空气-SRNA-4催化剂磁稳定床的流动特性

床层压降、最小流化速度、固含率及其分布和气相返混系数是气固磁稳定反应器放大与优化所必需的基础数据.采用压降法、光电法及瞬态点源示踪技术试验研究了以SRNA-4催化剂为固相的气固磁稳定床的流动特性.试验结果表明:最小流化速度、最小流化状态下的床层空隙率与磁场强度无关;固含率的径向分布基本均匀;磁场强度的增大抑制了颗粒的运动,使得局部固含率略微增加;空塔气速的增加促进了气固磁稳定床的膨胀,使得固含率减小;粒径较小时,随磁场强度及气速的变化贝克来数(Pe)变化不大;粒径较大情况下,Pe随气速增大而减小,随着磁场强度的增大,先增大后减小.试验获得了最小流化速度、固含率和床层高度的关联式,预测值与试验值吻合良好.     

流化床-提升管耦合反应器内固含率的轴向分布及流动发展

在耦合流化床反应器大型冷模实验装置上,考察了不同表观气速下FCC颗粒在耦合流化床内截面平均密度的轴向分布. 结果表明,反应器轴向固含率可分为底部流化床区域和上部提升管区域. 前者的密相区平均固含率随表观气速增大而减小;后者的平均固含率随表观气速Ug增大而增大,Ug<0.58 m/s时固含率分布均匀,Ug=0.70~1.04 m/s时提升管出口出现约束返混区(>8.62 m),Ug>1.16 m/s时提升管底部出现密度重整区(3.82~4.57 m)、加速平稳区(4.57~8.62 m)和出口返混区(>8.62 m). 确定了耦合反应器内提升管区域截面平均固含率的影响参数,并利用实验数据回归了平均固含率的轴向分布经验模型,计算值与实验值吻合较好.     

耦合流化床提升管内固含率径向分布及沿轴向的发展

针对催化汽油辅助反应器改质降烯烃工艺,结合提升管与流化床的特点,建立了一套提升管与流化床耦合反应器大型冷态实验装置. 在不同操作条件下,采用PV-4A型光纤密度仪测定了提升管内固含率沿径向的分布规律. 结果表明,固含率径向分布整体上呈现中心小、边壁大的环-核结构分布特征;沿轴向向上,各径向位置上的固含率在颗粒加速区逐渐降低,在充分发展区趋于稳定,在颗粒约束返混区又有所升高;各径向位置上的固含率随表观气速增大或颗粒循环强度减小而减小,且均匀性变好;提升管上部流化床内颗粒静床高度只对颗粒约束返混区内固含率径向分布有影响,而对颗粒加速区和充分发展区的固含率径向分布影响较小;当表观气速较低或颗粒循环强度较大时,颗粒约束返混区上部局部固含率最大值出现在无因次半径f=r/R=0.7附近,此时局部无因次固含率es*=es/ 沿轴向在H>5.33 m时不再具有相似性;通过比较径向不均匀指数,得到轴向各区固含率径向分布趋于均匀的程度依次为：充分发展区>颗粒约束返混区>颗粒加速区. 利用实验数据回归出了局部固含率径向分布关联式,其平均相对误差在6%以内.     

磁稳定床羰基化合成碳酸二苯酯的冷模实验

以磁性催化剂Pd/La0.5Pb0.5MnO3为固相、N2为气相、纯水为液相在磁稳定床上进行冷模实验,探索磁稳定床的流动特性,为磁稳定床氧化羰基化合成碳酸二苯酯提供数据。考察了不同操作条件对固相催化剂在磁稳定床中流化状态的影响,并通过流体力学软件FLUENT对实验进行计算模拟。结果表明:催化剂可以在流化床中达到完全流化状态,且起始流化速度随液体流速增大、外加磁场强度的增大及分布板开孔率减小而增大,床层高度随气相流速和液相流速减小而减小,随磁场强度的减小而增大,固相分布随床层高度减小而趋于密集,在实验气相流速范围内,床层的平均气相含率与气体流速基本呈直线上升关系。FLUENT软件模拟结果与实验过程完全吻合。     

