微型气液固三相等温微分浆态床反应器的优化

针对气液固三相浆态床催化反应中,传递、反应、催化剂的原位表征均比较复杂的问题,为了有利于气、固相均匀分散于液相和反应温度在反应器中实现等温,通过对气液固三相反应工艺特性和反应器性能要求的分析,对微型气液固三相浆态床反应器进行了优化。根据微型浆态床对气液固三相反应分析的要求,采用图像法研究了分布器为G1、G2、G3,砂板直径为2、2.5、3 cm反应器中的流体力学性能特征,考察了气体流速、温度、反应器直径及气体分布器对气含率、气泡尺寸、气泡上升速率以及气泡分布的影响,并进行流体动力学模拟计算,确定了微型浆态床反应器的直径为2 cm,气体分布器为G3砂板的反应器结构,该反应器可以应用于反应过程中间态及液体产物生成过程的测试。     

计算流体力学在填充床反应器中的应用进展

在使用计算流体力学(CFD)方法模拟填充床反应器时,为了描述填充床中的气液流动情况,目前主要运用基于体积平均法的双流体数学模型,辅以空隙率分布,填料润湿效率以及轴向扩散等经验关联式来计算填充床中的压降、持液量、停留时间分布等重要参数。近年来填充床反应器CFD数学模型韵几个研究重点是动量交换系数、毛细管压力以及床层空隙率的非均匀分布性。简要介绍了涓流床、固定床、填料塔等填充床反应器及其内部构件研究中CFD软件模拟的应用进展情况和发展趋势。     

三相循环流化床的小型冷模试验研究

三相循环流化床在化学工程、生物工程及废水处理等领域中均有着广泛的应用。试验采用固体取样法测定了反应器内的固含率分布；采用压降发测定了反应器内的气含率分布；采用压强脉动法确定了反应器在试验操作条件下的流型。试验结果表明：在试验考察范围内反应器的压强在轴向上均呈线性分布；固含率沿反应器轴向分布平缓；反应器内气含率随轴向位置的升高而缓慢增大，径向分布基本上是均匀的；气含率受配料浓度影响不大．受表观气速的影响较大；反应器各轴向位置脉动能量的主频范围差异不大。这表明整体上反应器全床均处于比较均匀、脉动较低的过渡流湍动状态。     

色谱技术测定传递系数和吸附系数讲座(七)

<正> 在上一讲中介绍的色谱技术测定传递系数和吸附系数的应用局限于气固体系。但它们也能应用于气液、液固或气液固三相的体系。本讲中要介绍它们在浆化反应器(slurry reactor)和涓流床反应器(trickle-bed reactor)中的应用。 一、浆化反应器     

气液固三相移动床中流型的声发射检测

本文采用声发射检测分析了气液固三相移动床中的各相运动信息，实现了三相移动床中涓流-脉冲流的识别，并进一步分析了不同条件下脉冲流的演变规律。结果表明，滴流床中气液流型为脉冲流时，声信号在时域上会形成能量包，可据此实现涓流-脉冲流的准确识别，且该识别准则对于三相移动床同样适用。固相移动导致的床层空隙率增大会使三相移动床中脉冲流形成的条件变得更加苛刻。气液达到稳定脉冲后，固相颗粒对于气液的带出作用会在一定程度上增大三相移动床中的气液脉冲频率。     

气-液-固反应器介绍

一、气—液—固反应器的型式根据固体颗粒的运动状态不同,气—液—固反应器可分成下列两类基本型式。 1.固体颗粒静止不动这种型式称为固定床。它有三种操作方式:(1)气、液并流向下,(2)气、液并流向上,(3)气、液逆流(通常是气体向上,液体向下)。固定床气—液—固相反应器中,以(1)、(3)两种操作方式居多,即液体成薄膜沿固体颗粒的表面流下,气体则成连续相以并流或逆流的方式通过静止的颗粒层,称为涓流床反应器,如图1所示。在涓流床反应器中,流动情况接近活塞     

气液固三相环流反应器的研究进展

综述了气液固三相环流反应器的类型及工作原理、气液固三相环流反应器的特性参数(气含率、固含率、循环液速、液相体积传质系数、轴向分散系数)的测量方法和影响因素，介绍了特性参数的数学模型。并对现有模型进行了评述。对今后的研究提出一些建议。     

