气-固流化床中颗粒的内循环流动

从多尺度范围考察了气－固流化床内尾涡颗粒流和乳化相颗粒流的运动规律,将分散的尾涡颗粒流和乳化相颗粒流连续介质化,从流变学角度定义了颗粒流粘度,用流体力学方法建立了内循环流动结构的多尺度、连续介质流模型,较好地揭示了颗粒循环流动的规律。实验观测支持模型预测结果。     

气固流化床中大差异双组份颗粒分级特性的实验研究

为解决清洁汽油生产工艺中存在的能量利用问题,需开发一种能使两种温度不同的催化剂直接混合换热,然后实现催化剂再次分离的组合流化床再生器.在一套φ500 mm×7000 mm的大型冷模装置上对密度相近、粒径差异较大的双组份颗粒形成的气固流化床中稀、密相间颗粒分级特性进行了系统的实验研究,结果表明表观气速、混合颗粒平均停留时间以及混合进料浓度是影响颗粒分级的主要因素,停留时间阈值可用于表征气体分布板形式对分级的影响.利用实验数据回归得到了分级效率的经验模型,模型计算值与实验值吻合较好.     

Application of Magnetically Stabilized Fluidized Beds for Cell Suspension Filtration from Aqueous Solutions

Abstract

A magnetically stabilized fluidized bed (MSFBs) utilizing a transverse magnetic field was used to retain cells from cell suspension. The magnetic field permits bed expansion without mixing of the magnetic particles. The bed porosity increased by 75% when the magnetic field intensity increases to 110 mT. The effect of the magnetic field, suspension flow rate, bed height, initial concentration, and pH on the breakthrough curves was studied. According to the experimental results, increasing the initial concentration, flow rate, and pH leads to early breakthrough and inefficient deposition. Additionally, increasing the field intensity and bed height delays the breakthrough point.     

气固流化床中双组分混合颗粒密相床的膨胀

在一套φ500 mm×12500 mm大型冷模实验装置上对大差异双组分混合颗粒体系的密相床床膨胀规律进行了实验研究,考察了表观气速、床层高径比和小颗粒质量分率对混合颗粒体系床膨胀的影响.实验结果表明:基于空隙率表示的床膨胀系数随床层高径比的增大而减小,在床层高径比为2.4后基本不再变化;小颗粒质量分率在0.4附近时,基于空隙率的床膨胀系数达到一最小值.通过对实验数据的分析,得到了基于空隙率的床膨胀系数的数学模型,模型计算值与实验值吻合较好.     

Entrainment Rate of Coarse Particles at Different Temperatures in Gas Fluidized Beds

Based on available experimental data, an empirical relationship is developed for the entrainment rate of coarse particles at the exit of gas‐fluidized beds, including the effects of fine particles in the bed, temperature, gas velocity, particle size and density, and column size. It predicts well the influence of fine particles on the entrainment rate of coarse particles, taking into account the momentum of the fine particles and the effect of superficial gas velocity. It also accounts well for the influence of temperature at different solid densities and gas velocities.     

Granular Temperature in Bubbling Fluidized Beds

In the CFD simulation of industrial‐scale bubbling fluidized beds, coarse grids are necessary due to limited computation resources, which creates a problem about how to characterize the effect of meso‐scale bubbling structures on the particulate phase stresses and inter‐phase interaction force. In this paper, the two‐phase theory of bubbling fluidization is applied in the analysis of the fluctuation characteristics of solid volume fractions and then it was used to establish a simple model for granular temperature in bubbling fluidized beds, which is based on the local pseudo‐thermal energy balance. It was shown that the granular temperature obtained experimentally is well predicted by the present model.     

微小流化床流化特性分析

在内径4.3, 5.5, 10.5, 15.5, 20.5和25.5 mm的6个气固微小流化床中,考察了石英砂和不同粒径的催化裂化催化剂的流化特性. 研究了流化床尺寸、颗粒及流化介质物性对微小流化床床层压降及最小流化速度的影响. 结果表明,不同颗粒及流化介质的微小流化床床层压降实验值均小于计算值. 传统的压降关联式不能直接用于微小流化床. 其最小流化速度随床径减小呈指数增大,在高径比1:1~3:1范围内,最小流化速度随料高增大近似呈线性增大,其增大速度随床径增大而变缓. 基于实验数据得出了微小流化床最小流化速度的关联式.     

