GATE 2022 MT – Question 51
Molten steel at 1873 K weighing 100 metric tons is desulfurized using 1250 kg of synthetic slag by equilibration. If the sulfur content in the steel is reduced from 0.015 mass% to 0.0025 mass%, the desulfurizing index is _______ (round off to the nearest integer).
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Correct answer: 400 to 400
Explanation
Sulfur removed is $100000(0.00015-0.000025)=12.5$ kg. Assuming initially sulfur-free slag, 1250 kg slag then contains 1 mass% sulfur. The index is slag/steel sulfur concentration: $L_S=1/0.0025=\boxed{400}$.