Modern DAF units using parallel plate technology are quite compact.
Picture shows a 225 m³/h DAF.

Froth flotation is a selective process for separating minerals from gangue by using surfactants and wetting agents. The selective separation of the minerals makes processing complex (that is, mixed) ores economically feasible. The flotation process is used for the separation of a large range of sulfides, carbonates and oxides prior to further refinement. Phosphates and coal are also processed by flotation technology. Froth is foam consisting of bubbles in a liquid. ... Minerals are natural compounds formed through geological processes. ... Tailings, also called gangue, are the rejected material from mining and screening operations. ... Surfactants, also known as wetting agents, lower the surface tension of a liquid, allowing easier spreading. ... Formally, sulfide is the dianion, S2−, which exists in strongly alkaline aqueous solutions formed from H2S or alkali metal salts such as Li2S, Na2S, and K2S. Sulfide is exceptionally basic and, with a pKa > 14, it does not exist in appreciable concentrations even in highly alkaline water. ... Ball-and-stick model of the carbonate ion, CO32− For other meanings, see Carbonate (disambiguation) In chemistry, a carbonate is a salt or ester of carbonic acid. ... An oxide is a chemical compound containing at least one oxygen atom and other elements. ... In chemistry, a phosphate is a polyatomic ion or radical consisting of one phosphorus atom and four oxygen. ... Coal Example chemical structure of coal Coal is a fossil fuel formed in ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ...

The flotation process is also widely used in industrial waste water treatment plants, where it is applied to remove fats, oil, grease and suspended solids from waste water. These units are called Dissolved air flotation (DAF) units.^[1] In particular, dissolved air flotation units are used in removing oil from the wastewater effluents of oil refineries, petrochemical and chemical plants, natural gas processing plants and similar industrial facilities. Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids. ... In the context of creating Plutonium at the Hanford Site, effluent refers to the cooling water that is discharged from a nuclear reactor that may or may not be radioactive. ... View of Shell Oil Refinery in Martinez, California. ... Petrochemicals are chemical products made from raw materials of petroleum (hydrocarbon) origin. ... A Chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. ... A natural gas processing plant Natural gas processing plants are used to purify the raw natural gas extracted from underground gas fields and brought up to the surface by gas wells. ...

History

William Haynes in 1869 patented a process for separating sulfide and gangue minerals using oil and called it bulk-oil flotation. The modern froth flotation process was invented in 1901 by C.V Potter in Australia and in 1902 by G.D Delprat^[2] in Holland. In the early times, only naturally occurring chemicals such as fatty acids and oils were used as flotation reagents in a large quantity. Since then, the process has been adapted to apply to a wide variety of materials to be separated, and additional collector agents, including surfactants and synthetic compounds have been adopted for various applications. Froth is foam consisting of bubbles in a liquid. ... This article is about a region in the Netherlands. ... Not to be confused with fats. ... A reactant or reagent is a substance consumed during a chemical reaction. ... Surfactants, also known as wetting agents, lower the surface tension of a liquid, allowing easier spreading. ...

Principle of operation

Froth flotation commences by comminution (that is, crushing/grinding), which is used to increase the surface area of the ore for subsequent processing and break the rocks into the desired mineral and gangue, which then has to be separated from the desired mineral. The ore is ground into a fine powder. The desired mineral is rendered hydrophobic by the addition of a surfactant or collector chemical. The particular chemical depends on the mineral is being refined. As an example, pine oil is used to extract copper (see copper extraction). This slurry (more properly called the pulp) of hydrophobic mineral-bearing ore and hydrophilic gangue is then introduced to a water bath which is aerated, creating bubbles. The hydrophobic grains of mineral-bearing ore escape the water by attaching to the air bubbles, which rise to the surface, forming a foam or a scum (more properly called a froth). The froth is removed and the concentrated mineral is further refined. Look up comminution in Wiktionary, the free dictionary. ... Tailings, also called gangue, are the rejected material from mining and screening operations. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... Surfactants, also known as tensides, are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids. ... For other uses, see Copper (disambiguation). ... The Chino open-pit copper mine in New Mexico. ... The adjective hydrophilic describes something that likes water (from Greek hydros = water; philos = friend). ... Tailings, also called gangue, are the rejected material from mining and screening operations. ... Sea foam on the beach Foam on a cappuccino Fire-retardant, foamed plastic being used as a temporary dam for firestop mortar in a cable penetration in a pulp and paper mill on Vancouver Island, British Columbia, Canada. ... Look up Scum in Wiktionary, the free dictionary. ... Froth is foam consisting of bubbles in a liquid. ...

