ag mills - metso outotec

ag mills - metso outotec

AG milling extends itself to many applications due to the range of mill sizes available. AG mills can accomplish the same size reduction work as two or three stages of crushing and screening, a rod mill and some or all of the work done by a ball mill.

The range of mill sizes and versatile applications allow AG milling to be accomplished with fewer lines than conventional set-ups. This, in turn, contributes to lower capital and maintenance costs for an AG mill circuit.

The Metso Outotec Qdx4TM mill drive provides the next step in the evolution of change in mill drive architecture, while allowing the system to be built with components that are within current manufacturing capabilities. We are essentially providing up to twice the power transmission of a conventional dual pinion drive.

autogenous and semi-autogenous mills | flsmidth

autogenous and semi-autogenous mills | flsmidth

Since the early 1980s, we have been designing and manufacturing Semi-Autogenous (SAG) and Autogenous (AG) Grinding Mills under the Fuller-Traylor brand. Semi-autogenous grinding uses a minimal ball charge in the range of 6-15% while autogenous grinding uses ore only.

SAG and AG Mills operate by lifting ore/grinding media and dropping it on the operating bed of the mill charge. High impacts from lifting ore and media promote impact breakage which is the primary mechanism for size reduction in the mill. Via the use of sophisticated instruments and software, we closely monitor the mill impact location to boost the grinding efficiency of your operation.

The mills can be operated in open circuit, feeding downstream secondary grinding, or operated in closed circuit as single stage mills generating a finer product size. Single stage SAG Mills are very beneficial in reducing CAPEX for plants with a staged throughput approach. When future tonnage is to be increased, the SAG Mill can feed downstream ball milling to boost capacity.

Fuller-Traylor SAG/AG Mills range in size from 4.3m through 12.2m in diameter with powers as high as 28,000 kW. Our team of product engineers continually improves SAG/AG Mill designs in order to provide the most robust, safe, and efficient grinding mills available.

Your operation requires a SAG or AG Mill that is flexible, durable, cost-efficient and tailored to your specific needs and use cases. That's why we offer a full product range from 4.3m to 12.2m in diameter with multiple options for configuration of designs to suit your operation:

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.

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cancers | free full-text | sinonasal squamous cell carcinoma, a narrative reappraisal of the current evidence | html

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autogenous ag & sag mills for sale

autogenous ag & sag mills for sale

Starting as small as 13 feet (4 m) in diameter on 330 HP and as large as 24 (14.5 m) in diameter on 3,300 HP, the 911MPE Semi & FullyAutogenous Mills tumble crushed ore without iron or steel grinding media. They are used when the crushed ore pieces are hard enough to perform all the grinding.SAG mills tumble mainly ore but they use up to 15% volume of steel balls to assist grinding. Semi-autogenous mills are more common.

The AG Millor SAG grinds primary crusher product and prepares it for final grinding in a ball mill. Its product is usually passed over a large vibrating screen to separate oversize pebbles from correct-size particles. The correct-size material is sent forward to a ball mill for final grinding. The oversize pebbles are recycled through a small eccentric crusher, then back to the SAG orautogenous grinding mill. This procedure maximizes ore throughput and minimizes electrical energy consumption.

The autogenous mill itself is a coarse-grinding device, consisting of tumbling drum with a 25% to 40% volume filling of ore. Metallic or manufactured grinding media is not used. Autogenous mills are fed run-of-mine ore or primary crusher product that is <25 cm (10). Inside the mill, largepieces break into smaller pieces a few inches in size. These natural pebbles act as the grinding media the autogenous mill. The main modes of breakage are thought to be impact breakage and abrasion.

Many circuit configurations are possible, but essentially the autogenous or SAG mill is operated as a single-stage primary mill, or it can be followed by secondary pebble or ball milling. The semi & autogenous mill is often operated in closed circuit with a trommel screen or external vibrating screen classifying the discharge. Circulating loads are low compared with those in ball mill circuits, because autogenous mills do not benefit from high-circulating loads in the same way ball mills do. Intermediate crushers are sometimes used to crush the largest pieces in the recycle stream.

Autogenous grinding implies by definition the grinding of ore by itself. Autogenous mills can be operated in tandem with secondary grinding mills (either a ball or a pebble mill) or they can be operated as single-stage mills in closed-circuit with a classification or sizing device. If a critical size builds up in the charge of the autogenous mill, it is usually extracted through pebble ports and crushed for recycle. Autogenous mills rely upon attrition grinding for their operation.

Disintegration and size reduction of some ores is possible in tumbling mills without the aid of grinding media. Grinding mills in which comminution takes place without grinding aids are known as Autogenous Grinding (AG) mills or Fully Autogenous Grinding mills (FAG). These mills use large lumps of rock as the grinding media. Mills that use intermediate size rock or pebbles as a grinding medium are also autogenous mills but are known as pebble mills.

The disintegration and size reduction of ores in AG mills is brought about by a combination of impact, attrition and abrasion forces during mill rotation. Particles at the toe of the mill charge receive the maximum impact forces from falling rocks and other grinding media. Particles in the body of the mill charge partly slide from different heights and are subjected to attrition and abrasion resulting in size reduction.

The operation of AG & SAG mills therefore involves the use of cheaper grinding media as a replacement for expensive steel balls and rods which greatly affect the wear on liners. They are therefore less expensive to operate. It is necessary that the ore should provide a sufficient amount of lumps that would last for a reasonable time to act as the grinding medium. Such ores have been described as competent ores. Ores that break up easily arc referred to as either non-competent or incompetent ore.

SAG Mill grinding relies on the addition of balls to the primary mill which are required to break up harder and coarser pieces and also to grind mid-size and and particles. It is used to grind ores which require fracturing across grain or crystalline boundaries in addition to attrition grinding. Again, circuits can be designed for either single or two-stage operation and occasionally a crusher might be added to deal with a buildup of particularly hard critical size material.

