Étude de l'extraction des métaux de valeur contenus dans les poussières de four à arc électrique

NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Zinc recovery from EAF dust through thermal reduction

International audienceElectric arc furnace dust (EAFD) generated during the recycling of steel-scrap is classified as a hazardous waste for landfilling. This is because it contains leachable heavy metals such as zinc, lead, ... Recovery of these metals could result in both resources conservation and resolving waste disposal problems. A study of the thermal reduction of a sample of EAFD was carried out in an inert gas atmosphere using coke as a reducing agent. Preferential volatilization of zinc and lead was achieved during the reduction process at about 800 °C. More than 96 % of both zinc and lead were removed from the dust and were recovered in the condensates. The treatment residue was essentially composed of iron oxides and almost free from heavy metals

Kinetics of hematite chlorination with Cl2 and Cl2 + O2: Part I. Chlorination with Cl2

International audiencePreliminary tests of the chlorination of two iron oxides (wüstite and hematite) in various chlorinating gas mixtures were performed by thermogravimetric analysis (TGA) under non-isothermal conditions. Wüstite started to react with chlorine from about 200 °C generating ferric chloride and hematite as the final reaction products. The presence of a reducing and oxidizing agent in the chlorinating gas mixtures influenced the chlorination reactions of both iron oxides, during non-isothermal treatment, only at temperatures higher than 500 °C.The chlorination kinetics of hematite with Cl2 have been studied in details between 600 and 1025 °C under isothermal chlorination. The values of the apparent activation energy (Ea) were about 180 and 75 kJ/mol in the temperature ranges of 600–875 and 875–1025 °C, respectively. The apparent reaction order with respect to Cl2 was found to be 0.67 at 750 °C. Mathematical model fitting of the kinetics data was carried out to determine the most probable reaction mechanisms

Some kinetics aspects of chlorine-solids reactions

International audienceThe present paper describes detailed kinetics investigations on some selected chlorine-solid reactions through thermogravimetric measurements. The solids studied in this article include chemical pure oxides and sulfides as well as their natural bearing materials. The chlorinating agents employed are gaseous mixtures of Cl2+N2 (chlorination), Cl2+O2 (oxychlorination), and Cl2+CO (carbochlorination). Results are presented as effects of various parameters on the reaction rate of these solids with these chlorinating agents. It was observed that the reactivity of these solids towards different chlorinating agents varied widely. Sulfides could be chlorinated at room temperature, while carbochlorination of chromium (III) oxide was possible only above 500 degrees C. The variation of the chlorination rate of these complex materials with respect to gas velocity, composition and temperature enabled us to focus some light on the plausible reaction mechanisms and stoichiometries. The obtained results were used for selective removal of iron from chromite concentrates, extraction of valuable metals from sulfide materials, purification of MgO samples, etc