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Particuology 2024年第4期87卷 133-146页

作者： Haichao Zhao Conghui Gu Bingyang Xu Yuan Liu Mingpu Du Kaiyuan Deng Jingyu Zhu Iana Voronina Zhulin Yuan School of Energy and Power Jiangsu University of Science and TechnologyZhenjiang212100China China Tobacco Jiangxi Industrial Co.Ltd. Nanchang330096China Institute of Mechanics and Power Engineering Ogarev Mordovia State UniversitySaransk430005Russia Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and EnvironmentSoutheast UniversityNanjing210096China

A bended ribbon biomass particle model was developed to explore the dynamic transport properties inside a riser reactor.Residence time distribution(RTD)of the particles was analyzed by using the Eulerian-Lagrange method.The effects of sampling height,particle density,particle size and gas-to-solid mass ratio on RTD were investigated.The coupled Computational Fluid Dynamics and Discrete Element Method(CFD-DEM)model was verified firstly by experimental data on pressure drop and residence time distribution density function.The simulation results demonstrated that the ribbon biomass particles display a typical annular-core spatial distribution during transportation.The RTD of particles exhibit an approximate single-peaked normal distribution.The mean residence time(MRT)can reach up to 0.7 s when the particle density is 1200 kg/m^(3).Particle with higher density has longer mean residence time.The flow patterns are closer to plug flow if particle length over 12 mm.The particle flow pattern is not sensitive to changes in particle density and size,while the gas-to-material mass ratio has a significant impact on it.

关键词： riser Gas-solids two-phase flow Ribbon biomass particles Residence time distribution CFD-DEM

Investigation on gas-solids hydrodynamics and matching enhancement in feedstock injection zone of double-level nozzle riser

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Particuology 2023年第4期75卷 165-176页

作者： Xiuying Yao Jun Xu Yiping Fan Chunxi Lu Fuwei Sun State Key Laboratory of Heavy Oil Processing China University of PetroleumBeijing102249China China Kunlun Contracting&Engineering Co LtdBeijing100037China

With the development of current energy economy,it is necessary to improve the product distribution of fluid catalytic cracking process,which is achieved by a riser reactor with double-level of nozzles.The new riser is constructed by adding a level of secondary nozzle 0.5 m below the main nozzle of traditional riser.This paper investigates the gas-solids flow and oil-catalyst matching feature based on the optical fiber and tracer technologies.According to the distribution of solids holdup,particle velocity and dimen-sionless jet concentration,the feedstock injection zone can be divided into the upstream flow control region,the main flow control region,and the secondary flow control region in the radial direction.The size of the regions is changed by the jet gas velocity and axial height.There is a poor match of secondary nozzle jet to particles below the main nozzle.The jet gas from secondary nozzles can improve the matching effect of oil-catalyst near the wall and reduce the probability of coking above the main nozzle.

关键词： Gas-solids flow Matching Feed injection zone Double-level nozzles riser

Linear analysis of the dynamic response of a riser subject to internal solitary waves

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Applied Mathematics and Mechanics(English Edition) 2023年第6期44卷 1023-1034页

作者： Dalin TAN Xu WANG Jinlong DUAN Jifu ZHOU Key laboratory for Mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing 100190China Beijing Electro-Mechanical Engineering Institute Beijing 100074China School of Engineering Sciences University of Chinese Academy of SciencesBeijing 100049China

The flow field induced by internal solitary waves(ISWs)is peculiar wherein water motion occurs in the whole water depth,and the strong shear near the pycnocline can be generated due to the opposite flow direction between the upper and lower layers,which is a potential threat to marine risers.In this paper,the flow field of ISWs is obtained with the Korteweg-de Vries(Kd V)equation for a two-layer fluid system.Then,a linear analysis is performed for the dynamic response of a riser with its two ends simply supported under the action of ISWs.The explicit expressions of the deflection and the moment of the riser are deduced based on the modal superposition method.The applicable conditions of the theoretical expressions are discussed.Through comparisons with the finite element simulations for nonlinear dynamic responses,it is proved that the theoretical expressions can roughly reveal the nonlinear dynamic response of risers under ISWs when the approximation for the linear analysis is relaxed to some extent.

