GLS-LR中相含率与循环液速的研究进展

介绍了气液固三相环流反应器(GLS-LR)的工作原理及类型,概述了GLS-LR的气含率、固含率、循环液速等特性参数的测量方法,并指出了其优缺点;讨论了这三个特性参数随操作条件的变化规律;汇总并评述了气含率与循环液速的预测模型。     

固体颗粒对三相气升式环流反应器流动特性的影响

将液相视为连续相,气相和固相视为分散相,同时考虑各相之间的相互作用,结合气液固三相流体的动力学理论,建立气液固三相环流反应器三流体湍流流动的Eulerian模型.采用计算模拟软件Fluent对三相环流反应器的流动状况进行模拟,考察表观气速、固含率、颗粒大小对反应器的气含率以及液体流动速度的影响.模拟结果较好地解释了气升式环流反应器内的三相流体行为,模型与实验结果较好地吻合,表明了模型的可行性.     

高固含率三相鼓泡淤浆反应器气液传质研究及其采用两种气体分布器的比较

以空气-水-黄沙以及空气-液体石蜡-黄沙两种系统为对象，在常压下用溶氧仪研究了采用小孔式及金属烧结板两种分布器的高固含率三相淤浆反应器的气液传质特性，以及固含率和表观气速等因素对容积气液传质系数kLa的影响，最后得到采用上述两种气体分布器的高固含率三相淤浆床关于容积气-液传质系数的经验关联式。实验证明，金属烧结板具有更好的气液传质特性。     

环流反应器研究进展

介绍了环流反应器的类型及其工作原理 ,总结了环流反应器的研究及应用现状 ,分析了特性参数气含率、循环液速、液相体积传质系数的影响因素 ,并对流动模型进行了归纳 ,以期对有关工作者及研究者提供一定的借鉴作用。     

高长径比气液固三相内环流反应器的流体动力学

在高径比为22的三相内环流反应器中,常温常压下,根据动量平衡原理建立了空气-水-石英砂三相物系的循环液速模型,并建立了上升区气含率、上升区固含率和底部换向区阻力系数模型;考察了在不同颗粒粒径下,表观气速对上升区固含率和液体循环速度的影响。结果表明:当粒径(ds)≤0.3mm时,上升区固含率随表观气速的增加变化呈平缓趋势,当0.3mmds≤1.2mm时,上升区固含率随表观气速的增加而呈先下降后增加的趋势;不同粒径下上升区循环液速均随表观气速的增加而增加;气含率、固含率和循环液速的计算值和实验值吻合较好,其平均相对误差分别为6.32%、4.56%和11.97%。     

多相气升式环流反应器局部相含率和环流速度

气升式环流反应器流动特性研究大多都局限于流动参数的平均特性研究,涉及气-液-固系统流动特性的研究也较少。在200×2500mm气升式环流反应器内,实验研究了空气-水两相及空气-水-玻璃珠三相体系中局部气、固相含率以及浆(液)相环流特性等随操作条件以及液、固相物性的变化规律。结果表明:1两相体系导流筒中截面平均气含率轴向分布有局部极大值,而固体和乙醇的加入使得气含率轴向分布平缓;2两相体系循环液速在导流筒中呈径向抛物分布,在环隙分布较均匀,加入固体和乙醇后对循环速度分布和大小影响不大;3三相体系中导流筒内固含率沿轴向升高呈增大趋势,环隙内轴向分布均匀;导流筒内、外固含率径向分布均不均匀,以近壁处为大;加入乙醇后对固含率分布影响不大。     

三相环流反应器中的局部相含率

将压差法与气-液相间滑移速度相结合,提出了利用压差法测量三相区局部相含率的新方法,将测得的局部固含率进行轴向平均并与由颗粒装填量计算所得的固含率进行比较,证明了此方法的可靠性. 利用所提出的测量方法,考察了三相环流反应器中气含率和固含率随操作条件的变化规律. 结果表明,气含率随表观气速的升高而增大,且随轴向位置的升高而增大;大颗粒具有破碎气泡的作用,能够增大反应器内的气含率;固含率随表观气速的增加而降低,且沿轴向变化较大. 表观气速较高时,固含率沿轴向近似呈S形分布.     

