Prediction of the porosity of multi-component mixtures of cohesive and non-cohesive particles

This paper presents an experimental and theoretical study of the packing of mixtures of cohesive (fine) and non-cohesive (coarse) particles. The experimental results, produced by means of a standard funnel packing method with glass beads as experimental materials, are first used to depict the similarity between the packings of fine and coarse particles. On this basis, the so-called linear packing model is extended to estimate the porosity of mixtures of fine and coarse particles with a wide size range. Its interaction functions and equivalent packing size are determined empirically. The applicability of the resultant model is demonstrated by the good agreement between the predicted and measured results for typical packing systems, including particles with the Gaudin–Schuhmann distribution or with a mixture size distribution. Finally, the packing of particles with a lognormal distribution, involving both cohesive and non-cohesive particles, is investigated in detail. This example also demonstrates how the proposed model can be used to solve a packing problem.     

Numerically packing spheres in cylinders

A novel approach has been developed to numerically pack spheres in cylinders. The packing algorithm uses a simple sequential technique that is based on a dimensionless packing parameter. The dimensionless packing parameter includes both axial and radial variables in order to determine a sphere's sequential placement within a cylindrical packing structure. The numerical simulation has been applied to the loose packing of identical spheres in cylindrical containers with D/d ≥ 2.0. The predicted results for the mean porosity and the radial porosity distributions are validated against the available experimental data for spheres in cylindrical containers. The simulated results are highly accurate and the simple packing algorithm requires minimal computational prerequisites.     

Radial porosity in packed beds of spheres

A functional approach has been developed to investigate the radial porosity of mono-sized spheres in cylinders. Analytical and semi-analytical equations have been developed to calculate the local radial porosity and the radial porosity distribution, respectively, within a cylindrical packing structure. The analytical equations are based upon fundamental principles and are simple, straightforward and provide highly accurate results for the radial porosity with minimal computational prerequisites. The analytical equations have been developed for the fixed packing of identical spheres in cylindrical containers with D/d ≥ 2.0. The predicted results for the local radial porosity and the radial porosity distributions are benchmarked with an existing analytical equation and available experimental data, respectively, for mono-sized spheres in cylindrical containers.     

Experimental study of the packing of mono-sized spheres subjected to one-dimensional vibration

The packing of mono-sized spheres under one-dimensional (1D) vibration is studied experimentally. The effects of operational conditions, such as vibration amplitude A and vibration frequency ω, and feeding method on packing density have been analyzed. The results indicate that there exist optimum values for A and ω to achieve the maximum packing density. The effects of A and ω cannot be represented by a single parameter (i.e. vibration intensity Γ = Aω²), but should be considered separately. The number of particles fed per batch affects the packing density significantly within a range of one to four layers per batch, but otherwise has no visible effect. Through the extrapolation on packing density using different sized containers, packing density can reach 0.636 in the total feeding method and 0.663 using the batch-wise feeding method. The values, however, are affected by material properties. The experimental results have therefore testified our previous numerical work on the transition from random loose packing to random close packing [An et al., Phys. Rev. Lett. 95, 205502 (2005)].     

Effect of vibration condition and inter-particle frictions on the packing of uniform spheres

We present a numerical study of the packing of uniform spheres under three-dimensional vibration using the discrete element method (DEM), focusing on the effects of vibration condition (amplitude and frequency) and inter-particle frictions (sliding and rolling frictions). The results are analysed in terms of packing density, coordination number (CN), radial distribution function (RDF) and pore structure. It is shown that increasing either the vibration amplitude or frequency causes packing density to increase initially to a maximum and then decrease. Both vibration frequency and amplitude should be considered to characterize the effect of vibration process on packing structure. The sliding and rolling frictions between particles can decrease packing density since they dissipate energy, although the effect of rolling friction is less significant. In line with the change of packing density, microstructural properties such as CN, RDF and pore distribution also change: a looser packing often corresponds to smaller CN, less peaked RDF and larger but more widely distributed pores.     

