Ball mill is important grinding equipment in the beneficiation plant, used for grinding ores to powders before they are magnetically or chemically processed. How Many Types of Ball Mill? There are many manufacturers producing ball mills on the market, how to choose the right one suits for your production? Here are a quick introduction and classification of ball mills for your reference.
1. Short-cylinder ball mill: The length (L) of the cylinder is less than twice the diameter (D) of the cylinder, that is, the ball mill with L 2D is a short-cylinder ball mill. Single-bin structure ball mill, which is mainly used for coarse grinding or primary grinding, has high efficiency.
2. Rod mills usually equipped with steel rod which diameter mostly between 50-100mm, need a longer grinding time. The number of bins in a rod mill is generally two to four, and there are some differences in the grinding media loaded in each bin. To ensure the final effect of grinding, the staff will place the cylindrical steel rod in the first bin, and the steel ball or steel segment in several other bins.
3. The grinding media in the gravel mill mainly include pebbles, gravel, sandstone, ceramic balls, etc. Gravel mills mostly use porcelain or granite as lining boards, and are widely used in the production fields of cement, ceramics and so on.
1. Overflow type: discharge ore through the hollow shaft. When the ore discharge surface is higher than the slurry surface, the finished product is discharged and the ore is automatically discharged by gravity, thus the overflow ball mill saves energy.
2. Grate discharge ball mill: the ore is discharged through the grate plate. The grating part can strictly control the minerals discharge size that meets the demand, it has a good effect on fine particle grinding.
2. The intermittent ball mill can not continuous operation, at the same specification, its output is lower. The feeding and discharging time is set according to the characteristics of the grinding material. The intermittent ball mill is suitable for the mixing and grinding of materials, lower power consumption. Many ball mill has been transformed into continuous, so users do not have to worry about the production output problem.
1. Central transmission ball mill: The driving power of this type of mill is in the center of the fuselage, and the motor realizes the operation of the ball mill through a reducer. During operation, the hollow shaft in the center of the ball mill drives the grinding body to rotate under the drive of the power system.
1. Wet ball mill: Water is added at the same time as the material is fed, and the material is discharged into a certain concentration of slurry and discharged. In a closed-circuit system, it is composed of a closed-circuit operation with a hydraulic classification device.
2. Dry ball mill: Some discharges are drawn by air current, and the mill and wind classification device form a closed circuit. For example, the cement mill adopts self-flow discharge. The capacity of the dry ball mill is larger, and the energy-saving effect of wet ball mill is better.
1. According to the working conditions and material characteristic Minerals that cannot be touched with water, minerals that are sticky after adding water, and the mining plant in areas where water resources are scarce, are suitable for grinding with a dry ball mill. Under other conditions, it is better to use a wet ball mill which has a better grinding effect, and energy-saving performance. 2. Energy consumption Choose an energy-saving ball mill or ordinary ball mill according to the capacity of electric power supply and energy consumption limitation. 3. Capacity If you require high capacity, choose a continuous ball mill. The vibrating feeder can automatically feed, so the continuous ball mill can keep running for 24 hours. JXSC provides you free selection service, engineers online!
Selecting the types of ball mill is mainly up to the production capacity, namely processing capacity. There are many factors that are related to the processing capacity of ball mill, such mineral grindability, particle size of feeding and final product, type and size of grinding machine, shape of the lining board and size matching, shape, size and shape of grinding medium, matching proportion and its physical and mechanical properties, mill speed, medium charge ratio, slurry concentration, as well as the type of classifier and working system.
It is mainly used for rough grinding, and the grain size of mineral products is mostly 1 ~ 3mm, even 0.5mm in gravity separation plant. It the particle size is too fine, the grinding efficiency will be reduced greatly. Due to the moving influence of the grinding rod, the diameter of the rod mill should not be larger than 4500mm, and the length of rod mill should not be larger than 6000mm. When combining with the ball mill, the matching ratio of rod mill and ball mill should be 1:2.
It is mainly used for rough grinding, especially used for single grinding or the first stage of two-stage grinding. In a closed-circuit grinding, the grinding fineness is generally 50% ~ 70%-0.074mm. and grid type ball mill is often used with spiral classifier.
