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    28 December 2024, Volume 24 Issue 12
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2024, 24(12):  0. 
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    Review
    Research progress on preparation of microbubbles by ejectors
    Mian QIAO Yuan GONG Lanying WANG Zhuo YANG Chunlei LI Yuqin TIAN Wenfei YUE
    The Chinese Journal of Process Engineering. 2024, 24(12):  1375-1386.  DOI: 10.12034/j.issn.1009-606X.224165
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    Ejectors are employed for efficient mixing of gases and liquids, as well as for producing a substantial number of microbubbles. They are characterized by low equipment costs, high energy efficiency, and suitability for large-scale industrial applications. However, the current ejector techniques for microbubble production suffer from a wide distribution in bubble sizes. Moreover, the structural parameters and operational conditions of ejectors exert significant influence over microbubble size. The following patterns in microbubble size variation have been identified based on the factors mentioned above. It has been demonstrated that reducing the length and diameter of the mixing section, and increasing the angle and cross-sectional ratio of the diffusion section effectively decrease bubble size. However, the angle of the contraction section has a minor impact on bubble size. The narrowing of the range of gas bubble sizes can be achieved by a reduction in the gas flow rate and an increase in the liquid flow rate, with the bubble size exhibiting a linear relationship to the gas volume ratio. Utilizing computational fluid dynamics (CFD) simulations and particle image velocimetry (PIV) technology to investigate gas-liquid transfer mechanisms within the ejector, it is evident that efficient gas-liquid shear at the nozzle outlet of the suction chamber and within the mixing section is critical for microbubble formation, while the diffuser section is the site for bubble breakage and refinement. Furthermore, the application scenarios of microbubble production using ejectors are discussed, and future research directions are proposed.
    Research Paper
    Design and heat transfer performance of impinging jet arrays for physical tempering of ultra-thin glass
    Zhijie LI Keqian ZHU Jinhan LIN Zhongqiang ZHANG Guanggui CHENG Jianning DING
    The Chinese Journal of Process Engineering. 2024, 24(12):  1387-1397.  DOI: 10.12034/j.issn.1009-606X.224106
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    To meet the high-efficiency and uniform heat transfer requirements in the gas-suspended ultra-thin glass physical tempering heating furnace, a parametric design study on impinging jet arrays with return holes was conducted, particularly focusing on low jet heights. A three-dimensional numerical heat transfer model of high-temperature array jet impingement heat transfer was established, and the thermophysical properties of high-temperature gas were analyzed. Numerical simulations were conducted to investigate the effects of different design parameters on the transient heat transfer of impinging jets. Reynolds numbers (Re) ranging from 2000 to 10 000 were set. Under a certain mass flow rate, variations in the dimensionless reflux hole diameter (D1/D) from 1 to 3 and the dimensionless jet spacing (S/D) of 4, 5, and 7 were considered. Surface-averaged Nusselt number and temperature variation coefficient were used to illustrate the performance in terms of average heat transfer and uniformity. The results indicated that in the impinging jet array model with return holes at low jet heights, as Re varies from 2000 to 10 000, the surface average Nusselt number increased by 243.3%, and heat transfer uniformity improved by 90.9%. The diameter of the return holes had a significant effect on heat transfer. The ratio of the diameter of the return hole to the diameter of the jet hole (D1/D) increased from 1 to 3, and the average Nusselt number first increased and then decreased. When D1/D=2, the average heat transfer effect showed a turning point, and the average Nusselt number was always higher than that of the corresponding traditional array jet. A smaller return holes diameter led to a gradual reduction in the maximum velocity difference between the return holes and the jet holes, thus demonstrating excellent heat transfer uniformity. Additionally, reducing the ratio of jet holes spacing to diameter (S/D) improved heat transfer uniformity. At S/D=4 and D1/D=1, the heat transfer uniformity was maximally improved by 46.24% compared to the corresponding traditional array jet impingement. These research findings provide a theoretical foundation for the design and application of efficient impinging jet structures.
