Flocculation kinetics and aggregate structure of kaolinite mixtures in laminar tube flow.
Flocculation kinetics and aggregate structure of kaolinite mixtures in laminar tube flow.
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DOI：
10.1016/j.jcis.2010.11.068
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发表时间：
2011-03
影响因子：
9.9
通讯作者：
F. Vaezi G.;R. S. Sanders;J. Masliyah
中科院分区：
文献类型：
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作者：
F. Vaezi G.;R. S. Sanders;J. Masliyah
絮凝通常用于化学和矿物工业中的各种固-液分离过程中，以分离所需产品或处理废物流。本文介绍了一种研究层流管流中絮凝过程的实验技术。与更复杂的剪切场（例如搅拌槽）相比，该方法允许对骨料所暴露的剪切速率进行更现实的估计。采用直接抽样法，以尽量减少抽样对骨料结构的影响。骨料沉降速度和图像分析的组合被用来量化骨料的结构。聚集体尺寸，密度和分形维数被认为是最重要的聚集体结构参数。两种方法测定集料分形维数的结果吻合较好。考虑了平流通过骨料多孔结构和过渡区阻力系数对骨料密度的影响。该技术被施加到调查絮凝动力学和高岭土颗粒的聚集体结构的演变与阴离子絮凝剂的条件下类似的油砂细尾矿。使用良好控制的两阶段聚集过程形成聚集体。详细的统计分析进行调查的动态平衡条件的建立方面的骨料尺寸和密度的演变。在絮凝开始的90秒内获得平衡稳态条件;之后，没有观察到聚集体结构的进一步变化。虽然较长的絮凝时间内的剪切场可以想象导致聚集体结构构象，统计分析表明，这并没有发生在所研究的条件。结果表明，这里采用的技术和实验条件产生具有明确定义的，可再现的结构的聚集体。
Flocculation is commonly used in various solid–liquid separation processes in chemical and mineral industries to separate desired products or to treat waste streams. This paper presents an experimental technique to study flocculation processes in laminar tube flow. This approach allows for more realistic estimation of the shear rate to which an aggregate is exposed, as compared to more complicated shear fields (e.g. stirred tanks). A direct sampling method is used to minimize the effect of sampling on the aggregate structure. A combination of aggregate settling velocity and image analysis was used to quantify the structure of the aggregate. Aggregate size, density, and fractal dimension were found to be the most important aggregate structural parameters. The two methods used to determine aggregate fractal dimension were in good agreement. The effects of advective flow through an aggregate’s porous structure and transition-regime drag coefficient on the evaluation of aggregate density were considered. The technique was applied to investigate the flocculation kinetics and the evolution of the aggregate structure of kaolin particles with an anionic flocculant under conditions similar to those of oil sands fine tailings. Aggregates were formed using a well controlled two-stage aggregation process. Detailed statistical analysis was performed to investigate the establishment of dynamic equilibrium condition in terms of aggregate size and density evolution. An equilibrium steady state condition was obtained within 90s of the start of flocculation; after which no further change in aggregate structure was observed. Although longer flocculation times inside the shear field could conceivably cause aggregate structure conformation, statistical analysis indicated that this did not occur for the studied conditions. The results show that the technique and experimental conditions employed here produce aggregates having a well-defined, reproducible structure.