液固磁稳定床研究进展

鉴于液固磁稳定床在石油化工、生化工程及环境工程等领域具有广阔的应用前景,本文从流体力学特性、传质过程、返混与扩散等几个方面,对液固磁稳定床的研究进展进行了综述。     

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。     

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。     

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.     

磁稳定床研究进展

介绍了磁稳定床的流体力学特性、传质传热特性及磁稳定床在己内酰胺加氢精制过程中工业应用的进展情况。     

液固两相磁稳定床中试冷模研究

在磁稳定床冷模中以水为液相,非晶态合金催化剂(SRNA-4)为固相,探索磁稳定床反应器流动特性,并考察电磁线圈的放大效应,为工业磁稳定床反应器的设计提供数据。     

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.     

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 …     

磁稳定床及磁性催化剂的研究进展

对磁稳定床及磁性催化剂在石油化工和生物工程等领域的应用进行了归纳总结。磁稳定床已经应用于催化加氢、烟尘净化、干法选煤、生化分离、固定化生物反应器、细胞培养等过程。与传统工艺相比,磁稳定床兼有固定床和流化床的优点,能强化受传质传热限制的反应过程,提高反应效率,在实际应用中显示出独特的优越性。磁性催化剂的设计与开发是磁稳定床应用的关键,目前磁性催化剂以包覆型催化剂为主,其共同特点是具有适宜的磁性和低温反应活性,利于反应操作。磁稳定床及其磁性催化剂的研究开发是催化剂工业发展的一个新方向。     

磁稳流化床研究与应用进展

磁稳流化床（MSFB）作为一种新型反应器,兼具固定床和流化床的众多优点,具有巨大的应用前景。本文综述了MSFB近年来在基础研究和应用上取得的进展。基础研究方面主要介绍了磁场强度和液相流速对床层结构的影响,以及床层空隙率、操作稳定性和传递特性等研究情况;应用方面介绍了MSFB在生物化工、能源和环境工程等领域的应用。最后分析了MSFB目前存在的不足,如对于一定的反应体系未找到相应合适的磁性催化剂、操作温度高于磁性载体的居里温度时,MSFB将无法操作、磁场发生装置释放出大量的热量对磁性载体和反应过程产生影响、难以确定稳定操作区域。并指出其今后的主要研究方向为磁性载体催化剂的研究与开发及对MSFB的稳定性判据、传热、传质、强化反应过程机理、反应器放大规律、工业化应用装置设计等方面的研究。     

Sulfur dioxide adsorption in a magnetically stabilized synthetic-anionite bed

Removal of low-percentage SO₂ from gases by adsorption in magnetically stabilized beds of a synthetic anionite-synthetic magnetite mixture in an axial magnetic field was studied. The mixture-stabilization conditions were established, and the volumetric mass-transfer coefficients were estimated as a function of the operating conditions.     

纳米级颗粒气液固三相流化床性能研究

文中评述了国内外有关纳米级颗粒气液固三相流化床性能研究的现状及进展,建议从应用小波分析技术、开发先进测试技术、采用计算机实验、三相流直接数值模拟技术等方面深化和拓展纳米级颗粒气液固三相流化床性能的实验与理论研究。     

液固和气液固微型流态化研究进展

在百年流态化的研究过程中,涉及到直径不同的流化床。但是,多以流化床的大型化为研究目标,对微型流化床及其本身特性的研究很少。作为专门处理固体颗粒的流态化单元过程,其装置的微型化将兼具微通道反应器和宏观流化床各自的优点,是流态化研究的重要方向。鉴于气固微型流化床已有全面的国内外进展综述,本文仅对液固和气液固微型流化床的国内外研究进展进行分析。结论性内容包括：液固微型流化床床径减小,壁面效应增强,最小流化液速实验值大于Ergun公式计算值;需对描述液固均匀膨胀流化规律的Richardson-Zaki方程加以修正。气液固微型流化床内存在4种典型流型：半流化、弹状流、分散鼓泡流和液体输送流;由于床径减小,出现半流化状态,依据压降表观液速关系曲线等无法确定最小流化液速;气液固微型流化床的反应性能得以有效提升;最后给出了进一步研究的方向,以期为后续研究提供参考。     

