How do you make ferro silicon

Ferrosilicon (FeSi) is an alloy of iron and silicon, typically containing 15% to 90% silicon. It is produced in an electric arc furnace by reducing silica (SiO₂) with carbon (coke or coal) in the presence of iron (usually scrap iron or iron ore). Here's a step-by-step guide to making ferrosilicon:

Raw Materials Required:

Silica (SiO₂) – Usually high-purity quartz or sand (≥98% SiO₂).

Carbon Reductant – Coke, coal, or charcoal.

Iron Source – Steel scrap, iron ore (hematite/magnetite), or mill scale.

Electrodes – Graphite or carbon electrodes for the electric arc furnace.

Fluxes (optional) – Lime (CaO) or dolomite (MgO) to adjust slag properties.

Production Process:

1. Raw Material Preparation

Crush and wash silica to remove impurities.

Mix silica, carbon, and iron in the required ratio (depends on desired FeSi grade).

Example: For FeSi75 (75% Si), the mix is ~1.8–2.2 parts SiO₂, 1 part carbon, and iron to balance.

2. Charging the Electric Arc Furnace (Submerged Arc Furnace, SAF)

The mixture is fed into a high-temperature (1500–2000°C) submerged arc furnace.

Electrodes create an arc that melts the charge while carbon reduces silica:

SiO2+2C→Si+2CO↑SiO2​+2C→Si+2CO↑

The silicon dissolves into molten iron to form ferrosilicon.

3. Slag Formation & Tapping

Impurities (Al₂O₃, CaO, MgO) form slag, which floats on top.

The molten FeSi (denser) is tapped from the bottom into ladles.

Slag is removed separately.

4. Casting & Crushing

Molten ferrosilicon is cast into molds or granulated (water-quenched for fine sizes).

After cooling, it is crushed and sized for sale.

Key Parameters:

Temperature: ~1600–1800°C for standard grades (FeSi45–FeSi75).

Energy Consumption: ~8000–9000 kWh/ton of FeSi75.

Silicon Recovery: ~85–90% (some Si is lost as SiO gas).