It can be used for one stage grinding, second stage grinding or the regrinding operation of intermediate products. At present, Overflow ball mill is mainly used for the second grinding and regrinding of intermediate product with hydrocyclone. When the overflow ball mill is used for the first stage of grinding, it is often equipped with the spiral classifier. Large ball mill (generally larger than 4,000mm) usually adopt overflow ball mill and hydrocyclone as the grinding circuit, which not only simplifies the mill structure, but also facilitates maintenance.
When using these two types of ball mill, it is very important to pay attention to the grinding medium. Usually, the self-grinding medium indicator is obtained by self-grinding medium tester, and the testing result is used to determine whether the mineral has good grinding medium, and whether the mineral need for the autogenous, semi-autogenous grinding industrial test. After industrial test, the types of ball mill can be calculated by the empirical formula.
The utilization rate of coal mine energy is relatively high, because there are a lot of slag produced by coal industry smelting every year. In order to avoid these slag damage to the environment and increase the recycling utilization rate, slag grinding mill is a more thorough and effective way of utilization.
Source: guikuang By Administrator Posted: 2019-02-22 As we all know that the Raymond mill is one of the common use stone powder making machines, compare with other grinding mills, the Raymond mill usually is more stable and efficient. However, after a 
Source: GuikuangBy Administrator Posted: 2019-02-22 In the field of fluorite grinding, Raymond mill will be one of the most popular machines for fluorite powder grinding. As a common grinding mill for fluorite powder processing, fluorite Raymond mill is an excellent high efficiency equipment. It has scientific principles and design structure, high productivity, low energy consumption, 
Source: guikuang By Administrator Posted: 2019-02-25 As a common grinding plant, Raymond Mill can be used in fine powder making of barite, calcite, potassium feldspar, talc, marble, limestone, dolomite, fluorite, lime, activated clay, activated carbon, bentonite, kaolin, cement and phosphate rock, and other Non-flammable and 
Source: Guikuang By Administrator Posted: 2019-2-21 Generally speaking, the price of Raymond mill usually more cheaper than other grinding mills, and compare with other grinding mills, the Raymond mill usually has a stable performance, the capacity of Raymond mill can up to 20 t/h, and 
The common types of ball mill used in the mineral processing mainly include cement ball mill, tubular ball mill, ultra-fine laminating mill, cone ball mill, ceramic ball mill, intermittent ball mill, overflow ball mill, grid ball mill, wind discharge ball mill, double bin ball mill, energy-saving ball mill. But the types of ball mill are also varying according to the different sorting conditions.
Short cylinder ball mill: the cylinder length(L) is less than two times of the cylinder diameter(D), that is, the ball mill with L2D is the short cylinder ball mill. It is usually a single-bin structure, mainly used for coarse grinding or first-stage grinding. Because of its high operation efficiency, two or three ball mills can be used in series at the same time, which has a wide application.
The grinding medium in the gravel ball mill mainly includes pebbles, gravel, sand, porcelain balls, etc. The gravel ball mill adopts porcelain material or granite as the lining board, which is widely used in the field of colored cement, white cement and ceramics.
Center driving ball mill: The driving power end of this ball mill is in the center of the ball mill. And the motor realizes the operation of the ball mill through reducer. During the operation, the hollow shaft in the center of the ball mill drives the mill body to rotate under the driving of the power system.
Wet ball mill: Adding water when feeding, the discharging material is discharged when it is in a certain concentration of slurry. The wet ball mill forms the closed circuit operation with the hydraulic classification equipment in the closed circuit system.
There are many kinds of manufactured goods used by people in their everyday life. While some of them may plainly be solids or liquids, their composition varies diametrically. Solid objects like salt are relatively homogenous solids but certain others like alum, metallic products, amorphous materials, and even some electrical appliances are derived from a heterogeneous mixture of solids. Expectedly, the procedure of blending elements of opposing properties is a cumbersome task for industries, especially because any negligence poses a significant risk of loss of quality.
Keeping this in mind, ball mills were designed by engineers for blending and grinding materials useful in manufacturing of paints, pyrotechnics, ceramics, etc. Essentially, a ball mill is a hollow cylindrical chamber that is fixed to an axis. Upon operation, it rotates by its axis on a set speed and the balls occupying its chamber space collide with the materials placed inside.
