应用无因次数组法研究气-固两相磁稳流化床动力学行为

在磁稳流化床（MSFBs）中,应用实验测量技术研究了局部固含率分布和磁稳区域。该研究开发了一个与磁场有关的无因次数组（Er）。应用无因次分析方法提出了与3个无因次数组Er,Ar,RP有关的用来计算稳定区域的无因次关联式。     

磁流化床磁稳流化区域的确定及影响因素

通过对磁流化床中四种铁磁颗粒（其平均粒径dp范围为231～512mm）流化特性的实验研究,得出磁流化床的磁稳流化区域与磁场强度、颗粒粒径之间的变化关系。在此基础上,运用量纲分析法,得到磁稳流化区域与磁重势能比Er、阿基米德数Ar、雷诺数Re等无量纲数之间的关系,并回归得出确定磁稳流化区域的实验关联式。同时,对实验关联式进行了显著性检验,结果表明,Er对磁稳区域的大小影响最为显著,Ar次之,Re则最不显著。     

Liquid-phase mass transfer of magnetic ion exchangers in magnetically influenced fluidized beds: I. DC fields

Fluidized beds of magnetic ion exchangers exhibit special features because of the additional influence of magnetic forces, which cannot be achieved in conventional fluidized or fixed beds. Specific choice of the magnetic parameters, such as particle magnetization, field strength and frequency of the external magnetic field, allows various operating conditions to be attained, the extremes of which may be described by the terms Magnetically Stabilized Fluidized Bed (MSFB) and Magnetically Stirred Reactor (MSR). The experiments conducted in this work show that liquid fluidized MSFBs exhibit a marked decrease in mass transfer compared to conventional fluidized beds operated under the same conditions. We have demonstrated a correlation between the transition from a fluidized bed to a magnetically stabilized fluidized bed and an increase in the value of a newly defined dimensionless number, M^*. Provided that the physical properties (magnetization, density and diameter) of the particles are known, it is then possible to obtain a first estimate with regard to the magnetic field required for attaining an MSFB. The experimental data clearly show that the magnitude of the decrease in liquid-side mass transfer associated with this transition is influenced mainly by the ratio between the flow velocity, u, and the minimum fluidization velocity of the particles, u_mf. Based on this observation, an empirical correlation is presented, which allows an estimation of the Sherwood number, Sh, of an MSFB to be made as a function of the parameters M^* and u/u_mf.     

C类物料磁场流态化(Ⅰ)──机理研究

本文系统地研究了磁场改善C类物料流化质量的机理，并在此基础上推导出气泡大小与磁场强度等操作条件之间的数学模型；本研究还对铁磁性物质在流化床内发生凝聚的现象进行了分析，得到能预报铁磁性物质发生凝聚的无因次数．     

Application of Magnetically Stabilized Fluidized Beds for Cell Suspension Filtration from Aqueous Solutions

Abstract

A magnetically stabilized fluidized bed (MSFBs) utilizing a transverse magnetic field was used to retain cells from cell suspension. The magnetic field permits bed expansion without mixing of the magnetic particles. The bed porosity increased by 75% when the magnetic field intensity increases to 110 mT. The effect of the magnetic field, suspension flow rate, bed height, initial concentration, and pH on the breakthrough curves was studied. According to the experimental results, increasing the initial concentration, flow rate, and pH leads to early breakthrough and inefficient deposition. Additionally, increasing the field intensity and bed height delays the breakthrough point.     

用波动理论确定气固磁流化床的临界稳定区

在气固磁流化床双相模型基础上借助波动理论分析了气固磁流化床内的空隙率波动,导出了气固磁流化床的临界稳定流化区.由此确定的稳定流化范围与实验结果较好地吻合.     

磁稳定床轴向液体分散特性

1 INTRODUCTION Magnetically stabilized beds (MSB) have at- tracted many research interests, owing to the unique feature of combination of characteristics for packed bed and conventional fluidized bed, especially in the field of biotechnology processes such as bioseparation or immobilized enzyme catalyzed systems. However, there are few reports about the effects of physical properties of fluids on the axial liquid dispersion coef- ficients in both L-S and G-L-S MSB. Siegell[1] , Goetz …     

Le lit fluidisé stabilisé magnétiquement: caractéristiques et possibilités d'application

Particulate fluidization can be obtained in a wide variety of velocity ranges, when fluidizing magnetizable particles under a uniform magnetic field.In this work, the behaviour of the magnetically stabilized fluidized bed is presented, as well as its applications; the limitations due to the loss of magnetic properties in certain conditions are also considered.     

