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Micro-flow structure at regime transition from bubbling to turbulent fluidization in a fluidized bed

Particuology 2024年第6期89卷 117-130页

作者： chaoyu yan Yue Yuan Xiaoyang Wei Jesse Zhu State Key Laboratory of Heavy Oil Processing Beijing Key Laboratory of Process Fluid Filtration and SeparationCollege of Mechanical and Transportation EngineeringChina University of PetroleumBeijing 102249China China Beacons Institute The University of NottinghamNingbo315100China Department of Chemical and Biochemical Engineering University of Western OntarioLondonOntarioN6A 5B9Canada

Gas-solid fluidized beds have found extensive utilization in frontline manufacturing,in particular as low-velocity *** fluidization status,the bubbling or turbulent flow regime and the transition in between,determine the system performance in practical *** the convoluted hydrodynamics are quantitively evaluated through numerous data-processing methodologies,none of them alone can reflect all the critical information to identify the transition from the bubbling to the turbulent ***,this study was to exploit a coupling data processing methodology,in the combination of standard deviation,power spectrum density,probability density function,wavelet transform,and wavelet multiresolution method,to jointly explain the micro-flow structure at the regime transition from bubbling to turbulent *** transient differential pressure fluctuation was measured for the evaluation in a fluidized bed(0.267 m i.d.×2.5 m height)with FCC catalysts(d_(p)=65μm,ρ_(p)=1780kg/m^(3))at different superficial gas velocities(0.02–1.4 m/s).The results show that the onset of turbulent fluidization starts earlier in the top section of the bed than in the bottom *** wavelet decomposition displays that the fluctuation of differential pressure mainly concentrates on the sub-signals with an intermediate frequency *** sub-signals could be synthesized into three types of scales(micro-scale,meso-scale,and macro-scale),representing the multi-scale hydrodynamics in the fluidized *** micro-scale signal has the characteristic information of bubbling fluidization,and the characteristic information of turbulent fluidization is mainly represented by the meso-scale *** work provides a systematic comprehension of fluidization status assessment and serves as an impetus for more coupling analysis in this sector.

关键词： Flow regime transition Bubbling fluidization Turbulent fluidization Micro-flow structure Differential pressure fluctuation

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Effect of static bed height in the upper fluidized bed on flow behavior in the lower riser section of a coupled reactor

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Particuology 2009年第1期7卷 19-25页

作者： Dewu Wang Chunxi Lu chaoyu yan State Key Laboratory of Heavy Oil China University of Petroleum Beijing 102249 China

To study olefin reduction by using an auxiliary reactor for FCC naphtha upgrading, a large-scale cold model of a riser-bed coupled to an upper fluidized bed was established. The effect of static bed height in the upper fluidized bed on narticle flow behavior in the lower riser was investigated experimentally. A restriction index of solids holdup was used to evaluate quantitatively the restrictive effect of the upper fluidized bed. Experimental results show that, under the restrictive effect of the upper fluidized bed, the riser could be divided into three regions in the longitudinal direction： accelerating, fully developed and restriction. The axial distribution of solids holdup in the riser is characterized by large solids holdup in the top and bottom sections and small solids holdup in the middle section. Overall solids holdup increased with increasing static bed height in the upper fluidized bed, while particle velocity decreased. Such restrictive effect of the upper fluidized bed could extend from the middle and top sections to the whole riser volume when riser outlet resistance is increased, which increases with increasing static bed height in the upper fluidized bed. The upper bed exerts the strongest restriction on the area close to the riser outlet.

关键词： Coupled reactor Riser Fluidized bed Static bed height Flow behavior Restriction

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内构件对提升管内气固流动特性影响的研究进展

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石化技术 2024年第3期31卷 13-16页

作者：阮宇军严超宇中国石化燕山分公司发展规划部北京102500 中国石油大学(北京)重质油国家重点实验室北京102249

提升管内气固沿轴径向分布不均匀的固有特性是影响气固接触效率及反应选择性的重要因素。本文就内构件对于提升管内气固轴径向的浓度分布、颗粒的混合及传热行为的实验研究工作进行了综述,不同研究者的研究结果表明,适宜的内构件能够改... 详细信息

提升管内气固沿轴径向分布不均匀的固有特性是影响气固接触效率及反应选择性的重要因素。本文就内构件对于提升管内气固轴径向的浓度分布、颗粒的混合及传热行为的实验研究工作进行了综述,不同研究者的研究结果表明,适宜的内构件能够改善提升管内气固分布状态,提高气固混合及传质传热效果,有利于提高反应速率和选择性。

关键词：提升管内构件气固混合流动特性流化床

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Experiments and simulations of gas-solid flow in an airlift loop reactor

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Particuology 2011年第2期9卷 130-138页

