利用光导纤维表征并流下行流化床中颗粒聚凝体的动态特征(英文)

Characterizing cluster dynamics in co-current downflow CFB using optical fiber probe

利用光导纤维来表征并流下行流化床中颗粒聚凝体的动态特征。下行床的直径为0.1m、床高10m,操作气速为3.5～10m·s-1,颗粒流率为50～200kg·m-2·s-1。所用颗粒为催化裂化FCC颗粒,直径67μm,密度为1500kg·m-3。研究中首先用灵敏度分析方法建立起确认颗粒聚凝体的最佳条件,由此从所测得的瞬时颗粒浓度数据来获得颗粒聚凝体的各种特性(频率、时间分率、存在时间及平均浓度)。研究发现颗粒聚凝体的性质明显地受到操作条件的影响(气体速度与颗粒流率)以及局部颗粒浓度的影响。颗粒聚凝体的性质亦沿着下行床的轴向与径向发生很大变化。在充分发展段,下行床中心比近壁处有着更强的形成颗粒聚凝体的趋势。靠近下行床的底部,颗粒聚凝体性质沿轴向分布的变化比较缓和。

The dynamic properties of clusters were studied in a concurrent downflow CFB reactor （downer） using optical fiber solids concentration signals.The downer reactor （0.1 m i.d.and 10 m high） was operated at gas velocities ranging from 3.5 to 10 m·s-1 and solids flux from 50 to 200 kg·m-2·s-1.The particles used in this research were FCC catalyst,with average size of 67 μm and a density of 1500 kg·m-3.Sensitivity analysis was first conducted to establish the optimum settings for determining cluster parameters.Aggregate properties （frequency,time fraction,existence time and average solids concentration） were established using transient solids concentration data,based on the results of the sensitivity analysis.The cluster properties were affected strongly by the operating conditions （gas velocity and solids flux） and by the local mean solids concentration.The cluster properties also varied strongly with axial and radial positions in the downer.In the fully developed section,the core region shows high clustering tendency than the wall region.Smooth axial profiles of cluster properties were observed towards the bottom.