三相牛顿流体缩放型导流筒气升式内环流反应器研究

从气相含率、液体循环速度和体积氧传质系数方面研究三相牛顿流体条件下的缩放型导流筒气升式内环流反应器内的流体力学与传质特性。内导流筒分别采用一种传统圆柱型和三种不同结构参数的缩放型, 实验条件为空气 水 树脂三相系统。实验结果表明, 与传统圆柱型导流筒相比较, 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。圆柱型导流筒反应器的液体循环量（ Ａｒ·ＵＬｒ） 大于各含缩放型导流筒反应器的液体循环量。在固含率分别为０ ％ ,３ ％ ,６ ％ 及９ ％ 条件下, 气相含率和体积氧传质系数随固含率的增大而提高, 液体循环速度随固含率的增大而减少。此外还在Ｈｉｇｂｉｅ 穿透理论和Ｋｏｌｏｍｏｇｏｒｏｆｆ 各向同性理论的基础上建立了体积氧传质系数与操作条件及管结构参数之间的关联式     

气升式反应器流动行为研究Ⅰ——平均气含率的影响

在一个体积为8L（直径96mm，高为1800mm）带导流筒的气升式反应器内，模拟两相（空气－水，空气－水－乙醇）系统和三相（空气－水－玻璃珠，空气－水－乙醇－淀粉）系统，改变给气流量，导流筒直径，乙醇浓度，玻璃珠直径，固含率，淀粉含量、系统渡，以及操作方式考察了以上因素对气升式反应器内平均气含率的影响。     

气升式反应器内三相条件下流动行为研究Ⅱ——循环液速的影响

在一个体积为8L（直径96mm,高为1800mm）带导流筒的气升式反应器内,模拟两相（空气-水,空气-水-乙醇）系统和三相（空气-水-玻璃珠,空气-水-乙醇-淀粉）系统,改变给气流量,导流管直径,乙醇浓度,玻璃珠直径,固含率,淀粉含量,系统温度,以及操作方式考察了以上因素对气升式反应器内循环液速的影响。研究表明：随着上升气体表观速度的增加,导流简直径的增加,床内循环液速也增加;在固含率一定条件下,固含物粒径烊大,循环液速也越大;溶液浓度增加,循环液速也增加;床层中的固含率增加,而循环液速减小;系统温度增加,循环液速增加;环隙给气方式可以与中心导流简给气方式都可采用,但是环隙给气时怕循环液速小于中心导流筒给气方式的循环液速。     

导流管型鼓泡塔中水和低浓度CMC液体的循环

在装置不同直径导流管的鼓泡塔中采用“颗粒示踪法”测定低浓度ＣＭＣ溶液的流体循环时间ｔｃ值，实验观察到低深度ＣＭＣ溶液的表面张力在０．０４１８－０．０６１２Ｎ．ｍ＾－１对ｔｃ值无影响，ｔｃ值民表观气速、导流管直径、长度和塔径的比值及液体的表观粘度有关，用进气量θｇ和液体循环量为θＬ的比值Ｈ定量表示塔内上述参数对液体循环的影响，关联中心区区充气和环隙区充气塔的实验值，对空气一水、低浓度ＣＭＣ溶液分别建     

气升式反应器流动行为研究Ⅰ──平均气含率的影响

在一个体积为 8L(直径 96mm ,高为 180 0mm)带导流筒的气升式反应器内 ,模拟两相(空气 -水 ,空气 -水 -乙醇 )系统和三相 (空气 -水 -玻璃珠 ,空气 -水 -乙醇 -淀粉 )系统 ,改变给气流量 ,导流筒直径 ,乙醇浓度 ,玻璃珠直径 ,固含率 ,淀粉含量 ,系统温度 ,以及操作方式考察了以上因素对气升式反应器内平均气含率的影响。     

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.     

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。     

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。     

气升式环流反应器在不同体系下的循环液速和局部气含率

在气升式环流反应器中,分别研究了空气—水、空气-0．1％乙醇水溶液和空气-水-活性污泥体系中的循环液速以及气含率随操作条件的变化规律。实验结果表明,循环液速随着表观气速的增加而增大,不同体系中的循环液速差别不大;导流筒内、外不同高度处的局部气含率均呈自下向上增大的趋势,且导流筒内部气含率高于导流筒外部的气含率。体系的聚并特性对平均气含率和局部气含率有较大影响。     

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.     

三重环流生物流化床的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自行设计新型结构的三重环流生物流化床的流体力学与传质特性。流化床反应器的有效体积２３Ｌ,实验条件是以空气为气相,水为液相,树脂为固相,固含率分别为０％,３％,６％和９％。实验结果表明,气相含率是影响反应器流体力学和传质特性的主要因素,气相含率增大可降低液体循环速度,增大体积氧传质系数。     

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.     

