Ultra-fine grinding mechanism of inorganic powders in a stirred ball mill

An experimental investigation on grinding mechanism for calcite used in a stirred ball mill was carried out. The slurry concentration and the amount of grinding aids were chosen as main experimental factors of the grinding process. The effect of grinding aids on particle size distribution and grinding efficiency, defined as the increases of specific surface area per the specific grinding energy, was investigated. It was demonstrated that the grinding rate for calcite could be improved by addition of grinding aids. The grinding energy efficiency by adding a specific grinding aids was improved approximately 45.2% in comparison with and without grinding aids (n=700rpm, J=0.7, d_B= 1.0 mm, C_s=60wt%). This paper was presented at the ‘First Asian Particle Technology Symposium’ held at Bangkok between December 13 and 15, 2000.     

Ultra-fine grinding mechanism of inorganic powders in a stirred ball mill

Recently, in various industrial processes, the need for fine particles, especially submicron-sized particles, has increased in the field of preparing raw powders such as fine ceramics and high value added products. Therefore, the research in fine grinding has gained more importance, especially, in submicron grinding. In the previous paper, a series of wet grinding experiments using inorganic powders by a stirred ball mill were performed. The grinding consumption power was measured, and the grinding rate constant, K, in the grinding kinetics equation was examined, based on a grinding kinetics analysis of experimental specific surface area with particle size distribution of ground products obtained under various grinding conditions. Also the effect of grinding aids on grinding rate constant K was investigated. It was confirmed that the grinding rate constant K, when using grinding aids improved by 1.95% and 25.6% for a 60 wt% and 70wt% slurry concentrate, respectively, when compared with the case of the absence of grinding aids. It was found that grinding aids have an important effect on increasing the grinding rate, especially for a slurry of high concentration.     

Effect of media size in stirred ball mill grinding of coal

As a prerequisite to producing super-clean coal with any physical coal-cleaning process, such as microbubble flotation, the feed coal must be micronized to liberate finely disseminated mineral matter. The stirred ball mill is regarded as one of the most efficient devices for micronizing coal. Using a 13.4 cm batch mill, the optimum operating conditions have been determined in terms of media size, feed size and media type. The rate of breakage determined with monosized feeds are compared on the basis of specific energy consumption. It has been found that a 20:1 ball size/particle size ratio gives optimum grinding conditions.     

Semi-autogenous grinding mill pebbles as a vertically stirred mill medium

ABSTRACT

Semi-autogenous grinding pebbles were used as a grinding medium and compared to steel balls in terms of their effect the flotation behavior of the products and their industrial application. The pebbles increased the rate of copper recovery from the concentrated products by 3.30% to 86.89%. Industrial application showed that using pebbles instead of steel balls reduced over-comminution by 8.05% and increased the recovery rate by 1.81% when the copper grade of the concentrate was equal. Hence, pebbles are a viable and beneficial alternative to steel balls as the grinding medium in vertical mills.     

Analysis of ball movement for research of grinding mechanism of a stirred ball mill with 3D discrete element method

A simulation of the three-dimensional motion of grinding media in the stirred media mill for the research of grinding mechanism has been carried out by 3-dimensional discrete element method (DEM). The movement of ball assemblies was graphically displayed with some snapshots from start of the milling to 0.20 s. From these simulation results, the grinding zone in the mill was confirmed to be distributed into two regions, which is near the stirrer and the side wall of mill around the stirrer. The power changing the rotation speed of stirrer was examined based on the micro interactive forces at all the contact points between ball-to-ball and between ball-to-stirrer. DEM is a very powerful tool for the microanalysis of movement of balls, which could not have been solved by a conventional experimental method.     

Identification of the grinding mechanisms and their origin in a stirred ball mill using population balances

The objective of this work was to understand the origin of the stresses and the nature of the grinding mechanisms in a high-shear ball mill. The ball mill used was a Dynomill and the grinding media consisted of zirconium oxide beads. The ground powder was a poorly water soluble product. The particle size distribution was analyzed with laser diffraction.A population balance model enabled to calculate the breakage function from the experimental data. The breaking parameters were used to determine the grinding mechanism at different grinding conditions. The grinding mechanism depends on the orientation and intensity of the forces applied on the particles. The grinding mechanisms were determined from the grinding experiments and correlated to the movement of the grinding media in the grinding chamber and the applied mechanical stresses.The observed grinding mechanisms are cleavage and some fracture for coarse particles , cleavage and abrasion for intermediate particles and cleavage for fine particles (smaller than ).The grinding mechanisms are related to the movement of the grinding media in the grinding chamber. Cleavage and abrasion of particles are the result of compression forces and shear in the centrifuged packed bed of grinding beads. The grinding mechanism does not change when changing the operating conditions and the packed bed of media is similar in the studied ranges of operating conditions.     

