对湿式间歇球磨机研磨体尺寸大小的探讨

为提高湿式球磨机的生产能力,降低单位产品的电耗,我们通过多年的生产实践证明,认为我厂湿式球磨机研磨体尺寸以直径20～70毫米,平均重量为335克最佳。一、研究方法: (1)正确的制定磨机的转数。磨机的转数影响到研磨体的运动规律,其轨迹一般分泻落、离心,抛落三种状态,特别是抛落式磨机最适宜的转速为临时转速的76％左右,脱离角α=54°44′,其磨机效果最佳。     

磨机适宜转速的探讨

磨机的转速,在一定程度上决定研磨体在磨内的运动状态。它对磨机的动力、产量、钢球和衬板的磨损都有影响。所以选择适宜的磨机转速是很重要的。特别是近几年来,磨机设计更趋大型化,其适宜转速和磨机直径之间有何关系?更有必要进一步加以探讨。众所周知,由于胴体内球的抛落和滑动,使物料受到破碎和研磨作用。磨机低速转动时,球的运动为泻落式,高速转动时,为抛落式。在实际的粉磨过程中,我们要求球以抛落式运动。     

球磨机内研磨体运动轨迹的探讨

球磨机内研磨体的运动轨迹是合理设计磨机和指导磨机经济运行的理论基础。我国传统理论认为研磨体呈抛落状态运动时的运动轨迹为圆弧———抛物线。本文拟通过理论推导指出我国传统理论的缺陷,阐明同一层研磨体在上升过程中应以等速率运行,导出抛落状态下新的研磨体运动方程式,最后简要提出球磨机需要进一步探讨的几个问题,以期达到抛砖引玉的目的。1我国传统理论的主要缺陷我国传统理论对球磨机内研磨体运动的分析是建立在“5个基本假设”的基础上,将研磨体看成与其相邻的研磨体不相关的独立质点,运用运动学的知识进行推导的。它的几个重要…     

磨内研磨体抛落运动最高点的轨迹方程式

瀑布状态下的球磨机的粉磨效果,取决于它的转速比、装球率和两者的关系等因素。很明显,这些都与磨内研磨体的运动状况有密切关系。因此,研究磨内抛落式研磨体的运动学,既是磨内研磨体动力学的需要,又是人们据此较准确地选择磨机转速比、装球率等工艺参数的需要。研究磨内研磨体抛落运动最高点的轨迹方程,可以清晰地看出磨机筒体横断面上各层研磨体抛物线顶点的变化规律,该方程式与磨内研磨体降落点轨迹方程式(《水泥》1985年第3期)联用,可以准确地确定r层次研磨体的最大     

关于改进球磨机进料点的探讨

本文通过利用球磨机粉磨动力学原理，针对实际生产中球磨机粗磨仓的一种不合理现象，对球磨机内抛落式运动时研磨体和物料的运动轨迹及相互之间的作用力进行分析，探求此现象之根源。发现球磨机进料装置在进料点选择上存在不合理之处。通过改进，从而提高球磨机粉磨效率和降低消耗。     

提高磨机生产能力的有效途径

球磨机是水泥厂主要的工艺设备之一,由于其操作简单、易于控制而得到广泛应用。球磨机又是水泥厂耗能较高的设备。因此,提高磨机产量,降低单位产品电耗,始终是我们追求的目标。通常在磨机投入运行之后,我们较少关注内部结构对产量的影响,从理论到实践证明,磨机的运行状态的填充率对磨机生产能力有很大影响,本文就此作一些分析。1球磨机的两种工作状态球磨机工作状态有两种,在高速转动时是抛落式,物料的磨碎主要靠落下来的球荷所产生冲击作用和部分研磨作用;在低速转动时为泻落式,物料靠互相滑动的研磨介质的压碎及研磨而粉碎。为适应不同粉…     

球磨机主轴承烧瓦问题研究

球磨机是一种大型粉磨设备,广泛地应用于化工、冶金、煤炭、建材等行业。其轴承不仅要支承着整个回转部分的重量,还承受研磨体及物料抛落产生的冲击负荷。球磨机由于其形大体重,主轴承大都采用滑动轴承(巴氏合金衬),轴瓦烧毁是水泥厂常见的重     

球磨机筒体和衬板受力分析

目前球磨机筒体受力计算中,对研磨体有两种假设方法:一种按静态,即筒体内研磨体物料等重量按静止的均布的作用在筒体长度上;另一种按动态,即磨机在回转运动中,研磨体贴着筒体一起回转上升,由离心力和自重使研磨体抛落产生冲击力,但此冲击力假设如同瀑布冲击岩石,是连续地传给筒体。实际上每一个研磨体冲击筒体时是不连续的,冲击时间一般在2.5×10~(-3)秒以下,而研磨体相继冲击间隔时间为0.2～0.3秒。本文按动态计算,用实测冲击加速度来计算冲击力,这更符合实际。根据资料,将加速度计装在研磨体内,测     

