fri sag mills for iron ore grinding

sag or ball mill circuit in iron ore crushing&grinding - grinding & classification circuits - metallurgist & mineral processing engineer

Without looking at the tonnages involved and the ore characteristics it cannot be determined. Both are efficient depending on your ore. The actual efficiency of one over the other is dependent on the ore friability and grinding index and the the final size desired out of the circuit.

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gearless ag/sag mills - metso automation - pdf catalogs | technical documentation | brochure

Metso Minerals Industries, Inc. 240 Arch Street, P.O. Box 15312 York, Pennsylvania , USA 17405-7312 Phone: + 1 717 843 8671 Fax: +1 717 845 5154 www.metsominerals.com E-mail: [email protected] Gearless Autogenous/ Semi-Autogenous Mills

The sights and sounds of large grinding mills in operation are impressive to even the most seasoned mill operator. Grinding systems are a symbol of the application of brute force to extract mineral wealth from nature and are a major and critical part of any mineral processing facility. Autogenous (AG) grinding is the size reduction of material in a tumbling mill utilizing the feed material itself as grinding media. SemiAutogenous (SAG) grinding is the size reduction of material in a tumbling mill utilizing the feed material plus supplemental grinding media. The most common supplementary...

grinding mills - an overview | sciencedirect topics

Grinding circuits are fed at a controlled rate from the stockpile or bins holding the crusher plant product. There may be a number of grinding circuits in parallel, each circuit taking a definite fraction of the feed. An example is the Highland Valley Cu/Mo plant with five parallel grinding lines (Chapter 12). Parallel mill circuits increase circuit flexibility, since individual units can be shut down or the feed rate can be changed, with a manageable effect on production. Fewer mills are, however, easier to control and capital and installation costs are lower, so the number of mills must be decided at the design stage.

The high unit capacity SAG mill/ball mill circuit is dominant today and has contributed toward substantial savings in capital and operating costs, which has in turn made many low-grade, high-tonnage operations such as copper and gold ores feasible. Future circuits may see increasing use of high pressure grinding rolls (Rosas et al., 2012).

Autogenous grinding or semi-autogenous grinding mills can be operated in open or closed circuit. However, even in open circuit, a coarse classifier such as a trommel attached to the mill, or a vibrating screen can be used. The oversize material is recycled either externally or internally. In internal recycling, the coarse material is conveyed by a reverse spiral or water jet back down the center of the trommel into the mill. External recycling can be continuous, achieved by conveyor belt, or is batch where the material is stockpiled and periodically fed back into the mill by front-end loader.

In Figure 7.35 shows the SAG mill closed with a crusher (recycle or pebble crusher). In SAG mill operation, the grinding rate passes through a minimum at a critical size (Chapter 5), which represents material too large to be broken by the steel grinding media, but has a low self-breakage rate. If the critical size material, typically 2550mm, is accumulated the mill energy efficiency will deteriorate, and the mill feed rate decreases. As a solution, additional large holes, or pebble ports (e.g., 40100mm), are cut into the mill grate, allowing coarse material to exit the mill. The crusher in closed circuit is then used to reduce the size of the critical size material and return it to the mill. As the pebble ports also allow steel balls to exit, a steel removal system (such as a guard magnet, Chapters 2 and 13Chapter 2Chapter 13) must be installed to prevent them from entering the crusher. (Because of this requirement, closing a SAG mill with a crusher is not used in magnetic iron ore grinding circuits.) This circuit configuration is common as it usually produces a significant increase in throughput and energy efficiency due to the removal of the critical size material.

