Hello, my partner! Let's explore the mining machine together!

[email protected]

how many ball mill in cement

how to improve the output of cement ball mill - zhongde heavy industries co.,ltd

how to improve the output of cement ball mill - zhongde heavy industries co.,ltd

Cement ball mill is the key equipment for grinding fine powder mainly used in cement industry. It also can grind many kinds of ores like iron ore, slag, copper ore, gold ore in ore beneficiation plant.

NOTE: please feel free to fill out the form below in detail and you can also send a message to us([email protected]) we will send you latest price within 24 hours.Besides, you can click Chat Online on the right hand side to get quotation online

the cement mill

the cement mill

Cement clinker is usually ground using a ball mill. This is essentially a large rotating drum containing grinding media - normally steel balls. As the drum rotates, the motion of the balls crushes the clinker. The drum rotates approximately once every couple of seconds.The drum is generally divided into two or three chambers, with different size grinding media. As the clinker particles are ground down, smaller media are more efficient at reducing the particle size still further.

Grinding systems are either 'open circuit' or 'closed circuit.' In an open circuit system, the feed rate of incoming clinker is adjusted to achieve the desired fineness of the product. In a closed circuit system, coarse particles are separated from the finer product and returned for further grinding.Gypsum is interground with the clinker in order to control the setting properties of the cement. Clinker grinding uses a lot of energy and the cement becomes hot - this can result in the gypsum becoming dehydrated, with potentially undesirable results - see the link at the bottom of this page for more information.

Articles like this one can provide a lot of useful material. However, reading an article or two is perhaps not the best way to get a clear picture of a complex process like cement production. To get a more complete and integrated understanding of how cement is made, do have a look at the Understanding Cement book or ebook. This easy-to-read and concise book also contains much more detail on concrete chemistry and deleterious processes in concrete compared with the website.

Almost everyone interested in cement is also concerned to at least some degree with concrete strength. This ebook describes ten cement-related characteristics of concrete that can potentially cause strengths to be lower than expected. Get the ebook FREE when you sign up to CEMBYTES, our Understanding Cement Newsletter - just click on the ebook image above.

how to improve ball mill performance

how to improve ball mill performance

Application of value engineering techniques to grinding process modelling led to the identification of two basic functions of the ball mill-classifier circuit. In terms of a specified circuit product size which is used to differentiate between coarse or oversize material and fines or undersize material, these basic functions are (a) breakage of the coarse material and (b) removal of the fines. It was proposed that it may be useful to relate circuit design and operating variables to these basic circuit functions, which although related, are conceptually quite distinguishable. If each could be quantified by a suitable parameter, then either or the two together may be correlated to overall circuit efficiency, and hence used to link individual design and operating variables to overall circuit performance.

Major design and operating variables in closed circuit ball milling of a specified feed to a desired product size are summarized in Table 1. The purpose of process modelling is to establish cause and effect relationships between physical design and operating variables and the performance objectives of the circuit. Subsequently, output and efficiency can be maximized. The fundamental issue addressed by ball mill circuit modelling is thus depicted in Figure 1 (McIvor, 1989).

In the simplest form of plant experimentation, a key performance parameter (such as the fineness of the final product) is measured with and without a specific change to the circuit. Within the constraints imposed by the accuracy of measurements and assumptions about the constancy of other inputs (including the ore characteristics), the relative values of this parameter are used to evaluate the effect of the change on circuit performance.

Bond work index analysis takes this method of experimentation several steps further. During comparative testwork, variations in the ore grindability, grinding energy input, and feed and product sizing are measured and accounted for through the grinding circuit model embodied in the work index formulation. For each set of data, both the circuit operating work index and the laboratory test work index of the circuit feed are determined. Relative work index efficiencies with and without the change to the circuit can then be calculated and compared.

Consider a ball mill circuit processing material of a given feed size and at a given throughput rate to a target product size, the latter which once again distinguishes the fines from the coarse material. The production rate of fines or new product size material can be calculated from the circuit feed and product size distributions and the throughput rate of the circuit. Based on the energy expended in the ball mill, the production rate of new product size material (tonnes/h) equals the amount produced per unit of energy applied (tonnes/kwh) times the rate at which energy is applied (kwh/h). The rate at which energy is applied is the power draw of the ball mill. If we then define the production per unit, of energy applied as the energy specific production rate of the circuit, then we can write the following equation:

All the production of new product size material takes place in the mill as coarse is ground into fines. However, the proportion of the total mill power applied to size reduction of coarse particles is equal to the fraction of coarse solids inventory, or the so defined circuit classification system efficiency.

The mill specific grinding rate reflects both the efficiency of the mill environment in breaking the coarse particles, as well as the grindability characteristic of the ore over the particular size reduction range.

To arrive at a term which reflects only the efficiency of the mill environment, we must factor out the grindability of the ore, such as the net grams per revolution measured in a Bond work index test. This will yield the specific grinding rate in the plant ball mill relative to the measured specific grinding rate in a standard test mill, and may be termed the grinding rate ratio.

The grinding rate ratio may be considered dimensionless because each revolution of the test mill requires a fixed amount of power. It is based on breakage of only the coarse material in both the plant ball mill and the standard laboratory test mill. It is therefore proposed that the grinding rate ratio is a direct measure of the relative overall breakage efficiency of the environment of the plant ball mill.

