Principles of Flotation Flotation concentration method utilizes the differences in physico chemical surface properties of particles. Hydrophobic (water repellent) particles float with air bubbles to form a froth. Wetted hydrophilic particles sink. Hydrophobicity increases with the contact angle btw particles and bubbles. Chemical reagents are used in flotation. Flotation is a selective separation process. Flotation is the most important and versatile mineral processing technique used in mining industry.
APPLICATION OF FLOTATION Flotation can be successfully applied to both metallic and industrial minerals given below for removing impurities and improving quality: Apatite/Phosphate, Barite, Calcite, Dolomite, Feldspar, Fluorspar, Graphite, Iron Ore, Kyanite, Magnesite, Monazite, Potash, Pyrochlore, Quartz/Silica Sand, Scheelite etc.
MECHANICAL FLOTATION MACHINE Froth flotationFroth flotation is achieved when particles are separated based on their surface potential. Hydrophobic particles are recovered to the froth, whereas hydrophilic particles are discharged with the tailings stream.
PHOSPHATE MINERALS Phosphate minerals are those minerals that contain the tetrahedrally coordinated phosphate (PO 4 3-) anion along with the freely substituting arsenate (AsO 4 3-) and vanadate (VO 4 3-). Chlorine (Cl-), fluorine (F-), and hydroxide (OH-) anions also fit into the crystal structure.minerals phosphateanionarsenatevanadateChlorinefluorinehydroxide The phosphate class of minerals is a large and diverse group, however, only a few species are relatively common. Examples include: triphylite Li(Fe,Mn)PO4triphylite monazite (Ce,La,Y,Th)PO4monazite Apatite group Ca5(PO4)3(F,Cl,OH)Apatite –hydroxylapatite Ca5(PO4)3OHhydroxylapatite –fluorapatite Ca5(PO4)3Ffluorapatite –chlorapatite Ca5(PO4)3Clchlorapatite pyromorphite Pb5(PO4)3Clpyromorphite vanadinite Pb5(VO4)3Clvanadinite erythrite Co3(AsO4)2·8H2Oerythrite amblygonite LiAlPO4Famblygonite lazulite (Mg,Fe)Al2(PO4)2(OH)2lazulite wavellite Al3(PO4)2(OH)3·5H2Owavellite turquoise CuAl6(PO4)4(OH)8·5H2Oturquoise autunite Ca(UO2)2(PO4)2·10-12H2Oautunite carnotite K2(UO2)2(VO4)2·3H2Ocarnotite phosphophyllite Zn2(Fe,Mn)(PO4)24H2Ophosphophyllite PO 4 3- anion
DEPOSITS Rock phosphate can also be found on USA, Egypt, Israel, Morocco, Navassa Island, Tunisia, Togo, S. Arabia and Jordan have large phosphate mining industries as well.EgyptIsraelMoroccoNavassa IslandTunisiaTogo Jordan
USE OF PHOSPHATE Phosphates were once commonly used in laundry detergent in the form trisodium phosphate (TSP), but, because of algae boom-bust cycles tied to emission of phosphates into watersheds, phosphate detergent sale or usage is restricted in some areas.detergenttrisodium phosphate In agriculture, phosphate is one of the three primary plant nutrients, and it is a component of fertilizers. Rock phosphate is quarried from phosphate beds in sedimentary rocks. In former times, it was simply crushed and used as is, but the crude form is now used only in organic farming. Normally, it is chemically treated to make superphosphate, triple superphosphate, or ammonium phosphates, which have higher concentration of phosphate and are also more soluble, therefore more quickly usable by plants.agricultureplantfertilizersRockquarriedsedimentary rocks organic farmingsuperphosphatetriple superphosphateammonium phosphatessoluble Fertilizer grades have three numbers; the first is the available nitrogen, the second is the available phosphate (expressed on a P2O5 basis), and the third is the available potash (expressed on a K2O basis). Thus a 10-10-10 fertilizer would contain ten percent of each, with the remainder being filler.nitrogenpotash Surface runoff of phosphates from excessively-fertilized farmland can be a cause of phosphate pollution, leading to eutrophication (nutrient enrichment), algal bloom, and consequent oxygen