作者： chaoyu yan Chunxi Lu Yiping Fan Rui Cao yansheng Liu State Key Laboratory of Heavy Oil Processing China University of Petroleum Beijing 102249 China

The hydrodynamics in a gas-solid airlift loop reactor was investigated systematically using experimental measurements and CFD simulation. In the experiments, the time averaged parameters, such as solid frac- tion and particle velocity, were measured by optical fiber probe. In the simulation, the modified Gidaspow drag model accounting for the interparticles clustering was incorporated into the Eulerian-Eulerian CFD model with particulate-phase kinetic theory. Predicted values of solid fraction and particle velocity were compared with experimental results, validating the drag model and the simulation. The results show that the profiles of particle velocity and solid fraction are uniform in annulus. However, the core-annulus structure appears in other three regions （draft tube region, bottom region and particle diffluence region）, which presents the similar heterogeneous feature of aggregative fluidization usually occurred in nor- mal fiuidized beds. Simulated profiles of particle residence time distribution indicate that the airlift loop reactor should be characterized by near perfect mixing.

关键词： Airlift loop FeactoFHydrodynamicsGas-solid two phases flowCFDDrag force model

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Constraint strength and axial/radial particle velocity profiles for an integrated riser outlet

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Particuology 2015年第4期13卷 179-186页

作者： Dewu Wang chaoyu yan Chunxi Lu Rui Li Bin Zhao Shaofeng Zhang School of Chemical Engineering Hebei University of Technology State Key Laboratory of Heavy Oil Processing China University of Petroleum Engineering Research Center of Seawater Utilization Technology of Ministry of Education Hebei University of Technology

To study axial/radial profiles of particle velocity in the affected region of an integrated riser outlet, a cold model was developed for the integrated riser reactor combining the gas-solid distributor with the fluidized bed. Constraints, related to the gas-solid distributor and the upper fluidized bed, imposed on the particle flow in the riser outlet region, were investigated experimentally. The experimental results showed that with increasing superficial gas velocity, these constraints have strong influences on particle flow behavior, the particle circulation flux in the riser, and the height of the static bed material of the upper fluidized bed. When the constraints have greater prominence, the axial profile of the cross-sectionally averaged particle velocity in the outlet region initially increases and then decreases, the rate of decrease being proportional to the constraint strength. Along the radial direction of the outlet section, the region where the local particle velocity profile tends to decrease appears near the dimensionless radius r/R = 0.30 initially and then, with increasing constraint strength, gradually extends to the whole section from the inner wall. Based on the experimental data, an empirical model describing the constraint strength was established. The average relative error of the model is within 7.69%.

关键词： Combined fluidized bed Riser Outlet structure Particle velocity Constraint strength

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A criterion for flow mechanisms through vertical sharp-edged orifice and model for the orifice discharge coefficient

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Petroleum Science 2011年第1期8卷 108-113页

作者： Cao Rui Liu yansheng yan chaoyu State Key Laboratory of Heavy Oil Processing China University of PetroleumBeijing 102249China

According to the experimental data of the orifice discharge coefficient for the flow through a vertical sharp-edged orifice obtained in the previous study of this work,a theoretical criterion for flow mechanisms of small orifice（***-walled orifice and nozzle） and large orifice（***-walled orifice） was proposed based on the ratio of orifice diameter to plate *** can help explain the dissipation of the mechanical energy loss in the flow process for the two flow mechanisms under different operating *** main parameters such as orifice diameter,plate thickness and liquid head were correlated,and a semi-empirical model for orifice coefficient and an empirical model with high precision at the stable region were developed.

关键词： Orifice discharge coefficient theoretical criterion model ratio of orifice diameter to plate thickness Reynolds number liquid head

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Investigation of Different Coke Samples Adhering to Cyclone Walls of a Commercial RFCC Reactor

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China Petroleum Processing & Petrochemical Technology 2016年第1期18卷 8-14页

作者： Li Xiaoman Song Jianfei Sun Guogang yan chaoyu Wei Yaodong State Key Laboratory of Heavy Oil Processing China University of Petroleum

The microstructure and properties of the coke samples collected from 4 different wall regions of the cyclone in the reactor of a residue fluid catalytic cracking unit(RFCCU) were analyzed by using the scanning-electron microscope(SEM), and the possible coke formation processes were investigated as well. The results showed that some of the heavy nonvolatile oil droplets entrained in the flowing oil and gas mixture could possibly deposit or collide on the walls by gravity settling or turbulence diffusion, and then were gradually carbonized into solid coke by condensing and polymerization along with dehydrogenation. Meanwhile some of fine catalyst particles also built up and integrated into the solid coke. The coke can be classified into two types, namely, the hard coke and the soft coke, according to its property, composition and microstructure. The soft coke is formed in the oil and gas mixture's stagnant region where the oil droplets and catalyst particles are freely settled on the wall. The soft coke appears to be loose and contains lots of large catalyst particles. However, the hard coke is formed in the oil and gas mixture's flowing region where the oil droplets and catalyst particles diffuse towards the wall. This kind of coke is nonporous and very hard, which contains a few fine catalyst particles. Therefore, it is clear that the oil and gas mixture not only carries the oil droplets and catalyst particles, but also has the effects on their deposition on the wall, which can influence the composition and characteristics of deposited coke.