磁流化床稳定性分析

应用Foscolo的颗粒床模型分析了磁流化床稳定性,得到了磁流化床的稳定判据;根据得到的判据分别对层流和湍流情况分析了磁场对磁流化床稳定性的影响。     

Magnetically assisted gas–solid fluidization in a tapered vessel: First report with observations and dimensional analysis

The article presents first experimental results on gas–solid fluidization in a tapered bed in presence of an external transverse magnetic field that creates a novel branch in magnetically assisted fluidization. Phase diagrams similar to those used to describe cylindrical beds have been created to distinguish the bed regimes occurring under the action of two principle macroscopic variables such as field intensity and gas flow rate. A detailed analysis and parallelism to the bed behaviour exhibited by non‐magnetic spouted beds of cohesive particles have been performed. Principle process variables such as bed depth, field intensity, particle size, cone angle have been detected. A dimensional analysis utilizing a “pressure transform” of the initial set of variables has been applied to develop scaling relationships. Examples of scaling experimental data pertinent to the minimum spouting point and involving the magnetic granular Bond number have been developed.     

液固磁稳定床流体力学特性

The hydrodynamic characteristics of liquid-fluidized magnetically stabilized beds (MSB) with commercial amorphous nickel alloy catalyst (SRNA- 4) as solid phase and water as liquid phase in a cold model experimental apparatus of Φ140 mm were investigated. The influence of magnetic field intensity on bed structure, pressure drop, minimum fluidization velocity, transition velocity, and liquid holdup were investigated. Mathematical models for minimum fluidization velocity, transition velocity, liquid holdup were established respectively. The operating phase diagrams of liquid-fluidized MSB with SRNA-4 catalyst of two different sizes were obtained.     

Magnetically stabilized fluidization: modelling and application to mixtures

A mathematical model of the magnetically stabilized fluidized bed, based on the arrangement of particles following field lines, is proposed.Magnetic stabilization has also been applied to fluidized beds with mixtures of magnetizable and non-magnetizable particles (sintered nickel—silica, steel—copper, steel—silica). The behaviour of these systems is studied, as well as the influence of the magnetic material mass fraction on the delay of bubbling. The results obtained show that the magnetic stabilization can be applied not only to the fluidization of magnetizable materials but also to non-magnetizable particles, if a certain fraction of magnetizable material is present.Correlations are proposed to calculate the transition velocity as a function of gas—solid properties and operating conditions.     

液固磁稳定床中的传热与传质特性研究

以电化学方法测定了SRNA-4催化剂为固相的液固磁稳定床中的液固传质系数,采用浸没的微型传热探头测量了液固传热系数。实验结果表明：随磁场强度、液体黏度的增大,液固传质系数及传热系数减小;增加表观液速,传质系数、传热系数均增大。进而建立了由物性参数及操作参数估算液固传质Sherwood数及液固传热Nusselt数的关联式,实验值与预测值吻合良好,可为磁稳定床反应器的放大设计和操作优化提供一定的依据。     

镍基非晶态合金加氢催化剂与磁稳定床反应器的开发与工业应用

报道了开发镍基非晶态合金加氢催化剂的实验室研究、中试研究及工业应用研究结果。向非晶态合金中加入少量原子半径大的其他元素，使非晶态合金的晶化温度由360℃提高到520℃；在含镍非晶态合金中加入铝，然后用碱将铝抽出，使非晶态合金比表面积由1m^2/g增加到100m^2/g以上；在建立30t/a非晶态合金生产示范装置中，自行设计了特殊的喷嘴和选用适宜的坩埚材质，使生产成品率由20％左右提高到95％以上，利用副产的偏铝酸钠，合成NaY分子筛，形成了整体的清洁生产过程；重点介绍了非晶态合金加氢催化剂经在三个工厂工业应用成功，三项工业应用成果每年为企业创造直接效益6700万元。还报道了对磁稳定床反应器的研究开发，经在20kt/a磁稳定床加氢示范装置上3500h试验，其生产效率比釜式加氢过程提高4倍，催化剂消耗减少50％。     

Influence of transverse rotating magnetic field on enhancement of solid dissolution process

