cement industry news from global cement

cement industry news from global cement

Switzerland: Holcim has unveiled its new corporate brand identity as part of the change in group name from LafargeHolcim. The new group logo consists of a white letter H, for Holcim, on a two-tone green and blue backdrop. The group says that the new identity unites its market brands behind its purpose of building progress. The change is intended to mark its transformation into a global leader in innovative and sustainable building solutions and signify its focus on developing green cities, smart infrastructure and improved standards of living globally.

Chief executive officer Jan Jenisch said, Our world is changing in many ways, with population growth, urbanisation and the climate challenge. We are determined to play our part to accelerate low-carbon and circular construction so that we build a net-zero future and raise living standards for everyone. Our new group identity sends a signal to the world that we are fully committed to building progress for people and the planet.

Kazakhstan: Steppe Cement sold 841,000t of cement in the first half of 2021, up by 10% year-on-year from 765,000t in the first half of 2020. Revenues in the period were US$38.8m, up by 22% to from US$31.9m. Average cement delivery prices increased by 11% in the reporting period.

Azerbaijan: The US-based American Petroleum Institute (API) has certificated Norm Cements cement plant in Bakus Garadagh district. The Turan Information Agency News has reported that the certificate confirms that the plant meets the highest standard for oil well cement. This will enable the company to begin the export of oil well cement produced at the plant.

India: The Department for Promotion of Industry and Internal Trade (DPIIT) of the Indian government has established the Cement Industry Development Council (CIDC) to coordinate the cement sectors efforts towards eliminating waste, maximising efficiency, increasing standards and lowering prices. The Economic Times newspaper has reported that the DPIIT has appointed Dalmia Bharat chief managing director Puneet Dalmia as head of the CIDC. An initial task for the council will be to recommend steps towards securing full cement capacity utilisation.

India: The Telangana State Pollution Control Board has ordered Cement Corporation of India and Penna Cements to pay pollution fines for breaches of particulate matter restrictions at their respective cement plants at Tandur in Vikarabad district. The Times of India newspaper has reported that both companies exceeded legal limits eight times between November 2019 and July 2021. The board fined Cement Corporation of India US$3210 and Penna Cements US$4410.

thyssenkrupp industries india

thyssenkrupp industries india

We have till date supplied and commissioned over 135 sugar plants with major expansions including more than 550 sugar cane mills, more than 5400 batch and continuous centrifugal machines and more than 200 boilers.

Access to World Class Technology of Krupp, Buckau Wolf, PHB, PWH, O&K, Demag Lauchhammer , Weserhutte & Robins.More than 23 complete material handling plants with repeat orders in India and Abroad. Repeat orders from Neyveli Lignite Corporation (NLC) for specialized mining equipment.

Complete Thermal Power Plants on EPC Basis. CFBC boilers. Stoker fired boilers. Waste heat recovery boilers. Oil/Gas fired boilers. Biomass fired boilers.

gebr. pfeiffer

gebr. pfeiffer

Gebr. Pfeiffer supplies innovative plant solutions for cement, coal, lime, gypsum and ceramics on which you can rely 100 %. We only give our word if we know we can keep it. And we keep what we have promised. Extremely reliable and with excellent results. For sustainable economic success. What can we do for you?

The contract was awarded not only because of the customers satisfaction with the first mill but also because of the Pfeiffer mill grinding the kaolin much more efficiently than its competitors mills.

The essential modules of all three MVR mills will have the same design and therefore be interchangeable; the advantages in terms of spare parts management and maintenance of the mills will be significant.

In addition to short specialist talks, the two-day event was an opportunity for knowledge transfer between mineral processing specialist Gebr. Pfeiffer and leading figures from various cement companies in India.

As part of the companys expansion strategy to spread grinding plants across the whole of India, Shree Cement will now equip a grinding plant near Pune in the state of Maharashtra with a Pfeiffer mill.

The contract includes the supply and installation from the top of the foundation up. It comprises the complete process equipment, electrical equipment and automation system as well as the complete building on EPC basis.

More than 50 attendees were welcomed, representing clients from all over the MENA region who were given the opportunity to profit from the Pfeiffer experts experiences and to use them for the Pfeiffer mills in operation at their works.

