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Particuology 2024年第6期89卷 258-269页

作者： Martin Oelofse Robert Rack Marcelle Hilden Peter Langguth Department of Pharmaceutical Technology and Biopharmaceutics Johannes Gutenberg UniversityMainzGermany Carbon Advanced Solutions GmbH HeuchelheimGermany

Spraying parameters during particle agglomeration processes can affect the agglomeration kinetics and particle *** study was conducted to better understand the influence of the spraying parameters in a fluidized bed wet agglomeration process,and the influence on the stability characteristics of carbon tablets.A formulation based on fine carbon and peroxide powder,as well as carboxymethyl cellulose as a binder,was used to produce agglomerates in a first production *** in a second production step carbon tablets with a high porosity were molded for the customer goods *** optimization of the compressive strength of these carbon tablets was the goal of the *** agglomerates were produced with a laboratory scale granulator called“ProCell”and were compressed with a five-cavity mechanical *** screening of the agglomeration process parameters and their influence on the agglomerates quality,as well as the performance characteristics of the carbon tablets,were investigated using a multilevel factorial *** experimental runs were done by varying atomized air pressure and feed rate of the *** was determined by the design *** findings of the statistical trials showed that low atomized air pressure and a low feed rate lead to a higher tablet compressive strength.

关键词： Wet agglomeration fluidized bed Design of experiments Carbon agglomerates and tablets

CFD-DEM study of impacts of the porous distributor medium on fluidization characteristics of a 2D-fluidized bed

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Particuology 2024年第4期87卷 54-73页

作者： Fei Wang Yishan Zeng Hao Yan School of Mechanical Engineering Hefei University of TechnologyHefei230009China

Gas-solid bubbling fluidized beds are widely used in chemical,energy,construction,and other industrial fields due to their excellent fluidization performance.2D-fluidized beds with planar rectangular columns of finite thickness are widely used in fluidized bed studies,and it is essential for understanding the hydrodynamics of gas-particle ***,the distributor(porous medium)at the bottom of the bed has a crucial influence on the fluidization performance of the 2D-fluidized *** this work,the fluidization mechanism and gas-solid dynamic characteristics of the fluidized bed under three porous media are studied by CFD-DEM coupled with the porous medium model,and the accuracy of numerical simulation is verified by a high-speed photography *** show that with the increase in the flow resistance of the porous medium,the average and standard deviation of the bubble diameter decrease,and the time and position of particles in the dead zone to participate in the core-annular flow *** a low fluidization velocity,the dead zone in the bed can be considerably reduced by increasing the flow resistance.

关键词： fluidized bed CFD-DEM Porous medium Bubble dynamics Solid mixing

Segregation of binary particles in gas-solid fluidized bed

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Frontiers of Chemical Science and Engineering 2024年第6期18卷 113-121页

作者： Yaxiong Yu Feng Lu Xuan He Fei Wei Chenxi Zhang Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing 100084China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China Ordos Laboratory Ordos 017010China Institute for Carbon Neutrality Tsinghua UniversityBeijing 100084China

Particle segregation and mixing behavior play a crucial role in industrial *** study investigates the saturated jetsam fraction,which indicates the maximum capacity of flotsam to entrain jetsam,in an initially separated binary fluidized bed with particle size *** to the value of saturated jetsam fraction,three distinct regimes-segregation,mixing,and an intermediate regime-are ***,intriguing relationships between the saturated jetsam fraction and superficial gas velocity are observed,exhibiting monotonic trends in both the segregation and mixing regimes,while a unique volcano-shaped curve in the intermediate ***,a comprehensive entrainment model based on two-fluid model elucidates the observed phenomena,emphasizing the significance of mixing behavior in fluidized layer on the saturated jetsam *** work offers potential insights for evaluating segregation in industrial applications.

