Simulated random packing of equal spheres

PACS, a computer program to simulate very slow settling of rigid equal spheres into a randomly packed bed, is described. Simulated packings of 6,000, 10,000, and 15,000 spheres are anisotropic. Mean void fraction is 0.42 and mean number of nearest neighbours 6.0. There are numerous cases of four spheres arranged in a tetrahedron, but no larger ordered regions. These findings, plus local voidage, distribution of circles in a section, angular distribution, and radial distribution are compared to theoretical and experimental results.     

Simulation of random packing of polydisperse particles

An optimization based model that simulates random packings of polydisperse particles to mimic porous media systems is presented in this paper. The model simulates systems with properties that map back to physically measured quantities. The model is composed of three main procedures: detachment of an existing sphere from a target sphere by moving its center to a new position, movement of an existing sphere to touch the target sphere, and addition of a new sphere to touch the target sphere. Each procedure is performed to satisfy a constrained nonlinear optimization formulation. Input parameters include radius and coordination numbers density functions. A monodisperse and polydisperse packings were simulated by incorporating physically based properties of glass bead packings obtained from 3D computed tomography images. In each simulated system, the packing density obtained was very close to the packing density of the physical system. The packings were tested for isotropy, homogeneity and randomness and then compared to experimental microtomography images. Findings indicate that the packings generated were isotropic, homogenous, random, and in a good agreement with the experimental data.     

填料因子变化时散堆填料泛点气速数值算法

泛点气速是填料塔设计的重要参数,Eckert关联图为目前工程上运用较为广泛的泛点气速求取方法。文中基于散堆填料的Eckert关联图,在考虑泛点填料因子f随液体泛点喷淋密度Lf变化的条件下,提出了泛点气速uf的数值算法;推导出泛点气速uf的表达式为一个高度非线性化方程,并给出了该方程的2种求解方法。同时举例计算了一个散堆填料的泛点气速,并和著名的塔器流体力学计算软件(WPTR)计算结果做了对比。结果表明:文中的计算结果和WPTR的结果完全吻合;所使用的方程求解方法 Aitken-Steffensen具有快速、稳定的收敛性,可用于散堆填料的泛点气速计算。     

海水脱硫散堆填料塔的流体力学计算

采用体积平均法建立了描述散堆填料塔内气、液两相的流动模型;通过数值计算,获取了在不同液气比下塔内流体速度、孔隙率分布及压力分布,并就压力损失与实验值进行了对比,预测值与实验值吻合较好,趋势完全一致。分析海水速度分布图发现,靠近壁面处存在显著的壁流现象,并在沿流方向上液体有向壁区积聚的趋势,壁流现象变得更严重。由3种填料径向孔隙率分布图可看出,近壁面处的孔隙率明显高于中间区域,这是形成壁流的原因所在。     

低泡型塑料散装塔填料研制与应用

为了满足工业上对新型填料易于更换和提高分离效率的要求，北京化工研究院研制出一种“低泡玻纤增强的聚丙烯填料”。它具有传质效率高、压降低、对于液相低泡沫、防腐蚀性好、价格低廉等优点，可以代替传统的增强ＰＰ填料和不锈钢填料，已通过化工部鉴定。     

Mobilisation of oil blobs in the pore space of a random sphere packing

A model for the movement of blobs of oil trapped in the pore space of a random packing of equal spheres is proposed in which the progress of the advanc head is expressed in terms of its probability of advancing under an imposed pressure gradient. Two mechanisms are developed, one permitting branching a the other not. Each is tested against existing experimental data. Both mechanisms give qualitative but not quantitative agreement with the experiments.     

Computer simulation of isotropic, homogeneous, dense random packing of equal spheres

A computer program generated 3000 interpenetrating spheres in a cubic container (with periodic boundary conditions which ensured complete continuity at all boundaries) and used a relaxation technique to reduce overlaps. When the average overlap fell below (exceeded) an empirical value, sphere radii were increased (decreased). This simulated vibration caused the nominal solids fraction to increase slowly to 0.6381. Further iterations with a very gradual decrease in sphere radii produced an overlap-free packing with a density of 0.6366. This packing, which is isotropic and homogeneous, is characterized by very few contacts and many non-touching neighbours. The radial distribution function is similar to that obtained experimentally. In particular, the first peak is split into two maxima.     

