三段进气环流反应器气泡参数与传质特性研究

多级环流反应器通常在段间安装多孔分布板或其它内构件,增加了流体流动的阻力,导致环流液速降低。为此,今在多级环流反应器研究的基础上,设计了一种新型三段进气、多级环流反应器,利用新通入气体的抽提力和喷射力,缓解了段间的流动压降,并加速气泡的破碎;重点考察了进气量在各段中的分配比例对分段进气多级环流反应器流体力学的影响。应用多通道电导探针气泡特征参数测量仪和溶解氧分析仪分别测量气泡参数(气含率、气泡速度、气泡直径)及体积传质系数。实验结果表明:三段同时进气时,气泡直径明显减小,气液接触比表面积增加显著;体积传质系数远高于多级环流反应器,最大值约为多级环流反应器的2.3倍。根据修正双膜理论,计算得到了三段进气时体积传质系数的经验关联式,较好地反映出体积传质系数的变化规律。     

超声内环流气升式反应器传质性能的研究

研究了超声内环流气升式反应器中空气-水-离子交换树脂体系的气液传质与液固传质性能.分别采用电极动态法和离子交换树脂法实验测定了气液传质和液固传质系数.重点考察了表观气速、超声电功率对于气液传质系数以及液固传质系数的影响.实验表明,内环流气升式反应器中表观气速对于气液传质性能影响较大,而超声作用对气液传质影响不大.该反应器中液固传质系数随表观气速的增加而增大;无超声作用情况下,当表观气速达到一定程度时,液固传质系数保持一恒定值.超声作用时,气速增加到4 cm·s-1左右,传质系数达到最大值,随后液固传质系数随着表观气速的增加而逐渐减小,传质系数仍然大于无超声作用时的值.超声对液固传质有较强的促进作用,电功率在150 W左右时,超声对液固传质的促进作用最佳,是不加超声作用时传质系数的两倍左右;但随着电功率的进一步增大,液固传质系数呈现下降趋势.     

Modeling of Mass Transfer in an Internal Loop Airlift Reactor

A complete mass transfer model was established for an internal loop airlift reactor. All sections of the reactor, including bottom, riser, top, and downcomer, were taken into account. A numerical method was developed to solve the mass transfer model. The effectiveness of the model was validated by experimental measurements. Based on numerical results of the model, the dynamical mass transfer process in the reactor was analyzed in detail. Some mass transfer characteristics of the airlift reactor were revealed. The results indicated that the proposed model well predicted the mass transfer in the internal loop airlift reactor.     

低高径比气升式环流反应器数值模拟分析

利用商用计算流体力学软件Fluent,利用Euler-Euler双流体模型,重点针对好氧反应的特点,对一种具有低高径比(H/D=1.67)的环流气升式反应器内的气液两相流动及混合性能进行研究,描述出反应器内气含率和环流液速等参数的详细分布,分析模拟结果,气液速度分布和气含率分布等与实际情况基本吻合,从而证实了计算结果的有效性,为工业实际应用提供一定参考。     

用于微生物石油脱蜡的新型气升环流反应器

本文报导了一种新型气升环流反应器,对反应器中液相流型、气含率与操作条件之间的关系进行了实验考察。利用气升环流反应器强化传质和混合的原理,将一个100m^3鼓泡塔反应器改造成三管循环的气升环流反应器,发酵试验结果表明气升环流反应器微生物脱蜡周期比原鼓泡反应器缩短4倍,气升环流反应器能耗比鼓泡反应器降低约30％。     

低高径比气升式环流反应器数值模拟分析

气升式反应器因其结构简单，有良好的混合传热性能，便于操作等优点已广泛用于化工、生物化工等行业。利用商用计算流体力学软件Fluent，利用Euler—Euler双流体模型，重点针对好氧反应的特点，对一种具有低高径比（H/D=1．67）的环流气升式反应器内的气液两相流动及混合性能进行研究，描述出反应器内气含率和环流液速等参数的详细分布，分析模拟结果，气液速度分布和气含率分布等与实际情况基本吻合，从而证实了计算结果的有效性，为工业实际应用提供一定参考。     

Experimental Study and CFD Simulation of Hydrodynamic Behaviours in an External Loop Airlift Slurry Reactor

The local hydrodynamic behaviours in an external loop airlift slurry reactor, including the gas holdup, bubble rise velocity, bubble size, were measured with a fibre optic probe. The liquid circulation velocity was measured with an ultrasound Doppler velocimetry. Two‐dimensional simulations were carried out in the framework of Two‐Fluid formulation coupled with a k‐? turbulence model. The lateral forces and interphase turbulence were taken into account and good agreement between the experimental and simulation results was obtained. The simulations show that the lateral forces and interphase turbulence have noticeable influence and should be included in the CFD model.     