关键词： fluidized bed segregation binary bubbles entrainment

Study on a semi-resolved CFD-DEM method for rod-like particles in a gas-solid fluidized bed

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Particuology 2024年第4期87卷 20-36页

作者： Liping He Zhengxian Liu Yongzhi Zhao Department of Mechanics School of Mechanical EngineeringTianjin UniversityTianjin300350China Insttute of Process quipment College of Energy EngineeringZhejiang UniversityHangzhou30027China

Based on a semi-resolved CFD-DEM coupling method,this study proposed a method that uses the minimum distance between the fluid grid and the particle boundary as a reference value to determine the degree of influence of the target fluid grid on the particle's drag force.A fluidized bed of rod-like particles was chosen as a typical case to investigate the effect of different fluid grid scales on various fluidized bed characteristic *** calculation performance of the semi-resolved and unre-solved CFD-DEM coupling algorithm on key fluidized bed characteristic parameters such as average pressure drop,particle frequency distribution with bed height,and particle orientation distribution were *** was found that the semi-resolved CFD-DEM coupling algorithm gradually obtained results with higher consistency with decreasing fluid grid scale for key parameters such as particle frequency distribution with bed height,particle orientation distribution,and time-history mixing index,exhibiting a phenomenon similar to grid independence in fluid *** comparing with experimental results,it was verified that the semi-resolved CFD-DEM coupling algorithm can be applied to simulate multi-granular gas-solid systems with fluid grid scales equivalent to particle *** algorithm solves the limitation of fluid grid scale in the unresolved CFD-DEM coupling framework and improves the grid adaptability of the CFD-DEM coupling simulation algorithm.

关键词： CFD-DEM Semi-resolved method Fluid-solid flow Non-spherical particle fluidized bed

Three-dimensional dynamic characterization of square-nosed slugging phenomena in a fluidized bed

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Particuology 2022年第8期20卷 35-46页

作者： Yaswanth Pottimurthy Dawei Wang Cody Park Shalin Patil Andrew Tong Liang-Shih Fan Willam G.Lowrie Department of Chermical and Biomolecular Engineering.The Ohio State Univrsity ColumbusOH 43210USA

Slugging represents one of the major regimes in fluidization,which occurs in small diameter beds with large bed height-to-diameter ratio or in large diameter beds with internals that resemble multiple small diameter fluidized *** types include round-nosed slug,wall slug and square nosed *** of the slugs have been mainly focused on round-nosed or wall slugs known as half *** occurring in Geldart group A particle *** square-nosed slug typically occurring for Geldart group D particles appears to be regarded as simple in its *** Electrical Capacitance Volume Tomogra phy(ECVT)imaging of the square-nosed slugging phenomena conducted in this study reveals *** is the structure of the square nosed slug is,in fact,complex,particularly with respect to its dynamic variation in *** *** study examines experimentally the hydrodynamic character-istics of the square-nosed fluidization ***,simultaneous measurements from multiple ECVT sensors provide non-inv asive,continuous,*** imaging of the entire flow region of the slugging bed and hence enabling the dynamic characterization of the evolution of the *** analysis of the 3D images reconstructed for real time gas-solid volume fraction profile of the slugging fluidized bed indicates that there are three different *** bottom fluidization zone,the gas slug zone,and the solid slug zone,co-existing in the *** three zones present different hydrodynamic characteristics during the slug *** is found that varying the gas velocity of the slugging bed mainly varies the maximum length of the gas slug zone,while it only has a minor effect on the lengths of the bottom fluidization zone and solid slug *** also has an insignificant efect on the solid volume fraction of the three zones.

