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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select Particle-resolved simulation of typical packing structures in olefin catalytic cracking reactor Fei XU Feiguo CHEN Xiaoxing LIU Hao WU Bona LU Zhicheng LIU Jiawei TENG The Chinese Journal of Process Engineering    2021, 21 (12): 1419-1429.   DOI: 10.12034/j.issn.1009-606X.221006 Abstract （291）      PDF （4929KB）（73）       Knowledge map    Save Understanding the flow behaviors and pressure distribution in the interstitial void space among particles is of great importance for improving operating parameters of fixed bed chemical processes, like OCC (olefin catalytic cracking) process. Particle-resolved simulation method is extensively adopted in simulations of fixed bed reactors due to its ability of accurate describing fluid dynamics in packing structures, but its mesh generation process is rather difficult when the packing structure is complex. This study realized a particle-resolved simulation method of typical packing structures in the OCC fixed bed reactor through developing an immersed boundary method, which was based on the porous media model (PMM-IBM) and mesh adaption technology. This method simplified mesh generation process and reduces the computational cost. Compared to the uniform mesh, the total mesh number of the packing structure was reduced about 80% after the mesh adaption. The key parameters of the PMM-IBM were first determined by comparing the forces acting on the particle surface between PMM-IBM and body-fitted mesh method. Further, for three different bed-to-particle diameter ratios, the voidage, pressure and velocity distribution of the packing structures were simulated. It was found that the maximum local axial velocity in the packing structures was 10 times higher than the inlet velocity. The radial distribution of the average axial velocity was consistent with that of the average axial voidage, which showed an oscillation attenuation trend along the center of the bed. Moreover, the pressure drop was almost consistent with the results from Reichelt empirical correlation. Finally, the mass transfer and the main reaction of OCC were considered. The mass fraction variation of the reactant according to pore size and porosity was predicted, which provided the possibility for including the external flow structures and variations in future work. Related Articles | Metrics Select Numerical simulation of multi-stage side-blowing mixing characteristics in iron bath reactor Yibo HE Wenke GUO Yihong LI Guangming LIU Xin CUI The Chinese Journal of Process Engineering    2021, 21 (12): 1430-1439.   DOI: 10.12034/j.issn.1009-606X.221279 Abstract （207）      PDF （3822KB）（42）       Knowledge map    Save Based on the water model experiment of an iron bath smelting reduction reactor with thick slag layer, numerical simulation is taken out to study the stirring characteristics of the molten bath by double-layer side-blowing lance under different injection angles (40°, 45°, 50°) and different horizontal insertion depths (60, 120, 180 mm), and the accuracy of numerical simulation is verified by the results of water model experiment. By observing the flow field of the molten pool in the gas-liquid two-phase flow and the diffusion of the tracer, the proportion of the weak flow zone and the dead zone and the mixing time under different side-blowing conditions are analyzed, the results show that: the horizontal insertion angle of the side-blowing lance has a more significant influence on the stirring characteristics of the molten pool than the horizontal insertion depth. The horizontal injection angle and insertion depth of the side-blowing lance affect the swirling flow area and the number of swirling flows generated in the molten pool. When the horizontal injection angle of the side-blowing lance is larger and the horizontal insertion depth is deeper, the volume of the weak flow zone or the dead zone in the molten pool is smaller, which is more conducive to the stirring and mixing of the molten pool. The best injection conditions are obtained from the numerical simulation: the upper injection angle is 50°, the insertion depth is 60 mm, the lower injection angle is 50°, and the insertion depth is 120 mm. In addition, the mixing time of molten bath under different gas flow rates are also studied. It is obtained that the mixing time of molten bath is the shortest when the single gas flow rates of upper and lower lance are 8.58 and 10.43 Nm3/h, respectively. Related Articles | Metrics Select Uniformity of flow field in SCR denitrification reactor of cement kiln Xiaofei XU Yangyang GUO Hong GAO Xue WANG Tingyu ZHU The Chinese Journal of Process Engineering    2021, 21 (12): 1440-1450.   DOI: 10.12034/j.issn.1009-606X.220370 Abstract （211）      PDF （1228KB）（37）       Knowledge map    Save Fluent software was used to simulate the flow field in the selective catalytic reduction (SCR) denitrification reactor, based on the standard k-ε model, porous media model, material transport model, DPM model. A single gas phase flue gas was used to analyze the effects of different rectifying grids spacing, rectifying grid height, rectifying grid position and baffle number, baffle angle on the uniformity of the flue gas flow field. The influence of the smoke with different components in a single gas phase under the optimal scheme can be concluded. The gas verified under different loads, as well as different loads under DPM dual-phase coupling conditions. The results showed that the maximum incident angle was less than 90° from the absence of the rectification grid to the addition of the rectification grid, and the vortex above the catalyst disappeared. When the spacing of the rectifying grid was 107 mm, the height of the rectifying grid was 200 mm, and the rectifying position was flushed with the lower edge of the entrance, the velocity distribution deviation coefficient at 100 mm of the upper layer of the first catalyst layer reduced to 19%. When the number of baffles was 7, and the baffle angle was 18.2°, the most suitable situation, the velocity distribution deviation coefficient at 100 mm above the first layer of catalyst was 11.91%, and the maximum incident angle was 3.14°. When the flue gas with different components in a single gas phase and different loads were simulated under the best parameters, it met with the engineering requirements. Using DPM two-phase coupling, comparing the particles with a single gas phase under the Rosin-Rammler distribution condition, it was found that the average velocity at 100 mm above the first layer of catalyst increased to a certain extent, the velocity standard deviation had a small change, and the velocity distribution deviation coefficient was correspondingly reduced. Related Articles | Metrics Select Functional mechanism and performance of gas wave ejector feedback structure Yiming ZHAO Haoran LI Minghao LIU Dapeng HU The Chinese Journal of Process Engineering    2021, 21 (12): 1451-1462.   DOI: 10.12034/j.issn.1009-606X.221016 Abstract （279）      PDF （3998KB）（52）       Knowledge map    Save The gas wave ejector is a new type of dynamic equipment that uses gas pressure waves to realize the pressure energy exchange process. Because of high efficiency, simple structure and low energy consumption, the gas wave ejector has broad application prospects in many production processes.According to the working principle of this equipment, the reversed compression waves formed at the medium pressure port could result in a large decrease of the equipment performance or even lead to the loss of function at high medium backpressure. Therefore, a workable feedback structure was proposed in this work to optimize the performance of the gas wave ejector by avoiding the formation of redundant compression waves under high medium backpressure conditions. The functional mechanism and performance of this structure were studied in detail by numerical simulation and experimental methods. By means of numerical simulation, the functional mechanism of the feedback structure to weaken the reversed compression waves through pre-compression was demonstrated. Meanwhile, the effective and evaluating criteria of this structure were proposed by the results of numerical simulation. To ensure the efficient operation of this structure, the minimum pressure in the flow channel of the stable-pressure region should be less than the medium port backpressure. And the efficiency improvement of this structure was positively correlated with the average pressure difference in the flow channel of stable-pressure region with or without feedback structure. By the experimental methods, the correctness of the numerical simulation was verified, and the actual application consequence of the feedback structure was obtained. By the application of this feedback structure, the maximum lifting capacity of equipment efficiency and ejection rate could reach about 6.93% and 5.43%, respectively. The investigation results demonstrated that the feedback structure was easy to implement and supplied a positive application effect under high medium backpressure conditions, which proved its promising application value. Related Articles | Metrics Select Comparative study of fluid residence time distribution and flow pattern in baffle equipment Zhangfan GAO Muyi FAN Shaobei LIU Xiong ZOU Weixing HUANG The Chinese Journal of Process Engineering    2021, 21 (11): 1269-1276.   DOI: 10.12034/j.issn.1009-606X.220363 Abstract （389）      PDF （1447KB）（308）       Knowledge map    Save The flow pattern in the equipment can be the main performance index for its internal structure. Innovation of process equipment is to optimize its internal structure for desired flow pattern. Numerical simulation, as a primary research approach of fluid flow pattern, is not easy and economical to perform in large-scale or complex equipment, but the residence time distribution (RTD) experiment has the advantages of simplicity and convenience. In order to estimate the flow pattern with RTD experiments, taking the typical baffle structure as an example, several groups of structures were designed to compare and analyze the residence time distribution and the flow patterns corresponding to the structures, which can provide clues for short circuits judgement and determination of reasonable structures. The results showed that the short circuit and dead zone in the equipment were relativistic. The peak time and tailing of the RTD density function curve can be used to judge the short circuit and dead zone in the equipment. This conclusion can provide a theoretical basis for equipment design. The number of tanks in the multi-tank series model and the peak time and variance of the RTD curve were used to analyze the influence of flow rate, baffle gap area and plate spacing on the fluid flow pattern in the equipment. With the study of the pressure drop and the comprehensive consideration of the energy consumption and performance of the equipment, the most suitable tanks number, peak time and variance were put forward based on RTD experiments to determine the reasonable structure of the equipment, which provided a reference for the structural design of industrial baffle equipment. Related Articles | Metrics Select Numerical study on performances of a super vortex quick separation system at riser outlet under oil steam conditions Zhiliang ZHANG Haijun CHEN Tao CHEN Pei MOU Anjun LI Wenjun LI The Chinese Journal of Process Engineering    2021, 21 (11): 1277-1286.   