规整填料塔液相混合的研究

本文采用点源脉冲示踪的方法考察了装填２５０ Ｙ 型金属板波纹规整填料的填料塔中的轴向及径向返混。在规整填料塔的顶部注入 Ｋ Ｍｎ Ｏ４ 作为示踪剂,从塔的底部的不同径向位置取样。通过最优化方法计算出轴向返混系数 Ｄｚ 和径向返混系数 Ｄｒ,研究了液相和气相对规整填料的返混的影响,并就液相和气相对返混影响做了初步解释。实验结果表明：径向扩散系数和轴向扩散系数随气速和液体流速的增大而增大。得到轴向和径向混合系数的彼克列数（ Ｐｅｚ , Ｐｅｒ） 与液相和气相的表观雷诺数（ Ｒｅ１ , Ｒｅｇ） 的关联式。     

循环浆态床气液传质系数的研究

以空气-水-玻璃微珠和空气-石蜡油-玻璃微珠两种三相系统为研究对象,在常温常压下分别考察了液体介质的粘度等物性因素,表观气速、固含率、液体循环量等操作因素,气体分布器、分隔板等结构因素对循环浆态床反应器气液传质特性的影响.实验结果表明,气液传质系数随表观气速的增加而增加,随液体粘度和固含率的增大而减小,当表观气速和固含率增加到一定程度后,传质系数趋于稳定;低气速下,玻璃烧结板的传质效果较好,而较高气速时,多孔板和新型锐孔分布器的传质效果较好;分隔板能显著增大气液传质系数.对多孔板分布器实验数据进行了拟合,得出气液传质系数的经验关联式,关联式计算值与实验结果吻合良好.     

气液并流向上填充鼓泡塔液体混合特性的研究

在内径为165 mm气液并流向上填充鼓泡塔中采用示踪法考查了表观气速、表观液速、液体黏度、填料大小等因素对液体轴向混合特性的影响。根据实验结果得出:Peclet准数随表观液速的增加而增大,轴向返混程度减小,而随表观气速或液相黏度的增加而Peclet准数略有减小,轴向混合程度增加。同时,填料的引入明显减少轴向混合程度,随着填料直径的增加,Peclet准数明显减少,轴向混合程度增大。根据实验结果,关联了实验范围内Peclet准数的计算式,为填充鼓泡塔反应器的设计与放大提供了一定的指导作用。     

气液固三相流化床局部相含率

在以焦末为固相、空气为气相、水为液相的三相流化床中研究了局部气含率和局部固含率径向分布。实验用流化床内径100 mm,高1.7 m,焦末粒度1.07 mm。分别采用电导探针法和光纤法测定局部气含率和局部固含率。结果表明:表观气速为0.35—0.71 cm/s,表观液速为2.12—3.54 cm/s时,局部气含率在流化床中沿径向r/R=0—0.8处分布较均匀,在靠壁面处下降至约0.5%,且随表观液速增加而减小,随表观气速增加而增大,且在距分布板轴向高度分别为370 mm和470 mm时趋势一致,大小沿轴向增加,在表观气速一定时,液速小于2.12 cm/s时,气含率沿径向减小的趋势较明显。局部固含率沿径向分布较均匀,基本不随表观气速变化而变化,随表观液速增大而增大,且在距分布板轴向高度分别为370 mm和470 mm时趋势一致,大小沿轴向减小。     

流化床提升管中脱油油砂颗粒固含率的轴向分布

针对油砂直接流化焦化工艺,建立了一套大型冷模提升管循环流化床装置. 粒度测试结果表明,该脱油油砂颗粒属宽筛分混合颗粒,且细颗粒含量较多,粒度分布宽(1~>2000 mm). 在不同操作条件下,采用多点压力密度测量仪测定了提升管内压力梯度和截面平均固含率沿提升管轴向的分布. 实验结果表明,脱油油砂颗粒在提升管内截面的平均固含率随表观气速增大而减小,随颗粒循环强度增大而增大;固含率沿提升管轴向的分布为C型,即上下两端较浓、中间较稀,且沿提升管自上而下分为3个区域：颗粒约束返混区(>12 m)、充分发展区(4~12 m)和颗粒加速区(<4 m);在相同操作条件下,脱油油砂颗粒在提升管内截面的平均固含率高于FCC颗粒,加速段与约束返混段长度大于FCC颗粒;确定了脱油油砂颗粒在提升管内截面平均固含率的影响参数为ep', Fr及Hr/Dr;通过实验数据回归得到提升管内截面平均固含率轴向分布的经验模型,计算与实验值吻合较好.     

