title: Characteristics and settling behaviour of particles from blast furnace flue gas washing.
abstract: A lot of particles from iron-making are removed with blast furnace off-gas and routed to the gas cleaning system. As water is used for cleaning the gas, the produced wash water contains a large amount of particles such as valuable Fe and C. However, the presence of zinc prevents recycling. In addition, the high amount of calcium results in uncontrolled scaling. Therefore, the properties of the wash water from scrubber and sludge, from the Finnish metal industry (SSAB Raahe), were evaluated in this study. Size fractionation of wash water revealed that Fe, Zn, Al, Mn, V, Cr and Cd appeared mainly in the larger fractions (>1.2 μm) and Na, Mg, Si, Ni, K, Cu and As appeared mainly in the smaller fractions (<1.2 μm) or in dissolved form. Calcium was found both in the larger fractions and dissolved (∼60 mg/L). Most of the particles in wash water were included in the 1.2-10 μm particle size and were settled effectively. However, a clear benefit was observed when using a chemical to enhance particle settling. In comparison to 2.5 h of settling without chemical, the turbidity was further decreased by about 94%, iron 85% and zinc 50%. Coagulation-flocculation experiments indicated that both low and high molecular weight cationic polymers could provide excellent purification results in terms of turbidity. Calcium should be removed by other methods. The particles in sludge were mostly in the 2-4 μm or 10-20 μm fractions. Further sludge settling resulted in high solids removal.
authors.affiliation: University of Oulu, Chemical Process Engineering, P.O. Box 4300, FIN-90014 University of Oulu, Oulu, Finland. Electronic address: jenni.kiventera@oulu.fi.
authors.forename: Jenni
authors.initials: J
authors.lastname: Kiventerä
authors.affiliation: University of Oulu, Chemical Process Engineering, P.O. Box 4300, FIN-90014 University of Oulu, Oulu, Finland. Electronic address: tiina.leiviska@oulu.fi.
authors.forename: Tiina
authors.initials: T
authors.lastname: Leiviskä
authors.affiliation: SSAB, P.O. Box 93, FI-92101 Raahe, Finland. Electronic address: kirsi.keski-ruismaki@ssab.com.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Keski-Ruismäki
authors.affiliation: University of Oulu, Chemical Process Engineering, P.O. Box 4300, FIN-90014 University of Oulu, Oulu, Finland. Electronic address: juha.tanskanen@oulu.fi.
authors.forename: Juha
authors.initials: J
authors.lastname: Tanskanen
mesh_terms: D005387:Finland; D005427:Flocculation; D005740:Gases; D007501:Iron / Q000032:analysis; D008669:Metallurgy / Q000379:methods*; D008670:Metals / Q000032:analysis; D010316:Particle Size; D012722:Sewage / Q000737:chemistry; D062065:Wastewater / Q000032:analysis* / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis; D015032:Zinc / Q000032:analysis
chemical_list: D005740:Gases; D007501:Iron; D008670:Metals; D012722:Sewage; D062065:Wastewater; D014874:Water Pollutants, Chemical; D015032:Zinc
keywords: Flocculation; Scrubber wash water; Settling; Size fractionation; Sludge