气提式环流反应器中局部传质特性研究

本文在环流反应器中液相单级返混较小的情况下,提出了测量上、下两流区局部容积传质系数的稳态和动态物理吸收法,对两法的误差来源和适用条件进行了分析讨论,并用该两法对环流反应器的局部传质特性进行研究,发现气相循环比是环流反应器传质特性的一个重要参数.文中应用动量衡算导出了气相循环比的理论关联式.     

导流筒分布器位置对环隙气升式气固环流反应器流体力学性能的影响

环流反应器的研究绝大多数都局限于气液、气液固系统,涉及气固环流反应器的研究较为稀少,且大多针对气升式气固环流反应器和喷动床。本文研究了一种处理A类粒子的环隙气升式气固环流反应器,考察了操作条件和导流筒分布器位置对床层密度分布、环流速度和质量流率的影响。发现将分布器位置下移后可以有效地改善区域的流化质量、减小滑移区,床层密度沿径向的分布得到了明显改善,颗粒环流质量流率有了明显提高;进气位置以上r/R<0.367的床层得到了良好的流化,但是0.367相似文献   

环隙气升式气固环流反应器内流体力学特性的理论分析

环流反应器的研究与应用一直局限于气液与气液固体系,将环流反应器移植到气固体系是一个具有独创性的探索。针对工业化中气固环流反应器的缺陷,提出了一种新型的环隙气升式气固环流反应器。并对床层空隙率、颗粒流动速度进行了实验研究与理论分析。建立了环隙区床层空隙率模型,发现环隙区床层空隙率随着环隙区表观气速的增加而增加;环隙区靠近导流筒外壁一侧颗粒流动速度明显大于靠近反应器内壁一侧,导流筒区颗粒流动速度沿径向的分布受气体分布器结构影响较大;环隙区颗粒流动速度基本不随轴向位置的变化而变化,导流筒区颗粒的流动属于密相输送,颗粒环流所受到的阻力主要集中在底部区域,其次为气固分离区,底部区域阻力大小由床层流化质量和导流筒下端距反应器底部的间隙所决定;建立了颗粒环流速度模型,发现环流速度随环隙区表观气速的增加而增加。     

三相外环流反应器的液相返混特性和气液传质特性

主要研究了气速与固相对三相外环流反应器液相返混特性和气液传质特性的影响规律,并用“组合模型”分析了反应器各局部区域的返混情况。实验结果表明:液相返混主要由循环返混所致,约占95%以上;固相的存在对液相返混特性和气液传质特性均有显著的影响。研究结果对开发这类反应器具有重要意义。     

环隙气升式气固环流反应器内床层密度的实验研究

针对工业化中气-固环流反应器存在的缺陷,提出了一种新型的环隙气升式气固环流反应器. 在一套冷模装置内系统地考察了局部床层密度分布. 实验中实现了稳定、连续的环隙气升式环流,环流推动力随着环隙区表观气速的增加而增加,随着导流筒区表观气速的增加而减小,当导流筒区表观气速为0.2 m/s时,颗粒环流方向改变为中心气升式. 受结构特性的影响,催化剂密度在导流筒区和环隙区沿径向的分布具有一定的不均匀性,在底部r/R≤0.47区域颗粒未能充分流化,床层密度接近820 kg/m3,在底部0.47≤r/R≤1.0区域颗粒流化较好,床层密度小于450 kg/m3;随着环隙区表观气速由0.2 m/s增加至0.54 m/s,环隙区、导流筒区平均密度分别降低约70和33 kg/m3,随着导流筒区表观气速由0.06 m/s增加至0.2 m/s,环隙区平均密度增加约90 kg/m3,导流筒区平均密度降低约33 kg/m3.     

