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ball mills - metso outotec

ball mills - metso outotec

With more than 100 years of experience in developing this technology. Metso Outotec has designed, manufactured and installed over 8,000 ball and pebble mills all over the world for a wide range of applications. Some of those applications are grate discharge, peripheral discharge, dry grinding, special length to diameter ratio, high temperature milling oprations and more.

All equipment adheres to the applicable standards set by ASTM, NEMA, AGMA, AWS, and ANSI. Reliable and effective grinding mills includes being safe throughout. When the mills are quoted we make sure to include any and all safety components needed.

Metso Outotec process engineers welcome the opportunity to assist you with circuit and circuit control design as well as start-up, operation, and optimization of the milling plant. Automatic operation saves power, grinding media, and liner wear, while increasing capacity.

To ensure top-of-the-line operation, software can be developed to suit the most complicated circuits and complex ores. Our engineers can specify or supply computer control systems for your sophisticated circuit needs. These controls are feasible for also smaller installations.

Three types of tests are available for mill power determinations. In most cases one of two bench scale tests is adequate. First, a Jar Mill grindability test requires a 5 lb. (2 kg) sample and produces a direct measured specific energy (net Hp-hr/t) to grind from the design feed size to the required product size. The second test, a Bond Work Index determination, results in a specific energy value (net Hp-hr/t) from an empirical formula.

If time permits and the user wishes, grinding circuits are set up and continuous tests are run to simulate plant operation. These tests require two or three days for each ore type and approximately 1,000 pounds of material for each day of testing. Variations in ore hardness or circuit design may require larger samples.

Metso Outotec Premier horizontal grinding mills are customized and optimized grinding solutions built on advanced simulation tools and unmatched expertise. A Metso Outotec Premier horizontal grinding mill is able to meet any projects needs, even if it means creating something novel and unseen before.

Metso Outotec Select horizontal grinding mills are a pre-engineered range of class-leading horizontal grinding mills that were selected by utilizing our industry leading experience and expertise. With developing a pre-engineered package, this eliminates a lot of the time and costs usually spent in the engineering and selection stages.

calculate and select ball mill ball size for optimum grinding

calculate and select ball mill ball size for optimum grinding

In Grinding, selecting (calculate)the correct or optimum ball sizethat allows for the best and optimum/ideal or target grind size to be achieved by your ball mill is an important thing for a Mineral Processing Engineer AKA Metallurgist to do. Often, the ball used in ball mills is oversize just in case. Well, this safety factor can cost you much in recovery and/or mill liner wear and tear.

forged steel balls suppliers | hot rolled steel balls

forged steel balls suppliers | hot rolled steel balls

Allstar Forged Steel Ball is hammer forged from selected high quality carbon and alloy steels. By hammer forged, the balls have good density and strengthsin favor ofimpact grinding.And rigidly managed forging process ensuring spherical ball shape.

Allstar Hot Rolled Steel Ball rolled direct from selected high quality carbon and alloy steels bar, followed by in-line heat treatment and uniform quenching, tailored to give even hardness throughout.

The forged steel ball is the high quality of our professional experts provides in the marketplace. In addition, we can more assemble for used to advanced technology with some changes to occur in this dynamic global environment. In the main factor, this process is available for firsthand the efforts due to make the absolute customer satisfaction. The forged steel ball is selected from the best quality of carbon and alloy steels as well as forged due to more density and strengths.

Most importantly, we can accept the all grinding with enhanced the forging process ensuring spherical ball shape is very reliable and supplies grinding products for your customer needs. However, we can optimize the many services and we can improve operational efficiency due to allowing the profitability and minimizing costs and losses. On another hand, this raw material is the automatic type of equipment from more development of all access with any treatment technique and strict quality control system.

Are you looking for high quality forged steel ball for wide application? All Star Industry Group Limited is the unique supplier of the optimized product solutions for the mineral processing. All the ball grinding featured by uniform hardness with more resistance to wear and impact for low breakage of supported by advanced manufacturing equipment and scientific manufacturing process. In addition, the best quality of our professional experts and more than the largest markets place. We can assemble for more technology and prepared for the changes to occur in this dynamic global environment. It is also available for people and learns firsthand the efforts due to make the absolute customer satisfaction. The forged steel ball is selected from the high-quality carbon and alloy steels. This hammer forged due to more density and strengths for more impact grinding with enhanced the forging process ensuring spherical ball shape.

