液固流态化流区及其变迁

本文在两种不同的有机玻璃床中(φ50×1200+φ100×500 mm),采用示踪粒子的方法,对液固流态化的流况及其随液速的变迁进行了研究。实验发现,液固流态化的流况随液速的增大,首先由固定床进入均匀散式流化;当液連增大到某一值(本文称为起始湍流速度)后,床层将进入湍流流化状态;再进一步增大液速,则床层变成下部湍流流化和上部均匀散式流化共存的流化状态。在本实验条件范围内,实验测得的湍流流化床层高度与有关的参数关系为而床层的总高可由Richardson方程式求得。     

液固和气液固微型流态化研究进展

在百年流态化的研究过程中,涉及到直径不同的流化床。但是,多以流化床的大型化为研究目标,对微型流化床及其本身特性的研究很少。作为专门处理固体颗粒的流态化单元过程,其装置的微型化将兼具微通道反应器和宏观流化床各自的优点,是流态化研究的重要方向。鉴于气固微型流化床已有全面的国内外进展综述,本文仅对液固和气液固微型流化床的国内外研究进展进行分析。结论性内容包括：液固微型流化床床径减小,壁面效应增强,最小流化液速实验值大于Ergun公式计算值;需对描述液固均匀膨胀流化规律的Richardson-Zaki方程加以修正。气液固微型流化床内存在4种典型流型：半流化、弹状流、分散鼓泡流和液体输送流;由于床径减小,出现半流化状态,依据压降表观液速关系曲线等无法确定最小流化液速;气液固微型流化床的反应性能得以有效提升;最后给出了进一步研究的方向,以期为后续研究提供参考。     

固体表面活性对液固流态化的影响

用硅烷化试剂对改性聚苯醚（PPO）颗粒进行表面脱活性处理，发现其流化性能得到改善，同时水在颗粒间流动的阻力略有减小。     

宽粒体系液固流态化随机理论数学模型

用快速切割流化床研究了宽粒级液固流态化的轴向混合和分离,测定了粒度分布、平均粒径和空隙度沿床高的变化.证实了颗粒的运动有随机性.用马尔柯夫过程建立了一个随机游走模型,描述了流化床中宽粒体系的混合和分级特性.对钛铁矿和石英砂(粒径0.04～0.40mm)进行了检验.结果表明,体系的初始流态化速度、膨胀性质、粒度分布以及平均粒径和空隙度沿床高的变化的测定结果,同模型的预测值很好符合.     

液—固磁场流态化模型及普遍化相图

本文考察了磁场流态化的基本特征,并结合实验分析了均匀磁场中液-固流态化模型参数的变化规律,对Ma 和 Kwauk 提出的指数模型作了补充,使之与经典流态化加以统一,并在此基础上获得了磁场流态化的普遍化关系图。完善后的模型可根据经典流态化的基础数据直接预示磁场作用下流态化的一些特征,模型计算结果与水-钢丸系统的实验数据吻合较好。     

液固流态化列管换热器（FBHX）的研究

本文介绍了一种新型液固流态化换热器（ＦＢＨＸ）,该装置具有高效连续在线除垢自洁的特点,可提高传热系数,延长正常运行周期。     

管程内循环液固流态化换热器在冷冻工段的应用

采用湘潭大学流态化换热器技术，对四台冰机水冷凝器进行改造，使１９９５年夏季冰出口压力比１９９４年同期同负荷下降低０．０９ＭＰａ降低了消耗。     

利用液固流态化技术测量煤炭密度组成的研究

介绍了应用液固流态化技术测定煤炭密度组成的研究及应用情况;阐述了利用压差测试法测定煤样密度组成的原理;并探索利用此项技术建立起液固流态化浮沉装置自动测试系统。     

气液固三相循环流态化

<正>由于三相流化床反应器在石油化工、湿法冶金、环境工程和煤的液化等工业领域得到越来越广泛的应用,近年来对传统的三相流化床进行了大量的基础研究并取得了很大进展。以往的研究大部分是针对低液速(u_l相似文献   

流态化工程研究的前沿课题

流态化工程在当前和今后的技术进步中已显示出了强大的生命力。本文介绍了流态化工程在国民经济中的作用、快速流态化与传统流态化的区别。讨论了气液固三相流态化行为。提出了流态化技术的发展前景。     

STOCHASTIC BEHAVIOR OF FLUIDIZED PARTICLES IN A LIQUID-SOLID FLUIDIZED BED

In a liquid-solid fluidized bed, the apparently irregular or stochastic behavior of particles gives rise to various flow regimes depending on parameters such as the particle size, liquid flow rate, static bed height and axial position in the bed. It is highly plausible that this irregular behavior manifests itself as pressure fluctuations; thus, the effects of these parameters on the particle behavior or the particle flow regime were investigated through measurement and spectral analysis of the pressure fluctuations. The results indicate that the amplitude of pressure fluctuations exhibits a maximum and that the decay constant in the autocorrelation function attains its minimum at the intermediate liquid flow rate where the particle flow regime undergoes transition from the cluster circulation to the individual quasi random motion. The model composed of the periodic and stochastic components of pressure fluctuations, is in good accord with the experimental results in terms of both the autocorrelation and power spectral density functions.     

DISPERSION AND FLUCTUATION OF FLUIDIZED PARTICLES IN A LIQUID-SOLID FLUIDIZED BED

Axial dispersion coefficient and fluctuating frequency of fluidized particles have been determined in a liquid-solid fluidized bed by resorting to the relaxation method from the histograms of pressure fluctuation in the bed. Dependence of the axial dispersion coefficient and fluctuating frequency of fluidized particles on the liquid flow rate and particle size, and further on the bed porosity has been discussed. The axial dispersion coefficient and fluctuating frequency of particles have attained their maxima with increasing liquid flow rate and bed porosity, and those values increase with an increase in particle size under fully fluidized concitions. It also has been found that the axial dispersion coefficient shows its maximum at the liquid flow rate where the fluctuating frequency of particles reaches its maximum point.     