deficit. This can lead to anoxia for fish and other aquatic organisms in the same manner as phosphate-based detergents.Surface runoffalgal bloomanoxiafish Phosphate compounds are occasionally added to the public drinking water supply to counter plumbosolvency.plumbosolvency The food industry uses phosphates to perform several different functions. For example, in meat products, it solubilizes the protein. This improves its water-holding ability and increases its moistness and succulence. In baked products, such as cookies and crackers, phosphate compounds can act as part of the leavening system when it reacts with an alkalai, usually sodium bicarbonate (baking soda). Phosphate minerals are often used for control of rust and prevention of corrosion on ferrous materials, applied with electrochemical conversion coatings
PHOSPHATE FLOTATION Collophane, the principal phosphate mineral occuring in the phospate deposits of the Southeastern US, floats readily with crude fatty acids and soaps, fuel oil and soda ash, caustic soda or amonia. “Double flotation” method is used in US Florida plants by using both fatty acid and amine types of collectors. “Single flotation” is employed at N.Africa and Middle Eastern phosphate operations by using either a fatty acid or an amine type of collector. Cytec’s Aero 727, 727J and 728 promoters have been successfully used where only fatty acid float approach is practiced. Cytec’s Aero 8651 fatty amine promer is utilized in operations running an amine float. In the reverse flotation, Cytec Acco-Phos 950 depressant (20-100 g/t) minimizes phosphate loses into the silica froth product using amine collectors. In the treatment of sedimentary pebble phosphates, Aero 845 can be used in conjuction with fatty acids.
US DOUBLE PHOSPHATE FLOTATION Desliming (Hydrocyclones) conditioner Rougher fl. Phosphate- Silica Sep. Flot Silica (final tails) pH=9-9.5 (sodaash/NaOH) Crude fatty oil Fuel-oil 70%S T C F Conditioning with H 2 SO 4 +washing to remove reagents pH=6.5-7 Fatty/ether amine Silica (gangue) Phosphate Conc. Cleaner fl. Silica Removal Reverse Flot. + - Slimes (-10 ) conditioner FEED
LIME STONE/CALCITE Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO 3 ). lsedimentary rockmineral calcitecalcium carbonate Limestone often contains variable amounts of silica in the form of chert or flint, as well as varying amounts of clay, silt and sand as disseminations, nodules, or layers within the rock.silica chertflintclaysiltsand
USES OF LIMESTONE The manufacture of quicklime (calcium oxide) and slaked lime (calcium hydroxide);quicklimeslaked lime Cement and mortar;Cementmortar Pulverized limestone is used as a soil conditioner to neutralize acidic soil conditions; Crushed for use as aggregate—the solid base for many roads;aggregate Limestone is especially popular in architecture as building stone/ material;architecture Geological formations of limestone are among the best petroleum reservoirs;Geological formationspetroleum As a reagent in desulfurizations;reagentdesulfurizations Glass making; Toothpaste; Added to bread as a source of calcium Iron impregnations in limestone
LIME STONE/CALCITE (CaCO 3 ) FLOTATION Natural limestone/calcite deposits contain various types of silicates and graphite impurities. For applications like paper fillers the calcite has to have a low grade of abrasive silicates as well as a high brightness. Even very low amounts of graphite is detrimental to the brightness. Beneficiation of limestone by froth flotation utilizing Aero 845 promoter can be simple process. Limestone is floated with/without prior desliming with the emulsion of Aero 845 and number 5 fuel oil. Silicates can be depressed by Na 2 SiO 3 (500-1000 g/t). Compared to fatty acids, Aero 845 promoter (Pet. Sulphonate type anionic collector) offer the advantage of better product control at a saving in total collector usage.
