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.     

磁场流化床在生化工程中的应用

磁场流化床（Magnetically Fluidized Bed,以下简称MFB）是将磁场引入普通流化床,采用磁敏性颗粒为床层介质的流固相处理,MFB利用磁场调节颗粒和流体的运动,使流化床具有更宽的操作范围和适应性,其中,在一定磁场和流动条件下形成的磁稳定流化床（Magnetically Stabilized Fluidized Bed,以下简称MSFB）更是瘘有固定床的流固接触特性和流化床的压降低,传热传质效率高的优点,操作范围较普通流化床变宽,磁场流化床在生化工程领域已经地固穹生物反应器,发酵液固液分离,连续亲合色谱,细胸分离,以及植物细胞和酵母细胞培养等过程,本文介绍了磁场流化床的基本原理和特性及其在生化工程中的应用情况,并分析了该技术进一步应用所面临的困难和发展前景。     

液固磁稳定床中固含率分布与液相返混特性

固含率分布和液相返混系数是液固磁稳定反应器放大与优化所必需的基础数据。采用床层膨胀高度法、光电法及瞬态点源示踪技术,研究了以SRNA-4催化剂为固相的液固磁稳定床中固含率分布和液相返混特性。试验结果表明,固含率轴向分布基本均匀,径向为“扁-陡曲线”分布。固含率随磁场强度和颗粒尺寸的增大而增大,随液体粘度和空塔液速的增大而减小。轴向液相返混系数随磁场强度和液体粘度的增大而减小,随空塔液速和颗粒尺寸的增大而增大。回归得到了固含率和轴向普朗特准数的关联式,预测值与试验值吻合良好。     

Removal of Fine Particles from Gases in a Magnetically Stabilized Fluidized Filter

Abstract

A magnetically stabilized fluidized filter has been used to remove aerosols from gaseous streams, and its performance has been compared to that of an equivalent fixed bed. The filter grains were magnetite particles in the 250 to 795 μm size range. Talc powder was used to prepare the test aerosols. The mode in which a number of variables, including the collector size, the applied magnetic field, the gas velocity, and the aerosol size, affect the degree of agreement between experimental and predicted data has been analyzed. The comparisons yielded good results, suggesting that the behavior of these filters may be predicted from the existing theory initially developed for fixed beds.     

RETRACTED ARTICLE: Optimization of Biodiesel Production Using a Magnetically Stabilized Fluidized Bed Reactor

A biodiesel production process using magnetically stabilized fluidized bed reactor (MSFBR) has been developed based on the refined cottonseed oil. The reactant flow rate and magnetic field intensity effects on the nanometer magnetic catalyst behavior in the column were investigated. Orthogonal experiments (L₄(2)³) were applied to optimize the best transesterification reaction conditions. Reaction temperature, methanol to oil molar ratio, and reactant flow rate were the main factors to influence transesterification conversion efficiency. These three factors chosen for the present investigation were based on the results of single-factor tests. The optimum transesterification reaction conditions of cottonseed oil were determined in MSFBR as follows: methanol to oil molar ratio 8:1, 40 cm³ min⁻¹ reactant flow rate, 225 Oe magnetic field intensity and reaction temperature of 65 °C, the conversion efficiency reached 97% in 100 min. The cold filter plugging point and kinematic viscosity of cottonseed oil biodiesel were higher than that described by Chinese specifications of biodiesel because of the special fatty acid profiles of cottonseed oil. The activity stability of the nanometer magnetic solid catalyst in MSFBR was much better than that in the autoclave stirred reactor (ASR).     

流化床喷雾造粒技术进展

本文介绍了流化床喷雾造粒技术,包括造粒机理、操作方式、影响因素等。流化床喷雾造粒是将溶液、悬浮液或熔融液喷雾到已经干燥或不完全干燥颗粒的流化床床层内,在同一设备内一步完成蒸发、结晶、干燥或化学反应的造粒过程。流化床造粒操作对颗粒的尺寸、形状要求不高,所得到的产品无结块、具有良好的流动性能。与其他传统的造粒方法相比,流化床造粒具有工艺流程简单、设备装置紧凑、投资省、生产强度大等优点,越来越引起人们的关注。     

生物流化床的类型及特点

介绍了各种用于废水处理的生物流化床,对其结构组成、特点、适用范围及处理效果进行了分类阐述,重点总结了好氧流化床与厌氧流化床的发展概况,并指出了今后进一步研究与应用生物流化床的努力方向。     

Effects of Particle Shape and Size Distribution on Sorption and Flow Performance in Electrically Stabilized Expanded Beds

Abstract

Use of the electrically stabilized expanded bed is an approach to the improvement of the performance of processes in beds of solid sorbents. Particle motion in a fluidized bed of nonconducting particles such as molecular sieves is halted when the bed is “frozen” by a strong electric field imposed across the bed. This allows sorption performance to approach that of fixed beds while maintaining the low pressure drops which—are characteristic of fluidized beds. Beds with axial and radial electrode geometries function equally well in the sorption of carbon dioxide (C0₂2) from nitrogen (N₂). The effects of particle shape and particle size distribution on bed stabilization are presented. Particle shape was varied from spherical to the irregular forms that are characteristic of crushed particles. The sorption performance was not appreciably different with particles having various shapes.     