The above described parameters for system breakage and classification system efficiency factor the overall task of the ball mill circuit into its two distinct basic functions, namely, fines generation and fines removal. The effect of design and operating variables on each can be studied separately, and when the product of the two is maximized, maximum overall circuit efficiency will be achieved. Equation 2 may be re-written as:

This has been termed the ball mill circuit functional performance equation (McIvor, 1989). It states that the output of new product size material of a ball mill circuit with a given feed size is determined by:

a. the total mill power draw; b. the classification system efficiency, which defines the fraction of the total mill power effectively applied to the grinding of coarse material; c. the grindability characteristic of the ore over the size reduction range of the circuit; and, d. the breakage efficiency of the ball mill environment on the coarse material.

While all four factors clearly influence the circuit output, overall circuit efficiency will be determined by classification and breakage efficiency. Specific design and operating variables can now be considered in terms of their individual effects on classification and breakage efficiency, and subsequently on the overall efficiency of the circuit. This provides an intermediate level of ball mill circuit performance characterization, as shown in Figure 5.

how to improve cement ball mill performance in closed circuit grinding system

how to improve cement ball mill performance in closed circuit grinding system

There are many factors that may affect the ball mills working efficiency and product quality during the operation. In this article, we will discuss the measures that can improve the ball mills performance.

The particle size of the feed material is an important process parameter that restricts the grinding efficiency of the ball mill. Due to the different physical and chemical properties and microhardness of the materials (the grindability of materials in raw meals decreases in clinkers), the clinker discharged from the cement kiln must be pretreated to reduce its particle size so as to increase the output and reduce the power consumption of the ball mill.

From table 1 we can learn that if the particle size of the feed material is reduced from 25 mm to less than 2 mm, the mill output can be increased by at least 60%, which is relatively consistent with the actual production.

There are two methods for clinker pretreatment: pre-crushing and pre-grinding. 1) The pre-crushing uses a crusher to crush the clinker before grinding, which can reduce the diameter of clinker particle to 5 ~ 8mm. 2) The pre-grinding adds a roller press to the cement grinding system. In this system, the clinker is extruded circularly, dispersed and separated, and becomes powder with diameter less than 2 mm;

The gradation of grinding media is also an important factor in improving the efficiency of ball mills. A reasonable gradation can only be calculated after analyzing the performance of the mill, the property of the feed material, and equipment layout in the closed-circuit grinding system.

The size of the grinding media is calculated based on the grinding capacity of the mill and the size of the feed material. Because of the complex movement of the grinding media and the material in the mill, and because the actual production situation of each cement plant is different, it is difficult to determine a universally applicable grading rule. Only through long-term production practice can we get the appropriate gradation scheme.

The gradation of grinding media is constantly changing in the process of mill operation, and the wear law of different size of grinding media is also different. Therefore, the supplementary of grinding media can only keep the loading capacity relatively balanced, but can not keep the gradation consistent.

The stable grinding process largely depends on the material of grinding medium. Different materials of grinding media lead to different wear consumption. If the hardness and wear resistance of the grinding media are poor, it is easy to deform and crack during the operation, which not only affects the grinding efficiency and blocks the grate gap, but also makes the partition device difficult to discharge material, and finally leads to the deterioration of the mill operation. Therefore, improving the quality of the grinding media is an effective way to ensure the long-term stable operation of the mill, otherwise, no matter how reasonable the grading scheme is, it is difficult to ensure that the expected grinding effect can always be achieved.

Once the grinding media and other equipment is properly selected for the grinding system, then the gradation can be determined according to the particle size of the feed material. However, no matter how reasonable the grading scheme is, it is always relative.

The ball bearing height of ball mills can be different due to different specifications, diameters, rotating speeds and liner forms of the ball mills. And the potential energy produced by different height of the ball is completely different. Therefore, the reasonable grinding ball diameter should not only match with the mill specifications, but also adapt to the liner form of the mill.

Large size mills with lifting liner bring grinding balls to higher heights and generate stronger impact force, so the diameter of grinding balls can be smaller. The ball diameter should be different according to the aging degree of the inner liner: new liners bring grinding balls to higher height, so the ball size can be smaller.

It can be seen from the experiment that when a grinding ball with a diameter of 70 mm falls freely from the height of 40 cm, its potential energy can completely crush a clinker particle with a diameter of 25 mm. Therefore, the minimum ball diameter should be selected on the premise of sufficient impact energy to increase the number of grinding balls, increase the impact times of balls on materials, and improve the grinding efficiency.

Table 2 and table 3 show the relationship between the material particle size and the grinding ball diameter for reference only. When determining the ball diameter, it is necessary to adjust it according to the cement plants own situation.

energy efficient cement ball mill from flsmidth

energy efficient cement ball mill from flsmidth

You decide whether to operate the mill in open or closed circuit, with or without a pre-grinder and with side or central drive, according to your plant layout and end product specifications. Even the lining types are tailored to your operating parameters.

In addition, the large through-flow areas enable the mill to operate with large volumes of venting air and a low pressure drop across the mill. This reduces the energy consumption of the mill ventilation fan and keeps your energy costs down.

The mill is based on standard modules and can be adapted to your plant layout, end product specifications and drive type. The horizontal slide shoe bearing design enables much simpler foundations and reduced installation height, making installation quicker and less expensive.

Our shell linings are designed to suit the task at hand. In our two-compartment cement mills, the first compartment (for coarse grinding) has a step lining suitable for large grinding media. It protects the shell while ensuring optimum lifting of the mill charge. In the second compartment (and also in our one-compartment cement mills) we use a corrugated lining designed to obtain the maximum power absorption and grinding efficiency. For special applications, we can supply a classifying shell lining for fine grinding in the mill.