The feed to an autogenous or semi-autogenous mill is usually primary crushed. When considering the necessity to crush run-of-nine ore, the expected behaviour of the primary mill towards a coarser feed and the maximum lump size which is physically acceptable to the mill relative to that originating in run-of-mine ore have to be investigated.

Autogenous grinding work is conducted in a separate pilot setup. The crude ore is crushed to a maximum size of 9 in. and screened into 3 sizes. The primary mill is 5- ft. in diameter. The length can be varied from 2 ft. to 5 ft. in 4 and/or 11 in. increments. The secondary grinding circuit uses a 3 ft. diameter by 5 ft. long pebble or ball mill. Three hydroseparators ranging from 2 to 6 ft. in diameter and a 5 ft. thickener are used as required in the circuit. There are 3 types of filters and a variety of pumps, cyclones, screens, magnetic separators and the other auxiliary equipment required to complete the concentrating and material handling aspects of the pilot plant.

The pover draw of an autogenous mill is directly proportional to the charge volume, which, in turn, is maintained by feed rate. This investigation showed no significant difference in the grinding power requirement, or the metallurgy of the product, with changes in volume. However, if an autogenous mill level is too high, centrifuging will begin. This was observed to begin around the 40% level while operating at 76% of critical speed. P. M. & Co. commercial installations are designed to draw full power at 30% mill volume. The commercial autogenous mills are controlled by setting power draw and automatically regulating feed rate to maintain this set point. Therefore, it is impossible for the mills to centrifuge, or shutdown because of motor overload.

The effect of percent solids in the autogenous mill was tested. With a trunnion discharge mill, varying the % solids showed no change in either mill throughput or power requirement. A peripheral discharge mill produced a coarser grind with a corresponding increase in throughput at lower % solids. This is probably caused by faster transport through the mill giving a product sized closer to the mill discharge screen opening. The choice of mill solids must be made for metallurgical and economic reasons and the optimum would vary with ore type and desired grind.

The effect of a ball charge, equal to 2% of the autogenous mill volume, was a coarser grind in open circuit. This transfers some of the grinding from the lower operating cost autogenous mills to the higher cost ball mills, which is usually not economical. The use of balls in the primary mill is also more expensive because of increased liner wear and the cost of the steel media itself.

The single most important element in pilot plant testing is the accurate determination of the power. The power readings are a combination of grinding power and electrical-mechanical inefficiencies. To obtain the net grinding power, a dynamometer, or Prony brake test, was conducted on the pilot autogenous mill both empty and filled with crushed gravel. The brake was attached to the feed end of the mill and by varying the pressure to the drum, the mill motor could be varied from no load to maximum draw. The reason for completely filling the mill with crushed rock was to duplicate the weight of the grinding charge, including water, at 30% mill volume without adding torque. Therefore, the mechanical and electrical inefficiencies are the same as when the mill is grinding ore. With this method, net grinding power is determined. The horsepower requirement of a commercial size mill is calculated by adding the inefficiencies of its power train to this net figure.

The economic advantages of the primary autogenous mill over the conventional rod mill are due to the following factors: (1) autogenous mill feed requires less crushing; therefore, the capital and operating costs of the ore preparation are lower; (2) the autogenous mill uses no steel grinding media so liner wear costs are less; (3) large autogenous mills are available, which means fewer units are required and grinding mill maintenance expense is reduced.

The metallurgical advantages of autogenous milling are: (1) liberation at a coarser grind due to less cross grain breakage. This produces equivalent concentrate grade at a coarser size. Also the product is easier to dewater and pelletlze. (2) A primary autogenous mill can be designed and controlled to produce grinds over a wide range while still maintaining high efficiency. This is not practical in a rod mill.

semi autogenous and autogenous grinding mills market size, share, trends, industry 2023

semi autogenous and autogenous grinding mills market size, share, trends, industry 2023

Semi-autogenous grinding (SAG) and autogenous grinding mills are used for grinding large chunks of materials into smaller pieces which can be later used for processing. Such mills are used in the primary stage of grinding process where pieces of raw materials need to be grounded for further processing or sorting. These mills are typically powered using electricity and depending on the required power have different configurations such as central drive, single pinion, dual pinion and gearless mechanical set-up. AG and SAG mills are extensively used in the mining industry for extracting minerals such as metals, oil shale, limestone, rock salt, coal, gemstones, dimension stones, gravel and clay.

Autogenous grinding (AG) mills are tumbling mills which do not require a dedicated grinding media and use the ore itself for grinding. Ores which are comprised of sufficient competent pieces are amenable to AG mills. For such ores, AG mills perform crushing, fine and coarse grinding steps of size reduction. On the other hand, semi-autogenous grinding (SAG) mills use steel balls as an additional grinding media. The use of steel balls enables such mills to grind ores with varying hardness and amount of grinding media. As a result, SAG mills are ideal for treating wide variety of feed materials as well as sticky ores.

One of the key factors driving this market is the need for energy efficient solutions as grinding is one of the most energy consuming stages in mining. Also, to widen the scope and to increase the efficiency of grinding process, requirements such as ability to grind abrasive materials, high availability and low operating costs are expected from the mills used for grinding process. Thus, a semi-autogenous and autogenous grinding mill is preferred for grinding in mining industry on account of its extremely high availability rate, high throughput and low energy consumption. However, grinding in such mills becomes a complex process as the feed rate and mineralogical properties of the ore dictate the mill properties. This makes the grinding process difficult to assess and control in autogenous and semi-autogenous mills. Moreover, these mills often require repair and maintenance for wear and tear caused by the churning of heavy residue bearing materials. The emergence of high pressure grinding rollers (HPGR) based circuits as an energy efficient alternative to SAG-based circuits also pose a threat to the conventional SAG market.

Over the years, AG and SAG mills have found several applications in the mining industry. These mills are used as industrial mining equipment to perform tasks such as processing, crushing, separating and locating of precious metals from mined coal. Precious metal industries such as gold, platinum, silver and copper use AG and SAG mills extensively. Other metals such as lead, nickel and zinc also are extracted using AG and SAG mills. Key players in AG and SAG market are KHD Humboldt Wedag International AG, Polysius AG and Koppern Equipment Inc. from Germany, FLSmidth & Co. A/s from Denmark, SGS Group and ABB Ltd. from Switzerland, Metso Oyj and Outotec Oyj from Finland, CITIC Heavy Industries Co. Ltd. and SGI Group from China.

