Study of CO2injection on the desulfurization of low-titanium slag

Abstract

A new idea that the low-titanium slag (LTS) used in the steelmaking process after CO2injection desulfurization is proposed in this paper. The CO2injection process mainly involves the grinding of low-titanium slag, mixing of slag and water, CO2injection, filtration, and then obtains the low sulfur and low titanium slag. The effects of cooling rates (water cooling, air cooling, crucible cooling, and furnace cooling) and CO2injection on the desulfurization of LTS were studied by both experimental and thermodynamic calculations. The results showed that sulfite and sulfate ions couldn’t be removed from LTS using this method, and the main removal substance in slag was sulfide ion S2−. The desulfurization mechanism with CO2injection was that the CO2injection reacted with H2O to form H2CO3, and then the H+disrupted from H2CO3reacted with the S2−in the slag to achieve desulfurization. During the desulfurization process, the desulfurization reaction was mainly determined by S2− + CO2(aq) + H2O (l) = CO32− + H2S(g) within the first 5 min, and then the main desulfurization reaction was S2− + 2CO2(aq) + 2H2O(l) = 2HCO3− + H2S(g). As the cooling rate decreasing, the desulfurization rate of LTS increased. The desulfurization effect of furnace-cooled slag is the highest in four kinds of slag. The desulfurization rate of furnace-cooled slag reaches 72.28%, which is 4.34, 1.75 and 1.15 times than that of water-cooled slag, air-cooled slag and crucible-cooled slag, respectively. The optimal rate of desulfurization is 80.0%.