Kinetic modeling of titania reduction by a methane-hydrogen-argon gas mixture

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 2001-06, Vol.32 (3), p.465-473
• Main Authors: GUANGQING ZHANG, OSTROVSKI, O
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Metallurgical fundamentals; Metals. Metallurgy; Production of metals
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-001-0032-8

This article describes kinetic modeling of titania reduction and carburization by methane-containing gas, based on experimental data reported previously by Zhang and Ostrovski. A sequence of titania reduction to titanium oxycarbide was observed experimentally; reaction mechanisms are given. A two-interface shrinking-core model and a crackling-core model are employed for the kinetic modeling of the reduction and carburization process. The rates of Reactions [1] and [2] are both controlled by the chemical-reaction stage. For the intrinsic chemical-reaction control, the extent of the reaction as a function of reaction time is well described analytically. The two models give close results that are consistent with experimental data obtained at 1473-1773K and a methane partial pressure up to 8 kPa. Reaction [1] is of the first order with respect to methane and of one-half to first order with respect to hydrogen. The apparent activation energy of reaction [1] is 124 kJ/mol for the two-interface shrinking-core model and 126 kJ/mol for the crackling-core model. Reaction [2] is of the first order with respect to methane and is independnet of hydrogen concentration. Nevertheless, hydrogen plays an important role in the reduction/carburization process, as it suppresses the decomposition of methane and deposition of solid carbon. The apparent activation energy of the reaction is 161 kJ/mol for the two-interface shrinking-core model and 191 kJ/mol for the cracking-core model.