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Why is sintering used before zinc concentrate enters a zinc-lead blast furnace?

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sphalerite — zinc processing Sphalerite from Baxter Springs, Kansas.

Sintering is a critical preparatory step for the zinc-lead blast furnace because the furnace requires a strong, lumpy feed to operate effectively.1

Complex sulfide ores must undergo sintering to remove sulfur and consolidate fine concentrates into a durable, porous material. During this process, fine concentrates are mixed with crushed returned sinter and fired on a moving grate, resulting in a hard, lumpy cake that is ideal for the furnace environment.21

This method is particularly necessary when the grade of the concentrate is low or when the lead content exceeds 3 percent, as these conditions make other roasting methods difficult to manage. Additionally, the sintering process allows for the recovery of sulfur dioxide, which is then utilized in the production of sulfuric acid.1