锥形流化床混凝工艺混凝反应特征和机制初探

研究了以锥形流化床作为混凝装置时混凝反应的控制因素,以及该工艺的混凝效率和形成絮体特征,并对该工艺的混凝机制进行了探讨.结果表明,填充颗粒性质、床高和表观流速等参数的变化会引起床内速度梯度G和反应时间T的变化.设置沉淀时间为20min,该工艺对高岭土悬浊液的混凝效率随着Camp值GT的增加呈上升趋势.G值在169.2～189.7s-1区间内时,混凝效果受反应时间的影响较敏感.但当G值低于169s-1时,过低的G值限制了颗粒的碰撞,混凝效果随反应时间的增加不再升高.分析认为,锥形流化床反应器内部颗粒的无规则运动产生涡旋和沿床高方向表观流速逐渐减小等特征使其作为混凝装置具有可行性.但在相近的G和反应时间下,与机械混凝装置相比,该锥形流化床混凝装置形成的絮体当量尺寸较大,但平均密度稍小.

Flocculation Characteristics and Mechanism of a Conical Fluidized-Bed Reactor

Controlling parameters, flocculation efficiencies and flocs characteristics in a conical fluidized bed were studied, and the flocculation mechanism of this reactor was discussed. The results showed that the changes of the properties of packed particles, bed height and liquid superficial velocity would cause the changes of velocity gradient (G) and reaction time (T). The removal fraction (RF) of kaolin clay suspension increased with increasing of the value of GT, when the sediment time was 20 min. The RF was greatly affected by T, when G was within 169.2-189.7s^-1. However, when G was less than 169 s^-1, it was so low that limited the collision among particles, which flattened increase of RF by increasing the T. It is the vortex caused by random movement of particles and vertically gradually decreased liquid superficial velocity in the conical fluidized bed that makes it applicable on flocculation. The flocs formed in the conical fluidized bed, were slightly larger in size and smaller in density than those in the mechanical mixing device, when close G and T were applied in two reactors. Better flocculation and sediment performance could be expected when the reactor and the reaction condition was improved.