Thermo-mechanical finite element analysis of a fused cast AZS block applied to a glass melting furnace during the heating step

Abstract

There is a great motivation to understand the best-operating practices for glass melting furnaces to improve their quality, increase the process energy efficiency and extend the working life of the refractory. Electrofused AZS (Alumina-Zirconia-Silica) refractories are used for furnace linings due to their good corrosion resistance and mechanical properties at high temperatures. Operating conditions can influence their performance, limiting the service life of the furnace. Computer simulations have proven to be useful for analyses wherein testing is difficult and involves certain risks for experiments and validations. Therefore, this work investigates the thermal and mechanical behavior of AZS blocks with a metal electrode support, which present cracks along the furnace heating-up. The simulations were carried out using the finite element method (FEM) to determine the AZS block temperature and maximum principal stress fields during furnace heating. Considering the refractory properties with the temperature, the results showed that the maximum principal stress reaches the modulus of rupture of AZS, after 42 h when the block hot face temperature is 145 °C. Analyses of the effects of a cooling system, heating curve and alternative hole designs to support the electrodes are also shown. In the case of cooling, there are no positive effects from the refractory behavior point of view, reaching the maximum allowable stress value after 40 h for the best scenario. Regarding the heating curves, the thermal and mechanical profiles and the location at it reaches the maximum principal stress were equivalent to that of the reference. Finally, changing the hole geometry showed that the crack initiation time was slightly longer than the reference, 43 and 44 h for the conical and single diameter holes, respectively. The critical region was observed closer to the hot face for the conical case, which can be interesting for further analysis to consider some post-cracking effects.