Study of a titaniferous magnetite chlorination at high temperature

The chlorination of a titaniferous magnetite with low content in Ti and Fe has been studied between 1273 and 2273 K. Most of the hercynite and ilmenite initially present are decomposed during the gas-solid phase reaction between 1273 and 1823 K. Considerable ilmenite decomposition and FeCl₃evolution already occur at 1273 K, leaving a residue consisting of TiO₂, Fe₂O₃-TiO₂ (pseudobrookite), and about 50 pct of each of the Cr and Mg initially present. X-ray diffractograms shown the formation of Al₂TiO₅ which contributes to the stabilization of TiO₂ up to 1773 K, above which temperature significant decomposition of Al₂TiO₅ is observed. At the melting point of the titaniferous magnetite sample (around 1823 K), the presence of both solid and liquid phases result in a considerable decrease in the chlorination rate. In this respect, heating the sample under helium up to the melting point, so that liquid and solid phases are obtained at equilibrium, yields two structures replacing the magnetite present just prior to melting. One of these structures is of the spinel Fe₂TiO₄ type, while the other is a combination of the spinel types MgAl₂O₄, FeAl₂O₄, and MgCr₂O₄. When the sample is chlorinated, a high proportion of the initial Cr (90 pct) and Ti (80 pct) are found in the chlorination residue at the early stages of fusion, together with 13 pct of the initial Fe. Chlorination of the liquid phase between 1823 and 2273 K shows a steady decrease of Ti and Cr in the chlorination residue, associated with an increase of Fe content.