At present, 98.5% of the world's annual iron ore consumption is processed by blast furnaces. Therefore, the mainstream of modern ironmaking is the blast furnace method. However, this does not mean that the blast furnace ironmaking method has no disadvantages. The larger the blast furnace, the better its economy. However, various countries and regions have inconsistent demands for steel production, so they also need a new ironmaking method that is economical and can use local resources flexibly and rationally. In particular, in areas where scrap steel was used to make steel in the past, it is hoped that a new raw material iron with stable chemical composition and price can be produced instead of scrap steel.
Beginning around the First World War, in periods and regions where steel demand soared, research and experiments on non-blast furnace ironmaking methods continued. Especially in the 1950s, with Europe as the center, the rapid iron smelting method was faced with steel demand. The direct reduction ironmaking method can be classified based on the type of reducing agent used, the form of the reaction device, the type of product, and the current ironmaking process and its scale.
From ore to steel, gas or solid fuel is used as a reducing agent to reduce iron ore in a solid state to an iron-containing solid product with a high degree of metallization. This method breaks the traditional ironmaking method, which requires high-quality coke, and the direct reduction method uses natural gas or low-quality non-smelting metals as energy sources. Direct reduced iron is easily oxidized in contact with water. In order to avoid oxidation and facilitate storage and long-distance transportation, the process of hot-pressing the baked DRI into blocks is adopted). Direct reduced iron contains more than 90% of iron, has stable chemical composition, low content of impurities (carbon, silicon), very few trace elements, and the composition is close to iron. It is a high-quality steelmaking raw material. Because this kind of iron retains a large number of micro-pores formed when oxygen is lost, it looks like a sponge under a microscope, so it is also called sponge iron. In metallurgical production, it is used instead of scrap steel as raw material for steelmaking. With the rapid development of electric furnace steelmaking, scrap steel resources are becoming increasingly scarce, and direct reduced iron has received extensive attention.