An example SABC-A circuit is the Cadia Hill Gold Mine, New South Wales, Australia (Dunne et al., 2001). The project economics study indicated a single grinding line. The circuit comprises a SAG mill, 12m diameter by 6.1m length (belly inside liners, the effective grinding volume), two pebble crushers, and two ball mills in parallel closed with cyclones. The SAG mill is fitted with a 20MW gearless drive motor with bi-directional rotational capacity. (Reversing direction evens out wear on liners with symmetrical profile and prolongs operating time.) The SAG mill was designed to treat 2,065t h1 of ore at a ball charge of 8% volume, total filling of 25% volume, and an operating mill speed of 74% of critical. The mill is fitted with 80mm grates with total grate open area of 7.66m2 (Hart et al., 2001). A 4.5m diameter by 5.2m long trommel screens the discharge product at a cut size of ca. 12mm. Material less than 12mm falls into a cyclone feed sump, where it is combined with discharge from the ball mills. Oversize pebbles from the trommel are conveyed to a surge bin of 735t capacity, adjacent to the pebble crushers. Two cone crushers with a closed side set of 1216mm are used to crush the pebbles with a designed product P80 of 12mm and an expected total recycle pebble rate of 725t h1. The crushed pebbles fall directly onto the SAG mill feed belt and return to the SAG mill.

SAG mill product feeds two parallel ball mills of 6.6m11.1m (internal diameterlength), each with a 9.7MW twin pinion drive. The ball mills are operated at a ball charge volume of 3032% and 78.5% critical speed. The SAG mill trommel undersize is combined with the ball mills discharge and pumped to two parallel packs (clusters) of twelve 660mm diameter cyclones. The cyclone underflow from each line reports to a ball mill, while the cyclone overflow is directed to the flotation circuit. The designed ball milling circuit product is 80% passing 150m.

Several large tonnage copper porphyry plants in Chile use an open-circuit SAG configuration where the pebble crusher product is directed to the ball mills (SABC-B circuit). The original grinding circuit at Los Bronces is an example: the pebbles generated in the two SAG mills are crushed in a satellite pebble crushing plant, and then are conveyed to the three ball mills (Mogla and Grunwald, 2008).

Pulverizer systems, which integrate drying, grinding, classification, and transport of the ground fuel to the burners, can present the greatest problems when switching coals/fuels (Carpenter, 1998). Low quality fuels may have grinding properties that are markedly different from the pulverizer design coal (Kitto and Stultz, 2005; Vuthaluru et al., 2003). Consequently, problems are experienced with pulverizer capacity, drying capacity, explosions, abrasive wear of the pulverizer grinding elements, erosion of the coal classifiers and/or distributors, coal-air pipes, and burners.

Whenever there is a loss of a pulverizer, the operator should light oil burner/s to help the operating group of pulverizers to stabilize the flame. At the same time, the operator should bring down the load matching to the capability of the running puverizer/s. Effort should be made to cut in standby pulverizer/s depending on draft fan group capability. Faults in electric supply, if there are any, can then be inspected and rectified. In the case of jamming in the pulverizer internals, the affected pulverizer should be cooled and cleaned and prepared for the next operation.

a pulverizer that is tripped under load will be inerted as established by equipment manufacturer, and maintained under an inert atmosphere until confirmation that no burning or smouldering fuel exists in the pulverizer or the fuel is removed. Inerting media may be any one of CO2, Steam or N2. For pulverizers that are tripped and inerted while containing a charge of fuel, following procedure will be used to clear fuel from the pulverizer:1.Start one of the pulverizers2.Isolate from the furnace all shut-down or tripped pulverizers3.Continue to operate the pulverizer until empty4.When the operating pulverizer is empty, proceed to another tripped and inerted pulverizer and repeat the procedure until all are cleared of fuel

NFPA 85 recommends the pulverizer system arrangement should be such as to provide only one direction of flow, i.e., from the points of entrance of fuel and air to the points of discharge. The system should be designed to resist the passage of air and gas from the pulverizer through the coal feeder into the coal bunker. To withstand pulverizer-operating pressures and to resist percolation of hot air/gas, a vertical or cylindrical column of fuel at least the size of three coal-pipe diameters should be provided between the coal-bunker outlet and the coal-feeder inlet as well as between coal-feeder outlet and the pulverizer inlet. Within these cylindrical columns there will be accumulation of coal that will resist percolation of hot air/gas from the pulverizer to the coal bunker. All components of the pulverized coal system should be designed to withstand an internal explosion gauge pressure of 344kPa [9].

