逆向气体射流对下行床颗粒混合的影响

Solids Axial and Radial Mixing Behavior in Downer with Gas Jet in Reverse Direction

下行床入口结构的研究一直被人们所重视。今在内径为0.192m的下行床中颗粒达到均匀分布的部位,沿床四周均布了三个45度方向逆流场气体射流入口,在此处设立气体入口可以使颗粒分散与气固快速接触不再同时进行。采用磷光颗粒示踪技术对下行床有逆流场射流气体存在时颗粒的轴径向混合行为进行了研究。这种逆流场射流气体对下行床颗粒的轴向混合行为无明显影响,在各操作条件下下行床内颗粒均能以接近平推流的方式运动;但该射流气体可以大大加强颗粒的径向混合,有利于气固接触,在下行床颗粒径向混合越差的操作条件下,射流气体对颗粒径向混合的影响效果越明显。下行床的这种入口结构具有良好的应用前景。

Inlet configuration is very important to downer reactor. Three upward gas jet nozzles were symmetrically installed at an angle of 45 degree on a certain position of the downer where the solids have been dispersed well. Phosphor tracer method was used to study the solids mixing behavior in the downer. The gas jet and its operating condition have insignificant influence on the solids axial mixing behavior, and yet the flow pattern of the solids is still nearly plug flow, similar to that of the downer without gas jet. But the solids radial Peclet number decreases exponentially with the increase of jet gas velocity, which will benefit the gas/solids contact. The influence of the gas jet on the radial solids mixing is remarkable at high solids fraction and high gas velocity. This kind of inlet avoids the difficulty of the simultaneous accomplishing of particle distribution and gas/solids quick contact, which is promising in its usage.