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china ore grinding steel ball,grinding mill steel ball,mill machine steel balls manufacturer

china ore grinding steel ball,grinding mill steel ball,mill machine steel balls manufacturer

Product categories of Ball Mill Balls, we are specialized manufacturers from China, Ore Grinding Steel Ball, Grinding Mill Steel Ball suppliers/factory, wholesale high-quality products of Mill Machine Steel Balls R & D and manufacturing, we have the perfect after-sales service and technical support. Look forward to your cooperation!

Forged Steel Ball The forged grinding steel ball has its advantage in surface impact resistance toughness low breakage and low out of round rate We use the most advanced forging methods and the advanced equipment to press onto the steel raw material so as to obtain the forging piece with certain mechanical properties...

Shandong Shengye Grinding Ball Co Ltd specialized in manufacturing Grinding Media Ball for 20 years with strict quality control system The grinding steel ball are the means used to crush or grind material coal cement mineral in a mill According to the material to be crushed or ground grinding steel ball can have...

Shandong Shengye Grinding Ball Co Ltd specialized in manufacturing Grinding Steel Ball for 20 years with strict quality control system The grinding steel ball are the means used to crush or grind material coal cement mineral in a mill According to the material to be crushed or ground grinding steel ball can have...

Forged Steel Grinding Media for Ball Mills All round steel bars used for the production of forged steel balls are sourced from State owned standarded steel groups near our factory All ShengYe forged grinding media are manufactured to international quality standards and the processes include a quench temper stage for...

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stirred mill - an overview | sciencedirect topics

stirred mill - an overview | sciencedirect topics

Vertical stirred mills are usually charged with media occupying 80% of the mill volume which is in sharp contrast to tumbling mills that are seldom charged more than 40% of their volumes to allow space for the tumbling action to develop. The stirred mills are charged with a media size of 1012mm and operated at a maximum tip speed of 38m/s. The Metso detritor mill, however, has a maximum tip speed of 1112m/s. Even though a finer ground product is obtained with higher speeds, a limit has to be imposed. This is to allow the separation of media and mineral particles at the top of the mill where a settling zone develops. The ultrafine ground product is usually discharged as it passes through the separating screen. It also takes with it fine media product. The Metso detritor mill uses a screen size of 300m to retain sand when used as a media.

During operation a small amount of heat is generated. This affects the viscosity of the slurry. According to Kwade [7], if the viscosity of the slurry is too high the grinding efficiency is reduced as activity in the grinding chamber is inhibited and the contact between the grinding media and the particles is decreased resulting in less abrasive action on the mineral particles. Thus, the heat generated during media stirring could assist in lowering the slurry viscosity and hence benefit grinding efficiency.

The stress intensity and the number of stress events determine the specific energy to achieve a certain product fineness. The number of stress events is a function of mill operating parameters such as grind time, stirrer speed, percent solids and media size. The relationship between stress intensity and specific energy was shown by Kwade as indicated in Figure10.10.

The stress energy available to particle breakage is distributed in different sections of the mill, being maximum near the tip of the stirrer. For a satisfactory grind and size reduction of all particles, the residence time of the slurry in the mill is the prime factor. Experience so far indicates that about 3060seconds of travel time through a mill is adequate.

It may be noted that all the stress energy generated are not transferred to the mineral particles and the media hardness and media size affects the product size. The portion of the stress energy transferred to the particles depends on the Youngs modulus of both the grinding media and the particles [8].

The Vertimill is a vertical stirred mill that uses a helical screw to impart motion in the charge. Mechanically, the Vertimill is a very simple machine with an agitating screw suspended into the grinding chamber, supported by spherical roller bearings, and driven by a fixed speed motor through a planetary gearbox. Figure 8.14 presents a schematic diagram of the Vertimill. The screw rotates slowly such that the ball charge and slurry are not fluidized, but settle under gravity. The screw action pulls the ball charge up the center of the mill, and the charge eventually cascades over the edge of the screw, creating a general downward flow pattern at the mill perimeter. This pattern of flow, coupled with the low velocities involved, ensures that the grinding media and particles stay in contact with one another, thus enabling the efficient transfer of the drive energy into attrition and abrasion breakage throughout the charge. The operating conditions of the Vertimill are very similar to those of the conventional ball mill in the sense that the percentage solids of the feed should be kept in the range of between 65% and 75% by mass. The power draw of the mill is directly linked to the mass of balls within the mill. The distinct advantage that the VTM has over the conventional ball mill is its ability to use media smaller than 25mm more effectively.