DOI: 10.12034/j.issn.1009-606X.220408 Abstract （306）      PDF （2485KB）（111）       Knowledge map    Save In recent years, there are many reports on super vortex quick separation (SVQS) system using air instead of oil steam, but the performance parameters such as separation efficiency are not very accurate, moreover the influence of oil steam properties on the performance of the system has not been studied. In order to promote the industrial application of SVQS system and accurately evaluate its performance, the flow fields at a series of oil steam model with different densities and viscosities in a ?600 mm×4150 mm SVQS system were simulated by the commercial software FLUENT 2019 R3. The influences of oil steam properties on the dimensionless tangential velocity and pressure drop were studied respectively by single factor analysis. The distribution law of residence time of different oil steam in SVQS were analyzed by employing the scalar transport equation. The simulation result showed that the dimensionless tangential velocity of oil steam in SVQS increased as the density increasing or decreasing of viscosity and the maximum dimensionless tangential velocity can reach 0.912. Both density and viscosity had logarithmic function relations with the dimensionless maximum tangential velocity. The residence time of oil steam in SVQS reduced with the increasing of density of oil steam or the decrease of viscosity that the minimum average residence time was 6.279 s. It was found that the pressure drop and drag coefficient were not only affected by the structural parameters of the SVQS system, but also impacted by the viscosity of oil steam. Both pressure drop and drag coefficient had a logarithmic function relationship with the viscosity of oil steam. Meanwhile, the formulas of dimensionless tangential velocity, pressure drop and resistance coefficient related to oil steam parameters were obtained by fitting, which had good universality and can provide data for the structural optimization of SVQS system. Related Articles | Metrics Select Analysis of characteristics of liquid falling film flow on corrugated sheet packing Junhua LIAO Peng XUE Mengjing ZHAO Junjie LIU Ling JIN The Chinese Journal of Process Engineering    2021, 21 (11): 1287-1296.   DOI: 10.12034/j.issn.1009-606X.220422 Abstract （308）      PDF （8880KB）（159）       Knowledge map    Save The falling film flow characteristics of the liquid in corrugated sheet packing are the key factors affecting its mass transfer performance. In this work, a falling film flow experimental bench was built and combined with computational fluid dynamics to study the falling film flow of the corrugated sheet, the influence of spray density and corrugation tilt angle on flow characteristics was analyzed, and quantitative information of average liquid film thickness and the effective wetting area was obtained through three-dimensional simulation. The results showed that the three-dimensional CFD model can accurately predict the liquid falling film flow behavior and calculate the characteristic parameters. The flow of liquid on the corrugated sheet was not homogeneous but was classified as two kinds of forms: groove flow and rivulet flow. As the spray density was low, the liquid flow formed a groove flow in the trough while it changed as rivulet flow along the adjacent ripples when the spray density reached 400 m3/(m2?h), compared with channel flow, the rivulet form was more beneficial to increase the contact area of gas and liquid. However, no matter which flowed mode, the overall wettability of the corrugated sheet was poor, and the thickness distribution of the liquid film was not uniform, which was not conducive to mass transfer. The tilt angle of the corrugation had a greater influence on the flow characteristics of the falling film, after extensive research on the tilt angle, it was found that when the tilt angle was 90°, it was more conducive to increasing the effective wetting area and reducing the average liquid film thickness. The results of this study have theoretical guiding significance for controlling the liquid film thickness and increasing the effective wetting area during the falling film flow, and also have application value for improving the corrugated sheet structure and increasing the mass transfer efficiency. Related Articles | Metrics Select Simulation of gas-liquid two-phase flow and atomization characteristics of Y-type nozzle for heavy oil burner Zhiqi WANG Liuming CHEN Bingying XIAO Baoqi XIE The Chinese Journal of Process Engineering    2021, 21 (10): 1167-1176.   DOI: 10.12034/j.issn.1009-606X.220336 Abstract （334）      PDF （2034KB）（158）       Knowledge map    Save Heavy oil burner is the key component of asphalt mixing equipment. However, heavy oil is not easy to atomize due to its high viscosity and surface tension, which results in low combustion efficiency and high pollutant discharge in heavy oil burners. Y-type atomizing nozzle is widely used in heavy oil atomization because of its simple structure and wide adjustment range. A large number of experiments and simulations were carried out on the atomization characteristics of heavy oil. However, the existing research only analyzed the atomization characteristics from the aspects of structure or atomization parameters, ignoring the gas-liquid two-phase flow characteristics in the nozzle. Therefore, the research on the gas-liquid two-phase flow and atomization characteristics of Y-type atomizing nozzle has an important guiding role in the design of heavy oil burner. In order to improve the quality of heavy oil atomization, computational fluid dynamics software were used to explore the influence of nozzle structure parameters (mixing chamber length, inlet diameter ratio, angle between air and fuel inlet) and atomization parameters (mass flow rate of oil, air inlet pressure, temperature of oil) on the gas-liquid two-phase flow and heavy oil atomization characteristics of Y-type nozzle. The results showed that the structure parameters and atomization parameters directly affected the oil film thickness and gas-liquid two-phase velocity difference in the nozzle. Under different parameters, the change rule of gas-liquid rate and droplet Sauter mean diameter was opposite. Considering the two atomization performance indexes, the optimal length of mixing chamber was 15~20 mm, the reasonable range of inlet angle was 60°~75° and the optimal inlet diameter ratio was 1.0~1.1. In order to ensure the better atomization effect of heavy oil, the air inlet pressure should be greater than 0.5 MPa, the above parameters obtained by simulation provide guidance for the structure optimization design and operation parameter setting of Y-type nozzle. Related Articles | Metrics Select Influence of inlet dust concentration on characteristics of a new cyclone particle bed coupling separator Jinzhuang FU Ming CHANG Yiping FAN Chunxi LU The Chinese Journal of Process Engineering    2021, 21 (10): 1177-1186.   DOI: 10.12034/j.issn.1009-606X.220339 Abstract （290）      PDF （1212KB）（133）       Knowledge map    Save Nowadays, the production and combustion of fossil fuels make the emission of particulate pollutants increasing day by day. Researchers are actively developing new high efficiency dust removal separator to reduce the emission of pollutants. The studies on the separation technology of single cyclone separator and single particle bed filter are extensive but on the coupling separator of cyclone separator and particle bed are scarce. Therefore, the study of the cyclone particle bed coupling separator has broad application prospect. In order to investigate the influences of the inlet dust concentration on the pressure drop and the dust removal efficiency of a new cyclone-granular bed coupling separator, a large scale cold model experiment was carried out. The results showed that with an increase of the inlet dust concentration, the pressure drop of the separator tenders large and the speed of pressure drop increased rapidly when reaching an equilibrium state. The reason is that the inlet dust concentration increases, the dust in the built-in particle bed increases, the bed porosity decreases and the pressure drop increases. With the decrease of the inlet dust concentration, the separation efficiency of the separator increased. The dust content in the particle bed of the separator was also related to the regeneration efficiency. As the concentration of the regeneration dust source decreased, the time duration of the pressure drop reaching equilibrium became short. Furthermore, based on the experimental data, the empirical formula of separator pressure drop and regeneration dust source concentration was given. When the concentration of regeneration dust source reduced from 58.18% to 23.67%, the pressure drop reduced from 1.5 kPa to 1.2 kPa. With the decrease of the concentration of the regeneration dust source, the dust removal efficiency of the separator decreased slightly. The influence of inlet dust concentration and the regeneration dust source concentration on the pressure drop of separator coincided with each other, while the effect on the separator efficiency was different. Related Articles | Metrics Select Multi-scale CFD simulation of fluidization characteristics in a methanol-to-olefin fluidized bed Kun HONG Manqian CAO Wenxuan WANG Ya'nan GAO The Chinese Journal of Process Engineering    2021, 21 (9): 1012-1022.   