EAF shells' work environment

Definition of EAF shells

Arc furnace Electric arc furnace is an electric furnace for smelting ore and metal at high temperature generated by electrode arc. When gas discharge forms an arc, the energy is very concentrated, and the arc zone temperature is above 3000 ℃. For smelting metal, the electric arc furnace is more flexible than other steelmaking furnaces, can effectively remove impurities such as sulfur and phosphorus, the furnace temperature is easy to control, and the equipment covers a small area, which is suitable for melting high-quality alloy steel refining.

Work environment of water-cooled lower shell

The furnace shell is usually cylindrical, with a truncated conical bottom and a spherical disc bottom, with good strength. The furnace shell bears the weight of the furnace lining and metal, as well as the thermal stress caused by the thermal expansion of the furnace lining. Generally, the temperature in most areas of the furnace shell is about 200 °C. The furnace shell temperature is higher when the furnace lining is partially burned. On some small furnaces, the mechanisms such as furnace top lifting, electrode lifting and tilting are all directly connected with the furnace shell, and there are furnace door, steel outlet, etc on the furnace shell. 

The furnace shell is required to have sufficient mechanical strength and stiffness. The furnace shell shall be densely welded with horizontal and vertical stiffeners, and it shall be reinforced around the opening. There is a specially welded reinforcing ring on the upper edge of the furnace shell. The reinforcing ring is usually water-cooled to prevent deformation. However, the whole furnace body tends to deform because it cannot expand freely. Some large electric furnaces adopt cage shaped furnace shell. Except that the furnace shell and bottom of the furnace are welded by steel plate, the upper half of the furnace shell is cage shaped, and the vertical and horizontal steel parts are welded into the internal furnace shell steel plate. Recently, water cooling blocks can be directly hung in the cage furnace shell as the furnace wall. The horizontal support can be made of steel pipe as the water supply and drainage main pipe of the water cooling block. For the furnace with a diameter of 3~4m, the furnace shell and lining can be replaced as a whole, which speeds up the furnace repair time. On the larger furnace, the furnace shell is made into upper and lower parts that can be disassembled, the joint shall avoid the slag line, and the upper steam generator shell and furnace wall can be lifted away together. Many holes shall be drilled evenly on the steel plate of the furnace shell to eliminate the moisture during oven drying.

The hearth diameter of large blast furnace is large, and the cooling of the cooling stave in the circumferential direction is not enough to dissipate the heat distributed by the steam generator in the center of the furnace bottom. If it is not cooled, the furnace bottom will be seriously eroded downward. Therefore, the central part of the bottom of large blast furnace should be cooled by installing air cooling and water cooling pipes. Compared with air cooling, water cooling has higher cooling intensity, lower power consumption, further thinning of furnace bottom thickness and more applications. At present, the bottom sealing plate is mostly used in large blast furnaces, and the water-cooling pipe is set above the sealing plate, so the furnace shell opening reduces the strength and sealing, but the cooling effect is good; The water cooling pipe is set below the sealing plate, which has no damage to the furnace shell, but the cooling effect is poor.