How Is Silicon Metal Produced In Eight Steps

How is silicon metal produced？The production of silicon metal involves several steps, from the extraction of raw materials to the final purification of silicon metal. The process generally follows these key stages:

Raw Material Extraction:

The primary raw material for silicon production is quartz (silicon dioxide, SiO2), which is abundant in the form of sand or quartzite. Other raw materials may include coal, wood chips, and iron.

Conversion of Quartz to Silicon:

The quartz undergoes a carbothermic reduction process, typically in an electric arc furnace. The process involves combining quartz with carbon (usually in the form of coal or coke) to produce silicon and carbon monoxide.

Reaction: SiO2 + 2C → Si + 2CO

Formation of Silicon Alloy (Ferrosilicon):

The product of the reduction process is typically a silicon alloy called ferrosilicon. Ferrosilicon contains iron, silicon, and small amounts of other elements. This alloy is often produced in electric arc furnaces.

Electric Arc Furnace (EAF):
Quartz, carbon, and iron are melted in an electric arc furnace at high temperatures.
The reduction of quartz by carbon results in the formation of silicon and carbon monoxide.
The iron present in the mixture contributes to the formation of ferrosilicon, an alloy containing iron and silicon.

Separation and Purification:

The produced ferrosilicon is then subjected to separation processes to extract the silicon. One common method is the use of a refining process known as the Siemens process.

Siemens Process:
Ferrosilicon is mixed with a flux (usually calcium oxide) and heated in an electric furnace.
The calcium oxide reacts with the iron, forming calcium silicate, which can be easily separated from the molten silicon.

Chemical Refining:

The separated silicon undergoes additional chemical refining steps to further reduce impurities. One common method involves the reaction with hydrochloric acid to form volatile silicon compounds.

Chemical Reaction: Si + 4HCl → SiCl4 + 2H2

Distillation:

The volatile silicon compounds are subjected to distillation to separate impurities, leaving purified silicon behind.

Solidification and Crushing:

The purified silicon is then cast into solid forms such as ingots, blocks, or granules. It may be crushed or ground into smaller particles based on the desired application.

Packaging and Distribution:

The final silicon metal product is packaged and prepared for distribution to various industries, including electronics, metallurgy, and chemical manufacturing.

It’s important to note that the specific methods and technologies used in silicon metal production can vary among producers, and advancements in technology may lead to modifications in the process for increased efficiency and reduced environmental impact.