Even though our team is very much looking forward to meeting our business partners in person again, which due to the current situation is not possible, sales, service and all support functions are still available via e-mail, telephone and video chat. Our supervisors and commissioning engineers are also there for you as far as possible and if feasible.

At the end of March, we received an inquiry from the Kaiserslautern District Medical Association as to whether we could pass on protective equipment to doctors in private practice in Kaiserslautern to enable them to continue providing appropriate care for their patients. Of course, we were pleased to be able to do so.

BIGBOSS CEMENT Inc., (BBCI) with a plant located in the province of Pampanga, Philippines has recognized the advantages of this modular plant concept, comprising a 4-roller vertical roller mill, and is of the opinion that ready2grind meets the requirements and provides the highest plant availability.

cement industry news and events from world cement with the latest news updates | world cement

cement industry news and events from world cement with the latest news updates | world cement

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The MOU allows for the potential integration of Carbon Upcyclings CO2-embedded concrete additive into Lafarge operations, while exploring opportunities to expand Carbon Upcyclings operating capacity by developing larger processing facilities.

The Mineral Products Association (MPA) believes that new requirements for biodiversity net gain, and application of the metric, could lead to worse outcomes for nature than those delivered through the current minerals planning system.

The Global Cement and Concrete Association (GCCA) and World Economic Forum have launched Concrete Action for Climate (CAC), a collaborative platform that will help drive the industrys journey to carbon neutral concrete by 2050.

The company has announced that it has been recognised by the Texas Aggregates & Concrete Association (TACA), earning awards for outstanding safety performance at eight of its operations across the Lone Star State.

ncl industries plans mattapalli cement plant expansion to 3.6mt/yr and establishment of new grinding plant - cement industry news from global cement

ncl industries plans mattapalli cement plant expansion to 3.6mt/yr and establishment of new grinding plant - cement industry news from global cement

India: NCL Industries is planning to expand its 2.7Mt/yr Mattapalli plant in Suryapet district, Telangana, to 3.6Mt/yr capacity at a cost of US$13.5m. The work includes the installation of vertical roller mills to replace the plants ball mills. Times of India newspaper has reported that the company says that it will complete the expansion by 2022.

Its plan also involves the establishment of a new 660,000t/yr grinding plant at nearby Anakapalle, at a cost of US$26.9m. The producer will invest a further US$810,000 in setting up three new ready-mix concrete plants in Hyderabad and Vizag, bringing its total number of concrete plants in the state to eight.

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 vertical roller mill

cement vertical roller mill

This cement mill is widely used in the grinding of cement raw meal, slag(GGBS plant), cement clinker, raw coal and other raw materials. It gathers grinding, drying and powder selecting as a whole, with high grinding efficiency and high drying capacity ( the maximum handling material moisture is up to 20% ). The vertical mill adopts dynamic powder selecting device, which comes with high powder-selecting efficiency and convenient adjustment of fineness.After crushed by crusher, the large materials become small ones and are sent to storage hopper by elevator, and then evenly sent to the upper distribution plate of the turn plate by vibrating feeder and sloping feeding pipe.The grinding disc is driving by motor through reducer.

The material falls to grinding disc from the feed opening. The materials are driven to the edge of disc by the centrifugal force and crushed into fine powders by rollers. Then, the hot air from the nozzle take the fine powder to high effiency classsifer.

Great Wall Company's GRMK series Vertical cement mill in the production of cement specific surface area up to 3800 cm/ g with stable and reliable quality, it already have been the ability completely to replace tube mill.

According to the display of pulverized coal measured data, it can be saving electricity above 30% use of vertical roller mill production per ton cement clinker than traditional ball mill, and the power saving effect is very remarkable.

There is a low vibration and noise in overall system, and equipment with whole sealing, system working under negative pressure with no dust overflow, clean environment. Therefore, cement vertical roller mill meets the national environmental protection requirements. With working mechanism changing, cement vertical roller mill can be reduced friction and improved service life.

