Which risk increases when a blast furnace's refractory lining degrades during iron production?

💡 Explanation

When the refractory lining degrades, heat transfer to the outer steel shell increases because the insulating properties are reduced, leading to localized overheating and weakening of the shell. Therefore, furnace shell failure probability increases, rather than CO breakthrough, methane production, or slag issues, which involve different chemical processes or material properties.

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