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semiautogenous mills market 2021 by business boosting strategies, type (autogenous mills, semiautogenous mills, ,), share estimation, revenue potential, forecast outlook till 2026 - the cowboy channel

semiautogenous mills market 2021 by business boosting strategies, type (autogenous mills, semiautogenous mills, ,), share estimation, revenue potential, forecast outlook till 2026 - the cowboy channel

The objectives of Semiautogenous Mills market 2021 is to examine, define, segment, and project the size primarily based on company, product type, end user and key regions. The report covers the market panorama and its growth potentialities over the approaching years and discussion of the key carriers powerful on this market. the major innovative key players involve in the market are (Metso, FLSmidth, CITIC, Outotec) etc.

Global "Semiautogenous Mills Market" (2021-2026) Research Report presents an in-depth evaluation of the market size, share, drivers, restraints, and so on. Additionally, this report consists of the approximate observation of various segments in terms of universal growth, development, opportunity, business strategies, techniques, etc. for the forecast period of 2026. The report carries the basics produced and improvements by distinctive application Share and The latest trend gaining momentum in the market that will increase focus about Semiautogenous Mills. The report elements a comprehensive analysis of business factors like global Semiautogenous Mills size, recent technological advances, and inventions. The research report is composed of: the creation of the market, key players, opportunities, restraints, product and type classification, and universal market analysis.

Semiautogenous Mills are so-called due to the self-grinding of the ore: a rotating drum throws larger rocks of ore in a cascading motion which causes impact breakage of larger rocks and compressive grinding of finer particles. It is similar in operation to a SAG mill as described below but does not use steel balls in the mill. Also known as ROM or "Run Of Mine" grinding.Since the COVID-19 virus outbreak in December 2019, the disease has spread to almost 100 countries around the globe with the World Health Organization declaring it a public health emergency. The global impacts of the coronavirus disease 2019 (COVID-19) are already starting to be felt, and will significantly affect the Semiautogenous Mills market in 2020.COVID-19 can affect the global economy in three main ways: by directly affecting production and demand, by creating supply chain and market disruption, and by its financial impact on firms and financial markets.The outbreak of COVID-19 has brought effects on many aspects, like flight cancellations; travel bans and quarantines; restaurants closed; all indoor events restricted; over forty countries state of emergency declared; massive slowing of the supply chain; stock market volatility; falling business confidence, growing panic among the population, and uncertainty about future.

The report has been curated after observing and studying various factors that determine regional growth like the economic, environmental, social, technological, and political status of the actual region. Also, the analysts have studied the info of revenue, sales, production, and manufacturers of every region. This section analyses region-wise revenue and volume for the forecast period of 2015 to 2026. These analyses will help the reader to know the potential worth of investment during a particular region.

On the basis of the end users/applications, this report focuses on the status and outlook for major applications/end users, consumption (sales), market share and growth rate for each application, including:

The report offers an in-depth assessment of the growth and other aspects of the Semiautogenous Mills market in important regions, including the U.S., Canada, Germany, France, U.K., Italy, Russia, China, Japan, South Korea, Taiwan, Southeast Asia, Mexico, and Brazil, etc. Key regions covered in the report are North America, Europe, Asia-Pacific and Latin America. From a global perspective, this report represents the overall Semiautogenous Mills market size by analyzing historical data and future prospects.

The report shall also incorporate available investment opportunities in the Semiautogenous Mills market for stakeholders to invest in along with the detailed analysis of the competitive landscape and function offerings of key players. These insights provided in the record would advantage key players to prepare strategies for the destiny and benefit a robust role within the worldwide market.

With tables and figures helping analyze worldwide Global Semiautogenous Mills market trends The report also presents the market competition landscape and a corresponding detailed analysis of the Semiautogenous Mills market and the report is inclusive of the pivotal driving forces influencing the key players of the Semiautogenous Mills market and their impact on the revenue scale of this business sphere.

1 Study Coverage1.1 Semiautogenous Mills Product Introduction1.2 Market Segments1.3 Key Semiautogenous Mills Manufacturers Covered: Ranking by Revenue1.4 Market by Type1.4.1 Global Semiautogenous Mills Market Size Growth Rate by Type1.4.2 Type 11.4.3 Type 21.4.4 Others1.5 Market by Application1.5.1 Global Semiautogenous Mills Market Size Growth Rate by Application1.5.2 Application 11.5.3 Application 21.6 Coronavirus Disease 2019 (Covid-19): Semiautogenous Mills Industry Impact1.6.1 How the Covid-19 is Affecting the Semiautogenous Mills Industry1.6.1.1 Semiautogenous Mills Business Impact Assessment - Covid- Supply Chain Challenges1.6.1.3 COVID-19s Impact On Crude Oil and Refined Products1.6.2 Market Trends and Semiautogenous Mills Potential Opportunities in the COVID-19 Landscape1.6.3 Measures / Proposal against Covid- Government Measures to Combat Covid-19 Impact1.6.3.2 Proposal for Semiautogenous Mills Players to Combat Covid-19 Impact1.7 Study Objectives1.8 Years Considered2 Executive Summary2.1 Global Semiautogenous Mills Market Size Estimates and Forecasts2.1.1 Global Semiautogenous Mills Revenue 2015-20262.1.2 Global Semiautogenous Mills Sales 2015-20262.2 Semiautogenous Mills Market Size by Region: 2020 Versus 20262.2.1 Global Semiautogenous Mills Retrospective Market Scenario in Sales by Region: 2015-20202.2.2 Global Semiautogenous Mills Retrospective Market Scenario in Revenue by Region: 2015-20203 Global Semiautogenous Mills Competitor Landscape by Players4 Breakdown Data by Type (2015-2026)5 Breakdown Data by Application (2015-2026).11 Company Profiles11.1 Company Profiles 111.1.1 Company Profiles 1 Corporation Information11.1.2 Company Profiles 1 Description, Business Overview and Total Revenue11.1.3 Company Profiles 1 Sales, Revenue and Gross Margin (2015-2020)11.1.4 Company Profiles 1 Semiautogenous Mills Products Offered11.1.5 Company Profiles 1 Recent Development

