Blast furnace tapping requirements

Carbothermal reaction requires temperatures in excess of 2000°C. After ca. 1 to 2 h the continuously operating furnace is tapped with an auxiliary electrode. The liquid silicon (m.p. 1413°C) is collected in pans or ingot molds. If necessary, further metallurgical processes such as slag extraction or air blasting with reactive gases can be carried out to rid the silicon melt of included metallic and non-metallic impurities, before the silicon solidifies into brittle blocks. 

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