The service of refractories in sintering machine ignition furnaces

Conclusions

In the service of chamotte roof burner blocks and wall parts in sintering machine ignition furnaces, impregnation of their surface layer with iron and calcium oxides contained in the sinter charge occurs with an increase in the working zone of the refractory in the quantity of glassy phase as the result of the formation of a low-melting (1070°C) eutectic in the CaO-FeO-Al₂O₃-SiO₂ system. This leads to contraction and fusion of the surface layer, which with sharp variations in temperature fails by spalling. This process occurs most intensely in the burner blocks, which are under more severe service conditions. Failure of the mullite roof refractory also occurs by spalling but primarily as the result of its insufficient original heat resistance. To increase the service life of the furnace as a whole high heat resistant mullite-corundum refractories must be used in the roof, including for the burners.