Pre-sales Service: The wide product range enables us to provide our customers with stand-alone machines or complete processing plants. Based on our customers request and budget, our experts make efficient, reliable solutions. Following customers order we produce strictly, whats more, before placing the order every customer has the chance to visit XinXiang Great Wall (Chaeng) working machines or complete plant in the site. To ease the trip for every visitor to China, in particular the first-time visitor, we provide FOR FREE all relevant visitor-friendly services including invitation letter preparation, hotel reservation, airport pick-up, incity transportation, and sightseeing guide, etc. After-sales Service: Experienced technicians guidance is available on the phone, and on the internet. One or more engineers will be dispatched to the quarry site to help install the customers plants. Necessary training about machine daily maintenance to local workers is provided also. After-Sales department is made of well-trained employees and installation engineers, the installation engineers are special and professional members of XinXiang Great Wall (Chaeng), they are now strategically located home and abroad, working for our customers.

Pre-sales Service: The wide product range enables us to provide our customers with stand-alone machines or complete processing plants. Based on our customers request and budget, our experts make efficient, reliable solutions. Following customers order we produce strictly, whats more, before placing the order every customer has the chance to visit XinXiang Great Wall (Chaeng) working machines or complete plant in the site.

To ease the trip for every visitor to China, in particular the first-time visitor, we provide FOR FREE all relevant visitor-friendly services including invitation letter preparation, hotel reservation, airport pick-up, incity transportation, and sightseeing guide, etc.

After-sales Service: Experienced technicians guidance is available on the phone, and on the internet. One or more engineers will be dispatched to the quarry site to help install the customers plants. Necessary training about machine daily maintenance to local workers is provided also.

After-Sales department is made of well-trained employees and installation engineers, the installation engineers are special and professional members of XinXiang Great Wall (Chaeng), they are now strategically located home and abroad, working for our customers.

products for cement and mining i flsmidth

products for cement and mining i flsmidth

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.

cement mills and raw mills for high throughput rates

cement mills and raw mills for high throughput rates

High throughput rates, permanent plant availability , optimized maintenance concepts features of the MVR mill and the patented MultiDrive enabling Gebr. Pfeiffer to meet the ever rising expectations of the industry. Thanks to the innovative drive and active redundancy, an unintended stop of the grinding process is practically excluded. No matter what type of material has to be ground cement raw material, cement clinker or granulated blast-furnace slag and how different their grindability and abrasiveness may be, the MVR mill ensures throughput rates of a different dimension, around the clock, reliably and on the long term. Forget about downtime. With Pfeiffer you will grind on a grand scale.

An MVR mill may have up to six grinding rollers and up to six drive units. Thus both systems are actively redundant meaning that one or several rollers can be taken out of the system for maintenance work while mill operation continues. The same applies to the independent drive modules of the MultiDrive.

High drying capacity, short dwell time of the material to be ground, and remote control of grinding pressure and classifier rotor speed ensure a fully automatic operation of the MVR mill even with varying raw material characteristics.

Thanks to the geometry of the grinding rollers in combination with their specific suspension, there is always a parallel grinding gap, ensuring a homogeneous compaction of the material to be ground. Moreover, due to the symmetric shape of the grinding roller tires, these can be turned when worn.

Up to six stationary grinding rollers roll on a rotating grinding table. The material is drawn in between the rollers and grinding table and ground by pressure and shear. The required pressure forces are produced by a lever system comprising, among others, a roller arm, along with a hydropneumatic tension system. After being rolled over by the rollers, the material is conveyed to a stationary nozzle ring due to the rotation of the grinding table. Gases (air or hot gas) flow through this nozzle ring, take up the ground and dried material and convey it to the classifier where it is separated by the rotating wheel (rotor) into grits and fines. The grits fall back into the grinding zone whereas the fines leave the classifier with the gas flow for being separated in cyclones or a filter.

Up to six stationary grinding rollers roll on a rotating grinding table. The material is drawn in between the rollers and grinding table and ground by pressure and shear. The required pressure forces are produced by a lever system comprising, among others, a roller arm, along with a hydropneumatic tension system. After being rolled over by the rollers, the material is conveyed to a stationary nozzle ring due to the rotation of the grinding table. Gases (air or hot gas) flow through this nozzle ring, take up the ground and dried material and convey it to the classifier where it is separated by the rotating wheel (rotor) into grits and fines. The grits fall back into the grinding zone whereas the fines leave the classifier with the gas flow for being separated in cyclones or a filter.

