气固两相流中局部颗粒质量流率的测量新方法

Previous works have shown that the suction probe cannot be used to accurately measure the upward and downward particle fluxes independently. A new method using a single optical probe to measure the local solid flux is presented. The measurement of upward, downward and net solid fluxes was carried out in a cold model circulating fluidized bed (CFB) unit. The result shows that the profile of the net solid flux is in good agreement with the previous experimental data measured with a suction probe. The comparison between the average solid flux determined with the optical measuring system and the external solid flux was made, and the maximum deviationturned out to be 22%, with the average error being about 6.9%. These confirm that the optical fiber system can be successfully used to measure the upward, downward and net solid fluxes simultaneously by correctly processing the sampling signals obtained from the optical measuring system.     

LOCAL HOLDUPS AND LIQUID INTERSTITIAL VELOCITY IN LARGE-DIAMETER THREEPHASE FLUIDIZED BED

Radial profiles of local gas and solid holdups and liquid interstitial velocity were measured in a largediameter three-phase fluidized bed, and a systematic study was carried out in comparing the present data with those obtained in small-diameter beds. Radial profiles of local gas holdup were found to be parabolic; the distribution of local solid particle holdup could be expressed by Eq. (9); liquid interstitial velocity was well described by the modified circulating flow model.     

组合式流化床中以高钙镁钛渣为原料制取TiCl4

This paper describes a new method for producing TiCl4 by chloridizing materials of high content CaO and MgO, in which a combined fluidized bed is used as a reactor to avoid agglomeration between particles caused by molten CaCl2 and MgCl2. The combined fluidized bed consists of at least a riser tube and a semi-circulating fluidized bed. Two kinds of high titanium slag, in which the total mass content of CaO and MgO is 2.03% and 9.09% respectively, are employed to examine the anti-agglomeration effect and the conversion of the materials when the temperature ranges are between 923.15K and 1073.15K, gas apparent velocity 0.7-1.1m·s-1, and inlet amount of solid materials is 4.6-7.0kg·h-1. It is found that the anti-agglomeration effect in the combined fluidized bed is satisfactory and the new method can achieve a TiCl4 production capacity of 14.0-75.4t·m-2·d-1 in relation to 25.0-40.0t·m-2·d-1 from the conventional bubble bed. Furthermore, low-temperature chloridization, for example, at 923K or 973K, can also be used to produce TiCl4 and avoid agglomeration.     

耦合反应器提升管段颗粒速度分布及约束特性

A large-scale cold model experimental setup of a riser-fluidized bed coupled reactor was established according to the olefin reduction technology with an auxiliary reactor for FCC naphtha upgrading.Distributions of particle velocity in the riser section were experimentally investigated in the setup.Furthermore,the restriction index of particle velocity was defined to quantitatively show the restriction effects of the riser outlet lotus-shaped distributor and the upper fluidized bed on the particle flow behavior in the riser.The experimental results showed that the riser could be divided into two regions in the longitudinal direction,i.e.,lower traditional transport region and upper restriction region.In the longitudinal direction,the averaged cross-sectional particle velocity in the traditional transport region increased firstly,and then tended to be smooth,while decreased in the restriction region.With the increase of static bed height in the upper fluidized bed,the local particle velocity decreased,and the tendency of change in the core region is more than that in the wall region.Restriction effects of the lotus-shaped distributor and the upper fluidized bed on particle flow behavior enhanced with the increases of superficial gas velocity,solids flux and static bed height in the upper fluidized bed.In the same cross-section,outlet restriction effects enhanced with the increase of the dimensionless radial position r/R,and would not change when r/R≥0.5.     

声场对细粒的床层膨胀的影响(英文)

Fine particles are difficult to fluidize due to strong interparticle attraction.An attempt has been made to study the bed expansion of silica gel(dp=25μm) powder in presence of an acoustic field.A 135 mm diameter fluidized bed activated by an acoustic field with sound intensity up to 145 dB and frequency from 90 Hz to 170 Hz was studied.The effects of sound pressure level,sound frequency and particle loading on the bed expansion were investigated.Experimental results showed that,bed expansion was good in presence of acoustic field of particular frequency.In addition,it was observed that in presence of acoustic field the bed collapses slowly.     

