Dust formation in electric arc furnace: birth of the particles

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4. Interpretation

In EAF, 60 % of dust come from projections of liquid metal and slag (see part I). These projections from the bath can be attributed to the CO-bubble burst. The mechanisms involved in the formation of those projections in EAF can be slightly different from those met in our experiment, particularly owing to the presence of a slag, either foaming or not. Nevertheless, the results we have obtained give useful information for the understanding and the quantification of dust formation in EAF.

Jet drops come from the disintegration of the upward jet created after the removal of the bubble cap. Their number increases when the bubble size decreases, and their size represents 12 to 18 % of the parent bubble size. The size of CO-bubbles formed in EAF remains little known. However, analyses of foaming slag samples and numerical calculations indicate that their sizes are probably between 2 and 20 mm [8]. According to our results, such bubbles are expected to produce jet drops whose sizes vary from 0.2 mm to almost 4 mm, which is much larger than most of the particles found in EAF dust samples. As observed in our laboratory furnace, jet drops are not exhausted by the fume extraction system and are likely to fall back into the steel bath. Jet drops can thus hardly contribute to dust formation from bubble burst in EAF.

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