流态化多级速度梯度混凝反应对絮体的保护作用

多级速度梯度的建立理论上可为絮体的成长创造更理想的环境。目前对流化床混凝工艺的研究多是基于单级速度梯度开展的。以粒径为800 μm 和1 200 μm的树脂颗粒为固相，建立多级速度梯度流化床混凝装置，探讨絮体的成长与形态特征。研究结果表明：在单级速度梯度流化床混凝装置中，当以1 200 μm树脂颗粒为固相颗粒、混凝时间为50.3 s时，絮体发生破碎，混凝效率较混凝时间为41.8 s时降低3%；相同初始填充高度的多级速度梯度条件下，絮体尺寸随着混凝时间的延长而逐渐增加，由5.7 μm成长至70.0~75.0 μm，同时混凝效率也较单级速度梯度下提高了5%~10%。絮体之间的碰撞为絮体成长的主要模式。

Protection of the Flocs by the Multi-Stage Velocity Gradients Based on Fluidized Station

Theoretically, multi-stage velocity gradients contribute to a more suitable environment for flocs growth. However, most studies on the fluidized bed flocculator were based on the single stage velocity gradient by now. Multi-stage velocity gradients were set up with 800 μm and 1 200 μm resin particles as solid phases in this work, and the growth and morphological characteristics of the formed flocs were especially studied. The formed flocs were broken according to size distribution figure in the single-stage velocity gradient fluidized bed with solid phase of 1 200 μm resin particles and a flocculation time of 50.3 s. As a result, the flocculation efficiency decreased 3% as compared with that operated for a flocculation time of 41.8 s. It should be noticed that the size of the flocs increased continuously from 5.7 μm to 70.0-75.0 μm as the flocculation time extended in the multi-stage velocity gradient fluidized bed flocculator. Meanwhile, the flocculation efficiency increased 5%-10% compared with the bed operated under single-stage velocity gradient. The collision among the mini-flocs was the main growth model of the flocs.