Dust formation in electric arc furnace: birth of the particles

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Film drops are emitted during the disintegration of the liquid cap which covers the bubble at the surface of the bath. Their morphology and their size range are very close to those of the particles contained in EAF dust. The amount of projections produced by bubble burst in EAF varies between 0.016 and 0.028 kg m-3 [8]. These figures are close to those derived from our laboratory experiments (see table 1). Further associated with the conclusion of the jet drop size study, they show that, when a bubble bursts, it is mostly the film drops that contribute to dust formation. Our results also reveal a significant decrease of the amount of film drops resulting from bubble burst when the bubble size decreases. Moreover we brought out the existence of a critical bubble size (around 4.5 mm) under which no film drop is detected. While this phenomenon was already evidenced by Spiel [14] for air-water systems, it had never been observed in the case of liquid steel.

From these results, it appears that it should be possible to reduce dramatically the amount of dust produced in EAF by decreasing the CO-bubble sizes, ideally between 1 and 4 mm. The latter bound prevents the film drop formation and the former one avoids the emission of jet drops small enough to be carried up. Such an objective may be difficult to reach since the CO-bubble formation is a rather spontaneous process. Nevertheless, a solution could be to better control the decarburization reaction, for example by favoring nucleation at the expense of growth.

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