DOI: 10.12034/j.issn.1009-606X.221187 Abstract （340）      PDF （2353KB）（222）       Knowledge map    Save In recent years, China has successfully developed coal-based methanol to olefins (MTO) production processes and technologies, which has promoted the rapid development of the coal-to-olefins industry and guaranteed national energy security. The fluidized bed reactor is the core reaction device for the industrial production of methanol to olefins. It is of great significance to deeply understand the fluidization characteristics of the MTO fluidized bed through computational fluid dynamics. It can give more accurate guide for optimization and amplification of MTO fluidized bed. In this work, the multi-scale computational fluid dynamics (CFD) method which is coupling of bubble-based EMMS drag and traditional TFM is adopted to perform 3D simulation of the multi-phase flow behavior inside an industrial-scale MTO fluidized bed. This multi-scale CFD method involves in the influence of the bubble-based structure on the gas-solid drag coefficient. Thus, it can more accurately predict the "S-shaped" distribution of the axial particle concentration inside the MTO fluidized bed, which is consistent with experimental data. The predicted radical distribution of particle concentration presents the classic "core-annulus" flow structure. The predicted distribution of the averaged gas/particle axial-velocity in the radial direction is also mutually confirmed with the actual situation. This multi-scale CFD method significantly improves the predictive ability of the traditional TFM based on uniform drag for the macroscopic flow field. In future, the focus will be put on extending this multi-scale CFD method to the optimization design and reaction characteristics of MTO fluidized bed. Related Articles | Metrics Select Simulation and experimental study of fluid flow in the bed of columnar particles in a tubular fixed bed reactor Zirui ZHU Xuedong LIU Liangxiong JIANG Yutong GU Tao PENG Junjie YIN Meihua LIU Wei JIANG The Chinese Journal of Process Engineering    2021, 21 (9): 1022-1032.   DOI: 10.12034/j.issn.1009-606X.220288 Abstract （416）      PDF （4564KB）（239）       Knowledge map    Save In view of the large number and large scale of tube bundles in the tubular fixed bed reactor, a single tube bundle was selected as the characteristic structure of the study. For the tube bundles filled with columnar particles of different diameters, the method of program coordinate positioning was adopted and the physical model of the columnar particle bed was established. DEM and CFD numerical simulation methods were used to explore the influence of the ratio of the inner diameter of the reaction tube to the equivalent surface area spherical equivalent diameter of columnar particles (Di/dp) on the fluid flow in the cylindrical particle bed. A single-tube fixed-bed reactor test device was established, and the differential pressure test method was used for experimental research. The results showed that when Di/dp increased from 5.37 to 12.75, the porosity of the bed and the uniformity of fluid distribution were improved, and the influence of the wall effect was weakened from the center of the bed to the tube wall. Based on the numerical simulation and experimental results, the bed pressure drop Ergun formula was corrected with constant coefficients for the columnar particle bed with Di/dp=12.75. The CFD simulation calculation results were in good agreement with the fitting formula. The research results provided guidance value for the design and application of fixed bed reactor. Related Articles | Metrics Select Influence of heat transfer coefficient of laminar cooling on metal materials temperature field Demin CHEN Yinghui LIU Biao LU Kai TANG Suojun WANG Guang CHEN The Chinese Journal of Process Engineering    2021, 21 (9): 1033-1041.   DOI: 10.12034/j.issn.1009-606X.220250 Abstract （311）      PDF （1035KB）（136）       Knowledge map    Save The cooling intensity of laminar cooling determines the microstructure of metal materials, thus affecting the performance of the product, while the heat transfer coefficient directly affects the cooling intensity. In this work, a method for obtaining the heat transfer coefficient of laminar cooling is presented. Through the process analysis, the distribution form of the heat transfer coefficient was a piecewise function which was composed of half wave sine and straight line with the nozzle as the center. The characteristic parameters of the piecewise function can be achieved by some calculations, which involved the structural parameters, operational parameters and experimental data. The experimental bench verified the accuracy of this method. The calculation results showed that when the amplitude is increased by 1 W/(m2?K), the relative decline of the metal material surface temperature reached maximum in the final area, which was -0.36 m2?K2/W, and the maximum relative change of section temperature difference was 0.07 m2?K2/W. When the period decreased by 1 s, the relative increment of surface temperature of metal materials reached the maximum value of 13.24 K/s in the last region, and the section temperature difference showed periodic changes with a range of -2.5~0 K/s. Related Articles | Metrics Select Analysis on gas-phase flow characteristics in multi-spiral gas-liquid vortex separator Peng ZUO Xiuying YAO Chunxi LU The Chinese Journal of Process Engineering    2021, 21 (9): 1042-1053.   DOI: 10.12034/j.issn.1009-606X.220277 Abstract （292）      PDF （2696KB）（121）       Knowledge map    Save In the Fischer-Tropsch synthesis process, light oil with high temperature is cooled to light oil droplets and non-condensing gas. Gas-liquid (or gas-droplet) separation and operation stability are directly related to both the stability and long period running of production process. Due to its structural complexity, fluid short circuit and wax jams, Fischer-Tropsch cycle heat exchanger is difficult to meet the industrial requirements. Hence, a multi-spiral gas-liquid vortex separator with simple structure, low pressure drop and big separation capacity was designed by drawing the super-vortex quick separator from gas-solids system. The CFD method was used to study the gas-phase flow field distribution characteristics in the MSGLVS. According to its structural characteristics and pressure distribution, the separator was divided into feed pipe zone, spiral arm zone, annular zone and separation zone. The simulation results showed that more than 60% of the total resistance loss of gas flow existed in the spiral arm. Discharged from the spiral arm, the gas was separated into three streams. One was upward counterclockwise gas along closure cover, another was corresponding downward gas and the others was upward clockwise gas in the region between spiral arm and feed pipe. Transverse vortices with zero axial velocity increased the pressure drop and liquid entrainment in the annular zone. The maximum tangential and axial gas velocities were kept at |r/R|=0.972 in the annular zone and the rotation angle of upward-flowing gas was always at 37.43° relative to the vertical direction, which demonstrated the good stability of separator. In the separation zone, there was a clear interface between upward and downward axial velocities. The tangential velocity conformed to the distribution of Rankine vortex along the radial direction, which was beneficial to the separation between gas and liquid phases. All tangential and axial velocities at different positions had a good linear relationship with the inlet gas velocity. The tangential velocities at |r/R|=0.893 (in the spiral arm zone) and 0.972 (in the annulus zone ) were most sensitive to inlet gas velocity. Related Articles | Metrics Select Multi-factor effects on and correlation of maximum spouting pressure drop in spout-fluid bed Shuang FU Dongxiang WANG Jianfeng YU Hai'an JIN The Chinese Journal of Process Engineering    2021, 21 (8): 918-925.   DOI: 10.12034/j.issn.1009-606X.220256 Abstract （368）   HTML （4）    PDF （2325KB）（114）       Knowledge map    Save The maximum spouting pressure drop (Δpm) is one of the important parameters for the design and operation of the spout-fluid bed. Almost all the literature correlations for predicting the Δpm were developed from single-component particles or spherical particles, and hence were with some limitation in actual application. In view of this, with binary particle mixtures, single-component spherical particles and non-spherical particles as experimental materials, the Δpm was studied based on a rectangular spout-fluid bed with cross section of 200 mm×20 mm, height of 1600 mm and conical base angle of 60°. The results showed that the Δpm increased with the static bed height, particle density, particle sphericity and deposition component ratio, and decreased with the fluidized gas velocity. While with the increase in particle size or spout nozzle size, it went down firstly and then up with a minimum pressure drop. For non-spherical particles and binary particle mixtures, the variation of total pressure drop with superficial spouting gas velocities was found to be similar with that of single-component spherical particles, while the fluctuation range of total pressure drop was larger under the same conditions. Based on the 854 sets of measured data by experiments, a predicting correlation of the Δpm was proposed by dimensional analysis method, which was in good agreement with the measured data in this work and the experimental data in literature. Related Articles | Metrics Select Numerical simulation of the effect of magnetic fiber diameter on trapping Fe-based fine particles Zhongjian JIA Yongfa DIAO Li′an ZHANG Minghao CHU Henggen SHEN The Chinese Journal of Process Engineering    2021, 21 (8): 926-934.   