Number of Spare Pulverizers: To overcome forced outage and consequent availability of a number of operating pulverizers it is generally considered that while firing the worst coal one spare pulverizer should be provided under the TMCR (Turbine Maximum Continuous Rating) operating condition. In certain utilities one spare pulverizer is also provided even while firing design coal, but under the BMCR (Boiler Maximum Continuous Rating) operating condition. Practice followed in the United States generally is to provide one spare pulverizer for firing design coal, in larger units two spare pulverizers are provided. However, provision of any spare pulverizer is not considered in current European design [5].

Pulverizer Design Coal: The pulverizer system should be designed to accommodate the fuel with the worst combination of properties that will still allow the steam generator to achieve the design steam flow. Three fuel properties that affect pulverizer-processing capacity are moisture, heating value, and HGI, as discussed earlier.

Unit Turndown: The design of a pulverizer system determines the turndown capability of the steam generator. The minimum stable load for an individual pulverizer firing coal is 50% of the rated pulverizer capacity. Normally in utility boilers, the operating procedure is to operate at least two pulverizers to sustain a self-supported minimum boiler load. Thus, the minimum steam generator load when firing coal without supporting fuel is equal to the full capacity of one pulverizer. Therefore, a loss of one of the two running pulverizers will not trip the steam generator because of loss of fuel and/or loss of flame.

Pulverizer Wear Allowance: A final factor affecting pulverizer system design is a capacity margin that would compensate for loss of grinding capacity as a result of wear between overhauls of the pulverizer (Figure 4.6). A typical pulverizer-sizing criterion is 10% capacity loss due to wear.

The grinder consists of a body with a conical inner surface in which is arranged an internal moving milling cone. The two cones form the milling chamber. On the axle of the internal moving milling cone a debal-ancing vibrator is fitted, which is driven through a flexible transmission. During vibrator rotation, the centrifugal force is generated, leading the internal cone to roll along the inner cone surface of the grinder body without clearance, if material is absent in the milling chamber or across a material layer. Such innercone movement difference is possible owing to the absence in these machines of kinematic limitation of inner cone amplitude. Thus, KID does not have a discharging gap as for eccentric crushers, therefore, the diametric annular between cones is received by coincidence of their axes.

The idea of using the vibrator drive of the cone crusher appeared as long ago as 1925 (US Patent 1 553 333) and then its later versions (German Patent 679 800, 1952; Austrian Patent 200 598, 1957; and Japanese Patent 1256, 1972) were published. In the Soviet Union, the first experimental KID specimens had been created by the early 1950s. Now, in the various branches of industry in the Commonwealth of Independent States, KIDs with capacity from 1 to 300 t/h are produced.

The basic KID feature absence of rigid kinematic bondings between the cones allows the inner moving cone to change its amplitude depending on the variation of grindable material resistance or to stop if a large non-grindable body is encountered; but this is not detrimental and does not lead to plugging. Another KID feature is the nature of the crushing force. In KID, the crushing force is the sum of the centrifugal force of debalance of the inner cone by its gyrating movement. Such force is determined by mechanics and does not depend on the properties of the processed material. The crushing force acts as well on idle running as the result of gapless running in of cones. Therefore, the stability of the inner cone on its spherical support during idle running is ensured.

The grinder consists of a body with a conical inner surface in which is arranged an internal moving milling cone. The two cones form the milling chamber. On the axle of the internal moving milling cone, an unbalanced vibrator is fitted, driven through a flexible transmission. During vibrator rotation, centrifugal force is generated, leading the internal cone to roll along the inner cone surface of the grinder body without clearance if a material that is being grinded is absent in the milling chamber or on this material layer. Such inner cone varying movement is possible owing to the absence in these machines of kinematic limitation of inner cone amplitude. KID does not have a discharging gap as do ordinary cone crushers; therefore, the diametric annular between cones is received by coincidence of their axes.

