How does the QSL process treat unroasted lead concentrates?

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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.

The QSL process treats unroasted, or "green," lead concentrates by feeding them directly into a refractory-lined reactor without prior drying or briquetting.1

To manage the process, the moisture content of the concentrates is maintained at 7–8 percent to minimize the generation of dust. Once inside the reactor, the charge undergoes the following stages:1

Oxidation: The unroasted material is oxidized within a molten bath through the submerged injection of oxygen, which is blown into the reactor through tuyeres at the bottom. This stage produces a flue gas containing lead and zinc oxides, while approximately 80 percent of the zinc from the charge is captured in the slag.1
Reduction: Metal oxides are reduced to metal when they come into contact with carbon monoxide, which is generated by the injection of natural gas through the bottom tuyeres.1