The constant collision with the balls leads to the breaking down of minerals and their subsequent mixing with each other. On to their seemingly decent designs, innovative ball mill manufacturers in India have introduced a number of features that further facilitate the manufacturing processes. Some of the varieties of ball mills available in the market today can be listed as follows:
Ball mill manufacturers of India are increasingly experimenting with the form, structure, and design of ball mills to keep up with the pace of advancing industries. Thereby, promising a thriving manufacturing business, supplemented by sophisticated machines and active personnel.
Ball mill machine is a kind of mining and cement milling equipment with the highest application ratio in the industrial field. Because internal ball mill grinding media are mostly spherical in different specifications and materials, so it is named ball mill machine.
End cover: The end cover is provided at both ends of the cylinder body, which is connected with the cylinder body by screws. There are holes in the middle of the end cover to facilitate feeding and discharging.
The ball mill working process is carried out in the cylinder. After the ball mill grinding media in the cylinder body is brought to a certain height with the rotation of the cylinder body, the ball mill grinding media falls due to its self-weight, and the raw materials in the cylinder body are severely impacted by the grinding media.
On the other hand, due to the revolution and rotation of the grinding media along the cylinder axis in the cylinder body, the extrusion and peeling force of materials are generated between the grinding media and the contact area between the grinding media and the cylinder body, thereby grinding the material.
The ball mill grinding media is generally spherical or small cylindrical steel cylpebs, the material can be steel, ceramic, glass, and even rubber. Because ball mill grinding media of different materials and sizes can be selected, the ball mill machine can be used to grind raw materials with various properties and hardness.
The most common grinding medium in ball mill is spherical steel grinding medium. These steel balls are generally made of iron and carbon alloys, sometimes with the addition of chromium element. Through the blending of these elements, a grinding media steel ball with extremely high hardness and wear resistance is created. Steel balls are usually made by forging or casting.
As a ball mills supplier with 22 years of experience in the grinding industry, we can provide customers with types of ball mill, vertical mill, rod mill and AG/SAG mill for grinding in a variety of industries and materials.
The ball mill accepts the SAG or AG mill product. Ball mills give a controlled final grind and produce flotation feed of a uniform size. Ball mills tumble iron or steel balls with the ore. The balls are initially 510 cm diameter but gradually wear away as grinding of the ore proceeds. The feed to ball mills (dry basis) is typically 75 vol.-% ore and 25% steel.
The ball mill is operated in closed circuit with a particle-size measurement device and size-control cyclones. The cyclones send correct-size material on to flotation and direct oversize material back to the ball mill for further grinding.
Grinding elements in ball mills travel at different velocities. Therefore, collision force, direction and kinetic energy between two or more elements vary greatly within the ball charge. Frictional wear or rubbing forces act on the particles, as well as collision energy. These forces are derived from the rotational motion of the balls and movement of particles within the mill and contact zones of colliding balls.
By rotation of the mill body, due to friction between mill wall and balls, the latter rise in the direction of rotation till a helix angle does not exceed the angle of repose, whereupon, the balls roll down. Increasing of rotation rate leads to growth of the centrifugal force and the helix angle increases, correspondingly, till the component of weight strength of balls become larger than the centrifugal force. From this moment the balls are beginning to fall down, describing during falling certain parabolic curves (Figure 2.7). With the further increase of rotation rate, the centrifugal force may become so large that balls will turn together with the mill body without falling down. The critical speed n (rpm) when the balls are attached to the wall due to centrifugation:
where Dm is the mill diameter in meters. The optimum rotational speed is usually set at 6580% of the critical speed. These data are approximate and may not be valid for metal particles that tend to agglomerate by welding.
The degree of filling the mill with balls also influences productivity of the mill and milling efficiency. With excessive filling, the rising balls collide with falling ones. Generally, filling the mill by balls must not exceed 3035% of its volume.
