液速陡变时液固流化床中颗粒浓度的变化模型  

Dynamic model of particle holdup with abrupt liquid velocity change in liquid-solid fluidized bed

作　　者：李笛[1] 张发根[1] 曾振祥[2] 

机构地区：[1]广州大学环境科学与工程学院珠江三角洲水质安全与保护实验室,广东广州510006 [2]湘潭大学机械工程学院,湖南湘潭411105

出　　处：《化学工程》2011年第10期63-67,共5页Chemical Engineering(China)

基　　金：广州市属高校科技计划项目(08C080);广东省科技计划项目(2010B030900008)

摘　　要：在液速陡变时,分别考察了铅直管液固流化床内粒径为225μm和511μm的玻璃微珠的体积分数分布随时间变化的规律,发现大小颗粒在不同的液速变化幅度下都呈现出同样的体积分数变化趋势。联立颗粒速度和颗粒的连续方程式模拟颗粒的体积分数变化过程,建立了一个相对简单的颗粒体积分数变化的数学模型。在模型中,用定常状态的空隙率方程式计算的颗粒速度来体现液相的波动,将变化过程中颗粒的轴向扩散系数当作不变的常数,只与变化前后的空塔液速和粒径有关。模拟结果与实验数据有很好的一致性,尤其在粒径较小、液速变化幅度不大时,预测的准确性更高。The dynamic response of the solid holdup of single-sized particle systems with a step increase and decrease in the liquid fluidization velocity within a vertical column was experimentally investigated by using sieved spherical glass beads with average diameters of 225 μm and 511 μm.Regardless of the particle size and the magnitude of change in liquid fluidization velocity,a similar tendency was observed with regard to the transition of solid holdup profiles between the initial and the final steady state of the particles in a single-sized system.A simple mathematical model was developed for particle holdup change.In the model,the particle velocities calculated by the void functions of steady state were combined with the continuity equation of the solid phase including the diffused flux.Under the current experimental conditions,the diffusion coefficients were regarded as constant in the axial direction within the process,which only depend on the initial and final superficial liquid velocity,and the diameter of the particles.The model results agree fairly well with the experimental values.In the case of smaller particles or lower change in the magnitude of liquid fluidization velocity,the models yield more exact descriptions.

关 键 词：液固流化床 颗粒浓度 液相速度 瞬间变化 数学模型 

分 类 号：TQ021[化学工程]