Производство стали из железной руды и лома

Process for producing steel from iron ore and scrap

Steelmaking is the process of producing steel from iron ore and/or scrap. In steelmaking, impurities such as nitrogen, silicon, phosphorus, sulfur and excess carbon (the most important impurity) are removed from the sourced iron, and alloying elements such as manganese, nickel, chromium, carbon and vanadium are added to produce different grades of steel. Steelmaking has existed for millennia, but it was not commercialized on a massive scale until the mid 19th century. An ancient process of steelmaking was the crucible process. In the 1850s and 1860s, the Bessemer process and the Siemens Martin process turned steelmaking into a heavy industry. Today there are two major commercial processes for making steel, namely basic oxygen steelmaking, which has liquid pig iron from the blast furnace and scrap steel as the main feed materials, and electric arc furnace (EAF) steelmaking, which uses scrap steel or direct reduced iron (DRI) as the main feed materials. Oxygen steelmaking is fueled predominantly by the exothermic nature of the reactions inside the vessel; in contrast, in EAF steelmaking, electrical energy is used to melt the solid scrap and/or DRI materials. In recent times, EAF steelmaking technology has evolved closer to oxygen steelmaking as more chemical energy is introduced into the process. Steelmaking is one of the most carbon emission intensive industries in the world. as of 2020, steelmaking is responsible for about 10% of greenhouse gas emissions. To mitigate global warming, the industry will need to find significant reductions in emissions.

Steelmaking has played a crucial role in the development of ancient, medieval, and modern technological societies. Early processes of steel making were made during the classical era in Ancient China, India, and Rome. Cast iron is a hard, brittle material that is difficult to work, whereas steel is malleable, relatively easily formed and a versatile material. For much of human history, steel has only been made in small quantities. Since the invention of the Bessemer process in 19th century Britain and subsequent technological developments in injection technology and process control, mass production of steel has become an integral part of the global economy and a key indicator of modern technological development. The earliest means of producing steel was in a bloomery. Early modern methods of producing steel were often labor intensive and highly skilled arts. See:
finery forge, in which the German finery process could be managed to produce steel. blister steel and crucible steel. An important aspect of the Industrial Revolution was the development of large scale methods of producing forgeable metal (bar iron or steel). The puddling furnace was initially a means of producing wrought iron but was later applied to steel production. The real revolution in modern steelmaking only began at the end of the 1850s when the Bessemer process became the first successful method of steelmaking in high quantity followed by the open hearth furnace.

Modern steelmaking processes can be divided into three steps: primary, secondary and tertiary. Primary steelmaking involves smelting iron into steel. Secondary steelmaking involves adding or removing other elements such as alloying agents and dissolved gases. Tertiary steelmaking involves casting into sheets, rolls or other forms. Multiple techniques are available for each step. Furnaces can convert up to 350 tons of iron into steel in less than 40 minutes compared to 10–12 hours in an open hearth furnace.

Electric arc furnace steelmaking is the manufacture of steel from scrap or direct reduced iron melted by electric arcs. In an electric arc furnace, a batch ("heat") of iron is loaded into the furnace, sometimes with a "hot heel" (molten steel from a previous heat). Gas burners may be used to assist with the melt. As in basic oxygen steelmaking, fluxes are also added to protect the lining of the vessel and help improve the removal of impurities. Electric arc furnace steelmaking typically uses furnaces of capacity around 100 tonnes that produce steel every 40 to 50 minutes.

In HIsarna ironmaking process, iron ore is processed almost directly into liquid iron or hot metal. The process is based around a type of blast furnace called a cyclone converter furnace, which makes it possible to skip the process of manufacturing pig iron pellets that is necessary for the basic oxygen steelmaking process. Without the necessity of this preparatory step, the HIsarna process is more energy efficient and has a lower carbon footprint than traditional steelmaking processes.

Steel can be produced from direct reduced iron, which in turn can be produced from iron ore as it undergoes chemical reduction with hydrogen. Renewable hydrogen allows steelmaking without the use of fossil fuels. In 2021, a pilot plant in Sweden tested this process. Direct reduction occurs at The iron is infused with carbon (from coal) in an electric arc furnace. Hydrogen produced by electrolysis requires approximately 2600 kWh per ton of steel. Costs are estimated to be 20–30% higher than conventional methods. However, the cost of emissions add to the price of basic oxygen production, and a 2018 study of Science magazine estimates that the prices will break even when that price is €68 per tonne , which is expected to be reached in the 2030s.

Secondary steelmaking is most commonly performed in ladles. Some of the operations performed in ladles include de oxidation (or "killing"), vacuum degassing, alloy addition, inclusion removal, inclusion chemistry modification, de sulphurisation, and homogenisation. It is now common to perform ladle metallurgical operations in gas stirred ladles with electric arc heating in the lid of the furnace. Tight control of ladle metallurgy is associated with producing high grades of steel in which the tolerances in chemistry and consistency are narrow.

Coal and iron ore mining are very energy intensive, and result in numerous environmental damages, from pollution, to biodiversity loss, deforestation, and greenhouse gas emissions. Iron ore is shipped great distances to steel mills.