APPLICATION OF DRIFT-FLUX MODEL IN LIQUID-SOLID CIRCULATING FLUIDIZED BED

Solids circulation rate and solids holdup are experimentally investigated in a liquid-solid circulating fluidized bed that covers a wide range in solid and liquid flow rates, particle size, and density. The drift-flux model, which is extensively used to describe the flow behavior of gas-liquid systems, is modified in the present work and for the first time applied to the experimental data of a liquid-solid circulating fluidized bed. The distribution parameter C_o is evaluated using the drift-flux model from the present experimental data and also from the data available in the literature. It is found from the analysis that the value of the distribution parameter lies in the range of 0.78 to 0.99, which is a reverse trend to the liquid-gas system. The weighted average drift velocity (u_sj) is well correlated to the terminal velocity of the particle. The solid holdup predicted using this model agrees with the experimental results.     

LIQUID-SOLID MASS TRANSFER IN A THREE PHASE DRAFT TUBE FLUIDIZED BED REACTOR

Liquid-solid mass transfer coefficients in a three phase draft tube fluidized bed reactor have been measured using spherical ion exchange particles. The particle diameters ranged from 655 to 1119μm and solids volume fractions of approximately 5 and 10% were employed in water at 28°C. The experimental data can be successfully correlated using a Reynolds number derived using Kolmogoroffs theory of isotropic turbulence, although it is doubtful whether isotropic turbulence actually prevails in the fluidized bed over the range of conditions employed. Comparison with correlations determined for bubble columns and gas-liquid fluidized beds is performed. A model which considers the draft tube reactor as comprising two distinct fluid mechanical regions is developed to explain the apparently lower values of mass transfer coefficients obtained in a draft tube as opposed to conventional fluidized bed reactor.     

液固反应-再生循环流化系统连续合成十二烷基苯

在新型液固循环反应-再生流化系统中研究了十二烷基苯的合成。探讨了反应转化率、表观反应速率常数、催化剂活性因子等随接触及操作时间的变化规律。分析了新工艺中的产物分布。预测了具有工业意义转化率的反应器结构尺寸和操作条件。     

变孔径分布板减小液固流化床中液相返混

引言流化床亲合色谱蛋白质分离新方法综合了亲和吸附的快速、高选择性与液固流化床液相负荷大、传质速率高等优点,尤其是生物细胞可随液相穿透空隙率较大的吸附剂颗粒床层,因此该方法是构成连续分离-反应相耦合的蛋白质生产工艺的有效手段．但不足之处是流化床内的液相返混会严重影响分离效率,因此必须采取措施加以抑制．国外有采用磁稳定流化床来减小液相返混,但要添加体积比44％的磁性颗粒且要在75G_s的磁通密度下操作,有可能影响产品的生物活性．鉴于此,可采取不外加场源的稳定化措施来减小液相返混．本文通过对液固流化床液相返…     

快速流化床提升管中气固流动行为的非线性分析

对φ100mm×16m、FCC固体颗粒的快速流化床提升管内环-核流动区局部颗粒含量脉动行为进行了非线性分析,用Kolmogorov熵表征了其气固流动行为.结果表明,Kolmogorov熵沿提升管环-核流动区径向有3个显著变化区域,以此为依据将提升管环-核流动区的气固流动行为沿径向分成3个流域：单颗粒随机运动控制的核心流域;单颗粒混沌控制的过渡流域;边壁控制的环形流域.同时,从颗粒对垂直气固流动系统中气固湍动程度影响的角度,解释了Kolmogorov熵的径向分布特征及其与流动结构的关系.     

液－固喷动流化床的膨胀特性和液体混合

在φ１０４ｍｍ×１５００ｍｍ的液－固喷动流化床内，对２种不同孔径的喷嘴分别进行喷动流化，利用轴向扩散柱塞流模型得到了液体轴向扩散系数。讨论了流体速度、床层空隙率、颗粒物性和喷嘴孔径等因素对液体轴向扩散系数的影响，并得到了轴向扩散系数的关联式。另外，还研究了床层的膨胀特性，得到了床层空隙率的关联式。     

液固循环流化床两相流动模型

引　言流化床换热器具有防、除垢和强化传热等优点 ,在化工、食品、海水淡化、废水处理等领域具有广阔的应用前景[1].目前 ,流化床换热器历经散式流化床、内循环流化床 ,已发展到外循环流化床换热器[2 ],它要求在较稀的颗粒浓度 (颗粒浓度小于 5% )、较高的流速 ( 1～ 3ｍ·ｓ- 1)下操作 .流化床换热器中液体流动及颗粒运动状态的研究对流化床换热器的设计和操作具有重要意义 ,但人们对循环流化床换热器中颗粒运动情况的研究还很缺乏 .考虑到循环流化床换热器中的每根换热管都可作为一个独立的循环流化床对待[3].本文试图建立一滑移速度模型…     

液-固流化床中单个变形气泡的上升速度

以气泡在上升运动过程中的受力分析为基础,建立了描述单个变形气泡在液－固流化床中上升速度的理论模。应用该模型分别对球形和球帽形气泡在液－固流化床中的上升速度进行了计算,并将计算民在不同的床内压力,温度与颗粒相体积分数下气泡上升速度的实验测量数据进行了比较。