The mill productivity also depends on many other factors: physical-chemical properties of feed material, filling of the mill by balls and their sizes, armor surface shape, speed of rotation, milling fineness and timely moving off of ground product.
where b.ap is the apparent density of the balls; l is the degree of filling of the mill by balls; n is revolutions per minute; 1, and 2 are coefficients of efficiency of electric engine and drive, respectively.
A feature of ball mills is their high specific energy consumption; a mill filled with balls, working idle, consumes approximately as much energy as at full-scale capacity, i.e. during grinding of material. Therefore, it is most disadvantageous to use a ball mill at less than full capacity.
The ball mill is a tumbling mill that uses steel balls as the grinding media. The length of the cylindrical shell is usually 11.5 times the shell diameter (Figure 8.11). The feed can be dry, with less than 3% moisture to minimize ball coating, or slurry containing 2040% water by weight. Ball mills are employed in either primary or secondary grinding applications. In primary applications, they receive their feed from crushers, and in secondary applications, they receive their feed from rod mills, AG mills, or SAG mills.
Ball mills are filled up to 40% with steel balls (with 3080mm diameter), which effectively grind the ore. The material that is to be ground fills the voids between the balls. The tumbling balls capture the particles in ball/ball or ball/liner events and load them to the point of fracture.
When hard pebbles rather than steel balls are used for the grinding media, the mills are known as pebble mills. As mentioned earlier, pebble mills are widely used in the North American taconite iron ore operations. Since the weight of pebbles per unit volume is 3555% of that of steel balls, and as the power input is directly proportional to the volume weight of the grinding medium, the power input and capacity of pebble mills are correspondingly lower. Thus, in a given grinding circuit, for a certain feed rate, a pebble mill would be much larger than a ball mill, with correspondingly a higher capital cost. However, the increase in capital cost is justified economically by a reduction in operating cost attributed to the elimination of steel grinding media.
In general, ball mills can be operated either wet or dry and are capable of producing products in the order of 100m. This represents reduction ratios of as great as 100. Very large tonnages can be ground with these ball mills because they are very effective material handling devices. Ball mills are rated by power rather than capacity. Today, the largest ball mill in operation is 8.53m diameter and 13.41m long with a corresponding motor power of 22MW (Toromocho, private communications).
Planetary ball mills. A planetary ball mill consists of at least one grinding jar, which is arranged eccentrically on a so-called sun wheel. The direction of movement of the sun wheel is opposite to that of the grinding jars according to a fixed ratio. The grinding balls in the grinding jars are subjected to superimposed rotational movements. The jars are moved around their own axis and, in the opposite direction, around the axis of the sun wheel at uniform speed and uniform rotation ratios. The result is that the superimposition of the centrifugal forces changes constantly (Coriolis motion). The grinding balls describe a semicircular movement, separate from the inside wall, and collide with the opposite surface at high impact energy. The difference in speeds produces an interaction between frictional and impact forces, which releases high dynamic energies. The interplay between these forces produces the high and very effective degree of size reduction of the planetary ball mill. Planetary ball mills are smaller than common ball mills, and are mainly used in laboratories for grinding sample material down to very small sizes.
Vibration mill. Twin- and three-tube vibrating mills are driven by an unbalanced drive. The entire filling of the grinding cylinders, which comprises the grinding media and the feed material, constantly receives impulses from the circular vibrations in the body of the mill. The grinding action itself is produced by the rotation of the grinding media in the opposite direction to the driving rotation and by continuous head-on collisions of the grinding media. The residence time of the material contained in the grinding cylinders is determined by the quantity of the flowing material. The residence time can also be influenced by using damming devices. The sample passes through the grinding cylinders in a helical curve and slides down from the inflow to the outflow. The high degree of fineness achieved is the result of this long grinding procedure. Continuous feeding is carried out by vibrating feeders, rotary valves, or conveyor screws. The product is subsequently conveyed either pneumatically or mechanically. They are basically used to homogenize food and feed.
CryoGrinder. As small samples (100 mg or <20 ml) are difficult to recover from a standard mortar and pestle, the CryoGrinder serves as an alternative. The CryoGrinder is a miniature mortar shaped as a small well and a tightly fitting pestle. The CryoGrinder is prechilled, then samples are added to the well and ground by a handheld cordless screwdriver. The homogenization and collection of the sample is highly efficient. In environmental analysis, this system is used when very small samples are available, such as small organisms or organs (brains, hepatopancreas, etc.).
