A further link between laboratory analysis and industrial process optimization - The size effect on drying of refractory castables

 Ceramic materials display different special features such as refractoriness, erosion and corrosion resistance and, nowadays, increased attention has been given to its energy barrier capabilities. However, one of its most important features is its capability of being used for building structures several meters long, weighting multiple tons. Hydraulic bonded castables need to be carefully dried in order to prevent explosive spalling due to pressurization of water vapor. Usually, this process is studied in laboratory conditions within controlled environments on samples with few centimeters. The large discrepancy between such size scales can be one of the reasons why even though drying is a broadly studied subject, the industrial practice is still based on semi-empirical rules. Thus, the current work focused on better understanding the effect of the sample volume in its mass loss behavior. That was attained by using conventional (5 cm x 5 cm cylindric samples) and macro thermogravimetry tests (with 20 x 20 x 20 cm3 and 30 x 30 x 30 cm3 cubic samples) for compositions with and without polymeric fibers. The results pointed out that the difference in size led to distinct thermal gradients within the sample, and different temperatures of changes on the inflection of the sample’s heating rate. Different mass loss profiles were observed, especially considering the sample without the drying additives. These results show that when modelling the drying of the lining of industrial equipment, besides considering of the heating protocol the volume of the object needs to be accounted for.