PNEUMATICALLY CONTROLLED MULTI-STAGE FLUIDIZED BED AND ITS APPLICATION IN SOLVENT RECOVERY FROM A PLANT WASTE GAS

The downcomer is the key component of a multi-stage fluidized bed.A pneumatically controlleddowncomer has been devised,consisting of a fully fluidized dipleg followed by a conical spout for upwarddischarge in dense phase.Such a design has been found to insure against bridging of solids in descent andagainst spouting of solids from a lower layer caused by gas by-passing.In experimental investigations,flow characteristics are measured including the pressure drops of thedifferent fluidized beds and of the downcomers for various gas and solids flow rates as well as the solidsresidence time distribution,operating either with a multiplicity of gas sources for the various downcomersor with only two gas sources.In a particular design,a multi-stage ftuidized bed with dual gas supply,inwhich one half is incorporated centrally in the other,has been tested on pilot scale for recovering solventfrom low concentration ethylene dichloride streams of a plant waste gas.Main test results obtained wereas follows:adsorption rate>97%concentration of waste gas<25 mg/m~3active carbon loss<0.1%This kind of conical downcomer in which the solids arc either transported from a high- to a low-pressure region,or from a low- to a high-pressure region,is also used to control the solids discharge ofcyclone diplcgs or the feeding and discharging in other solids circulation systems.     

垂直稀相气力输送实验研究

An experimental study of vertical gas conveying of Geldart-D powder as a dilute phase is performed in a pipe of length 22m and internal diameter 0.05m using a fluidized blow tank at gas velocity ranging from 5m.S-1 to 13m.s-1 and loading ratio up to about 30. The characteristics of gas conveying, such as pressure drop, the choking velocity and the minimum primary velocity of the fluidized blow tank, are discussed in detail.     

电容层析成像技术在分离器料腿浓度测量中的应用

Accurate solid concentration measurement plays a key role in the process industry. Measurements analyzed offline can be used to estimate process efficiencies, to identify problems in a flow, and to validate computational models. Online measurements can be used for active control. Electrical capacitance tomography (ECT) is a unique measuring technique with great potential in multiphase flow measurement. Experimental studies are carried out on a solid concentration measurement in a cyclone separator dipleg, using ECT. In this experiment eight electrodes are selected for the ECT sensor that is placed on the straight tube of the dipleg. The fluctuating characteristics according to the screw feeder and the effect of the airflow rate from the top of the cyclone are analyzed. The feasibility and reliability of the method are verified by the experimental results.     

Correlation between hysteresis of gas-liquid mass transfer and liquid distribution in a trickle bed

The hysteresis of gas-liquid mass transfer rate and the corresponding radial liquiddistribution in a trickle bed reactor are measured to provide evidence for the correlation between thesetwo behaviors.Experimental results indicate that the hysteresis of gas-liquid mass transfer originatesfrom the nonuniformity of the hydrodynamic state of gas-liquid flow and the radial maldistributionof local k_(gia) corresponds very well to the radial maldistribution of liquid flow in the bed.The localliquid flow rate is also found to be nonuniform in the azimuthal direction.In view of maldistributedliquid flow even in the pulsing flow regime,the conventional plug flow model seems oversimplifiedfor describing the behavior of a trickle bed.     

天然气水合物生成焓的实验研究

This paper reports the measurements of enthalpies of natural gas hydrates in typical natural gas mixture containing methane, ethane, propane and iso-butane at pressure in the vicinity of 2000 kPa (300 psi) and 6900 kPa(1000psi). The measurements were made in a multi-cell differential scanning calorimeter using modified high pressure cells. The enthalpy of water and the enthalpy of dissociation of the gas hydrate were determined from the calorimeter response during slow temperature scanning at constant pressure. The amount of gas released from the dissociation of hydrate was determined from the pumped volume of the high pressure pump. The occupation ratio (mole ratio) of the water to gas and the enthalpy of hydrate formation are subject to uncertainty of 1.5%.The results show that the enthalpy of hydrate formation and the occupation ratio are essentially independent of pressure.     