The main objective of this work is to study the effect of transverse rotating magnetic field (TRMF) on the enhancement of solid dissolution process in the novel type reactor (TRMFR). The application of magnetically driven fluidization (MDF with homogeneous and heterogeneous systems) on mass transfer process is presented. A study of the effect of ferromagnetic particles content on solid–liquid mass transfer has been made. The experimental investigations are provided for the explanation of the influence on the dissolution process of a solid body to surrounding its dilute solution in a novel type reactor with the ferromagnetic particles suspended. The mass transfer coefficient is calculated from a kinetic equation and correlated in the relationship including standard and magnetic dimensionless numbers. The overall enhancements due to TRMF and MDF were compared. Unique correlating relations were obtained to generalize the experimental database. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Numerical simulation of particle motion in a gradient magnetically assisted fluidized bed

Flow behavior of magnetizable particles is simulated in a two-dimensional gradient magnetically assisted bubbling fluidized bed. The motion of particles is simulated by discrete element method (DEM) with the consideration of external magnetic forces at a constant gradient magnetic field along bed height. The distributions of velocity and concentration of magnetizable particles are analyzed at the different magnetic field intensities. The simulations show a significant effect on the motion of particles with vertical magnetic-fields applied. When the magnetic field strength is increased to a value at which the fluidization of strings starts, the particles are found to form straight-chain aggregates in the direction of the magnetic field. At very high magnetic field strengths, defluidization is observed. Gas pressure drop of bed decreases with the increase of magnetic-flux densities. The granular temperature of particles increases, reaches a maximum, and then decreases with the increase of magnetic-flux density. Through the analysis of the motion of particles, it is concluded that the moderate strength magnetic field gives a high fluctuation of particles and distribute gas more evenly in the bed.     

空气-SRNA-4催化剂磁稳定床的流动特性

床层压降、最小流化速度、固含率及其分布和气相返混系数是气固磁稳定反应器放大与优化所必需的基础数据.采用压降法、光电法及瞬态点源示踪技术试验研究了以SRNA-4催化剂为固相的气固磁稳定床的流动特性.试验结果表明:最小流化速度、最小流化状态下的床层空隙率与磁场强度无关;固含率的径向分布基本均匀;磁场强度的增大抑制了颗粒的运动,使得局部固含率略微增加;空塔气速的增加促进了气固磁稳定床的膨胀,使得固含率减小;粒径较小时,随磁场强度及气速的变化贝克来数(Pe)变化不大;粒径较大情况下,Pe随气速增大而减小,随着磁场强度的增大,先增大后减小.试验获得了最小流化速度、固含率和床层高度的关联式,预测值与试验值吻合良好.     

Silver recovery from spent photographic solutions by a magnetically assisted particle bed

The work presents experimental results on silver cementation from spent photographic fixer thiosulphate solutions by iron in magnetically controlled particle beds. Axial magnetic field created by Helmholtz pair was used. The increase in the fluid flow rate yields an increased silver recovery due to reduction in the external mass transfer resistance irrespective of the particle bed structures used for cementation. The field intensity slightly boosts the silver recovery and results in granular structures appearing at the surface of the deposits. The bed structures when the iron is used as a particle beds in column operation has major role in the efficient performance of the cementation process. With flow rate slightly exceeding the minimum fluidization point in the absence of a field the preferable operating regimes are: a fixed bed (FB) and moderately expanded magnetically stabilized beds (MSB) regimes, both of them with the Magnetization FIRST mode. However, when high flow throughputs are required, the frozen beds with the Magnetization LAST exhibit higher separation efficiencies and higher mass transfer coefficients than those with FB and MSB.     

The effect of interparticle forces on fluidization regimes in the magnetized fluidized beds

This paper investigated the influence of interparticle forces on the quality of fluidization in a magnetically stabilized fluidized bed (MSFB), where we can “artificially” create interparticle forces (F_attr) of any magnitude by applying an external magnetic field to ferromagnetic particles. A theoretical model was proposed which predicts the transition point from a homogeneous to a heterogeneous fluidization as a function of the magnitude of the interparticle force and other physical characteristics of both particles and fluids that are usually observed in fluidizationρ _p, ρ_f,μ, d_p, ε). The concept of the elastic wave velocity, U_e, and the continuity wave velocity, U_ε, was introduced. In particular, the interparticle force manipulated by an externally applied magnetic field was taken into account in addition to a general consideration of a conventional fluidized bed. Bubbles form in a bed when the continuity wave velocity becomes faster than the elastic wave velocity. The simulation demonstrated the proposed model could predict the transition point of fluidization regime with reasonable accuracy.