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Blast furnaces are apparatuses that extract metal from ore by removing oxygen from metal oxide. These tall, cylindrical smelting furnaces are fed from the top with a mix of ore, coke, and a flux, commonly limestone, while preheated compressed air is introduced under pressure from the bottom. As the contents become molten, the metal sinks and impurities, called slag, float to the top. Blast furnaces were first used in China more than 2,000 years ago. When did they appear in Europe? Discuss
Source: The Free Dictionary