In fact, the entire mill is protected with bolted on lining plates designed for the specific wear faced by each part of the mill. This attention to detail ensures both minimal wear and easy maintenance. When a wear part has reached the end of its life, it is easily replaced.

The grinding media are supplied in various sizes to ensure optimum grinding efficiency. The STANEX diaphragm is designed to maximise the effective grinding area, enabling a higher throughput. It is fitted with adjustable lifters to ensure the material levels in each compartment are right. Best of all, the STANEX diaphragm works for all applications, even when material flow rates are high and the mill feed is moist.

The mills are typically driven by our FLSmidth MAAG LGDX side drive - gearing rated to the latest proven AGMA standards. The mill drive is provided with an auxiliary drive for slow turning of the mill. The LGDX includes two independent lubrication systems, one which services the girth gear guard and intakes more dust, and a second which supplies oil for the fast-rotating gearing and bearings and stays clean. If requested, however, the mills can be provided with a central drive: the FLSmidth MAAG CPU planetary gearbox. The mill design differs slightly, depending on whether the side or central drive is chosen.

Each grinding compartment has two man-hole covers to give easy access for maintenance. As there are minimal moving parts, the maintenance requirement is low and simple changes like replacing wear linings and topping up grinding media can be completed quickly and easily. Horizontal slide shoe bearings prevent oil spillages from the casing and offers easy replacement of slide shoes.

Buying a new mill is a huge investment. With over a century of ball mill experience and more than 4000 installations worldwide, rest assured we have the expertise to deliver the right solution for your project. Our ball mill is based on standard modules and the highly flexible design can be adapted to your requirements. The mill comprises the following parts.

The mill body consists of an all-welded mill shell and a T-sectional welded-up slide ring at either end, the cylindrical part of which is welded onto the ends of the shell. The mill shell has four manholes, two for each grinding compartment.

Each slide ring runs in a bearing with two self-aligning and hydrodynamically lubricated slide shoes. One of the slide shoes at the drive end holds the mill in axial direction. In the others, the slide rings can move freely in axial direction to allow for longitudinal thermal expansion and contraction of the mill body.

The slide shoes are water-cooled, and each bearing is provided with a panel-enclosed lubrication unit including oil tank, motorised low- and high-pressure oil pumps, as well as an oil conditioning circuit with motorised pump for heating/cooling and filtration of the oil.

The stationary steel plate inlet duct leads the venting air into the mill. It is equipped with a manually operated throttle valve and a pressure monitor to adjust the pressure at the inlet end, thus preventing dust emission from the inlet. The feed chute is lined with bolted-on wear plates and slopes down through the air duct to the mill inlet opening.

The more control you have over the mill, the better your grinding efficiency is likely to be. Our ball mills include monitoring systems to continuously measure the material and air temperatures as well as the pressure at the mill exit. The venting of the mill is adjusted by a damper in the inlet to the mill fan. And the material fill level is continuously monitored by means of sensors. For ball mills operating in closed circuit, the circulation load is monitored by weighing the flow of reject material from the separator. These measures ensure you achieve optimum mill performance, giving you the quality, efficiency, safetyand reliability that you need.

FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.

ball mills - an overview | sciencedirect topics

ball mills - an overview | sciencedirect topics

A ball mill is a type of grinder used to grind and blend bulk material into QDs/nanosize using different sized balls. The working principle is simple; impact and attrition size reduction take place as the ball drops from near the top of a rotating hollow cylindrical shell. The nanostructure size can be varied by varying the number and size of balls, the material used for the balls, the material used for the surface of the cylinder, the rotation speed, and the choice of material to be milled. Ball mills are commonly used for crushing and grinding the materials into an extremely fine form. The ball mill contains a hollow cylindrical shell that rotates about its axis. This cylinder is filled with balls that are made of stainless steel or rubber to the material contained in it. Ball mills are classified as attritor, horizontal, planetary, high energy, or shaker.

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.

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 the movement of particles within the mill and contact zones of colliding balls.

By the rotation of the mill body, due to friction between the mill wall and balls, the latter rise in the direction of rotation until a helix angle does not exceed the angle of repose, whereupon the balls roll down. Increasing the rotation rate leads to the growth of the centrifugal force and the helix angle increases, correspondingly, until the component of the weight strength of balls becomes larger than the centrifugal force. From this moment, the balls are beginning to fall down, describing certain parabolic curves during the fall (Fig. 2.10).

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 remain attached to the wall with the aid of centrifugal force is:

where Dm is the mill diameter in meters. The optimum rotational speed is usually set at 65%80% of the critical speed. These data are approximate and may not be valid for metal particles that tend to agglomerate by welding.

where db.max is the maximum size of the feed (mm), is the compression strength (MPa), E is the modulus of elasticity (MPa), b is the density of material of balls (kg/m3), and D is the inner diameter of the mill body (m).

The degree of filling the mill with balls also influences the 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 30%35% of its volume.

The productivity of ball mills depends on the drum diameter and the relation of drum diameter and length. The optimum ratio between length L and diameter D, L:D, is usually accepted in the range 1.561.64. The mill productivity also depends on many other factors, including the physical-chemical properties of the feed material, the filling of the mill by balls and their sizes, the armor surface shape, the speed of rotation, the milling fineness, and the timely moving off of the ground product.

where D is the drum diameter, L is the drum length, b.ap is the apparent density of the balls, is the degree of filling of the mill by balls, n is the revolutions per minute, and 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, that is, during the grinding of material. Therefore, it is most disadvantageous to use a ball mill at less than full capacity.

