导向管充气喷动床流体力学性能

在内径92mm的有机玻璃床内,对导向管充气喷动床的操作相图、床层压降、最小喷动速度及最大弃气速度进行了研究.实验采用4种颗粒为实验物料并采用空气为 喷动和弃气气体,通过对实验数据的回归得到用于计算或判别导向管弃气喷动床最小喷动速度和最大充气速度的计算式,以便为其设计和操作提供依据.     

加压喷动床中细颗粒喷动特性

在内径分别为 186mm和 80mm的加压喷动床中 ,以空气为喷动介质 ,在 10 1～ 70 0kPa的压力范围内考察了几种不同粒度的细颗粒在加压下的喷动特性 .研究结果表明在不同的Re_t 内压力对最小喷动速度的影响不同 .实验还发现 ,随着压力的升高 ,喷动区直径增大 ,稳定操作区域增大 ,加压可明显改善喷动床的操作稳定性     

双喷嘴矩形喷动床中最小喷动速度的实验研究

在双喷嘴矩形喷动床内,以空气为喷动气体,研究了最小喷动速度的变化规律和影响因素。实验表明,双喷嘴矩形喷动床的最小喷动速度与颗粒粒径、床层高度及操作温度有关。并在综合考虑床层高度以及气体和固体颗粒的物性的基础上,得出了双喷嘴矩形喷动床最小喷动时雷诺数的经验关联式。     

狭缝式矩型喷动床中多粒度颗粒体系的最小喷动速度

在150 mm×50 mm×1100 mm的矩形喷动床中,采用宽度为2, 4, 6 mm 的3种狭缝式气体分布板,研究了单一粒度组成和多粒度组成玻璃珠的最小喷动速度. 实验证明,矩形喷动床的最小喷动速度与物料的粒度和组成有关. 给出了最小喷动速度与颗粒粒径和粒度组成的关联式,作出了多粒度组成颗粒体系最小喷动速度的相图.     

双喷嘴矩形喷动床流动性能实验研究

在120 mm×240 mm的双喷嘴矩形不锈钢床内,对新型双喷嘴矩形导流管喷动床的最小喷动速度和喷动高度进行了研究,考察了喷动气速、粒径、静床层高度、导流管直径、导流管安装位置对最小喷动速度和喷动高度的影响。结果表明:最小喷动速度随颗粒直径、导流管直径、导喷距的增大而增大,随静床层高度的增大而减小;喷动高度随喷动气速的增大而增大,随导流管直径的增大而减小,受静床层高度和导喷距的影响不大,并得出了最小喷动速度的关联式。     

导向管喷流床的最小喷动速度的研究

在内径９２ｍｍ的有机玻璃床内,使用四种没的物料,以空气作为喷动相流气体,综合考虑了床层的几何尺寸,以及气体和固体本身的物性,研究了导向管喷流床的最小喷动速度,得出了导向管喷流床的最小喷动速度的经验公式,以便对其设计和操作提供参考     

喷动流化床流动形态变化的试验研究国家

在一个可视化的半圆柱喷动流化床试验台上研究了喷动流化床的流形变化规律。研究表明：随着喷动气量和流化气量的改变,床内会呈现不同的流动形态：固定床、带射流的流化床、喷动床、充气喷动床和喷动流化床。同时研究了量小喷动速度和最小喷动流化速度随喷动管内径、颗粒粒径、静止床高的变化规律,归纳了预测量小喷动速度和最小喷动流化速度的试验关联式,绘制了喷动流化床的流形划分相图。     

双喷嘴矩形喷动床压降的实验研究

在双喷嘴矩形喷动床内,以空气为喷动气体,研究了最大喷动压降与操作压降的变化规律和影响因素。实验表明：双喷嘴矩形喷动床的最大喷动压降和操作压降与颗粒粒径、床层高度及表观气速有关,而操作压降还与床体结构有关。在综合考虑各影响因素的基础上,得出了双喷嘴矩形喷动床最大喷动压降的经验关联式。     