In the past 20 years, more than 60 Vertimill machines have been sold for iron ore applications, with more than 20 of those in the last 2 years alone. Table 8.2 lists examples of the Vertimill in Brazilian iron ore applications. The Metso Vertimill is very common in regrind applications, but the industry quickly realized its potential in coarser applications as well.

where P is the shear power (W), the viscosity of the mill contents (N.s m2) (for which a relationship was given), the angular velocity (rad s1), and V the shear volume (referring to all the shear surface pairs between an impeller and the mill chamber). With appropriate calibration the predicted power matched the measured power for the data of Gao et al. (1996) and Jankovic (1998).

The IsaMill milling technology is a large-scale commercial high-speed stirred mill that is currently under development for coal micronising applications. The technology achieves very high energy efficiencies by using small milling balls in a high intensity configuration (>300 kWmm3). It is claimed that the technology (Fig.15.7) can produce coal with 90% of the particles less than 20m.

IsaMill technology is receiving serious consideration as part of a CSIRO investigation into preparing micronised coal for coal/water fuel in a diesel engine to deliver base-load power (see Section15.10.1).

Vibratory mills use oscillatory motion of the mill shell to agitate the media. As for the stirred mills, the active grinding zone encompasses the entire mill volume. The grinding energy is supplied by the inertia of the media and is not limited by gravity. In principle, high energy can be supplied to quite fine media, making these devices attractive for ultrafine grinding applications. By very careful matching of media size, powder size, and energy input (based on vibrational amplitude and frequency) it should be possible to achieve quite high grinding efficiencies. Unfortunately, mechanical design for reliability and low maintenance is not simple. Problems in these areas have tended to limit their large-scale application.

Different kind of mills are suitable for grinding, mechanical alloying and mechanical milling such as horizontal mills (tumbler ball mill), stirred mill (attritor, e.g. Szegvari attrition mill1), planetary ball mill, vibrating mill (tube vibrating mill, Sweco vibrating mill and shaker vibrating mill (e.g. Spex is a lab-scale mill3)). Their working principles and operating conditions are summarised in Fig. 12.1 and Table 12.1. The classification on a scale of increasing mill energy is: horizontal ball mill, attritor, planetary ball mill and vibrating ball mill. For example, a process that takes only a few minutes in the SPEX mill can take hours in an attritor and a few days in a commercial tumbler ball mill.

The choice of a milling technique is determined by many parameters. For example, attrition mills are more efficient than tumbler ball mills for mixing and blending WC-Co cutting tool powders because of short milling time, production of fine particle size (submicron sized) and enhanced smearing of Co onto carbide particles. However, as the product output is relatively low with attrition mills, tumbler ball mills are usually used for production runs of over 100kg/day. Moreover, powder contamination, which is an important criterion for many applications, can be due to the initial purity of the powder, the milling equipment (design), the milling operating conditions (mill speed, balls size and material, atmosphere) and/or the use of process control agent. It increases with milling time, milling intensity and with the reduction of the difference of strength/hardness between the powder and the milling balls.

There are in general two methods by which nanoparticles can be produced using high-energy milling: (i) milling alone and (ii) combining chemistry and milling (referred to as chemical-mechanical milling or mechanochemical processing). It is suggested that these methods offer the advantage of being easily scaled. References [19 and 20] are good starting points for further reading.

High-energy milling processes involve the comminution of bulk materials. The principle of comminution is centred on applying physical forces to bulk material so as to effect breakage into smaller sizes. The forces required to effect breakage are usually a combination of either impact or shear. Material is introduced into a milling chamber in which grinding (milling) media are contained. Milling occurs when the media is made to move either by stirring (using a rotor) or by shaking/vibrating the chamber and contacts the bulk material thus imparting, depending on the milling parameters, either impact or shear forces on it. Breakage can occur through a variety of mechanisms and are generally described as attrition, abrasion, fragmentation or chipping and occur both at the macro and microscopic level [21]. This is illustrated in Figs 1.3 and 1.4

The rate at which comminution occurs is dependent on the size and frequency with which forces are applied. Breakage is influenced by both extrinsic and intrinsic factors. Intrinsic factors include such things as material properties (hardness, density, size) whilst extrinsic factors are determined by the amount of energy put into the system and the efficiency with which that energy is translated to the milling process. The latter is determined by variables such as vibrating frequency (in a rotorless mill), rotor speed (in a stirred mill), mill design, media size and loading, solids loading and whether the milling is performed dry or wet. These variables dictate which force regime predominates (i.e. shear or impact) which in turn dictate milling rate and efficiency. In high-speed stirred mills the effect of mill tip speed, media size and density can be evaluated simultaneously using the grinding media 'stress intensity' approach and an illustration of this is summarised in Fig. 1.5 which shows a plot of product particles size (starting size 45 m, product size 26 m) versus stress intensity for a pin mill using a zinc concentrate.

