Abstract:

In a two-dimensional bed with Geldart D glass beads particles, the gas-solid flow process in the rolling fluidized-bed was investigated as well as the time-averaged total pressure drop, which produced when the gas passing through the fluidized bed, under the range of different superficial gas velocities U_g=0.267—0.978 m/s, the rolling amplitudes Θ=5°—15°, and the rolling periods T=8—20 s. The influence of bed rolling on the gas-solid flow characteristics was analyzed by comparing to that in the conventional vertical and inclined beds. It turned out that, when the average angular velocity ω_ave>2(°)/s, the value of the time-averaged total pressure drop in the rolling fluidized bed was lower than that in the vertical bed. Moreover, it was higher than that in the inclined bed, which had the same maximum inclination angle as it in the rolling fluidized bed. The pressure drop caused by inertial force was less than 0.15 kPa, which had little effect on the pressure drop of the bed. The inertial force had little effect on the pressure drop of the bed. The phenomenon of gas accumulation appeared near the wall, which was caused by the inclination of the bed. The gas-solid flow characteristics in the rolling fluidized bed were mainly affected by the gas accumulation. Thus, there existed the defluidization regions, e.g., the fixed beds and moving beds. The particle amounts in the fluidization regions were then reduced as well as the static pressure in the vertical direction of the bed. The existence of the non-fluidized area will also cause the gas velocity in the fluidized area to be higher than the superficial gas velocity of the vertical bed. The ratio of the apparent velocity of the two in this paper is 1.04—1.49.

Key words: fluidized-bed, bubble, aggregation, rolling condition, gas-solid flow, pressure drop

摘要：

采用二维床及D类玻璃珠颗粒，在表观气速U_g=0.267~0.978 m/s、摇摆幅值Θ=5°~15°、摇摆周期T=8~20 s的实验条件下，对摇摆流化床内气固流动过程及气体通过流化床的时均总压降进行了研究，并通过与常规直立床和倾斜床进行对比，分析了床体摇摆对气固流动的影响。结果表明，在平均角速度ω_ave>2(°)/s的条件下，当初始装料量和表观气速相同时，气体通过摇摆流化床的时均总压降低于直立床，高于相同最大倾角时的倾斜床；惯性力所产生的压降在0.15 kPa以下，其对床层压降的影响较小，床体倾斜导致气体向边壁区域聚集是影响摇摆流化床内气固流动特性的主要因素，由此导致床内存在固定床和下行移动床状态的非流化区域，使得处于流化区域的颗粒量减少，同时还降低了流化床层在竖直方向的静压。非流化区域的存在还会造成流化区域的气速高于直立床表观气速，两者表观气速之比为1.04~1.49。

关键词: 流化床, 气泡, 聚集, 摇摆工况, 气固流动, 压降