Milling time in tumbler mills is longer to accomplish the same level of blending achieved in the attrition or vibratory mill, but the overall productivity is substantially greater. Tumbler mills usually are used to pulverize or flake metals, using a grinding aid or lubricant to prevent cold welding agglomeration and to minimize oxidation [23].

Cylindrical Ball Mills differ usually in steel drum design (Fig. 2.11), which is lined inside by armor slabs that have dissimilar sizes and form a rough inside surface. Due to such juts, the impact force of falling balls is strengthened. The initial material is fed into the mill by a screw feeder located in a hollow trunnion; the ground product is discharged through the opposite hollow trunnion.

Cylindrical screen ball mills have a drum with spiral curved plates with longitudinal slits between them. The ground product passes into these slits and then through a cylindrical sieve and is discharged via the unloading funnel of the mill body.

Conical Ball Mills differ in mill body construction, which is composed of two cones and a short cylindrical part located between them (Fig. 2.12). Such a ball mill body is expedient because efficiency is appreciably increased. Peripheral velocity along the conical drum scales down in the direction from the cylindrical part to the discharge outlet; the helix angle of balls is decreased and, consequently, so is their kinetic energy. The size of the disintegrated particles also decreases as the discharge outlet is approached and the energy used decreases. In a conical mill, most big balls take up a position in the deeper, cylindrical part of the body; thus, the size of the balls scales down in the direction of the discharge outlet.

For emptying, the conical mill is installed with a slope from bearing to one. In wet grinding, emptying is realized by the decantation principle, that is, by means of unloading through one of two trunnions.

With dry grinding, these mills often work in a closed cycle. A scheme of the conical ball mill supplied with an air separator is shown in Fig. 2.13. Air is fed to the mill by means of a fan. Carried off by air currents, the product arrives at the air separator, from which the coarse particles are returned by gravity via a tube into the mill. The finished product is trapped in a cyclone while the air is returned in the fan.

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).

Modern ball mills consist of two chambers separated by a diaphragm. In the first chamber the steel-alloy balls (also described as charge balls or media) are about 90mm diameter. The mill liners are designed to lift the media as the mill rotates, so the comminution process in the first chamber is dominated by crushing. In the second chamber the ball diameters are of smaller diameter, between 60 and 15mm. In this chamber the lining is typically a classifying lining which sorts the media so that ball size reduces towards the discharge end of the mill. Here, comminution takes place in the rolling point-contact zone between each charge ball. An example of a two chamber ball mill is illustrated in Fig. 2.22.15

Much of the energy consumed by a ball mill generates heat. Water is injected into the second chamber of the mill to provide evaporative cooling. Air flow through the mill is one medium for cement transport but also removes water vapour and makes some contribution to cooling.

Grinding is an energy intensive process and grinding more finely than necessary wastes energy. Cement consists of clinker, gypsum and other components mostly more easily ground than clinker. To minimise over-grinding modern ball mills are fitted with dynamic separators (otherwise described as classifiers or more simply as separators). The working principle is that cement is removed from the mill before over-grinding has taken place. The cement is then separated into a fine fraction, which meets finished product requirements, and a coarse fraction which is returned to mill inlet. Recirculation factor, that is, the ratio of mill throughput to fresh feed is up to three. Beyond this, efficiency gains are minimal.

For more than 50years vertical mills have been the mill of choice for grinding raw materials into raw meal. More recently they have become widely used for cement production. They have lower specific energy consumption than ball mills and the separator, as in raw mills, is integral with the mill body.

In the Loesche mill, Fig. 2.23,16 two pairs of rollers are used. In each pair the first, smaller diameter, roller stabilises the bed prior to grinding which takes place under the larger roller. Manufacturers use different technologies for bed stabilisation.

Comminution in ball mills and vertical mills differs fundamentally. In a ball mill, size reduction takes place by impact and attrition. In a vertical mill the bed of material is subject to such a high pressure that individual particles within the bed are fractured, even though the particles are very much smaller than the bed thickness.

Early issues with vertical mills, such as narrower PSD and modified cement hydration characteristics compared with ball mills, have been resolved. One modification has been to install a hot gas generator so the gas temperature is high enough to partially dehydrate the gypsum.

For many decades the two-compartment ball mill in closed circuit with a high-efficiency separator has been the mill of choice. In the last decade vertical mills have taken an increasing share of the cement milling market, not least because the specific power consumption of vertical mills is about 30% less than that of ball mills and for finely ground cement less still. The vertical mill has a proven track record in grinding blastfurnace slag, where it has the additional advantage of being a much more effective drier of wet feedstock than a ball mill.

The vertical mill is more complex but its installation is more compact. The relative installed capital costs tend to be site specific. Historically the installed cost has tended to be slightly higher for the vertical mill.

Special graph paper is used with lglg(1/R(x)) on the abscissa and lg(x) on the ordinate axes. The higher the value of n, the narrower the particle size distribution. The position parameter is the particle size with the highest mass density distribution, the peak of the mass density distribution curve.

Vertical mills tend to produce cement with a higher value of n. Values of n normally lie between 0.8 and 1.2, dependent particularly on cement fineness. The position parameter is, of course, lower for more finely ground cements.