A variety of mills are commercially available and range from tumbling, shaker, vibratory, planetary and stirred ball mills. Production of nanoparticles using this technique is sometimes limited by the need for extended milling times, material properties and contamination issues. Attrition methods allow the production of alloys and composites that cannot be synthesised by conventional casting methods. They have also gained attention as non-equilibrium processes resulting in solid state alloying beyond the equilibrium solubility limit and the formation.

The types of nanoparticles produced by the attrition milling technique are generally alloys or single-phase powders. When a single-phase elemental powder (or intermetallic) is milled, grain size asymptotically reduces to a range of 330 nm [19]. For alloys produced by this method, unstable intermediate substances are formed, from mixing and diffusion as a consequence of repeated deformation and folding of the different metals. These intermediates allow the chemical reactions necessary for alloy formation to occur [11].

For non-metallic compounds (carbides, oxides, etc.) the reduction in grain size is consequent on fracturing and cold welding and the limit to minimum grain size is determined by the minimum size that does not support nucleation and propagation of cracks within the grain. For metallics, on the other hand, it is thought that the reduction in grain size is a process where localised plastic deformation is induced, subgrains are formed (by eradication of dislocations) which combine (through intimate mechanical contact) to form discrete grains. The latter process is analogous to recrystallisation observed during hot forming of metals and alloys but in these circumstances at low temperatures. In intermetallics, the process is thought to be different again in that grain formation is due to nucleation (on a nanoscale) followed by a limited growth of the generated phase [20,23]. There are numerous examples in the literature of alloy and mixed metal oxide production using this technique [20,28]. Few examples can be found where single-phase powders or particles are produced at the nanoscale level [24,25].

In this technique, a large number of small grinding media are agitated by impellers, screws, or disks in a chamber. Breakage occurs mainly by the collision of the media. There are designs of the mill with a vertical or horizontal rotating shaft with wet or dry systems (Fig. 2.19).

The medium agitating mill is one of the most efficient devices for micronizing materials and has been in regular use for the production of fine particles and mechanical alloying processes. A typical stirred mill with a vertical rotating shaft and horizontal arms is shown in Fig. 2.20. This stirring action causes a differential movement between balls and the material being milled, thus a substantially higher degree of surface contact than is achieved in tumbling or vibratory mills is ensured. Milling takes place by impact and shear forces. The rotating charge of balls and milling product form a whirl where the milling product is impacted by balls moving in various trajectories.

The attrition mill agitator rotates at speeds ranging from 60rpm for production units to 300rpm for laboratory units and uses media that range from 3 to 6mm while ball mills use large grinding media, usually 12mm or larger, and run at low rotational speeds of 1050rpm. Power input to attrition mills is used to agitate the medium, not to rotate or vibrate heavy drums. Therefore, specific energy consumption of attrition mills is significantly less than with ball mills. Table 2.4 offers a comparison of grinding mills by rotational velocity. In the attrition grinding process, grinding time is related to medium diameter and agitator speeds [12], within given limits, as:

where t is grinding time required to reach a certain medium particle size; k is a constant that varies with the suspension being processed and the type of medium and mill being used; d is the diameter of the grinding medium; and n is shaft movement, in rpm.

Attrittion mills are classified as batch-, continuous-, or circulation-type mills. In the batch mill, material is loaded into the chamber and ground until the desired dispersion and particle size are achieved. Chamber walls are jacketed so that either hot or cold water can be circulated to control and maintain the temperature of the charging. The batch attrition mills can process high-density material, such as tungsten carbide, as well as viscous materials. They are also suitable for dry grinding and for producing dispersion-strengthened metals by means of mechanical alloying.

Continuous attrition mills, more appropriate for large production output, consist of a tall, jacketed chamber through which previously prepared slurry is pumped in at the bottom and discharged at the top. Grids located at the bottom and top retain the grinding medium, as shown in Fig. 2.21.

The circulation grinding system comprises an attrition mill and a large holding tank, generally 10 times the volume of the grinding unit. The attrition mill contains grids that restrain the medium while the slurry passes through. Usually, the contents of the holding tank are passed through the system at a rate of 10 times per hour. The slurry can be monitored continuously and processing is stopped when the desired particle size dispersion is achieved.

