喷动流化床的最小喷动流化速度和床层压降

在一喷动流化床（直径 ５０ ｍｍ）实验台上采用 ０．６３～１．６０ ｍｍ的神府原煤颗粒,在连续进料的情况下进行了最小喷动流化速度以及固定流化气、改变喷动气和固定喷动气、改变流化气的床层压降变化的实验研究．结果表明,最小喷动流化速度可以参考鼓泡流化床的临界流化速度的计算方法;床层压降变化证实,喷动流化床具有良好的调节能力．     

串行流化床内气固流动控制

针对化学链燃烧分离CO₂技术特点,在一串行流化床（循环床+喷动床）冷态实验装置上,以CaSO₄载氧体为实验原料（d_p= 0.6 mm）,研究串行流化床气固流动特性。基于床内压力分布特征,提出将循环床（空气反应器）沿床高方向划分为鼓泡段和快速流化段2个流型区域,将喷动床（燃料反应器）沿床高方向划分为喷动段、鼓泡段和悬浮段3个流型区域,得出串行流化床内气固流动控制机理。研究并考察了循环床流化风速度、喷动床喷动风速度对串行流化床内反应器间（空气反应器和燃料反应器）气体串混、颗粒循环速率以及床层压降的影响。研究结果表明,流化风是床内颗粒循环的驱动力,流化风速度应控制在 3.77～4.05 m·s^-1;喷动风速度对床内颗粒循环以及系统稳定运行起着关键作用,建议将喷动风速度控制在0.42～0.56 m·s^-1。     

城市固体废弃物（MSW）加压裂解的喷动流化床流动和扩散规 …

在一个加压喷动流化床冷态实验装置上研究了加压条件下床中的气固流动状态和气体在各部分的扩散特性。实验设备主体为圆柱形结构,高３．５ｍ,同径０．２ｍ。采用聚苯乙烯和玻璃珠为物料,空气为流化介质,二氧化碳为扩散示踪气体。实验结果表明：加压喷动流化床与常压喷动流化床中气固流动状态差异较大,其喷动流化速度与Ｐ＾－０．５成正比。实验还发现,气体由压喷动流化床中气固流动状态异较大,其喷动流化速度与Ｐ＾－０．５正     

生物质快速热解流化床反应器气力进料特性

为探究不同工况下热解流化床反应器的气力进料特性,设计并搭建了流化床反应器气力进料冷态试验装置。生物质原料和床料分别采用落叶松颗粒和石英砂颗粒,通过试验测得了本装置的最小流化速度,研究了流化气速、喷动气速、流量比、初始静床高、石英砂粒径、落叶松粒径对流化床反应器气力进料特性的影响。试验结果表明：流化气速和喷动气速的增加均会提高进料率;流化气使床料流化并为落叶松颗粒提供进料空间,喷动气为落叶松颗粒提供动能,并平衡一部分床层压力;落叶松与石英砂粒径的增加对进料效果不利;流量比在1.9~2.7范围内进料率高且稳定性好。本文构建了生物质、床料与气体的三相流物理及数学模型,开展试验对模型进行验证,结果表明其预测误差为±13%。     

等离子体-喷动流化床性能研究

等离子体-喷动流化床结合了先进的等离子体技术与喷动流化床装置,由流过中心喷口的等离子射流(喷动床)以及通过分配器的辅助流化气流(流化床)组成,目前对等离子体-喷动流化床的操作特性及基本现象研究较少。本研究中,搭建了一套等离子体-喷动流化床装置并进行了性能测试,直流等离子体炬功率12 kW,流化物料采用石英砂颗粒。研究中使用上部内径为198 mm柱状、下部为60°锥体的锥柱形反应器,以等离子体射流作为喷动气流,氮气作为流化气流构成了等离子体-喷动流化床。对比研究了物料在常温下与等离子体条件下在装置内的流动情况;在等离子体状态下研究了喷动流化床内物料的磨损情况;测试了等离子状态下喷动流化床装置内的温度分布。研究结果表明:在等离子体条件下实现物料喷动流化所需的气体流量大大减少,高温区集中于物料喷动流化区,体系的能量利用效率高,该装置适宜进行生物质等离子体热解或气化。     