Quantification of the mechanisms governing the packing of iron ore fines

An investigation of the effect of moisture content on the bulk density of iron ore fines has been carried out. Particle size distribution, density of agglomerates and angle of repose in both wet and frozen states were measured as a function of moisture content. Based on the experimental results, the mechanisms governing the relationship between bulk density and moisture content, i.e. the density of agglomerates, the inter-particle friction, tightened size distribution and agglomerate deformation, were quantitatively analysed. The results suggest that when moisture content is small, less than 6.5% for the ore fines considered the mechanism of agglomerate deformation can be ignored, and the mechanisms of inter-particle friction and tightened size distribution result in a decrease in bulk density. When moisture content is large, the mechanism of agglomerate deformation becomes effective too, which, together with the mechanism of inter-particle friction, results in an increase in bulk density after it reaches a minimum value. The density of agglomerates also affects the relationship between bulk density and moisture content, resulting in a decrease in bulk density as moisture contents increases, like the mechanism of tightened size distribution but with a smaller effect. The findings should be useful to the development of strategies for controlling the bulk density of ore fines in practice.     

Experimental study on the packing of uniform spheres under three-dimensional vibration

Densification of mono-sized sphere packings under three-dimensional (3D) vibration is experimentally studied. The effects of an operational condition, such as vibration amplitude and frequency and feeding method, on packing density are systematically investigated. The results indicate that the dense packings can be achieved by proper control of both vibration amplitude and frequency. The feeding method plays an important role in densification. Higher packing densities can be obtained when the number of particles fed per batch is less than one layer. Packing density decreases with increasing number of particles fed per batch, but keeps constant when the number of particles per batch is larger than three layers. Through the extrapolation on packing density obtained from different sized containers, the maximum packing density is 0.69 for the total feeding method and 0.74 for the batch-wise feeding under the present experimental condition. The formation of ordered structure is discussed based on the particle interlayer diffusion.     

规整填料在精馏过程中的应用

主要通过对填料塔内规整填料和塔内构件的分析和应用,阐述了该技术在精馏过程中的优越性及发展方向。     

填料因子的确定方法和物理意义

本文提出了确定填料因子的简便方法，探讨了填料因子的物理意义。认为引入湿填料因子和液泛填料因子是不恰当的，推荐按Ｋｉｓｔｅｒ－Ｇｉｌｌ经验关联式计算国产填料的泛点压降。     

填料塔污垢分析及清洗方式的制定

在简要论述填料塔污垢危害的基础上,采用多种电子检测方法,对填料塔污垢的成分进行了精确的分析,并对结垢机理进行了说明论述。通过对填料塔污垢的结垢、溶垢实验,可知物料的成分、浓度以及填料材质对垢层厚度均有一定影响。填料塔中的高分子聚合物污垢成分复杂,结垢厚度不一,不溶于水并且不易与设备表面分离,所以清洗方式根据物理清洗与化学清洗的技术特点,选用化学清洗,为清洗效果更佳同时结合物理清洗方式进行。通过此论述可定制填料塔的清洗方式,以及对深入了解填料塔污垢结垢机理有较好的参考价值。     

Accurate Determination of Moisture Content of Organic Soils Using the Oven Drying Method

The accuracy of moisture content values determined for organic soil using the oven drying method is dependent on the oven drying temperature. Some charring of the organic fraction occurs at the standard oven drying temperature of 110 ± 5°C; pore water remains in the soil when temperatures below 100°C are used. A new technique to determine the specific oven drying temperature that yields the correct value of the moisture content for organic soils is presented. Routine moisture content tests should be conducted at the standard oven drying temperature; moisture content values determined on the basis of the recommended oven drying temperature of 60°C include a larger error. A moisture content parameter is introduced to facilitate direct comparison of moisture content values calculated on the basis of different oven drying temperatures.     

Accurate Determination of Moisture Content of Organic Soils Using the Oven Drying Method

Abstract

The accuracy of moisture content values determined for organic soil using the oven drying method is dependent on the oven drying temperature. Some charring of the organic fraction occurs at the standard oven drying temperature of 110 ± 5°C; pore water remains in the soil when temperatures below 100°C are used. A new technique to determine the specific oven drying temperature that yields the correct value of the moisture content for organic soils is presented. Routine moisture content tests should be conducted at the standard oven drying temperature; moisture content values determined on the basis of the recommended oven drying temperature of 60°C include a larger error. A moisture content parameter is introduced to facilitate direct comparison of moisture content values calculated on the basis of different oven drying temperatures.     

