絮凝体形态学和密度的探讨(Ⅱ)——致密型絮凝体形成操作模式

A study on the morphology and density of flocs Ⅱ.Operation modes for compact floc formation

论述了致密型絮凝体形成操作的两种模式 :脱水收缩和逐一附着 ,前者通过长时间机械搅拌进行 ,后者通过上向流造粒流化床操作进行 .实验结果表明 ,两种操作均可生成接近于球型的致密化团粒 ,但脱水收缩条件下生成的团粒仍具有颗粒有效密度随粒径增大而降低的特点 ,其分形维数为 2 40— 2 47.而逐一附着条件下生成的团粒密度基本上与粒径无关 ,可认为其分形维数接近于 3.通过讨论上向流造粒流化床操作条件 ,并将实验得到的致密型絮凝体密度和常规絮凝体密度进行比较 ,说明用该方法实现逐一附着型絮凝操作是促使絮凝体致密化的有效途径 .

Two operation modes for compact floc formation\|mechanical syneresis and one\|by\|one attachment were discussed,the former being realized by long\|period mechanical agitation and the later by the fluidized pellet bed operation.Experimental results showed that spherical pellets of high density were obtained by both methods.However,the pellets formed by mechanical syneresis still showed a tendency of decrease in their density with increase in particle size,and the fractal dimension of such kind of pellets was about 2.40—2.47.In contrast,the pellets formed through one\|by\|one attachment had almost identical density regardless particle size,and the fractal dimension was considered to be near 3.The optimum condition for fluidized pellet bed operation was also discussed and comparison was made on the density of compact flocs with that of random flocs formed by conventional operation.The fluidized pellet bed method proved to be the most effective way to achieve floc compaction.