费托合成浆态床速度分布和浓度分布的模拟及其影响规律

提出了浆态床速度分布的一维流体力学模型和合成气液相浓度分布的二维扩散模型,用于描述浆态床液相返混对费托合成反应的影响。模型计算结果与示范工厂数据符合良好。计算表明,液相返混状态对合成气转化率有显著影响。利用模型考察了空塔气速对合成气转化率和空时产率的影响规律,随气速增加,合成气转化率单调下降,空时产率先增大后缓慢降低;塔径放大后,中心液速和液相循环流率都增大,浆料返混加剧,费托合成反应转化率降低。     

磁稳定床轴向液体分散特性

1 INTRODUCTION Magnetically stabilized beds (MSB) have at- tracted many research interests, owing to the unique feature of combination of characteristics for packed bed and conventional fluidized bed, especially in the field of biotechnology processes such as bioseparation or immobilized enzyme catalyzed systems. However, there are few reports about the effects of physical properties of fluids on the axial liquid dispersion coef- ficients in both L-S and G-L-S MSB. Siegell[1] , Goetz …     

以非晶态合金催化剂SRNA-4为固相的气液固磁稳定床的界面传质研究

1 INTRODUCTION Magnetically stabilized beds (MSB) exhibit an unique combination of packed-bed and fluidized-bed properties. Gas-liquid-solid (G-L-S) three-phase MSB has recently attracted more attention in the field of biotechnology processes (such as bioseparation or immobilized enzyme systems) and chemical engi- neering(such as the hydrogenation reaction system). The interphase mass transfer behavior plays an im- portant role in the optimal operation of practical MSB. However, many…     

Macroscopic properties of liquid-solid circulating fluidized bed with viscous liquid medium

Experiments were conducted in a liquid-solid circulating fluidized bed to study the effect of liquid viscosity and solids inventory on pressure gradient, critical transitional liquid velocity, onset average solids holdup, axial solids holdup distribution, average solids holdup and solids circulation rate in circulating fluidization regime with riser operated in fixed inventory mode. The results indicate that critical transitional liquid velocity decreases with increase in liquid viscosity. The onset average solids holdup, on the other hand, increases with increase in either auxiliary liquid velocity or solids inventory. The variation of axial solids holdup distribution, average solids holdup and solids circulation rate with liquid viscosity when solid inventory was 0.15 m was dissimilar with either 0.25 m or 0.35 m solid inventory. Correlations were proposed for estimating the average solids holdup and are satisfactorily compared with experimental values.     

液固磁稳定床中的传热与传质特性研究

以电化学方法测定了SRNA-4催化剂为固相的液固磁稳定床中的液固传质系数,采用浸没的微型传热探头测量了液固传热系数。实验结果表明：随磁场强度、液体黏度的增大,液固传质系数及传热系数减小;增加表观液速,传质系数、传热系数均增大。进而建立了由物性参数及操作参数估算液固传质Sherwood数及液固传热Nusselt数的关联式,实验值与预测值吻合良好,可为磁稳定床反应器的放大设计和操作优化提供一定的依据。     

液固磁稳定床流体力学特性

The hydrodynamic characteristics of liquid-fluidized magnetically stabilized beds (MSB) with commercial amorphous nickel alloy catalyst (SRNA- 4) as solid phase and water as liquid phase in a cold model experimental apparatus of Φ140 mm were investigated. The influence of magnetic field intensity on bed structure, pressure drop, minimum fluidization velocity, transition velocity, and liquid holdup were investigated. Mathematical models for minimum fluidization velocity, transition velocity, liquid holdup were established respectively. The operating phase diagrams of liquid-fluidized MSB with SRNA-4 catalyst of two different sizes were obtained.     

