Avaliação do comportamento de corrosão de concretos refratários contendo ZnAl2O4 via simulações termodinâmicas

Abstract

The main characteristic of refractory ceramics is the capacity to withstand thermo-chemicalmechanical stresses at high temperatures for long periods of time, which allows this material to be applied in a diverse industrial field. In the case of steel industry, refractories play an essential part being used, for example, as equipment’s lining, that contributes for the viability of this production process. However, choosing the most suitable composition and kind of refractory is still a challenge, as the steel making process are done in aggressive conditions (in presence of slag, corrosive gas, high temperature, etc.) that can favor wear and the reducing of average service life of these ceramic products. In this context, development of refractories that can withstand these conditions without premature failure is of great interest. These failures can occur as result of two main problems, (i) corrosive wear by the chemical attack of the slag, (ii) unwanted residual expansions due to the in-situ formation of new phases in the microstructure at high temperatures. Thus, it is necessary to understand the phase transformations that may appear in the refractories when exposed to its working condition and in contact with the slag. Knowing that, the objective of this present work is to compare the compositions of aluminous refractory castables containing ZnAl2O4 spinel, and in the presence of 0-1% -weight of SiO2 in the total formulation or 2,7%-weight of SiO2 in the matrix which is the most reactive part of the refractory, identifying the possible phases that may be formed at high temperatures and the transformations involved in the contact of this refractory with the synthetic slag. To attain this data, it was performed thermodynamic simulations, using a software called FactSage, to predict the chemical behavior of the materials at 1500ºC.With the results of these simulations it was verified that the addition of silica in the composition of the castables studied entailed in a reduction of the corrosion behavior and in the penetration of the slag. Furthermore, the AZMS and AMS materials, that contained MgO in their composition, presented the best results, since they had less dissolution of the refractory in the slag and had the highest resulting viscosity, entailing a reduction in corrosion and liquid penetration.