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Why are lead concentrates roasted before traditional blast-furnace smelting?
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lead processing
A zinc-lead blast furnace and lead-splash condenser. This technology is utilized mainly for producing zinc while managing both lead and zinc from raw materials, a technique that was highly influential in 20th-century smelting.
In traditional lead processing, lead concentrates must be roasted before being charged into a blast furnace for two primary reasons:1
- Sulfur Removal: Roasting eliminates the majority of the sulfur present in the concentrate, converting it into sulfur dioxide gas, which is often captured to produce sulfuric acid.1
- Agglomeration: The process fuses the fine flotation products into a brittle, lumpy material known as sinter. This agglomeration is essential because, if left as fine particles, the concentrate would be blown out of the blast furnace by the air blast.1
During this roasting process, fluxing materials are added to create a prefluxed sinter consisting of lead, zinc, iron, and silicon oxides, which is then suitable for efficient reduction smelting. While traditional methods rely on this roasting step, newer technologies such as the QSL and KIVCET processes allow for the direct reduction of unroasted lead sulfide concentrate.12