Separator efficiency is defined as specific power consumption reduction of the mill open-to-closed-circuit with the actual separator, compared with specific power consumption reduction of the mill open-to-closed-circuit with an ideal separator.

As shown in Fig. 2.24, circulating factor is defined as mill mass flow, that is, fresh feed plus separator returns. The maximum power reduction arising from use of an ideal separator increases non-linearly with circulation factor and is dependent on Rf, normally based on residues in the interval 3245m. The value of the comminution index, W, is also a function of Rf. The finer the cement, the lower Rf and the greater the maximum power reduction. At C = 2 most of maximum power reduction is achieved, but beyond C = 3 there is very little further reduction.

Separator particle separation performance is assessed using the Tromp curve, a graph of percentage separator feed to rejects against particle size range. An example is shown in Fig. 2.25. Data required is the PSD of separator feed material and of rejects and finished product streams. The bypass and slope provide a measure of separator performance.

The particle size is plotted on a logarithmic scale on the ordinate axis. The percentage is plotted on the abscissa either on a linear (as shown here) or on a Gaussian scale. The advantage of using the Gaussian scale is that the two parts of the graph can be approximated by two straight lines.

The measurement of PSD of a sample of cement is carried out using laser-based methodologies. It requires a skilled operator to achieve consistent results. Agglomeration will vary dependent on whether grinding aid is used. Different laser analysis methods may not give the same results, so for comparative purposes the same method must be used.

The ball mill is a cylindrical drum (or cylindrical conical) turning around its horizontal axis. It is partially filled with grinding bodies: cast iron or steel balls, or even flint (silica) or porcelain bearings. Spaces between balls or bearings are occupied by the load to be milled.

Following drum rotation, balls or bearings rise by rolling along the cylindrical wall and descending again in a cascade or cataract from a certain height. The output is then milled between two grinding bodies.

Ball mills could operate dry or even process a water suspension (almost always for ores). Dry, it is fed through a chute or a screw through the units opening. In a wet path, a system of scoops that turn with the mill is used and it plunges into a stationary tank.

Mechanochemical synthesis involves high-energy milling techniques and is generally carried out under controlled atmospheres. Nanocomposite powders of oxide, nonoxide, and mixed oxide/nonoxide materials can be prepared using this method. The major drawbacks of this synthesis method are: (1) discrete nanoparticles in the finest size range cannot be prepared; and (2) contamination of the product by the milling media.

More or less any ceramic composite powder can be synthesized by mechanical mixing of the constituent phases. The main factors that determine the properties of the resultant nanocomposite products are the type of raw materials, purity, the particle size, size distribution, and degree of agglomeration. Maintaining purity of the powders is essential for avoiding the formation of a secondary phase during sintering. Wet ball or attrition milling techniques can be used for the synthesis of homogeneous powder mixture. Al2O3/SiC composites are widely prepared by this conventional powder mixing route by using ball milling [70]. However, the disadvantage in the milling step is that it may induce certain pollution derived from the milling media.

In this mechanical method of production of nanomaterials, which works on the principle of impact, the size reduction is achieved through the impact caused when the balls drop from the top of the chamber containing the source material.

A ball mill consists of a hollow cylindrical chamber (Fig. 6.2) which rotates about a horizontal axis, and the chamber is partially filled with small balls made of steel, tungsten carbide, zirconia, agate, alumina, or silicon nitride having diameter generally 10mm. The inner surface area of the chamber is lined with an abrasion-resistant material like manganese, steel, or rubber. The magnet, placed outside the chamber, provides the pulling force to the grinding material, and by changing the magnetic force, the milling energy can be varied as desired. The ball milling process is carried out for approximately 100150h to obtain uniform-sized fine powder. In high-energy ball milling, vacuum or a specific gaseous atmosphere is maintained inside the chamber. High-energy mills are classified into attrition ball mills, planetary ball mills, vibrating ball mills, and low-energy tumbling mills. In high-energy ball milling, formation of ceramic nano-reinforcement by in situ reaction is possible.

It is an inexpensive and easy process which enables industrial scale productivity. As grinding is done in a closed chamber, dust, or contamination from the surroundings is avoided. This technique can be used to prepare dry as well as wet nanopowders. Composition of the grinding material can be varied as desired. Even though this method has several advantages, there are some disadvantages. The major disadvantage is that the shape of the produced nanoparticles is not regular. Moreover, energy consumption is relatively high, which reduces the production efficiency. This technique is suitable for the fabrication of several nanocomposites, which include Co- and Cu-based nanomaterials, Ni-NiO nanocomposites, and nanocomposites of Ti,C [71].

Planetary ball mill was used to synthesize iron nanoparticles. The synthesized nanoparticles were subjected to the characterization studies by X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques using a SIEMENS-D5000 diffractometer and Hitachi S-4800. For the synthesis of iron nanoparticles, commercial iron powder having particles size of 10m was used. The iron powder was subjected to planetary ball milling for various period of time. The optimum time period for the synthesis of nanoparticles was observed to be 10h because after that time period, chances of contamination inclined and the particles size became almost constant so the powder was ball milled for 10h to synthesize nanoparticles [11]. Fig. 12 shows the SEM image of the iron nanoparticles.

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.[44] 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.