The vibratory ball mill is another kind of high-energy ball mill that is used mainly for preparing amorphous alloys. The vials capacities in the vibratory mills are smaller (about 10 ml in volume) compared to the previous types of mills. In this mill, the charge of the powder and milling tools are agitated in three perpendicular directions (Fig. 1.6) at very high speed, as high as 1200 rpm.
Another type of the vibratory ball mill, which is used at the van der Waals-Zeeman Laboratory, consists of a stainless steel vial with a hardened steel bottom, and a single hardened steel ball of 6 cm in diameter (Fig. 1.7).
The mill is evacuated during milling to a pressure of 106 Torr, in order to avoid reactions with a gas atmosphere. Subsequently, this mill is suitable for mechanical alloying of some special systems that are highly reactive with the surrounding atmosphere, such as rare earth elements.
A ball mill is a relatively simple apparatus in which the motion of the reactor, or of a part of it, induces a series of collisions of balls with each other and with the reactor walls (Suryanarayana, 2001). At each collision, a fraction of the powder inside the reactor is trapped between the colliding surfaces of the milling tools and submitted to a mechanical load at relatively high strain rates (Suryanarayana, 2001). This load generates a local nonhydrostatic mechanical stress at every point of contact between any pair of powder particles. The specific features of the deformation processes induced by these stresses depend on the intensity of the mechanical stresses themselves, on the details of the powder particle arrangement, that is on the topology of the contact network, and on the physical and chemical properties of powders (Martin et al., 2003; Delogu, 2008a). At the end of any given collision event, the powder that has been trapped is remixed with the powder that has not undergone this process. Correspondingly, at any instant in the mechanical processing, the whole powder charge includes fractions of powder that have undergone a different number of collisions.
The individual reactive processes at the perturbed interface between metallic elements are expected to occur on timescales that are, at most, comparable with the collision duration (Hammerberg et al., 1998; Urakaev and Boldyrev, 2000; Lund and Schuh, 2003; Delogu and Cocco, 2005a,b). Therefore, unless the ball mill is characterized by unusually high rates of powder mixing and frequency of collisions, reactive events initiated by local deformation processes at a given collision are not affected by a successive collision. Indeed, the time interval between successive collisions is significantly longer than the time period required by local structural perturbations for full relaxation (Hammerberg et al., 1998; Urakaev and Boldyrev, 2000; Lund and Schuh, 2003; Delogu and Cocco, 2005a,b).
These few considerations suffice to point out the two fundamental features of powder processing by ball milling, which in turn govern the MA processes in ball mills. First, mechanical processing by ball milling is a discrete processing method. Second, it has statistical character. All of this has important consequences for the study of the kinetics of MA processes. The fact that local deformation events are connected to individual collisions suggests that absolute time is not an appropriate reference quantity to describe mechanically induced phase transformations. Such a description should rather be made as a function of the number of collisions (Delogu et al., 2004). A satisfactory description of the MA kinetics must also account for the intrinsic statistical character of powder processing by ball milling. The amount of powder trapped in any given collision, at the end of collision is indeed substantially remixed with the other powder in the reactor. It follows that the same amount, or a fraction of it, could at least in principle be trapped again in the successive collision.
This is undoubtedly a difficult aspect to take into account in a mathematical description of MA kinetics. There are at least two extreme cases to consider. On the one hand, it could be assumed that the powder trapped in a given collision cannot be trapped in the successive one. On the other, it could be assumed that powder mixing is ideal and that the amount of powder trapped at a given collision has the same probability of being processed in the successive collision. Both these cases allow the development of a mathematical model able to describe the relationship between apparent kinetics and individual collision events. However, the latter assumption seems to be more reliable than the former one, at least for commercial mills characterized by relatively complex displacement in the reactor (Manai et al., 2001, 2004).