三相强制外循环环流反应器内的局部气泡行为

为适应新兴的工艺过程，提出一种带有强制外循环的中心气升式内环流反应器。根据结构特点及流动状态不同，将强制外循环环流反应器分为6个流动区域，即环流反应器底部区、气体分布器影响区、浆液进料影响区、导流筒上行区、气液分离区和环隙区。研究了不同流动区域内的局部气泡特性。发现不同流动区域内气泡直径沿径向的分布有较大差异，倒锥形底部结构显著影响了环流气泡的数量与直径。推导出了不同流动区域内平均气泡直径的理论模型，模型结果与实验数据吻合较好。     

下喷式环流反应器传质特性研究

本文以空气-水为实验体系,考察了下喷式环流反应器的传质特性与空塔气速、液速以及反应器结构尺寸等参数的关系。得出了最优的导流筒直径与反应器直径之比为0.4—0.5,给出了谊反应器容积传氧系数的计算关联式:与其它反应器相比,该反应器表现出良好的传质特性,具有较大的容积传氧系数。     

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.     

缩放型导流筒气升式内环流生物反应器流体力学与传质特性

从气相含率、液体循环速度和体积氧传质系数方面研究缩放型导流筒气升式内环流生物反应器内的流体力学与传质特性。实验结果表明,与传统圆柱形导流筒相比较,缩放型导流筒气相含率和体积氧传质系数分别提高８％和１０％以上。气相含率和体积氧传质系数随固含率的增加而提高,液体循环速度随固含率的增加而减小;同一内管反应器随介质粘度的增加,体积氧传质系数减小。此外还在Ｈｉｇｂｉｅ穿透理论和Ｋｏｌｏｍｏｇｏｒｏｆｆ各向同     

多室气升式环流反应器传质特性

以Higbie的渗透理论为基础,建立了多室气升式环流反应器体积传质系数的模型方程．用亚硫酸钠空气氧化法测定反应器的比表面积和体积传质系数,讨论了表观气速和催化剂浓度对它们的影响,并验证了模型的适用性。     

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.     

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.     

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.     

油性微乳液的循环气升式反应器的流体力学和传质性能研究简

This study reports an experimental investigation on hydrodynamics and mass transfer characteristics in a 15.6x10-3 m3 external loop airlift reactor for oil-in-water micro-emulsions with oil to water volume ratio （φ） rang- ing from 3% to 7% （by volume）. For comparative purposes, experiments were also carried out with water. Increase in φ of micro-emulsion systems results in an increment in the gas holdup and a decrease in the volumetric gas-liquid oxygen transfer coefficient and liquid circulation velocity, attributed to the escalation in the viscosity of mi- cro-emulsions. The gas holdup and volumetric mass transfer coefficient for micro-emulsion systems are signifi- cantly higher than that of water system. Two correlations are developed to predict the gas holdup and oxygen trans- fer coefficient     

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.     

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。     

气升式三相内环流生物反应器内流体力学和传质性能的实验研究

本文通过实验研究了气升式三相内环流反应器在非牛顿流体中的流体动力学特性和传质性能.考察了表观气速、导流筒与反应器截面积之比、固体粒子加入量及CMC溶液浓度等操作条件对气升式三相内环流生物反应器中导流筒与环隙内液体循环速度、气含率、固含率及气-液体积传质系数等流动与传质特性参数的影响.     

Hydrodynamics in an Internal Loop Airlift Reactor with a Convergence‐Divergence Draft Tube

Gas holdup and liquid circulation of one conventional draft tube and three different convergence‐divergence draft tubes in an internal loop airlift reactor were investigated. Experiments were carried out in two‐phase systems with air‐water and air‐CMC (carboxyl methyl cellulose) solution and three‐phase system with air‐water‐resin particles. The two‐phase drift‐flux model was used to estimate gas holdup for three‐phase Newtonian and two‐phase non‐Newtonian systems. It is shown that gas holdup in convergence‐divergence draft tubes is higher than that in a conventional draft tube and increases with superficial gas velocity. Variation of the structural parameters of convergence‐divergence draft tubes has little effect on gas holdup in the two‐phase and three‐phase system. The mathematical model, which is based on a drift‐flux model, was developed to describe the liquid circulation velocity in the reactor satisfactorily.