气升式三相内环流反应器中相含率的研究

在一个6．36L的气升式内环流反应器中,以空气-NaCl水溶液-K树脂为实验体系,在导流筒内的表观气速为1．21～7．28cm·s^-1时,考察了平均气含率、平均固含率随表观气速的变化规律,研究了转向面积比、NaCl水溶液浓度与平均气含率之间的关系。在均匀鼓泡流区域用模型方程Eg=aUgb来关联平均气含率,其中模型参数6=0．766,a与转向面积比、NaCl水溶液浓度关系为a=3．45×10^-5＋0．0146（Sb／Sr）0．0185＋1．35W。     

气升式内循环反应器的数值模拟和结构参数

采用Euler-Euler双流体模型对内循环反应器(高1240 mm,直径165 mm,导流筒高590 mm)进行数值模拟,考察了表观气速、导流筒结构(导流筒内径比Dt/D,底隙高度)对反应器内上升区、下降区流体力学参数(气含率、液体速度)的影响. 结果显示,表观气速、导流筒内径、底隙高度对反应器气含率、液体速度有很大影响,随表观气速增加,反应器上升区、下降区气含率都增加,导流筒内径比为0.58时更易实现气液循环,底隙高度为30 mm时反应器内下降区气含率、气液速度都最小;气液分离器角度越大,进入下降区的气体越多,当气液分离器角度为45o时,能更好地实现气液循环.     

螺旋气升式内环流反应器流动特性

以水和空气两相系统为研究对象,建立螺旋气升式内环流反应器冷模实验装置,采用压差法测定导流筒升流区气含率,用电导法分别实测了升流区液相速度和反应器混合时间,研究螺旋气升式内环流反应器的流动特性,并与传统气升式内环流反应器的流动特性进行对比研究。结果表明,加螺环后反应器气含率明显增加,平均增幅为20%,升流区液相表观速度减小,混合时间增加。     

Scale Effects on Hydrodynamic and Mass Transfer Characteristics of External Loop Airlift Reactors

Gas hold-up and oxygen transfer have been investigated in two geometrically similar external loop airlift reactors of linear scale ratio of 2. In mass transfer experiments, the sampling location was found to be important as significantly different k_La values can be obtained. The variations of k_La with probe location have been explained in terms of non-uniform hydrodynamic properties and the results obtained have been validated by means of high speed video camera recordings. At higher gas flowrates, the gas hold-up was significantly higher in the large-scale reactor. It was found that in order to maintain the gas hold-up or k_La constant in both the small- and large-scale reactor, the small-scale reactor required 25% and 27% more power input per unit volume of liquid respectively. © 1997 SCI.     

气液外环流反应器中气泡行为的实验研究

详细考察了气液外环流反应器中上升管、下降管的气泡行为随轴向、径向的变化规律. 由于外环流反应器的结构特点,发现在上升管底部存在偏流,并对分布板区气泡行为随角向的变化规律进行了研究. 分析实验结果得出,气含率和气泡速度均随表观气速的升高而升高;在上升管内,气含率和气泡速度自中心向边壁逐渐降低,而沿轴向变化很小;在分布板区,由于受分布器及下降管的影响,使气含率和气泡速度在不同角向存在不同的径向分布. 在下降管中,气含率自中心向边壁逐渐降低,而气泡速度则基本不变;且下降管中的气体循环率随表观气速的升高而升高.     

ILAR中醇及电解质对非牛顿流体中气-液传质的影响

在-气升式内环流反应器中试验考察了非牛顿流体羧甲基纤维素钠(CMC)中的气泡聚并现象以及表面活性物质对液相体积传质系数的影响。结果表明,非牛顿流体中气-液传质效率随黏度的增加而降低,其原因是黏度增加使Taylor泡的尾流趋于稳定,降低了液相扰动,气泡间易聚并,从而气-液传质效率低。向非牛顿流体中添加醇类物质会影响气-液传质行为,对于聚合物含量低的流体,添加微量醇可以促进气-液传质,聚合物含量高的非牛顿流体,微量醇的加入反而不利于气-液间传质过程。非牛顿流体在ILAR上升管中的气含率随着黏度的增加变化不大,而下降管中的气含率有所提高。     

Hydrodynamics of a Multi‐Stage Internal Loop Airlift Reactor

The local hydrodynamic properties in a multi‐stage internal loop airlift reactor were investigated in this study. The gas‐liquid two‐phase flow hydrodynamic properties, including gas holdup, bubble velocity, bubble diameter, and liquid circulation velocity at various stages were measured by dual electrical resistivity probes and conductivity cells. Detailed studies on the gas holdup, bubble velocity, bubble diameter, and liquid circulation velocity were conducted with respect to various values of superficial gas. The Zuber and Findlay drift flux model was used to represent the variation of slip velocity with total gas‐liquid velocity at various stages and the model fits the data well.     

