Influence of P2O5 on Dissolution Behavior of Lime in Molten Slag

• Published in: ISIJ International Vol. 57; no. 10; pp. 1710 - 1717
• Main Authors: Kakimoto, Shohei, Kiyose, Akihito, Murao, Reiko
• Format: Journal Article
• Language: English
• Published: The Iron and Steel Institute of Japan 01.01.2017
• Subjects: 2CaO·SiO2; confocal laser-scanning microscope; dephosphorization slag; dissolution; high-temperature laser microscope; hot-metal dephosphorization; lime; P2O5
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.ISIJINT-2017-094

Dissolution of lime into molten slag is an important phenomenon in hot-metal dephosphorization treatment and should be suitably promoted in order to obtain an effective refining reaction and to recycle slag as some environmental resources. A lot of research has been conducted on the phenomenon, but the influence of P2O5 on the dissolution behavior of lime has never been studied despite the presence of P2O5 in the slag obtained during actual operation.In this study, the dissolution behavior of lime in CaO–SiO2–FeO or CaO-SiO2-FeO-5.2 mass% P2O5 molten slag was investigated via a high-temperature laser microscope, an optical microscope, and a scanning electron microscope/energy dispersive spectroscopy (SEM/EDS) in order to clarify the influence of P2O5 on the dissolution behavior of lime. We conclude that the addition of P2O5 to the slag accelerates the dissolution of lime in the molten slag mainly by increasing the CaO equilibrium content in the liquid slag saturated with 2CaO·SiO2.P2O5 is a product of the dephosphorization reaction, and basically, its content is preferred to maintain low content for dephosphorization based on equilibrium theory. However, the experimental results obtained in this study clarify that the presence of P2O5 in molten slag is effective for the promotion of the dephosphorization reaction when the reaction is limited by the dissolution of lime.