气升式反应器中三相体系进行半连续操作的气含率和传质特性研究

就出现在细胞培养等气液固三相体系在气升式反应器(ALR)中气含率和传质系数同反应器结构参数、固含量及操作条件之间的关系作了理论推导,在不同结构形式的 ALR 中对空气/0.15NaCl 溶液(内含不同数量的固体颗粒)体系作了实验测定,估计了模型中的待定参数,求出气含率(■)和氧的传质系数(K_Lα):■由此可推算二氧化碳的传质系数,并讨论了反应器高度和气体分布器的影响。     

强制浆液外循环三相气升式内环流反应器的气含率特性

在有机玻璃制成的组合反应器(φ0.284×3.0 m)内,采用空气、水和玻璃微珠(密度为2420 kg/m3和平均粒径为5.92×10-4 m)的气液固三相体系考察了不同表观气速下环流反应器内不同流动区域的径向局部气含率和内、外环轴向平均气含率分布特性.局部气含率采用电导探针法测定,轴向平均气含率由局部气含率的截面积分得出.结果表明气含率均随表观气速的增大而增大;外环循环流入内环的气泡量少;在相同条件下外环的气含率远远低于内环的气含率.浆液外循环的引入和新型气体分布器的采用可以增大导流筒内气体与浆液两相的接触面积和湍动强度,从而使传递过程得到了强化.     

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。     

Liquid holdup in columns packed with structured packings: Countercurrent vs. cocurrent operation

An experimental study of the liquid holdup and the liquid holdup axial profile in a square section column with structured packing is carried out. Both cocurrent and countercurrent operations are examined. A conductivity technique to estimate liquid holdups is proposed and calibrated against values measured by the drainage method. Liquid holdups estimated by this technique follow the same trends as those previously found by other methods. Axial profiles of liquid holdup in the cocurrent and countercurrent operation are illustrated for liquid velocities below the loading point, and for solutions of different viscosity and foaming character. Variations between operation modes are larger for the foaming liquid than for the other liquid solutions employed.     

高长径比三相内环流反应器中细颗粒相含率和循环液速的分布研究

在高径比为22的三相内环流反应器中,在常温常压下以空气-水-石英砂为物系,研究了在不同粒径下上升区固含率、下降区固含率和上升区循环液速随表观气速的变化规律和不同粒径下轴向固含率的分布情况,以及在固体体积分数不同的条件下,平均气含率和上升区气含率随表观气速的变化情况。结果表明:当粒径(ds)≤0.3 mm时,上升区固含率随表观气速的增加呈平缓变化趋势,下降区固含率随表观气速的增加而增加;当0.3 mm相似文献   

纤维和小颗粒填充滴流床的流体力学性能比较

在内径为０．０４７ｍ的有机玻璃管内，采用空气水为介质，对纤维，小玻璃珠填充滴流床的流体力学性能进行了考察。结果表明，因为均为滴流床，流体力学性能有某些相似这处，但又由于纤维和小玻璃珠存在不同的性质和尺寸，滴流床内流道结构的巨大差异，使得两种床层内流体操作范围，床层空隙率，流型过渡，床层和，持液量，流体力学滞后现象等都存在显著差异。     

Identification of Various Transition Velocities in a Bubble Column Based on Kolmogorov Entropy