Flow Regime Transitions in an Internal‐Loop Airlift Reactor

The flow regime transitions of the riser and downcomer in an internal‐loop airlift reactor are investigated. Analysis of the effects of mean value, standard deviation and chaotic time series on pressure fluctuation signals is recorded to determine the transition of the hydrodynamics in the riser and downcomer of the internal‐loop airlift reactor. Two major chaotic invariants, the correlation dimension and the largest Lyapunov exponent, are employed to indicate the regime transitions. The regime transitions are determined by the sudden increase and decrease of the chaotic invariants, which are computed by the pressure fluctuation signals obtained by varying the gas flow velocity. The determination of chaotic invariants predicts that there is no heterogeneous phase existing in the downcomer of the internal‐loop airlift reactor. The experimental observations agree well with the predicted results.     

下喷自吸环流反应器内局部气泡平均直径及其径向分布

引　言喷射环流反应器因具有规整的流型、良好的分散效果、相对低的功耗及较好的相间传递特性等优点 ,而广泛应用于化学工业、生物及环境化工领域 ,如发酵、废水和废气处理等 ,以及化学工业中众多的多相反应[1,2 ].鉴于下喷环流反应器和自吸各自的特点 ,文献 [3]开发出了新型高效反应器———下喷自吸环流反应器 ,并对该反应器性能进行了系统的研究 .开展下喷自吸环流反应器内局部气泡大小及其分布的研究 ,不仅对了解该反应器内混合、相间作用和相间耦合的微观流动与传质机理及其传递特性具有极其重要的意义 ,而且也为此类反应器的工业放大…     

An Experimental Study of the Hydrodynamic Characteristics of External Loop Airlift Contactors

Global hydrodynamic characteristics—gas hold-up and liquid circulating velocity—were measured in two external loop airlift contactors. Geometrical parameters, such as the height of the airlift, the design of the phase separator, the gas sparger and operating parameters, were found to have significant effects on global hydrodynamic characteristics. In particular, circulation velocity was found to be dependent on liquid volume. To predict gas hold-up in the riser, a simple model, which gives good agreement with experimental data obtained with various airlift geometries, was proposed. © 1997 SCI.     

浆态床鼓泡反应器(SBCR)的研究进展

文章综述了浆态床鼓泡反应器的研究进展。主要介绍了浆态床鼓泡反应器中流型、相含率、气泡动力学等流体力学特性以及操作条件对流体力学特性的影响,并对浆态床鼓泡反应器的发展提出展望。     

浆料鼓泡塔反应器部分流体力学参数研究综述

本文综述了浆料鼓泡塔反应器的主要流体力学参数－流域,气泡的大小和上升速度,相含率和固定颗粒悬浮的临床气速等－的测定和影响因素。简要介绍了国外采用的汉体力学参数测定方法－动态气体逸出法。     

Experimental Study on the Hydrodynamics and Mass Transfer Characteristics of Ultrasonic Loop Airlift Reactor

The promoting effect of ultrasonic wave on the hydrodynamics and mass transfer characteristics of the loop airlift reactor was studied. The gas holdup, liquid circulation velocity, mixing time and overall volumetric mass transfer coefficient were examined and compared, with and without ultrasonic wave in the reactor. The experimental results show that ultrasound has almost no notable effect on the gas holdup, but has a tendency to decrease gradually the liquid circulation velocity and increase the overall volumetric mass transfer coefficient; and the effect on the mixing time is relatively complex. At low superficial gas velocity, the low powered ultrasound promotes the radial mixing of fluid; with the ultrasonic power increasing, ultrasonic vibration obstructs the axial mixing of fluid. Moreover, the effect of ultrasonic wave on the mixing time gradually decreases with the increase in the superficial gas velocity. Therefore there exists an optimal ultrasonic power for hydrodynamics and mass transfer. Correlations were also proposed for the hydrodynamics and mass transfer characteristics of the reactor.