Video Transcript
In the manufacturing of iron in a blast furnace, which two raw materials are necessary for the main process? (A) Hematite and limestone, (B) bauxite and limestone, (C) hematite and lime, (D) bauxite and coke, or (E) hematite and water.
Blast furnaces are used to extract iron from its ore. Options (B) and (D) contain bauxite. This is an ore of aluminum, but the question specifies the manufacturing of iron. So neither option (B) or option (D) can be the answer to this question. Options (A), (C), and (E) include hematite. This is an iron ore, so either option (A), (C), or (E) can be the answer to this question.
The hematite forms part of what we call the charge. The charge continually fuels the blast furnace. It is what is needed for the reactions in the blast furnace to take place. The charge also contains coke, which is the product of heating coal. The other key component of the charge is limestone. Limestone is key to the main process, as it removes the impurity sand. Limestone is primarily composed of calcium carbonate. When this is heated, as it would be in the furnace, calcium oxide and carbon dioxide are formed. The calcium oxide then reacts with sand impurities, which can be thought of as silicon dioxide, producing calcium silicate, the main component of a byproduct called slag.
So, as hematite and limestone are important materials for the extraction of iron from iron ore, we can determine that option (A), hematite and limestone, is the correct answer to this question, not option (E), hematite and water, or option (C), hematite and lime. Lime is another name for calcium oxide, which is a key part of this process. But the question asks which two raw materials. Calcium oxide is formed from the raw material limestone; it is not itself one of the raw materials. So option (C), hematite and lime, is not the correct answer to this question. Therefore, the answer to the question “In the manufacturing of iron in a blast furnace, which two raw materials are necessary for the main process?” is (A), hematite and limestone.
