流化床中烟丝颗粒的流动特性

Fluidization characteristics of tobacco particles in fluidized bed

为深入研究气流干燥原理,优化工艺参数,改进和开发气流干燥设备,对烟丝物料在流化床中的流化特性进行了研究.通过所建立实验装置,分析了送风量与进料量对烟丝在流化床内的数量浓度分布的影响.采用欧拉方法进行数值模拟,并进行了实验验证和对比,两者吻合较好.研究结果表明:流化过程中烟丝物料在流化床内分布不均匀,在近壁区域尤其是床内四角处,烟丝的数量浓度明显高于床内其他位置.数值模拟和实验研究均发现了烟丝在气流干燥过程中的结团现象和结团发生的主要区域,在此基础上提出了对流化床进行改进的方案,并进行了数值实验.结果表明,所提方案能够有效防止和减少结团的产生,为解决烟丝结团问题提供了很好的理论支持.

To study the drying principle of pneumatic drying, optimize the technological parameters and improve and develop the tobacco drying equipments, the process of tobacco fluidization in a fluid- ized bed is studied. Using the established experimental equipment, the effects of air flow rate and material flow rate on the particle distribution in the fluidized bed are analyzed. The Euler model is employed to simulate the process and the relative experimental verification and comparison are performed. The simulation results are in good agreemental with the experiment findings. The study shows that particle distribution in the fluidized bed is not uniform. The volume fraction of particles is usually dilute in the near-wall region, especially the four angle regions. The volume fractions in these regions are greater than the other parts of the bed. The results also indicate the clustering phenomenon and the relative clustering areas. According to these results, an improvement of the fluidized bed is brought out and the relative numerical experiment is performed. The result shows that clustering phenomenon can be reduced by the improvement, which provides a useful way to solve the clustering problem.