关键词： Gas-solid flow fluidized bed Square-nosed slugging Electrical Capacitance Volume Tomography

Carbon dioxide desorption behavior of potassium carbonate supported on gamma-alumina solid sorbent in wet fluidized bed under steam atmosphere

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Particuology 2023年第10期81卷 15-24页

作者： Sasitron Angkanawisan Dimitri Gidaspow Pornpote Piumsomboon Benjapon Chalermsinsuwan Fuels Research Center Department of Chemical TechnologyFaculty of ScienceChulalongkorn University254 Phayathai RoadPathumwanBangkok10330Thailand Center of Excellence on Petrochemical and Materials Technology Chulalongkorn University254 Phayathai RoadPathumwanBangkok10330Thailand Department of Chemical and Biological Engineering Armour College of EngineeringIllinois Institute of Technology10 West 35th StreetChicagoIL60616United States Advanced Computational Fluid Dynamics Research Unit Chulalongkorn University254 Phayathai RoadPathumwanBangkok10330Thailand

Since the carbon dioxide(CO_(2))capture using solid sorbent is a reversible reaction,the solid sorbent can be regenerated by the desorption ***,the desorption process is one of the key important processes for the CO_(2)capture ***,most of the literature studies focus on the desorption of solid sorbent under an N_(2)***,the desorption process of the solid sorbent is inappropriate in the real system because the system will need another process to separate CO_(2)and nitrogen(N_(2))after the desorption *** study focused on the CO_(2)desorption of potassium carbonate supported on gamma-alumina(K2CO3/γ-Al_(2)O_(3))in a wet fluidized bed under a steam atmosphere by using the multiphase computational fluid dynamics(CFD)*** effects of water thickness and dry restitution coefficient on CO_(2)desorption rate were investigated to provide a realistic particle collision behavior and to explore their effects on CO_(2)desorption ***,the effect of steam velocity on the hydrodynamic behaviors of fluidization which on CO_(2)desorption rate was *** simulated results demonstrated that all the parameters,water thickness,dry restitution coefficient,and steam velocity had significantly affected system hydrodynamics and CO_(2)desorption rate in the wet fluidization desorption ***,the effect of desorption temperature on CO_(2)desorption rate was evaluated for finding the appropriate temperature for CO_(2)desorption process of K2CO3/γ-Al_(2)O_(3).The results showed that the appropriate desorption temperature for CO_(2)desorption under steam atmosphere was the temperature over 150℃.

关键词： CO_(2)desorption fluidized bed K_(2)CO_(3)/Y-Al_(2)O_(3) Restitution coefficient Wet fluidization Computational fluid dynamics

Scale-up and thermal stability analysis of fluidized bed reactors for ethylene polymerization

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Chinese Journal of Chemical Engineering 2023年第10期62卷 281-290页

作者： Xiaoqiang Fan Jingyuan Sun Jingdai Wang Zhengliang Huang Zuwei Liao Guodong Han Yongrong Yang Ningbo Research Institute Zhejiang UniversityNingbo 315100China State Key Laboratory of Chemical Engineering College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 310027China Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology Hangzhou 310027China Sinopec Tianjin Company Tianjin 300271China

A set of hydrodynamic similarity laws is applied to the scale-up of ethylene polymerization fluidized bed reactors(FBRs)under the condensed mode *** thermal stability of open-loop controlled FBRs is investigated by the homotopy continuation *** the Hopf bifurcation point is selected as an index of the thermal stability *** simulation results show the similarity in state variables,operation parameters,the space-time yield(STY),and the thermal stability of FBRs with different ***,the thermal stability behaviors and similarity of the closed-loop controlled FBRs with different scales are *** observed similar trend of Hopf bifurcation curves reveals the similarity in the thermal stability of closed-loop controlled FBRs with different scaling *** general,the results of the thermal stability similarity confirm that the hydrodynamics scaling laws proposed in the work are applicable to the scale-up of FBRs under the condensed mode operation.