11.2 Company Profiles 211.2.1 Company Profiles 2 Corporation Information11.2.2 Company Profiles 2 Description, Business Overview and Total Revenue11.2.3 Company Profiles 2 Sales, Revenue and Gross Margin (2015-2020)11.2.4 Company Profiles 2 Semiautogenous Mills Products Offered11.2.5 Company Profiles 2 Recent Development

11.3 Company Profiles 311.3.1 Company Profiles 3 Corporation Information11.3.2 Company Profiles 3 Description, Business Overview and Total Revenue11.3.3 Company Profiles 3 Sales, Revenue and Gross Margin (2015-2020)11.3.4 Company Profiles 3 Semiautogenous Mills Products Offered11.3.5 Company Profiles 3 Recent Development

11.4 Company Profiles 411.4.1 Company Profiles 4 Corporation Information11.4.2 Company Profiles 4 Description, Business Overview and Total Revenue11.4.3 Company Profiles 4 Sales, Revenue and Gross Margin (2015-2020)11.4.4 Company Profiles 4 Semiautogenous Mills Products Offered11.4.5 Company Profiles 4 Recent Development.12 Future Forecast by Regions (Countries) (2021-2026)13 Market Opportunities, Challenges, Risks and Influences Factors Analysis13.1 Market Opportunities and Drivers13.2 Market Challenges13.3 Market Risks/Restraints13.4 Porters Five Forces Analysis13.5 Primary Interviews with Key Semiautogenous Mills Players (Opinion Leaders)14 Value Chain and Sales Channels Analysis14.1 Value Chain Analysis14.2 Semiautogenous Mills Customers14.3 Sales Channels Analysis14.3.1 Sales Channels14.3.2 Distributors

The market is changing rapidly with the ongoing expansion of the industry. Advancement in technology has provided todays businesses with multifaceted advantages resulting in daily economic shifts. Thus, it is very important for a company to comprehend the patterns of market movements in order to strategize better. An efficient strategy offers the companies a head start in planning and an edge over the competitors.Industry Researchis a credible source for gaining market reports that will provide you with the lead your business needs.

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is this the end of italy's iconic valley of the mills? - atlas obscura

is this the end of italy's iconic valley of the mills? - atlas obscura

On a hot, sunny morning in June 2006, Reginald Van de Velde was walking in the center of Sorrento, the famous Italian town on the Gulf of Naples, when something struck him. I was walking on a footbridge to get back to my car, says the Belgian photographer, and noticed something unusual under the bridge. Intrigued, Van de Velde leaned out over the bridges protective fence. Then I saw it, this haunting ruin completely covered in vegetation.

Indeed, about 30 feet below Sorrentos Via Fuorimura lies a deep gorge jacketed in lush, dense vegetation. At its center stands a six-story building, a mill that had been abandoned at the start of the 20th century. Thick layers of moss, sprawling ferns, and climbing, creeping plants of all sorts had enveloped the building, making it look more like a natural rock formation than a human artifact.

Van de Velde, who specializes in ruin photography, thought he had found one of the best abandoned shots of his career. He reached for his camera, but the battery was dead. Few hours later, in front of his laptop, he Googled Sorrento abandoned ruin, but not much came out.

Nearly a decade later, that same ruin became one of the most famous abandoned places on the internet. In 2014 Instagram featured it as a photo of the day, attracting 300,000 comments. Atlas Obscura created an entry for it in 2015, and the next year Buzzfeed named it one of the worlds top beautifully haunted abandoned places.

Thousands of online comments echo the emotions described by Van de Velde: wonder, curiosity, a strong desire to see the place in person. More than 2,700 people have marked it Want to Go on Atlas Obscura, but only a few hundred report having been there. But getting there now is likely to leave a very different impression than the one Van de Velde had. Today, the much-loved ruin has lost its covering of vegetation and parts of its decaying structure, following a controversial restoration. In May 2020, in response to a backlash over the changes, local authorities stopped all work on the site. Few weeks later, Van de Velde reached out to Atlas Obscura to find out what the heck happened.

Located in the center of Sorrento, Il Vallone dei Mulini, or the Valley of the Mills, is a geological oddity. Like other gorges along the jagged Sorrentine coastline, it was formed some 35,000 years ago after the eruption of the Phlegraean Fields, an active volcano west of Naples. The lava flows created the dramatic cliffs and canyons that now form natural borders between the towns of Meta, Piano di Sorrento, SantAgnello, and Sorrento.

Unlike the other volcanic gorges of the peninsula that open to the sea, the Valley of the Mills was sealed off in 1866, when local authorities decided to build a piazza where the valley opened onto the coast. That portion of the gorge was filled with debris and volcanic tuff, covered with cement, and topped with pebbles. Piazza Tasso, now an iconic landmark of Sorrento, cut the valley from constant sea breezes, so the gorge has a microclimate unlike any other place on the Sorrentine Peninsula.

Humidity reaches 80 percent there, and vegetation started to fill the valley. But people have found it oppressive. A 16th-century warehouse and 19th-century mill, once bustling with millworkers, carpenters, and laundry women, were eventually abandoned. The humidity took over, helping spread a lush carpet of green over the abandoned structures.

When approached from Sorrentos city center, the valley appears to be a little enchanted kingdom of its own. The thick canopy of centuries-old holly oak block out honking cars and sputtering motorbikes, leaving an echoing soundtrack of chirping birds and buzzing bugs.