A further obvious condition for the successful development of a mathematical description of MA processes is the one related to the uniformity of collision regimes. More specifically, it is highly desirable that the powders trapped at impact always experience the same conditions. This requires the control of the ball dynamics inside the reactor, which can be approximately obtained by using a single milling ball and an amount of powder large enough to assure inelastic impact conditions (Manai et al., 2001, 2004; Delogu et al., 2004). In fact, the use of a single milling ball avoids impacts between balls, which have a remarkable disordering effect on the ball dynamics, whereas inelastic impact conditions permit the establishment of regular and periodic ball dynamics (Manai et al., 2001, 2004; Delogu et al., 2004).
All of the above assumptions and observations represent the basis and guidelines for the development of the mathematical model briefly outlined in the following. It has been successfully applied to the case of a Spex Mixer/ Mill mod. 8000, but the same approach can, in principle, be used for other ball mills.
The Planetary ball mills are the most popular mills used in MM, MA, and MD scientific researches for synthesizing almost all of the materials presented in Figure 1.1. In this type of mill, the milling media have considerably high energy, because milling stock and balls come off the inner wall of the vial (milling bowl or vial) and the effective centrifugal force reaches up to 20 times gravitational acceleration.
The centrifugal forces caused by the rotation of the supporting disc and autonomous turning of the vial act on the milling charge (balls and powders). Since the turning directions of the supporting disc and the vial are opposite, the centrifugal forces alternately are synchronized and opposite. Therefore, the milling media and the charged powders alternatively roll on the inner wall of the vial, and are lifted and thrown off across the bowl at high speed, as schematically presented in Figure 2.17.
However, there are some companies in the world who manufacture and sell number of planetary-type ball mills; Fritsch GmbH (www.fritsch-milling.com) and Retsch (http://www.retsch.com) are considered to be the oldest and principal companies in this area.
Fritsch produces different types of planetary ball mills with different capacities and rotation speeds. Perhaps, Fritsch Pulverisette P5 (Figure 2.18(a)) and Fritsch Pulverisette P6 (Figure 2.18(b)) are the most popular models of Fritsch planetary ball mills. A variety of vials and balls made of different materials with different capacities, starting from 80ml up to 500ml, are available for the Fritsch Pulverisette planetary ball mills; these include tempered steel, stainless steel, tungsten carbide, agate, sintered corundum, silicon nitride, and zirconium oxide. Figure 2.19 presents 80ml-tempered steel vial (a) and 500ml-agate vials (b) together with their milling media that are made of the same materials.
Figure 2.18. Photographs of Fritsch planetary-type high-energy ball mill of (a) Pulverisette P5 and (b) Pulverisette P6. The equipment is housed in the Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR).
Figure 2.19. Photographs of the vials used for Fritsch planetary ball mills with capacity of (a) 80ml and (b) 500ml. The vials and the balls shown in (a) and (b) are made of tempered steel agate materials, respectively (Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR)).
More recently and in year 2011, Fritsch GmbH (http://www.fritsch-milling.com) introduced a new high-speed and versatile planetary ball mill called Planetary Micro Mill PULVERISETTE 7 (Figure 2.20). The company claims this new ball mill will be helpful to enable extreme high-energy ball milling at rotational speed reaching to 1,100rpm. This allows the new mill to achieve sensational centrifugal accelerations up to 95 times Earth gravity. They also mentioned that the energy application resulted from this new machine is about 150% greater than the classic planetary mills. Accordingly, it is expected that this new milling machine will enable the researchers to get their milled powders in short ball-milling time with fine powder particle sizes that can reach to be less than 1m in diameter. The vials available for this new type of mill have sizes of 20, 45, and 80ml. Both the vials and balls can be made of the same materials, which are used in the manufacture of large vials used for the classic Fritsch planetary ball mills, as shown in the previous text.
Retsch has also produced a number of capable high-energy planetary ball mills with different capacities (http://www.retsch.com/products/milling/planetary-ball-mills/); namely Planetary Ball Mill PM 100 (Figure 2.21(a)), Planetary Ball Mill PM 100 CM, Planetary Ball Mill PM 200, and Planetary Ball Mill PM 400 (Figure 2.21(b)). Like Fritsch, Retsch offers high-quality ball-milling vials with different capacities (12, 25, 50, 50, 125, 250, and 500ml) and balls of different diameters (540mm), as exemplified in Figure 2.22. These milling tools can be made of hardened steel as well as other different materials such as carbides, nitrides, and oxides.