关键词： internal solitary wave(ISW) riser dynamic response linear analysis

Corrosion Behavior of High-Strength Steel for Flexible riser Exposed to CO_2-Saturated Saline Solution and CO_2-Saturated Vapor Environments

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Acta Metallurgica Sinica(English Letters) 2019年第5期32卷 607-617页

作者： Da-Zheng Zhang Xiu-Hua Gao Lin-Xiu Du Hong-Xuan Wang Zhen-Guang Liu Ning-Ning Yang R.D.K.Misra State Key Laboratory of Rolling and Automation Northeastern University Neptune Offshore Engineering Development Co. Ltd School of Material Science and Engineering Jiangsu University of Science and Technology Department of Metallurgical Materials and Biomedical Engineering University of Texas at El Paso

The corrosion behavior of high-strength steel used for flexible riser exposed to CO_(2-)saturated saline solution and CO_(2-) saturated vapor environments was studied through immersion experiment and electrochemical corrosion experiment. The corrosion behavior and mechanism of the tested steel were analyzed on the basis of corrosion kinetics, nature of corrosion products, corrosion product morphology, elemental distribution and polarization curves. The experimental results showed that the microstructure of the tested steel was bainitic microstructure. The corrosive activity of the tested steel exposed to CO_(2-) saturated vapor environment was significantly lower than that exposed to CO_(2-) saturated saline solution environment.On prolonging the exposure time, the corrosion rate gradually decreased, the corrosion heterogeneity increased, and the dimensions of FeCO_3 crystals gradually became small. At later stages of corrosion, the corrosion current density decreased significantly and the anodic Tafel slope increased, indicating that the corrosion process was strongly inhibited. The corrosion mechanism of low-alloy steel with bainitic microstructure was proposed based on experimental results.

关键词： Flexible riser High-strength bainitic steel CO2 corrosion Electrochemical behavior

Dynamic Response Study of Steel Catenary riser Based on Slender Rod Model

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China Ocean Engineering 2019年第1期33卷 57-64页

作者： LIU Zhen GUO Hai-yan College of Engineering Ocean University of China

A numerical model of the steel catenary riser(SCR) is built based on the slender rod model. The slender rod model,which describes the behavior of the slender riser in terms of the center line position, can solve the geometrical nonlinearity effectively. In a marine environment, the SCR is under the combined internal flow and external loads,such as wave and current. A general analysis considers only the inertial force and the drag force caused by the wave and current. However, the internal flow has an effect on the SCR; it is essential to explore the dynamic response of the SCR with the internal flow. The SCR also suffers the lift force and the fluctuating drag force because of the current. Finite element method is utilized to solve the motion equations. The effects of the internal flow, wave and current on the dynamic response of the SCR are considered. The results indicate that the increase of the internal flow density leads to the decrease of the displacement of the SCR, while the internal flow velocity has little effect on the SCR. The displacement of the SCR increases with the increase of the wave height and period. And the increasing wave period results in an increase in the vibration period of the SCR. The current velocity changes the displacements of the SCR in x-and z-directions. The vibration frequency of the SCR in y-direction increases with the increase of the current velocity.

