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How does the Betterton-Kroll process remove bismuth from lead?
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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.
The Betterton-Kroll process, also known as the Asarco process, is a pyrometallurgical method used to remove bismuth from lead bullion.12
The process involves the following steps:
- Addition of Reagents: Calcium and magnesium are added to a molten lead-bismuth bath.1
- Compound Formation: Bismuth reacts with these metals to form compounds that possess higher melting points and lower densities than the surrounding molten lead.12
- Separation: Because these compounds are lighter than lead, they rise to the surface of the melt, where they are removed as a solid dross or skimmed off.12
- Recovery: The removed bismuth can subsequently be recovered from the calcium and magnesium through treatment with chlorine.1
Typically performed after softening, desilvering, and dezincing, this method can reduce bismuth content in lead to between 0.005 and 0.01 percent.2