Depending on the abrasiveness of the material to be ground and areas to be protected, different wear materials are used on our vertical roller mills. Alloy cast iron as per DIN 1695, hardfaced cast iron or composite materials with high-chromium inserts in ductile base materials: the grinding elements designed by Pfeiffer are made of high-quality materials ensuring a long lifetime. The housings and other mill components, too, are protected against wear with highly wear-resistant steel plates or hardfaced composite plates. Components which are specifically exposed to wear like gas outlet ducts have additional ceramic liners. All this is for optimum protection and short maintenance shutdown.

The highest wear occurs on the wear parts of the grinding elements as is the case with any type of vertical mill. Therefore, ease of replacement and regeneration is a major feature of the mill. The MVR mill has a modern hydraulic system used in operation and for maintenance alike. With this new type of roller suspension, the rollers can be swung out of the mill in a controlled way for ease of replacing the one-part grinding roller tires. The segmented wear parts of the grinding table are replaced, using a lifting device and the maintenance drive. Moreover, the rollers can be swung out separately. Hence grinding operation can be continued while maintenance work is done. The parts concerned can be regenerated both inside the mill and outside. Forget about downtime and maintenance problems! With active redundancy and easy maintenance you are up to date!

review on vertical roller mill in cement industry & its performance parameters - sciencedirect

review on vertical roller mill in cement industry & its performance parameters - sciencedirect

India is the world's second largest producer of cement and produces more than 8 per cent of global capacity. Due to the rapidly growing demand in various sectors such as defense, housing, commercial and industrial construction, government initiative such as smart cities & PMAY, cement production in India is expected to touch 550600 million tones per annum (MTPA) by the end of year 2025.

With recent growth and success journey there is also a threat approaching to cement industry that its input cost is increasing. Power cost, fuel cost, raw material cost have doubled up in recent years whereas cement price has not hiked in that fashion. Also 40% of the cement production costs are energy costs out of which more than 60% of the total electricity is used in grinding circuits. In order to survive and sustain in the market they need to increase their profitability which can only be achieved by increasing productivity and reducing power consumption. High productivity and low power costs can be achieved by increasing output, lowering breakdowns and optimizing the energy consuming grinding process.

The objective of the study, is to draw attention to the need of Cement grinding process optimization to minimize power consumption and achieve higher productivity. In the study the advantages of vertical roller mill are discussed over ball mills. VRM construction, its process and parameters which affects the performance and productivity of vertical roller mill are discussed. Also the consequences of variations in parameter explained. With proper optimization of these parameters, the productivity of vertical roller mill can be improved and performance stability can be achieved by addressing root causes.. This study can benefit the organizations using VRM and are not able to utilize its full productivity due to some bottlenecks or constraints.

reference report mvr vertical roller mill with multidrive for cement grinding in australia

reference report mvr vertical roller mill with multidrive for cement grinding in australia

There is an unbroken trend in the cement industry for reliable, cost and energy efficient plants. Gebr. Pfeiffer focuses on these challenges, always playing a pioneering role when it comes to satisfying the markets high demands with new technologies. The Port Kembla project of Australias leading cement producer Cement Australia is an example of a reliable, cost and energy efficient cement production plant. This project saw Gebr. Pfeiffer supply a grinding plant, consisting of an MVR vertical roller mill and a MultiDrive system, meeting the highest standards. The Port Kembla plant is designed to produce 1.1 million tpa of slag and cement at about 4,000 cm/g acc. to Blaine.

In order to reduce costly installation works on site as far as is possible, units were to be delivered to site in preassembled condition. And here is where the MultiDrive system held a trump card: each of Port Kemblas three individual 1920-kW drive units, consisting of motor and gear unit and weighing about 25 t in total, can be transported by air.

As regards the operation of the plant, the customer set high standards on reliability and availability. His aim was to operate the plant fully automatically at least at night and by no more than 5 people during the day. This high level of reliability could only be achieved with a vertical mill from Gebr. Pfeiffer in combination with a MultiDrive system. An MVR 6000 C-6 with six rollers was chosen. Each of the rollers can be swung out individually for maintenance or other works. In such a case the mill continues in operation, still achieving a minimum capacity of 83 %.

