Which outcome arises when a blast furnace's internal temperature falls below the iron melting point?

💡 Explanation

When temperature falls too low, incomplete combustion of coke occurs because of insufficient energy, leading to a mixture of unreacted ore, coke, and flux solidifying to form a blockage called a 'scaffold'. Therefore, a scaffold forms, rather than increased emissions, better slag separation, or accelerated corrosion, which require different thermal conditions.

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• Which structural challenge did Roman engineers overcome to build durable concrete aqueducts?
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