THERMODYNAMIC ASPECTS OF METAL OXIDES RECOVERY BY ALUMINUM AND TITANIUM IN THERMIT WELDING OF RAILS

Abstract

The paper presents a comparative assessment of the thermodynamic properties(∆_rH°(T), ∆_rG°(T)) of thermite reactions with aluminum and titanium in the metal oxide – aluminum and metal oxide – titanium systems under standard conditions. Iron, manganese, silicon and chromium oxides were taken as components of the reactions for calculating the thermodynamic properties. The thermodynamic analysis of 6 reactions with aluminum and 30 reactions with titanium was carried out. It follows from the calculations that all the reactions considered are thermodynamically probable. However, the reactions of both aluminum and titanium with iron oxides are the most likely to occur and, accordingly, the greatest heat release, the least likely to occur and, accordingly, heat release are observed during the reduction of silicon oxide. Reactions with manganese and chromium oxides occupy an intermediate place. In terms of reducing ability, titanium is not inferior to aluminum, and in the case of a reaction with iron oxides, it even surpasses it, especially in the temperature range of more than 2000 K. The enthalpy of reactions of reduction of iron oxides by titanium are in the same range of values as the enthalpy of reactions of reduction by aluminum (from –450 to –400 kJ). The thermodynamic analysis has shown that the use of titanium as a reducing agent in thermite welding is quite acceptable along with aluminum.