关键词： FCC reactor cyclone coke formation microstructure characteristics

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气固环流燃烧器内颗粒流动行为

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化工学报 2010年第6期61卷 1357-1366页

作者：严超宇卢春喜中国石油大学(北京)重质油国家重点实验室北京102249

针对石油焦及气化余焦的燃烧特点和流态化特性,提出了一种采用气固密相环流烧焦与快速床管式烧焦技术相组合的新型燃烧器结构。在不同操作条件(导流筒区表观气速0.772～1.674m.s-1,环隙区表观气速0.223～0.519m.s-1,装置系统的颗粒外循... 详细信息

针对石油焦及气化余焦的燃烧特点和流态化特性,提出了一种采用气固密相环流烧焦与快速床管式烧焦技术相组合的新型燃烧器结构。在不同操作条件(导流筒区表观气速0.772～1.674m.s-1,环隙区表观气速0.223～0.519m.s-1,装置系统的颗粒外循环强度40.8～229.4kg.m-2.s-1)及两类颗粒体系下,采用光纤测量仪对组合燃烧器环流段内颗粒流动特性进行了系统的实验研究。结果表明,两类颗粒体系的固含率和颗粒轴向速度在导流筒区、底部区和颗粒分流区床层内沿径向的分布规律为中心区小、边壁区大的环-核型分布,体现了气固流化床典型聚式流态化的非均一性特征;在环隙区,受环流段结构的影响,两类颗粒体系的固含率和颗粒轴向速度参数沿床层径向的分布相对较均匀;混合颗粒体系的固含率、颗粒轴向速度较单一石英砂颗粒体系的要小,细颗粒的加入在一定程度上能改善气固混合的均匀程度;两类颗粒体系在底部区和颗粒分流区的径向流动具有剪切破碎气泡的作用,有利于环流段内气固的充分混合接触。

关键词：流化床燃烧器环流气固两相流动行为

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Robotic Polishing of the Meat Grinder Blade under Path Planning and Controlled Force

Robotic Polishing of the Meat Grinder Blade under Path Plann...

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作者： Xinrui Liang Imran Mohsin Yaohui Xu chaoyu yan Kai He Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences China University of Petroleum University of Chinese Academy of Sciences Shenzhen Key Laboratory of Precision Engineering The Chinese University of Hong Kong

In recent years,industrial robots have been widely used in many applications such as assembling,stacking,welding,spraying and ***,the surface grinding and polishing are the applications which are still required a lot of improvement especially for the curved and free form *** commonly used articulated robots are suitable candidates for such surfaces because its end effector can provide orientations required for polishing of the free from *** the reachability,tool path planning and the contact force between polishing tool and surface are other two important factors which required proper *** paper presents the robotic polishing of the meat grinder blade under suitable path planning and controlled ***-Aided Manufacturing（CAM） software Mastercam is used to achieve the trajectory path of the robot during the polishing *** are conducted to prove the adopted methodology.

关键词： Surface polishing Path planning Force control Free form surface Computer-aided manufacturing

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提升管与气-固环流床层耦合反应器的流体力学特性及流动模型

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化工学报 2010年第9期61卷 2235-2242页

作者：王德武卢春喜严超宇河北工业大学化工学院天津300130 中国石油大学(北京)重质油国家重点实验室北京102249

针对催化汽油辅助反应器改质降烯烃技术,在一套提升管与气-固环流床层耦合反应器大型冷模实验装置上,研究了上部环流床层的流体力学特性。结果表明,在环流床层与提升管耦合操作的情况下,床层内颗粒环流存在两种推动力,分别为静压差推动... 详细信息

针对催化汽油辅助反应器改质降烯烃技术,在一套提升管与气-固环流床层耦合反应器大型冷模实验装置上,研究了上部环流床层的流体力学特性。结果表明,在环流床层与提升管耦合操作的情况下,床层内颗粒环流存在两种推动力,分别为静压差推动力和颗粒喷射推动力;环隙与导流筒之间的整体平均固含率差随导流筒表观气速增加而增加,随颗粒外循环强度增加而降低;颗粒环流速度随导流筒表观气速和颗粒外循环强度增加而增加。通过对环流床层进行动量衡算,建立了提升管与环流床层耦合流动的数学模型,模型平均相对误差在15.95%以内。

关键词：耦合反应器气-固环流床流体力学特性环流推动力流动模型

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