LOCAL CHAOS CHARACTERISTICS IN A SELF ASPIRATED REVERSED FLOW JET LOOP REACTOR

The local chaos characteristics of the time series pressure fluctuations of gas liquid two phase flow in a self aspirated reversed flow jet loop reactor are studied by the deterministic chaos analysis technique. It is found that the estimated local largest Lyapunov exponent is positive in all cases and the profile is similar to that of the local fractal dimension in this reactor. The positive largest Lyapunov exponent shows that the reactor is a nonlinear chaotic system. The obvious distribution indicates that the local nonlinear characteristic parameters such as the Lyapunov exponent and the fractal dimension could be applied to further study the flow characteristics such as the flow regine transitions and flow structures of the multi phase reactors.

LOCAL NONLINEAR CHARACTERISTICS OF GAS LIQUID SOLID THREE PHASE SELF ASPIRATED REVERSED FLOW JET LOOP REACTOR

Hursts rescaled range (R/S) analysis and Wolfs attractor reconstruction technique have been adopted to estimate the local fractal dimensions and the local largest Lyapunov exponents in terms of the time series pressure fluctuations obtained from a gas liquid solid three phase self aspirated reversed flow jet loop reactor,respectively.The results indicate that the local fractal dimensions and the local largest Lyapunov exponents in both the jet region and the tubular region inside the draft tube increase with the increase in the jet liquid flowrates and the solid loadings,the local fractal dimension profiles are similar to those of the largest Lyapunov exponent,the local largest lyapunov exponents are positive for all cases,and the flow behavior of such a reactor is chaotic.The local nonlinear characteristic parameters such as the local fractal dimension and the local largest Lyapunov exponent could be applied to further study the flow properties such as the flow regime transitions and flow structures of this three phase jet loop reactor.

Modeling of Continuous Cross-flow Microfiltration Process in an Airlift External-loop Slurry Reactor

New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reactor. The pores blocking models were created based on the standard blocking law and the intermediate blocking law, and then the cake layer models were developed based on the hydrodynamic theory in which the calculation method of porosity of cake layer was newly corrected. The Air-Water-FCC equilibrium catalysts cold model experiment was used to verify the relevant models.Results showed that the calculated values fitted well with experimental data with a relative error of less than 10%.

FLOW AND DIFFUSION IN SELF-ASPIRATED REVERSE FLOW JET LOOP REACTOR

1 INTRODUCTIONGas and liquid distributions in a self-aspirated reverse flow jet loop reactor dependchiefly on the aspiration and the breakup against gas phase by the liquid nozzle aswell as the redistribution in the draft tube.It has also been noted that effective diffu-sion or backmixing in the reactor has great influence on the flow and mass transferrates.In this case,accurate descriptions about the fluid flow and diffusion conditions inthe reactor are most necessary for effective amplification of them.

FRACTAL STUDIES IN A SELF-ASPIRATED REVERSED FLOW JET LOOP REACTOR

1 INTRODUCTIONSelf-aspirated reversed flow jet loop reactors,characterized by a well defined flow pat-tern,well better dispersing effects,relatively low power consumption and a high masstransfer coefficient,are widely used in chemical engineering,especially in biochemicalengineering.The characteristics of such reactors are highly random or stochastic due tothe influence of a variety of phenomena such as jetting and bubbling of the

Hydrodynamics and Mass Transfer in a Modified Three-phase Airlift Loop Reactor

A modified internal-loop airlif reactor （MIALR） with a continuous slurry phase was studied to investigate the local hydrodynamic characteristics, including gas holdup, bubble size, bubble rise velocity and local mass transfer properties. Based on the analysis of geometrical construction and fluid properties of gas and slurry, MIALR was divided into six flow regions. In these flow regions, the local hydrodynamic characteristics were investigated over a wide range of operating variables. Furthermore, a new method was developed to measure the dissolved oxygen concentration. The volumetric mass-transfer coefficient in six flow regions was also calculated for comparison.