    Effect of jet angle on mixing performance of central multi-stranded jet reactor
    Ding WANG Zongyong WANG Lixun MA Aobang DING Zhanhua XU
    The Chinese Journal of Process Engineering. 2024, 24(12):  1398-1406.  DOI: 10.12034/j.issn.1009-606X.224111
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    In order to explore the relationship between the relative flow direction and the mixing performance of the jet and the cross-flow of the central multi-strand jet reactor, the concept of three-dimensional jet angle represented by normal angle α and rotation angle θ was proposed and defined, and the mixing performance of various jet angles in space was simulated by fluent multiphase flow model. Firstly, the conditions of the numerical simulation were determined by the combination of numerical simulation and experiment, so as to ensure the accuracy of the simulation and conform to the regularity of the experiment. The results showed that under the mixture model, the concentration field obtained by the simulation was close to the distribution law obtained by the experiment, so the simulation can better reflect the internal concentration distribution of the reactor. Secondly, the reactor under the research angle was analyzed through the simulation, the qualitative analysis was carried out through the concentration contour of each section, and the quantitative analysis of the separation intensity of the cross-section, and the change law of the angle on the swirl intensity in the reactor were studied. It was found that θ=67.5° is the ideal rotation angle, and the reactors showed a good mixing effect at this angle. With the increase of θ, the pitch of the fluid trajectory at the mixing development section decreased gradually, and the swirling intensity increased gradually. The pressure drop of the inlet and outlet sections increased with the increase of the rotation angle, and the increase amplitude increased with the increase of the normal angle. At α=30°, θ=90° the slope of the separation intensity decreased the most, indicating that it can make the separation strength reach 0.05. With the increase of θ, the pitch of the mixed development section decreased and the swirling effect increased. The distance of the jet hitting the wall was proportional to the α and inversely proportional to θ.
    Process simulation of catalytic cracking of C5+ mixed olefins by-product of MTO to produce ethene and propene
    Rongheng GOU Mengfan YIN Tao ZHENG Jiawei ZHU Rui ZHANG Haiyan LIU Zhichang LIU Xianghai MENG
    The Chinese Journal of Process Engineering. 2024, 24(12):  1407-1416.  DOI: 10.12034/j.issn.1009-606X.224127
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    Methanol to olefin (MTO) is one of the important ways to produce ethene and propene, and mixed olefins are the main by-products of MTO process. C5+ mixed olefins by-product of MTO is currently sold at a low value in CHN Energy Xinjiang Chemical Company Limited, and has not been effectively utilized. In order to explore the high-value utilization way of C5+ mixed olefins by-product of MTO, its composition and physical properties were tested. It was found that the content of C5~C8 olefins in mixed olefins by-product of MTO was more than 80wt%, in addition, a small amount of alkanes, aromatics and oxygen compounds were contained. The catalytic cracking experiments of mixed olefins were carried out on a fixed-bed experimental device. Under the conditions of 0.1 MPa, 620℃, and mass space velocity of 3.53 h-1, the yields of ethene and propene were 15.31wt% and 26.94wt%, respectively. Combined with the process of MTO industrial plant, this study designed the process of mixed olefins catalytic cracking to produce ethene and propene, simulated the process based on Aspen Plus software, and optimized the operation parameters of the distillation column with high energy consumption. It was found that the optimal number of theoretical stages, feed stage and reflux ratio of the condensate stripping tower were 24, 12, and 1.2, respectively; those of the depropane tower were 20, 10, and 0.4, respectively; those of the deethane tower were 28, 9, and 3.4, respectively; those of ethene refining tower were 50, 21, and 7.5, respectively; those of propene refining tower were 54, 29, and 5.7, respectively; and those of light hydrocarbon separation tower were 12, 7, and 0.8, respectively. Finally, the product purity of ethene and propene reached 99.9wt% and 99.6wt%, respectively. The economic potential analysis results showed that compared with direct low value sales, the product income of mixed olefins catalytic cracking was 1.3 times of the original income.
