溢流管式多层流化床的计算

多层流化床沿着床高垂直地建立起浓度梯度和温度梯度,能使流化床中固体的停留时间分布得较均匀,是强化流化操作的一条重要途径。应用在催化反应中可以提高产品的转化率,在矿物焙烧过程中充分地利用了热交换逆流操作的原理。前人在这方面已进行了很多工作。溢流管式多层床在设计中需要确定操作风速、层数、层与层之间的高度、筛板的自由截面积,溢流管的长度和直径等参数。这些参数与多层床流体动力学和溢流管的最大下料量密切有关。多层床设计要求:能实现连续操作、结构简单、阻力小和效率高。     

多层流态化床的研究Ⅱ 气-固系

本文研究了气-固系多层流态化床（溢流管式,“B”型）中溢流管的工作性能及传热计算方法。提出了初步的关联影响溢流管固体流率的各因素的方法。在传热部分,作者根据流化床中气- 固相温度接近相等的特点,运用气-液系统中平衡级的概念导出多层流态化床传热计算的公式。     

多层流化床床层及溢流管中气固流动特性的模拟

采用多孔介质模型描述两床层间的气体分布板,开发了一种多层流化床典型结构单元的计算流体动力学(CFD)模拟方法,研究了操作气速对多层流化床床层流化状态及其溢流管内颗粒流动特性的影响.结果表明:层间溢流管内颗粒料位具有缓冲作用,使得颗粒进入下床层后被迅速均匀分散,保证了下床层固相均匀性.流化气速增大,下床层进入溢流管的气体...     

气控式多层流化床及其在净化排放气中的应用

溢流管是多层流化床的关键构件。本文设计的由下料料腿和锥斗组成的气控式锥形溢流管,由于物料在料腿中处于流态化状态,在锥斗中以气固顺流浓相向上输送,因此,这种溢流管可以防止物料在料腿中的架桥和喷料。 试验中测定了多气源和双气源两种气控式多层床的流动特性,包括各床层和溢流管压降以及固体停留时间分布。在回收低浓度二氯乙烷的中间工厂试验中,采用了具有同心圆的双气源多层流化床,获得以下主要结果: 吸附率>97%,排放气浓度<25mg/m~3,活性炭损失<0.1%。 这种能使固体物料由高压区输至低压区,或从低压区输至高压区的气控锥形溢流管结构,亦可用于旋风器料腿的返尘以及在循环系统中固体物料的连续加、排装置。     

锥斗溢流管的移动床上输(摘要)

本文在前人工作及文献调查的基础上,对锥斗溢流管的移动床上输进行了实验探索及理论研究。本文首先在锥斗溢流管中实现了移动床向上输送,并通过实验找出了实现稳定的移动床上输的锥斗的锥角和高度,以及与之相配合的气控点位置。此外,还研究了固体下料率、锥斗溢流管各部压力降、窜气量及气控气量等相互之间的关     

带导流管多层流化床流体力学特性实验研究

多层流化床的应用范围受操作可调性和稳定性等因素限制。在改变传统筛板结构的基础上,研究了传统穿流板多层流化床和导流管多层流化床床层压降随表观气速和进料速率的变化规律,实验结果表明,导流管多层流化床不仅大幅减小了床层压降、提高了床体处理能力和可调范围,而且也改善了物料的流化质量。此外,当料层达到一定高度时,导流管多层流化床还具有喷动流化床的特性,同时导流管还具有溢流物料的作用,进一步加大了气固传质效率和床体处理能力。在流体力学分析的基础上,推导出导流管多层流化床床层压降的关联式,得到了床层压降随进气气速和进料速率的关系,与实验数据基本吻合。     

多分支井井控中阻流器压力分析

在多分支井中有多个井眼发生溢流时,这在钻井完井中存在高风险,其中之一便是井控问题,本文通过分析多分支井井控过程中阻流器压力变化,来解释井下溢流行为,从而为分支井井控提供可靠的方法。     

千屈菜生态浮床对景观水体的净化作用

在水污染处理方面。生态浮床与传统物理化学方法相比,因其具有较好的景观效应及生态效应而越来越多地被利用到景观水体的净化中。选取干屈菜为研究植物,利用人工模拟方法,设计连续进出水试验装置,调节水力负荷,模拟自然河流状态,将丽娃河水泵入试验系统,水体经过生态浮床系统,由出水口溢流排出。实验数据表明（根据《地表水环境质量标准》...     

