Characterization of Galvanizing Flue Dust and Recycling Possibilities

Abstract

Waste generation is a part of every technological process, including galvanizing. The presented paper deals with the characterization of flue dust generated in the process of hot-dip galvanizing, and proposes possible methods for zinc recycling. The flue dust is released into the atmosphere as a white fume above the zinc bath, which is caused by the decomposition of ammonium chloride and zinc chloride present in the flux. This dust is classified as hazardous waste and is a material with a particle size below 90 µm. In addition to zinc and iron compounds, it contains water vapor and oils. The presented elemental, phase, and other characteristic methods of flue dust are important for the subsequent selection of a suitable method for processing the material. At present, this waste is not processed separately due to its low production, which is approximately 0.3 kg per 1 tonne of galvanized steel. The proposed hydrometallurgical recycling method enables the processing of flue dust on a small scale and enables the recovery of high-purity zinc in the form of metallic zinc or zinc oxide.

Utilization of Galvanizing Flue Dust Residue: A Sustainable Approach towards Complete Material Recycling

“…The fumes are largely composed of ammonium chloride, which decomposes according to Reaction (1) into ammonia and hydrochloric acid, which is very reactive and forms chloride compounds with other metals. The unreacted ammonia and acid are cooled over the bath to form solid NH 4 Cl, which is part of the white fumes [19].…”

“…30%), chlorine (approx. 10%), ammonia, Fe, and other constituents such as Pb, Cu, Al, Sn, Mg, Ca, and Si [19,[23][24][25][26][27]. Due to its higher solubility and content of elements, it is categorized as hazardous waste (K061) according to environmental protection agencies [28,29], which was also confirmed by leachability test [19].…”

“…To utilize the material potential of GFD and to prevent landfilling, this type of waste can be processed hydrometallurgically or pyrometallurgically together with zinc ash, as this waste has a similar chemical composition [23][24][25]. A detailed characterization of GFD was carried out in a previous article [19]. The treatment of GFD is currently the subject of only a small number of scientific studies.…”