无序环流混合器的流体力学特性和颗粒混合特性

摘要

The hydrodynamic characteristics and particle mixing behavior in andisordered air-loop mixer with an internal diameter of ?286 mm without draft tube were investigated. In the experiment, the catalytic fluid cracking (FCC) gas catalyst was employed as fluidized medium. Under the experimental conditions of the superficial gas velocity 0.3-0.5 m/s in the central area, 0.1 m/s in the annulus zone and particle feeding mass flow rate 0.25-1.00 kg/s (based on the cross-section area of the draft tube, the cross-sectional density of the bed in the mixer was measured using a PV-6D particle velocity-density analyzer and the Radial Non-uniformity Index (RNI) under different operating conditions was also given. The dimensionless temperature distribution of the cross section of the mixer was measured using the thermal particle tracer technology.The mixing index was introduced to quantitatively describe the degree of particle mixing under different operating conditions. At the same time, comparison between the conventional and the disordered loop mixers was made. The results showed that the density of the inner bed in the disordered circulation mixer was low in the center region and high in outer region. With the increase of the mass flow rate, theRNI decreased and then increased. With the increase of superficial gas velocity, theRNI increased. The mixing index of pre-mixing zone was 0.7-0.9. Under the experimental conditions of high mass flow rate and low superficial gas velocity, the cross section mixing index in downcomer outlet zone was lower than that under other experimental conditions.In addition, the mixing capacity of the disordered air-loop mixer was superior to that of the conventional circulation mixer.%在内径为?286 mm的无序环流混合器装置中,研究了无序环流混合器的流体力学特性和颗粒混合特性.以催化裂化(FCC)平衡剂为颗粒相,在中心区表观气速为0.3~0.5 m/s,边壁区表观气速为0.1 m/s,系统循环强度为0.25~1.00 kg/s的操作条件下,采用PV-6D型颗粒速度密度测量仪测量了混合器内床层各截面密度,并给出不同操作条件下的截面不均匀指数(RNI);采用热颗粒示踪技术给出了混合器内各测量截面的无因次温度分布,并引入混合指数用来定量描述不同操作条件下的颗粒混合程度,同时对比了传统环流混合器与无序环流混合器的混合能力.结果表明,无序环流混合器内部床层密度呈现中心低,边壁高的分布模式.随着循环强度的增加,RNI先减小后增大,随着表观气速的增加,RNI增大.预混合区混合指数为0.7~0.9,在高循环量,低中心区表观气速条件下(Gs为1.00 kg/s,ugd为0.3 m/s),下料管进料影响区的截面混合指数低于其他操作条件.另外,无序环流混合器混合能力优于传统环流混合器.