A rigorous breakage matrix methodology for characterization of multi-particle interactions in dense-phase particle breakage

Broadbent and Calcott's breakage matrix methodology has been used for more than 50 years to model various comminution processes and to determine breakage functions from experimental data. The methodology assumes first-order law of breakage and neglects mechanical multi-particle interactions that are especially prevalent in dense-phase comminution processes and breakage tests. Although several researchers severely criticized this aspect of the methodology, Baxter et al. (2004, Powder Technol. 143–144:174–178) were the first to modify the methodology toward determining the elements of a feed-dependent breakage matrix. However, no non-linear breakage matrix has ever been constructed from experimental data using the modified approach. In this study, a critical analysis of this modified approach has been performed, and the non-linear breakage matrix was fundamentally derived from a non-linear population balance model. Different approaches were proposed to identify the breakage functions based on the nature of available breakage tests on multiple mono-dispersed feed samples and at least one poly-dispersed sample. Using the derived equations, available experimental data on the breakage of a binary mixture of coarse and fine limestone particles in uniaxial compression test were fitted to quantify the multi-particle interactions. Superior fitting capability of rational approximation to the effectiveness factor was demonstrated.     

高速绣花机不同工况振动特性研究

针对高速绣花机工作转速和振动共同作用时引起的绣花质量和断线率问题,从横梁和转轴出发找到了解决问题的方法。通过对某公司生产的高速ZY-EMSD-A920型绣花机的研究、采点及测试、数据处理分析、计算机模拟验证探讨了不同工况引起的振动位移变化和振动变化程度。结果表明：横梁水平方向的振动和上转轴运动引起的振动对绣花机断线率的影响最大,为今后绣花机结构改进和新机型的开发提供了新的参考依据。     

活性石灰回转窑用耐火砖损坏原因及对策

分析了活性石灰回转窑用耐火材料的损坏原因,认为炉衬的附着物质与氧化硅和氧化铁的反应有关,硅酸钙与CaO是结圈的主要成分.改善耐火材料可以提高其使用寿命.     

赛络纺缎彩纱质量控制体会

为开发赛络纺缎彩纱,通过分析赛络纺缎彩纱的纺纱原理及特点,对细纱机进行了相关改造,针对纺纱过程中出现的色差、缺股、粗细节纱、有色纤维混入本色纱线等问题采取了一系列措施,使赛络纺缎彩纱得以顺利生产.指出:赛络纺缎彩纱具有独特的风格,但生产中质量控制有一定难度.只有从原料、工艺、管理等各方面采取有效措施才能生产出高质量的纱线.     

几类细纱断头问题的原因分析

探讨细纱断头原因及解决办法.对生产实践中几类细纱断头问题结合实例进行了原因分析并提出了解决办法.减少细纱断头是一项系统工程,主攻方向是控制气圈,稳定张力,改善纱条均匀度,提高单纱强力,降低强力不匀,尤其是减少张力突变和强力弱环.生产中要结合实际,分析查找断头原因,具体情况具体分析,针对存在问题采取相应措施,才能取得降低断头,提高产质量及节能降耗的预期效果.     

连铸坯中心偏析对LX72A钢帘线合股断丝的影响

70 t BOF-LF-Φ380 mm CC-开坯成150 mm×150 mm方坯-CR和200 t BOF-LF-200 mm×200mm CC-CR两种工艺路线所生产的Φ5.5 mm盘条经拉拔成Φ0.22 mm钢帘线合股过程的断丝率为Φ380mm圆铸坯工艺-2.86次/t,200 mm×200 mm方坯工艺-<1次/t。检验结果表明,圆坯工艺生产的盘条严重的中心偏析是大量断丝的主要因素,150mm×150 mm轧坯的宏观碳偏析高达1.11。采用断面尺寸200 mm×200 mm以上的方坯连铸工艺流程,中间包钢水过热度15～25℃,拉速恒定,采用结晶器和末端电磁搅拌,可有效地减轻中心偏析。     

Simulation of Turbulent Emulsification in a Sonolator Mixer: Interpretation of Drop Breakage Time

The simulation of dilute emulsions in a model ACIP2 Sonolator is investigated using computational fluid dynamics and population balance methods. Two breakage frequency models are used that differ in the expression of the drop breakage time. Drop breakage modeling based on homogenous isotropic turbulence (HIT) shows poor agreement of the Sauter mean diameter when compared to the experiments; simulations with the empirical model from Alopaeus et al. yield better agreement. By perturbing the classical HIT spectrum, it is shown that the breakage time in the empirical model corresponds to a non‐isotropic energy spectrum. Such spectra have been observed in the non‐isotropic near field in a model A Sonolator, which provides a plausible explanation of why the empirical model performs better than the HIT‐based model.     

Dispersion of oil droplets in rotor–stator mixers: Experimental investigations and modeling

Forming emulsions by mixing of immiscible liquids, water and silicone oils was carried out by applying the in-line high-shear rotor–stator mixers. In experimental part investigations were carried out using experimental rig consisting of two tanks and an in-line Silverson rotor-stator (150/250) MS; the system was operated in a multiple pass (MP) mode, which can be compared with a single pass (SP) mode experiments. Emulsification of 1 wt.% silicone oils (Dow Corning 200 fluid) with viscosities of 9.4, 48 and 339 mPa s was investigated. Emulsions were stabilized by adding 0.5 wt.% of sodium laureth sulphate. Effects of rotor speed, number of passes and the drop viscosity on the drop size were investigated.Numerical simulations were carried out using the k–ɛ model of turbulence and the multiple reference frame method (MRF) linked to the population balance equation. The population balance was expressed and solved using the quadrature method of moments (QMOM). The breakage kernel for drops whose diameter falls within the inertial subrange of turbulence was defined based on the multifractal model of intermittent turbulence.     

A micro–macro constitutive model for rock considering breakage effects

The paper proposes a three-scale binary medium-based constitutive model on the basis of the meso structures and micro components to describe the elasto-plastic mechanical behavior of mudstone samples. Based on the breakage mechanism of geomaterials, mudstone samples are considered as two different materials(bonded and frictional elements) at mesoscales. From micro to meso scales, given the similar but different mineralogy composition and porosity of the bonded and frictional elements at microsca...     

风力烟丝输送系统的改进

为解决使用过程中存在的烟丝造碎大和烟丝组分分离及烟丝填充能力降低等问题,对风力烟丝输送系统进行了改进:确定合理的风速;采用变频调速技术,以及设置瞬间补风装置削减风速峰值等方式,提高风速的稳定性;吸丝管风速实现独立调节;改进吸丝管的用料;采用无振动转塔式喂料机,防止烟丝分层;提高电控系统的自动化程度。改进后风力烟丝输送过程中烟丝造碎率降低了0.94%,每年可节约成本约500万元。