Much of the bottom of the valley is shaded by the walls and overstory, enhancing the sense of mystery and leading to speculation about who or what resides in the steamy realm. In the 19th century, local farmers believed that elves came out at night, lighting candles to ward off evil spirits. Recent surveys by the World Wide Fund for Nature (WWF) did not find elves, but rather rare owls and bats that found a hospitable habitat there. To them, the old structures were simply part of the landscape.

But recent restoration works have changed this. The mill has undergone a revamp that might as well be the architectural equivalent of the infamous, much-ridiculed Ecce Homo fresco in Spain, which was botched beyond recognition in an amateur restoration attempt.

Sorrento has been a travel destination since at least Roman times, when the wealthy started to build sumptuous vacation homes all along the peninsula. A plaque outside the Correale Museum, which hosts archaeological remains from Roman times to the 18th century, lists the names of the notable artists and writers who visited the city throughout the centuries: Johann Wolfgang von Goethe, Friedrich Nietzsche, and Leo Tolstoy, among others.

It was particularly during the second half of the 19th century that Sorrento became a spot for the emergent European middle class, according to Annunziata Berrino, a contemporary historian at the University of Naples. In an 1820 travel guide, English writer Mariana Starke promoted Sorrento as a secluded paradise where locals showed great attention and kindness to foreigners (something that is still true today).

The Valley of the Mills played no small part in the towns fame, even then. In the 19th century, artists belonging to the Romantic movement traveled around Europe in search of landscapes that triggered strong emotions, Berrino says. The Valley of the Mills fitted with that aesthetic.

English writer Octavian Blewitt cited the valleys wildness as a must-see for artists, while French writer and painter Turpin de Criss described it as being wrapped in a mysterious undertone. By the mid 1800s, images of the valley were being shared by the periods Instagrampostcards sent all over Europe by enthusiastic visitors.

After Italys unification in 1861, travel around the country became easier, Berrino says, and Sorrentos future as a tourist hub solidified. Locals started to put rooms up for rent, sailors created ad-hoc boat tours, and young men took jobs as porters.

An entry from a travelogue by theologian and travel writer Camillo Mapei in 1864 already described the town as crowded with tourists, mostly English ones. The issue only became more acute over time. Outside of the impact of the pandemic, Sorrento is currently experiencing overtourism, says Francesca Coppola, a graduate student in tourism management from Ca Foscari University in Venice, who wrote a thesis on the impact of tourism on the town. Hospitality has developed at the expense of local livability and the environment.

A quick walk around town reveals telling signs. The narrow cobbled streets of the historic city center are filled with gift shops, with nary a grocery store or local-filled cafe to be found. Short term rentals have pushed residents out, Coppola says, and most natural sites are now home to restaurants or hotels.

To most Italians, Sorrento is a town of lemons, specifically limonaie, the latticed groves of lemon trees used to make local and globally known liquor Limoncello. But rapid, tourism-driven urbanization led to their disappearance in the city, Coppola says. Many limonaie were turned into parking lots, and today the only one left in Sorrento proper is owned by the municipal government.

We need to understand what is happening to the Valley of the Mills by looking at Sorrentos wider economic context, says Claudio DEsposito, head of the local chapter of the WWF. This was one of the very few sites that was not generating income from tourism and it does not surprise me that it eventually became a target for tourism developers.

In 2019 local papers announced that the long-abandoned ruin of the Valley of the Mills was going to be restored to some kind of former glory. The mills blades will turn again, stated the local newspaper.

The news came as a shock to many locals. Most people thought the mill belonged to the government, Coppola says, adding that the municipal government used to light it up and put a nativity scene on its roof for Christmas, something that is usually done for public buildings only. Despite this widespread assumption, the mill had until recently been owned by the family that had built it in the 19th century, the Mathieus. Descendants of the original owners had put the mill up for sale in 2012.

The only bidder, a restoration company called Maccheronificio S.r.l., owned by Mariano Pontecorvo, secured the property for 300,000. Local environmental groups, including the WWF, see this deal as the source of much of the current controversy. Local governments should have tried to take the building and turn it into a conservation site, DEsposito says, But they did not even try to buy it.

Right after the deal, the WWF lodged a complaint with Italys Ministry of Culture, citing a law that favors public bodies over private bidders in auctions of buildings of historic or artistic value. But because no local authority had even tried to make a deal, the complaint had no grounds.

For a few years, the new owners of the mill left the property untouched. But in 2019, a restoration plan was announced. Many observers in Sorrento and visitors from around the world, including Van de Velde, had hoped the restoration work would focus on preventing the ruin from collapsing. But the owners had a different idea in mind.

In March 2019, workers opened a path from the top of the gorge all the way down to the valley floor. Mini excavators were used to remove vegetation and clear the area around the abandoned building. Scaffolding went up, and when it was eventually removed, photos of the refurbished mill started to circulate online.

One of the defining characteristics of the ruin was the way light filtered through its open windows, playing with leaves and shadow to add to the overall visual impact and sense of mystery. Now, they put in modern windows and even ventilation systems Van de Velde says. Its just not what I expected when I heard they were restoring it.

He was not the only one who was profoundly disappointed. Mario Russo, an archaeologist who has worked on many sites in the Sorrentine Peninsula, says that owners should have opted for a conservative restoration. The mill should have remained a ruin, he says, They should have prevented crumbling with as little changes as possible.

The restoration work also affected the delicate ecosystem of the valley. Vegetation has been cut back, including holly oaks that were removed to make way for excavators. This will highly increase the risk of landslide, DEsposito says, as the trees played a vital role in stabilizing the soil and absorbing rainfall during storms.

After gathering evidence of the environmental impact of the project, the WWF filed a lawsuit against Maccheronificio S.r.l. But by mid-March 2020, the pandemic came down on Italy like a hammer. It wasnt until May that local authorities visited the site. After a quick inspection, they decided to put it under seizure and freeze all work at the site to run a investigation. Restoration works have been conducted against local landscape protection laws, prosecutors told national newspaper La Repubblica, adding that project documents failed to clearly explain the final goal of the restoration project.