    Study on adsorption and oxidation mechanisms of H2S in blast furnace gas on hydroxyl iron oxide
    Xudong LIU Yuran LI Shuwen PENG Li LIU Wenqing XU Tingyu ZHU
    The Chinese Journal of Process Engineering. 2024, 24(12):  1417-1424.  DOI: 10.12034/j.issn.1009-606X.224002
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    Precipitation method was used to prepare hydroxylated iron oxide (α-FeOOH) adsorbent to test its adsorption capacity for H2S using a fixed bed gas chromatography platform in this work. It was found that its sulfur capacity reached 63.8 mg/g, and the effects of O2 and H2O atmospheres on sulfur capacity were tested. It was found that there were optimal concentrations for O2 and H2O under the selected conditions, being 0.3vol% and 3vol%, respectively. The physicochemical properties of adsorbents and the occurrence forms of sulfur-containing components were characterized by XRD, XPS, TG, and CO2-TPD. It was found that the main sulfur-containing species were elemental sulfur and sulfate (SO42-) after α-FeOOH adsorbed H2S. The role of O2 in the reaction was analyzed by pre-adsorbing oxygen test. The adsorbed oxygen promoted the formation of sulfur elemental, while the presence of gaseous O2 increased the proportion of SO42-. In situ diffuse reflectance infrared spectroscopy showed the intermediate products adsorbed by H2S. H2S combined with the lattice oxygen or hydroxyl groups on α-FeOOH surface to generate HS-, and then HS- was further oxidized by Fe3+ with electron transfer to generate elemental sulfur, or HS- was oxidized by O2 to generate SO42-. This work provides a theoretical basis for the optimization of adsorbent preparation and the application of blast furnace gas purification technology.
    Effect of sulfur-containing flue gas on CO2 capture of MFM-136 and co-adsorption mechanism of flue gas components
    Li XU Na GENG Wen LIU Jinglei TIAN Tingyu ZHU Mingshui YAO Yangyang GUO
    The Chinese Journal of Process Engineering. 2024, 24(12):  1425-1434.  DOI: 10.12034/j.issn.1009-606X.224094
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    In the global transition towards a sustainable low-carbon economy, achieving a balance between high adsorption capacity and long-term stability of the adsorbent is crucial. In this study, MFM-136 with Kagome configuration was selected as the research object. The structure of MFM-136 was analyzed by XRD, BET, FT-IR, TG and SEM. The CO2 adsorption performance of MFM-136 was investigated by a series of gas adsorption experiments. The competitive adsorption relationship between impurity gas and CO2 was further identified by CO2 breakthrough experiment and in situ DRIFTS experiment, and revealed the co-adsorption mechanism of impurity gas and CO2 on MFM-136 surface. The adsorption experiment results showed that the adsorption capacity of MFM-136 for CO2 and H2O at 298 K was 3.0 and 11.94 mmol/g, respectively. The micro pore size (0.59 nm) of MFM-136 and the multiple adsorption sites in its skeleton enabled MFM-136 to selectively adsorption CO2 at room temperature. The adsorption selectivity of CO2/N2 reached 24 at 298 K, the Qst reached 23 kJ/mol, and the adsorption capacity was completely regenerated after degassing at 120℃ for 30 min. The results of breakthrough experiment and in situ DRIFTS experiment showed that the O2 promoted the chemisorption of CO2. The chemisorption of SO2 mainly occurs on the surface of the adsorbent to form sulfate and sulfite. Under O2-containing conditions, NO will react with O2 to form NO2, which will generate strong chemisorption on the surface of the adsorbent and generate corresponding nitrate and nitrite species. The water vapor not only promotes the chemical adsorption of CO2 and the production of bicarbonate, but also promotes the competitive adsorption between CO2 and SO2, NO.
