【作者】 林海波；

【导师】 黄卫星；

【作者基本信息】 四川大学 ， 化工过程机械， 2003， 硕士

【摘要】 气固循环流态化是一种高效气固接触技术，在工业上有广泛的应用，但目前的研究主要是集中在FCC之类的A类颗粒，在更广范围研究不同颗粒的循环流化行为对循环流化床技术在工业上的扩展应用有重要意义。实验在U_g=4.6～11.4m／s，G_s=16～210kg／m~2s的多组操作条件下，选粗重颗粒(砂子：体积平均粒径461.6μm，表观密度2710.5kg／m~3)为研究颗粒，在10.5m高循环流化床提升管11个高度截面上对压力梯度进行系统的测试，得出提升管中截面平均颗粒浓度；并测量了5个高度截面上11个径向位置的局部颗粒浓度。 气固提升管中，截面平均颗粒浓度沿轴向呈上稀下浓的不均匀分布，随床层高度增加轴向分布一般逐渐均匀；截面平均颗粒浓度的轴向分布形式受U_g和G_s影响，在不同的操作条件下，除常规观察到的直线型、单调指数型分布外，粗重颗粒还表现出另外两种不同的分布类型。提升管中粗重颗粒的局部颗粒浓度沿径向的不均匀分布规律也与FCC颗粒有不同的行为，颗粒浓度并不总在边壁区达到最大；边壁区颗粒浓度轴向变化幅度最大；随着床层高度的增加，同一截面颗粒浓度径向分布的不均匀程度减小。操作条件对下部浓相段影响较明显，且随床层高度的增加逐渐减弱，并趋于稳定。增大G_s或减小U_g，提升管中各截面颗粒平均浓度增大，轴向分布的不均匀度也增大，由直线型向其他分布类型转变。增大G_s或减小U_g，提升管内任何位置的局部颗粒浓度都增大，径向不均匀性也增大，沿轴向的变化更加明显，边壁区颗粒局部浓度对G_s、U_g变化的敏感性比其它径向位置大。研究结果表明，粗重颗粒浓度的轴向和径向分布及操作条件对浓度分布的影响与目前关于FCC颗粒的实验结果有明显差异，本文研究结果对于认识颗粒物性对循环流化行为的影响具有重要意义。更多还原

【Abstract】 Gas-solid circulating fluidization, as a high efficient gas-solid contact technology, is widely used in process industries. However, most investigations at present are focusing on the A sort solids (e.g. FCC). To promote the application of this technology in industries, it is necessary to research the circulating fluidization of particles with different properties. In this work, sands as typical coarse particles with the bulk mean diameter of 461.6um and the apparent density of 2710.5kg/m3 were selected for this experiment. The mean solids holdups on 11 axial levels and the local solids holdups at 11 radial locations on 5 axial levels in a 10.5m high riser were systematically measured with the superficial gas velocity ranging from 4.6 to 11.4m/s and the solids circulation rate from 16 to 210kg/m2s.The results show that the axial distributions of the cross-sectional averaged solids holdups in riser are non-uniform. Generally, from the bottom to the top of the riser, the axial profiles of the averaged solids holdups become more uniform with the increased riser height. The axial profiles of the averaged solids holdups change greatly with the variations of superficial gas velocity Ug and solids circulating rate Gs. With different conditions, new distribution patterns of solids holdups are found. The radial distributions of the local solids holdups are non-uniform along the whole riser, showing different behaviors from those of FCC particles. The local solids holdups near the riser wall do not always reached the maximum. From the riser’s bottom to its top, the solids holdups near the riser wall changed greatly, and the radial non-uniformity of local solids holdups decreased with the increasing of the height.Based on the variations of operation conditions, the change of averaged solids holdups at the bottom is more obvious than in the upper section, and it trends to weaken along the increased height and finally comes to a steady state. With the increase of the solids circulating rate Gs or the decrease of the superficial gas velocity Ug, the averaged solids holdups will be increased and become morenon-uniformly distributed along the whole riser height, and the axial profiles of the averaged solids holdups will change from linear curve to other profile curves. With increasing Gs or decreasing Ug, both of the radial non-uniformity and the local solids holdups anywhere in riser will be increased and vary more obviously. It is found that with varying Gs or Ug, the local solids holdups near the riser wall will change more sensitively than at other radial positions of the same cross-section. As a result, the axial and radial distribution profiles of solids holdups and the effects of Gs or Ug on solids distribution profiles are different from those of FCC. The results of this thesis are significantly important for the understanding of the effects of solid properties on circulating fluidization.更多还原