Basic Oxygen Steelmaking Slag: Formation, Reaction, and Energy and Material Recovery

Basic oxygen steelmaking (BOS) slag, a product of hot metal element (e.g., Si, Mn, Fe, P) oxidation and flux (e.g. lime, dolomite) dissolution, plays a critical role in the production of high-quality crude steel, although its behavior inside the BOS vessel (formation and reaction with metal droplets and gas) is still not clear and its recycling has always been challenging. Herein, examples of BOS-slag-related research conducted by the present authors are introduced, in addition to a critical review of relevant research reported in the literature. This includes four important topics: 1) slag formation, i.e., dissolution of lime in the BOS slag; 2) in situ observation of high-temperature behavior of BOS slags; 3) transient phenomena in BOS slags due to metal droplet–slag–gas reactions; and 4) energy and material recovery from molten BOS slags. This article aims to provide state-of-the-art understanding and new research ideas on these research topics. An emphasis is placed on methods that seek to in situ probe the evolution of the slag and to document its physical and chemical changes.