In addition to meeting the highest requirements in terms of reliability, the mill also satisfies the demand for ease of maintenance. The mill combined with the MultiDrive system is a success story, allowing high throughput rates to be achieved very uniformly and reliably.

A procedure for the production of cement, patented by Gebr. Pfeiffer as early as 2005, was applied in Kembla. In this procedure, the gypsum is first calcined in separate hammer mill and then fed to the vertical roller mill. This allows the properties of the cement to be adjusted in an optimum way through the gypsum component with comparably little effort.

A key advantage of the patented procedure lies in the thermal energy savings in the order of 300 % and more, because only the gypsum in the separate gypsum calcining plant, and not all cement components in the MVR mill, must be processed at higher temperatures.

A positive side effect of this procedure is that, if the gypsum calcining plant is suitably adjusted, a silo-safe cement is produced. This prevents unwanted chemical reactions during storage, as well as the associated problems when the cement is discharged from the silo.

The Pfeiffer MVR mill with MultiDrive in Port Kembla operates at a maximum level of reliability and energy efficiency. All targets set by the customer were more than fulfilled. The plant is operated at an average capacity of more than 200 t/h and all guaranteed performance values have been exceeded.

world's largest vertical roller mill underway at shah cement

world's largest vertical roller mill underway at shah cement

With an 8.1-metre grinding table and six grinding rollers powered by an 11.6-megawatt gearbox, the FLSmidth OK 81-6 Mill has milled its first cement at Shah Cements Muktarpur Plant, Munshiganj, Bangladesh.

Shah Cement Industries Ltd. of the Abul Khair Group is one of Bangladeshs largest cement producers. The FLSmidth vertical roller mill (VRM) was chosen to produce a full range of cement types at the Muktarpur Plant. Driven by two 5.8 MW FLSmidth MAAG Max Drive gear systems, the impressive mill is the biggest VRM ever to be installed in a cement plant in terms of dimension, operating capacity and installed power.

The worlds largest VRM was successfully put into operations in September 2018, and plant management at Shah Cement is extremely impressed with its outstanding performance. In just a few weeks, it has achieved a highly satisfactory production capacity with low energy consumption.

Hafiz Sikander, Director of Operations, Cement Division of Shah Cement Industries Ltd., says: We are proud to have the worlds largest vertical roller mill as part of our operations. We selected the FLSmidth OK 81-6 Mill for its exceptional efficiency and reduced power consumption and we are expecting it to deliver as promised. As the largest single-unit grinding mill in the industry, we expect it to meet our production requirements for many years.

Supporting Shah Cements versatility in high quality cement production, the mill is designed to produce OPC, PPC, PSC and slag cement types. It is producing PPC at a capacity of 500 tonnes per hour @ 3500 Blaine with 15% slag.

In addition to the OK Mill, FLSmidth supplied the process and layout engineering, along with site advisory. The supporting equipment included FLSmidth Pfister weigh feeders, FLSmidth Airtech process bag filters, process fans and auxiliary equipment from raw material hopper discharge to process bag filter discharge.

Shah Cement management believes that FLSmidth was the best choice as partner for this significant project, a decision made in 2016. Mr. Hafiz Sikander comments: We have worked with FLSmidth for many years, and we have always been able to rely on the high level of service at all stages.

Located at Muktarpur, Munshigonj, Shah Cement Industries Ltd. is the largest cement producing plant in Bangladesh, with a capacity of 8.0 million metric tonnes per year. As one of the countrys leading cement brands, Shah Cement is the only cement company featuring in the list of Consumer Prestigious Brands of Bangladesh. The company is part of the Abul Khair Group, the largest business conglomerate in Bangladesh.

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.

operation guide for vertical roller mill in cement plant | agico cement

operation guide for vertical roller mill in cement plant | agico cement

The vertical roller mill (VRM) is a type of grinding machine for raw material processing and cement grinding in the cement manufacturing process. In recent years, the VRM cement mill has been equipped in more and more cement plants around the world because of its features like high energy efficiency, low pollutant generation, small floor area, etc.

