Treatment of Hot Metal Desulfurization Slag With CO₂ Gas in the Temperature Range of 873 K to 1473 K for Better Recycling of the Slag

High sulfur content in hot metal desulfurization slag is one of the major barriers for recycling of the slag in the ironmaking and steelmaking process. How to effectively remove sulfur from the hot metal desulfurization slag is a crucial step for improving its recyclability. Thermodynamic analysis shows that CO₂ is a better oxidation gas for sulfur removal from the hot metal desulfurization slag than O₂ in terms of removal efficiency of sulfur while maintaining high recyclability of the treated slag by keeping iron in the slag separable with magnetic separators. A sulfur removal experiment with about 100 g hot metal desulfurization slag sample in each test run was conducted within the temperature range of 873 K to 1473 K (600 °C to 1200 °C). Compared to sulfur removal by oxygen, carbon dioxide is more effective, up to 40 pct removal at 1173 K (900 °C) and around 90 pct removal above 1273 K (1000 °C). High temperature, high gas velocity and long treatment time are favorable to complete removal of sulfur from the hot metal desulfurization slag. After being treated with CO₂ above 1273 K (1000 °C) for 60 minutes, sulfur content in the hot metal desulfurization slag became sufficiently low and the treated hot metal desulfurization slag is expected to be highly recyclable as substitutes of scrap, iron ores and fluxes in the ironmaking and steelmaking process.