【作者】 王德英；

【导师】 沈自求；

【作者基本信息】 大连理工大学 ， 化学工程， 2005， 博士

【摘要】 深层过滤技术自诞生以来,在人类的生活和生产实践中始终起着举足轻重的作用。尤其在当前水资源日趋短缺、水污染加剧的形势下,提高过滤工艺的出水水质和处理效能,拓宽应用范围已成为国内外水处理领域新的研究课题。 纤维束滤床为一种新型深层过滤装置,具有过滤速度高、出水水质好、阻力小、截污容量大等优点,目前已在许多工艺中应用。然而,由于过滤过程的固有复杂性和瞬时性,迄今人们对它的研究尚不充分,还仅局限于床层结构、出水水质、水头损失等宏观现象的观察,没能对滤床过滤的动力学和水头损失特性进行深入的研究,也没能对积泥形态进行科学、合理的描述,更没能建立过滤过程的水头损失方程和动力学模型。因此,对纤维束滤床过滤过程理论的深入研究以指导滤床的设计与操作十分必要。 本文开展不同直径的悬浮颗粒、不同表观滤速等操作参数下的对比实验,探讨悬浮颗粒直径、表观滤速等操作参数对纤维束滤床过滤过程特性的影响,在此基础上,对积泥形态学的研究方法进行了探讨,建立了过滤水头损失方程及动力学模型,并用级数解法求解了建立的动力学模型。论文主要内容如下: 论文概述了目前国内外深层滤料,特别是纤维滤料及过滤工艺技术的研究成果及进展,简要介绍了悬浮颗粒的去除机理,概述了积泥形态学的最新研究成果,并讨论了积泥形态对过滤过程特性的影响,综述了纤维滤床的水头损失的研究进展,并重点讨论了基于池模型的水头损失方程,较详尽地评述了比较实用的动力学模型的最新研究进展。 本文开展了不同直径的悬浮颗粒、不同表观滤速等操作参数下的直接过滤实验,实验结果给出了悬浮颗粒直径、表观滤速等操作参数下的颗粒去除率及水头损失,实验获取的相关数据为过滤动力学模型和水头损失方程的建立提供依据。 传统的积泥形态学研究难以客观、真实地反映积泥的本质,也难以为过滤的水头损失方程、动力学模型的研究提供科学的依据。本文应用分形几何理论分别描述了积泥孔隙周界曲线,孔隙尺寸分布及积泥表面的分形特性。结果表明,不仅积泥孔隙自身是一个分形结构,积泥孔隙尺寸分布具有分形特性,而且积泥表面也具有自相似性的特点,其生长已具有分形动力学的特征。各种方法测定的分维数均与过滤的动力学和水头损失特性具有相关性。因此,积泥孔隙周界曲线的分维数、孔隙尺寸分布的分维数和积泥表面的分维数可作为描述积泥形态的重要参数,并且有可能为过滤的动力学模型和水头损失方程的建立提供新思路。 简要讨论了适用于描述纤维滤料的多孔介质模型,鉴于纤维束滤床的结构特点,选摘要二亩亩亩石石石石石石亩亩百奋亩亩亩亩亩亩亩亩亩亩亩亩亩亩亩亩亩亩亩石百‘石石石亩亩亩亩奋亩石石石言石亩亩亩苗亩择圆柱池模型用于建立过滤的水头损失方程,并首次提出了“方向系数”的概念用以修正水流方向与纤维轴向间的关系。方程计算值与实验结果比较表明,二者合理一致。水头损失方程的建立为进一步研究开发及应用纤维束滤床奠定了基础。 关联无量纲重力数群、伦敦数群及相对尺寸数群得到纤维束滤床初始收集效率表达式,并由所得结果可知,上向流纤维束滤床过滤时悬浮颗粒的去除以截阻和伦敦一范德华力作用为主,重力作用甚微,这与颗粒状滤料下向流过滤时悬浮颗粒的去除机理完全不同。在应用单位床单元概念和圆柱池多孔介质模型基础上导得了清洁滤床过滤系数的无量纲数群关联式,并在“过滤系数是滤床比表面积和空隙流速的函数”假设条件下,得到了以无量纲数群和比积泥量表达的的过滤系数半经验公式。公式计算值与实验结果比较表明,二者吻合良好。最后得到了上向流纤维束滤床过滤的动力学模型。 用级数解法求解了建立的动力学模型。模型.预测值与实验数据比较表明,二者吻合良好。这说明级数解法是可行的,从而也证明了所建立的动力学模型的正确性。该模型的建立为预测纤维束滤床过滤动力学行为提供了一种可靠的方法。关键词:纤维束;深层过滤;积泥形态;分形;水头损失;动力学更多还原

【Abstract】 It has been a topic of great significance so far to research the effluent quality and efficiency of depth filtration and extension of its application, due to intensification of water pollution and shortage of water resources.As a new type of filtering device, fibrous bundle media filter, with the features of high rate filtration , high quality effluent .small resistance to flow and great retaining capacity , is employed in many techniques. However, theoretical investigation have not been as successful, mainly due to the inherent complexities and the transience of filtration processes. It is, therefore, fundamental work to investigate the theories necessary for the designing and operating of filter.An experiment for comparison of suspended particles of different diameter, different superficial filtration velocity and different operation parameters was conducted. The results of experiment show the influence of diameter of suspended particles, superficial filtration velocity and operation parameters on characteristics of filtration processes. On the basis of experimental study an analysis of deposit morphology, head loss equation and dynamics model of fibrous bundle media depth filtration was established.An experimental study was conducted about the influence of diameter of suspended particles and different superficial filtration velocity on removal efficiency of particles and head loss of fibrous bundle media direct filtration. The relevant data of the experiment will contribute to the establishment of head loss equation and dynamics model.The morphology of deposits formed during filtration was photographed with scanning electron microscope and was determined by using the fractal theory. The results show that not only the pore structure of deposits is a fractal object,but also the distribution of pore sizes possesses fractal characteristics, and the surface of deposits has a self-similar structure.An equation of head loss of fibrous bundle media filter is derived on the basis of cylinder cell model, and for the first time , a new concept of direction factor is advanced and used to revise the relationship between flow direction and axes of fiber. Moreover, comparison between dimensionless permeability predicted by various equations and experimental data indicates that the new equation established agrees reasonably well with the experimental data.On the basis of experimental study, and by using unit bed element and cylinder cell model, clean bed filter coefficient was derived by correlating dimensionless groups for London, relative size and gravity. It has shown that the suspended particle removal mechanism can be described by parameters representing the interception and London--Ven der walls force, semi-empiric expression of filter coefficient was established under the assumption that filter coefficient is the function of the specific area and the interstitial velocity. Furthermore, on the basis of phenomenological model and cylinder cell porous media model, a dynamics model was developed. Moreover, comparison between the semi- empiric expression predictions and experimental data show that both agree with each other.The series method has been developed to solve the dynamics model. Results from these solutions are compared with the experimental data , and the predicted results are in good agreement with the experimental data. It is also indicated that the dynamics model is reasonable.更多还原