As of March 2021, investigations are ongoing. The owner of the mill, Pontecorvo, believes that prosecutors will not find any wrongdoing. We did not cut down any trees, he says. All we did was to remove infesting plants. However, in photos shared by the WWF, the removal of a range of vegetation is evident. They cut down many plants, including hornbeams, ash trees, and ferns, DEsposito says, which poses a real risk to the many species that depend on those trees.

Prosecutors also assert that the restoration works violated local heritage protection laws. However, the project had been approved by the local Soprindenteza, the government body tasked with monitoring projects that impact the countrys cultural patrimony. When local supervisors approve a project it can be hard to block it further down the road, Russo says. The real question, he says, is why it was approved in the first place.

Whatever the outcome of the investigation, the future of the Valley of the Mills has shifted, and where it goes will largely depend on which vision of conservation prevails. To the WWF and other environmental groups, the valley should remain untouched, save for minor interventions to prevent the collapse of the old mill. This is the only place of Sorrento untouched by urbanization, DEsposito says, Its like a window on our geological past and it should be kept that way.

According to Pontecorvo, the building should be a functioning mill once again, open to tourists (for a fee) and free for locals. We want to reactivate the mills blade, he explains, and create a footpath that leads people down to the mill.

Of course, this proposition runs counter to the conditions that made this place stand out to countless artists and visitors for centuries, the otherworldly atmosphere that seemed to exist outside the flow of time itself, the way the human-made merged with ferns and moss, light and shadow. And theres no guarantee that redevelopment of the mill will make the site any more appealing to visitors or locals. Recreating a functional mill will inevitably mean losing the unique charm of this place, Russo says, and I doubt that it would be easy to bring people inside the building given its humidity.

Berrino, who has curated a digital archive about artistic and historical records of the valley, believes that the mill could be open to the public, but without putting the surrounding ecosystem at risk. I have proposed something like a suspended bridge, says DEsposito, who is also not opposed to finding a sustainable way for visitors to take a closer look at the ruin.

For now, the building remains in private hands, but the recently elected mayor of Sorrento, Massimo Coppola, believes that his government can put pressure on the owners to preserve its identity somehow. We will fight to prevent further modifications to the mill, he says, and for the unique character of the place to be preserved.

Tourism experts such as Coppola believe that fans from around the world could play a big role in what happens next. If enough people will advocate for a conservative restoration, stakeholders will pay attention, she says, citing the example of Poveglia, an island near Venice that was put up for sale in 2014 and was eventually declared a public good and preserved after a petition was signed by more than 4,000 people. Tourism can be a precious resource, as long as it does not put at risk the authenticity of this place.

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focus on italy | | may 03, 2018 20:27

focus on italy | | may 03, 2018 20:27

Italy has a diverse grains sector, with the countrys climate and taste for pasta making durum wheat an important crop. It needs to import wheat to fulfill the needs of its milling industry. Its by far the European Unions biggest producer of soy, as well as its biggest producer of rice. Politically, Italy has been a strong opponent of genetically modified crops, while it is now pushing to develop advanced biofuels.

According to the International Grains Councils (IGC) forecast, total Italian grains production in 2018-19 will be 15.7 million tonnes, up from 14.7 million tonnes in 2017-18. Wheat production is forecast at 7.9 million tonnes, up from 7 million in 2017-18, with the IGC noting that rains had improved the outlook in previously dry areas, while corn production is set to rise to 6.3 million tonnes from 6 million. Sorghum production is forecast at 300,000 tonnes in 2018-19, up from 200,000 the previous year. Durum wheat production, which is also included in the wheat total, in 2018-19 is forecast at 4.5 million tonnes, compared with 4.2 million the year before.

The European grain sector organization COCERAL forecasts Italys 2018 production of oilseeds at 1.536 million tonnes, up from 1.397 million in 2017. Soybeans dominate with 2018 production forecast at 1.258 million tonnes, up from 1.140 million the year before. Rapeseed production in 2018 is forecast at 24,000 tonnes, down from 25,000 the year before and sunflower seed production is forecast at 22,000 tonnes, up from 19,500 the prior year.

An annual attach report on the rice sector, published in May 2017, notes that Italy is the largest rice producer in the E.U. According to the latest figures from the Italian Rice Association (Enterisi), Italys 2016-17 rice area is expected at 234,134 hectares (ha), 3% more than 2015-16, driven by the higher profitability of the sector compared to corn and soybeans.

The report explains that rice cultivation is mostly located in Northern Italy (Piemonte, Lombardia, and Veneto regions) where water is relatively abundant and the rice crop can be raised in flooded fields. According to the attach, around 84% of the rice grown in Italy is Japonica, while the rest is Indica.

Increasing rice imports from Cambodia, Myanmar, Guyana, and Surinam with duty-free market access under Everything But Arms (EBA) agreements is blamed for the decrease in the Indica area and the fall is likely to be offset by the increased area expected for the round grain Japonica variety. Source: Euromonitor

According to the Italian milling sector organization ITALMOPA, which quotes 2016 statistics, there are 358 mills in Italy, using 11.031 million tonnes of wheat a year to produce 7.751 million tonnes of flour. Of that, 5.413 million tonnes of common wheat went to produce 4.006 million tonnes of flour and 5.618 million tonnes of durum wheat went to produce 3.745 million tonnes of durum flour. The country imports some 60% of its wheat needs, with Infofarine citing France, Germany, Austria and Hungary as major suppliers in the E.U., as well as the United States and Canada outside.

Referring to common wheat flour mills alone, the industrys Infofarine website describes the long-term consolidation of the industry, with 821 mills in 1990, 356 in 2000 and 259 in 2010. By 2014 there were 233 mills with a capacity of over 10 tonnes a day, with a national daily capacity of 28,144 tonnes. There are 131 mills in the north of the country, 68 in the center and 34 in the south. By region, there are 41 in Piedmont, 37 in Emilia Romagna, 26 in Veneto and 20 in Lombardy and Marche.