Experimental study on the effects of big particles physical characteristics on the hydraulic transport inside a horizontal pipe

This paper presents an experimental study of the physical characteristic effects of large particles on hydraulic transport in a horizontal pipe. The particles are spherical and are large with respect to the diameter of the pipe (8%, 10%, 16%and 25%). Experiments were done to test the important parameters in solid transport (pressure, velocity, etc.). As a result, the relationship between the pressure gradient forces and the mixture velocity was sub-stantially different from the pure liquid flow. However, in a single-phase flow a monotonous behavior of the pres-sure drop curve is observed, and the curve of the solid particle flow attains its minimum at the critical velocity. The regimes are characterized with differential pressure measurements and visualizations.     

封闭多井油藏中的压力恢复分析

A general method has been developed for analyzing pressure buildup data from a well located in a system with both production and injection wells in a closed, bounded two-phase flow reservoir. The proposed method enables one to calculate the total mobility or permeability-thickness product, the skin factor, the average drainage-area pressure and the injection-production ratio （at the instant of shut-in） with accuracy from pressure buildup （or falloff） data dominated by a linear trend of reservoir pressure. Out of thousands of well tests, several typical field examples have been presented to illustrate the application of the proposed method for analyzing pressure transient data from a well located in a water-injection multiwell reservoir. And the possible application of this method to heterogeneous systems such as naturally fractured reservoirs is also discussed. Approaches to aid practicing engineers in verifying the buildup interpretation （or recognizing the interference of offset wells） are presented. Extension of the presented method to a gas well located in a multiwell gas reservoir is also suggested     

三维混合层中大涡结构与扩散颗粒的相互作用

In order to understand the interaction between large-scale vortex structure and particles, a two-way coupling temporal mixing layer laden with particles at a Stokes number of 5 with different mass loading planted initially in the upper half region is numerically studied. The pseudospectral method is used for the flow fluid and the Lagrangian approach is employed to trace particles. The momentum coupling effect introduced by a particle is approximated to a point force. The simulation results show that the coherent structures are still dominant in the mixing layer, but the large-scale vortex structure and particle dispersion are modulated. The length of large-scale vortex structure is shortened and the pairing is delayed. At the same time, the particles are distributed more evenly in the whole flow field as the mass loading is increased, but the particle dispersion along the transverse direction differs from that along the spanwise direction, which indicates that the effect by the addition of particle on the suanwise large-scale vortex structure is different from the streamwise counterpart.     

基于人工神经网络的滴流床脉冲流频率的预测

An extensive database (946 measurements) for the frequency of pulsing flow in trickle beds was established by collecting the experimental results published over past 30 years. A new correlation based on artificial neural network (ANN) to predict the pulsation frequency was developed. Seven dimensionless numbers (groups) employed in the proposed correlation were liquid and gas Reynolds, liquid Weber, liquid Eǒtvǒs, gas Froude, and gas Stokes numbers and a bed correction factor. The comparisons of performance reported in the of literature and present correlations show that ANN correlation is a significant improvement in predicting pulsation frequency with an average absolute relative error (AARE) of 10% and a standard deviation less than 18%.     

精馏塔的压降测量研究(英文)

Pressure drops are of major importance for distillation/absorption columns. This paper mainly discusses how to correctly measure, interpret and use pressure drop data. The possible causes of incorrect pressure drop measurements are studied including the effects of pressure tap dimensions, locations, and vapor condensation etc. The effect of the static head of vapor on the pressure drop data and column pressures is evaluated. Variations of sec-tional pressure drops along the column are investigated based on the experimental data obtained from commercial size distillation columns at Fractionation Research, Inc. (FRI). For a packed column, it is found that the spacing between the liquid distributor and the top of the bed affects the overall pressure drop measurements, which is con-firmed by a fundamental fluid dynamics analysis.     

