Dissolution Behavior and Phase Evolution During Aluminum Oxide Dissolution in BOF Slag
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INTRODUCTION
THE annual production of steelmaking slags adds up to a huge quantity. Nearly 32.4 million tonnes and 326 million tonnes of steel slag were produced in EU and globally[1,2] respectively, during the year 2016. Basic Oxygen Furnace (BOF) slag makes up for nearly half of the steel slag produced in Europe.[1] Therefore, the valorization of BOF slag is essential. The utilization of BOF slag for high added value products depends on the composition and mineralogy of the solidified slag. Hot stage slag engineering is an effective way to change the properties of the slag in the liquid state in order to control the properties of the solidified slag without affecting the quality of the steel.[3,4] One of the preferred ways is to undertake this step after slag has already been transferred in the slag pot during the converter process. The hot stage engineering can involve processes such as the addition of slag modifiers such as Al2O3 or SiO2 to the slag. These
GAURAV TRIPATHI, ANNELIES MALFLIET, BART BLANPAIN, and MUXING GUO are with the Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44 Bus 2450, Leuven 3001, Belgium. Contact e-mail: [email protected] Manuscript submitted December 5, 2018. Article published online May 7, 2019. 1782—VOLUME 50B, AUGUST 2019
additions are done in order to achieve a desired mineralogy and for the stabilization of specific minerals in the slag. The presence of free CaO or MgO can lead to volume instability of the slag, as these phases tend to undergo expansive hydration.[5] The modifiers added in the slag, after dissolution, can react with these unstable phases, thereby stabilizing the solidified slag. Hot stage engineering can also involve introducing additives to facilitate the faster dissolution of the added slag modifiers and the separation of the metallic phases from the slag. The dissolution rate of solids into fluids has been studied from many perspectives. In the fields of materials and chemical engineering, dissolution has been studied related to leaching of metal ores, absorption, or the dissolution of oxide inclusions for clean steel production, refractory corrosion, etc.[6–15] The dissolution of solid oxides into molten slags has been studied extensively. The rotating finger setup has been employed to study the kinetics of dissolution into a variety of slags.[6–8,16–21] Nakashima et al. studied the dissolution of Al2O3 in Blast Furnace (BF) and soda slag using the rotating finger method in the range of 1400 C to 1600 C.[6] Yu et al. used a similar setup to study the Al2O3 dissolution in mold fluxes.[7] Amini et al.[8] studied the dissolution of CaO in synthetic silicate slags with the additions of composition modifiers like SiO2,
METALLURGICAL AND MATERIALS TRANSACTIONS B
FexO, and CaF2. In some more recent studies,[22–24] the effects of slag modifiers like Ca2F and Na2O on Al2O3 dissolution have been studied. Confocal Scanning Laser Microscopy (CSLM) has also been used as a powerful tool for in-situ observation of the dissolution process in a variety
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