催化精馏塔装填方式的研究进展

综述了催化精馏塔催化剂的 4种装填方式 ,即板式塔装填方式、填充式装填方式、悬浮式装填方式和催化剂散装填料的技术进展 ,介绍了这些方式的优缺点及适用范围 ,提出了装填方式的发展趋势。     

注塑成型保压阶段的分析

本文主要研究二维矩形模腔的非等温、可压缩无定形聚合物的保压阶段。流体是广义牛顿型的，可压缩行为服从Ｔａｉｔ的ｐ—ｖ—Ｔ状态方程。本文在展示保压阶段速度、压力的分布，密度沿着厚度方向的变化的基础上，讨论了保压阶段压力和密度的分布对最终产品的内应力、收缩和翘曲的影响。研究结果表明，保压阶段是注塑成型过程中一个非常复杂的阶段，其压力、温度、速度、密度的变化强烈地依赖于熔体的粘度和模腔的边界条件     

超高压填料组失效及其预防措施

介绍超高压填料的使用情况和失效特征,并提出对策及预防失效方案。     

铝塑复合医药包装材料胶粘剂的研究

介绍了铝塑复合医药包装材料胶粘剂的制备,共聚单体及合成路线的选择,丙烯酸类加入量,增粘剂种类及其加入量和铝箔涂胶量对剥离强度的影响,及其在医药包装方面的应用。     

污水泵用软填料密封改造

针对污水泵的实际工况,分析了其软填料密封失效的原因,设计了污水泵用机械密封,取得了良好的密封效果。     

Pore, surface and fillet moisture in centrifuged beds of coarse coal

The moisture content of the coarse coking coal product from the centrifuges of preparation plants was investigated to evaluate the contribution of three types of water: that held internally in pores, that in fillets at points of contacts between the particles, and the moisture covering the surface. A standardised laboratory centrifuge test was used to measure the total non-centrifugable moisture (NCM) content and also the quantity held in internal pores, called NCM_i. The fillet moisture NCM_f was estimated by means of a formulation which relies on experimentally measured holdup volumes, supplemented by a physical model. The surface moisture NCM_s could then be derived by difference. The NCM_f, which depends on the body force, the particle size and the surface tension and contact angle of the liquid, ranges from effectively zero for large particles to 10% for fines. The surface moisture NCM_s is of the order of 0.5% for high rank coals and increases to 1.5% for lower rank coals.     

Packing effect and pozzolanic reaction of fly ash in mortar

This research is to study the effect of particle size of fly ash on packing effect and pozzolanic reaction of mortar when 20% of fly ash is used to replace Portland cement type I. Both effects can be determined by using fly ash and insoluble material which have almost the same particle size to replace Portland cement type I. Normally, the compressive strength of fly ash mortar is contributed from hydration reaction, packing effect, and pozzolanic reaction. For mortar mixed with insoluble material, the compressive strength is due to hydration reaction and packing effect. Thus, compressive strength due to pozzolanic reaction can be determined from the difference in compressive strength between fly ash mortar and insoluble material mortar. The results show that the strength activity index of fly ash mortar depends on the median particle size of fly ash and curing ages of mortar samples. At early ages, the strength activity index of fly ash mortar due to packing effect is higher than that due to pozzolanic reaction. At the ages of 3 to 90 days, the difference in strength activity index due to packing effect of fly ashes with median particle size of 2.7 and 160 μm is almost constant about 22% of the strength of standard mortar (STD). The differences in strength activity index due to pozzolanic reaction of fly ashes with median particle size of 2.7 and 160 μm are 3%, 20%, and 27%, respectively, at the ages of 3, 28, and 90 days.     

规整填料在化肥工业吸收塔上的应用

介绍规整料与新型分布器的特性，及其在中、小型化肥厂的脱硫、脱碳、铜洗等工艺中应用的生产数据和成功范例。