DOI: 10.12034/j.issn.1009-606X.220241 Abstract （263）   HTML （3）    PDF （2967KB）（94）       Knowledge map    Save In order to achieve ultra-low emissions of fine particles in the steel industry, magnetic fibers are proposed to improve the trapping efficiency of Fe-based fine particles. Based on CFD-DPM (Discrete Phase Model), the effect of traditional fiber and magnetic fiber diameter on the trapping efficiency of Fe-based fine particles and the filtration resistance of the fiber was studied. The results showed that there was no obvious difference in filtration resistance between magnetic fiber and traditional fiber. When the wind speed was 0.10 m/s, for fibers with a diameter in the range of 35~45 μm, the increase in diameter can significantly increase the filtration resistance. Traditional fibers had a low trapping efficiency for particles with a particle size of less than 2.5 μm. As the particle size increase, the trapping efficiency gradually increased. When the wind speed was in the range of 0.01~0.10 m/s, as the wind speed increased, the traditional fiber trapping efficiency decreased first and then increased. For the trapping efficiency of particles with a particle size of 4.5 μm, the traditional fiber diameter had an optimal range of 15~25 μm. For particles with a particle size of less than 2.5 μm, the increase in the diameter of the magnetic fiber had a relatively small effect on the improvement of the trapping efficiency. When the particle size was greater than 2.5 μm, increasing the fiber diameter can significantly improve the trapping efficiency. When the wind speed was in the range of 0.01~0.05 m/s, increasing the fiber diameter had a significant effect on improving the magnetic fiber trapping efficiency; when the wind speed was 0.08~0.10 m/s, the effect of the change in fiber diameter on the trapping efficiency was smaller. The quality factor of magnetic fiber decreased with the increase of fiber diameter. When the fiber diameter was in the range of 10~35 μm, the decreasing rate of the quality factor of increasing fiber diameter was small, and when the fiber diameter was in the range of 35~45 μm, the decreasing rate of quality factor was larger. Related Articles | Metrics Select CFD-PBM numerical simulation on the breakup and coalescence process of dispersed phase droplet in Kenics static mixer Zongyong WANG Liang WANG Huibo MENG The Chinese Journal of Process Engineering    2021, 21 (8): 935-943.   DOI: 10.12034/j.issn.1009-606X.220202 Abstract （363）   HTML （4）    PDF （1222KB）（184）       Knowledge map    Save CFD-PBM coupling method was used to numerically simulate the breakup and coalescence process of dispersed phase oil droplets in Kenics static mixer. The discrete method was used to solve the population balance model, aggregation kernel and breakage kernel adopt Luo model and turbulent model respectively. A mixture-multiphase model and a realizable k-ε turbulence model were also used. First, by comparing three different initial particle sizes, the influence of initial particle size of the droplet difference on the results was excluded, and the accuracy of the simulation results was verified by comparing with the experimental data. Secondly, the influence of parameters such as Reynolds number, element numbers and element aspect ratio on the particle size of the droplet was analyzed, and the evolution rule of the particle size of the droplet was revealed during the flow of dispersed phase in Kenics static mixer. The results showed that the particle size of the droplet at the outlet of the static mixer decreased with the increase of Reynolds number, and then the critical trend appeared. The particle size of the droplet decreased faster at the first few elements position of the static mixer. The higher the Reynolds number was, the shorter the flow distance required for oil droplets to break to achieve a stable particle size. The number of elements had a significant effect on particle size only at low Reynolds number. At the same Reynolds number, the smaller the aspect ratio was, the smaller the outlet the particle size of the droplet was, and the shorter the flow distance was required to achieve stability. It can be seen from the contour diagram that the change of rotation direction of elements and fluid separation action were the important reasons for droplet breakage. In addition, this can also explain why the smaller the aspect ratio was, the better the emulsification effect was. Related Articles | Metrics Select Numerical simulation of hollow catalyst with pores in gas-solid reaction system Qiuying WU, Lingkai KONG, Ji XU, Wei GE, Shaojun YUAN The Chinese Journal of Process Engineering    2021, 21 (7): 774-785.   DOI: 10.12034/j.issn.1009-606X.220229 Abstract （403）   HTML （14）    PDF （1654KB）（283）       Knowledge map    Save In the gas-solid flow, fluid and particle usually aggregate to form dense-phase and dilute-phase respectively, resulting in unbalanced mass transfer and reaction rates between the dense- and dilute-phase. The unbalance of dilute- and dense-phase reduces the overall efficiency of the reactor. To solve this problem, a hollow catalyst particle with pores structure is designed. It is aimed to enhance the overall efficiency of fluidized reactors by improving the mass transfer rate between the dense- and dilute-phase. Dense- and dilute-phase are widely distributed during fluidization processes, which can be respectively described by the cluster system and single particle system. In these two phases, the flow, reaction process and mass transfer process of hollow porous particles are studied by numerical simulation, and compared with the solid spherical particle system at the same fluidization condition. Then, the frequency of particle clusters formation and breakage is studied under various fluidization conditions. The time scale is analyzed to measure the possibility of gas transport in the fluidization process. It is found that the time-scales of the mass transfer, the reaction, and the movements of particles between the dilute- and dense-phase could be at the same order for some fluidization conditions. Thus, hollow porous catalyst particle can store the reacting material in the dilute-phase efficiently. When moving to the dense phase, the particle would release the reacting material to provide additional material for the dense-phase reaction. When the reaction is faster than the mass transfer, the overall reaction rate of the hollow porous catalyst system is 26.92%~29.55% higher than that of the solid spherical catalyst system at the studied conditions. It could be predicted that this hollow porous catalyst would be capable to improve the overall reaction efficiency of large gas-solid fluidized bed reactors due to wider distributions of the dilute- and dense-phase. Table and Figures | Reference | Related Articles | Metrics Select Research on internal structure optimization and energy storage characteristics of electric water heater Li WU, Jie HE, Jinli LU, Yafang HAN, Ze HONG The Chinese Journal of Process Engineering    2021, 21 (7): 786-793.   DOI: 10.12034/j.issn.1009-606X.220206 Abstract （364）   HTML （5）    PDF （1073KB）（134）       Knowledge map    Save The energy consumption of electric water heater in China has a large proportion of total energy consumption. Therefore, it is of great significance to optimize the energy consumption process of electric water heater. The phase change materials (PCM) have the characteristics of high energy storage density and approximately constant temperature in the process of phase transition. In addition, the thermal conductivity of phase change materials can be enhanced by adding nanometer materials such as graphite. Therefore, it has obvious advantages in heat energy storage and utilization of phase change materials. So, the phase change energy storage technology can be applied to electric water heater to adjust the energy storage process and the goal of "peak shifting" also can be achieved. In this work, the energy storage characteristic of energy storage water heater with phase change material were researched employing numerical simulation method. Four different structural models were established and the influent of inlet and outlet piping construction, electric heating tube arrangement, insulation structure on flow and heat transfer characteristics of water in water heater were discussed. And the influence of energy storage layer thickness on energy storage of electric water heater were researched. The results showed that, compared with the vertical heating tube, the water temperature distribution of horizontal heating tube was more uniform during heating process, and the heating efficiency was improved by about 2.2%. When the inlet tube diameter increased to 1.5 times, the output status of hot water can be excellent improved, and the hot water output efficiency can be increased 17.9%. The addition of phase change materials can increase the water temperature by 10.6% under the condition of same heat preservation time (36 h). The results of this study can provide data support for structural optimization of electric water heater and application of phase change energy storage technology. Table and Figures | Reference | Related Articles | Metrics Select A correlation model of drag coefficient for bubbles/droplets in a wide Reynolds number range Shenggao GONG Ningning GAO Lelin ZENG Anwu LI Xiaoyu LIU Qing TANG Laibing LI The Chinese Journal of Process Engineering    2021, 21 (6): 649-657.   DOI: 10.12034/j.issn.1009-606X.220166 Abstract （375）      PDF （483KB）（121）       Knowledge map    Save It is of great significance to predict the drag coefficient CD and the rising velocity of fluid particles (i.e. bubbles or droplets) accurately because they are helpful to estimate the phase holdup distribution, liquid phase velocity distribution, fluid particle residual time and mass transfer rate in the reactor. However, most of the correlations in the literature to estimate CD are piecewise, only valid in the low Reynolds number (Re) range and difficult to be extended to different experimental systems. In the view of these shortcomings, based on the experimental and theoretical results, this work proposed a new mathematical correlation model which can describe CD evolution observed by experiments in a wide Re range, and complied a program to solve the multi-dimensional unconstrained linear optimization problem to determine the model parameters. The new fluid particle CD correlation showed a good prediction ability and reasonably predicted the fluid particle CD value measured by different researchers under different experimental systems (e.g. air?water, air?glycerol, air?glycerol?water, n-butanol?water, n-octanol?water, toluene?water etc.) and different operating conditions (e.g. bubble: 0.1<Re<104, 10?11<Mo<7; droplet: 5<Re<2000, 10?11 <Mo<10?6). In addition, the rising velocities of fluid particles were predicted by combining the new fluid particle CD correlation and single fluid particle motion equation. The predicted terminal velocity and rising velocity of fluid particles also were consistent with the results of different experimental systems. The above predictions presented that the new CD correlation model was universal, reasonable and reliable to some extent. Related Articles | Metrics Select Numerical simulation on fluid flow past a circular heterogeneous porous particle Chunyu WANG Chenggong LI Mao YE The Chinese Journal of Process Engineering    2021, 21 (6): 658-670.   