    Study on gas phase oxidation of CO in flue gas catalyzed by steam
    Bin LIU Zhengyi TANG Jie GAO Yi CHUN Mengbo DAI Tiejun CHUN
    The Chinese Journal of Process Engineering. 2024, 24(12):  1435-1441.  DOI: 10.12034/j.issn.1009-606X.224028
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    The iron and steel industry, as one of the lifebloods of the national economy, has become a key focus of attention in the field of energy conservation and emission reduction as the goals of carbon peaking and carbon neutrality continue to advance. Iron ore sintering is the second largest carbon emission process in the iron and steel industry after blast furnace ironmaking. Existing studies indicate that steam injection onto the sintering bed surface can improve the fuel combustion efficiency of the sinter layer, increase the sintering index, and reduce CO emission concentration of flue gas. In this work, the mechanism of CO emission reduction by injection of steam onto the sintering bed surface was studied. The effect of steam on CO gas oxidation at high temperatures was studied by using a fixed bed experiment to simulate the injection steam onto the sintering bed surface. The results showed that the steam in the gas phase system can significantly promote the oxidation of CO. The gas phase oxidation of CO almost did not occur in the condition of no water vapor, and the steam promoted CO oxidation significantly when the volume fraction was above 2.0%. The CO oxidation reaction catalyzed by steam starts at 650℃, and the reaction accelerates with the increase of temperature. A stable and continuous reaction interval appears at 700℃ and above. With the volume fraction of steam increasing, the beginning time of CO gas phase oxidation was advanced and the duration was extended. Under the conditions of O2 and CO volume fractions of 2.0% and 2.5%, respectively, the steam volume fraction of 12.0% can promote the highest CO oxidation efficiency, and the CO oxidation efficiency can reach at 99.95%. The research was of great significance for improving the theory of steam injection technology on sinter surfaces and guiding production practice.
    The mechanism study on flotation of ilmenorutile based on Bayan Obo niobium-bearing minerals with 1-hydroxyoctane-1,1-bisphosphonic acid as collector
    Wei XU Min ZHANG Hongdong YU Fangfang CHEN Guan PENG Jing LI
    The Chinese Journal of Process Engineering. 2024, 24(12):  1442-1452.  DOI: 10.12034/j.issn.1009-606X.224116
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    This study proposed an improved method for synthesizing 1-hydroxyoctane-1,1-bisphosphonic acid (HOBA), and ilmenorutile (one of the important representative niobium-bearing minerals in Bayan Obo) was selected as the research object. Compared with octyl hydroxamic acid (OHA), the flotation mechanism of the synthetic ilmenorutile and HOBA is systematically investigated through contact angle, Zeta potential, FTIR, SEM-EDS, and XPS methods. The results show that under acidic conditions, HOBA can be chelated with ions on the surface of ilmenorutile and stably adsorbed on the surface of ilmenorutile through chemical adsorption, which could improve the floatability of ilmenorutile. Its selectivity for ilmenorutile was significantly better than that of OHA, well explaining the superior flotation results of HOBA over OHA for the actual niobium-bearing minerals in Bayan Obo. Solution chemistry calculation provided more information for the interaction of HOBA and ions on the surface of ilmenorutile in the flotation process, and the reasons for the inhibition effect of Ce3+ and the synergetic enhancement effect of Pb2+ in the interaction between HOBA and ilmenorutile were further discussed. This study indicates that HOBA can serve as an effective collector for ilmenorutile and other niobium-bearing minerals in Bayan Obo under appropriate pH range and ion conditions, and the optimization of its synthesis route provide the possibility for industrial application.