垂直内挡板对流态化流体动力学及谷物干燥特性之影响

The effect of vertical internal baffles on the particle mixing and grain drying characteristics in a batch fluidized bed column is investigated. Experimental work was carried out in a 3 m high rectangular fluidized bed dryer of cross sectional area of 0.15 mx0.61 m at different operating conditions using paddy, a group D particle, as the fluidizing material. The results of the study showed that the fluidized bed dryer system with vertical internal baffles gave better particle mixing effect in the bed of particles than that without vertical internal baffles. This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking up the large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bed of particles before finally erupting at the bed surface. This improves the contacting efficiency and enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate was obtained in the falling rate period because the higher contactin efficiency increases the evaporation rate at the particle surface. However, the drying rate in the diffusion regiol shows little improvement because the moisture diffusivity does not depend on the contacting efficiency. The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapid drying stage in a two stage drying strategy for paddy. The insertion of vertical internal baffles into a fluidized bed system improves the processing of Group D particles in a fluidized bed system especially if the system is large in scale.     

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%.     

The Ejffect of Vertical Internal Baffles on Fluidization Hydrodynamics and Grain Drying Characteristics

The effect of vertical internal baffles on the particle mixing and grain drying characteristics in a batch fluidized bed column is investigated. Experimental work was carried out in a 3m high rectangular fluidized bed dryer of cross sectional area of 0.15 m×0.61 m at different operating conditions using paddy, a group D particle, as the fluidizing material. The results of the study showed that the fluidized bed dryer system with vertical internal baffles gave better particle mixing effect in the bed of particles than that without vertical internal baffles. This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking up the large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bed of particles before finally erupting at the bed surface. This improves the contacting efficiency and enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate was obtained in the falling rate period because the higher con     

THE RADIAL DISTRIBUTION OF HEAT TRANSFER COEFFICIENT IN FAST FLUIDIZED BED

This paper presents an experimental study on the axial and radial distributions of heat transfer coefficients in a fastfluidized bed operated at ambient temperature.The following formula is recommended to correlate the local heat transfer coefficients in fast fluidized beds:where a,n_1 and n_2 are functions of radial positions.     

MODEL FOR PREDICTING THE LATERAL DISPERSION COEFFICIENT OF SOLIDS IN GAS-SOLIDS FLUIDIZED BEDS

The lateral mixing of solids in a gas-solids fluidized bed is very complicated.It can be caused by:(a)bubble movement through the bed,(b)bubble burst at the bed surface,and(c)gross particle circulation in thebed.However,experiments show that the major factors effected the lateral mixing of solids are the bubblemovement through the bed and the bubble burst at the bed surface.Thus a model with two mixing re-gions,i.e.mixing in bubble rising region and mixing in bubble breaking region,was proposed.Based on thismodel,an equation for predicting the lateral dispersion coefficient of solids in gas-solids fluidized beds wasderived without any adjustable parameter.The calculated values by this equation are well comparable withthe observed data including the present work and the other investigations.     

Model for Calculation of Agglomerate Sizes of Nanoparticles in a Vibro‐fluidized Bed

The behavior of SiO₂ nanoparticles and the effects of operating conditions on nanoparticle agglomerate sizes have been investigated under conditions created in a vibro‐fluidized bed (VFB). The experimental results reveal that the vibrations imposed in the bed can suppress slugging and/or channeling, in contrast to conventional fluidization with upflow only. The vibrations imposed in the particle bed affect both the minimum fluidization velocity and the agglomerate size, both of which decrease with increases in the energy introduced to the bed by the vibrations. The effect of vibrations on the agglomeration in vibro‐fluidized beds of nanoparticles depends on the critical vibration frequency corresponding to a minimum agglomerate size. Both the amplitude and the frequency of the applied vibrations have significant effects on the agglomerate size. The experimental results and the consequent analysis reveal that increasing levels of vibrations in the bed yields finer agglomerates. The Richardson‐Zaki scaling law combined with Stokes law permits the prediction of agglomerate sizes and the extent of initial bed voidage. The average agglomerate sizes predicted are in good agreement with those determined experimentally.     

PDPA测量体积对测量结果的影响

本文采用激光相位多普勒粒子分析仪（PDPA）测量气固两相流局部颗粒的运动速度和粒度．通过比较在不同测量体积下测得的颗粒直径、速度及捕获粒子的速率，发现PDPA的测量体积对测量结果有明显的影响，特别是对较密的气固两相流影响非常显著．为了正确测量气固两相流中粒子大小和瞬时流动特性，木文提出PDPA测量体积不能小于或远大于被测粒子的平均体积；设置适当的测量体积，有利于测量较密集的颗粒流体系统．     

Description et modélisation des structures globale et locale des lits fluidisés en régime turbulent

In order to study the structure of turbulent beds, local instantaneous and time-averaging suspension densities were determined with a needle capacitance probe. The probe can be moved radially across the bed at different axial locations in two experimental set-ups (an 82 mm and a 200 mm i.d. stainless-steel column). The measured density fluctuation signals were analyzed by means of average amplitude, standard deviation and dominant frequency. It is shown that the turbulent fluidized bed presents an intermediate structure between the bubbling and the fast fluidized bed regimes. The profile of the void fraction presents an important radial gradient but only a slight axial variation. The spectral density of local void fluctuations increases from the axis of the column to the near wall. This is related to the gradual increase in the solid aggregate size. Two new correlations which predict respectively an average and a local void fraction in turbulent fluidized beds are developed.     