DOI: 10.12034/j.issn.1009-606X.220213 Abstract （260）      PDF （1488KB）（127）       Knowledge map    Save The two-phase flow of porous particles widely exists in industrial processes. However, the internal structure of most porous particles is heterogeneous, which has been homogenized in previous studies and may affect the interaction between the particle and the fluid. Therefore, the volume-average macroscopic control equation based on the intrinsic phase average velocity was used to describe the fluid flow inside and outside the porous particles. Then, an improved lattice Boltzmann method (LBM) was used to solve the macroscopic control equation. Two-dimensional fluid flow around and through a heterogeneous porous particle was simulated numerically. By introducing difficult-to-permeable regions to adjust the internal porosity of porous particle, the effect of heterogeneity on the force of particle and evolution of flow field was simulated. The results showed that the heterogeneous structure could induce the lift force of the particle and realize the longitudinal mass transfer inside the particle compared to the homogeneous porous particle. Moreover, both the lift force and the mass transfer strength increased with the increase of the hard-to-penetrate area and Da number due to the asymmetric interaction between the particle and the fluid, but showed a peak value with Da number increasing to sufficiently large, mainly because of the effect of the internal structure diminished as the great quantity of fluids through the particle. On account of the lift force and mass transfer in the longitudinal, the presence of the hard-to-penetrate area also generated the wake vortex behind the particle to no longer be symmetrically distributed at a lower Re number, and to fall off at the Re number around 38, which enhanced the intensity of the disturbance of the flow field. In general, the existence of heterogeneous structure inside particle has an important influence on the force of the particle-fluid system and the evolution of the flow field, which is worth considering in future research. Related Articles | Metrics Select Effect of winglet pair geometry parameters on fluid flow characteristic in helical channels with semicircular cross section Yaxia LI Xiaohang SHI Jing ZHANG Li ZHANG Bin GONG Jianhua WU The Chinese Journal of Process Engineering    2021, 21 (6): 671-679.   DOI: 10.12034/j.issn.1009-606X.220224 Abstract （246）      PDF （2252KB）（110）       Knowledge map    Save Experimental and numerical methods have been employed to study the influence of winglet pair geometry parameters on fluid flow and vortices characteristics in helical channels with semicircular cross section. The curvature ratios of helical channels are within the range of δ=0.05~0.125. Simulated data of three dimensional velocities have good agreements with those obtained by Laser Doppler velocimeter when δ=0.067. The results showed that the longitudinal vortices induced by the wing pair developed spirally along the main flow and strengthened the vortices produced by centrifugal force to a certain extent. The larger the Reynolds number was, the closer of the vortices were to the centerline of the cross section. There may be additional vortices in the range of 7.09~13.04 times of wing height behind the winglet pair when δ≥0.1. The value of La/b was used to indicate the occurrence position of the additional vortices. La/b value increased with the increasing of Reynolds number and the aspect ratio of the winglet, but it decreased with the increasing of curvature ratio and attack angle. As curvature ratio and the aspect ratio of the wing increasing, the strength of the combined longitudinal vortices would be enhanced and the affecting range of combined vortices in the helical channel became larger at the same time. The maximum strength of the combined longitudinal vortices was 6.48 times that of the smooth helical duct in the studied range. The longest affecting range of combined vortices reached the length of about 20 times the wing height in the helical channel. The aspect ratio of the wing and dimensionless thickness had significant impacts on flow resistance. Related Articles | Metrics Select Research on mathematical modeling of particle classification process based on vertical mill separator Penghao GENG Yanxin CHEN Yanfei YAO Bo ZHAO Ding HAN The Chinese Journal of Process Engineering    2021, 21 (6): 680-686.   DOI: 10.12034/j.issn.1009-606X.220161 Abstract （367）      PDF （791KB）（71）       Knowledge map    Save In this work, the experiment was carried out through the pilot test platform for vertical mill, and the change rule of the classification performance of the classifier under different system air volumes and classifier speeds were compared and analyzed. The cumulative distribution function of the normal distribution was used to correlate the operating parameters of the classifier with the collection probability of particles of different particle sizes. The test data of the system air volume and the speed change condition of the powder separator were used to fit the mean and variance in the model. A mathematical model can be established to quantitatively analyze the relationship between the system air volume, the speed of the separator and the particle classification efficiency. The fitted standard deviation of the verified regression was RMSE=0.0046, the deviation between the predicted value and the true value was small, and the coefficient of determination R-square=0.9863, which was close to 1, the model had higher credibility. Under the conditions of known system air volume and separator speed, the model prediction curve of the classification efficiency of the separator basically coincided with the test curve, and the model prediction effect was good. Related Articles | Metrics Select Effect of slag nails on heat transfer of water-cooled gasifier Ying XIA Haoyong KAN Hui FAN Ping LI The Chinese Journal of Process Engineering    2021, 21 (6): 687-694.   DOI: 10.12034/j.issn.1009-606X.220220 Abstract （302）      PDF （857KB）（162）       Knowledge map    Save The water-cooled wall of the gasifier plays an important role in maintaining the safe and stable operation of the gasifier under high temperature and pressure. The ANSYS software was used to simulate the temperature distribution on the inner wall surface of the water-cooled wall. The effects of three conditions including slag nails, no slag nails, and replacement of slag nails by gills of equal area on the heat transfer process were investigated. The influence of the arrangement of nails on the temperature of water-cooled wall was researched. The results showed that the slag nails can effectively improve the heat transfer efficiency and take away the excess heat in the gasifier in time. The slag nails with a small angle and a triangular arrangement had better heat transfer efficiency and more uniform temperature distribution. This simulation calculation was significant for the design of heat transfer structure and long-term safe operation of water-cooled wall gasifier. Related Articles | Metrics Select Comparison and study on the flocculation effect of peppermint water-extraction solution by different folded-plate flocculators Ying FENG Qingjin ZHANG Jianwei ZHANG Tianyang ZHANG The Chinese Journal of Process Engineering    2021, 21 (6): 695-703.   DOI: 10.12034/j.issn.1009-606X.220186 Abstract （236）      PDF （1047KB）（66）       Knowledge map    Save As a part of the excellent culture of the Chinese nation, traditional Chinese medicine have been favored by more and more people in recent years due to its high safety and low side effects. At present, most of the researches on impurity removal of traditional Chinese medicine by flocculation were based on the flocculation operating conditions, such as flocculation temperature, pH value of the traditional Chinese medicine solution and different flocculants. In order to optimize the structure of the folded-plate flocculator and enhance the flocculation effect of the Chinese medicine liquid. Vortex distribution and vorticity in the flow field of the same wave folded-plate flocculator and the opposite wave folded-plate flocculator were simulated and analyzed by FLUENT. Taking the peppermint water-extraction solution as the research object, using chitosan as a flocculant, flocculating the peppermint water-extraction solution by different folded-plate flocculators, let clear layer height, sedimentation velocity, total flavonoid retention rate, flocculation rate, absorbance and fractal dimension of flocs index, the influence of different inlet flow rates on flocculation for the effect of flocculant by different folded-plate flocculators were discussed. Results showed that the vortex positions of the same wave folded-plate flocculator were respectively unilateral vortex, and the vortex position of the opposite wave folded-plate was distributed on the two sides of the folded plate, under the same inlet flow rate, the vorticity generated by the same wave folded-plate flocculator was smaller than that of the opposite wave folded-plate flocculator. The flocculation effect of the same wave and the opposite wave folded-plate flocculator on the mint water extract showed a trend of first increasing and then decreasing, the optimal flocculation inlet flow rate of the same wave folded-plate flocculator was 0.068 m/s, the total flavonoid retention rate of the peppermint water-extraction solution was 91.2% , the flocculation rate was 85.3%, the optimal flocculation inlet flow rate of the opposite wave folded-plate flocculator was 0.051 m/s, the total flavonoid retention rate of the peppermint water-extraction solution was 91.8%, the flocculation rate was 85.4%. Related Articles | Metrics Select Staged injection and aerodynamic characteristics of staggered lobe nozzles in aeroengine combustor Lijun WANG Kuo MEN Yijun XU The Chinese Journal of Process Engineering    2021, 21 (5): 506-515.   DOI: 10.12034/j.issn.1009-606X.220057 Abstract （311）      PDF （3076KB）（119）       Knowledge map    Save A 13 lobe nozzles with a 5×5 fork row aero-engine staged combustion chamber water model test bench was set up to achieve different working loads by changing the staged injection mode of each nozzle. The aerodynamic flow field characteristics of the model combustion chamber under two kinds of loads, such as 30% and cruise, were studied by water simulation tracer experiments and mathematical modeling under the two-stage and three-stage combustion organization modes. The aerodynamic characteristics of complex vortex structure and vorticity induced by each level of flap nozzle in size, shape, interaction and evolution were studied by experiments and numerical simulation for the two fractional combustions when the oil and gas ratio under the two loads was changed. The results showed that the vortex structure of the two kinds of staged injection modes can be divided into initial section, transition section and development section. The vortex systems have undergone evolution and interaction from independence to merger and reorganization, and then evolve into new vortex systems. When the oil?gas ratio increased, it had a greater impact on the transition of the two kinds of staged injections. The calculation results of the air and water model flow fields were consistent with the experimental results, which verified the feasibility and credibility of the research results. Related Articles | Metrics Select Numerical simulation of dust-cleaning performance of new structure microporous membrane filter plate Zhe LIU Lumin CHEN Fuping QIAN Mengmeng YE Min WEI Yunlong HAN Jinli LU The Chinese Journal of Process Engineering    2021, 21 (5): 516-529.   