Liquid-fluidized magnetically stabilized beds

The fluid mechanics of liquid-fluidized magnetically stabilized beds (MSBs) have been studied to determine their operating characteristics and properties. Experiments were conducted to study the operating regimes, bed expansion and pressure drop, and axial liquid dispersion.Several regimes exist for magnetized, liquid-fluidized beds. These include the unfluidized or packed, stable, roll-cell, and random motion regimes. The transition between the stable and roll-cell regimes was found to be strongly dependent on the type of fluid distributor grid used. A hysteresis was found in both the pressure drop and bed expansion behavior. With decreasing liquid velocity, the pressure drop through the bed fell immediately to a value below the weight of the bed and the bed remained expanded even after the liquid flow had ceased. The height of the bed in the stable regime was found to depend on the liquid velocity but not on the strength of the magnetic field.Contacting experiments indicate axial dispersion in a liquid-fluidized MSB to be nearly the same as for packed beds and independent of the path taken to the stable operating condition.     

Small-sized dense magnetic pellicular support for magnetically stabilized fluidized bed adsorption of protein

A small-sized dense magnetic pellicular support (MPS) for magnetically stabilized fluidized bed (MSFB) adsorption of protein has been fabricated by introducing magnetic colloids and glass beads during the emulsification of 4% agarose solution. The MPS was identified with a mean density of 1.40 g/ml and a size range of 70-. The support has a good magnetization property with little residual magnetization after the field was removed. After cross-linking and reducing, the MPS was coupled with diethylaminoethyl (DEAE) groups to create an anion exchanger DEAE-MPS. The fluidization behavior of the support was examined in an MSFB with transverse magnetic field and the results were compared with those obtained in expanded bed. As a result, an optimum field intensity of 250 Gs was found to give the lowest axial dispersion of the MSFB. At the optimum field intensity, BSA adsorption at 208 and 283 cm/h showed that the dynamic binding capacity in MSFB was about 60% higher than that in expanded bed mode. It was attributed to the reduced backmixing in the MSFB compared to that in expanded bed. The results indicate that the dense MPS is promising for MSFB protein adsorption at elevated flow rates.     

Integration of magnetically stabilized bed and amorphous nickel alloy catalyst for CO methanation

A novel process for the methanation of CO, involving an amorphous nickel alloy (ANA) catalyst incorporated in a magnetically stabilized bed (MSB), has been developed. The effects of varying the operating conditions on the reaction yield and catalyst lifetime have been investigated. The new process was shown to be markedly superior to existing processes for CO methanation in that the concentration of CO in an H₂-rich gas mixture could be reduced from 2000 ppm to less than 1 ppm at a temperature of 433 K, a pressure of 3.0 MPa, a gas hourly space velocity of , and a magnetic field intensity of 40 kA/m. Compared with conventional fixed bed processes, the operating temperature of the ANA/MSB process can be decreased by about 100 K and the gas velocity can be increased by a factor of 5-10. In durability tests, the ANA catalyst does not undergo any significant structural change and retains its initial high activity. These preliminary results indicate that the novel process has good prospects for application in the petrochemical industry.     

Solid-liquid mass transfer in a gas-liquid-solid fluidized bed

Solid-liquid mass transfer in co-current two- and three-phase fluidized beds of water, air and benzoic acid pellets is studied. An axial dispersion model is used to describe the liquid flow when evaluating the solid-liquid mass transfer. The axial concentration profile of benzoic acid in the liquid is compared to that obtained experimentally and is found to be accurate. Three-phase fluidized bed solid-liquid mass-transfer coefficients are higher than the corresponding two-phase bed coefficients. The mass-transfer coefficient increases with increasing gas rate and is independent of liquid rate over the entire range studied. The mass-transfer coefficient also appears to be dependent on particle size, but only at high gas rates. At low or zero gas rates, k is nearly independent of particle size. A generalized correlation is developed which accurately and conveniently predicts the mass transfer in both two- and three-phase fluidized beds. Comparison to the solid-liquid mass-transfer characteristics of slurry bubble columns is also performed.     

Distribution of bubble properties in a gas-liquid-solid fluidized bed

The behavior of bubbles in a cocurrent gas-liquid-solid fluidized bed was investigated in a column of 76.2 mm ID in this study. The particles used were glass beads of 3 and 6 mm and a binary mixture of these particles. A novel dual electrical resistivity probe system was developed and utilized to obtain bubble properties including bubble size and rise velocity. The distributions of the bubble properties in the gas-liquid-solid fluidized bed were evaluated for three flow regimes: the dispersed bubble flow regime; the coalesced bubble flow regime; and the slug flow regime.