1. IRON ORE FLOTATION

2. Economically Important Iron-Bearing Minerals
Name
Crystal System
Chemical Fromula
Specific Gravity
Iron Content
Magnetite
Cubic
FeO.Fe2O3
72.4
Hematite
Hexagonal-rhombohedral
Fe2O3
70.0
Martite
Geathite
Rhobohedral
Fe2O3.H2O
62.9
Limonite
Mixed, chiefly geothite
2Fe2O3.3H2O
60.0
Siderite
FeCO3
48.2
Pyrite
FeS2
46.6
The most important minerals are the oxides.
Upon firing, all minerals will be converted to the most suitable Fe2O3 form.

3. Impurities Slag-forming Deleterious impurities
Acidic: silica (SiO2) and alumina (Al2O3)
Basic: lime (CaO) and magnesia (MgO)
Deleterious impurities
Sulfur, phosphorus, and other metallic oxides
Most ores have an excess of SiO2 and Al2O3; ash of coke used for fuel is composed of these oxides.
Therefore, a basic flux, e.g. Limestone, must be added.
Most other impurities, especially sulfur and phosphorus, impart undesirable properties to steel.

4. Market Specifications-1
The average iron content of ores and agglomerated products has steadily increased,
Grade of marketable ores are based not only on chemical analysis but also on the structural quality (particle size)
Marketable ores; coarse ore (+10 mm), sinter ( mm), pellets.
Pellets have provided the most substantial technical and economical advantages.

5. Market Specifications-2
Hematite, lump grade: 62.5% Fe
Pellets for blast furnace charge: 65% Fe and <5% SiO2
Pellets for direct reduction: <67% and <2% SiO2+Al2O3
Sulfur can be reduced to the desired level during iron making, but this cases extra cost.
Phosphorus/iron weight ratio < 0.002

6. Concentration Methods
Magnetic separation
Low intensity ( Tesla)
High intensity ( Tesla)
Magnetic roastig: Roasting ( °C) in reducing environment to convert hematite to magnetite.
Gravity separation
Sedimentation
Spirals
Heavy media
Jigging

7. Flotation-1 Used for Direct flotation Reverse Flotation
non-magnetic iron ores
As a final concentration stage to improve concentrate grade
Direct flotation
Iron oxide is floated
Anionic reagents, such as petroleum sulfonates or fatty acids, are most commonly used
Reverse Flotation
Flotation of gangue, mainly silica
Cationic collectors at pH 11-12
Use organic depressants (starch or guar gum) to depress iron minerals
Activation of silica by Ca2+ and use of anionic collectors

8. Flotation-2 Separation of apatite
Flotation of iron minerals at pH 6.5 using anionic collector
Use flourosilisic acid and sodium silicate to depress apatite
Reverse flotation of apatite at pH 8.5
Depress iron minerals by organic depressants

9. Tilden Concentrator Flowsheet