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。     

半圆柱形液固导向管喷动流化床流型的研究

本文以平均粒径为0．9mm的玻璃珠为流化颗粒,常温水为流化介质,在直径为97mm的半圆柱形液固导向管喷动流化床中,通过对喷动区和环隙区单位床高压降-流速曲线的分析并结合实验现象的观察,确定了喷动区和环隙区的流型及流型转变速度,在此基础上提出了液固导向管喷动流化床的流型图。研究结果表明,环隙达到流态化后,在较大的喷动液流速范围内,颗粒层能维持在较低的膨胀牢状态下。这对流化床电极非常有利;液固导向管喷动流化床有较大的操作弹性。     

三维整体式喷动-流化床结构优化与流动数值模拟

为了对环隙区内的颗粒堆积层产生局部流化作用,提出了一种在喷动床锥体处开一定数量侧喷嘴的整体式多喷嘴喷动-流化床结构,并采用双流体模型(TFM)对三维整体式多喷嘴喷动-流化床内的气固两相流动行为进行了数值模拟。通过计算流体力学(CFD)模拟获得了喷动床内颗粒体积分数、颗粒速度及流场均匀度分布情况,并将模拟结果与传统喷动床进行了对比,同时对锥体处开孔直径等关键参数进行了优化分析。结果表明:与常规喷动床相比,三维整体式多喷嘴喷动-流化床结构能有效增强喷动床环隙区与喷射区颗粒的径向混合,特别是流化了喷动床环隙区底部颗粒的流动死区。颗粒流场均匀度(CV)值随着床层高度的增加而上升,表明多喷嘴对颗粒流场的均匀化效应主要体现在喷动床柱锥区,当A_i/A_z=0.67时,侧喷嘴对喷动-流化床内整体的颗粒流化作用达到最佳。     

喷动流化床流动特性研究

选用密度与尿素相近而粒度不同的三种模拟物料，在内径为１８２ｍｍ的有机玻璃喷动流化床中，对喷动流化床的流体力学行为进行了研究。测定了不同物料最大操作区所对应的静床高及喷动流化气速与床层压降、床层空隙率分布的关系。为喷动流化床尿素造粒热态试验提供了可资借鉴的设计及操作依据     

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。     

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.     

喷动流化床及其在煤加工方面的应用

论述了喷动流化床的主要技术进展,讨论了其主要流体动力学特性如喷动气流动形式、床层压降、固体循环速率、最小喷动气速和颗粒停留时间等以及喷动流化床在煤加工方面的应用如裂解、气化和燃烧等．指出了喷动流化床发展前景．     

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。     

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.     

Hydrodynamics of spouted and spout-fluidized beds at high temperature

Hydrodynamic parameters were investigated in a 0.15 m diameter half-column spout-fluidized bed at temperatures up to 880°C for ratios of auxiliary air flow to total air flow from 0 to 0.62 and four narrow size ranges of silica sand. Equations in the literature gave poor agreement with the minimum spouting velocity over the entire temperature range. For large particles U_m generally increased with temperature, while for small particles it decreased. Auxiliary air had more influence at elevated temperatures than at room temperature. Pulsations leading to choking appeared to cause spout termination at elevated temperatures. The McNab and Bridgwater (1977) equation correctly predicted the observed trends for maximum spoutable bed depth at high temperatures.     

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.     

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.     

A Discussion on Minimum Spout Velocity and Jet Penetration Length

The similarity and difference between the flat‐bottom and cone‐bottom cylindrical spouted beds, conical spouted beds and vertical upward jets in fluidized beds have been analyzed in this paper based on the effects of geometrical parameters on the minimum spouting velocity and operating stabilities of the spouted beds. The effect of angle on minimum spouting velocity was found to be only significant within the range of 30 to 60 degrees cone angles. Minimum spouting velocity in deep cylindrical spouted beds was proportional to the square root of the static bed height, but was proportional to the static bed height in conical spouted beds and large cylindrical spouted beds with small height‐to‐diameter ratio. The relationship between the minimum spouting velocity and the static bed height was consistent with that between jet velocity and the vertical jet penetration length in jetting fluidized beds.     

Aerodynamics of a novel rotating jet spouted bed

A novel rotating jet spouted bed (RJSB) is developed and tested. It consists of a rotating air distributor with two radially located spouting air nozzles. The effects of bed height, distributor rotational speed, nozzle diameter and particle properties on the flow characteristics were examined. Various flow regimes were mapped as functions of distributor rotational speed and superficial air velocity for different materials and column dimensions. Empirical correlations were developed for the minimum spouting velocity, peak pressure drop and steady spouting pressure drop.