三相环流反应器流体力学行为

气升式三相环流反应器综合了鼓泡塔和机械搅拌釜的优良性能,具有结构简单、无机械传动部件、易密封、造价低、容易实现工业放大等优点,在石油、化工、电化学和生物化工等领域得到了广泛应用．随着能源形势的日趋紧张,环流反应器在液相法合成甲醇、浆态床一步法合成二甲醚、煤液化等过程中的应用得到许多研究人员的重视,并取得了重要的研究进展．由于目前对其内部流动行为尚缺乏系统的认识,进行工业设计和操作过程中仍显理论指导不足     

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。     

新型多级环流反应器流体力学研究

在传统的单级内环流反应器的基础上,对导流筒进行了改进,发展了一种新型多级环流反应器。研究了表观气速、开孔率、反应器底部结构等操作参数对整体平均气含率、局部气含率以及各级环流液速等流体力学行为的影响,从而确定了反应器的最佳结构。文中提出的新型多级环流反应器在石油化工、生物化工和环境工程等多个领域有广泛的应用前景。     

气升式环流反应器特性参数的研究进展

介绍了气升式环流反应器的工作原理、分类及流型,综述了气升式环流反应器的流体力学特征参数(主要包含气含率和循环液速)、混合及传质特性参数的测量方法和影响因素。介绍了气含率和循环液速的数学模型,并评述了现有模型。展望了气升式环流反应器进一步的研究方向与发展前景。     

气升式环流反应器特性参数的研究进展

介绍了气升式环流反应器的工作原理、分类及流型,综述了气升式环流反应器的流体力学特征参数(主要包含气含率和循环液速)、混合及传质特性参数的测量方法和影响因素。介绍了气含率和循环液速的数学模型,并评述了现有模型。展望了气升式环流反应器进一步的研究方向与发展前景。     

外环流反应器中气含率和循环液速的研究

本文通过空气-水体系,对三种不同结构的外环流反应器中的气含率数据进行了关联,得到了有意义的模型关联式.对环路进行了阻力计算,得到了包含结构参数的阻力方程.计算发现模型关联式与阻力方程联立求解,可以很好地预测不同结构的外环流反应器中的气含率和循环液速,从而为该反应器的工程放大提供了依据.     

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   

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%。     

两级气液内环流反应器内气含率和循环液速

基于多釜串联可以有效减小返混的原理,通过引入特殊设计的级间构件构建了一种新型的两级内环流反应器。实验研究了级间构件形式、表观气速、表观液速和气液分离器对每一级内气含率和循环液速的影响。实验结果表明,表观气速对反应器二级(上一级)中上升管与下降管气含率之差和循环液速影响较大,而对一级(下一级)的影响较小;各级内上升管和下降管的气含率均随表观液速的增大而减小,但影响程度较小。基于推动力和阻力平衡建立了预测反应器中每一级的气含率和循环液速的流体力学模型,模型预测值与实验结果吻合较好。     

大颗粒三相环隙气升式环流反应器流体力学行为

研究了大颗粒体系气升式环流反应器的流体力学行为,考察了表观气速和颗粒质量分数对床层膨胀高度、循环液速和固含率分布的影响。实验结果表明,按颗粒的运动状态不同可以将反应器内的流动分为3个区域,即固定床区域、膨胀床区域和循环床区域,各流动区域内的流动行为存在显著差异。随着颗粒质量浓度的增大,起始流化气速和最小循环气速均显著增大。基于三相流化床的流化模型和环流反应器的特点建立了相应的数学模型,对大颗粒三相气升式环流反应器的起始流化气速和最小循环气速进行了预测,模型预测值与实验测量值吻合良好。     

EFFECTS OF GEOMETRY ON HYDRODYNAMICS IN EXTERNAL-LOOP AIRLIFT REACTORS

Experimental investigations were carried out in model external-loop airlift reactors. Two reactors of laboratory scale (riser liquid height ranged between 1.16-1.56 m, riser diameter 0.03 m, A_D/A_R ratio between 0.111-1,000, total liquid volume V_T = (1.189-2.446).10^-3m³) and pilot-plant scale (riser liquid height of 4.4 and 4.7 m, respectively, riser diameter 0.200 m, A_D/A_R ratio of 0.1225 and 0.040 m, total liquid volume, V_T = (0.144-0.170) m³) were used.

The influences of reactor geometry characterized by some parameter as: A_D/A_R ratio, liquid height in riser and downcomer and liquid height in gas separator, together with the amount of introduced air, on the basic hydrodynamic design parameters: gas holdup and liquid circulation velocity were analysed.

The influence of gas sparger design on gas holdup and liquid velocity was found to be negligible.

The experimental liquid circulation velocity was correlated using a simplified form of the energy balance in airlift reactors, valid for external-loop airlift reactors with almost complete phase separation at the top.

An original dimensionless correlation for gas holdup prediction involving superficial velocities of gas and liquid, cross sectional areas, dispersion height, riser diameter, as well as Froude number, was obtained.     

