The furnace cover brick also has three or four rounds of bricks on the arch angle beam, and then the "t" shaped beam is built, and then the end work is carried out in three electrode holes. The furnace cover is made of herringbone brick, the middle belt bars support each other closely, the layout is symmetrical, the load is uniform, the structure is firm, it has the advantages of easy repair and high service life.
The special-shaped brick is better than the standard brick in the selection of refractory brick. The shape of firebrick is smooth, the thickness is uniform, the length is consistent, and there is no lack of edge and coke,
The height difference between bricks and bricks shall not be 5mm. The fireclay shall be evenly scraped, thin and full, and the joints shall be staggered. The bricks shall be built one by one and the bricks shall be knocked strictly. After bricklaying, the brick should be baked and dried to reduce the spalling and block falling caused by temperature change. The baking temperature is 500 ~ 660 ℃ for insulation.
The vulnerable parts of furnace cover are the center of three electrode holes, the No.2 electrode hole and the arch foot brick of furnace cover ring. How to improve the life of these parts. Water cooled sealing ring with reasonable structure shall be adopted; the content of Al2O3 in the brick shall be increased and the glass phase shall be reduced to improve the fire resistance and slag resistance, and the expansion shall be uniform; or the high alumina brick shall be boiled with asphalt, and various brick types shall be adopted to avoid hanging the brick on the furnace top. The electrode chuck shall be adjusted every time the furnace cover is changed to keep the electrode in vertical alignment.
The thickness of brick furnace cover is generally 230-350mm, and the upper limit is taken for large capacity star furnace (above 30t furnace).
In recent years, unburned high alumina brick (with phosphate or resin as binder) has been used to build furnace cover in China. Due to crystal transformation of unburned brick in use, microcracks are formed and stress concentration produces relaxation effect. Because of the existence of micro cavities and microcracks, the volume expansion of the brick in the heating process is reduced, and the phenomenon of thermal shock peeling is not easy to occur. Therefore, the high temperature strength, toughness and crack resistance of unburned brick are better than that of monolithic fired brick. The service life can be greatly improved.