Infofarine puts the average annual production per mill in Italy at around 16,500 tonnes, which it points out is well below the average in the United Kingdom, which it puts at around 73,250 tonnes, Germany at around 22,250 tonnes and Spain at around 20,000, but greater than in France at around 9,950 tonnes and Poland around 7,250 tonnes.

However, the general attitude toward genetically engineered (GE) crops remains hostile, the report noted. The national media debate on GE crops and plant experimentation has made it politically unpalatable to support GE research and cultivation.

Further acceptance of GE crops may center on how to respond to the misinformation circulating about health and environmental risks, in addition to having a candid discussion with the agricultural community about the costs of Italys anti biotech policies, the attach report said. The rising cost of feed materials and a greater understanding of just how prevalent consumption is of products that already rely on GE inputs may become a critical factor.

In February 2016, Italys Agriculture Minister Maurizio Martina made a distinction between innovative biotechnologies and GMOs (genetically modified organisms), the attach said. He advocated for innovation involving cisgenesis and gene-editing, but not transgenic modification.

Biodiesel in Italy is produced mainly from imported rapeseed (40%), soybeans (30%), and palm oil (25%), the report said. The remainder is made of recycled vegetable oils, sunflower oil, and animal fats.

A further attach report in June 2017, covering the E.U. as a whole, forecast Italian fuel ethanol consumption in 2018 at 285,000 tonnes. Italian output of traditional biodiesel in 2018 was forecast at 570 million liters, down from 625 million the year before, with hydrogenated vegetable oil (HVO) capacity rising to 1.090 billion liters in 2018, from forecast production of 323 million the year before.

Italy is pushing to develop advanced biofuels and in March, the European Commission approved a 4.7 million support scheme for advanced biomethane and biofuels in Italy, which, according to the EC, supports the production and distribution of advanced biofuels and advanced biomethane.

semi autogenous grinding mill - an overview | sciencedirect topics

semi autogenous grinding mill - an overview | sciencedirect topics

An 8m4m SAG mill was progressively filled through a charging chute 1.0m in diameter. The charge consisted of mineral plus balls plus water. The total charge volume was increased progressively such that the fractional fillings of the mill volumes after each increase were: 0.1, 0.2, 0.3, 0.4 and 0.5. Assume that the porosity of the bed remained unchanged at 40% and 40% slurry was charged. Estimate:

As mined ore is typically less than 0.25m in size. It is ground to a particle size of 80% passing 100m in a semi-autogenous grinding mill then sent on to leaching using sulfuric acid and sulfur dioxide under atmospheric conditions. A schematic flowsheet of this part of the process is shown in Figure 30.4.

Cobalt is in the trivalent form in heterogenite. Because trivalent cobalt is unstable in solution, heterogenite does not dissolve without reducing the cobalt to the divalent state. This reduction is achieved by bubbling sulfur dioxide with minimal air into the sulfuric acid solution during leaching (Miller, 2009). The concentration of the sulfur dioxide is approximately 10%. The leaching of heterogenite is given by the following reaction:

The resulting solution is then separated from unleached solids by counter-current decantation, washing then filtration. The solids are discarded and the solution is transferred to solvent extraction to separate Cu2+ from Co2+.

Mines can be economic at any size, depending upon the Cu grade of their ore. Thus, copper mines operate at production rates between 10 000 tonnes of ore per day (a high-grade operation) to 250 000 tonnes per day (a large open-pit operation; ICSG, 2010).

Concentrators vary similarly. A new large concentrator unit typically consists of a semi-autogenous grinding mill, high pressure grinding rolls, two ball mills, and a flotation circuit. It can treat up to 170 000 tonnes of ore per day (Sartain, 2010). Larger concentrators consist of multiples of this basic concentrating unit.

Smelters are almost always large because their minimum economic output is that of a single, fully used high intensity smelting furnace. These furnaces typically smelt up to 4 000 tonnes of concentrate per day.

Copper refineries are usually sized to match the anode output of an adjacent smelter. The advantage of having a smelter and refinery at the same site is the presence of shared site facilities, particularly for anode casting and anode scrap re-melting. A few refineries treat the anodes from several smelters. The largest electrorefineries produce up to 1 100 tonnes of copper cathodes per day (ICSG, 2010).

Prior to smelting, the nickel and cobalt need to be concentrated from their sulfide ores. This is done by crushing and grinding the ores to liberate the nickel- and cobalt-bearing minerals from the other minerals. The ground ore is processed through two stages of flotation. The first stage of froth flotation separates the nickel-, cobalt-, and copper-bearing minerals from the gangue rock and pyrrhotite. The second stage of froth flotation separates the nickel- and cobalt-bearing minerals from the copper-bearing minerals. This produces a nickel- and cobalt-rich concentrate and a copper-rich concentrate.

A typical comminution circuit for NiCo sulfide ore is presented in Figure 2.2.7 [1]. Size reduction occurs through a primary crusher followed by semi-autogenous grinding (SAG). Large rocks are screened from the overflow and are sent through a pebble crusher, which recirculates the ore back to the SAG mill. The smaller material after SAG milling is classified by hydrocycloning. The oversized material is further reduced in size by ball milling and then classified again through cycloning. Each ore has its own target size for size reduction, which depends on mineral liberation.

Figure 2.2.7. Typical comminution flow sheet for preparing small flotation feed particles from as-mined sulfide ore pieces [1]. One stage of crushing and two stages of grinding are shown. The crushing is open circuit, i.e., there is no recycle loop. The two grinding circuits are closed circuit, i.e., oversize material is recycled for recrushing or regrinding to specified particle sizes. (All particle sizes are diameter.)

