Rates and mechanisms of dust generation in oxygen steelmaking

• Published in: Steel Research 2001-09, Vol.72 (9), p.324-330
• Main Authors: Gritzan, Arnd, Neuschütz, Dieter
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Iron and steel making; Metals. Metallurgy; Oxygen or pneumatic steel making; Production of metals
• ISSN: 0177-4832; 1869-344X
• DOI: 10.1002/srin.200100126

To understand the mechnisms governing dust generation in oxygen steelmaking, dust samples were taken every min during the refining process from the dust‐laden off‐gas at the horizontal duct of the 200 t BOF vessel no.3 at TKS Dortmund. The oxygen blowing rate and hence the CO formation rate remained nearly constant during the entire blow. Dust content, particle size distribution, and chemical composition of the dust were determined with special attention to top‐charging of lime, scrap and fluxes. The dust consisted of very fine droplets (< 1 μm) most of which formed agglomerates in the size range 1 to 200 μm. As the Mn:Fe ratio in the dust samples was found to be nearly equal to that in the molten metal, evaporation processes did not noticeably contribute to dust generation, which is therefore caused almost entirely by bubble bursting. Top charging always raised the dust emission rate for a short period of time without altering the dust composition. Apparently, the material added from the top enhanced heterogeneous nucleation in the slightly supersaturated liquid metal. Except for the top‐charging effect, the dust generation rate decreased steadily with blowing time by a factor of about 10. The high momentum of the oxygen jet impinging on the melt surface causes numerous splashes to be ejected which after a parabolic flight fall back into the melt. These splashes quickly dissolve oxygen which forms CO and leads to bubble bursting on the splash surfaces. With decreasing carbon content the splashes tend to form a solidified shell during their flight so that oxygen pick up and CO formation rates decrease. The refining process is gradually shifted from the splashes to the bulk melt, where CO formation again leads to bubble bursting but the slag present above the metal melt acts as a filter for the film and jet droplets so that the total dust emission decreases strongly. Geschwindigkeit und Mechanismen der Staubbildung im Blasstahlverfahren. Zum besseren Verständnis der Staubbildungsvorgänge in Blasstahlverfahren wurden am Querkamin des LD‐Konverters Nr. 3 im Werk Dortmund von TKS jede Minute Staubproben aus dem Abgas während der gesamten Blaszeit entnommen, in der die Sauerstoffblasrate und damit annähernd auch die CO‐Bildungsrate konstant waren. Staubgehalte, Korngrößenverteilungen und Zusammensetzung wurden insbesondere als Funktion des Chargierens von Kalk, Schrott und Flußmitteln von oben bestimmt. Der Staub bestand aus sehr feinen Tröpfchen (< 1 μm), die