喷动床研究与进展

叙述了近年来出现的几种改型喷动床，包括多喷头喷动床、喷动流化床、带导向管的喷动床、性粒子旋转射流式喷动床、射流喷动床的研究与进展。它们在传统柱锥形喷动床的基础上，通过增加喷口、导向管、流化气、惰性粒子或增加喷动气速等方法，来克服原有喷动床应用的局限性，拓展其应用领域。     

大尺寸喷动床最低喷动速度的估算

最低喷动速度是喷动床设计的重要参数之一。过去人们习惯采用Mathur-Gisher公式来计算,但由于该公式是建立在小直径床层(D_c=0.076～0.3m)实验的基础上的,故在大直径床层上应用时,产生明显的偏差。本文通过实际数据分析,提出了大直径喷动床层最低喷动速度计算的经验公式。     

Liquid spouting of pulp fibers in a conical vessel

Pulp fibers can be spouted in water in a conical vessel. The entities which are spouted are fiber flocs rather than individual fibers. Synthetic fibers, which do not flocculate, cannot be spouted. For comparison, rigid spherical particles were spouted with water in the same conical vessel. Liquid spouting of rigid particles was similar to gaseous spouting. For pulp spouting, the minimum spouting velocity is proportional to the mass of fibers in the bed and inversely proportional to the diameter of the inlet. For rigid particles, the minimum spouting velocity is proportional to the height of the bed and inversely proportional to the square of the diameter of the inlet. A model for the minimum spouting velocity was developed for pulp spouting.     

Spouting of two-dimensional beds with draft plates

Two slotted two-dimensional spouted bed units with flexible bed dimensions were used with draft plates to study spouting pressure drop and minimum spouting superficial velocity. The data were collected while varying slant angle, spout width, separation distance, length of bed, height of bed, and size of bed (geometrical similarity) using shelled corn, soybean, and wheat. The variables which affect the spouting pressure drop and air flow through the beds are discussed. Empirical correlations are developed following the principles of dimensional analysis and similitude. The developed correlations agree closely with the collected data.     

Hydrodynamic Characteristics of a Powder‐Particle Spouted Bed with Powder Entrained in Spouting Gas

Spouting of 3.7 mm polyvinyl chloride particles in a cone‐based cylindrical column is subjected to entrainment of FCC powder in the spouting air. It is found that the powder entrainment reduces the minimum spouting velocity, increases the bed pressure drop and reduces the maximum spoutable bed height. At any given bed height and value of U/U_ms, there is a critical value of powder loading ratio above which spouting gives way to slugging.     

A comparative hydrodynamic study of two types of spouted bed reactor designs

In order to properly design and scale up spouted beds, one needs to predict the minimum spouting velocity of specific systems having different bed dimensions, and properties of particle and spouting gas. Because of inherent complexity of predicting minimum spouting velocity, the prevailing approach has been to use empirical correlations, a number of which are available in the literature. Central jet distributors are commonly used in the experimental studies reported in the literature. Circular slit distributor is a new concept in which air is supplied to the bed of particles through a circular slit. This paper presents results of an experimental study on the hydrodynamics of central jet and circular slit distributors. In this paper a fully connected feed-forward neural network model was used to predict the minimum spouting velocity of central jet and circular slit spouted beds. A neural network model was also developed to predict minimum fluidization velocity. The actual experimental data obtained from published literature and from the experiments carried out in this study were used for training and validating the models. The minimum spouting and fluidization velocities predicted using the neural network models developed in this study show a better approximation to the actual experimental values than those obtained from correlations available in the open literature. The position of flow regime of circular slit spouted bed was also established relative to the flow regimes of central jet spouted bed and fluidized bed.     

The spouting regime map,bubbling characteristics and bed expansion of deep beds of large hollow polyethylene spheres

The high velocity spouting regime of a deep bed containing 9.6 mm hollow polyethylene spheres of density 394 kg/m³ was investigated in a 152.4 mm flat bottom cylindrical half column with a 50.8 mm inlet. A bed height vs gas velocity regime diagram is presented showing the conditions under which type II spouting is observed. The transition velocity from bubbling to type II spouting is determined using the autocorrelation of the pressure fluctuations in the bed. The bubbling characteristics of the bed are described. Bed expansion in bubbling and type II spouted beds are reported.