How is ferro silicon produced?

Ferro silicon (FeSi) is an alloy of iron and silicon, typically containing around 15% to 90% silicon by weight. It is produced through a high-temperature reduction process in submerged arc furnaces. The key steps involved in the production of ferro silicon are as follows:

1. Raw Material Preparation:

• Quartz or Silica (SiO₂): The primary source of silicon, which should be of high purity.

• Iron Source: Typically, iron scrap, iron ore, or mill scale is used as the iron source.

• Reducing Agents: Carbonaceous materials like coke, coal, or charcoal serve as reducing agents to extract silicon from silica.

2. Smelting Process:

• Submerged Arc Furnace: The mixture of quartz, iron source, and carbonaceous material is fed into a submerged arc furnace. The furnace consists of three carbon electrodes that provide the necessary heat by forming an electric arc.

• Reduction Reaction: The furnace operates at temperatures of 1,500°C to 2,000°C. At these temperatures, the carbon in the reducing agents reacts with the silicon dioxide in quartz to produce silicon monoxide (SiO) gas and carbon monoxide (CO) gas. The silicon monoxide further reacts with the remaining quartz to produce silicon, which then combines with iron to form ferro silicon.

  SiO2+2C→SiO+2COSiO+C→Si+CO

  SiO+C→Si+COSi+Fe→FeSi

  Si+Fe→FeSi
  

• Separation of Alloy and Slag: The molten ferro silicon settles at the bottom of the furnace, while the lighter slag floats on top. The slag is removed, and the ferro silicon is tapped from the furnace.

3. Casting and Cooling:

• Casting: The molten ferro silicon is cast into molds, ingot molds, or on sand beds to cool and solidify.

• Cooling: The cast ferro silicon is allowed to cool, forming solid lumps or ingots.

4. Crushing and Sizing:

• Once solidified, the ferro silicon is crushed and ground into the desired particle sizes, typically ranging from coarse lumps to fine powders, depending on customer specifications.

5. Quality Control:

• The final product is analyzed for silicon content, iron content, and other impurities to ensure it meets the required specifications.

Environmental Considerations:

• Gas Emissions: The smelting process generates significant quantities of carbon monoxide and silicon monoxide gases. These are often captured and treated to reduce environmental impact.

• Energy Consumption: The production of ferro silicon is energy-intensive, leading producers to adopt energy-efficient practices and technologies to minimize consumption.

Applications:

• Deoxidizer: In steelmaking, ferro silicon is commonly used as a deoxidizer to remove oxygen from molten steel, improving its quality.

• Alloying Agent: It is used to add silicon to steel and cast iron, enhancing their properties such as hardness, strength, and corrosion resistance.

• Other Uses: Ferro silicon is also used in the production of silicon steel for transformers, as well as in the manufacturing of certain types of silicon-containing chemicals.

Ferro silicon production is a critical part of the ferroalloy industry, and its production methods are continuously optimized to improve efficiency and reduce environmental impact.

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