流动方向对徨流化床中颗粒混合行为的影响

对徨流化床提升管及下行床两种不同气固流动方式对颗粒混合行为的影响进行了较为深入的对比分析，发现在影响循环流化床颗粒混合的众多因素（如操作条件、床层直径、颗粒性质及床层内构件等）中，气固流动方向是影响颗粒轴向混合的最主要因素。当气固流动为顺重力场时（下行床），颗粒的轴向混合很小，流型接近平推流；当气固流动为逆重力场的提升管时，轴向颗粒混合将成倍增大，颗粒流动远离平推流流动。分析表明，下行床中颗粒混合     

操作条件和床结构对床层平均空隙率的影响

研究了操怍压力、操作温度和床结构特性对床层膨胀的影响,随着操作压力的提高床层膨胀比明显增大,操作温度的提高则导致床层膨胀比略有下降,在设有塔型构件、垂直管束、脊型构件Ⅰ和脊型构件Ⅱ的流化床中,床层膨胀行为与床径几乎无关,而对于自由流化床,床层膨胀尚为床径的函数。在计入上述影响因素条件下,根据系统试验数据回归得以下关联式(试验范围为U=0.1-0.8m/s,T=50-500℃,P=0.1-0.8MPa,D=57-475mmm,A、B 类颗粒):ε_f=G·(Ly/Ar)~(0.0691)根据气泡两相理论,由床层膨胀试验结果,可推出处于湍动流态化操作下的自由床和构件床的气泡平均当量直径 D_(Be)计算式:     

催化裂化再生器最佳操作气速的选择

催化裂化是炼油加工中最重要的二次加工过程,其再生烧焦操作条件的选择是影响反应-再生系统作用的关键之一。本文从流态化工程的角度出发,探讨了密相再生器最佳操作气速的选择依据,并提出了选择最佳气速的定量算式。此外,还分析了影响最佳气速的各个因素。     

磁场控制下的流-固相反应装置研究进展

一、前言流-固相反应装置在石油、化工、冶金、环保、轻工等部门中已广泛应用。无论是催化反应还是非催化反应装置,相间接触状况对反应的转化率和收率都有重要的影响。流     

环形截面提升管内颗粒的运动行为

采用PDPA(phase Doppler particle analyzer system)及磷光颗粒示踪技术对环形截面提升管中颗粒的运动行为进行了研究。与传统提升管相比，环形截面提升管中颗粒速度分布的均匀性有所改善，其最高速度与最低速度之差变小。环形截面提升管最大速度值出现在相对径向位置φ=0.3-0．4处。与传统提升管相似，环形截面提升管内颗粒的轴向返混较严重，停留时间分布曲线存在较明显的拖尾，其中颗粒的轴向Peclet数与传统提升管也处于同一数量级范围。提升管床结构的改变并未显著改变其中气固流动的微观相结构，稀相与密相颗粒团微观两相仍然存在，这种微观相结构是造成颗粒严重返混的决定性原因：稀相中的颗粒与密相颗粒团中的颗粒分别造成了颗粒停留时间分布曲线的前峰与拖尾峰。     

气-固并流下行快速流态化的研究(I)

研究气-固并流顺重力场运动中气-固两相之间的相互作用,并依此将气-固运动过程分为第Ⅰ、Ⅱ加速段及恒速段.在直径为φ140mm,高为5.8m的下行快床中,测定了不同操作条件下(μ_g=1.3-10m/s,G_a=30-180kg/m~2·s)床层压力梯度轴向分布及第Ⅰ加速段长度的变化规律,同时考察了颗粒特性对上述过程的影响.     

气刀操作条件对聚丙烯密相脉冲气力输送行为的影响

在一管线水平长１９ｍ、垂直长１１ｍ、内径５０ｍｍ的密相脉冲气力输送实验台上进行了气刀操作条件对管道输送行为影响的实验研究．结果表明：气刀操作条件对管道输送气速、输送能力、固气比、能耗等均有明显影响．确定最佳的气刀操作条件需综合考虑发送压力、输送结构、物料物性等因素．     

EFFECT OF OPERATING TEMPERATURE AND PRESSURE ON THE TRANSITION FROM BUBBLING TO TURBULENT FLUIDIZATION

Experiments have been carried out to investigate the effects of operating temperature(50 to 500℃)andpressure(1×10~5 to 8×10~5 Pa)on the transition from bubbling to turbulent fluidization by computer analysisof the pressure fluctuation in dense phase.In order to reveal the influence of particle properties on the tran-sition process,eight kinds of particles were employed.A empirical correlaton which takes into accountthe effects of temperature and pressure is recommended for the prediction of transition velocity     

Phase holdup and liquid dispersion in gas-liquid-solid circulating fluidized beds

Axial and radial profiles of gas and solids holdups have been studied in agas-liquid-solid circulating fluidized bed at 140mm i.d..Experimental results indicate that the axialand radial profiles of gas and solids holdups are more uniform than those in a conventionalfluidized bed.Axial and radial liquid dispersion coefficients in the gas-liquid-solid circulating fluidizedbed are investigated for the first time.It is found that axial and radial liquid dispersioncoefficients increases with increaes in gas velocity and solids holdup.The liquid velocity has littleinfluence on the axial liquid dispersion coefficient,but would adversely affect the redial liquiddispersion coefficient.It can be concluded that the gas-liquid-solid circulating fluidized bed hasadvantages such as better interphase contact and lower liquid dispersion along the axial directionover the expanded bed.     

PARTICLE FLOW PATTERNS IN THE RISER AND DOWNER OF CIRCULATING FLUIDIZED BED

This paper presents an experimental study on the flow patterns of FCC particles in a 140 mm ID Circulating Fluidized Bed with concurrent upflow and downflow gas-solid suspension. Based on the distribution of local particle velocity and particle concentration measured by a Fiber-Optical Probe Laser Doppler Velocimeter and a Fiber Optical Probe System respectively, the different flow patterns of local particls concentration, local particle velocity, local particle fluctuating velocity and sectionally average particle velocity in concurrent upflow and downflow gas-solid system have been investigated. It is found that the particle flow in the concurrent downflow is much more uniform radially than that in the concurrent upflow riser. The investigation of flow patterns in different flow systems is of significance to the development of a new gas-solid reactor.