    Effect of alkali metal cation modulated supported cobalt catalyst on reductive amination
    Xiaobo HONG Zaiyin HUANG Qida DING Zeying LIU Hongyan WANG Xuecai TAN Yaofeng WANG
    The Chinese Journal of Process Engineering. 2024, 24(12):  1453-1465.  DOI: 10.12034/j.issn.1009-606X.224139
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    Benzylamine, with its diverse applications in medicine, pesticides, dyes and spices, has garnered the attention for its industrial significance. While benzylamine can be synthesized through the reductive amination of benzaldehyde, the catalysts employed are often complex and expensive. In this work, we report a series of alkali metal cation-modulated cobalt catalysts supported on silica (Co-M/SiO2) prepared via a simple impregnation method. The catalysts were evaluated for the reductive amination of benzaldehyde. Notably, the best catalyst Co-Na/SiO2 (Co2+:Na+=1:1.5),obtained the conversion of benzaldehyde to 100% and the selectivity of benzylamine to 94.6%. The doped catalyst increased benzylamine selectivity by 24.6 percentage points and decreased benzyl alcohol byproduct formation by 17.1 percentage points. Characterization of the catalysts (XRD, XPS, TEM, Raman, NH3-TPD, CO2-TPD, H2-TPD, TGA) provided insights into the structural and morphological properties of the catalysts. Results indicated that cobalt in the Co-Na/SiO2 catalyst primarily existed in the Co0 and CoOx form, and the addition of Na+ changed the binding energy of Co0 species in the catalyst through electron transfer. Moreover, the Co-Na/SiO2 catalyst offered a balanced distribution of acid-base sites and optimal hydrogen adsorption capacities, favoring the reductive amination. The in situ DRIFTS experiments were utilized to illustrate the differences between species adsorption abilities and reaction processes over Co-Na/SiO2 and Co/SiO2 catalysts. Results revealed that the Co-Na/SiO2 catalyst had a superior ability to reduce benzaldehyde amines to benzylamine compared to the Co/SiO2 catalyst, as it could inhibit the formation of benzyl alcohol byproduct. This work provides a cost-effective and highly active cobalt-based catalyst preparation strategy for reductive amination, paving the way for future research in designing efficient catalysts for this important transformation.
    Deep salt separation of zero discharge nanofiltration concentrate from steel industry wastewater
    Fengze CHEN Mengjie LUO Yuzhu SUN Hongjuan HOU Wenjun YU Jiajie YANG Wahepu TUXUN Chenxi KOU
    The Chinese Journal of Process Engineering. 2024, 24(12):  1466-1476.  DOI: 10.12034/j.issn.1009-606X.224123
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    Water, as an important natural resource, is an indispensable resource for human life and production. Industrial water usage accounts for a large proportion of the total water consumption in the country, with the steel industry being one of the water-intensive industrial processes. The production of steel from raw materials requires a large amount of water, so the full utilization of the wastewater generated in the steel industry process is of great practical significance. For the nanofiltration concentrated wastewater generated in the steelmaking process, selective electrodialysis can not only greatly remove Cl- to obtain water for slag flushing, but obtain a high-purity and concentrated NaCl solution. In this study, selective anion and cation exchange membranes are replaced in the membrane stack, with the anion exchange membrane playing a key role in the system by separating Cl- and SO42-. The effects of different operating modes, voltages, volume ratios, and temperatures on the separation efficiency of Cl- and SO42- are explored, and pilot-scale long-term verification experiments are conducted. The experimental results indicate that constant voltage operation mode is more suitable for deep separation of Cl- and stable membrane operation. Under different voltages, membranes exhibit a high SO42- rejection rate, exceeding 97%, and reduces Cl- concentration below 1000 mg/L in the diluted chamber, resulting in a mass ratio of SO42- to Cl- greater than 10. Pilot-scale selective electrodialysis operated under 20 V at room temperature for 2 months demonstrates that the selective electrodialysis method has strong adaptability to fluctuations in wastewater concentration. It can effectively remove Cl- ions, stabilizing the concentration of Cl- in the desalination chamber to below 1000 mg/L. The mass ratio of SO42- to Cl- exceeds 10 by far, achieving a sulfate retention rate of over 94.5%. The energy consumption remains relatively stable, ranging from 0.254 to 0.278 kW?h/kg NaCl.
