Effect of preroasting on the preoxidation of vanadium in high-carbon stone coal

The effect of preroasting on the preoxidation and sodium roasting of vanadium in high-carbon stone coal was investigated through the study of the change of the phase and valence distribution of vanadium. The result indicated that the ore should be subject to high-temperature preroasting treatment of approximately 800 degrees C for a certain time before sodium roasting to achieve a higher oxidation ratio of vanadium. During preroasting at 600 degrees C, the oxidation of the reducing component completed substantially, and the removal of hydroxyl in mica occurred. After preroasting at 800 degrees C, the reaction of hydroxyl removal of mica completed, and vanadium oxidation was not hindered. Preroasting at temperatures below 800 degrees C could only oxidize the V4+ of mica surface and could not oxidize the V3+ presented in the mica lattice, resulting in a small amount of V5+ appearing in the preroasted slag. The stage of carbon removal was controlled by chemical reaction and was mainly affected by temperature. When the preroasting temperature was reduced to below 600 degrees C, the oxidation time of carbon was found to be prolonged. The temperature was not sufficient to expand the spacing of the mica laminated structure, making it difficult to create favorable conditions for the oxidation of vanadium during the sodium roasting process.