In spite of the traditional approaches used for gas-solid reaction at relatively high temperature, Calka etal.[58] and El-Eskandarany etal.[59] proposed a solid-state approach, the so-called reactive ball milling (RBM), used for preparations different families of meal nitrides and hydrides at ambient temperature. This mechanically induced gas-solid reaction can be successfully achieved, using either high- or low-energy ball-milling methods, as shown in Fig.9.5. However, high-energy ball mill is an efficient process for synthesizing nanocrystalline MgH2 powders using RBM technique, it may be difficult to scale up for matching the mass production required by industrial sector. Therefore, from a practical point of view, high-capacity low-energy milling, which can be easily scaled-up to produce large amount of MgH2 fine powders, may be more suitable for industrial mass production.

In both approaches but with different scale of time and milling efficiency, the starting Mg metal powders milled under hydrogen gas atmosphere are practicing to dramatic lattice imperfections such as twinning and dislocations. These defects are caused by plastics deformation coupled with shear and impact forces generated by the ball-milling media.[60] The powders are, therefore, disintegrated into smaller particles with large surface area, where very clean or fresh oxygen-free active surfaces of the powders are created. Moreover, these defects, which are intensively located at the grain boundaries, lead to separate micro-scaled Mg grains into finer grains capable to getter hydrogen by the first atomically clean surfaces to form MgH2 nanopowders.

Fig.9.5 illustrates common lab scale procedure for preparing MgH2 powders, starting from pure Mg powders, using RBM via (1) high-energy and (2) low-energy ball milling. The starting material can be Mg-rods, in which they are processed via sever plastic deformation,[61] using for example cold-rolling approach,[62] as illustrated in Fig.9.5. The heavily deformed Mg-rods obtained after certain cold rolling passes can be snipped into small chips and then ball-milled under hydrogen gas to produce MgH2 powders.[8]

Planetary ball mills are the most popular mills used in scientific research for synthesizing MgH2 nanopowders. In this type of mill, the ball-milling media have considerably high energy, because milling stock and balls come off the inner wall of the 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.

In the typical experimental procedure, a certain amount of the Mg (usually in the range between 3 and 10g based on the vials volume) is balanced inside an inert gas atmosphere (argon or helium) in a glove box and sealed together with certain number of balls (e.g., 2050 hardened steel balls) into a hardened steel vial (Fig.9.5A and B), using, for example, a gas-temperature-monitoring system (GST). With the GST system, it becomes possible to monitor the progress of the gas-solid reaction taking place during the RBM process, as shown in Fig.9.5C and D. The temperature and pressure changes in the system during milling can be also used to realize the completion of the reaction and the expected end product during the different stages of milling (Fig.9.5D). The ball-to-powder weight ratio is usually selected to be in the range between 10:1 and 50:1. The vial is then evacuated to the level of 103bar before introducing H2 gas to fill the vial with a pressure of 550bar (Fig.9.5B). The milling process is started by mounting the vial on a high-energy ball mill operated at ambient temperature (Fig.9.5C).

Tumbling mill is cylindrical shell (Fig.9.6AC) that rotates about a horizontal axis (Fig.9.6D). Hydrogen gas is pressurized into the vial (Fig.9.6C) together with Mg powders and ball-milling media, using ball-to-powder weight ratio in the range between 30:1 and 100:1. Mg powder particles meet the abrasive and impacting force (Fig.9.6E), which reduce the particle size and create fresh-powder surfaces (Fig.9.6F) ready to react with hydrogen milling atmosphere.

Figure 9.6. Photographs taken from KISR-EBRC/NAM Lab, Kuwait, show (A) the vial and milling media (balls) and (B) the setup performed to charge the vial with 50bar of hydrogen gas. The photograph in (C) presents the complete setup of GST (supplied by Evico-magnetic, Germany) system prior to start the RBM experiment for preparing of MgH2 powders, using Planetary Ball Mill P400 (provided by Retsch, Germany). GST system allows us to monitor the progress of RBM process, as indexed by temperature and pressure versus milling time (D).

The useful kinetic energy in tumbling mill can be applied to the Mg powder particles (Fig.9.7E) by the following means: (1) collision between the balls and the powders; (2) pressure loading of powders pinned between milling media or between the milling media and the liner; (3) impact of the falling milling media; (4) shear and abrasion caused by dragging of particles between moving milling media; and (5) shock-wave transmitted through crop load by falling milling media. One advantage of this type of mill is that large amount of the powders (100500g or more based on the mill capacity) can be fabricated for each milling run. Thus, it is suitable for pilot and/or industrial scale of MgH2 production. In addition, low-energy ball mill produces homogeneous and uniform powders when compared with the high-energy ball mill. Furthermore, such tumbling mills are cheaper than high-energy mills and operated simply with low-maintenance requirements. However, this kind of low-energy mill requires long-term milling time (more than 300h) to complete the gas-solid reaction and to obtain nanocrystalline MgH2 powders.

Figure 9.7. Photos taken from KISR-EBRC/NAM Lab, Kuwait, display setup of a lab-scale roller mill (1000m in volume) showing (A) the milling tools including the balls (milling media and vial), (B) charging Mg powders in the vial inside inert gas atmosphere glove box, (C) evacuation setup and pressurizing hydrogen gas in the vial, and (D) ball milling processed, using a roller mill. Schematic presentations show the ball positions and movement inside the vial of a tumbler mall mill at a dynamic mode is shown in (E), where a typical ball-powder-ball collusion for a low energy tumbling ball mill is presented in (F).

cement ball mill - jxsc machine

cement ball mill - jxsc machine

The cement ball mill is mainly used for grinding the finished products and raw materials of cement plants, and is also suitable for grinding various ore and other grindable materials in industrial and mining enterprises such as metallurgy, chemical industry, and electric power. Cement grinding is the last process of cement production, it is to mix cement clinker and a small amount of gypsum, and then grind the mixture to a certain fineness, that is cement. You may also interest in the ball mill product price, lime ball mill, quartz ball mill. Cement grinder types Cement ball mills can be divided according to discharge method: grate ball mills and overflow mills, and can be divided into wet mills and dry mills according to their processing conditions.

