Characteristics of Submerged Arc Furnace Melting Silicon

Submerged arc furnace melting silicon also known as electric submerged arc furnaces smelting of metallurgical-grade silicon, is the most important method for industrial silicon production (Si content typically 98.5% ~ 99.7%). Essentially, it involves a strongly endothermic chemical reaction in which silicon dioxide (SiO₂, mainly derived from quartz or silica) is reduced using a carbonaceous reducing agent (such as petroleum coke, charcoal, coal, etc.) under high temperature and a reducing atmosphere.

Submerged Arc Furnace Melting Silicon

1. Silica (Quartz): 

The core raw material. High SiO₂ content (>99%), low impurity content (Al, Fe, Ca, etc.), suitable particle size (typically 50-150mm), and thermal stability (to avoid high-temperature cracking) are required.

2. Reducing Agents:

• Petroleum coke: 

Most commonly used, high fixed carbon content, few impurities, but relatively poor reactivity.

• Charcoal: 

Good reactivity, high porosity, but expensive and low strength.

• Bituminous coal/blue carbon: 

Provides a certain level of activity as a supplement, at a lower cost.

• Mixtures: 

These are typically mixed in proportion to balance activity, purity, and cost.

3. Electrodes:

• Self-baking electrodes: 

Formed by the self-sintering of electrode paste within the furnace; commonly used in large ferrosilicon furnaces; low cost.

• Graphite/carbon electrodes: 

Well-pre-sintered, with uniform resistance and stable performance; the mainstream choice for large industrial silicon furnaces. Electrode consumption is one of the main costs.

4. Auxiliary materials: 

Sometimes a small amount of steel/iron scrap is added (to adjust the iron content in the silicon product or to produce ferrosilicon alloys).

• Core equipment: 

Submerged arc furnace. A silicon smelting furnace is a huge "submerged arc resistance furnace."

• Furnace body: 

Circular or elliptical, consisting of a furnace shell, a refractory lining (carbon bricks, high-alumina bricks, etc.), and a water cooling system.

• Electrode system: 

Typically three large electrodes arranged in an equilateral triangle, adjustable in height to regulate current and arc position.

• Power Supply System: 

The transformer has a large capacity (one 25MVA melting furnace has an annual silicon production capacity of approximately 20,000 tons), converting high-voltage electricity into high-current, low-voltage industrial electricity.

• Charging System: 

The prepared furnace charge is continuously or semi-continuously added to the furnace.

• Flue Gas Purification System: 

Treats flue gas containing large amounts of SiO dust and CO, recovering heat or dust.

• Silicon Outlet/Casting System: 

The silicon outlet is opened periodically to release molten silicon for casting and crushing.

(For the detailed submerged arc furnace silicon production flow, please click the link to view the article.)

Products & Applications

Products: 

Silicon smelting furnaces can produce metallurgical-grade silicon (MG-Si), typically containing 98.5%-99.7% Si, with Fe, Al, and Ca as the main impurities.

Applications:

• 1. Aluminum Alloy Industry (largest consumer): 

As an additive to improve strength and fluidity.

• 2. Organosilicon Industry: 

Used in the production of silanes, siloxanes, etc.

• 3. Raw materials for polycrystalline/semiconductor silicon: 

Metallurgical-grade silicon requires further purification (such as the Siemens process or metallurgical methods) before it can be used in solar cells and electronic chips.

In summary, submerged arc furnace melting silicon is a continuous metallurgical process that uses electricity as the core energy source and carbothermal reduction as the core chemical reaction, carried out in a complex high-temperature system.

Its core technology lies in maintaining a stable high-temperature reaction "crucible" through meticulous raw material control and operational management, achieving efficient, energy-saving, and environmentally friendly large-scale production.

For any questions or needs regarding submerged arc furnaces, silicon smelting furnaces, and other metal smelting furnaces, please feel free to contact us.

E-mail: alice@srfurnace.com  / Tel: +86 15686041999 (Alice)

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Xi'an Sanrui Electric Furnace