生产水煤浆用新型超细搅拌球磨机的研究

介绍一种新型超细搅拌球磨机,用于磨制生产水煤浆用超细煤粉;分析了该机的结构特点、工作原理、性能特点以及磨矿介质粒径的选取等;论述了磨机各组成部分的技术特点。     

The investigation of grinding kinetics of power plant solid fossil fuel in ball mill

The kinetics of batch dry grinding of power plant solid fossil fuel, from the feeds of sieve sizes −3.350 + 2.360, −2.360 + 1.700, −1.180 + 0.850, −0.425 + 0.300 and −0.212 + 0.150 mm have been determined using a Bond ball mill with a mixture of five ball sizes. The mill used has a diameter of 30.5 cm, length of 30.5 cm, providing a total mill volume of 22.272 cm³ with a total mass of 20.125 g steel ball mixtures of 38.10, 31.75, 25.40, 19.05 and 12.70 mm diameters. The balls occupied 22% of mill volume. The speed of rotation of the mill was chosen as 70 rpm. The specific rates of breakage (S_i) and primary breakage distribution (B_i,j) values, called as grinding breakage parameters, were determined for those feed size fractions to simulate the product size distributions for comparison to the experimentally obtained data. As the feed sizes increase, the S_i values also increase, that is, faster breakage values from higher to lower values were in the order of solid fossil fuel by comparing to its α values. Breakage distribution functions were found non-normalizable. It is dependent upon the initial feed particle sizes. In other words, the simulations of product size distributions for fossil fuels were in good agreement with the experimental data using a ball mill simulation program, called JKSimMet.     

球磨机研磨体快速分级装置应用实践

水泥行业的快速发展,使球磨机也不断向大型化和自动化方向发展,在磨机运行一段时间后,仓内的研磨体会出现磨损、变形、窜仓等现象,级配会发生变化,从而降低粉磨生产效率。介绍采用球磨机研磨体快速分级装置,将研磨体快速分级,有利于球磨机精准合理级配,有效解决现有技术中研磨体分级难题,使磨机研磨体及时合理级配,提高磨机的效能,减小劳动强度,提高工作效率,易于操作控制,具有很好的推广价值。     

Kinetics of fine wet grinding in a laboratory ball mill

The kinetics of batch wet grinding of quartz from a feed of 600×425 μm to a product of 80% less than 8 μm have been determined using sieving and laser diffractometer sizing for size analysis. A dispersing agent was added while proceeding to longer grinding times to prevent particle agglomeration in the mill. The specific rates of breakage (S_i) values obtained were higher than those of dry grinding of quartz at the same experimental conditions, but the primary breakage distribution (B_i,j) values were the same. Non-first order grinding was observed with continued decrease of the specific rates of breakage for finer grinding. The simulations of the product size distributions were in good agreement with the experimental data, providing the decrease in rates was included.     

Production of zinc ferrite in a mechano-chemical reaction by grinding in a ball mill

Zinc ferrite was obtained by prolonged dry grinding of stoichiometric powder mixtures of ZnO + -Fe₂O₃ or ZnCO₃ + -Fe₂O₃. The kinetics of transformation was studied by X-ray diffraction, Mössbauer spectroscopy and DTA. Crystallite size reduction followed the process, and defect structures resulted. The carbonate decomposed as a necessary step in the process. In the mixture of NiO + -Fe₂O₃, nickel ferrite was not obtainable, although considerable grain size reduction was observed. This was attributed to the inverse spinel configuration of the nickel ferrite, differing from the normal spinel configuration of the zinc ferrite. In the -Fe₂O₃ and the zinc ferrite, iron ions occupy octahedral sites, while in ZnO and the ferrite, zinc ions occupy tetrahedral sites, and metal ion—oxygen distance is almost identical. These facilitate the transformation. In the nickel ferrite, iron ions occupy both sites, which calls for high strains of -Fe₂O₃ before it can undergo transformation. Further implications of the processes are discussed.     