The VRM cement mill has a more complex structure than other types of cement mills, so we need to ensure the following aspects are normal during the operation, or the machine may not be able to function well.

Too thick material layer will reduce the grinding efficiency of the vertical roller mill. When the pressure difference of the mill reaches the limit, the material layer will collapse and affect the operation of the main motor and the discharge system.

There are many factors that may make mill body vibrate, including the grinding pressure, material layer thickness, air volume and temperature, accumulator pressure, wear condition of the roller and the grinding plate, etc.

The grinding pressure of the mill should be adjusted according to the fed quantity, the particle size, and the grindability of the material. It must be well controlled to maintain the thickness of the material layer, reduce the vibration of the mill body, and ensure that the stable operation of the mill.

Increasing the grinding pressure will improve the grinding capacity of the mill, but the grinding capacity will stop increasing when the grinding pressure reaches a certain critical point. If the set pressure of the hydraulic cylinder is too high, it will only increase the driving force and accelerate the wear of parts, but not improve the grinding capacity.

On the other hand, too high grinding pressure will cause the thickness of the material layer to decrease, which further leads to the increase of the vibrating speed of the mill and accelerates the wear speed of the parts.

The gas temperature at the discharging port can be increased by increasing the opening of the hot air door and reducing the opening of the circulating air door. However, when the gas temperature exceeds 130 , the equipment will also be damaged. For example, the dividing wheel at the lower part of the cyclone will expand and get stuck, and the lubricating grease of the grinding roller will dry and crack, which is also unfavorable to the tail dust collection bag.

In vertical roller mills, the air volume in the mill is determined by the material feed rate. The air volume can be controlled by adjusting the power of the circulating fan of the mill or the opening of the exhaust fan at the kiln tail.

If the air volume is too large, the pressure difference in the mill and the current of the main motor will decrease, the thickness of the material layer will become thin, and the vibration degree of the mill body will become strong.

If the air volume of the system is too small, the thickness of the material layer, the pressure difference in the mill, and the current of the main motor will increase, and so will the vibration speed of the mill.

When operating the vertical roller mill, the operator must control the inlet and outlet air valves to make the air volume of the system in a balanced state, so as not to affect the air pressure at the back end of the rotary kiln.

cement grinding - cement plant optimization

cement grinding - cement plant optimization

Highly energy intensive unit operation of size reduction in cement industry is intended to provide a homogeneous and super fine (3000-4000 Blain) cement. Grinding operation is monitored for following parameters to ensure objectivity and economy of operation.

Chemical analysis of cement, generally on hourly basis. Product fineness, Blain surface and 45-micron residue. Cement SO3, % Grinding aid usage, grams/tonne Cement moisture, % Production rate, tonnes/hour Operating hours as run factor in % Specific power consumption (SPC) kWh/tonne.

Grindability and Power Consumption.Among various theories of comminution, most commonly accepted which is relevant to ball /tube mills is Bond's theory, which states that power input in comminution process is proportional to the surface generated in the process and the grindability of the material. To measure grindability, Bond developed 'Bond's Work Index' (BWI), a 'test mill' and a testing procedure for WI. With the help of this we can work out power required to grind a material from a given feed size to a product of given fineness.

Water Spray in Cement Mills.Water spray installed generally in second compartment of ball mill to control cement temperature. Cement discharge temperature should be kept below about 110oC but, the same time should allow some 60% dehydration of gypsum to optimize cement strength without excessive false set. Water spray is controlled with mill outlet gas or material temperature. A hardware interlock is recommended with mill main drive to avoid accidental spray in mill.

Grinding aids are generally added to the ball mill to reduce electrostatic agglomeration of fine particles and to reduce coating formation on grinding media which reduces grinding efficiency. The optimum addition rate should be determined carefully to enhance grinding efficiency. Grinding aids also serve to reduce coating problems in cement storage and enhances cement strengths.

Ball Mill.Ball mills with high efficiency separators have been used for cement grinding in cement plants all these years. Ball mill is a cylinder rotating at about 70-80% of critical speed on two trunnions in white metal bearings or slide shoe bearings for large capacity mills. Closed circuit ball mill with two compartments for coarse and fine grinding are generally found in cement plants for cement grinding. Compartments (filled with grinding media) are divided by a double diaphragm with flow control to utilize maximum mill length for effective grinding.