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     

Hydrodynamics in airlift loop section of petroleum coke combustor

Based on the combustion characteristics of petroleum coke, a coupled gas-solid fluidized bed combustor is proposed in this work. The overall circulating system of the fluidized bed mainly consists of a dense-phase airlift loop section and a dilute-phase riser section. In different operating conditions, the particle flow behaviors in the airlift loop section were investigated systematically by using optical fiber probe. The experimental results show that the airlift loop section can be divided into four regions, namely, the draft tube, the annulus, the bottom region and the particle diffluence region, in which the average cross-sectional solids fraction and the particle velocity are different. The overall solids fraction difference between the draft tube and the annulus provides a driving force for particle circulation flow in the airlift loop section, and the driving force increases with increasing the superficial gas velocity in the draft tube. The ratio of the particle mass flux in the annulus to that in the riser ranges from 8 to 16. The particle circular velocity in the annulus also increases with increasing the superficial gas velocity in the draft tube. Moreover, a model about the particle circular velocity is established on the basis of energy equilibrium principle.     

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。     

Volumetric Mass Transfer Coefficient of Oxygen in An Internal Loop Airlift Reactor with a Convergence‐Divergence Draft Tube

Experimental measurements of hydrodynamics and the volumetric mass transfer coefficient of oxygen (VMTCO) in an internal loop airlift reactor with different types of draft tubes are reported for the two‐phase systems, air/water and air/carboxyl methyl cellulose (CMC) solution, and a three‐phase system, air/water/resin particle, respectively. The properties of convergence‐divergence draft tubes with three different structural parameters are compared with those of the conventional column draft tube. The results indicate that gas holdups in convergence‐divergence draft tubes are higher than those in conventional draft tubes, the volumetric mass transfer coefficient of oxygen increases with increasing superficial air flow rates. The convergence‐divergence draft tubes all show higher mass transfer capacity than the traditional ones. A 10% higher mass transfer coefficient is observed for the three structural parameters. In the air/CMC system, the volumetric mass transfer coefficient of oxygen decreases with increasing bulk viscosity, while in the three‐phase system VMTCO increases with the resin particle loading. The correlation equation of the volumetric mass transfer coefficient with the operating conditions and structural parameters is established.     

CFD Simulation of hold-up and liquid circulation velocity in a membrane airlift reactor

A two-dimensional model was used to consider circulation velocity and hold-up in a membrane bioreactor. Membranes were located and simulated (using computational fluid dynamics (CFD)) with three different distances of 5, 7 and 9 mm in an airlift reactor and compared with the results obtained from an airlift reactor without membrane. Gas hold-up in the riser decreased with increasing membrane layers distance. The liquid circulation velocity increased with increasing membrane layers distance. Further, liquid velocity increased bubble rising and decreased gas hold-up in the draft tube when membrane was not used in the draft tube. The simulated data were compared with the experimental data and good agreement was observed.     

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     

气升式气-固环流汽提器的流体力学行为

In this paper, the principles of airlift loop reactor in gas-liquid and gas-liquid-solid systems are extended to gas-solid system. The models on bed average voidage in draft tube and the particle circulation velocity in a gas-solid loop reactor are deduced. The experiments are also conducted on a Φ600 mm×7000 mm reactor. The catalyst voidage and catalyst circulation velocity are measured at different radial and axial positions in draft tube and annulus, respectively. The experimental data are analyzed systemically and represented satisfactorily by the proposed models.     

Modeling of modified airlift loop reactor with a concentric double-draft tube

In this work, mathematical modeling based on the tanks-in-series model was employed to characterize the performance of a novel modified airlift loop reactor. Liquid mixing characteristics, i.e., mixing time and circulation time, were employed to describe the performance of the proposed reactor. These values were determined by using the classical tracer response technique in a column 18.5 cm in diameter and 90 cm in height, and two concentric draft tubes 14 and 8.5 cm in diameter and 80 cm in height. Matlab 7.1 software was used to solve the model equations in the Laplace domain and determine the model parameter. A comparison between the numerical solution and experimental data showed that the applied model can accurately describe the behavior of a modified airlift reactor. Experimental results in the homogeneous bubble flow regime showed that the proposed airlift reactor configuration with a double-draft tube significantly improves the liquid mixing quality compared to a conventional concentric-tube airlift reactor with an identical operating volume. By using this high-performance reactor, the mixing and circulation times can be reduced by up to 48.3% and 35.5%, respectively.