下喷式环流反应器气含率研究

本文从奈维—斯托克斯运动方程出发,结合体系特性及反应器内流体流动状况,建立了计算下喷式环流反应器气含率的模型方程式,并依实验结果确立了模型参数.该模型方程式适用于牛顿型与非牛顿型流体体系.     

下喷式环流反应器的气含率特性

本文以空气-水和空气-CMC 水溶液为实验体系,研究了气速、液速、体系物性以及反应器结构尺寸等参数对下喷式环流反应器全塔平均气含率的影响,得出最优的导流筒直径与反应器直径之比为0.57,提出了牛顿型与粘度较低的非牛顿型流体体系中气含率的计算关联式:■_G=0.3157[(D_E/D_R)~2-1.14D_E/D_R+0.55]~(-3.312)·n~(0.9142)·((ρ_G·μ_G)/(ρ_L·μ_L))~(0.01899)·Fr_■~(0.3884)·Fr_L~(0.2918)     

环隙气提式环流反应器中的气含率和液相循环流动

在筒体直径310mm、高2000mm的环隙气提式环流反应器实验装置中,对上流区的气含率、液相循环流动等流体力学特性作了研究.用漂流通量模型描述了上流区的气含率;通过对体系的能量耗散机理进行分析,基于体系总能耗最小的原理推导出液相循环流动方程,结果表明:用此方程能较好地模拟这种反应器内的液相循环状况.     

上喷式环流反应器中影响整体气含率的因素探讨

基于甲苯三氧化硫磺化反应工艺的需要,设计了一种分布式多喷嘴新型结构的上喷式环流反应器。测定了表现气速,单位体积功耗、静液位和两相喷嘴结构分布等对反应器平均整体气含率的影响,在试验数据的基础上,得到了各参数间的关联式,结果表明,分布式喷嘴结构可获得较佳性能。     

外环流反应器热态气含率研究

在直径250mm、高4500mm的外环流反应器内研究了六种物系在不同温度和较宽的操作气速及物性范围内热态气含率的变化规律,由能量耗散原理导出了气液相界比表面积和气含率的理论模型,并由实验确定了模型参数K_f。理论推导结果与实验回归结果相近。     

多室气升式环流反应器的气含率研究

在四流道的多室气升式环流反应器中 ,常温常压下 ,以空气作为气相 ,以水、0 .5 %、1%、5 %NaCl及 0 .5 %、1%、5 %Na2 SO4 作为电解质 ,考察上升区气含率与操作气速及电解质密度的变化规律。并用回归分析的方法 ,建立了上升区气含率与电解质密度的半经验关联式 ,用该式得到的上升区气含率的计算值和实验值的平均相对偏差为 2 .5 8%。     

旋流气升式环流反应器的局部气、固含率研究

新开发的有机玻璃制成的旋流气升式环流反应器高为2m、内径75mm,内部的导流筒(材料为PVC)高1.5m、内径30mm、壁厚1mm且装有10组扇形翅片。以空气-水为两相物系、空气-水-K树脂为三相物系,常温常压下,利用直接取样法和压差法测量了上升区局部的气含率、固含率,研究了不同底部间隙、不同固体装填体积分数下表观气速和轴向高度对上升区气含率、固含率的影响规律。结果表明:在均匀鼓泡流时上升区气含率随着表观气速的增大而增大,随着固体装载量的增加而下降;在非均匀鼓泡流时,三相物系的气含率高于两相物系的气含率。随着上升区轴向高度的增大,上升区局部气含率变化不大;底部间隙越大,气含率越小。在轴向高度较低时上升区固含率随着轴向高度的增大而减小,轴向高度较高时上升区固含率基本保持不变。     

三相多室气升式环流反应器气含率的研究

在1个4流道的三相多室气升式环流反应器中,以空气-水-K树脂为体系,采用压差法测量气含率,考察了上升室气体表观速率、固体装载量对上升室与下降室气含率的影响.结果表明:上升室的气含率随着该室气体表观速率增加而增加,而随着另一上升室气体表观速率增加而略有降低;下降室的气含率随着该室气体表观速率增加呈现3种变化趋势,而随着另...     

气液喷射式环流反应器气含率及传质比表面积的研究

研究了气速、液速对喷射式环流反应器气-液传质比表面积以及全塔、导流管和环隙部分的平均气含率的影响。提出将喷射式环流反应器中传递性能参数随操作条件的变化规律进行分区研究可简化放大过程。根据实验数据和文献数据,获得了计算敏感区域全塔平均气含率(?)和气液传质比表面积a_R的关联式: (?)=7.18×10~(-4)U_g~(0.55)Re_1~(1.24)D~(-0.64) a_R=644U_(g)~(0.44)(ρ_L/V_R)~(0.46)     

多管环流反应器的气含率研究

提出了一种新型结构的多管式环流反应器,对于空气－水体系,在每个上升管气速为０～０．１６ｍ／ｓ和管径比Ｄｄ／Ｄｒ＝０．３～１．０范围内,研究了两个上升管气速及不同管径比时上升管气含率的变化规律,同时研究了分离箱中静液高及分离箱结构参数与下降管气含率之间的关系。提出了在鼓泡流区域内上升管气含率模型方程：Ｅ１＝αＵｂｇ１－ｃＵｇ３     

Gas holdup in a two‐phase reversed flow jet loop reactor

Experimental investigations have been carried out in Reversed Flow Jet Loop Reactor (RFJLR) to study the influence of liquid flow rate, gas flow rate, immersion height of two‐fluid nozzle in reactor and nozzle diameter on gas holdup without circulation, that is, gas–liquid mixture in draft tube only (E_gd) and gas holdup with circulation loop (E_g). Also critical liquid flow rate required for transition from draft tube to circulation loop has been determined. Gas holdup was measured by isolation valve technique. Gas holdup in draft tube and circulation loop increased with increase in liquid flow rate and gas flow rate. It is observed that the increased flow rate is required for achieving a particular value of gas holdup with larger nozzle diameter. Nozzle at the top edge of draft tube have higher gas holdup as compared to other positions. It has been noted that, no significant recirculation of gas bubbles into the top of draft tube from annulus section has been observed till a particular liquid flow rate is reached. A plot of gas holdup with no circulation and with circulation mode determines minimum liquid flow rate required to achieve complete circulation loop. Critical liquid flow rate required to achieve complete circulation loop increases with increase in gas flow rate and is minimum at lowest immersion height of two‐fluid nozzle.     

