american technology iron ore g rinding ball mill with

vertimill vertical grinding technology reduces energy consumption by 30% in anglo american's regrinding circuit - metso outotec

For the Anglo American venture, Metso supplied 16 Vertimill VTM-1500-WB model grinding mills. The circuit comprises two regrinding lines, each composed of 8 mills, each with a power of 1.1 megawatts (MW), and four cyclone batteries for grading iron ore."Minas-Rio uses 17.9 MW of power in its regrinding process while the application with ball mills would be 25.6 MW; this represents a significant reduction of 7.7 MW", says Rodrigo Vilela, Director of Operation of Anglo American's Minas-Rio system, part of Anglo American's Iron Ore Business Unit in Brazil.

According to Vilela, the granulometry of the iron ore in the Minas-Rio System at the end of the regrinding process is 80% less than 36 micrometers. The iron ore from the underflow of the regrinding cyclones feeds the Vertimill grinding mills through the lower part and the resulting product is transported to the top of the mills, towards the concentrate thickener, the last step of the milling process.

Metso has over 100 years of experience in designing and building mills and three decades of success with Vertimill grinding mill applications. Since their launch in 1979, more than 440 Vertimills have been sold worldwide.

Among the characteristics of the Vertimill, the reduction in capacity stands out it can operate with a minimum energy consumption of 20%, making it ideal for regrinding applications and other applications with highly variable flows. The product offers a number of advantages over traditional ball mills, such as lower operating costs and greater energy efficiency (from 25 to 35%). Another benefit that stands out is the low maintenance, since the thread coatings are the only significant components of wear.

Metso's solution brought a number of differentiators to the Anglo American project: the use of the mills reduced the creation of ultrafine particles, noise emissions and the number of peripherals, as well as providing simpler and safer civilian bases due to less exposure to movable parts.

The Minas-Rio Project is considered to be the largest mining venture in the world and comprises four initiatives: the opening of a mine and the installation of an iron ore processing plant, both in Minas Gerais, the construction of a pipeline and the implementation of a terminal in the Au Port, Rio de Janeiro. Currently, the operation is in the ramp-up phase to reach the nominal production capacity of 26.5 million tons of iron ore per year in the second quarter of 2016.

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.

vertical mill simulation applied to iron ores - sciencedirect

The application of vertical mills in regrind circuits is consolidated. This type of mill is now attracting interest in primary grinding applications, due to its higher efficiency when compared to ball mills, which are usually used at this stage. In this study, a coarse sample of iron ore was tested in a pilot scale grinding circuit with a vertical mill. Other three samples of pellet feed had already been tested with the methodology used in this study. The sample of coarse iron ore was characterized in laboratory tests carried out in a small batch ball mill. Selection and breakage function parameters were determined from the laboratory tests. The parameters were then used for simulating the pilot scale tests using Modsim software. The model previously implemented in Modsim has been successfully applied to represent the vertical mill operated with different ores. The simulations produced particle size distributions that were very close to the actual size distributions, and the predictions were accomplished only by imputing the calibrated parameters from the batch tests, the power draw and the feed size distribution of the pilot tests. The methodology is therefore useful for scale-up and simulation of vertical mills, only requiring laboratory tests that can be carried out in standard laboratory batch ball mills with small amounts of samples.

flexible milling and grinding solutions that last | flsmidth

With years of experience in the cement and mining industries and over 3000 mills sold worldwide, FLSmidth continues to develop its range of efficient milling and grinding solutions. This experience and know-how, as well as close collaboration with our customers, means we can deliver advanced milling and grinding technology solutions that puts us at the forefront as a partner.

We know that you strive to increase production while saving on CAPEX, operation and maintenance costs. Further, consideration for the environment is a priority for production industries, making energy-efficient designs highly sought after. So, these are our priorities when designing milling and grinding equipment to meet your needs.

Milling and grinding of raw material, minerals and cement is a rough process, with highly abrasive and hard feed materials that can accelerate equipment wear and tear. This leads to increased costs for equipment and spare parts replacement, and costly maintenance. It is crucial that the equipment used for milling and grinding can withstand such harsh materials. Our range of milling and grinding technologies have been tried and tested around the globe. Our vertical roller mills, horizontal mills, hydraulic roller presses and stirred mills have for many years offered efficient milling and grinding, flexibility, cost savings and easier maintenance. Whatever the application, one of our robust milling and grinding solutions will be suitable for grinding all types of feed materials including hard rock ores, raw, cement or slag. We work closely with you to realise the potential of the technology that will benefit you. Some of the features you can benefit from in our milling and grinding solutions include:

With the knowledge and experience gained throughout the years, we ensure that you have the best milling or grinding solution possible, whether you are working in the cement industry or mining industry.

For the cement industry, our Hydraulic Roller Press is suitable for water-scarce locations as it does not require water for deagglomeration of feed material in the roller press. It is also adaptable to three different types of grinding setups: pre-grinding, semi-finish grinding and finish grinding. The OKTM mill can skilfully grind raw or cement feed material and offers parts commonality, simplifying spare parts inventory and facilitating easy switching of parts between vertical roller mills. Our ATOX coal mill has large rollers with great grinding capability of all types of coal, tolerating moisture levels up to 20 percent.