The idea of using the vibrator drive of the cone crusher appeared as long ago as 1925 (US Patent 1,553,333) and then its later versionsGerman Patent 679,800 (1952), Austrian Patent 200,598 (1957), and Japanese Patent 1256 (1972)were published. The first experimental KID specimens were created in Russia in the early 1950s. Subsequently, in the various branches of industry in the Soviet Union, KIDs with a capacity from 1 to 300t/h were produced. The manufacture of KIDs under license from Soviet Union was developed in Japan in 1981.

The basic KID featurethe absence of rigid kinematic bonding between the conesallows the inner moving cone to change its amplitude, depending on the variation of grindable material resistance, or to stop if a large nongrindable body is encountered. This is not detrimental and does not lead to stopping the debalance. Another KID feature is the nature of the crushing force. In KID, the crushing force is the sum of the centrifugal force of debalance and the inner cone by its gyrating movement. Such force is determined by mechanics and does not depend on the properties of the processed material. This characteristic in combination with the resilient isolation of KID from the foundation allows a two-fold increase in the inner cone vibration frequency.

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Autogenous (AG) and semi-autogenous (SAG) mills have been used for over 20 years for the coarse grinding of diverse ores (including gold, copper and iron ores). They offer advantages with regard to capital costs and operating expense compared to the secondary and tertiary crushers used in conventional size-reduction systems.

The AG/SAG mill is normally installed upstream of a tube mill operating in closed circuit with hydrocyclones. The material discharged from the AG/SAG mill is either fed directly to the tube mill or first screened. If a screen is used, the screen overflow of the AG/SAG mill is returned for further grinding - either directly or via a crusher. The screen underflow is fed into the pump sump together with the material discharged from the tube mill. The coarse material discharged from the hydrocyclones is normally returned to the tube mill, or in special cases to the SAG mill. The fine material discharged from the hydrocyclones (product) is fed to the downstream dressing process. Polysius uses a design of circumferential bearing arrangement for AG/SAG and tube mills with straight end walls that provides clear advantages compared to the conventional mill design with trunnion bearing and conical end walls, such as:

grinding - mineral processing

The final fineness of the product mainly depends on the number of times the ore particles pass through the grinder. The longer the grinding, the smaller the particle size. Separate crushing and grinding steps are necessary, the ball mill can only receive the broken ore particle, and then grind to the grinding fineness required for flotation.

In order to separate the concentrate from the ore, the ore should be ground fine enough to release the target mineral from the non-mineral grains. The degree of grinding required for this depends on the size of the mineral particles in the ore. A laboratory-scale flotation test is usually required on materials of different particle sizes to determine the grinding particle size required to release the target minerals.The fineness of the ore particles produced by grinding is crucial to recover the minerals by flotation. The most common grinding machines are semi-automatic (SAG) and automatic (AG) mills and ball mills.

Determining an optimal grinding size can maximize the recovery of target minerals in the subsequent flotation process.The grinding size is too large, and some ore particles and non-ore particles cannot be separated, thus preventing their flotation. If the particle size is too fine, the bubbles that rise during the flotation will push the very fine ore-containing particles away, preventing them from contacting the bubbles, thereby reducing their ability to be recovered into the concentrate.In addition, extremely fine rock and iron sulfide particles may agglomerate with extremely fine sulfide ore particles, preventing the ore particles from floating.

According to the test, the particles usually need to be ground to a diameter of about 100 mm to release minerals from each other. When the particles are less than about 10 mm, this is not conducive to the flotation effect.Grinding operations are very power-hungry, which is another reason to avoid excessive grinding.

The crushed products are ground in SAG or AG mills. The self-grinding machine can grind ore without grinding media such as iron ball, or steel rod, as long as the hardness of the ore is sufficient for the rolling ore to grind by itself.A large vibrating screen is used to sieve the ground products to separate the oversized particles. A small cone crusher to recover the oversized material, and then sent them return to the SAG or AG mill for re-grinding. The correct size material is sent to the ball mill for final grinding.

