Iron Ore Desulfurization Methods & Processes

Iron ore desulfurization is the process of removing sulfur-bearing minerals and reducing sulfur content in iron ore before further beneficiation or ironmaking. Sulfur is an undesirable impurity because excessive sulfur in the feed can negatively affect iron ore concentrate quality, blast furnace operation, and the properties of the final iron and steel products. Therefore, effective desulfurization is an important part of iron ore beneficiation and pretreatment.

The appropriate desulfurization method depends largely on the sulfur content, mineralogical composition, liberation characteristics, magnetic properties, and particle size of the ore. Common methods include magnetic separation, flotation, roasting, hydrometallurgical treatment, and, in some cases, biological treatment or combinations of several processes.

 

Iron Ore Desulfurization Methods

The desulfurization of iron ore mainly improves its quality and reduces environmental emissions during subsequent processing. There are many methods and processes for iron ore desulfurization, including:

Magnetic Separation

Magnetic separation utilizes magnetic properties to separate sulfur-bearing minerals from iron ore. The ore is subjected to a magnetic field, and the sulfur-bearing minerals are attracted to the magnetic surface while the iron ore particles remain unaffected. The separated sulfur-bearing minerals can be further processed or discarded.

Flotation

Flotation is a commonly used technique for desulfurizing iron ore. In this process, finely ground ore is mixed with water and chemicals, such as collectors and frothers. Air is then bubbled through the mixture, causing the sulfur-bearing minerals to attach to the air bubbles and rise to the surface as froth, while the iron ore particles sink to the bottom. The froth containing sulfur can be removed, leaving behind desulfurized iron ore.

Roasting

Roasting involves heating the iron ore at high temperatures in the presence of air or oxygen. This process oxidizes the sulfur in the ore, converting it into sulfur dioxide gas (SO2) or other sulfur compounds, which can be easily separated from the iron ore. Roasting can occur in a rotary kiln, fluidized bed reactor, or other suitable equipment.

Biological Desulfurization

Biological methods involve using microorganisms to remove sulfur from iron ore selectively. Certain bacteria or fungi can oxidize the sulfur compounds in the ore, converting them into soluble forms that can be washed away. Biological desulfurization is an environmentally friendly approach, but it is still under development and has yet to be widely used on an industrial scale.

Hydrometallurgical Processes

Hydrometallurgical methods use chemical leaching agents to dissolve and remove sulfur from iron ore. One example is the acid-leaching process, where the ore is treated with an acid solution that selectively dissolves the sulfur minerals. The leaching solution is then separated from the solid residue containing desulfurized iron ore.

Combination Methods

Various combinations of the above methods can be employed to achieve effective desulfurization, depending on the specific characteristics of the iron ore and the desired sulfur removal efficiency.

 

The selection of the desulfurization method depends on factors such as the sulfur content and mineralogy of the iron ore, the desired sulfur removal efficiency, the economic viability of the process, and environmental considerations. Different iron ore deposits may require different desulfurization approaches. Therefore, it is essential to conduct thorough testing and evaluation to determine the most suitable method for a particular ore.

 

 

Iron Ore Desulfurization Processes

The iron ore desulfurization process of pyrrhotite, pyrite-associated iron ore, includes grinding, desulfurization, magnetic separation-flotation combined desulfurization process, and roasting-magnetic separation-flotation combined desulfurization process.

• Iron ore with fine particle size and single sulfur content: It is suitable for adopting grinding and desulfurization processes;
• Strongly magnetic iron ores containing various types of sulfur: The magnetic separation-flotation combined desulfurization process is suitable;
• Weakly magnetic iron ores containing various types of sulfur: The roasting-magnetic separation-flotation combined desulfurization process is suitable.

Associated Iron Ore Desulfurization And Iron Separation Technology

1. Stage grinding, stage separation, desulfurization, and iron separation process

Grinding fineness significantly influences mineral processing indicators. Products with different grinding fineness have different particle size compositions, thus affecting minerals’ monomer dissociation and selectability. Fine-grained iron ore requires Fine grinding to dissociate the mineral monomers. For iron ore with finer particle size and a single sulfur-containing type (pyrite and pyrrhotite), stage grinding and stage separation processes are usually used to increase iron and reduce sulfur.

 

2. Magnetic separation-flotation combined desulfurization and iron separation process

The magnetite currently selected in China contains a large amount of pyrrhotite and pyrite due to its fine particle size, which makes the negative impact of magnetic agglomeration in the separation very obvious. It is increasingly difficult to improve the concentrate grade by relying on a single magnetic separation method. Combining magnetic separation with anion reverse flotation can achieve complementary advantages in the process of magnet ore separation, which is beneficial to improving the grade of magnet ore separation concentrate. The magnetic separation-flotation combined process is one of the more effective processes for increasing iron and reducing sulfur in high-pyrite iron ore in China.

 

3. Roasting-magnetic separation-flotation combined desulfurization process

The reduction roasting magnetic separation process of domestic iron ore has not been widely used due to the high cost and low grade of iron concentrate. This process is mainly suitable for iron ores with significant burning losses, such as limonite and siderite. For weakly magnetic iron ore with low theoretical grade and various sulfur-containing types, iron ore concentrate with low impurity content can be obtained through a combined roasting-magnetic separation-flotation process, significantly improving product quality.

 

Conclusion

After undergoing desulfurization, iron ore demonstrates significant technical and economic advantages. The process yields multiple measurable benefits:

1. Economic Value Creation

• Increases iron grade by 3-5% on average
• Boosts recovery rates by 5-8 percentage points
• Reduces downstream processing costs by 15-20%

2. Operational Advantages

• Stabilizes blast furnace operations by maintaining sulfur content below 0.02%
• Decreases coke consumption by 8-12% in subsequent ironmaking
• Extends refractory lifespan in smelting equipment

3. Environmental Compliance

• Reduces SOx emissions by 30-50% from subsequent processing
• Lowers energy consumption per ton of output by 10-15%
• Ensures compliance with increasingly stringent emissions regulations

Modern desulfurization methods show particular effectiveness when tailored to specific ore characteristics:

• Flotation achieves 75-85% sulfur removal for sulfide-rich ores
• Combined processes can reach 90%+ desulfurization efficiency
• Emerging biological methods show promise for low-grade deposits

The strategic implementation of these technologies creates sustainable competitive advantages, transforming environmental compliance into economic value while future-proofing operations against evolving regulatory requirements.