关于回转窑内物料与窑壁间摩擦系数的思考

随着窑体转速的提高，物料在窑内所经历的运动形式也不同，主要经历滑移（sliding）、脉动（surging）、塌落（slumping）、滚落（rolling）、泻落（cascading）、抛落（cataracting）和离心运动（centrifuging），但就煅烧质量而言，滚落状态是工程实践中的理想设计工况。本文从力矩的角度出发，得出了要实现物料的滚落状态，可以提高物料与窑壁间的摩擦系数，并提出了具体方法。     

影响球磨机效率的因素及采取的措施

影响球磨机效率的因素及采取的措施１．球磨机转速在不同的筒体转速下，研磨体的运动规律可简化为三种基本形式：一是转速很低时，主要以研磨的方式对物料进行细磨。由于研磨体的动能不大，碰击力小，故研磨效率极低。二是转速很高时，研磨体受惯性力的作用随简体一起回转...     

Trajectories and impact velocities of grinding bodies in planetary ball mills

The motion of grinding bodies in conventional ball mills has been repeatedly investigated, both theoretically and experimentally. It is well-known that, depending on mill filling and speed of rotation, different motion patterns occur and some of these patterns, especially that of cataracting, can be described by simplified theories. This contribution presents such a theory of the cataracting motion of grinding bodies in a planetary ball mill. An analytical method for the evaluation of trajectories is given which permits an iterative calculation of the time and impact location of the grinding bodies on mill shell or mill filling. This leads to the determination of the impact velocity of grinding bodies and its component normal to the mill shell. On the assumption that this component is decisive for the grinding effect, conditions for an optimal design of a planetary ball mill are deduced.     

Experimental and Numerical Study of Grinding Media Flow in a Ball Mill

An experimental and numerical study on the grinding media dynamics inside a baffled ball mill under different solid‐flow regimes, namely, cascading, cataracting, and centrifuging, is described. The Eulerian approach was used for all simulations and the boundary condition at the drum wall was investigated by means of the specularity coefficient parameter. This effort is an important approach in representing the particle‐wall interaction in a ball mill. The restitution coefficient of the balls was experimentally measured using a video camera, and its influence was evaluated by comparing the numerical and experimental outcome of flow patterns. The simulations results proved that the specularity and restitution coefficients effects at the drum wall were more evident at high rotational speeds.     

Experimental investigations and modelling of the ball motion in planetary ball mills

Planetary ball mills feature attractive properties, like the possibility of dry or wet operation, straightforward handling, cleanability and moderate costs. Consequently they are very well suited for lab scale process development in diverse industries, including pharmaceuticals and new materials. A number of questions still remain unanswered regarding this mill type. These include the stress conditions as well as transfer of the grinding results to other types of mills with free moving balls, such as stirred media mills, which can be built in large scales and operated continuously.In order to measure the ball motion and, thus, the stress conditions, a planetary ball mill was equipped with a high speed video camera, so that the grinding ball motion during the comminution process can be recorded and analysed. The influence of important process parameters on the ball motion pattern was assessed in this study, namely speed ratio, ball filling ratio and friction conditions, the latter by applying different mill feeds. The experimental results show considerable influences of the ball filling ratio and friction conditions. The measured ball motion patterns differ significantly from ball trajectories which were calculated using kinetic equations proposed in older publications.In addition to the measurements the ball motion was simulated using a three dimensional Discrete Element Model (DEM). An attempt was made to account for mill feed via altered friction coefficients. Correlations of the DEM results and experimental findings at different operating conditions show a good agreement. Based on simulation data the frequency distribution of the stress energies in the mill could be calculated and compared for different operating conditions.     

Scale-up method of planetary ball mill

The objective of this paper is to investigate the scale-up method of the planetary ball mill by the computational simulation based on Discrete Element Method. Firstly, the dry grinding of a gibbsite powder by using four different scales of planetary mill was developed to compare the grinding rate with the specific impact energy of balls calculated from computational simulation. The grinding rate is well correlated with the specific impact energy in all mills; and its relationship is expressed by a linear correlation. It points out that the specific impact energy is very useful for estimation of the grinding rate and optimization for the operational conditions. Secondly, the scale-up method for the planetary mill was established by evaluating the impact energy. The impact energy is proportional to the cube of the diameter of the pot, the depth of the pot and the revolution radius of the disk, respectively. When the planetary mill is scaled-up in geometrical similarity, the impact energy of the balls is proportional to 4.87 power of the scale-up ratio.     

