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International audience; Recycling of steel in electric arc furnaces generates a flue dust known as electric arc furnace dust (EAFD). EAFD contain appreciable amount of Fe, Zn, and Pb. It is also toxic due to the heavy metal content and fine particle size. Landfilling or waste disposal of EAFD is banned in many industrialized countries. Processing of EAFDs for recovery of valuable metals such as Zn and Pb could be beneficial to both resource and environmental conservation. This paper presents the lab scale results of an innovative approach of EAFD treatment method for selective recovery of Zn and Pb and producing a residue suitable for recycling in the iron and steel industry. Chlorination of different oxide constituents of EAFD such as ZnFe2O4 and Fe2O3, in their pure form, was studied between 600 - 1050 oC. The results suggest that, oxygen partial pressure has a significant effect on retarding the rate of chlorination/volatilization of iron. The results were extrapolated for treatment of EAFD. It was observed that, more than 99 % Zn and 97 % Pb could be recovered as volatile chlorides (in the condensates) at 800 oC, without having any iron impurity. The chlorination residue was found to contain 2.5 times more iron than the original EAFD. The iron present in the residue is mostly hematite, which could facilitate their recycling back in the iron and steel industry.

International audience; This study deals with the reduction of Fe3O4 by H2 in the temperature range of 210–950 °C. Two samples of Fe3O4 produced at 600 and 1200 °C, designated as Fe3O4(600) and Fe3O4(1200), have been used as starting material.Reduction of Fe3O4(600) by H2 is characterized by an apparent activation energy ‘Ea’ of 200, 71 and 44 kJ/mol at T < 250 °C, 250 °C < T < 390 °C and T > 390 °C, respectively. The important change of Ea at 250 °C could be attributed to the removal of hydroxyl group and/or point defects of magnetite. This is confirmed during the reduction of Fe3O4(1200). While transition at T ≈ 390 °C is probably due to sintering of the reaction products as revealed by SEM.In situ X-rays diffraction reduction experiments confirm the formation of stoichiometric FeO between 390 and 570 °C. At higher temperatures, non-stoichiometric wüstite is the intermediate product of the reduction of Fe3O4 to Fe.The physical and chemical modifications of the reduction products at about 400 °C, had been confirmed by the reduction of Fe3O4(600) by CO and that of Fe3O4(1200) by H2. A minimum reaction rate had been observed during the reduction of Fe3O4(1200) at about 760 °C. Mathematical modeling of experimental data suggests that the reaction rate is controlled by diffusion and SEM observations confirm the sintering of the reaction products.Finally, one may underline that the rate of reduction of Fe3O4 with H2 is systematically higher than that obtained by CO in the explored temperature range.

International audience; his study deals with the reduction of Fe2O3 by H2 in the temperature range of 220–680 °C. It aims to examine the rate controlling processes of Fe2O3 reduction by H2 in the widest and lowest possible temperature range. This is to be related with efforts to decrease the emission of CO2 in the atmosphere thus decreasing its green house effect.Reduction of hematite to magnetite with H2 is characterized by an apparent activation energy ‘Ea’ of 76 kJ/mol. Ea of the reduction of magnetite to iron is 88 and 39 kJ/mol for temperatures lower and higher than 420 °C, respectively. Mathematical modeling of experimental data suggests that the reaction rate is controlled by two- and three-dimensional growth of nuclei and by phase boundary reaction at temperatures lower and higher than 420 °C, respectively.Morphological study confirms the formation of compact iron layer generated during the reduction of Fe2O3 by H2 at temperatures higher than 420 °C. It also shows the absence of such layer in case of using CO. It seems that the annealing of magnetite's defects around 420 °C is responsible for the decrease of Ea.The rate of reduction of iron oxide with hydrogen is systematically higher than that obtained by CO.

International audience

International audience; Electric 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.

International audience

Procédé pour la synthèse des ferrates de métaux alcalins ou alcalino-terreux par la voie solide, caractérisé en ce qu'il consiste à faire réagir: un sel de fer, un hydroxyde des métaux alcalins ou alcalino-terreux et du chlore gazeux. L'invention a également pour objet les ferrates ainsi obtenus.