To reduce the carbon content in pig iron and obtain the desired carbon content of steel, the pig iron is re melted and oxygen is blown through in a process called basic oxygen steelmaking, which occurs in a ladle. In this step, the oxygen binds with the undesired carbon, carrying it away in the form of carbon dioxide gas, an additional source of emissions. After this step, the carbon content in the pig iron is lowered sufficiently and steel is obtained.

Further carbon dioxide emissions result from the hot blast, which is used to increase the heat of the blast furnace. The hot blast pumps hot air into the blast furnace where the iron ore is reduced to pig iron, helping to achieve the high activation energy. The hot blast temperature can be from 900 °C to 1300 °C (1600 °F to 2300 °F) depending on the stove design and condition. Oil, tar, natural gas, powdered coal and oxygen can also be injected into the furnace to combine with the coke to release additional energy and increase the percentage of reducing gases present, increasing productivity. If the air in the hot blast is heated by burning fossil fuels, which often is the case, this is an additional source of carbon dioxide emissions.

The steel industry produces 7 8% of CO2 emissions created by humans (almost two tonnes for every tonne of steel produced), and it is one of the most energy consuming industries on earth. There are several carbon abatement and decarbonization strategies in the steelmaking industry, which on the basic manufacturing process used. Options fall into three general categories: switching the energy source from fossil fuels to wind and solar; increasing the efficiency of processing; and innovative new technological processes. All three may be used in combination. "Green steel" is the term used for manufacturing steel without the use of fossil fuels, that is, zero emission products. However, not all companies claiming to produce green steel meet this criterion. Some merely reduce emissions. Australia produces nearly 40% of the world's iron ore, and the government, via the Australian Renewable Energy Agency (ARENA), is helping to fund many research projects involving direct reduced ironmaking (DRI) to increase green steel and iron production. Large companies such as Rio Tinto, BHP, and BlueScope are developing green steel projects. CO2 emissions vary according to energy sources. When sustainable energy such as wind or solar are used to power the process, either in electric arc furnaces or to create hydrogen as a fuel, emissions can be reduced dramatically. European projects from HYBRIT, LKAB, Voestalpine, and ThyssenKrupp are pursuing strategies to reduce emissions. while a 2017 study showed that emissions are reduced by 56.5% with carbon capture and storage, and reduced by 26.2% if only the recycling of the reducing agents is used. To keep the carbon captured from entering the atmosphere, a method of storing it or using it would have to be found. Another way to use the top gas would be in a top recovery turbine which then generates electricity, which could be used to reduce the energy intensity of the process, if electric arc smelting is used. Carbon could also be captured from gases in the coke oven. as of 2022, separating the CO2 from other gases and components in the system, and the high cost of the equipment and infrastructure changes needed, have kept this strategy minimal, but the potential for emission reduction has been estimated to be up to 65% to 80%. Known as hydrogen direct reduction (HDR), this is the most prominent among green steel technologies. This differs from conventional steel making processes, in which carbon in coke is used as the reductant (to strip oxygen from iron ore), which creates iron and carbon dioxide. Where hydrogen is generated from a renewable energy source as both the
alternative reductant and the fuel, the greatest gain in CO2 emissions is achieved. As of 2021, only ArcelorMittal in France, Voestalpine in Austria, and TATA in the Netherlands were committed to using green hydrogen to make steel from scratch. HDR is employed in the HYBRIT project in Sweden. However, this approach requires a substantial amount of renewables to produce the needed renewable hydrogen. For the European Union, it is estimated that the hydrogen demand for hydrogen based steelmaking would require 180 GW of renewable capacity.

Another developing possible technology is iron ore electrolysis, where the reducing agent is simply electrons as opposed to H2, CO, or carbon. Expanding a pilot plant in Woburn, Massachusetts, and building a production facility in Brazil, it was founded by MIT professors Donald Sadoway and Antoine Allanore. A research project which involved the steel company ArcelorMittal tested a different type of iron ore electrolysis process in a pilot project called Siderwin. It operates on relatively low temperatures (around 110 °C), while the Boston Metal process operates on high temperatures (~1.600 °C). as of March 2023 ArcelorMittal is investigating whether the company wants scale up the technology and build a larger plant, and expects an investment decision by 2025.

Scrap in steelmaking refers to steel that has either reached its end of life use, or was generated during the manufacture of steel components. Steel is easy to separate and recycle due to its inherent magnetism and using scrap avoids the emissions of 1.5 tons of CO2 for every ton of scrap used. as of 2023, steel has one of the highest recycling rates of any material, with around 30% of the world's steel being made from recycled components. However, steel cannot be recycled forever, and the recycling processes, using arc furnaces, use electricity. This process can reduce emissions by an estimated 20%.

The HIsarna ironmaking process was described above as a way of producing iron in a "cyclone converter furnace" without the pre processing steps of choking/agglomeration, which reduces the CO2 emissions by around 20%. One speculative idea is and ongoing project by SuSteel to develop a hydrogen plasma technology that reduces the oxides with hydrogen, as opposed to with CO or carbon, and melts the iron at high operating temperatures. and iron ore electrolysis are still in the research or semi industrial stage.