带翼阀旋风分离器料腿内动态压力的分析研究

在大型流化床装置上,采用动态压力传感器测定了翼阀置于流化床的稀相空间和密相空间两种情况时料腿内的动态压力。通过对二级料腿稳定排料和周期性排料的数据分析得出,料腿内动态压力的变化与料腿内颗粒质量流率的大小密切相关,翼阀埋没在密相时料腿内的压力波动比较平缓,料腿的周期性排料时压力波动频率约0.01Hz,料腿内稀相段压力波幅比密相段略小,料腿内压力波动的原因是由于气固两相在快速下行过程中存在密度差和速度差。     

带翼阀旋风分离器料腿内静压分布试验研究

在φ800mm×12000mm流化床试验装置上,用多点压力测量仪测量料腿内的静压分布。试验结果表明,二级料腿内气固两相流的流态一般由入口旋转段、稀相下落段和下部密相段3部分组成,料腿内的料封高度随料腿两端负压差的增大而升高,颗粒质量流率对轴向空隙率影响明显,翼阀浸没在密相床时颗粒流动稳定性和流动失流化的机会都增加。     

Effect of the Solid Loading on a PFBC Cyclone with Pneumatic Extraction of Solids

This paper presents the effects of solid loading on the performance of a cyclone with pneumatic extraction of solids. The cyclone is a non‐conventional design, especially used for hot‐gas cleaning applications such as pressurized fluidized bed combustors (PFBC). A scaled‐down cold‐flow model was employed for the research. Experiments were conducted at 9–14 m/s inlet gas velocities, inlet solid loadings ranging from 30 to 230 g/kg gas, and bottom gas extraction percentages from 0.3 to 1.5%. Experimental results of pressure drop resistance coefficients and collection efficiency were compared with literature predictions. At PFBC operating conditions, cyclone geometry and solid concentration are the main parameters influencing cyclone pressure drop and collection efficiency. The vortex penetration in dipleg causes lower pressure drop values and higher collection efficiencies than predicted. These parameters can be suitably predicted for PFBC cyclones by introducing a modified penetration length in Muschelknautz's model [1]. For the present cyclone design, a new correlation of pressure drop, including the influence of solid loading, is proposed. A new method for detecting cyclone fouling, not previously addressed, is also presented, based on the evolution of the pressure drop resistance coefficient. An enhanced separation efficiency has been found, related to collection efficiency, which is especially important for particle sizes below 10 μm revealing agglomeration effects.     

Numerical and Experimental Study of Catalyst Loading and Body Effects on a Gas‐Liquid Trickle‐Flow Bed

The influence of tortuosity and fluid volume fractions on trickle‐flow bed performance was analyzed. Hydrodynamics of the gas‐liquid downward flow through trickle beds, filled with industrial trilobe catalysts, were investigated experimentally and numerically. The pressure drop and liquid holdup were measured at different gas and liquid velocities and in two different loading methods, namely, sock and dense catalyst loading. The effect of sharp corners on hydrodynamic parameters was considered in a bed with rectangular cross section. The reactor was simulated, considering a three‐phase model, appropriate porosity function, and interfacial forces based on the Eulerian‐Eulerian approach. Computational fluid dynamics (CFD) simulation results for pressure drop and liquid holdup agreed well with experimental data. Finally, the velocity distribution in two types of loading and the effect of bed geometry in CFD results demonstrated that pressure drop and liquid holdup were reduced compared to a cylindrical one due to high voidage at sharp corners.     

