The ball mill is the key equipment to crush the material after being crushed. This type of mill is equipped with a number of steel balls in its cylinder as grinding medium. When the barrel rotates, the grinding medium is attached to the wall lining of the barrel due to inertial centrifugal force. After rotating with the barrel body and reaching a certain height, the material in the barrel body will break due to gravity.
It is widely used in cement, silicate products, new building materials, refractories, fertilizers, black and non-ferrous metal beneficiation and glass and ceramics industries. It grinds various ores and other grindable materials dry or wet. Ball mill is suitable for grinding various ores and other materials. It is widely used in mineral processing, building materials and chemical industry. It can be divided into dry and wet grinding methods. According to the different ways of discharging, it can be divided into two types: grid type and overflow type.
Everything we make use of in our day to day activities passes through a milling process. Cement used in building, the cereals we eat, toiletries, paints used in making our house presentable, and the tiles that beautifies the house we live in, all went through a milling process. A ball mill is a grinder which is used to grind, blend and mix materials like chemicals, ores, pyrotechnics, paints, mineral dressing process, paint and ceramic raw materials. Its working principle is impact and attrition. Ball milling have proved to be effective in increasing solid-state chemical reactivity and production of amorphous materials. Milling operations are carried out either wet or dry.
Power The difference between the result gotten from using wet and dry milling are most of the time very large. This difference is attributed to the power. The power to drive a wet ball mill is said to be 30% lesser than that of a similar dry ball mill.
Nature Of Materials In the production of some products both wet ball and dry ball milling processes are required. The grinding of the raw mix in a cement plant, can be carried out either wet or dry but because of the nature of the cement can, grinding it has to be carried out dry.
Quality The quality expected will be the determinant of which ball milling process to be used. For example, if pyrotechnic materials is grounded dry, it gives a product superior characteristics compared to the one which was grounded wet. The grinding of aluminium for the preparation of paint is most of the time carried out using a wet milling process since the method introduces stearic acid, or other antiflocculent
Environment The advantages Wet ball milling has over dry milling are higher energy efficiency, lower magnitude of excess enthalpy, better heat dissipation and absence of dust formation because of the aqueous environment it is being performed.
Introduction Of Active Surface Media Wet ball milling allows easy introduction of surface active media having to do with the reduction of the required energy for the inhibition of aggregation of fine particles. Due to wide adoption, it is only theoretically possible to introduce such material or substance in gaseous or vapour form into dry ball milling. The only practicable method of introducing substance in gaseous form is wet ball milling.
Cost In the production of ethanol, wet ball milling is the process used, because of its versatile process. It produces more products than dry ball milling, but in terms of efficiency, capital, and operating cost, most ethanol plants in the USA prefer to use dry ball milling process. In other words, dry ball milling is cost efficient in ethanol production than wet ball milling. With the above, you should be able to weigh which of the ball milling process is appropriate and cost efficient for your production needs.
Ball mills are used for grinding of rocks, cement clinker and limestone from 10 to 100mm feed sizes down to sub-millimetre product. They are typically rotating cylinders with diameters from 3 to 6m and lengths from 6 to 12m. The flow of particulate solids within these mills can be modelled using the discrete element method (DEM). Typically, such modelling is done for short durations of a few mill revolutions and either in two dimensions or using thin three-dimensional slices through the center of the mill with periodic boundary conditions in the axial direction. This facilitates an understanding of the radial motion of the charge, estimation of power draw and of liner wear, but it cannot provide information about axial transport within the mill. In this paper, we examine the axial transport in dry ball mills. This requires simulation of the entire mill and the full volume of the charge for significant periods of time (thousands of revolutions). We use a simple model for grate discharge that allows prediction of the time varying axial distribution of different particle sizes within a discharging ball mill. The distributions of sub-grate size fines is shown to satisfy a one-dimensional diffusion equation with the diffusion coefficient decreasing with grate size. A pulse test, where a single mass of fines in injected at the feed end, is able to quantify the residence time distribution of the fines.
Description of stressing conditions via DEM and a heuristic layer thickness model.Determination of breakage mechanism and specific energy by the stressing intensity.Validation of DEM data due to linear relation of simulated and experimental power.
Planetary ball mills at laboratory scale are widely used for grinding and alloying processes. However, in contrast to other mill types, no applicable mechanistic model exists to describe the stressing conditions and their effect on particle breakage, so that processes are empirically evaluated so far. Within this study, the stressing conditions are determined by simulations based on the discrete element method including the contact model of Hertz and Mindlin. The contact model parameters are carefully calibrated by a series of experiments, so that it is finally possible to validate the simulation results by comparison of measured and calculated power values. The correlation of stressing conditions and breakage rates of alumina powder demonstrates the effect of stressing on breakage kinetics and breakage mechanism. It allows calculating the active mass in dependence on process parameters by an extension of Schnerts active mass model.
Altogether, the presented stressing model features analytical functions for the mill-related stressing conditions and highlights the importance of stressing intensity as process determining parameter, which defines the required number of material-related stressing events and the specific energy.