Wilfley table

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Wilfley Table
WILFLEY TABLES - Kennecott Copper Corporation, On Copper River and Northwestern Railroad, Kennicott, Valdez-Cordova Census Area, AK HAER AK,20-MCAR,1-117.tif
Wilfley tables, Kennicott, Valdez-Cordova, Alaska
ClassificationShaking table
Industry Mining, Mineral processing
ApplicationMineral separation and concentration
Fuel source Electric
PoweredYes
ComponentsShaking table, riffles, oscillating motor
Inventor Arthur Redman Wilfley
Invented1896
Other NamesWet table, water table

The Wilfley Table is commonly used for the concentration of heavy minerals from the laboratory up to the industrial scale. It has a traditional shaking (oscillating) table design with a riffled deck. [1] It is one of several brands of wet tables used for the separation and concentration of heavy ore minerals which include the Deister Table and Holman Table, all built to handle either coarse or fine feeds for mineral processing. [2]

Contents

The Wilfley Table became a design used world-wide due to the fact it significantly increased the recovery of silver, gold and other precious metals. [3] Such was the table's widespread use that it was included in Webster's Dictionary, [4] and has been in constant use by miners and metallurgists since its invention. [5]

Origin

The Wilfley Table was conceived by Arthur Wilfley, a mining engineer based in Kokomo, Colorado in the United States. As a silver mine operator, Wilfley spent many years refining his separation table design in order to make the extraction of silver more economic. Rather than using heating processes (smelting) to concentrate the ore, Wilfley had been experimenting on mineral separation by use mineral density contrasts. [6]

Wilfley was able to perfect a mechanical solution for the recovery of gold and silver from low-grade ores by means of the Wilfley table. [3] [5] The first Wilfley table was built on a preliminary scale in May 1895. [7] [8] The first full-sized table was used in Wilfley's own mill in Kokomo, in May 1896, while the first table sold for installation was placed in the Puzzle Mill, Breckinridge, Colorado, in August 1896. [7] Patented in 1897, [9] the Wilfley table made mining lower-grade ores profitable. Pulverised ore, suspended in a water solution, was washed across a sloping riffled vibrating table so that metals separated as they drained off. [6] [9]

The Wilfley Table was said to have revolutionised ore dressing worldwide and more than 25,000 were in service by the 1930s. [3]

Mineral separation

Oblique section of modern Wilfley (wet) table WilfleyTableOblique.svg
Oblique section of modern Wilfley (wet) table

The Wilfley Table was built to solve a problem common in the recovery of heavy ore minerals; approximately 90% of gold grains, platinum group minerals, sulphides, arsenides/antimonides and tellurides, in source rocks are silt-sized (<0.063 mm (0.0025 in)). [10] Concentration of these minerals requires preconcentration techniques that include recovery of this fraction. Preconcentration may involve any number of methods including jigs, spirals, shaking tables, Knelson concentration, dense media separation, panning and hydroseparation. The Wilfley Table exploits preconcentration on the basis of density to separate minerals. It can recover silt to coarse sand-sized heavy minerals for a broad spectrum of commodities including diamonds, precious and base metals, and uranium. [10]

Design and operation

The table, like most shaking tables, consists of a riffled deck with a gentle tilt on a stable support to counteract the table's oscillation. A motor, usually mounted to the side, drives a small arm that shakes the table along its length. The riffles are typically less than 10 mm (0.39 inches) high and cover more than half the table's surface. [10] [11] Varied riffle designs are available for specific applications. The riffles run longitudinally, parallel to the long dimension of the table. The table's shaking motion is parallel to the riffle pattern.

Deck construction varies from wood to hard-wearing fiberglass where the riffles are formed as part of the mold. The decks are lined with high coefficient-of-friction materials (linoleum, rubber or plastic), which assists in the mineral recovery process. [11]

During operation, a slurry of <2 mm (0.079 inches) sample material consisting of about 25% solids by weight is fed with wash water along the top of the table, perpendicular to the direction of table motion. [10] [11] [12] The table is shaken longitudinally, using a slow forward stroke and a rapid return strike that causes particles to migrate or crawl along the deck parallel to the direction of motion. [6] [10] [11] [12] [13] [14] Particles move diagonally across the deck from the feed end and separate on the table according to size and density. Water flow rate, table tilt angle and intensity of the shaking motion must be properly adjusted for effective mineral recovery. [6] [10]

The riffles cause mineral particles to stratify in the protected inter-riffle regions. [12] The finest and heaviest particles are forced to the bottom and the coarsest and lightest particles remain at the top. Particle layers migrate across the riffles with addition of new slurry feed and continued water wash. [12] [14] The riffles are tapered and flatten (disappear) towards the concentrate end of the table. The taper of the riffles causes migrating particles of progressively finer size and higher density to be brought into contact with the flowing film of water that tops the riffles; lighter material is washed away as tailings and middlings. Final concentration takes place in the unriffled region at the end of the deck where the layer of material at this stage is usually only a few particles deep. [11] [12] [14]