Science of flotation

To be effective on a given ore slurry, the surfactants are chosen based upon their selective wetting of the types of particles to be separated. A good surfactant candidate will completely wet one of the types of particles, while partially wetting the other type, which allows bubbles to attach to them and lift them into a froth. The wetting activity of a surfactant on a particle can be quantitated by measuring the contact angles that the liquid/bubble interface makes with it. For complete wetting the contact angle is zero. Wetting of different fluids. ... Image from a video contact angle device. ...

Another consideration, especially important for heavy particles, is to balance the weight of the particle with the surfactant adhesion and buoyant forces of the bubbles that would lift it.

For typical values of metal densities and surface tensions, if the bubbles are larger than the ore particles, and the particles are or less that 1 mm radius, then particles will rise into the froth layer if:^[3]

where is the radius of the particles, is the average surface tension between the three pairs of phases (particle, flotation solution, air), is the mass density of the particles, and is the acceleration of gravity (9.81 m/s²). This box:      Surface tension is a property of the surface of a liquid that causes it to behave as an elastic sheet. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... Gravity is a force of attraction that acts between bodies that have mass. ...

For particles larger than the bubbles, they too can rise into the froth, each buoyed by a swarm of bubbles, under similar conditions as those expressed in the inequality.^[3]

Flotation equipment

Diagram of froth flotation cell.

Schematic of Dissolved Air Flotation unit

Flotation can be performed in mechanically agitated cells or tanks, in tall flotation columns and in several other units including the Jameson cell. Image File history File links FlCell. ... Image File history File links FlCell. ...

Mechanical cells use a large mixer and diffuser mechanism at the bottom of the mixing tank to introduce air and provide mixing action. Flotation columns use air spargers to introduce air at the bottom of a tall column while introducing slurry above. The countercurrent motion of the slurry flowing down and the air flowing up provides mixing action. Mechanical cells generally have a higher throughput rate, but produce material that is of lower quality, while flotation columns generally have a low throughput rate but produce higher quality material. Mechanical flotation cell used for mineral concentration. Numbered triangles show direction of stream flow. A mixture of ore and water called pulp [1] enters the cell from a conditioner, and flows to the bottom of the cell. Air [2] or sometimes nitrogen is passed down a vertical impeller where shearing forces break the air stream into small bubbles. The mineral concentrate froth is collected from the top of the cell [3], while the pulp [4] flows to another cell.

The Jameson cell uses neither impellers nor spargers, instead combining the slurry with air in a downcomer where high shear gives excellent bubble particle contacting.

In dissolved air flotation (DAF), which is used in wastewater treatment, air is dissolved into the flotation solution under high pressure. When the solution is released into the flotation chamber, the reduced pressure causes much of the dissolved air to come out of solution to form bubbles in the same way that dissolved carbon dioxide forms bubbles when a beer bottle is opened.
Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids. ...

Mechanics of flotation

The following steps are followed: Image File history File links FlCirc. ... Image File history File links FlCirc. ...

1. Grinding to liberate the mineral particles
2. Reagent conditioning to achieve hydrophobic surface charges on the desired particles
3. Collection and upward transport by bubbles in an intimate contact with air or nitrogen
4. Formation of a stable froth on the surface of the flotation cell
5. Separation of the mineral laden froth from the bath (flotation cell)

Simple flotation circuit for mineral concentration. Numbered triangles show direction of stream flow, Various flotation reagents are added to a mixture of ore and water (called pulp) in a conditioning tank. The flow rate and tank size are designed to give the minerals enough time to be activated. The conditioner pulp [1] is fed to a bank of rougher cells which remove most of the desired minerals as a concentrate. The rougher pulp [2] passes to a bank of scavenger cells where additional reagents may be added. The scavenger cell froth [3] is usually returned to the rougher cells for additional treatment, but in some cases may be sent to special cleaner cells. The scavenger pulp is usually barren enough to be discarded as tails. More complex flotation circuits have several sets of cleaner and re-cleaner cells, and intermediate re-grinding of pulp or concentrate.

Chemicals of flotation

Collectors

Xanthates are the salts of xanthic acid, C2H5OCS2H. Many xanthates have a yellow colour, which gives the compound its name (Greek xanthos means yellow). ... This article or section is in need of attention from an expert on the subject. ...

Frothers

Pine oil is an oil manufactured by the steam-distillation of pine (Pinus sylvestris) needles, twigs and cones. ... This article does not cite any references or sources. ... Xylenol or dimethylphenol is a benzene derivative with two methyl groups and a hydroxyl group. ...

Modifiers

pH modifiers such as: For other uses, see PH (disambiguation). ...

