The blast furnace is a shaft type furnace operating by the counterflow technique: the descending burden of sinter and coke, charged from the top of the furnace, is heated and reduced by the combustion gases ascending from the tuyere zone where a hot air blast is injected to burn C to CO. Coke consumption is about 50 kg/t sinter product. In the sinter process, a mix of iron ore fines, lime, and coke (almost pure carbon) is charged in a thick layer onto a moving conveyor (Dwight Lloyd process) and partially melted to form a porous mixture of iron oxides and gangue. The iron feedstock of the blast furnace is the sinter, which is produced in the sinter plant. As this operation yields energy, additional scrap is introduced in order to control temperature but also to reduce the carbon footprint. The raw iron is then transformed into crude steel in the oxygen converter. Sintered iron ores are reduced to raw iron in the blast-furnace. 1.2 Steel production 1.2.1 The blast-furnace-basic oxygen converter route Ingot routes are only used to cast very thick and heavy plates and some special steels. Flat products, including quatro plates and coils, and long products, including hot rolled sections, wires, and light shapes, are normally produced from the continuous casting process. This process step is generally referred to as Secondary or Ladle steelmaking.ĭuring the last step of steelmaking, the steel is cast either into slabs, blooms, or billets on a continuous casting machine, or into ingots depending on the final product. At the same time, its content of carbon, manganese, and microalloying elements such as niobium, vanadium, and titanium can be adjusted. Low energy costs and availability of recycled scrap ensure the competitiveness for the second process route.īefore casting, the steel can be refined in the ladle by various processes according to specifications with respect to its deoxidation state inclusion content and levels of phosphorus, sulphur, nitrogen, and hydrogen. High production rates and low impurity steel production give a dominant role to the first process route. The respective shares in crude steel production of these two main process routes are around 70% (BOF) and 30% (EAF). Investments into this switch are being made in Europe. To eliminate fossil fuel use in iron and steel making, renewable hydrogen gas can be used in place of natural gas to produce DRI. Direct Reduction Iron (DRI) is produced from the direct reduction of iron ore (in the form of lumps, pellets, or fines) into iron by a reducing gas produced from natural gas, as is done today, or hydrogen, which will be used in the near future. In the last two decades, new technology to produce refined iron has emerged. In both routes, the process consists of producing refined iron to which the required alloying elements to produce the finished steel specification are added.
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