Britannica Sources used in this answer

What role does coke play in a zinc-lead blast furnace?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

sphalerite — zinc processing Sphalerite from Baxter Springs, Kansas.

In a zinc-lead blast furnace, metallurgical coke serves two essential functions: it acts as a fuel and as a chemical reducing agent.12

Fuel: When preheated air is blown through the furnace tuyeres, it provides oxygen that reacts with the coke. This combustion generates the high temperatures necessary to melt the furnace charge, which consists of sintered zinc and lead concentrates.12
Reducing Agent: The combustion of coke also produces carbon monoxide, which acts as a reducing gas within the furnace shaft. This gas is critical for the reduction of zinc oxide and lead oxide into their respective metallic forms.12

By facilitating these reactions, coke enables the extraction of zinc as a vapor—which is subsequently captured in a lead-splash condenser—and the production of molten lead and slag that collect in the furnace hearth.12