Sparingly soluble salts flot. R=100% Mole/l R=0% Calcite flot. recovery depends on NaOl concentration and HC chain length of the collector. In general, when the collector length of the HC chain is increased, the concentration of collector necessary for flotation is reduced. Complete flot. No flot. pH:6- 9
GRAPHITE CONCENTRATION TECHNOLOGY Graphite is one of the allotropes of carbon. Unlike diamond, graphite is an electrical conductor.allotropes of carbondiamondelectrical conductor Graphite holds the distinction of being the most stable form of solid carbon ever discovered. It may be considered the highest grade of coal, just above anthracite and alternatively called meta-anthracite, although it is not normally used as fuel because it is hard to ignite. coalanthracite
CLASSIFICATION OF GRAPHITE There are three principal types of natural graphite, each occurring in different types of ore deposit: (1) Crystalline flake graphite (53%) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken and when broken the edges can be irregular or angular (Madagascar-open pit, 410-950 $/t) (2) Amorphous graphite occurs as fine particles (Mexico- Underground mines, 240-260 $/t) (3) Lump graphite (also called vein graphite) occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline aggregates, and is probably hydrothermal in origin (Sri Lanka- Underground mines).
USE AREAS OF GRAPHITE MAJOR USE AREAS REFRACTORIES (High temperature applications- Melting Point 3927°C) Coarse flakes Graphite crucibles Carbon-magnesite/alumina bricks (95-99% C) Monolitics (gunning and ramming mixtures) Continuous casting ware (nozzles, troughs) STEEL MAKING Amorphous or fine flaked Carbon rising in molten steel Lubricating dies during hot metal extrution EXPANDED GRAPHITE Flakes Made from flake graphite using chromic acid sulphuric acids to produce foils Can be used to insulate molten metal in ladle, fuel cells and heat sinks for laptop computer MINOR USE AREAS BRIKE LINING/SHOES FOR HEAVY TRUCKS FOUNDRY FACING and LUBRICANTS PENCIL LEAD Zn-C BATTERIES ELECTRIC MOTOR BRUSHES GRAPHITE(CARBON) FIBERS/NANOTUBES Made from amourphous or fine flakes Substitute for asbestos Amourphous or fine flakes are used High temp. dry lubricant Powder graphite+clay Powdered fine flaked graphite Powder graphite Reinforced/antistatic/conductive plastics/ concreates/rubbers
IMPURITIES and PROPERTIES Minerals associated with graphite include quartz, calcite, micas, iron meteorites, and tourmalines.quartz calcitemicasironmeteoritestourmalines In 2005, world natural graphite production was 1.05 million t and China was the top producer of graphite with about 80% world share followed by India and Brazil. Graphite has various characteristics. Thin flakes are flexible but inelastic, the mineral can leave black marks on hands and paper, it is diamagnetic, adsorbant, conducts electricity, and displays superlubricity. Its best field indicators are softness, luster, density and streak.superlubricity
GRAPHITE BENEFICIATION METHODS Vary from a complex flotation at Europe and USA mills to simply hand sorting and screening with/without milling of high-grade ores in Sri Lanka. Certain soft flake-type graphite ores, (like in Madagascar) need no primary crushing and grinding. GRAPHITE MILLING ONLY Graphite can be ground to a fine powder for use as a slurry in oil drilling; in zirconium silicate, sodium silicate and isopropyl alcohol coatings for foundry molds; and for calcined petroleum coke, which is used as a carbon raiser in the steel industry.oil drillingzirconiumsilicatesodium silicateisopropyl alcohol foundrypetroleumcokesteel Rough graphite is typically ground and packaged at a graphite mill. Since the Work Index of graphite is high, power consumption during grinding will be high. Environmental impacts from graphite mills consist of air pollution including fine particulate exposure of workers and also soil contamination from powder spillages leading to heavy metals contaminations of soil. Dust masks are normally worn by workers during the production process to avoid worker exposure to the fine airborne graphite and zircon silicate.soil contaminationheavy metalszircon
GRAPHITE FLOTATION Since graphite is naturally hydrophobic (i.e. floats easily), impurites can easily be removed by direct flotation process. Flotation process can be applied to low carbon and high silica containing graphite ores. 1. DESLIMING STEP for removing clay minerals, 2. ROUGHER FLOTATION to produce a concentrate with 60-70% C. 3. REGRINDING+CLEANER FLOTATION to reach 85% C. 4. SCREENING to produce 75-95%C. - 0.5 mm graphite can be floated using fuel-oil/kerosene as the promoter and pine-oil/F-77/MIBC as frother at natural pH. Na 2 SiO 3 /HF can be used as silicate depressant.
