Anthracite baked in tunnel kiln and carbon blocks produced with metallurgical coke as main raw materials produce annular fracture and abnormal erosion in the hearth carbon blocks during production. After the fracture and iron infiltration, the cracks gradually expand and form a molten iron infiltration layer. In order to eliminate the influence of annular fracture of hearth carbon blocks on the service life of the hearth, the quality of carbon blocks (micropores and ultra-micropores, high thermal conductivity, high corrosion resistance) is improved by improving the quality of raw materials for producing carbon blocks (changing to electric calcined anthracite) and adding additives. The key to extending the service life of the lining is to rely on high thermal conductivity to form a condensed protective layer (graphite carbon deposits, slag and iron mixed solidification) on the working surface of the carbon block, so that the carbon refractory bricks are no longer corroded.
How to choose the material of the combined bricks in the hearth? Choice of the material of the iron mouth combined bricks Iron mouth combined bricks are currently generally designed with composite brown corundum bricks or corundum-mullite bricks. The ability of these two materials to resist erosion by molten iron is not ideal, and the iron mouth depth is unstable in production. According to the production practice of Anshan Iron and Steel's 2580m3 and 1000m3 blast furnaces, when aluminum-carbon-silicon carbide composite bricks are used for the taphole, the taphole depth is relatively stable and easy to maintain. Therefore, it is more appropriate to choose aluminum-carbon composite bricks.
Choice of materials for tuyere composite bricks
Tuyere composite bricks are currently generally designed with composite brown corundum refractory bricks or corundum-mullite bricks. Since the tuyere composite bricks are the part with the largest temperature difference in the furnace, it is necessary to select refractory materials with good resistance to rapid cooling and heating and slag erosion. According to foreign experience and the production practice of Anshan Iron and Steel's No. 10 blast furnace, carbon materials are better. After the furnace adopts the carbon block-ceramic cup lining structure, the blast furnace smelting law has changed significantly, mainly manifested in:
(1) The temperature gradient of the furnace refractory lining layer has changed significantly, and the temperature gradient of the furnace lining close to the slag iron surface has increased. Half a year after the furnace was opened, the temperature of the contact surface between the ceramic cup layer and the carbon block is normally within the range of 800-950℃. If it is lower than 750℃ (a difference of more than 100℃), it indicates that the furnace wall is thick.
(2) The physical heat of molten iron increases. For blast furnaces of the same volume, under the condition that the Sic content of pig iron is not much different, the molten iron temperature increases by 18-21℃ compared with that of blast furnaces without ceramic cups.
(3) Under normal production conditions, when the silicon content of pig iron is about 0.35%, it is equivalent to the physical heat level of blast furnaces without ceramic cup layers when the silicon content of pig iron is 0.50%-0.55%. Therefore, the refractory bricks silicon content of pig iron can be reduced by 0.15%-0.20%, and the coke ratio can be reduced by an average of 6-8kg/t.
(4) After the furnace temperature increases, the fluidity of slag iron improves, which improves the adaptability of the furnace condition to changes in external conditions.
(5) When the furnace temperature is continuously (2-3 times) lower than the lower limit specified by the thermal system, the slag iron can still flow normally.
(6) When the first iron is discharged after a long period of air stoppage (more than 8 hours), the physical heat of the slag iron increases, the fluidity improves, and the iron mouth is easy to be exposed.
(7) When the furnace temperature is high for a long time (Si is in the range of 0.5%~1.0%) and the sulfur content is low, the furnace wall is prone to thickening, which needs to be prevented.
