Oxidative Leaching of Zinc and Alkalis from Iron Blast Furnace Sludge

• Published in: Metals (Basel ) Vol. 9; no. 9; p. 1015
• Main Authors: Soria-Aguilar, Ma. de Jesus, Davila-Pulido, Gloria Ivone, Carrillo-Pedroza, Francisco Raul, Gonzalez-Ibarra, Adrian Amilcare, Picazo-Rodriguez, Nallely, Lopez-Saucedo, Felipe de Jesus, Ramos-Cano, Juan
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 2019
• Subjects: Alkalies; Alkaline cleaning; alkalis; Alkalizing; Ammonium chloride; Aqueous solutions; aqueous treatment; Blast cleaning; Blast furnace chemistry; Blast furnace gas; Carbon; Chemical reactions; Chloride; Design of experiments; Dust; Ferric ions; Gases; Iron; Iron and steel making; iron and steelmaking wastes; Leaching; Oxidation; Oxidizing agents; Ozone; Potassium oxides; Recycling; Sludge; Sulfuric acid; zinc; Zinc compounds; Zinc ferrites; Zinc oxides; United States > US
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met9091015

The sludge from a wet-off gas cleaning system of the iron blast furnace (BF) contains significant amounts of iron; however, they cannot be recycled due to their high content of zinc and alkalis. These compounds are detrimental to the optimal performance of iron and steelmaking furnaces. In this work, a comparative laboratory study to reduce zinc and alkali contained in the blast furnace sludge (BFS) is presented. The effect of leaching parameters such as oxidant (i.e., ferric ion, oxygen or ozone), aqueous solution media (i.e., 0.2 M NH4Cl, 0.2 M HCl and 0.1 M H2SO4) and temperature (i.e., 27 and 80 °C) on Zn and alkalis (Na2O and K2O) removal were studied by applying an experimental design. The results obtained show that Zn and K2O removal of 85% and 75% were achieved under the following conditions: Ozone as an oxidant agent and 0.1 M H2SO4 as an aqueous medium, temperature had no significant effect. The results are supported by thermodynamic diagrams and the possible chemical reactions are mentioned. Although the results also indicate that leaching under the above conditions dissolves up to 9% of iron, this loss is much less than leaching without the oxidizing conditions generated by the ozone. The BFS obtained from this treatment could be recirculated to the iron or steelmaking processes to recover iron values.