Efficiency

Wilfley table diagrams illustrating the distribution of tailings materials, middlings and concentrated ore WilfleyTableDiagrams.svg
Wilfley table diagrams illustrating the distribution of tailings materials, middlings and concentrated ore

Mineral separation is hampered by several factors, with particle size being particularly important. As the slurry feed grainsize increases, the efficiency of separation tends to decrease. [11] [12] Separation efficiency is also affected by the stroke of the table (frequency and length); fine feed requires a higher speed and shorter stroke than a coarse feed. A frequency of 200 to 325 strokes per minute is typical. [11] [13] [14]

When Wilfley tables were originally employed to rework tailing dumps, the tables were found to enhance mineral recovery by some 35–40% percent compared to existing processes, [15] though this is not always the case. [16]

Optimisation of table setup can have a significant impact on the recovery of ore. Using magnetite as a synthetic ore to test recovery on a Wilfley Table, Mackay et al. (2015) found that an optimised table setup (i.e. table inclination, wash-water flow rate, material feed rate, table speed, stroke amplitude, feed grade and feed density) increased magnetite recovery by a factor of 3.7. [6]

The Wilfley table, like any wet table, is one of the most metallurgically efficient forms of gravity concentration, being used to treat the smaller, more difficult flow-streams, and to produce finished concentrates from the products of other forms of gravity system. [12] Additional efficiencies are gained in the treatment of low grade feeds where two or even three decks are stacked one above the other allowing for continuous feeding. [12]

Modern usage

A small Holman-Wilfley 2000 table processing alluvial gold. The gold, middlings and tailings form discrete bands across the table Wilfley Table with gold.jpg
A small Holman-Wilfley 2000 table processing alluvial gold. The gold, middlings and tailings form discrete bands across the table

Modern applications of the Wilfley table (and other wet shaking tables) are predominantly observed in the following roles: [17]

  1. Laboratories. Small shaking tables are an excellent tool for see if a material will be responsive to gravity separation techniques
  2. Gold rooms. Wilfley tables typically act as rougher tables on gravity gold concentrate ahead final concentration methods (e.g. panning)
  3. High value heavy mineral concentrate cleaners.  In mining, the vast majority of Wilfley-type tables are installed globally to concentrate (e.g.) tin, tungsten, tantalum, niobium, zircon, rutile, leucoxene, xenotime, monazite
  4. Zircon finishing table – a specialist application

Tables are now also being used in the recycling of electronic scrap to recover precious metals. [12]

Related Research Articles

Extractive metallurgy is a branch of metallurgical engineering wherein process and methods of extraction of metals from their natural mineral deposits are studied. The field is a materials science, covering all aspects of the types of ore, washing, concentration, separation, chemical processes and extraction of pure metal and their alloying to suit various applications, sometimes for direct use as a finished product, but more often in a form that requires further working to achieve the given properties to suit the applications.

<span class="mw-page-title-main">Placer deposit</span> Accumulation of valuable minerals formed by gravity separation

In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the Spanish word placer, meaning "alluvial sand". Placer mining is an important source of gold, and was the main technique used in the early years of many gold rushes, including the California Gold Rush. Types of placer deposits include alluvium, eluvium, beach placers, aeolian placers and paleo-placers.

Gold cyanidation is a hydrometallurgical technique for extracting gold from low-grade ore by converting the gold to a water-soluble coordination complex. It is the most commonly used leaching process for gold extraction. Cyanidation is also widely used in the extraction of silver, usually after froth flotation.

<span class="mw-page-title-main">Hydrocyclone</span> Cyclonic separators making use of gravity

Hydrocyclones are a type of cyclonic separators that separate product phases mainly on basis of differences in gravity with aqueous solutions as the primary feed fluid.

<span class="mw-page-title-main">Copper extraction</span> Process of extracting copper from the ground

Copper extraction refers to the methods used to obtain copper from its ores. The conversion of copper ores consists of a series of physical, chemical, and electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, and other factors.

<span class="mw-page-title-main">Froth flotation</span> Process for selectively separating of hydrophobic materials from hydrophilic

Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, where it was one of the great enabling technologies of the 20th century. It has been described as "the single most important operation used for the recovery and upgrading of sulfide ores". The development of froth flotation has improved the recovery of valuable minerals, such as copper- and lead-bearing minerals. Along with mechanized mining, it has allowed the economic recovery of valuable metals from much lower-grade ore than previously possible.

<span class="mw-page-title-main">Mineral processing</span> Process of separating commercially valuable minerals from their ores

Mineral processing is the process of separating commercially valuable minerals from their ores in the field of extractive metallurgy. Depending on the processes used in each instance, it is often referred to as ore dressing or ore milling.