海水脱硫散堆填料塔的数值模拟及传质计算

采用体积平均法建立了描述散堆填料塔内气、液两相的流动模型;在双膜理论的基础上建立了平均体积传质模型。通过数值计算,获取了在不同液气比下塔内流体速度、孔隙率分布、压力分布及脱硫效率,并就压力损失和脱硫效率与实验值进行了对比,预测值与实验值吻合较好,趋势完全一致。分析填料塔内海水的速度分布矢量图和填料塔中间高度断面上的速度分布图发现,靠近壁面处存在着显著的壁流现象,并在沿流方向上液体有向壁区积聚的趋势,壁流现象变得更严重。由3种填料径向孔隙率分布图可看出,近壁面处的孔隙率明显高于中间区域,表明这是形成壁流的原因所在。     

A random packing structure of equal spheres — statistical geometrical analysis of tetrahedral configurations

A random packing structure constructed by a computer simulation of the slow settling of rigid spheres into a randomly packed bed is investigated, where the bulk-mean volume fraction of the particles is 0.582. Each sphere settled on three others forms a tetrahedron, whose detailed geometrical configuration is successfully examined by a statistical geometrical analysis.     

The onset of blob motion in a random sphere packing caused by flow of the surrounding liquid

Entrapped liquid blobs in the pore space of a packing of equal spheres were made visible by matching the refractive index of the spheres with that of the bulk fluid filling the pore space. By pumping bulk fluid through the surrounding pore space an experimental determination of the curvature difference between the ends of the blobs at the onset of mobilisation was made. This was repeated for blobs with special histories. The probability of blob movement was calculated. Good agreement between the theory and experiments was found.     

填料塔中规整填料及相关装置的设计

介绍了颗粒型填料和规整填料,分析了气液再分布装置的设计要求、喷淋密度确定、设计计算、结构设计等,指出溢流槽式再分布器是适应性较好的分布器,特别适用于大流量操作。     

填料塔的填料层高度和塔径计算实例

用闲置金属鞍环填料对填料塔进行防腐处理。介绍了利用现有引风机的条件下,填料塔塔径、塔高的计算示例。     

Supported catalytic packing prepared from ceramic packing for reactive distillation of ethyl acetate

In this work, a strategy of “etching-modification filling-graft copolymerization” was proposed to load the acidic ionic polyionic liquid on the smooth ceramic surface. In this way, commercial ceramic Raschig rings were successfully transformed into the supported catalytic packing for the reactive distillation, and were further evaluated with esterification reaction of ethyl acetate by means of the fully mixed reactor, the ultrasonic destruction, the cyclic catalysis reaction and the lab-scale distillation column experiment. This catalyst coating has good adhesion with the substrate. It can withstand 24 h of ultrasound damage and shows good stability in three cycle catalytic experiments. This kind of coated catalyst has better catalytic activity than the commercial Amberlyst 15 dry. In the lab-scale reaction distillation, the supported catalyst Raschig ring can achieve a higher conversion in comparison with the tea bag catalytic packing of Amberlyst 15 dry under some conditions.     

成皂反应过程中的液膜振荡

试验发现,由Ca(OH)2饱和水溶液、油酸的煤油溶液和CTAB水溶液组成的W1／O／W2三相体系,其油水界面产生了pH、电势及电导率的不规则振荡。通过组份替换和添加物的比较,解释了产生振荡的原因和机理。振荡产生于油酸与钙碱之间的成皂反应。其生成的表面活性剂-钙皂为关键组份,CTAB是主要助剂。反应结束后,通以交流电,还发现了可逆振荡现象,并据乳液性能进行了解释。     

国外高效液相色谱柱填料生产技术的新发展介绍

介绍了最近几年国外在高效液相色谱填料生产方面的新发展，着重介绍３项专利技术－Ｒｘ技术，Ｓｂ技术和末端带帽技术对填料的色谱行为和性能带来的革命性变化，以及１９９２年发展起来的专门分离手性体的填料。