关键词： Stability Scale-up Polymerization Bifurcation theory fluidized bed

Development and assessment of algorithms for DEM-LES simulations of fluidized bed

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Particuology 2023年第12期83卷 241-257页

作者： Fatima Ez-Zahra El Hamra Radouan Boukharfane UM6P College of Computing Mohammed Ⅵ Polytechnic University(UM6P)BenguerirMorocco

The use of high-fidelity Discrete Element Method(DEM)coupled with Computational Fluid Dynamics(CFD)for particle-scale simulations demands extensive simulation times and restricts application to small particulate ***-CFD simulations require good performance and satisfactory scalability on high-performance computing platforms.A reliable parallel computing strategy must be developed to calculate the collision forces,since collisions can occur between particles that are not on the same processor,or even across processors whose domains are *** present paper describes a parallelization technique and a numerical verification study based on a number of tests that allow for the assessment of the numerical performance of DEM used in conjunction with Large-Eddy Simulation(LES)to model dense flows in fluidized *** fluid phase is computed through solving the volume-averaged four-way coupling Navier-Stokes equations,in which the Smagorinsky sub-grid scale tensor model is ***,the performance of Sub-Grid Scale(SGS)turbulence models applied to fluidized bed Reactor(FBR)configurations has been assessed and *** developed numerical solver represents an interesting combination of techniques that work well for the present purpose of studying particle formation in fluidized beds.

关键词： DEM-LES fluidized bed Computational efficiency Numerical accuracy

Particle convective heat transfer near the wall in a supercritical water fluidized bed by single particle model coupled with CFD-DEM

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Particuology 2023年第2期73卷 47-58页

作者： Tianning Zhang Zhen Wan Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering(SKLMFPE) Xi'an Jiaotong UniversityXi'an710049ShaanxiChina Xi'an Electronic Engineering Research Institute Xi'an710100ShaanxiChina

Supercritical water fluidized bed(SCWFB)is a promising reactor to gasify biomass or *** optimization design is closely related to wall-to-bed heat transfer,where particle convective heat transfer plays an important *** paper evaluates the particle convective heat transfer coefficient(h_(pc))at the wall in SCWFB using the single particle *** critical parameters in the single particle model which is difficult to get experimentally are obtained by the computational fluid dynamics-discrete element method(CFD-DEM).The contact statistics related to particle-to-wall heat transfer,such as contact number and contact distance,are also *** results show that particle residence time(τ),as the key parameter to evaluate h_(pc),is found to decrease with rising velocity,while increase with larger thermal boundary layer thickness.τfollows a gamma function initially adopted in the gas-solid fluidized bed,making it possible to evaluate h_(pc) in SCWFB by a simplified single particle *** theoretical predicted h_(pc) tends to increase with rising thermal gradient thickness at a lower velocity(1.5 U_(mf)),while first decreases and then increases at higher velocity(1.75 and 2 U_(mf)).h_(pc) occupies 30%-57%of the overall wall-to-bed heat transfer coefficient for a particle diameter of 0.25 *** results are helpful to predict the overall wall-to-bed heat transfer coefficient in SCWFB combined with a reasonable fluid convective heat transfer model from a theoretical perspective.

关键词： Supercritical water fluidized bed Particle residence time Discrete element method Single particle model

Numerical simulation of local and global mixing/segregation characteristics in a gas–solid fluidized bed

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Chinese Journal of Chemical Engineering 2022年第4期35卷 72-86页

作者： Zhen Wan Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Researches on solids mixing and segregation are of great significance for the operation and design of fluidized bed *** this paper,the local and global mixing and segregation characteristics of binary mixtures were investigated in a gas–solid fluidized bed by computational fluid dynamics-discrete element method(CFD-DEM)coupled approach.A methodology based on solids mixing entropy was developed to quantitatively calculate the mixing degree and time of the *** mixing curves of global mixing entropy were acquired,and the distribution maps of local mixing entropy and mixing time were also *** comparing different operating conditions,the effects of superficial gas velocity,particle density ratio and size ratio on mixing/segregation behavior were *** showed that for the partial mixing state,the fluidized bed can be divided into three parts along the bed height:complete segregation area,transition area and stable mixing *** areas showed different mixing/segregation *** gas velocity promoted the local and global mixing of binary *** increase in particle density ratio and size ratio enlarged the complete segregation area,reduced the mixing degree and increased the mixing time in the stable mixing area.

关键词： Discrete element method Solids mixing Binary mixtures fluidized bed