三相流化床液相径向和轴向扩散的研究

本文对二维扩散模型的示踪剂瞬态点源注入进行了解析及模拟计算.用微型电极检测不同径向位置的示踪剂浓度,由计算机对输出信号自动采集、实时分析,同时对三相流化床液相径向和轴向扩散系数等模型参数进行估值.     

脉冲鼓泡流化床压力波动特性的模拟

在分析脉冲气流作用下均匀鼓泡流化床的波动结构和波动机理的基础上,建立了反映其压力波动特性的二维离散单元模型。根据脉冲鼓泡流化床的特点,提出了模型离散单元的划分方法,确定了系统的模型参数。采用直接数值积分的方法,对床层的压力波动进行了模拟研究,计算与实验结果基本上一致。     

循环流化床气体-颗粒团聚物两相流体动力特性的研究

基于气固两相流体动力学,建立循环流化床内气体-颗粒团聚物两相流动模型,模拟计算循环流化床内气固两相流动.理论预测得到循环流化床内颗粒团聚物的形成,得到颗粒"环-核"流动结构,模拟计算颗粒相浓度和速度以及气相速度分布与前人实验结果的趋势基本吻合.     

高密度循环流化床研究现状及展望

对高密度循环流化床的研究现状进行了综述，并与低密度循环流化床进行了比较，分析了研究高密度循环流化床，特别是高密度下行床的重要意义，提出了开展高密度循环流化床研究所面临的一些重要问题.     

Numerical Simulation of Particle Segregation in Vibration Fluidized Beds

The influence of vibration parameters on the segregation phenomenon of a binary mixture in a vibration fluidized bed is investigated. Initially, the mixture composed of spherical balls with different densities but same diameter is in a perfect mixing state in the bed. The motion of particles is simulated based on the discrete element method. The effects of friction coefficient, vibration frequency, amplitudes, and gas velocity are analyzed. The coefficient of segregation to the degree of particle segregation is calculated for different operating conditions. The segregation degree in the vibration fluidized bed is found to be higher than that in the bed without vibration. The curve for the segregation degree exhibits a single peak value which represents the optimal segregation result.     

气-固流化床中颗粒的内循环流动

从多尺度范围考察了气－固流化床内尾涡颗粒流和乳化相颗粒流的运动规律,将分散的尾涡颗粒流和乳化相颗粒流连续介质化,从流变学角度定义了颗粒流粘度,用流体力学方法建立了内循环流动结构的多尺度、连续介质流模型,较好地揭示了颗粒循环流动的规律。实验观测支持模型预测结果。     

Design of Magnetic Graphene Oxide Containing Magnetically Stabilized Fluidized Bed System for Dopamine Adsorption in the Presence of Ascorbic Acid and Uric Acid

Magnetic separation technology is a quick and easy method for sensitive and reliable detection, separation, and purification of biomolecules from any medium. Dopamine plays a crucial role for human metabolism; hence the development of selective and robust interference free methods for dopamine (DA) detection is of great importance. In the present study, we have reported an alternative method for the detection of DA which overcomes interference by coexisting compounds. We have designed a magnetically stabilized fluidized bed system (MSFB) by using fluorescein isothiocyanate (FITC) conjugated magnetic graphene oxide sheets (magGOs) as preconcentrator and diagnostic tool. In the presence of coexisting molecules, ascorbic acid (AA) and uric acid (UA), FITC-magGOs showed selectivity to DA as 39- and 34-folds, respectively. Compared with DA, a negligible amount of AA and UA were captured by FITC- magGOs non-specifically. Maximum DA adsorption capacity of FITC-magGOs was found to be 46.21 mg/g. The characteristics of the DA adsorption behavior were described by the application of the Langmuir isotherm model with monolayer adsorption more accurately. All experiments were carried out in the neutral solutions at around physiological pH.     

流化床中旋风下料管的物理模型

In most industrial fluidization units, two- or three-stage cyclone systems are used to clean the product gases. To return the solids to the bed, these cyclones are fitted with diplegs. By pass of gas from the bed through the dipleg is partially overcome by the back pressure build-up in the dipleg and by adding a trickle valve at the bottom of the dipleg. Diplegs of primary cyclones, operating at a high solid loading behave differently from diplegs of secondary and tertiary cyclones which operate at low solid loading. Both types have been investigated by pressure drop measurements, visual observation and by measurements of the air flow rate flowing up the riser. The primary dipleg was also studied using electrical capacitance tomography. The results are reported hereafter and will give a first indication towards the right design of the dipleg and the selection of the trickle valve. The influence of gas flow in the dipleg on the conversion in a catalytic fluidized bed reactor is found to be negligible.