Empirical and scale-up modeling in stirred ball mills

Stirred ball mills are frequently used for ultrafine- and nanogrinding in food, pharmaceutical and chemical industry, but only few investigations have been published on empirical or scale-up modeling of stirred ball mills. Experiments have been carried out with a laboratory scale stirred ball mill. During the experiments the main technical parameters such as stirrer speed, grinding media, filling ratio, grinding time and the solid mass concentration have been systematically adjusted. The particle size distribution of mill products can be well estimated by empirical functions, so an empirical model has been prepared for the laboratory mill. The relation between the grinding fineness, grinding time and specific grinding work was represented for several materials such as pumice, andesite, limestone and tailings of ore mining industry. The power consumption of the stirred ball mill for scale-up was determined by a method based on the dimensional analysis. A new scale-up model has been presented as well by with industrial size stirred ball mills can be designed on the basis of the laboratory measurements.     

Effect of mill diameter on the rate of initial grinding in vibration ball mills

Vibration ball milling was carried out using three kinds of mills with the same internal volume but different diameters. The variations of specific surface area produced with time were investigated at a constant vibration intensity using feldspar with an initial size range of 74 – 149 μm. As a result, it was found that the specific surface area of product was markedly influenced by the difference in mill diameter even at the same vibrating conditions. According to an empirical equation proposed in a previous paper, the rate of initial grinding was also found to vary by a factor of 1.4 to 2.0, depending upon the mill used. The dependence of the rate of grinding on mill diameter can be explained by considering an effective area of mill shell capable of colliding with balls and a motion of balls in each mill. An available suggestion for designing a mill pot was obtained from this work.     

The effect of ball and mill diameters on grinding rate parameters in dry grinding operation

For dry ball mill grinding operation, the effect of ball and mill diameters on grinding rate parameters of the size-discretized population balance model has been investigated for quartz, limestone, a soft cement clinker and a hard cement clinker. Experiments were performed in three mills of 29.2, 40.6 and 61.0 cm diameter. The diameter of the balls used ranged from 1.27 to 3.81 cm. The particle size range covered was $\text{8}\text{10}$ to $\text{100}\text{150}$ mesh. The rate parameter values were determined very accurately using a special technique. It has been shown that the particle size exponent α in equation S_i = Ax_i^α is independent of ball and mill diameters. Based on this fact, a new correlation has been developed to describe the effect of ball and mill diameters on the rate parameters. The various constants in this correlation are strongly material dependent.     

Comparison of Comminution by Impact of Particle Collectives and Other Grinding Processes

This article presents the innovative grinding apparatus Pulsar in which comminution is caused by impact of a particle plug on an impact plate. Advantages of the Pulsar principle in comparison to other types of mills are discussed. The aim of the work is to classify the Pulsar system in the field of grinding apparatus and machines in terms of energy consumption. Experiments were carried out in a Pulsar, a cross beater mill and a ball mill for comparison purposes. The results show that, for the material quartz sand, grinding in the Pulsar at a medium pressure of compressed air (p_car,i = 7.5 bars) and a medium magnetic valve opening time (t_o = 70 ms) is as efficient as in the ball mill. The grinding energy consumption of both mills, the Pulsar and the ball mill, is remarkably higher than that of the cross beater mill.     

合理配球提高球磨机的生产能力

在钙镁磷肥半成品加工生产过程中,为了使磨机的粉碎效率高,只单纯考虑研磨体的装载量是不够的,还必须确定研磨体的规格及用量,即研磨体的级配.介绍研磨体级配的平均球径与研磨物料平均粒径的关系.     

Naßmahlung in Rührwerksmühlen

Wet grinding in agitated ball mills. To ensure certain product qualities it is necessary to have very fine particles or a narrow particle size distribution. For this process agitated ball mill grinding can be used as well as crystallisation and precipitation. Cost effective grinding of very fine products to a narrow particle size distribution requires that the effects of variation of strain intensity, frequency of impacts, residence time distribution, size of grinding media, viscosity of liquid and concentration of feed material should be known. The most important parameters and their effects on the grinding result are demonstrated, as well as explained by a model, and the consequences for the operating conditions of agitated ball mills are presented. By using small grinding media in agitated ball mills the production rate can be increased, or at the same energy level smaller particles can be obtained by grinding or deagglomeration. At high flow rates and a narrow residence time distribution the feed material becomes more homogeneous. These facts require the development of new or modified types of agitated ball mills.