In-Situ measurement of gas emission by pyrolysis of various ceramic materials used for submerged-entry nozzle refractory

Abstract

High-temperature heat treatment was performed on Submerged-Entry Nozzle (SEN) refractory materials, coupled with in-situ gas analysis, to identify the emitted gas species. Various SEN refractories, including “oxide-based” ones containing SiO2(s) and C(s), exhibited a carbothermic reaction: SiO2(s) + 3C(s) = SiC(s) + 2CO(g). The emission of CO(g) was confirmed for the first time using a quadrupole mass spectrometer, while the emission of SiO(g) was not observed. An ”oxide-less” refractory composed of AlON–AlN–BN emitted only N2(g). Considering the reactivity of CO(g) in the reoxidation of molten steel passing through the SEN, it is crucial to minimize CO(g) emissions during continuous casting. The extent of CO(g) emission was discussed with respect to the compositions of the refractories. This study elucidates the gas emission mechanism of SEN refractories, which is the main cause of initial clog deposit growth. The effectiveness of the oxide-less refractory in suppressing CO(g) emission was demonstrated. © 2023 Elsevier Ltd and Techna Group S.r.l.