DOI: 10.12034/j.issn.1009-606X.220126 Abstract （283）      PDF （1374KB）（131）       Knowledge map    Save In order to explore the influence of different factors on the dust-cleaning performance of the new structure microporous membrane filter plate used in the rotary pulse-jet cleaning microporous membrane dust collector, the CFD method was used to simulate the flow field of pulse-jet cleaning, and the accuracy of the numerical calculation model was verified by comparing with the experimental data in the literature. On this basis, the influence of pulse-jet pressure, pulse-jet distance, diameter ratio of the end to the inlet of the injection pipe, nozzle diameter, and length of filter plate on the average peak pressure of the wall surface of the new structure filter plate were studied, and the law of the change of the side pressure of filter plate with the pulse-jet time was explored. At the same time, a five-factor three-level orthogonal test was designed, and the average peak pressure of the filter plate was used as the design index to analyze and obtain the best pulse-jet cleaning system parameters. The results showed that the average peak pressure of the filter plate can be increased by increasing the pulse-jet pressure, the nozzle diameter and reducing the diameter ratio of the end to the inlet of the injection pipe, which was beneficial to improve the dust-cleaning performance of the new structure microporous membrane filter plate. The pulse-jet distance had little effect on the average peak pressure of the filter plate wall, but increasing the pulse-jet distance can effectively reduce the size of the negative pressure at the top of the filter plate, the reduction of the negative pressure on the top of the filter plate was beneficial to increase the service life of the microporous membrane filter plate. The side pressure of the filter plate changed with the pulse-jet time, making the filter plate at different times. The pressure distribution of the side wall was different. With the increase of the length of the filter plate, it had a negative impact on the dust-cleaning effect of the middle and lower part of the new structure microporous membrane filter plate. Related Articles | Metrics Select Performance analysis of dimpled tube based on skewness and kurtosis Wenling LIAO The Chinese Journal of Process Engineering    2021, 21 (5): 530-540.   DOI: 10.12034/j.issn.1009-606X.220101 Abstract （283）      PDF （3488KB）（137）       Knowledge map    Save In this work, the numerical simulation model of the hexagonal tube with different parameter dimples has been established considering thermal-hydraulic performance. The effect of dimple types, dimple depth, and dimple diameter on the flow field characteristics, and heat transfer characteristics of dimple tubes were discussed under Reynolds numbers between 5000 and 40000. Skewness and kurtosis of dimpled tube wall surface were calculated by discrete method, and then the thermal-hydraulic performance of dimpled tube was analyzed based on the influence of dimple parameters on skewness and kurtosis. The results showed that the dimpled tube had a better thermal-hydraulic performance due to the recirculation flows and flow separation was a significant increase, and the effect of pit dimple was better than that of bulge dimple. In addition, the influence of different dimple types was that the less the skewness, the better the thermal-hydraulic performance of the heat transfer tube. However, for the pit dimple tube, the larger skewness and the smaller the kurtosis was, the better comprehensive performance of the thermal-hydraulic got. With the increase of the pit dimple depth and diameter, the skewness gradually increased, while the kurtosis value gradually decreased. Related Articles | Metrics Select Numerical simulation of influence of fiber layers with different arrangement structures on performance of PM2.5 capture Minghao CHU Yongfa DIAO Li'an ZHANG Jiawei ZHUANG The Chinese Journal of Process Engineering    2021, 21 (5): 541-549.   DOI: 10.12034/j.issn.1009-606X.220152 Abstract （270）      PDF （2411KB）（125）       Knowledge map    Save Based on the discrete phase model, the trapping performance of fiber layers with different arrangement structures under two trapping mechanisms of interception and inertial impaction was simulated by numerical simulation method. The effects of particle diameter, inlet velocity and fiber layer filling rate on the trapping performance of fiber layers with different arrangement structures were analyzed. The results showed that large particle size particles with inertial impaction as the main trapping mechanism were more easily affected by the arrangement structure of fiber layers. The vertical arrangement structure effectively improved the trapping performance of large particle size particles by fiber layers, and the trapping performance showed a trend of increasing first and then decreased with the increase of particle diameter. The trapping efficiency of fiber layers with different arrangement structures for large particle size increased with the increase of inlet velocity. The trapping efficiency of fiber layers with single-layer vertical arrangement structure was higher than that of the other two arrangement structures, and its trapping performance decreased with the increase of inlet velocity. The trapping efficiency of fiber layers with different arrangement structures increased with the increase of filling rate, while the trapping performance decreased with the increase of filling rate. Compared with the fiber layers with the three arrangement structures, under the conditions of low filling rate and low inlet velocity, the single-layer vertical arrangement structure fiber layer had the most obvious improvement in the trapping performance of large particle size particles. The single-layer vertical arrangement structure fiber layer had the highest trapping rate for particulate matter. Related Articles | Metrics Select Effect of area ratio of variable cross-section dividing manifolds on performance of fluid distribution in high Reynolds number Honggang YANG Nan WANG Yi WANG Lei YAO Xiaofan CAI The Chinese Journal of Process Engineering    2021, 21 (5): 550-557.   DOI: 10.12034/j.issn.1009-606X.220393 Abstract （303）      PDF （736KB）（122）       Knowledge map    Save As a fluid distribution device, the dividing manifold is widely used in engineering systems such as air supply ducts, heat exchangers, and large bag filters. The flow distribution uniformity of the dividing manifold directly affects the overall performance of the system. A geometric model of dividing manifold was proposed to prevent dust accumulating with consideration of the problem of preventing dust and particles from accumulating in dust-containing airflow in practical engineering. With the aim of providing theoretical guidance and basis for the design of shunt manifold, the numerical simulation study on the fluid distribution performance of dividing manifolds with different main pipe shapes and area ratios was carried out to obtain the optimal flow distribution uniformity of the dividing manifold. The effects of Re, main pipe shape and area ratio (AR) on the flow distribution performance of the dividing manifold were analyzed. The results showed that at high Reynolds number, the flow distribution uniformity of dividing manifold was hardly affected by the inlet Reynolds number. When the inlet Reynolds number and area ratio remained unchanged, the flow distribution uniformity of the manifold with a triangular main pipe shape was obviously better than that of the other two main pipe shapes. As the increase of area ratio of the dividing manifold, the flow distribution uniformity index U of the dividing manifold generally decreased. When the area ratio was greater than 1.0, the flow distribution uniformity of all dividing manifolds was decreased. When the area ratio was between 0.8 and 1.0, the flow distribution uniformity index of dividing manifold did not change significantly. Related Articles | Metrics Select Analysis and evaluation of oil-water two-phase centrifugal separation performance in horizontal pipe Lei XING Minghu JIANG Lixin ZHAO Yi QIAO Guoxin HAN The Chinese Journal of Process Engineering    2021, 21 (5): 558-566.   DOI: 10.12034/j.issn.1009-606X.221002 Abstract （242）      PDF （3454KB）（105）       Knowledge map    Save The particle image velocimetry technology, separation performance experiment and numerical simulation methods of separation performance were applied to analyze the separation performance of three kinds of hydrocyclones. The method for evaluating the performance of oil?water two-phase separation in a horizontal circular pipe was established. The results showed that the helix separator and the diversion vane separator can form axial reflux in a axial central region of the flow field, and there were different locus of zero vertical velocity in the two structures. When the inlet Reynolds number was 6.68×104, although the diversion vane separator formed a rotating flow with the maximum tangential velocity, the attenuation rate of tangential velocity was also the largest, and the value of maximum tangential velocity attenuation rate within the 500 mm length was 94.05%. The oil core formed by the helix separator had a better degree of aggregation with the maximum oil volume fraction at the axis of the pipe. In order to quantitatively evaluate the performance of separators with different structures, the calculation method of oil?water separation efficiency in circular pipe was established by taking the concentration of oil core and the extension length of oil core in the pipe. By comparing the separation efficiency of the three structures under different Reynolds numbers, the helix separator showed the best separation performance. When the inlet Reynolds number increased in the range of 4.14×104~10.7×104, the oil?water separation efficiency of the helix separator increased from 16.6% to 82.1%, which was higher than those of the other two structures. The evaluation results of oil?water separation efficiency showed the consistent regularity as the experimental results, which verified the accuracy of the proposed separation efficiency evaluation method. Related Articles | Metrics Select Effect of aerator arrangement on aeration performance in oxidation ditch Xiaofei XU Wenze WEI Xin DONG Fengxia LIU Wei WEI Zhijun LIU Chin. J. Process Eng.    2021, 21 (4): 394-400.   