Electric arc furnace

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The Electric Arc Furnace (EAF) uses high-current electricity to convert iron into steel. It uses steel scrap (i.e., steel that is being recycled from other sources, such as buildings and construction), Direct Reduced Iron (DRI), or sometimes supplemental pig iron from the Blast Furnace (BF) as raw materials, and electricity to heat the furnace. The output of the EAF is molten steel.

After charging the steel scrap and iron into the furnace, high-voltage electric arcs (delivered via graphite electrodes) are used to generate heat and melt the mixture. At times, the walls of the EAF have additional burners to add oxygen, carbon, or natural gas. This can support the development of slag and the utilization of heat.[1] The raw (molten) steel is separated from the waste matter (known as slag) and each is poured off individually. At this point, the steel can be further customized through the addition of different alloys or be cast into the desired shape, like ingots or slabs.

The EAF route has the potential of emitting only a fifteenth of the average Blast Furnace-Basic Oxygen Furnace (BF-BOF) plant emissions per tonne of steel produced, making it one of the most promising green steel production processes.[2] The level of emissions reduction depends on the energy and iron inputs. To melt the iron and produce steel, electricity generated from either fossil fuels or low-carbon energy sources can be used. To reduce emissions within the primary (ironmaking) process, EAF plants can use DRI or scrap. When utilizing low-emissions electricity to power the process, and low-emissions iron as the resource input, emissions in the steel production process can be almost eliminated.[2][3][4]

Scrap-based EAF production results in approximately 0.3 tonne CO2/ tonne crude steel on average,[5] while natural gas-based DRI-EAF production results in approximately 1.4 tonne CO2/ tonne crude steel.[5] Coal can also be used in DRI-EAF production, with average emissions ranging from 1.3-1.8 t CO2/ t crude steel for the COREX/FINEX process and 3.2 t CO2/ t crude steel for the rotary kiln process. Hydrogen-based DRI-EAF production results in an average 0.71 t CO2/ t[5] crude steel, though actual emissions vary widely depending on the production route of the hydrogen.

The primary challenge in the wide adoption of the EAF route is the lack of available scrap and low-emissions electricity required for the production of low-emissions steel at scale. This makes the expansion of affordable green electricity and better recycling systems two important targets to achieve a green transition in the industry. An additional challenge of the EAF process is that it may result in specific, sometimes undesired, steel properties. It is less oxidizing and has less intense mixing of the slag and metal than the production via the BF-BOF route, resulting in the steel having higher carbon and nitrogen contents. If nitrogen content is not lowered using other technologies, it makes the steel more brittle. Nevertheless, this process can create various compositions of steel and generally permits greater additions of alloys than would be possible through Basic Oxygen Furnaces.[6]

In comparison to a BF-BOF plant, scrap-based EAFs are cheaper to build as they do not require the construction of blast furnaces, coke ovens, and sinter plants to produce iron. EAF plants can also be shut down if production is not needed, while BF-BOF plants need to be operated constantly, even if working below capacity. Plant owners generally need to produce fewer tons of steel per year to cover their running costs, although this number will vary greatly depending on iron and electricity prices.[6]

References

  1. "AIST Steel Wheel". apps.aist.org. Retrieved 2023-12-19.
  2. 2.0 2.1 Iron and Steel Technology Roadmap - Towards more sustainable steelmaking (IEA, 2020)
  3. How to Avoid a Climate Disaster - The Solutions We Have and the Breakthroughs We Need (Gates, 2021)
  4. Swalec, C. & Shearer, C. (2021). Pedal to the Metal. Global Energy Monitor.
  5. 5.0 5.1 5.2 "Iron and Steel Technology Roadmap – Analysis - IEA". IEA. Retrieved 2021-07-06.
  6. 6.0 6.1 Wente, E., Nutting, J., & Wondris, E. F. (n.d.). steel—Primary steelmaking | Britannica [Encyclopedia Britannica]. Steel. https://www.britannica.com/technology/steel

External links

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Abeckford21 (talk) 23:40, 29 June 2021 (UTC)