RCEES OpenIR  > 环境水质学国家重点实验室
Alternative TitleTheoritical and experimental study of floc structure, strength and its controlling
Thesis Advisor王东升
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline环境工程
Keyword絮体结构 絮体强度 分形 水处理工艺 Floc Structure Floc Strength Fractal Water Treatment Processes.
Abstract混凝是水处理过程的重要工艺。由于絮体结构和强度特征对于水处理工艺的重要影响,因此成为了目前混凝领域研究的重点和热点问题。深入了解絮体的结构和强度特征,将有助于有针对性的采取调控措施,改善絮体形状,提高处理效果。 本文根据统计力学的理论框架,分析了絮凝过程并从物理角度导出了絮体的分形结构,探讨了分形维数与外界控制条件的关系。在此基础之上,根据能量守恒对模型进行了理论计算,发现在湍流条件或外界能量交换强烈的情况下,分形维数较高;反之,若在层流条件或能量交换较弱的条件下,则分形维数较低。并将理论计算结果与实验结果进行比较,得到一致的结论。 本文利用几种不同的水力条件,考察了铝—高岭土絮体的结构、强度和粒径分布,引进了一种基于分形维数的絮体强度计算方法来表征絮体的强度。并将根据该计算方法所得的结果与传统的絮体强度因子进行了比较。实验结果显示絮体的分形维数随着剪切条件的增加而增加。而絮体的强度按照如下的次序排列:逐渐增加的剪切条件所形成的絮体强度>60rpm条件下形成的絮体>逐次递减的剪切条件所形成的絮体>40rpm条件下所形成的絮体。 本文还利用SiO2-Alum絮体在电中和条件和卷扫条件下,根据几种不同的水力条件,考察了颗粒物形貌对絮体性状的影响。结果表明在相同的水力条件下,球形颗粒比无定形颗粒更容易形成结构密实的絮体。此外,本文还研究了不同混凝剂对于絮体性状的影响,并结合理论推导对实验结果进行了分析。
Other AbstractCoagulation and flocculation play a significant role in the drinking water and wastewater treatment. Floc structure and strength, a classical but challenged issue in the study of flocculation, directly affect the removal efficiency of colloid particles. A better understanding of the structure and strength of flocs will be of significant important in improving the efficiency of water treatment processes. Based on the statistical mechanics, a new dynamic framework was employed to analyze the coagulation processes. The fractal dimension of floc structure was physically derived out, and the relationship between fractal dimensions and some controlling factors was discussed. In order to check the available of theoretical framework, theoretical calculation was provided and comparison between theoretical analyses and the experimental results were conducted. In order to study the floc structure, the structure, strength and size distribution of flocs, alum-kaolin flocs formed under different mechanisms were investigated at various hydraulic conditions. Furthermore, a new method based on the fractal theory was employed to analyze the strength of flocs. The relationship between fractal dimensions and floc size distribution was then discussed with controlled experiments, providing comparison between calculation results of the new method and the strength factor. The results show that both floc size and fractal dimension of flocs decrease as the increasing of the shear rate and the floc strength follows the hierarchy: gradually increased shear rate from 40 rpm to 60 rpm > stable 60 rpm shear rate > gradually decreased shear rate from 60 rpm to 40 rpm> stable 40 rpm shear rate. Moreover, SiO2-Alum flocs formed under charge-neutralization and sweeping flocculation were investigated at various hydraulic conditions. The relationship between particle morphology and floc structure and strength was discussed based on the controlled experiments. The result shows that the spherical particles are easier to establish the more compact flocs than amorphous particles. Finally, the relationship between the diversity of flocculants and the structure of flocs was discussed based on some experiments. In sum, this paper tried not only to give a reasonable description of the floc structure but also to reveal the dynamic mechanisms
Subject Area水处理工程
Document Type学位论文
Recommended Citation
GB/T 7714
武若冰. 絮体结构、强度与性状调控的理论和实验研究[D]. 北京. 中国科学院研究生院,2007.
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