Abstract:

The experiment investigated the influence of non-uniform air distribution configuration on the residence time distribution(RTD) of large particles in a fluidized bed with an inclined air distribution plate. The results indicate that, an increase in the discharging velocity makes the E(t) curve more flat and fluctuating, with the mean residence time (MRT) growing exponentially. With an increasing air velocity in the high-gas-flow-rate-zone (HGFRZ), the segregation of tracers is initially dominant and gives way to the mixing process at the late stage. There is an optimal range of the HGFRZ gas velocity for separation. A high air velocity in the low-gas-flow-rate-zone (LGFRZ) induces an intensive mixing and a longer MRT. Additionally, the effects of tracers property are studied, as well. Regarding the particle shape, a spherical and smooth surface is good for the separating and results in a short MRT. As far as the size concerned, its impact couples with that of the density. For the dense particles, a large size causes a short MRT. However, for the light ones, a large size brings about a long MRT. Many characteristics of RTD curves from current works, such as the shape, fluctuation, peak time and value, properly reveal the particle flow and mixing behaviors in fluidized beds. These achievements are supposed to provide tangible references to the mechanism exploring of the internally circulating stream, and the engineering applications of fluidized beds with multiple components.

Key words: fluidized bed, uneven air supply, particle, residence time distribution, experimental investigation

摘要：

试验考察了非均匀布风配置对大颗粒在倾斜布风板流化床内停留时间分布的影响规律。结果表明，排渣管风速增加，E(t)曲线变平、波动增加，平均停留时间(MRT)呈指数增长；高风速区风速升高，先是分离过程占优，后转变为返混能力占优，MRT先减后增，存在一个适宜于分离的运行风速窗口；低风速区风速加快，混合能力增强，MRT变长。此外，还探讨了物性参数的影响。示踪物球形度越高、表面越光滑，越有利于分离，MRT变短。而尺寸的影响则与密度相关，对于重质示踪物，尺寸增加，MRT变短；而对于轻质示踪物，尺寸变大，MRT变长。试验所得停留时间分布(RTD)曲线形状、波峰时刻、峰值、波动等信息能够充分反映床内的颗粒流动与混合过程；对于内循环流动机理的探索、多组分流化床的工程应用具有一定的参考意义。

关键词: 流化床, 非均匀布风, 粒子, 停留时间分布, 试验研究