Thermodynamic Calculation And Experimental Investigation On The Reduction Of Ilmenite

The reduction of ilmenite is one of the key steps of preparation of Ti(C,N) reinforced iron-based composites by carbothermic reduction. The investigation on the thermodynamics and reaction mechanism of redution has its practical and theoretical value on the stipulation on the process conditions of Ti(C,N) reinforced iron-based composites.Thermodynamic calculation of the reduction of ilmenite under various temperatures, effects of various reductant on impurities in ilmenite and the reaction mechanism of the reduction of ilmente was calculated and investigated in present work. The reduction sequence of ilmenite was suggested and the effects of impurities on reduction were canalyzed..The results show that the reduction of FeTiO3 to TiO2 has the most strong driving force at the range of 973K~1373K, the reduction of FeTiO3 to TiO has the most strong driving force at the range of 1373K~1573K, the reduction of FeTiO3 to TiN has the most strong driving force at the range of 1573K~1773K, and that reduction of FeTiO3 to TiC has the most strong driving force at the range of 973K~1373K. The free energy changes of the reduction of FeTiO3 to TiO2 and the reduction of Ti2O3 to TiO remain positive below 1873K. Among the reactions of various titanium oxides to TiC or TiN, transformation of Ti3O5 to TiN has the most strong driving force at the range of 1573K~1773K, and formation of Ti3O5 to TiC has the most strong driving force at the range of 1773K~1873K. The thermodynamic calculation of the reduction of various oxide impurities shows that at the desired range of temperature(T<1873K), C and Si can only reduct MnO to the elemental phase; Al can reduct MnO, SiO2 and MgO to the elemental phase; Mg can reduct SiO2, MnO and Al2O3 to the elemental phase; Ca can reduct MnO, MgO, Al2O3 and SiO2 to the elemental phase. The curves in thermal analysis graphs shows that the first endotherm peak was formed by the reduction of FeTiO3 to TiO2 at the temperature of 797.1℃, the second endotherm peak was formed by the gasification of C and the reduction of TiO2 to Ti3O5 and Ti(O,C) at the temperature of 1137℃, and that the third endotherm peak was formed by the formation of Ti(C,N) from Ti(O,C) and N2 and Fe3C from Fe and C. The reduction sequence of ilmenite under the atmosphere of N2 can be concluded as FeTiO3→TiO2→Ti3O5→Ti(O,C) →Ti(C,N). Among these, the main products of 2-hour reduction at 750℃ were FeTiO3, TiO2 and C,those at 850℃ were FeTiO3, Fe, TiO2 and C, those at 1100℃ were Fe, Ti3O5, TiO2 and C, those at 1350℃ were Fe, Ti(C,O) and C, those at 1400℃ were Fe, Ti(C,N) and C, and those at 1500℃ were Fe, Ti(C,N), C and Fe3C. The results show that at the range of 1350℃~1500℃, redution of FeTiO3 to Fe and Ti(C,N) is feasible under the atomosphere of N2 and that the theoretical analyses of the reduction of impurities and the proportion of C, N and O in Ti(C,N,O) are basically consistent with the experiment results...