细长颗粒流化过程取向性的数值模拟研究

Numerical Simulation on Orientation of Slender Particles During the Process of Fluidization

细长颗粒的循环流化在工业生产中具有非常广泛的应用背景。取向性是细长颗粒的一个重要特性,它对细长颗粒的循环流化具有重要的影响,但国内关于细长颗粒取向性特性的研究还处于起步阶段。文中根据实际冷态循环流化床的结构及运行参数,采用数值模拟方法,对床内的气固两相流场进行了模拟,发现并揭示了细长颗粒的取向性的一些特性。细长颗粒的取向性在水平方向上呈现出均匀性,在竖直方向上表现出较强的不均匀性。细长颗粒多以竖直方向的姿态在提升管内流动;流场风速越大,竖直姿态流动的颗粒数量百分比越大;床高增加,竖直姿态流动颗粒数量百分比略有减小;细长颗粒长径比对颗粒的取向性没有明显影响。

Circulating fluidization of slender particles is applied widely in industry production. The orientation reflects the posture characteristic of moving slender particles during the process of fluidization. The orientation is one of the most important behaviors of slender particles and it evidently affects the circulating fluidization of slender particles. But, the study on orientation of slender particles is still at the beginning in our country. Based on the actual structure and operating parameters of normal-state circulating fluidized bed, numerical simulation was adopted to study the gas-solid two-phase flow. The behavior of horizontal and vertical orientation of slender particles was revealed and studied. It is found that the horizontal orientation of slender particles is even and the vertical orientation of slender particles is uneven. Most of slender particles move with a vertical posture in the riser; the percentage of slender particles moving with a vertical posture in riser increases with the increase of fluidization velocity and decreases with the bed height, and the orientation of slender particles has no relation with the slenderness ratio.