DOI: 10.12034/j.issn.1009-606X.220123 Abstract （303）      PDF （1115KB）（129）       Knowledge map    Save The experimental study of oxygen transfer performance of clean water and activated sludge mixed liquor in a pilot-scale oxidation ditch of microporous aeration had been carried out. The effect of different aerator arrangement modes (cross, abreast and centralized) on oxygen transfer efficiency were investigated in the experiment. Moreover, the standard oxygen transfer efficiency (SOTE) and oxygen transfer efficiency (OTE) were used as parameters of oxygen transfer performance in the clean water and activated sludge mixed liquor, respectively. The results showed that the oxygen transfer efficiency was affected by the aerator arrangement mode significantly, and the oxygen transfer performances between clean water and activated sludge mixed liquor were different. The oxygen transfer efficiency under the cross aerator arrangement mode was the highest, the abreast aerator arrangement mode was the second, and the centralized aerator arrangement mode was the lowest. In the activated sludge mixed liquor, when the DO concentration was between 1.3 mg/L and 1.7 mg/L, the oxygen consumption of nitrogen removal in different aerator arrangement modes was almost the same. However, the aerator arrangement mode had greater impact on oxygen consumption of COD removal. Compared to the SOTE in the clean water, the OTE in the activated sludge mixed liquor was lower, and the OTE was about 85% of SOTE. Moreover, the OTE was less affected by the aerator arrangement mode than SOTE. To evaluate the aeration performance in the activated sludge mixed liquor, the ratio Z (OTE/SOTE) of oxygen transfer efficiency between the activated sludge mixed liquor and clean water was introduced. Contrary to the regularity of oxygen transfer efficiency under different aerator arrangement modes, the OTE/SOTE was the largest in the centralized aerator arrangement mode and the smallest in the cross aerator arrangement modes. The OTE and SOTE was close under the aerator arrangement mode of low oxygen transfer efficiency. Related Articles | Metrics Select Effect of arrangement of multiple groups of twisted slices on product yield in ethylene cracking furnace Xingchen HE Juan WANG Jia ZHANG Jiayi WAN Jiangyun WANG Yu MAO Chin. J. Process Eng.    2021, 21 (4): 401-409.   DOI: 10.12034/j.issn.1009-606X.220082 Abstract （262）      PDF （1359KB）（92）       Knowledge map    Save The production of ethylene by cracking furnace is the most commonly used method in industrial and furnace tube is the main place where cracking reactions occur. The internal components of the twisted slices are added to furnace tube and the purpose is to improve the coupling between the flow field and the temperature gradient field, so as to enhance the heat exchange of the fluid and to promote the increase of products in the cracking reaction. U-shaped tube of ultra-selective cracking furnace was selected as the research object, based on naphtha cracking raw material. The furnace tubes were built into different multiple groups of twisted slices for numerical simulation to obtain the temperature distribution and the mass fraction distribution of ethylene and other products. Simulation results showed that the twisted slices can effectively reduce the temperature gradient between the tube wall and the core fluid, and the heat exchange effect of the furnace tube with 3 groups of twisted slices placed in the outlet section was the best. The yield of ethylene and butadiene in the furnace tube increased linearly along the axial distance, while the yield of propylene decreased at the exit stage in the later period of reaction. The L2R3-type tube with two twisted slices placed in the inlet section and three twisted slices placed in the outlet section had higher yield of triene, which was 1.29 times that of the smooth tube. Related Articles | Metrics Select Influence of scrap on bath flow characteristics of converter Xiaobin ZHOU Shiheng PENG Yong LIU Duogang WANG Chin. J. Process Eng.    2021, 21 (4): 410-419.   DOI: 10.12034/j.issn.1009-606X.220131 Abstract （290）      PDF （1134KB）（132）       Knowledge map    Save The current study focus on the flow characteristics and the effects of scrap on the bath flow with the help of mathematical model which is built based on the physical model of a 250 t converter. The results showed that the mixing time was a decreasing function of the flow rate of bottom blowing when the flow rate was relatively low (<40 L/min). On the contrary, excessive high flow rate of the bottom blowing would not contribute on the decreasing of the mixing time which demonstrated that increasing flow rate was not favorable for decreasing the mixing time if the flow rate was higher than the critical value. With increasing the scrap volume, the plume formed in the bottom blowing moved towards to the bath wall. Meanwhile, the maximum velocity of the plume increased from 0.24 m/s to 0.40 m/s when the bottom flow rate was 50 L/min compared to the flow rate of 15 L/min. The kinetic energy of the bath was increased while the volume ratio of the low-velocity zone was decreased when the scrap volume increased. The volume ratio of the low-velocity zone can be decreased 89.46% when 40 t scrap was added into the bath compared to that of no scrap addition. Specifically, compared to that of 15 L/min when 60 t scrap was added, the transfer indexes decreased 2.98%, 6.27% and 8.68% when the bottom flow rate increased to 25, 40 and 50 L /min, respectively. The effects of the scrap volume on the energy transfer index was also investigated and the results showed that increasing the scrap volume was benefit to increase the energy transfer index for the bath and large volume of the scrap greatly increased the energy transfer index. When the bottom flow rate was 25 L/min, the energy transfer index increased 2.48% and 41.41% when the scrap volume increased to 10 and 60 t, respectively. Related Articles | Metrics Select Experimental study on pressure drop characteristics and minimum fluidization velocity of gas-solid micro-fluidized bed Yaqi SHI Yanjun LI Yupeng DU Wanzhong REN Chin. J. Process Eng.    2021, 21 (4): 420-430.   DOI: 10.12034/j.issn.1009-606X.220332 Abstract （388）      PDF （634KB）（216）       Knowledge map    Save The fluidization characteristics of Geldart group A and Geldart group B particles were investigated in four gas?solid micro fluidized beds with different inner diameters ranging from 3 to 20 mm, respectively. At the same time, the variation rules of the minimum fluidization velocity affected by some important factors, such as bed geometry, operating conditions and physical-phase properties were studied. The result showed that the bed pressure drop characteristics in the gas?solid micro fluidized bed were closely related to the used particle type, and the flow characteristics of two types of particles were significantly different under various flow states. In the fixed bed stage, compared with Geldart group B particle, the interaction between the A particles and the wall was stronger, leading to greater deviation of the experimental pressure drop value from the calculated value derived from the pressure formula of traditional fluidized beds. While in the fluidized bed stage, the larger particle size and density of Geldart group B particles showed higher bubble coalescence and rupture degree in the fluidized bed, which intensified the collision among different particles and increased the energy loss, as a result the pressure drop of the whole fluidized beds showed a higher experimental value. The minimum fluidization velocity of the gas?solid micro fluidized bed was not only related to the general operating conditions and gas/solid phase properties but also influenced observably by the inside diameter and the height of the static bed. The minimum fluidization velocity increased gradually with the decreased of bed diameter and increased of the static bed height. An empirical correlation to predict the minimum fluidization velocity of the micro fluidized bed was proposed within the scope of the experimental investigation under the condition of some important influencing factors. Related Articles | Metrics Select Effects of pole plate's concave?convex shapes on flow characteristics in water electrolyzer Jun LI Juan WANG Jia ZHANG Shuo ZOU Xingchen HE Jiayi WAN Chin. J. Process Eng.    2021, 21 (3): 251-258.   DOI: 10.12034/j.issn.1009-606X.220077 Abstract （472）      PDF （2690KB）（258）       Knowledge map    Save At present, spherical concave?convex combination structure is widely used in the plate of pressure-filtered water electrolyzer. The purpose is to enhance the disturbance degree of flow and make the distribution of electrolyte more uniform. In order to further improve the flow field distribution, five different concave?convex combination structures were combined with the electrolytic cell plate structure. The flow characteristics and flow field distribution characteristics in different concave?convex combination structures were analyzed and compared by numerical simulation method. The results showed that there were negative velocity distribution regions in the velocity component uz of the five structure channels, which was dominated by circulation flow, and the turbulent kinetic energy was also larger in this region, among which case C and case E structure were most obvious. The local vortices showed the vortices moved from the edge of the depression structure to the interior of the depression, and the details of the vortices flow were closely related to the the concave?convex structure. The distribution of the mean vorticity flux and the vorticity value showed that the concave?convex structure mainly affected the local vorticity intensity, but had little influence on the overall flow, and the local vorticity value in case B was the largest. The uniformity of the flow field distribution was related to the shape and size of the windward face of the concave?convex structure, among which case D teardrop structure had the best uniformity of flow field distribution and case C ellipsoid structure was the worst. Related Articles | Metrics Select Application of cutoff distance selection in molecular dynamics simulation of LJ argon system Chenyang SUN Chaofeng HOU Wei GE Chin. J. Process Eng.    2021, 21 (3): 259-264.   