LOCAL LIQUID-PHASE OHARAOTERISTIOS OF THE SELF-ASPIRATED REVERSED FLOW JET LOOP REAOTOR

The local liquid--phase characteristics of the gas--liquid two-phase and gas--liquid--solid threephase self-aspirated reversed flow jet loop reactor with a concentric gas--liquid injection nozzle were studied experimentally. They facilitate the evaluation of local phenomena. The local instantaneous liquid velocities at different axial positions of the reactor were measured by using the modified pilot tube.The local liquid-phase turbulent structural parameters such as time-averaged velocity. turbulent nuctuating velocity and turbulent micro scale were calculated with the aid of the statistical theory of turbulence. In particular, effects of liquid jet flowrates and solid loadings on the profiles of the liquid--phase turbulent structural parameter both in the jet effective region and in the tubular region inside the draft tube were discussed.

IMPROVING SOLIDS SUSPENSION USING DEFLECTING BAFFLES IN GASLIFT LOOP REACTORS

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Study on dynamic characteristics of fission products in 2 MW molten salt reactor

In this study,a numerical flow model of the fission products(FPs)in the primary loop system of a molten salt reactor(MSR)was established and solved using Mathematica 7.0.The simulation results were compared with those of the ORIGEN-S program in the static burnup mode,and the deviation was found to be less than 10%,which indicates that the results are in good agreement.Furthermore,the FPs distribution in the primary loop system under normal operating conditions of the 2 MW MSR was quantitatively analyzed.In addition,the distribution phenomenon of the FPs under different flow rate conditions was studied.At the end of life,the FPs activity in the core region(including active region,and upper and lower plenum regions)accounted for 77.3%,and that in the hot leg #1,main pump,hot leg #2,heat exchanger,and cold leg region accounted for 1.2%,16.15%,0.99%,2.5%,and 1.9%,respectively,of the total FPs in the primary loop under normal operating conditions.The proportion of FPs in the core decreased with the increase in flow rate in the range of 2.24-22,400 cm^3 s^-1.The established analytical method and conclusions of this study can provide an important basis for radiation safety design of the primary loop,radioactive source management design,thermal-hydraulic safety analysis,and radiochemical analysis of FPs of 2 MW MSRs.

二级环流反应器中收缩-膨胀隔板的性能优化

通过在二级环流反应器两级之间安装具有收缩-膨胀形状的隔板,可以有效减小两级之间的液相回流流量,但同时会增加流体流动阻力。为了在减小液相回流流量的前提下减小流动阻力,本研究对隔板进行优化设计。首先通过模拟计算获得不同隔板下的压降和液相回流流量,随后对数据进行拟合,得到压降、液相回流流量与结构参数的关联式。计算结果表明当表观气速较小时,隔板宽度对压降影响较大,高度的影响较小。表观气速增大时,隔板高度对压降的影响变大。在所有气速下,隔板宽度是影响液相回流流量的决定因素。最后通过多目标优化,获得了在不同表观气速下最优隔板的Pareto前沿。

环流生物反应器降流区输氧浓度影响因素

环流生物反应器降流区输氧浓度主要受导流筒直径、导流筒溢流堰口高度及曝气量等因素影响,其对反应器污水脱氮除磷处理效果有重要影响。为考察以上影响因素对降流区输氧能力影响,采用数值模拟与实验结合的方法对环流反应器降流区输氧能力进行研究,通过自定义程序耦合Higbie传质理论模拟氧传质,对比不同曝气强度下反应器溶解氧浓度及溢流量模拟与实测值,结果显示误差在8%以内,表明数值模拟模型及方法正确可行。随后探究了曝气量、导流筒直径及导流筒溢流堰口高度对降流区输氧能力的影响。结果表明:曝气量由20 L/min增至50 L/min时,氧体积传质系数由2.04 h^(-1)增至4.45 h^(-1);导流筒直径由325 mm降至250 mm时,氧体积传质系数由3.99 h^(-1)增至4.42 h^(-1);导流筒溢流堰口高度由10 mm增至25 mm时,氧体积传质系数由4.17 h^(-1)降至4.00 h^(-1);增大曝气量和减小导流筒直径能明显提升降流区输氧能力。总之,可通过调整曝气量,导流筒直径及导流筒溢流堰口高度控制降流区输氧能力,以构建耗缺氧区域。通过响应面分析,得到导流筒直径250 mm、导流筒溢流堰口高度10 mm时,反应器降流区输氧能力较优。