IRON ORES Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey to rusty red. The iron itself is usually found in the form of magnetite (Fe 3 O 4 ), hematite (Fe 2 O 3 ), limonite or siderite. Hematite ores containing 66% Fe can be fed directly into iron making blast furnaces. Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel. 98% of the mined iron ore is used to make steel.rocksminerals metallicironiron oxidesmagnetite hematitelimonitesideritepig ironsteel Brazillian hematite
Consumption and economics Iron is the world's most commonly used metal. It is used primarily in structural engineering applications, automobiles, and general industrial applications (machinery). Iron-rich rocks are common worldwide, but ore-grade commercial mining operations are dominated by few countries. mining World production averages one billion metric tons of raw ore annually. The world's largest producer of iron ore is the Brazilian mining corporation CVRD, followed by Australian company BHP Billiton and the Anglo-Australian Rio Tinto Group.CVRDBHP BillitonRio Tinto Group China, Japan and S. Korea are currently the largest consumer of iron ore/steel. which translates to be the world's largest steel producing country.
LOW GRADE IRON ORE BENEFICIATION Due to the high density of hematite (5.3) relative to silicates (2.7), beneficiation usually involves a combination of crushing and milling as well as heavy liquid separation.silicates This is achieved by passing the finely crushed ore over a bath of solution containing bentonite or other agent which increases the density of the solution. When the density of the solution is properly calibrated, the hematite will sink and the silicate mineral fragments will float and can be removed. bentonite
FLOTATION OF IRON ORE Due to increased demand for iron ore products low in silica and phosphorous plus increased world competition, quality considerations have become more and more important. Dephosphorization of iron ores is necessary. The results obtained in plant operations vary, depending on ore type and the process. Direct flotation of iron ores was practiced for many years using Aero899R promoter (1-2 kg/t) along with number 5 fuel oil at pH 3-5 adjusted by H 2 SO 4 following high solids conditioning. Reverse flotation of silica with etheramine collectors+frother (Aerofroth or Oreprep) has been the traditional route for many years to produce a final iron ore concentrate. While removing silica from the iron ore, fine iron particles should not excessively lost.
FINE IRON ORE PELLETS Iron ore fines and flotation concentrates should be pelletized with bentonite before being charged into the blast furnace to produce pig-iron which is used in steel production. Iron pellets
HEAVY MINERAL SANDS Sand is a naturally occurring granular material comprised of finely divided rock and mineral particles.granular materialrockmineral Sand is transported by wind and water and deposited in the form of beaches, dunes, sand spits, sand bars (placer deposits) etc.beachesdunessand spitssand bars The most common constituents of sands are silica (SiO 2 ), usually in the form of quartz, iron oxides, zircon, rutile, ilmenite, monazite, garnet.silicaquartz Heavy mineral sands are a class of ore deposit which is an important source of zirconium, titanium, thorium, tungsten, rare earth elements, the industrial minerals diamond, sapphire, garnet, and occasionally precious metals or gemstones.orezirconiumtitaniumthorium tungstenrare earth elements diamondsapphiregarnetgemstones
Grade and Tonnage Distribution The grade of a typical heavy mineral sand ore deposit is usually low. The lowest cut-off grades of heavy minerals, as a total heavy mineral (THM) concentrate from the bulk sand, in most ore deposits of this type is around 1% heavy minerals, although several are higher grade. Of this total heavy mineral concentrate (THM), the components are typically Zircon, from 1% of THM to upwards of 50% of THM,Zircon Ilmenite, generally of 10% to 60% of THMIlmenite Rutile, from 5% to 25% of THMRutile Leucoxene, from 1% to 10% of THMLeucoxene Trash minerals, typically magnetite, garnet and chromite which usually account for the remaining bulk of the THM contentmagnetitegarnetchromite Slimes, typically minerals as above and heavy clay minerals, too fine to be economically extracted. Modern open-pit mining practises tend to favor dry mining rather than dredging operations, due to the advent of electrostatic mineral separation processes.dry miningdredging Black sand conc.
