FCC提升管内粒径分布对颗粒混合行为的影响

采用磷光颗粒示踪技术对一种宽筛分颗粒 (粒径小于 2 0 μm细颗粒的体积分数为 2 4 5 % )与一种常规的催化裂化催化剂的轴径向混合行为进行了对比研究。与常规颗粒相比 ,宽筛分颗粒体系的轴向返混略有减弱 ,而其径向混合能力大大降低 ,这与宽筛分颗粒体系中细颗粒的团聚有很大关系。在FCC提升管中 ,催化剂中细颗粒含量增加 ,必将减弱颗粒的径向混合能力进而降低径向上的传质、传热能力 ,对反应极为不利。粒径分布对于提升管反应器非常重要 ,应引起足够的重视。

Influence of Particle Size Distribution on Solids Mixing Behavior in FCC Riser

The phosphor tracer method was used to investigate the influnce of particle size distribution on axial and radial mixing behavior of solids in FCC riser.A study on the mixing behavior of wide-size-distribution particles and normal-size-distribution FCC particles was conducted.Compared with that of normal-size-distribution particles,the axial back mixing of wide-size-distribution particles was only slightly impaired as a result of the antigravity flow mechanism in the riser.However,the radial mixing was greatly decreased probably owing to agglomeration of the fines.The agglomeration became serious when the solids fraction increased,leading to significant decrease in the solids radial mixing.When used in FCC reactor,FCC catalyst having too much fine particles will be harmful to mass and heat transfer,which is undesirable to the reaction.Thus the particle size distribution in a riser reactor should be taken into full consideration.