FUNDAMENTALS OF A CENTRIFUGAL FLUIDIZED-BED
FUNDAMENTALS OF A CENTRIFUGAL FLUIDIZED-BED
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DOI：
10.1002/aic.690330504
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发表时间：
1987-05-01
期刊：
影响因子：
3.7
通讯作者：
CHEN, YM
中科院分区：
文献类型：
--
作者：
CHEN, YM
对于许多用途，流化床具有高传热和传质速率、温度均匀性和颗粒高流动性的优点。这些特征对于连续操作的大规模气-固反应系统特别重要，因此在许多工业过程中具有广泛的应用，例如FCC、流化焦化等。在大多数这些方法中，使用垂直流化床。在垂直颗粒床中，当通气增加到使得颗粒上的重力被间隙气流施加的流体阻力抵消的点时，颗粒床被流化。然而，如果引入大量过量的曝气，它只会形成非常迅速地通过床的大气泡或段塞。在这种情况下，由于大量的旁路，气固接触变得相当差。在一些操作中，例如煤燃烧和干燥，为了减小反应器尺寸，优选具有高的表观气速。在这种方法中，垂直床变得不利，因此，一个相对较新的概念，离心流化床，被引入用于这一特殊目的。离心流化床是一个圆柱形的桶，围绕其对称轴旋转，并在半径的向内方向引入曝气以使颗粒分散。与垂直床中的固定重力场不同，离心床中的体积力变为由转速和铲斗半径确定的可调节参数。通过使用比重力大得多的强离心场，颗粒床能够承受大量的充气而不会严重形成大气泡，并且在高充气速率下的气-固接触得到改善。
For many purposes, a fluidized bed has the merits of high heat and mass transfer rates, temperature homogeneity, and high flowability of particles. These features are particularly important for continuously operating, large-scale gas-solid reacting systems, and hence have wide applications in many industrial processes, such as FCC, fluid coking, and others. In most of these processes, vertical fluidized beds are used. In a vertical particle bed, when the aeration is increased to a point such that the gravitational force on the particles is counterbalanced by the fluid drag exerted by the interstitial gas flow, the particle bed is fluidized. However, if a large excess amount of aeration is introduced, it simply forms large bubbles, or slugs, that pass the bed very rapidly. In such a case, the gas-solid contact becomes rather poor, due to extensive bypassing. In some operations, such as coal combustion and drying, in order to reduce the reactor size it is preferred to have high superficial gas velocity. In such processes the vertical bed becomes handicapped, so a relatively new concept, the centrifugal fluidized bed, is introduced for this special purpose. A centrifugal fluidized bed is a cylindrical bucket rotating about its axis of symmetry with aeration introduced in the inward direction of the radius to fluidize the particles. Instead of having a fixed gravitational field as in a vertical bed, the body force in a centrifugal bed becomes an adjustable parameter that is determined by the rotation speed and the bucket radius. By using a strong centrifugal field much greater than gravity, the particle bed is able to withstand a large amount of aeration without serious formation of large bubbles and the gas-solid contact at a high aeration rate is improved.