USE OF SAND Sand is often a principal component of concrete.concrete Molding sand, also known as foundry sand, is moistened or oiled and then shaped into molds for sand casting. This type of sand must be able to withstand high temperatures and pressure, allow gases to escape, have a uniform, small grain size and be non-reactive with metals.Molding sandfoundrysand casting It is the principal component in glass manufacturing.glass Graded sand is used as an abrasive in sandblasting and is also used in media filters for filtering water.abrasivesandblastingmedia filterswater Brick manufacturing plants use sand as an additive with a mixture of clay and other materials for manufacturing bricks.Brickmanufacturing plantsclay Sand is sometimes mixed with paint to create a textured finish for walls and ceilings or a non-slip floor surface.painttextured Sandy soils are ideal for certain crops such as watermelons, peaches, and peanuts and are often preferred for intensive dairy farming because of their excellent drainage characteristics.soilswatermelonspeachespeanutsdairy farming Sand is used in landscaping, it is added to make small hills and slopes (for example, constructing golf courses).landscapinggolf Beach nourishment - transportation to popular beaches where seasonal tides or artificial changes to the shoreline cause the original sand to flow out to sea.Beach nourishmentbeaches Sandbags are used for protection against floods and gun fire. They can be easily transported when empty, then filled with local sand.Sandbagsfloodsgun Sand castle building is a popular activity. There are competitive sand castle building competitions (See sand art and play).Sand castlesand art and play Sand animation is a type of performance art and a technique for creating animated films.Sand animationperformance artanimated films Aquaria are often lined with sand instead of gravel. This is a low cost alternative which some believe is better than gravel.Aquaria Railroads use sand to improve the traction of wheels on the rails.Railroads
GLASS SANDS BENEFICIATION CONCENTRATION OF HEAVY MINERALS Gravity (sluices, spirals, shaking tables, Reichert cones), magnetic (low/high intensity dry/wet) and high tension separation methods can be used together to treat/upgrade the heavy content of the beach sands. GLASS SAND FLOTATION FOR IRON IMPURITY REMOVAL After removal of the Fe-bearing impurities, some plants separate feldspar from quartz by floating feldspar with amines at pH 3 using HF. Some glass sand operations, naturally-occuring organic colloids may make a fatty acid float of iron-bearing minerals preferable. After desliming, the pulp is conditioned at high solids with Aero 700 series promoters at pH 8-9 adjusted with soda ash or caustic soda. Fuel oil may be added to the flotation circuit for froth control.