Grinding media contain balls of different sizes in designed proportions with large sizes in feed end and small sizes in discharge end. About 27 to 35 % volume of mill is filled with grinding media. Equilibrium charge is that charge where compensation for wear can be done by balls of one size only usually the largest size in the compartment. Grinding media could be made of forged steel, cast steel or even cast iron. To economize grinding media consumption, presently grinding media used are high chrome steel balls.

Mill shell is lined with lining plates to protect it from wear, high chrome steel liners are now commonly preferred to give longer life. Lifting liners are used to enhance impact in first compartment, where coarse grinding is dominated by impact. In second compartment which is longer in size (L>1.5D), classifying liners are used to ensure media classification along the length of mill with large size balls near mid partition and smaller balls at mill discharge end.

Ball mills are of 'bucket elevator' type for cement grinding, material is taken by conveyors to a separator where coarse was returned to the mill and fine sent to cyclone separator or bag filter for collection.

Different drive arrangement for ball mills are in existence. Commonly existing arrangement is mill drives with a girth gear and a pinion driven by motor with a gear box. Larger mills have a twin drives of half the ratings on either side of same girth gear. In central drive arrangement both the girth gear and pinion are avoided by connecting gear box output shaft directly to mill.

Closed circuit ball mills are existing with all types of separators () grit, mechanical and high efficiency in cement industries. Presently high efficiency separators are common to achieve maximum energy optimization. Brief description of separators is presented at the end.

Mill drive power or mill differential pressure to control mill feed rate. Mill Sound level to control filling level inside mill with feed rate. Mill outlet gas temperature. Mill outlet material temperature. Cement temperature. Outlet gas flow determined from mill inlet and outlet drafts or flow meters installed.

Vertical Roller Mills.In Vertical Roller mill 2 - 4 rollers (lined with replaceable liners) turning on their axles press on a rotating grinding table (lined with replaceable liners) mounted on the yoke of a gear box. Pressure is exerted hydraulically. This mill also has a built in high efficiency separator above the rollers to reduce circulation loads and consequently reducing differential pressure across the mill.

The mill is started either with the rollers in lifted-up position, or with the hydro-pneumatic system at low pressure. In grinding mode, actual metal to metal contact should be prevented by limit switches or a mechanical stop and by consistent feed. In VRMs the material cycle time is usually less than a minute against several minutes for a ball mill or tube mill. Thus, control response should be accordingly faster. In case mill feed fails action should be taken within no more than 45 seconds or excessive vibration will cause mill shut-down. Moreover, the vertical mills are subject to vibrations if material is too dry to form a stable bed. Therefore, provision is made for controlled spray water inside the mill During mill operation magnetic separator and metal detector should be always functional to ensure to exclude tramp metal which can damage the grinding surfaces.

Roller Press.Roller press consists of two rollers lined with wear resistant material. One roller is fixed and the other one is movable to exert pressure, applied hydraulically. A roller press looks similar to a roll crusher. However, the pressure exerted between rollers is very high - of the order of 400 kg/cm2 as compared to roll crushers. Feed is fed over the total width of the rollers by a central chute. About 30 % material gets pulverized to the required product fineness. Roller press output pre-ground material is fed to a ball mill operating in closed circuit. Ball mill required is smaller in size and larger grinding balls are no more required.

Separators Several types of separator are employed in mill circuits and there are numerous variations of each type: Mechanical separators Mill discharge material is fed onto a rotating dispersion plate whence it is spread off into a rising air stream. Coarse particles either fall directly from the dispersion plate or are rejected between the auxiliary fan blades and the control valve. Fine dust is taken along with main fan flow and is detrained as the gas flows downwards loses momentum (velocity) and diversion through the return vanes. Controlling parameters are the number of auxiliary blades, the clearance between auxiliary blades and control valve, and the radial position of the main fan blades