The Kolmogorov entropy (KE) algorithm was applied successfully to gas holdup fluctuations measured in a 0.102 m I.D. stainless steel bubble column equipped with a perforated plate distributor (19 holes ?? 1 mm). Nitrogen was used as the gas, while both 1‐butanol and gasoline were used as liquids. 1‐Butanol was aerated at pressures, P = 0.1 and 0.5 MPa, whereas gasoline was aerated at P = 0.1 and 0.2 MPa. Based on the peaks in the KE values under the pressures examined in both liquids, the boundaries of the following five regimes were identified: bubbly flow, first transition, second transition, coalesced bubble (4‐region flow) and coalesced bubble (3‐region flow). As the pressure increases to P = 0.5 MPa in 1‐butanol, all four transition velocities shift to higher superficial gas velocity, u_G. In addition, in gasoline at P = 0.2 MPa and u_G ≤ 0.017 m s^–1, the existence of a chain bubbling regime was detected, whereas in 1‐butanol at P = 0.5 MPa and u_G ≤ 0.02 m s^–1, both laminar and turbulent chain bubbling subregimes were identified. It was found that in 1‐butanol under ambient pressure, the second and fourth transition velocities occur earlier than in gasoline.     

Hydrodynamics of a cocurrent downflow of gas and foaming liquid through the packed bed. Part II. Liquid holdup and gas pressure drop

In the present study the results of experiments have been presented whose aim was to determine the values of liquid holdup as well as gas pressure drop through the packing for systems foaming under the pulse flow regime. On the basis of 245 experimental points for the pulse flow regime the verification of the models describing the hydrodynamics of the system has been performed. Attention was focused on the models of Benkrid et al. (Chem. Eng. Sci. 52 (1997) 4021), Pina et al. (AIChE J. 47 (2001) 19) and Fourar et al. (Chem. Eng. Sci. 56 (2001) 5987). It has been concluded that none of the models analysed describes the hydrodynamics of the foaming systems with enough accuracy. Next, based on our own data-base the verification has been carried out of parameters of Benkrid et al. (Chem. Eng. Sci. 52 (1997) 4021) (‘drift flux’ model for _L and boundary layer model for ΔP/H) and Pina et al. (AIChE J. 47 (2001) 19) models as well as the estimation of the values of F*-functions of Fourar et al. (Chem. Eng. Sci. 56 (2001) 5987) model. Using as the criterion the accuracy of estimation of the values of (ΔP/H) the best results have been obtained by applying Fourar et al. (Chem. Eng. Sci. 56 (2001) 5987) model (for the Ergun constants determined experimentally). The introduction of the estimated F*-functions into the equations of the model (Eqs. 11 and 12) makes it possible to estimate the liquid holdup with the average absolute relative error not exceeding 9.8% and the pressure drop with an error less than 26%.     

Modulation of liquid holdup along a trickle bed reactor with periodic operation

Temporal variations of the liquid holdup in a mini-pilot scale trickle bed reactor cold-mockup, induced by an ON-OFF liquid flow modulation strategy of operation, are explored at different axial positions. The reactor is packed with porous beads of γ-Al₂O₃ and the liquid holdup is approximately estimated with a conductimetric technique, using probes that mimic the packing. The effects of the liquid and gas superficial velocities, the bed depth and the cycling parameters, cycle period and split, on the liquid holdup modulation are examined for a wide range of conditions. For slow and intermediate cycle periods, the liquid holdup time dependence observed during the dry period is represented by an exponential function. The characteristic value of the decay is correlated to the examined variables. The correlation allows reconstruction of the liquid holdup time dependence along the column.     

环流反应器流体力学参数测定技术研究

介绍了环流反应器流体力学参数的测定方法,这些参数包括气含率、循环液速、固含率、气泡大小及速度。综述了这些参数测量方法的原理、设备及优缺点,评价了它们目前的发展状况及动向,提出了参数测定方法今后工作的重点,对于环流反应器的流体力学研究具有重要的指导意义。     

小颗粒滴流床反应器的流体力学研究

在内径为０．０４７ｍ，床层高０．７ｍ的滴流床反应器内，采用空气－水－玻璃珠（１．８，３．１８ｍｍ）体系，在常温、常压下进行实验。气、液流速分别在０．０５４－０．２３ｋｇ／（ｍ＾２ｓ）和３．２０－１４．７３ｋｇ／（ｍ＾２ｓ）内，用电导信号脉动法、压降波动法结合目测法测定了滴流床的流动状态及其变化，实验结果可用于确定不同操作条件下的流动状态。本研究还分别是用差计、示踪剂法和体积法对滴流床的压降，总持流