纤维填充滴流反应器的流体力学

<正> 1 引言 近期的研究表明,无机纤维催化剂(玻璃纤维、碳纤维、氧化铝纤维等)具有较高的活性、选择性和稳定性,如氧化铝纤维为载体的裂解汽油加氢。但到目前为止,有关纤维滴流床的化工数据几乎未见报道。本工作的目的是对纤维滴流床进行流体力学研究,考察操作条件、填料性质、填充方式变化时流体流动性质如压降、持液量等的变化规律,以求建立计算压降和持液量的关联式,为纤维滴流床反应器的设计和放大提供基础数据。     

CIRCULATION OF GAS AND LIQUID PHASES IN EXTERNAL-LOOP AIRLIFT REACTORS

The effects of the horizontal connection length (0.3 ≤ L_c ≤ 0.6 mrpar;, the cross-sectional area ratio of downcomer-lo-riser (0.28≤A_d/A_r≤0.53rpar;, and the superficial gas velocity on the circulation gas flow rate were studied. The circulation liquid velocity, the downcomer gas holdup, and the bubble size in the downcomer were also investigated. In order to measure the circulation gas flow rate, a gas-liquid separator was installed at the bottom connection between riser and downcomer. Both of the circulation gas flow rale and the circulation liquid velocity strongly depended on the superficial gas velocity as well as the cross-sectional area ratio of downcomer-to-riser and the horizontal connection length. An useful correlation for the circulation gas flow rate was obtained in terms of the superficial gas velocity, the cross-sectional area ratio of downcomer-to-riser and the horizontal connection length.     

MASS TRANSFER AND HYDRODYNAMICS IN AN AIRLIFT REACTOR WITH VISCOUS NON-NEWTONIAN FLUID

In an internal loop airlift reactor of 55L working volume,the gas-liquid volumetric oxygenmass transfer coefficient k_Lα,gas holdup ε_G and liquid circulation time t_c were measured with the sol-ution of carboxymethyl cellulose(CMC)to simulate the performance of a reactor with highly viscousbroth.Electric conductivity and oxygen probes were used to measure the local gas holdup,liquidcirculation time and oxygen mass transfer coefficient in the individual sections of the reactor(riser,downcomer and the gas-liquid separating section at the top of the reactor)and the total reactor,respectively.The values of k_Lα for the riser,downcomer and separation sections of the reactor were alsoestimated and compared with that for the total reactor.The results show that,both k_Lα and ε_G in-crease but t_c decreases with increasing gas velocity.Correlations and comparisons with works reportedin the literature are also presented.Data show that the methods developed for k_Lα measurements inthe individual section and     

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     

LOCAL HYDRODYNAMICS IN AN EXTERNAL LOOP AIRLIFT SLURRY REACTOR WITH AND WITHOUT A RESISTANCE-REGULATING ELEMENT

The hydrodynamic behavior of an external loop airlift slurry reactor (ALSR) with and without a resistance-regulating element was studied with a fiber optic probe and ultrasound Doppler velocimetry. The influences of the superficial gas velocity and solid holdup on the global gas holdup and radial profiles of the suspension circulation velocity in the downer and of gas holdup, bubble size, and bubble rise velocity in the riser were studied. Local measurements allow a better understanding of the flow behavior in the reactor and can be used for CFD modeling and validation. Experimental results show that the resistance-regulating element increases the gas holdup and decreases the suspension circulation velocity, indicating that an optimum design of the flow resistance is needed to obtain the maximum gas-liquid volumetric mass transfer coefficient for a specific superficial gas velocity. A high superficial gas velocity and low solid holdup are favorable for increased uniformity of the radial profile of the gas holdup and bubble rise velocity. Hydrodynamic models that predict the gas holdup and suspension circulation velocity were developed for an ALSR with and without a resistance-regulating element. Good agreement was obtained between measured and predicted values.     

表观气速对气升式环流反应器性能的影响

利用计算流体力学(CFD)数值模拟方法.采用Euler法双流体模型研究了表观气速对气液两相气升式环流反应器的液体循环速率和气含率的影响.实验结果与数值模拟结果吻合较好.结果表明.气含率和液体速率在反应器内分布不均匀,气含率在相同的径向位置变化很小,液体速率随着表观气速的增加而增加.     

LOCAL HYDRODYNAMICS IN AN EXTERNAL LOOP AIRLIFT SLURRY REACTOR WITH AND WITHOUT A RESISTANCE-REGULATING ELEMENT

The hydrodynamic behavior of an external loop airlift slurry reactor (ALSR) with and without a resistance-regulating element was studied with a fiber optic probe and ultrasound Doppler velocimetry. The influences of the superficial gas velocity and solid holdup on the global gas holdup and radial profiles of the suspension circulation velocity in the downer and of gas holdup, bubble size, and bubble rise velocity in the riser were studied. Local measurements allow a better understanding of the flow behavior in the reactor and can be used for CFD modeling and validation. Experimental results show that the resistance-regulating element increases the gas holdup and decreases the suspension circulation velocity, indicating that an optimum design of the flow resistance is needed to obtain the maximum gas-liquid volumetric mass transfer coefficient for a specific superficial gas velocity. A high superficial gas velocity and low solid holdup are favorable for increased uniformity of the radial profile of the gas holdup and bubble rise velocity. Hydrodynamic models that predict the gas holdup and suspension circulation velocity were developed for an ALSR with and without a resistance-regulating element. Good agreement was obtained between measured and predicted values.     

两相并流小颗粒滴流床反应器的压降和持液量的研究

在空气、水和小的固体玻璃或氧化铝球形颗粒床层中,测定了两相并流时压降和持液量。测定了流体流率、颗粒粒度及材质,分别对压降和持液量的影响,比较了大颗粒和小颗粒的特性,探计了前人的一些关联式,取得了满意结果。