Algunos aspectos cinéticos de las reacciones de sólidos con cloro

The 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 °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.Este trabajo describe detalladas investigaciones cinéticas en algunas reacciones seleccionadas de cloro-sólido a través de medidas termogravimétricas. Los sólidos estudiados en este artículo incluyen óxidos químicos puros y sulfuros, así como sus materiales naturales de soporte. Los agentes de cloración empleados son mezclas de gases de Cl2+N2 (cloración), Cl2+O2 (oxicloración) y Cl2+CO (carbocloración). Los resultados se presentan como efecto de varios parámetros en el porcentaje de reacción de estos sólidos con los agentes de cloración. Se ha observado que la reactividad de estos sólidos a través de diferentes agentes de cloración varía ampliamente. Los sulfuros se pudieron clorar a temperatura ambiente mientras que la carbocloración del óxido de cromo (III) sólo fue posible por encima de los 500 °C. La variación del porcentaje de cloración de estos materiales complejos con respecto a la velocidad del gas, composición y temperatura permitió arrojar alguna luz en los posibles mecanismos de reacción y estequiometrías. Los resultados obtenidos se han usado para la eliminación selectiva del hierro de concentrados de cromo, extracción de metales valiosos de materiales sulfhídricos, purificación de muestras de MgO, etc.Peer reviewe

The recycling of bayer electrofilter fines for diverese applications

3 pages, 1 figure, 1 table.-- En: 1st Spanish National Conference on Advances in Materials Recycling and Eco – Energy Madrid, 12-13 November 2009.-- Editors: F. A. López, F. Puertas, F. J. Alguacil and A. Guerrero.Aluminum is the second most used metal after iron due to its singular properties that makes its alloys useful in many applications. Despite of its great importance, the obtaining processes (Bayer_Hall-Heroult tandem) produce an important environmental impact. Generated waste and pollutants should be minimized and treated. The laboratory of Metallurgy of the Escuela de Minas de Oviedo is investigating the uses of industry wastes from alumina/aluminum industry since over 30 years. This paper presents one of the research lines followed for the recycling of electrostatic filter fines from alumina calcination furnace to produce industrial quality aluminum sulfate, alums and abrasives.Peer reviewe

Development of an Ultra-Low Carbon MgO Refractory Doped with α-Al2O3 Nanoparticles for the Steelmaking Industry: A Microstructural and Thermo-Mechanical Study

The effect of α-Al2O3 nanoparticles (up to 5 wt.%) on the physical, mechanical, and thermal properties, as well as on the microstructural evolution of a dense magnesia refractory is studied. Sintering temperatures at 1300, 1500, and 1600 °C are used. The physical properties of interest were bulk density and apparent porosity, which were evaluated by the Archimedes method. Thermal properties were examined by differential scanning calorimetry. The mechanical behavior was studied by cold crushing strength and microhardness tests. Finally, the microstructure and mineralogical qualitative characteristics were studied by scanning electron microscopy and X-ray diffraction, respectively. Increasing the sintering temperature resulted in improved density and reduced apparent porosity. However, as the α-Al2O3 nanoparticle content increased, the density and microhardness decreased. Microstructural observations showed that the presence of α-Al2O3 nanoparticles in the magnesia matrix induced the magnesium-aluminate spinel formation (MgAl2O4), which improved the mechanical resistance most significantly at 1500 °C

Caracterización y propiedades de las bentonitas de Amotape (Región Grau-Perú)

Las bentonitas son uno de los recursos minerales no metálicos más abundantes en la Región Grau (Perú). En el presente trabajo se evalúan en forma sistemática las características físico-químicas y mineralógicas del mineral procedente de cinco yacimientos de la zona de Amotape, cuyas reservas estimadas en una primera evaluación ascienden a L7 millones de TM. Los resultados de los análisis químicos y mineralógicos, nos determinan que las bentonitas son del tipoWyoming. Las posibles aplicaciones pueden concretarse en la preparación de lodos de perforación, arenas de fundición y peletización en menas de Hierro.Bentonitas are one of the non-metallic mineral resources more abundant in Grau Region (Peru). The physicochemical and mineralogical characteristics of ore from fíve deposits in the Amotape Zone are systematically evaluated in the present paper. Ore reserve are estimated in 1.7 millón tonnes. By chemical and mineralogical analyses the bentonites can be assimulaated to Wyoming type. Possible apptications for these bentonites may be the preparation of drilling muds, foundry sands and iron ore pelletising.Peer reviewe

Yariación de las propiedades físicas del óxido de cinc con la temperatura

Variación de las propiedades físicas del óxido de cinc obtenidos por reacción homogénea en fase gaseosa del cinc vapor y el oxígeno. Se estudia igualmente la variación de las características superficiales de los polvos de ZnO con la temperatura de calcinación en atmósfera de aire. Se pone de manifiesto el escaso crédito que tienen algunas propiedades físicas: tamaño de partícula, diámetro de poro y área superficial, si se pretende significar el valor absoluto de las mismas dadas las especiales características que intervienen en la fabricación de los polvos de ZnO.Los autores quieren hacer patente su público agradecimiento a la Fundación para el Fomento en Asturias de la Investigación Científica Aplicada y la Tecnología (FICYT) y a la Asturiana de Cinc S. A. (AZSA) por el apoyo técnico y financiero realizado durante el desarrollo del Proyecto de Investigación «Caracterización de los polvos de óxido de cinc», así como a todas aquellas personas que han participado en la elaboración del presente trabajo.Peer reviewe

Arsenic in the cooper´s minerals: An option from the pirometalurgy

En: 1st Spanish National Conference on Advances in Materials Recycling and Eco – Energy Madrid, 12-13 November 2009.-- Editors: F. A. López, F. Puertas, F. J. Alguacil and A. Guerrero.-- 3 pages, 3 figures.The purpose of this paper presented at RECIMAT-09 is to address, briefly and as clearly as possible, expectations which may have arisen from the basic and applied research regarding the increasing problem of pollution caused by arsenic derived from copper metallurgy. In addition to the metallurgical problem which has not been resolved on an industrial scale, there are difficulties with the environment, with energy variables (both exothermic and endothermic reactions) and materials or by-products related to nanoscience and nanotechnology. This type of product may originate from the emergence of new solid phases due to condensation vapour. Finally, since large amounts of high quality AS2O3 metal are being produced naturally through this process, this would be a good time to look at the situation as a real opportunity rather than a problem that must be avoided. We need think only about what it would mean to lower costs and thus prices in the electrical industry - electronic: semiconductor and photovoltaic solar energy, mass and the economic feasibility of the chalcogens (chemical combinations between elements of the III and VI columns in the Periodic Chart) [1].The authors of this work wish to thank the Ministry of Education and Science in Spain (MEC): MAT2003-00502, the Ministry of Foreign Affairs and Cooperation (MAEC): MAEC-AECID-B/1629/04; B/2884/05; B/5814/06, B/7648/07.Peer reviewe