The ball mill is the fine grinding machine connect the SAG or AG mill and flotation machine. Ball mills produce fine particles with a uniform size for flotation, its grinding medias commonly are steel ball. The ball mill rolls grinding media together with the ore, as the ore grinds, these balls initially 5-10 cm in diameter but gradually wear out.Grinding is always carried out under wet conditions, with about 70% solid mixture in water.This procedure maximizes ore production and minimizes power consumption.

what's the difference between sag mill and ball mill - jxsc machine

A mill is a grinder used to grind and blend solid or hard materials into smaller pieces by means of shear, impact and compression methods. Grinding mill machine is an essential part of many industrial processes, there are mainly five types of mills to cover more than 90% materials size-reduction applications.

Do you the difference between the ball mill, rod mills, SAG mill, tube mill, pebble mill? In the previous article, I made a comparison of ball mill and rod mill. Today, we will learn about the difference between SAG mill vs ball mill.

AG/SAG is short for autogenous mill and semi-autogenous mill, it combines with two functions of crushing and grinding, uses the ground material itself as the grinding media, through the mutual impact and grinding action to gradually reduce the material size. SAG mill is usually used to grind large pieces into small pieces, especially for the pre-processing of grinding circuits, thus also known as primary stage grinding machine. Based on the high throughput and coarse grind, AG mills produce coarse grinds often classify mill discharge with screens and trommel. SAG mills grinding media includes some large and hard rocks, filled rate of 9% 20%. SAG mill grind ores through impact, attrition, abrasion forces. In practice, for a given ore and equal processing conditions, the AG milling has a finer grind than SAG mills.

The working principle of the self-grinding machine is basically the same as the ball mill, the biggest difference is that the sag grinding machine uses the crushed material inside the cylinder as the grinding medium, the material constantly impacts and grinding to gradually pulverize. Sometimes, in order to improve the processing capacity of the mill, a small amount of steel balls be added appropriately, usually occupying 2-3% of the volume of the mill (that is semi-autogenous grinding).

High capacity Ability to grind multiple types of ore in various circuit configurations, reduces the complexity of maintenance and coordination. Compared with the traditional tumbling mill, the autogenous mill reduces the consumption of lining plates and grinding media, thus have a lower operation cost. The self-grinding machine can grind the material to 0.074mm in one time, and its content accounts for 20% ~ 50% of the total amount of the product. Grinding ratio can reach 4000 ~ 5000, more than ten times higher than ball, rod mill.

Ball mills are fine grinders, have horizontal ball mill and vertical ball mill, their cylinders are partially filled with steel balls, manganese balls, or ceramic balls. The material is ground to the required fineness by rotating the cylinder causing friction and impact. The internal machinery of the ball mill grinds the material into powder and continues to rotate if extremely high precision and precision is required.

The ball mill can be applied in the cement production plants, mineral processing plants and where the fine grinding of raw material is required. From the volume, the ball mill divide into industrial ball mill and laboratory use the small ball mill, sample grinding test. In addition, these mills also play an important role in cold welding, alloy production, and thermal power plant power production.

The biggest characteristic of the sag mill is that the crushing ratio is large. The particle size of the materials to be ground is 300 ~ 400mm, sometimes even larger, and the minimum particle size of the materials to be discharged can reach 0.1 mm. The calculation shows that the crushing ratio can reach 3000 ~ 4000, while the ball mills crushing ratio is smaller. The feed size is usually between 20-30mm and the product size is 0-3mm.

Both the autogenous grinding mill and the ball mill feed parts are welded with groove and embedded inner wear-resistant lining plate. As the sag mill does not contain grinding medium, the abrasion and impact on the equipment are relatively small.

The feed of the ball mill contains grinding balls. In order to effectively reduce the direct impact of materials on the ball mill feed bushing and improve the service life of the ball mill feed bushing, the feeding point of the groove in the feeding part of the ball mill must be as close to the side of the mill barrel as possible. And because the ball mill feed grain size is larger, ball mill feeding groove must have a larger slope and height, so that feed smooth.

