Phase Change Cooling and Crystallization Characteristics of Blast Furnace Slags with Various MgO/Al₂O₃ Ratios

Abstract

The chemical composition of the blast furnace (BF) slag is an intrinsic factor of crystallization characteristics. Therefore, a good understanding of the effects of the main components of BF slag on the coupling relationship between the BF slag phase change cooling and crystallization characteristics is essential and crucial to achieving the simultaneous collection of high-performance glassy slag and high-temperature air during the dry heat recovery process. In this paper, differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and scanning electron microscopy (SEM) are adopted to obtain the physicochemical properties, crystal phase content, crystal phase type, and morphology of four synthetic BF slags with various MgO/Al 2 O 3 ratios. Moreover, the temperature−time curve inside the slag during the phase change cooling process is used to reflect the crystallization temperature region, crystal phase growth time, and growth mode. The results indicate that the primary crystal phase transforms from merwinite to akermanite as the MgO/Al 2 O 3 ratio decreases from 1.5 to 1.0, which results in a significant variation in the crystal phase latent heat, crystallization onset and ending temperatures, crystal phase content, and growth rate. Moreover, the decrease in the MgO/Al 2 O 3 ratio and the transformation of the crystal type give rise to the decline in the critical cooling rate and the increase in the critical supercooling degree. Furthermore, with a decrease in the average cooling rate, the average growth rate of the crystal phase presents a peak value.

Effect of Minor Oxide and Residual Carbon on Coal Ash Crystallization Behavior and Slag Properties during Coal Gasification: Critical Literature Review and Thermodynamic Simulation

“…Each component’s influence on the slag’s crystallization behavior has been investigated. However, it has to be pointed out that the effect of other components is unavoidable when one component is changed . Therefore, it is impossible to isolate only one component’s effect.…”

“…However, it has to be pointed out that the effect of other components is unavoidable when one component is changed. 37 Therefore, it is impossible to isolate only one component’s effect. So far, the investigations have primarily focused on the effect of the major component on the crystallization behavior and the viscosity of the molten slag.…”

Synthetic Slag Production Method Based on a Solid Waste Mix Vitrification for the Manufacturing of Slag-Cement

“…Blast furnace slag is one of the most abundant solid by-products of the iron-making process, with between 300 and 350 kg of BFS per ton of pig iron produced [8]. Blast furnace slag from the iron making industry is mainly composed of CaO, SiO 2 , and Al 2 O 3 [9].…”