Gas holdup and overall volumetric mass transfer coefficient in a modified reversed flow jet loop reactor

Experiments were conducted in a modified reversed flow jet loop reactor having the liquid outlet at the top of the reactor to determine the gas holdup and overall volumetric mass transfer coefficient in the air-water system. The influence of gas and liquid flow rates, and the draft tube to reactor diameter ratio were studied. It was observed that both gas holdup and volumetric mass transfer coefficient increased with increased gas and liquid flow rates and were found to be significantly higher in the modified reactor compared to the conventional one. The optimum draft tube to reactor diameter ratio was found to be in the range of 0.4 to 0.5. Empirical correlations are presented to predict gas holdup and overall volumetric mass transfer coefficient in terms of operational and geometrical variables.     

Influence of geometry on gas holdups in a reversed flow jet loop reactor

The effects of ratio of draft tube to reactor diameter (D_d/D), liquid nozzle diameter (d_N), aeration tube diameter (d_G) and immersion height of the two-fluid nozzle into the draft tube (H_N) on overall and annulus gas holdups for the air-water system were evaluated experimentally in a reversed flow jet loop reactor over wide ranges of gas and liquid flow rates. Both the gas holdups increased with increasing gas and liquid flow rates and with decreasing d_N and H_N. The influence of d_G on gas holdups is found to vary with gas flow rates. Correlations are proposed to predict gas holdups.     

Effect of liquid viscosity on gas holdups in a reversed flow jet loop reactor

The effect of draft tube diameter and liquid viscosity on overall and annulus gas holdups were studied in a reversed flow jet loop reactor. The draft tube diameter to reader diameter ratio (D_d / D) and liquid viscosity were varied in the ranges 0.34-0.67 and 1.5-43 mPa. s, respectively. The maximum gas holdup was obtained when the D_d / D value ranged btween 0.47 and 0.61. The gas holdup decreased with increasing viscosity. Empirical correlations are presented to predict the gas holdups.     

分布器结构对环流反应器气含率分布的影响

采用κ-ε二方程模型和欧拉多相流模型,对一种单筒单级气升式气液环流反应器内的湍流气液两相流进行了全尺寸的数值模拟研究,考察了采用3种不同气体分布器时反应器内气含率和流速分布的细节.模拟结果表明不同结构的分布器对总体气含率和内筒中的两相速度分布有很大影响,因而对气含率分布和气液两相接触效果有较大影响,从而对反应过程产生影响.单环分布器产生的气液两相接触效果较差,对于反应过程很不利.对于大直径的环流反应器推荐使用多环分布器.计算所得的整体气含率与实测的整体气含率进行了对比,吻合较好.     

Hydrodynamics in down flow jet loop reactor

Gas holdup and liquid circulation time were measured in a down flow jet loop reactor for air–water system. It was observed that the circulation time decreases with an increase in nozzle diameter, draft tube to column diameter ratio and liquid velocity. Th gas holdup increases with an increase in gas and liquid velocities. The optimum draft tube to column diameter ratio was found to be 0.438. Correlations for gas holdup and circulation time involving operational and geometrical variables are presented.     

多室环流反应器气含率的三维数值模拟与分析

在常温常压条件下,以空气为气相、水为液相,对多室气升式环流反应器内气液两相流动状态进行了数值模拟,采用Euler两相流模型模拟了不同表观气速条件下各室气含率的分布情况。数值模拟计算结果表明,上升室气含率随表观气速的增大近似呈线性增长;各上升室气含率受自身表观气速的影响较大,而受另外一上升室表观气速的影响较小。     

Simulation and experimentation on the gas holdup characteristics of a novel oscillating airlift loop reactor

BACKGROUND: The classical airlift loop reactor (ALR) has been widely used in petrochemical, biochemical, energy and environmental processes due to such advantages as simple structure, without motional mechanism, easy sealing and low energy consumption. A novel ALR has been designed using forced periodic reversible ventilation, termed an airlift reversible loop reactor (ARLR). RESULTS: Using computational fluid dynamics (CFD) simulation and experimental validation, the mass transfer characteristics of the ARLR were studied. The simulation results predicted the experimental data well, especially at low ventilation capacity. The oscillation period had significant effects on gas holdup and the mass transfer coefficient of the ARLR. When ventilation capacity was increased from 0.22 to 3.49 vvm, compared with central airlift and annular airlift reactors, ARLR increased the mass transfer coefficient by 9–31% and 10–58%, respectively, according to simulation results, and by 11–25% and 14–58%, respectively, according to experimental data. CONCLUSION: The results showed that the ARLR could significantly enhance gas holdup and mass transfer coefficient compared with traditional central airlift and annular airlift reactors. Results indicated that the optimum oscillation period decreased with increase of ventilation capacity. ARLR has the potential for application in aerobic fermentation. © 2012 Society of Chemical Industry