High efficiency separators, 3rd generation separators were introduced to improve the mechanical separator's fines recovery efficiency. Examples of these separators are O-Sepa (FLSmidth), Sepol (ThyssenKrupp) A simplified process flow these separators is as follows. Material is fed onto a rotating dispersion plate via air slide, whence it is dispersed off into the classifying air stream. Separator loading is recommended to be up to about 2.5kg feed/M3 air flow. Vortex is formed by the rotor which classifies particles between centrifugal force and the inward air flow. The fine fraction exits upwards/downwards with the air sucked by ID fan passes through cyclone separators or a bag filter for product collection, while the coarse fraction falls and is discharged from the bottom and send back to mill for regrinding. Fineness is controlled by rotor speed (increasing speed increases fineness).

cement grinding machine selection: vertical roller mill vs roller press

cement grinding machine selection: vertical roller mill vs roller press

Grinding machines are indispensable equipment in cement plants. In the process of cement production, the cement plant needs to complete the grinding of pulverized coal, raw meal powder, and cement products. The purpose of grinding is to increase the specific surface area of the material and reduce the particle size of the powder, so as to achieve the activity required by the next process.

Tube mill has been used as the main grinding equipment in the cement industry for a long time, and it is still widely used because of its simple structure, easy operation, and low price. However, the energy utilization rate of tube mills is only 2% ~ 20%, which is very low. With the continuous development of grinding technology, there are two kinds of cement grinding equipment with lower energy consumption, one is vertical roller mill, and the other is roller press.

Both the vertical roller mill and roller press apply the working principle of material bed milling. During the grinding process, only a small part of material particles directly contact with the grinding parts of the mill; but under the action of grinding parts, material particles form a material bed, and through the stress transmission and interaction between the particles, they are cracked, broken, and crushed.

For vertical roller mill, the grinding parts are rollers and grinding disc. The pressure required for grinding mainly comes from the rollers. At present, the loading force is mainly formed by hydraulic pressure. The material is fed into the grinding disc from the center or side of the upper housing, and the material layer is formed in the process of moving on the grinding disc. When the material passes between the roller and the grinding disc, the grinding is completed under the extrusion and shear force between them.

For roller press, the grinding parts are two rollers of the same size. The materials fall vertically from the top to the two rollers to form the material bed. Under the extrusion force of the two rollers, materials are ground to fine particles. There are two transmission modes of roller press, namely double drive, and single drive. The double drive roller press is the more popular type. The transmission device of a single drive roller press has only one set to drive one roller, and the other roller is driven by connecting with the former one with a gear train.

In a vertical roller mill, the material on the grinding disc is restricted by the air duct ring, but the side of the material between roller and disc is not restricted. In roller press, in addition to the restriction between the two rollers, side baffles will also be set on the sides of both ends of the roller, which will limit the side of the material bed of the roller press.

Because the grinding area of the roller press is restricted from all sides, the increase of applied energy will also increase the fine powder and specific surface area of material. But for vertical roller mills, the growth rate of that of material will gradually decrease. From this point of view, roller press is superior to vertical mill.

In a vertical mill, there generally are two or more grinding rollers. The contact area between the grinding roller and the grinding disc is large, and the energy utilization rate is higher than that of the roller press. Moreover, the materials are generally milled on the grinding disc by several grinding rolls repeatedly. From this point of view, the vertical mill is better than the roller press.

When grinding cement products, a grinding system composed of a roller press or an external circulation vertical mill + a powder concentrator + a tube mill is generally selected. Taking grinding P o42.5 cement as an example, the pre grinding closed-loop system composed of roller press or external circulation vertical mill and powder concentrator has a circulation load rate of 200% 300%, and the specific surface area of the selected materials is 180-280m2 / kg. The following table lists the main machine preparation and the product particle size of several cement grinding systems.

The particle shape of the materials from the roller press and the vertical roller mill is also different. The vertical mill grinds the material by two forces, the extrusion force and the shearing force between the roller and the grinding disc; the roller press grinds the material by only one force, the force between the two grinding rollers. When the material is ground to a certain fineness, most of the fine powders from the vertical mill are irregular and prismatic, and the fine powders from the roller press are mainly irregular flake and strip particles. From the particle shape, the fine powder from vertical mill is closer to that from tube mill, and the fine powder from vertical mill is more suitable for making cement products than that from roller press.

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