China's Refractories

《中国耐火材料》英文版

China's Refractories ›› 2024, Vol. 33 ›› Issue (2): 35-40.DOI: 10.19691/j.cnki.1004-4493.2024.02.006

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The Role of the Size Effect on the Drying of Refractory Castables—How Its Under-standing Could Narrow the Gap between Laboratory Studies and Industrial Reality

M. H. MOREIRA1,*, H. PENG2, S. Dal PONT3, V. C. PANDOLFELLI1   

  1. 1 Materials Engineering Department, Federal University of São Carlos (UFSCar), São Carlos 13565-905, Brazil;
    2 Materials Innovation, Elkem Silicon Products Development, Kristiansand 4621, Norway;
    3 CNRS, Grenoble INP, 3SR, Université Grenoble Alpes, Grenoble 38000, France
  • Online:2024-06-15 Published:2024-07-04
  • Contact: *e-mail: moreira.murilo@gmail.com
  • About author:Murilo Henrique Moreira obtained his bachelor’s degree in Materials Engineering from Universidade Federal de São Carlos in 2019, followed by a master’s degree in Materials Science and Engineering from the same institution in 2021. Currently he is a PhD candidate in Materials Science and Engineering at the same university (PPGCEM/UFSCar) under supervision of Prof. Victor Carlos Pandolfelli. He is a FIRE Alumna (Federation for International Refractory Research and Education) and has experience in the area of computational simulations (using Finite Elements, Finite Volume and Finite Differences Methods). His current works focus on the development of numerical models and on the direct visualization of the drying of refractory castables aiming to enhance the safety, sustainability, and efficiency of water removal processes in monolithics.

Abstract: Refractories have unique capabilities such as sustaining their shape and properties at extreme conditions such as the combination of high temperatures and thermal shock, contact with molten metals and slags and in some circumstances resistance to erosion from abrasive particles. Given the large processing output of the heavy industries such as the cement and steel ones which both require high temperature processes, the refractories structures span various meters and weight of several tons. As the water removal stage of hydraulic bonded castables in industrial sites takes hours (10-60 h) due to the risk of explosive spalling, efforts to mitigate it are commonly studied. This has provided theoretical understanding of the general aspects of drying and important tools, such as the thermogravimetry analysis (TGA), for the design of refractory compositions with higher explosive spalling resistance. However, the optimization of this process is still far from the industrial reality especially because the actual linings that require the drying are orders of magnitude larger than the samples considered in the laboratory tests. Therefore, this study proposed the analysis of the sample volume effect on the water removal dynamics through TGA of high alumina castables with calcium aluminate cement. Conventional φ5 cm×5 cm cylindrical samples were assessed in a laboratory scale equipment whereas macro TGA were carried out considering 20 cm×20 cm×20 cm and 30 cm×30 cm×30 cm cubic samples. Additionally, the effect of polymeric fibers was also considered. It was found out that the different thermal gradients within the macro TGA samples resulted in an inflection on the sample’s heating rate and that the mass loss was affected by the volume considered, especially for the composition without additives. These findings highlight the requirement of carefully taking into consideration the different dimensional sizes and thermal gradients in the samples when analyzing and interpreting the laboratory studies, and especially when trying to extrapolate such results to the industrial reality.

Key words: drying, refractory castables, size effect, thermogravimetry analysis