The process of steelmaking blast furnace

2023-12-15 15:44:00

The steelmaking blast furnace is the most important and core equipment in steel production. It is the process of reducing iron oxide in ore to metallic iron through high-temperature reduction reactions of raw materials such as iron ore and metallurgical coke, while removing other impurities, to produce pure molten iron for subsequent steel treatment and casting production.

The process of blast furnace mainly includes the following steps: loading, melting, deoxidation reduction, carbon reduction, desulfurization, dephosphorization, impurity removal, and iron tapping.

The first stage is the loading stage. In the material basket at the upper part of the blast furnace blast hole, various raw materials such as ore, coke, limestone, and reheating agent are loaded in a certain proportion. Ore is the main raw material for iron ore, coke is the main raw material acting as a reducing agent and fuel, limestone is used to capture and stabilize impurities in sulfur and iron ore, and the role of the reheating agent is to adjust the composition of the slag and prevent it from forming steam.

Next is the melting stage. Above the feed inlet of the blast furnace, ignition and air supply are carried out, and air is mixed with fuel to supply the furnace hearth, gradually increasing the temperature inside the furnace and rapidly melting raw materials such as iron ore and coke. The fuel burned in the furnace provides heat, allowing the raw materials to reach a suitable melting temperature.

Then comes the deoxygenation reduction stage. In the middle of the blast furnace, the reducing gas comes into direct contact with the furnace charge, and through chemical reactions, the iron oxide (Fe2O3) in the iron ore is reduced to metallic iron (Fe), while generating a large amount of gases such as CO and CO2. Reducing gas is mainly generated outside the furnace, and it is supplied into the furnace through the furnace drum tuyere. It reacts with the oxides in the furnace material to complete the iron reduction process.

Next is the carbon reduction stage. The coke in the furnace material undergoes an oxidation-reduction reaction at high temperature, reacting reducing gases such as CO and H2 with the carbon inside the coke to generate CO2 and H2O. It further reacts with the reducing gas in the ore to further reduce the oxides in the ore to metallic iron. The reduction effect of carbon is an important link in the reduction process of blast furnace, and it is also the main source of producing blast furnace slag.

Then comes the desulfurization and dephosphorization stages. In the lower part of the blast furnace, due to the strong reducibility of reducing gas, a strong reduction zone is formed inside the furnace. In this area, the reducing gas directly contacts the furnace material, reacts with harmful impurities such as sulfur and phosphorus in the ore, converting them into gas products, and most of them are discharged out of the furnace together with the furnace gas. In this way, the blast furnace can achieve the purpose of desulfurization and dephosphorization, and improve the quality of molten iron in the furnace.

Next is the impurity removal stage. A chemical reaction zone of steel slag is formed between the slag iron layer and the molten iron layer inside the blast furnace. In this area, through the micro solubility and adsorption of steel slag on molten iron, some impurities in the molten iron are captured and diluted, allowing it to solidify into blast furnace slag. This achieves the removal of impurities from the molten iron.

The final stage is the iron casting stage. After a series of reactions and treatments, the molten iron produced in the furnace gradually meets the requirements for iron production. The molten iron is discharged through the tapping hole of the blast furnace, and through subsequent continuous casting and other processes, steel of different shapes and specifications is produced.

In summary, the process of steelmaking blast furnace is a complex one, which involves multiple steps such as loading, melting, deoxygenation reduction, carbon reduction, desulfurization, dephosphorization, impurity removal, and tapping to convert raw materials into pure molten iron, which is used for subsequent steel treatment and casting