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.
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