Hydrodynamics of a slurry airlift reactor at high solid concentrations

The hydrodynamics of a slurry airlift reactor at high solid concentrations were experimentally studied. The influences of the average solid concentration, superficial gas velocity and particle size on the radial and axial profiles of the solid holdup, average gas holdup and liquid circulation velocity were investigated. The local solid holdup was measured with an electrical conductivity probe. At low solid concentrations or high superficial gas velocities, the radial profile of the solid holdup was uniform. At high solid concentrations, the radial profile of the solid holdup was nonuniform, with higher values near the wall. This radial nonuniformity increased with decreased superficial gas velocity or increased average solid concentration. The axial profile of the cross-sectional average solid holdup was uniform at all conditions in this work, even at high solid concentrations. The average gas holdup and liquid circulation velocity increased with the superficial gas velocity but decreased with the average solid concentration. A mathematical model based on the balance of the transverse lift force and turbulent dispersion force was proposed to predict the radial profile of the solid holdup. Reasonable predictions were obtained from this model with an adjustable model parameter.     

Effects of internals on phase holdup and backmixing in a slightlyexpanded-bed reactor with gas-liquid concurrent upflow

Five different internals were designed, and their effects on phase holdup and backmixing were investigated in a gas-liquid concurrent upflow reactor where the spherical alumina packing particles of three diameters (3.0, 4.5 and 6.0 mm) were slightly expanded under the conditions of varied superficial gas velocities (6.77×10^-2-3.61×10^-1 m·s^-1) and superficial liquid velocities (9.47×10^-4-2.17×10^-3 m·s^-1). The experimental results show that the gas holdup increases with the superficial gas velocity and particle size, opposite to the variational trend of liquid holdup. When an internal component is installed amid the upflow reactor, a higher gas holdup, a less liquid holdup and a larger Peclet number characterizing the weaker backmixing are obtained compared to those in the bed without internals under the same operating conditions. Additionally, the minimal backmixing is observed in the reactor equipped with the internals with a novel multi-step design. Finally, empirical correlations were proposed for estimating gas holdup, liquid holdup and Peclet number with the relative deviations within 11%, 12% and 25%, respectively.     

HYDRODYNAMICS, MIXING AND MASS TRANSFER IN A LARGE DIAMETER JET BUBBLE COLUMN

Experimental measurements for the axial and radial variations in gas holdup, axial and radial dispersion coefficients, volumetric gas-liquid mass transfer coefficient and liquid phase circulation velocity in a cone of a large diameter (122 cm) jet bubble column are presented. Two diameters of the inlet nozzle, namely 10.16 cm and 15.24 cm, three superficial gas velocities (based on cylinder diameter), 3 cm/sec, 6 cm/sec and 8 cm/sec and two superficial liquid velocities, 0.3 cm/sec and 0.6 cm/sec, are examined. The experimental data are obtained for two different bed heights.

The experimental data showed significant axial and radial variations in the gas holdup. The volumetric average gas holdup was higher at higher gas velocity and larger nozzle diameter and somewhat higher at lower liquid velocity. The axial dispersion was high while the radial dispersion was low. The volumetric gas-liquid mass transfer coefficient was larger at higher gas velocity and larger nozzle diameter. The liquid recirculation begins only at the upper end of the cone. In general, experimental data indicate that a jet bubble column provides a high degree of mixing and transport rates.     

液-固流化床中滤料流场及固含率分布

用PV4A测速仪和CFD数值模拟的方法对液-固流化床内滤料(固体颗粒)的流动行为进行了研究,得出了流化床内滤料的流场分布状况.试验结果表明:流化床中铜锌合金(KDF)滤料的运动速度和固含率随流化床高度的增加分别呈现出先上升后下降的趋势;而沿径向从中心至管壁则呈下降趋势.模拟结果显示的固相运动速度和体积分率的轴径向分布趋势与试验测定结果基本吻合.