International audience; Jarosite contains up to 15 % of heavy metal compounds 'HMC', The current waste disposal methods will not be allowed in the near future due to new environmental regulations and pollution risks. For these reasons, thermal treatments of raw or decomposed jarosite, in controlled atmospheres, were investigated. The aim of these treatments is to decontaminate the jarosite and/ or to recover the HMC for recycling,According to physico-chemical characteristics of the samples, the thermal treatments in controlled atmospheres N2, CO+N2 and Cl2+air lead to the extraction rate that vary from 93 to 98 %, Heavy metal compounds were separated by cooling the gaseous phase. The treatments' residue was almost free from HMC. Between 700 degrees C and 800 degrees C, the chlorinating treatment was successful of eliminating more than 97 % of HMC contained in four different samples.

International audience; Annual production of European industrial wastes is about one billion tons. On the other hand, intensive farming and important urban centers generate large quantities of liquid manure or sanitary organic wastes. These wastes are a threat for the soil and water resources. The cost of their individual waste disposal or treatment decreases the competitiveness of enterprises and limits the development of rural areas. Coprocessing of these wastes is possible using the VarTech® reactor. The operating conditions of this reactor are about 250 to 300°C and 120 to 150 atmospheres. These conditions allow the decomposition of the organic wastes and the reduction of solid industrial ones thus eliminating both with a reasonable economic cost. The coprocessing of the jarosite and these organic wastes was successfully tested. This new approach can be extended to a wide variety of industrial solid wastes and organic residues

International audience; One of the major sources of the SOX emissions is the metallurgical processing of metal sulfides of Cu, Ni, Pb, Zn, etc. Although new technologies for metal sulfide smelting decrease these emissions, the generated quantity of sulfur oxides is considered as a serious threat to environment. Moreover, these emissions may be considered as an economic loss of the marketable sulfur. On the other hand, conversion of sulfur oxides to H2SO4 requires its consumption on the production sites as the cost of its transportation and stocking are important. Besides, the current state of the sulfuric acid market and the new regulations make the conversion of SOX to sulfuric acid less attractive. This paper deals with the low temperature treatment of complex sulfide ores 'CSO' or concentrates 'CSC' under neutral, reducing and chlorinating atmospheres or their combination. Treatment of CSC with nitrogen, at temperatures lower than 1000°C, allows the decomposition of the pyritic matrix to pyrrhotite and the volatilization of sulfur and As, Cd, Bi, Hg, Ge, Pb, etc., compounds. Using the same reactor, a reducing atmosphere will lead to the reduction of sphalerite to zinc and to a solid containing Cu°, Fe° and silicoaluminates. Selective dissolution of copper may be done by a hydrometallurgical process. Generated hydrogen sulfide could react with pyrrhotite to form pyrite and hydrogen. A flow - sheet of the suggested process is proposed. Complete chlorination of chalcopyrite concentrate was possible above 300°C. Iron and sulfur chlorides were fully volatilized and recovered by selective successive cooling of the gas phase. The chlorination residue is composed of valuable metals' chlorides. However, such process generates hazardous sulfur chlorides 'SXCly'. A part of sulfur chlorides such as SCl2 can be recycled as a chlorinating agent of metal sulfides. On the other hand, SXCly was either hydrolyzed, leading to the recovery of more than 90 pct of elemental sulfur or reduced by hydrogen, at temperatures lower than 600°C allowing the recovery of up to 90 pct of elemental sulfur. A flow sheet for the chlorination of metal sulfides and the treatment of sulfur chlorides is suggested.

International audience; About forty percent of the SOx emissions are generated during the processing of metal sulfides of Cu, Ph, Zn, Ni, etc. Although new technologies for metal sulfide's smelting allow the production of H2SO4 with a reasonable cost and decrease the emissions of sulfur oxides, the generated quantity of SOx is considered as a serious threat to environment.This paper suggests alternatives for low temperature processing of complex sulfide ores or concentrates 'CSO or CSC' under neutral, reducing and chlorinating atmospheres or their combination.At T > 400 degrees C, The neutral and reducing treatments allow the decomposition of pyrite and the partial recovery of sulfur as S degrees and H2S, At 300 degrees C, the chlorinating treatment of CSC is fast, exothermic and allows the separation of FeCl3 from the valuable elements' chlorides. It also generates SyClx that can be either reduced by H2 or hydrolyzed in presence of sodium sulfide. The recovery rate of elemental sulfur with respect to the sulfur input exceeds 90 %.