Since the power of the autogenous tumbling mill is relatively small, it is appropriate to choose dynamic and static pressure bearing. The ball bearing liner is made of lead-based bearing alloy, and the back of the bearing is formed with a waist drum to form a contact centering structure, with the advantages of flexible movement. The bearing housing is lubricated by high pressure during start-up and stop-up, and the oil film is formed by static pressure. The journal is lifted up to prevent dry friction on the sliding surface, and the starting energy moment is reduced. The bearing lining is provided with a snake-shaped cooling water pipe, which can supply cooling water when necessary to reduce the temperature of the bearing bush. The cooling water pipe is made of red copper which has certain corrosion resistance.

Ball mill power is relatively large, the appropriate choice of hydrostatic sliding bearing. The main bearing bush is lined with babbitt alloy bush, each bush has two high-pressure oil chambers, high-pressure oil has been supplied to the oil chamber before and during the operation of the mill, the high-pressure oil enters the oil chamber through the shunting motor, and the static pressure oil film is compensated automatically to ensure the same oil film thickness To provide a continuous static pressure oil film for mill operation, to ensure that the journal and the bearing Bush are completely out of contact, thus greatly reducing the mill start-up load, and can reduce the impact on the mill transmission part, but also can avoid the abrasion of the bearing Bush, the service life of the bearing Bush is prolonged. The pressure indication of the high pressure oil circuit can be used to reflect the load of the mill indirectly. When the mill stops running, the high pressure oil will float the Journal, and the Journal will stop gradually in the bush, so that the Bush will not be abraded. Each main bearing is equipped with two temperature probe, dynamic monitoring of the bearing Bush temperature, when the temperature is greater than the specified temperature value, it can automatically alarm and stop grinding. In order to compensate for the change of the mill length due to temperature, there is a gap between the hollow journal at the feeding end and the bearing Bush width, which allows the journal to move axially on the bearing Bush. The two ends of the main bearing are sealed in an annular way and filled with grease through the lubricating oil pipe to prevent the leakage of the lubricating oil and the entry of dust.

The end cover of the autogenous mill is made of steel plate and welded into one body; the structure is simple, but the rigidity and strength are low; the liner of the autogenous mill is made of high manganese steel.

The end cover and the hollow shaft can be made into an integral or split type according to the actual situation of the project. No matter the integral or split type structure, the end cover and the hollow shaft are all made of Casting After rough machining, the key parts are detected by ultrasonic, and after finishing, the surface is detected by magnetic particle. The surface of the hollow shaft journal is Polished after machining. The end cover and the cylinder body are all connected by high-strength bolts. Strict process measures to control the machining accuracy of the joint surface stop, to ensure reliable connection and the concentricity of the two end journal after final assembly. According to the actual situation of the project, the cylinder can be made as a whole or divided, with a flanged connection and stop positioning. All welds are penetration welds, and all welds are inspected by ultrasonic nondestructive testing After welding, the whole Shell is returned to the furnace for tempering stress relief treatment, and after heat treatment, the shell surface is shot-peened. The lining plate of the ball mill is usually made of alloy material.

The transmission part comprises a gear and a gear, a gear housing, a gear housing and an accessory thereof. The big gear of the transmission part of the self-grinding machine fits on the hollow shaft of the discharge material, which is smaller in size, but the seal of the gear cover is not good, and the ore slurry easily enters the hollow shaft of the discharge material, causing the hollow shaft to wear.