DOI: 10.12034/j.issn.1009-606X.220107 Abstract （968）      PDF （512KB）（327）       Knowledge map    Save In Lennard-Jones (LJ) potential argon system investigated by molecular dynamics simulation, the different cutoff distances are frequently applied to calculate the interactive force between atoms, and some reports have given out the influence of the cutoff distances on the simulation systems. More and more calculations suggest to use 4.5? or even larger truncation distances (? is the diameter of argon atom) to obtain the more accurate thermodynamic properties of the systems. In this work, a simple method was proposed to solve the problem of superheating encountered in the calculation of melting point by direct heating, where an independent track and ensemble at each temperature point are run. And then, the effect of different cutoff distances on the phase diagrams of the melting and boiling points of argon system in the NPT ensemble was studied. The melting point was in good agreement with the experimental and theoretically calculated values when the cutoff distance of 2.5? was used. However, the deviation from the experimental melting point became more evident when the larger cutoff distances were employed. In order to find out the underlying mechanism behind the deviation, the radial distribution functions and velocity autocorrelation function at the melting points and different thermodynamic states of the liquid argon with different cutoff distances were analyzed. It was found that the same thermodynamic properties can be obtained at the corresponding thermodynamic state points under different truncation distances. The mapping between the different thermodynamic state points was understandable due to the different thermodynamic states at the same temperatures under the varied truncation distances, and was beneficial to significantly reduce the computational workload at the smaller cutoff distance. This work proposed an exploratory way for the selection of the cutoff distance in the simulation of liquid argon, where the truncation distance of 2.5? can meet the requirements of computational accuracy and performance in the simulations. Related Articles | Metrics Select Simulation of pores-scale reaction?diffusion coupling for the design of catalyst structure Gelin WEI Chengxiang LI Wei GE Jinbing LI Chin. J. Process Eng.    2021, 21 (3): 265-276.   DOI: 10.12034/j.issn.1009-606X.220111 Abstract （536）      PDF （9419KB）（288）       Knowledge map    Save Most catalysts have complicated pore structures, and the coupling of reaction and diffusion processes in the pores determines the overall performance of catalysts. Understanding the reaction-diffusion coupling in the pores is important for better design of catalysts to improve their performance. In this work, the coupling of reaction and diffusion of reactants and products in catalyst pore structures was simulated by using the hard-sphere/pseudo-particle modeling (HS-PPM) approach which is combined with a simplified lumped reaction model for the C4 olefin cracking process. A controllable approach was proposed to construct more realistic model for the pore structure in catalyst materials, with which the effect of porosity, pore diameter and pore volume ratio could be studied independently and quantitatively. In addition to the effectiveness factor ?, a quantitative parameter JC was proposed to characterize the coupling of reaction and diffusion processes. The results showed that JC tended to be zero, which indicated that the overall diffusion process was significantly limited due to the competition between reactant diffusion and product diffusion in the complex pores. The reactant molecules were mainly diffused into the catalyst through the larger pores, and the larger product molecules were also mainly diffuse out of the catalyst through the larger pores. The competition between these two processes made it difficult for the reactants to diffuse into the pore, and the products to diffuse out of the pore, which led to the decrease of the overall performance of the catalyst albeit the potentially high reaction rate allowed by the intrinsic kinetics. The simulation approach used in this study could be helpful for the design of pore-scale structure of catalyst materials. Related Articles | Metrics Select Numerical simulation of flow field characteristics of gas?liquid mixed impinging stream reactor Dong GUO Haifeng LIANG Chin. J. Process Eng.    2021, 21 (3): 277-285.   DOI: 10.12034/j.issn.1009-606X.220114 Abstract （357）      PDF （1106KB）（231）       Knowledge map    Save Impinging stream reactors have been widely applied in industry with the advantages of efficient mass transfer and strong interaction between phases. Based on the traditional impinging stream reactor, a novel two-way accelerating tube coaxial opposing impinging stream reactor was constructed. The flow field mixing characteristics simulation was carried out in the reactor with air as the continuous phase and liquid water as the discrete phase. The high-speed gas?liquid mixed flow process at different gas flow rates was analyzed. Moreover, the changes of velocity, pressure distribution, particle diameter and stagnation time in the internal flow field were explored. The results showed that the flow field distribution was symmetrical above the impact surface, and the pressure and velocity at the stagnation point fluctuated most violently. With the increase of initial gas phase velocity, the flow field velocity rose slowly, then decreased slowly, and finally decreased sharply, and the pressure in the flow field decreased slowly, then increased slowly, after increased sharply and gradually coincided in the form of the double peaks of M-type. In addition, the pressure value at stagnation point increased non-linearly. When the initial gas velocity uout=30 m/s and uin=15 m/s, the velocity and pressure gradient of impact region were the largest, the turbulent kinetic energy was the strongest. Furthermore, the average diameter of the droplets in the new reactor was smaller and the residence time was longer, which were obviously superior to traditional reactor. Related Articles | Metrics Select Lattice Boltzmann simulation of mass transfer process affected by a moving particle Rui HE Chongzhi QIAO Limin WANG Shuangliang ZHAO Chin. J. Process Eng.    2021, 21 (2): 125-133.   DOI: 10.12034/j.issn.1009-606X.220323 Abstract （713）      PDF （3757KB）（221）       Knowledge map    Save In the catalytic reaction system, the internal and external diffusion have a great impact on the total reaction rate through the influence on the mass transfer process. The internal diffusion in porous channels has been well investigated by statistical mechanics on the influence of wettability, roughness, and electric properties of channel walls. By contrast, the influence of external diffusion needs to be further studied such as, how the active motion of particles impacts the mass transfer. Herein, by using the lattice Boltzmann method coupled with mass transfer process, the influence of the forced rotation or vibration of the catalyst particle was studied. A circular particle with constant interfacial boundary concentration was considered, and the immersed moving boundary and non-equilibrium extrapolation methods were chosen to treat the liquid?particle interface. The effects of rotational speed, vibrational amplitude, and frequency on mass transfer were investigated. The simulations indicated that when only considering diffusion, particle rotation inhibited mass transfer. The higher the rotation speed, the worse the mass transfer, while the overall suppression effect was not significant. The particle streamwise vibration enhanced mass transfer significantly. The lock-on frequency was about 1.9, and the enhancement amplitude reached 10%. Increasing the amplitude and Reynolds number strengthened the mass transfer, and the lock-on frequency moved towards the low frequency direction, while the Schmidt number had little effect on the value of the lock-on frequency. The transverse vibration was also compared with the streamwise one and showed greater enhancement of Sherwood number at a lower frequency. This numerical results not only demonstrated the feasibility of the lattice Boltzmann method for simulating the forced convection mass transfer process but also provided a route for enhancing mass transfer. Related Articles | Metrics Select Simulation of flow characteristics of radial flow absorber for oxygen production by vacuum pressure swing adsorption Yikun SHI Ruijiang LI Xuedong ZHU Haican FANG Zibin ZHU Chin. J. Process Eng.    2021, 21 (1): 18-26.   DOI: 10.12034/j.issn.1009-606X.220029 Abstract （545）      PDF （1640KB）（198）       Knowledge map    Save Vacuum pressure swing adsorption (VPSA) for oxygen generation is a complicated dynamic process. Understanding the flow characteristics is essential for the design and improvement of radial flow adsorber. A two-dimensional radial flow adsorber model of VPSA for oxygen generation was established based on the Fluent porous medium model with user defined functions. The flow characteristics of the first and second cycle in radial flow adsorber were analyzed. The effects of particle diameter, the perforated-plate opening ratios and the cross section ratio of central channel to outer channel were discussed. The results showed that the flow distribution and adsorption efficiency of radial adsorber were affected by the volume of both the central channel and the outer channel, which needed to be carefully considered when designing. The concentration and recovery rate of oxygen can be increased when smaller particles were used, which also improved the flow distribution. The increase of the cross sectional area ratio of central channel and outer channel was beneficial to flow distribution. The radial non-uniformity of velocity reduced with the decrease of the perforated-plate opening ratio of the central channel and outer channel, and the influence of perforated-plate opening ratio of central channel was more significant than that of the outer channel. Related Articles | Metrics page Page 1 of 5 Total 180 records First page Prev page Next page Last page