Reduction of perovskite-geikielite by methane–hydrogen gas mixture: Thermodynamic analysis and experimental results.

The present study investigated the reduction and carbonization behavior of perovskite-geikielite by using CH 4 –H 2 gas mixture, which aimed to recycle the titanium resource in titanium-bearing blast furnace slag. Thermodynamic phase equilibrium analysis in the CaTiO 3 –CH 4 –H 2 , MgTiO 3 –CH 4 –H 2 and CaTiO 3 –MgTiO 3 –CH 4 –H 2 systems was performed by FactSage. The analysis indicated that CaTiO 3 could be ultimately reduced and carbonized to TiC x O y by CH 4 –H 2 gas mixture at temperature above 1300 °C, while the temperature for reduction of MgTiO 3 was above 1200 °C. MgTiO 3 is found to be reduced prior to CaTiO 3 in the CaTiO 3 –MgTiO 3 –CH 4 –H 2 systems. The reduction experiments of perovskite-geikielite were carried out in a temperature range of 1300 °C to 1450 °C in a flowing CH 4 –H 2 atmosphere. Experimental results showed that perovskite-geikielite could be reduced completely to TiC x O y at 1400 °C and above after 8 h reduction, while geikielite was reduced prior to perovskite. The reduction and carbonization extent of samples increased with increasing time and temperature when in a low temperature range (below 1400 °C). However, a much higher temperature (above 1400 °C) would hinder further carbonization of TiC x O y for the production of deposited carbon. Addition of iron oxides to sample strongly facilitated the reduction reaction, and even promoted the reduction of titanium to be completed at only 1300 °C after 8 h reduction. The gas-solid reaction provided a low temperature method to reduce and carbonize perovskite and geikielite, and thus it provided a possible way to use titanium-bearing blast furnace slag. Unlabelled Image • A novel method to reduce and carbonize perovskite and geikielite was proposed. • Thermodynamic and experimental study on the reduction by CH 4 -H 2 was performed. • The ratio of TiC/TiO in TiC x O y reduced from CaTiO 3 and MgTiO 3 has been estimated. • The reduction mechanism of gas-solid reaction with CH 4 -H 2 was discussed. [ABSTRACT FROM AUTHOR]