Figure 2.21. Photographs of Retsch planetary-type high-energy ball mill of (a) PM 100 and (b) PM 400. The equipment is housed in the Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR).
Figure 2.22. Photographs of the vials used for Retsch planetary ball mills with capacity of (a) 80ml, (b) 250ml, and (c) 500ml. The vials and the balls shown are made of tempered steel (Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR)).
Both Fritsch and Retsch companies have offered special types of vials that allow monitoring and measure the gas pressure and temperature inside the vial during the high-energy planetary ball-milling process. Moreover, these vials allow milling the powders under inert (e.g., argon or helium) or reactive gas (e.g., hydrogen or nitrogen) with a maximum gas pressure of 500kPa (5bar). It is worth mentioning here that such a development made on the vials design allows the users and researchers to monitor the progress tackled during the MA and MD processes by following up the phase transformations and heat realizing upon RBM, where the interaction of the gas used with the freshly created surfaces of the powders during milling (adsorption, absorption, desorption, and decomposition) can be monitored. Furthermore, the data of the temperature and pressure driven upon using this system is very helpful when the ball mills are used for the formation of stable (e.g., intermetallic compounds) and metastable (e.g., amorphous and nanocrystalline materials) phases. In addition, measuring the vial temperature during blank (without samples) high-energy ball mill can be used as an indication to realize the effects of friction, impact, and conversion processes.
More recently, Evico-magnetics (www.evico-magnetics.de) has manufactured an extraordinary high-pressure milling vial with gas-temperature-monitoring (GTM) system. Likewise both system produced by Fritsch and Retsch, the developed system produced by Evico-magnetics, allowing RBM but at very high gas pressure that can reach to 15,000kPa (150bar). In addition, it allows in situ monitoring of temperature and of pressure by incorporating GTM. The vials, which can be used with any planetary mills, are made of hardened steel with capacity up to 220ml. The manufacturer offers also two-channel system for simultaneous use of two milling vials.
Using different ball mills as examples, it has been shown that, on the basis of the theory of glancing collision of rigid bodies, the theoretical calculation of tPT conditions and the kinetics of mechanochemical processes are possible for the reactors that are intended to perform different physicochemical processes during mechanical treatment of solids. According to the calculations, the physicochemical effect of mechanochemical reactors is due to short-time impulses of pressure (P = ~ 10101011 dyn cm2) with shift, and temperature T(x, t). The highest temperature impulse T ~ 103 K are caused by the dry friction phenomenon.
Typical spatial and time parameters of the impactfriction interaction of the particles with a size R ~ 104 cm are as follows: localization region, x ~ 106 cm; time, t ~ 108 s. On the basis of the obtained theoretical results, the effect of short-time contact fusion of particles treated in various comminuting devices can play a key role in the mechanism of activation and chemical reactions for wide range of mechanochemical processes. This role involves several aspects, that is, the very fact of contact fusion transforms the solid phase process onto another qualitative level, judging from the mass transfer coefficients. The spatial and time characteristics of the fused zone are such that quenching of non-equilibrium defects and intermediate products of chemical reactions occurs; solidification of the fused zone near the contact point results in the formation of a nanocrystal or nanoamor- phous state. The calculation models considered above and the kinetic equations obtained using them allow quantitative ab initio estimates of rate constants to be performed for any specific processes of mechanical activation and chemical transformation of the substances in ball mills.
There are two classes of ball mills: planetary and mixer (also called swing) mill. The terms high-speed vibration milling (HSVM), high-speed ball milling (HSBM), and planetary ball mill (PBM) are often used. The commercial apparatus are PBMs Fritsch P-5 and Fritsch Pulverisettes 6 and 7 classic line, the Retsch shaker (or mixer) mills ZM1, MM200, MM400, AS200, the Spex 8000, 6750 freezer/mill SPEX CertiPrep, and the SWH-0.4 vibrational ball mill. In some instances temperature controlled apparatus were used (58MI1); freezer/mills were used in some rare cases (13MOP1824).
