Abstract: The particle residence time distribution (RTD) in a cross-flow bubbling fluidized bed needs to be strictly controlled due to its significant influence on the gas-solid mixing behavior and the reaction process. Based on the Eulerian-Eulerian two fluid model combined with species transport equation, the influence of different internal baffle designs and its numbers on the gas-solid flow behavior and particle RTD characteristics in a cross-flow bubbling bed was investigated. The three vertical baffle designs such as overflow baffles, underflow baffles, and side flow baffles were adopted, and the number of baffles 1~13 was selected. Besides, particle transport behavior between chambers in the fluidized bed was analyzed using the particle recirculation coefficient. The simulation results showed that all the three baffle designs can obtain narrow RTD and limit the back-mixing of particles. For the three baffle designs, the side flow baffles led to the lateral solids concentration gradient in the bed, while the underflow baffles resulted in the local lateral solids concentration gradient in each chamber, indicating the designs of baffles had obvious effect on the driving force of particle transport. It had also been observed that both the side flow baffles and the underflow baffles can reduce the transport resistance, but the overflow baffles caused the severe backflow of particles. In addition, increasing the number of baffles can make the particle flow tended to the plug flow, resulting the rise of average residence particle time. The decreasing trend of the particle recirculation coefficient can also be observed with the increase of baffles number, which meant the particle back-mixing could be suppressed. In this study, the side flow baffles were the best design for the present cross-flow bubbling bed.

Key words: cross-flow bubbling bed, vertical baffles, residence time distribution, particle transport, numerical simulation

摘要： 基于欧拉双流体模型耦合组分输运方程对三维横流矩形鼓泡流化床内气固两相流动行为进行了数值模拟，在挡板数1~13范围内探究了挡板形式(溢流板、底流板和侧流板)对颗粒流动状态及停留时间分布的影响规律。使用颗粒再循环率ˉR评估了流化床内腔室间的颗粒输运行为。结果表明，三种挡板形式均能提高床内颗粒停留时间的均一性，减弱颗粒返混，且颗粒流动随挡板数量增加趋于平推流，增加挡板数量有利于延长颗粒平均停留时间；采用侧流板可使床内形成横向固含率梯度，而底流板则使各腔室内出现“左低右高”的局部固含率梯度，表明挡板形式影响了颗粒输运行为的驱动力；此外，溢流床具有更高的颗粒再循环率，颗粒逆流现象严重，侧流板和底流板则能更好调节腔室间的颗粒输运行为，三种挡板形式下的颗粒再循环率均随挡板数量增加呈现降低趋势，而挡板数量对底流床的颗粒再循环率影响更大。

关键词: 横流鼓泡流化床, 竖直挡板, 停留时间分布, 颗粒输运, 数值模拟