Characterization of industrial incinerating wastes have been conducted by Thermogravimetric Analysis (TGA), Scanning Electron Microprobe (SEMP), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). During the treatment of incinerating residues with free temperature increase (20-1.000 °C) in air, some weight losses determinations have been observed, indicating an incompleted incineration. XRD characterization reveáis the presence of poorly crystallized phases in these slags. Data from SEMP were statistically treated with the purpose to determine the pseudostructure of these solids. This allows estimation of the possible association of elements in the amorphous solid, and, consequently, to forsee their adequated treatment. La caracterización de los residuos de incineración industriales se ha hecho por análisis termogravimétrico (ATG), microsonda electrónica (MSE), difracción de rayos X (DRX) y microscopio electrónico de barrido (MEB). Durante el tratamiento de los residuos de incineración con subida libre de temperatura (20-1.000 °C) en atmósfera de aire, se han observado diversos valores de pérdida de peso, que testimonian una incineración incompleta. La DRX revela la presencia de fases mal cristalizadas en estas escorias. Los datos de la MSE se han tratado estadísticamente con el fin de determinar la "pseudo-estructura" de estos sólidos. Todo ello permite hacer una estimación de la posible proximidad de los elementos en el sólido amorfo y, en consecuencia, prever el tratamiento necesario de estos sólidos.

International audience; Characterization of industrial incinerating wastes have been conducted by Thermogravimetric Analysis (TGA), Scanning Electron Microprobe (SEMP), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). During the treatment of incinerating residues with free temperature increase (20-1.000 °C) in air, some weight losses determinations have been observed, indicating an incompleted incineration. XRD characterization reveals the presence of poorly crystallized phases in these slags. Data from SEMP were statistically treated with the purpose to determine the pseudo-structure of these solids. This allows estimation of the possible association of elements in the amorphous solid, and, consequently, to forsee their adequated treatment.

International audience; The chlorination behaviors of two chalcopyrite concentrates and their pure constituents in Cl2+N2 were investigated by thermogravimetric analysis (TGA) in nonisothermal conditions up to 1000 °C. The effect of temperature on the reaction of chlorine with both concentrates was studied between 170 °C and 300 °C under isothermal conditions. The effects of gas flow rate, chlorine content of the gas mixture, and reaction time on the reaction rate were also investigated. The reaction products were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results showed that the kinetics of chlorination of chalcopyrite concentrates generating chlorides of Cu, Pb, Zn, Fe, and S was rapid at about 300 °C. The iron and sulfur chlorides were volatilized, leading to a residue containing valuable metal chlorides.

International audience; Hydrated ferrous sulfate is a by-product of titanium and surface treatment industries. The majority of this product has to be disposed as a waste. Disposal is a significant extra cost for these industries. Recently, the ferrous sulfate partially dehydrated was successfully used for the synthesis of a new superoxidant material containing iron in hexavalent state (Fe-VI).The kinetics of dehydration of FeSO4. 7H2O under neutral, oxidizing and chlorinating atmospheres were studied by thermogravimetric and differential scanning calorimetry analysis. The obtained products were analyzed by X-ray diffraction and Mossbauer spectroscopy. The effects of temperature, gas velocity, type of sulfate, etc, on the dehydration rate were defined.

International audience; Extraction of basic metals from sulfides by conventional pyrometallurgical processing leads to the emission of SO2. To avoid this inconvenient, low temperature selective chlorination of sulfide concentrates could be an alternative. However, such process generates hazardous chlorides SxCly. A part of sulfur chlorides such as SCl2 can be recycled as a chlorinating agent of metal sulfides. Hydrolysis of sulfur chlorides, using a solution containing Na2S.9H2O, led to the recovery of more than 90 pct of elemental sulfur. Reduction of SxCly by hydrogen was investigated between 300 °C and 800 °C. About 70 and 90 pct of elemental sulfur were recovered from SCl2 and S2Cl2, respectively. A flow sheet for the chlorination of metal sulfides and the treatment of sulfur chlorides was suggested.