循环流化床提升管中的轴向和径向固体负荷

1 INTRODUCTIONThe determination of the solids hold-up and local solidfluxes is of paramount importance in the study ofthe hydrodynamics of a two-phase flow.Several tech-niques have been used during the past decades(Table1).These methods can be classified in two groups,depending on their possible disturbance of the two-     

HYDRODYNAMICS OF MAGNETOFLUIDIZED ADMIXTURE BEDS

Hydrodynamic behavior of a magnetofluidized bed is investigated over a wide range of magnetic-field intensity values as a function of superficial air velocity. The bed comprises of different proportions of copper and iron particles and is contained in a Plexiglas column of 0.102 m internal diameter. The uniform constant magnetic field is created by a Helmholtz electromagnet. In particular, the bed pressure drop is measured as a function of superficial air velocity and characteristic bed voidage and fluidizing velocities are determined at minimum fluidization and bubbling bed conditions. These characteristic properties of the magnetically stabilized fiuidized beds are reported as a function of magnetic-field intensity, and are correlated by suitable expressions. These will be useful for prediction purposes related to design and operation.     

HYDRODYNAMICS OF MAGNETOFLUIDIZED ADMIXTURE BEDS

Hydrodynamic behavior of a magnetofluidized bed is investigated over a wide range of magnetic-field intensity values as a function of superficial air velocity. The bed comprises of different proportions of copper and iron particles and is contained in a Plexiglas column of 0.102?m internal diameter. The uniform constant magnetic field is created by a Helmholtz electromagnet. In particular, the bed pressure drop is measured as a function of superficial air velocity and characteristic bed voidage and fluidizing velocities are determined at minimum fluidization and bubbling bed conditions. These characteristic properties of the magnetically stabilized fiuidized beds are reported as a function of magnetic-field intensity, and are correlated by suitable expressions. These will be useful for prediction purposes related to design and operation.     

基于颗粒流运动论的喷动流化床气固流动行为三维模拟

1 INTRODUCTION Spout-fluid beds have been of increasing interest in the petrochemical, chemical and metallurgic indus-tries since spout-fluid beds can reduce some of the limitations of both spouting and fluidization by su-perimposing the two type of systems[1―4]. In recent years, spout-fluid beds have become an alternative for gas/solid contactors in coal gasification. Spout-fluid bed coal gasifiers have been adopted for APFBC-CC (advanced pressurized fluidized bed combus-tion-combined…     

二苯并呋喃在活性炭上的吸附相平衡和动力学

The adsorption of dibenzofuran on three commercial granular activated carbons （ACs） was investigated by dynamic experiment to correlate the adsorption equilibrium and kinetics with the structure of activated carbons. Physical properties including surface area, average pore diameter, micropore area and micropore volume of the activated carbons were characterized by N2 adsorption experiment on ASAP2010. To calculate the adsorption parameters, adsorption isotherm data were fitted to the Langmuir equation, and adsorption kinetic data were fitted to the linear driving force （LDF） diffusion model. From the correlation results, it is concluded that the adsorption equilibrium and diffusion coefficient of dibenzofuran on activated carbon are controlled respectively by the total adsorbent surface area and the adsorbent pore diameter.     

烯烃聚合流化床反应器内动结块的声发射检测

烯烃聚合流化床反应器近分布板区域的动结块是分布板堵塞的诱因,严重影响流化床的正常操作,甚至引发事故。本文在冷模实验装置中,使用声发射技术对近分布板区域的动结块进行检测,分别对比了正常流化、加入丝状结块和加入块状结块时近分布板区域声信号能量和频谱的差异。实验发现,与正常流化时相比,加入结块使得声信号能量下降,且加入块状结块时声信号能量下降更为显著;加入结块后声信号频谱的低频部分（0~20 kHz）和高频部分（70~150 kHz）均出现不同程度的降低,且高频部分下降比低频部分更为显著,块状结块导致的下降比丝状结块更为显著。实验结果表明,声发射技术可以用于流化床反应器内近分布板区域动结块的检测。