Abstract
The carbochlorination kinetics of pure Nb 2 O 5 and Ta 2 O 5 by gas mixture (C1 2 + CO + N 2 ) between 380 and 1,000 °C is studied. A calculation of the standard free energy of the carbochlorination reactions is made. A diagram of the phases stability is drawn. The influence of the gas flow, temperature and the pardal pressure of Cl 2 and CO at temperatures below 650 °C on the reaction rate is studied. The apparent activation energy is approximately 75 and 110 kJ/mol for Nb 2 Os and Ta 2 O 5 , respectively. At temperatures above 650°C the Arrhenius diagram presents an anomaly which may be attributed to the decomposition of the COCl 2 formed in situ. The apparent reaction order of the carbochlorination of these oxides against Cl 2 +CO is approximately 2. The carbochlorination rates of these oxides are much greater than those of chlorination by Cl 2 + N 2 . The carbochlorination kinetics of tin furnace slag leaching concentrates containing tantalum and niobium compounds are also studied and compared with the carbochlorination kinetics of the pure oxides.
Highlights
INTRODUCTIONThe tantalum and niobium metáis have applications in advanced technologies such as electronics, v ' Trabajo recibido el día 17 de febrero de 1999 y aceptado en su forma final el 8 de julio de 1999
The tantalum and niobium metáis have applications in advanced technologies such as electronics, v ' Trabajo recibido el día 17 de febrero de 1999 y aceptado en su forma final el 8 de julio de 1999.(*) University of Missouri-Rolla, School of Mines and Metallurgy
The carbochlorination kinetics of Nb205 and Ta205 have been studied by thermogravimetric analysis using a CAHN thermobalance, model C 1000, with a sensitivity of 0.01 mg
Summary
The tantalum and niobium metáis have applications in advanced technologies such as electronics, v ' Trabajo recibido el día 17 de febrero de 1999 y aceptado en su forma final el 8 de julio de 1999. (*) University of Missouri-Rolla, School of Mines and Metallurgy. 210 Fulton Hall, 65409 Rolla, MO (EE.UU.). Current methods of tantalum and niobium extraction, from minerallurgical concentrates or from tin furnace slags, are often polluting or costly (3 y 4). These reasons have led several teams to research different possibilities for recovering these elements. Complementing data from the literature (6 y 7), the aim of the study presented below has been to better understand the mechanisms susceptible to (c) Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España (by-nc) http://revistademetalurgia.revistas.csic.es controlling the carbochlorination reactions of puré Ta205 and Nb205 and in this way improve their extraction from leaching concentrates
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