Intensive grinding of powders in an electro-magneto-mechanical mill

The paper presents the results of high-energy grinding in the electro-magneto-mechanical (EMM) mill. Ground powder is treated in a very specific and intensive way owing to several field forces operating simultaneously in the EMM mill. The grinding power in the centre of the mill's working chamber is in the order of 2 MW/m³, which is much more than in ordinary mills. Therefore, the grinding time is very short, i.e., several tens of seconds. The self-disintegrated Fe–Al–Si powders of 155 μm on average undergo size reduction to 8 μm after 120 s. Over 25% of the total weight get the size of less than 1.3 μm. Very hard materials, such as SiC and B₄C reduce their grain size over 30 times after 120 s of grinding in the EMM mill. The results of the grinding of Fe₂O₃ powder are even better. In ball mills, vibration and planetary mills, similar results can be achieved after a period several hundreds times longer. The treatment of Fe–Al–Si powder presented here is intended as the preparation procedure for sintering, plasma spraying or laser surface alloying.     

高效节能H型环球式磨机

阐述了环球式磨机的特点及研磨机制，通过各种磨机的性能比较，说明了环球式磨机各项运转参数的合理性及其独特的结构设计和正压运转系统。     

研磨体质量对球磨机产质量的影响

0前言 长钢集团自筹资金2.2亿元,本着"世界先进,国内一流"的建设理念,于2003年8月建成当时在全国规模最大、设备最先进、自动化程度最高、环境优美的矿渣水泥生产基地--长钢集团瑞吕水泥有限公司.该生产线采用矿渣和熟料分别粉磨,再进行搅拌均化的生产新工艺,充分利用炼铁高炉废渣生产各种环保、绿色的水泥产品,减少了资源浪费和环境污染,获得良好的经济效益和社会效益.     

Open and closed circuit dry grinding of cement mill rejects in a pilot scale vertical stirred mill

In this study, separator rejects of a closed circuit cement tube milling were dry ground in a 10-l pilot scale vertical stirred mill. Tests were done as open and closed circuit. The results were evaluated by size distributions, Blaine surface area of the products and the specific energy consumed during the tests. Mill capacity and the stirring speeds were the investigated parameters for the open circuit tests, whereas closed circuit tests were carried out at a constant stirring speed but variable discharge rate. Five speed levels used in the open circuit grinding tests are 200, 400, 600, 800 and 1000 rpm. The capacities were determined to obtain product Blaine surface areas in the limits between 2000 and 5000 cm²/g. Closed circuit tests have resulted in 87%, 182% and 452% circulating loads.     

Constrained model predictive control in ball mill grinding process

Stable control of grinding process is of great importance for improvements of operation efficiency, the recovery of the valuable minerals, and significant reductions of production costs in concentration plants. Decoupled multi-loop PID controllers are usually carried out to manage to eliminate the effects of interactions among the control loops, but they generally become sluggish due to imperfect process models and a close control of the process is usually impossible in real practice. Based on its inherent decoupling scheme, model predictive control (MPC) is employed to handle such highly interacting system. For high quality requirements, a three-input three-output model of the grinding process is constructed. Constrained dynamic matrix control (DMC) is applied in an iron ore concentration plant, and operation of the process close to their optimum operating conditions is achieved. Some practical problems about the application of MPC in grinding process are presented and discussed in detail.     

联合粉磨系统双立磨带单球磨的技术改造

介绍了2台CKP240立磨和2台Φ4.8 m×9.5 m球磨机的双闭路水泥联合粉磨系统,2018年、2019年在平均分步电耗较高的情况下进行提产改造,采用了双立磨带单球磨运行的工艺模式,既能保证灵活生产,提高运行效率,又能在提高台时产量的同时降低能耗。     

Energy efficiency of cement finish grinding in a dry batch ball mill

Dry grinding experiments on cement clinker were carried out using a laboratory batch ball mill equipped with torque measurement. The specific energy was found to be dependent on operating parameters and clinker environment. Additional compounds such as gypsum and pozzolanic tuff improve energy efficiency. The optimal parameters allowing maximising the energy efficiency factor were determined. Energy efficiency factors were obtained both on the crude material (size minus 2.8 mm) and on a sieved fraction (1-0.71 mm). They demonstrate that a low initial rate of breakage implies higher energy efficiency. On the contrary, conditions ensuring an initial maximal rate of breakage lead to an increase of the energy consumption.