Submerged Arc Furnace Smelting Ferrosilicon Raw Material Processing Technology

Submerged arc furnace smelting ferrosilicon : At present, the raw materials for ferrosilicon production are mainly silica, semi-coke and iron oxide scale. They are put into the furnace in blocks during smelting. The raw silica requires a silicon dioxide content of more than 96% and a particle size of 30-180mm. Semi-coke requires a fixed carbon content of more than 80% and a particle size of 5-18mm. Iron oxide scale requires a ferric oxide content of more than 70%, and there is no requirement for particle size. These three raw materials can produce various grades of ferrosilicon according to their different proportions.
In China, ferrosilicon furnace smelting production mainly follows this old method. In order to ensure the air permeability and temperature uniformity during the smelting process, the raw materials must have a certain particle size.
Silica is one of the mineral resources with the largest reserves in nature. It is also the most difficult ore to reduce in the world. It must be achieved under high temperature conditions. Its reduction temperature is as high as 1700℃ or above under normal pressure. In this way, the oxygen in silica can react chemically with the carbon in the blue carbon, and the carbon monoxide produced can overflow and burn; the silicon in silica can react with the iron in the iron oxide scale to produce a product such as ferrosilicon alloy. In order to achieve such a high reduction temperature, electrode heating must be used. In general, the current smelting process consumes about 9,000 degrees of electricity per ton of ferrosilicon produced in submerged arc furnaces.

Submerged Arc Furnace Smelting Ferrosilicon: Raw Material Processing Technology

1. Raw material selection:

• Silica: As the main raw material, the silicon dioxide content in silica should be greater than 93%, and the silicon dioxide content in high-quality silica can be as high as 98% or more. At the same time, the content of harmful impurities in silica should be low, and it must have good anti-explosion properties.
• Reducing agent: Blue charcoal or coke is often used as a reducing agent, requiring a high fixed carbon content (such as 80-84% fixed carbon content of blue charcoal), low ash, volatile matter and moisture content, and a certain mechanical strength and resistivity.
• Iron oxide: As an iron raw material, the content of ferric oxide in the iron oxide should be greater than 70%.
• Silicon powder: Contains more than 70% silicon dioxide and is used to adjust the raw material ratio.

2. Crushing & screening:

• Crushing silica, blue charcoal, and blue charcoal to a suitable particle size. For example, the silica particle size is generally controlled at 30-100mm (large electric furnace) or 25-60mm (small electric furnace), and the blue charcoal particle size is 5-18mm or finer.
• Remove oversized or undersized particles through screening equipment to ensure uniform raw material particle size.

3. Grinding:

• Grind the crushed silica, blue charcoal, blue charcoal and other raw materials to a powder surface with a particle size of ≤0.063mm. The grinding process can increase the specific surface area of the raw materials, which is conducive to the subsequent batching and mixing.

4. Batching & mixing:

• According to the variety and specification requirements of ferrosilicon smelting in the submerged arc furnaces, the raw materials such as silica powder, blue carbon powder, iron oxide powder, and silicon micropowder are batched in a certain proportion. For example, a typical batching ratio is: silica powder 45-55%, blue carbon powder 25-35%, iron oxide powder 10-20%, and silicon micropowder 3-5%.
• Pour the batched raw materials into a mixer, add an appropriate amount of clean water and 2% water glass as a binder, and stir thoroughly for 3-5 minutes to mix the raw materials evenly.

5. Pressing & molding:

• The evenly mixed raw materials are sent to a double-roll ball press or a billet press, and pressed into billets or balls under a molding pressure of 1.2-2.0MPa. The shape and size of the billet or ball can be adjusted according to actual needs, such as the length × width × thickness of the duck egg-shaped ball = 50mm × 40mm × 30mm.
• The pressed billet or ball is sent to the raw material site for stacking, and then put into the furnace for submerged arc furnace smelting ferrosilicon after drying until the moisture content is below 2%.