Following comminution, particles are separated by froth flotation. A typical flotation circuit to produce a nickel-, cobalt-, and copper-rich concentrate from gangue (oxides and pyrrhotite) is shown in Figure 2.2.8 [1,24,25]. The principles of froth flotation are (1) sulfide minerals in a slurry are normally wetted by water (e.g., are hydrophilic) but certain minerals (pentlandite and chalcopyrite) can selectively react with chemicals (collectors) making them hydrophobic, (2) unwanted materials (rock and pyrrhotite) do not react with collectors and remain hydrophilic, (3) collisions between ~1mm diameter rising air bubbles and the hydrophobic particles cause attachment of said particles to the rising bubbles, and (4) the hydrophilic particles do not attach to the rising bubbles. Thus, hydrophobic particles float to the top of the flotation cell while hydrophilic particles remain in the bulk slurry. Another chemical called a frother is added to stabilize the air bubbles with the hydrophobic particles long enough for the particles to be collected.

Figure 2.2.8. Schematic flotation circuit for floating pentlandite particles from oxide rock and pyrrhotite particles [1]. The process is continuous. It treats about 3000tons of ground 2.4% Ni ore and produces about 360tons of 18% Ni concentrate, dry basis (~90% pentlandite recovery to concentrate). Note particularly flash flotation. It recovers about half the ores pentlandite at above the plants overall concentrate grade (%Ni). The plants mechanical cells are ~30m3 each. The column (cleaner) cells are ~150m3 each. Regrind ball mill product size is controlled to ~50m (diameter) by cyclones in closed circuit ball mill, not shown.

Multiple stages of flotation are used to insure the highest possible recovery of pay minerals at an acceptable grade for efficient subsequent processing. To improve the recovery and grade of flotation, several chemicals are used. The most common collector is xanthate. Short-chain aliphatic alcohols and polyglycols are far and away the most common pentlandite flotation frothers [26,27]. Finally, the pH of the slurry is natural near 9 or controlled to 910 by the addition of lime or soda ash to depress pyrrhotite flotation.

The concentrate from the first flotation circuit is treated in a second flotation circuit to produce a nickelcobalt-rich concentrate and a copper-rich concentrate. The second flotation circuit is a slightly different configuration of flotation equipment than that shown in Figure 2.2.8, but the general idea is the same. The only major difference is in the size of the equipment (smaller because less material is processed), the chemistry (to separate chalcopyrite from pentlandite), and fine grinding using a stirred mill. The copper-rich particles are floated away from the nickel-rich particles by raising the pH of the slurry to ~12 by the addition of CaO. Fine grinding improves the grade of the copper concentrate and the recovery of nickel to the nickel concentrate by increasing mineral liberation.

It has been estimated that approximately 2% of the world's energy usage is applied to mineral comminution, and around a quarter of this is used specifically in metalliferous ore grinding [1] where it is typically the most energy intensive set of operations [2]. The purpose of comminution in ore processing is to reduce particle size in order to improve liberation of valuable minerals and so enable separation from the undesirable gangue to improve grade and recovery. This involves several crushing stages, followed by grinding stages. These crushing stages usually involve several unit operations in series, such as jaw crushers, cone crushers, hammer mills, and autogenous or semi autogenous grinding mills to reduce particle size from the scale of boulders down to several millimetres. The final stage of crushing is increasingly carried out using high pressure grinding rolls (HPGRs), which involve the relatively efficient process of the slow compression of a particle bed, and can produce a fine feed for the grinding circuit [3], in some cases even making the coarser grinding stages redundant [4,5].

Conventional grinding is typically carried out by tumbling mills. These can be rod mills which are suitable for relatively coarse grinding, and ball mills which are practically capable of grinding down to finer sizes. Both types use a rotating shell containing either rod or ball shaped grinding media, which are lifted and dropped as the mill rotates, grinding the charge down with impact and attrition forces. Conventional grinding with ball mills can comminute particles down to around 100m [6].

If economical, subsequent fine and ultrafine grinding takes place, using either ball mills or stirred media mills. The definition of fine and ultrafine grinding varies, but fine grinding is often considered to take place below P80 values (the size that 80wt% of particles pass below) of 100m [7] and ultrafine grinding below P80 values of 20m [8] with lower size limits of several m [9].

In the mining industry, the ideal target particle size for comminution is the liberation size, the size around which the valuable mineral can be effectively separated from the gangue by physical or chemical methods [10] (usually froth flotation), thereby minimising gangue particles in the concentrate and minimising valuable mineral particles lost to the tailings. The liberation size is related to the mineral grain size, although not necessarily equal to it; since it is rare that a mineral preferentially fractures at the grain boundaries, the liberation size is often significantly below the mineral grain size [11].

The optimum grade in the final concentrate depends primarily on a balance between the cost of further comminution and beneficiation versus the cost of extracting the metal from the concentrate. Metal extraction is carried out either by pyrometallurgical processes (i.e. smelting or roasting) or through hydrometallurgy (i.e., leaching, followed by a purification step such as precipitation or electrowinning to deposit the metal from the solution). In the case of hydrometallurgy, finer particle sizes increase leaching rate [12] as well as valuable metal recovery. Flotation tailings often undergo regrinding in order to liberate middling and locked valuable mineral grains from larger gangue particles, with the optimum grinding duty balancing the required energy input of liberation with the value of the material that would otherwise be lost.

The most economical ores available, with the highest grades and largest liberation sizes, tend to be exploited first. Consequently, the average ore quality of many metals has decreased over the decades. For example, in the case of copper, the mean ore grade in the United States declined greatly from 1.8% in 1932 [13] to 0.34% in 2010 [14], and additionally the remaining ores in the case of many metals are becoming increasingly fine-grained [8]. These trends result in a finer liberation size requirement, and more ore comminution per unit mass of metal, and so fine and ultrafine grinding are becoming increasingly important.

Ball mills have traditionally been used for fine grinding of minerals, and in these cases smaller ball sizes than in conventional grinding are used to increase contact area and decrease collision intensity [15], and lower mill speeds are used to cause the media to cascade rather than cataract, shifting the typical forces experienced from impact and towards attrition [16]. Despite such modifications, inefficiency rapidly increases when grinding below 75m and ball mills are rarely economical below around 30m [6]. Stirred media mills are increasingly replacing ball mills for fine and ultrafine grinding, typically having around 3040% less power consumption than ball mills when grinding to the same product size [8].

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