DOI: 10.12034/j.issn.1009-606X.223189
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    In response to the increasingly serious problem of heavy metal pollution in water bodies, engineering magnetic nanoparticles are widely used in wastewater treatment and remediation. In order to reduce the environmental pollution during the material preparation process, it is of great significance to improve its practicality in environmental protection technology. In this experiment, a new type of magnetic flake zero valent iron ferric oxide (nZVI-Fe3O4) with fissure structure was prepared by disproportionation. The physicochemical properties and structure of the material were characterized by multiple characterization techniques. The effects of pH, temperature, and the initial concentration of heavy metal ion solution on the removal efficiency of Zn(II) and Pb(II) by nZVI-Fe3O4 were studied. The experimental results showed that the removal of Pb(II) and Zn(II) by nZVI-Fe3O4 reached an equilibrium state in about 60 min. Under the conditions of a solution pH of 6, temperature of 25℃, and a dosage of 1 g/L of nZVI-Fe3O4, nZVI-Fe3O4 can reduce Zn(II) and Pb(II) in 10 mg/L simulated wastewater to trace levels within 5~30 minutes. As the pH value of the solution decreased, the adsorption efficiency of nZVI-Fe3O4 on Pb(II) decreased. The research results indicated that the removal process of nZVI-Fe3O4 followed the Langmuir model, indicating that it was a chemical adsorption process, and the maximum adsorption capacity of Zn(II) was 13.52 mg/g, while the maximum adsorption capacity of Pb(II) was 26.50 mg/g. Thermodynamic studies had shown that the removal process was spontaneous adsorption. The research results showed that nZVI-Fe3O4 mainly enriched Zn(II) and Pb(II) through adsorption co-precipitation. nZVI-Fe3O4 can be recovered through an external magnetic field, and experiments had shown that nZVI-Fe3O4 had good application prospects in removing Pb(II) and Zn(II) in wastewater treatment.
    Porous PLGA microsphere as a vaccine adjuvant against COVID-19
    Lingjiao ZOU Yu ZHANG Hua YUE Guanghui MA
    The Chinese Journal of Process Engineering. 2024, 24(3):  360-370.  DOI: 10.12034/j.issn.1009-606X.223218
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    Poly (lactic-co-glycolic acid) (PLGA) nano-/microspheres have been proven to be effective as vaccine adjuvants. In current studies, the investigations on PLGA vaccine delivery microspheres have mainly focused on improving antigen loading/adsorption efficiency or co-delivery of multiple adjuvants to enhance the immunization effect. However, there is still a lack of discussion on the impact of the structural diversity of microspheres in promoting the vaccination effects. By rationalizing the design of the microsphere structure, we describe that the development of an effective SARS-CoV-2 vaccine adjuvant was achieved by the post-loading of SARS-CoV-2 antigen into porous PLGA microspheres, which provided non-destructive loading and prolonged release of antigen. In this work, PLGA porous microspheres and solid microspheres were prepared with the emulsification method, and there was no significant difference in microsphere particle size and surface potential between the two, except for the porous microspheres having cavities internally and tiny pores on the surface. Such characteristics of "large inner pores and tiny outer pores" enabled the antigen encapsulation efficiency to reach 10.81% at the antigen input concentration of 5.71 mg/mL. In terms of prolonging the in vivo retention of the antigen, the release endpoint in the antigen-loaded porous microspheres was prolonged to 15 days compared with that of the free antigen at 3 days and that of the solid microsphere-mixed antigen at 5 days. Concerning the enhancement of humoral immunization, compared with the solid microsphere vaccine group mixed with SARS-CoV-2 antigen, the porous microsphere vaccine group loaded with SARS-CoV-2 antigen had a higher onset of effect as the maximum value of the IgG titer rising rate, Vmax was 1.73 times higher; and the onset of effect was much earlier, as the time to reach the Vmax was 2.8 days earlier; also, the IgG antibody titer of which was higher during 6~16 weeks post-immunization, presenting a better antibody maintenance effect.
    Deep mining of risk weaknesses for petrochemical processes based on alarm logs
    Yingqi ZHU Qianlin WANG Dongsheng ZHANG Zhan DOU Jianwen ZHANG
    The Chinese Journal of Process Engineering. 2024, 24(3):  371-380.  DOI: 10.12034/j.issn.1009-606X.223202
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    There are highly dangerous factors in the complex petrochemical processes. The raw materials and products have the characteristics of flammable, explosive, toxic, or harmful. The major dangers would be easily caused by a slight carelessness. During the complex petrochemical processes, a great number of potential risk information is contained in the process alarm logs, which is conductive to reveal the root cause of danger incidents and prevent the occurrence of safety accidents. It is important to make full use of alarm logs for the complex petrochemical processes. Therefore, a deep mining method of risk weaknesses for petrochemical processes is proposed based on alarm logs in this work. Firstly, a word embedded technology-Word2Vec is introduced to pre-process the text-type alarm logs and make them to vectorial data, so the text-type alarm logs are converted and quantized. The Pearson correlation coefficient is further applied to analyze the relationship between these alarm logs and obtain the correlation matrix. Secondly, according to the theory of complex networks (CN), the correlation matrix should be transformed into a Boolean matrix, and then the risk character network could be established for complex petrochemical processes. Thirdly, the technique for order preference by similarity to an ideal solution (TOPSIS) is used to accurately assess the node importance of the established network model. This work involves three indicators: degree centrality, proximity centrality, and eigenvector centrality. Finally, the risk weaknesses of petrochemical processes can be deeply mined based on the priority of network node importance. A diesel hydrotreating unit is selected as the test case. Results show that the proposed method can accurately and effectively mine the process alarm logs with the alarm levels of "High High (HH)" and "High (HI)", which is consistent with the actual operating conditions of petrochemical processes.