Detailed Numerical Modeling and Simulation of Fe₂O₃−Al Thermite Reaction

Abstract

A thermite reaction is a self-propagating exothermic reaction with many practical applications in welding processes, material synthesis, pyrotechnic and initiator technologies. Motivated by the above-mentioned, the present study involves modeling and simulation of common hematite-aluminum thermite reaction with the aim of predicting temperature levels and radial burning speeds in a thin disk ignited at the center. Balance equations of species and energy conservation were solved in one dimension space by applying a finite difference method, considering no species transport and a one-step mechanism. The Arrhenius equation was adopted to model the kinetics rate. Phase change and temperature dependence of the thermochemical properties were also considered. Analyses of spatial and temporal meshes revealed that numerical results were independent of the grid used. Predictions show that the ignition procedure affects the formation of the reaction-front, higher temperatures, and longer ignition zones can start the self-sustained reaction earlier. However, once the reaction wave is established, its velocity and peak temperature are the same, independent of the initial temperature profile. Simulations herein also show that an increase of the activation energy and decrease of the pre-exponential factor slows down the reaction speed considerably, impacting on accurate prediction of reactionwave velocity. Further, the activation energy influences the burning velocity much more drastically than the pre-exponential factor. The maximum temperature observed in the model is around the melting temperature of alumina (2327 K), which is in agreement with the experimental results reported in the literature.

Thermodynamics of thermite reactions for a new thermal plug and abandonment process

“…As mentioned earlier, the objective of this contribution is to investigate the complex mechanisms of thermite reactions with the help of thermodynamics. Accordingly, in this work we search for the most promising thermite mixture to be used as an energetic material for application in a new process, here recalled as "Thermal Plug & Abandonment" of mature oil wells [6][7][8]15]. In pursuing this goal, we apply thermodynamic analysis to compare three thermite mixtures of reactants, namely, "2Al + Fe 2 O 3 ," "2Al + 3CuO" and "3Be + Fe 2 O 3 ."…”

“…In an early article [15], simulations were performed using a simplified combustion model for the Fe 2 O 3 -2Al thermite reaction, which assumed Arrhenius-type kinetics. However, the physicochemical mechanisms of thermite-type reactions are still far from being completely understood [16].…”

“…The processes involved are complex and accounts for phase changes, species decomposition, diffusion, fluidized particle motion, droplet collision, among other phenomena that are difficult to measure experimentally in such a fast and high-temperature reaction. Therefore, the objective of this contribution is to shed some light on the complex mechanisms of thermite reactions via thermodynamics analysis, not entirely accounted for in [15] and approximated by a constant heat generation model in [7] or by a prescribed time-varying heat flux in [17]. It is also important to emphasize that in references [7] and [17] the porous thermite mixture zone where the exothermal reaction takes place was not included.…”

“…Accordingly, thermodynamics principles can already give some important information about this kind of reaction such as adiabatic flame temperature, the heat of combustion, and the final products of the reaction at equilibrium conditions. Ultimately, the work herein intends to contribute to the identification of promising thermite mixtures for specific application, in particular to plug and abandonment of mature oil wells [6][7][8]15] Before leaving Sect. 1, it is important to emphasize the contribution herein.…”

Chemical and Structural Analysis of Newly Prepared Co-W-Al Alloy by Aluminothermic Reaction

“…The reaction takes place very quickly. In this process, the high affinity of aluminum for oxygen is used, and a more stable metallic oxide (Al 2 O 3 ) is formed [6,7]. The general equation is:…”