The main working part of the cement grinding mill is a rotary cylinder mounted on two large bearings and placed horizontally. The cylinder is divided into several chambers by a partition plate, and a certain shape and size of grinding bodies are installed in each chamber. The grinding bodies are generally steel balls, steel forgings, steel rods, pebbles, gravel, and porcelain balls. In order to prevent the cylinder from being worn, a liner is installed on the inner wall of the cylinder. When the cement grinding machine rotates, the grinding media adheres to the lining surface of the inner wall of the cylinder under the action of centrifugal force and frictional force with the lining surface of the inner surface of the cylinder, and rotates with the cylinder and is brought to a certain height. Under the action of gravity, it falls freely. When falling, the grinding media acts as a projectile and impacts the material at the bottom to crush the material. The cyclic motion of the abrasive body rising and falling is repeated. In addition, during the rotation of the mill, the grinding body also slides and rolls, so the grinding action occurs between the grinding body, the liner and the material, making the material fine. As new materials are continuously fed at the feed end, there is a material level difference between the feed and discharge end materials to force the material to flow, and the axial thrust of the impact material when the grinding body falls also breaks the material flow. Air movement also helps material flow. Therefore, although the mill barrel is placed horizontally, the material can slowly flow from the feed end to the discharge end to complete the grinding operation.

Ball mill liner The liner of cement dry-type ball mill can be divided into ceramic, granite, rubber, high manganese, magnetic liner and other materials. The function of liner is mainly to protect the cylinder from the direct impact of materials and steel balls and extend the service life. At the same time, the liner plate can also adjust the running track of materials. Generally, the head grinding bin is equipped with hard liner plate, which can enhance the impact force of materials and accelerate grinding. The liner plate of the fine grinding bin is corrugated liner plate or flat liner plate, which can enhance the grinding effect of materials.

Ball mill grinding medium The grinding medium of cement dry ball mill includes steel ball, steel rod, steel pipe, stone, porcelain ball, etc. the steel ball is divided into cast iron, bearing steel, carbon steel and other materials, and the diameter of steel ball varies from 15mm to 125mm. The steel bar is short cylindrical or conical, which has line surface contact with the material and strong grinding effect.

Cement ball mill advantages 1. It has strong adaptability to materials, continuous production and large processing capacity. The equipment has stable performance, is convenient for large-scale production, and meets the needs of large-scale production of modern enterprises. 2. The crushing ratio is large, the feeding size can reach 50 mm, the discharging particle size can be controlled, and the particle quality is good. 3. Cement dry-type ball mill is mainly used for grinding raw materials and clinker (finished products and raw materials) in cement plant, and also for grinding various ores and other grindable materials in metallurgy, chemical industry, electric power and other industrial and mining enterprises. It can be used for open flow grinding and circular flow grinding composed of powder concentrator. 4. The structure is reasonable, firm and can be operated under negative pressure. Cement dry ball mill has good sealing performance, environmental protection, simple maintenance, safe and reliable operation. Disadvantages But at present, the overall efficiency of cement dry-type ball mill grinding is low and energy consumption is large. Although the rolling bearing transmission mode is used now, the cement mill process is still the most power consuming part of the enterprise. Moreover, the cement dry-type ball mill is generally medium and long grinding, with large investment and high cost.

The application of ball mill in cement industry dates back more than 100 years. The ball mill for cement grinding plant is mainly of high fineness, dry grinding method, and the process is mainly of open circuit process and closed circuit process. The equipment of ball mill used in cement plant includes vertical cement mill, roller press and ball mill, etc.

The cement ball mill in cement plant is usually divided into 2-4 silos, the most representative of which are the new type of high fineness cement ball mill and open flow high fineness cement ball mill. There are three cement processing circuits. 1. Open circuit grinding The ball mill in the cement plant for open circuit grinding consists of grinding bin, dust collector and ball mill. Advantages: the cement plant process is the simplest, with less investment and simple operation and maintenance. Disadvantages: serious over grinding in the mill, low efficiency, difficulty in fineness adjustment of finished products, high power consumption.

2. Closed circuit grinding Closed-circuit grinding is widely used in cement mills all over the world. Cement grinding unit is widely used in the United States, Germany, France, Japan and other developed countries. For example, 95% of cement in Japan comes from closed-circuit grinding. The cement plant machinery of closed-circuit grinding consists of feeding system, finished product bin, powder concentrator and dust collection equipment. The process is relatively complete. The disadvantages are a large investment, many equipment and complex operation.

According to many years of practical production experience, JXSC summarizes that cement producers with a production capacity of fewer than 30 tons per hour are suitable for open circuit grinding, and closed-circuit grinding for large-scale production can be more economical.

Matters need attention 1. Cement has corrosion, which affects the service life of steel ball and increases the production cost. 2. Different wear-resistant microelements in different materials of wear-resistant steel balls will be damaged, which will cause poor wear-resistant effect and serious waste of clinker grinding mill. 3. During cement grinding, the material temperature may be higher than 100 , leading to dehydration of most gypsum or complete dehydration, causing coagulate of cement, which requires corresponding cooling measures, including mill ventilation, cylinder water cooling, etc. 4. After each clinker grinding, clean the cement grinding system, so as to avoid inconvenience to the next start-up due to slag material deposition.

