How do I use a blast furnace - part 1

Blast furnace operation refers to the monitoring, judgment and control of blast furnace ironmaking process. The task of blast furnace operation is to maintain stable, smooth and efficient production, so as to achieve the purpose of high output, good quality, low consumption and long furnace life. The contents of blast furnace operation include: the formulation and control of basic operation system, the judgment and adjustment of furnace conditions, the diagnosis and treatment of abnormal furnace conditions, slag and iron tapping operation, slow air operation, air suspension and re air, blast furnace startup, blast furnace stuffy and blast furnace shutdown.

Blast furnace's operating system

In order to achieve the goal of high efficiency, high quality, low consumption and long life, the basic operation system must be formulated according to the raw materials and fuel conditions used in the blast furnace, the status of equipment and the type of iron smelted. It includes heat system, slagging system, air supply system and charging system. There is an internal relationship between various basic operating systems, which should be comprehensively considered when formulating the basic operating system. For example, the charging system can affect the distribution of charge and gas flow, and the air supply system also affects the distribution of gas flow. The two must be considered together. For another example, the slag making system and thermal system must also be comprehensively considered: when the slag alkalinity is set low, the silicon content of pig iron cannot be set too low, otherwise, the sulfur content of pig iron is too high, which will affect the quality of pig iron; On the contrary, when the basicity of slag is high or MgO in slag is high, the silicon content of pig iron can be set lower. The air supply system is also related to the thermal system: when the furnace temperature is high (such as smelting cast pig iron or ferromanganese), the smelting intensity is lower; When the furnace temperature is low, the smelting intensity should be higher.

Blast furnace's slagging system

It is called blast furnace slagging system to determine the composition and alkalinity of slag according to raw materials, fuel conditions and smelting iron. Therefore, the blast furnace slag with good melting, fluidity and stability and strong desulfurization and alkali discharge capacity is obtained. Slag basicity (CaO / SiO2 or (CaO + MgO) / SiO2) is an important parameter of slag making system. High alkalinity and high desulfurization efficiency; On the contrary, the desulfurization efficiency is low. The selection of alkalinity is mainly based on the sulfur content of raw materials and fuels. However, the slag with high alkalinity has high melting point, poor fluidity and poor stability, which is not conducive to the smooth operation of the furnace and consumes more coke. Therefore, on the premise of ensuring that the sulfur content of pig iron meets the requirements, the slag with low alkalinity should be selected. The alkalinity (CaO / SiO2) of smelting pig iron is mostly between 1.0 and 1.25; Smelting and casting pig iron; In order to avoid hearth accumulation and facilitate silicon reduction, the alkalinity should be lower than the former. When smelting raw materials with high alkali metal content, in order to facilitate slag alkali discharge, it is advisable to select low alkalinity. When smelting ferromanganese, in order to improve the yield of manganese, the alkalinity should be higher, and CaO / SiO2 reaches about 1.50. MgO in slag composition is generally controlled at 6% ~ 12%, which is conducive to improving slag fluidity and desulfurization, obtaining low silicon and low sulfur iron required by steel-making furnace, and discharging alkali from slag. Al2O3 should not exceed 15%, otherwise the fluidity of slag is poor.