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The carbochlorination of a chromite concentrate was studied between 500 ЊC and 1000 ЊC using boat experiments. The reaction products were analyzed by scanning electron microscopy (SEM), x-ray diffraction (XRD), and chemical analysis. The carbochlorination of a chromite concentrate at about 600 ЊC led to the partial selective elimination of iron, thus increasing the Cr/Fe ratio in the treated concentrate. Total carbochlorination of the chromite concentrates and volatilization of the reaction products was achieved at temperatures higher than 800 ЊC. The kinetics of the chromite carbochlorination was studied between 750 ЊC and 1050 ЊC using thermogravimetric analysis (TGA). The results were discussed in terms of the effects of gas flow rate, temperature, partial pressure of Cl 2 ϩ CO, and Cl 2 /CO ratio on the carbochlorination process. It was observed that the temperature effect changed significantly with the progress of the reaction. The initial stage of the carbochlorination was characterized by an apparent activation energy of about 135 and 74 kJ/mol below and above 925 ЊC, respectively, while a value of about of 195 kJ/mol was found for the remainder of the carbochlorination process.

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Chlorination and carbochlorination of tantalum and niobium low-grade concentrate (LGC) and highgrade concentrate (HGC), obtained by leaching of tin slag, were studied using Cl 2 ϩ N 2 and Cl 2 ϩ CO ϩ N 2 gas mixtures. Thermogravimetric analysis and conventional boat experiments were performed between 200 ЊC and 1000 ЊC. Chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to characterize the samples and reaction products. Chlorination of LGC led to the recovery of about 95 pct of tantalum and niobium compounds at 1000 ЊC. However, the tantalum and niobium chlorinated compounds were contaminated by chlorides of Fe, Mn, etc. For HGC, chlorination at 1000 ЊC allowed the extraction of about 84 and 65 pct of the niobium and tantalum compounds, respectively. The recovered condensates were composed of pure tantalum and niobium chlorinated compounds. The apparent activation energies E a for the chlorination of LGC and HGC, between 850 ЊC and 1000 ЊC, were 166 and 293 kJ/mole, respectively. At temperatures lower than 650 ЊC, the apparent activation energies for the LGC and HGC carbochlorination were 116 and 103 kJ/mole, respectively. Total extraction of the tantalum and niobium compounds was achieved by the carbochlorination of the LGC at 1000 ЊC. The generated tantalum and niobium chlorinated compounds were contaminated by the chlorides of Fe, Mn, Al, and Ca. The carbochlorination of the HGC at 500 ЊC allowed complete extraction and recovery of pure tantalum and niobium compounds. These results confirm the importance of obtaining an HGC from tin slag before its subsequent chlorination. The carbochlorination of such a concentrate could be an efficient process for the recovery of relatively pure tantalum and niobium chlorinated compounds at low temperatures.