In metallurgical processes tank leaching is a hydrometallurgical method of extracting valuable material from ore.

Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: i.e. the components of the mixture have different specific weight. Every gravitational method uses gravity as the primary force for separation. One type of gravity separator lifts the material by vacuum over an inclined vibrating screen covered deck. This results in the material being suspended in air while the heavier impurities are left behind on the screen and are discharged from the stone outlet. Gravity separation is used in a wide variety of industries, and can be most simply differentiated by the characteristics of the mixture to be separated - principally that of 'wet' i.e. - a suspension versus 'dry' -a mixture of granular product. Often other methods are applied to make the separation faster and more efficient, such as flocculation, coagulation and suction. The most notable advantages of the gravitational methods are their cost effectiveness and in some cases excellent reduction. Gravity separation is an attractive unit operation as it generally has low capital and operating costs, uses few if any chemicals that might cause environmental concerns and the recent development of new equipment enhances the range of separations possible.

A Knelson concentrator is a type of gravity concentration apparatus, predominantly used in the gold mining industry. It is used for the recovery of fine particles of free gold, meaning gold that does not require gold cyanidation for recovery.

<span class="mw-page-title-main">Hemerdon Mine</span> Tungsten and tin mine in Devon, England

Hemerdon Mine, also known as Hemerdon Ball Mine, Hemerdon Bal Mine and (briefly) previously as Drakelands Mine is a tungsten and tin mine. It is located 11 km northeast of Plymouth, near Plympton, in Devon, England. It lies to the north of the villages of Sparkwell and Hemerdon, and adjacent to the large china clay pits near Lee Moor. The mine had been out of operation since 1944, except for the brief operation of a trial mine in the 1980s. Work started to re-open it in 2014, but it ceased activities in 2018. It hosts the fourth largest tin-tungsten deposit in the world.

<span class="mw-page-title-main">Spiral separator</span> Device for separating/sorting slurry or particles

The term spiral separator can refer to either a device for separating slurry components by density, or for a device for sorting particles by shape.

A vacuum ceramic filter is designed to separate liquids from solids for dewatering of ore concentrates purposes. The device consists of a rotator, slurry tank, ceramic filter plate, distributor, discharge scraper, cleaning device, frame, agitating device, pipe system, vacuum system, automatic acid dosing system, automatic lubricating system, valve and discharge chute. The operation and construction principle of vacuum ceramic filter resemble those of a conventional disc filter, but the filter medium is replaced by a finely porous ceramic disc. The disc material is inert, has a long operational life and is resistant to almost all chemicals. Performance can be optimized by taking into account all those factors which affect the overall efficiency of the separation process. Some of the variables affecting the performance of a vacuum ceramic filter include the solid concentration, speed rotation of the disc, slurry level in the feed basin, temperature of the feed slurry, and the pressure during dewatering stages and filter cake formation.

Jig concentrators are devices used mainly in the mining industry for mineral processing, to separate particles within the ore body, based on their specific gravity.

The IsaMill is an energy-efficient mineral industry grinding mill that was jointly developed in the 1990s by Mount Isa Mines Limited and Netzsch Feinmahltechnik ("Netzsch"), a German manufacturer of bead mills. The IsaMill is primarily known for its ultrafine grinding applications in the mining industry, but is also being used as a more efficient means of coarse grinding. By the end of 2008, over 70% of the IsaMill's installed capacity was for conventional regrinding or mainstream grinding applications, with target product sizes ranging from 25 to 60 μm.

Sepro Mineral Systems Corp. is a Canadian company founded in 1987 and headquartered in British Columbia, Canada. The outcome of the acquisition of Sepro Mineral Processing International by Falcon Concentrators in 2008, the company's key focus is the production of mineral processing equipment for the mining and aggregate industries. Sepro Mineral Systems Corp. also provides engineering and process design services. Products sold by Sepro include grinding mills, ore scrubbers, vibrating screens, centrifugal gravity concentrators, agglomeration drums, and dense media separators. The company is also a supplier of single source modular pre-designed and custom designed plants and circuits.

<span class="mw-page-title-main">Jameson cell</span> Machinery for processing minerals

The Jameson Cell is a high-intensity froth flotation cell that was invented by Laureate Professor Graeme Jameson of the University of Newcastle (Australia) and developed in conjunction with Mount Isa Mines Limited.