关键词： steel catenary riser slender rod model internal flow dynamic response

Characteristics of clusters in the jet influence zone of riser

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Particuology 2021年第2期19卷 118-127页

作者： Zihan Yan Yiping Fan Jun Xu Chunxi Lu Chunming Xu State Key Laboratory of Heavy Oil Processing College of Chemical Engineering and EnvironmentChina University of Petroleum-BeijingBeijing 102249China

By analyzing solid holdup signals in the jet influence zone of risers,the characteristics of clusters were studied.The solid holdups inside clusters and their distribution ranges were calculated under the cases of both upward and downward feed jets.Moreover,the effects of the jet velocity on the cluster characteristics were analyzed.The solid holdups inside clusters have higher values and wider distribution ranges in the upward feed injection zone than in the downward zone,implying that the number of individual particles in a cluster is unstable under the influence of upward jets.For the case of downward jets,cluster formations in the jet influence zone of risers can more easily maintain stability,offering a better mixing environment for jets and particles.As the jet velocity increases,the solid holdups inside clusters in the riser wall of the upward injection zone increase accordingly,while the distributions of solid holdups inside clusters have no significant changes if the feed jets are downward.This phenomenon confirms that improved operational flexibility can be obtained if downward jets are mixed with the prelift gas-solid flow in risers.

关键词： riser Cluster Jet Solid holdup

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

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

Effect of baffles on performance of fluid catalytic cracking riser

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Particuology 2018年第3期16卷 18-30页

作者： Milinkumar T. Shah Vishnu K. Pareek Geoffrey M. Evans Ranjeet P. Utikar Department of Chemical Engineering Curtin University Western Australia Australia Department of Chemical Engineering University of Newcastle New South Wales Australia

Increasing demand of automobile fuel and a need to process heavier crude oil makes it imperative to find improvements to the design of existing fluid catalytic cracking （FCC） units. Several modifications to the design of the riser section of FCC units have been suggested in previous studies including： improved feed nozzle designs, multiple nozzle configurations, internal baffles, and novel two-stage-riser systems. In this study, we investigate the effects of baffles on the performance of FCC risers using computational fluid dynamics simulations. In this study, predictions from a basis model （without baffles） are compared with those from four different configurations including：（i） 5-cm baffles at 5-m spacing, （ii） 7.5-cm baffles at 5- m spacing, （iii） 10-cm baffles with 5-m spacing, （iv） lO-cm baffles at 2.5-m spacing, and （v） lO-cm baffles at 1-m spacing. The baffles force the catalyst away from wails toward the center of the riser, enhancing the radial dispersion of the catalyst and the heat transfer inside the riser. The use of longer baffles and smaller spacings further increases the dispersion, yielding more homogeneous radial profiles. The changes in the radial dispersion result in variations in the conversion, yields, and pressure drops. The baffles increase conversion of vacuum gas oil （VGO） and the yield of gasoline. However, the simulations showed that longer baffles and a larger number of baffles did not always give a higher yield or higher conversion. Among the simulated configurations, the 5-cm baffles at 5-m spacing gave the highest conversion of VGO, whereas the 10-cm baffles at 1 -m spacing resulted in the highest yield of the gasoline. Thus, rational optimization of baffle configurations is required to achieve optimal performance.

关键词： Fluid catalytic cracking riser Baffles Computational fluid dynamics

Numerical Simulation on Gas-Solid Two-Phase Turbulent Flow in FCC riser Reactors(Ⅱ) Numerical Simulation on the Gas-Solid Two-Phase Turbulent Flow

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Chinese Journal of Chemical Engineering 1998年第1期6卷 25-32页

作者：高金森徐春明林世雄郭印诚王希麟 State Key Laboratory of Heavy Oil Processing Petroleum University Department of Engineering Mechanics Tsinghua University

Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion model for FCC riser reactors given in Part Ⅰ of the present paper.Detailed information about the turbulentflow fields in the riser reactor obtained revealed the basic characteristics of the gas-solid two-phase turbulentflows when heat transfer and catalytic cracking reactions were co-existing in the riser.Results showed that thedistributions of the flow,the turbulence kinetic energy and the catalyst particle concentration are not uniform inthe axial,radial and tangential directions.The most complicated part of the riser reactor is the feed injectingzone.The complicated configuration of the turbulent gas-solid two-phase flows would exert a great influence onthe results of interphase heat transfer and cracking reactions.

关键词： commercial riser reactor flow-reaction model turbulent flow numerical simulation flow field