Study on the protective effect of the dense slag layer on converter lining

In this paper, the protective effect of the dense slag layer on the furnace lining is investigated through comparative sampling of residual bricks. The physical and chemical properties of the residual brick samples were tested, and the result showed that sample NO.1 had 7.9% higher bulk density, 37.6% lower apparent porosity, 41% higher flexural strength, and 14.3% higher compressive strength than sample NO.2. The residual carbon of sample NO.1 was normal, while the residual carbon oxidation loss rate of sample NO.2 was 36%. X-ray diffractomer (XRD), optical microscope (OM), and EDS: scanning electron microscope-Energy Dispersive Spectrometer (SEM+EDS) were adopted to study the physical phase composition, microscopic morphology, and mineral phase composition and distribution of the dense slag layer. The slag layer was found to be highly alkaline and oxidizing, with 58-73% RO phase, 17-26% phosphorus-rich phase, and 6-16% base phase in the mineral phases. The FactSage 8.1 thermodynamic software was used to simulate and calculate the melting temperature of each mineral phase. The presence of the high melting point phase and RO phase in the dense slag layer is an important reason for its ability against high temperature and high oxidation. The formation of the dense slag layer was related to the saturated solubility of MgO. The results indicated that the extremely unstable saturated solubility of magnesia had a greater effect on the dissolution rate of magnesia particles. External temperature and oxidation changes are important factors affecting the saturated solubility of MgO in the slag layer, and reducing the internal-external heat and mass transfer rate could effectively improve the service life of the furnace lining.