| Froth Flotation |
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Information AboutFroth Flotation |
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William Haynes in 1869 patented a process for separating sulfide and gangue minerals using oil and called it ''bulk-oil flotation''. The froth flotation process was invented in 1905 simultaneously by A.H. Higgins in England and by G.A. Chapman in Australia . In the early times, only naturally occurring chemicals such as fatty acids and oils were used as flotation Reagent s in a large quantity. Froth flotation commences by Comminution , 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 . This slurry 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 rises to the surface, forming a foam. The foam is removed and the concentrated mineral is further refined. FLOTATION EQUIPMENT Flotation can be performed in mechanically agitated cells or tanks, in tall flotation columns and in several other units including the jameson cell. 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. 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. CHEMISTRY OF FLOTATION Collectors Xanthates:
Dithiophosfates.
Frothers Frothers include:
Modifiers PH modifiers such as:
Cation ic modifiers:
Anion ic modifiers:
Organic modifers: Sulfide Flotation Oxide and Silicate Flotation MECHANICS OF FLOTATION The following steps are followed: # Grinding to liberate the mineral particles # Reagent conditioning to achieve hydrophobic surface charges on the desired particles # Collection and upward transport by bubbles in an intimate contact with air or nitrogen # Formation of a stable froth on the surface of the flotation cell # Separation of the mineral laden froth from the bath (flotation cell) FLOTATION OPERATIONS Sulfide Ores:
Non-Sulfide Ores: SEE ALSO EXTERNAL LINKS
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