Dry milling can provide reduced transportation costs compared to wet grinding because 50% of the gross weight is liquid in many wet slurry processes. Because the removal of the liquid from a wet grinding process involves not only another process step but also requires large amounts of energy, dry grinding can provide reduced energy costs. Another advantage is the elimination of waste liquid disposal.

Attrition mills find application for hard materials such as carbides and hard metals where conventional tumbling and vibratory ball mills are less efficient. The principal advantages of attrition mills for mixing and blending tungsten carbide with cobalt as binder metal cutting tool powders include a short milling time, the production of fine particle size (submicron sizes), and the enhanced coating of cobalt onto the surface of tungsten carbide particles [25]. Attrition mills effectively grind metals in inert atmospheres, such as in solid state or mechanical alloying.

Previous work (Heitzmann [8]) performed with coloured tracer experiments in a glass body version of a four blades Dyno mill showed that the action of the stirrer - beads system was first to delimit four perfectly mixed cells centered on each of the four blades. Further, it has been shown that classical models (plug flow, cascade of perfectly mixed cells, dispersion models) were unable to correctly represent RTD experiments. An internal recirculation loop model, with a single adjustable parameter R (see Figure 1), was considered and gave very good results in continuous milling of suspensions of known grinding kinetics (Berthiaux et al. [9]).

Another important conclusion of this work was concerned with the physical meaning of the recirculation ratio R which is undoubtedly linked with the local hydrodynamic conditions, such as porosity, stirrer speed of rotation N, and perhaps mill flow-rate Q. It was also suggested that there exists an optimum value of R that leads to the best continuous grinding conditions (see Figure 2). For example, low values of R benefits the flow itself as it approaches plug flow through tanks in series, while it clearly slows down the kinetics of grinding because the bead - particle collisions are of a lower intensity. In the absence of kinetic data, typical R-values should then range between 0.5 and 5.

The procedure followed to obtain these RTD curves becomes tedious when dealing with a greater number of perfectly mixed cells, or better said a greater number of stirring blades, as it is the case for other types of mills. In general, the analytical or numerical derivation of the RTD from any complex model is in fact highly subjected to errors when done by the classical transfer function method. Particularly, many problems can be incurred when hypotheses are made to simplify the mathematical equations, which may lead to unrealistic dynamic behaviour (see Gibilaro et al. [10]). The advantage of using the Markov chain approach lies in the fact that it is systematic, and its application does not depend on the complexity of the flow scheme.

A Markov chain is a system which can occupy various states, and whose evolution is defined once an initial state and the probability transitions between the states are fixed. It can therefore be said that a Markov chain does not have memory. In the case of flow problems (Fan et al. [11]), the system is a fluid element, the states are the perfectly mixed cells of the flow model (as plug flow can be represented by a series of such cells), and the probability transitions are fixed by elementary mass balances.

For example (Figure 3), the probability pii of remaining in cell i is exp(t/i), where t is the time interval under which the system is observed, and i is the geometric residence time corresponding to cell i. The other transitions pij depend then on the flow rate ratios and on the value of 1- exp(t/j), which is the probability of getting out of cell i during t. All these information are then collected in a probability transitions matrix P, whose rows (i) and columns (j) are the pijs. Further, the initial state of the system is represented by a single row E0, being En the state of system after n transitions (steps of duration t), which is available from the following matrix product (Eq.1):

The last element of En, which is the collecting cell or outlet of the network, represents therefore the dynamic response of the system to a perturbation that may be a tracer impulse: E0=[1 0 0]. Simulation of the RTD curve of the model is further performed by letting t become smaller and smaller until the stability of the solution is ensured.

comparison of energy efficiency between ball mills and stirred mills in coarse grinding - sciencedirect

comparison of energy efficiency between ball mills and stirred mills in coarse grinding - sciencedirect

Stirred mills are primarily used for fine and ultra-fine grinding. They dominate these grinding applications because greater stress intensity can be delivered in stirred mills and they can achieve better energy efficiency than ball mills in fine and ultra-fine grinding. Investigations were conducted on whether the greater performance of stirred mills over ball mills in fine grinding can be extended to coarse grinding applications. Four different laboratory ball mills and stirred mills have been tested to grind seven ore samples with feed sizes ranging from 3.35mm to 150m. A case study on full scale operations of a 2.6MW IsaMill replacing the existing 4MW regrind ball mill at Kumtor Gold Mine in Kyrgyzstan is also included. This paper summarizes the major findings from these investigations.

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