For the mining industry, our semi-autogenous (SAG) grinding mill uses a minimal ball charge in the range of 6-15 percent. It is primarily used in the gold, copper and platinum industries as well as in the lead, zinc, silver, and nickel industries. Autogenous (AG) grinding mills involve no grinding media as the ore itself acts as the grinding media.

Our ball mills are the most robust design in the industry, available with either geared or gearless drive arrangements. The cost-effective FT Series mills are smaller, gear driven and feature hydrodynamic lubrication.

Understanding the challenges you face when milling and grinding hard feed material, we have built our technologies to last. We have paid particular attention to the wear parts because they are right there where the action is, making it all happen. We hardface them with the toughest

There is no doubt that milling and grinding cement and other feed material is tough work. We offer well-designed technologies to endure virtually any hard rock ore or raw material, with differing moisture levels and particle size. Whatever your milling and grinding needs are, FLSmidth is your trusted partner.

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.

development of a novel grinding process to iron ore pelletizing through hpgr milling in closed circuit | springerlink

The earliest industrial application of high pressure grinding rolls (HPGR) at comminution was in 1984 in the cement industry. Since then, the equipment has been widely applied in mining activities. Despite the rapid spread across the industry, several challenges are still present in the equipments application, especially considering the complex ore breakage behaviour reported for this process. The pellet feeds HPGR comminution was recognized as fundamental to efficiently increase the particle surface area (e.g., blaine specific area, BSA) at a lower energy and water consumption level (Chapman et al. in J Southern Afr Instit Mining Metall 113:407413, 2013). The present study considers a novel milling process applying only HPGR as a re-regrind stage after concentration. The amount of successive ground product recirculation into the machine to achieve the required particle size for the pelletizing process was investigated. The study compared the ball wet milling process with the innovative processing technology for hematitegoethite ores. Green pellet balling and induration processes were simulated in bench and pilot scale. The milling results showed a considerably steep increase in BSA after each recirculation step into the HPGR, although compared with the ball-milled product the size fraction <45m% increased a modest five percentage points after three recirculation cycles, remaining steady until the last recirculation step. As a result, the green pellet generated presented higher concentration of pellets between 10 and 16mm (%10-16mm), with a higher drop number than typically observed when produced with ball-milled feedstock. Consequently, on the induration process, a higher pellet deformation was observed during the pot grate loading. Despite that, the fired pellets still presented an outstanding performance in cold crush strength (CSS) considered suitable to an industrial application.

Athayde M, Bagatini MC (2018) Iron ore concentrate particle size controlling through application of microwave at the HPGR feed. Mining Metall Explor 36(2):353362. https://doi.org/10.1007/s42461-018-0013-y

Chapman NA, Shackleton NJ, Malysiak V, Oconnor CT (2013) Comparative study of the use of HPGR and conventional wet and dry grinding methods on the flotation of base metal sulphides and PGMs. J Southern Afr Instit Mining Metall 113:407413

Forsmo SPE, Samskog PO, Bjrkman BMT (2008) A study on plasticity and compression strength in wet iron ore green pellets related to real process variations in raw material fineness. Powder Technol 181(3):321330

Thomazini, A.D., Trs, E.P., de Assis Dutra Macedo, F. et al. Development of a Novel Grinding Process to Iron Ore Pelletizing through HPGR Milling in Closed Circuit. Mining, Metallurgy & Exploration 37, 933941 (2020). https://doi.org/10.1007/s42461-020-00202-z

grinding cylpebs

Our automatic production line for the grinding cylpebs is the unique. With stable quality, high production efficiency, high hardness, wear-resistant, the volumetric hardness of the grinding cylpebs is between 60-63HRC,the breakage is less than 0.5%. The organization of the grinding cylpebs is compact, the hardness is constant from the inner to the surface. Now has extensively used in the cement industry, the wear rate is about 30g-60g per Ton cement.

Grinding Cylpebs are made from low-alloy chilled cast iron. The molten metal leaves the furnace at approximately 1500 C and is transferred to a continuous casting machine where the selected size Cylpebs are created; by changing the moulds the full range of cylindrical media can be manufactured via one simple process. The Cylpebs are demoulded while still red hot and placed in a cooling section for several hours to relieve internal stress. Solidification takes place in seconds and is formed from the external surface inward to the centre of the media. It has been claimed that this manufacturing process contributes to the cost effectiveness of the media, by being more efficient and requiring less energy than the conventional forging method.

Because of their cylindrical geometry, Cylpebs have greater surface area and higher bulk density compared with balls of similar mass and size. Cylpebs of equal diameter and length have 14.5% greater surface area than balls of the same mass, and 9% higher bulk density than steel balls, or 12% higher than cast balls. As a result, for a given charge volume, about 25% more grinding media surface area is available for size reduction when charged with Cylpebs, but the mill would also draw more power.

buy ore ball mill for mineral processing | iron & gold ore ball mill

Ore ball mill sometimes called ore grinding mill, is generally used in mineral processing concentrator, processing materials include iron ore, copper ore, gold ore, molybdenum ore and all kinds of nonferrous metal ore. The core function of the ore ball mill is to grind the materials, and also to separate and screen different mineral materials, and to separate the tailings, which is very important to improve the quality of the selected mineral materials.

