[Blog 6] How does it work a Blast Furnace?
The main manufacturing process for the production of iron is the reduction of iron ore using coke in a blast furnace. These two materials are introduced at the top of the blast furnace, which will take about 6 hours to descend. The largest blast furnaces at present can produce 10 – 13 kt of hot metal a day. They are about 34 m in inner height (distance from the raw material entrance to the hot metal exit) and 16 m in diameter, with an internal volume in the range 5000 – 5500 m3. It has a vertical cylindrical structure, externally covered with a shell of steel and internally with refractories. Between the shell and the refractories, the structure is cooled by staves. Staves are cooling gadgets having one or more inside channels through which water flows.
To reduce the burden while descending, a reducing agent gas (mostly CO and H2) rises in counterflow in 5 to 10 seconds. This gas is formed in the bottom of the furnace by combustion of the coke with pressurized air enriched with O2, which is blown in through the tuyeres. Auxiliary fuels, like pulverized coal and natural gas, may be introduced into the furnace to reduce the quantity of coke that is fed in with the burden.
Inside the blast furnace, the process is as follows. In the upper part, the burden is rapidly heated from the ambient temperature to about 800 ºC while the gas (coming from the middle zone) cools down from 900 ºC to 100 – 200 ºC as it leaves the furnace top. At this temperatures, the hematite (Fe2O3) is reduced to magnetite (Fe3O4), and then to wüstite (FeO).
- 3Fe2O3+CO → 2Fe3O4+CO2
- 3Fe2O3+H2 → 2Fe3O4+H2O
- Fe3O4+CO → 3FeO+CO2
- Fe3O4+H2 → 3FeO+H2O
In the middle zone of the blast furnace, the temperature ranges between 800 and 1000 ºC. At this temperatures, the wüstite is reduced following indirect reduction.
- FeO+CO → Fe+CO2
- FeO+H2 → Fe+H2O
Finally, next to the tuyeres, at temperatures higher than 1000 ºC, the iron oxide is reduced directly by carbon.
- FeO+C → Fe+CO
At the tapping temperatures (usually 1350 – 1450 ºC) the dissolved carbon in the liquid iron varies from 2.5 to 4.5%. Apart from carbon, hot metal contains small quantities of silicon, manganese, and other elements, which come from the reduction of the impurities present in the burden (e.g., SiO2, MnO and P2O5).
The pressurized gas (1.2 – 3.5 bar) leaving the blast furnace at the top is expanded in a gas turbine to produce electrical power, and also integrated in other sub-processes such as air heating. Additional equipment includes the air unit separation for the oxygen provision. The specific carbon emissions of this production route are about 1.1 tCO2 per ton of pig iron.
Project info
1 April 2021 – 30 June 2023
Total budget: 188,442.24 €
Spain
• University of Zaragoza
Japan
• Waseda University (Nakagaki Lab)
Austria
• K1-MET GmbH
General coordinator
M. Bailera (mbailera@unizar.es)
University of Zaragoza
Further information: cordis.europa.eu
[1] A review on CO2 mitigation in the Iron and Steel industry through Power to X processes. M Bailera, P Lisbona, B Peña, LM Romeo. Journal of CO2 Utilization, Volume 46, 1 April 2021, Pages 101456.
[2] CO2 recycling in the Iron and Steel Industry via Power-to-Gas and Oxy-Fuel Combustion. J Perpiñán, M Bailera, LM Romeo, B Peña, V Eveloy. Energies, Volume 14, 29 October 2021, Pages 7090.
[3] Revisiting the Rist diagram for predicting operating conditions in blast furnaces with multiple injections. M Bailera, T Nakagaki, R Kataoka. Open Research Europe, Volume 1:141, 29 November 2021.
[4] Synthetic natural gas production in a 1 kW reactor using Ni–Ce/Al2O3 and Ru–Ce/Al2O3: Kinetics, catalyst degradation and process design. M Bailera, P Lisbona, B Peña, A Alarcón, J Guilera, J Perpiñán, LM Romeo. Energy, Volume 256, 1 October 2022, Pages 124720.
[1] The global warming paradox of the colder winters
[2] Decarbonization of the industry: why electrification is not enough
[3] What is Power to Gas?
[4] How does it look a methanation plant? (laboratory at Unizar)
[5] Why the reutilization of CO2 must be smart?
[6] How does it work a Blast Furnace?
[7] Power to X routes for the decarbonization of ironmaking
[8] How does it look a blast furnace simulation? (Aspen Plus software)
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 887077.
Project info
1 April 2021 – 30 June 2023
Total budget: 188,442.24 €
Spain
• University of Zaragoza Japan
• Waseda University (Nakagaki Lab) Austria
• K1-MET GmbH
General coordinator
M. Bailera (mbailera@unizar.es)
University of Zaragoza
Further information: cordis.europa.eu
[1] A review on CO2 mitigation in the Iron and Steel industry through Power to X processes. M Bailera, P Lisbona, B Peña, LM Romeo. Journal of CO2 Utilization, Volume 46, 1 April 2021, Pages 101456.
[2] CO2 recycling in the Iron and Steel Industry via Power-to-Gas and Oxy-Fuel Combustion. J Perpiñán, M Bailera, LM Romeo, B Peña, V Eveloy. Energies, Volume 14, 29 October 2021, Pages 7090.
[3] Revisiting the Rist diagram for predicting operating conditions in blast furnaces with multiple injections. M Bailera, T Nakagaki, R Kataoka. Open Research Europe, Volume 1:141, 29 November 2021.
[4] Synthetic natural gas production in a 1 kW reactor using Ni–Ce/Al2O3 and Ru–Ce/Al2O3: Kinetics, catalyst degradation and process design. M Bailera, P Lisbona, B Peña, A Alarcón, J Guilera, J Perpiñán, LM Romeo. Energy, Volume 256, 1 October 2022, Pages 124720.
[1] The global warming paradox of the colder winters
[2] Decarbonization of the industry: why electrification is not enough
[3] What is Power to Gas?
[4] How does it look a methanation plant? (laboratory at Unizar)
[5] Why the reutilization of CO2 must be smart?
[6] How does it work a Blast Furnace?
[7] Power to X routes for the decarbonization of ironmaking
[8] How does it look a blast furnace simulation? (Aspen Plus software)
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 887077.