导向挡板对催化裂化颗粒湍动流化床 流动特性的影响

Effects of louvre baffles on hydrodynamic properties of turbulent fluidized beds of FCC particles

关键词:  导向挡板  流化床  颗粒  流体动力特性  湍流

Key words:  louvre baffles  fluidized bed  particle  hydrodynamic property  turbulence

摘要:

针对一个具有一层导向挡板的催化裂化颗粒流化床，在500 nun x 30 mm x 6000 mm的大型二维流化床冷模装 置中,考察了湍动流化状态下的气固流动现象、床层密度分布、压力脉动和床层膨胀率，并与自由床中的气固流动规 律进行了对比。结果表明:流化床中加人挡板后，其下部将会出现一个低密度区，而在其上部则会出现一个高密度 区;挡板的加入将大大降低床层的压力脉动,压力脉动和挡板下方气垫的高度分别在一定程度上反映了挡板对气泡 破碎的能力和抑制颗粒返混的能力;相比自由床,挡板床具有较小的起始湍动速度和较大的床层膨胀率。

Abstract:

In a large-sized 2-D cold model installation with the size of 500 mm x 30 mm X6000 mm, phenomena of gas and solid flow, axial density profiles, pressure fluctuation and bed expansion ratio of a turbulent fluidized bed with one layer of louvre baffle were compared with those of the fluidized bed without baffles. The experimental results show that a low-density region and a high-density region will appear under the baffle and above the baffle respectively in the baffled fluidized bed. The pressure fluctuation will decrease greatly and a void layer will appear under the baffle in the baffled bed. The decrease of pressure fluctuation reflects the ability of louvre baffles on splitting bubbles. However ^ the thickness of the void Layer reflects the different abilities of louvre baffles on restraining the backmixing of particles across the baffle. Compared with the fluidized bed without baffles,the louvre baffled bed has a low initial turbulent velocity and a great bed expansion ratio.