Cement mill price Cement ball mill specially used for grinding cement clinker and other materials in building materials, cement production, metallurgical ceramics, electric power and petrochemical industry. JXSC can design and manufacture special cement ball mill equipment according to the output and fineness requirements of users. Contact us for machine selection and a price quotation.

ball mill for cement grinding cement ball mill | ball mill manufacturers

ball mill for cement grinding cement ball mill | ball mill manufacturers

The cement industry is a high energy consumption industry. Improving production efficiency and reducing energy consumption are the manufacturing principles that cement enterprises have been following. Cement ball mill is a kind of important cement equipment in the process of raw material preparation and finished product grinding in cement plants. It is mainly used to grind limestone, clay, and other cement raw materials, as well as calcined clinker. As we all know, in the whole process of cement manufacturing, the power consumption of traditional cement ball mill accounts for about two-thirds of the whole plant. According to statistics, the power consumption per ton of cement production is no less than 70 kW / h, but the effective utilization rate of this part of electric energy is very low. In order to improve the output of the cement ball mill grinding system and reduce energy consumption, we have done some researches and analysis and finally, find out effective solutions.

The application of pre-grinding technology is the main way to greatly increase the output of cement ball mill grinding system. According to the theory, it can be divided into pre-crushing and pre-grinding.

Pre-crushingit means to set up a fine crusher in front of the ball mill. Parts of the grinding tasks undertaken by the ball mill coarse grinding chamber are handed over to the high efficient fine crusher. This method features low investment and obvious effect, but it is necessary to solve the problem of material iron removal because the metal impurities such as iron in clinker will cause destructive damage to the crusher. After adding the pre-crushing equipment, the internal structure of the cement ball mill should be adjusted accordingly. As the particle size of the material is greatly reduced, the crushing capacity of the coarse grinding chamber should be appropriately reduced and then improve its grinding capacity.

Pre-grindingit refers to adding a grinding machine in front of the cement ball mill to increase the output of the original grinding system by a large margin. This method features large investment and relatively complex process but it can increase the output of cement ball mill by up to 50%. The equipment used for pre-grinding mainly includes rod mill, cement roller press, etc.

The function of cement separator is to reduce the unnecessary grinding amount of cement ball mill and improve its grinding efficiency by screening out the particles with certain fineness in time. The key technologies of cement separators are dispersion, classification, and collection.

Classification means that after materials are dispersed, the separator will make full use of the air classification function to separate the coarse and fine particles and send them to their respective outlets.

The JD series cyclone air separator is a new type of high-efficiency cement separator. Its powder selection efficiency is more than 80%, with small size, lightweight, flexible layout, and other characteristics. Besides, its system adopts a negative pressure operation with no dust pollution, so it is very suitable for cement manufacturing.

After referring to the characteristics of the closed-circuit grinding process, a new type of closed-circuit grinding system is formed by a cement ball mill and high-efficiency powder separator. The practice shows that the effect of increasing production and saving energy of this system is remarkable, which is more than 30% higher than that of the open-circuit grinding system and ordinary closed-circuit grinding system. It provides a new technical approach for increasing cement output and saving energy.

Redetermine the chamber length and adjust the grinding media gradation and material flow rate according to the material characteristics are very important for adding a pre-grinding system and powder separator, as well as the internal transformation of cement ball mill. Actually, each chamber of the ball mill has the function of crushing and grinding, but the degree is different. The main function of the coarse grinding chamber is crushing, so it should select large-diameter steel balls as the grinding media. The fine grinding chamber is used for grinding, so small diameter balls are more suitable. Materials are filled between these grinding mediums. The grinding efficiency depends on the contact area. If the contact area is large, there will be more grinding opportunities, and the product production rate per unit time will be high.

Grinding chambers adopt lining plates to enhance their function. The new high-efficiency lining plates on the market now integrate and optimize the functions of various lining plates so that one kind can give full play to the advantages of various types, maximizing the use of energy and reducing reactive power loss.

Due to the influence of many factors, such as the change of material particle size and grindability, the reasonable grinding media gradation is not constant, but relative. After a period of production, with the continuous wear of steel balls, their total load becomes smaller. We need to supplement the grinding media regularly.

AGICO Group is an integrative enterprise group. It is a Chinese company that specialized in manufacturing and exporting cement plants and cement equipment, providing the turnkey project from project design, equipment installation and equipment commissioning to equipment maintenance.

Related News
  1. buzwagi gold mining ball mill
  2. ball mill and clay grinding
  3. jinshibao high quality ore dressing ball mill
  4. chicago low price small lime system sand production line price
  5. tqmj500-b chocolate ball mill machine by batch
  6. liner for ball mill in pondicherri
  7. cost of grinding in gold production stone crusher for sale
  8. new quartz mineral processing production line in tokyo
  9. ball bearing
  10. monrovia high quality small kaolin ceramic ball mill manufacturer
  11. dust control for gravel driveway durango
  12. jaw crusher manufacturer in haryana
  13. rentable concrete flotation machines in pittsburgh
  14. kyoto high quality portable gold mine impact crusher
  15. canada portable rock circular vibrating screen
  16. rotary dryer hopper
  17. crushing equipment for sale florida
  18. elevator replacement cost
  19. xcf air inflation floatation cell flotation machinery
  20. bagasse briquetting machine