Effect of CO₂ Content in Quicklime on Dissolution Rate of Quicklime in Steelmaking Slags

Abstract

The dissolution rate of lime in the molten slag is important for the efficient of steelmaking reactions. The dissolution rates of quicklime were conventionally measured by a rotating cylinder method, and they were quite lower compared with the estimated rates from actual steelmaking operations. Previously, the authors reported that the quicklime used in the actual operation had a much faster dissolution rate than completely calcined lime. During the dissolution of quicklime used in the actual operation, quicklime emits CO 2 gas twice, and the second gas formation effectively enhances the dissolution rate. Though the dissolution rates of quicklime with a CO 2 content of 0, 2, 4, and 9 mass% had been analyzed, the dissolution rates were scattered. The reason for this scattering of the data was that the CO 2 content of individual quicklime samples varied significantly within the same grade of quicklime, because the samples used in the previous study were produced by a rotary kiln process. Consequently, the dissolution rates were inconclusive, and the effect of the CO 2 content in quicklime on the dissolution rate of quicklime could not be fully clarified. In this study, the CO 2 content was controlled through the laboratory-based preparation of spherical quicklime samples and thus, the effect of the CO 2 content on the dissolution rate of quicklime in the molten slag could be precisely analyzed. Eventually, this approach allowed to propose the dissolution rate of quicklime with gas formation due to the thermal decomposition of the CaCO 3 core existing in the center of quicklime samples.

Removal of Phosphorus from High-phosphorus Iron Ore with Preliminary Reduction Treatment and Physical Concentration

“…The sample for the electrical pulse disintegration test was prepared so the P was concentrated in the C 2 S phase, not the metallic phase, as shown in a previous study. 3) The target basicity and percent Fe t O in the sample were 2.0 and 60 mass%. Under these conditions, the P-concentrated C 2 S phase, low P metallic Fe, and the low melting point oxide phase coexisted.…”

“…In a previous study, when high-P iron ore was reduced with lime and graphite at an appropriate blending ratio and temperature, most of the P was concentrated as 3CaO•P 2 O 5 (hereinafter abbreviated as C 3 P) in the 2CaO•SiO 2 (hereinafter abbreviated as C 2 S) phases, coexisting metallic Fe containing low P, and the Fe oxide-containing phases. 3) If only the P-concentrated phases can be separated from the reduction product, then the P can be reduced before the ironmaking process; consequently,…”

Management of Lime in Steel

“…Loss on ignition depicts the total weight loss that is associated with water and carbon dioxide evolutions, quantified by recording the sample weights before and after controlled heating. The soft burnt lime with about 3% LOI, produced under controlled condition, is reactive and ideal for steelmaking process, while hard burnt lime with low LOI is difficult to dissolve in the steel bath [28,29]. Higher LOI (>2%) indicates that both or either moisture and carbon dioxide content are on the higher side and undesirable in the steelmaking process.…”

Limestone Dissolution in Converter Slag: Kinetics and Influence of Decomposition Reaction

“…5 and 3, it can be noted that a greater stirring energy density is supplied by CO 2 bubbles at the stagnation stage of limestone dissolution, whereas the stirring energy density are below 2.0 W/(kg slag) during the coupling stage from 60 to 300 s. In view of the fact that limestone dissolution in converter slag proceeds mainly in the coupling and sole dissolution stages, the CO 2 bubbles generated from decomposition reaction could provide a certain enhancement of limestone dissolution, which is similar to the reports about enhancement of quicklime dissolution rate by CO 2 from residual limestone. 26,27)…”