双流化床反应器间气体泄漏规律的数值模拟

建立了描述双流化床化学链燃烧反应器内气固两相流动的数学模型,采用计算流体动力学方法,模拟考察了提升管和鼓泡床相耦合的双流化床内不同单元之间气体泄漏产生原因和影响因素。化学链燃烧系统压力平衡的分析结果表明,反应器间的气体泄漏主要发生在溢流装置和鼓泡床之间;增大溢流装置表观气速,气体泄漏增大,而增大提升管或鼓泡床表观气速时,气体泄漏会随之减小;化学链燃烧系统内颗粒总藏量增加时,气体泄漏会减小;颗粒粒径减小后反应器之间气体泄漏降低。其研究结果对其他循环流化床反应器的设计与工程放大也有一定的借鉴作用。     

基于水力模型的合流制溢流调蓄池运行效能评估

合流制溢流调蓄池是合流制系统控制溢流污染的有效手段,但受排水系统布置特殊性、水质水量传输规律复杂性、降雨的随机性等因素影响,通过基于截流倍数计算得到调蓄的设计规模,其运行效能难以通过理论计算校核控污效益。文中结合工程案例,借助水力模型,模拟设计调蓄池对不同强度降雨下的溢流污染控制过程,获得调蓄池溢流污染控制效能特性曲线。结果表明,新增调蓄池可显著削减20 mm以下小雨径流污染峰值和总量,全年可控制83%的降雨事件不发生溢流,溢流次数可降低至17次/年,年污染物削减率可达43%。研究成果可为合流制溢流污染调蓄池的设计提供指导反馈,可在实际工程中推广应用。     

气液两相并流下行通过堆叠筛板填料的压降特性

堆叠筛板填料已在核电站放射性气体除气塔中得到成功应用。针对这一新型填料的应用设计,在较广泛的气液流量下,对气液并流下行通过不同规格堆叠筛板填料的阻力特性进行了系统的实验。实验填料共6种规格,孔径参数包括6、10和14 mm,不同孔径填料对应不同的孔间距、板间距,每种孔径填料具有正方形和正三角形两种筛孔分布方式。通过压降数据分析,研究了流动参数和几何参数（孔径、开孔率、布孔方式、板间距）对气液两相并流通过填料的流动行为及压降特性的影响;结合多孔板阻力系数经验公式提出了堆叠筛板填料干板阻力系数的计算模型,模型很好地反映了不同几何参数对干板阻力系数的影响,预测偏差在5%范围以内;基于均相流模型提出了堆叠筛板填料气液两相压降的预测模型,模型预测偏差在10%范围以内。研究工作对堆叠筛板填料塔的应用设计及进一步的传质动力学研究有一定参考价值。     

Solids flow characteristics in loop-seal of a circulating fluidized bed

The hydrodynamics of solids (FCC) recycle in a loop-seal (0.08 m) at the bottom of the downcomer (0.08 m-I.D.x4.0 m-high) in a circulating fluidized bed (0.1 m-I.D.x 5.3 m-high) have been determined. Solid flow rate through the loop-seal increases linearly with increasing aeration rate. At the same aeration rate, the maximum solid flow rate can be obtained at a loop-seal height-to-diameter ratio of 2.5. The effects of solid inventory, solid circulation rate and gas velocity on pressure balance around the CFB have been determined. At a given gas velocity and solid circulation rate, pressure drops across the downcomer and loop-seal increase linearly with increasing solids inventory in the bed. At a constant solid inventory, pressure drops across the riser and the downcomer increase with increasing solid circulation rate but decrease with increasing gas velocity in the riser. The obtained solid flow rate has been correlated with pressure drop across the loop-seal.     

PROFILING SOLIDS FLOW FROM BINS

The bulk flow rate of particulate solids from bins and other storage vessels has been studied extensively since Ketchum's work in 1919.⁶ The flow patterns and behavior of individual particles as they approach and pass through the discharge opening, however, have received little attention. This study was undertaken to see how free flowing particles are distributed in the discharge stream from the bin, to establish something comparable to the velocity profile in a liquid flowing through a pipe.

Solids flowing by gravity through an opening in the bottom of a vessel do not move in the same way as a liquid issuing from the same opening. For one thing, solids flow at a fixed rate, virtually independent of the depth of solids in the bin, whereas liquid flow rate depends on the head. Solid particles in motion occupy more space than close-packed solids at rest; if particles are to move from a stationary bed, therefore, the solid mass must expand and the bulk density must fall. One particle must move over others on its way to the discharge opening; at the opening it separates from its fellows and drops freely away. The discharge stream consists of particles all moving at nearly the same velocity, and there is no “velocity distribution” as such; instead there is a distribution across the discharge stream of the frequency of particles passing through a given horizontal plane.     