GARNET X 3 Y 2 (SiO 4 ) 3 Garnet is a group of minerals that can be used as gemstones and abrasives (Mohs hardness 6-7.5). Garnets are most often seen in red, but are available in a wide variety of colors. Spec. Gr. is btw 3.1-4.3. Major varieties X Y (SiO 4 ) 3 USE AREA Pyrope Mg 3 Al 2 Si 3 O 12 Almandine Fe 3 Al 2 Si 3 O 12 abrasive Spessartite Mn 3 Al 2 Si 3 O 12 gemstone Andradite Ca 3 Fe 2 Si 3 O 12 Grossular Ca 3 Al 2 Si 3 O 12 Uvarovite Ca 3 Cr 2 Si 3 O 12 gemstone Garnet species’s light transmission properties can range from the gemstone-quality transparent specimens to the opaque varieties used for industrial purposes as abrasives. crystalMolecular model
Uses & Concentration of GARNETS Pure crystals of garnet are used as gemstones. Garnet sand is a good abrasive, and a common replacement for silica sand in sand blasting. Mixed with very high pressure water, garnet is used to cut steel and other materials in water jets. Garnet sand is also used for water filtration media.gemstonesabrasivewater jets water filtration Garnets can be concentrated from sands by gravity+ electrostatic+magnetic separation methods along with monazite. Almandine in gneissic rock, hardness 6-7.5, abrasive Spessartine (the yellow mineral) gemstone Pendant in uvarovite, a rare bright-green garnet.
LIBERATION OF KAOLIN Liberation size for KAOLIN 4-6 m. Liberation size for FELDSPAR 200-300 m. Liberation size for QUARTZ 700 m. KAOLIN CAN EASILY BE CONCENTRATED BY CLASSIFICATION ACCORDING TO PARTICLE SIZE USING SCREENS AND HYDROCYCLONES Before concentration: For soft kaolins→Attrition scrubbing for dispersing clays For hard kaolins→crushing/grinding are required. (Due to remaining fine silica product, quality is low) CLASSIFICATION CONCENTRATION – DRY (Crushing+dry grinding+air classification) –(requires selective mining operation) – WET (Magnetic separation+flotation+hydrocyclones) –(complex flowsheet, but product quality is very high)
The production process includes: disintegration and classification, hydrocycloning, thickening, filter- pressing and drying. Product range: kaolin for ceramic, kaolin for paper, glass silica sand, dry and wet classified silica sand, ground kaolin, chamotte.
Process The extraction plant is situated adjacent to the quarrying operation to enable the waste to be returned to backfill. Crude kaolin from the quarry is first made into a slurry with water. This slurry passes through a series of washing and classification steps in order to remove the quartz and mica impurities. This results in a pure kaolin product which is completely devoid of free silica. The kaolin is filtered in filter presses and the filter cake is pressed into pellet form prior to drying in gas-fired dryers. The final kaolin pellets contain 10% moisture on average. These are packaged and despatched to customers in the ceramic, paint, paper and other industries. A dry powder product is also produced for those industries that cannot tolerate moisture, such as the rubber, plastic and pesticide industries. The dry powder is produced by passing the kaolin pellets through an attritor and classifier with simultaneous drying with hot air. Water from the drying process is recovered and recycled to the extraction plant through a return water pipeline.
MAJOR IMPURITIES (Kaolin is used in fine size range. Flotation efficiency diminishes with the size of particles. Kaolin is used as a white pigment thus colored impurities must be removed). Anatase (TiO 2 ): Fine sized anatase contains considerable amount Fe and gives brownish tint to the clays. This mineral may be removed by fatty acid flotation after activating with divalent cations to produce coating grade (bright) clays. Yoon et al. (2003) found that alkyl hydroxametes were much more effective than fatty acids in floating colored anatase impurity from clays. No activation is necessary and retention times in flotation are shorter than fatty acids. Iron oxides
KAOLIN FLOTATION CARRIER FLOTATION and CARRIERLESS FLOTATION can be used. Collector: Fatty acids.
POTASH Potash is the most important source of potassium in fertilizers. Flotation is one of the major methods to upgrade the potash. Normally fatty acids are used as collectors for flotation. However, this type of collectors is not always suitable for the treatment of complex phosphate ores when calcite and dolomite are present. Calcite and dolomite tent to co-float with phosphate giving low concentrate grades. Potash can be separated from halite by reverse flotation.