The balls are made of stainless steel, agate (SiO2), zirconium oxide (ZrO2), or silicon nitride (Si3N). The use of stainless steel will contaminate the samples with steel particles and this is a problem both for solid-state NMR and for drug purity.
However, there are many types of ball mills (see Chapter 2 for more details), such as drum ball mills, jet ball mills, bead-mills, roller ball mills, vibration ball mills, and planetary ball mills, they can be grouped or classified into two types according to their rotation speed, as follows: (i) high-energy ball mills and (ii) low-energy ball mills. Table 3.1 presents characteristics and comparison between three types of ball mills (attritors, vibratory mills, planetary ball mills and roller mills) that are intensively used on MA, MD, and MM techniques.
In fact, choosing the right ball mill depends on the objectives of the process and the sort of materials (hard, brittle, ductile, etc.) that will be subjecting to the ball-milling process. For example, the characteristics and properties of those ball mills used for reduction in the particle size of the starting materials via top-down approach, or so-called mechanical milling (MM process), or for mechanically induced solid-state mixing for fabrications of composite and nanocomposite powders may differ widely from those mills used for achieving mechanically induced solid-state reaction (MISSR) between the starting reactant materials of elemental powders (MA process), or for tackling dramatic phase transformation changes on the structure of the starting materials (MD). Most of the ball mills in the market can be employed for different purposes and for preparing of wide range of new materials.
Martinez-Sanchez et al.  have pointed out that employing of high-energy ball mills not only contaminates the milled amorphous powders with significant volume fractions of impurities that come from milling media that move at high velocity, but it also affects the stability and crystallization properties of the formed amorphous phase. They have proved that the properties of the formed amorphous phase (Mo53Ni47) powder depends on the type of the ball-mill equipment (SPEX 8000D Mixer/Mill and Zoz Simoloter mill) used in their important investigations. This was indicated by the high contamination content of oxygen on the amorphous powders prepared by SPEX 8000D Mixer/Mill, when compared with the corresponding amorphous powders prepared by Zoz Simoloter mill. Accordingly, they have attributed the poor stabilities, indexed by the crystallization temperature of the amorphous phase formed by SPEX 8000D Mixer/Mill to the presence of foreign matter (impurities).
Ball mill is a very important mineral grading equipment, which is indispensable for mineral processing, building materials, metallurgy and chemical industry. With the need of market, a variety of different types of ball mills have emerged. According to different standards, there are many types of ball mills.
1. Short Cylinder Ball Mill: The ball mill with the cylinder length (L) less than 2 times of the cylinder diameter, i.e. the ball mill with L 2D is short cylinder ball mill, which is usually of single bin structure, mainly used for rough grinding or primary grinding operation, and can realize the wide use of 2-3 ball mills in series.
3. Gravel Mill: The grinding medium mainly includes pebble, gravel, sand, porcelain ball, etc. Most of the gravel mills use porcelain or granite as lining plates, which are widely used in the production of color cement, white cement, ceramics and other fields.
1. Tail Discharge Mill: The head and tail of tail discharge mill are used as the inlet and outlet of materials. When the mill is working, the material is fed from the inlet end and discharged from the other end.
2. Middle Discharge Mill: The inlet of the middle discharge mill is at both ends, and the outlet is in the middle of the mill. Generally, materials are fed from both ends and then discharged from the middle of the cylinder.
1. Center Drive Ball Mill: The drive power device is in the center of the fuselage, and the motor realizes the operation of the ball mill through the reducer. In operation, the hollow shaft in the center of the ball mill drives the grinding body to rotate under the drive of the power system.
1. Wet Type Ball Mill: Water is added at the same time of feeding, and the material is discharged into a certain concentration of slurry. In the closed-circuit system, it forms a closed-circuit operation with the hydraulic grading equipment.
1. Vertical Ball Mill: The vertical ball mill is a new type of ball mill which places the cylinder upright. Through a large number of experiments, it is found that the vertical ball mill has the advantages of high grinding efficiency, low energy consumption and low noise.
2. Horizontal Ball Mill: The horizontal ball mill is used for grinding and dispersing under the closed condition to prevent solvent volatilization. It is especially suitable for fine grinding and mixing of high-purity materials.