流化床喷雾造粒技术进展

本文介绍了流化床喷雾造粒技术,包括造粒机理、操作方式、影响因素等。流化床喷雾造粒是将溶液、悬浮液或熔融液喷雾到已经干燥或不完全干燥颗粒的流化床床层内,在同一设备内一步完成蒸发、结晶、干燥或化学反应的造粒过程。流化床造粒操作对颗粒的尺寸、形状要求不高,所得到的产品无结块、具有良好的流动性能。与其他传统的造粒方法相比,流化床造粒具有工艺流程简单、设备装置紧凑、投资省、生产强度大等优点,越来越引起人们的关注。     

循环流化床的沸腾传热

A model is proposed to predict boiling heat transfer coefficient in a three-phase circulating fluidized bed (CFB), which is a new type of evaporation boiling means for enhancing heat transfer and preventing fouling. To verify the model, experiments are conducted in a stainless steel column with 39 mm ID and 2.0 m height, in which the heat transfer coefficient is measured for different superficial velocities, steam pressures, particle concentrations and materials of particle. As the steam pressure and particle concentrations increase, the heat transfer coefficient in the bed increases. The heat transfer coefficient increases with the liquid velocity but it exhibits a local minimum.The heat transfer coefficient is correlated with cluster renewed model and two-mechanism method. The prediction of the model is in good agreement with experimental data.     

脉动流化床的数值模拟

运用Fluent 6．3中的欧拉-欧拉模型模拟传统流化床与锯齿形波脉动进气流化床的运动特性，并进行对比，针对沿床高的气泡高度、当量直径及内压等因素进行分析，得出脉动锯齿形波进气流化效果比传统流化效果明显提高。     

Bed Expansion – Extending Correlations for Fluidized Beds with Inserts to Open Fluidized Beds

Bed expansion occurs during the operation of gas‐fluidized beds and is influenced by particle properties, gas properties and distributor characteristics. It has a significant bearing on heat and mass transfer phenomena within the bed. A method of predicting bed expansion behavior from other fluidizing parameters would be a useful tool in the design process, dispensing with the need for small‐scale trials. This study builds on previous work on fluidized beds with vertical inserts to produce a correlation that links a modified particle terminal velocity, minimum fluidizing velocity and distributor characteristics with bed voidage in the relationship with P as the pitch between holes in the perforated distributor plate.     

流化床内部构件评选

在φ109mm流态化床里评选内部构件之后,在φ360mm流态化床里,通过邻二甲苯氧化制苯酐反应,以苯酐收率作为检验指标,对四种内部构件再次作了评选。获得的结果与以前是相同的,即斜片挡板效果最好,多孔板次之,垂直管束最不理想。但横向挡板与垂直管束联用时,效果与间隔小的横向挡板相当。回归方程指出,垂直管束构成的床层对温度和气速的敏感性较差,说明两者的气-固流动形态是不一样的。     

磁场流化床在生化工程中的应用

磁场流化床（Magnetically Fluidized Bed,以下简称MFB）是将磁场引入普通流化床,采用磁敏性颗粒为床层介质的流固相处理,MFB利用磁场调节颗粒和流体的运动,使流化床具有更宽的操作范围和适应性,其中,在一定磁场和流动条件下形成的磁稳定流化床（Magnetically Stabilized Fluidized Bed,以下简称MSFB）更是瘘有固定床的流固接触特性和流化床的压降低,传热传质效率高的优点,操作范围较普通流化床变宽,磁场流化床在生化工程领域已经地固穹生物反应器,发酵液固液分离,连续亲合色谱,细胸分离,以及植物细胞和酵母细胞培养等过程,本文介绍了磁场流化床的基本原理和特性及其在生化工程中的应用情况,并分析了该技术进一步应用所面临的困难和发展前景。     

离心流化床动力学模拟

在前人研究的基础上,进一步地考虑了离心流化床在初始流化后气速增大引起的床层膨胀,通过引入气速与空隙率变化函数关系建立了离心力场气固流态化的动力学模型,得出了空隙率和床层膨胀关系式,从而得出床层压降的计算公式。理论预测的针对不同转速、不同颗粒的床层压降与临界速度的关系与实验数据吻合良好,能更准确地预测实验结果。     

Homogeneous Fluidization Characteristics of Vibrating Fluidized Beds

The effects of vibration parameters, operating conditions and material properties on fluidization quality were investigated by the measurement and analysis of voidage fluctuation signals in a vibrating fluidized bed with a diameter of 148 mm. The fluctuation deviation of the bed voidage and the enhancement index of the bed derived can describe bed homogeneity and its extension. A new criterion of homogeneity, consisting of the material parameter (Ar), operating parameters (H₀, u/u_mf) and vibration parameters (a, ω), is proposed to predict a suitable range of homogeneous fluidization. Experimental results on eight kinds of solids, five static bed heights and different vibration parameters were used to propose guidelines for the reasonable selection of operating conditions for vibrating fluidization and better operating conditions.     

Some Drying Aspects of Multistage Fluidized Beds

Multistage fluidized beds with and without downcomers to the horizontal perforated plates are used to dry food materials under different experimental conditions. The influence of various operating parameters such as inlet temperature of the heating medium, flow rate of the heating medium, material flow rate, and number of stages have been investigated. The performance of multistage fluidized beds with and without downcomers is compared and the difference in performance is explained based on stagnancy and short-circuiting of materials in each stage.