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。     

煤间接液化费托合成浆态床反应器的研究进展

随着煤炭间接液化技术在百万吨级商业示范装置上的成功应用，作为其核心设备的费托合成浆态床反应器，涉及气液固三相湍流流动、传热传质及反应，其随反应器直径放大及内构件结构布局的变化而发生改变，进而影响反应器性能的多个复杂过程，导致在反应器设计、放大及操作优化上面临巨大挑战，科研及工业界仍然持续重视。本综述分析了影响浆态床反应器流体力学性能的主要因素，对浆态床反应器的流型、气含率、气泡行为、传热等研究进行了总结。介绍了浆态床反应器核心内构件的结构特点及发展状况，回顾了浆态床在费托合成反应过程中的工业应用历程，并展望了费托合成浆态床的研究趋势。     

气液并流向上填充床流体力学特性

研究了气液并流向上填充床的流体力学特性，如：流型、压降、以Ｃ／Ｃｏ及Ｐｅｒ表示的液相径向混合情况。填料为直径３．５，５．７，７．５ｍｍ的玻璃球；塔径８１ｍｍ，塔高１０００ｍｍ。结果表明，气液并流向上的床层压降大于滴流床，而液体径向混合的均匀程度优于滴流床。     

Onset of pulsing in gas-liquid trickle bed filtration

When liquid suspensions containing low concentration of fine solids are treated in catalytic packed bed gas-liquid-solid reactors, which are operated in trickle flow or near the transition between trickle and pulse flow, plugging develops and increases the resistance to two-phase flow. Also due to obstruction, such accumulation of fines in the catalyst bed shifts progressively the flow pattern from trickling to pulsing flow. The progressive onset of pulsing flow along the packed bed was estimated using a sequential approach based on combining a “large time-scale” unsteady-state filtration solution of two-phase flow with a “short time-scale” solution of a linear stability analysis of two-phase flow. Space-time evolution and two-phase flow of the deposition of fines in trickle bed reactors under trickle flow regime was described using a one-dimensional two-fluid model based on the volume-average mass and momentum balance equations and volume-average species balance equation for the fines. The model hypothesized that plugging occurred via deep-bed filtration and incorporated physical effects of porosity and effective specific surface area changes due to the capture of fines, inertial effects of phases, and coupling effects between the fines filter rate equation and the interfacial momentum exchange force terms. The transition between trickle flow and pulse flow regimes was described from a stability analysis of the solution of the transient two-fluid model around an equilibrium state of trickle flow under pseudo steady state conditions. The impact of liquid superficial velocity, viscosity and surface tension, gas superficial velocity and density, feed fines concentration, and fines diameter on the transition between trickle and pulse flows in the presence of fines deposition was analyzed.     

On flow regime transition in trickle bed: Development of a novel deep-learning-assisted image analysis method

An image analysis method was developed based on deep-learning algorithms to extract phase fractions quantitatively in a rectangular trickle bed, and the average identification error was lower than 5%. Furthermore, the flow regime transition in the trickle bed was studied. In trickle-to-pulse flow transition, the trickle flow could be further classified into the stable trickle flow and accelerated one. The SD of liquid fractions and the peak width at half-height of the probability density curve of liquid fractions were close to zero in stable trickle flow, increased rapidly in accelerated trickle flow, and remained approximately constant in pulse flow. In bubble-to-pulse flow transition, dispersed bubbles in bubble flow induced the outliers outside the upper boundary of the boxplot of gas fraction, while alternative appearance of gas-rich zone and liquid-rich zone in pulse flow induced outliers outside both the upper and lower boundaries of the boxplot of gas fraction.     

A cellular automata model for liquid distribution in trickle bed reactors

A cellular automata model for liquid distribution studies in trickle bed reactors is presented. It is a potential tool for describing non-uniform distribution of gas and liquid in a trickle bed. This non-uniformity may arise from a wide range of potential sources, such as improper distribution of the feed, random or radial porosity variation, wall effect, partial wetting of the catalyst, and gas-liquid surface tension related effects. Axial and radial dispersion of the liquid flow are inherently included in the model, since the fundamental model probability parameters are directly related to the dispersion coefficients. The present model is extremely fast due to simple single-event modeling, and it is well suited for parallelization. Three examples of the model performance are shown. In the first a liquid jet spreading from a point source is followed, and in the second, effect of radial porosity profile to wall flow is examined. The third example illustrates the potential of the model to predict pulsing flow regime.     

