Abstract:

To study the effects of solid holdup on the characteristics of bubble behavior in an ebullated-bed reactor, dynamic gas disengagement was used in a plexiglas column of 7.0 m in height and 0.3 m in diameter under the condition of solid concentration from 9.8% (vol) to 39.0% (vol) by the total liquid and solid volume in the superficial gas velocity of 2.16-21.62 cm/s. The total gas holdup, bubble rise velocities, fractions and diameters of large and small bubbles were measured separately. The results show that the total gas holdup increases with the increase of superficial gas velocity, and decreases with the increase of solid holdup. With the increase of superficial gas velocity, the fraction, rising velocity, and diameter of large bubbles all increase. While for small bubbles, only their holdup increases obviously, but their rising velocity and diameter tend to decrease. With the increase of solid holdup, the rising velocity and diameter of large bubbles increase remarkably, but their holdup decreases slightly. When the solid content exceeds 19.5%(vol), the rising rate of small bubbles decreases to almost zero. When the solid content reaches 29.3%(vol), the small bubbles almost disappear.

Key words: fluidized-bed, gas-liquid-solid mini-fluidized bed, residence time distribution, laminar flow, multiphase flow

摘要：

采用动态气体逸出法，在高7.0 m、直径0.3 m的有机玻璃塔中研究了固含率对沸腾床反应器内气泡行为特性的影响。在表观气速2.16~21.62 cm/s和固含率9.8%~39.0%（体积分数）范围内测定了反应器内的总气含率、大小气泡含率、大小气泡上升速度及其尺寸等参数。结果表明：总气含率随着表观气速的增大而增大，随着固含率的增大而减小。随着表观气速的增大，大气泡含率、大气泡直径及其上升速度均呈增大趋势；小气泡含率明显增大，但小气泡上升速度和直径趋于减小。随着固含率的增大，大气泡含率略有降低，但大气泡直径及其上升速度都明显增大；当固含率超过19.5%（体积分数）后，小气泡上升速度几乎下降为0；当固含率达到29.3%（体积分数）时，小气泡基本消失。

关键词: 沸腾床, 气泡分布, 两级气泡模型, 气含率, 固含率