气控式多层流化床及其在净化排放气中的应用

溢流管是多层流化床的关键构件。本文设计的由下料料腿和锥斗组成的气控式锥形溢流管,由于物料在料腿中处于流态化状态,在锥斗中以气固顺流浓相向上输送,因此,这种溢流管可以防止物料在料腿中的架桥和喷料。 试验中测定了多气源和双气源两种气控式多层床的流动特性,包括各床层和溢流管压降以及固体停留时间分布。在回收低浓度二氯乙烷的中间工厂试验中,采用了具有同心圆的双气源多层流化床,获得以下主要结果: 吸附率>97%,排放气浓度<25mg/m~3,活性炭损失<0.1%。 这种能使固体物料由高压区输至低压区,或从低压区输至高压区的气控锥形溢流管结构,亦可用于旋风器料腿的返尘以及在循环系统中固体物料的连续加、排装置。     

Study of liquid spreading from a point source in a trickle bed via gamma-ray tomography and CFD simulation

Gamma-ray tomography and a liquid collecting device have been used to detect liquid spreading from a single point source in a trickle bed. This basic configuration has been chosen to evaluate the radial spreading of liquid flow through a fixed bed. The experimental data are used to validate the two-dimensional (2D) computational fluid dynamic model (CFD) developed at the CREL laboratory for gas/liquid trickle flows inside a fixed bed [Jiang et al., 2002. A.I.Ch.E. Journal 48, 701-730]. The data obtained show the influence of liquid and gas flow rates and the impact of pre-wetting condition on liquid distribution evolution along fixed bed axis. The comparison between experimental data and simulation results shows a significant effect of the capillary pressure term on prediction of the radial spreading of the liquid flow. Several physical models for the capillary pressure term are tested in order to select the closure law that allows a proper prediction of liquid spreading at trickle flow conditions.     

Application of Magnetic Resonance Imaging (MRI) for investigation of fluid dynamics in trickle bed reactors and of droplet separation kinetics in packed beds

Magnetic Resonance Imaging technique was used to investigate the fluid dynamics of multiphase flow in two different applications: (a) stationary two-phase flow in trickle beds, and (b) time-dependent droplet separation in granular bed filters. The experiments were carried out with different gas/liquid systems at either atmospheric conditions or at elevated pressure and temperature. Two-dimensional and three-dimensional image data were then evaluated to quantify the porosity profiles and gas/liquid distribution in packed beds. The results compare well with data from integral measurements.     

Hydrodynamics and flow regime transition study of trickle bed reactor at elevated temperature and pressure

The hydrodynamics in a trickle bed reactor (TBR) in non-ambient conditions are studied for air-water and air-acetone (pure organic liquid of low surface tension) systems. A flow map experiments for air-water and air-acetone systems are performed in a pilot plant reactor of 0.05 m i.d. and 1.25 m height. It has been demonstrated from the experimental results that the pressure drop tends to increase with increasing superficial gas and liquid velocity and reactor pressure, while it tends to decrease with increasing bed temperature. The results also show that the dynamic liquid holdup increases with increasing liquid velocity and decreases with increasing superficial gas velocity, reactor pressure and bed temperature. The dynamic liquid holdup and pressure drop values are obviously higher than those measured for air-water system at the same fluid fluxes, reactor pressure and bed temperature due to the surface tension effects. For higher reactor pressure and temperature, the trickle to pulse transition boundary shifts towered higher superficial velocities of both gas and liquid.     

基于钙链制氢的双流化床气固流动特性

钙链制氢是一项新颖的制取富氢合成气技术,由此设计并搭建了一套双流化床反应器,该反应器由气化反应器、煅烧反应器、碳酸化反应器、旋风分离器、立管和流动密封阀组成。采用两种不同粒径的白刚玉,研究了该双流化床反应器的气固流动特性,研究了物料总量、颗粒粒径、L阀、气化反应器和煅烧反应器的风速对固体流率的影响,固体流率随着L阀和气化反应器风速的增加而增加。同时研究了L阀风量与固体流率之间的关联式,通过量纲分析和多元线性拟合,得到了它们之间的回归方程,研究结果表明：实验结果和拟合结果吻合得比较好,可以较好地反映L阀风量与固体流率之间的关系。     

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.