The ore ball mill designed by our company, which is represented by gold ore ball mill and iron ore ball mill, is manufactured with high-quality materials and advanced technology. They have the characteristics of high efficiency, energy-saving, green environmental protection, simple operation, stable operation, and low failure rate, and have a good reputation in the industry.

The crushing ratio of the ore grinding mill is very large, and it is easy to adjust the fineness of the grinding product. The ore grinding mill has strong sealing performance and can be operated under negative pressure. It is widely used in chemical industry, metallurgy, new building materials and other fields.

We offer different types of ore ball mills for customers to choose from. There are energy-saving ore ball mill, dry and wet ball mill,wet grate ball mill, andwet overflow ball mill. Customers can choose to purchase according to material conditions.

Mineral processing is the most important link in the entire production process of mineral products. It is a process of separating useful minerals from useless minerals (usually called gangue) or harmful minerals in a mineral raw material by physical or chemical methods, or a process of separating multiple useful minerals The process is called mineral processing, also known as ore processing.

The first step in the ore processing is to select the useful minerals. In order to select useful minerals from ore, the ore must be crushed first. Sometimes, in order to meet the requirements of subsequent operations on the particle size of materials, it is necessary to add a certain ore grinding operation in the process.

The preparation before beneficiation is usually carried out in two stages: crushing screening operation and mineral classification operation. Crusher and ore ball mill are the main equipment in these two stages.

As a ball mills supplier with 22 years of experience in the grinding industry, we can provide customers with types of ball mill, vertical mill, rod mill and AG/SAG mill for grinding in a variety of industries and materials.

iron ore grinding process,process design for grinding stage,closed circuit grinding technology | prominer (shanghai) mining technology co.,ltd

Generally, the conventional process can be applied except for ore with a lot of mud and high humidity. The self-grinding and semi-self-grinding processes have high power consumption and should be selected carefully.

There is no strict restriction on the upper limit and particle size distribution of the products in the open-circuit grinding process. Because the ore to be ground passes through the grinding machine only once, the product size is relatively coarse. This type of process is commonly used in the first stage of the single-stage rod milling process or the first stage of the two-stage grinding process with rod mills. The ore can be ground from 20-25 mm to about 3 mm at a time. The open-circuit grinding process is simple, the production capacity is large, no grading and return ore facilities are required, the construction speed is fast, the production operation and maintenance are easy, and it is generally used for rough grinding.

In closed-circuit grinding, the returned sand from the classifier is mostly finer than the original ore. The returned sand is mixed with the ore newly fed into the mill, so that the average particle size of the ore particles in the mill is reduced, and the content of ore particles close to the particle size of the grinding product increases. The gap around the coarse-grained ore is filled with fine-grained sand. It is beneficial to form a more favorable meshing between the crushing medium and the ore particles. Along the entire length of the grinding machine, the ratio of the size of the ball to the average diameter of the ore particles is relatively stable. The material flows faster in the grinding machine. Therefore, the productivity of the closed-circuit grinding machine is generally higher than that of the open-circuit grinding machine, and the product size is smaller. Fine, uniform particle size, less over-crushing. Closed-circuit grinding can also improve the selective grinding of heavy minerals.

The beneficiation practice shows that in each grinding section, the grinding ratio has a suitable value, and the grinding ratio of the conventional ball milling section is generally about 80-100. An excessively large primary grinding ratio is uneconomical. The grinding efficiency is low, the energy consumption is high, and the product is easily crushed, which affects the sorting effect and economic benefits. Practice has shown that the more difficult to grind the ore, the less economically reasonable it is to use one-stage grinding process for fine grinding. The two-stage grinding process can overcome the shortcomings of the one-stage grinding process. It can reasonably distribute the load according to the difference in the particle size of the materials in the grinding mills and the properties of the wear-resistant materials, and it is easy to select the appropriate medium size and ratio according to the different feed and product particle sizes of the two-stage mills.

When the grindability of the ore is very poor and the grinding particle size is required to be extremely fine, or the concentrate grade is required to be high and the ore is fine-grained or unevenly embedded, or the old concentrator wants to improve the original grinding When operating the production capacity, three-stage or multi-stage grinding process can be used. For ore that is extremely easy to slush, in order to improve the efficiency of grinding and beneficiation, prevent excessive crushing, and recover the dissociated useful minerals as soon as possible, the stage grinding and stage separation process can be used. In this way, the use of selective grinding can effectively recover useful minerals. Large-scale iron ore concentrators that adopt a staged grinding process can sort and discard coarse-grained tails after one stage of grinding if the iron ore properties are suitable.

Prominer has been devoted to mineral processing industry for decades and specializes in mineral upgrading and deep processing. With expertise in the fields of mineral project development, mining, test study, engineering, technological processing.