    Effects of ambient wind speed and side-confinement on the flame spread behavior of wire combustion
    Meng ZHANG Xinjie HUANG Peng XU Hailong DING Shuaishuai WANG Changlong WANG Pengyuan ZHANG
    The Chinese Journal of Process Engineering. 2024, 24(12):  1477-1485.  DOI: 10.12034/j.issn.1009-606X.224095
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    In actuality, wire-confined combustion occurs frequently. Its fire threat is more likely to spread due to ambient wind speed. In this work, the flame spread behavior and characteristics of two types of polyethylene wires (the diameter of the copper core is 6 and 8 mm, respectively, and the thickness of the polyethylene insulation layer is 3 and 2 mm, respectively) under side-confined conditions (the side-confined distance is 10~40 mm) and horizontal wind speed (v=0.2, 0.5, and 0.8 m/s) are studied experimentally. The experimental results reveal that as the wind speed increases, the flame height gradually decreases, and the flame width grow first increases and then decreases. The side-confinement promotes wire burning, but as wind speed increases, this effect eventually weakens. When the horizontal wind speed is low, the heat transfer of the gas phase improves while the heat transmission of the solid phase is reduced. As wind speed increased, the heat transfer mode altered, and heat transfer between the gas and solid phases weakened. This is mostly due to the tilt effect of the flame, which increases thermal radiation and convection in the preheating zone. At the same time, because wind speed lowers the temperature of the gypsum board, the gypsum board's thermal radiation and convection are lowered as well. Furthermore, the horizontal wind alters the "heat source" and "cooling" effects of the copper core. The copper core's "cooling" effect grows as wind speed and diameter increase.
    Preparation and optimization of altrenogest self-microemulsion drug delivery system
    Yueli WANG Dongbo LI Chao LI Wei ZHANG Gang SHU Hao ZHANG Hualin FU
    The Chinese Journal of Process Engineering. 2024, 24(12):  1486-1496.  DOI: 10.12034/j.issn.1009-606X.223359
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    In order to improve the solubility and oral bioavailability of altrenogest in vivo, a self-microemulsion drug delivery system (ALT-SMEDDS) was developed and characterized. The study delved into the influencing factors and self-emulsifying mechanism of ALT-SMEDDS. Experimentation involved saturation solubility tests to discern the drug-carrying capacity of various excipients, while physical and chemical compatibility experiments were employed to ascertain the judicious compounding of these excipients. The formulation composition and the excipient dosage range of ALT-SMEDDS were systematically screened using pseudo ternary phase diagrams, and the effects of the ratio of oil phases and the mass ratio of emulsifiers to co-emulsifiers (Km) on the formation of self-microemulsions were also investigated. Further refinement of the formulation was achieved through the application of central composite design-response surface methodology (CCD-RSM). Through the regression model, and results of variance analysis, it was obtained that the self-emulsifying time was greatly affected by Km, which increased with the Km, while the average particle size was greatly affected by the oil phase, and which increased with the proportion of the oil phase. When the oil phase is ethyl oleate (22.0wt%), the surfactant was Tween80 (54.2wt%) and the co-surfactant was Transcutol HP (23.8wt%), ALT-SMEDDS exhibited a clear and transparent appearance with excellent flowability. The self-emulsifying time of ALT-SMEDDS was 35.76±1.10 s. The droplets displayed a rounded and homogeneous structure, devoid of adhesion. The average particle size of ALT-SMEDDSD was 18.39±0.03 nm, the PDI was 0.083±0.090, and the Zeta potential was -1.12±0.12 mV, indicating stability within the range of 10~1000 fold dilution. ALT-SMEDDS showcased an impressive cumulative release of 91.41% at 48 h in vitro, signifying a substantial improvement compared to the original drug release of 32.42%. With its reliable prescription, high emulsification efficiency, uniform microemulsion particle size distribution, and overall stability, ALT-SMEDDS emerges as a promising candidate for enhancing the in vitro release of ALT. This sets a solid foundation for the prospective clinical application of ALT-SMEDDS in improving the therapeutic efficacy of ALT.