High-frequency vibrating screens are the most important screening machines primarily utilised in the mineral processing industry. They are used to separate feeds containing solid and crushed ores down to less than 200 μm in size, and are applicable to both perfectly wetted and dried feed. The frequency of the screen is mainly controlled by an electromagnetic vibrator which is mounted above and directly connected to the screening surface. Its high-frequency characteristics differentiate it from a normal vibrating screen. High-frequency vibrating screens usually operate at an inclined angle, traditionally varying between 0° and 25° and can go up to a maximum of 45°. They should operate with a low stroke and have a frequency ranging from 1500 to 9000 RPM. Frequency in High frequency screen can be fixed or variable. Variable High Frequency screen is more versatile to tackle varied material condition like particle size distribution, moisture and have higher efficiency due to incremental increase in frequency. G force plays important role in determining specific screening capacity of screen in terms of TPH per sqm. G force increases exponentially with frequency.

In metallurgy, mineral jigs are a type of gravity concentrator, separating materials with different densities. It is widely used in recovering valuable heavy minerals such as gold, platinum, tin, tungsten, as well as gemstones such as diamond and sapphire, from alluvial or placer deposits. Base metals such as iron, manganese, and barite can also be recovered using jigs.

<span class="mw-page-title-main">Arthur Wilfley</span> American mining engineer and inventor (1860–1927)

Arthur Redman Wilfley was a mining engineer and inventor who worked much of his life in Colorado, in the United States.

References

  1. ↑ Mitchell, C. J.; Styles, M. T.; Evans, E. J. (1997). The design, construction and testing of a simple shaking table for gold recovery: laboratory testing and field trials. Nottingham, UK: British Geological Survey Unpublished Report WC/97/061.
  2. ↑ Falconer, A. (2003). "Gravity Separation: Old Technique/New Methods". Physical Separation in Science and Engineering. 12 (1): 31–48. doi: 10.1080/1478647031000104293 .
  3. 1 2 3 Niebur, J. E. (1982). Arthur Redman Wilfley: Miner, Inventor, and Entrepreneur. Denver, CO, USA: Colorado Historical Society. p. 245. ISBN   0942576004.
  4. ↑ "Wilfley table". Merriam-Webster. Retrieved 7 September 2023.
  5. 1 2 Strong, T. R.; Driscoll, R. L. (2016). "A process for reducing rocks and concentrating heavy minerals" (PDF). Open-File Report. Reston, Virginia, USA: U.S. Geological Survey Open-File Report 2016–1022. doi:10.3133/ofr20161022.
  6. 1 2 3 4 5 Mackay, D. A. R.; Simandl, G. J.; Luck, P.; Grcic, B.; Li, C.; Redfearn, M.; Gravel, J. (2015). "Concentration of carbonatite indicator minerals using a Wilfley gravity shaking table: A case history from the Aley carbonatite, British Columbia, Canada" (PDF). British Columbia Geological Survey Paper. 2015 (1): 189–195.
  7. 1 2 Richards, R. H. (1908). "The Wilfley Table I" (PDF). Papers and Discussions Presented Before the [Coal] Division. 38. American Institute of Mining, Metallurgical, and Petroleum Engineers: 556–580.
  8. ↑ "Wilfley Table". 911 Metallurgist. Retrieved 7 September 2023.
  9. 1 2 McAllister, B. (1965). "Office profile: Denver". H&S Reports. 2: 16–22. Retrieved 3 September 2023.
  10. 1 2 3 4 5 6 McClenaghan, M. B. (2011). "Overview of common processing methods for recovery of indicator minerals from sediment and bedrock in mineral exploration". Geochemistry: Exploration, Environment, Analysis. 11 (4): 265–278. Bibcode:2011GEEA...11..265M. doi:10.1144/1467-7873/10-IM-025. S2CID   130103401 – via ResearhGate.
  11. 1 2 3 4 5 6 7 Silva, M. (1986). "Placer gold recovery methods" (PDF). California Department of Conservation, Division of Mines and Geology, Special Publication. 87.
  12. 1 2 3 4 5 6 7 8 9 Wills, B. A. (1988). Mineral Processing Technology - An Introduction to the Practical Aspects of Ore Treatment and Mineral Recovery. Chapter 10: Gravity concentration (PDF). Pergamon. doi:10.1016/C2009-0-11089-9. ISBN   9780080349374.
  13. 1 2 Richards, R. H. (1940). A Text Book of Ore Dressing. New York, USA: McGraw-Hill.
  14. 1 2 3 4 Fuerstenau, M. C.; Han, K. N. (2003). Principles of Mineral Processing. Littleton, Colorado, USA: Society for Mining, Metallurgy, and Exploration. ISBN   9780873351676.
  15. ↑ "Arthur Redman Wilfley". Mining and Minerals Education Foundation. Retrieved 3 September 2023.
  16. ↑ Dunn, T. S.; McBride, R. N. (1914). "An investigation in concentrating a certain tailing on Wilfley tables". Bachelors Theses. Missouri, USA: Missouri School of Mines and Metallurgy. Unpublished Bachelors Thesis.
  17. ↑ Webber, D. (13 June 2017). "Holman or Wilfley - Demystifying shaking tables". Linkedin. Retrieved 8 September 2023.
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