Cura de refratários à base de MgO via micro-ondas contendo, ou não, fontes de carbono

Abstract

Curing is an essential process for the manufacture and development of refractory materials and is now largely carried out by heating at relatively low temperatures compared to the working temperature for the material, with controlled heating rates and, in some cases, with atmospheric humidity temperature control, through the use of thermal ovens. Another way of curing the refractory ceramic material involves the use of conventional industrial furnaces that operate using unidirectional flames. This conventional process generates a temperature gradient in ceramic materials leading to non-homogeneous heating of the structure, a longer demand for the curing process to be completed, concentration of thermal stresses within the material and generates harmful gases to the environment that are released into the atmosphere. In this way, an alternative that has been studied to mitigate these factors, which on an industrial scale make a considerable difference, is the use of microwaves to perform the curing procedure of refractory materials, since, by this method, the heating of the material occurs more homogeneously throughout its structure, offering other advantages such as shorter curing time and risk of structural damage, as well as avoiding the release of polluting gases. In this work, the aim was to understand the operation of curing and heating using the microwave process through the study of already known literature. Computer simulations were performed to predict the behavior of a material when subjected to the curing process inside a microwave cavity. Experiments were also carried out with physical samples to reproduce the simulation models studied and developed to prove the effectiveness of the healing process using microwaves on an experimental scale. During the experimental practices, resin materials supplied by RHI Magnesita S.A. were used. with a majority composition of electrofused magnesium oxide and graphite, in addition to a conventional microwave device that has been adapted to carry out the curing process in a comparative way with the industrial method used. Due to the lack of literature on microwave curing systems and on the behavior of refractory materials in microwave curing, both the system developed and adapted for the analyses, as well as the sample composition and analysis conditions, were corrected and improvements during the tests carried out to provide results that are increasingly faithful and comparable to the conventional industrial curing method.