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Neighborhood Relationships of Widely Distributed and Irregularly Shaped Particles in Partially Dewatered Filter Cakes
Transport in Porous Media ( IF 2.7 ) Pub Date : 2021-04-23 , DOI: 10.1007/s11242-021-01600-7
Erik Löwer , Florian Pfaff , Thomas Leißner , Urs A. Peuker

A more thorough understanding of the properties of bulk material structures in solid–liquid separation processes is essential to understand better and optimize industrially established processes, such as cake filtration, whose process outcome is mainly dependent on the properties of the bulk material structure. Here, changes of bulk properties like porosity and permeability can originate from local variations in particle size, especially for non-spherical particles. In this study, we mix self-similar fractions of crushed, irregularly shaped Al2O3 particles (20 to 90 µm and 55 to 300 µm) to bimodal distributions. These mixtures vary in volume fraction of fines (0, 20, 30, 40, 50, 60 and 100 vol.%). The self-similarity of both systems serves the improved parameter correlation in the case of multimodal distributed particle systems. We use nondestructive 3D X-ray microscopy to capture the filter cake microstructure directly after mechanical dewatering, whereby we give particular attention to packing structure and particle–particle relationships (porosity, coordination number, particle size and corresponding hydraulic isolated liquid areas). Our results reveal widely varying distributions of local porosity and particle contact points. An average coordination number (here 5.84 to 6.04) is no longer a sufficient measure to describe the significant bulk porosity variation (in our case, 40 and 49%). Therefore, the explanation of the correlation is provided on a discrete particle level. While individual particles < 90 µm had only two or three contacts, others > 100 µm took up to 25. Due to this higher local coordination number, the liquid load of corresponding particles (liquid volume/particle volume) after mechanical dewatering increases from 0.48 to 1.47.



中文翻译:

部分脱水滤饼中分布广泛且形状不规则的颗粒的邻域关系

对于固液分离过程中的散装物料结构的特性,要有更透彻的了解,对于更好地理解和优化工业上已建立的工艺(例如滤饼过滤)至关重要,饼滤的工艺结果主要取决于散装物料结构的特性。在此,诸如孔隙率和渗透率的整体性质的变化可能源于粒径的局部变化,尤其是对于非球形颗粒而言。在这项研究中,我们混合了破碎的不规则形状的Al 2 O 3的自相似部分颗粒(20至90 µm和55至300 µm)成双峰分布。这些混合物的细粉体积分数各不相同(0、20、30、40、50、60和100%(体积))。在多峰分布式粒子系统的情况下,两个系统的自相似性可改善参数相关性。在机械脱水后,我们使用无损3D X射线显微镜直接捕获滤饼的微观结构,因此,我们特别关注填料结构和颗粒与颗粒之间的关系(孔隙度,配位数,粒径和相应的水力隔离液体区域)。我们的结果揭示了局部孔隙率和颗粒接触点的广泛变化。平均配位数(此处为5.84至6.04)不再足以描述明显的整体孔隙率变化(在我们的情况下,40%和49%)。因此,在离散粒子级别上提供了相关性的解释。当<90 µm的单个颗粒只有两个或三个接触,而其他> 100 µm的颗粒最多吸附25个。由于较高的局部配位数,机械脱水后相应颗粒的液体负荷(液体体积/颗粒体积)从0.48增加到1.47。

更新日期:2021-04-23
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