Numerical assessment of diffusion-convection-reaction model for the catalytic abatement of phenolic wastewaters in packed-bed reactors under trickling flow conditions

Computational fluid dynamics (CFD) modeling of trickle-bed reactors with detailed interstitial flow solvers has remained elusive mostly due to the extreme CPU and memory intensive constraints. Here, we developed a comprehensible and scalable CFD model based on the conservative unstructured finite volume methodology to bring new insights from the perspective of catalytic reactor engineering to gas-liquid-solid catalytic wet oxidation. First, the heterogeneous flow constitutive equations of the trickle bed system have been derived by means of diffusion-convection-reaction model coupled within a Volume-of-Fluid framework. The multiphase model was investigated to gain further evidence on how the effect of process variables such as liquid velocity, surface tension and wetting phenomena affect the overall performance of high-pressure trickle-bed reactor. Second, as long as the application of under-relaxation parameters, mesh density, and time stepping strategy play a major role on the final corroboration, several computational runs on the detoxification of liquid pollutants were validated accordingly and evaluated in terms of convergence and stability criteria. Finally, the analysis of spatial mappings for the reaction properties enables us to identify the existence of relevant dry zones and unveil the channeling phenomena within in the trickle-bed reactor.     

文丘里卷吸型气液分配器液体分配性能的结构参数研究

为了改善滴流床用的内卷吸型气液分配器的液体分散差的现象,提出了一种文丘里卷吸型气液分配器,并对其结构参数进行了参数化研究,定量认识卷吸型分配器的结构参数对其气液分配性能的影响。在冷态实验装置上进行了文丘里卷吸型气液分配器性能实验,建立了耦合群体平衡模型的欧拉-欧拉两相流模型,数值模拟了文丘里卷吸型气液分配器气液两相分配流动过程。冷模实验结合数值模拟,系统性考察了各结构参数对卷吸型气液分配器的液体分布均匀性、喷淋半径以及压降的影响。结果表明,采用具备缩-扩结构的文丘里管作为降液管能够有效提升卷吸型分配器的分布均匀度和喷淋半径,并显著降低压降。通过正交试验,获得了主要结构参数与分配性能的相关性,给出了结构参数与性能指标的经验关联式。降液管的扩张段是改善液体分配性能的关键结构,其扩张角为30°时液体分配性能最好。     

气液固三相湍流流动的E/E/L模型与模拟

采用基于双流体模型与粒子分散模型相结合的方法 ,建立了一个用于描述气液固三相湍流流动的Eulerian/Eulerian/Lagrangian模型 (简称E/E/L模型 ) .在Euler坐标系中考虑了气液两相 ,利用双流体模型来表述气液两相的相互关系 ;同时在Lagrange坐标系中考察了颗粒的运动 ,并把颗粒对气液两相的影响耦合于双流体模型中 .以流化床内气液固三相湍流流动为例进行的数值模拟结果与实验结果吻合良好 .所提出的模型及其模拟具有很好的准确性和可靠性 ,为研究气液固三相湍流流动提供了一种新的途径     

Hydrodynamics of trickle bed reactors at high pressure: Two-phase flow model for pressure drop and liquid holdup, formulation and experimental validation

A large experimental database has been established at IFP on the same experimental setup to measure simultaneously pressure drop and liquid holdup in packed bed reactor operated in trickle for a large range of operating conditions. The varying parameters are liquid viscosity and density, gas density, bed particle shape and size. The range for gas density range is particularly large (from 1.3 to ), thanks to the use of dense gas to simulate very high pressure conditions. This data bank has been first used to compare the prediction accuracy of the different models from the literature. Finally, the mechanistic model proposed by Attou et al. [1999. Modelling of the hydrodynamics of the cocurrent gas-liquid trickle flow through a trickle-bed reactor. Chemical Engineering Science 54, 785-802] has been improved by adding a new formulation for liquid film tortuosity in two-phase flow conditions. This model has been validated over the whole data range and the accuracy has been checked with data external to the data bank. The prediction accuracy is significantly increased when compared with the best available models for pressure drop and liquid retention in trickle flow reactors.     

EXPERIMENTAL STUDY ON GAS-HOLDUP AND GAS-LIQUID INTERFACIAL AREA IN TPCFBs

A new fiber optic probe system has been developed for measuring the gas-holdup ε_g and bubble size distribution P_s(d_b) in multiphase reactors. Experiments have been carried out in a gas-liquid-solid three-phase circulating fluidized bed (TPCFB) with 140mm inner diameter and 3 m height, in which air, tap water and 0.4 mm glass beads are used as the gas, liquid and solid phase, respectively. Based on the measured data, the gas-liquid interracial area a, one or the most important parameters concerning the mass transfer, has been derived. The radial profile of the gas holdup and the gas-liquid interracial area, and the influence or main operating conditions have been studied experimentally in TPCFBs.     

气升式反应器在发酵工业中的应用研究进展

气升式反应器是一种用于气液两相或气液固三相过程的接触式反应装置,简要综述了气升式反应器在发酵工业中的应用研究进展,按照集成强化的思路开发的气升式膜生物反应器被重点介绍。