多室内环流反应器中液体循环量的试验验证与模拟

目的对液相氧化脱硫多室内环流反应器液体循环量的影响因素进行模拟和验证。方法采用CFD数值模拟,基于欧拉-欧拉多相流模型,对液相氧化脱硫多室内环流反应器进行气液两相流模拟,考查了酸气流量和空气流量对液体循环量的影响。结果利用数值模拟得到的液体循环量与利用靶式流量计测得的液体循环量误差小于10%。当酸气中H 2S体积分数不超过3%时,液体循环量(z)与酸气流量(x)、空气流量(y)之间的关系式为:z=-474.996+0.358 x+0.4873 y。结论欧拉-欧拉两相流模型能够准确地预测液相氧化脱硫反应器内液体循环量。

多室气升式环流反应器的流动特性研究

提出一种具有四流道多室气升式环流反应器，并导出其内流体能否环流流动的判据。采用空气－水体系在较宽的气速范围内，考察反应器内的流动状态、循环液速以及各室的气含率。通过函数叠加的方法，提出适用于鼓泡流、过渡流和腾涌流等不同流型的平均含气率的经验关联式：Ｅｉ＝αＵβｇ＋γｅｘｐ〔……〕〔－δ（Ｕｇ－θ）２〕

环流反应器的流动、混合与传递特性

由于环流反应器内存在定向循环,与鼓泡塔反应器相比,其混合性能大幅提升,已广泛应用于许多工业过程,如发酵、反应器结晶等工业过程,近年来成为国内外学者研究的热点。针对环流反应器内操作条件下的流动形态、流体力学(包括相含率分布、循环液速、混合时间以及离集指数等)及传质/传热特性,总结了其最新研究进展,分析了相含率尤其是固含率变化对反应器中关键参数如循环液速和化学反应速率的影响,展望了从机理上研究相互耦合的多相流动、传质/传热和化学反应规律,为进一步推动其工业应用提供参考。

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。

液固环流反应器结构特性对固体流动的影响

在不同的导流筒直径、喷嘴直径和喷嘴位置对液固环流反应器中固体流动行为进行考察。实验结果表明,导流筒直径增加时,固体流速减小。固体相含率先增加后减少,对固体相含率而言,当导流筒直径与反应器直径之比为0 5时,固体相含率最大;喷嘴直径增加时,固体流速和固体相含率都降低;随着喷嘴高度由低到高,固体流速增加,而固体相含率降低。

带导流筒的下喷环流反应器的模拟及研究

本文通过引入二维拟均相κ－ε模型方程，建立了描述气液下喷环流反应器内管流区流体流动规律的数学模型，并进行了求解，模型值与试验值吻合较好。以空气－水－玻璃球为研究物系，对有导流筒的下喷式环流反应器中局部液相性能进行了较深入研究。

环管反应器内液固两相流的数值模拟

为了对环管反应器内液固两相的流动形态进行研究,建立了以颗粒动力学为基础的Euler-Euler双流体模型。在浆液流速远大于自由沉降速度的情况下,模拟了不同浆液入口速度时的环管反应器上升段压力降,同时对管道内液固两相流中的一些重要参数进行了数值研究:在入口液固两相体积分布均匀的情况下,环管反应器上升段、弯管段以及下降段液固两相体积分布和液固两相速度均不一样,在弯管段由于离心力存在而引起管道内二次流,使得固相颗粒甩向弯管的外侧壁,引起固相体积分数在弯管外侧壁明显增大,管道内固体颗粒相分布不均。在浆液速度v=3m·s-1时,液相和固相的速度有一定的速度差,随着入口速度增大,速度差变小;当浆液速度v=7m·s-1时,固体颗粒相速度分布与液相速度基本相同,两者之间的滑移速度可以忽略。计算结果与传统经验公式的比较表明模型能有效地描述环管反应器内压力降和反应器内浆液流动形态。

环流技术在石油炼制领域中的研究与应用

环流技术在生物工程、废水处理、有机化工、煤直接液化等领域得到了较多的研究和应用,这些研究多集中于气-液、液-固及气-液-固体系。近年来,环流技术的研究延伸到了气-固体系,应用范围也拓展到了石油炼制领域。本文重点概述了气-固环流技术在石油炼制领域中催化裂化装置的粗旋快分、汽提器、外取热器、降烯烃反应器及石油焦燃烧器等装备中的研究与应用进展,同时也对气-液环流技术在渣油悬浮床加氢、气-液-固环流技术在水合物法分离炼厂气中氢气技术上的研究与应用情况进行了综述。

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。