PROFILING SOLIDS FLOW FROM BINS

The bulk flow rate of particulate solids from bins and other storage vessels has been studied extensively since Ketchum's work in 1919.⁶ The flow patterns and behavior of individual particles as they approach and pass through the discharge opening, however, have received little attention. This study was undertaken to see how free flowing particles are distributed in the discharge stream from the bin, to establish something comparable to the velocity profile in a liquid flowing through a pipe.

Solids flowing by gravity through an opening in the bottom of a vessel do not move in the same way as a liquid issuing from the same opening. For one thing, solids flow at a fixed rate, virtually independent of the depth of solids in the bin, whereas liquid flow rate depends on the head. Solid particles in motion occupy more space than close-packed solids at rest; if particles are to move from a stationary bed, therefore, the solid mass must expand and the bulk density must fall. One particle must move over others on its way to the discharge opening; at the opening it separates from its fellows and drops freely away. The discharge stream consists of particles all moving at nearly the same velocity, and there is no “velocity distribution” as such; instead there is a distribution across the discharge stream of the frequency of particles passing through a given horizontal plane.     

鼓泡床内气体分布器设计及其对水力学的影响

本文比较了目前常用的几种分布器，通过照像法观察了三种分布器（单孔板、多孔板和烧结金属板）上的气泡形成过程，然后测定了这三种分布器的于板压降和湿板压降，并就它们对水力学条件的影响进行了考察。其结果对鼓泡床内分布器的设计具有一定的参考价值。     

Pressure drop and gas bypassing in recirculating fluidized beds

The effect of different operating and design parameters on the pressure drop profile for a recirculating fluidized bed has been studied. A mathematical model was developed for the pressure drop in the recirculating fluidized bed. The different parameters considered were flow rate, inventory of solids and spacing between the draft-tube bottom and the distribution plate. Geldart D and B particles were used for the study. The gas bypassing from the jet towards the downcomer was calculated on the basis of the mathematical model and the effect of various parameters on gas bypassing were analyzed.     

底部间隙对多室环流反应器流动特性的影响

在空气-水-石英砂三相多室气升式环流反应器(MALR)中,调节底部转角连接处间隙高度分别为18,28,38mm,在表观气速1.2～4.2cm/s范围内,实验研究了底部阻力系数、相含率、循环液速随反应器底部间隙的变化规律。结果表明,随着底部间隙的增大,底部转角处的局部阻力系数减小,循环液速增大,流体夹带进入下降室的气泡和固体颗粒均增多,下降室的气含率和固含率均增大。     

三维上流式反应器床层流动和返混特性

采用内径为280 mm的上流式反应器,以空气模拟气相、甘油和水混合溶液模拟渣油。用3种不同粒径的氧化铝球形工业催化剂颗粒为填充颗粒,考察了不同模拟物系的颗粒粒径、颗粒密度、液相黏度、不同床层的高径比和不同操作条件对上流式反应器内床层压降及其波动、床层轴向返混的影响规律。得到模拟工业运行物系和操作条件的上流式反应器床层总压降关联式,相对误差在12%以内。床层总压降均随床层高径比、颗粒密度和液相黏度增加而增大,但随颗粒粒径的增大而减小,床层压降波动随表观气速增加而增大。填充颗粒粒径越小、颗粒密度越小、高径比越大,床层内轴向返混越严重;床层内压降和轴向返混均随表观气速的增加而增大。     

高通量塔板悬挂式降液管击穿漏气的气液相研究

采用空气-水物系,在直径为500mm的有机玻璃塔中对底部分别开有8个和12个液流孔的悬挂式降液管的漏气进行了研究,并在假设漏入降液管的气体产生的压降与板压降相等的基础上建立了击穿漏气模型.结果表明,当塔内的气体流量逐渐增大,漏入的气体以气柱的形式连续进入降液管时,降液管液层被击穿,降液管无法正常操作.根据实验数据得到了击穿漏气模型的关联式,关联式的计算值与实验值吻合较好.开有12个液流孔的降液管在液流孔的真实漏气气速为1.40 m/s时,漏入的气体会击穿降液管液层.