Contribution of Mineralogical Phases on Alkaline Dissolution Behavior of Steelmaking Slag

Abstract

To suppress alkaline elution from steelmaking slag through microstructure control, in this study, several mineralogical phases identified in industrial steelmaking slag were synthesized, and their dissolution behaviors were investigated. The results indicated that in addition to free CaO and free MgO, 2CaO•SiO 2-3CaO•P 2 O 5 (C 2 S-C 3 P) is another reason for alkaline elution from steelmaking. To suppress the amount of C 2 S-C 3 P in steelmaking slag, reducing the slag basicity by the compositional modification of slag at the hot stage was considered. To determine the optimum composition, the contribution of newly formed primary crystalline phases must be clarified. Some primary crystalline phases in the CaO-SiO 2-FeO x-MgO-Al 2 O 3 system were synthesized, and their dissolution behaviors were evaluated. The results indicated that the formation of α-CaO•SiO 2 (α-CS), β-CaO•SiO 2 (β-CS), 3CaO•2SiO 2 (C 3 S 2), 2CaO•MgO•2SiO 2 (C 2 MS 2), and 3CaO•MgO•2SiO 2 (C 3 MS 2) must be restrained in slag modification. Based on the results, a slag with multiple components and low basicity was synthesized, and the suppression of alkaline elution by reduction of slag basicity and microstructure control was confirmed. Moreover, a method to predict Ca dissolution and pH change during the dissolution of slag by the combination of each crystal phase was proposed.

Kinetics of Calcium Leaching from Particulate Steelmaking Slag in Acetic Acid Solution

“…There are many studies about discussing the dissolution mechanism of Ca from steelmaking slag in iron and steel field. [15][16][17][18] Zhang et al 15) investigated the dissolution behavior from steelmaking slag into seawater and found that the more Ca of slag with large CaO/SiO 2 ratio dissolved than that with small ratio. Zhu et al 16) reported that the amount of α-CaO•SiO 2 , β -CaO•SiO 2 , 3CaO•2SiO 2 , 2CaO•MgO•2SiO 2 and 3CaO•MgO•2SiO 2 in steelmaking slag should be restrained to suppress the Ca elution.…”

“…[15][16][17][18] Zhang et al 15) investigated the dissolution behavior from steelmaking slag into seawater and found that the more Ca of slag with large CaO/SiO 2 ratio dissolved than that with small ratio. Zhu et al 16) reported that the amount of α-CaO•SiO 2 , β -CaO•SiO 2 , 3CaO•2SiO 2 , 2CaO•MgO•2SiO 2 and 3CaO•MgO•2SiO 2 in steelmaking slag should be restrained to suppress the Ca elution. In addition, several researchers carried out the kinetics analysis of Ca leaching from slag into water using kinetics models in order to clarify the leaching mechanism precisely.…”

Research of iron extraction from primary steelmaking slag

“…However, modern electric steelmaking is characterized by the production of a by-products significant number. Among them, it is possible to distinguish primary steelmaking slag (10-12% of the melting mass); secondary slag from the bucket-furnace unit (up to 2.5% of the melting mass); dust (up to 1.5% of the melting mass) [6,7]. In the Pavlodar region of the Republic of Kazakhstan, in the production of steel at the electric steelmaking enterprises of Casting LLP and KSP Steel LLP, the resulting electric steelmaking slags and dust are stored in slag heaps and are practically not used.…”

Kinetic Analysis Considering Particle Size Distribution on Ca Elution from Slags in CaO–SiO₂–MgO–Al₂O₃–Fe₂O₃ System

“…However, they did not considere the effect of particle size distribution in the rate equation. Zhu, et al 15) reported effects of mineralogical phases on alkaline dissolution from steelmaking slag. They assumed the formation of a surface layer on the particle of slag, and adopted the rate equation of diffusion control through this layer.…”