沸腾炉炉底形状对气固两相流动特性的影响

Effect of Furnace Hearth Shape on Gas–Solid Fluidization Characteristics in a Fluidized Furnace

采用CFD模拟了沸腾炉内气-固相互作用的过程,分析了不同弧度炉底条件下,颗粒瞬时浓度分布、颗粒的速度大小和方向随时间变化、床层中心处压降随高度变化、颗粒在径向的浓度变化规律.结果表明,当表观气速为0.24m/s时,平底的中心气流较强,而弧形炉底可有效发展边壁气流,通过模拟得到弧形炉底炉内中心线上的压力在高度为350~450 mm处有突降过程,当炉底弧度为60o时,颗粒浓度分布较为均匀,增强了主反应段的内循环.而炉底弧度为90°和0°时,颗粒浓度在中心或边壁处较大,分布不均匀,在主反应段不能有效形成内循环.相对于炉底弧度为90°和0°,弧度为60°的气泡数量较多,且直径小于50 mm的气泡比率较大.模拟结果通过与实体模型实验平台拍摄的气体-颗粒的流动图谱和检测数据的比较分析得到了验证.60°弧度的炉底可以有效减少细颗粒的扬析量和提高流化质量.

The interaction between gas and particles in a fluidized furnace was simulated using CFD software. The distribution of instantaneous particles concentration, change of velocity and orientation of particles with time, pressure drop with height at the center of bed, and radial concentration distribution of particles under various arc degrees of furnace bottom were investigated. The results showed that the gas from the center of flat bottom was stronger than that from the arc bottom, when the superficial velocity was 0.24 m/s. The center pressure dropped suddenly at the height of 300~400 mm, the inner loop in the region of reaction was reinforced, and the particles concentration was distributed equally when the arc degree of bottom was 60°, the portion of bubbles with the diameter less than 50 mm was higher and the number of bubbles was more than that under the arc degrees of 90° and 0°. The simulated results agreed with the experimental ones of photographs and parameter change curves of gas–particles flow. A better fluidization could be achieved under the arc degree of furnace bottom at 60°.