• Lime CaO
• Soda ash Na₂CO₃
• Caustic soda NaOH
• Acid H₂SO₄, HCl

Cationic modifiers: Calcium oxide (CaO), commonly known as burnt lime, lime or quicklime, is a widely used chemical compound. ... Sodium carbonate (also known as washing soda or soda ash), Na2CO3, is a sodium salt of carbonic acid. ... Sodium hydroxide (NaOH), also known as lye, caustic soda and (incorrectly, according to IUPAC nomenclature)[1] sodium hydrate, is a caustic metallic base. ... For other uses, see acid (disambiguation). ... A cation is an ion with positive charge. ...

• Ba²⁺, Ca²⁺, Cu⁺, Pb²⁺, Zn²⁺, Ag⁺

Anionic modifiers: An anion is an ion with negative charge. ...

• SiO₃^2-, PO₄^3-, CN^-, CO₃^2-, S^2-

Organic modifers:

• Dextrin, starch, glue, CMC

Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch. ... Starch (CAS# 9005-25-8, chemical formula (C6H10O5)n,[1]) is a mixture of amylose and amylopectin (usually in 20:80 or 30:70 ratios). ... Look up glue in Wiktionary, the free dictionary. ...

Specific ore applications

v • d • e Separation processes Processes Acid-base extraction · Chromatography · Crystallization · Dissolved air flotation · Distillation · Drying · Electrochromatography · Filtration · Flocculation · Froth flotation · Liquid-liquid extraction · Recrystallization · Sedimentation · Solid Phase Extraction · Sublimation Devices API oil-water separator · Centrifuge · Mixer-settler · Protein skimmer · Spinning cone · Still · Sublimation apparatus Multiphase systems Aqueous two phase system · Azeotrope · Eutectic

The Chino open-pit copper mine in New Mexico. ... Fluorite (also called fluorspar) is a mineral composed of calcium fluoride, CaF2. ... For other uses, see Tungsten (disambiguation). ... This article is about the chemical element. ... General Name, Symbol, Number tantalum, Ta, 73 Chemical series transition metals Group, Period, Block 5, 6, d Appearance gray blue Standard atomic weight 180. ... This article is about the metallic chemical element. ... Coal Example chemical structure of coal Coal is a fossil fuel formed in ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... Barring a few exceptions, almost every element or compound is found in an impure state i. ... Acid-base extraction is a procedure using sequential liquid-liquid extractions to purify acids and bases from mixtures based on their chemical properties. ... For the Second Person album, see Chromatography (album). ... Frost crystallization on a shrub. ... Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids. ... Laboratory distillation set-up: 1: Heat source 2: Still pot 3: Still head 4: Thermometer/Boiling point temperature 5: Condenser 6: Cooling water in 7: Cooling water out 8: Distillate/receiving flask 9: Vacuum/gas inlet 10: Still receiver 11: Heat control 12: Stirrer speed control 13: Stirrer/heat plate... Drying is a mass transfer process resulting in the removal of water moisture or moisture from another solvent, by evaporation from a solid, semi-solid or liquid (hereafter product) to end in a solid state. ... Electrochromatography is a chemical separation technique in analytical chemistry, biochemistry and molecular biology used to resolve and separate mostly large biomolecules such as proteins. ... This article is about operation of solid-fluid separation. ... This article needs additional references or sources for verification. ... Liquid-liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds based on their solution preferences for two different immiscible liquids, usually water and an organic solvent. ... Insulin crystals Recrystallization is an essentially physical process that has meanings in chemistry, metallurgy and geology. ... Sedimentation describes the motion of particles in solutions or suspensions in response to an external force such as gravity, centrifugal force or electric force. ... This article does not cite any references or sources. ... Image File history File links ChemSepProcDiagram. ... An API oil-water separator is a device designed to separate gross amounts of oil and suspended solids from the wastewater effluents of oil refineries, petrochemical plants, chemical plants, natural gas processing plants and other industrial sources. ... This article is about the scientific device. ... Mixer-settlers are used when there will only be one equilibrium stage in the process. ... A protein skimmer or foam fractionator is a device used mostly in saltwater aquaria to remove organic compounds from the water before they break down into nitrogenous waste. ... The term still is a contraction of the verb to distill. A still is an apparatus used to distill miscible or immiscible (eg. ... Simple sublimation apparatus. ... Aqueous biphasic systems (ABS)or aqueous two phase systems are clean alternatives for traditional organic-water solvent extraction systems. ... This article needs more context around or a better explanation of technical details to make it more accessible to general readers and technical readers outside the specialty, without removing technical details. ... A eutectic or eutectic mixture is a mixture of two or more elements which has a lower melting point than any of its constituents. ...

See also

• Flocculation
• Dissolved air flotation (DAF)

This article needs additional references or sources for verification. ... Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids. ...

References