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How does roasting remove sulfur from lead concentrate?

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Metallurgy — 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 the context of lead processing, roasting is a critical step used to remove sulfur from lead concentrate, which is primarily composed of the mineral galena (lead sulfide).12

The process functions through an oxidation reaction. The lead concentrate is mixed with fluxing materials, such as limestone or iron ore, and spread onto a moving grate. Air is then blown through the mixture at high temperatures, typically reaching 1,400 °C (2,550 °F). During this process, the sulfur in the concentrate—along with added coke—acts as a fuel and is combusted to form sulfur dioxide gas.1

This gas is typically captured and recovered as a valuable by-product for the production of sulfuric acid. The roasting process also serves to agglomerate the fine concentrate particles into a brittle, lumpy material known as sinter, which is better suited for subsequent treatment in a blast furnace.1