The big gear of the ball mill fits on the mill shell, the size is bigger, the big gear is divided into half structure, the radial and axial run-out of the big gear are controlled within the national standard, the aging treatment is up to the standard, and the stress and deformation after processing are prevented. The big gear seal adopts the radial seal and the reinforced big gear shield. It is welded and manufactured in the workshop. The geometric size is controlled, the deformation is prevented and the sealing effect is ensured. The small gear transmission device adopts the cast iron base, the bearing base and the bearing cap are processed at the same time to reduce the vibration in operation. Large and small gear lubrication: The use of spray lubrication device timing quantitative forced spray lubrication, automatic control, no manual operation. The gear cover is welded by profile steel and high-quality steel plate. In order to enhance the stiffness of the gear cover, the finite element analysis is carried out, and the supporting structure is added in the weak part according to the analysis results.

The self-mill adopts the self-return device to realize the discharge of the mill. The self-returning device is located in the revolving part of the mill, and the material forms a self-circulation in the revolving part of the mill through the self-returning device, discharging the qualified material from the mill, leading the unqualified material back into the revolving part to participate in the grinding operation.

The ball mill adopts a discharge screen similar to the ball mill, and the function of blocking the internal medium of the overflow ball mill is accomplished inside the rotary part of the ball mill. The discharge screen is only responsible for forcing out a small amount of the medium that overflows into the discharge screen through the internal welding reverse spiral, to achieve forced discharge mill.

The slow drive consists of a brake motor, a coupling, a planetary reducer and a claw-type clutch. The device is connected to a pinion shaft and is used for mill maintenance and replacement of liners. In addition, after the mill is shut down for a long time, the slow-speed transmission device before starting the main motor can eliminate the eccentric load of the steel ball, loosen the consolidation of the steel ball and materials, ensure safe start, avoid overloading of the air clutch, and play a protective role. The slow-speed transmission device can realize the point-to-point reverse in the electronic control design. When connecting the main motor drive, the claw-type Clutch automatically disengages, the maintenance personnel should pay attention to the safety.

The slow drive device of the ball mill is provided with a rack and pinion structure, and the operating handle is moved to the side away from the cylinder body The utility model not only reduces the labor intensity but also ensures the safety of the operators.

developments in iron ore comminution and classification technologies - sciencedirect

Hematite and magnetite, the two predominant iron ores, require different processing routes. High-grade hematite direct shipping ores (DSOs) generally only require crushing and screening to meet the size requirements of lump (typically between 6 and 30mm) and fines (typically less than 6mm) products. Low-grade hematite ores require additional beneficiation to achieve the desired iron content, but the comminution of these ores still generally only involves crushing and screening, which is not particularly energy-intensive. Conversely, fine-grained magnetite ores require fine grinding, often to below 30m, to liberate the magnetite from the silica matrix, incurring greater costs and energy consumption. The comminution energy consumption could be over 30kWh/t, an order of magnitude higher than for hematite ores. However, with the depletion of high-grade deposits and strong demand for steel, a greater number of low-grade deposits are being developed.

To operate viably and sustainably, there is a need to reduce costs and energy consumption, particularly of the energy-intensive grinding required for low-grade magnetite deposits. This chapter reviews current iron ore comminution and classification technologies and presents some examples of flowsheets from existing operations. New trends and advances in comminution technologies are presented and discussed, particularly with regard to the impact on energy, operating, and capital costs.

autogenous and semi-autogenous (ag/sag) mills brochure - metso corporation - pdf catalogs | technical documentation | brochure

Metsos AG/SAG mills accomplish the same size reduction work as 2 or 3 stages of crushing and screening The feed size for these mills is limited to the maximum size that can be practically conveyed and introduced into the large mill feed chutes. And the product of the large AG/SAG grinding is either a finished size ready of processing, or an immediate size for further grinding in a ball mill, pebble mill, VERTIMILL or a stirred media detritor (SMD). Grinding circuit design AG/SAG mills are normally used to grind run-offmine ore or primary crusher product. Feed size to the mill is limited...

Making the big difference to our customers Everything we do is based on deep industry knowledge and expertise that makes the big difference to our customers. Decades of close customer collaboration and adapting to our customers ever changing needs have transformed us into a knowledge company. www.metso.com [email protected] Subject to alteration without prior notice Brochure No. 1484-05-16-ESBL/Sala - English 2016 Metso

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